Recycling Indium From Waste Liquid Crystal Display Panel By Vacuum Carbon-reduction

With the advantages of small volume, light quality and low power consumption, liquid crystaldisplay (LCD) has been used in most of appliances. However, a large number of LCD products arecoming into discarding period due to their short life-cycle,3-5using years in general, and the endlessrequirement for new products. The indium content of LCD panel is even higher than that of Zincblende which is considered to be the most important indium-carrier mineral. Therefore, the recyclingand reuse of indium from waste LCD panel become particularly important. So far, two main methods ofrecycling indium including acid leaching and chlorinated separation method have been studied anddeveloped. However, these two methods are still in laboratory stage because of some disadvantages:volatile acid gas, long process time and high reaction temperature. This study investigated the recoveryof indium from waste LCD panel using vacuum carbon-reduction.First of all, the thermodynamic analysis and dynamics analysis of recovery of indium from In2O3by vacuum carbon-reduction were investigated. The results showed that the increasing of vacuumdegree and reaction temperature were conductive to reduction reaction. The saturated vapor of metallicindium was higher than that of metallic tin. The reduction reaction was controlled by chemical reactionat1123~1173K and was effected by the both of chemical reaction and diffusion mass transfer at1223K, and the apparent activation energy was160kJ/mol.Then high purity In2O3was investigated. The results indicated that the recovery rate of indiumwas increased with the increasing of temperature, vacuum degree and addition of carbon powder undercertain conditions. In addition, the L9(34) orthogonal design performed with In2O3powder showed that system pressure made the maximum effect on the recovery rate of indium, followed by temperature,then the amount of carbon powder, and finally the reaction time. The recovery rate of indium reached93wt%in the conditions of1223K,30wt%carbon addition,30min, and1Pa. XRD analysisindicated that high purity indium could be selectively recovered on condensing zone.Based on the above analysis and experiments, the experiment of recovery of indium from wasteLCD power was performed. The results showed that the recovery rate of indium was increased with thedecreasing of particle size of LCD glass powder, besides, the extension of heating time would not causetoo much impact on the recovery rate of indium after reaction30min, and most of tin was left inglass residue. The recovery rate of indium from waste LCD panel could reach90wt%under theconditions of1Pa for system pressure,1223K for temperature,30min for reaction time, and30wt%for addition of carbon powder.According to the above experiment results, the process of vacuum carbon-reduction can recoverindium from waste LCD panel efficiently. In addition, no hazardous waste liquids or gases wereproduced during the whole process. To sum up, this study provides a promising technology withoutnegative impact to the environment for the recovery of indium from waste LCD panel.