Thermal Reduction - Vacuum Distillation To Recover Metal Indium From ITO Scrap

With the development of electronic information technology,ITO target is mainly used for the production of liquid crystal display transparent electrode.Now more than 560 tons of indium is used for ITO target indium every year,accounting for more than 80%of the total consumption of indium.ITO thin films are prepared by ITO target magnetron sputtering method,however,the utilization rate of targets are low.The ITO target process,in which the utilization rate of target sputtered coated films is just up to 30%,produces a lot of scraps and cutting powder which contains more than 80%indium.So the Study on Recovery of Metal Indium from Indium-Tin-Oxide has a great significance.In this paper,the indium-tin from the ITO target scraps are recycled by the CO reduction-vacuum distillation separation methed.In the present study,the thermodynamic analysis and kinetic analysis of the preparation of indium-tin alloy by CO reduction of indium oxide and tin oxide were investigated.The effects of the reaction temperature,the flow rate of CO,time and reduction reaction were studied.The results of the thermodynamic calculations showed that with the increase of temperature,the indium oxide and tin oxide were more easily reduced by CO.The univariate experimental results indicated that the optimum reaction conditions were temperature 950℃,CO flow rate 40ml/min and time 50min,in which the recovery rate of indium-tin alloy was more than 97%,the recovery rate of indium was more than 99%,and the recovery rate of tin was more than 98%.And the experimental conditions were optimized by response surface method.It could be obtained that the reaction was in the control of the diffusion mass transfer stage at the temperature of 750℃～850℃ from the reduction kinetic curve of the indium tin oxide mixture.When the temperature rose to 950℃,the reaction of indium tin oxide was controlled by chemical reaction and diffusion mass transfer,and its apparent diffusion activation energy was 52.85kJ/mol.Through the experiment of indium oxide and tin oxide was reduced by CO,It was feasible to prepare indium tin alloy with indium oxide and tin oxide CO reduction method.The results showed that When the reduction temperature was 950℃,CO flow rate was 40ml/min,the reduction time was 50min,and the particle size was more than 200 mesh,the results showed that the content of indium was 90.43%and the content of tin was 9.5%.Besides,the recovery of indium was up to 99%,and the recovery of tin was up to 98%.Here,We addressed the crude indium by the vacuum distillation multi-stage condensation.The results showed that the volatile matter was respectively concentrated in the 1～10 condensation plates.The best conditions were as follows:The indium was mainly distributed in the 3～7 condensation plates,the impurity elements of Cu,Cd,Fe,Al,Sn and Pb,T1 were respectively distributed in 1～2 and 8～10 condensation plates,when distilled at a vacuum furnace pressure from 10 to 15 Pa and a temperature of 1400℃ for 60min.Recovery efficiency of 99.9%and 99.99%was respectively 53.87%and 36.7%.