Degradation of amine-based water treatment polymers during chloramination as N-nitrosodimethylamine (NDMA) precursors.
Recent studies indicated that water treatment polymers such as poly(epichlorohydrin dimethylamine) (polyamine) and poly(diallyldimethylammonium chloride) (polyDADMAC) may form N-nitrosodimethylamine (NDMA) when in contact with chloramine water disinfectants. To minimize such potential risk and improve the polymer products, the mechanisms of how the polymers behave as NDMA precursors need to be elucidated. Direct chloramination of polymers and intermediate monomers in reagent water was conducted to probe the predominant mechanisms. The impact of polymer properties including polymer purity, polymer molecular weight and structure, residual dimethylamine (DMA), and other intermediate compounds involved in polymer synthesis, and reaction conditions such as pH, oxidant dose, and contact time on the NDMA formation potential (NDMA-FP) was investigated. Polymer degradation after reaction with chloramines was monitored at the molecular level using FT-IR and Raman spectroscopy. Overall, polyamines have greater NDMA-FP than polyDADMAC, and the NDMA formation from both polymers is strongly related to polymer degradation and DMA release during chloramination. Polyamines' tertiary amine chain ends play a major role in their NDMA-FP, while polyDADMACs' NDMA-FP is related to degradation of the quaternary ammonium ring group.
Park
Sang-Hyuck
SH
School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Wei
Shuting
S
Mizaikoff
Boris
B
Taylor
Amelia E
AE
Favero
Cedrick
C
Huang
Ching-Hua
CH
D000498:Allyl Compounds / Q000737:chemistry; D000586:Amination; D000588:Amines / Q000737:chemistry*; D003956:Dialysis; D004123:Dimethylamines / Q000737:chemistry; D004128:Dimethylnitrosamine / Q000737:chemistry*; D054879:Halogenation; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D018508:Water Purification
D000498:Allyl Compounds; D000588:Amines; D004123:Dimethylamines; D011108:Polymers; D000644:Quaternary Ammonium Compounds; C508190:diallyldimethylammonium chloride; C034516:dimethylamine; D004128:Dimethylnitrosamine