Mathematical modeling approach for the green synthesis of high-performance nanoporous zeolites Na-X optimized for water vapor sorption

Abstract

A mathematical approach and green synthesis were employed to develop high-performance nanoporous zeolites with a high water vapor sorption capacity and to optimize the synthesis parameters using natural raw kaolin as the starting alumina-silicate material. The Box-Behnken design model with four factors was employed to elucidate the experimental matrix. The physicochemical and structural properties of the synthesized zeolite were characterized using XRD, FTIR, TG/DSC, 27Al and 29Si solid-state MSA NMR spectroscopy, Raman spectroscopy, FE-SEM, and N2 sorption isotherms. The obtained zeolite sample exhibited a BET surface area of 772.19 m2/g and a microspore volume of 0.16 cm3/g. The maximum water vapor uptake capacity at 25 °C and the highest relative pressure was determined to be 12.1137 mmol/g. The isosteric heat of adsorption and average entropy change were calculated to be − 41.340 KJ·K−1 and 115.308 J·mol−1·K−1, respectively. The resulting zeolite demonstrated excellent stability after five consecutive cycles of water vapor adsorption. The experimental data were fitted using five different isotherm and three kinetic models, and the accuracy of each model was assessed using error functions. GAB model and pseudo-first-order kinetic model exhibited the highest correlation coefficient. The nanoporous zeolite sample obtained through the surface response methodology is well-suited for industrial applications.