Bioprecipitation Synthesis Of Sulfidated Nanoscale Zero-valent Iron For Selective Hydrodechlorination Of Trichloroethylene

As a typical soil and groundwater pollutant,halogenated hydrocarbons have gradually become a research hotspot due to their characteristics of being slightly soluble in water and difficult to be degraded by microorganisms in engineering.Nanoscale zero-valent iron?nZVI?is widely used as a remediation material for halogenated hydrocarbon pollution,but it still has limitations in practical engineering applications,such as easy agglomeration and hydrogen evolution reaction?HER?.In order to improve the electronic utilization rate of nZVI,the participation of nZVI in HER must be suppressed.Recent studies have shown that sulfidation of nZVI,called sulfide nanoscale zero-valent iron?S-nZVI?,can effectively inhibit its participation in HER,thereby greatly improving the utilization rate of electrons.The currently used sulfide reagents are easy to cause environmental pollution and threaten human health.For example,sodium sulfide?Na₂S?and sodium dithionite?Na₂S₂O₄?have a pungent odor and generate H₂S that is toxic to human.In order to overcome the above-mentioned disadvantages,based on the engineering technology means that sulfate reducing bacteria?SRB?can treat sulfate wastewater,this study proposed a biological precipitation method to prepare S-nZVI?BP-S-nZVI?,which not only avoided the use of traditional sulfurization reagents,but also provided a new synthetic idea for the preparation of S-nZVI.We used SRB to deposit FeS₂ in situ on the nZVI surface to prepare BP-S-nZVI.Compared with nZVI,the reaction of BP-S-nZVI with trichloroethylene?TCE?showed higher reactivity and stronger electron selectivity.We investigated the influence of the pH of the culture medium,the S/Fe molar ratio and the pH of the reaction system on the degradation of TCE by BP-S-nZVI,and also explored the synergistic mechanism of the sulfurization treatment.The experimental results showed that the S/Fe molar ratio and the pH of the reaction system had a greater influence on the degradation effect of TCE.During the preparation of BP-S-nZVI,no by-products were produced,which was green,safe,efficient and low-cost,and also met the needs of groundwater pollution restoration.This method effectively overcame the problem of chemical preparation of S-nZVI,and provided a basis for large-scale production of highly active groundwater remediation materials.