| With the water pollution,fossil fuel depletion,energy crisis become increasingly serious,it has become an important research direction to open up new renewable energy sources.Microbial fuel cells(MFCs)can achieve the dual purposes of wastewater biological treatment and electric energy recovery,and have been widely considered as a new renewable energy source.Based on the energy balance analysis,using MFC can convert wastewater biological treatment into a process of net energy output.Proton exchange membranes are one of the core components of MFC and used to separate anode and cathode compartments,impede matrix diffusion and oxygen infiltration,and transport protons.The physicochemical properties and anti-fouling ability of the proton exchange membrane have a significant impact on the electrical production and the stability of electrical production of MFC.Therefore,this article focuses on the performance of proton exchange membranes in MFC and its related important scientific issues.The main conclusions summarized are as follows:1.PVDF-g-PSSA was prepared through the free radical graft copolymerization initiated by BPO pyrolysis of sodium styrene sulfonate(SSS)with the ozone pre-activated PVDF,using the technology of grafting modification of polymer bulk.Then,PVDF-g-PSSA proton exchange membrane was prepared by the solvent volatilization phase transformation method.In this process,because the react between the peroxide groups produced by ozone pre-activation and free radicals produced by BPO pyrolysis generated more grafting sites,the degree of grafting of the graft reaction was improved.When the mass ratio of SSS/PVDF was 5:1,the water uptake of the PVDF-g-PSSA membrane(PPSSA)was 25.00%,the IEC was 0.58 meq/g,the proton conductivity was 0.046 S/cm,and the mechanical and thermodynamic stability of the membrane was best.Compared with commercial Nafion 117 membrane,it was demonstrated that the MFC using PVDF-g-PSSA proton exchange membrane showed good performance of electricity production when sodium acetate was treated.2.Ti O2/PVDF-g-PSSA and Ti O2-SO3H/PVDF-g-PSSA hybrid composite proton exchange membranes were prepared by the introduction of hydrophilic nano-materials Ti O2 and Ti O2-SO3H into the PVDF-g-PSSA.The mechanism of Ti O2 and Ti O2-SO3H on the physical and chemical properties of hybrid composite membranes was systematically analyzed.The results showed that:1)The good capacity of water absorption of hydroxyl(Ti-OH)formed by Ti O2 can increase the water uptake,swelling rate and hydrophilicity of the hybrid composite membranes.2)Due to the addition of an appropriate amount of Ti O2-SO3H,the high-density sulfonic acid groups in the hybrid composite membrane formed well-connected ion cluster channels,and introduced a large number of strong hydrophilic acidic sites,which promoted the proton conductivity,water uptake and hydrophilicity of the hybrid composite membranes.However,when the content of Ti O2-SO3H was more than 5.0 wt%,the effect of the“steric hindrance”became dominant,which limited the increase of the proton conductivity of the hybrid composite membranes.3.PVDF-g-PSSA membrane was modified by graphene oxide(GO)and sulfonated graphene oxide(SGO),and the GO/PVDF-g-PSSA(GO/PPSSA)and SGO/PVDF-g-PSSA(SGO/PPSSA)hybrid composite membranes were prepared.The results showed that:1)With the content of SGO increased from 0.1 wt%to 1.0 wt%,the water uptake,IEC,proton conductivity and hydrophilicity of the SGO/PPSSA hybrid membranes increased gradually.The water uptake(32.56%),IEC(1.24 meq/g),proton conductivity(0.083 S/cm)and hydrophilicity of the SGO/PPSSA-1.0 hybrid membrane was superior to Ti O2-SO3H/PVDF-g-PSSA and Nafion 117 membrane.2)Due to the substitution of-OH functional group in SGO by sulfonic acid group,the SGO/PPSSA-1.0 membrane exhibited higher water uptake and proton conductivity than that of GO/PPSSA-1.0 membrane.The reason why the proton conductivity of SGO/PPSSA hybrid composite membrane was significantly improved was the formation of the convenient proton transport path,and the proton conduction was promoted by the Grothus mechanism and Vehicle mechanism.3)The MFC system using SGO/PPSSA-1.0 hybrid composite membrane had higher maximum power density and stability of electrical production than that of Nafion 117 membrane,and SGO/PPSSA-1.0 membrane had better anti-fouling ability,so it becomes an ideal proton exchange membrane for MFC.4.The PVDF-g-PSSA hybrid composite membranes coated sensors were prepared.A new method for membrane fouling micro-evaluation of proton exchange membrane in MFC system based on QCM-D technique was established.The adsorption behavior and mechanism of BSA and SA(the representatives of typical pollutant proteins and saccharide in MFC system)on the membrane surface were analyzed,and the dominant role of BSA in causing membrane fouling of proton exchange membrane was determined.Because different hydrophilic groups were introduced by Ti O2-SO3H and SGO,a hydrated layer was formed on the surface of the membrane,which effectively hinder the adsorption of BSA,the adsorption mass of BSA on the surface of Ti O2-SO3H and SGO hybrid composite membranes was smaller than that of PPSSA and Nafion 117 membrane,and the structure of the adsorption layer was more loose.It was proved that the addition of hydrophilic inorganic substances can improve the anti-fouling properties of hybrid modified proton exchange membrane.5.The feasibility of the MFC system based on PVDF-g-PSSA membrane to degrade refractory phthalate esters(PAEs)and easily degradable sodium acetate(Na Ac)and generate electricity was investigated.When using 2 g/L sodium acetate(Na Ac)+50 mg/L phthalate esters(PAEs)mixture as fuels,the voltage of the MFC was stable at about 333 m V and the maximum power density was the highest(46.01 m W/m2),indicating that phthalates can be used as fuel for MFC.The mixture of sodium acetate and phthalate esters resulted in the increase of the current density and the decrease of the internal resistance of MFC,thus improving the power generation.The removal efficiencies of DBP and DEHP were improved and higher than 70%when the MFC was operated in closed circuit.It was proved that the specific redox process and promoted microbial oxidation in MFC were the main reasons for its improved removal efficiencies of DBP and DEHP.MFC system provides a new idea to realize the efficient degradation of organic matter in wastewater and energy resource utilization. |
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