Improved leaching of Cu, Sn, Pb, Zn, and Al from waste printed circuit boards by electro-generated Cl2 in HCl solution

Abstract

This paper investigated the improved leaching of Cu, Sn, Pb, Zn, and Al from waste printed circuit boards (WPCBs) by electro-generated Cl2 in HCl solution through multiple leaching cells in series, double intake pipes, and bubble stone for leaching. The leaching agents in the leaching cell include Cl2(aq), HCl, HClO, and Cl3-. The leaching rate and leaching speed of Zn, Sn, Al, and Pb exceeded that of Cu. Leaching time and HCl concentration have a strong impact on the dissolution of Cu, whereas the effect of the electrolytic current and the leaching temperature is comparably weak. The series of leaching cells improved the effective utilization of Cl2 and increased the treatment capacity of the WPCBs. Bubble stones significantly enhanced the efficiency and rate of leaching. Reduction of the size of the Cl2 gas bubbles improved the leaching kinetics. The leaching rate of Cu reached 87.22%, whereas the leaching rate of Zn, Sn, Al, and Pb exceeded 90% after 100 min. Our experimental data provide a reference for electrolytic leaching recovery of metals from WPCBs, and our method improves the metal leaching and electrolytic efficiency in practice.