Impact of Surfactants on the Efficacy of Iron Oxide Dispersants

Abstract Surfactants form a unique class of compounds that are used in a variety of applications including laundry detergents, dish washing liquids, agrochemicals, pharmaceuticals, petroleum processing, mineral ores, personal care, floor cleaners, paints, coatings, fuel additives, and photographic films. In the present work a variety of surfactants containing different functional groups (i.e., anionic, non-ionic, amphoteric, cationic) has been used to study their influence on the performance of polymeric iron oxide dispersants. Effects of dispersant dosage, time, and polymer architecture have been investigated. The polymers tested include homopolymers of acrylic acid, maleic acid, methacrylic acid, 2-acrylamido-2-methylpropane sulfonic, 2-ethyloxazoline, and acrylic acid, maleic acid based copolymers containing different functional groups. It has been found that polymer performance as dispersant depends on dosage and polymer architecture. Results on the evaluation of surfactants suggest that compared to polymers, surfactants are ineffective iron oxide dispersants. Results on the impact of cationic surfactant (e.g., cetyltrimethyl ammonium chloride, CTAC) suggest that CTAC exhibits an antagonistic effect on the performance of polymers. It has also been found that cationic polymer (e.g., polydiallyldimethyl ammonium chloride) shows much stronger antagonistic effect than CTAC on the efficacy of polymers used as iron oxide dispersants in industrial water systems. The antagonistic behavior shown by cationic surfactant and cationic polymer on the performance of polymers has been explained in terms of cationic – anionic interactions.