Surfactant adsorption on plastic surfaces

Abstract

Surfactant adsorption on a hydrophobic surface plays an important role in many industrial applications, for example detergency, adhesion, and wetting. In order to effectively utilize the surfactant, the surfactant adsorption isotherm must be well understood. In this research, surfactant adsorptions on plastic surfaces were investigated. Three surfactant representatives used were sodium dodecyl sulfate (anionic surfactant), cetyl trimethylammoniumbromide (cationic surfactant) and t-cetylphenol polyethoxylate (nonionic surfactant). The plastics used for adsorption study were high-density polyethylene (HDPE) and polypropylene (PP). For HDPE in solutions of at pH 6, the maximum adsorption of SDS was greater than CTAB and Triton X-114. This was consistent with the zeta potential of the HDPE, which has a positive potential at pH 6. At lower pH, the zeta potential is more positive, therefore the maximum adsorption of SDS on HDPE was higher. As expected, adding electrolyte shifts the adsorption isotherm to lower equilibrium concentration while the maximum adsorption remained constant. For PP, the zeta potential was relatively close to zero. The maximum adsorption of SDS and CTAB on PP were approximately equal. As expected, changing the pH had no effect on the zeta potential of PP.