Treatment of explosives wastewater by electro-fenton process

Abstract

Wastewater generated from munitions production facilities contains very concentrated explosive materials. Due to its very acidic and high organic content, this wastewater is not appropriate to be directly treated by a conventional biological process. This research investigated the treatability of explosives wastewater by the electro-Fenton process. Degradations of 2,4,6,-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in 10 mM Na₂SO₄ electrolytes have been studied in a bench-scale electro-Fenton reactor. The surface methodology was applied for the experimental design and optimization. Goodness of the model was examined by the analysis of variance and the coefficient of determination. Effects of hydrogen peroxide to ferrous ratio, ferrous concentration, current, and pH on the removal of TNT, RDX, and HMX by electro-Fenton method have been investigated by using Box-Behnken statistical experiment design. The pseudo 1st-order rate and hydrogen peroxide efficiency have also been investigated. The optimum current, pH, ferrous, and hydrogen peroxide to ferrous ratio for the removal of 78 mg/L TNT, were 0.66 A, 3.0, 0.05 mM, and 1.8, respectively. For 40 mg/L RDX or 2.2 mg/L HMX, the optimum conditions were 0.04 A, 2.6, 0.8 mM, and 3, respectively. The removal efficiency and oxidation rates were significantly correlated with pH while the H₂O₂ efficiency decreased as H₂O₂ increased.