Investigation of mercury removal and gold recovery methods from amalgaming wastes

A significant amount of world gold production was produced by amalgamation and still continues to be produced. It is an important need to recover the high gold content in the wastes of the inefficient amalgamation process and to remove the environmentally harmful mercury. The use of the cyanidation for this purpose is prohibited because it causes different problems. The aim of the study is to develop a new dissolution process, which will allow the combined recovery of mercury and gold from amalgamation wastes. The characterization results showed that these tailings are consisted of more than 90% quartz and contained with a 4,5 and 80 g/t gold and mercury, respectively. The gravity recoverability tests were carried out, and the best gold recovery result observed was 70%. Gold and mercury recoverability with cyanidation and organic reagents was investigated comparatively, and the chemical processes of dissolution with organic reagents were explained. In glycination, it was observed that the temperature and pH of leach, reagent concentration, oxidizing type and amount were effective parameters. Similar to cyanidation, glycine leaching under similar conditions (pH: 10-11 at 20-25℃) and shorter times (6-8 h) at close reagent concentrations (Glycine: 2 g/L, KMnO4: 2 g/L), gold (>90%) and higher mercury (>90%) gains were reached. Similar results were obtained in post-leaching recovery processes. It was determined that mercury could be selectively removed by pre-stripping. Studies show that Au and Hg can be recovered from amalgamation tailings by glycine leaching with high yields and can be an important alternative to cyanidation.