Effect of an electrolyte on Adsorptive Micellar Flocculation (I): Increased selectivity in the presence of monovalent–monovalent electrolyte

The presence of monovalent salt increases selectivity in the removal of organic compounds by Adsorptive Micellar Flocculation over a narrow range of flocculant concentrations. The combination of the presence of NaCl and pollutant is seen to enhance the hydrophobicity of the Al3+/laurylsulphate micellar flocculates around the threshold flocculant concentration. The results suggest that two major groups of compounds may be defined. First, compounds which are attracted to the flocculate mostly by hydrophobicity, with transfer enhanced by complexation processes. Second, compounds that adsorb at the surface of surfactant flocculates due to complex formation. Phenol and 2,4-dichlorophenoxybutyric acid are examples of the first group, and benzoic acid and phthalic acid are examples of the second. The hydrophobic compounds separate in the enhanced hydrophobicity region. The relative affinity of the various compounds to distribute between flocculate and water may differ by a factor of up to 100.