The adsorption isotherms of nonionic surfactants Triton X-100 and Triton X-305 onto carbon black from water and cyclohexane solns. were measured at 15?and 30? A Langmuir type isotherm from water solution and a BET type isotherm from cyclohexane solution were obtained; the standard changes of free energy (DG0), enthalpy (DH0) and entropy (DS0) in adsorption processes were calculated A pos. value of DS0 from water solution and a neg. value of DS0 from cyclohexane solution were obtained. The contact angles of water for the systems graphite/water/air and graphite/water/cyclohexane as functions of surfactant concentration were measured. The contact angle of water on graphite always decreases monotonously with increasing surfactant concentration From these results it is concluded that the adsorption of Triton type nonionic surfactants at carbon black/water and graphite/water interfaces is monolayer, and the mols. heading their hydrophobic group (iso-C8H17C6H4) attachs the carbon black surface and the polyethylene glycol chain towards the polar medium, i.e., water. A model is proposed to explain the adsorption of Triton-type nonionic surfactants at carbon black/cyclohexane and graphite/cyclohexane interfaces, with their S-type isotherms.

Key words: WATER, ADSORPTION, CONCENTRATION, SURFACE CHEMISTRY, CARBON BLACK, CARBON BLACK, NON IONIC SURFACTANTS, CYCLOHEXANE, GRAPHITE, SURFACE ANALYSIS