Removal of sodium perfluorononyloxybenzenesulfonate (OBS) as an emerging PFAS contaminant from aquatic environments by magnetic ultrafine hydrotalcite adsorption-CPAM coagulation technique: Combined performance and mechanism.

The demand for effective remediation of aqueous per- and polyfluoroalkyl substances (PFAS), especially emerging PFAS, has constantly increased over the last few years. Although adsorption and coagulation are well-established techniques for PFAS remediation, adsorption reaction requires a long equilibrium time; coagulation performance deteriorates when PFAS concentration becomes lower. To address the challenges, an integrated approach which synergistically combined adsorption and coagulation was proposed in this study, using perfluorononenoxybenzenesulfonate (OBS) as the target emerging PFAS to evaluate performance. Ultrafine magnetic hydrotalcite (FeO@LDHs), synthesized via a simple ball-milling process, served as the adsorbent in this approach. Such ultrafine material not only enhanced floc formation during coagulation but also showed rapid OBS adsorption via anion exchange. Cationic Polyacrylamide (CPAM) as the optimal coagulant contributed to OBS removal through electrostatic attraction driven by [RN] groups and hydrophobic interactions involving its alkyl chains. Under optimal dosage of CPAM (25 mg·L) and FeO@LDHs (50 mg·L), the combined magnetic coagulation process achieved 99.89 % of OBS removal within 30 mins. Such combined method still showed effective performance in the presence of hydrocarbon organic competitors, achieving above 90 % removal of OBS from firefighting training wastewater with an acceptable dosing increase. The adsorption-coagulation technique provides a promising and fast solution for treating PFAS wastewater, such as firefighting and industrial wastewater.