Mechanism Of Pyridine Degradation By Visible Light Catalysis And Direct Coupling Of Microorganisms

Pyridine is toxic to organisms in the environment,with carcinogenicity,teratogenicity and mutagenicity.Intimate coupling photocatalysis and biodegradation（ICPB）has the ability to degrade organic pollutants efficiently.Therefore,it is particularly important to effectively degrade pyridine.In this study,pyridine was used as the target pollutant,visible light as the light source,activated sludge as the biological seed source,and visible light catalysis microbe coupling system was constructed.Explore the degradation mechanism of pyridine by ICPB,and provide theoretical basis and possible practical methods for the efficient degradation of refractory organic pollutants.（1）The ICPB system was constructed with polyurethane sponge as carrier,domesticated activated sludge as biological seed source and Ti O₂ as photocatalyst,and the operating conditions of pyridine degradation were discussed.SEM-EDS and XRD images showed that Ti O₂ was successfully loaded on the sponge carrier.FESEM images proved that microorganisms attached stably on Ti O₂/sponge composite carrier.Under the best operating conditions of the experiment（5%carrier dosage,1000 Lux light intensity,initial p H 6）,the degradation efficiency of 50 mg/l pyridine was 87.36%.ICPB can operate stably in the three cycle experiment with glucose as the external carbon source.In the third cycle experiment,the pyridine degradation rate reaches 98.07%,and the TOC removal rate reaches 90.65%.（2）The pyridine degradation rates of four systems including adsorption+photolysis（AD+P）,microorganism alone（B）,photocatalysis alone（PC）and ICPB for 12 h were compared.The degradation efficiency of pyridine by ICPB system was 96.64%.The degradation rates of pyridine were increased by 83.96%,44.18%and 50.03%,respectively.TOC removal rate of ICPB system is 83.44%,which is 72.86%and 31.82%higher than PC and B systems,respectively.The degradation kinetics analysis showed that the degradation of pyridine by ICPB conformed to the quasi first-order kinetic equation.Free radical trapping experiment and electron spin resonance（ESR）detection showed that h⁺、e^-、·OH and·O₂^-were the main active groups for the degradation of pyridine in ICPB system.Through three-dimensional fluorescence,it was found that the content of soluble microbial by-products and aromatic proteins increased with the degradation of organic matter.The results of HPLC-MS showed that pyridine went through a series of oxidation-reduction and microbial participation processes,and the final intermediate products were further degraded into small molecules,producing 2,3-dihydroxypropionaldehyde,succinic acid,dihydroxysuccinic acid and 2-maleic acid,which were mineralized and degraded,and finally produced CO₂ and H₂O.（3）The analysis results by FESEM and confocal microscope showed that the microorganisms attached well to the sponge after ICPB operation,and the microbial biomass on the carrier remained stable.The results of high-throughput sequencing analysis showed that the microbial community in the ICPB system had evolved before and after the reaction.At the level of microbiota,Proteobacteria and Actinobacteriota are the dominant bacteria in the microbial community.At the microbial genus level,the proportion of pyridine degrading bacteria Rhodococcus,gemmobacter,Acidovorax and Azoarcus increased after ICPB operation,playing an important role in the ICPB system.（4）In the study on the performance of the system in the treatment of coking wastewater,after 16 hours of ICPB operation,the coking wastewater achieved good degradation effect.The removal rate of COD_Cr by ICPB was 77.92%,which was 71.82%higher than that of AD+P system,50.73%higher than that of B system,and 20.50%higher than that of PC system.The BOD₅ removal rate was78.72%,the decolorization rate was 66.67%,and the water quality index reached the discharge standard.