Study On The Microbiological Method For Bioleaching Gold And Copper From Waste Circuit Boards

In recent years,due to the huge output and potential ecological threats and the value of secondary metal resources of electronic waste,the treatment and disposal technology of e-waste has become a hot spot of international research.In the treatment technology,because of its environmental protection and low cost,biometallurgy has received more attention.Based on the biometallurgical mechanism,the paper used a two-step method to bioleach metals from waste circuit boards.First,Aspergillus niger is used to bioleach base metals such as copper and zinc from waste circuit boards,and then Bacillus megaterium is used to bioleach precious metals such as gold from waste circuit boards.Through the change of the pH value of the medium and the change of the dry weight of the strain,the paper studies the growth characteristics of Aspergillus niger and the characteristics of organic acid production.The organic acid produced by Aspergillus niger is then used to bioleach copper from the waste circuit boards.According to the growth state of the bacteria after being activated and cultured,the growth curve of this experiment was drawn.The copper leaching efficiency of Aspergillus niger was explored by changing the amount of bacteria liquid,powder,sucrose,temperature and pH value in the culture medium.When the amount of powder added was 0.1 g,the pH value was 5,the number of bacteria was 1.33×10¹²,and the amount of sucrose added was 90 g/L,the bioleaching rate of copper from waste circuit boards by Aspergillus niger could be maintained at 90.0%.The highest leaching rate could reach 96.4%.According to the growth curve of Bacillus megaterium,in this paper,Bacillus megaterium was used to explore the leaching efficiency of gold in the pretreated powder by adjusting the number of powder and bacteria,and the pH value.When the added amount of waste circuit board powder was 0.1 g,the number of bacteria was 1.05×10¹⁰,and the pH was 9,Bacillus megaterium could bioleach up to 38.0%of the gold in the waste circuit board.After cost-benefit analysis of equipment power consumption and reagent consumption,as well as the value of gold and copper recovery,it was concluded that this experiment could have a profit of 1292 yuan when the microbiological two-step method was used to leaching 1 ton of waste circuit boards.During the entire experiment,only microorganisms bioleached gold and copper from the waste circuit boards,and no other leaching agents were used.Compared with other metallurgical methods,it not only reduces the consumption of reagents,but also avoids the generation of pollutants.In addition,the cost of this method is relatively low,and it is an environmentally friendly technology,which has certain application prospects.