Two alternative process routes for recovering pure indium from waste liquid crystal display panels

Abstract

Recovering indium from liquid crystal display (LCD) screen waste is important from a sustainability point of view for several reasons: the environmentally hazardous metals are not landfilled, the recovery process involves lower CO2 emissions than primary production, and supply from secondary sources matches the continuously increasing demand of indium. In this study, two alternative process routes for recycling the critical metal, indium, from LCD panel waste were studied and compared using laboratory and bench-scale experiments. The first process was a conventional hydrometallurgical process that involves manual dismantling, hammer mill crushing of the glass, cross-current sulfuric acid leaching of the metals, and liquid-liquid extraction separation of indium. Using this process, over 99% pure indium solution can be produced with a recovery yield of over 70%. The second process is novel because it includes (manual) scraping of the indium tin oxide (ITO) layer from the glass panels, followed by sulfuric acid leaching of the metals. The yield of indium was over 80%, and the purity of the resulting solution was over 99%. The solutions obtained from either of the suggested processes were sufficiently pure for cementing indium in high purity. The novel process appears much more straightforward and economically more feasible because the polarizing filter need not be removed and the liquid-liquid extraction purification step is excluded. Moreover, less amount of leaching acid is required.

Adhesion-Increased Carbon Nanowalls for the Electrodes of Energy Storage Systems

“…Indium tin oxide (ITO) and titanium nitride (TiN) were used as the intermediate layer. ITO is a typical transparent conducting oxide (TCO) and is intensively studied for displays and liquid crystal panels [18][19][20], among others, while TiN is a typical interlayer [21,22] with excellent thermal stability and chemical safety, and with high fine hardness. These two widely used materials were deposited to a thickness of about 150 nm using a four-inch ITO or TiN target, with a radio frequency (RF) magnetron sputtering system.…”

Membrane Filtration Enhanced Hydrometallurgical Recovery Process of Indium from Waste LCD Panels

“…Therefore, the purpose was not to optimize the performance of the liquid-liquid extraction but to study the abovementioned issues with simple batch experiments. The approach used, of extracting the metals to D2EHPA and selectively stripping indium, has already been shown to produce > 99% pure solution, with 97% yield [27].…”

“…The purity of the indium in the stripping product was 74%, indicating quite a good purification performance, as the purity in the feed to the liquid-liquid extraction was only 10%. Moreover, if more than one stage in the loading were to be used, the purity would be improved, since, when the organic phase becomes highly saturated, the indium replaces most of the iron in the solution [27]. Some deterioration of the hammer mill blades was observed during the experiments, likely causing high iron concentrations in the crushed glass raw material.…”

Liquid-Liquid Extraction of Indium(III) from the HCl Medium by Ionic Liquid A327H+Cl− and Its Use in a Supported Liquid Membrane System

“…Hydrometallurgical recovery of indium from a material containing it requires some steps: the first is to leach the solid product, and in the case of indium, as expected, mineral acids and aqua regia is the media to dissolve the element [3,4], though incursions in the use of bioleaching [5] and deep eutectic solvents [6] are also known. Once dissolved, the approaches to recover the metal include ion exchange [7], precipitation [8], membranes [9,10], counter-current foam separation [11], electrowinning [12], cementation [4], but the main interest seemed to be in the use of solvent extraction using conventional extractants, such as 8-hydroxyquinoline derivatives [13], D2EHPA [14], TBP (tributyl phosphate [15], methylimino-dioctylacetamide (MIDOA) [16], ionic liquids (Cyphos IL101 and Aliquat 336 [17], Cyphos IL104 [18], A324H + Cl − [19], PJMTH + HSO 4…”

“…Hydrometallurgical recovery of indium from a material containing it requires some steps: the first is to leach the solid product, and in the case of indium, as expected, mineral acids and aqua regia is the media to dissolve the element [ 3 , 4 ], though incursions in the use of bioleaching [ 5 ] and deep eutectic solvents [ 6 ] are also known. Once dissolved, the approaches to recover the metal include ion exchange [ 7 ], precipitation [ 8 ], membranes [ 9 , 10 ], counter-current foam separation [ 11 ], electrowinning [ 12 ], cementation [ 4 ], but the main interest seemed to be in the use of solvent extraction using conventional extractants, such as 8-hydroxyquinoline derivatives [ 13 ], D2EHPA [ 14 ], TBP (tributyl phosphate [ 15 ], methylimino-dioctylacetamide (MIDOA) [ 16 ], ionic liquids (Cyphos IL101 and Aliquat 336 [ 17 ], Cyphos IL104 [ 18 ], A324H + Cl − [ 19 ], PJMTH + HSO 4 − [ 20 ]), or chloride-rich deep eutectic solvents [ 21 ]; in all the above cases, the extraction efficiencies of the different extractants were high, i.e., exceeding 95%, though the experimental conditions vary from one investigation to another, i.e., pH 2 [ 13 ] against a medium rich in HCl [ 15 , 19 ], a type of an acidic medium, i.e., HCl [ 16 ] against sulphuric acid [ 20 ], and varying extractant concentrations [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ].…”