Selective removal of organic phosphonates via coupling hyper-cross-linked resin with nanoconfined hydrated oxides

Abstract

Phosphonates, featuring organic skeletons binding phosphonic acid group, are ubiquitous in wastewaters and natural waters. Highly efficient removal of trace phosphonates is desirable to ensure the water quality and to prevent eutrophication. Commercially available hyper-cross-linked resins modified by amino groups have been proved to exhibit preferable adsorption of various organic acids from aqueous systems via synergetic effect of various interactions (electrostatic interaction, van der Waals interaction, π-π interaction, etc.) but seem relatively ineffective for phosphonates. In this study, we proposed a new strategy via coupling a commercial resin NDA88 with nanoconfinement of Hydrated ferric oxide (HFO) for selective removal of phosphonates. The resultant HFO@NDA88 shows an adsorption capacity of 15.0 mg P/g towards a model phosphonate (nitrilotris(methylenephosphonic acid)), higher than those of the NDA88 host (7.9 mg P/g) and the bare HFO (7.4 mg P/g). Remarkably, compared to NDA88 and HFO, HFO@NDA88 exhibits much higher resistance to the interference of various anions and other substances at much greater levels, particularly the organic analogue nitrilotriacetic acid and phosphate. Such superior selectivity is believed to result from the cooperative contributions of the host NDA88 as well as the embedded nano-HFO. Moreover, HFO@NDA88 shows excellent reusability and satisfactory performance in fixed-bed water treatment. This work provides a rational design of nanocomposite adsorbents for highly selective removal of phosphonates from complicated water matrix.