Fabrication of graphene-based membrane for separation of hazardous contaminants from wastewater

Graphene-based materials have gained popularity recently for various applications. Most of the graphene-based composites have been developed using either graphene oxide (GO) or reduced-graphene oxide (rGO), using solvent processing, in situ polymerization, or melt processing method. The presence of GO can enhance the membrane surface charges, thus, higher rejection toward heavy metal ions. GO as additives in polyvinylidene fluoride composite membrane have improved membrane surface hydrophilicity, which is highly useful to reduce membrane fouling tendency in wastewater treatment. Layer-by-layer (LbL) approach (by constructing GO framework) has successfully produced composite nanofiltration membranes that can reject heavy metal ions (Pb2+, Ni2+, and Zn2+) higher than 95%. GO membrane interlinked with multiwalled carbon nanotubes were also fabricated on polyacrylonitrile support and recorded 93.4% of rejection for chelated strontium ions in an alkaline solution. Polyethersulfone/GO/polyacrylic acid membrane, on the other hand, has demonstrated a significant color removal efficiency of 54% with enhanced flux improvement, antifouling ability, and better color rejection capability. Separation membrane via LbL deposition of GO nanosheets, which were cross-linked by 1,3,5-benzenetricarbonyl trichloride, on a polydopamine-coated polysulfone support, showed membrane fluxes with approximately 4–10 times higher than most of the commercial nanofiltration membranes in addition to high rejection efficiency of 95% for Rhodamine WT, a moderate rejection rate of 66% for methylene blue and relatively low rejection (6%–46%) for monovalent and divalent salts. Undoubtedly, graphene-based membranes can be considered as highly promising materials to enhance the removal of hazardous contaminants, especially heavy metal ions and dyes, in wastewater treatments.