Study On Bioleaching Of Low-grade Nicopyrite In Jinchuan By Thiobacillus Ferrooxidans

Microbiohydrometallurgy is a discipline of metallurgy, which values the use of microorganism acquiring metals by transforming the metal ions in mines into the liquor. Compared with traditional smelting technologies, microbiohydrometallurgy has the advantages of little pollution, low cost and making full use of the energy. It can be applied to treat low-grade ores, complex ores and even high-grade ores. Moreover, it is a new technology to replace traditional smelting technologies. The acquirement of excellent bacterium can accelerate the industrial appliance of microbiology leaching. Studying into the bacterium features and the mechanism of nicopyrite leaching has great significances for improving leaching technologies, for updating leaching methods and for increasing leaching rate.In this thesis, a strain of bacteria with high oxidation ability of Fe²⁺ and high nicopyrite bioleaching rate was isolated from acid mine drainage (AMD). And through analysis of the bacteria's morphological and molecular features, it is identified as Thiobacillus ferrooxidans, and named YC. Several experiments have been observed, which are studying the growth feature of YC, studying the durance and the domestication of heavy metal ions, studying the utilization of various energy resources, and studying the tentative reaction mechanism of bioleaching of low-grad nicopyrit in Jinchuan. The results demonstrate as follows:Ferrous icons oxidization rate of YC can reach 340mg/L·h. After 20 days of bioleaching of low-grad nicopyrite in Jinchuan, the bioleaching rate can reach ninety percent, and its activity is better than others'. YC isolated belongs to Thiobacillus ferrooxidans, gram negative, diameter about 0. 4μm, length about 0.8-1.2μm, with flagella. The optimal condition for growth in 9K culture dish is 30℃, pH value 1.5-2.2. Cultivating by shaking dishes to logarithm growth period, concentration can reach 6.5×10⁸ /ml. Heavy metal ions are harmful for YC and by domestication it can make the extreme concentration of YC enduring heavy metal ionsρ(Mg²⁺)=25g/L,ρ(Cu²⁺)=15g/L,ρ(Ni²⁺)=35g/L, which fits the acquirements for industrial leaching nicopyrite. The ability of YC oxidization ferrous ions is better than YC oxidization sulphur. In the course of bioleaching of low-grad nicopyrite in Jinchuan, the direct bioleaching effect of absorption bacterium and indirect effect of free bacterium are simultaneous. Absorption is an important process of bioleaching.