Chemical oxidation of unsymmetrical dimethylhydrazine transformation products in water

Abstract

Oxidation ofunsymmetrical dimethylhydrazine(UDMH) during a water treatment has several disadvantages including formation of stable toxic byproducts. Effectiveness of treatment methods in relation to UDMHtransformation products is currently poorly studied. This work considers the effectiveness of chemical oxidants in respect to main metabolites ofUDMH -1-formyl-2,2-dimethylhydrazine (FDMH), dimethylaminoacetontrile (DMAAN), N-nitrosodimethylamine (NDMA) and 1-methyl-1H-1,2,4triazole (MTA). Experiments on chemical oxidationby Fenton's reagent, potassium permanganate and sodium nitritewere conducted. Quantitative determination was performed by HPLC. Oxidation products were identified by gas chromatography-mass spectrometry in combination with solid-phase microextraction. FDMHwascompletely oxidized by Fenton's reagent with formation of formaldehyde N-formyl-N-methyl-hydrazone, 1,4-dihydro-1,4-dimethyl-5H-tetrazol-5-one by the action of potassium permanganate and N-methyl-N-nitro-methanamine in the presence of sodium nitrite. Oxidation of FDMHalso resulted in formation of NDMA. Oxidation of DMAANproceeded with formation ofhydroxyacetonitrile, dimethylformamide and 1,2,5-trimethylpyrrole. After 30 days,DMAAN was not detected in the presence of Fenton's reagent and potassium permanganate, but it's concentration in samples with sodium nitrite was 77.3 mg/L.