Isolation And Identification Of A Strain Of Acidithiobacillus Ferrooxidans And Study On Anti-biooxidation Mechanism By Surface Passivation Agent Triethlenetetramine(teta)

Acidthiobacillus ferrooxidans (A. f) which exists in acid mine drainage and tailings is one of the most important and lucubrated bacteria in bioleaching process at the present. The capacity of tailings in China is more than one hundred million tons with several million tons of growth rates every year. A. f strain can accelerate the weathering of tailings and leaching process of heavy metals which threaten the environment of neighboring region.This research intended to get a new passivating program to passivate the mine tailings without pre-oxidation. It studied on the growth and characteristic of A. f strain and chemical and biological situation of sulfide minerals under passivation at the micro level. It aimed to find new methods of inhibiting the oxidation of tailings and slowing the release of heavy metals in different ways. The main content of the research includes: the isolation and identification of an A. f strain named by DBS-8 and researches on anti-biooxidation mechanism by surface passivation agent triethlenetetramine (TETA).Taking 9K medium with Fe²⁺ as energy source, a strain DBS-8 which had high Fe²⁺ and elemental sulfur oxidation activity was obtained. After PCR amplification of 16S rRNA and DNA testing, DBS-8 was identified as an A. f strain and its phylogeny was constructed. Then, an orthogonal experiment was designed to investigate the impact of inoculums volume﹑initial pH﹑concentration of ferrous﹑temperature and concentration of ammonium sulfate on the growth of the strain. The order of the above factors which affected the growth of strain DBS-8 most is: pH> inoculum> temperature> ammonium sulfate concentration > the initial ferrous concentration. This showed that pH impacted the growth of A. f strain most. Through destroying the acid environment, it can inhibit the growth of the bacteria to the maximum extent.In addition, through using TETA to passivate the tailing surface, the capability of its anti-chemical oxidation and anti-biological oxidation both before and after passivating was studied. Results showed that TETA had certain effect on the leaching process. However, as the time went, its effect became weak. After 60 days of leaching process, the effects of inhabitation of the leaching rate of Cu²⁺,Zn²⁺,Cd²⁺,Mn²⁺ ions were weak while its effect of inhabitation of the leaching rate of Fe3+ was high to range from 73% to 79%. This was possibly due to the instability of TETA. Trough long-term leaching, TETA fell out for erosion. In the meantime, the bacteria decreased the leaching concentration of heavy metals in contrast. It is possibly related to the absorption to the metals or the formation of metal chelates. It slowed down the growth of the bacteria for lack of Fe²⁺ for energy resource. As a result, the effect of bioleaching to promote the metal leaching rate is less than the absorption by bacteria to lead to a related low concentration of metal ions. For the complicated composition of the tailings and the diversity of effects to the leaching concentration of heavy metals in the leaching solution, the thesis made a preliminary study on the effects of surface passivator TETA and bioleaching mechanism of mine tailings. However, optimization of the passivating technology and the detailed mechanism of bioleaching need further research.