Removal Of Diclofenac Via Coupling BioPdNPs Catalytic And A H₂-based Membrane Biofilm Reactor From Water

With the rapid development of the pharmaceutical industry,the elevated consumption of diclofenac（DCF）has caused increased discharge of diclofenac wastewater,which threat to the ecosystem and human health.In view of some shortages of high cost,low efficiency with palladium catalyst or biodegradation to removal diclofenac separately,and develops a Membrane biofilm reactor（MBf R）coupled with biological palladium（Bio Pd）catalyst to achieve high efficient removal diclofenac.The removal performance of DCF by MBf R coupled with Bio Pd catalyst（Bio Pd-MBf R）was tested.Meanwhile,the microbial community composition and structures was characterized,and the intermediate products of DCF degradation were identified.The results of the bio-palladium synthesis experiment proved that about of 99%soluble Pd was reduced to insoluble Pd nanoparticles in the biofilm.Pd Pd NPs were dispersed either on the bacterial cell surface or in the extracellular polymeric substance（EPS）,indicating well-dispersed Pd nanoparticles synthesized and stabilized in the biofilm matrix using H₂-based membrane biofilm reactor at mild conditions.In batch tests,Effect of DCF concentration and nitrate（NO₃^-）concentrationon the catalytic performance of Bio Pd-MBf R was investigated,and explore its reaction kinetics.The results proved that the process could be described by pseudo-first order kinetic,DCF concentration had significantly effect on the rate and extent DCF removal.The removal effect of DCF by the Bio Pd-MBf R could be improved by increasing the DCF concentration.Bio Pd-MBf R had the best DCF removal effect when the influent concentration of DCF was 0.5?mg/L with the NO₃^--N concentration at 10 mg/L,and a highest DCF removal was observed at 67%.NO₃^-had negative impact on DCF removal,and this negative impact increased as the influent NO ₃^-concentration increased.Over 78 days of continuous operation,Bio Pd-MBf R had the ability of long-term removal of DCF and cocontaminating nitrate.When DCF was the only electron acceptor,DCF degradation achieved the best removing efficiency of 95%and removal flux of 0.0097 g/m²/d at steady state.There were three intermediates products of DCF identified by LC-MS,and three possible degradation pathways of DCF were inferred.Bacteria（such as Sporomusa,Xanthobacter）related to DCF-degradation were enriched in biofilm,inferring that the removal process of DCF in Bio Pd-MBf R owing to the catalytic reduction by Pd NPs,microbial reduction,and the synergistic reduction of microbial and Pd NPs catalysis.