Analysis Of Proton Exchange Membrane Fouling Mechanism And Its Application In Microbial Fuel Cells

In this paper,the pollution mechanism of proton exchange membrane and the application of proton exchange membrane in microbial fuel cell were studied.The dissipative quartz crystal microbalance(QCM-D)combined with contact angle and Zeta potential was used to analyze the bovine serum albumin(BSA)and sodium alginate(SA)adsorption of PVDF-g-PSSS membrane under three different grafting amounts.At the same time,the BSA and SA adsorption of PVDF-g-PSSS membrane in three different ionic strength was compared with the DuPont Nafion membrane.In the macroscopic aspect,the protein and polysaccharide content of the extracellular polymer(EPS)on the membrane surface of the microbial fuel cell were analyzed.The adsorption of EPS on the membrane was investigated by QCM-D.In addition,the effect of membrane fouling on the long-term operation of the system was investigated by the change of microbial fuel cell(MFC)performance before and after the new membrane.The main conclusions are as follows:1)With the increase in the proportion of hydrophilic sulfonic acid groups,on the one hand grafted sulfonic acid groups reduce the PVDF and hydrophilic pollutants sodium alginate(SA)hydrogen bonding,while the hydrophilic group make the membrane form a hydrated layer to hinder the adsorption of pollutants,resulting in a rapid decline in SA adsorption of PVDF-g-PSSA membrane.The adsorption of bovine serum albumin(BSA)also decreased with the increase of the proportion of hydrophilic sulfonic acid group.However,the adsorption capacity of BSA of PVDF-g-PSSA membrane(SSS: PVDF = 5: 1)was still large.The adsorption capacity of BSA is 90 times than of SA,BSA is the main membrane of pollutants compared with SA.2)With the increase of ionic strength,the membrane potential of the self-made membranePVDF-g-PSSA tends to decrease.The Nafion membrane potential is increasing and the electronegativity is very small,and both membrane moisture is decreasing.With the increase of ionic strength,the |-ΔD/ΔF| values of the BSA adsorption layer on two membrane increase in order,the adsorption layer is more viscoelastic.This conclusion is not consistent with the DLVO theory,at the same time as the opposite of this fact that membrane moisture decreases.The effect of membrane moisture and electronegativity on the two membranes is not the dominant factor.The |-ΔD/ΔF| values of the BSA adsorption layer on PVDF-g-PSSA membrane is 2 to 3 times than of Nafion membrane,which indicates that the PVDF-g-PSSA membrane is better resistant to BSA.3)With the increase of ionic strength,the amount of SA adsorbed increase and the adsorption capacity of PVDF-g-PSSA membrane are always smaller than that of Nafion membrane,but the difference of SA adsorption capacity is shrinking,indicating that the SA adsorption is Less affected by the membrane itself.In addition,the SA adsorption of the two membranes at high ionic strength is difficult to achieve equilibrium,which is in contrast to the faster equilibrium of BSA at high ionic strength,and the late adsorption capacity is large,so SA is one of the main pollution of proton exchange membrane at high ionic strength.4)The extracellular polymer(EPS)on PVDF-g-PSSA membrane is less fluid,polysaccharide and protein content are significantly higher than the polysaccharide and protein content of EPS in system sludge.The QCM-D down frequency of the EPS in system sludge is22.8% of BSA(20mg / L),and protein content of organic matter accounted for 9%.The down frequency of the EPS on the membrane is 29.8% of BSA,and protein content of organic matter accounted for 20.3%..The higher the concentration of organic matter is,the slower the adsorption rate.This is consistent with the experimental results.5)The new membrane was replaced after 6 months of operation.The internal resistance of Nafion membrane microbial fuel cell increased by 21.5%,power density decreased by33.3%,COD degradation rate decreased from 93.4% to 87.6%,Coulomb efficiency decreased from 5.14% to 4.25%.The internal resistance of PVDF-g-PSSA membrane microbial fuel cell increased by 20.5%,power density decreased by 22.4%,COD degradation rate decreased from90.73% to 86.1%,Coulomb efficiency decreased from 93.4% to 87.6%.The internal resistance,power density,COD and Coulomb efficiency of PVDF-g-PSSA membrane microbial fuel cell is less affected by membrane pollution,stronger pollution resistance,long-term operation more stable.However,it should be noted that PVDF-g-PSSA membrane microbial fuel cell has high internal resistance,low COD degradation rate and efficiency Kurun and other shortcomings,so in-depth study of anti-pollution and excellent performance of the modified proton exchange membrane is of great significance to the long-term practical application of proton exchange membrane microbial fuel cell.