Separation and Recovery of Gallium and Indium from Simulated Zinc Refinery Residue by Liquid−Liquid Extraction

Abstract

The separation and recovery of gallium and indium from zinc refinery residue, using liquid−liquid extraction, has been investigated. The major components with the exception of zinc can be removed by extraction with tri-n-butyl phosphate at low aqueous acidity, and gallium and indium can be separated from the remaining major component, zinc, by extraction with bis(2-ethylhexyl)phosphoric acid (D2EHPA) using the correct conditions, at which effective separation may be feasible. Extraction equilibrium formulations for the ternary system containing gallium, indium, and zinc have been established up to high conversion conditions of the extractant to metal complexes, when D2EHPA is employed as the extractant and kerosene as the diluent. The scrubbing behavior for the process can also be expressed by the proposed extraction scheme. Simulation work based on the equilibrium studies shows that indium may be recovered effectively from the mixture of gallium and zinc with 98.9% overall fractional recovery and 100% purity when using 5.0 × 10-2 mol/L D2EHPA. Gallium may then be recovered from zinc with 87.9% overall fractional recovery and 99.1% purity using 1.0 × 10-2 mol/L D2EHPA.