LAUSR

Abstract Reverse osmosis (RO) has been increasingly applied in municipal wastewater reuse facilities. Nitrate (N) and phosphate (P) -laden reject streams from RO demand near-complete NP removal before inland brine disposal to avoid serious eutrophication effects. In addition, elevated nitrate and fluoride levels in groundwater is a threat to public drinking water safety. Selective removal of both nitrate and phosphate, or fluoride through a single adsorbent is promising because of its small footprints, minimum sludge production, and potential NP recovery. This study presents a new ion exchange adsorbent, NSR-NanoZr, for simultaneous selective removal of both nitrate and phosphate, or fluoride. NSR-NanoZr is fabricated by doping zirconium oxide nanoparticles (ZrO2-Nano) into a nitrate selective resin (NSR), which tributyl quaternary ammonium functional groups contribute to the nitrate selectivity and Lewis acid-base interactions between ZrO2-Nano and ligands result in the high affinity towards phosphate and fluoride. Lab-scale studies showed that NSR-NanoZr exhibited a completely reversal selectivity and removed both NP selectively from municipal secondary wastewater for multiple cycles. Synergistic application of a weak-acid cation exchanger (WAC) enhanced the phosphate capacity of NSR-NanoZr due to the amphoteric sorption behavior of the ZrO2-Nano. Field-scale studies demonstrated the potential of NSR-NanoZr in removing fluoride together with nitrate.