Aluminum-based electrocoagulation for residual fluoride removal during per- and polyfluoroalkyl substances (PFASs) wastewater treatment

The residual fluorion (F-) generated during per-and polyfluoroalkyl substances (PFASs) treatment presents a new environmental burden, while minimum attention has been redirected to its removal. In this study, Al-based electrocoagulation (EC) technique was optimized to effectively remove the residual F- during PFASs waste-water treatment. At EC's optimal operating conditions, it can achieve over 81.7 % removal efficiency within 30 min. Furthermore, EC exhibited a stable performance on removing F- across a wide range of pH (3-11), and could form stable flocs under neutral pH conditions. The in-depth characterization of flocs has revealed the dynamic change of Al-F species along the EC process, and removal mechanisms were proved to be a combination of complexation, ion exchange, hydrogen bonding and precipitation. In addition, the optimized EC showed stable removal efficiency of F- with the co-existence of multiple PFASs. Hence, we have effectively removed the residual F- during PFASs wastewater treatment, and provide new insights to better understand the defluorination mechanisms in the EC process.