PVA-integrated graphene oxide-attapulgite composite membrane for efficient removal of heavy metal contaminants

Graphene oxide (GO) is an excellent membrane-forming material with unique two-dimensional transport channels and excellent adsorption properties for heavy metal contaminants. However, swelling under cross-flow conditions and long-term water immersion leads to poor separation performances. To improve the stability of GO membrane materials, we propose a PVA-integrated graphene oxide/attapulgite membrane (GOAP) with a 3D microstructural arrangement of "brick-mortar-brick." The addition of PVA as mortar reinforces the strength of the structures via induced hydrogen bonding within the 3D water transport network. Furthermore, the Al2O3 ceramic substrate pre-treated with (3-aminopropyl) triethoxysilane (APTES) provided high mechanical stability to the composite membrane, extending the membrane's stability beyond a month of immersion without swelling or shedding. The PVA-integrated GO/ATP composite membrane maintained a rejection rate of 99% for Cu2+ solution (100 mg/L) in a 26-h continuous with nearly 100% rejection for various metals ions such as Cu2+, Ni2+, Pb2+, and Cd2+. The membrane exhibited a water flux of 20.7 L.m(-2).h(-1), which was 15.9-fold high than the pure GO membrane (GOM). The high water flux and heavy metal filtration rate with superior stability proved the practical suitability of the composite film for removing heavy metal ions.