Conversion of cerium and lanthanum from rare earth polishing powder wastes to CeO2 and La0.6Ca0.4CoO3

In the present work, a feasible approach was developed for the recovery of cerium and lanthanum from rare earth polishing powder wastes to synthesize shape-controlled CeO2 and perovskite-type La0.6Ca0.4CoO3 powders. The process proposed here includes six steps: (i) Pre-roasting treatment, (ii) H2SO4 digestion and water leaching, (iii) double salt (NaRE(SO4)(2)center dot xH(2)O) precipitation, (iv) conversion of NaRE(SO4)(2)center dot xH(2)O into RE-carbonate, (v) oxidation and separation of cerium and lanthanum, and (vi) oxalic salt precipitation conversion and calcinations to synthesize CeO2 and glycine-nitrate combustion process to get La0.6Ca0.4CoO3.The recovery yield for the total process was 91.73% for cerium and 90.45% for lanthanum. In the preparation process of CeO2 and La0.6Ca0.4CoO3, CeO2 powders with controlled shapes were obtained by modifying the final pH value in the precipitate transformation from Ce(OH)(4) to cerium oxalate and subsequent calcinations. On the other hand, based on the polarization curves, the prepared La0.6Ca0.4CoO3 exhibited a good catalytic activity for oxygen reduction reaction, showing potential applications in zinc-air batteries.