Reduction of N-Nitrosodimethylamine with Granular Iron and Nickel-Enhanced Iron. 2. Mechanistic Studies

Abstract

To elucidate the reduction mechanism of N-nitrosodimethylamine (NDMA) by granular iron, various electrochemical experiments using a mercury electrode were conducted. The studies included differential pulse voltammetry and exhaustive potentiostatic electrolysis. The results of the NDMA electroreduction experiments were compared with the results obtained in the column and batch experiments of Part 1 of this study. The results show that (1) electroreduction of NDMA occurs at potentials more negative than -1.3 V and this potential cannot be achieved under the conditions of the column and batch experiments and (2) different reduction products of NDMA were observed in the electrochemical tests relative to the column and batch tests. That is, dimethylamine (DMA) and nitrous oxide were formed in the electrochemical reduction experiments, whereas ammonia and DMA were produced in the column and batch experiments. The difference in product formation and more importantly the fact that the iron cannot reach the potentials required for electroreduction indicate that the reduction of NDMA on iron cannot take place by direct electron transfer. The process of catalytic hydrogenation was found to be consistent with all experimental observations and is proposed as the alternative mechanism.

N-Nitrosodimethylamine (NDMA) as a Drinking Water Contaminant: A Review

“…Zero-valent iron catalyzes NDMA transformation by hydrogenation Odziemkowski et al, 2000). This reduction reaction leads to the formation of dimethylamine and ammonia as final products.…”

Factors influencing the photodegradation of N-nitrosodimethylamine in drinking water

“…In consideration of a novel disinfection by-product, the formation mechanism [12][13][14], detection methods [15][16][17][18][19], and treatment methods for degradation of NDMA [20][21][22][23][24][25] were investigated widely. NDMA is a semivolatile organic chemical, soluble in water, and not likely to be biodegraded or adsorbed to particulate matter [26].…”

Kinetics of zero-valent iron reductive transformation of the anthraquinone dye Reactive Blue 4

“…The reduction mechanism involves several steps: diffusion to metal surface, adsorption to the metal surface, transfer of electrons from the metal surface to the adsorbed contaminant resulting in chemical reduction, desorption of product(s), and diffusion of product(s) to the bulk solution [11]. Recent studies have reported that contaminants are reduced by adsorbed atomic hydrogen (nascent hydrogen) and not by direct transfer of electrons from the ZVI surface [12,13].…”