Bioleaching of carbide waste using spent culture of Acidithiobacillus bacteria: Effective factor evaluation and ecological risk assessment

Abstract

This study investigates the bioleaching of Li, Ni, Cu, Zn, and Ba from carbide slag using presecreted metabolites (spent cultures) of Acidithiobacillus ferrooxidans ( A. ferrooxidans ) and Acidithiobacillus thiooxidans (A. thiooxidans ). The effects of pH (1–3), pulp density (0.1%–2% w/v), and contact time (up to 8 days) in achieving high metal recovery were determined. The highest metal biosolubilize rate was achieved at a pH of 1.5, pulp density of 0.5% w/v, and retention time of 6 days. Results showed that the spent cultures of A. ferrooxidans and A. thiooxidans recovered 100% of Ni and Li, respectively. In addition, the results of the spent of mixed culture revealed an improved metal recovery compared with individual strain mediums. Furthermore, investigations on the pollution indexes of the leached slag revealed that leaching using spent of mixed culture was more effective than other leaching methods. Investigation of the contamination factor, ecological risk factor, pollution load index, and geo-accumulation index demonstrated that the metabolites of A. ferrooxidans and the spent of mixed culture significantly improved the waste quality in terms of reducing heavy metals pollution. • Bioleaching of carbide slag waste using spent culture was studied. • Pure A. ferrooxidans and A thiooxidans and mixed culture were examined. • The optimum condition was pH: 1.5, pulp density: 0.5% w/v, and contact time: 6 days. • Ecological risk assessment before and after bioleaching was demonstrated.