Effect of Acid Treatment on the Structure of Natural Zeolite from the Shankanay Deposit

Natural clinoptilolite from the Shankhanai deposit (Kazakhstan) was modified via acid and thermal treatments to improve its physicochemical and catalytic properties. The zeolite was activated using 10% nitric acid alone, nitric acid followed by thermal treatment (600 °C), and a mixed acid solution (10% HNO₃ + 5% CH₃COOH) followed by mild thermal treatment (280 °C). Structural, textural, and thermal changes were characterized by XRD, FTIR, BET, TGA, SEM, and EDX. While nitric acid improved surface area (BET up to 59.9 m²/g), it compromised crystallinity. The mixed acid approach effectively enhanced porosity and acidity while preserving structural integrity. Preliminary catalytic testing in thiophene hydrodesulfurization showed improved conversion (up to 20.7%) in the absence of active metals, confirming the potential of modified zeolite as a catalyst support. The dual-acid method presents a promising, eco-friendly pathway for producing thermally stable and catalytically active zeolitic materials.