Enriching indium from zinc sulfate solution bearing high iron and indium containing

Enrichment of indium from zinc sulfate solution containing high iron and indium was studied by zinc calcine pre-neutralization and zinc cementation for indium precipitation under the pre-neutralization process. The effect of the dosage of pre-neutralization zinc calcine on the liquid acidity after the pre-neutralization and the effect of the liquid acidity on the leaching of indium from the calcine were discussed. Under a certain experimental condition, the optimal condition in pre-neutralization process was put forward: the dosage of zinc calcine was 1.4 times of theoretic value, the temperature of pre-neutralization was 70 to 75℃, the time of pre-neutralization was 30 min, and the concentration of solution was about 1.2 g·L-1. Under the process of zinc-dust cementation, the pH of solution, time, temperature and the dosage of zinc-dust could affect the precipitation and the pH of solution was a major factor. The optimal condition was put forward: pH of solution was 4.0, the temperature of the process of zinc-dust cementation was 80 to 85℃, the time of the process was 1 h, the dosage of zinc-dust was 6 g·L-1, and In3+ concentration of the solution after cementation was 3 mg·L-1. Under the optimal condition, the precipitation rate of indium was more than 98%; the content of indium sediment from precipitation was 1.5% to 3.0%. The X-ray diffraction(XRD) analysis of the cementation residue showed that the main form of element indium in the cementation residue was In(OH)3, which meant that the main reaction in the cementation process was hydrolyzation of indium. During the cementation process, the acidity of zinc sulfate solution decreased, which accelerated the hydrolyzation and precipitation of indium.