Thin film nanocomposite reverse osmosis membrane incorporated with UiO-66 nanoparticles for enhanced boron removal

Abstract

The removal of boron from seawater remains a challenge and now receives increasing attention worldwide. Boron removal rates offered by conventional reverse osmosis membranes through one-pass desalination processes are not sufficient to achieve WHO standard. In this paper, the UiO-66 nanoparticles, a metal-organic framework (MOF), are proposed to incorporate into the polyamide (PA)-based thin film nanocomposite (TFN) reverse osmosis (RO) membrane for boron removal due to their inherent porous structure, narrow pore size, and strong adsorption to boron. At an optimum blending concentration of 0.05% (w/v), The UiO-66 TFN membrane showed a ∼50% increase in water flux and a marginal increase in rejection compared with the benchmark thin film composite (TFC) membrane in the brackish water desalination test. In a simulated seawater desalination test, the UiO-66 blended TFN membrane promotes the boron rejection by ∼11% compared with the benchmark membrane. The simultaneous increase of water flux and boron rejection at low blending concentrations are likely attributed to the highly porous structure which provides additional pathways for water transport and the strong adsorption to boron which indued a further pore narrowing effect to its intrinsic pore size of ∼6.1 Å. Therefore, this work provides a new and facile approach to enhance the boron removal rate of the polyamide-based RO membrane via the incorporation of UiO-66 nanoparticles.