Efficient capture of phosphate from wastewater by a recyclable ionic liquid functionalized polyacrylonitrile fiber: a typical “release and catch” mechanism

Abstract

The enrichment and separation of phosphorus-containing compounds from wastewater can prevent eutrophication and can be used to recycle non-renewable resources. Herein, we developed a recyclable functionalized polyacrylonitrile fiber (PAN_AF–Cl) capable of loading an ionic liquid to adsorb phosphate in water. The results demonstrated that the PAN_AF–Cl reached the adsorption equilibrium within 5 min, with a maximum phosphate adsorption capacity of 15.49 mg P g⁻¹. The fiber exhibited a wide range of pH adaptability with maximum adsorption capacity at the pH value of 5. A pseudo-second-order kinetic model and Langmuir isotherm model could better fit the adsorption of phosphate by the PAN_AF–Cl, indicating that the adsorption process belongs to monolayer chemisorption. Furthermore, the PAN_AF–Cl retains its considerable phosphate removal ability when Cl⁻, NO₃⁻, etc. coexisting ions are included. It also exhibited a low adsorption limit (0.0184 mg P L⁻¹) in actual wastewater and can be recycled at least 5 times. Moreover, the fiber revealed a high removal efficiency of above 90% for phosphate in simulated wastewater under continuous flow conditions. Besides, a “release and catch” ion exchange adsorption mechanism of PAN_AF–Cl for phosphate is proposed. Altogether, this study concludes that PAN_AF–Cl as an efficient phosphate adsorbent has high practical value for phosphate recovery and water purification.