ZIF-67 modified MXene/sepiolite composite membrane for oil–water separation and heavy metal removal

Abstract

In this study, polyvinylpyrrolidone (PVP) was used as a cross-linking agent leading to ZIF-67 in-situ grow on the surface of sepiolite (Sep) to increase the specific surface area and space volume of Sep. Subsequently, a hydrothermal synthesis method was used to form a stable super-hydrophilic composite membrane from the composite MXene by polydopamine. Compared to the MXene/PDA/Sep (MPS) composite membrane, the composite membrane with ZIF-67 exhibited improved hydrophilicity and heavy metal separation. In addition, the introduction of negatively charged Sep@ZIF-67–24 (SZ-24) increased the number of adsorption active sites and negative potential for the surface of the membrane, and this was conducive to the demulsification and adsorption of oil–water emulsions. The MXene/PDA/Sep@ZIF-67–1 (MSZ-1) composite membrane had excellent separation effects on surfactant-stabilized emulsions (SSEs) and surfactant-free emulsions (SFEs) oil–water emulsions which were above 99.4 %. Furthermore, the separation effect on oil–water, under extreme water conditions, was greater than 99 %. The MSZ-1 composite membrane can achieve excellent separation of heavy metal ions, especially Cu2+ that the rejection was 79.9 %, under high flux and extreme conditions. Therefore, the MSZ-1 composite membrane has broad application prospects in oil–water treatment and heavy metal separation.