Preparation And Characterization Of Anti-biofouling Ultrafiltration Membrane

Water shortage is becoming serious with the growth of population and rapid development of industry. As an effective means to address the shortage of water, the membrane water treatment technology has been rapidly developed. However, fouling of membrane limited the further application of membrane technology due to its negative influence on membrane performance and operating costs. Thus, researchers dedicated to finding ways to control the membrane fouling. In recent years, the construction of antibacterial membrane surface has become a new research direction, which is expected to solve the membrane fouling especially biofouling problems. In this paper, the antibacterial membrane modified with the acrylamide containing capsaicin derivative moiety was prepared.Firstly, the covalently binding of HMBA and MBHBA onto the PES and PSf ultrafiltration membrane surface was performed respectively via surface UV-induced graft polymerization method, and then we investigated the effects of hydrophilic monomer AA or IA on grafting efficiency and antibacterial properties of HMBA and MBHBA. The results indicate that HMBA has significant influence on the hydrophilicity of membrane surface (water static contact angle was reduced to 50°or so), while that of MBHBA modified membrane increased significantly. The addition of IA in monomer solutions inhibits the reaction activity of HMBA. Not the same as the influence of IA on HMBA modified membrane, the presence of AA greatly promoted the graft polymerization of MBHBA on the membrane surface. The antifouling performance of IA and HMBA copolymerized graft membrane was improved significantly and water flux recovery rate can reach 96%, and the same with AA and MBHBA copolymerized graft membrane. Most importantly, graft of HMBA and MBHBA causes significant improvement of the antibacterial efficiency, which can reach 100% when DG of HMBA and MBHBA is over 0.2 and 0.15 against E. coli, respectively. Simultaneously, the addition of hydrophilic monomer does not affect the antibacterial activity of modified membrane. It can be clearly seen from SEM images that E. coli has an obvious collapse. This result implies that the antibacterial mechanism of modified membrane is contacting sterilization.Secondly, the study synthesized two copolymers (PHMBA and PMBHBA) by using HMBA and MBHBA as raw material respectively, and then fabricated three kinds of hollow fiber membrane (PES, PES/PHMBA and PES/PMBHBA) by blending copolymers as antimicrobial agents and PES. Characterization results of membrane performance indicated that the addition of copolymers made the membrane to form a more complex network structure, which improved the porosity and mechanical strength of the membrane. The hydrophilicity of the membranes modified in the presence of PHMBA and PMBHBA is slightly higher than the pristine membrane. The filtration performance of the modified membrane has also been ameliorated with the addition of PHMBA and PMBHBA. Pure water flux is increasing with the increasing of the hydrophilicity and the porosity, while the BS A retention rate is increasing due to the decreasing of the pore size of the modified membranes. Meanwhile, compared to the pristine membrane, the antifouling and antibacterial properties of the modified membrane have been greatly improved.A seawater filter testing laboratory for a period of 10 days was performed to detect long-term antibiofouling property of the modified membrane. Compared to the raw membrane (flux decay rate and flux recovery rates were 78% and 34%, respectively), the data of the modified membrane have been significantly improved, reached 45% and 67%, respectively. The modified membrane exhibited a good antibacterial performance after immersing in the E. coli suspension for 36h and almost all the E. coli on the surface of the membrane were killed. The results indicated that the modified membranes showed better long-term antibiofouling performance than the raw membrane.In fact, amide group is not stable to alkaline hydrolysis. Therefore, the study of chemical stability of the modified membrane was performed. The modified membrane was immersed in NaOH solution (pH≈14). After several days, the antibacterial functional groups of the graft polymers on the membrane surfaces do not reduce, indicating the antibacterial material had good chemical stability.