*Article* **Hydrometallurgical Treatment of Waste Printed Circuit Boards: Bromine Leaching**

**Hao Cui 1,\* and Corby Anderson <sup>2</sup>**


Received: 15 March 2020; Accepted: 30 March 2020; Published: 2 April 2020

**Abstract:** This paper demonstrates the recovery of valuable metals from shredded Waste Printed Circuit Boards (WPCBs) by bromine leaching. Effects of sodium bromide concentration, bromine concentration, leaching time and inorganic acids were investigated. The most critical factors are sodium concentration and bromine concentration. It was found that more than 95% of copper, silver, lead, gold and nickel could be dissolved simultaneously under the optimal conditions: 50 g/L solid/liquid ratio, 1.17 M NaBr, 0.77 M Br2, 2 M HCl, 400 RPM agitation speed and 23.5 ◦C for 10 hours. The study shows that the dissolution of gold from waste printed circuit boards in a Br2-NaBr system is controlled by film diffusion and chemical reaction.

**Keywords:** shredded waste printed circuit boards; precious metals; bromine; leaching kinetics
