Fundamental Research Of Bio-leaching Phosphate Rock By Bacteria Thiobacillus Thiooxidans

High pollution, great investment Capital and not able to utilize low-grade phosphate ores are disadvantages of traditional phosphate fertilizer industry. This paper proposes a new method to produce bio-fertilizer. Bacteria Thiobacillus thiooxidans (Abbreviated as T.t) is used to oxidize elemental sulfur and to produce diluted sulfuric acid, and this bacterial acid is used to dissolve phosphate rock. This process does not use industrial sulfuric acid and can utilize low-grade phosphate ores. It has potential market prospect.With the same pH and volume, the bacterial acid solution and diluted sulfuric acid dissolve almost the same quantity of phosphate ores. It means that these two acid solutions have similar property and the new method is feasible in principle. Ordinary method is better than Batch method for bio-leaching phosphate ores. The optimum pH and time for bio-leaching process are studied to be I .6?.2 and 28 days respectively.The property of bacterial adsorption was studied systematically. The equilibrium time of bacterial adsorption is between 20 to 60 minutes. The pH value of solution does not affect the adsorption, but the concentration of the attached cell decreases when the concentration of sulfur particles in solution increases. Under equilibrium condition, the concentration of attached cell and free cell are fitted to Langmuir Isotherm Equation. It is measured to be:XI/XA =l.368*10?X1 +4.700The pH value affects the growth of bacteria. The best pH value for culturingIIbacteria is 2.50, and the bacteria grow best and oxide sulfur fastest under this condition. The optimum culture temperature is 30 C. A 10 C decrease in temperature decreases bacterial activity severely, whereas a 10 揅 rise just decreases it slightly.From the kinetics experiment of bacterial growth, the bacterial growth yield YA and the specific growth rate p,1 were measured to be 9~947x l0?Cells /Kg Sulfur and 3.4003Day?respectively.From the comparison of bio-leaching phosphate ores, calcium fluorine phosphate and calcium phosphate, fluoride ion was found to have decisive influence on the growth of bacteria. The higher concentration of fluoride ion in culture solution, the longer the lag phase of bacterial growth and the lower growth rate of bacteria become. The bacterial ability of enduring fluoride can be improved by fluorine-resistance teaming process. We increased it from 1 Oppm fluorine to 20ppm.