Adsorption Process of Methyl Orange Dye onto Zinc Hydroxide Nitrate: Kinetic and Thermodynamic Studies

Zinc hydroxide nitrate (ZHN) was used as an anionic adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. ZHN was characterized via X-ray diffraction (XRD) and infrared spectroscopy (FTIR) techniques. Investigations were carried out to see how the adsorption of MO was affected by factors such as initial MO concentration, contact time and temperature. Adsorption isotherms were analyzed using the Langmuir and Freundlich equations, with the first one being the better result for the equilibrium data. Adsorption kinetics was studied through applying pseudo-first and pseudo-second-order kinetic models, and the experimental data were better fitted to the pseudo-second-order model. The activation energy was determined using the Arrhenius equation to be 105.45 kJ mol−1, revealing the chemical nature of the adsorption process. The thermodynamic parameters were also determined, showing the adsorption of MO onto ZHN to be a non-spontaneous and exothermic process. The experimental results showed ZHN as a potential adsorbent with adsorption capacity for removing anionic dyes from water medium.