| In the past 10 years,with the rapid development of new energy vehicles,the demand for new energy batteries has grown rapidly,and the market demand for battery-grade manganese sulfate as the precursor to new energy battery synthesis has also increased tremendously.Battery-grade manganese sulfate is prepared by continuously removing K+,Na+,Ca2+,Mg2+and heavy metal ions from industrial-grade manganese sulfate as raw material.Among these ions,the removal of calcium and magnesium ions is of paramount importance in the preparation of battery grade manganese sulfate.At present,the technology of removing calcium and magnesium ions for battery-grade manganese sulfate production at home and abroad has complicated and high energy consumption without economic feasibility for large batch production line.In this thesis,industrial-grade manganese sulfate was used as raw material and subjected to a combination of chemical pretreatment and chemical strengthening to obtain the standard of battery-grade manganese sulfate.The main ideas are:The first is the removal of calcium and magnesium ions from manganese sulfate solution.The second is the separation of manganese sulfate crystal from the treated manganese sulfate solution.It is concluded that the rates of calcium and magnesium removal from this experimental technical route reached 91.6%and 95.7%,respectively.The main findings are as follows:（1）In the chemical pretreatment section,the substance A was used as the filter medium,which can effectively filter out the insoluble and slightly soluble ultrafine calcium and magnesium flocs in the manganese sulfate solution.The mechanism of calcium and magnesium removal of substance A as a filter medium is:A was found to be a filter medium with a slightly soluble metal mineral chemical activity,the filterability of mineral pores,and strong natural surface adsorption.In addition,manganese dioxide,as an amphoteric oxide,exists in the form of a perovskite structure such as Ba Mn O3 or Sr Mn O3.As Ca,Mg,Ba,and Sr belong to the same main group,Ca2+and Mg2+are able to form Cax[AO3]y and Mgx[AO3]y perovskite structures.XRD analysis of the filtered A filter media showed that there are symbiotic forms of Ca[A]and Mg[A]can be formed by combining Ca2+and Mg2+in the filtered A.（2）Add complexing agent in recrystallization process.The complexants bound to calcium and magnesium ions in the manganese sulfate solution,forming stable calcium and magnesium complexes.This process reduced the concentration of magnesium and calcium ions in the solution and increased the yield of manganese sulfate crystal with less calcium and magnesium ions.In this stage,temperature used for the evaporation in the crystallization process is 100℃with complexants ratio B to C is 2:1.The concentration of complexant A added is 0.75 g/l,and complexant B is 0.15 g/l.（3）.It was found that the content of calcium and magnesium ions was reduced significantly after the combined with centrifugal separation after adding substance D in the double salt centrifugation section,calcium and magnesium ions were precipitated and separated in the form of Ca SO4?2H2O and Mg SO4?7H2O.The ions were precipitated by substance D without introducing new ions and some manganese ions form manganous oxide.Then the manganous oxide was dissolved in sulfuric acid and returned to the electrolyte for recycling.The double salt centrifugation was done by adding pure D to manganese sulfate solution,followed by adjusting the p H of manganese sulfate solution to p H>7.0 with 60℃reaction temperature.The mixture was centrifuged in 10000 RPM for more than 25 min.（4）This treatment used short experimental route and low energy consumption.After amplification experiment concluded:one chemical strengthening filtration,two recrystallization and one chemical pretreatment,the content of calcium and magnesium ions in the industrial-grade manganese sulfate could meet the requirements of Hg/t4823-2015 battery-grade manganese sulfate. |
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