Study On Gold Leaching From The Waste Printed Circuit Boards By Pseudomonas Fluorescens

The number of electronic waste grows exponentially every year as a result of technological advancements and changes in consumer goods,especially high tech products.If green and high efficient recycling technology can be used in dealing with e-waste and resource recovery,the twin purpose of protecting the environment and solving the problem of resource scarcity can be realized.Considering the possibility of achieving the application of biological metallurgy from laboratory research to large-scale production,Pseudomonas fluorescens with the ability of rapid propagation was used in leaching of gold from typical electronic waste-waste printed circuit boards(WPCB)in the paper.In order to achieve the maximum gold leahicng efficiency,acid leaching process pre-treated the WPCB firstly,then Pseudomonas fluorescens was cultured and acclimated for understanding its growth and metabolism.The gold leaching process is limited by many factors,such as the characteristics of different bacteria,oxygen level,temperature,substrate,pH,the PCB type and composition,pulp density,the pretreatment of circuit board and so on.In order to obtain a higher leaching rate of gold,the factors of pH,the type of substrate and the amount of WPCB material were selected to do every single-factor experiment in this paper.The content of gold increased from 0.035 mg/g to 0.12 mg/g through the pretreatment acid leaching process.The leaching rate of gold increased with the the increase of pH in leaching solution,and increased first and then decreased with the increase of the amount of bacteria in 150 mL culture medium.The leaching rate of gold decreased with the increase of pulp density,and the impact was great that the leaching rate of gold reached 41.75% with 0.5 g WPCB power added.The type of substrate also affected the leaching rate,when glycine and methionine were together used as precursors for cyanide production,the leaching rate in the later stage of gold leaching will be greatly improved to 54.20%.This is because there is a synergistic effect between the two substrates.The addition of metal ions and nutrients can signicantly improve the leaching rate of gold,especially after the addition of appropriate amount of NaCl,gold leaching rate can reach 66.62%.According to the analysis of economic benefit,leaching gold from 1 tons of waste printed circuit board with Pseudomonas fluorescens can obtained a net profit of 1000 yuan.What is the most important is that bioleaching not only can realize economic benefits,but also aquire great enviromental benefit.