Table 3 Comparison between leaching results with thiourea and cyanide
Flotation concentrate containing gold calcine cyanidation leaching thiourea
Mineral Au/S/ As/ gold leaching residue containing thiourea / (gt -1 ) gold leaching residue containing sodium cyanide (gt -1 ) % % yield gold / dosage / yield gold / dosage /
/% (gt -1 )(kg.t -1 ) /% (gt -1 )(kg.t -1 )
sequence
number
1 35.00 44.4 16.8 54.0 94.3 3.7 4.0 91.9 4.9 4.9
2 21.0 34.4 16.8 32.0 94.1 2.4 5.1 81.0 7.6 10.0
3 46.00 24.8 25.3 72.0 90.5 8.5 4.5 87.0 11.7 4.5
4.3 Thiosulfate method In the non-cyanide gold extraction study, the thiosulfate method is superior to the chlorination method and the thiourea method because it is leached in an alkaline medium. As early as 1957, the Soviet Union studied the dissolution thermodynamics of pure gold in ammonia thiosulfate solution. In 1972, Japan studied the catalytic effect of Cu2+ on S2O2-3 gold dissolution and its influencing factors. In 1981 the United States S2O2-3 leaching studies containing copper, manganese refractory gold ores have been. In 1983, the Soviet Union obtained a patent for the treatment of complex gold deposits containing copper and manganese with thiosulfate. The United States buttonmont company established a bacterial pretreatment (carbon and arsenic ) thiosulfate heap leaching plant in the Carlin Gold Mine.
Domestic research on thiosulfate leaching gold started late. After 1984, Shenyang Gold Institute, Shenyang Mining and Metallurgy Institute, Northeastern University, Institute of Chemical Metallurgy, Chinese Academy of Sciences, Central South University of Technology and other units carried out thiosulfate gold extraction Basic theoretical research and technical development work of the method. According to the report, although thiosulfate has the advantage of high leaching index, the leaching conditions are demanding and require leaching at a temperature of 50-60 ° C. The leaching system requires SO 2 or sulfite as a stabilizer and Cu 2+ as a catalyst. The test results of a copper-bearing gold concentrate in Shandong by thiosulfate method [18] show that for gold concentrate containing Au 153.62 g/t, Ag 443.5 g/t and Cu 4.71%, at normal temperature and pressure Under the condition, compared with the cyanidation method, the amount of the leaching agent was equivalent by the thiosulfate method, but the leaching time was shortened by 18 h, and the leaching rates of gold and silver were increased by 8.22% and 25.73%, respectively. At present, the domestic thiosulfate method gold extraction process is still in the engineering research stage, and needs to be further improved and promoted.
4.4 Method bromide and chlorine Similarly, bromo gold leaching is a stronger agent has received U.S. Patent [19] As early as 1881 Gusev (Shaff) bromide using gold leaching method. Later, the research was interrupted due to the widespread application of the cyanidation gold extraction process. Until the 1990s, with the emphasis on environmental protection, the bromination method re-emerged attention and research. In 1990, the United States introduced the organic bromide Geobrom series of agents: 3113, 3400, 5500, of which the Geobrom 3400 containing Br 34% had the best effect. In addition, Australia has achieved good results with inorganic bromide as a gold leaching agent.
In recent years, the relevant domestic units have carried out research on gold extraction of gold flotation gold concentrate containing 32.5 g/t by bromination method. The test results show that [20]: flotation gold concentrate is desulfurized by calcination at 600-650 °C. The leaching rate of gold and bromine in HCl medium for 12h can make the gold leaching rate reach 99%, but the research work is still in the laboratory stage, and the research in the United States and Australia has entered the practical stage of engineering.
5 Conclusion (1) China is one of the world's largest gold producers, and it is also a country with rapid development of gold production. Like other countries, China faces serious challenges in resources and environmental protection in the development of gold production.
(2) The Chinese government attaches great importance to the pollution of mercury and cyanide in gold production, and has taken many effective measures to alleviate and mitigate their pollution, but there is still a big gap compared with advanced countries.
(3) Accelerate the development of high-efficiency re-election equipment that can replace the amalgamation method, and actively develop non-cyanide gold extraction technology with industrial application prospects. Starting from cutting off pollution sources, we can better solve the contradiction between gold production development and environmental pollution.
About the author: Luo Jiaxuan, professor-level senior engineer at the Research Management Office.
Luo Jiayu (Beijing Research Institute of Mining and Metallurgy, Beijing 100044, China)
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