| In order to deal with the issue of high energy consumption faced by the anodic oxidation process when treating refractory organic pollutants,this study proposed a novel technology,biocathode-electrocatalytic membrane reactor(BECMR),by coupling the O2 reducing biocathode with the electrocatalytic membrane to replace the water reduing abiotic cathode.Major findings of this study are as follows:The BECMR was constructed using graphite felt as the cathode and MnOx/Ti electrocatalytic membrane as the anode.Operated at 0.7 V,the cathode potential of the BECMR was increased after 15 d and the current was generated after 17 d,suggesting the succusseful start-up of the BECMR.The BECMR was found to be able to start up at a lower applied votage than the ECMR.On the biocathode of BECMR,the dominant phylum was proteobacteria with a relative abundance of about 89.3%,followed by bacteroidetes with a relative abundance of 7.9%.The dominant genera were pseudomonas and acinetobacter with the relative abundances of 30.2%and 25.7%,respectively.The ability of these bacteria to reduce O2 to H2O led to the increased cathode potential in BECMR.Based on the thermodynamic theory,the increased cathode potential was the reason for the lower start-up voltage of BECMR.Using the phenol solution as the feed,after inoculation,3 BECMRs successfully started up at the applied voltages of 0.7 V,1.0 V and 1.3 V,respectively,with graphite felt as the cathode and MnO./Ti membrane as the anode.The startup time of BECMR-0.7V and BECMR-1V were shorter than that of BECMR-1.3V.When the hydraulic retention time was 23.8 min,the TOC removal efficiencies of BECMR-0.7V and BECMR-1V for 2 mM phenol were 50.0%and 42.1%,respectively.BECMR-0.7V and BECMR-1V showed little difference in the TOC removal with the stainless steel chemical cathode ECMR(STEEL-ECMR).This was because phenol was removed by diffusion from the anode to cathode through cationic exchange membrane,rather than the electrocatalytic oxidation process.Using the methylene blue(MB)solution as the feed and constructed the BECMRs,BECMR-1V had better removal effect than BECMR-0.7V.Under the hydraulic retention time of 35.7 min and the methylene blue concentration of 150 mg/L,the MB removal rate was 78.1%and 37.7%,the TOC removal were 40.2%and 22.1%,and the organic removal loading was 16.7 mg(m2·h)and 9.2 mg/(m2·h),respectively.Methylene blue removal rate,TOC removal and organic removal loading of BECMR were significantly higher than those of STEEL-ECMR.MB removal rate,TOC removal rate and organic removal load of BECMR were significantly higher than those of STEEL-ECMR under the same condition.Moreover,when achieving the same TOC removal,both the external voltage and energy consumption of BECMR-1Vere significantly lower than that of STEEL-ECMR,with the former energy consumption of 19.7 KWh/kg TOC,the latter external voltage of 1.95 V and energy consumption of 44.7 KWh/kg TOC respectively.The BECMR required a much lower applied voltage and energy consumption than the STEEL-ECMR.The removal of methylene blue was closely related to electrochemical process.Hydroxyl radicals were detected at the anode under electric filed,which was believed to play a major role in the removal of methylene blue. |
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