Removal of Naphthalene and 2, 4-Dinitrotoluene from Soils by Using Carboxymethyl-β-Cyclodextrin

Abstract

Spillage of petroleum and petroleum products from the underground storage tanks has caused significant contamination of groundwater aquifers by organic contaminants. These compounds are generally difficult to remove since the chemicals are hydrophobic, having a low solubility and therefore prefer to adsorb onto the soil. The ability of carboxymethyl-β-cyclodextrin (CMCD) to increase the solubilities of contaminants in soils was studied. Furthermore, studied partitioning of soil-contaminants and CMCD-contaminants were also included. Soils consisting of 7.4% clay content and 2.2% organic carbon content were used as contaminated soils. Naphthalene and 2, 4-dinitrotoluene (2, 4-DNT) were selected as the representative low polarity organic contaminants. In the batch studies, the partition coefficient between soil-naphthalene and soil-2, 4-DNT were 51.3 and 5.6 L/kg. In addition, 269.2 and 22.4 L/kg were determined from the partitioning between CMCD-naphthalene and CMCD-2, 4-DNT respectively. The results from column experiments showed that CMCD greatly enhanced the removal of naphthalene and 2, 4-DNT from soils. Using 0.01 N NaNO₃ as the flushing agent, 32 and 40% of naphthalene and 2, 4-DNT were removed. Meanwhile, 70 and 72% naphthalene and 2, 4-DNT were removed after 2 g/L CMCD solution was flushed through the soil columns.