Micellar‐enhanced ultrafiltration of chromate anion from aqueous streams

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Abstract
Micellar‐enhanced ultrafiltration can be used to remove multivalent anions or cations from aqueous streams. In the removal of chromate ions (CrO), the cationic surfactant hexadecylpyridinium chloride is added to the solution, and the chromate ions preferentially adsorb at the surface of the highly charged surfactant micelles. The solution is processed by ultrafiltration, using a membrane with pore sizes small enough to block the passage of the micelles and adsorbed ions. The permeate solution has a chromate concentration less than 0.1% that in the original stream. A new equilibrium model, combining the simple two‐phase polyelectrolyte theory of Oosawa with thermodynamic activity, material‐balance, and charge‐balance equations, successfully correlates ultrafiltration and equilibrium dialysis results for chromate solutions.