Adsorption of Sodium Hexadecyl Sulfate and Triton X from Binary Aqueous Solutions at Thermally Graphitized Carbon Black

Adsorption of anionic sodium hexadecyl sulfate (SHS) and nonionic Triton X surfactants with different ethoxylation degree: TX-45, TX-100 and TX-300 from their individual and mixed aqueous solutions at the surface of thermally graphitized carbon black (CB) was studied. It was found that at low solution concentrations addition of the nonionic surfactant increases the amount of SHS adsorbed from SHS/Triton X mixtures compared to SHS amount adsorbed from its individual solution. These findings might be explained by decreasing in electrostatic repulsion between SHS ions due to inclusion of the molecules of the nonionic surfactant in the mixed adsorption layer. At higher solution concentrations, adsorption of SHS decrease as a result of displacement of SHS ions from the mixed adsorption layer by Triton X molecules. It was established that the composition of the mixed adsorption layer at CB surface notably differ from the composition of the surfactant mixture in the bulk solution. The mixed adsorption layer is enriched with the molecules of the nonionic surfactants and this conclusion is confirmed by the results of measuring zeta potential of CB particles with the adsorbed surfactants.