Bioleaching of copper from tailings by fermentation broths of Aspergillus niger in pellet form

Abstract

Owing to the substantial amounts of metals embodied in tailings, they are potential viable sources of metals. This work aims at developing a technique to microbially recover copper present in tailings. Based on orthogonal design, the effects of different variables, such as temperature, fermentation time, inoculum size and medium components, on pellet morphology of A. niger were investigated in shake flasks. Leaching of copper from its tailings was conducted using fermentation broths of Aspergillus niger with different pellet morphology. Copper extraction gradually increased with reduction in pellet diameter of A. niger. A large amount of compact smooth pellets with a diameter of 0.96 mm were obtained under the optimum fermentation conditions of 30°C , 0.8% inoculum size(OD600=0.1), 30% potato-sucrose contents, 65 h fermentation time. After 3 days of leaching, copper extraction reached 83.25% with the fermentation broths aforementioned at 30°C, 180 r·min.