Study On The Mechanism Of Reducing Of Bacillus Subtilis To The U,Pb,Cr Enrichment Plants

The disposal of a large number of enriched organisms generated in the bioremediation of radioactive contaminated environment is one of the bottlenecks to restrict the application of bioremediation engineering.In order to solve this problem,this paper studies Bacillus subtilis selected in the earlier stage to analyze the decomposition rate of cellulose and hemicellulose and the enrichment rate of uranium,and verifies the tolerance,adsorption degree and adsorption machine of Bacillus subtilis to different heavy metals and the influence of heavy metals on the adsorption through a single heavy metal containing uranium,lead,chromium and compound pollution,which provides a certain reference the rapid reduction of uranium and associated heavy metals.The experimental results show that:（1）Bacillus subtilis can decompose hyperaccumulator with U under liquid fermentation.Electron microscope observation showed that long term soaking would lead to loose surface structure of straw and would be beneficial for decomposition of Bacillus subtilis.The results showed that the decomposition rate of cellulose in the 0 mg/kg^-11 group was 48.04%,the decomposition rate of hemicellulose was 74.71%,the cellulose decomposition rate of uranium concentration in the 400 mg/kg^-11 group was 69.01%,and the decomposition rate of hemicellulose was 52.47%.The decomposition rate of cellulose increased with increasing uranium concentration,and the decomposition rate of hemicellulose decreased with increasing uranium concentration.（2）Bacillus subtilis could tolerate uranium from 25 mg·kg^-11 group to 100 mg·kg^-1group,and the adsorption rate in the 25 mg·kg^-11 group,50 mg·kg^-11 group,75 mg·kg^-1group and 100 mg 79.77%,was 81.36%,80.21%,79.77%and 79.56%when being 72 h,which showed that the adsorption rate decreased with increasing uranium concentration;the adsorption rate of Bacillus subtilis on lead increased with increasing lead concentration.At the same time,lead would cause Bacillus subtilis to enter the decay period in advance,and the adsorption rate of lead concentration 25 mg·L^-1-100 mg·L^-11 at 24 h was 94.50%,85.52%,81.27%,and 77.76%when being 24 h and appeared desorption after 24h.The effect of chromium on Bacillus subtilis was larger,but the Bacillus subtilis could still adsorb a large amount of chromium and after adsorption equilibrium,the adsorption rates of 25 mg·L^-1,50 mg·L^-1,75 mg·L^-11 and 100 mg·L^-11 were respectively 91.57%,90.07%,88.98%and 85.08%when being 36h.The adsorption rate decreased with increasing chromium concentration.Judging from the relationship between adsorption rate and time,the main types of adsorption of Bacillus subtilis on uranium were various and the adsorption of lead and chromium was mainly physical adsorption.（3）It was found that the substances that could be combined with uranium in Bacillus subtilis were mainly protein,phosphorus containing compounds,and hydroxyl containing compounds by Fourier transform infrared spectroscopy and the characteristic absorption peaks of uranium appeared on the infrared map and the substance of Bacillus subtilis combined with lead was mainly protein and some alcohols on the bacteria and the adsorption of chromium by Bacillus subtilis mainly depended on protein.It was found that there was a scaly structure on the surface of the bacteria after adding uranium by electron microscope,which hydrolyzed the cell wall of Bacillus subtilis and separated its binding substance with uranium and confirmed that the substance was a protein.（4）The orthogonal experiments of uranium,lead and chromium showed that uranium and the adsorption of uranium had a significant negative correlation（r=-0.6016*）and chromium and the adsorption of uranium had a very significant positive correlation（r=0.7320**）,and the adsorption of chromium on uranium was negatively correlated（r=-0.3983）.Uranium had a negative correlation with lead adsorption（r=-0.4476）,and lead had a negative correlation with lead adsorption（r=-0.0.2947）,and chromium had a very significant negative correlation with lead adsorption（r=-0.7190**）.Uranium had a negative correlation with chromium adsorption（r=-0.0.1158）,and lead had a positive correlation with chromium adsorption（r=0.0.0789）,and chromium had a very significant negative correlation with chromium adsorption（r=-0.8123**）.