Bioleach Ing Copper From Waste Printed Circuit Boards By Acidithiobacillus Ferrooxidans

Waste printed circuit boards (WPCBs)treatment and resource recycle is the hotspot in electronic waste reducing, harmless and recycling research. Biohydrometallurgy is an efficient approach to green treatment and recycling WPCBs with environment friendly, equipment simple and operation cheap. In this paper, bioleaching copper kinetics and mechanisms from WPCBs was studied by Acidithiobacillus ferrooxidans, which is one of the most important bacteria in biohydrometallurgy. And commercial application of bioleaching WPCBs by Acidithiobacillus ferrooxidans wasevaluated through the shake flask-column leaching experimental. In addition, the influence of maintain leaching solution pH by adding acid on bioleaching copper was analysed. The main conclusions of this work are drawn as follows:(1)The influence mechanism of bioleaching WPCBs, such as amounts of WPCBs, the electronic components in WPCBs and bacteria was elucidated, and renderedbioleaching copper fromWPCBswithout dismantled electronic componentsispossible when the leaching solution pH is maintained by adding acid in bioleaching process. The results show that Fe+produced by the leaching reaction can be oxidized fast by Acidithiobacillus ferrooxidans. Thus the Fe2+-Fe3+cycle process can be ongoing. The concentration of Cu2+reached2120mg/L and was20times of leaching copper without bacteria. More H+is consumedand lead to the pH of leaching solution increase fast when the amount of WPCBs is more than the maximum amounts allowable in leaching solution or leach copper from WPCBs without dismantled electronic components.The oxidizing activity of bacteriais affected and the Fe3+is consumed and form secondary minerals such as jarosite by hydrolytic reactions when the pH of leaching solution rises. Thus, the Fe2+-Fe3+cycle processis destroyed. The copper recovery rate was significantly increased from55.3%to96.8%and the Zinc recovery rate was increased from55.7%to83.8%when the H+is complemented by adding H2SO4.(2) The kinetic of bioleaching copper from WPCBs and its changes was elucidated, and the model relationship of H+consumption and copper bioleaching was analysed. The result shows that the control step of copper recovery is the shrinking core model because the external diffusionprocess of leaching agent and resultant are not affected unter shake flasks. Additionally, the formation process of secondary minerals such as jarosite is inhibited when the pH of leaching solution is adjusted at2.25(±0.05). Furthermore, the diffusion process of leaching agent and resultant are not affected because the product layer of secondary minerals cannot be formed. So the bioleaching kinetics of copper varies from the internal diffusionmodel to the second-order model (chemical control), and is in conformance with H+consumption.(3) The kinetic of column bioleaching copper WPCBs was stuied and the application field of optimized model was analysed. The results show that the internal diffusion process of leaching agent and resultant are not affected because the particle of secondary minerals such as jarosite is too small than the WPCBs sample, and the product layer is loose structure. The control step of copper recovery isthe external diffusion because the particle of WPCBs is static and the external diffusion layer is too thick. The kinetic of column bioleaching is significantly different from the shake flasks bioleaching.