Study On The Optimum Cultivation Of Thiobacillus Ferrooxidans And The Performance Of Sulfur Dioxide Removal

In this paper,the growth characteristics of Thiobacillus ferrooxidans were studied.Dielectric Barrier Discharge Plasma was used to mutate and select highly effective strains.The strains with good characters were obtained by domestication and culture,and the strain was immobilized and desulfurization.At first of the experiment,a single colony was obtained by purifying and culturing Thiobacillus ferrooxidans.The effects of initial pH,culture temperature and inoculation amount on the growth of Thiobacillus ferrooxidans were studied.Secondly,the effects of discharge time and discharge power on the bacteria induced by dielectric barrier discharge were investigated to determine the optimal mutagenic conditions.The mutant strains were domesticated with low pH value and high temperature,and strains with stable genetic traits were selected to obtain excellent strains.Furthermore,the effects of carrier,temperature and pH on the immobilization were investigated.The efficiency of sulfur dioxide removal by Thiobacillus ferrooxidans was investigated by changing the concentration of SO₃^2-and Fe²⁺in the desulphurization system.The experimental results show:?1?Thiobacillus ferrooxidans belongs to the Gram-negative bacteria.It was short rod shape,the individual is very small,and about 1 micron or so.The optimum growth conditions were as follows:the initial pH was 2.0,the culture temperature was 30?,and the inoculation amount was 10%.?2?When the discharge power was constant,the mutation rate increased at the beginning and then decreased with the increase of discharge time,and the rate reached the maximum when the mutation time was 180s.when the discharge time was constant,with the change of power,the lethality rate increased first,but after that,a slight decline in lethality,then continue to increase;The mutation rate increased first and then decreased.When the power was 50W,the mutation rate reached its maximum.The mutation time was180s,the discharge distance was 4mm,and the power was 50W,the mutation rate reached a maximum value of 21.9%.?3?After continuous low pH and high temperature acclimation thiobacillus ferrooxidans has been basically adapted in the pH=1.5 and a temperature of 45?environment.In the high temperature environment with low pH value,the tolerance of the excellent bacterial strain obtained by domestication was better than that of the initial strain.Immobilization experiments showed that the porous balls is suitable as a carrier for immobilization.The optimum conditions for the immobilization of Thiobacillus ferrooxidans were as follows:the initial pH was 2.0,and the culture temperature was 30?.?4?When the concentration of SO₃^2-was 1.59g·L^-1,the oxidation efficiency of SO₃^2-oxidized by Thiobacillus ferrooxidans was 71.7%within 5h.The oxidation rates of T-1 and T-3 to SO₃^2-were 66.9%and 54.2%,respectively.When the concentration of Fe²⁺is 0.4g·L^-1,the oxidation rate of SO₃^2-is the fastest,which is 0.052g·L^-1·h^-1.