Recovering rare earths,lithium and fluorine from rare earth molten salt electrolytic slag using sub-molten salt method

Viewing the problem of high ene rgy consumption in the process of recovering rare earths from rare earth molten salt electrolysis slag,an environmentally friendly and low carbon process by sub-molten salt decomposition was developed.The thermodynamic analysis of sub-molten salt reaction indicates that the recovery of rare earths from the slag using sub-molten salt medium is thermodynamically feasible.In this process,the rare earth fluoride and lithium in the slag are almost transformed into rare earth hydroxide,sodium fluoride and lithium hydroxide,fluorine and lithium are transferred into the washing solution,and the rare earths in the residues can be leached into solution by acid leaching.Under the optimum reaction conditions of reaction temperature 200℃,reaction time 3 h,NaOH initial concentration 80%,NaOH-Slag mass ratio 3:1,the leaching efficiency of rare earths,fluorine and lithium can reach to 99.05%,98.23% and 99.22%.After evaporation,the fluorine and lithium in the washing solution can be obtained in the forms of sodium fluoride and lithium fluoride,the recovery efficiency reach 95.5%and 92.8%,respectively.The RE oxides(99.53%) can be obtained from the leaching solution after precipitation and roasting.