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Kinetics of simultaneous recovering of Au and Ag from CTs by chloridizing volatilization methods

Weiwei Wang, Zhengyao Li, Shanshan Yang, Kai Ma, Xin Gao, Shaoqi Han, Shaochun Hou, Hecheng Miao

Physicochemical Problems of Mineral Processing

2023

Vol. 59, iss. 6

art. no. 172522

Cyanide Tailings (CTs) are known as hazardous resources that accumulate hundreds of millions of tons, threatening the ecological environment. This work proposes an eco-friendly and efficient way to recover gold and silver from CTs. The effects of calcium chloride dosage, silicon dioxide dosage, pellet moisture content, roasting temperature, and roasting time on Au and Ag chloridizing volatilization were studied. The kinetics of simultaneously recovering of gold and silver from cyanide Tailings by chlorination roasting was investigated. It was determined that the chloridizing volatilization rates increased with increasing calcium chloride dosage, temperature and decreasing silicon dioxide dosage, pellet moisture content. The chloridizing volatilization kinetics followed a shrinking core model, with inter-diffusion through gangue layer as the rate determining step. This finding is in accordance with the apparent activation energy (Ea) of 24.01 kJ•mol-1 (Au) and 24.62 kJ•mol-1 (Ag). The orders of reaction with respect to moisture content, temperature, calcium chloride dosage and silicon dioxide dosage were also achieved. The rate of reaction based on diffusion-controlled process can be expressed by semi-empirical equations. The control steps of the gold and silver recovery process were investigated by the kinetic study, which provided theoretical guidance for the optimization of the method.

Activating flotation of chalcopyrite using CuSO4 and H2O2 from the cyanide tailings

Ai G., Yan H., Qiu T., Liu C.

Physicochemical Problems of Mineral Processing

2018

Vol. 54, iss. 2

578--589

The effects of CuSO4 and H2O2 on the flotation behavior of cyanide chalcopyrite were investigated by flotation tests, microcalorimetry and X-ray photoelectron spectroscopy (XPS). The underlying activation mechanism was studied in the perspective of micro-thermodynamics and surface properties. The flotation results indicated that cyanide chalcopyrite was strongly inhibited by sodium cyanide, with the maximum flotation recovery of 22.5% only. CuSO4 and H2O2 significantly improved the flotation of cyanide chalcopyrite, and the flotation recovery was increased to 92.28% and 84.35%, respectively. The micro-thermodynamics results indicated that the adsorption heat of butyl xanthate on cyanide chalcopyrite surface increased after the addition of CuSO4 and H2O2, as well as the reaction order. CuSO4 and H2O2 can significantly improve the adsorption of butyl xanthate on the surface of cyanide chalcopyrite by decreasing the apparent activation energy by 80.11% and 66.54%, respectively. XPS analysis indicated that the CuCN was generated on the surface of cyanide chalcopyrite, leading to the loss of sulfur and inhibiting the adsorption of collectors. As a result, the flotation of cyanide chalcopyrite was depressed. It is considered that, CuSO4 and H2O2 can improve the flotation of cyanide chalcopyrite by eleminating CuCN from its surface and increasing the concentration of S by 57.02% and 37.48%, respectively.