Soil-Washing Effluent Treatment by Selective Adsorption of Toxic Organic Contaminants on Activated Carbon

The recovery of Tween 80 from a liquid residue, obtained after washing of a contaminated soil with p-Cresol, was studied by selective adsorption of p-Cresol with activated carbons. A modified expression of the Langmuir equation was succesfully used to predict the adsorption isotherms of p-Cresol in the absence and presence of different surfactant concentrations. The presence of surfactant seems to modify the adsorption equilibrium, but it does not produce any significant influence on the adsorption kinetic of p-Cresol. A mathematical model was developed to predict the optimum activated carbon dosage demanded to reduce the p-Cresol concentration as a function of the surfactant concentration, also obtaining the corresponding surfactant loss. The regenerated solution was favorably used as washing solution in a new contaminated soil. These results indicate that this technique can be adequate to recover the surfactant solution, with a relatively minimal loss, for a subsequent application.