Recycling And Deep Processing Of Indium In Waste Liquid Crystal Displays

In recent years,liquid crystal display products have been widely used in the electronics industry,and a large number of waste liquid crystal displays have been produced after the electronic products are scrapped.Due to the lack of effective recycling technology,these waste displays are landfilled,incinerated along with other solid waste,or temporarily collected by some e-waste treatment enterprises.Indium is an important raw material for conductive coating on ITO glass of waste liquid crystal display.More than 70%of the world's indium is used to produce ITO target.Indium reserves are limited and dispersed in the earth's crust,with no separate deposits.If the indium in the waste liquid crystal display can be recycled and utilized,it will not only have economic benefits,but also protect the environment and save resources.In this thesis,the rapid analysis method of metal elements in waste LCD screens is studied.A process route for recovering indium from waste liquid crystal displays is designed.The experiments of enrichment and purification of indium by acid leaching,impurity removal and electrolysis are carried out.Semi-quantitative analysis of ITO glass acid leaching solution by ICP-MS showed that there were more than 40 elements in the leaching solution,many of which come from glass substrates.ICP-MS was used to conduct quantitative analysis of ITO glass leaching solution,and nitric acid was determined to be used as leaching agent to immerse the ITO glass under ultrasonic assisted conditions.In quantitative analysis,the linear correlation coefficient of each element standard curve was above 0.999,and the recoveries of standard addition were between 80.62%and 118.52%.The vast majority of test results had a relative standard deviation of less than 2%.The leaching study of indium in ITO glass was carried out.The effects of three key leaching conditions,such as acid concentration,solid-liquid ratio and leaching time,on element leaching rate were investigated by single factor experiment and orthogonal experiment.The optimum leaching process parameters were as follows:nitric acid concentration of 6 mol/L,solid-liquid ratio of 1:6,reaction time of 25 min.According to the difference of the solubility product of the insoluble electrolyte,the impurities in the acid leaching solution were removed by a stepwise precipitation method.The sponge indium obtained by replacing the zinc powder was placed into a solution of In₂?SO₄?₃to carry out an electrolytic purification experiment of indium.The effects of electrode materials,electrolyte pH and temperature on the indium products deposited by the cathode were investigated.The current efficiency was highest under the condition that the electrolyte had a pH of 2,a water bath temperature of 35?,and a voltage of 2.0 V,and the obtained indium product was dense and flat.