Selective Removal of Perfluorobutyric Acid Using an Electroactive Ion Exchanger Based on Polypyrrole@Iron Oxide on Carbon Cloth

Perfluorobutyric acid (PFBA) is one type of perfluoroalkyl and polyfluoroalkyl substances (PFASs) and is widely used as an industrial compound. The removal of PFBA has attracted considerable scientific interests in recent decades because it causes environmental pollution and human diseases. Currently, the adsorption method has been used commonly to remove PFASs from wastewater. However, it is usually limited by the inevitable "secondary waste" produced in this treatment process. In this work, PFBA can be effectively removed by synergistic electrical switching ion exchange (ESIX) and a new type of nanostructured ion exchanger. Herein, the nanostructured ion exchanger has been designed and synthesized by coating a polypyrrole (PPy)@Fe₂O₃ nanoneedle on carbon cloth (PPy@Fe₂O₃ NN-CC). Results show that the PPy@Fe₂O₃ NN-CC nanocomposite enhances ion exchange speed and efficiency, which ensures its high adsorption capacity and rapid regeneration property, thereby reducing secondary waste. Moreover, ESIX based on the PPy@Fe₂O₃ NN-CC nanocomposite has high selectivity for adsorption of PFBA over other common anions in water, such as Cl^-, SO₄^2-, and NO₃^-.