Anti-biofouling Strategies And Mechanisms Of Polyamide Membrane

Membrane technology is one important branch of water pollution control.It has been widely used in seawater desalination,wastewater reuse,and food production for its high-efficiency,economy and rapidity.However,membrane fouling is the biggest obstacle for its further use.It is vital to explore the method to release membrane fouling.In this study,we investigated antibacterial peptide Nisin,which is extensively used in medical antibacterial field.Meanwhile,the photothermal material Pd@Ag nanosheet has been studied as well.We investigate the impact of nisin on the initial bacterial attachment to membranes,its anti-biofouling properties,and characterize a non-monotonic correlation between nisin concentration and biofilm inhibition.Nisin was found to inhibit B.subtilis(G+)and P.aeruginosa(G-)attachment to both the nanofiltration membrane and the PES membrane.To determine the mechanism of action,we investigated the polysaccharides,protein and eDNA as target components.We found that the quantities of polysaccharides and eDNA were significantly changed,resulting in bacterial death and anti-adhesion to membrane.However,there were no discernable impacts on protein.We postulated that nisin could prevent irreversible biofouling by decreasing adhesion,killing bacteria and reducing biofilm formation.We examined membrane flux behavior through bench-scale cross-flow experiments at a set concentration of nisin(100 μg·mL-1),with membrane behavior being confirmed using CLSM images.Results showed that nisin could enhance anti-biofouling properties through both anti-adhesive and anti-bacterial effects,and therefore could be a novel strategy against biofouling of membranes.We investigated that surface modifications with photothermal material Pd@Ag could reduce the propensity of membranes for biofouling.The membrane was pre-coated with polydopamine as platform for immobilization of Pd@Ag into the NF membrane.After modification,the physicohemical properties of the membrane and the effects of modification on the membrane permselectivity and antifouling properties were evaluated experimentally.Meanwhile,photothermal effect was estimated by radiating NIR light.After NIR radiating,the surface temperature has abviously risen.It shows that Pd@Ag has better conversion efficiency.Due to the photothermal effect and anti-bacterial effect of Pd@Ag,the adhesion rate of membrane has decreased after 24 hours adhesion,indicating that the prepared modified membrane Pd@Ag-PDA/NF270 showed good static anti-bacterial and anti-adhesion properties.The results of measuring the permeate flux by filtering the artificial wastewater with bacteria indicate that the decrease of the membrane permeate flux slowed down significantly after NIR light radiating.Less bacteria attached to the membrane surface.The subsequent backwash showed that the modified membrane was easier to clean and the recovery of permeate flux was better after cleaning by water.The modified membrane Pd@Ag-PDA/NF270 prepared in this paper shows excellent antibacterial and anti-adhesive properties and can effectively control membrane biofouling.