Adsolubilization Behavior of 2-Naphthol into Adsorbed Anionic Surfactant and Poly(vinylpyrrolidone) at an Alumina/Water Interface

Abstract

Adsolubilization of 2-naphthol in a polymer-surfactant layer on alumina has been studied. Two systems are explored: poly(vinylpyrrolidone) (PVP-sodium dodecyl sulfate (SDS) and PVP-sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol OT). Under a constant feed concentration of PVP, the adsolubilized amounts of 2-naphthol increase sharply at low surfactant concentration, reach a maximum, and then decrease with the surfactant concentration. This sharp increment is attributed to a formation of complex between PVP and surfactant on alumina. The subsequent decrease in the adsolubilization is caused by the decrement of PVP adsorption and by partitioning 2-naphthol into a bulk complex of PVP-surfactants and surfactant micelles. Compared with two systems, although the adsorbed amount of SDS becomes considerably smaller with increasing feed concentration of PVP than that of Aerosol OT, the maximum adsolubilized amounts of 2-naphthol are not so different with the feed concentration of PVP. From fluorescence measurements, it is found that the polarity of SDS adsorbed layer on alumina upon addition of PVP is significantly decreased, whereas that of Aerosol OT is hardly changed upon addition of PVP. In the PVP-SDS system, the increment in the adsolubilization of 2-naphthol is correlated with the polarity change of the adsorbed layer, while in the PVP-Aerosol OT system it is attributed to the increase of the hydrophobic capacity by adsorption of PVP-Aerosol OT