Consistency of the interfacial tracer technique: experimental evaluation

Miscible displacement experiments were conducted using sodium dodecylbenzenesulfonate (SDBS) and cetylpyridinium chloride (CPC) as interfacial tracers to measure non-aqueous phase liquid (NAPL)–water interfacial areas (anw) in columns packed with silanized glass beads which were coated with either n-decane or perchloroethylene (PCE). The consistency of the interfacial tracer technique was evaluated by showing that: (1) anw values measured with two tracers for two NAPLs were similar; (2) the interfacial adsorption isotherm estimated from the surfactant retardation factors was comparable to that predicted from interfacial tension data and the Gibbs adsorption equation; and (3) the measured anw values were comparable with those estimated from a simple geometrical analysis of the solid surface area of the glass beads of known size and shape.