Abstract: The adsorption isotherms of Triton X-100(TX 100) on a flamehydrolyzed silica (CAB-O-SIL) from aqueous solutions and from sodium chloride(1.0 mol/L) at 290.7K and 304.2 Khave been determined.The results show that the adsorption increases with increasing temperature and salinity.Based on the theory of surfactant adsorption we proposed previously,the equilibrium constant of surface micellization(K),surface micelle aggregation number(n_sm),surface micelle concentration(smc) and the standard thermodynamics functions(△G⁰_am, △S⁰_am,△H⁰_am of surface micellization are calculated.The results show the value of n_sm increases with increasing temperature,In addition,similar to the micellization in bulk solution,the surface micellization is also an entropy-driven process.The effects of TX100(with or without 1.0 mol/Lsodium chloride) on the aggregative stability of silica suspension have also been investigated.In the low concentration range of TX 100, the stability of suspension increases with increasing concentration of TX 100.Above the surface micelle concentration(smc) of TX 100, the stability of suspension decreases with increasing concentration of TX 100.However if the concentration approaching to the cmc of TX 100,the stability of suspension increases again,The addition of sodium chloride enhances the surface micelle formation and results in a depression of stability of suspension,Based on the adsorp tion isotherms of TX 100,a model concerning surface micellization is proposed to explain the above experimental results reasonably.

Key words: Nonionic surfactants, Silica, Mechanism of adsorption, Surface micellization, Stability of suspension