Preparation And Performance Of Modified Polysulfone UF Membranes With Capsaicin Derivative Structure

Polysulfone (PS) is a kind of polymer membrane materials with high mechanical performance, easy formation and excellent chemical properties. At present, it has been widely used in the preparation of UF membranes. Membrane fouling is a major technical issue in the use of membranes for water and wastewater treatment. There has been extensive research on improving the anti-fouling properties of membranes by adding antibacterial dipolymer into the PS casting solution. We are therefore motivated to incorporate capsaicin-mimic materials with two carbon-carbon double bonds as an anti-fouling agent via a new method "in situ polymerization-blending" to fabricate high performance PS membranes.First, the antibacterial homopolymer PHMADBA was synthesized through a free radical initiated pomerization from capsaicin derivative structure N-(2-hydroxyl-3-methyl acrylamide-4, 6-dimethyl benzy) acrylamide (HMADBA) and initiator AIBN. Structures of these homopolymers were confirmed using the infrared absorption spectrum (FT-IR) and thermos gravimetric analysis.A given amount of HMADBA and AIBN were added into the PS casting solution, and a kind of new antibacterial PS/PHMADBA UF membrane named modified PS/PH UF membrane was prepared through "in situ polymerization-blending" immersion precipitation phase inversion. Another two membranes only containing HMADBA or AIBN were prepared to further prove that HMADBA existed as polymer instead of monomer. The result indicated that HMADBA monomer was in-situ-polymerized and blended into M6 membrane successfully. It showed that incorporating a small quantity of HMADBA into the membrane improved the permeate flux and rejection when the membranes were tested with a model humic acid (HA) solution.On the basis of above experiment, the effects of HMADBA on the membrane structure, separation performance and antibacterial property were evaluated. The results were as follows. When HMADBA was added, the thickness of membranes changed inconspicuously. The membranes blended with hydrophobic material HMADBA had relatively high contact angles of around 80°. The tensile strength of PS/PH membranes increased with the passage of time. It is due to the fact that the remaining C=C in PS/HMDA membranes gradually polymerized or cross-linked when exposed to environment. When the content of HMADBA was 3 wt%, the membrane separation performance was enhanced with the steady flux of 108.42 L/m2h for 5 mg/L HA solution, meanwhile, the rejection was changed slightly. Moreover, the modified PS/PH membrane had an excellent antibacterial property and the antibacterial rate was up to 64.58%, which was better than the PS membrane.In order to investigate the anti-organic-fouling properties of these four UF membranes (including PS membrane, PS/PH membrane with 1 wt%,2 wt%,3wt% HMADBA in membrane casting solution, respectively.) filtration and clearing experiments were carried out. The flux recovery rate was used as a parameter for evaluating the anti-organic-fouling property.5 mg/L HA solution were used as the feed. The results showed that the steady fluxes of the modified PS/PH membrane with 3wt% HMADBA in membrane casting solution was 100.9 L/m2h, which was higher than the unmodified UF membrane (80.8 L/m2h). Therefore, the modified UF membrane with 3wt% HMADBA was the best in antifouling property among all other testing membranes.