Experimental Study On Vacuum Carbothermal Reduction-distillation Of ITO Waste Targe

Indium,as an important rare and rare metal,is mainly used in the form of ITO(Indium Tin Oxide)for the manufacture of transparent conductive films,liquid crystal displays,plasma displays and other electronic components.The current industrial method of producing ITO films is mainly magnetron sputtering coating method,whose utilization rate is only 30%,and the remaining part becomes waste target material.In addition,the production process of the target also produces edges and chips,which are important raw materials for the preparation of recycled indium,so it is especially important to recover indium metal from the waste ITO target.In this paper,we systematically study the recovery of indium metal from ITO waste target by one-step reduction distillation method,based on the technical idea of "one-step vacuum carbon thermal reduction-distillation".Firstly,the thermodynamic calculation of the carbon thermal reduction of indium oxide and tin oxide was carried out to determine the temperature range of the reduction reaction of indium oxide and tin oxide in vacuum environment and the required thermodynamic conditions;secondly,the experimental study of the vacuum carbon thermal reduction reaction of ITO waste targets was carried out to obtain the influence of various factors on the reduction rate of indium.Secondly,the experimental study of the vacuum distillation of indium-tin alloy was carried out to obtain the influence of temperature on the recovery rate of indium.The effect of temperature on the recovery rate of indium was studied.Finally,the process conditions of one-step vacuum carbon thermal reduction distillation for indium metal recovery were studied.The thermodynamic analysis of indium oxide by carbon thermal reduction and the carbon thermal reduction experiment of ITO waste target showed that the reduction rate of indium oxide in indium-tin alloy was about 99% with the temperature of 900 ℃,holding time of 120 min,vacuum degree of 10-20 Pa and carbon powder addition of16 wt%.The experiments of vacuum distillation separation of indium-tin alloy show that:the distillation temperature is 1200 °C,the holding time is 60 min,the pressure inside the furnace is 10-20 Pa,the recovery rate of indium in the vacuum distillation process of indium-tin alloy is about 96%,and the crude indium content is about 99.85%.The experiments of vacuum carbon thermal reduction-distillation to recover indium metal show that: after full reduction under the conditions of reduction temperature of 900 ℃,holding time of 120 min,carbon powder addition of 16 wt%and vacuum degree of 10-20 Pa,then vacuum distillation: distillation temperature of1200 ℃,holding time of 60 min and vacuum degree of 10-20 Pa,the recovery rate of indium is 98.55%.The direct recovery of indium metal from ITO waste targets can be achieved by one-step vacuum carbon thermal reduction distillation.