Enhanced hydrophilic properties and performance evaluation of PVDF-TiO2-nZVI-SiO2 nanocomposite membranes for the remediation of heavy metal contaminated wastewater

Abstract

Exposure to heavy metal contaminated water causes irreversible harm to humans and the environment. Despite the recent progress in nanofiltration for heavy metal remediation, advanced innovations are necessary to improve its effectiveness and membrane hydraulic performance. In this article, a hydrophilic multifunctional PVDF-TiO2-nZVI-SiO2 nanocomposite membrane material was developed using a phase inversion technique for the remediation of lead and hexavalent chromium contaminants. The synthesized TiO2-nZVI-SiO2 nanocomposite and PVDF-TiO2-nZVI-SiO2 nanocomposite membranes were characterized via various characterization techniques including FESEM, FTIR, EDX, XRD, XPS, TGA, water contact angle, and solvent content analysis. The novel TiO2-nZVI coated SiO2 nanocomposite membranes were fabricated by varying TiO2-nZVI-SiO2 nanocomposite loadings from 0.1 g (M1) to 0.3 g (M5) and the optimal modification was determined via detailed performance evaluation under varying concentrations viz. 20 ppm, 30 ppm, 40 ppm and 50 ppm. The removal efficiencies of the PVDF- TiO2-nZVI-SiO2 membranes were consistently stable despite increase in nanocomposite loadings with optimum membrane (M5) achieving 99.8% removal efficiency during the 50 minutes filtration operation. The TiO2-nZVI-SiO2 nanocomposite combines synergistic redox reaction and hydrophilic properties via TiO2-nZVI and stabilization against particle aggregation from the surface SiO2. Long-term stability study, the influence of contaminant type and loading on PVDF- TiO2-nZVI-SiO2 membrane and hydraulic performance corroborated sustained hydraulic properties and stable performance exceeding 90% across all contaminant loadings.