A hydrometallurgical method of energy saving type for separation of rare earth elements from rare earth polishing powder wastes with middle fraction of ceria

This study described a hydrometallurgical method to investigate the separation of rare earth elements（REEs）from rare earth polishing powder wastes（REPPWs）containing large amounts of rare earth oxides with a major phase of CeO2 and minor phases of La2O3,Pr2O3,and Nd2O3 using a process devised by the authors.The suggested approach consisted of five processes：the synthesis of NaR E（SO4）2·xH2O from rare earth oxides in Na2SO4-H2SO4-H2 O solutions（Process 1）,the conversion of NaR E（SO4）2·xH2O into RE（OH）3 using NaO H（Process 2）,and the oxidation of Ce（OH）3 into Ce（OH）4 using air with O2 injection（Process 3）,followed by Processes 4 and 5 for separation of REEs by acid leaching using HCl and H2SO4,respectively.To confirm the high yield of NaR E（SO4）2·xH2O in Process 1,experiments were carried out under various Na2SO4 concentrations（0.4–2.5 mol/L）,sulfuric acid concentrations（6–14 mol/L）,and reaction temperatures（95–125 oC）.In addition,the effect of the pH value on the separation of Ce（OH）4 in HCl-H2 O solutions with Ce（OH）4,La-,Pr-,and Nd（OH）3 in Process 4 was also investigated.On the basis of above results,the possibility of effective separation of REEs from REPPWs could be confirmed.

Kinetics study on leaching of rare earth and aluminum from polishing powder waste using hydrochloric acid

In this study,a novel hydrometallurgical process consisting of hydrochloric acid three-stage countercurrent leaching and solvent extraction was proposed to recover rare earth oxide(REO)from the rare earth polishing powder waste(REPPW).The effects of HCl concentration,liquid-solid ratio(L/S ratio),temperature and time on the leaching yields of rare earths(in REO)and aluminum(in Al2O3)were studied.The result shows that the leaching yields of REO and Al2O3 are 90.96%and 43.89%respectively under the optimum leaching parameters of HCl concentration=8.00 mol/L,L/S ratio=4 mL/g,leaching temperature=353 K and leaching time=180 min.Meanwhile,the leaching kinetics of REO and Al2O3 were investigated in this study.The leaching behaviors of REO and Al2O3 follow a shrinking sphere/core model and the general leaching process is controlled by the surface chemical reaction.The leaching activation energies of REO and Al2O3 are 9.86 and 13.68 kJ/mol,respectively.The leaching yield of each substance in three-stage countercurrent leaching is improved substantially compared with single-stage leaching,with a change from 90.96%to 95.38%for REO and from 43.89%to 46.22%for Al2O3,respectively.Especially,the total concentration of REO in three-stage countercurrent leaching solution is greatly increased to above 300 g/L,and the acidity of which is decreased to ca.pH=2,which is conducive to subsequent solvent extraction directly.High purity REO(99.92%)is obtained by solvent extraction separation,oxalate precipitation and calcination.The total recovery yield of REO is 85.13%.

稀土抛光粉产业发展现状与前景

This article briefly introduces the current industrial development status of rare earth polishing powder at home and abroad,summarizes and classifies the types and production processes of existing rare earth polishing powder,analyzes its technical status and existing problems,and the application prospects of rare earth polishing powder.