Study on the influence of various factors in the hydrometallurgical processing of waste printed circuit boards for copper and gold recovery

• Published in: Waste management (Elmsford) Vol. 33; no. 4; pp. 935 - 941
• Main Authors: Birloaga, Ionela, De Michelis, Ida, Ferella, Francesco, Buzatu, Mihai, Vegliò, Francesco
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.04.2013; Elsevier
• Subjects: Analysis of Variance; Applied sciences; Copper; Copper - isolation & purification; Electronic Waste; Exact sciences and technology; Gold; Gold - isolation & purification; Hydrogen Peroxide; Other wastes and particular components of wastes; Oxidative leaching; Pollution; Printed circuit boards; Recycling; Sulfuric Acids; Temperature; Thiourea; Thiourea - chemistry; Wastes; Gold; Thiourea; Printed circuit boards; Copper; Oxidative leaching; Hydrogen peroxide; Printed circuit board; Lixiviation; Oxidation; Thioureas; Dissolution; Hydrometallurgy
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2013.01.003

► Gold recovery from waste computer printed circuit boards by thioureation. ► Leaching with sulfuric acid and hydrogen peroxide was firstly applied for base metals removal. ► The effects of oxidative leaching parameters on metals extraction was studied by ANOVA. ► After 90% Cu removal at a particle of size <3mm, 45% dissolution of Au was noticed. ► 69% Au extraction yield was obtained after 75% of Cu removal for <2mm particle size. The present lab-scale experimental study presents the process of leaching waste printed circuit boards (WPCBs) in order to recover gold by thioureation. Preliminary tests have shown that copper adversely affects gold extraction; therefore an oxidative leaching pre-treatment was performed in order to remove base metals. The effects of sulfuric acid concentration, hydrogen peroxide volume and temperature on the metal extraction yield were studied by analysis of variance (ANOVA). The highest copper extraction yields were 76.12% for sample A and 18.29% for sample D, after leaching with 2M H2SO4, 20ml of 30% H2O2 at 30°C for 3h. In order to improve Cu removal, a second leaching was performed only on sample A, resulting in a Cu extraction yield of 90%. Other experiments have shown the negative effect of the stirring rate on copper dissolution. The conditions used for the process of gold extraction by thiourea were: 20g/L thiourea, 6g/L ferric ion, 10g/L sulfuric acid, 600rpm stirring rate. To study the influence of temperature and particle size, this process was tested on pins manually removed from computer central processing units (CPUs) and on waste CPU for 3½h. A gold extraction yield of 69% was obtained after 75% of Cu was removed by a double oxidative leaching treatment of WPCBs with particle sizes smaller than 2mm.