Kinetic effects in surfactants transport through sand

The kinetics of solubilization and sorption of nonionic surfactants should be considered for efficient design of surfactant-enhanced aquifer remediation. Experimental evidence suggests that nonionic surfactant sorption onto aquifer sediments is not an equilibrium process, but is rate limited and may comprise different sorption regimes. Several different experiments were conducted in laboratory-scale column systems to evaluate the kinetics of sorption of Triton X-100 (C{sub 8}PE{sub 9.5}) onto Lincoln fine sand. Unusual two-step breakthrough curves were observed in each of the column tests. An early breakthrough at a fraction of the influent concentration was followed by a prolonged plateau. In each case, a transition from this plateau to a second breakthrough curve was observed as surface coverage approached 2.4 {mu}mol/g. The elution curves did not show a step-wise behavior; a rapid decrease in surfactant concentration was followed by prolonged tailing at low concentrations. A two-stage, sorption kinetic model was used as a first approximation to describe the breakthrough and the elution curves.