Removal of Cationic and Anionic Dyes from Textile Waste Effluent using a Magnetic Nanocomposite made of Activated Carbon and Magnesium-Doped Bismuth Ferrite

The (BiMgFeO4/activated carbon) composite has been developed deploying glycine as fuel in a self-combustion process. It was employed to remove methyl green (MG), a cationic dye, and methyl orange (MO), an anionic dye, from aqueous solutions. It was characterized by specific surface area measurement (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). FTIR spectra showed three bands located around 548.18 cm-1, 973. cm-1, and 1577.01 cm-1 attributed to the stretching vibrations of Bi-O, Fe-O, Mg-O, and O-H, respectively. The SEM images revealed a highly porous and irregular structure beneficial for the effective diffusion of dye molecules. The sample contains a notable proportion of holes with different sizes of pores. The microcavities observed on the adsorbent surface were conducive to good diffusion of the dye molecules. The composite's mesoporous structure was deduced by BET analysis, which allowed us to determine the material's specific surface area of 20.289 m2/g and its pore diameter of 7.54 nm. X-ray diffraction showed peaks attributed to Fe3O4, MgO, and Bi2O3 (confirming the presence of BiMgFeO4 ferrite) and other peaks attributed to dehydrated hemicellulose and carbon/graphite (confirming the use of activated carbon). The various experimental parameters affecting the performance of this reaction, such as temperature, contact time, initial dye concentration, and adsorbent mass, were studied. The composite's pH zero charge point (pHPZC) was found to be 8.77. The equilibrium isotherms were described using the Freundlich and Langmuir adsorption models. The equilibrium time was a function of the starting dye concentration in the adsorption tests. Adsorption equilibrium for (BiMgFeO4/activated carbon) was formed after 120 min, according to adsorption kinetic analysis. Moreover, the results revealed that pseudo-second-order kinetics could correctly characterize the adsorption of MO and MG on the composite. Adsorption isotherms confirmed that the adsorption process of both dyes onto the (BiMgFeO4/activated carbon) composite was successful. The Langmuir model appears to be best suited to the adsorption of MO and MG on the(BiMgFeO4/activated carbon), with a maximum adsorption capacity of 196.078 mg.g-1 and 192.307 mg.g-1 respectively, at 298 K. The adsorption of the two dyes was spontaneous and exothermic, in line with the thermodynamic parameters associated with the sorbent/adsorbate system. The determination of the isosteric heat of adsorption revealed that physisorption takes place with weak intermolecular interactions between the two dyes and the composite surface.