Cross-current leaching of indium from end-of-life LCD panels

• Published in: Waste management (Elmsford) 2015-08, Vol.42, p.180-187
• Main Authors: Rocchetti, Laura, Amato, Alessia, Fonti, Viviana, Ubaldini, Stefano, De Michelis, Ida, Kopacek, Bernd, Vegliò, Francesco, Beolchini, Francesca
• Format: Article
• Language: English
• Subjects: ABUNDANCE; Byproducts; CARBON DIOXIDE; Critical raw material; Cross-current leaching; Electronic Waste - analysis; Emission analysis; ENVIRONMENTAL PROTECTION; ENVIRONMENTAL SCIENCES; INDIUM; Indium - chemistry; LCD panel; LEACHING; Liquid crystal displays; LIQUID CRYSTALS; Liquid Crystals - chemistry; MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; MATERIALS RECOVERY; Mining; OPERATING COST; Panels; Recycling - methods; Refuse Disposal; SOLID WASTES; SULFURIC ACID; Urban mining; Waste Management - methods; ZINC
• ISSN: 0956-053X; 1879-2456
• DOI: 10.1016/j.wasman.2015.04.035

[Display omitted] •End-of-life LCD panels represent a source of indium.•Several experimental conditions for indium leaching have been assessed.•Indium is completely extracted with 2M sulfuric acid at 80°C for 10min.•Cross-current leaching improves indium extraction and operating costs are lowered.•Benefits to the environment come from reduction of CO2 emissions and reagents use. Indium is a critical element mainly produced as a by-product of zinc mining, and it is largely used in the production process of liquid crystal display (LCD) panels. End-of-life LCDs represent a possible source of indium in the field of urban mining. In the present paper, we apply, for the first time, cross-current leaching to mobilize indium from end-of-life LCD panels. We carried out a series of treatments to leach indium. The best leaching conditions for indium were 2M sulfuric acid at 80°C for 10min, which allowed us to completely mobilize indium. Taking into account the low content of indium in end-of-life LCDs, of about 100ppm, a single step of leaching is not cost-effective. We tested 6 steps of cross-current leaching: in the first step indium leaching was complete, whereas in the second step it was in the range of 85–90%, and with 6 steps it was about 50–55%. Indium concentration in the leachate was about 35mg/L after the first step of leaching, almost 2-fold at the second step and about 3-fold at the fifth step. Then, we hypothesized to scale up the process of cross-current leaching up to 10 steps, followed by cementation with zinc to recover indium. In this simulation, the process of indium recovery was advantageous from an economic and environmental point of view. Indeed, cross-current leaching allowed to concentrate indium, save reagents, and reduce the emission of CO2 (with 10 steps we assessed that the emission of about 90kg CO2-Eq. could be avoided) thanks to the recovery of indium. This new strategy represents a useful approach for secondary production of indium from waste LCD panels.