Gold recovery from shredder light fraction of E-waste recycling plant by flotation-ammonium thiosulfate leaching. (July 2018)

• Record Type: Journal Article
• Authors: Jeon, Sanghee; Ito, Mayumi; Tabelin, Carlito Baltazar; Pongsumrankul, Rongrit; Kitajima, Naho; Park, Ilhwan; Hiroyoshi, Naoki
• Is Part Of: Waste management. Volume 77(2018)
• Page Start: 195
• Page End: 202
• Publication Date: 2018-07
• Subjects: E-waste -- Shredder light fraction -- Recycling -- Gold recovery -- Flotation -- Ammonium thiosulfate leaching; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2018.04.039
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: Au and base metals in SLF were separately recovered by flotation. Over 99% of Au was recovered from SLF by flotation as froth products. Over 90% of base metals were recovered from SLF by flotation as tailing products. Au extraction efficiency by ammonium thiosulfate solutions improved after flotation. Abstract: This paper describes the recovery of gold (Au) from shredder light fraction (SLF) of a recycling plant by flotation and leaching. SLF is typically sent to landfills as waste, but it still contains substantial amounts of Au, and other metals like Cu and Fe. The SLF sample used in this study contains 0.003% of Au, 12% of Cu, and 10% of Fe. Flotation results showed that over 99% of Au and 50% of combustibles were recovered in froth while most of the base metals were recovered in tailing. SEM-EDX of froth products indicates that Au floated via two mechanisms: (1) flotation of Au-plated plastic particles, and (2) agglomeration of fine Au particles together with plastic particles due to kerosene-induced hydrophobic-hydrophobic interactions followed by the flotation of these agglomerated particles. Combustibles in froth/tailing were analyzed by ATR-FTIR, and the results showed that plastics in the froth were mostly sulfonated polystyrene (PS) and acrylonitrile butadiene styrene (ABS) while those in tailing were polyurethane (PU) and polyethylene terephthalate (PET). Contact angle measurements of plastic particles suggest that PS and ABS are more hydrophobic than PU and PET. Most of the base metals in the tailing had either bent or twisted shapes because they were mostly made up of wires. In flotation, these large and heavy particles are unaffected by bubbles and simply sink. Leaching results using ammonium thiosulfate solutions showed that Au extraction increased from 33 to 51% after flotation.