COMPARATIVE ADSORPTION OF ETHOXYLATED ISONONYLPHENOL FROM WATER AND N-DECANE ON SILICA-GEL

Adsorption isotherms of ethoxylated isononylphenol (the average degree of ethoxylation is 6) from water and n-decane on silica gel were meas ured. The equilibrium value of adsorption of this nonionic surfactant from a 10 mmol/dm(3) solution in n-decane (which is close to limiting value) is lower than that from aqueous solution (for the plateau regio n) by a factor of approximately 2.5. The adsorption isotherm from n-de cane is satisfactorily approximated by the Williams-Henry equation, th us indicating the presence of localized (but energetically heterogeneo us) adsorption sites.