Study On Extraction Of Metal From Waste Circuit Board By Two-step Microbial Method

With the rapid development of technology,electronic waste has become the fastest growing waste in the world.If the main metal resources in electronic waste can be recycled and reused by an environmentally friendly biometallurgical method,it can not only reduce environmental pressure,but also obtain secondary metal resources,which has important environmental protection and economic value.Aspergillus niger is an acid-producing fungus with high recovery efficiency for base metals such as copper.Bacillus megaterium is a cyanogen-producing bacteria that has a good leaching effect on precious metals such as gold.However,according to existing academic research,there are few studies on the use of these two microorganisms to extract metals from waste printed circuit boards(WPCB).This study can be divided into two parts.Firstly,the use of Aspergillus niger for biological leaching of copper,pretreatment of waste circuit boards,and at the same time,the chemical leaching of copper in waste circuit boards for comparison of leaching efficiency,and secondly,exploring the effect of Bacillus megaterium.The growth status and the efficiency of bioleaching gold,and a variety of influencing factors are explored,and experiments are optimized.The copper immersion efficiency of Aspergillus niger is affected by many factors.The highest Aspergillus niger was obtained when the culture temperature was 30?,the substrate concentration was 110 g/L,the initial pH was 4,the amount of inoculated bacteria was 5.49×10¹³ cfu,and the amount of waste circuit board powder was 0.225 g.The copper immersion efficiency is 73.6%.Bacillus megaterium can be acclimated under alkaline conditions to improve the gold leaching rate.Under the leaching conditions of the amount of waste circuit board powder added is 0.15g,the concentration of glycine is 7.0 g/L,the inoculation and domestication pH=9.5 and the bacterial quantity of Bacillus megaterium is 6.3×10¹² and other suitable culture physical parameters,the gold leaching rate was 38.5%.Nutrient salts can further affect the gold leaching efficiency of Bacillus megaterium.When the concentration of NaCl is 0.34 mol/L,the gold leaching rate of Bacillus megaterium reaches the highest leaching rate of 47.4%,and the effect of other nutrients is lower than that of NaCl.This topic uses two-step method of Aspergillus niger and Bacillus megaterium to extract metals from waste circuit boards.The extraction of metals from waste circuit boards is achieved with high efficiency,which has social benefits such as green environmental protection and ecological sustainability.Environmental benefits,economic benefits and other perspectives provide a theoretical basis for the subsequent large-scale application of biometallurgical technology.