Modification And Anti-biofouling Mechanisms Of Ultrafiltration Membranes With Nanoparticles By The In-situ Embedment Approach

Membrane biofouling is the key issue that limits the broader application of ultrafiltration in water and wastewater treatment.By in-situ embedment approach,membranes surface-modified with nanoparticles showed a great improvement in anti-adhesion performance.To further study the anti-adhesion mechanisms of different nanoparticles,the in-situ embedment method were optimized,and nano-alumina and nano-titania embedded ultrafiltration membranes with different coverage ratios were prepared.The basic properties and anti-adhesion performance of membranes were evaluated by roughness test,filtration test,contact angle measurement,bacterium inactivation test and bacterial adhesion experiments.The relationship between bacterial adhesion and the basic properties of membrane was studied.To better interpret the improving anti-adhesion performance,the adhesion forces between bacteria and different membranes were tested by atomic force microscopy(AFM).By changing the concentration of nanoparticles in the coagulation bath,nano-alumina embedded membranes with coverage ratio of 6.7%,13.7%,36.8% and 41% were prepared,and nano-titania embedded membranes with coverage ratio of 12.3%,17%,22.4% and 27.7 % were prepared in the coagulation bath of pH 4.Compared to the unmodified membrane,the membrane resistances of nano-alumina embedded membranes with different coverage ratios decreased by 44.6%,47.4%,49.0% and 77.8%,and the contact angle changed from 70.8° to 68.2°,68.5°,65.3° and 59.5°,respectively.The embedment of nano-titania in the membrane surface both increased the membrane resistance and the hydrophilicity slightly.The membrane resistances of nano-titania embedded membranes with different coverage ratios increased by 16.7%,74.9%,17.5% and 20.7%,and the contact angles are 69.3°,74.1°,71.7° and 66.2°,respectively.The membranes modified by both nanoparticles had no antibacterial effect on E.coli and P.aeruginosa,but the anti-adhesion ability were significantly improved.The P.aeruginosa adhesion on nano-alumina embedded membranes were reduced by 44.3%,85.6%,91.4% and 94.9%,respectively,and the adhesion on nano-titania embedded membranes were reduced by 65.7% 78.1%,93.0% and 92.3% respectively.Through adhesion force test,the adhesion force between P.aeruginosa and the unmodified membrane was 22.5 nN.For nano-alumina embedded membranes,the adhesion force were 12.9,13.2,7.7 and 5.7 nN,respectively.For nano-titania embedded membranes,the adhesion force were 17.9,3.13,2.32 and 4.20 nN,respectively.With the coverage ratio of nanoparticles increasing,the P.aeruginosa adhesion on different membrane surfaces were positively correlated with the adhesion forces significantly.Therefore,the improvement of anti-adhesion performance could attribute to the decrease of adhesion force between P.aeruginosa and membranes after the nanoparticles were embedded.