Synthesis of Rice Husk-Derived Magnetic Biochar Through Liquefaction to Adsorb Anionic and Cationic Dyes from Aqueous Solutions

Abstract

Rice husk-mediated magnetic biochar (RH-MBC) was manufactured in the present study by liquefaction method. It is applied on the anionic and cationic dyes to investigate their dye adsorption capacity from aqueous solutions. Characterization of the prepared materials has been conducted by the Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope, energy-dispersive X-ray, transmission electron microscopy, Brunauer–Emmett–Teller, vibrating sample magnetometer and point of zero charge (PZC) analysis. From the analyses, it is revealed that the manufactured RH-MBC is super-magnetic and more porous with higher surface area compared with its parent materials. After investigating the adsorption data with different adsorption isotherm and kinetic models, the data were best-fitted with Freundlich model and pseudo-second-order model. The present material shows higher adsorption capacity for representative cationic dye CV (80.04 mg/g) rather than the anionic dye EBT (5.09 mg/g). From the FTIR, XRD, PZC and isotherm studies, it is revealed that the dyes adsorption onto the RH-MBC mainly happened due to the presence of the functional groups like C–O, Fe3O4, –OH, C=C and C–O. It is concluded that the novel functionalized RH-MBC is an approach to use the waste material (rice husk) to use for wastewater treatment and highly efficient for cationic dyes adsorption. Additionally, due to its super-magnetic properties, it is easily separable by using external magnetic field.