Recovery of indium from jarosite residues of zinc refinery by a hydrometallurgical process

Abstract

Indium is a strategic element essential in technological development; its recovery from jarosite produced as waste in a Zn refinery operated using a hydrometallurgical flowsheet was studied. Indium content in the residue was 86 mg/kg. A laboratory optimization for the indium extraction processes was done using multifactorial regression analysis. First, the optimal leaching conditions were determined: stirring time 97.7 h; HCl concentration 6.8 M and using a ratio 9.403 g of residue per 50 mL of leaching solution obtaining 96.8% of leaching yield. Secondly, two extraction methods were evaluated, using either a solvent extraction or polymeric inclusion membranes. The proposed optimal conditions for solvent extraction are: aqueous to organic phase ratio 10; feeding phase pH 3.0, 40%(V/V) D2HEPA in kerosene and a stirring time of 4.5 min with 2 consecutive extractions resulting in 83.2% of indium recovery, giving an indium concentration of 97.1 mg/L. The optimal conditions for indium recovery using polymeric inclusion membranes are: stirring time of 3.1 h, a mass ratio of 1.44 (mD2HEPA/mPVC), a feeding phase pH = 3.0 and [HCl] 6.0 M in the re-extraction phase with 100% indium recovery and an indium concentration of 110 mg/L after ten extractions. The polymer inclusion membranes (PIMs) offer more advantages for indium recovery because of its high reusability, lower cost, simple operation process and little environmental pollution. The co-extraction of Fe(III) was minimized, reducing Fe(III) to Fe(II) using Fe° and Sn(II). A selective precipitation using ammonia was carried out to enrich and purify indium, and to recover it in solid form as indium hydroxide. The methodology proposed in this study that managed to efficiently extract In from a metallurgical waste could be the basis for developing methodologies to the extraction of In and/or other strategic elements from other metallurgical waste, given the reuse of these wastes as alternative sources of strategic elements.