Research And Application On Selective Bioleaching Of High Sulfur Low Copper Secondary Copper Sulfide Ore

To solve bottleneck technical issues of biohydrometallurgy technology development on high sulfur low copper secondary copper sulfide ore, such as excess acid, iron accumulation and water balance difficulties, methods like MLA mineral composition analysis, electrochemical cyclic voltammetry, real-time PCR analysis, clone library analysis and high-throughput sequencing were used to systematic study selective bioleaching and industrial application. The thesis revealed chalcocite and pyrite biological dissolution mechanism, solved problem of matching biological, physical and chemical factors with mineral selective leaching under open heap bioleaching environment and identified migration mechanisms of acidophiles around the heap, which provided theoretical guidance and practical experience for the whole process of copper sulfide ore bioleaching.Based on the differences of lattice features between chalcocite and pyrite, the electrochemical dissolution mechanism of pure chalcocite and pyrite was studied, revealing the selective bioleaching law of the two minerals. The selective bioleaching of chalcocite and selective inhibition of pyrite could be achieved by controlling the potential and the activity of sulfur-oxidizer. During bioleaching process, chalcocite generates Cu S first, further produces Cu2+, and has a higher dissolution rate at 0.25 V(vs. Ag/Ag Cl); pyrite generates Fe2+ first, further produces Fe3+, and dissolves at potential high of 0.65 V(vs. Ag/Ag Cl). Comparison the chalcocite and pyrite oxidation ability of iron-oxidizer and sulfur-oxidizer system, the inoculation of sulfur-oxidizer could low down pyrite oxidation.The selective leaching process parameter and microbial population dynamics were carried out. Results showed that at lower p H(1.2), the bioleaching of chalcocite was beneficial, but resulted in rapid dissolution of pyrite. At higher p H(1.5), sulfur oxidizer in the system could be maintained at a higher proportion and the proportion of sulfur oxidizer in the ore surface was higher than iron oxidizer, but in the final phase of leaching cycle, iron oxidizer would be dominated again. By restriction oxygen content, inoculation of sulfur oxidizer, controlling temperature, p H value, the growth of iron-oxidizer was effectively inhibited and the sulfur-oxidizer dominant community structure bioleaching system was constructed. Thus, the oxidation of Fe2+ by iron-oxidizer was depressed, and the leaching system was maintained at lower redox potentials. After 185 days leaching, compared to non-controlled conditions, copper leaching rate was basically unchanged under 40 °C and with aeration of N2 or CO2, and ultimately, reached 77.37 %, but iron leaching rate decreased from 24.86 % to 16.53 %.Based on the growth and territorial characteristics of industrial bacteria culture process, a new method integrating inoculation of heap bioleaching with mining pit water was established, which ensured the efficient bacteria amplification and inoculation, and meanwhile increasing the sulfur-oxidizer adaptability and comprehensive utilization of copper, acid and pit water, without new water utilized. By using engineering technologies, such as spraying and leisure regulation, free acid neutralization and raffinate COD concentration control, the oxygen concentration was restricted inside the heap, solution p H was controlled at 1.5~1.7, heap temperature around 40 °C and ORP less than 760 m V(vs. SHE) were achieved. Jarosite was self-generated in the heap, hence reducing the content of iron in the solution, and sulfur oxidizer dominated microbial community was formed. After 227 days leaching, copper leaching rate was 82.4 %, and iron leaching rate was controlled at 6.2 %, thus the efficient leaching of copper sulfide and inhibition of pyrite dissolution was achieved. The material balance results showed that copper, iron and water balance errors were 4.2 %, 3.1 %, and 0.5 %, respectively, indicating the material balance was quite accurate. The research achievements solved problems such as excess acid, iron accumulation and water balance from the beginning, and have been industrialized with cathode copper cost of 21300 RMB per ton. Compared with foreign advanced bioleaching technology, Zijinshan copper selective heap bioleaching technology is at the leading level, with significant technical, economic, and enviromental advantages.For the first time, the acidophiles migration mechanisms around Zijinshan copper heap bioleaching plant were revealed. Through six years of comprehensive research, we found that the 16 S r RNA gene sequences of acidophiles in the soil and water around the heap were different with acidophiles in the heap. The 16 S r RNA gene homologies between them is less than 98.5 % and 98 %, which shows that they are not the same strain and the acidophiles in the soil and water are the background microorganisms. Acidophilic microorganisms were not found in all the air samples. Moreover, unless pit water contained copper, iron metal element, the heap bioleaching process only had minor influence to physical and chemical index of the soil and water around, such as, the p H value, Eh, copper, iron, sulfate, COD, SS. The Tingjiang river water samples met the water quality standards of GB3832-2002 in class II, which showed that heap bioleaching process under normal operation had little effect on the surrounding soil and water, and the acidophiles in the heap can not migrate through the soil, water and air.