Ultra-hydrophilic layered titanate nanosheet-based nanofiltration membrane with ultrafast water transport for low energy consumption desalination

Abstract

Nanofiltration (NF) membranes have significant applications to solve global water scarcity issues. An ultra-hydrophilic inorganic NF membrane was fabricated using ultra-hydrophilic layered titanate H1.07Ti1.73O4·nH2O nanosheets (HTO-ns), which exhibits high selectivity for desalination and small molecule separations while maintained an ultrafast water transport at low operating pressure. This membrane would be a low-energy consumption NF membrane. To fabricate the HTO-ns membrane, a straightforward technique, namely, the self-adjusting membrane thickness process (SAMTP), was developed by the restacking process of negatively charged HTO-ns with cations on a porous polytetrafluoroethylene (PTFE) substrate. A large-scaled high-quality HTO-ns membrane can be fabricated on a PTFE substrate surface-modified with a silane coupling agent of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and Cu2+ adsorption. There are two kinds of nanochannels for water transport through the membrane, namely, interlayer nanochannels and nanosheet edges chink nanochannels. The excellent separation performances were contributed by the interlayer nanochannels and Donnan exclusion effect of the negatively charged HTO-ns. The SAMTP technique developed in this study could also be applied simply to fabricate other metal oxide nanosheet membranes, which would open a new avenue to the high-performance ultra-hydrophilic inorganic nanosheet-based membranes for low energy consumption separation processes.