Adsorption and Desorption of 2,4,6-Trinitrotoluene by Soils

摘要

Soil samples collected from 12 Army Ammunition Plants were characterized by chemical and physical tests. Tests included pH, particle size distribution, cation exchange capacity, electrical conductivity, percent organic carbon, and extractable iron, manganese, aluminum, and calcium. Soils were found to be primarily silty loams, low in organic carbon. Trinitrotoluene (TNT) reached a steady state of adsorption with test soils (i.e., no change in TNT solution concentration) within 2 hr of contact. Desorption kinetics indicated that desorption was also rapid. A steady state of desorption occurred within 2 hr with more than half of the adsorbed TNT being removed. Batch adsorption isotherms were linear with an average adsorption coefficient (soil concentration/solution concentration, or Kd of 4.0. However, Kd varied with soil type. The TNT adsorption correlated most highly with cation exchange capacity, extractable iron, clay content, and present organic carbon. Sequential desorption indicated that almost all of the adsorbed TNT was desorbed after three desorption cycles. Therefore, soil sorption of TNT will not effectively prevent mobility of TNT in the environment unless more strongly adsorbed degradation products are formed.