Synthesis and Evaluation of Mordenite Zeolite (MOR Zeolite) for Selective Caffeine Adsorption From Green Tea Extract

Tea (Camellia sinensis) is prized for its polyphenols, which dictate flavor and confer health benefits, yet its inherent caffeine content poses health risks to vulnerable populations. Therefore, developing methods for producing decaffeinated tea extract is important. This study aims to synthesize mordenite zeolite from kaolin and evaluate its potential application for selective caffeine adsorption in the production of decaffeinated tea beverage. Characterization via x-ray diffraction (XRD) confirmed the formation of a crystalline mordenite structure. Brunauer-Emmett-Teller (BET) analysis demonstrated a specific surface area of 77.9989 m²/g, though residual kaolinite and mica impurities limited the micropore volume to 0.084875 cc/g. We investigated the caffeine adsorption behavior in simulated and green tea extract solutions. In simulated caffeine solutions (400-2000 mg/L), optimal adsorption was achieved at pH 2, yielding a removal efficiency of 90.69% and an adsorption capacity of 14.5 mg/g. However, pH 3 was used for adsorption in the green tea extract, resulting in 85.84% caffeine removal while retaining 78.15% of total polyphenols. The adsorption kinetics of caffeine in both systems were well represented by the pseudo-first-order with R² > 0.99. PRACTICAL APPLICATIONS: Mordenite zeolite (MOR zeolite) can selectively remove caffeine from green tea extract, creating decaffeinated tea solution while preserving most of its beneficial polyphenols. This process could be applied to industrial manufacturing of green tea extract that is low in caffeine, which is suitable for health-conscious consumers, pregnant women, children, and elderly individuals who want the health benefits of tea without caffeine's side effect.