Highly efficient removal of methylene blue from aqueous solution by magnetic biochar prepared from hawthorn seeds

Magnetic biochar was prepared in one step with simultaneous activation and magnetization processes under CO2 atmosphere in the presence of a mixture of FeCl(3)6H(2)O and hawthorn seeds as precursor. The magnetic biochar used as a potential adsorbent for the removal of methylene blue (MB) from aqueous solution was characterized by BET, FTIR, SEM and vibrating sample magnetometer. The produced magnetic biochar showed a high surface area of 489.166 m(2)/g, a pore size of 2.16 nm, a pore volume of 0.26 cm(3) /g and a saturation magnetization of 29.84 emu/g. Batch adsorption studies were performed at different initial dye concentration, pH and temperature. The adsorption capacity of the magnetic biochar showed a good result for the adsorption of MB (147 mg/g). Of the two models used, the Langmuir isotherm fitted the equilibrium data better than the Freundlich isotherm. The kinetics study showed that the adsorption of MB was fitted better with pseudo-second-order kinetics model and the intra-particle diffusion process was one of the main mechanisms controlling the adsorption rate. Moreover, thermodynamic parameters showed that the process of adsorption was endothermic and spontaneous. The experimental results showed that the magnetic biochar would be promising for practical wastewater treatment.