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

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) com-posite 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 compos-ite membrane has broad application prospects in oil-water treatment and heavy metal separation.(c) 2022 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

In this study, polyvinylpyrrolidone (PVP) was used as a cross-linking agent to facilitate the growth of ZIF-67 on the surface of sepiolite (Sep), resulting in an increased specific surface area and space volume. The composite membrane MXene/PDA/ Sep@ZIF-67-1 (MSZ-1) demonstrated excellent separation efficiency for surfactant-stabilized emulsions (SSEs) and surfactant-free emulsions (SFEs) oil-water emulsions, as well as for heavy metal ions, especially Cu2+. The MSZ-1 composite membrane shows great potential for applications in oil-water treatment and heavy metal separation.