CoFe₂O₄/ Mg_0.9Ni_0.1O Nanocomposites with Potential Application in Adsorption: Synthesis, Characterization and Malachite Green Removal

(CoFe₂O₄)_1-x/(Mg_0.9Ni_0.1O)_x nanocomposites, with weight fraction x = 0, 0.1, 0.2, 0.4, 0.8 and 1, have been synthesized by co-precipitation method followed by high-speed ball milling technique. The structural and optical properties of the prepared samples have been studied. XRD analysis confirmed the formation of the two pure phases CoFe₂O₄ and Mg_0.9Ni_0.1O, without the formation of any impurities or minor phases in the nanocomposites. Transmission electron microscopy (TEM) followed by high-resolution TEM (HRTEM) and SAED were used to study the morphology, crystallinity and lattice spacing, respectively. TEM micrographs revealed the co-existence of spherical particles for both pure phases and their nanocomposites. The second-order kinetic model was employed to investigate the adsorption efficiency of the nanocomposites for removing malachite green (MG) dye from the solution. Among the prepared samples, superior adsorption performance was revealed by (CoFe₂O₄)_0.2/(Mg_0.9Ni_0.1O)_0.8 and Mg_0.9Ni_0.1O. (CoFe₂O₄)_0.2/(Mg_0.9Ni_0.1O)_0.8 nanocomposites were chosen as the best candidate among all samples as they possess magnetic properties which makes them easily removed from the solution after the adsorption process. Different adsorption isotherms (Langmuir, Freundlich, and Temkin isotherms) were used to determine the adsorption isotherm, and the results are consistent with the Langmuir theoretical model. The adsorption was further investigated by varying adsorbent concentration, pH of MG solution and reaction temperature.