Reduction Of Cr(â…¥) Pollutants In Water By Electro-active Bacteria Community Coupled With Photocatalyst

Photocatalysts with visible light response have attracted much attention due to their ability to utilize the green and clean sun on a larger scale.This type of photocatalyst,such as bismuth tungstate（Bi₂WO₆）,has broad application prospects in the field of pollution control due to its stability and non-toxicity.Under visible light excitation,it can generate photogenerated electrons and holes to degrade or mineralize pollutants into non-toxic inorganic ions.However,the photo excited electrons transferred to the surface of the photocatalyst are easily recombined with holes without timely utilization,leading to waste of photo generated electrons and limiting their photocatalytic efficiency.Coupling conductive nanomaterials on the surface of catalysts is a common way to improve the utilization of photo generated electrons and thereby improve the efficiency of heavy metal reduction.In addition,in order to solve this problem,some studies directly coupled the microorganisms with pollution degradation ability to the photocatalyst.It was found that photoluminescent electrons were captured by microorganisms as electron donor,promoting microbial activity,thereby reducing the electron hole surface recombination rate of the photocatalyst and improving the photocatalytic performance.But currently,most of them choose a single strain to construct a coupling system,which limits its promotion and application.Therefore,this study selected electroactive bacteria and bacterial communities that have the ability to reduce heavy metals to couple with bismuth tungstate for research.By optimizing bismuth tungstate and studying various elements in the coupling system,a highly efficient coupling system between photocatalysts and electroactive bacterial communities was obtained,achieving effective utilization of photoelectrons and efficient reduction of Cr（VI）.The specific research is as follows:Firstly,bismuth tungstate with high biological affinity was prepared and characterized.Bi（NO₃）·5H₂O and Na₂WO₄·2H₂O were used as raw materials by hydrothermal method to prepare bismuth tungstate with high photocatalytic performance and effective binding with electroactive bacteria through optimizing and adjusting the pH during the preparation process.The morphology and structure of bismuth tungstate were characterized by XRD,SEM,TEM,EDS,FT-IR,and UV-Vis DRS,demonstrating the successful preparation of high biological affinity bismuth tungstate.Secondly,construct an electroactive bacteria coupled bismuth tungstate system and optimize the conditions.Selecting the electroactive mode strain MR-1 as a microbial component,the synergistic effect between it and bismuth tungstate was studied.By optimizing the concentration of photocatalysts,electroactive bacteria,and system pH in the system,a coupling system was obtained where electroactive bacteria and bismuth tungstate can efficiently synergistically reduce Cr（VI）.Compared with the Cr（VI）reduction efficiency of pure photocatalytic and pure biological systems,the coupled system significantly improves the reduction performance,demonstrating the efficient synergy between bismuth tungstate and electroactive bacteria.Finally,a coupling system between electroactive bacterial community and bismuth tungstate was constructed and applied to the reduction and removal of Cr（VI）.Couple the electrically active bacterial community in activated sludge with bismuth tungstate according to optimized parameters,and add genetically engineered bacteria that can express the conductive protein Omca as a biological conductive material to solve the problem of electron transfer between photocatalysts and microorganisms being limited to one layer near the catalyst surface.In the reduction test of Cr（VI）,compared to photocatalytic and biological systems,the coupled system exhibits higher Cr（VI）reduction ability.By characterizing the electrochemical performance of the coupled system and measuring the extracellular polymer content,the mechanism of improving the reduction performance of the coupled system was studied.This indicates that the electroactive microbiota can effectively utilize photogenerated electrons,enhance its own electrical activity,and thereby promote the efficient reduction of Cr（VI）.This study obtained a coupled photocatalyst system of electrocatalytic microbiota,demonstrating the efficient synergistic effect of electrocatalytic microbiota and photocatalyst,and achieving efficient reduction of Cr（VI）,providing a scientific basis for the practical application of photocatalytic coupled microbial technology for the reduction and removal of heavy metals.