Study On Biodecolorization Characteristics And Mechanism Of Azo Dyes Catalyzing By Redox Mediator Functional Materials

Azo dyes are the most widely used dyes and have carcinogenic,teratogenic and mutagenic properties.The dye wastewater is also recognized as one of the refractory wastewater.Biological methods are widely used in dyes wastewater treatment processes.Nevertheless,the breakage of azo bonds under the anaerobic conditions is the rate-limiting step of this process.In recent years,the study of redox mediators provides ideas for improving the anaerobic decolorization efficiency.But,continuous dosing of water-soluble mediators causes secondary pollution.Insoluble mediators,especially immobilized mediators,have received extensive attention.However,at present,there are still some problems about immobilized mediators such as as low catalytic efficiency,high mass transfer,and easy detachment.Based on the above background,this study aims to develop novel immobilized redox mediator functional materials and investigates their catalytic performance for biodecolorization of azo dyes.?1?Fe₃O₄ magnetic nanoparticles were prepared and coated by chemical precipitation and St?ter method.And then the surface was modified with amino group by a silane coupling agent and ammonia.Anthraquinone-2-sulponic acid sodium salt monohydrate?AQS?was oxidized to anthraquinone-2-sulfonyl chloride.Finally,under basic conditions,the immobilization of AQS?FeSi@AQS functional material?is prepared by forming amide bonds.Fourier transform infrared spectroscopy?FTIR?analysis showed that AQS successfully modified to the surface of Fe₃O₄ nanoparticles.Elemental analysis and thermogravimetric analysis showed that the mass fraction of AQS on FeSi@AQS was 21.12%.At the same time,the rate of anaerobic biodecolorization of Reactive Brilliant Red K-2BP was increased to 2.1 times by FeSi@AQS,and the rate of decolorization of the other four azo dyes was also catalyzed.Besides FeSi@AQS can be effectively recovered and separated under the magnetic field.?2?The non-quinone redox mediator neutral red?NR?was immobilized by condensation reaction.The polyacrylic acid?PAA?hydrogel with a high swelling ratio was used as the carrier material to achieve immobilization and obtained PAA-NR functional material.FTIR analysis demonstrated that neutral red was successfully immobilized on the hydrogel.SEM micrographs show that PAA-NR has a three-dimensional pore structure with pore size of about 100?m.At the same time,PAA-NR increased the rate of anaerobic biodecolorization of Reactive Brilliant Red K-2BP to 13.5 times and the results could be reused.?3?The electron transfer mechanism of biodecolorization with PAA-NR was studied in detail by the use of inhibitors,and it was concluded that complex I,complex II,and complex IV may be involved in the process of anaerobic biodecolorization of Reactive Brilliant Red K-2BP.During the process,PAA-NR as an electron transfer enhanced the extracellular electron transfer between azoreductase and azo dyes,and thus the rate of biodecolorization was increased.This study explored the preparation methods of two novel functional materials and these functional materials were effective catalysis of azo dye anaerobic decolorization.Also the decolorization mechanism of azo dyes was further studied.It provides theoretical and technical support for the efficient biological treatment of azo wastewater.