Indium Recovery from the Acid Elute of Waste Indium Tin Oxide Glass by Bipolar Membrane Electrodialysis with Ethylenediaminetetraacetic Acid as a Chelating Agent

Selective leaching of indium from spent LCD screens by siderophore desferrioxamine E

Given the criticality of indium (In) in high-tech applications, spent LCD screens can represent a viable secondary In resource. In this work, an innovative and alternative technology to selectively leach In from spent LCD screens using a microbial chelating agent, desferrioxamine E (DFOE), was developed. Indium was concentrated from spent LCD screens by implementing an adapted pre-treatment procedure, allowing the isolation of an indium-rich glassy fraction. During leaching, the competition between aluminum (Al) and In for complexation with DFOE leads to the precipitation of In(OH)3 at low DFOE concentrations (12-240 µM). After adjusting the optimal conditions (fraction size: 0-36 μM, pH: 5.5, S/L ratio: 1 g/L, 25 °C), the In leaching yield reached 32%, ten times higher than Al over 90 days with 5 mM DFOE. Thus, achieving high In recovery is possible through i) prolonging leaching durations, ii) selective leaching, and iii) minimizing Al interference. This is the first attempt to selectively leach In using a selected siderophore from end-of-life products with high concentrations of non-targeted elements (i.e. Al, Si, and Ca). This study demonstrates the potential of generating indium-rich leachates, which can be subsequently processed through the GaLIophore technology for In refining.

The Pseudo-Protic Ionic Liquids TOAH+Cl- and TODAH+Cl- as Carriers for Facilitated Transport of In(III) from HCl Solutions

A study of indium(III) transport across an immobilized liquid membrane using the pseudo-protic ionic liquids TOAH⁺Cl^- and TODAH⁺Cl^- as carriers has been carried out using batch experiments. Metal transport is investigated as a function of different variables: hydrodynamic conditions in the feed (375-1500 min^-1) and receiving (500-750 min^-1) phases, HCl (0.5-7 M) and indium (0.01-0.2 g/L) concentrations in the feed phase and carrier (1.25-40% v/v) concentration in the membrane phase. Indium is conveniently recovered in the receiving phase, using a 0.1 M HCl solution. Models are reported describing the transport mechanism, which consists of a diffusion process through the feed aqueous diffusion layer, fast interfacial chemical reaction, and diffusion of the respective indium-pseudo-protic ionic liquid through the membrane. The equations describing the rate of transport are derived by correlating the membrane permeability coefficient to diffusional and equilibrium parameters as well as the chemical composition of the respective indium-pseudo-protic ionic liquid system, i.e., the carrier concentration in the membrane phase. The models allow us to estimate diffusional parameters associated with each of the systems; in addition, the minimum thickness of the feed boundary layer is calculated as 3.3 × 10^-3 cm and 4.3 × 10^-3 cm for the In-TOAH⁺Cl^- and In-TODAH⁺Cl^- systems, respectively.