Selective Cultivation Of Acidithiobacillus Thiooxidans And Its Application In Bioleaching Of Phosphate Ore

With the development of bioleaching, people pay more attention to the bacteria which play important role in the course of bioleaching. Acidithiobacidlus generally have the ability to derive energy from low-valence sulfur compounds, such as elemental sulfur, polysulfide, sulfite and metal sulfide. This ability has been applied to the bacterial leaching of sulfide ores, desulfurization of coal and so on.In this paper, a strain of bacteria was isolated from acid mine drainage from a coal mine in Anhui, and identified as Acidithiobacillus thiooxidans. The morphological characteristics are as follows: the length of At. t is 1-1.5um, G^-, single polar flagella. With regard to the growth feature, it can grow under pH 0:5-5.0, and at temperature 25-35℃. The optimal condition for growth is pH2.0-3.5, 28-30℃. At. t is able to derive energy from elemental sulfur and other low-valence sulfur compounds, using amino nitrogen as nitrogen source and CO₂ as carbon source.After further isolation and purification, a strain of At. t that can be used effectively in the leaching of low-grade phosphate ore was isolated. Its characteristics of morphology and cultivation were studied. Through the investigation of the effect of different solid culture medium components on the isolation and purification of At. t, the optimum isolation conditions were determined as using a double-layer plate with chemoautotrophic bacterium At. t spread onto the upper Starkey solid culture medium layer, and heterotrophic microbe Rhodotorula sp. spread onto the bottom agar layer, resulting in significantly increased density and reduced forming time of the bacterial colony.According to the experiment of leaching the low-grade phosphate ore with dilute sulfuric acid, it has shown that dilute sulfuric acid can leach the phosphate ore but with a very low leaching rate. Then experiments on the leaching of low-grade phosphate ore were made using the isolated At. t strain. The influence of factors including culture medium, the addition of surfactant and pulp concentration on the leaching of phosphate ore with the cultivated At t was studied. Through preliminary experiments, it was concluded that it can reach its best effect on the leaching of phosphate ore under the following conditions: Starkey culture medium was selected, inoculated quantity of bacteria was 10%(10mL bacteria /100mL culture medium), using 1g/100mL sulfur powder and 1g/100mL phosphate ore with the addition of 100 cm³/m³ Tween80 surfactant.