Fixed-bed study and modeling of selective phenanthrene removal from surfactant solutions

Recovering and then recycling surfactant solution is required in the surfactant-enhanced remediation (SER) of contaminated sites and groundwater to reduce operating costs and prevent secondary contamination. In this study, fixed-beds with activated carbon were employed to selectively remove phenanthrene from Triton X-100 (TX100) aqueous solution as a potential model system for the recovery of surfactant solution in SER. The effects of various operating conditions such as flow rate, bed height, and influent phenanthrene concentration on the performance of the fixed beds were investigated. The sorption of TX100 in the fixed-bed can rapidly reach saturation, but the effluent concentrations of phenanthrene are much lower than its influent concentrations, even with a great volume of solution flowing through the columns. The total removal percentage of phenanthrene from effluent solution was greater than the sorption loss of TX100 under all experimental conditions. The corresponding selectivity parameters for phenanthrene removal versus surfactant sorption were all greater than 4.0, a selectivity value representing 80% phenanthrene removal and 80% surfactant retention. Moreover, better selectivity was obtained at a higher bed height and lower flow rate, but had little dependence on the influent phenanthrene concentration. The constant-pattern model and the apparent partition coefficient were applied successfully to describe and predict the breakthrough curves of TX100 and phenanthrene in fixed-bed columns. The results suggested that fixed-beds could be effectively used to recover surfactant solutions from the washing effluents in SER. (C) 2015 Elsevier B.V. All rights reserved.