Adsolubilization of dihydroxybenzenes into CTAB layers on silica particles

Abstract

The adsolubilization of dihydroxybenzenes (catechol and hydroquinone) into cetyltrimethylammonium bromide (CTAB) layers on silica particles have been investigated by dye method and UV spectrum. It is found that the adsolubilization amount of catechol increases with increasing the concentration of CTAB, reaches a maximum value at the critical micelle concentration (CMC), and then decreases with further increment of CTAB concentration. For hydroquinone, different phenomenon is observed. The maximum adsolubilization amount reaches at critical surface aggregation concentration (CSAC) instead of CMC of the CTAB and then decreases to constant values. In order to analyze the adsolubilization difference between catechol and hydroquinone, we determined the interaction between them and CTAB in the bulk solution by measuring the diffusion coefficient of dihydroxybenzenes with ultramicroelectrode (UME). The individual contributions to the overall apparent diffusion coefficient of dihydroxybenzenes in CTAB solutions were also calculated. The results indicate that more hydroquinone than catechol could interact with CTAB molecules. However, rarely hydroquinone could interact with CTAB micelles compared with catechol. It is suggested that the substitution positions of hydroxyl lead to the difference of the interaction between dihydroxybenzenes and CTAB, which is responsible for the difference of the adsolubilization.