Aqueous solubility enhancement and desorption of hexachlorobenzene from soil using a plant-based surfactant

Abstract

A plant-based surfactant extracted from fruit pericarps of Sapindus mukorossi (Ritha) is proposed for remediation of contaminated soil from a local hazardous waste site. Natural surfactants can be prepared using a very simple water extraction of fruit pericarp powder. Natural surfactant solutions are employed to enhance the aqueous solubility of a hydrophobic organic compound, hexachlorobenzene (HCB), and to desorb HCB from soils in batch and one-dimensional flow-through soil column experiments. The solubility of HCB in natural surfactant solutions increased linearly with surfactant concentration beyond the critical micelle concentration. The mass of dry Ritha powder required to solubilize 1 mg of HCB in 1 liter of water was comparable to sodium dodecylsulfate solution and other commercial surfactants. HCB concentration in the aqueous solutions approached 90% of the HCB solubility in the respective natural surfactant solutions when soils contaminated to high levels were used for desorption. HCB recovery was up to 90% of the total HCB for soils contaminated with lower levels. Desorption behavior observed for natural surfactant solutions was similar to SDS solutions. Natural surfactant solutions performed more efficiently than a simple water flood in recovering HCB from one-dimensional soil columns. The HCB concentration in the effluent was found to be as high as 80% of the surfactant-enhanced HCB solubility in respective solutions. The results of this study provide a strong case for pursuing natural surfactant solutions in further research.