The appearance of adsorption ability of modified zeolites for sodium dodecylsulfate from its aqueous solution

Hydrophobic faujasite-type zeolites were prepared by the treatment of hydrophilic Na-Y_4.6 with silicon tetrachloride (SiCl₄) by way of dealumination-silicon exchange reaction. Hydrophilic-hydrophobic characters of these zeolite surfaces were evaluated by measurements of immersional heats into water orn-hexane. Adsorption rates of sodium dodecylsulfate (SDoS) on these zeolites from its aqueous solution and their adsorption characteristics were investigated, and compared with those on ZSM-5 with various Si/Al ratios.The adsorption ability of SDoS into zeolite micropores developed on the zeolite only when it was modified to some extent. The adsorption rates of SDoS were very slow and proved to be affected by molecular diffusion in zeolite pores. They depended on hydrophilic-hydrophobic character of zeolites as well as on pore structures. Adsorption isotherms of SDoS were of Langmuir type, which indicates that the adsorption occurred typically into zeolite pores. Adsorbed amount of SDoS depended on the balance of hydrophilic-hydrophobic character and number of cation site of zeolite surfaces, and had a maximum in case of ZSM-5 zeolites.