Adsorption coefficients of 2,4-DNT in soils and clay minerals

Contamination of soil and water by explosives is widespread and often caused by various military activities. 2,4-DNT is commonly used as a military explosive. This explosive may enter to the environment from the processes in which it is made and used. Dinitrotoluenes (DNT's) are intermediates in the production of the explosive trinitrotoluene (TNT) and precursors in synthesis used in the manufacture of polyurethanes. Improper disposal practices associated with TNT manufacturing have resulted in contamination of the soils and water with dinitrotoluenes. In this study, samples of 2,4-DNT were allowed to interact with soil and clay samples to evaluate the adsorption behavior. The behavior of 2,4-DNT was evaluated in soil samples and clay fractions from the Ap and A horizon of the Jobos Series at Isabela, PR and from the University of Puerto Rico at Mayaguez, PR. The clay fraction was separated from the other soil components (sand and silt) by centrifugation.;High performance liquid chromatography (HPLC) was used to obtain adsorption coefficients (Kd values) for the interactions between 2,4-DNT-soil and 2,4-DNT-clay. The adsorption process for 2,4-DNT-soil and 2,4-DNT-clay were described by the Freundlich isotherm model. Values for the correlation factor (R2) near one were obtained in the linear representation of the Freundlich model for the soil and clay samples. Ap horizon shows a greater maximum adsorption (11.87L/kg) than the others. The higher organic matter content of the Ap horizon (4%) may have contributed to the higher 2,4-DNT adsorption observed. In the case of the 2,4-DNT-clay interaction, the sample of the University of Puerto Rico at Mayaguez Campus showed a maximum adsorption (12.73L/kg). The higher adsorption on this clay fraction may be the result of a larger surface area (231.97m2/g).