Colloid-Enhanced Ultrafiltration of Chlorophenols in Wastewater: Part III. Effect of Added Salt on Solubilization in Surfactant Solutions and Surfactant–Polymer Mixtures

ABSTRACT

The solubilization of three phenolic solutes in micellar solutions and surfactant–polymer mixtures is studied: 2-monochlorophenol (MCP), 2,4-dichlorophenol (DCP), and 2,4,6-trichlorophenol (TCP). The equilibrium dialysis (ED) technique is used to determine the solubilization equilibrium constant as a function of added NaCl concentration. The added salt enhances the solubilization ability of surfactant micelles, but it only slightly affects the solubilization constant of surfactant–polymer aggregates. The solubilization constant for the surfactant–only systems is greater than that for the surfactant–polymer systems. In the micellar solution, the solute with a low water solubility shows a greater solubilization constant than the solute with a higher water solubility; the solubilization constants increase in the order MCP < DCP < TCP. However, in the surfactant–polymer mixtures, the solubilization constant of DCP can exceed that of TCP due to two opposing effects: ion-dipole interaction, and water solubility or hydrophobicity. Understanding and quantifying this solubilization phenomenon is crucial to optimization of the performance of colloid-enhanced ultrafiltration separation processes.

Key Words::

• Colloid-enhanced ultrafiltration
• Solubilization
• Surfactant–polymer interaction
• Phenolic solutes