Sequential biologically assisted extraction of Cu and Zn from printed circuit boards (PCB)

The increased production and use of electrical and electronic equipment leads to obsolescence and disposal problems, necessitating materials recovery and recycling. This paper reports results on metal bioleaching from printed circuit boards (PCBs) using chemolithotrophic bacteria isolated at different sulphide ore biotopes in Armenia. Different ways of generating lixiviants were investigated, namely using combination of Acidithiobacillus ferrooxidans 61 and Acidithiobacillus thiooxidans SO-1 bacteria generating biogenic Fe2(SO4)3 and biogenic H2SO4. The sequence between these leaching agents permitted design of a 2-step process based on acidolysis and redoxolysis to leach non-ferrous metals from PCBs. To compare the efficiency of the sequential bioleaching of PCBs, several experimental runs were realised under the six modes at 10% pulp density. The flasks-based tests have witnessed almost complete recovery of Cu with the rest of the metals reaching extraction degree above 80%.