Adsorption of perchlorate in water by FeCl3/dodecyldimethylammonium-chloride-modified activated carbon: Synergistic effect and mechanistic study

Perchlorate (ClO 4 - ) is a stable monovalent ion with a tetrahedral structure that is difficult to remove from the environment. In this study, granular activated carbon (GAC) was modified with FeCl 3 and the quaternary ammonium salt dodecyldimethylammonium chloride (DDAC) for the removal of perchlorate from water. The optimal reagent loading was found to be 2.5 g of GAC modified with 5 g of FeCl 3 and 2.5 mmol/L of DDAC, generating Fe(5)-DDAC-GAC with a perchlorate adsorption of 31.59 mg/g and removal rate of 62.62 %. The adsorption of ClO 4 - by modified activated carbon is more in line with the quasi-primary kinetic model and the Langer-Muir isotherm model. Fe(5)-DDAC-GAC showed good adsorption of perchlorate under weak-acidic to neutral conditions, with optimal adsorption at pH 4 (33.93 mg/g and a removal rate of 67.25 %). The effect of interfering ions on the adsorption of ClO 4 - decreased in the order CO 3 2- > SO 4 2- > BrO 3 - > PO 4 3- . The saturated Fe(5)-DDAC-GAC could be regenerated by NaCl or ultrasonication, with NaCl regeneration being more efficient (66.6 % (NaCl) vs. 55.5 % (ultrasonication) of the initial adsorption capacity). • Successful preparation of activated carbon modified with ferric chloride and DDAC. • Fe(5)-DDAC-GAC with a perchlorate adsorption of 31.592 mg/g and removal rate of 62.62 %. • The mechanism of action of modified carbon is electrostatic adsorption and surface hydrophobicity.