title: Recovery of valuable materials from waste liquid crystal display panel.
abstract: Associated with the rapid development of the information and electronic industry, liquid crystal displays (LCDs) have been increasingly sold as displays. However, during the discarding at their end-of-life stage, significant environmental hazards, impacts on health and a loss of resources may occur, if the scraps are not managed in an appropriate way. In order to improve the efficiency of the recovery of valuable materials from waste LCDs panel in an environmentally sound manner, this study presents a combined recycling technology process on the basis of manual dismantling and chemical treatment of LCDs. Three key processes of this technology have been studied, including the separation of LCD polarizing film by thermal shock method the removal of liquid crystals between the glass substrates by the ultrasonic cleaning, and the recovery of indium metal from glass by dissolution. The results show that valuable materials (e.g. indium) and harmful substances (e.g. liquid crystals) could be efficiently recovered or separated through above-mentioned combined technology. The optimal conditions are: (1) the peak temperature of thermal shock to separate polarizing film, ranges from 230 to 240 degrees C, where pyrolysis could be avoided; (2) the ultrasonic-assisted cleaning was most efficient at a frequency of 40 KHz (P = 40 W) and the exposure of the substrate to industrial detergents for 10 min; and (3) indium separation from glass in a mix of concentrated hydrochloric acid at 38% and nitric acid at 69% (HCl:HNO(3):H(2)O = 45:5:50, volume ratio). The indium separation process was conducted with an exposure time of 30 min at a constant temperature of 60 degrees C.
authors.affiliation: Department of Environmental Science and Engineering, Tsinghua University, China. jinhui@tsinghua.edu.cn
authors.forename: Jinhui
authors.initials: J
authors.lastname: Li
authors.forename: Song
authors.initials: S
authors.lastname: Gao
authors.forename: Huabo
authors.initials: H
authors.lastname: Duan
authors.forename: Lili
authors.initials: L
authors.lastname: Liu
mesh_terms: D000148:Acids, Noncarboxylic / Q000737:chemistry; D003247:Conservation of Natural Resources; D006256:Hazardous Waste; D006358:Hot Temperature; D007204:Indium / Q000302:isolation & purification; D050866:Liquid Crystals / Q000032:analysis*; D014465:Ultrasonics; D018505:Waste Management / Q000379:methods*
chemical_list: D000148:Acids, Noncarboxylic; D006256:Hazardous Waste; D007204:Indium