USING SURFACTANTS TO ENHANCE DRAINAGE FROM A DEWATERED COLUMN

Abstract

Our objective was to determine the efficacy of surfactants as secondary recovery agents to enhance drainage from a previously dewatered sand column. Seventeen surfactants at concentrations of 0, 0.01, 0.1, 1.0, 10.0, and 100 g (solid) or ml (liquid) surfactant per liter of water were evaluated. Anionic, cationic, and nonionic classes of surfactants were represented. Surfactant solutions (150 ml) were added to the top of dewatered sand columns (0.1-m diameter by 0.5-m length), and column outflow was measured. Each treatment was replicated four times. Between surfactants additions, columns were cleaned with 500 ml of methanol and 750 ml of tap water. Outflow significantly increased as the log of surfactant concentration increased, but no surfactant class was significantly more efficient than any other class. Surface tension was significantly correlated with log of concentration (-0.73) and outflow (-0.42). This indicated that decreases in surface tension are associated with increases in column dewatering. Outflows from the less than 1 g or ml surfactant per liter of water treatment were not significantly different from the blank (no surfactant). Surfactant chemistry was additionally evaluated using several Igepal DM surfactants with differing numbers of ethyleneoxy (EO) units. Maximum outflow occurred at EO ratios of 15.3, indicating that surfactant chemical structure is also important. The high concentration of surfactant required to show significant benefits (1 g or ml per L) probably precludes use of surfactants as secondary recovery agents for water.