Hexavalent Chromium Adsorption on Natural and Modified Mordenite and It’s Regeneration Pathways

Water contamination with hexavalent chromium (Cr(VI)) is a major environmental and health issue, as this ion is highly toxic and possesses strong carcinogenic properties. The novelty of this work lies in the utilization of locally abundant Georgian natural Mordenite (Ratevani deposit) and the systematic comparison of acid- and alkali- modified forms for Cr (VI) removal, combined with a detailed investigation of multiple regeneration pathways using environmentally friendly and cost-effective desorbing agents. In this study, we explore the effectiveness of chemically modified mordenite for the removal of Cr(VI) from aqueous solutions. The structure and morphology of natural and modified samples were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Acid (1 M HCl) and alkali (1 M NaOH) treatments were applied to enhance surface properties and affinity for Cr(VI) oxyanions. Batch adsorption tests evaluated the influence of contact time, pH, initial concentration, adsorbent dose, and temperature. Results showed rapid kinetics (equilibrium in 5–10 min), highest removal efficiency under acidic conditions (pH 2), and superior performance of acid-modified mordenite (up to 95% removal at 20 mg/L). The process was found to be endothermic. Regeneration studies revealed that 0.2 M EDTA provided the highest desorption efficiency (>90%) with good stability over multiple cycles. This work contributes to the development of low-cost, regionally available adsorbents and provides practical regeneration strategies for sustainable Cr (VI) remediation in water treatment.