Removal Rates of Major and Trace Components of an Organic Film Using Aqueous Nonionic Surfactant Solutions

Abstract

This work examines the cleaning of organic films composed of a primary component (abietic acid) mixed with trace amounts of a second contaminant (benzoic acid). Films were removed from a rotating disk in the presence of aqueous solutions of two poly(ethylene glycol) alkyl ether surfactants: C 12 E 5 and C 16 E 8 . With C 12 E 5 the abietic acid was removed from the disk in three successive cleaning stages - solubilization, shear removal, and rollup - whereas the benzoic acid was almost completely removed during the initial solubilization stage. Also, with C 12 E 5 the results show that the micellar solubilization rate of the trace contaminant is directly proportional to its concentration in the film. The ratio of the molar removal rates of benzoic acid to abietic acid with C 12 E 5 is an order of magnitude greater than the ratio of the mole fractions of the two components in the contaminant film. Solutions of C 16 E 8 removed the abietic acid by only the solubilization and rollup stages. The ratio of the molar removal rates of benzoic acid to abietic acid with C 16 E 8 was equal to the ratio of the mole fractions of the two components in the contaminant film. A mathematical model is proposed to quantify the simultaneous removal of benzoic acid and abietic acid during the micellar solubilization stage. The model takes into account the mass-transfer rate between the film and the bulk solution, as well as the micellization rates at the film/surfactant solution interface. The model adequately represents the experimental data.