Recent investigations have shown that engineered nanomaterials such as carbon nanotubes (CNTs) are a source and precursor for disinfection byproduct (DBP) formation. The aim of this study was to extend previous research of CNTs by investigating the potential for other classes of CNTs to generate disinfection byproducts (DBP) during chlorination. We examined particular types of CNTs with surface groups analogous to suspected model precursors for DBP formation.Specifically, we conducted experiments to determine the formation of haloacetic acids (HAAs) and N-nitrosodimethylamine (NDMA) via the chlorination of carbon nanotubes.
Polymer coated CNTs generated the greatest total HAA concentration of up to 170 μg-HAA/mg-CNT. Results showed that the presence of surface oxide groups (e.g. surface carboxylic acid groups) promotes HAA formation. We observed a reasonably strong correlation between the extent of HAA formation and the concentration of surface oxygen on the CNT surface. Results also showed that CNTs behave similar to model precursors for di- and trichloroacetic acid formation (DCAA and TCAA, respectively).
Nitrogen containing CNTs have been shown as source of N-nitrosodimethylamine (NDMA). Surprisingly, CS PEG, which does not contain N, produces NDMA when reacted with ethylenediamine (EDA). Ultimately, EDA is contributing N to CS PEG by sorbing to the CNT surface, which is the likely source of N for NDMA formation. At lower EDA concentrations, NDMA production is limited by available EDA. Conversely, at higher EDA concentrations, NDMA production is limited by available chlorine that is in competition with EDA and the CNT surface.