TECHNICAL FIELD

The present disclosure relates to field of metallurgy. The disclosure particularly relates to method for recovering manganese from manganese ore while preventing formation of dithionate. Said method is improved, simple and economical for recovering manganese from the manganese ore.

BACKGROUND OF THE DISCLOSURE

Extraction of manganese from lean manganese ore and sub-grade manganese ore is usually faced with problem of controlling the amount of iron extracted along with manganese. Leaching carried out at a pH range of 1 to 1.5 during extraction of manganese leads to overlapping reduction potential of manganese and iron, as a result, both manganese and iron is extracted together leading to higher percentage of iron in the manganese which is not desirable.

To avoid dissolution of iron and manganese during leaching, leaching was noted to be carried out with sulphur compounds. Addition of sulphur compounds during leaching though controlled dissolution of iron with manganese, it led to the formation of dithionate ions in solution with levels greater than 5 g/1. It was noted that generation of dithionate in the leach solution leads to increase in the capital cost due to involvement of additional process operation, such as oxidation and aging to remove dithionate. Also, it was noted that longer residence time is required to oxidize the dithionate levels from about 5 g/1 to below 1 g/1, which leads to lower productivity and the process becomes capital intensive.

Further, it was noted that, utilization of sulphur compounds, such as sulphur dioxide as lixiviant during leaching of manganese from high iron bearing ores (30 to 40 wt%) tends to leach more than 8 g/1 of iron with manganese. In other words, the issue of dissolution of iron and manganese during leaching persisted which led to leaching of undesired amounts of iron along with manganese and/or formation of dithionate ions during leaching.

Thus, there is a need for improved and economical process for extraction for manganese which addresses the above noted drawbacks relating to dissolution of iron along with manganese and formation of dithionate during leaching. To overcome the above noted drawbacks, the present disclosure describes an improved method of extraction of manganese from manganese ore without formation of dithionate and significantly reduces the dissolution of iron with manganese during leaching.

STATEMENT OF THE DISCLOSURE

Accordingly, the present disclosure describes an improved, simple and economical method for extracting/recovering manganese from manganese ore, wherein dithionate formation is prevented and dissolution of iron alongside manganese is significantly reduced or negligible.

The method for recovering manganese from manganese ore while preventing formation of dithionate, comprises- mixing the manganese ore with sulphur to generate pellets, followed by roasting to obtain roasted pellets; mixing the roasted pellets with solvent to obtain slurry; leaching the slurry with sulphuric acid to obtain leach solution, followed by filtering to obtain leach liquor; and purifying the leach liquor to obtain pregnant leach solution (PLS), followed by recovering the manganese.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

In order that the present disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, where:

Figure 1 illustrates flow chart depicting the method of recovering manganese from manganese ore according to the present disclosure.

Figure 2 illustrates Scanning Electron Microscope (SEM) image depicting roasted sulphated pellets, wherein 1, 2, 6 and 7 (in the image) represent micro structure of Fe2O3.

Figure 3 illustrates X-ray diffraction plot of roasted manganese ore depicting manganese sulphate as major product. Figure 4 illustrates a plot depicting Mn and Fe recovery from sulphated manganese ore after leaching at temperature of about 400 °C with S 02/02= 0.6.

DETAILED DESCRIPTION OF THE DISCLOSURE

Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. By means of further guidance, term definitions are included for better understanding of the present disclosure.

As used herein, the singular forms ‘a’, ‘an’ and ‘the’ include both singular and plural referents unless the context clearly dictates otherwise.

The term ‘comprising’, ‘comprises’ or ‘comprised of’ as used herein are synonymous with ‘including’, ‘includes’, ‘containing’ or ‘contains’ and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.

Reference throughout this specification to ‘some embodiments’, ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure, thus, the appearances of the phrases ‘in some embodiments’, ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification may not necessarily all refer to the same embodiment. It is appreciated that certain features of the disclosure, which are for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The present disclosure relates to simple, efficient and economical method for recovering manganese from manganese ore including but not limited to lean manganese ore, sub-grade manganese ore and low grade high iron bearing manganese ore. Said method involves treatment of manganese ore through pyro-hydrometallurgical processing for selective extraction/recovery of manganese.

In some embodiments of the present disclosure, the method prevents formation of dithionate during recovering manganese from the manganese ore. In other words, the steps followed in the described method for recovering manganese prevents formation of dithionate. Inventors have particularly identified that sulphating roasting (roasting in presence of sulphur) of manganese ore prevents generation of dithionate.

In some embodiments of the present disclosure, the method for recovering manganese from manganese ore while preventing formation of dithionate, comprises- mixing the manganese ore with sulphur to generate pellets, followed by roasting to obtain roasted pellets; mixing the roasted pellets with solvent to obtain slurry; leaching the slurry with sulphuric acid to obtain leach solution, followed by filtering to obtain leach liquor; and purifying the leach liquor to obtain pregnant leach solution (PLS), followed by recovering the manganese.

In some embodiments of the present disclosure, the mixing of the manganese ore with sulphur comprises- mixing pulverized manganese ore with sulphur powder and binder in presence of moisture and pelletizing to obtain pellets.

In some embodiments of the present disclosure, the pulverization of the manganese ore is carried out by crushing the manganese ore in primary crusher including but not limited to jaw crusher to reduce the size of the manganese ore, followed by subsequently reducing size of the manganese ore by feeding the ore into ball mill or roll pulveriser to achieve pulverized manganese ore having predetermined size which are amenable for roasting and leaching. The pulverized ore used for the pellet making is have a size distribution of about -75+25 micron. In some embodiments of the present disclosure, the sulphur powder is in an amount ranging from about 20% to 80%, including all the values in the range, for instance, 21%, 22%, 23%, 24% and so on and so forth.

In some embodiments of the present disclosure, the binder is selected from a group comprising sodium, aluminium silicate and a combination thereof.

In some embodiments of the present disclosure, the binder is in an amount ranging from about 20% to 80%, including all the values in the range, for instance, 21%, 22%, 23%, 24% and so on and so forth.

In some embodiments of the present disclosure, the moisture content is ranging from about 3% to 7%, including all the values in the range, for instance, 3.1%, 3.2%, 3.3%, 3.4% and so on and so forth.

In some embodiments of the present disclosure, ratio of sulphur powder to manganese ore is ranging from about 0.1 to 0.8. In an embodiment, the ratio of sulphur powder to manganese ore is about 0.1, about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7 or about 0.8.

In some embodiments of the present disclosure, the pellets have size ranging from about 4 mm to 6 mm, including all the values in the range, for instance, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm and so on and so forth.

In some embodiments of the present disclosure, the pellets have strength ranging from about 80 Kgf to 150 Kgf, including all the values in the range, for instance, 81Kgf, 82 Kgf, 83 Kgf, 84 Kgf and so on and so forth.

In some embodiments of the present disclosure, the mixing of the manganese ore with sulphur, comprises- pulverising the manganese ore to achieve predetermined size of the manganese ore; mixing the pulverized manganese ore, the sulphur powder and the binder in presence of moisture; and pelletizing the mixture to obtain sulphur containing manganese pellet. In some embodiments of the present disclosure, the pellets are subjected to roasting at a temperature ranging from about 400 °C to 650 °C, including all the values in the range, for instance, 401 °C, 402 °C, 403 °C, 404 °C and so on and so forth.

In some embodiments of the present disclosure, the roasting is carried out for a duration ranging from about 30 minutes to 120 minutes, including all the values in the range, for instance, 31 minutes, 32 minutes, 33 minutes, 34 minutes and so and so forth.

In some embodiments of the present disclosure, the roasting of the pellets is carried out in presence of sulphur dioxide having partial pressure ranging from about 0.1 atm to 0.6 atm. In an embodiment, the partial pressure of the sulphur dioxide is about 0.1 atm, about 0.2 atm, about 0.3, about 0.4 atm, about 0.5 atm or about 0.6 atm.

In some embodiments of the present disclosure, during roasting of the sulphur containing manganese pellets in presence of the sulphur dioxide, air is supplied at a flow rate ranging from about 2 LPM to 10 LPM, including all the values in the range for instance, 2.1 LPM, 2.2 LPM, 2.3 LPM, 2.4 LPM and so on and so forth.

In some embodiments of the present disclosure, during roasting of the pellets in a device including but not limited to furnace, feedback control loop is established for addition of air at a flow rate of about 2 LPM to 10 LPM depending on the exit of SO2 from the device, which has direct relationship with partial pressure of SO2 during roasting.

In some embodiments of the present disclosure, the roasting of the sulphur containing manganese pellets is carried out under the atmosphere of O2, N2 and SO2 by maintaining partial pressure of the SO2 to a range of about 0.1 atm to 0.6 atm.

In some embodiments of the present disclosure, the roasted pellets are subjected to cooling until the desired temperature of the pellets are achieved. The roasted pellets are cooled to about 80 °C to 100 °C under non-oxidation environment.

In some embodiments of the present disclosure, roasting of the pellets leads to reduction of manganese ore. In some embodiments of the present disclosure, during roasting the manganese ore in the pellets is partly converted to mixture of manganese oxide and manganese sulphate along with mixture of iron present as hematite and magnetite.

The inventors have particularly identified that roasting of the sulphur containing manganese pellets with sulphur dioxide at a temperature ranging from about 400 °C to 650 °C, for a duration ranging from about 30 minutes to 120 minutes prevents formation of dithionate during leaching. In an embodiment, the roasting described herein is selective reductive roasting using combination of sulphur (in the pellets) and sulphur dioxide, which converts manganese from higher oxidation state to lower oxidation state.

In an embodiment, the Figure 2 illustrates Scanning Electron Microscope (SEM) image depicting roasted sulphated pellets, wherein 1, 2, 5 and 7 (in the image) represent micro structure of Fe2O3.

In an embodiment, the Figure 3 illustrates X-ray diffraction plot of roasted manganese ore depicting manganese sulphate as major product.

In some embodiments of the present disclosure, the roasted pellets are mixed with solvent to obtain slurry.

In some embodiments of the present disclosure, the solvent is selected from a group comprising water, recycled liquor, sulphuric acid and a combination thereof.

In some embodiments of the present disclosure, the slurry has pulp density ranging from about 10% to 25%, including all the values in the range, for instance, 10.1%, 10.2%, 10.3%, 10.4% and so on and so forth.

In some embodiments of the present disclosure, prior to mixing the roasted pellets with solvent, the pellets are pulverized to achieve size ranging from about 50 micron to 150 micron, including all the values in the range, for instance, 51 micron, 52 micron, 53 micron, 54 micron and so on and so forth. In some embodiments of the present disclosure, the slurry is prepared by mixing the pulverized roasted pellet with recycled water and mother liquor from manganese sulphate crystallization.

In some embodiments of the present disclosure, the slurry was mixed sufficiently for a duration ranging from about 15 to 60 minutes.

In some embodiments of the present disclosure, the slurry has pH ranging from about 3.0 to 5.5. In an embodiment, pH of the slurry is at least 4.

In some embodiments of the present disclosure, the slurry is subjected to leaching in presence of sulphuric acid to obtain leach solution. In an embodiment, dosing of the sulphuric acid during leaching is carried out in such manner that the pH of the leach solution is maintained in a range of about 3 to 3.5. In other words, the dosing of the sulphuric acid during the leaching is controlled based on the pH of the leach solution.

In some embodiments of the present disclosure, the sulphuric acid during leaching is added in an amount ranging from about 2 vol% to 10 vol%, including all the values in the range, for instance, 2.1 vol%, 2.2 vol%, 2.3 vol%, 2.4 vol% and so on and so forth, to maintain pH of the solution ranging from about 3 to 3.5.

In some embodiments of the present disclosure, during leaching, additive selected from a group comprising sodium, sulphur, oxygen, hydrogen and any combination thereof is added in an amount ranging from about 0.5 vol% to 3 vol%, including all the values in the range for instance, 0.6 vol%, 0.7 vol%, 0.8 vol%, 0.9 vol% and so on and so forth.

In some embodiments of the present disclosure, the leaching is carried out in continuous arrangement followed by co-current manner and dosing of the sulphuric acid to maintain pH in the range of about 3 to 3.5 in counter current manner. It is noted that, this way of leaching involving continuous arrangement, co-current manner and by counter current manner provides for improved control over manganese dissolution with higher productivity.

In some embodiments of the present disclosure, the leaching is carried out at a temperature ranging from about 45 °C to 60 °C, including all the values in the range, for instance, 46 °C, 47 °C, 48, °C, 49 °C and so on and so forth, for a duration ranging from about 60 minutes to 180 minutes, including all the values in the range, for instance, 61 minutes, 62 minutes, 63 minutes, 64 minutes and so on and so forth. In an embodiment, the leaching is carried until desired values of Mn (II), Fe (II) and Al (III) in the solution is achieved.

In some embodiments of the present disclosure, upon stopping the leaching process, the leach solution is subjected to filtration by technique selected from a group comprising filter press, drum filter and belt filter, to obtain leach liquor. In an embodiment, the filtration is carried out to separate solid and liquid in the leach solution to obtain leach liquor. In the obtained leach liquor, there is no presence of dithionate and free SO2 is below 0.1 g/1.

In some embodiments of the present disclosure, the leach liquor is subjected to purification to obtain pregnant leach solution (PLS). In an embodiment, total iron in the PLS is less than lg/1, preferably less than 0.5 g/1, more preferably less than 0.2 g/1.

In some embodiments of the present disclosure, purification of leach liquor removes metal selected from a group comprising iron, aluminium, copper, zinc, cobalt, arsenic, lead and any combination thereof.

In some embodiments of the present disclosure, purification of leach liquor is carried out by adding additive mixture and hydrated lime slurry.

In some embodiments of the present disclosure, the additive mixture comprises an oxidizing agent and acid. In an embodiment, the oxidizing agent is selected from a group comprising hydrogen peroxide, sodium perchlorate, manganous oxide, potassium permanganate and any combination thereof and the acid is selected from a group comprising, citric acid, acetic acid, ascorbic acid, sulphuric acid, tartaric acid and any combination thereof.

In some embodiments of the present disclosure, the additive mixture is in an amount ranging from about 20 vol% to 50 vol%, including all the values in the range, for instance, 21 vol%, 22 vol%, 23 vol%, 24 vol% and so on and so forth.

In some embodiments of the present disclosure, the hydrated lime slurry is in an amount ranging from about 10% to 25%, including all the values in the range for instance, 11%, 12%, 13%, 14% and so on and so forth. In some embodiments of the present disclosure, in the purification of leach liquor, the additive mixture is added to the liquor, followed by holding for a duration ranging from about 1 hour to 2 hours. The oxidizing agent in the additive mixture oxidizes Fe (II) to Fe (III). Addition of hydrated lime slurry into liquor increase the pH of the liquor to a range of about 4.4 to 6.3. In an embodiment, purification of leach liquor precipitates Fe and Al as hydroxides.

In some embodiments of the present disclosure, the PLS has pH ranging from about 3.2 to 7.7, including all the values in the range for instance, 3.3, 3.4, 3.5, 3.6 and so on and so forth.

In some embodiments of the present disclosure, the PLS comprises about 85 g/L to 110 g/L Mn, about 10 ppm to 80 ppm of Fe, about 5 ppm to 20 ppm of Cu, about 5 ppm to 20 ppm of Co and about 0.5 g/1 to 1.2 g/1 of Al.

In some embodiments of the present disclosure, the PLS is subjected to purification by addition of sulphide compound.

In some embodiments of the present disclosure, the sulphide compound is selected from a group comprising sodium hydro sulphide, ammonium sulphide, potassium hydrosulphide, sodium bisulfate and a combination thereof.

In some embodiments of the present disclosure, the sulphide compound is in an amount ranging from about 10 wt % to 30 wt%, including all the values in the range for instance, 10.1 wt%, 10.2 wt%, 10.3 wt% 10.4 wt% and so on and so forth.

In some embodiments of the present disclosure, the purification of PLS with sulphide compound removes heavy metal selected from a group comprising zinc, copper, nickel, cobalt and any combination thereof and leads to formation of manganese sulphate.

In some embodiments of the present disclosure, the solution after purification by adding sulphide compound comprises about 83 g/L to 98 g/L Mn, about 5 ppm to 20 ppm of Fe

In some embodiments of the present disclosure, the manganese sulphate is subjected to filtration by technique selected from a group comprising nanofiltration, adsorption and ion exchange to remove traces of impurities including but not limited to Fe, Ni, Co, As, Pb, Zn, Se and K. In some embodiments of the present disclosure, the manganese sulphate is subjected to electrowinning to obtain electrolytic manganese metal (EMM), wherein the electrowinning is carried out by mixing the manganese sulphate with additive and sulphur dioxide.

In some embodiments of the present disclosure, the additive employed during electrowinning is selected from a group comprising selenium, oxygen, nitrogen, hydrogen, sulphur, oxygen, carbon and any combination thereof. In an embodiment, the additive is in an amount ranging from about 0.5 wt% to 10 wt%, including all the values in the range, for instance, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt% and so on and so forth.

In some embodiments of the present disclosure, the sulphur dioxide employed during electrowinning is in amount ranging from about 200 ppm to 1000 ppm, including all the values in the range, for instance, 201 ppm, 202 ppm, 203 ppm, 204 ppm and so on and so forth.

In some embodiments of the present disclosure, the solution obtained from the electrowinning is subjected to manganese sulphate crystallization. In an embodiment, the crystallization is carried out by adjusting pH of the solution to a range of about 4.0 to 6.0, including all the values in the range, for instance, 4.1, 4.2, 4.4, 4.5 and so on and so forth.

In some embodiments of the present disclosure, the solution obtained from the electrowinning is subjected to production of manganese carbonate.

In some embodiments of the present disclosure, the manganese carbonate is produced by alkaline precipitation. In an embodiment, the alkaline precipitation is carried out by adjusting pH of the solution to 6.0 to 8.5, including all the values in the range, for instance, 6.1, 6.2, 6.3, 6.4 and so on and so forth, by employing salt selected from a group comprising sodium carbonate, ammonium carbonate, ammonium bicarbonate and any combination thereof.

In an embodiment, the Figure 1 provides a flow chart depicting the method of recovering manganese from manganese ore according to the present disclosure. Below is the non-limiting illustration of the method of recovering manganese from the manganese ore including but not limited to lean manganese ore, sub-grade manganese ore and low grade high iron bearing manganese ore- Manganese ore is fed to crushing and grinding circuit and screened to obtain minus 30 fraction. This fraction is fed to primary crusher, such as jaw crusher followed by grinding in pulveriser circuit with separation carried out through air classifier circuit. The desired size of fraction of the manganese ore is sent to pelletization circuit, wherein the pulverized ore is mixed with sulphur fines and binder, in presence of desired moisture content. The mixture is mixed thoroughly in mixing drum and eventually passed through pelletization disc to obtain pellets having size ranging from about 4 mm to 6mm, followed by drying the pellets for a duration of about 2 days.

The dried pellets are passed through induration furnace to sulphate the manganese ore to reduce the manganese to manganese sulphate for a predetermined duration for induration. The pellets are fired in a rotary tube furnace, with three heating zones. The pellets are pre-heated to a temperature of about 200 °C for a duration of about 20 minutes. The pre-heated pellets are fired at a temperature of about 500 °C for about 1 hour so that the reduction reaction between manganese oxide and sulphur can be carried out. During the process of reduction, sulphur present in the pellet starts reduction of manganese as per the following reactions (R1 to R6) 2MnO2(s) = Mn2O3(s) + 0.502(g) R1 S(s) = S(l) R2

S(l) + 02(g) = S02(g) R3

0.5 Mn2O3(s) + S02(g) + 0.5 02(g) = MnSO4(s) R4

1/3 Mn3O4(s) + S02(g) +1/3 02(g) = MnSO4(s) R5

MnO(s) + l/2O2(g) + S02(g) = MnSO4(s) R6

After reduction, roasted pellets are cooled under SO2 environment to minimize the oxidation of manganese.

Pre-cooled manganese ore pellets are pulverized to desired size before leaching.

The pulverized fractions of the pellets are mixed with hot water and sulphuric acid to dissolve manganese sulphate in water. During the sulphating process, there is part of MnO which also forms manganese sulphate in reaction with sulphuric acid. During this process, pH of slurry is maintained for dissolution of manganese from the sulphated ore.

The slurry (having more than 10 wt% solids, less than about 120 g/1 of manganese sulphate) is subjected to leaching (condition- temperature of less than 100 °C and pH ranging from about 3 to 3.5). Leaching is carried out for a duration of about 0.5 hour to 1 hour depending on input manganese concentration, concentration of added sulphuric acid and residence time of the reactor. During leaching there is no evidence of formation of dithionate and free SO2 present in the leach liquor is below 0.1 g/1. The following reactions (R7-R9) occur during leaching. MnS04(s) + H20(l) = MnS04(aq.) R7

MnO(s) + H2SO4(1) = MnSO4(aq.) R8

FeSO4 + H2O(1) = FeSO4(aq.) R9

Upon completion of leaching, filtration of the slurry is carried out. During filtration, some part of iron hydroxide which was generated in-situ is filtered. Solids obtained is washed thoroughly to reclaim any residual manganese. The sludge obtained after filtration mostly contains a complex of (MgFe)SO4 and the sludge contains MgSC above 90%.

Further, the leach liquor is subjected to purification to obtain pregnant leach solution (PLS), followed by filtration to remove iron. Iron free PLS solution is passed to sulphidizing (by adding sulphide compound) process for removal of heavy metals, including but not limited to nickel, zinc, cobalt and copper as their respective sulphides. Following the sulphidizing step, the heavy metal precipitates are removed by fine cartridge filtration and subsequently the purified manganese sulphate solution is stored for preparation of manganese salts or subjected to electrowinning (EMM section).

During electro winning, part of the solution is subjected to electrodepositing to obtain electrolytic manganese metal (EMM)and part (solution of MnSCU) is bled out of the electro winning. The part of bled out MnSCL solution is taken to purification section to remove heavy metals which is passed through adsorbent bed and eventually for preparation of manganese sulphate, wherein the solution is subjected to evaporation and crystallization. Subsequently, manganese carbonate is also produced by employing alkaline precipitation.

In an embodiment of the present disclosure, according to the method described above, the manganese is recovered as electrolytic manganese metal (EMM), manganese sulphate or manganese carbonate.

The above described method for recovering manganese is simple and efficient in recovering high purity manganese in the form of EMM, manganese sulphate or manganese carbonate and efficient in preventing formation of dithionate during leaching. The method is environmentally friendly with significant amount of waste water recycling with minimal discharge of off gas and water.

It is to be understood that the foregoing description is illustrative not a limitation. While considerable emphasis has been placed herein on particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Similarly, additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein.

Descriptions of well-known/conventional methods/steps and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above-described embodiments, and in order to illustrate the embodiments of the present disclosure, certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments may be practiced and to further enable those of skill in the art to practice the embodiments. Accordingly, following examples should not be construed as limiting the scope of the embodiments herein.

EXAMPLES

Example 1: Recovering Manganese from low grade manganese ore lumps

Low grade manganese ore lumps are employed in this Examples. Table 1 provides chemical analysis of the manganese ore.

Table 1.

The manganese ore was crushed to size distribution of less than 1mm using jaw crusher and pulveriser based system. The oversized particles were screened and sent again for crushing. Crushed manganese ore which ws sorted out from the dry circuit was sent to the pelletization circuit. Pulverized manganese ore was mixed with sulphur powder in a ratio of about 0.75, followed by adding about 2.5 g of binder and moisture of about 5 g and subjected to pelletization process to obtain pellets of size of about 4 mm and having strength of about 2.5 kg/pellet.

The pellets (sulphur containing manganese pellets) were roasted in a roasting furnace under a partial pressure of SO2 by recycling part of the SO2 from the exist gas. A controlled flow of air was maintained during the roasting. Roasting was carried out at a temperature of about 500 °C for a duration of about 45 minutes.

Roasted manganese ore was crushed to a size of about 100 micron through a pulveriser circuit. The pulverized roasted ore was mixed with water from recycle stream and fresh water to obtain slurry having pulp density of about 25% and charged into leach reactor for leaching process. During leaching, dosing of the sulphuric acid was carried out in a manner that pH of the leach solution is maintained at about 3.5. Dosing of the sulphuric acid during the leaching is controlled based on the pH of the solution. During leaching, intermittent liquid solutions are tested for Mn (II), Fe (II) and Al (III) dissolved in the solution. Upon reaching the desired value of Mn concentration of 85 gpl, the leaching is stopped, and the solution was allowed to stabilize.

The leach solution was subjected to filtration through filter press for solid liquid separation and cake washing was carried out to wash out manganese values from the solid cake. The wash liquor was separately recycled in subsequent batch.

The leach liquor obtained was subjected to purification by adding additive mixture of oxide (about 30 wt% to 40wt% of hydrogen peroxide) and acid. Subsequently, hydrated lime slurry of about 20 wt % was added and pH of the solution was increased to about 5.5-6.0 to precipitate iron, and aluminium as hydroxide cake. This purification of leach liquor led to pregnant leach solution (PLS). Table 2 provides chemical analysis of PLS

Table 3 provides chemical analysis of the solution after removal of iron from PLS through filtration.

Table 3 Further, the PLS was subjected to purification through sulphidization by addition of about 30 wt% of sodium hydro sulphide with continuous monitoring of Eh and pH for about 1 to 4 hours to remove heavy metals, such as zinc copper, nickel, cobalt and arsenic. Table 4 provides chemical analysis of solution after sulphidization.

Table 4

Purified PLS is subjected to manganese sulphate preparation, wherein the PLS is adjusted and conditioned to pH of about 4.5 and further was to evaporation and crystallization to obtain manganese sulphate.

During this process there was no evidence of formation of dithionate.

Example 2: Recovering manganese (manganese carbonate) from low grade manganese ore lumps

The procedure under Example 1 was followed to obtain purified PLS.

The purified PLS was subjected to extracting manganese as manganese carbonate by increasing pH of the solution to about 8.0 by addition of alkali or ammonium carbonate.

Example 3: Recovering manganese (EMM) from low grade manganese ore lumps

The procedure under Example 1 was followed to obtain purified PLS.

The purified PLS was sent to electrowinning cell for production of manganese metal by electrodeposition. During the process about 0.5 gm additive was added and about 500 ppm SO2 was mixed to the solution and was sent to electrowinning circuit to obtain electric manganese metal (EMM).

The foregoing description of the specific embodiments reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Throughout this specification, the term ‘combinations thereof’ or ‘any combination thereof’ or ‘any combinations thereof’ are used interchangeably and are intended to have the same meaning, as regularly known in the field of patents disclosures.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.