Preparation of activated biochar-supported magnetite composite for adsorption of polychlorinated phenols from aqueous solutions

For this study, we applied activated biochar (AB) and its composition with magnetite (ABFe₃O₄) as adsorbents for the removal of polychlorophenols in model wastewater. We comprehensively characterized these adsorbents and performed adsorption tests under several experimental parameters. Using FTIR, we confirmed successful synthesis of AB-Fe₃O₄ composite through cetrimonium bromide surfactant. We conducted adsorption tests using AB and AB-Fe₃O₄ to treat model wastewater containing polychlorophenols, such as 2,3,4,6-Tetrachlorophenol (TeCP), 2,4,6-Trichlorophenol (TCP), and 2,4-Dichlorophenol (DCP). Results of the isotherm and the kinetic experiments were well adapted to Freundlich's isotherm model and the pseudo-second-order kinetic model, respectively. Main adsorption mechanisms in this study were attributed to noncovalent, π-electron acceptor-donor interactions and hydrophobic interactions judging from the number of chloride elements in each chlorophenol and its hydrophobic characteristics. We also considered the electrostatic repulsion effect between TeCP and AB, because adsorption performance of TeCP at basic condition was slightly worse than at weak acidic condition. Lastly, AB-Fe₃O₄ showed high adsorption selectivity of TeCP compared to other persistent organic pollutants (i.e., bisphenol A and sulfamethoxazole) due to hydrophobic interactions. We concluded that AB-Fe₃O₄ may be used as novel adsorbent for wastewater treatment including toxic and hydrophobic organic pollutants (e.g., TeCP).