Recovery of rare earths from the green lamp phosphor LaPO ₄ :Ce ³⁺ ,Tb ³⁺ (LAP) by dissolution in concentrated methanesulphonic acid

, LAP). The optimised conditions were afterwards applied to a real lamp phosphor waste residue, that was obtained after removal of yttrium and europium from lamp phosphor waste powder by a hydrometallurgical process. The leaching can be carried out at lower temperatures than digestion in concentrated sulphuric acid or fused alkali. The process takes advantage of the much higher solubility of the rare-earth methanesulphonates compared to the corresponding sulphates, so that solvent extraction can be performed directly on the leachate after dilution, without the need of several additional steps to convert the rare-earth sulphates into chlorides or nitrates.