RDX degradation by chemical oxidation using calcium peroxide in bench scale sludge systems

Abstract

The ability of calcium peroxide (CaO2) to degrade hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in contaminated soil slurries using CaO2-based modified Fenton oxidation was investigated. Results showed that increasing the CaO2 dose increased degradation rates of RDX and pH. RDX concentrations decreased to below detection after 18 h with 2 M and 2.5 M CaO2, after 30 h with 1.5 M CaO2, after 54 h with 1 M CaO2, but 0.1 M CaO2 achieved no significant RDX removal. Increasing the soil organic matter content decreased the rate and extent of RDX degradation. RDX degradation products 4-nitro-2,4-diazabutanal (NDAB) and methylenedinitramine (MEDINA) were quantified, and the greater accumulation of NDAB than MEDINA suggests denitration of RDX was the most likely initial degradation step. Isotopic ratios for nitrogen and oxygen associated with RDX oxidation are also consistent with either nitrification of NH4+ from soil or precipitation. Existing technologies merely only extract energetics from soils for treatment ex situ, whereas the approach introduced herein destroys RDX in situ with a one-step application.