Magnetic Iron Oxide Kaolinite Nanocomposite for Effective Removal of Congo Red Dye: Adsorption, Kinetics, and Thermodynamics Studies

Abstract

AbstractMagnetic iron oxide/kaolinite (MK) composite was synthesized using co-precipitation method and characterized by XRD, FTIR, SEM/EDX, TGA, XPS, VSM, and zeta potential analyses. The synthesized composite consisting of kaolinite halloysites with small clusters of iron oxide on its outer surface was used in batch experiments to adsorb Congo red dye at different temperatures. The adsorption data were fitted to three different isotherms with Langmuir adsorption isotherm best fitting the adsorption data. The maximum adsorption capacity of MK adsorbent was found to be around 45.59 mg/g. Adsorption kinetics data obtained at three different temperatures were fitted to pseudo-first-order and pseudo-second-order models, where the latter model was able to better interpret the obtained kinetics data with a pseudo-second-order rate constant of 8.60 × 10−2 g.mg−1.min−1. Further analysis of the kinetic data revealed that the adsorption mechanism could be explained via intraparticle diffusion model. Thermodynamic parameters ΔG°, ΔH°, and ΔS° for the adsorption process were determined with the results revealing the adsorption process to be favorable, endothermic, and physical in nature. Finally, comparison with other adsorbents showed that the synthesized MK composite exhibits significant potential to be used as an adsorbent for the removal of organic pollutants from aqueous solutions.