TITLE: METHODS OF RECOVERING VANADIUM IN THE FORM OF A VANADIUM

ELECTROLYTE AND USES THEREOF

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority to United States Provisional Patent Application No. 63/261 ,219, filed September 15, 2021 , the contents of which is incorporated herein by reference in its entirety.

FIELD

[0002] The present application relates to a method of recovering vanadium in the form of a vanadyl sulfate solution from a secondary source of vanadium such as oil fly ash and petroleum coke using a reductive leaching process using a saccharide and sulfuric acid. The vanadyl sulfate solution can be used as a vanadium electrolyte in a vanadium redox flow battery (VRFB).

BACKGROUND

[0003] Vanadium is a transition metal and mainly consumed as an alloy additive. Its demand is expected to increase due to the rapid development of vanadium redox flow battery (VRFB) for renewable energy storage.

[0004] Major sources for vanadium include primary sources such as ores, and secondary sources such as vanadium slag, petroleum coke (petcoke), oil fly ash, vanadium rich petroleum residue, vanadium spent catalysts and stone coal. For example, oil fly ash (OFA) is a solid waste generated during the combustion of heavy fuel oil and residue oil. OFA is known to be rich in vanadium and its level can reach up to more than 6% depending on the origin of the fuel [1 , 2], Petcoke is a byproduct of the crude oil refining process also known to be high in vanadium content. Due to increasing consumption of vanadium rich fuel for energy, large generation of OFA and petcoke makes them a substantial source for vanadium. Further, recovering valuable metals, such as vanadium from secondary waste sources is a promising alternative solution to avoid disposal to landfill which raise environmental concerns.

[0005] One approach for vanadium extraction from secondary sources is salt roasting. In salt roasting process, the vanadium source is roasted with, for example, NaCI or Na2COs to form water soluble NaVO3[3], However, drawbacks of this method are extensive energy requirement and concerns over air emission.

[0006] In some raw secondary sources, such as OFA and petcoke, vanadium (IV) is dominant with small fraction of vanadium (V), therefore, it can be leached out effectively by weak acid along with other metals and then vanadium is selectively recovered from the leachate. However, the profitability of this approach flocculates heavily depending on the vanadium content of the vanadium source, for example, OFA, which shows a significant variation from 0.5% to more than 7%. For low vanadium secondary sources, direct leaching is unfavorable because of high acid and water consumption per unit amount of vanadium recovered. To overcome this issue, pre-roasting is an option which concentrates vanadium content to more than 15%, but the majority of vanadium is oxidized to a much less soluble form, so more acid and energy input (higher leaching temperature and pressure) are needed. To facilitate the vanadium leaching, a reducing agent can be applied to significantly increase the solubility of vanadium.

[0007] Tavakoli, Dornian and Dreisinger [4] tested the leachability of V2O5 in mild acidic pH with sodium sulfite (Na2SOs) and found that leaching efficiency was improved. Wu, Wang, Bao and Li [5] demonstrated the improvement of leaching vanadium from V2Os'WO3/TiO2 catalyst from 73.4% to over 85% with oxalic acid concentration from 0.1 mol/L to 1 mol/L at 90 °C, S:L ratio of 1 g:20 mL. Both reducing agents showed good results but their low stability or solubility in high acidic condition may impact their applicability in generating highly concentrated leachate.

[0008] Chinese Patent No. 101289705 discloses extracting vanadium from the iron-smelting waste residues of vanadium iron ores, using hydroxyl compounds such as ethylene glycol, glycerol, glucose or sucrose.

SUMMARY

[0009] The Applicants have developed an efficient process of recovering vanadium in the form of a highly pure vanadyl sulfate solution from a secondary source of vanadium comprising a reductive acid leaching step using a saccharide as a reducing agent. [0010] Accordingly, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution (optionally highly pure vanadyl sulfate solution), the method comprising: leaching a vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution (optionally highly pure vanadyl sulfate solution) from the vanadyl sulfate leachate, wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof.

[0011] The present application also includes a method of recovering vanadium in the form of a vanadyl sulfate solution (optionally highly pure vanadyl sulfate solution) from a secondary source of vanadium, the method comprising: roasting the secondary source of vanadium to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution (optionally highly pure vanadyl sulfate solution) from the vanadyl sulfate leachate, wherein the secondary source of vanadium is selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal, and combinations thereof.

[0012] In an embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution (optionally highly pure vanadyl sulfate solution) from the vanadyl sulfate leachate comprises: extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; and stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce a used extractant and the vanadyl sulfate solution (optionally highly pure vanadyl sulfate solution).

[0013] In an embodiment, the method further comprises regenerating the extractant from the used extractant.

[0014] In an embodiment, the method further comprises recovering one or more additional metals or metal compounds.

[0015] In an embodiment, when the secondary source of vanadium is selected from oil fly ash and petroleum coke (petcoke), the method of the application further comprises a method of recovering nickel comprising: adjusting the pH of the raffinate to about 5 to about 6; adding an oxidizing agent to the raffinate with a pH of about 5 to about 6 to form Fe(OH)s precipitate and a second raffinate; separating the Fe(OH)s from the second raffinate; adjusting the pH of the second raffinate to a pH of about 7 to about 8 with a carbonate base to form a NiCOs precipitate and a third raffinate; and separating the NiCOs from the third raffinate with a pH of about 7 to about 8 to produce the NiCOs.

[0016] The present application also includes a highly pure vanadyl sulfate solution produced by the methods of the application. [0017] The present application also includes a vanadium electrolyte produced by the methods of the application.

[0018] In an embodiment, the vanadium electrolyte is for use in a vanadium redox battery.

[0019] The present application also includes a vanadium flow redox battery comprising the vanadium electrolyte of the application.

[0020] The present application also includes a method of improving the leaching rate of vanadium from a secondary source of vanadium, the method comprising leaching a vanadium rich substance with a leaching solution to produce a vanadyl sulfate leachate and a leached substance, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar, wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof, and wherein the leaching rate of the vanadium is improved compared to the leaching rate of vanadium under identical conditions except in the absence of the saccharide.

[0021] The present application also includes a leaching solution for leaching a vanadium rich substance, the leaching solution comprising: sulfuric acid at a concentration of 4 molar to 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar, wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof.

[0022] In an embodiment, the methods of the application comprise, consist of or consist essentially of the embodiments of the methods of the application as described herein.

[0023] Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the application, are given by way of illustration only and the scope of the claims should not be limited by these embodiments, but should be given the broadest interpretation consistent with the description as a whole.

DRAWINGS

[0024] The embodiments of the application will now be described in greater detail with reference to the attached drawings in which:

[0025] Figure 1 is a flowchart showing an exemplary method of the application.

[0026] Figure 2 is a graph showing the metal leaching rates at different H2SO4 concentrations, glucose concentration 1 mol/L, leaching temperature 60°C, leaching time 4 hours, S:L=1g:2ml.

[0027] Figure 3 is a graph showing the metal leaching rates at different glucose concentration, H2SO4 Concentration 7 mol/L, temperature 60°C, leaching time 4 hours, S:L=1g:2ml.

[0028] Figure 4 are graphs showing metal leaching rates with and without glucose, H2SO4 Concentration 6 mol/L, glucose concentration 0.2mol/L, leaching temperature 80°C, leaching time 4 hours, S:L=1 g:2ml.

[0029] Figure 5 are graphs showing the metal leaching rates at different leaching temperatures, H2SO4 Concentration 7 mol/L, glucose concentration 0.2mol/L, leaching time 4 hours, S:L=1g:2ml. [0030] Figure 6 are graphs showing the metal leaching rates at roasting temperature, H2SO4 concentration 4mol/L and 6mol/L, glucose concentration 0.2mol/L, leaching temperature 80 °C, leaching time 4 hours, S:L=1g:2ml.

[0031] Figure 7 is a graph showing the comparison of glucose and sucrose, H2SO4, Concentration 6mol/L, glucose and sucrose quantity 36g/L (equivalent to 0.2mol/L glucose), leaching temperature 80°C, leaching time 4 hours, S:L=1g:2ml.

DETAILED DESCRIPTION

I. Definitions

[0032] Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the present application herein described for which they are suitable as would be understood by a person skilled in the art.

[0033] The term “method(s) of the application” and the like as used herein refers to a method of producing a vanadyl sulfate solution, a highly pure vanadyl sulfate solution and/or a vanadium electrolyte as described herein.

[0034] The term “and/or” as used herein means that the listed items are present, or used, individually or in combination. In effect, this term means that “at least one of” or “one or more” of the listed items is used or present. The term “and/or” with respect to pharmaceutically acceptable salts and/or solvates thereof means that the compounds of the application exist as individual salts and hydrates, as well as a combination of, for example, a solvate of a salt of a compound of the application.

[0035] As used in the present application, the singular forms “a”, “an” and “the” include plural references unless the content clearly dictates otherwise. For example, an embodiment including “a solvent” should be understood to present certain aspects with one solvent, or two or more additional solvents.

[0036] In embodiments comprising an “additional” or “second” component, such as an additional or second solvent, the second component as used herein is chemically different from the other components or first component. A “third” component is different from the other, first, and second components, and further enumerated or “additional” components are similarly different. [0037] As used in this application and claim(s), the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0038] The term “consisting” and its derivatives as used herein are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, and also exclude the presence of other unstated features, elements, components, groups, integers and/or steps.

[0039] The term “consisting essentially of”, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and/or steps as well as those that do not materially affect the basic and novel characteristic(s) of these features, elements, components, groups, integers, and/or steps.

[0040] The term “suitable” as used herein means that the selection of the particular compound or conditions would depend on the specific synthetic manipulation to be performed, the identity of the molecule(s) to be transformed and/or the specific use for the compound, but the selection would be well within the skill of a person trained in the art. All process/method steps described herein are to be conducted under conditions sufficient to provide the product shown. A person skilled in the art would understand that all reaction conditions, including, for example, reaction solvent, reaction time, reaction temperature, reaction pressure, reactant ratio and whether or not the reaction should be performed under an anhydrous or inert atmosphere, can be varied to optimize the yield of the desired product and it is within their skill to do so.

[0041] The terms "about", “substantially” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word. [0042] The term “oil fly ash” or “OFA” as used herein refers to a solid waste product generated from the combustion of oil such as heavy fuel oil.

[0043] The term “petroleum coke” or “petcoke”, as used herein refers to a byproduct of the crude oil refining process.

[0044] The term “vanadium rich petroleum residues”, as used herein refers to final fractions from the distillation of crude oil.

[0045] The term "carbonaceous material" as used herein refers to a material containing organic hydrocarbon content.

[0046] The term “vanadium spent catalyst” as used herein refers to catalyst comprising vanadium that has been withdrawn from process, for example, for having completed its lifecycle.

[0047] The term “vanadium slag” as used herein refers to a by-product generated from steel making process.

[0048] The term “vanadyl sulfate” or “vanadium oxide sulphate” or “vanadyl (IV) sulfate” as used herein refers to compounds having the chemical formula VOSO4 and hydrates thereof, for example VOSO4(H2O)x wherein x is 0 to 6.

II. Methods of the Application

[0049] The Applicants have developed an efficient process of recovering vanadium in the form of a vanadyl sulfate solution from a secondary source of vanadium having a high concentration of vanadium comprising a reductive acid leaching step using a saccharide as a reducing agent. For example, the Applicants have found that saccharides such as glucose, sucrose and starch can be used as effective reducing agents to increase the leaching rate of vanadium in a reductive acid leaching step with sulfuric acid in a process of recovering vanadium in the form of a vanadyl sulfate solution. In an embodiment, the Applicants have shown that a vanadium rich substance such as a vanadium rich substance produced from a secondary source of vanadium, such as roasted oil fly ash (OFA), can be leached using a saccharide as the reducing agent, for example, glucose, in a reductive acid leaching step with sulfuric acid, to produce a highly concentrated vanadyl sulfate leachate solution with a leaching rate of vanadium of up to 95%. In an embodiment, a leaching rate of vanadium of greater than 90% is achieved in about 1 hour of leaching time. Further, vanadium can be recovered from the highly concentrated vanadyl sulfate leachate in the form of a vanadyl sulfate solution having a purity of, for example, about 99.6%. This highly pure vanadyl sulfate solution can be optionally further concentrated if necessary and used as an electrolyte in a vanadium redox flow battery (VRFB).

[0050] Vanadium rich substances can be produced by roasting secondary sources of vanadium which comprise carbonaceous material such as oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal. The Applicants have also shown that roasting such secondary sources of vanadium at relatively low temperatures enhances the leaching rate of the vanadium in the method of the application.

[0051] The Applicants have also shown that the reductive acid leaching step with the roasted vanadium rich source in the presence of a saccharide can be performed with low volumes of the leaching solution such as with a solid-to-liquid (S:L) ratio of up to 1 g:2mL of vanadium rich source to leaching solution. The low volumes of leaching solution provides a highly concentrated vanadium-rich leachate. For example, when using a solid-to-liquid (S:L) ratio of 1g:2mL of vanadium rich substance such as roasted oil fly ash and a leaching solution comprising a saccharide, for example, glucose in sulfuric acid, a highly concentrated vanadyl sulfate leachate solution is produced, for example, up to 60g/L. A high S:L ratio also reduces the need for sequencing leachate treatment (e.g pH adjustment). Therefore, the method of the application is more efficient compared to, for example, an otherwise similar method except for the use of the saccharide as the leaching agent, or for example, compared to other conventional methods such as alkaline roasting with water leaching and direct acid leaching. The fast leaching kinetics and high S:L ratio are advantageous in terms of sizing of the leaching process (for example, smaller equipment, smaller volume of reagents, and less waste). Further, the method of the application generates less emissions and requires less energy input which in turn leads to significantly lower costs. Advantageously still, additional metals such as nickel can be recovered from the raffinate produced after recovering vanadium from the vanadyl sulfate leachate. Further, the extractant used in the method may be regenerated contributing to the efficiency of method.

[0052] The Applicants have found that the method of the application also produces a highly pure vanadyl sulfate solution. In an embodiment, the Applicants have found that when using, for example, glucose as the reducing agent, and leaching vanadium from a vanadium rich source as roasted oil fly ash (OFA) a vanadyl sulfate solution having a purity of about 99.6% is obtained.

[0053] The vanadyl sulfate solution formed from the method of the application can be used as an electrolyte in a Vanadium Redox Flow Battery (VRFB). Since the method of the application produces a highly concentrated and highly pure vanadyl sulfate solution, the vanadyl sulfate solution of the application can be used in a VRFB with less processing, for example, further concentrating compared to, for example, a vanadyl sulfate solution produced by a conventional process.

[0054] Accordingly, the method of the application advantageously uses secondary sources of vanadium at significantly lower costs in an efficient process to produce a vanadyl sulfate solution that can be used as an electrolyte in a VFRB battery, for renewable energy storage.

[0055] Accordingly, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution from a secondary source of vanadium, the method comprising: leaching a vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate, wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof.

[0056] It would be appreciated by a person skilled in the art that the secondary source of vanadium is as-received or is a raw or unprocessed secondary source of vanadium that has not been subjected to a pretreatment step.

[0057] It would also be appreciated by a person skilled in the art that vanadium slag and spent vanadium catalysts comprise a high concentration of vanadium as- received. Accordingly, when the secondary source of vanadium is selected from vanadium slag and spent vanadium catalysts, the secondary source of vanadium is the vanadium rich substance (i.e., the vanadium slag or the spent vanadium catalysts. Therefore, in an embodiment, the method comprises: leaching a vanadium rich substance selected from vanadium slag and spent vanadium catalysts, or a mixture thereof with the leaching solution as defined above to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate. In an embodiment, the vanadium rich substance is vanadium slag. In an embodiment, the vanadium rich substance is spent vanadium catalysts.

[0058] In an embodiment, the as-received vanadium slag or spent vanadium catalysts comprises coarse particles of the vanadium slag or the spent vanadium catalysts, and therefore the as-received vanadium slag or spent vanadium catalysts is milled into finer particles before leaching with the leaching solution. Accordingly, in an embodiment, when the secondary source of vanadium is selected from vanadium slag and spent vanadium catalysts, the method further comprises the step of milling a vanadium rich substance selected from vanadium slag and spent vanadium catalysts to provide a milled vanadium rich substance and leaching the milled vanadium rich substance with a leaching solution. In an embodiment, the milled vanadium rich substance is milled vanadium slag. In an embodiment, the milled vanadium rich substance is milled spent vanadium catalysts.

[0059] In an embodiment, the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof. A person skilled in the art would appreciate that a secondary source of vanadium comprising carbonaceous material selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof is roasted to reduce the carbon content of the secondary source of vanadium to produce a vanadium rich substance that has higher concentration of vanadium compared to the as-received secondary source of vanadium. Therefore, in an embodiment, when the secondary source of vanadium comprises carbonaceous material such as oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof, the secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal is roasted to produce the vanadium rich substance.

[0060] Therefore, when the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petcoke petroleum residues and stone coal and combinations thereof and the method comprises the step of: roasting the secondary source of vanadium to produce the vanadium rich substance.

[0061] Accordingly, in an exemplary method of the application, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution from a secondary source of vanadium, the method comprising: roasting the secondary source of vanadium to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate, wherein the secondary source of vanadium is selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal, and combinations thereof.

[0062] In an embodiment, the secondary source of vanadium is vanadium rich petroleum residues as-received. In an embodiment, the vanadium rich petroleum residues are the final fractions produced from the distillation of crude oil.

[0063] In an embodiment, the secondary source of vanadium is selected from oil fly ash, petroleum coke (petcoke), and stone coal and combinations thereof. In an embodiment, the secondary source of vanadium is selected from oil fly ash and petcoke and combinations thereof. In an embodiment, the secondary source of vanadium is petcoke. In an embodiment, the secondary source of vanadium is oil fly ash.

[0064] Accordingly, in an exemplary method of the application, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution the method comprising: roasting a secondary source of vanadium selected from oil fly ash and petroleum coke (petcoke) to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate. [0065] In an embodiment, the petcoke is a byproduct generated from the crude oil refining process.

[0066] In an embodiment, the OFA as-received is a solid waste product generated from the industrial combustion of oil. In an embodiment, the oil is heavy fuel oil or residue oil. In an embodiment, the oil is heavy fuel oil. Therefore, in an embodiment, the secondary vanadium source of vanadium is oil fly ash generated from the industrial combustion of heavy fuel oil. In an embodiment, the oil fly ash is generated from the combustion of heavy fuel oil from, for example, power plants or from oil sands. In an embodiment, the composition of fly ash varies depending upon, for example, the fuel that is combusted, and the combustion conditions.

[0067] In an exemplary method of the application, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution from oil fly ash the method comprising: roasting oil fly ash to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate.

[0068] In an embodiment, the vanadyl sulfate solution is a highly pure vanadyl sulfate solution.

[0069] In an embodiment, the amount of vanadium and other metals such as nickel, iron, aluminum, magnesium, calcium, sodium, silicone or sulfur in the secondary source of vanadium will depend upon the source of the secondary source of vanadium. In an embodiment, the amount of vanadium and other metals such as nickel, iron, aluminum, magnesium, calcium, sodium, silicone or sulfur in the secondary source of vanadium such as oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal as received which comprise carbonaceous material depends on the source of the secondary source of vanadium and the extent to which the hydrocarbon content has been removed by combustion during production of the secondary source of vanadium such which comprise carbonaceous material.

[0070] It would be appreciated by a person skilled in the art that secondary sources of vanadium comprise a naturally higher concentration of vanadium compared to that of a primary source, i.e., from mining. Therefore, in an embodiment, the secondary sources of vanadium as used herein refers to sources of vanadium that naturally comprise a high concentration of vanadium

[0071] In an embodiment, the secondary source of vanadium selected from petroleum oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal, and combinations thereof comprises about 1 % or more vanadium as received. In an embodiment, the secondary source selected from petroleum oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal of vanadium comprises about 1 % or more, about 1.3% or more, about 1.5% or more, about 1 .7% or more, about 2.0% or more, about 2.3% or more, about 2.5% or more, about 2.7% or more, about 3% or more, about 3.3% or more, about 3.5% or more, about 3.7% or more, about 4% or more, about 4.3% or more, about 4.5% or more, about 4.7% or more, about 5% or more, about 5.3% or more, about 5.5% or more, about 5.7% or more, about 6% or more, about 6.3% or more, about 6.5% or more, about 6.7% or more, about 7% or more vanadium as received. In an embodiment, the secondary source of vanadium comprises about 1 % or more, about 2% or more, about 3% or more, about 4% or more, about 5% or more, about 6% or more about 7% or more vanadium as received. In an embodiment, the secondary source of vanadium comprises about 1 % to about 25%, about 1 % to about 20%, about 1 % to about 15%, about 1 % to about 10%, about 1 % to about 5%, about 1 % to about 4%, about 1 % to about 3%, about 1 % to about 2%, about 1 .5% to about 25%, about 1 .5% to about 20%, about 1.5% to about 15%, about 1.5% to about 10%, about 1.5% to about 5%, about 1.5% to about 4%, about 1.5% to about 3%, about 2% to about 20%, about 2% to about 15%, about 2% to about 10%, about 2% to about 5%, about 3% to about 20%, about 3% to about 15%, about 3% to about 10%, about 3% to about 15%, about 5% to about 25%, about 5% to about 20%, about 5% to about 15% about 5% to about 10%, about 5% to about 8% and about 5% to about 7% vanadium as received. In an embodiment, the secondary source of vanadium comprises about 1 % to about 10%, about 1 % to about 5%, about 1 % to about 4%, about 1 % to about 3%, about 1 .5% to about 5%, about 1 .5% to about 4%, about 1 .5% to about 3% as- received. In an embodiment, the secondary source of vanadium comprises about 1 % to about 5% or about 1 .5% to about 5% vanadium as-received. In an embodiment, the secondary source of vanadium is selected from oil fly ash, petcoke, vanadium rich petroleum residue and stone coal and combinations thereof. In an embodiment, the secondary source of vanadium is selected from oil fly ash, petcoke and vanadium rich petroleum residue and combinations thereof. In an embodiment, the secondary source of vanadium is selected from oil fly ash and petcoke and combinations thereof.

[0072] In an embodiment, the secondary source of vanadium is oil fly ash or petcoke and combinations thereof. In an embodiment, the oil fly ash or petcoke comprises about 1 % or more vanadium as received. In an embodiment, the oil fly ash or petcoke comprises about 1 % or more, about 1.3% or more, about 1.5% or more, about 1 .7% or more, about 2.0% or more, about 2.3% or more, about 2.5% or more, about 2.7% or more, about 3% or more, about 3.3% or more, about 3.5% or more, about 3.7% or more, about 4% or more, about 4.3% or more, about 4.5% or more, about 4.7% or more, about 5% or more, about 5.3% or more, about 5.5% or more, about 5.7% or more, about 6% or more, about 6.3% or more, about 6.5% or more, about 6.7% or more, about 7% or more vanadium as received. In an embodiment, the oil fly ash or petcoke comprises about 1 % or more, about 2% or more, about 3% or more, about 4% or more, about 5% or more, about 6% or more about 7% or more vanadium as received. In an embodiment, the oil fly ash or petcoke comprises about 1 % to about 25%, about 1 % to about 20%, about 1 % to about 15%, about 1 % to about 10%, about 1 % to about 5%, about 1.5% to about 25%, about 1 .5% to about 20%, about 1 .5% to about 15%, about 1 .5% to about 10%, about 1 .5% to about 5%, about 1 .5% to about 4%, about 1 .5% to about 2%, about 1 .5% to about 3%, about 2% to about 20%, about 2% to about 15%, about 3% to about 20%, about 3% to about 15%, about 3% to about 10%, about 5% to about 25%, about 5% to about 20%, about 5% to about 15%, about 5% to about 10%, about 5% to about 8% and about 5% to about 7% vanadium as received. In an embodiment, the oil fly ash or petcoke comprises about 1 % to about 10%, about 1 % to about 5% vanadium, about 1 % to about 4% vanadium or about 1 % to about 3% vanadium as-received. In an embodiment, the oil fly ash or petcoke comprises about 1 % to about 10%, about 1 % to about 5%, about 1 % to about 4%, about 1 % to about 3%, about 1 .5% to about 5%, about 1.5% to about 4%, about 1.5% to about 3% vanadium as-received. In an embodiment, the oil fly ash or petcoke comprises about 1 % to about 5% or about 1 .5% to about 5% vanadium as-received.

[0073] In an embodiment, the secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residue, stone coal, vanadium slag and spent vanadium catalysts, and combinations thereof comprises one or more other metals selected from nickel, iron, aluminum, magnesium, calcium, sodium, silicone and sulfur. In an embodiment, the secondary source of vanadium is selected from oil fly ash and petcoke, and combinations thereof and further comprises nickel. In an embodiment, oil fly ash and petcoke comprises about one-third the amount of nickel compared to the amount of vanadium as-received. In an embodiment, the secondary source of vanadium selected from oil fly ash and petcoke, and combinations thereof further comprises about 0.3% or more, 0.5% or more, 0.7% or more, 1 .0% or more, about 1 .3% or more, about 1 .5% or more, about 1 .7% or more, about 2.0% or more, about 2.3% or more, about 2.5% or more, about 2.7% or more, about 3% or more, about 3.3% or more, about 3.5% or more, about 3.7% or more, about 4% or more, about 4.3% or more, about 4.5% or more, about 4.7% or more, about 5% or more nickel as-received. In an embodiment, the secondary source of vanadium selected from oil fly ash and petcoke and combinations thereof comprise about 0.3% or more, about 0.5% or more, about 0.7% or more, about 1 % or more, about 1 .5 % or more, about 2% or more, about 3% or more, about 4% or more or about 5% or more nickel as received. In an embodiment, the secondary source of vanadium selected from oil fly ash and petcoke, and combinations thereof comprises about 0.3% to about 15%, about 0.3% to about 10%, about 0.3% to about 5%, about 0.3% to about 3%, about 0.3% to about 2%, about 0.3% to about 1 %, about 0.5% to about 15%, about 0.5% to about 10%, about 0.5% to about 5%, about 0.5% to about 3%, about 0.5% to about 2%, about 0.5% to about 1 %, about 1 % to about 15%, about 1 % to about 10%, about 1 % to about 5%, about 1 .5% to about 15%, about 1 .5% to about 10%, about 1 .5% to about 5%, about 1.5% to about 4%, about 1.5% to about 3% nickel as received. In an embodiment, the secondary source of vanadium selected from oil fly ash and petcoke, and combinations thereof comprises about 1 % to about 10%, about 1 % to about 5% vanadium, about 1 % to about 4% vanadium or about 1 % to about 3% vanadium as-received. In an embodiment, the secondary source of vanadium selected from oil fly ash and petcoke and combinations thereof comprises about 0.3% to about 5%, about 0.3% to about 3%, about 0.3% to about 2%, about 0.3% to about 1 %, about 0.5% to about 5%, about 0.5% to about 3%, about 0.5% to about 2%, or about 0.5% to about 1 %, nickel as-received. In an embodiment, the secondary source of vanadium selected from oil fly ash and petcoke, and combinations thereof comprises about 0.3% to about 2%, 0.3% to about 1 %, about 0.5% to about 1 % or 0.5% to about 2%, nickel as-received.

[0074] In an embodiment, the secondary source of vanadium that further comprises one or more other metals is oil fly ash. In an embodiment, the oil fly ash further comprises one or more other metals selected from nickel, iron, aluminum, magnesium, calcium, sodium, silicone and sulfur. In an embodiment, the oil fly ash further comprises nickel. In an embodiment, oil fly ash comprises about one-third the amount of nickel compared to the amount of vanadium as-received. In an embodiment, the oil fly ash further comprises about 0.3% or more, 0.5% or more, 0.7% or more, 1 .0% or more, about 1 .3% or more, about 1 .5% or more, about 1 .7% or more, about 2.0% or more, about 2.3% or more, about 2.5% or more, about 2.7% or more, about 3% or more, about 3.3% or more, about 3.5% or more, about 3.7% or more, about 4% or more, about 4.3% or more, about 4.5% or more, about 4.7% or more, about 5% or more nickel as-received. In an embodiment, the oil fly ash comprises about 0.3% or more, about 0.5% or more, about 0.7% or more, about 1 % or more, about 1.5 % or more, about 2% or more, about 3% or more, about 4% or more or about 5% or more nickel as received. In an embodiment, the oil fly ash comprises about 0.3% to about 15%, about 0.3% to about 10%, about 0.3% to about 5%, about 0.3% to about 3%, about 0.3% to about 2%, about 0.3% to about 1 %, about 0.5% to about 15%, about 0.5% to about 10%, about 0.5% to about 5%, about 0.5% to about 3%, about 0.5% to about 2%, about 0.5% to about 1 %, about 1 % to about 15%, about 1 % to about 10%, about 1 % to about 5%, about 1.5% to about 15%, about 1.5% to about 10%, about 1.5% to about 5%, about 1.5% to about 4%, about 1.5% to about 3% nickel as received. In an embodiment, the oil fly ash comprises about 1 % to about 10%, about 1 % to about 5% vanadium, about 1 % to about 4% vanadium or about 1 % to about 3% vanadium as-received. In an embodiment, the oil fly ash comprises about 0.3% to about 5%, about 0.3% to about 3%, about 0.3% to about 2%, about 0.3% to about 1 %, about 0.5% to about 5%, about 0.5% to about 3%, about 0.5% to about 2%, or about 0.5% to about 1 %, nickel as-received. In an embodiment, the oil fly ash comprises about 0.3% to about 2%, 0.3% to about 1 %, about 0.5% to about 1 % or 0.5% to about 2%, nickel as-received.

[0075] In an embodiment, the oil fly ash or petcoke or combinations thereof comprises about 1 % to about 5% vanadium and about 0.3% to about 3% nickel, or about 1 % to about 3% vanadium and about 0.3% to about 1 % nickel as-received. In an embodiment, oil fly ash or petcoke or combinations thereof further comprises about 0.5% or more about 1 % or more, about 2% or more, or about 3% or more nickel. In an embodiment, oil fly ash or petcoke or combinations thereof further comprises about 0.5% or more or about 1 % or more nickel as-received.

[0076] In an embodiment, the oil fly ash or petcoke or combinations thereof comprises about 1 % or more vanadium and about 0.3% or more nickel as-received. In an embodiment, the oil fly ash or petcoke orcombinations thereof comprises about 3% or more or about 5% or more vanadium and about 0.3 % or more, about 1 % or more or about 3% or more nickel as-received.

[0077] In some embodiments, the secondary source of vanadium further comprises iron. It would appreciate by a person skilled in the art that iron leached from the vanadium rich substance in the process of recovering vanadium of the present application may be difficult to separate from the vanadium. Accordingly, in an embodiment, the secondary source of vanadium naturally comprises low concentrations of iron. In an embodiment, the secondary sources of vanadium selected from oil fly ash, petroleum coke (petcoke), petroleum residue, stone coal, vanadium slag and spent vanadium catalysts, and combinations thereof comprises less than about 0.5% iron, less than about 1% iron, less than about 2% iron, less than about 3%, less than about 4% iron, or less than about 2% iron, iron as-received. In an embodiment, the secondary source of vanadium comprises less than about 0.5% iron, less than about 1 % iron or less than about 3% iron as-received. In an embodiment, the secondary sources of vanadium is selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof comprising less than about 0.5% iron, less than about 1 % iron, less than about 2% iron, or less than about 3% iron as-received. In an embodiment, the secondary sources of vanadium is oil fly ash or petcoke comprising less than less than about 0.5% iron, about 1 % iron, less than about 2% iron, or less than about 3% iron as- received. In an embodiment, the secondary vanadium source is oil fly ash or petcoke comprising less than about 0.5% iron or less than about 1 % iron as-received.

[0078] In an exemplary embodiment, the oil fly ash or petcoke comprises about 1 % or more, about 3% or more or about 5% or more vanadium, about 1 % or more nickel and less than about 0.5% iron or less than about 1 % iron as-received. In an exemplary embodiment, the oil fly ash comprises about 1 % or more, about 3% or more or about 5% or more vanadium, about 1 % or more nickel and less than about 0.5% iron or less than about 1 % iron as-received.

[0079] In an exemplary embodiment, the percentage of various metals in the oil fly ash as-received is as according to Table 1 .

[0080] In an embodiment, when the secondary source of vanadium is selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal, the secondary source of vanadium comprises from about 2 and about 90, about 20 to about 90, about 30 to about 90, about 40 to about 90, about 50 to about 90, about 60 to about 90, about 60 to about 80 weight percent carbon. In an embodiment, when the secondary source of vanadium is selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal, the secondary source of vanadium comprises from about 50 to about 90, about 60 to about 90, about 60 to about 80 weight percent carbon. [0081] As described above, in an embodiment, the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal which comprise carbonaceous material. Therefore, in an embodiment, the vanadium rich substance is a secondary source of vanadium that has been roasted. Accordingly, in an embodiment, the vanadium rich substance is selected from roasted oil fly ash roasted petcoke, roasted vanadium rich petroleum residues, and roasted stone coal and combinations thereof. In an embodiment, the vanadium rich substance is roasted oil fly ash or roasted petcoke. In an embodiment, the vanadium rich substance is roasted oil fly ash.

[0082] In an embodiment, the step of roasting is performed at temperature of, about 550°C to about 750°C, about 550°C to about 700°C or about 550°C to about 650°C. In an embodiment, the step of roasting is performed at temperature of about 550°C to about 750°C, about 550°C to about 700°C or about 550°C to about 650°C. In an embodiment, the step of roasting is performed at temperature of about 550°C to about 650°C.

[0083] In an embodiment, the step of roasting is performed in the presence of air.

[0084] In an embodiment, the step of roasting a secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal is performed using any suitable roasting processes known in the art. In an embodiment, the step of roasting is performed in a muffle furnace or a rotary kiln.

[0085] When the secondary source of vanadium is selected from vanadium slag and spent vanadium catalysts, the secondary source of vanadium is the vanadium rich substance (i.e. , the vanadium slag or the spent vanadium catalysts. In an embodiment, the vanadium rich substance is selected from vanadium slag and spent vanadium catalysts, and combinations thereof.

[0086] In an embodiment, the vanadium slag or the spent vanadium catalysts or combinations thereof comprise about 5% to about 20%, about 6% to about 20%, about 7% to about 20%, about 8% to about 20%, about 9% to about 20%, about 9% to about 18%, about 9% to about 15%, about 9% to about 12%, about 10% to about 20%, about 10% to about 15%, about 12% to about 17%, about 12% to about 20%, about 15% to about 20% vanadium as-received. In an embodiment, the vanadium slag or the spent vanadium catalysts or combinations thereof comprise about 5% or more, about 6% or more, about 7% or more, about 8% or more about 9% or more, about 10% or more, about 11 % or more, about 12% or more, about 13% or more, about 14% or more, about 15 % or more, about 16% or more, about 17% or more, about 18% or more, about 19% or more, or about 20% or more vanadium as- received. In an embodiment, the vanadium slag or the spent vanadium catalysts or combinations thereof comprise about 9% or more vanadium as-received.

[0087] In an embodiment, the vanadium rich substance is selected from roasted oil fly ash, roasted petcoke, roasted vanadium rich petroleum residues, and roasted stone coal and combinations thereof. In an embodiment, the vanadium rich substance is selected from roasted oil fly ash and roasted petcoke. In an embodiment, the vanadium rich substance is roasted oil fly ash.

[0088] In an embodiment, the vanadium rich substance selected from roasted oil fly ash, roasted petcoke, roasted vanadium rich petroleum residues, and roasted stone coal and combinations thereof comprises about 10% or more, about 11 % or more, about 12% or more, about 13% or more, about 14% or more, about 15 % or more, about 16% or more, about 17% or more, about 18% or more, about 19% or more, or about 20% or more vanadium on a dry basis. In an embodiment, the vanadium rich substance comprises about 12% or more, about 13% or more, about 14% or more or about 15 % or more vanadium on a dry basis. In an embodiment, the vanadium rich substance is roasted oil fly ash or roasted petcoke. In an embodiment, the roasted oil fly ash or roasted petcoke comprises about 10% or more, about 11 % or more, about 12% or more, about 13% or more, about 14% or more, about 15 % or more, about 16% or more, about 17% or more, about 18% or more, about 19% or more, or about 20% or more vanadium on a dry basis. In an embodiment, the roasted oil fly ash or roasted petcoke comprises about 12% or more, about 13% or more, about 14% or more or about 15 % or more vanadium on a dry basis. In an embodiment, the roasted oil fly ash or roasted petcoke comprises about 15 % or more vanadium on a dry basis. [0089] In an embodiment, the vanadium rich substance is roasted oil fly ash or roasted petcoke or combinations thereof. In an embodiment, the roasted oil fly ash or roasted petcoke or combinations thereof further comprises about 4% or more, about 5% or more, about 6% or more, about 7% or more, or about 8% or more nickel on a dry basis. In an embodiment, roasted oil fly ash or roasted petcoke or combinations thereof further comprises about 4% or more, about 5% or more or about 6% or more nickel on a dry basis.

[0090] In an embodiment, the vanadium rich substance selected from roasted oil fly ash, roasted petroleum coke (petcoke), roasted petroleum residue, roasted stone coal, vanadium slag and spent vanadium catalysts, and combinations thereof and combinations thereof comprises less than about 4% iron, less than about 3% iron, less than about 2% iron, or less than about 1 % iron on a dry basis. In an embodiment, the vanadium rich substance selected from roasted oil fly ash, roasted petroleum coke (petcoke), roasted petroleum residue, roasted stone coal, vanadium slag and spent vanadium catalysts, and combinations thereof and combinations thereof comprises less than about 4% iron or less than about 3% iron on a dry basis.

[0091] In an embodiment, the vanadium rich substance is roasted oil fly ash or roasted petcoke. In an embodiment, the roasted oil fly ash or roasted petcoke further comprises less than about 4% iron, less than about 3% iron, less than about 2% iron, or less than about 1 % iron on a dry basis. In an embodiment, the roasted oil fly ash or roasted petcoke further comprises less than about 4% iron or less than about 3% iron on a dry basis.

[0092] In an exemplary embodiment, the percentages of various metals in the roasted oil fly ash are as according to Table 1 .

[0093] In an embodiment, the sulfuric acid concentration in the leaching solution is about 4 molar to about 9 molar, about 4 molar to about 8 molar, about 4 molar to about 7 molar, about 4 molar to about 6 molar, about 4 molar to about 5 molar, about 5 molar to about 7 molar, about 5 molar to about 6 molar or about 6 molar. In an embodiment, the sulfuric acid concentration is about 4 molar to about 8 molar, about 4 molar to about 7 molar, about 4 molar to about 6, about 5 molar to about 7 molar, about 5 molar to about 6 molar or about 6 molar. In an embodiment, the sulfuric acid concentration of is about 4 molar to about 7 molar. In an embodiment, the sulfuric acid concentration of is about 4 molar to about 6 molar.

[0094] In an embodiment, the saccharide concentration in the leaching solution is about 0.1 molar to about 0.8 molar, about 0.1 molar to about 0.7 molar, about 0.1 molar to about 0.6 molar, about 0.1 molar to about 0.5 molar, about 0.1 molar to about 0.4 molar, about 0.1 molar to about 0.3 molar, about 0.1 molar to about 0.2 molar, about 0.2 molar to about 0.9 molar, about 0.2 molar to about 0.8 molar, about 0.2 molar to about 0.7 molar, about 0.2 molar to about 0.6 molar, about 0.2 molar to about 0.5 molar, about 0.2 molar to about 0.4 molar, about 0.2 molar to about 0.3 molar, about 0.3 molar to about 0.9 molar, about 0.3 molar to about 0.8 molar, about 0.3 molar to about 0.7 molar, about 0.3 molar to about 0.6 molar, about 0.3 molar to about 0.5 molar, about 0.3 molar to about 0.4 molar, about 0.4 molar to about 0.9 molar, about 0.4 molar to about 0.8 molar, about 0.4 molar to about 0.7 molar, about 0.4 molar to about 0.6 molar, about 0.4 molar to about 0.5 molar, about 0.5 molar to about 0.9 molar, about 0.5 molar to about 0.8 molar, about 0.5 molar to about 0.7 molar, about 0.5 molar to about 0.6 molar. In an embodiment, the saccharide concentration is about 0.2 molar to about 0.6 molar, about 0.2 molar to about 0.5 molar, about 0.2 molar to about 0.4 molar, about 0.3 molar to about 0.4 molar, about 0.4 molar to about 0.6 molar, or about 0.4 molar to about 0.5 molar. In an embodiment, the saccharide concentration is about 0.9 molar, about 0.8 molar, about 0.7 molar, about 0.6 molar, about 0.5 molar, about 0.4 molar, about 0.3 molar, about 0.2 molar or about 0.1 molar. In an embodiment, the saccharide concentration is about 0.5 molar, about 0.4 molar, or about 0.3 molar. In an embodiment, the saccharide concentration is about 0.4 molar.

[0095] In an embodiment, the saccharide is any saccharide capable of reducing vanadium (V) to vanadium (IV) in sulfuric acid. In an embodiment, the saccharide is selected from one or more of monosaccharides, a disaccharide and polysaccharide. In an embodiment, the saccharide is selected from glucose (dextrose), fructose (levulose), galactose, ribose, xylose, lactose, maltose, sucrose and starch and combinations thereof. In an embodiment, the saccharide is selected from glucose, sucrose and starch, and a combination thereof. In an embodiment, the saccharide is selected from glucose and sucrose, and a combination thereof. In an embodiment, the saccharide is sucrose. In an embodiment, the saccharide is glucose. In an embodiment, the saccharide is D-(+)-glucose.

[0096] In an embodiment, the vanadium rich substance is leached with the leaching solution for a temperature and a time sufficient to leach the vanadium form the vanadium rich substance to produce the vanadyl sulfate leachate and the leached substance. In an embodiment, the vanadium rich substance is leached with the leaching solution at a temperature of about 50°C to about 95 °C, about 50°C to about 90 °C, about 50°C to about 85 °C, about 50°C to about 80°C, about 50°C to about 75°C, about 50°C to about 70°C, about 50°C to about 65°C, about 50°C to about 60°C, about 60°C to about 95 °C, about 60°C to about 90°C, about 60°C to about 80°C, about 60°C to about 70°C, about 70°C to about 90°C, about 75°C to about 90°C, about 80°C to about 90°C or about 85°C to about 90°C. In an embodiment, the vanadium rich substance is leached with the leaching solution a temperature of about 50°C to about 90 °C, about 60°C to about 90°C, about 50°C to about 80°C or about 60°C to about 80°C.

[0097] In an embodiment, the vanadium rich substance is leached with the leaching solution for about 1 to about 6 hours, about 1 to about 5 hours, about 1 to about 4 hours, about 1 to about 3 hours, or about 1 to about 2 hours. In an embodiment, the vanadium rich substance is leached with the leaching solution for about 1 to about 4 hours, about 1 to about 3 hours, or about 1 to about 2 hours, or about 1 hour. In an embodiment, the vanadium rich substance is leached with the leaching solution for about 1 to about 6 hours or about 1 to about 4 hours.

[0098] The Applicants have shown that the vanadium rich substance can be leached using low volumes of the leaching solution. Accordingly, in an embodiment, the vanadium rich substance is leached with the leaching solution at a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1 g:2ml or greater leaching solution volume. In an embodiment, the vanadium rich substance is leached with the leaching solution at a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution from about 1 g:2ml to about 1 g:20ml, about 1 g:2ml to about 1g:18ml, about 1 g:2ml to about 1g:15ml, about 1 g:2ml to about 1 g: 12ml, about 1g:2ml to about 1 g:10mL, about 1 g:2ml to about 1 g:9mL, about 1 g:2 to about 1 g:7mL, about 1 g:2ml to about 1 g:6mL, about 1 g:2ml to about 1 g:5mL, about 1 g:2ml to about 1 g:4mL, about 1 g:2ml to about 1g:3mL, or about 1 g:2ml. In an embodiment, the vanadium rich substance is leached with the leaching solution at a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution is from about 1 g:2ml to about 1 g:10mL, about 1 g:2 to about 1 g:7mL, about 1 g:2ml to about 1 g:5mL, about 1g:2ml to about 1 g:4mL, about 1 g:2ml to about 1 g:3mL, or about 1 g:2ml.

[0099] In an embodiment, the leaching of the vanadium rich substance with leaching solution comprises agitating the vanadium rich substance and leaching solution. In an embodiment, the agitating is by any method known in the art to agitate a heterogeneous reaction mixture. In an embodiment, the agitating is by agitator or shaker.

[00100] The Applicants have found that the leaching rate of the vanadium from the vanadium rich substance is increased compared to the leaching rate of the vanadium from a vanadium rich substance of an otherwise identical leaching step except without the saccharide. In an embodiment, the vanadium is leached from the vanadium rich substance at a leaching rate of equal to or greater than 90% in one hour when the leaching solution comprises 7 molar sulfuric acid, about 0.2 molar saccharide and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1 g:2ml and the leaching is performed a temperature of about 60°C. In an embodiment, the vanadium is leached from the vanadium rich substance at a leaching rate of equal to or greater than 96% in four hours when the leaching solution comprises 7 molar sulfuric acid, about 0.2 molar saccharide and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1 g:2ml and the leaching is performed at a temperature of about 60°C. In an embodiment, the vanadium is leached from the vanadium rich substance at a leaching rate of equal to or greater than 99% in one hour when the leaching solution comprises 7 molar sulfuric acid, about 0.2 molar saccharide and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1 g:2ml and the leaching is performed at a temperature of about 80°C. [00101] In an embodiment, the method further comprises separating the vanadyl sulfate leachate from the leached substance before the step of recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate. In an embodiment, the vanadyl sulfate leachate is separated from the leached substance using any suitable method of separating a liquid from a heterogeneous mixture known in the art. In an embodiment, the vanadyl sulfate leachate is separated from the leached substance using a separating unit. In an embodiment, the separating unit is a gravitational settler, hydrocyclone or centrifuge. In an embodiment, the step of separating the vanadyl sulfate leachate from the leached substance is by filtration.

[00102] In an embodiment, the vanadyl sulfate leachate is cooled before the step of separating. In an embodiment, the vanadyl sulfate leachate is cooled to a temperature of about 30°C to about 70°C, about 30°C to about 60°C, about 40°C to about 70°C, about 40°C to about 60°C or about 40°C to about 50°C. In an embodiment, the vanadyl sulfate leachate is cooled to a temperature of about 40°C to about 50°C.

[00103] The Applicants have shown that the method of the application produces a highly concentrated vanadyl sulfate leachate. In an embodiment, the vanadyl sulfate leachate produced from leaching the vanadium from the vanadium rich substance with the leaching solution has a concentration up to about 60g/L. In an embodiment, the vanadyl sulfate leachate produced from leaching the vanadium from the vanadium rich substance with the leaching solution has a concentration of about 30g/L to about 60g/L, about 30g/L to about 50g/L, about 30g/L to about 40g/L, about 40g/L to about 60g/L, about 50g/L to about 60g/L or about 40g/L to about 50g/L. In an embodiment, the vanadyl sulfate leachate produced from leaching the vanadium from the vanadium rich substance with the leaching solution has a concentration of about 30g/L to about 60g/L, about 40g/L to about 60g/L, or about 50g/L to about 60g/L. In an embodiment, the vanadyl sulfate leachate produced from leaching the vanadium from the vanadium rich substance with the leaching solution has a concentration of about 50g/L to about 60g/L, when the leaching solution comprises about 4 to about 6 molar sulfuric acid, about 0.2 molar saccharide and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1g:2ml.

[00104] In an exemplary embodiment of the application, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution, the method comprising: leaching a vanadium rich substance with a leaching solution at a temperature of about 50°C to about 90°C, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 7 molar, a saccharide at a concentration of about 0.4 molar to about 0.6 molar; and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1g:2ml or greater; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate, wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof.

[00105] In an embodiment, the vanadyl sulfate solution is a highly pure vanadyl sulfate solution.

[00106] In an exemplary embodiment of a method of the application, the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof. In an embodiment, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution from a secondary source of vanadium, the method comprising: roasting the secondary source of vanadium to produce a vanadium rich substance; leaching a vanadium rich substance with a leaching solution at a temperature of about 50°C to about 90°C, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 7 molar, a saccharide at a concentration of about 0.4 molar to about 0.6 molar; and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1g:2ml or greater; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate, wherein the secondary source of vanadium is selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal, and combinations thereof.

[00107] In an exemplary method of the application, the secondary source of vanadium is oil fly ash or petcoke and the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution, the method comprising: roasting oil fly ash or petroleum coke (petcoke) to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution at a temperature of about 50°C to about 90°C, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 7 molar, a saccharide at a concentration of about 0.4 molar to about 0.6 molar; and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1g:2ml or greater; to produce a vanadyl sulfate leachate and a leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate.

[00108] In an embodiment, the Applicants have shown that vanadium is recovered in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate by extraction with an extractant followed by stripping the loaded extractant with sulfuric acid. Accordingly, in an embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate comprises: extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; and stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce a used extractant and the vanadyl sulfate solution.

[00109] In an embodiment, the extractant is any extractant suitable for extracting vanadium from the vanadyl sulfate leachate. In an embodiment, the extractant is selective for vanadium and the extractant is any extractant suitable for selectively extracting vanadium from the vanadyl sulfate leachate. In an embodiment, the extractant is di(2-ethylhexyl)phosphoric acid (DEHPA, D2EHPA or HDEHP), 2- ethylhexylphosphonic acid mono-2-ethyl hexyl ester (EHEHPA), bis(2,4,4- trimethylpentyl)phosphinic acid (Cyanex 272), 2-ethylhexylphosphonic mono-2- ethylhexyl (PC88A) or combinations thereof. In an embodiment, the extractant is D2EHPA. In an embodiment, the extractant selectively extracts vanadium from the vanadyl sulfate leachate. In an embodiment, the D2EHPA selectively extracts vanadium from the vanadyl sulfate leachate.

[00110] In an embodiment, the extractant is a liquid at room temperature such as D2EHPA. In an embodiment, the extractant is used without an additional solvent to extract the vanadyl sulfate leachate. In an embodiment, the extractant is combined with a solvent to produce an extractant solution. Accordingly, in an embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate comprises extracting the vanadyl sulfate leachate with an extractant solution comprising an extractant to produce a raffinate and a vanadium-bearing extractant solution comprising a vanadium-bearing extractant, and stripping vanadium from the vanadium-bearing extractant the with sulfuric acid to produce a used extractant solution and the vanadyl sulfate solution.

[00111] In an embodiment, the solvent that is combined with the extractant to produce the extractant solution is selected from kerosene, n-heptane, n-dodecane and toluene and combinations thereof. In an embodiment, the solvent that is combined with the extractant to produce the extractant solution is kerosene. In an embodiment, the extractant is di-(2-ethylhexyl)phosphoric acid (DEHPA, D2EHPA or HDEHP) and the solvent that is combined with the D2EHPA to produce the extractant solution is kerosene.

[00112] In an embodiment, the vanadyl sulfate leachate is extracted with the extractant or the extractant solution comprising the extractant in ratio of about 1 :1 (v/v) of the vanadyl sulfate leachate to the extractant or the extractant solution.

[00113] In an embodiment, the step of extracting the vanadyl sulfate leachate with the extractant or the extractant solution comprising the extractant is repeated a number of times to sufficiently extract the vanadium from the vanadyl sulfate. In an embodiment, the step of extracting is repeated about 2 to about 6 times, about 3 to about 6 times, about 4 to about 6 times, about 4 to about 5 times, or about 4 times.

[00114] In an embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate further comprises adjusting the pH of the vanadyl sulfate leachate to a pH suitable for vanadium extraction with the extractant or extractant solution before the step of extracting the vanadyl sulfate leachate with the extractant or extractant solution. In an embodiment, the pH of the vanadyl sulfate leachate is adjusted to a pH suitable for vanadium extraction with the extractant or extractant solution before each extracting step of the vanadyl sulfate leachate with an extractant. In an embodiment, the pH is adjusted to about 2 to about 4, about 2 to about 3 or about 2.5. In an embodiment, the pH is adjusted to about 2.5. In an embodiment, the extractant is D2EHPA and the pH of the vanadyl sulfate leachate is adjusted to a pH of about 2 to about 3, or about 2.5. [00115] In an embodiment, the pH of the vanadyl sulfate leachate produced from leaching the vanadium from the vanadium rich substance is adjusted with base. In an embodiment, the base is an inorganic base. In an embodiment, the inorganic base is selected from sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate. In an embodiment, the inorganic base is selected from sodium hydroxide and sodium carbonate.

[00116] In an embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate further comprises separating the vanadium bearing extractant or vanadium bearing extractant solution from the raffinate. In an embodiment, the vanadium-bearing extractant or vanadium bearing extractant solution is separated from the raffinate by any suitable method known in the art to separate two non-miscible liquids. In an embodiment, the vanadium bearing extractant or vanadium bearing extractant solution is separated from the raffinate by separatory funnel, decanting or pipetting.

[00117] In an embodiment, the vanadium-bearing extractant or vanadium bearing extractant solution is stripped with sulfuric acid in ratio of about 1 :4 (v/v), o of about 1 :5 (v/v) or about o of about 1 :6 (v/v) sulfuric acid to vanadium-bearing extractant or vanadium bearing extractant solution. In an embodiment, the vanadium- bearing extractant or vanadium bearing extractant solution is stripped with sulfuric acid in ratio of about 1 :5 (v/v) sulfuric acid to vanadium-bearing extractant or vanadium bearing extractant solution. In an embodiment, the sulfuric acid concentration is about 1 .5 molar to about 3 molar, about 2 molar to about 3 molar, or about 2 molar. In an embodiment, sulfuric acid concentration is about 2 molar.

[00118] In an embodiment, the used extractant comprises a metal that is not vanadium. In an embodiment, the used extractant comprises iron. Therefore, in an embodiment, the used extractant is an iron-bearing extractant.

[00119] In an embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution further comprises separating the vanadyl sulfate solution from the used extractant or used extractant solution. In an embodiment, the vanadyl sulfate solution is separated from the used extractant or used extractant solution to produce the vanadyl sulfate solution by any suitable method known in the art to separate two non-miscible liquids. In an embodiment, the vanadium-bearing extractant or vanadium-bearing extraction solution is separated from the extractant or used extractant solution respectively, by separatory funnel, decanting or pipetting.

[00120] Therefore, in an embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate comprises: extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; separating the vanadium-bearing extractant and the raffinate; stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce a used extractant and the vanadyl sulfate solution and separating the vanadyl sulfate solution from the used extractant to produce the vanadyl sulfate solution.

[00121] In an exemplary embodiment, the step of recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate comprises: adjusting the pH of the vanadyl sulfate leachate to a pH suitable for vanadium extraction with an extractant; extracting the vanadyl sulfate leachate with the extractant to produce a vanadium-bearing extractant and a raffinate; separating the vanadium-bearing extractant and the raffinate; stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce a used extractant and the vanadyl sulfate solution and separating the vanadyl sulfate solution from the used extractant to produce the vanadyl sulfate solution.

[00122] In an embodiment, the step of extracting comprises: extracting the vanadyl sulfate leachate with an extractant solution comprising an extractant to produce a vanadium-bearing extractant solution comprising a vanadium-bearing extractant and a raffinate. [00123] In an embodiment, the vanadyl sulfate solution produced from the method of the application has a concentration of about 0.5 molar or more, about 1 molar or more, or about 1.2 molar or more. In an embodiment, the vanadyl sulfate solution has a concentration of about 0.5 to about 1.2 molar, about 0.5 to about 1 molar, or about 0.5 to about 0.75 molar. In an embodiment, the vanadyl sulfate solution has a concentration of about 0.5 to about 1 .0 molar.

[00124] In an embodiment, the vanadyl sulfate solution produced from the method of the application has a concentration of about 30 to about 40 g/L.

[00125] In an embodiment, the vanadyl sulfate solution produced from the method of the application is further concentrated. In an embodiment, the vanadyl sulfate solution is further concentrated to a concentration that is suitable for use with a vanadium redox flow battery. In an embodiment, the vanadyl sulfate solution is concentrated to a concentration of about 1 .5 molar or more. In an embodiment, the vanadyl sulfate solution is concentrated to a concentration of about 1.5 molar to about 2 molar.

[00126] In an embodiment, the vanadyl sulfate solution is concentrated by evaporation. In an embodiment, the evaporation is by distillation, open air evaporation, evaporation under vacuum, or rotoevaporation. In an embodiment, the evaporation is by rotoevaporation.

[00127] The Applicants have shown that the vanadyl sulfate solution obtained after stripping the vanadium from the vanadium bearing extractant with sulfuric acid before concentration (e.g., evaporation) has a purity of at least 99.3 weight percent on an all metals basis when analyzed by plasma-optical emission spectrometer (I CP- OES) (see, for example, Table 2). In an embodiment, the vanadyl sulfate solution analyzed by plasma-optical emission spectrometer (ICP-OES) comprises, on a weight percent basis of all metals analyzed, about 99.29 vanadium (V), about 0.42 iron (Fe), about 0.01 aluminum (Al), 0.02 magnesium (Mg), 0.01 calcium (Ca), 0.02 sodium (Na), 0.13 zinc (Zn), 0.01 arsenic (Ar), 0.01 Manganese (Mn), 0.00 cadmium (Cd), 0.04 lead (Pb) and 0.01 silicone (Si). In an embodiment, the amount of nickel (Ni), copper (Cu), chromium (Cr) and titanium (Ti) in the vanadyl sulfate solution are below the minimum detectable limit of the ICP-OES spectrometer. [00128] Therefore, in an embodiment, the vanadyl sulfate solution is a highly pure vanadyl sulfate solution. In an embodiment, the vanadyl sulfate solution produced from the method of the application has a purity of at least 99.3 on a weight percent all metals analyzed basis when analyzed by plasma-optical emission spectrometer (ICP-OES). In an embodiment, the vanadyl sulfate solution produced from the method of the application has a purity of about 95 or greater, about 96 or greater, about 97 or greater, about 98 or greater, about 99 or greater, about 99.3 or greater, about 99.5 or greater, about 99.6 or greater, about 99.7 or greater, about 99.1 , about 99.2, about 99.3, about 99.4, about 99.5, about 99.6, about 99.7 or about 99.8 on a weight percent all metals analyzed basis. In an embodiment, the vanadyl sulfate solution has a purity of about 99 or greater, about 99.3 or greater, about 99.5 or greater, or about 99.6 or greater on a weight percent all metals analyzed basis. In an embodiment, the vanadyl sulfate solution has a purity of about 99 or greater or about 99.3 or greater on a weight percent all metals analyzed basis. In an embodiment, the vanadyl sulfate solution has a purity of at least 99.6 based on a weight percent V, Fe, Ni, Mg and Al metals basis. In an embodiment, the vanadyl sulfate solution has a purity of 99.6 or greater based on a weight percent V, Fe, Ni, Mg and Al all metals analyzed basis.

[00129] Accordingly, in an exemplary embodiment, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution from a secondary source of vanadium, the method comprising leaching a vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and separating the vanadyl sulfate leachate from the leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate comprising extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce the vanadyl sulfate solution and a used extractant; and wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof.

[00130] In an exemplary embodiment, when the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof, the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution from a secondary source of vanadium, the method comprising: roasting the secondary source of vanadium to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, separating the vanadyl sulfate leachate from the leached substance, recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate comprising extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; and stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce the vanadyl sulfate solution and a used extractant solution; wherein the secondary source of vanadium is selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof.

[00131] In an exemplary method of the application, the secondary source of vanadium is oil fly ash and the present application includes a method of recovering vanadium in the form of a vanadyl sulfate solution, the method comprising: roasting oil fly ash to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, separating the vanadyl sulfate leachate from the leached substance, and recovering vanadium in the form of a vanadyl sulfate solution from the vanadyl sulfate leachate, comprising: extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; and stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce the vanadyl sulfate solution and a used extractant.

[00132] In an embodiment, the step of extracting described above comprises: extracting the vanadyl sulfate leachate with an extractant solution comprising an extractant to produce a vanadium-bearing extractant solution comprising a vanadium-bearing extractant and a raffinate.

[00133] In an embodiment, the vanadyl sulfate solution is for use as a vanadium electrolyte. Accordingly, in an embodiment, the vanadyl sulfate solution is a vanadium electrolyte, and the present application includes a method of recovering vanadium in the form of vanadium electrolyte from a secondary source of vanadium, the method comprising leaching a vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, and separating the vanadyl sulfate leachate from the leached substance, and recovering vanadium in the form of vanadium electrolyte from the vanadyl sulfate leachate, comprising: extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; and stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce the vanadium electrolyte and a used extractant; wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof.

[00134] In an exemplary embodiment, when the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof, the present application includes a method of recovering vanadium in the form of a vanadium electrolyte from a secondary source of vanadium, the method comprising: roasting the secondary source of vanadium to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, separating the vanadyl sulfate leachate from the leached substance, recovering vanadium in the form of a vanadium electrolyte from the vanadyl sulfate leachate comprising: extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; and stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce the vanadium electrolyte and a used extractant; wherein the secondary source of vanadium is selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal, and combinations thereof.

[00135] In a further exemplary method of the application, the secondary source of vanadium is oil fly ash and the present application includes a method of recovering vanadium in the form of a vanadium electrolyte, the method comprising: roasting oil fly ash to produce a vanadium rich substance; leaching the vanadium rich substance with a leaching solution, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar; to produce a vanadyl sulfate leachate and a leached substance, separating the vanadyl sulfate leachate from the leached substance, and recovering vanadium in the form of a vanadium electrolyte from the vanadyl sulfate leachate comprising: extracting the vanadyl sulfate leachate with an extractant to produce a vanadium-bearing extractant and a raffinate; and stripping the vanadium from the vanadium-bearing extractant with sulfuric acid to produce the vanadium electrolyte and a used extractant.

[00136] In an embodiment, the vanadyl sulfate solution is a highly pure vanadyl sulfate solution. Therefore, in an embodiment, a vanadyl sulfate solution which can be used as a vanadium electrolyte is produced by the method of the application. Accordingly, in an embodiment, the present application also includes a vanadyl sulfate solution produced by the methods of the application as described above. In an embodiment, the present application also includes a highly pure vanadyl sulfate solution produced by the methods of the application as described above. In an embodiment, the present application also includes a vanadium electrolyte produced by the methods of the application as described above.

[00137] In an embodiment, the vanadyl sulfate solution or vanadium electrolyte is for use as vanadium electrolyte in a vanadium redox battery.

[00138] Accordingly, in an embodiment, the present application also includes a vanadium flow redox battery comprising vanadyl sulfate solution (e.g., vanadium electrolyte) produced by the methods of the application described above.

[00139] In an embodiment, the used extractant is a metal bearing extractant such as an iron-bearing extractant. In an embodiment, the extractant can be regenerated from the used extractant by further stripping iron from the iron-bearing extractant. Accordingly, in an embodiment, the method further comprises regenerating the extractant from the used extractant or used extractant solution comprising the used extractant. In an embodiment, the step regenerating the extractant comprises: stripping iron from the used extractant with a suitable acid solution to produce the extractant and an acid salt, separating the extractant from the acid salt to obtain the extractant.

[00140] In an embodiment, the suitable acid is citric acid, oxalic acid or an inorganic acid. In an embodiment, the suitable acid is oxalic acid. [00141] In an exemplary embodiment, the step regenerating the extractant comprises: stripping iron from the used extractant with an oxalic acid solution to produce the extractant and iron oxalate, separating the extractant from the iron oxalate to obtain the extractant.

[00142] In an embodiment, the step of regenerating the extractant from the used extractant solution comprises: stripping iron from the used extractant in the used extractant solution with an oxalic acid solution to produce a used extractant solution comprising the extractant and iron oxalate, separating the used extractant solution comprising the extractant from the iron oxalate, and isolating the extractant from the used extractant solution comprising the extractant.

[00143] In an embodiment, the oxalic acid solution is an about 4% to about 8%, about 5% to about 8%, about 6% to about 8%, or about 7% (w/w) oxalic acid solution.

[00144] In an example, the volume ratio or extractant solution to oxalic acid solution is about 1 :1.

[00145] In an embodiment, the methods of the application further comprises optionally recovering one or more additional metals, for example, from the raffinate. In an embodiment, the additional metal is nickel. In an embodiment, the one or more additional metals are in the form of one or more metal compounds. Therefore, the method further comprises optionally recovering one or more additional metal compounds, for example, from the raffinate. In an embodiment, the additional metal compounds are nickel compounds.

[00146] Accordingly, in an embodiment, when the secondary source of vanadium is selected from oil fly ash or petroleum coke (petcoke) and/or the vanadium rich substance is roasted fly ash or roasted petcoke, the method further comprises recovering nickel. In an embodiment, the nickel is recovered from the raffinate produced after extracting the vanadyl sulfate leachate with an extractant to remove the vanadium. Accordingly, in an embodiment, when the secondary source of vanadium is selected from oil fly ash or petroleum coke (petcoke) and/or the vanadium rich substance is roasted fly ash or roasted petcoke, the method further comprises recovering nickel from the raffinate produced by the method described above, comprising adjusting the pH of the raffinate to about 5 to about 6; combining an oxidizing agent with the raffinate with a pH of about 5 to about 6 to produce Fe(OH)s and a second raffinate; separating the Fe(OH)s from the second raffinate; adjusting the pH of the second raffinate to a pH of about 7 to about 8 with a carbonate base to produce NiCOs and a third raffinate; and separating the NiCOs from the third raffinate with a pH of about 7 to about 8 to produce NiCOs.

[00147] In an embodiment, the pH of the raffinate is adjusted to about 5 to about 6 or about 7 to about using a base. In an embodiment, the base is an inorganic base. In an embodiment, the base is a hydroxide such as sodium hydroxide.

[00148] In an embodiment, the oxidizing agent is any oxidizing agent capable of oxidizing Fe(ll) to Fe(lll). In an embodiment, the oxidizing agent is H2O2 or NaCIOs.

[00149] The Applicants have found that saccharides such as D-(+)-glucose, sucrose and starch can be used as effective reducing agents in a reductive acid leaching step with sulfuric acid in a process of recovering vanadium. In an embodiment, the Applicants have shown that when a vanadium rich substance, such as roasted oil fly ash (OFA), is leached using a leaching solution comprising a saccharide as the reducing agent, for example, glucose, in a reductive acid leaching step with sulfuric acid, a highly concentrated vanadyl sulfate leachate solution is produced and a leaching rate of vanadium of equal to or greater than 90% in one hour when the leaching solution comprises 7 molar sulfuric acid, about 0.2 molar saccharide and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1 g:2ml and a temperature of about 60°C. In an embodiment, the vanadium is leached from the vanadium rich substance at a leaching rate of equal to or greater than 96% in four hours when the leaching solution comprises ? molar sulfuric acid, about 0.2 molar saccharide and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1 g:2ml and a temperature of about 60°C. In an embodiment, the vanadium is leached from the vanadium rich substance at a leaching rate of equal to or greater than 99% in one hour when the leaching solution comprises 7 molar sulfuric acid, about 0.2 molar saccharide and a solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution of about 1 g:2ml and a temperature of about 80°C

[00150] Accordingly, the present application also includes a method of improving the leaching rate of vanadium from a secondary source of vanadium, the method comprising leaching a vanadium rich substance with a leaching solution to produce a vanadyl sulfate leachate and a leachate, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar, wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof and wherein the leaching rate of the vanadium is improved compared to the leaching rate of vanadium under identical conditions except in the absence of the saccharide.

[00151 ] In an embodiment, the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof. In an embodiment, the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash and petroleum coke (petcoke). In an embodiment, the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash (i.e. , roasted oil fly ash).

[00152] In an embodiment, the secondary source of vanadium, the vanadium rich substance, sulfuric acid concentration, saccharide, saccharide concentration, solid to liquid ratio (S:L ratio) of the vanadium rich substance to the leaching solution, leaching temperature and time are as described above.

[00153] In an embodiment, the leaching rate of vanadium is selectively improved compared to the leaching rate of one or more additional metals from the vanadium rich substance under identical conditions. In an embodiment, the leaching rate of vanadium is selectively improved compared to the leaching rate of one or more of nickel, iron, magnesium and aluminum.

[00154] The present application also includes a leaching solution for leaching a vanadium rich substance, the leaching solution comprising: sulfuric acid at a concentration of about 4 molar to about 10 molar, and a saccharide at a concentration of about 0.1 molar to about 1 molar, wherein the vanadium rich substance is a secondary source of vanadium selected from vanadium slag and spent vanadium catalysts, and combinations thereof; or wherein the vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petroleum coke (petcoke), vanadium rich petroleum residues and stone coal and combinations thereof.

[00155] In an embodiment, vanadium rich substance is produced by roasting a secondary source of vanadium selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof. In an embodiment, the vanadium rich substance is roasted oil fly ash or roasted petcoke. In an embodiment, the vanadium rich substance is roasted oil fly ash.

EXAMPLES

[00156] The following non-limiting examples are illustrative of the present application. Example 1

MATERIAL AND METHODS

[00157] The sample fly ash (FA) is a composite mixture of OFA collected from different boiler units of a power plant. Before leaching experiments, the sample was pre-roasted in a muffle furnace at 550°C, 650°C, 750°C and 850°C for 6 hours. Particle size distribution of the raw and roasted FA samples was analyzed by a Horiba Partica LA-950. The mineral composition of the samples was by analyzed ICP-OES (Perkin-Elmer 5300 DV) after acid digested by HNO3 and HF.

[00158] For leaching experiments, roasted FA and glucose-H2SO4 solution was mixed at S:L=1g:2ml in a glass tube with cap and placed in a water bath shaker at elevated temperature, 120 RPM for four hours. After the reaction, samples were cooled down to room temperature and water was added to dilute the leachate to prevent vanadium crystallization at room temperature. After sufficient settling, the samples were further diluted and analyzed by ICP-OES.

RESULTS AND DISCUSSION

[00159] Figure 1 shows a general scheme of the method of the application for recovering vanadium from a secondary source vanadium and converting it to vanadyl sulfate solution A/RFB electrolyte. When the secondary source of vanadium is selected from oil fly ash, petcoke, vanadium rich petroleum residues and stone coal and combinations thereof, the secondary source is first roasted at above 550 °C to remove unwanted fractions such as carbon and organics and produce a vanadium rich substance (e.g roasted oil fly ash, roasted petcoke, roasted vanadium rich petroleum residues and roasted stone coal and combinations thereof). Then the vanadium and other metals in the vanadium rich substance are leached by sulfuric acid at above 60 °C with the assistance of a saccharide (e.g., glucose or sucrose) as a reducing agent to significantly improve the leachability of vanadium (V). After the leaching process, the vanadium in the leachate is selectively extracted by an extractant (e.g., D2EHPA diluted by kerosene) after pH adjustment for optimal efficiency. In the stripping process, the V bearing extractant is treated with sulfuric acid to strip off the vanadium and obtain a vanadyl sulfate solution. This vanadyl sulfate solution can be concentrated if necessary to meet the requirements of VRFB electrolyte. If the secondary source is oil fly ash or petcoke, nickel recovery can be further conducted via different methods such as precipitation, solvent extraction, or ion exchange resins.

[00160] The changes of elemental composition of FA before and after roasting are tabulated in Table 1 , which shows there are three major metallic elements, vanadium 5.14%, nickel 1.78%, magnesium 4.17% and Fe 0.81 %. Sulfur content of the raw oil fly ash (OFA) is 7.46% and after roasting at 550°C, sulfur content of the roasted OFA increases to 12.68% but total loss due to thermal decomposition is 42.37% and it increases gradually as the roasting temperature increases. After 850°C, the sulfur content of roasted FA drops to 5.76%, which is lower than the raw OFA. The table also shows that roasting greatly concentrates the metals that vanadium level increases around three times after 550°C roasting, which is much more favorable for metal recovery. Since roasting at 550°C shows less sulfur loss, good burn-off rate, and minimizes the formation of refractory aggregates. The roasted FA used for the leaching experiments was prepared under this condition.

Table 1. Properties of raw and roasted OFA

H2SO4 and Glucose Concentration

[00161] Figure 2 shows the metal leaching rates at different H2SO4 concentrations with 1 mol/L glucose, which indicates that all five metals cannot be effectively leached out without acid. When increasing the acid concentration until 4 mol/L, the leaching rate of all metals except aluminum increases significantly, from less than 10% to more than 90%. After that the increasing trend diminishes and the leaching rate of vanadium reaches almost constant leachability at acid concentration of 7mol/L.

[00162] The effect of glucose is shown in Figure 3. At an acid concentration of 7 mol/L and leaching temperature of 60°C, the vanadium leaching rate is about 87% and it increases to 106% with 0.2mol/L glucose. It seems that other metals are not affected by glucose, and therefore iron and aluminum cannot be fully leached out and remain as solid sediment. Although it cannot be seen from the results, it is noted that excess acid and glucose have a negative impact on the leaching process such as an increase in the viscosity of mixture and an increase in the side reaction (dehydration reaction) of glucose with high concentration acid especially at high temperature. Therefore, the leaching condition of acid concentration from 4mol/L to 6 mol/L, glucose concentration 0.2mol/L, S:L ratio of 1g:2ml is suggested.

[00163] Figure 4 shows the significant enhancement of vanadium leaching at lower acid concentration. At an acid concentration of 4 mol/L, the leaching rate of vanadium is only 40%, while it increases to 98% with the addition of 0.2mol/L glucose, even higher than 7 mol/L acid concentration without glucose, which is 93.6%, indicating over 40% of acid reduction. Further increasing the acid concentration gradually improves the leachability of the leaching solution without glucose, while it only adds about 10% more efficiency with the presence of glucose. Figure 4 also indicates that the leachability of other metals is more of a functional of acid concentration and unlike vanadium they can be effectively leached out at lower acid concentration except aluminum.

Effect of Leaching Temperature and Leaching Time

[00164] In addition to acid and glucose concentration, leaching temperature is another driving force that affects the kinetic of the leaching process. Generally, as shown in Figure 5, a higher leaching temperature accelerates the leaching process and increases the maximum leachability for vanadium, as well as iron and nickel. At 60°C, the leaching rate of vanadium is 90% at the first hour and slightly increases to 96% at four hours of leaching time. When the temperature is increased to 80°C, the leaching rate of vanadium reaches 99% at the first hour, indicating that an increase in the leaching temperature can significantly reduce the leaching time, and 1 hour of leaching reaction is able to produce good leaching efficiency. Further prolonging the leaching time from 1 hour to 4 hours was observed to achieve only an additional 10% improvement in efficiency.

Roasting Temperature

[00165] Among the major metals, the leachability of vanadium and iron are greatly impact by roasting temperature. As shown in Figure 6, at lower range of roasting temperature (550°C and 650°C), the leaching efficiency of vanadium shows little difference with 4 mol/L or 6 mol/L acid concentration. When temperature increases to above 750°C, leaching rate of vanadium with different concentrations show more than 20% difference, while this gap enlarges to 96% at the roasting temperature of 850°C, indicating that vanadium converts to insoluble form at high temperature and more acid is needed to meet the required leaching efficiency. Iron shows the decreasing trend as roasting temperature increases, while nickel and magnesium show insignificant change over increasing roasting temperature.

Glucose and Sucrose

[00166] Based on above results, it is shown that glucose can be an effective reducing agent that greatly improves the leachability of vanadium. Other abundantly available and low-cost saccharides, such as sucrose and starch, show similar capability. However, in preliminary experiment, starch was observed to be less soluble than the other two and also more viscose, which was found to affect the mixing, especially at high S:L ratio. Figure 7 compares the performance of glucose and sucrose and shows the identical performance for all major metals.

Example 2:

[00167] An exemplary method of the application is described below:

1 . The sample fly ash (FA) which was a composite mixture of OFA collected from different boiler units of a power plant as described for Example 1 was roasted at about 550 °C. 2. The roasted OFA was leached with sulfuric acid and glucose solution at solid to liquid ratio of about 1 g:2ml. The sulfuric acid concentration range was about 4 molar to about 10 molar per liter and glucose concentration range was about from 0.2 molar to about 1 molar per liter. The leaching temperature was about 50°C to about 90°C. The leaching time ranged from about 1 hour to about 6 hours with agitation.

3. After leaching, the leachate was cooled to about 40 °C to about 50°C (and water was added to prevent crystallization as necessary, for example, if the temperature dropped to room temperature). The liquid and any solid was filtered by gravitational separation or filtration.

4. The pH of the leachate was adjusted by an alkaline solution, for example sodium hydroxide and sodium carbonate (for example, 8M NaOH), to about 2.5.

5. The vanadium was extracted from the leachate using the solvent (D2EHPA diluted by kerosene) at aqueous to organic ratio of 1 :1 (v/v). The extraction with D2EHPA may be repeated. In this example, four extractions of the leachate with D2EHPA were conducted. The pH of the leachate was adjusted to 2.5 before each extraction.

6. After extraction, the vanadium in the V-bearing extractant (D2EHPA) was stripped off using 2M sulfuric acid at aqueous to organic ratio of 1 :5 (v/v).

7. The resultant purified vanadyl sulfate solution was concentrated by evaporation to meet the requirement for an electrolyte, e.g., 1.5-2 molar concentration.

8. The used extractant in the extraction solution contains Fe. The Fe can be stripped from the used extractant and the extractant can be regenerated with by stripping off the Fe from the used extractant using, for example, an oxalic acid solution (e.g 7% oxalic acid) at organic solvent to aqueous volume ratio of 1 :1.

[00168] Nickel recovery: 1. The raffinate (e.g., the leachate after extraction with D2EHPA to remove vanadium) contains nickel and can be further processed to extract the nickel

2. The pH of the raffinate is adjusted to 5 to 6 (e.g., using NaOH) and oxidizing agent (e.g., H2O2 and NaCIOs) is added to the raffinate to oxidize Fe(ll) to Fe(lll) and form Fe(OH)s precipitate.

3. The pH of the raffinate is then further adjusted to about 7 to 8 using, for example, Na2COs to precipitate Ni as NiCOs.

Example 3: Metal analysis of vanadyl sulfate solution by inductively coupled plasma-optical emission spectrometer (ICP-OES) [00169] A metal analysis of the vanadyl sulfate solution obtained from the method of Example 2 after stripping the vanadium from the vanadium bearing extractant with sulfuric acid before concentration (e.g., evaporation) was conducted using inductively coupled plasma-optical emission spectrometer (ICP-OES). The results of the ICP-OES analysis are provided in Table 2. Table 2: Metal analysis of the vanadyl sulfate solution

Analyzed by ICP-OES, average of the first four stripping solutions

** ND refers to “Not Determined” which means the concentration was too low to be accurately determined.

[00170] While the present application has been described with reference to examples, it is to be understood that the scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.

[00171] All publications, patents and patent applications are herein incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety. Where a term in the present application is found to be defined differently in a document incorporated herein by reference, the definition provided herein is to serve as the definition for the term.

FULL CITATIONS FOR DOCUMENTS REFERRED TO IN THE SPECIFICATION [00172] A number of publications are cited herein. Full citations for these references are provided below. Each of these references is incorporated herein by reference in its entirety into the present disclosure, to the same extent as if each individual reference was specifically and individually indicated to be incorporated by reference.

[00173] [1] M.A. Al-Ghouti, Y.S. Al-Degs, A. Ghrair, H. Khoury, M. Ziedan,

Extraction and separation of vanadium and nickel from fly ash produced in heavy fuel power plants, Chemical Engineering Journal 173 (2011) 191-197. https://doi.Org/10.1016/j.cej.2011.07.080

[00174] [2] M.H. Al-Malack, A.A. Bukhari, O.S. Al-Amoudi, H.H. Al-Muhanna,

T.H. Zaidi, Characteristics of Fly ash Produced at Power and Water Desalination Plants Firing Fuel Oil, International Journal of Environmental Research 7 (2013) 455- 466. 10.22059/ijer.2013.624

[00175] [3] P.C. Holloway, T.H. Etsell, Salt roasting of suncor oil sands fly ash,

Metall Mater Trans B 35 (2004) 1051-1058. DOI 10.1007/s11663-004-0061-1

[00176] [4] M.R. Tavakoli, S. Dornian, D.B. Dreisinger, The leaching of vanadium pentoxide using sulfuric acid and sulfite as a reducing agent, Hydrometallurgy 141 (2014) 59-66. https://doi.Org/10.1016/j.hydromet.2013.10.014

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