Recovery limitation due to metal loss to fiberglass particles during printed circuit board leaching and probable mechanisms

Absolute recoveries of target metals are rarely achieved in printed circuit board (PCB) leaching operations and this is ultimately a threat to complete cyclic material use. Leaching pulps contain high fractions of fiberglass particles, a ceramic material whose behavior in leaching pulps has not been studied but generally considered inert to lixiviants. Tests in this work, under basic and acidic lixiviants, show this is not so. Copper and zinc ions and ammine complexes, as well as iron ions were confirmed lost to fiberglass particles from basic and acid PCB leach solutions. Copper loss reached 0.695 mg per gram fiberglass particles in solution. Different mechanisms may apply in these interactions. Under the amine leaching, based on pH pzc study of fiberglass, it can be inferred that physisorption is responsible for losses observed. pH pzc of fiberglass was found to be 7.1. Hence, cationic complexes such as Cu(NH 3 ) 2 2+ and Zn(NH 3 ) 2 2+ under alkaline leaching conditions can be adsorbed. Under acid leaching, ion exchange is possible for losses observed. Fiberglass particles adsorb or exchange target metal ions during acidic and alkaline PCB leaching, thus limiting maximum possible recovery during recycling. These mechanisms are probable to understand and manage this loss.