Photolysis of 2,4-Dinitrotoluene and 2,6-Dinitrotoluene in Seawater

Abstract

The purpose of this experiment was to determine the rate of photolysis for 2,4-dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT) in salt water and pure water, examine the influence of salt concentration on the photolysis rate, and to identify the products of the photolysis of 2,4-DNT and 2,6-DNT in seawater. For the photolysis of 2,4-DNT in pure water, the half-life was longer than 100 h, whereas the photolysis half-life in salt water was ~15 h. For 2,6-DNT, the pure water photolysis half-life was close to 20 h, but the salt water photolysis half-life was only 5 h. The photolysis rate for 2,6-DNT in seawater was affected by the ionic strength of the parent solution and was independent of the identity of the salt. The photolysis of both DNTs in seawater resulted in a complex mixture of products that exhibit a distinct yellow color. Analysis by gas and liquid chromatography mass spectroscopy (GCMS, LCMS) following liquid–liquid extraction or solid phase extractions resulted in the confirmation of the corresponding dinitrobenzaldhydes and dinitrobenzoic acids as photolysis products and a probable azoxy compound among the photolysis products in seawater.