Electrolytic Recovery of Tin from Printed Circuit Boards (PCBs) Disassembled from Waste Liquid Crystal Displays (LCDs): Selection of H<sub>2</sub>SiF<sub>6</sub> + H<sub>2</sub>SO<sub>4</sub> + H<sub>2</sub>O<sub>2</sub> Leaching Solution over Two-stage Leaching in HNO<sub>3</sub> and HCl

Abstract

Waste PCBs (Printed Circuit Boards) from LCDs (Liquid Crystal Displays) contain valuable raw materials, Sn, Cu, and other noble metals. Among these, high purity tin was obtained by electro-winning after appropriate acid leaching of tin. For this, leaching and electro-winning process parameters were optimized for solution stability, dissolution and electrolytic efficiency. Two aqueous procedures were developed and tested for electro-winning at mass-production capable basis: (1) HCl leaching after preliminary HNO3 dissolution was quite effective in leaching high proportion of Sn as analyzed by ICP (Inductively Coupled Plasma) method. (2) Direct one-step leaching in H2SiF6 + H2SO4 + H2O2 was also tested and the solution was finally selected as electrolytes in electro-winning due to massproduction capability. The most efficient recovery of tin was observed after 7h electro-winning in aqueous H2SiF5 + H2SO4 + H2O2 maintained at 40oC: 96%-pure tin was obtained with 93.2% recovery rate. Keywords: Electronic waste, LCD, leaching solution, PCB, recovery, Tin.