Preferential Nitrate Removal from Water Using a New Recyclable Polystyrene Adsorbent Functionalized with Triethylamine Groups

The increasing concentration of nitrate in groundwater and surface water exerts negative effects on the aquatic environment and the safety of drinking water supplies. Efficient water decontamination from nitrate is a pressing but still difficult task. In this study, a new triethylamine-functionalized polystyrene microsphere (TPM) was synthesized through suspension polymerization followed by triethylamine surface modification. Its application for nitrate elimination was investigated through a series of batch and column experiments. Nitrate adsorption by TPM was a pH-dependent process with maximum capacity of 44.92 mg N/g in the neutral pH range, comparable to the commercial anion exchanger D201 under similar conditions. Possibly ascribed to the functionalized triethylamine exchange sites of longer alkyl chains, TPM exhibited prominent selectivity and preference toward nitrate, and its adsorption capacity was proved to be more than two times greater than that of D201 with the coexistence of high-level competing anion (e.g., sulfate). Meanwhile, TPM exhibited excellent anti-interference performance for dissolved organic matter (e.g., humic acid). More attractively, TPM could be continuously reused for nitrate elimination with stable performance assisted by a regular regeneration. In general, TPM adsorption could act as a promising alternative to traditional technology for water decontamination from nitrate.