Feasibility Study on Salting-In of Organic Pollutants To Enhance the Effectiveness of Ex-Situ Soil Washing

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Industrial and Engineering Chemistry Research


The feasibility of using a salting-in effect for leaching organic pollutants from subsurface materials was investigated. Two clay samples with contrasting properties and three well-characterized soil samples were spiked with nitrobenzene, a priority contaminant, and experimental desorption equilibrium studies were conducted. By using aqueous solutions of benzoic acid ammonium salt with a concentration range from zero to 72% of saturation, desorption isotherms were generated. The impact of salting-in on the leaching efficiency and the influence of soil properties on the process were examined. Qualitative criteria for feasibility were established. Results showed that the presence of salt caused a substantial increase in the amount of nitrobenzene leached from subsurface materials with low ion-exchange capacity, and the positive trends become more pronounced with increasing levels of salt concentration. In the case of subsurface materials with high ion-exchange capacity, however, solute-solid interaction was the controlling mechanism. Consequently, improvement in leaching efficiency due to increased liquid-side solubility was lessened or diminished. Both physical and chemical characteristics of soil samples had an impact on the levels of leaching achieved. Clay type and its percentage were the dominant factors. They were followed by organic matter content and surface properties. No significant level of salt adsorption on soil was observed. © 1997 American Chemical Society.