Abstract: In order to improve the leaching copper efficiency, microwave was used to enhance the leaching system ofA. thiooxidans. Plackett-Burman and Box-Behnken methods were used to optimize the enhanced bioleaching condition. Firstly, the significant factors identified by Plackett-Burman method were microwave power, irradiation time and leaching time. Secondly, the central values of above-mentioned three factors of Box-Behnken test were identified by the steepest ascent experiment, which were microwave power of 340 W, irradiation time of 3.60 min and leaching time of 6.80 d. And then, the experimental conditions of bioleaching copper withA. thiooxidanswere optimized using Box-Behnken method. The research showed that the microwave power, leaching time, the interactions of microwave power and leaching time plus irradiation time and leaching time had the significant influence on the bioleaching copper, whereas the effect of irradiation time was not significant. The optimal experimental condition predicted by model was as follows: microwave power 336.10 W, irradiation time 3.59 min and leaching time 6.82 d, and the predicted optimal value was 75.69%. The adjusted optimal condition was microwave power 336 W, irradiation time 3.60 min and leaching time 6.80 d, the experimental value was 75.41%±0.76%, indicating a high agreement between the predicted and experimental values.

Key words: microwave enhanced;Acidithioacillus thiooxidans, waste printed circuit boards, leaching copper, optimization