Mineral separation of manganese-containing ore

Abstract

A process (10) for extracting manganese from manganese-containing ore comprises roasting (12.2) a feed mixture of a particulate manganese-containing ore (26) comprising Mn and Fe and ammonium sulfate (24) at a first temperature T1 to provide a sulfonated mixture comprising MnSO4 (s) and FeSO4 (s). And roasting (12.3) the sulfonated mixture at a second temperature T2, which is higher than the first temperature T1, to form a leachable mixture (30) comprising MnSO4 (s) and Fe2O3 (s). MnSO4 (s) is leached (16) prior to Fe2O3 (s) from the leachable mixture (30) to provide a leach liquor (34, 38) rich in dissolved MnSO4.

Description

Technical Field

[0001] The present invention relates to the beneficiation of manganese-containing ores. In particular, the present invention relates to a method for extracting manganese from manganese-containing ores, and to manganese sulfate, manganese hydroxide and manganese oxide produced by the method. Background Art

[0002] MnSO4 is a valuable salt. In addition to the metal and alloy industry, the demand for MnSO4 is also growing in the electrochemical cell industry.

[0003] MnSO4 can be produced from manganese-bearing ores. South Africa accounts for about 78% of the world's manganese reserves, most of which are located in the Northern Cape Province. Typical manganese-bearing ores contain about 15% to about 50% Mn, in which manganese exists in the form of mixed oxides of different valences.

[0004] Many conventional processes are known in which manganese-containing ores are roasted (usually at a temperature of about 900° C. to about 1100° C. in the presence of carbon) to reduce the manganese in the ore (from Mn 3+ and Mn 4+ To Mn 2+ ), so that the reduced manganese can react with sulfuric acid (Mn 2+ Dissolved in sulfuric acid, while Mn 3+ and Mn 4+ will not dissolve). After leaching with sulfuric acid, solid impurities such as iron in the manganese-containing ore must be removed from the acidic manganese sulfate solution. Traditionally, this is done by alkaline precipitation using a precipitant such as calcium carbonate. However, if a precipitant containing calcium is used, gypsum (calcium sulfate) is formed. Not only does the gypsum have to be dumped (or cleaned and sold), but it is also difficult to wash the entrained manganese sulfate out of the gypsum. This often results in an undesirable reduction in manganese yield, i.e., manganese losses.

[0005] It would be desirable to have a process for extracting manganese from manganese-containing ores which would not suffer from at least some of the difficulties discussed above. Summary of the invention

[0006] According to the present invention, there is provided a method for extracting manganese from a manganese-containing ore, the method comprising:

[0007] roasting a feed mixture of a particulate manganese-containing ore containing Mn and Fe and ammonium sulfate at a first temperature T1 to provide a sulfonated mixture containing MnSO4(s) and FeSO4(s);

[0008] calcining the sulfonated mixture at a second temperature T2 higher than the first temperature T1 to form a leachable mixture comprising MnSO4(s) and Fe2O3(s); and

[0009] The MnSO4(s) is leached from the leachable mixture in preference to the Fe2O3(s) to provide a leachate enriched in dissolved MnSO4.

[0010] The method may comprise preventing or at least inhibiting the ingress of oxygen (eg air) into the atmosphere in which the feed mixture is roasted. In one embodiment of the invention, the feed mixture is therefore roasted in an atmosphere that is substantially free of oxygen.

[0011] "Essentially free of oxygen" means that, under steady state conditions of the process of the present invention, the atmosphere in which the feed mixture is roasted does not include free oxygen from the external environment of the apparatus in which the feed mixture is roasted, and the only free oxygen that may be present in the atmosphere in which the feed mixture is roasted is oxygen released or generated due to the decomposition of Fe2(SO4)3(s).

[0012] MnSO4 is typically leached from the leachable mixture using an aqueous lixiviant or aqueous solvent (eg, water).

[0013] The manganese-containing ore may have a Mn concentration of at least about 5 mass %, preferably at least about 10 mass %, and most preferably at least about 20 mass %. Typically, the Mn concentration of the manganese-containing ore does not exceed about 55 mass %.

[0014] The manganese-containing ore may have an Fe concentration of up to about 20 mass %, or up to about 15 mass %, or up to about 10 mass %. Typically, the Fe concentration in the manganese-containing ore is at least about 1 mass %.

[0015] Advantageously, MnSO4(s) is very soluble in water (i.e., about 70 g per 100 ml at 70°C), whereas Fe2O3(s) is insoluble in water. MnSO4 is leached from the leachable mixture using an aqueous leaching agent or aqueous solvent (e.g., water), thereby leaving a leach residue or tailings in which the mass ratio of Mn:Fe is much less than that in the leachate. In other words, the leachate is thus enriched in Mn relative to Fe, while the tailings are enriched in Fe relative to Mn.

[0016] The first temperature T1 may be in the range of about 300°C to about 550°C, preferably about 350°C to about 500°C, most preferably about 375°C to about 475°C, for example, about 450°C.

[0017] The second temperature T2 may be in the range of about 550°C to about 750°C, preferably about 600°C to about 725°C, most preferably about 650°C to about 700°C, for example, about 675°C.

[0018] In one embodiment of the present invention, a calciner (such as a rotary kiln, typically an externally heated or indirectly heated rotary kiln or calciner, etc.) is used to calcine the feed mixture and the sulfonated mixture during the calcination stage, wherein the calciner has a continuous calcination temperature increasing from the feed inlet calcination temperature to the leachable mixture discharge temperature, wherein at least one zone of the calciner has a calcination temperature corresponding to the temperature range of the first temperature T1, and at least one zone of the calciner has a calcination temperature corresponding to the temperature range of the second temperature T2.

[0019] Preferably, air is prevented or at least inhibited from entering the roasting furnace.

[0020] The roasting furnace may have at least one roasting temperature T having a temperature range lower than the first temperature T1. 初始 area.

[0021] Calcination temperature T 初始 It may be in the range of about 225°C to about 375°C, preferably about 250°C to about 350°C, most preferably about 275°C to about 325°C, for example about 300°C, provided that the temperature T employed is 初始 Lower than the first temperature T1 adopted.

[0022] The calcination temperature T 初始 The feed mixture is roasted at 40 °C for a period of about 30 minutes to about 360 minutes, preferably about 60 minutes to about 240 minutes, most preferably about 90 minutes to about 180 minutes, such as about 120 minutes.

[0023] The feed mixture may be roasted at the first temperature T1 for a period of about 30 minutes to about 360 minutes, preferably about 60 minutes to about 240 minutes, most preferably about 90 minutes to about 180 minutes, such as about 120 minutes.

[0024] The sulfonated mixture may be calcined at the second temperature T2 for a period of about 30 minutes to about 360 minutes, preferably about 60 minutes to about 240 minutes, most preferably about 90 minutes to about 180 minutes, for example about 120 minutes.

[0025] Without wishing to be bound by theory, the inventors believe that when the calcined carbon foam is heated to a temperature T1 or at a calcination temperature T2 in an atmosphere preferably substantially free of oxygen, the calcined carbon foam is heated to a temperature T3 or at a calcination temperature T4. 初始 When the mixture is calcined at the first temperature T1, the following decomposition and reduction reactions occur:

[0026] (NH4)2SO4(s)→NH3(g)+NH4HSO4(s) equation [1]

[0027] 3Mn x O y(s)+2NH3(g)→3xMnO(s)+N2(g)+3H2O(g),y=x+1Equation [2]

[0028] 3Fe x O y (s)+2NH3(g)→3xFeO(s)+N2(g)+3H2O(g),y=x+1Equation [3]

[0029] NH3(g) is a strong reducing agent, so the reduction reactions of Equations 2 and 3 occur at lower temperatures than the oxidation reactions employed in the process of the present invention.

[0030] The inventors also believe, without wishing to be bound by theory, that upon calcination at a first temperature T1 in an atmosphere preferably substantially free of oxygen, the following decomposition and oxidation / sulfonation reactions occur:

[0031] NH4HSO4(s)→NH3(g)+H2O(g)+SO3(g) equation [4]

[0032] MnO(s)+FeO(s)+2SO3(g)→MnSO4(s)+FeSO4(s) equation [5]

[0033] 2FeSO4(s)+2SO3(g)→Fe2(SO4)3(s)+SO2 equation [6]

[0034] At the second temperature T2, without wishing to be bound by theory, the inventors believe that the following decomposition reaction occurs:

[0035] Fe2(SO4)3(s)→Fe2O3(s)+3SO2(g)+1.5O2(g) equation [7]

[0036] Surprisingly, even though SO3(g) produced in the reaction of Equation 4 is highly oxidizing, Mn is not oxidized by SO3(g) compared to Fe, but instead water-soluble MnSO4 produced by the reaction of Equation 5 is still present. Therefore, it seems that SO3(g) selectively oxidizes FeSO4(s) over MnSO4(s).

[0037] Advantageously, at the second temperature T2, Fe2(SO4)3(s) decomposes, whereas MnSO4(s) does not decompose to any appreciable extent.

[0038] The method may include forming the feed mixture of particulate manganese-containing ore and ammonium sulphate.

[0039] Forming the feed mixture of particulate manganese-containing ore and ammonium sulphate may comprise mixing the particulate manganese-containing ore and particulate ammonium sulphate in a premixing stage.

[0040] Instead, forming the feed mixture of particulate manganese-containing ore and ammonium sulfate may include feeding the particulate manganese-containing ore and particulate ammonium sulfate into a roasting stage, for example, a roasting stage using a rotary kiln, and mixing the particulate manganese-containing ore and ammonium sulfate in the roasting stage.

[0041] The D90 particle size of the particulate manganese-containing ore may be in the range of about 25 μm to about 500 μm, preferably about 45 μm to about 250 μm, most preferably about 75 μm to about 212 μm, for example about 106 μm.

[0042] The D90 particle size of the particulate ammonium sulfate may range from about 25 μm to about 500 μm, preferably from about 45 μm to about 250 μm, most preferably from about 75 μm to about 212 μm, for example about 106 μm.

[0043] The method may include removing waste gas generated by roasting the feed mixture and roasting the sulfonation mixture. The waste gas may include H2O(g), N2(g), SO2(g) and O2(g).

[0044] The exhaust gas may also include SO3(g) and NH3(g).

[0045] The method may include cooling a leachable mixture obtained by roasting the sulfonation mixture at the second temperature T2, and then leaching MnSO4(s) from the leachable mixture.

[0046] The leachable mixture may be cooled to a temperature T3 in the range of about 15°C to about 60°C, preferably about 20°C to about 50°C, most preferably about 25°C to about 40°C, for example about 30°C.

[0047] Typically, the leachable mixture is cooled using water as a coolant, such as in a jacketed auger, where cooling water is passed through the jacket.

[0048] As indicated above, MnSO4(s) may be leached from the leachable mixture using an aqueous lixiviant or solvent at a temperature of about 50°C to about 90°C, preferably about 60°C to about 80°C, for example about 70°C.

[0049] The particulate manganese-containing ore and ammonium sulfate may be present in the feed mixture in a mass ratio of ore to ammonium sulfate of from about 1:1 to about 1:4, typically from about 1:2 to about 1:3. As will be appreciated, however, the desired mass ratio of ore to ammonium sulfate depends, among other factors, on the concentrations of Mn, Ca, Mg and Fe in the manganese-containing ore, and the excess ammonium sulfate required to achieve the desired manganese yield.

[0050] The leachable mixture may be leached for a leaching period of about 15 minutes to about 180 minutes, preferably about 30 minutes to about 120 minutes, most preferably about 45 minutes to about 90 minutes, for example about 60 minutes. In other words, during the leaching stage, the residence time of the leachable mixture may correspond to the leaching period.

[0051] Typically, the method comprises separating the leachate from the leach residue. The separation may be performed in any suitable solid-liquid separation manner, for example using filtration.

[0052] The method may include precipitating Mn(OH)2 from the leachate. Mn(OH)2 can be readily precipitated from the leachate using NH4OH or NH3(g) to produce a Mn(OH)2 precipitate and a (NH4)2SO4 solution. This precipitated MnO2 can be reacted with sulfuric acid to produce, for example, manganese(II) sulfate monohydrate of excellent purity suitable for use in electrochemical cells.

[0053] The method may include producing (NH4)2SO4 crystals or powder from (NH4)2SO4 solution, for example, by membrane separation and evaporation.

[0054] The method may include recovering (NH4)2SO4 crystals or powder obtained from the (NH4)2SO4 solution, ie, (NH4)2SO4(s), to form part of the feed mixture.

[0055] The process of the present invention can be carried out batchwise, semi-batchwise or as a continuous process.

[0056] The present invention extends to MnSO4 or Mn(OH)2 or MnO2 produced by a manufacturing process comprising a process as hereinbefore described for extracting manganese from a manganese-containing ore. DETAILED DESCRIPTION

[0057] The invention will now be described, by way of example only, with reference to the following examples and a single schematic diagram illustrating one embodiment of a continuous process for extracting manganese from a manganese-containing ore according to the invention.

[0058] Example

[0059] Manganese extraction tests were conducted using manganese-containing ores having compositions as listed in Table 1.

[0060] Table 1

[0061]

[0062]

[0063] 250 g of the manganese-containing ore in Table 1 was ground to 106 μm. Similarly, 250 g of (NH4)2SO4 was ground to 106 μm. The two powders of 106 μm were then blended to form a mixture, which was added to an open SiC crucible. The mixture was fired at 400°C for 30 minutes, and a substantially oxygen-free atmosphere was quickly provided in the crucible due to the release of the gas displacing the air, and then fired at 450°C for 1 hour, at 500°C for 1 hour, and finally at 670°C for 1 hour. 323.5 g of red powder was recovered.

[0064] 500 ml of water was added to the red powder to form a suspension, and the temperature of the suspension was raised to 60-70° C. After stirring for 15 minutes, the suspension was filtered and washed. 600 ml of manganese sulfate leachate was collected (refer to Table 1 for leachate composition). Manganese units collected from the theoretical amount of 2.5×42.7=106.75 g of manganese = 87100 mg / l×0.6l=52.26 g. Thus, 49% manganese recovery was achieved.

[0065] It can be seen from Table 1 that not only the Fe concentration in the leaching solution is reduced, but also some other harmful elements are reduced. The Mn / Mg mass ratio remains almost unchanged.

[0066] Repeating the experiment with 1 part ground ore: 2 parts ground (NH4)2SO4 achieved a manganese recovery of 76%. By varying the experimental conditions, for example by further increasing the mass ratio of manganese-containing ore: ammonium sulfate, it was demonstrated that >95% manganese recovery could be obtained.

[0067] Referring to the drawings, reference numeral 10 generally shows an embodiment of a continuous method for extracting manganese from manganese-containing ores according to the present invention. The method 10 generally comprises: a roasting stage, which comprises a slightly inclined externally heated or indirectly heated rotary kiln 12 (commonly referred to as a rotary calciner), a cooler 14; a leaching stage, which comprises a leaching vessel 16, a first filter 18, a precipitator 20 and a second filter 22.

[0068] The rotary kiln 12 is provided with an ammonium sulfate feed line 24 and a granular manganese-containing ore feed line 26. An exhaust gas extraction line 28 is provided near the discharge end of the rotary kiln 12.

[0069] A leachable mixture delivery line 30 leads from the rotary kiln 12 to the cooler 14 and from the cooler 14 to the leaching vessel 16. The leaching vessel 16 is a stirred vessel equipped with a mechanical stirrer and is also equipped with a water feed line 32.

[0070] A slurry delivery line 34 leads from the leach vessel 16 to the first filter 18 which is provided with a tailings removal line 36 and a filtrate delivery line 38 .

[0071] The filtrate delivery line 38 leads to the precipitator 20 , which is also provided with an NH 3 (g) feed line 40 and a slurry delivery line 42 .

[0072] The slurry delivery line 42 leads to the second filter 22 , which is provided with a Mn(OH) 2 precipitate withdrawal line 44 and an ammonium sulfate solution withdrawal line 46 .

[0073] In order to extract manganese from the manganese-containing ore (which also contains iron), a manganese-containing ore powder having a D90 particle size of about 106 μm is continuously fed into the rotary kiln 12 by means of a granular manganese-containing ore feed line 26. At the same time, ammonium sulfate powder having a D90 particle size of about 106 μm is continuously fed into the rotary kiln 12 by means of an ammonium sulfate feed line 24. The mass ratio of the powdered manganese-containing ore to the ammonium sulfate powder fed to the rotary kiln 12 depends on the composition of the manganese-containing ore. For the ores shown in Table 1, the mass ratio is about 1:2.4.

[0074] The mass ratio required for the manganese-containing ore in Table 1 can be determined as follows (based on 100 grams of manganese-containing ore):

[0075] Fe 13.2% required to form Fe2(SO3)3 = 0.236 mol × 1.5 = 0.354 mol SO3

[0076] Ca 5.3% required to form CaSO4 = 0.133 mol × 1 = 0.133 mol SO3

[0077] Mg 0.4% required to form MgSO4 = 0.017 mol × 1 = 0.017 mol SO3

[0078] Mn 42.7% required to form MnSO4 = 0.776 mol × 1 = 0.776 mol SO3

[0079] Ba required to form BaSO4 1.36% = 0.010 mol × 1 = 0.01 mol SO3 (Ba is not shown in Table 1)

[0080] Total SO3 required = 1.29 mol

[0081] Therefore, 100g of manganese-containing ore feed requires 1.29mol (NH4)2SO4×132g / mol=170.28g+15% of the excess used in the experiment=about 200g (NH4)2SO4, that is, the mass ratio of manganese-containing ore:ammonium sulfate is about 1:2.

[0082] An efficiency or Mn yield of about 80% was experimentally achieved. By using 20% ​​more (NH4)2SO4, it is believed that the sulfonation reaction will proceed almost to completion. This provides the required manganese-containing ore:ammonium sulfate mass ratio of about 1:2×1.2=1:2.4.

[0083] NH3(g) will always be present in excess, since for every mol SO3(g) released in the rotary kiln 12, 2 mol NH3(g) will be released (see Eq. 1 + Eq. 4).

[0084] The granular manganese-containing ore and ammonium sulphate are fed from a hopper (not shown) through an inlet seal (not shown, which is normally only used when the hopper does not provide an adequate seal against air ingress) to inhibit air from entering the rotary kiln 12.

[0085] In the rotary kiln 12, the particulate manganese-containing ore and the ammonium sulfate powder are mixed due to the rotation of the rotary kiln 12, and the resulting mixture is roasted in an atmosphere substantially free of oxygen over most of the length of the rotary kiln 12 as the mixture travels through the rotary kiln 12 due to the rotation of the rotary kiln and the slight inclination of the rotary kiln 12 relative to the horizontal plane.

[0086] In the inlet region 12.1 of the rotary kiln 12, the calcination temperature T is usually in the range of about 300° C. to about 350° C. 初始 The mixture is roasted or subjected to pyrolysis conditions (i.e., in an atmosphere substantially free of oxygen) for a period of about 60 minutes. As the mixture advances toward the discharge end of the rotary kiln 12, the mixture is roasted in the middle zone 12.2 at a first temperature T1, typically in the range of about 400° C. to about 500° C., for a period of about 180 minutes. Thereafter, the mixture enters the end zone 12.3 of the rotary kiln 12 near the discharge end of the rotary kiln 12. In the end zone 12.3, the mixture is roasted at a second temperature T2, typically in the range of about 550° C. to about 675° C., for a period of about 120 minutes. Thus, the total residence time of the material passing through the rotary kiln 12 is typically about 360 minutes.

[0087] In inlet region 12.1, ammonium sulfate decomposes in situ in a substantially oxygen-free atmosphere, possibly according to equation 1 described above, to form ammonia, which then reacts with manganese oxide and iron oxide, reducing these oxides, possibly according to equations 2 and 3 described above. Nitrogen and water vapor escape, and these gases, together with any unreacted ammonia, are removed through waste gas removal line 28.

[0088] In the intermediate region 12.2, in an atmosphere still substantially free of oxygen, more gaseous ammonia and sulfur trioxide are produced, possibly according to Equation 4 described above, and MnO(s) and FeO(s) react with sulfur trioxide to form MnSO4(s) and FeSO4(s), believed to be according to Equation 5 described above. FeSO4(s) further reacts with sulfur trioxide to form Fe2(SO4)3(s), believed to be according to Equation 6 described above.

[0089] In the end zone 12.3, it is believed that Fe2(SO4)3(s) may decompose according to equation 7 described above, thereby producing Fe2O3(s), SO2(g) and gaseous oxygen. SO2(g) and oxygen, water vapor and any unreacted sulfur trioxide are also removed from zones 12.2 and 12.3 by means of an offgas removal line 28.

[0090] As will be appreciated, instead of using a single rotary kiln 12 with multiple temperature zones, separate rotary kilns or other roasters may be used to roast the feed mixture and the sulfonation mixture at different temperatures. As will be appreciated, one advantage of using separate rotary kilns or other roasters is that it will be easier to eliminate oxygen from the atmosphere in which the feed mixture is roasted because the atmosphere in which the feed mixture is roasted can be separated from the atmosphere that decomposes the Fe2(SO4)3(s) and therefore may contain oxygen released by the decomposition of the Fe2(SO4)3(s).

[0091] The leachable mixture is withdrawn from the rotary kiln 12 through a discharge seal (not shown) and conveyed to the cooler 14 via the leachable mixture conveying line 30, wherein the leachable mixture is cooled to a temperature of about 30° C. using plant cooling water in an indirect heat transfer device and then conveyed to the leaching vessel 16 via the leachable mixture conveying line 30. Instead of or in addition to using a separate cooler 14, the rotary kiln 12 may have an integrated cooling zone.

[0092] Water is fed into the leaching vessel 16 by means of a water feed line 32 and mixed with the leachable mixture using a mechanical agitator of the leaching vessel 16. Typically, the leaching of the leachable mixture in the leaching vessel 16 is carried out using water as a leaching agent or solvent at a temperature of about 60° C. to 70° C. If desired, the leaching vessel 16 can therefore be a heated vessel. Alternatively, the leachable mixture and the water fed into the leaching vessel 16 can be at a sufficiently high temperature to ensure that the leaching is carried out at the desired temperature.

[0093] In the leach vessel 16, water leaches MnSO4(s) from the leachable mixture. The leachable mixture has a residence time of about 60 minutes in the leach vessel 16 and is then transferred to the first filter 18 as a slurry via the slurry transfer line 34.

[0094] In the first filter 18, the leach residue or tailings is separated from the slurry and removed by means of a tailings removal line 36. A leachate or filtrate rich in dissolved manganese sulfate is removed from the first filter 18 and transferred to the precipitator 20. As will be appreciated, since manganese sulfate is very soluble in water compared to FeSO3(s) which is substantially insoluble in water, the leach residue or tailings removed by means of the tailings removal line 36 is depleted in manganese sulfate, while the leachate or filtrate transferred to the precipitator 20 by means of the filtrate transfer line 38 is rich in magnesium sulfate, with most of the FeSO3(s) entering the leach residue or tailings.

[0095] In the embodiment of the process of the present invention illustrated in the figure, Mn(OH)2 is precipitated from the leachate fed to the precipitator 20. This is achieved by feeding gaseous ammonia to the precipitator 20 via the NH3(g) feed line 40 and precipitating Mn(OH)2. Although not shown, the precipitator 20 may be a stirred vessel.

[0096] The slurry of the Mn(OH)2 precipitate is transported to the second filter 22 via the slurry transport line 42, where the Mn(OH)2 precipitate is separated from the ammonium sulfate solution and removed via the Mn(OH)2 precipitate removal line 44. The ammonium sulfate solution is removed via the removal line 46.

[0097] The withdrawn ammonium sulfate solution may be processed, for example, by membrane separation and evaporation to produce ammonium sulfate crystals or powder, which are then recycled to the rotary kiln 12 as part of the ammonium sulfate in the ammonium sulfate feed line 24 .

[0098] The Mn(OH)2 withdrawn by means of the Mn(OH)2 precipitate withdrawal line 44 can be treated to convert the Mn(OH)2 into very pure MnO2. The resulting MnO2 can be reacted with sulfuric acid to produce, for example, manganese(II) sulfate monohydrate having excellent purity suitable for use in electrochemical cells.

[0099] As illustrated, process 10 advantageously does not require digestion of the roasted manganese-containing ore or concentrate with sulfuric acid. As illustrated, process 10 advantageously also does not require alkaline precipitation of soluble impurities such as Fe. Importantly, as illustrated, process 10 also allows for recovery of the bulk reagent (ammonium sulfate).

[0100] Manganese-containing ores typically contain high concentrations of Ca and Mg (see, e.g., Table 1). In the method of the present invention, as illustrated, so-called dead burnt gypsum or dead burnt plaster is advantageously formed. Thus, although anhydrous CaSO4 is formed in the method of the present invention, when leached with water, CaSO4 will not rehydrate to form CaSO4·2H2O. This greatly facilitates aqueous leaching, because CaSO4·2H2O acts as a sponge that will undesirably capture valuable MnSO4. Similar problems arise in conventional processes due to the formation of silica gel that is difficult to remove by filtration, but advantageously, in the method of the present invention, as illustrated, SiO2 that is easily removed by filtration is formed.

Claims

1. A method for extracting manganese from a manganese-containing ore, the method comprising: roasting a feed mixture of a particulate manganese-containing ore containing Mn and Fe and ammonium sulfate at a first temperature T1 to provide a sulfonated mixture containing MnSO4(s) and FeSO4(s); calcining the sulfonated mixture at a second temperature T2 higher than the first temperature T1 to form a leachable mixture comprising MnSO4(s) and Fe2O3(s); and The MnSO4(s) is leached from the leachable mixture in preference to the Fe2O3(s) to provide a leachate enriched in dissolved MnSO4.

2. A method according to claim 1, comprising preventing or at least inhibiting the ingress of oxygen into the atmosphere in which the feed mixture is roasted.

3. A method according to claim 1 or 2, wherein MnSO4(s) is leached from the leachable mixture using an aqueous leaching agent or an aqueous solvent.

4. The method according to any one of claims 1 to 3, wherein the first temperature T1 is in the range of 300°C to 550°C. The method according to claim 4 , wherein the first temperature T1 is 350° C. to 500° C., or 375° C. to 475° C.

6. The method according to any one of claims 1 to 5, wherein the second temperature T2 is in the range of 550°C to 750°C. 7 . The method according to claim 6 , wherein the second temperature T2 is 600° C. to 725° C., or 650° C. to 700° C.

8. The method according to any one of claims 1 to 7, wherein the feed mixture and the sulfonated mixture are roasted in a roasting furnace in the roasting stage, wherein the roasting furnace has a continuous roasting temperature increasing from a feed inlet roasting temperature to a leachable mixture discharge temperature, wherein at least one zone of the roasting furnace has a roasting temperature corresponding to the temperature range of the first temperature T1, and at least one zone of the roasting furnace has a roasting temperature corresponding to the temperature range of the second temperature T2.

9. The method according to claim 8, wherein the roasting furnace has at least one roasting temperature T having the temperature range lower than the first temperature T1. 初始 The calcination temperature T 初始 In the range of 225°C to 375°C.

10. The method according to claim 9, wherein the calcination temperature T 初始 250℃ to 350℃.

11. The method according to claim 9, wherein the calcination temperature T 初始 The temperature T is 275℃ to 325℃. 初始 Lower than the first temperature T1 adopted.

12. The process according to any one of claims 1 to 11, wherein the particulate manganese-containing ore and the ammonium sulphate are present in the feed mixture in a mass ratio of ore:ammonium sulphate of from 1:1 to 1:

4.

13. The process of claim 12, wherein the particulate manganese-containing ore and the ammonium sulphate are present in the feed mixture in a mass ratio of ore:ammonium sulphate of 1:2 to 1:

3.

14. A method according to any one of claims 1 to 13, comprising precipitating Mn(OH)2 from the leachate using NH4OH or NH3(g) to produce a Mn(OH)2 precipitate and a (NH4)2SO4 solution.

15. The method according to claim 14 comprises preparing (NH4)2SO4 crystals or powder from the (NH4)2SO4 solution, and recycling the (NH4)2SO4 crystals or powder obtained from the (NH4)2SO4 solution, i.e. (NH4)2SO4(s), to form part of the feed mixture.

16. MnSO4 or Mn(OH)2 or MnO2 produced by a manufacturing process comprising the method according to any one of claims 1 to 15.

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