Effect of pore size on cationic surfactant adsorption isotherms of molecular sieve MCM-41

Abstract

The new family of silica-based mesoporous materials designated as MCM-41 is known to be formed using organic- guest species to act as void filters, structure – directing agents and templates. In this study, MCM-41 materials samples of various pore dimensions (21A°, 26A°, 36A°) were synthesized. The studies of adsorption isotherms of quaternary ammonium cationic surfactants with different chain length (C8, C12, C16 ammonium salts) on the MCM-41 with different pore sizes were carried out to determine the effects of the pore size and the chain length on adsorption. The adsorbed amounts at saturation level decreased with increasing the tail length of the surfactant molecule as well as decreasing the pore size. The results indicated that the adsorption ability of surfactant depended on the pore size distribution of the molecular sieve MCM-41. The C8 surfactant, having the shortest tail length adsorbed more than the other two surfactants and the C16 surfactant, having the longest tail length adsorbed the least.