Study of plastics elimination in bioleaching of electronic waste using Acidithiobacillus ferrooxidans

Polystyrene, acrylonitrile butadiene styrene, and polypropylene are the main polymers in E-waste, existing about 31%, 16%, and 13%, respectively. In this research, the effects of the elimination of low-density materials (such as polymers and plastics) were studied using the shaking table method. Bioleaching of Cu and Ni against the original sample (Sample #1) and pre-treated sample without low-density materials (Sample #2) was compared. The amount of bioleached metals and growth characteristics (including pH, Eh, bacterial count) was investigated within 25 days. The analysis of Sample #1 showed that at pulp density of 15 g/l, 94% and 79% of Cu and Ni were recovered maximally, respectively, on 14th day. By using Sample #2, the recovery of Cu and Ni decreased to 87% and 74%, respectively, on 6th day. Chemical characteristics (including recovery, X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy, and field emission scanning electron microscope) before and after bioleaching of both E-waste samples confirmed that bioleaching was quite effective. This paper proved the great potential of the bio-hydrometallurgical route to recover heavy metals from electronic wastes, in which recovery of Cu and Ni is higher in the presence of low-density materials.