| Aiming at the problem of large amount of low-grade pyrolusite but low utilization rate in China,this paper studied and compared the reduction leaching characteristics of ferrous sulfate and ferrous sulfide on low-grade manganese oxide ore,and investigated the influence law of various factors on manganese leaching.In view of the difficulty of separating high concentration iron from manganese ore leaching solution,sodium sulfide was used as precipitant to remove iron,and the precipitate could be returned to the leaching process as reducing agent.The effects of various factors on the precipitation rate of iron and manganese in the process of sulfide precipitation were investigated.Compound extractant VS-101 was used as a new manganese extractant to extract and refine manganese ore leaching solution.The effects of various factors on manganese extraction rate and stripping were investigated,and battery grade manganese sulfate was successfully prepared.According to the chemical analysis results of the solution,using sodium sulfide to remove iron could selectively remove iron ions and control the loss rate of manganese by controlling the amount of sodium sulfide.Using sodium sulfide as precipitant to remove iron ions from manganese ore leaching solution,the optimized technical parameters were obtained:under the conditions that the amount of sodium sulfide was 1.5 times of the total iron in the solution,the temperature was 80℃,the reaction time was 1.0 h,the p H of the solution was 1.6,and the standing time was 1.0 h,the iron precipitation rate was 98.7%,the manganese precipitation rate was 4.2%,and the heavy metals were basically removed.The results of orthogonal experiment showed that with ferrous sulfate as reducing agent,the influence of various factors on manganese leaching rate was as follows:ferrous sulfate dosage>liquid-solid ratio>sulfuric acid dosage>temperature>leaching time.With ferrous sulfide as reducing agent,the influence of various factors on manganese leaching rate was as follows:ferrous sulfide dosage>temperature>sulfuric acid dosage>liquid-solid ratio>leaching time.Using ferrous sulfate as reducing agent to leach manganese from pyrolusite,the optimized technical parameters were as follows:at 90℃,the dosage of ferrous sulfate was 2.4 g/g ore,the dosage of sulfuric acid was 1.0 g/g ore,the leaching time was 30 min,the liquid-solid ratio was10 m L/g ore,and the stirring rate was 300 r/min,the manganese leaching rate was 93.6%.Using ferrous sulfide as reducing agent to leach manganese from pyrolusite,the optimized technical parameters were as follows:when the temperature was 90℃,the dosage of ferrous sulfide was 0.2 g/g ore,the dosage of sulfuric acid was 1.0 g/g ore,the leaching time was 60 min,the liquid-solid ratio was 10 m L/g ore,and the stirring rate was 300 r/min,the manganese leaching rate was 99.2%.Compared with ferrous sulfate,ferrous sulfide as reducing agent,the leaching rate of manganese was more affected by temperature and the amount of sulfuric acid,and the leaching reaction speed was slower,however,under the optimal leaching conditions,the leaching rate of manganese was about5%higher,and the iron content of leaching solution was lower.The main components of precipitation were Fe S2and Fe3O4,which also contain a small amount of Mn S and S.Fe3O4was oxidized by Fe S in the original precipitate.The precipitate could be used as reducing agent to leach manganese oxide ore,and the manganese leaching rate could reach more than 98%.Its reduction leaching effect was similar to that of ferrous sulfide.The new compound extractant named VS-101 was compared with traditional extractants P204 and P507 through theoretical analysis and experiment（one of the main components was used to represent VS-101）.VS-101 had higher HOMO（Highest Occupied Molecular Orbital）value and lower LUMO（Lowest Unoccupied Molecular Orbital）value,indicating that it had stronger electron donor ability than P204 and P507,and there was stronger induction effect in the molecule.Under certain experimental conditions,the extraction rate of manganese of VS-101could reach more than 95%,while under the same experimental conditions,the extraction rate of manganese of P204 and P507 was less than 70%.The effects of p H,extraction time,ratio,extractant concentration and saponification rate on the extraction rate were investigated.The optimized conditions were obtained:for 0.1 mol/L manganese sulfate solution,when 3<p H<5,phase ratio was 1:2,extractant volume concentration was 30%,saponification rate was 30%and extraction time was 15 min,the average manganese extraction rate was 91.3%.The purified liquid was extracted by two-stage countercurrent extraction by compound extractant VS-101,and the extraction rate of manganese ion was 94.0%.After two-stage washing and two-stage countercurrent stripping,the manganese stripping rate was 87.2%.Manganese sulfate was prepared after adsorption of activated carbon and evaporation.Through elemental analysis,the content of manganese in the product was 32.09%,and the content（wt%）of calcium,magnesium,potassium and sodium were respectively 2.8×10-3、7.9×10-3、4.1×10-3、5.6×10-3.The quality met the first-class requirements of the chemical industry standard manganese sulfate for batteries（HG/T 4823-2015）. |
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