Study On Mutagenizing Cultivation Of Thiobacillus Ferrooxidans And Improved Bioleaching Of Tellurium Ore

Because of the process short and simple, easy operation, low investment, lowenergy consumption, low cost, environmentally friendly and so on, so more peoplepay attention to bacterial leaching. Bacterial leaching has broad prospects forindustrial applications at the development and utilization of low-grade and refractorydevelopment mineral resources. A wide range of chemoautotroph microbes are themain bacterium used in bacteria leaching. Acidithiobacillus ferroxidans (At.f) was themost widely studied, because it can use oxygen from air to oxidize the reductive stateof iron and sulfur, from which it gains energy and produces acid to leach phosphorusfrom middle or low grade phosphate 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, electronicsand other fields. At present, the main exploiting technique for tellurium resources ischemical leaching, which recovery tellurium from the anode mud of copper refineries,and involve with acid or alkali, and have the characters of high requirement ofequipment, low rate of recovery. With the discovery of independent tellurium oredeposit in Shimian county, the exploiting technique for tellurium had entered a newfield. At present, the technology only can be used in middle-grade and high-gradetellurium ore, but high-grade tellurium ore is extremely limited and the majority ofwhich are lean ore. As national strategic resource, these low-grade ore and intractableunique resources are urgent developed. Therefore a new technology to extracttellurium for low-grade telluric bismuth ore is desiderated.Strain Z1was isolated through previous studies, which had leaching effect ontelluric bismuth ore. In this study, the strain Z1was activated, identified, biochemicaltested and mutated, in order to get a excellent strain, whose leaching rate of telluriumis stronger. This will not only reduce the grade and improve the recovery of telluriumand produce good economic benefit, but also can reduce the pollution of barren rockand waste residue, and lay the foundation for the industrialization of bacterial leachingof tellurium. The results showed that:1) The9K liquid culture medium originally changed from light green to paleyellow, finally into red-brown, while the strain Z1is generating precipitation during pure culture. The result of morphology indicated that three bacteria wereGram-negative, short rod-shaped, nomadic. Based on their morphology, culturalcharacteristics and the sequence of16S rDNA, the strain was determined asAcidithiobacillus ferrooxidans.2) The bacterial growth curve, which was described by the turbidimetry, showedthat the lag phase was0-20h, the logarithmic phase was20-48h, in which bacteriahad the fastest growth rate and the highest activity, and the stationary phase wasarriving after48h. The assay of Fe2+oxidation capacity indicated that the strain hadthe heavily Fe2+oxidation and the oxidation rates of it respectively was90.46%. Theoxidative capacity curves and bacterial growth curves were coincidence.3) The optimum culture conditions of strain Z1were determined by the responsesurface analysis (RSA): initial pH1.8, temperature30℃, inoculum size14%,culture volume60mL. The Fe2+oxidation rate reached98.39%, after leaching for48h under the conditions.4) The mutagenic strains were used for leaching of low-grade tellurium ore,which were mutagenized by ultraviolet mutagenesis, ultrasonic mutagenesis, NTGmutagenesis and compound mutation of the strain Z1, the result showed that the bestmutagenic method of strain Z1was compound mutation. The conditions of compoundmutation of strain Z1were determined by the response surface analysis (RSA):initialpH1.6, ultraviolet mutagenesis20min, ultrasonic mutagenesis11min and the NTGmutagenesis47min. Based on t in which the leaching rate would reach91.77%afterleaching for30days.5) The study on strengthen leaching of low-grade tellurium ore demonstrated thatthe optimum leaching conditions of strain ZYB-1were: initial pH1.5, inoculum size15%, temperature30℃,[Na2S2O3]=10g/L, in which the solid and liquid leachingrate would reach95.96%and94.47%after leaching for30days.