Application Research Of Dibenzyl Phosphate Ester In Rare Earth Transformation And Recovery

Rare earth(RE)is an important strategic resource,the research and development of new clean production technology of rare earth has attracted wide attention.At present,the Baotou mixed rare earth ore mainly adopts the“third-generation sulfuric acid smelting process”.The methods of transformation and enrichment of rare earth sulfate in Baotou mine's water leaching solution are as follows:(1)Organic phosphoric acid and naphthenic acid solvent extraction method for transformation.Generally,in order to improve the extraction efficiency,the extractant needs to be saponified,which will produce saponification wastewater;and the extraction process needs to consume a large amount of volatile organic solvents.(2)Ammonium bicarbonate precipitation method for transformation will consume a large amount of ammonium bicarbonate and produce a large amount of ammonia nitrogen wastewater.In addition,the process of neutralization and impurity removal of Baotou mine water leaching solution produces a large amount of calcium and magnesium impurities.With the development of science and technology,the consumption of nickel-metal hydride(Ni MH)batteries has increased year by year,and the number of discarded Ni MH batteries has also increased rapidly.If the discarded batteries are not properly recycled,the release and diffusion of harmful substances in the batteries will endanger human health and seriously pollute the environment;not only that,it also causes a large amount of waste of rare earth and valuable metal resources in Ni MH batteries.Therefore,efficient and clean recycling of discarded Ni MH batteries becomes particularly important.In order to explore a low-consumption and low-polluting rare earth separation and recovery method,based on the new phosphate ester extraction-precipitation method,this article has developed a new process for rare earth separation without organic solvents and saponification;this method can not only be used for transformation and enrichment of Baotou rare earths mineral water leaching solution,also can be used to separate and recover rare earth in waste Ni MH batteries.In view of the large amount of calcium and magnesium impurities in the Baotou mine's water leaching solution and the ammonia nitrogen wastewater generated during the recycling process,this paper studies the process of dibenzyl phosphate transformation and enrichment of rare earth sulfate in Baotou Mine's aqueous leaching solution.The extraction-precipitation performance of dibenzyl phosphate(DBP),diphenyl phosphate(DPP),triphenyl phosphate(TPP),diphenylphosphinic acid(DPPO),1,1'-Binaphthyl-2,2'-diylhydrogenphosphate(DHGP)have been studied for rare earth.As the results show,the order of extraction ability is DBP>DPP>DHGP>DPPO>TPP;the formed rare earth complexes have good thermal stability;the precipitation rate of DBP to rare earth is about 100%,and Ca²⁺and Mg²⁺are hardly precipitated,which can be used to selectively separate rare earth and calcium,magnesium;the total stripping rate of rare earth with HCl can reach 98.74%,DBP can be recycled;DBP can transform and enrich rare earth sulfate into high concentration chloride(187 g/L).Regarding the importance of waste Ni MH battery recycling,this paper proposes a novel Ni MH battery recovery process,which uses 2 mol/L sulfuric acid leaching,and dibenzyl phosphate extraction-precipitation method to separate and recover rare earth from Ni MH leachate.First the optimal leaching conditions of Ni MH batteries were studied;then the precipitation(extraction)capabilities of DBP,DPP,TPP,P204,P507 and POAA on the waste Ni MH leaching solution were compared.DBP has high precipitation efficiency for La³⁺,Ce³⁺,Pr³⁺and Nd³⁺,which can reach 97.84%,100%,100%and99.77%,respectively;the precipitation efficiency of Mn²⁺,Co²⁺and Ni²⁺is less than1.75%;the mechanism of the reaction is indicated to cation exchange by the slope method and infrared spectra;The precipitation particle size of DBP-RE is much larger than those of NH₄HCO₃,H₂C₂O₄,Ca O,Mg O;DBP-RE can be stripped twice with 3mol/L HCl,the total stripping rate is 98.6%,DBP can be effectively used in the cycles.After 5 cycles,the RE precipitation efficiency of DBP is still higher than 98.39%.