Degradation of 2,4,6-trinitrotoluene in water and soil slurry utilizing a calcium peroxide compound

Abstract

The degradation of 2,4,6-trinitrotoluene was examined in pure water and contaminated soil slurry using calcium peroxide as a source of solid hydrogen peroxide and oxygen. The extent of TNT oxidation was compared with that obtained by using hydrated lime, which is normally generated by slurrying CaO 2 in water and contained in CaO 2 technical formulation (∼50%, w/w). Complete TNT degradation occurred between 280 min, 0.1% CaO 2/Ca(OH) 2 and 20 min, 1% CaO 2/Ca(OH) 2. A large part of the generated oxidation products, 80–90%, were adsorbed on the solid calcium hydroxide, whereas the remaining 10–20% was detected in solution until 48 h. Removal of nitro groups was extremely effective in CaO 2 slurry, where all the nitrogen (3 mol per mol of TNT) was removed from TNT within 240 min. Respect to calcium hydroxide, the peroxy compound liberated H 2O 2 in solution, 370 mg l −1 at 0.2% CaO 2, w/v, which then decomposed within 480 min. Most of the 14C-TNT was retained more strongly on the calcium hydroxide generated by slurrying CaO 2. This pool remained adsorbed on the solid until pH dropped below 5.8. The treatment of a contaminated soil slurry, 700 mg TNT kg −1, reduced CH 3CN extractable TNT below 20 mg kg −1 at very low concentration of CaO 2/Ca(OH) 2, ∼0.2%, w/w. Both oxidants do not lead to soil sterilization as the phosphorus added to neutralize the pH serves as a source of nutrient for the soil biomass.