Synergistic effect of GO@SiO2 and GO@ZnO nano-hybrid particles with PVDF-g-PMMA copolymer in high-flux ultrafiltration membrane for oily wastewater treatment and antifouling properties

Abstract

In the Ultrafiltration (UF) region, the development of the membranes with ultra-water permeability and extraordinary oil rejection at the same time is highly desirable. Herein, a copolymer/nano-hybrid particles mixed matrix membrane was fabricated with high hydrophilicity and oil-in-water separation performance, originating from the synergistic effect between the prepared copolymer and nanoparticles. Accordingly, atom transfer radical polymerization (ATRP) method, especially considered as a promising grafting technique to modify polyvinylidene fluoride (PVDF), was utilized for the synthesis of the PVDF-g-PMMA copolymer. Furthermore, two different nano-hybrid particles including graphene oxide (GO) sheets separately decorated with ZnO and SiO2 were also synthesized. Then, different membrane compositions with various GO@ZnO and GO@SiO2 contents were fabricated, and then, the synergistic effect of each nano-hybrid particle with the PVDF-g-PMMA copolymer was evaluated. The prepared GO@ZnO and GO@SiO2 were used not only to modify ultrafiltration (UF) membranes for oil rejection but also to prevent protein BSA adsorption on the membrane surface based on their surface charge. The 4 wt.% PVDF-g-PMMA/0.3 wt.% GO@SiO2 and 4 wt.% PVDF-g-PMMA/0.3 wt.% GO@ZnO membranes provided outstanding separation performance (soybean oil rejections of 93.4% and 95.2%, respectively) and ultra- water permeability (312 and 326 L/m2.h.bar, respectively). Based on the results in terms of separation and filtration performances, the M5 membrane exhibited more efficient performance than M4 membrane. By increasing the amount of nano-hybrid particles, the overall finger-like voids, average pore size, and surface roughness of membranes decreased, making them ideal for application in the water treatment field. Also, the influence of hydrophilicity and charge density of GO@ZnO and GO@SiO2 nano-hybrid particles with the copolymer in the PVDF membrane was examined through conducting the antifouling experiment in two different pH values, in which a great performance was also obtained. Compared to previous researches, GO@ZnO and GO@SiO2 nano-hybrid particles with the copolymer in the PVDF membrane not only can generate ultra-high water permeability in low pressure but also provide >93% oil-in-water emulsion rejections.