Synthesis of heterogeneous metal organic Framework-Graphene oxide nanocomposite membranes for water treatment

Abstract

Textile wastewater is one of the most challenging streams for wastewater treatment as it is heavily contaminated with solid pollutants such as dyes. Nanofiltration (NF) membranes are a promising method to protect water resources by removing dyes and other organic contaminants from wastewater. In this study, novel NF membranes composed of a thin layer of graphene oxide (GO) and Zn-based metal–organic framework (ZIF-7) nanocomposites deposited on chitosan (CTS)-coated polyethersulfone (PES) substrate were fabricated to remove DIRECT RED 16 (DR16) dyes and humic acid from synthetic wastewater. The membrane structure was characterized using a variety of characterization methods such as SEM, XPS, FTIR, AFM, EDX, and water contact angle measurements. Introducing the GO-ZIF-7 nanocomposite layer improved the surface hydrophilicity of membranes by decreasing the contact angle from 84.9 % to 64.5 % for CTS-coated and 5GO-ZIF-7 modified membranes, respectively. This resulted in a greater dye removal rate for the modified membrane (∼94 %) compared to the original CTS-coated membrane (∼84 %). However, the pure water flux was reduced by 11.4 % due to the introduction of additional resistance layers. Furthermore, the addition of GO-ZIF-7 enhanced the antifouling and anti-biofouling characteristics of modified membranes against various organic and biological foulants, such as sodium alginate and Escherichia coli (E.coli). Overall, the fabricated membrane showed great dye filtration, antifouling, and anti-biofouling performances, by introducing high hydrophilicity, biocidal activities, and a negative surface charge to the membrane surface.