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Title:
RECOVERING SCANDIUM AND DERIVATIVES THEREOF FROM A LEACH SOLUTION LOADED WITH METALS OBTAINED AS A RESULT OF LEACHING LATERITIC ORES COMPRISING NICKEL, COBALT AND SCANDIUM, AND SECONDARY SOURCES COMPRISING SCANDIUM
Document Type and Number:
WIPO Patent Application WO/2016/209178
Kind Code:
A1
Abstract:
The invention comprises leaching lateritic ores used during the production of nickel-cobalt, or leaching of secondary scandium sources in which scandium is enriched within the precipitate during a pH controlled solution purification process. The invention relates to applying a solvent extraction method and recovering scandium and derivatives thereof from the mentioned sources for enriching and purifying the leach solution, having impurity elements within, in terms of scandium.

Inventors:
İPLİKÇİOĞLU ALI SAFDER (TR)
TOPKAYA YAVUZ ALI (TR)
Application Number:
PCT/TR2015/050161
Publication Date:
December 29, 2016
Filing Date:
November 06, 2015
Export Citation:
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Assignee:
META NİKEL KOBALT MADENCİLİK SANAYİ VE TİCARET ANONİM (TR)
International Classes:
C22B3/38; C22B59/00
Domestic Patent References:
WO2015009254A22015-01-22
Foreign References:
DE19858560A11999-07-08
US20140314639A12014-10-23
TR201308682A2013-07-18
Other References:
WANG WEIWEI ET AL: "Recovery of scandium from synthetic red mud leach solutions by solvent extraction with D2EHPA", SEPARATION AND PURIFICATION TECHNOLOGY, ELSEVIER SCIENCE, AMSTERDAM, NL, vol. 108, 11 February 2013 (2013-02-11), pages 96 - 102, XP028527311, ISSN: 1383-5866, DOI: 10.1016/J.SEPPUR.2013.02.001
HASLAM ET AL: "An investigation into the feasibility of extracting scandium from nickel laterite ores", TECHNICAL PROCEEDINGS / ALTA 1999 NICKEL/COBALT PRESSURE LEACHING & HYDROMETALLURGY FORUM : MAY 11 - 12, 1999, RENDEZVOUS OBSERVATION CITY HOTEL, PERTH, AUSTRALIA,, 11 May 1999 (1999-05-11), pages 1 - 18, XP009181633
XU S ET AL: "Review of the extractive metallurgy of scandium in China (1978-1991)", HYDROMETALLURGY, ELSEVIER SCIENTIFIC PUBLISHING CY. AMSTERDAM, NL, vol. 42, no. 3, 1 October 1996 (1996-10-01), pages 337 - 343, XP004040794, ISSN: 0304-386X, DOI: 10.1016/0304-386X(95)00086-V
Attorney, Agent or Firm:
PARAGON CONSULTANCY INCORPORATED (G.O.P, Ankara, TR)
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Claims:
CLAIMS

1. A method comprising the following steps:

• preparing a leach solution for an acid leaching process of lateritic nickel ores or secondary scandium sources,

• subjecting lateritic ores or secondary scandium sources, which are formed during the pH controlled leach solution purification step and are enriched within the precipitate, to an acid leaching process with the prepared leach solution,

• obtaining scandium and derivatives thereof with solvent extraction and precipitation methods from the leach solution loaded with metals obtained as a result of the mentioned leaching process, characterized in that the mentioned solvent extraction and precipitation methods comprise the following process steps: a) diluting an organic reagent termed DEHPA with kerosene and then, subjecting this to a pre-conditioning process, b) pre-conditioning said DEHPA chemical with a NH4SCN chemical after diluting it so that there is 2-15% DEHPA and 85-98% kerosene by volume, c) mixing the pre-conditioned (DEHPA + kerosene) mixture with the leach solution, obtained by leaching sources comprising scandium, to selectively extract scandium from the leach solution to the organic phase, and leaving impurity elements behind, d) mixing scandium loaded pre-conditioned (DEHPA + kerosene) mixture obtained in the process step c) with a reagent solution selected from the group consisting of HCI, H2SO4, HNO3 and NH4F in order to eliminate by scrubbing the impurity elements extracted to the organic phase together with scandium such that there is no or little loss of scandium

e) stripping the organic mixture obtained in the process step d) with a chemical containing a reagent selected from the group consisting of HNO3, NaOH and NH4F to enable scandium to be transferred to the strip solution phase again through the pre-conditioned (DEHPA + kerosene) mixture on which it is loaded, f) mixing the strip solution obtained in the process step e) with a reagent selected from the group consisting of NH4F, H2C2O4, (NH4)2CO3, Na2CO3 or NaOH to recover the scandium transferred to the strip solution phase with the stripping process in the form of solid scandium compounds from the solution phase. 2. The method according to claim 1 , characterised in that isodecyl alcohol is added to the (DEHPA + kerosene) mixture prior to pre-conditioning in the process step a).

3. The method according to claim 1 , characterised in that tributylphosphate is added to the (DEHPA + kerosene) mixture prior to pre-conditioning in the process step a).

4. The method according to claim 1 , characterised in that a pH controlled solution purification process is applied if the impurity elements concentration within the leach solution are very high prior to the process step a). 5. The method according to claim 1 , characterised in that the mixing ratio of the organic/ammonium thiocyanate solution mentioned in the process step b) is 1 /1 -10/1 by volume.

6. The method according to claim 1 , characterised in that with the leach solution mentioned in the process step c) the mixing ratio of the organic/solution phase is 1 /3 - 1 /20 by volume depending on the scandium concentration within the solution.

7. The method according to claim 1 , characterised in that the mixing ratio of the scandium loaded organic/solution phase ratio mentioned in the process step d) is 11λ -1 5/1 by volume. 8. The method according to claim 1 , characterised in that the mixing ratio of the organic/solution phase ratio mentioned in the process step e) is 1 /1 -30/1 by volume.

9. The method according to claim 1 , characterised in that scandium fluoride is obtained when the precipitating reagent mentioned in the process step f) is NH4F.

10. The method according to claim 1 , characterised in that scandium hydroxide is obtained when the precipitating reagent mentioned in the process step f) is NaOH.

11. The method according to claim 1 , characterised in that scandium oxalate is obtained when the precipitating reagent mentioned in the process step f) is

12. The method according to claim 1 , characterised in that scandium carbonate is obtained when the precipitating reagent mentioned in the process step f) is (NH4)2CO3 or Na2CO3.

Description:
DESCRIPTION

RECOVERING SCANDIUM AND DERIVATIVES THEREOF FROM A LEACH SOLUTION LOADED WITH METALS OBTAINED AS A RESULT OF LEACHING LATERITIC ORES COMPRISING NICKEL, COBALT AND SCANDIUM, AND

SECONDARY SOURCES COMPRISING SCANDIUM

Field of the Art

The invention relates to recovering scandium and derivatives thereof from a dirty leach solution having impurity elements therein formed after leaching lateritic ores used during the production of nickel-cobalt, or formed after leaching of secondary scandium sources in which scandium is enriched within the precipitate during a pH controlled solution purification step with solvent extraction and then a precipitation method.

State of the Art

When the distribution of the element scandium, a transition metal, on the Earth's crust is examined, it can be observed that it is generally distributed in ppm level within the crystal structure of over 100 different minerals. These minerals containing traces of scandium belong to generally uranium, tin, iron, tungsten, tantalum, zirconium, titanium and ores comprising rare earth elements. When historic processes are observed, as the production of scandium is carried out such that it is obtained as a by-product during the processing of these ores, the worldwide demand for scandium has not risen above amounts varying between 3 to 10 tonnes annually. That there is no reliable source to enable the continuity of demand for scandium has continually been an issue to date. Viewing studies on obtaining scandium from nickel ores comprising lateritic scandium, a business which obtains a product containing scandium from these ores and markets them on an industrial scale does not yet exist. However, in the solution obtained from leaching these lateritic ores it is suggested that all of said scandium-containing solution be directly subjected to a solvent extraction method for selectively recovering the scandium element found in relatively low concentrations with impurity elements from this dirty solution. Yet, as subjecting all of this solution obtained after the leaching process in this method to a direct solvent extraction method will cause the issue of processing large amounts of solution, many technical and economic challenges will arise during this process. Despite all of these mentioned disadvantages, the recent discovery of scandium generally at levels of 50-300 ppm in lateritic nickel ores forming approximately three quarters of nickel reserves in the world is promising for the potential of eliminating the struggle faced for finding sources until today.

US Patent Application No. 2014314639 is one of the applications which appears relating to research in the literature. This application comprises the step of purifying a pH controlled leach solution during the production of nickel-cobalt hydroxide from lateritic ores with hydrometallurgical methods. Depending on factors such as temperature and solution concentration used in the process, it can be seen that the element scandium is inclined to precipitate and that is enriched within the solid precipitate formed within this process in the range of pH 2.5 to pH 5.0. However, in said application, although it is stated that scandium may only be obtained with the solvent extraction method from the precipitate rich in scandium, neither the process steps applied during this method nor the reagents used in these steps have been indicated. Whereas, in Turkish Patent No. 2013/08682 belonging to the applicant, titled "Leaching of refractory lateritic ores comprising nickel, cobalt and scandium with acid under high pressure and recovering scandium from a leach solution loaded with metals, and from precipitates obtained during purification step.", although it is stated that from refractory nickel ores scandium may be obtained by a) preparing a leach solution for an acid leaching process under high pressure, b) subjecting an acid leaching process under high pressure with the prepared leach solution, c) solvent extraction method applied to a leach solution loaded with metals obtained as a result of said leaching process, but the details of the process steps applied during this method have not been indicated. In the said patent application, the scandium-containing solution is obtained after removing leach residues from the system with solid-liquid separation after the leaching process, and comprises therein undesired impurity elements together with scandium at a relatively low concentration. The impurity elements found together with scandium may be Fe, Al, Cr, Mn, Mg, Ni, Co, Ca, Cu, Zn, Si, etc. These said impurity elements contaminate the scandium product and make it harder for the product to be marketed.

In conclusion, due to the disadvantages mentioned above and the insufficiency of the present solutions regarding the subject, a need for making a development in the related field of the art was rendered necessary.

Object of the Invention

The present invention aims at applying a solvent extraction method consisting of the steps of pre-conditioning, extraction, scrubbing and stripping to a purified leach solution after excessive impurity elements have been refined in a pH controlled manner, if there are any, from a leach solution loaded with metals obtained as a result of leaching lateritic ores containing nickel, cobalt and scandium and/or secondary scandium sources formed as a result of precipitation which meets the aforementioned needs, eliminates all disadvantages and provides some additional advantages. It is aimed that scandium enriched and purified from impurities after these stages is recovered from the strip solution with the precipitation method.

The first object of the invention is to subject the scandium-containing solution obtained by leaching the aforementioned primary and secondary scandium sources to a pH controlled purification process by stepwise precipitating the impurity elements such as Fe, Al, Cr if it comprises excessively. Another object of the invention is to determine the organic based reagent and the pre-conditioning chemical to enable scandium to be selectively extracted to the organic phase through the leach solution during the extraction step and to ease stripping of scandium loaded onto the organic phase to be back-extracted to aqueous phase during the stripping step, after said pre-conditioning process. An ammonium thiocyanate compound was selected as said pre-conditioning reagent, and DEHPA was selected as the organic based reagent. The reason for this organic reagent being selected is that it is both cheaper and easier to obtain compared to other organic reagents. Another reason is that it enables scandium to be selectively loaded onto the organic phase in the solvent extraction stage, and scandium to be stripped from the organic phase which it is loaded on. A further object of the invention is to enable the present impurity elements to be left behind in the scandium-containing solution and scandium to be selectively extracted onto the organic reagent, after leaching sources comprising scandium and placing them into a leach solution with minimum impurity elements and maximum scandium yield, with the mentioned extraction process. For this reason, a mixture of pre-conditioned (DEHPA + kerosene) and leach solution-containing scandium is used in the extraction stage.

An even further object of the invention is to enable the impurity elements loaded onto the organic phase together with scandium to be removed from the organic such that there is no loss of scandium. As a technical term, this process is called the "scrubbing" process in literature. For this purpose, a reagent selected from the group consisting of HCI, H2SO4, HNO3 and NH 4 F is used.

Another object of the invention is to enable the transfer of scandium, loaded onto the organic phase, into a strip solution through the organic phase with the back- extraction process. As a technical term, this process is called the "stripping" process in literature. A reagent selected from the group consisting of HNO3, NaOH and NH 4 F is used to enable this purpose.

A further object of the invention is to enable recovering the scandium, taken into a solution phase after the stripping process, from a solution phase as solid scandium compounds with the mentioned precipitation process. For this purpose, a reagent selected from the group consisting of NH 4 F, H2C2O4, (NH 4 )2CO3, Na2CO3 or NaOH is used.

The structural and characteristic properties and all of the advantages of the invention will become clearer with the written detailed description by means of the following figure and the references to this figure and therefore the evaluation needs to be made taking this figure and detailed description into account. Figure Helping the Invention to Be Understood

Figure 1 is a flow chart of the process of the invention.

The drawing does not necessarily have to be scaled and the details, which are not necessary in order to understand the present invention may have been excluded. Furthermore, at least substantially equal elements or elements with at least substantially equal functions are shown with the same numbers.

Detailed Description of the Invention

In this detailed description, preferred embodiments of the recovery of scandium and derivatives thereof from a leach solution loaded with metals obtained as a result of leaching lateritic ores comprising nickel, cobalt and scandium, and secondary scandium sources formed as a result of pH controlled precipitation are described only for the better understanding of the subject and should not be considered as limiting to the scope of the invention.

The invention aims to refine the dirty leach solution obtained after leaching lateritic ores used during the production of nickel-cobalt, or after leaching of secondary scandium sources in which scandium is enriched within the precipitate during a pH controlled solution purification step if there are excessive impurity elements therein, and to enrich the scandium-containing leach solution in scandium with the solvent extraction stages of pre-conditioning, extraction, scrubbing, stripping and to purify this solution, and finally to recover scandium and derivatives thereof with precipitation method.

In Turkish Patent No. 2013/08682 belonging to the applicant, leaching of refractory lateritic ores comprising nickel, cobalt and scandium with sulphuric acid under high pressure and recovering scandium from a leach solution loaded with metals and from precipitates obtained via a pH controlled impurity removal step is disclosed. The scandium-containing solution obtained with a leaching process also comprises many undesired impurity elements (Fe, Al, Cr, Mn, Mg, Ni, Co, Ca, Cu, Zn, Si, etc.).

The invention relates to eliminating aforementioned impurity elements, and recovering scandium and derivatives thereof from the mentioned ores or secondary sources. Therefore, there are used process steps, reagents found within these process steps, and parameters, in which these reagents are suitable. Process steps of the invention:

Solution Purification: This relates to subjecting the scandium-containing solution obtained by leaching primary or secondary scandium sources to a pH controlled purification process by stepwise precipitating impurity elements such as Fe, Al, Cr if it comprises excessive impurity elements.

Pre-conditioning: This relates to determining an organic based reagent to enable scandium to be selectively extracted to the organic phase through the solution during the extraction step and at the same time to enable stripping of loaded scandium thereon during the stripping step. This organic reagent is conditioned by being passed through a pre-process with a certain chemical. The DEHPA organic reagent used within the pre-process is 2-15% vol. and the remaining 85-98% vol. is kerosene. The pre-conditioning process is carried out with 1 -3 molar NH 4 SCN (preferably 1 .5 molar). The volume ratio of the organic/ammonium thiocyanate solution used in the mixture may be within the range of 1 /1 -10/1 . Also, in addition to conditioning of the mentioned DEHPA chemical; isodecyl alcohol or TBP (tributylphosphate) reagents may be added into the (DEHPA + kerosene) mixture if necessary (e.g., if the formation of a third phase is observed or in order to enable a synergistic effect during the extraction step). The volume ratios of the isodecyl alcohol (preferably 5%) or TBP (preferably 1 %) to be added may vary between 1 - 10%. When these reagents are added, the volume ratio of the kerosene within the organic mixture is decreased according to the amount added.

NH 4 SCN: Ammonium thiocyanate

DEHPA: Di-2-ethylhexylphosphoric acid TBP: Tributylphosphate

Extraction: This relates to carrying out an extraction process to selectively extract and load scandium onto the organic reagent from impurity elements in the solution which is obtained by leaching scandium containing sources with minimum impurity elements and maximum scandium yield. During this extraction process, a (DEHPA + kerosene) mixture which has been pre-conditioned or has/has not had isodecyl alcohol or TBP added is used. In the extraction stage, scandium is transferred to the organic phase as a result of ion exchange by mixing the organic phase comprised of the (DEHPA + kerosene) mixture with a leach solution containing scandium. During this process, the organic/ solution phase ratio may vary between 1 /3 - 1 /20 (preferably 1 /10) by volume depending on scandium concentration within the solution. The solution obtained after the extraction step is termed a raffinate. The organic phase having the possibility of polluting this solution is cleaned by means of active carbon and valuable metals such as Ni, Co which remain in the Organic removed raffinate' are recovered with known methods. Scrubbing: After the extraction process with an organic based reagent, the reagents enabling the removal of impurity elements loaded onto the organic phase together with scandium such that there is a little or no loss of scandium; are H2SO4, HCI, HNO3 and NH 4 F. One selected from these reagents is mixed such that the scandium loaded organic phase/solution phase ratio is 1 /1 -15/1 (preferably 10/1 ) by volume by preparing the solution thereof at the concentrations stated below. Thus, the impurities such as Fe, Al, Ca, etc. polluting the organic phase loaded with scandium are transferred to the scrub solution phase, and the organic scrubbing step for removal of the impurities is completed.

Stripping: To be able to re-use the organic based reagent on which scandium is selectively loaded during solvent extraction, and to be able to recover enriched scandium loaded onto the organic phase, the solution of one of the reagents indicated below is mixed with the organic phase loaded with scandium and scrubbed from impurities by being prepared in specified concentrations. During stripping, the organic/solution phase ratio is selected as 1 /1 -30/1 (preferably 15/1 ) by volume. Thus, scandium is transferred to the strip solution phase by being enriched and the organic phase is recovered for reuse.

Precipitation: The precipitation process enabling the selective recovery of scandium from a solution enriched in terms of scandium obtained by stripping of scandium on the organic reagent, is carried out by preparing the solution with one of the following selected reagents at specified concentrations.

Application of the aforementioned process steps:

• During the pre-conditioning process, an organic reagent called DEHPA which is diluted with kerosene is used. The DEHPA chemical is prepared by being diluted such that there is 2-15% DEHPA and 85-98% kerosene by volume, and conditioned by mixing the NH 4 SCN chemical at a concentration of 1 -3 molar and the organic/solution phase ratio in the range of 1 /1 -10/1 by volume. The conditioned organic is then separated from the solution phase comprising NH 4 SCN with the help of a settler due to the difference in density. The separated conditioned organic phase is used in the following extraction step.

Also, prior to the conditioning of the mentioned DEHPA chemical; an isodecyl alcohol or TBP reagent may be added to the (DEHPA + kerosene) mixture if necessary (e.g., if the formation of a third phase is observed or in order to enable a synergistic effect during the extraction step).

• In the extraction step, the pre-conditioned DEHPA + kerosene) mixture prepared in the previous step is mixed with a scandium-containing leach solution for about 1 -15 minutes by means of a mixer such that the organic/solution phase ratio is in the range of 1 /3-1 /20 by volume. Thus, the scandium within the solution is selectively extracted onto the organic phase and enriched. After the extraction process, the organic phase and the raffinate phase of which the scandium has been removed are separated from each other in a settler unit due to the difference in density by letting the two phases to settle for about 1 -15 minutes. The scandium loaded organic phase which is separated from the raffinate phase is then transferred to the following scrubbing step.

• The scrubbing step is applied for scrubbing impurity elements such as Fe, Al, Ca, etc. loaded onto the organic reagent together with scandium. In this application, the solution of a reagent selected from the group consisting of

HCI, H2SO4, HNO3 and NH 4 F is used. During this process, a minimum or no loss of scandium from the organic phase to the scrub solution is aimed. While scrubbing, the organic/solution phase ratio is selected within the range of 1 /1 -15/1 by volume and mixing time during scrubbing is controlled between 1 -15 minutes. Then, the organic and scrub solution are separated from each other with a settler unit within about 1 -15 minutes. The organic phase loaded with scandium which is scrubbed from impurity elements thereon is transferred to the stripping step so that scandium is returned to the solution phase.

• In the stripping step, scandium present on the loaded and scrubbed organic phase is transferred into a strip solution. The solution of a stripping reagent selected from the group consisting of HNO3, NaOH and NH 4 F is used to enable this. Within the stripping stage, the scandium loaded organic/solution phase ratio is selected within the range of 1/1 -30/1 by volume and is mixed for 1 -15 minutes. After this mixing step, the organic phase and strip solution phase are separated from each other in a settler unit due to the difference in density by letting the two phases to settle for about 1 -15 minutes. The separated organic phase is then returned to the extraction step by being conditioned again if necessary to be used again in the solvent extraction stage. A new scandium rich solution is obtained with the stripping process afterwards by separating the stripped organic and strip solution from each other by the help of settler unit. This solution may generally comprise 500-8000 ppm scandium depending on the lateritic ore, or the secondary scandium source tenor or its concentration, respectively. Said stripping solution is then subjected to a precipitation process to obtain the scandium therein.

• The precipitation step recovers scandium from the strip solution phase in the form of solid scandium compounds. For this purpose, the solution of a reagent selected from the group consisting of NH 4 F, H2C2O4, (NH 4 )2CO3, Na2CO3 or NaOH is used. The solution of the mentioned reagents reacts with a solution rich in scandium obtained as a result of stripping. Scandium fluoride, scandium hydroxide, scandium oxalate, or scandium carbonate are obtained after the reaction depending on the precipitating reagent used. Also, if desired, SC2O3 is produced from these compounds.

In a preferred embodiment of the invention, the aforementioned solvent extraction process steps are generally performed at room temperature. The maximum temperature is controlled so as to prevent the organic phase from catching fire.

In a preferred embodiment of the invention, a washing step is applied to the organic phase by adding purified water or by adding 5-15 g/L ammonium sulphate to purified water when necessary to prevent pollution in transitions between the mentioned solvent extraction process steps.

Points to be taken into consideration in the invention:

• Safety measures should be taken to eliminate the risk of combustion of chemicals such as an organic reagent, kerosene, etc. which have a high possibility of combustion,

• A ventilation system, a fume hood or a similar system should be continually operated in order to provide protection from the smells which chemicals having adverse health effects and high vapour pressure may produce in a work environment,

• The conditions stated on safety sheets (MSDS) of chemicals should be complied with while working with acids, bases and various salts to be used during the process.