Enhancing dye wastewater treatment efficiency in ozonation membrane contactors by chloro- and fluoro-organosilanes' functionality on hydrophobic PVDF membrane modification

This work investigated the decolorization of dye wastewater using an ozonation membrane contactor. The hydrophobicity of a PVDF membrane was developed by applying novel plasma activation followed by grafting with methyltrichloroalkylsilane (PVDF-MTCS) and 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PVDF-FAS-C8) at different grafting times and grafting agent concentrations. After hydrophobic membrane modifications, the ozonation membrane performances were improved. The ozone flux of PVDF-FAS-C8 was higher and more stable, maintaining 88% of the initial flux after 20 h, compared to 79% and 53% for the PVDF -MTCS and original membranes, respectively. After 90 mins, COD removals of Direct Blue 71 (DB 71) and Reactive Red 239 (RR 239) by the ozonation membrane contactor using PVDF-FAS-C8 were 62.5% and 67.5%, and TOC removals were 20% and 23%, respectively, with almost complete decolorization. The releases of sulfate and nitrate ions confirmed the dye mineralization. By applying a PVDF - FAS - C8 membrane, energy consumption was 33.2% lower than when using the original membrane. The findings exhibited that the performance of ozonation membrane contactor improved was due to the role of the functionality on modified PVDF membranes. The PVDF - MTCS membrane had a higher silicon composition and better surface roughness than the PVDF - FAS - C8 membrane. The water contact angle (WCA) of the PVDF -MTCS membrane was higher than that of the PVDF - FAS - C8 membrane, increasing from 74.7 degrees (original) to 126.0 degrees and 112.7 degrees, respectively, after 6 h of grafting, leading to reduced membrane wetting.

Automated summary

This study investigated the decolorization of dye wastewater using an ozonation membrane contactor, and the performance of the ozonation membrane was improved by modifying the PVDF membrane.