Determination of adsorption and desorption isotherms of zeolite LTA (4A) by gravimetric method

Poós, Tibor (2026) Determination of adsorption and desorption isotherms of zeolite LTA (4A) by gravimetric method. DRYING TECHNOLOGY, 44 (9). pp. 1292-1302. ISSN 0737-3937

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Abstract

The moisture adsorption and desorption behavior of porous materials is significantly influenced by the size and shape of their pore structure. Zeolites are crystalline aluminosilicate materials with a highly porous structure and large internal surface area, which enable excellent adsorption and desorption properties. Among them, zeolite LTA (4 A) is one of the most widely used adsorbents in industrial drying, gas separation, and thermal energy storage applications due to its strong affinity for water molecules and high regeneration stability. In this study, the adsorption and desorption isotherms of Zeolite LTA (4 A) granular material (size range 1.7–2.4 mm) were determined at 30 °C, 40 °C, 50 °C, and 60 °C using a gravimetric measurement system. The obtained sorption isotherms exhibited S-shaped (sigmoidal) curves, characteristic of multilayer sorption mechanisms. The minor hysteresis loop indicates that the adsorption and desorption processes are governed by different physicochemical mechanisms, likely due to the heterogeneity of the pore structure. Various model equations, including modified BET, mod. Chung-Pfost, mod. GAB, mod. Halsey, mod. Henderson, and mod. Oswin models were fitted to the experimental data using non-linear regression analysis. The mod. GAB model demonstrated the best fit to the measured data, while all models, except for the mod. BET provided satisfactory correlations (R2 > 0:85). Furthermore, the isosteric heat of adsorption and desorption of the investigated material was determined within the temperature range of 30–40 °C. The obtained values varied between approximately 2550 and 3750 kJ*kg−1 depending on the moisture content of the material.

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