The Interaction Parameter in Binary Surfactant Mixtures of a Chelating Surfactant and a Foaming Agent

The micellisation in binary mixed surfactant systems of a chelating surfactant and a foaming agent has been studied by surface tension measurements in order to calculate the interaction parameter (beta). 2-dodecyldiethylenetriamine pentaacetic acid, 4-C(12)-DTPA, is an amphoteric chelating surfactant applicable for removing disturbing metal ions from industrial processes, or for heavy metal decontamination of soil or leachate. 4-C(12)-DTPA contains multiple donor atoms and forms very stable coordination complexes with metal ions. The metal complexes can easily be recovered from water by flotation, if the foaming is enhanced by a foaming agent with strong interactions to the chelating surfactant. Two foaming agents were examined, one cationic and one anionic. As expected, strong interactions were found between the negatively charged 4-C(12)-DTPA and the cationic dodecyltrimethylammonium chloride, DTAC. The influence of metal ion chelation, as well as pH, on the interaction parameter was also investigated.