Study On Screening And Culturing Of Biometallurgical Microorganisms And Their Leaching Process In Low-grade Tellurium Ore

Tellurium is a scattered element, whose content is fairly low in the earth crust, only6×10-7%, but has a pivotal role in the metallurgy, chemical industry, electronics and other fields. Traditional exploiting techniques for tellurium resources depend on the anode mud of copper refineries, and have the characters of low rate of recovery, which can’t meet the demand of tellurium gradually increased year by year. Because of its low cost, environmental friendly and high resource utilization, the biohydrometallurgy is particularly suitable for low-grade ore even refractory complex mineral, which is in line with the concept of sustainable development. Through screening and culturing of biometallurgical microorganisms from the acid sewage and soil and the optimization of their culture conditions, the bioleaching study on low-grade tellurium ore was carried out, which aimed to explore the leaching feasibility of low-grade tellurium ore. In this paper, the main contents and conclusions are as follows:(1) A mixed bacteria was obtained by enrichment from the acid sewage and soil near the thermal power plant of the Cui store, Chengdu. Primary study on the bioleaching of low-grade tellurium with the mixed bacteria showed that the leaching rate would reach78.6%after leaching25days at a temperature of30℃, with an initial pH of2.0.(2) Three pure bacteria (Z1, Z2and Z3) were obtained by isolation and purification from enrichment medium. The culture medium originally changed from light green to pale yellow, finally into red-brown, while generating precipitation during pure culture. The result of morphology indicated that three bacteria were Gram-negative, short rod-shaped, nomadic. Based on their morphology, cultural characteristics and the sequence of16S rDNA, three strains were determined as Acidithiobacillus ferrooxidans (At.f). (3) The bacterial growth curve, which was described by the turbidimetry method, showed that the lag phase was0-20h, the logarithmic phase was20-48h, in which bacteria had the fastest growth rate and the highest activity, and the stationary phase was arriving after48h. The pH of the solution was continuing to decline, and finally stabilized at about1.2after48h. The assay of Fe2+oxidation capacity indicated that three strains all had the heavily Fe2+oxidation and the oxidation rates of them respectively were90.38%,95.24%and97.32%. The oxidative capacity curves and bacterial growth curves were coincide.(4) The optimum culture conditions of strain Z3were determined by the response surface analysis (RSA):initial pH1.5, temperature30.1℃, inoculum size15.2%, culture volume63.3mL. The Fe2+oxidation rate reached98.51%, after leaching for48h under the conditions.(5) The study on leaching of low-grade tellurium ore demonstrated that the optimum leaching process of strain Z3were:initial pH1.5, temperature30℃, inoculum size15%, culture volume63.3mL, in which the leaching rate would reach78.34%after leaching for30days.