Bioleaching of copper from waste printed circuit board by potential bacteria isolated from a landfill

Abstract

Electronic waste has been identified as one of the fastest growing wastes generated globally that is predicted to surpass 111 million tons per year by 2050. Ewaste is becoming a worrying issue not just for its high volume generated, but also due to high composition of heavy metals it contains. This may contribute to potential environmental pollution if e-waste is not managed properly. High volume of e-waste leads to a new prospect of material acquisition through the concept of urban mining by extracting the valuable metals from the e-waste. This metal is usually extracted from components such as waste printed circuit board which houses valuable metals such as copper. Conventional extracting processes, however, pose harmful environmental effects as well as incur high cost. The purpose of the study is to introduce an alternative greener method of extraction which uses microbial activity to extract metals namely bioleaching. This study focuses on the isolation of bacteria sourced from the sanitary landfill to be used as the bacterial strain for bioleaching accompanied by minimal pre-processing to reduce the amount of secondary pollution from the pre-processing. The strains were grown in low pH medium, utilising their tolerance towards low pH condition for the copper bioleaching process. Four bacterial strains were isolated. Using 16S rRNA gene sequencing, the isolates were identified as Bacillus sp. strain SE, Bacillus sp. strain SC, Lysinibacillus sp. strain SE2 and Oryzobacter sp. strain S1A. All the isolates showed some bioleaching activity with strain SC being able to extract the highest amount of copper from the bioleaching with value of up to 23.36 ppm through the two-step bioleaching method. Strain SC was used to further evaluate the copper extraction by using pure copper strip to evaluate the mobilisation of copper by the strain microbial activity and it managed to mobilise 818.1 ppm of copper. These results suggest that the standalone bioleaching activity by strain SC is proven to perform effectively.