Eco-friendly and reagent recyclable gold extraction by iodination leaching-electrodeposition recovery

Abstract

Although iodination gold leaching is a clean, non-toxic and efficient non-cyanide gold leaching process, it still has the problems of high reagents cost and difficult leaching solution treatment. To solve these problems, a process of iodination leaching-electrodeposition recovery was proposed. Thermodynamic analysis confirmed the feasibility of iodination gold leaching, and the influence of different factors on gold leaching was studied. The result shows that roasting could effectively improve the gold leaching effect, the concentration of initial iodine and initial iodide ion had a significant effect on the gold leaching, and the gold leaching could be achieved under normal temperature and neutral conditions. The kinetic analysis shows that the gold leaching process conforms to the shrinkage kinetics model, and the control step was the solid film diffusion control. The apparent activation energy of this reaction was 8.642 kJ/mol, and the reaction order of initial iodine concentration and initial iodide ion concentration were 0.72 and 0.52, respectively. Gold was recovered from the leaching solution by electrodeposition with a recovery percentage of more than 99%. More importantly, the iodine was formed in the anode area, in other words, the reagents used for gold leaching were enriched in the anode area during the gold recovery process. The recovery percentage of iodine in the anode area reached 83%, and the anolyte could be recycled. This process fundamentally solves the problem of high cost of iodination leaching.