Study On Removal Mechanism Of Arsenic Mediated By Sulfate Reducing Bacteria

Arsenic(As)is a ubiquitous and toxic element in the environment.The exposure of high levels of As can cause serious health problems.At present,arsenic pollution has become a hot topic in the international environmental field.In the natural environment,microorganisms can directly or indirectly regulate the valence and occurrence of arsenic,thus affecting the migration and transformation of arsenic,which will lead to the increase of arsenic content in water.On the other hand,arsenic-containing soils can transfer arsenic through breeding crops,threatening human health.Therefore,the security of sludge containing As after removal As in natural environment is a very important.In this study,we use the sulfate-reducing bacteria(SRB)Desulfovibrio vulgaris DP4 to treat aqueous solutions containing high concentrations of arsenic and adsorbed arsenic and to explore the valence change,migration and removal mechanism of arsenic under SRB,which provides a theoretical basis for the restoration of the natural environment.Firstly,we investigated that the transformation and removal mechanism of arsenic mediated by sulfate reducing bacteria(SRB)Desulfovibrio vulgaris DP4 in high arsenic concentration water.The results showed that strain DP4 promoted the formation of thioarsenate,which was 1.67 times higher than that of Na₂S system.Through the detection of environmental factors of the system,combined with the previous studies,the process and influencing factors of arsenic-sulfur coupling are elaborated.And then,we investigated the effect of sulfate reducing bacteria(SRB)Desulfovibrio vulgaris DP4 on the migration and transformation of adsorbed arsenic on nanoparticles Goethite in a reducing environment.The experimental results show that DP4 promotes the desorption of adsorbed As(?)on the surface of goethite,and the release amount is 3.4 and 1.1 times of that of the control and Na₂S systems,respectively,and most of them are converted to dissolved thioarsenate.In addition,the release and reduction of iron in goethite is accompanied by the migration and transformation of arsenic,and the Eh provided by DP4 is significantly related to the total arsenic content.XRD and SEM-EDS results showed that the relative crystallinity of DP4 system was50%,that of Na₂S system was 64%,and that of control group was 109%.At the same time,minerals in DP4 system agglomerate and As,Fe and S in the solid sample were distributed synchronously.XANES results showed that after the completion of the 168 h culture experiment,81%of As(?)and 19%of As(?)were adsorbed on the arsenic in the DP4 system,and no arsenic-sulfur precipitation was detected.There is only the original As(?)in the group.Accordingly,it is speculated that the sulfate-reducing bacteria reduce the as-resorbed As(?)in situ.In summary,the existence of SRB promotes the formation of dissolved thioarsenate and promotes the migration and transformation of adsorbed arsenic on goethite,which provides a new perspective for us to understand the environmental fate of adsorbed arsenic on nanomaterials.