Removal of Magnesium Ion from Aqueous Solution by Natural Zeolite as Adsorbent: Kinetic, Equilibrium, Mechanism and Thermodynamic

Abstract

The adsorption of magnesium ions (Mg²⁺) from aqueous solutions using natural zeolites has garnered significant attention due to its high cation-exchange capacity and environmental compatibility. Despite extensive research, the combined effects of operational parameters on Mg²⁺ adsorption remain inadequately understood. This study investigated the effects of pH, adsorbent dosage, contact time, and temperature on Mg²⁺ adsorption by natural zeolite. The zeolite was chemically activated with 6N HCl to enhance its adsorption capacity. The optimal conditions for Mg²⁺ removal were found at pH 7 using 20 grams of zeolite and a 10-minute contact time, resulting in a maximum adsorption capacity of 0.191 mg/g. Thermodynamic studies revealed an endothermic adsorption process, with a positive enthalpy change (ΔH) of 44.64 kJ/mol and a positive entropy change (ΔS) of 121.99 J/mol·K, indicating increased randomness at the solid-solution interface. The adsorption kinetics followed a pseudo-first-order model, suggesting physical adsorption mechanisms. These findings provide critical insights for optimizing zeolite-based adsorption systems for water treatment applications.