Identification Of Pollutants During The Dismantling Process Of PCBs And Study On Extracting Technology Of Precious Metal

Recently,rapid development of electronic information industry leads to a large amount of electronic waste(E-waste),which is attracting extensive attention for the potential environmental pollution and valuable resource.Dismantling of waste printed circuit boards(WPCBs)and recycling of valuable metals become the bottleneck for the sustainable development.Meanwhile,environmental monitoring and pollution control is of much importance.In this sduty,comparison between different dismantling technologies is made by summarizing the main technologies.Based on the research on dismantling WPCBs by ionic liquid,the main pollutants in the process are assayed quantificationally.Three different kinds of hydrometallurgy are applied to the memory bank that in computers.Influence factors in each method are studied to determine the optimum conditions,which is the basis of future study.In the experiment on dismantling the WPCBs using ionic liquid,temperature is set up at 250?,270?and 290? respectively,and considered as the only input variation.Each group of experiment with 25 g of sample,250 ml of ionic liquid,60 min,and rotate speed at 45 rpm,is carried out.Minusing is used to calculate the gas quantity and the release quantity of heavy metals.The loss amount of ionic liquid contributes to 80% of the gas quantity at 290? and 270?,when the total amount is more than 15 g.The reaction diminished and the gas quantity decreased at 250?.In the experiments,Ni and Cr are undetected in the liquid;the release rate of Pb is lowest at 270? for the stability of PbO that formed at this temperature is higher;the release rate of Cu and Zn decreased with decreasing temperature.To reduce the environmental pollution,activated carbon adsorption device is useful and recycling of ionic liquid is necessary.Three kinds of hydrometallurgy are used to gold extraction from memory bank after nitric acid pretreatment.The solid-to-liquid ratio is more important than reaction time to the extraction efficiency in the aqua regia system and when the liquid-to-solid ratio is 8,the optimal extraction efficiency is 92.3%.In the acidic thiourea solution,the optimal extraction efficiency is 92.93% with liquid-to-solid ratio 10,35?,pH1.5,60 min,and the concentration of thiourea 12g/L.In the chlorate process,the optimal extraction efficiency is 93.32% with the concentration of hydrochloric acid 5mol/L,sodium chlorate 3g,liquid-to-solid ratio 10 and 5min.Comprehensive view,the chlorate process is advantageous for the easy accessibility and little pollution.