Bioleaching of indium from discarded liquid crystal displays

The present study is the first report on the bioleaching of indium (In) from discarded liquid crystal displays (LCDs) using adapted Acidithiobacillus thiooxidans. The adaptation of bacteria to the LCDs powder began with 1% (w/v) and continued up to 4% (w/v). Response surface methodology (RSM) was used to evaluate the effects of initial pH, pulp density, and initial sulfur concentration and optimize their values in order to maximize In and Sr recovery. Under optimum conditions of an initial pH of 2.6, pulp density of 1.6% (w/v) and initial sulfur concentration of 8.6 (g/l), 100% of In and 10% of Sr were recovered. The rate-controlling step in this process was determined using the shrinking core model, which suggests that both diffusion and chemical reaction play an important role in the overall bioleaching process. Scanning electron microscopy (SEM) analysis demonstrated the effectiveness of bacterial activity in bioleaching. In addition, the results confirmed that bioleaching was more effective than chemical leaching. The bioleaching from discarded LCDs by A. thiooxidans is a promising technology that can decrease the environmental hazard of this waste. The bioleaching results of present study supplied a method for large-scale industrial purposes.