Thin-film nanocomposite membranes with polyol-functionalized layered double hydroxides for boron removal via reverse osmosis

Post-treatment of the permeate from seawater desalination using conventional reverse osmosis (RO) membranes to remove electroneutral boron species is always challenging. In this study, the surfaces of layered double hydroxides (LDHs) have been modified with polyols, namely N-methyl-D-glucamine (GLU), using tannic acid (TA) as the binding agent. By optimizing the loading of the modified LDH nanofillers, the resultant thin-film nanocomposite (TFN) membrane shows an improved water permeance of 3.0 LMH bar 1 while maintaining a high salt rejection of 99.4 %. Moreover, this newly developed TFN membrane delivers a comparable boron rejection of 78.6 % when a feed containing 2,000 ppm NaCl and 15 ppm boron at pH 8 is used. The enhanced separation performance arises from the strong and extensive interactions between the polyols and boron species. This study may provide valuable insights to design next-generation TFN RO membranes for desalination and boron removal applications.