Arsenic Removal Peformance And Mechanis Of A High-efficiency Arsenic Removal Strain

With the rapid development of industrialization,heavy metal pollution had become more and more serious,and arsenic pollution in environment is one of them,which mainly comes from industrial production.As arsenic is difficult to degrade in the natural environment,it can be enriched in the food chain,which can cause serious harm to the human body.Usually arsenic enters the body mainly through the digestive tract,respiratory tract,skin and mucous,and is absorbed into the blood through the lungs,gastrointestinal tract,and mucous membranes.With the blood flow,it is distributed in brain,lung,heart,spleen,kidney,thymus,thyroid,aorta,intestinal wall,muscle,other body tissues and organs.Arsenic is very toxic,and 0.1g As₂O₃ can make people dead.This paper was based on 21 strains obtained from Da Tun Sea,Ge Jiu City,Yunnan Province,The arsenic removal efficiency was used as an indicator to screen out a strain with better arsenic removal effect.In this experiment,simulated arsenic wastewater was used to study the main factors affecting the arsenic removal effect of the bacteria.At the same time,the arsenic removal mechanism of the bacteria was studied from the aspects of biosorption and bioconversion.Finally,the arsenic removal performance and mechanism under the synergistic action of Fe³⁺and bacteria were explored.Specific contents are as follows:In the early stage,the arsenic removal efficiency was used as an indicator to screen out bacteria with better arsenic removal efficiency.The results of growth curve showed that the bacteria had been stable for 18-30 h,so the broth after 24 hours of bacterial solution was used as the fermentation liquid.16S r DNA identification results showed that the strain is Bacillus sp.According to the optimization experiment,the removal rate reached a maximum of 42.68%,when the add amount of fermentation liquid was 4 m L,10%Ca Cl₂ solution was 4 m L,the processing time was 2 hours,p H value was 8.Through the study of anions and cations in waste water,Cl^-and SO₄^2-had little effect on effect on the arsenic removal effect of the bacteria.The arsenic removal mechanism of the bacteria was studied from two aspects of biosorption and bioconversion.SEM analysis showed that,the shape of the bacteria that adsorbed trivalent arsenic had some deformation,which can be considered to be the result of the adsorption of As?III?on the surface.IR analysis showed thatthere were carboxyl groups,amino groups,hydroxyl groups,amide groups and polysaccharides in the sorption of As?III?by the bacteria.Transformation of arsenic species analysis showed that,Bacillus sp.had certain bioconversion and methylation effect on As?III?in water,which could transform As?III?into As?V?with lower toxicity,and could transform As?III?into MMA and DMA by methylation.Finally,the arsenic removal performance and mechanism under the synergistic action of Fe³⁺and Bacillus were investigated.The results showed that the removal efficiency of As?III?could reach about 64%under the synergistic action of Bacillus and Fe Cl₃;SEM and XPS analysis of surface,the removal of As?III?in water was mainly removed by the co-precipitation of iron hydroxide and Bacillus.Adsorption characteristics of the study showed that,under the synergistic action of Bacillus?inactivation?and Fe Cl₃,the adsorption process of As?III?in the water satisfies the pseudo-second-order kinetics model.The three-dimensional fluorescence spectrum analysis showed that the main substances in the mixed treatment solution after Bacillus and As?III?reaction were polysaccharides and protein substances.