What is it about?
For hydrometallurgical recovery of indium from glass cullet after dismantling of waste liquid crystal display (LCD), leaching is the rudimentary stage. Though size reduction of the cullet pieces adds convenience for recycling, from an efficiency and cost-effectiveness perspective regarding leaching process development, determining the proper cullet piece size is essential. Hence, in this study, leaching efficiency of indium as a function of cullet piece size was investigated, wherein the proper mechanical classification of crushed glass cullet could be addressed. The optimum conditions of 5 M mineral acid as the lixiviant, pulp density of 500 g/L, temperature of 75 °C, agitation speed of 500 rpm, and 2 h process time were kept constant for the leaching studies. It was concluded that the size of the waste LCD cullet inversely affected the leaching efficiency of indium. For efficient leaching, a smaller cullet size is recommended; hence, waste LCD should be crushed to pieces 1 mm or smaller. Indium leaching behavior comparison using HCl, HNO3, and H2SO4 revealed that all three mineral acids had similar leaching efficiencies. The reported process provides the missing link between physical dismantling and chemical processing for indium recovery via techno-economical-sustainable process development.
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Why is it important?
The reported process is important and novel, as it provides the missing link between physical dismantling and chemical processing for techno-economical-sustainable indium recovery. The process can advance the WEEE, RoHS, and EPR Directives further by a step and lead to eco-efficient and sustainable recycling of LCD waste.
Perspectives
The size of waste LCD cullet pieces has a significant effect on the leaching efficiency of indium and tin, which inversely affects the leaching behavior of ITO. As all the mineral acids tested had similar leaching efficiencies, 5 M HCl should be used for industrial application, considering subsequent indium purification and recovery. Lixiviant HCl recommended as other acids are either adversely affect environment or the process itself. For efficient leaching of indium from waste LCDs, the waste LCDs should be crushed to pieces 1 mm or smaller. Moreover, the optimum conditions for leaching should be as follows: lixiviant of 5 M HCl, a pulp density of 500 g/L, a temperature of 75 °C, an agitation speed of 500 rpm, and a process time of 2 h. The proposed leaching process can be a sustainable and eco-efficient process for the leaching of indium from LCD waste glass cullet. As larger pieces of LCD cullet have a relatively smaller surface area exposed to acid for leaching, the leaching efficiency is adversely affected. Hence, for efficient leaching, smaller pieces of cullet are recommended, as the smaller pieces have greater surface area exposure to acid, which leads to proficient leaching.
Dr Basudev Swain
Institute for Advanced Engineering (IAE)
Read the Original
This page is a summary of: Value Recovery from Waste Liquid Crystal Display Glass Cullet through Leaching: Understanding the Correlation between Indium Leaching Behavior and Cullet Piece Size, Metals, April 2018, MDPI AG,
DOI: 10.3390/met8040235.
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