Fabrication of anti-fouling and photocleaning PVDF microfiltration membranes embedded with N-TiO2 photocatalysts

Abstract

Polyvinylidene fluoride (PVDF) membranes are promising materials for purifying and recycling wastewater in cold regions due to their high mechanical strength and low temperature stability. However, in practical wastewater treatment services, PVDF is easily fouled by organic pollutants because of its hydrophobic characteristics. In addition, because of the large amount of reagent utilized in the conventional cleaning process, a new hydrophilic membrane with simple cleaning characteristics needs to be developed. In this work, a novel anti-fouling membrane (N-TiO2@PVDF) was obtained by implanting a N-TiO2 photocatalyst into a PVDF membrane. N-TiO2@PVDFshows a more homogeneous pore size distribution and a larger average pore diameter, which results in a higher water flux (1017.8 L/m2•h compared to 217.4 L/m2•h PVDF), higher model pollutant bovine serum albumin (BSA) solution flux and higher BSA rejection rate (92.3% compared to 81.4% for PVDF). Furthermore, N-TiO2@PVDF shows an outstanding hydrophilicity performance compared to the PVDF membrane. The water contact angle of N-TiO2@PVDF 14 decreases sharply from 93.7° (PVDF) to 53.5°, and the BSA adsorption amount decreases significantly from 1.41 mg/cm2 (PVDF) to 0.05 mg/cm2. The total fouling ratio of N-TiO2@PVDF is decreased to a value of 25.5% compared to a value of 70.3% for PVDF, and the irreversible BSA fouling ratio is even decreased to 5.8% compared to 57.2% for PVDF. This result indicates that N-TiO2@PVDF shows outstanding antifouling performance. The N-TiO2@PVDF membrane also has a photocleaning function, and the BSA flux recovery ratio reaches up to 94.7% under simulated sunlight irradiation for 2 h without additional treatment. The results obtained from hydroxyl radical (OH) detection indicate that OH degradation of organic pollutants is the dominant mechanism for the N-TiO2@PVDF photocleaning. This anti-fouling and photocleaning N-TiO2@PVDF membrane offers a solution to wastewater treatment problems of membrane brittleness and easy fouling in cold places. It can also be a good choice for the drinking water purification process.