Sandwich layered double hydroxides with graphene oxide for enhanced water desalination

Abstract

Layered double hydroxides (LDHs) are a class of two-dimensional (2D) clay compounds that consist of positively charged host layers and exchangeable interlayer anions. The stability of their assemblies in aqueous environment is a challenge due to the extremely high hydrophilicity, which limits their use in membrane-based technologies. Here, we propose a graphene oxide (GO) armour protection strategy to substantially improve the stability of LDH membranes in aqueous solution. The sandwich structured GO/LDH/GO membranes (GLGMs) possess a negative-positive-negative charge heterojunction in the vertical direction that effectively blocks the transport of both cations and anions, i.e., NaCl, but allows the permeation of water molecules. Following this mechanism, the GLGMs are used for desalination in a forward osmosis mode. A high rejection rate of over 95.2% for NaCl and water flux of over 2.1 L m−2 h−1 are achieved with simulated seawater.