Microwave-assisted leaching of rare earth elements (Y and Eu) from waste cathode ray tube phosphor

BACKGROUND Phosphor in discarded cathode ray tube (CRT) contained valuable metals, yttrium (Y) and europium (Eu), which are categorized as technology-critical elements (TCEs) in terms of their supply risk and importance in emerging technologies. Microwave-assisted leaching was applied to recover Y and Eu from waste CRT with sulfuric acid (H2SO4) solution as the leaching agent in the current study. It is aimed to develop an alternative leaching method of valuable metals from waste CRT phosphor. RESULTS The effects of microwave power and acid concentration on leaching efficiency of Y and Eu were investigated. Shrinking-core model could describe the leaching kinetics of Y and Eu well and it was controlled by chemical reaction and diffusion through the product layer. Higher leaching efficiency was found when microwave power increased from 200 to 600 W, and was also found as acid concentration increased from 0.5 to 2 mol L-1. Leaching efficiency of Y and Eu were 78.07% and 100%, respectively, for Y and Eu within 60 min at microwave power of 400 W, using 2 mol L-1 of H2SO4 at 10 g L-1 of solid to liquid ratio. Compared with conventional leaching, microwave-assisted leaching is an alternative technology that could shorten reaction time significantly. CONCLUSIONS The concentration of acid and microwave power affected microwave-assisted leaching of Y and Eu from waste CRT phosphor. Microwave-assisted leaching could be an alternative process for rare earth elements recovery. (c) 2019 Society of Chemical Industry