Environmentally friendly extraction of gold from refractory concentrate using a copper – ethylenediamine – thiosulfate solution. (20th March 2019)

• Record Type: Journal Article
• Authors: Wang, Qiang; Hu, Xianzhi; Zi, Futing; Yang, Peng; Chen, Yunlong; Chen, Shuliang
• Is Part Of: Journal of cleaner production. Volume 214(2019)
• Page Start: 860
• Page End: 872
• Publication Date: 2019-03-20
• Subjects: Roasting -- Refractory gold concentrate -- Response surface method -- Ethylenediamine -- Thiosulfate; Response surface methodology RSM -- X-ray diffraction XRD -- scanning electron microscopy SEM -- energy-dispersive X-ray spectroscopy EDS -- liquid-to-solid ratio L/S -- central composite design CCD -- atomic absorption spectrometry AAS -- inductively coupled plasma-atomic emission spectroscopy ICP-AES; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2019.01.007
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: The growing environmental concerns associated with the use of cyanides and their toxicity have led to the prohibition of cyanidation-based gold leaching in many countries, necessitating the search for other extraction methods. Herein, we show that thiosulfate leaching presents an alternative green way of gold extraction from S- and As-rich refractory gold concentrates, revealing the importance of oxidative ore pretreatment. Prior to leaching, samples were oxidized by roasting, with the optimum roasting temperature (642 °C) and time (240 min) determined using the response surface method. Subsequently, the roasted residues were subjected to cyanidation, copper – ammonia – thiosulfate system, and copper – ethylenediamine – thiosulfate system treatment. As a result, 18-h cyanidation achieved a gold extraction efficiency of 80.6%, with the consumption of NaCN equaling 1.05 kg/t, whereas the corresponding values for 1.5 h copper – ammonia – thiosulfate treatment equaled 63.0% and 11.3 kg/t. Importantly, 4 h copper – ethylenediamine – thiosulfate system treatment (5 mM copper ion, 10 mM ethylenediamine, 0.1 M thiosulfate, pH = 8–11, liquid-to-solid ratio = 3, stirring speed = 250 rpm) achieved a gold extraction efficiency of 80.3%, with the corresponding thiosulfate consumption equaling only 4.14 kg/t. Thus, copper – ethylenediamine – thiosulfate leaching proved to be an efficient, environmentally friendly, and low-cost method, being well-suited for gold extraction from roasted residues. Highlights: Copper – ethylenediamine – thiosulfate leaching is described as an alternative green way of gold extraction. Under optimal conditions, a gold extraction efficiency of 80.3% is achieved. The developed low-cost and environmentally friendly method is almost as effective as cyanidation.