Green recovery of cerium and strontium from gold mine tailings using an adapted acidophilic bacterium in one-step bioleaching approach

Background Enormous amounts of gold mine tailings (GMT) are produced as a result of mineral activities, but these mine tailings produced from previous ore processing still contain significant amounts of elements (e.g. strontium (Sr)) and rare earth elements (REEs) such as cerium (Ce). In this study, extraction of Ce and Sr from GMT using an adapted sulfur oxidizers acidophilic strain for developing a one-step bioleaching was performed for the first time. Methods Determination of the optimal conditions by response surface methodology (RSM), for maximizing Ce and Sr recovery, was carried out using influential factors of initial sulfur concentration, pH and pulp density. Significant findings The optimal values of pH, pulp density and initial sulfur concentration were 1.8, 2% (w v-1) and 0.55% (w v-1), respectively. The highest sulfate production was obtained in initial sulfur concentration of 0.5% (w v-1). In addition, among the various inhibition kinetic models, Tessier inhibition kinetic model was the most suitable based on the experimental data. In conclusion, the kinetic study of the process indicated that a high recovery of 75.8% of Ce and 86.4% of Sr was achieved from GMT under optimal conditions, where the chemical reaction was revealed to be the rate controlling step. Bioleaching of GMT by A. thiooxidans is a promising technology to reduce the environmental hazards of these wastes. The results showed that GMT can be a source of supply of Ce and Sr.