Synthesis of Magnetic Biochar Using Agricultural Waste for the Separation of Cr(VI) From Aqueous Solution

The agricultural waste, i.e., peanut husk, was modified with iron oxide employed in Cr(VI) removal from wastewater. In this study, standard biochar (BCPH) was prepared from the pyrolysis process from peanut husk. The prepared biochar was magnetized by impregnating the iron oxide onto the surface of the biochar to enhance the adsorption capacity of the adsorbent. The morphological analysis and physicochemical properties of the synthesized biochar (BCPH) and magnetic biochar (MBCPH) were evaluated systematically by SEM, XRD, BET surface area (S-BET) and point of zero charge (pH(ZPC)). Batch experiments were performed to evaluate the sorption mechanism and adsorption characteristics. The pH study revealed that maximum removal efficiency obtained in acidic condition (pH(solution) < pH(zpc)) of the solution. The pseudo-second-order reaction model is employed to kinetic data to determine the equilibrium time, maximum removal efficacy, and the adsorption rate constants of BCPH and MBCPH. The equilibrium time obtained at 90 min for MBCPH and 150 min for BCPH, and the corresponding maximum removal efficiency values are 95.27% and 45.56%, respectively. The isotherm data corroborated that the Freundlich model is the best fit model for both adsorbents. The maximum adsorption capacities were found 8.51 mg/g for BCPH and 75.66 mg/g for MBCPH, respectively. The results show that the uptake capacity of the MBCPH is increased nine times compared to biochar (BCPH). The study concluded that the magnetic biochar (MBCPH) has higher uptake capacity and that can be used as a promising adsorbent for the separation of Cr(VI) from aqueous solution.