Recovery of metals from electronic wastes using physical separation and hydrometallurgical methods

In this thesis, the characterisation of waste printed circuit boards (WPCBs) with a high base/precious metal content and their treatment by physical and hydrometallurgical methods for the recovery of contained metals was investigated. WPCBs were found to be hazardous waste in that they may cause water pollution due to their heavy metal content, Pb in particular. In the heavy media, magnetic and electrostatic separation tests, high recoveries for metals were obtained at the expense of relatively high copper and precious metal losses. Heavy media tests indicated the extensive liberation of metals (?97% Cu) at <1-1.4 mm. In the physical separation processes, separation efficiency was observed to decrease remarkably at <75-106 ? m. Sulphate (H2O2 or Fe3+ as oxidants) and chloride (Cu2+ or H2O2 as oxidants) leaching systems were investigated for the extraction of metals from WPCBs. In the peroxide assisted sulphate leaching tests, copper was selectively extracted over precious metals (Au, Ag and Pd) from WPCBs at high recoveries (>99%). The additives (ethylene glycol and polycarboxylate mixture) were determined to reduce the peroxide consumption by 1,2-9 fold and increase the extraction of copper by up to 34%. In the chloride media, the in-situ regeneration of Cu2+ by air/oxygen was required to achieve high metal recoveries. In the presence of air/oxygen (1 L/min) the extraction of copper and silver/palladium increased by 67% and 72-81% respectively. The addition of H2O2 was necessary for high gold extractions in the chloride leaching.Key Words: Waste electrical and electronic equipments, waste circuit boards, magnetic separation, electrostatic separation, hydrometallurgy, leaching, recycling