Adsorption of sodium dodecylsulfate on a hydrotalcite-like compound. Effect of temperature, pH and ionic strength

The study of the adsorption of surfactants on mineral oxides has received considerable attention. Extensive work has been done in order to better understand such processes. In the present study we investigated the influence of the temperature, pH and ionic strength on the adsorption of sodium dodecylsulfate (SDS) on a layered double hydroxide (LDH). The results were compared to those obtained for the adsorption of surfactants on mineral oxides which has already been explained by reported models. The influence of the analyzed variables was similar to those predicted for these models. Measurements of the electrokinetic potential of the suspensions of SDS-adsorbed LDH particles were made in order to monitor the variation of this potential as a function of the adsorption. The results showed a characteristic behavior of SDS-adsorbed LDH that can be related to an overpopulation of unimers in the electric double layer at concentrations near the critical micelle concentration (CMC). Scanning electron microscopy was used to obtain high magnification images of the SDS-adsorbed LDH particles, which showed a characteristic image for particles adsorbed at equilibrium concentrations ranging from the CMC to the highest concentration used. (C) 1999 Elsevier Science B.V. All rights reserved.