Mechanistic details of the removal of 2,4,6-trichlorophenol from aqueous solution by iron and nitrogen co-doped biochar: Characterization, performance, and mechanism studies

Research on synthesizing efficient composites and their application on chlorophenol-contaminated site remediation is needed. This research explored the iron and nitrogen co-doped biochars (Fe-N@BCs) for removing 2,4,6-trichlorophenol (TCP) from an aqueous solution. Specifically, Fe-N@BCs synthesized by co-pyrolysis of the mixture of iron (FeCl3), nitrogen (melamine and chitosan), and carbon (wood sawdust) at temperatures from 300 to 900degree celsius were characterized with multiple techniques to study the N and Fe species in Fe-N-BCs. Fe-N@BC900 showed the highest TCP removal efficiency due to superior graphitic moieties and C matrix, Fe species (Fe3C and alpha-Fe), and surface area. Experimental results of TCP removal by Fe-N@BCs were fitted with standard isotherm and kinetic models, and affecting factors on TCP removal by Fe-N@BCs were explored to study removal mechanisms. According to the characterization results of as-synthesized and used Fe-N@BCs, enhanced removal of TCP by Fe-N@BCs was attributed to the adsorption via pore-filling owing to the porous structure of Fe-N@BCs, H-bonding, electrostatic interactions, and pi- pi EDA interactions between TCP and Fe-N@BCs happened by co-doping of Fe and N species and reduction of TCP by Fe-N@BCs. Removal of TCP by Fe-N@BCs mainly depended on adsorption, while reduction was slightly involved in TCP removal. For assessing the real-world application of Fe-N@BCs, Fe-N@BC900 showed superior stability during reusability experiments as it showed >93% TCP removal efficiency after 4(th) run, and the TCP removal by Fe-N@BCs in real water conditions was satisfying. This study proposes the benign method for removing TCP by Fe-N@BCs from water and determining reaction mechanisms.