Izumi Tsuboi

Recovery of Rare Metals from Coal Fly Ash

A process has been developed to recover several rare metals such as Li, B, V and Ga from coal fly ash. The process consists of three serial operations; two-stage leaching with H2SO4 of different concentrations in series; concentrating of rare metals in the leach liquor with functional resins; and purification of each metal by solvent extraction. Li and B could be leached with dilute acid, the other undesirable transition metals being left in the residue. The two metals were then concentrated, respectively, with ΛLD-MnO2 and glucamic type resin, followed by purifcation by solvent extraction, employing a mixture of LIX51 and TOPO, and 2-ethyl-1,3-hexanediol. Ga and V were leached with 1.5 mol/l H2SO4 from the solid residue of the first leaching, and both were then concentrated with iminodiacetic type functional resin. The two metals were isolated and purified by solvent extraction employing TOMAC or D2EHPA.