Thermodynamics of the adsolubilization equilibrium of rhodamine B by surfactant-modified zeolites

The adsolubilization of the cationic dye rhodamine B (RB) into the adsorbed layers of dodecyl- (DTAB) and tetradecyltrimethylammonium bromide (TTAB) o n high silica mordenites (HSZ-1, HSZ-3) and P-type zeolite (PZ) was examine d quantitatively. The adsolubilization constant for the HSZ-1/TTAB system w as determined at temperatures from 10 to 40 degrees C. As the surfactant ad sorption increased, the adsolubilization of RE by the zeolite/surfactant co mplexes was enhanced. Adsolubilization of RE by HSZ-3/surfactant complexes required a critical quantity of adsorbed surfactant, whereas the PZ/TTAB co mplex needed only a very small quantity of adsorbed TTAB to adsolubilize RE . Both the adsolubilization constant and the maximum capacity were calculat ed using a Langmuir-type equation, and the enthalpy and entropy changes wer e determined for the HSZ-1/TTAB mixed system. The difference in the adsolub ilization mode of the three zeolite/surfactant complexes is discussed in re lation to the aggregation mode of the cationic surfactant.