Applied Researches On Thiobacillus Caldus And Novel Bio-Reactor

There is a long history for bioleaching of metals using microorganisms and it has applied in modern industry. Bioleaching has many advantages, such as low cost, high recovery of metals, little environment pollution and so on. It has been used to recover copper and uranium from wastes and low-grade ores. It is also suitable for high-grade sulfide ores and refined ores, and has a bright future in extraction of gold. In addition, it is also used for desulfurization of coal. The deliquescent rate of metal is correlated with the biomass of bacterium during bioleaching process of sulfide ores. So, microbial growth is generally a limiting step in the bioleaching process. Therefore, designing efficient bioreactor, studying the characteristics of microbial growth and optimizing cultivation conditions are important for improving the rate of bioleaching.The microorganisms used for bioleaching are mainly iron-oxidizing or sulfur-oxidizing bacteria which live in acid condition. The studies on microorganism species in the continuous bioleaching system indicates that some moderately thermophilic acidophilic bacteria whose optimum temperature is about 40~45, such as Thiobacillus caldus and Leptospirillum ferrooxidans, are the dominant species. The study indicates that moderate thermophilic acidophilic iron-oxidizing or sulfur-oxidizing bacteria play important roles in bioleaching process. Thiobacillus caldus is obligate autotrophy sulfur-oxidizing bacterium, rod-shaped, motile, flagellate, Gram-negative.In this research, the cultivation conditions of Thiobacillus caldus were studied in flask bottles and the major factors including culture temperature, pH and sulfur concentration were optimized. The optimal cultural conditions with Starky-S~0 medium are at 40-45℃, initial pH 2.5 and sulfur concentration 2.0 g/100mL.In the industrial application of bioleaching of unmanageable high-grade ores, such as gold refined ores, designing a high-efficient bioreactor is pivotal for improving efficiency. At present, the widely used bioreactor in industry is stired tank, which has the biggist disadvantage for its great shear strength that can damage the cells seriously. For this reason, the pulp concentration can bot be raised high, and it lowers down the working efficiency of the equipment.With regard to the shortcoming of the stired tank bioreactor, a novel airlift reactor will be developed in order to decrease the shear force and the cell damage, and increase the...