molecular cross-sectional surface areas of the surfactant mol-Adsorptions of Tween 80 and Span 80 (nonionic) surfactants ecules, the effective numbers of nearest solvent molecules from benzene, toluene, and xylene solutions onto activated charof the adsorbate, and the free energy changes of adsorptions coal (AC) and neutral alumina (AN) are studied at 30ΠC. A Langare studied. muir fit has been found. The molecular cross-sectional surface area of the adsorbed surfactant molecules under solvated and unsol-THEORY vated conditions are determined in different solvents on AC and AN. The results are rationalized, invoking horizontal adsorptions and solvent-solvation differences. The low free energy changes of Nonionic surfactants in nonpolar solvents possess very adsorptions found are indicative of physisorption. α§ 1996 Academic low critical micelle concentration (CMC) values. Therefore Press, Inc.
only dilute surfactant solutions are suitable for adsorption Key Words: nonionic surfactant adsorption; adsorption from studies. Under excess solvent conditions and in the presence organic solvents; surfactant adsorption on charcoal and alumina. of an adsorbent on which preferential and concomitant solvent adsorption takes place there is every possibility that when a surfactant adsorbs onto the adsorbent, the solvation