Role of strong ion exchange resins in nitrosamine formation in water

Abstract

N-Nitrosodimethylamine (NDMA) was formed when tap water was passed through a column containing only the anion exchange resin, thereby indicating that nitrosamine (NA) formation by the conventional acid catalyzed nitrosation reaction, as would be expected in the case of a mixed strong anion and cation resin system, was not the primary mechanism. The quaternary ammonium ion of the strong anion resin may be the amine precursor for NA formation. Strong anion and strong cation resins (Amberlite and Dowex brands ‡ ) were ineffective in concentrationg low levels of NDMA that were added to the influent. Accumulation of extremely low levels of NA already present in the water, therefore, also did not contribute importantly to the concentration of NA found in deionized water. In addition, the normal levels of cations and anions in water, and heavy metal ions were also not primarily responsible for this occurrence. There was, however, an unknown substance(s) in tap water that promoted NA formation. This unknown soluble substance(s) can be removed by activated carbon treatment or degassing techniques.