Kinetics of the alkaline hydrolysis of important nitroaromatic co-contaminants of 2,4,6-trinitrotoluene in highly contaminated soils.

Until this day, large amounts of TNT and related nitroaromatic compounds are found in soils. To obtain basic data for alkaline hydrolysis of these compounds as a novel remediation technology for contaminated soils, we investigated two soils (HTNT2, ELBP2) from two former ammunition plants in Germany. Hydrolysis was performed at pH 11 and pH 12 by addition of Ca(OH)2. During treatment at pH 12 the TNT content dropped to almost zero, and the content of the aminodinitrotoluenes (2A-4,6DNT, 4A-2,6DNT) and the 2,4-dinitrotoluene (2,4-DNT) decreased by about 75% (only HTNT2) and 63%, respectively. The experimental data were described using a pseudo-first-order kinetic. Furthermore, an increase of 2,6-DNT and trinitrobenzene (TNB) as well as in one case also of TNT was initially noted in addition to hydrolysis, leading temporarily to an increase of their total amounts of up to 147%, 986%, and 122%, respectively. The results demonstrate that alkaline hydrolysis is difficult when nitroaromatics except TNT represent the major contaminants. However, regarding 2,6-DNT and TNB higher reduction rates than calculated were actually achieved by alkaline hydrolysis. In the case that TNT is the only contaminant or if it is accompanied by certain lower concentrated nitroaromatics alkaline hydrolysis is a valuable remediation technology, especially for soils that are highly contaminated.