Abstract
Based on a “filter press backwash–chemical precipitation–gaseous membrane absorption” process, treatment of harmless cyanide tailings was conducted using cyanide tailings from a gold smelting enterprises (Yunnan Province, China) as the research object. The effects of air-drying time, backwash water parameters, initial pH of acidification, NaHS dosage, cyanide-containing water flow rate, and gaseous membrane stages on the process were investigated. Chemical composition, X-ray diffraction, and X-ray photoelectron spectroscopy analyses of the copper products were carried out. Results showed that the copper content in the copper product was 54.56%, and the chemical composition was mainly CuSCN, CuS, Cu2S, and CaSO4. Five cycles of experiments were carried out under optimal conditions; the results showed that the process can make the treated cyanide tailings meet the requirements of the technical specification for pollution control of cyanide leaching residue in the gold industry (TSPC) standard for storage in a tailings pond and a have certain stability. The average recovery rate of copper and total cyanide in elution water was 97.8% and 99.89%, respectively, and the average removal rate of thiocyanate was 94.09%.
Highlights
The cyanide gold extraction method was proposed by the British scientist MacArthur in 1890 [1]
The cyanide tailings after the filter press are directly stored in the tailing pond, and the filtrate is returned to the cyanide gold extraction system
The results show that the main reason for the substandard leaching toxicity of the cyanide tailings was the copper–cyanide complex in the cyanide tailings
Summary
The cyanide gold extraction method was proposed by the British scientist MacArthur in 1890 [1]. The cyanide extraction process inevitably produces a large amount of cyanide-containing waste, and the annual discharge of cyanide tailings of China’s gold industry exceeds 24.5 million tons. The technical specification for pollution controls of cyanide leaching residue in the gold industry (TSPC) was not promulgated in China until 1 August 2018 [3]. The cyanide tailings produced in the gold industry are mainly disposed of in open-air stockpiling and tailings pond storage, which occupies a large amount of land, and affects the environment and sustainable development of the mining area [4,5]. Cyanide tailings are a secondary resource, containing a large number of valuable metals such as gold, silver, copper, iron, sulfur, and so on [6,7]. Harmless treatment of cyanide tailings is beneficial to environmental protection, and beneficial to the recovery of valuable resources
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