Integration of the partition effect into the model of non-aqueous phase liquid solubilization by non-ionic surfactant

Accurately predicting the efficiency of surfactant-enhanced recovery of non-aqueous phase liquid (NAPL) using non-ionic surfactants requires a precise estimation of the kinetics of rate-limited solubilization under the effect of bulk partition. This study investigated the kinetics of surfactant partition from aqueous phase into liquid NAPL and its subsequent impact on the solubilization kinetics of dodecane. For all surfactants examined, the solubilization of dodecane by anionic rhamnolipid (RL) and SDBS, presenting NAPL-water interface adsorption loss only, closely followed the first-order mass transfer model under the assumption of constant solubility. In contrast, the solubilization of dodecane by non-ionic TX-100 showed significant deviations due to the progressive partition of TX-100 into the bulk of liquid dodecane. The first-order mass transfer model, based on the physical hypothesis of the two-film model, accurately depicted the dynamic partition loss of TX-100. The accuracy of the first-order mass transfer model in depicting the dynamic solubilization kinetics of dodecane by TX-100 was improved by setting the equilibrium solubility as variable to account for the effect of the bulk partition loss. The findings quantified the capability of surfactants to solubilize NAPL with considering the impact of bulk partition loss, providing insights into the fundamental processes of NAPL solubilization with the application of non-ionic surfactants.