Identifying Extraction Technology of Gold from Solid Waste in Terms of Environmental Friendliness

The demand for gold in the field of national storage, jewelry, and electronics has never been higher. However, gold extraction is not always welcomed by local residents because of the resulting environmental contamination. For more than a century, cyanide and aqua reiga were dominantly used for gold mining because of their low costs, high efficiencies, and easy operations. In this article, an improved chlorination process, a traditional cyanidation process, and a traditional aqua regia process were quantitatively analyzed and compared from the perspective of environmental impact. The Biwer-Heinzle method is employed. The results showed that the improved chlorination process had the lowest environmental hazard. The values of General Environmental Indices computed for the Inputs and Outputs were quite small, closing to the minimum values of 0 and 1, respectively, depending on the calculation approach used, via arithmetic average or via multiplication. The results also revealed that the aqua regia process had greater negative impact on the environment than the cyanidation process because aqua regia requires much higher concentrations and larger amounts. The findings provide a reference for the selection of gold extraction method and promote the gold extraction to be more environmentally-friendly.