Study On Bioleaching Of Low-grade Phosphate Ore With Acidithiobacillus Thiooxidans And Its Mechanism

Waksman medium was used for screening the appropriate microbe strain to bioleachlow-grade phosphate ore. Firstly, the microbe in the soil samples of mine was isolated with sulfuras the sole energy source. Then, the appropriate microbial strains, which could bioleachlow-grade phosphate ores, were screened according to the ability of bioleaching. One strainHY-01 which had high ability of bioleaching was obtained. Microbial identification wasconducted with morphological features, biochemical and physiological test, and 16S rDNAmolecular genetic identification. It was motile, gram-negative, and rod-shaped in (0.5 to 0.7) m(1 to 2) m. The strain grew optimally with initial pH 2.0-2.5 and temperature 37 . It couldgrow with potassium nitrate, ammonium nitrate, ammonirm carbonate, ammonium dihydrogenphosphate, ammonium sulfate and tryptone as nitrogen source. Elemental sulfur and pyrite couldbe used as energy sources, but nor could organic minerals and inorganic minerals includingsodium thiosulfate and ferrous sulfate. The 16S rDNA sequence was blasted in NCBI database,and the result showed that the strain HY-01 was similar to Acidithiobacillus thiooxidans. Theidentity was over 96%. In the phylogenetic tree, HY-01 was closely related to several strains inAcidithiobacillus thiooxidans. All these taxonomic studies of Strain HY-01 indicated that itbelonged to Acidithiobacillus thiooxidans.Strain HY-01 was used to bioleach low-grade phosphate ore. The optimal reductionconditions were obtained: 30 , pH 2.0, 120 r/min, 10 g/L phosphate Ore (small than -200mesh), 10 g/L pyrite and 30% inoculation amount of bacterium for bioleaching.In order to improve bioleaching rate, surfactant and amino acids were applied to theexperiments. The optimal concentration of Tween 20, Tween 40, Tween 60 and Tween 80 was 10g/ m~3, 300 g/ m~3, 50 g/ m~3, 150 g/ m~3 respectively. Among these, Tween 60 was the best one,which could make bioleaching rate increase 24.19%. Glycolamine could raise bioleaching rateby less than 1% rather than the other Amino acids. Furthermore, HY-01 was mutated by UV rays,microvave and NaNO2. The best mutant was mutated by NaNO2(0.6%, v/v) for30 minutes.Leaching solution, bacterium, extracellular polysaccharides and phosphate ore wereanalyzed. The results showed that At.t could be attached to ores within 50 minutes; in the processof bioleaching, there were a little organic acids and a lot of sulphuric acids which were moreefficient for bioleaching; Extracellular polysaccharides of At.t could improve bioleaching rate by1.80%; after bioleaching, the phosphate ore became to small, loose debris from large, angularparticles; furthermore, phosphorus in the ore decreased to1.68% from 9.31%.