| Microbial fuel cell(MFC)is an ideal way to solve the problem of environmental pollution and energy shortage simultaneously.However,the low power output and high operating cost of MFC still limit its application.Therefore,enhancing the power generation performance and promoting the practical application of MFC has become a common proposition in the field of MFC.With the in-depth study of nanotechnology and electricity generation mechanism,the coupling of photocatalysis and MFC has comprehensively utilized the advantages of both,realized the pollutants removal and synchronous electricity generation,showing extensive application prospect for actual wastewater treatment.In this work,On the basis of the controllable preparation of three-dimension(3D)graphene aerogel and semiconductor photocatalyst bismuth oxychloride(BiOCl),an ultra-light and compressible 3D bismuth oxychloride/reduced graphene oxide(BiOCl/RGO)aerogel with high activity,superior stability and recyclability was fabricated via a facile hydrothermal method.The photocatalytic degradation mechanism of antibiotic wastewater by BiOCl/RGO was investigated by various techniques.At the same time,the two-chamber MFC was constructed and operated,dynamic changes in power generation,electrochemical properties and microbial community structure were compared between the control microbial fuel cells and the oxytetracycline(OTC)or sulfamonomethoxine(SMM)treated MFC in long-term operation.Furthermore,a combined photoelectrocatalytic microbial fuel cell(photo-MFC)with BiOCl/RGO(BGA)photocathode was constructed to evaluate the feasibility of simultaneous removal of MO and OTC in each chamber,and generate energy to drive the photo MFC process without additional energy consumption.The synergetic mechanism of BGA was discussed through a series of studies under various conditions,including power generation,active species,electron transfer pathway and microbial community structure.This work realizes the combination of solar energy and MFC,and provides a new idea for pollutant treatment and practical application of MFC.The main research conclusions are as follows:(1)An ultra-light and compressible three dimensional bismuth chloride/reduced graphene oxide(BiOCl/RGO)aerogel was prepared by a simple hydrothermal method.The BiOCl/RGO aerogel(BGA)exhibit remarkable synergistic effects in adsorption and photocatalytic degradation due to their improved visible light response,low internal resistance and enhanced electron transfer capability.This not only reduces the diffusion distance between pollutants and photocatalyst,but also inhibits the recombination of electrons and holes,thus enhancing the photocatalytic activity.The optimized 40%BGA had the highest removal rate of OTC(93.31%),which was 1.43 times higher than that of pure BiOCl.Holes play a leading role in the degradation of OTC.At the same time,40%BGA has good stability and recoverability after 4cycles.After 40%BGA treatment,the biotoxicity of OTC to Escherichia coli DH5a was basically eliminated.(2)Dynamic changes in power generation and electrochemical performance of control microbial fuel cell(C-MFC)and oxytetracycline-treated MFC(O-MFC)during long-term operation were systematically compared.The results indicated that a high concentration of OTC(>5 mg·L-1)could inhibit microbial activity,resulting in the decline of voltage output and power density compared with the C-MFC.However,the inhibitory effect was gradually weakened after long-term operation.Electrochemical analyses demonstrated that long-term OTC acclimation reduced the ohmic and polarisation resistance of the anode,and promoted the anode electron transfer.More than 98.83±1.15%of 10 mg·L-1 OTC could be removed within 48 hours,and the antibacterial activity of the MFC effluent on Escherichia coli DH5?was conclusively eliminated.The diversity and richness of the microbial community decreased significantly after long-term OTC enrichment.The dominant group transferred from electroactive microorganisms Acinetobacter,Petrimonas,Spirochaetaceae and Delftia to OTC degradation groups Cupriavidus,Geobacter and Stenotrophomonas.(3)The effect of Sulfamonomethoxine(SMM)shock on the power generation performance and microbial community structure of MFCs was assessed under seasonal temperature variation.Stable voltage could be obtained in the range of 13-33°C without SMM addition(B-MFC),while dramatically decreased below 13°C.Power generation was significantly inhibited with the addition of 4 mg·L-1SMM(S-MFC)and slowly elevated with the prolongation of operation.Moreover,SMM aggravated the effect of low temperature in S-MFC,and it need longer time for the resilience of voltage compared to the B-MFC.92.83±1.54%of SMM(10 mg·L-1)could be degraded by S-MFC,and the biotoxicity of effluent was conclusively eliminated.The degradation intermediates and pathways of SMM were analyzed by ultrahigh-resolution electrospray time-of-flight mass spectrometry.High-throughput sequencing demonstrated that the addition of SMM reduced the activity and proportion of electroactive bacteria,promoted the enrichment of SMM degradation bacteria,and changed the structure and functional groups of anode microbial community.(4)The novel 3D BiOCl/RGO aerogel(BGA)was fabricated and used as a photocathode to construct a combined photoelectrocatalytic microbial fuel cell(BGA-PE-C).Owing to the lower cathodic internal resistance and enhanced reaction rate under light irradiation,the BGA-PE-C exhibits excellent power generation capacity(696.51±5.27 m V and 7.33±0.23 W·m-3)in comparison with the single MFC process(455.36±7.18 m V and 1.88±0.09 W·m-3).Meanwhile,the removal efficiency of OTC(10 mg·L-1)in the anode and MO(40 mg·L-1,p H=3)in the cathode rises to 98.93±0.15%and 97.28±0.64%respectively.Multiple processes,including biodegradation,photocatalysis and adsorption,participated in the mineralization of MO;the anode electrons mainly broke the azo bond,while the photocatalysis reaction could both degrade MO and intermediate products efficiently.The Geobacter are enriched and responsible for the enhanced power generation of the BGA photo-MFC.The synergistic effects of photocatalysis and MFC in BGA photo-MFC dramatically increase the removal of OTC and MO in their respective chambers while producing energy in situ to drive the process without extra energy consumption,and have a wide application prospects for actual wastewater treatment. |
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