Enhancing p-cresol extraction from soil

Soil washing is a potential technology for rapid removal of organic hydrocarbons sorbed to soils. In this work, p-cresol desorption with different non-ionic surfactants (Tween 80, Brij 30 and Triton X-100) was compared to cyclodextrine and citrate as solubilizer. A series of batch extraction experiments were conducted at 20 °C using the field soil with different extracting solutions at various concentrations to investigate the removal efficiency and to optimize the concentration of the extractant. The use of the different extracting agents was very selective to p-cresol extraction, minimizing soil organic matter releasing and maintaining the natural pH of the soil. The highest asymptotic values of desorption percentages were obtained for Tween 80 and Brij 30 at 48 h. However, Brij 30 ecotoxicity (EC50 = 0.5 mg L−1) is in the same order of that obtained for p-cresol, being this surfactant clearly ruled out. Liquid to solid ratio of 2.5 mL g−1 presented the best extraction results, while concentrations higher than 1 g L−1 for Tween 80 and Citrate did not produce any significant effect on the desorption efficiency. p-Cresol extraction efficiencies higher than 70% and 60% for Tween 80 and Citrate, respectively.

► Soil washing with five different extracting agents was analyzed.
► Extraction efficiencies increase when using non-ionic surfactants.
► Some solubilizers, very used in the literature, present ecotoxicity values really high.
► An optimization of the extraction conditions was performed for the best extracting agents.
► Extraction efficiencies higher than 70% and 60% for Tween 80 and Citrate was obtained.