Enhanced phosphate removal from wastewater by recyclable fiber supported quaternary ammonium salts: Highlighting the role of surface polarity

A novel quaternary ammonium salt functionalized polyacrylonitrile fiber with hydrophilic hydroxyl (PANT-C2-OHF) for phosphate removal was synthesized through simple chemical grafting reaction, which showed high removal efficiency and excellent reusability. [Display omitted] •Quaternized PANFs with polarity adjustable surface micro-environment are prepared.•PANT-C2-OHF with highest hydrophilicity shows the best phosphate removal capacity.•PANT-C2-OHF can be quickly saturated with phosphate within 5 min.•PANT-C2-OHF exhibits excellentrecyclability and reusability for 10 times.•PANT-C2-OHF can decrease phosphate concentration low than 0.02 mg P L−1. The application of fiber adsorbents in water treatment has recently received major attention due to its cost-effectiveness, good recyclability, and easy separation. Herein, we developed a novel strategy to prepare quaternary ammonium salt functionalized polyacrylonitrile fibers with a polarity tunable surface micro-environment to enhance the removal of wastewater phosphate. For this purpose, quaternized fibers with hydrophilic hydroxyl (PANT-C2-OHF) and hydrophobic alkyl with different chain lengths (PANT-C2F, PANT-C4F, PANT-C6F, and PANT-C8F) were constructed and characterized. Results of the adsorption experiment revealed that PANT-C2-OHF containing hydrophilic hydroxyl groups had the best adsorption capacity for phosphate (24.44 mg P g−1) within the adsorption equilibrium of 5 min. Furthermore, PANT-C2-OHF could effectively remove wastewater phosphate in a wide pH range (3–9), even in the presence ofCl-, CO32–, NO3–, etc. The adsorption kinetics and isotherms of PANT-C2-OHF for phosphate were better described by the pseudo-second kinetics and Langmuir isotherm models, indicating a monolayer chemical adsorption process. Besides, PANT-C2-OHF possessed excellent recyclability of at least 10 times and an extremely low adsorption limit for phosphate (0.02 mg P L-1) in actual wastewater. In brief, this study provides proof for PANT-C2-OHF as a new environmental adsorbent with high efficiency, selectivity, and reusability for removal and recovery of phosphate.