Coupling mechanochemical conversion with AlCl3 dissolution for La selective recovery from ceria-based polishing powder waste

Abstract

This work designed an alternative green process for selective and efficient recovery of La from the ceria-based polishing powder waste (CPPW) using mechanochemical and AlCl₃ dissolution coupling methods. First, LaOF phase in the CPPW was decomposed and converted into LaO(OH) and La₂O₃ under the mechanical force with NaOH as a co-grinding reagent. Then, a low-cost and green concentrated AlCl₃ solution, was used to selective dissolution of La in the as-obtained mechanochemical conversion products. By optimizing the mechanochemical and AlCl₃ dissolution conditions, a high extraction efficiency of La (96.8 %) and a high separation factor of La and Ce (>8.5 × 10³) were both achieved. The AlCl₃ dissolution kinetics of La species were conformed to solid-film diffusion control. Finally, >98 % purity of La₂O₃ product was successfully recovered from the as-obtained La-loaded AlCl₃ solution through simple Na₂SO₄ precipitation, NaOH conversion and H₂C₂O₄ precipitation.