TNT adsorption on clay minerals by HPLC

Several military bases and monitions facilities throughout the world are contaminated with toxic explosives like 2,4,6-trinitrotoluene (TNT). This is an energetic compound and the least mobile of the military explosives. For this reason TNT gives one of the largest soil contamination problems. To understand the adsorption mechanism between TNT explosive and soil environments, the mechanical method analysis is used in our laboratory in order to obtain the soil texture classification. In these experiments, soil samples from horizons Ap and A were obtained from Jobos Series at Isabela, Puerto Rico. Based on the USDA texture triangle, the soil from the Ap horizon is classified as sandy clay. In contrast, the soil from A horizon fall in the sandy clay loam class. The clay minerals were separated from the other soil components using the mechanical method analysis. Cation exchange capacity (CEC), surface area, percent of organic matter and pH were determined for the soil and clay samples. The CEC results for soil samples were 3.62 mequiv/100 g for Ap horizon and 2.67 mequiv/100 g for A horizon while for the clay samples the CEC was 13.12 mequiv/100 g and 12.50 mequiv/100 g, for the Ap and A horizons, respectively. The results obtained for surface area analysis were 85.32 g/m(2) and 51.19 g/m(2) for the two soil horizons and 189.71 g/m(2) and 163.87 g/m(2) for clay samples in the Ap and A horizons, respectively. These results indicate that the major adsorption could occur in the Ap horizon, specially in the clay fraction. A complete characterization of clay mineral samples using X-ray analysis reveals the present of kaolinite and quartz as main minerals. In order to obtain adsorption coefficients (K-d values), soil samples and the clay obtained from the mechanical method analysis, is being used for TNT adsorption studies by means of High Performance Liquid Chromatography (HPLC).