Nanocores Magnetic Humic Acid on Montmorillonite Nanoneedles for Adsorption Dye Via RSM: Adsorption Isotherm, Kinetic Modelling and Thermodynamic Studies

Abstract The current inquiry aimed at using core-shell Fe3O4@Humic acid/montmorillonite nanocomposites for removing methyl orange dye from an aqueous solution. The samples were characterized by FT-IR, TEM, SEM, XRD, BJH, and BET analytical methods. The efficiency removal has been utilized for 300 min reaction time using the response surface methodology by a design of five-factor-three-level central composite. The adsorption kinetics followed the pseudo-second-order rate kinetic model, showing an acceptable correlation (R2 > 0.99). Langmuir, Freundlich, Temkin, Dubinin–RadushKevich, and Harkins–Jura isotherms were utilized for the analysis of the equilibrium data. Also, we have estimated standard Gibbs free energy (∆G°), standard enthalpy (∆H°), standard entropy (∆S°), and the activation energy (Ea). The findings of this investigation suggest that the absorption of methyl orange on the adsorbent pursues the Frondelich isothermal formulation. The ∆G° values obtained showed physical absorption in this adsorption process. ∆H° showed that the dye adsorption mechanism was endothermic, and ∆S° indicated an increase in irregularity and the probability of contact between methyl orange molecules and the adsorbent surface in the dye adsorption process. Positive Ea values pointed out the nature of the endothermic absorption process. S* value was minimal and close to zero, which established the process of physical absorption.