Recovery of noble metals from floor sweeping jewelry waste by flotation-cyanide leaching

Recycling of materials is becoming progressively more significant for society due to the depletion of natural resources. Jewelry wastes are considered as secondary sources of raw material and contain a very high proportion of precious metals. Scraps and wastes from jewelry activities need to be pre-treated before refining to reduce costs and maximize the recovery of precious metals. In this paper, the recovery of gold (Au) and silver (Ag) from floor sweeping jewelry wastes (FSJW) of jewelry workshops using flotation followed by leaching process was studied. In flotation experiments, optimum pH value, particle size, type, and amount of reagent were the investigated parameters. Experimental results demonstrated that the flotation method was very successful in diminishing much of the waste fraction. A froth product, with more than 280 g/t Au and 2800 g/t Ag, was produced from a feed containing 174 g/t Au and 1834 g/t Ag with approximately 87% Au and 82% Ag recoveries. To investigate the dissolution behaviors of gold and silver, cyanide leaching tests were carried out directly on the feed and the froth product. 68% Au and 75% Ag in leach that were obtained with direct feed after 48 h of leaching in 12 g/L NaCN concentration at 40 °C and 1/5 solid/liquid ratio (w/w) were enhanced to 79% Au and 84% Ag when the froth sample was subjected to leaching under the same conditions.