Preparation, characterization, and application of magnetic activated carbon from termite feces for the adsorption of Cr(VI) from aqueous solutions

Magnetic carbon activated (MAC) Fe3O4-loaded activated carbon was developed using termite feces and sulfuric acid as the carbon-modifying agent. The key point of the synthetic strategy was that the carbonization, activation and Fe3O4 loading were accomplished simultaneously, via thermic activation/magnetization. The adsorptive characteristics of the MAC for removal of Cr(VI) were investigated. Batch adsorption experiments were performed using both AC and MAC. The evaluation of the adsorption kinetics, isotherm, and thermodynamics was investigated. Adsorption of Cr(VI) onto MAC was highly pH dependent and was found to be optimum at pH 3.0. Nonlinear regression analysis revealed that the Sips isotherm model provides a better correlation for Cr(VI) adsorption onto MAC. The maximum adsorption capacities, at 25 °C, depends on the conditions of preparation of the adsorbent, and were noted to be 60 mg/g for AC and 35, 44 and 66 mg/g for MAC-600, MAC-700 and MAC-800, respectively. The pseudo second-order model best fit the adsorption kinetics. The magnetic property in MAC ensured easy separation of adsorbent using a magnet, after adsorption from the aqueous solution.