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

Abstract

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.

Hexacyano Ferrate (III) Reduction by Electron Transfer Induced by Plasmonic Catalysis on Gold Nanoparticles

“…This oxidative ligandation by CN − might account for the small changes observed in the LSPR of Au-NPs@citrate in the presence of ST and the decrease in the LSPR band in the absence of ST (Figure S3), oxidation being more effective in that case. Indeed, it is well-known that cyanides are used to extract gold from mines via oxidation and complexation [44], as CN − has a great ability to complex with Au and form a stable complex Au(CN) 2 − .…”

“…The results demonstrate the effectiveness of using colloidal spherical gold nanoparticles to catalyze redox reactions under visible irradiation. Further work will focus on anisotropic Au nanoparticles (such as Au nanorods or Au nanostars), which absorb in a larger spectral range compared to spherical Au NPs and could be used to better harvest solar light for catalytic applications [44].…”

Mechanism of selective gold extraction from multi-metal chloride solutions by electrodeposition-redox replacement

“…Following the principles of green engineering, 14 sustainable gold production also encourages the development of ecofriendly, non-toxic extractants to replace commonly used cyanide. 15,16 Chloride-based processes of gold leaching have proven their efficiency and are considered a viable alternative to conventional hydrometallurgical technologies. 17,18 The efficient extraction of gold in aqueous chloride solutions is possible even with minor reagent addition.…”

Functional Polyselenoureas for Selective Gold Recovery Prepared from Catalyst-Free Multicomponent Polymerizations of Elemental Selenium

“…37,38 Nowadays, due to the extensive use of Au in the rapidly renewed electronic products, it is of great economic benefit to recover Au from waste electronic products as a means of recycling, considering that the Au content of discarded PCs and mobile phones (280 g/ton) is much higher than that from gold ore (5 g/ton). 39,40 While the traditional Au extraction methods require highly toxic inorganic cyanides and extreme pH conditions, accompanied by enormous dangers, lethal toxicity, high energy consumption, and complex posttreatment, [41][42][43] continuous endeavors have been made to improve the extraction of Au from industrial wastewater and electronic wastes. Recent approach took advantages of the affinity of Au for sulfur or nitrogen, in combination with the porosity of metal-organic framework (MOF) materials or property of bacteria to realize high enrichment efficiency.…”