N-nitrosodimethylamine formation during treatment with strong oxidants of dimethylamine containing water

Abstract

The aim of the paper is the evaluation of the possibility of NDMA formation, as a result of strong oxidants reacting with DMA. Summarized results of investigations on N-nitrosodimethylamine formation as a result of dimethylamine reactions with chlorine dioxide, ozone and hydrogen peroxide are presented. Preliminary results of experiments on NDMA formation as a result of DMA reactions with permanganate are also shown. The experiments on dimethylamine reactions with chlorine dioxide, hydrogen peroxide and permanganate were carried out at room temperature under static conditions. Ozonation experiments were carried out at room temperature in a semi-continuous mode. Water samples from all experiments described above were collected during the experiment itself and subsequently analyzed with HPLC-IE with UV-Vis detector at 230 nm. NDMA formation was also confirmed by GC-LRMS. NDMA forms as a result of chlorine dioxide, ozone, hydrogen peroxide or permanganate reactions with dimethylamine. both in the presence as well as in the absence of ammonia ions. The presence of nitrites and nitrates in a post-reaction mixture suggests that NDMA are formed as the result of DMA reactions with nitrites. Thus the mechanism of NDMA formation with these oxidants is different than that described by Mitch et al. and Choi et al. The results also showed a conversion ratio of DMA to NDMA of even up to a single percent (with relation to amines), a simultaneous decrease of NDMA formation potential with a decrease of pH, however, in the case of chlorine dioxide application, a maximum conversion ratio was observed, as well the NDMA formation potential is strongly dependent on the oxidant/DMA ratio.