Metal recovery from the mobile phone waste by chemical and biological treatments

Abstract

Recycling electronic waste is an important subject not only from the point of view of waste treatment, but also regarding the recovery of valuable metals. This research examined the stepwise recovery of metals in mobile phone waste using chemical treatment via pH swing and the biological method using biomineralization. In chemical treatment, the metal fraction attached to the printed circuit board (PCB) and camera parts were separated from the mobile phone waste and were then pulverized into particles with a size less than ~2 mm. The metal fraction was dissolved in aqua regia, and the pH of the solution was increased to 10.5 by adding NH4OH. The first precipitate was iron oxide, produced by raising the pH to 3.1~4.2 with NH4OH. Sequentially, copper chloride and rare earth-metal complex were produced at pH 5.7~7.7 and 8.3~10.5, respectively. In the biological method, the filtrate at pH 7.7 was added to a metal-reducing bacteria growth medium as a precursor. After two weeks of incubation, rhodochrosite and calcite were precipitated as nano-sized minerals. The results indicate that effective metal recovery of mobile phone waste is feasible using chemical and biological treatments, and the recovered metals and rare earth metals can be recycled into raw materials for various industries.