Removal of hydroxylamine by processes generating OH center dot radicals inaqueous solution

The oxidation of hydroxylamine in aqueous solution ([NH2OH](o) = 1 mM, pH = 7) by OH. radicals was studied using H2O2/UV and gamma-irradiation as radi cals generation processes. Nitrites and nitrates were identified as the maj or by-products in the aqueous phase. Their concentration depends on the exp erimental conditions, i.e. the presence or the absence of oxygen, and the c oncentration of hydrogen peroxide(H2O2). For the smallest initial concentra tions of H2O2 studied (below 10 mM), hydroxylamine was oxidized into gases of low solubility. It is assumed that these gases are mainly constituted of N-2 and N2O. Subsequently to the H-abstraction from the molecule of hydrox ylamine by OH. radicals, (NHOH)-N-. radical recombinations are favored in t he absence of oxygen and H2O2 and would lead to N-2. In the presence of oxy gen, NOH can be produced and can dimerise into N2O or react with NH2OH to f orm N-2. Reactions involving O-2 and H2O2, Or O-2(.-) can account for nitri tes then nitrates. (C) 1999 Published by Elsevier Science S.A. All rights r eserved.