Mesoporous Polymer Nanosponges Immobilized with Functional Polyols for Rapid Removal of Boric Acid and Organic Micropollutants

Rapid removal of boric acid is important in many applications such as seawater desalination, boron extracting and water treatment. Although regarded as the most widely used boron-specific adsorbents, ion-exchange resins are often criticized because of the limited adsorption capacity and slow adsorption rate. Herein we report a copper-free synthesis route of mesoporous nanosponges with cis-diols functionalized on the surface, which are used for rapid removal of boric acid and organic micropollutants from water. Different cross-linking reagents are used to regulate the surface morphology and porous structure of cyclodextrin (CD)-scaffolded nanosponges. Staudinger reaction is then conducted to generate amine groups on the primary face of CD for subsequent reaction with d-(+)-gluconic acid δ-lactone, which successfully immobilize high-density cis-diols on the surface for efficient chelating with boric acid. Functional polymer nanosponges have shown similar boron adsorption capacity as the commercial resins, while the time to reach equilibrium adsorption is reduced dramatically from up to 2 days to tens of minutes (up to 60 times faster). Uptake of bisphenol A by these porous polymers is fast and the equilibrium adsorption could be attained in less than 2 min. The presence of immobilized polyols indicates a synergistic effect due to the secondary bonding, which simultaneously decrease the adsorption time and enhance the adsorption capacity. These findings demonstrate the potential application of polyol-functionalized mesoporous nanosponges in rapid flow-through water treatment.