Hierarchically structured two-dimensional magnetic microporous biochar derived from hazelnut shell toward effective removal of p-arsanilic acid

Hierarchically structured two-dimensional magnetic microporous biochar (MMBC) derived from a biomass hazelnut shell was prepared and employed for effective adsorption of a typical organoarsenic compound p-arsanilic acid (p-ASA). By a simultaneous ZnCl 2 activation and FeCl 3 graphitization method, the as-fabricated MMBC possessed a hierarchical structure composed by two-dimensional graphene oxide-like flakes, a high specific surface area of 1172.7 m 2 g −1 and good ferromagnetic behavior. Adsorption batch experiments revealed that the MMBC had a higher adsorption capacity of 218.2 mg g −1 and removal efficiency of 87.3% toward the p-ASA than those of the pristine biochar (BC) and the microporous biochar without FeCl 3 graphitization (MBC). The adsorption kinetics dates were fitted well by the pseudo-second-order adsorption model, and the adsorption isotherms conformed well to both Langmuir and Freundlich model. Due to the rich oxygen-containing functional groups (C-O, C = O, Fe-O, Zn-O) and the complex Fe-based components, the adsorption mechanism is proposed to involve synergism between pore adsorption, electrostatic interactions, π-π interactions, hydrogen bonding and coordination interactions. Considering the easy access to biomass and high adsorption capacity to p-ASA, the current MMBC would have good potential applications for controlling the risk of organoarsenic compounds such as p-ASA in aquatic environment.