Enhancement Method And Mechanism Of Intimately Coupled Photocatalysis And Biodegradation

The carrier of intimately coupled photocatalysis and biodegradation（ICPB）is the porous sponge.Photocatalysis generates the easily bioconsumable intermediates at the exterior of the carriers and biodegradable products are consumed rapidly by the interior bacteria.ICPB has the feasibility and significant advantages for the removal and mineralization of biorecalcitrant organic pollutants.However,the ICPB system cannot keep the stable operation due to unstable catalyst shedding.This study discusses the optimized method of stable catalyst and the operating process parameters of the ICPB system,which provides a scientific basis for the scale-up and practical application of the ICPB system.Firstly,PVB and TiO₂ the binder and the photocatalyst.Response surface model（RSM）was used to optimize the preparation method of the PVB-TiO₂-Sponge:the sponge adsorption time was 20 h,the concentration of TiO₂ was 8g/L and mass fraction of PVB was 0.5 wt%.Under the optimal conditions,the removal rate of tetracycline（TCH）reached about 95%within 4 hours.The verification experiment indicated the feasibility of quadratic model.The morphological characterization,photodegradation experiments and cycle experiment further showed that proper concentration of PVB improved the stability of TiO₂.However,when the concentration of PVB reached 1 wt%,the system had lower photocatalytic performance.The ICPB system was successfully constructed,using PVB-TiO₂ and activated sludge as the photocatalyst and microbial seed source.The removal,mineralization efficiency and product toxicity of ICPB and P systems under TiO₂dosage and light intensity parameters were discussed.With the increase of TiO₂dosage,the removal rate of TCH and the mineralization efficiency of ICPB and P systems showed a trend of first increase and then decrease,but ICPB had a higher rate constant than that of P system.When the amount of TiO₂-sponge is too high（≥50%v/v）,the kinetic constant of ICPB reduced by 21.14%,due to the poor flowing sponge and the scattering and shielding of UV light.With the increase of light intensity,the degradation efficiency of ICPB on TCH removal showed an increasing trend.When the UV light intensity was too high（≥8000μw/cm²）,the microbial structure and protein in the ICPB system were destroyed,resulting the shedding of biofilms and the dissolution of soluble microbial metabolites（SMPS）and then reduced the stability of biomass.When the operating parameters were40%v/v of TiO₂ dosage and 6000μw/cm² of light intensity,the degradation rate of TCH in ICPB system had the best kinetic constant(2.8989 h^-1)and mineralization（36.92%）.