Purification of MnSO4 solution

Abstract

The method (10) for purifying the MnSO4 solution (34) comprises: (i) removing all of the MgSO4 solution present as an impurity; 2+ Cations and Ca 2+ The method includes the step (12) of precipitating impurities from the MnSO4 solution in the presence of a stoichiometric excess of fluoride anions (36), calculated based on the amount of fluoride anions required to react with the cations to produce CaF2 and MgF2, and (ii) in the presence of sulfide anions (52). The precipitation can be accomplished at a pH greater than 4 to produce a slurry or suspension (54) containing a purified MnSO4 solution as a carrier medium and a suspended precipitate containing MnS, MnF2, CaF2, and MgF2. The slurry or suspension is then separated (20) into a purified MnSO4 solution (56) and a precipitate (58), which is then reacted (24) with a non-MnSO4 SO4 salt (62) in a solid-state reaction to produce MnSO4 regenerated from the MnS and MnF2. The regenerated MnSO4 is recycled (76) to the purified MnSO4 solution (34), reducing Mn losses and improving MnSO4 yield.

Description

[Technical field]

[0001] The present invention relates to MnSO 4 The present invention relates to the purification of solutions. Specifically, the present invention relates to the purification of solutions. 4 The present invention relates to a method for purifying a solution. [Background technology]

[0002] High purity MnSO 4 The solution contains certain low levels of contaminants such as Ca, Co, Fe, Mg, Ni, and Zn, as well as MnSO with minimal Mn concentration. 4 The solution is commercially important for use, for example, in electrochemical cells and batteries. 4 Although various methods exist for purifying solutions, they tend to be cumbersome and expensive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] South African Provisional Patent Application No. 2022 / 05305 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional MnSO 4 MnSO is less cumbersome to handle and more economical than solution purification methods. 4 A method of purification of the solution may be desirable. [Means for solving the problem]

[0005] According to the present invention, MnSO 4 1. A method for purifying a solution, comprising the steps of: (i) MnSO as an impurity 4 All the Mg present in the solution 2+ Cations and Ca 2+ Reacts with cations to form CaF 2 and MgF 2in the presence of a stoichiometric excess of fluoride anions, calculated based on the amount of fluoride anions required to produce (ii) in the presence of sulfide anions, At pH above 4, MnSO 4 Precipitating impurities from the solution; Purified MnSO as a carrier medium 4 Solution, as well as MnS and MnF 2 , CaF 2 and MgF 2 producing a slurry or suspension comprising a suspended precipitate comprising: The slurry or suspension is added to the purified MnSO 4 Separating the precipitate into a solution and the precipitate; The precipitate is formed by solid-state reaction. 4 Other than SO 4 React with salts (sulfates) to produce MnS and MnF 2 Regenerated MnSO 4 and Regenerated MnSO 4 Purified MnSO 4 Reduce Mn loss by recycling to the solution, and MnSO 4 Yield-improving process A method is provided that includes: [Brief description of the drawings]

[0006] [Figure 1] 1 illustrates an embodiment of a method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] MnSO 4 The solution may be a pregnant leach solution.

[0008] MnSO 4 The solution may be contaminated with Ca, Co, Fe, Mg, Ni and Zn as impurities. Other contaminants may include Cu, K, Na, Si, Al, Sr and Pb.

[0009] In one embodiment of the present invention, MnSO 4 The solution is a leachate obtained from a roasting and leaching process, for example the roasting and leaching process for removing manganese from manganese-containing ores disclosed in South African Provisional Patent Application No. 2022 / 05305.

[0010] Typically, the method involves the use of MnSO 4 This includes adding a base to the solution to ensure the pH is above 4.

[0011] The base is NH 4 OH, e.g. 25%NH 4 OH solution. Advantageously, in the process of the invention, 4 The ammonium salts formed as a result of the addition of OH are decomposed downstream to produce a treatable gas.

[0012] Preferably, MnSO 4 The pH is adjusted to between about 5 and about 8, more preferably between about 5 and about 7, during precipitation of impurities from the solution.

[0013] A stoichiometric excess of fluoride anions can be obtained by adding a source of stoichiometric excess of fluoride anions, such as a water-soluble fluoride salt or hydrofluoric acid, to MnSO. 4 Preferably, a stoichiometric excess of fluoride anion is produced in solution, since it is usually less hazardous than a stoichiometric excess of a water-soluble fluoride salt, such as hydrofluoric acid, e.g., NH 4 It is produced by adding F·HF.

[0014] Typically, the method involves the use of MnSO 4 During precipitation of impurities from solution, MnSO 4 The step includes agitating the solution.

[0015] MnSO 4 The step of precipitating impurities from solution involves first adding a source of fluoride anions, followed by MnSO 4The step of ensuring a pH of greater than 4 by adding a base to the solution may be included.

[0016] Usually, mainly Ca and Mg cations are mixed with some MnF 2 In addition, a source of fluoride anions (i.e., CaF 2 or MgF 2 ), which constitutes the main component (i.e., the component with the highest concentration) of the precipitate. 2 Together with MnSO 4 It precipitates from the solution. However, MnSO 4 Other cations that are present in solution and form insoluble fluorides, e.g. insoluble Na 2 SiF 6 Na, which forms

[0017] The source of sulfide anions is MnSO 4 The sulfide anion can be produced by adding MnS, (NH 4 ) 2 S, H 2 S (gas) and mixtures of two or three thereof.

[0018] In a preferred embodiment of the invention, the source of sulfide anions is MnS.

[0019] Typically, the source of sulfide anions is MnSO 4 After the step of adding a base to the solution, MnSO 4 Thus, typically, in at least one embodiment of the present invention, MnSO 4 The process of precipitating impurities from a solution begins with the introduction of a source of fluoride anions in the form of MnSO 4 After the step of adding MnSO 4 The solution was then added base to ensure the pH was above 4, followed by addition of MnSO 4 Adding a source of sulfide anions to the solution.

[0020] MnS is from about 2 to about 0.0001 mole MnS / MnSO4 1. A concentration of between about 1 and about 0.0005 molar MnS / MnSO 4 liters of solution. 4 and more preferably between about 0.1 and about 0.001 moles MnS / liter of solution. 4 The concentration of the solution is, for example, about 0.06 molar MnS / MnSO 4 liter MnSO solution 4 can be added to the solution.

[0021] The slurry or suspension is added to the purified MnSO 4 The step of separating the solution and the precipitate can be accomplished using any conventional or suitable solid-liquid separation technique, such as filtration, gravity separation, or cyclone separation.

[0022] In a preferred embodiment of the present invention, the slurry or suspension is prepared by filtration of the purified MnSO. 4 The solution and the precipitate are separated. Advantageously, MnS is MnSO 4 CaF from solution 2 and MgF 2 filter aid for filtering small particles, and MnSO 4 It acts as a precipitating agent to precipitate transition elements such as Co, Fe, Ni, Cu and Zn from solution.

[0023] Typically, MnSO in the presence of fluoride anions 4 Precipitation of impurities from solution can be achieved at room temperature and atmospheric pressure.

[0024] MnSO in the presence of sulfide anions 4 Precipitation of impurities from solution can be achieved at a temperature in the range of about 5° C. to about 100° C., preferably in the range of about 30° C. to about 80° C., more preferably in the range of about 50° C. to about 70° C., for example at about 60° C.

[0025] Therefore, the method is 4 After addition of base to the solution, MnSO 4Heating the solution and introducing a source of sulfide anions, e.g., MnS, into the heated MnSO 4 The method may include adding to the solution.

[0026] The fluoride anion is MnSO 4 All the Mg present in the solution 2+ Cations and Ca 2+ Reacts with cations to form CaF 2 and MgF 2 In some embodiments, the fluoride anion may be present in a stoichiometric excess amount of at least 6 times the stoichiometric amount calculated based on the amount of fluoride anion required to produce

[0027] The fluoride anion is usually MnSO 4 All the Mg present in the solution 2+ Cations and Ca 2+ Reacts with cations to form CaF 2 and MgF 2 The fluoride anion may be present in a stoichiometric excess amount that is up to 9 times the stoichiometric amount calculated based on the amount of fluoride anion required to produce

[0028] The precipitate is formed by solid-state reaction. 4 Other than SO 4 The step of reacting with a salt may include drying the precipitate.

[0029] The precipitate is formed by solid-state reaction. 4 Other than SO 4 The step of reacting with a salt may include grinding the precipitate to reduce particle size.

[0030] The precipitate may be ground to give a particle size distribution with a D90 of less than about 1000 μm, preferably less than about 500 μm, more preferably less than about 250 μm, for example less than 106 μm.

[0031] Typically the precipitate is ground to give a particle size distribution with D10 of at least 10 μm.

[0032] The precipitate is formed by solid-state reaction. 4 Other than SO 4 The step of reacting with a salt is to form a precipitate by (NH 4 ) 2 SO 4 or NH 4 HSO 4 The method may include reacting with

[0033] SO 4 The salt may have a particle size distribution with a D90 of less than about 1000 μm, preferably less than about 500 μm, more preferably less than about 250 μm, for example less than 106 μm.

[0034] Usually, SO 4 The salt has a particle size distribution with a D10 of at least 10 μm.

[0035] Precipitates and SO 4 The solid state reaction with the salt may be carried out at a temperature within the range of about 375°C to about 525°C, preferably about 400°C to about 500°C, more preferably about 425°C to about 475°C, for example about 450°C.

[0036] SO 4 Salt (NH 4 ) 2 SO 4 If it is or contains MnF, the precipitate 2 is calculated according to reaction 1 as follows (NH 4 ) 2 SO 4 It may also react with. MnF 2 (Solid)+(NH 4 ) 2 SO 4 (Solid)→MnSO 4 (Solid)+NH 4 F HF (gas) + NH 3 (Gas)…(1)

[0037] SO 4 Salt (NH 4 ) 2 SO 4If the precipitate contains MnS, the MnS present in the precipitate is converted to MnS by reaction 2 (NH 4 ) 2 SO 4 It may also react with. MnS(solid)+4(NH 4 ) 2 SO 4 (Solid)→MnSO 4 (Solid)+4SO 2 (Gas) +4H 2 O(gas)+8NH 3 (Gas)…(2)

[0038] The method is to determine the precipitate 4 A part of the exhaust gas generated by the solid-phase reaction with salt is condensed to remove NH 4 The method may include the steps of condensing and recovering the F·HF, and producing a cooled exhaust gas.

[0039] The exhaust gases may be partially condensed at a temperature below about 240°C, preferably below about 200°C, more preferably below about 150°C, for example at about 100°C.

[0040] Typically, the exhaust gases will partially condense at a temperature of at least about 25°C.

[0041] The method comprises the steps of: extracting NH from the exhaust gas to act as a source of fluoride anions; 4 By recycling F HF, MnSO 4 The method may include providing a stoichiometric excess of fluoride anions to precipitate Ca and Mg impurities from solution.

[0042] The method comprises scrubbing the exhaust gas with an absorbent, e.g., water, to separate NH from the cooled exhaust gas. 3 The method may include a step of removing the gas.

[0043] The method comprises using SO to desulfurize the cooled exhaust gas. 2The method may include scrubbing the cooled exhaust gas in a scrubber. Alternatively, the method may include extracting NH 3 NH is used to extract 3 Scrubbers are also SO 2 Can act as a scrubber.

[0044] Regenerated MnSO 4 Recycled MnSO 4 MnSO as a solution 4 It may be recycled into the solution.

[0045] The method thus described is 4 Dissolve in water and reuse MnSO 4 The process may include a step of producing a solution. An insoluble waste stream may be produced which may be withdrawn from the process for disposal. This waste stream may act as a bleed stream to prevent or control the build-up of concentrations of Al, Ca, Co, Fe, K, Mg, Na, Ni and Zn in the process.

[0046] Regenerated MnSO 4 Dissolve in water and reuse MnSO 4 The step of forming the solution can be accomplished using water at room temperature.

[0047] Regenerated MnSO 4 Dissolve in water and reuse MnSO 4 The step of forming the solution can be accomplished by stirring.

[0048] The present invention was developed based on the following laboratory experiments and MnSO 4 BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the method according to the invention for purifying a solution is illustrated below by way of example with reference to the single drawing, in which: FIG.

[0049] Lab Experiments MnSO 4 Several laboratory experiments were performed to investigate various aspects of the method of the present invention for purifying a solution.

[0050] material A 4 liter volume of MnSO with the following analytical results shown in Table 1: 4 The pregnant leachate was used in the experiment.

[0051] [Table 1]

[0052] Fluoride Precipitation Fluoride precipitation was used to precipitate mainly Ca and Mg cations from the pregnant leach solution. Other cations were also precipitated as insoluble fluorides, e.g. Na 2 SiF 6 It is precipitated as MnF 2 Also precipitates.

[0053] MnF 2 CaF 2 and MgF 2 Although it is about 100 times more soluble than HF or NH 4 The addition of stoichiometric amounts of fluoride anions from a fluoride anion source such as F HF surprisingly produced MnSO 2 that met battery grade specifications. 4 No solution is given. Equilibrium exists and there is no problem with extremely pure MnSO 4 To make a solution, MnSO 4 All the Mg present in the solution 2+ Cations and Ca 2+ Reacts with cations to form CaF 2 and MgF 2 It has been determined that at least six and preferably seven times the stoichiometric amount of fluoride anion is required based on the amount of fluoride anion required to produce ammonium difluoride (NH 4 F HF) was chosen as the source of fluoride anion because it is less hazardous than HF solution. However, like HF, NH 4 F HF is not worth it, so NH 4 The consumption and loss of F HF should be minimized. Furthermore, for equilibrium, the MnF 2 Also precipitated partially, resulting in loss of Mn and MnSO 4The use of expensive reagents, the generation of hazardous fluoride waste, and the yield loss of Mn values ​​can all be mitigated by implementing at least some form of recycling.

[0054] Calculations for Fluoride Addition The first step is to add 4 liters of MnSO 4 The objective was to calculate the molar amounts of Mg and Ca in the solution. Ca = 0.593 g = 0.014825 mol Mg = 1.755 g = 0.072 mol Total moles (Ca+Mg) = 0.08705 moles / liter PLS.

[0055] and the NH required based on a stoichiometric excess of 7-fold. 4 The amount of F·HF was calculated as follows: Required NH 4 Amount of F HF added = 7 x 0.08705 mol / L x 57 g / mol NH 4 F HF x 4 liters = 138.93 g

[0056] experiment First, 4 liters of pregnant leachate was transferred into a 5 liter plastic polypropene beaker. 4 F HF was added with stirring. The pH dropped from about 6 or 7 to about 3. At this pH, no precipitation occurred. To this solution, 195 ml of NH 4 A solution of OH (25%) was added slowly with stirring until a pH of 5 was reached to produce a suspension. After stirring for 2 hours, the suspension was filtered. The resulting precipitate or filter cake was washed to remove MnSO trapped in the wet filter cake. 4 The washed filter cake was then dried at 150° C. to obtain 78.5 g of fluoride residue. The analytical results of the washed fluoride precipitate or filter cake, i.e., residue, are presented in Table 2.

[0057] [Table 2]

[0058] Fluoride precipitation occurs when MnSO 4 Although most of the Ca and Mg were removed from the pregnant leach solution, it was found that after filtration the remainder of the pregnant leach solution (i.e., the filtrate) still contained Ca and Mg levels above 50 ppm, causing the filtrate to not meet battery grade specifications which require Ca and Mg to be less than 50 ppm and a minimum Mn concentration of 32%. The reason for this is that MgF 2 and CaF 2 The solution to this problem presented as part of the present invention is to use CaF 2 and MgF 2 The addition of MnS acts as a filter aid to filter small particles of Co, Fe, Ni, Cu and Zn, and also acts as a precipitating agent to precipitate transition elements such as Co, Fe, Ni, Cu and Zn.

[0059] Sulfide Precipitation Just as fluoride precipitation forms an equilibrium, sulfide precipitation also forms an equilibrium. Experimentally, the equilibrium concentration is approximately 0.06 moles of MnS / liter of MnSO. 4 The pregnant leach liquor was found to be sufficient to act as a filter aid to assist in the removal of residual Ca and Mg, and is also sufficient to precipitate all of the transition elements, as can be seen from the calculations below.

[0060] Transition element calculations Moles of transition elements in 4 liters of pregnant solution: Co = 0.0983g = 0.0017 moles / liter Fe = 0.0139g = 0.00025 mol / L Ni = 0.0554g = 0.00095 moles / liter Zn = 0.0023g = 0.000034 moles / liter

[0061] Total moles of transition elements per 4 litres of pregnant solution = 0.011736 moles

[0062] Na 2 S(60%) and battery grade MnSO 4 The newly precipitated MnS was prepared via the reaction of MnS precipitates and Na 2 SO 4 A suspension of MnS (aq) was prepared. The MnS precipitate was filtered from the suspension and any Na 2 SO 4 Cleaned from contaminants.

[0063] A total of 0.24 moles of freshly precipitated wet MnS was added to the remaining 4 litres of pregnant leach liquor and heated to 60°C. After stirring at this temperature for 2 hours, the black precipitate was filtered to form a filter cake. The filter cake was washed to remove the trapped MnSO. 4 After removal and recycling, it was dried at 150°C, yielding 54 g of sulfide residue. Table 3 presents the analysis results of the sulfide precipitate. It is believed that the amount of MnS per litre of pregnant leach liquor could be further optimized to reduce the amount.

[0064] [Table 3]

[0065] Final, refined MnSO 4 The solution had the analytical results as shown in Table 4.

[0066] [Table 4]

[0067] The last row in Table 4 shows battery-grade MnSO 4 H 2 The maximum impurity levels of Ca, Co, Fe, Mg, Ni, and Zn that are permitted in O. The third row of Table 4 is the level of Ca, Co, Fe, Mg, Ni, and Zn impurities after precipitation of fluorides and sulfides.

[0068] Reuse of reagents From Table 1, the total Mn content of the pregnant leach solution can be calculated as follows: 4 liters x 127.6g / l = 510.4g Mn.

[0069] The Mn units lost to fluoride and sulfide precipitates can also be calculated as follows: Fluoride precipitate: 78.5g x 37.7% = 29.6g = starting MnSO 4 5.8% of the solution. Sulfide precipitate: 54g x 49.5% = 27g = starting MnSO 4 5.3% of the solution.

[0070] The fluoride precipitate and the sulfide precipitate were separately dry-ground to 106 μm. 67.2 g of the fluoride precipitate was mixed with 110 g of (NH 4 ) 2 SO 4 -106μm was added, blended and sintered in a 3Cr12 stainless steel tube at 450°C. The sintered product from the tube was soaked at temperature for 3 hours and cooled at room temperature to give a white cake weighing 101.6g. Nearly all of the product was found to be soluble in water.

[0071] MnF 2 and (NH 4 ) 2 SO 4 were reacted in the baked tube according to the solid-state reaction below. MnF 2 (Solid)+(NH 4 ) 2 SO 4 (Solid)=MnSO 4 (Solid)+NH 4 F HF (gas) + NH 3 (gas)

[0072] NH 4 F HF can be sublimed and condensed at temperatures below about 240 °C, e.g., below 100 °C, to recover approximately 90 to 99% of the available fluoride.

[0073] NH 3 (Gas) can be scrubbed, MnSO 4 Almost all of the (solid) was converted to MnSO 4 It can be reused back into the pregnant leachate.

[0074] For 20 g of sulfide precipitate, 130 g (NH 4 ) 2 SO 4 -106μm was added, blended and sintered in a 3Cr12 stainless steel tube at 450°C. The sintered product from the tube was soaked at temperature for 3 hours and cooled at room temperature to give a white cake weighing 29.6g. Nearly all of the product was found to be soluble in water.

[0075] MnS and (NH 4 ) 2 SO 4 were reacted in the baked tube according to the solid-state reaction below. MnS(solid)+4(NH 4 ) 2 SO 4 (Solid)=MnSO 4 (Solid)+4SO 2 (Gas) +4H 2 O(gas)+8NH 3 (gas)

[0076] 10 g samples of the white cake from both sintered products were dissolved in 50 ml water, filtered and analyzed, the analytical results are presented in Table 5.

[0077] [Table 5]

[0078] As described later, based on the analytical results shown in Table 5, the (NH 4 ) 2 SO 4 MnSO obtained from the solid-state reaction with 4The solution was used at the beginning of the experiment and was used as MnSO to recover the Mn value. 4 It is suitable for reuse in the pregnant leach solution.

[0079] Referring to the single figure, reference numeral 10 denotes MnSO 4 1 generally illustrates a method according to the present invention for purifying a solution. The process 10 is a continuous process and includes a precipitation stage 12 comprising a fluoride precipitation vessel 14, a pH adjustment vessel 16, and a sulfide precipitation vessel 18. The process 10 further includes a first filter 20, a drying and grinding stage 22, a rotary kiln 24, a dissolving vessel 26, a second filter 28, a cooling condenser 30, and an exhaust gas scrubber 32.

[0080] MnSO 4 A solution supply line 34 leads to the fluoride precipitation vessel 14 and also contains NH 4 The F·HF supply line 36 joins the fluoride precipitation vessel 14. An agitator 38 is provided in the fluoride precipitation vessel 14.

[0081] A solution transfer line 40 leads from the fluoride precipitation vessel 14 to the pH adjustment vessel 16, which is also equipped with an agitator 42. 4 An OH solution supply line 44 leads into the pH adjustment vessel 16 while a suspension transfer line 46 leads from the pH adjustment vessel 16 to the sulfide precipitation vessel 18 .

[0082] The sulfide precipitation vessel 18 is equipped with an agitator 48, a steam heating coil 50, and an MnS supply line 52.

[0083] A suspension transfer line 54 connects the sulfide precipitation vessel 18 to the first filter 20, which contains purified MnSO 4 A solution withdrawal line 56 and a filter cake transfer line 58 are provided. The filter cake transfer line 58 leads to the drying and grinding stage 22, which is provided with a pulverized precipitate withdrawal line 60 leading to the rotary kiln 24. The pulverized precipitate withdrawal line 60 contains (NH 4 )2 SO 4 Supply lines 62 join.

[0084] The rotary kiln 24 is a calcining kiln provided with an exhaust gas withdrawal line 64 and a sintered deposit withdrawal line 66 , which lead to the melting vessel 26 .

[0085] The dissolution vessel 26 is equipped with an agitator 68 and a water supply line 70 .

[0086] A suspension withdrawal line 72 connects the dissolution vessel 26 to the second filter 28, which is connected to a solid waste stream withdrawal line 74 and a MnSO 4 MnSO merging with solution supply line 34 4 A solution recycle line 76 is provided.

[0087] Process 10 is the process for the production of noble MnSO 4 or other MnSO containing impurities, inter alia, Ca, Co, Fe, Mg, Ni and Zn. 4 Used to purify solutions.

[0088] Noble MnSO 4 The leaching solution is MnSO 4 Solution supply line 34 supplies solution into fluoride precipitation vessel 14. A source of fluoride anions, i.e., NH 4 F HF, NH 4 F HF is fed into the fluoride precipitation vessel 14 via a feed line 36, and an agitator 38 is used to thoroughly mix the two feed streams to produce a well-mixed solution. 4 F HF is the noble MnSO 4 All Mg present as impurities in the leach solution 2+ Cations and Ca 2+ NH to ensure a stoichiometric excess of fluoride anions present in the fluoride precipitation vessel 14, equal to seven times the amount of fluoride anions required to react with the cations. 4 F·HF is supplied by a supply line 36 .

[0089] Although no visible fluoride precipitates in the fluoride precipitation vessel 14, the pH of the well mixed solution drops from about 6 or 7 to about 3. This well mixed solution with a pH of about 3 is then transferred by solution transfer line 40 to pH adjustment vessel 16 where a base, i.e., 25% NH 4 A sufficient amount of NH in the form of aqueous OH 4 OH to NH 4 OH solution is fed to pH adjustment vessel 16 by supply line 44 to raise the pH of the solution in pH adjustment vessel 16 to about 5. The higher pH in pH adjustment vessel 16 increases the pH of the CaF 2 , MgF 2 , and undesirable MnF 2 Fluorides such as sulfide, sulfur ions, etc. begin to precipitate. An agitator 42 is used to ensure that a suspension is formed and maintained in the pH adjustment vessel 16. The pH adjustment vessel is sized such that the average residence time is approximately 2 hours, after which the agitated suspension is transferred from the pH adjustment vessel 16 to the sulfide precipitation vessel 18 by a suspension transfer line 46.

[0090] Granular MnS is fed into sulfide precipitation vessel 18 via MnS feed line 52, and the suspension inside sulfide precipitation vessel 18 is agitated by agitator 48 and heated to about 60° C. by steam heating coils 50. Sulfides are precipitated in sulfide precipitation vessel 18, including sulfides of Ca, Mg, Co, Fe, Ni, and Zn. Thus, CaS precipitates and MgS precipitates are formed by the CaF 2 Precipitates and MgF 2 This also includes precipitates.

[0091] Particulate MnS is fed into sulfide precipitation vessel 18 at a ratio of about 0.06 moles of MnS per liter of suspension fed into sulfide precipitation vessel 18 by suspension transfer line 46.

[0092] The sulfide precipitation vessel 18 is sized to provide an average residence time of approximately 2 hours, after which the stirred suspension containing the suspended black precipitate is transferred by suspension transfer line 54 to the first filter 20, where the suspension is filtered to remove purified MnSO. 4 Refined MnSO extracted through extraction line 56 4 The solution or filtrate and the precipitate or filter cake are separated, which is MnF 2 , CaF 2 and MgF 2 and MnS, CaS, and MgS and transition metal sulfides and / or fluorides, which are removed by filter cake transfer line 58. Advantageously, MnS is 4 Small CaF precipitated from solution 2 and MgF 2 While acting as a filter aid for filtering out transition elements such as Co, Fe, Ni, Cu and Zn, it can also act as a precipitating agent for transition elements such as Co, Fe, Ni, Cu and Zn.

[0093] If desired or necessary, the filter cake may be washed with water in a conventional manner (not shown), e.g., to fluoride precipitation vessel 14, or to filter 20, or to dissolution vessel 26 with the filter cake wash water recycled to remove the captured MnSO. 4 can be extracted.

[0094] In the drying and grinding step 22, the filter cake or precipitate is dried in a conventional manner, for example at about 150° C., and then typically ground by dry grinding to a particle size distribution of D90 less than about 106 μm. The dried, ground precipitate is withdrawn by ground precipitate withdrawal line 60 and fed to the calcination rotary kiln 24. Granular (NH 4 ) 2 SO 4 Also, (NH 4 ) 2 SO 4 A feed line 62 feeds the rotary kiln 24 .

[0095] In the rotary kiln 24, the dried, crushed precipitate and granular (NH 4 ) 2 SO 4 are thoroughly mixed and heated to a high temperature of about 450 °C, while the MnF present in the dried, crushed precipitate is 2 and MnS, on the other hand (NH 4 ) 2 SO 4 With MnSO 4 This leads to the solid-state reaction according to reaction (1) and reaction (2) as described above to produce (solid).

[0096] After a reasonably long time at high temperature, e.g., about 3 hours, a solid material, i.e., MnSO 4 The sintered precipitate containing (solids) is withdrawn from the rotary kiln 24 by a sintered precipitate withdrawal line 66 and fed to the dissolution vessel 26. Water is also fed into the dissolution vessel 26 by a water supply line 70 with the resulting suspension formed in the dissolution vessel 26 being agitated by an agitator 68. Recycled MnSO 4 The solution is MnSO in water. 4 It is produced inside the dissolution vessel 26 as a result of dissolving (solid).

[0097] Reused MnSO 4 The suspension containing the solution is withdrawn from the dissolution vessel 26 by the suspension withdrawal line 72 and fed to the second filter 28, where the insoluble impurities are filtered off with recycled MnSO 4 It is separated from the solution and withdrawn via solid waste stream withdrawal line 74. Recycled MnSO 4 The solution is filtered through a second filter 28 to remove MnSO 4 MnSO 4 It is transported by the solution recycle line 76.

[0098] The exhaust gas from the rotary kiln 24 is withdrawn through an exhaust gas withdrawal line 64, cooled and partially condensed in the condenser 30. In the condenser 30, plant cooling water is used to condense a portion of the exhaust gas at a temperature of about 90° C. The condensed NH 4 F HF, NH 4 F HF is transported through the recycle line 78 and NH 4 The F HF feed line 36 joins the F HF feed line 36. In this manner, approximately 90% of the fluoride anions added to the process 10 are recovered and recycled to the fluoride precipitation vessel 14.

[0099] The cooled exhaust gas from the condenser 30 is transported by cooled exhaust gas line 80 to the exhaust gas scrubber 32, which extracts NH 3 (gas) and SO 2 Water is utilized via water supply line 82 for scrubbing the exhaust gas. The scrubbed exhaust gas is vented from the exhaust gas scrubber 32 to the atmosphere via vent line 84, while excess ammoniacal scrubbing solution is withdrawn via scrubber solution withdrawal line 86.

[0100] Although described as a continuous process, it can be understood that process 10 may be operated on a batch or semi-batch basis. For example, fluoride precipitation vessel 14, pH adjustment vessel 16 and sulfide precipitation vessel 18 may be combined into a single vessel operated on a batch basis.

[0101] Process 10 advantageously recycles a very large proportion of fluoride anions as described. By including process steps that limit Mn loss and recycle Mn (e.g., via rotary kiln 24, dissolution vessel 26, and second filter 28), process 10, as described, recycles MnSO 4 Advantageously, the process of the present invention increases the yield of noble MnSO 4Battery grade MnSO with less than 1 ppm Co, Fe, Ni and Zn, and less than 15 ppm Ca and Mg from the leach solution. 4 This allows the preparation of a solution. [Explanation of symbols]

[0102] 10 Process 12 Precipitation stage 14 Fluoride precipitation container 16 pH adjustment container 18 Sulfide precipitation vessel 20 First Filter 22 Crushing stage 24 Rotary Kiln 26 Melting container 28 Second Filter 30 Cooling condensation device 32 Exhaust gas scrubber 34 MnSO 4 Solution Supply Line 36NH 4 F HF supply line 38 Mixer 40 Solution transfer line 42 Mixer 44NH 4 OH solution supply line 46 Suspension Transfer Line 48 Mixer 50 Steam heating coil 52 MnS supply line 54 Suspension Transfer Line 56 Purified MnSO 4 Pulling line 58 Filter cake transfer line 60 Crushed Precipitate Extraction Line 62 (NH 4 ) 2 SO 4 Supply Line 64 Exhaust gas extraction line 66 Sintered Precipitation Drawing Line 68 Mixer 70 Water Supply Line 72 Suspension Pulling Line 74 Solid waste stream withdrawal line 76 MnSO 4 Solution Recycle Line 78NH 4 F / HF recycling line 80 Cooled exhaust gas line 82 Water Supply Line 84 Vent Line 86 Scrubber solution withdrawal line

Claims

1. MnSO ４ 1. A method for purifying a solution, comprising: (i) MnSO as an impurity ４ All Mg present in the solution ２＋ Cations and Ca ２＋ Reacts with cations to form CaF ２ and MgF ２ in the presence of a stoichiometric excess of fluoride anions, calculated based on the amount of fluoride anions required to produce (ii) in the presence of sulfide anions, At pH above 4, MnSO ４ Precipitating impurities from the solution; Purified MnSO as a carrier medium ４ Solution, as well as MnS, MnF ２ , CaF ２ and MgF ２ producing a slurry or suspension comprising a suspended precipitate comprising: The slurry or suspension is added to the purified MnSO ４ Separating the precipitate into a solution and the precipitate; The precipitate is formed by solid-state reaction into MnSO ４ Other than SO ４ React with salts (sulfates) to produce MnS and MnF ２ MnSO regenerated from ４ and Regenerated MnSO ４ Purified MnSO ４ Reduce Mn loss by recycling to the solution, and MnSO ４ Yield-improving process and

2. MnSO ４ 2. The method of claim 1 , wherein the solution is a pregnant leach solution.

3. MnSO ４ 10. The method of claim 1, comprising the step of adding a base to the solution to ensure a pH greater than 4.

4. MnSO ４ 10. The method of claim 1, wherein the pH is adjusted to between 5 and 8, or between 5 and 7, during precipitation of impurities from the solution.

5. A stoichiometric excess of fluoride anions is dissolved in a stoichiometric excess of a water-soluble fluoride salt or hydrofluoric acid in MnSO ４ The method of claim 1 , wherein the compound is produced by adding to a solution.

6. 6. The method of claim 5, wherein the stoichiometric excess of fluoride anion is produced by adding a stoichiometric excess of a water-soluble fluoride salt.

7. Water-soluble fluoride salts are NH ４ The method of claim 6, wherein the compound is F.HF.

8. The sulfide anion is MnS, (NH ４ ) ２ S, H ２ A source of sulfide anions selected from the group consisting of S (gas) and mixtures of two or three thereof is MnSO ４ The method of claim 1 , wherein the compound is produced by adding to a solution.

9. 9. The method of claim 8, wherein the source of sulfide anions is MnS.

10. MnSO ４ The step of precipitating impurities from a solution comprises first converting a source of fluoride anions into MnSO ４ After the step of adding to the solution, MnSO ４ After adding base to the solution to ensure the pH was above 4, MnSO ４ 10. The method of claim 1, further comprising the step of adding a source of sulfide anions to the solution.

11. The fluoride anion is MnSO ４ All Mg present in the solution ２＋ Cations and Ca ２＋ Reacts with cations to form CaF ２ and MgF ２ or a stoichiometric excess of at least 6 times the stoichiometric amount calculated based on the fluoride anion required to produce ４ The method of claim 1 , wherein the compound is in solution.

12. The precipitate is MnSO ４ Other than SO ４ The step of reacting with a salt is to form a precipitate (NH ４ ) ２ SO ４ or NH ４ HSO ４ The method of claim 1 , comprising reacting with

13. Precipitate SO ４ A part of the exhaust gas generated by the solid-phase reaction with salt is condensed to remove NH from the exhaust gas. ４ coagulating and recovering the F-HF; NH recovered from the exhaust gas to act as a source of fluoride anions. ４ By reusing F and HF, MnSO ４ Providing a stoichiometric excess of fluoride anions to precipitate Ca and Mg impurities from the solution. The method of claim 12 , comprising:

14. Precipitates and SO ４ 2. The method of claim 1, wherein the solid-state reaction with the salt is carried out at a temperature in the range of 375°C to 525°C, or in the range of 400°C to 500°C, or in the range of 425°C to 475°C.

15. Regenerated MnSO ４ However, recycled MnSO ４ MnSO as a solution ４ The method of claim 1 , wherein the solution is recycled.

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