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

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 A F–Cl) capable of loading an ionic liquid to adsorb phosphate in water. The results demonstrated that the PAN A F–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 A F–Cl, indicating that the adsorption process belongs to monolayer chemisorption. Furthermore, the PAN A F–Cl retains its considerable phosphate removal ability when Cl − , NO 3 − , 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 A F–Cl for phosphate is proposed. Altogether, this study concludes that PAN A F–Cl as an efficient phosphate adsorbent has high practical value for phosphate recovery and water purification.