Removal of Malachite Green via X-Faujasite Adsorption: A Multi-Model Investigation of Adsorption Kinetics and Thermodynamics

Abstract

Industrial effluents containing synthetic dyes, such as Malachite Green Oxalate (MG) from tanneries, pose a major ecological challenge. In this work, we investigate the potential of a newly developed X-Faujasite (X-FAU) as an effective sorbent for MG, prepared through hydrothermal synthesis. The obtained material was thoroughly examined using several analytical techniques, including XRD, FTIR, SEM-EDX, and BET analysis. Results indicated that X-FAU exhibits structural properties highly suitable for adsorption, characterized by high surface area, distinct porosity, and the presence of appropriate functional groups. The adsorption behavior of MG was systematically evaluated under varying operational parameters, including pH, adsorbent quantity, contact time, and temperature. Under optimized parameters, X-FAU achieved nearly complete dye removal (99.9%), with a maximum uptake capacity of 296.36 mg/g at pH 8.26. Kinetic analysis indicated that adsorption adheres to a pseudo-second-order model. The superior fit of the equilibrium data to the Langmuir isotherm strongly supports the assumption of monolayer adsorption on the X-FAU surface. Thermodynamic investigations further showed that MG uptake on X-FAU is spontaneous and endothermic, with higher temperatures favoring adsorption efficiency. Additionally, FTIR analysis confirmed robust interactions between MG molecules and the X-FAU structure. Overall, the findings highlight that X-FAU is a sustainable, efficient, and high-performance adsorbent, making it an excellent option for treating dye-polluted wastewater.