Reduction of N-Nitrosodimethylamine with Granular Iron and Nickel-Enhanced Iron. 1. Pathways and Kinetics

Abstract

Laboratory batch and column tests were conducted to examine the reduction pathways and kinetics of Nnitrosodimethylamine (NDMA) by iron (Fe) and nickelenhanced iron (Ni/Fe). A decrease in NDMA concentration and increases in dimethylamine (DMA) and ammonium were observed in both Fe and Ni/Fe columns. In the Fe column, the transformation process of NDMA appeared to follow pseudo-first-order kinetics with respect to NDMA, with an average half-life of 13(2 h. A small amount of nickel (0.25%) plated onto the iron greatly enhanced NDMA transformation rates. At early time the NDMA half-life in the Ni/Fe column was 2 min but as time progressed the halflife increased to 4 min, and departures from first-order kinetics were observed. The mass balances of carbon in DMA and nitrogen in DMA and ammonium improved over time and reached 100% and 90%, respectively, after NDMA had passed through the column for more than 50 pore volumes (PV). No 1,1-dimethylhydrazine, nitrous oxide, or methane were detected. Based on the electrochemical properties of NDMA, the transformation mechanism of NDMA with Fe and Ni/Fe is postulated to be catalytic hydrogenation, resulting in N-N bond breakdown to form DMA and ammonium as final products. Nickel, being a much stronger catalyst than Fe for catalytic hydrogenation, resulted in a much faster reduction rate of NDMA. Of several methods tested, flushing the Ni/Fe column with 0.01 N sulfuric acid proved to be the most effective in restoring the Ni/Fe activity. The rapid transformation rate on Ni/Fe and the formation of nontoxic products indicate that this material may be applicable for treating NDMA contaminated water, both in-situ and above ground.

Biotransformation of N -Nitrosodimethylamine by Pseudomonas mendocina KR1

“…Analyses of nitrate (NO 3 Ϫ ), nitrite (NO 2 Ϫ ), formate (HCOO Ϫ ), formaldehyde (HCHO), and methanol (CH 3 OH) were performed as previously reported (2,11). Methylamine and dimethylamine were analyzed by the method detailed in the work of Gui et al (8). The capture and quantification of 14 CO 2 were performed as described previously (4).…”

Mechanism of enhanced nitrate reduction via micro-electrolysis at the powdered zero-valent iron/activated carbon interface

“…3b, clearly increased as nitrate reduction continued. Mainly resulting from ammonium adsorption by iron [26] and/or activated carbon [27], the NH 4 + -N generated was somewhat less than NO 3 --N reduced. More interestingly, however, the increase of NH 4 + -N concentration was approximately the same as the decrease of NO 3 --N concentration between two different Fe 0 to AC mass ratio, which suggests ammonium as the major reduction product.…”

“…The adsorbed H + ion or H 2 O molecule on the AC surface thus accepts the electron and is converted to adsorbed atomic hydrogen (denoted as H ad ) under acidic or near-neutral condition, respectively. H ad , a more powerful reducing species than direct electron transfer [26,30], then rapidly reduces neighboring adsorbed nitrate into ammonium.…”

Bioremediation Approaches for Treating Low Concentrations of N-Nitrosodimethylamine in Groundwater

“…Methylamine and dimethylamine were analyzed as described by Gui et al (2000). The capture and quantification of 14 CO 2 were performed as described previously (Fournier et al, 2002).…”

“…Current technologies for treating NDMA in water include ultraviolet irradiation (UV) and adsorption to granular activated carbon (GAC). However, these methods are very expensive and/or ineffective for removing NDMA to required levels (Fleming et al, 1996;Gui et al, 2000). The objective of this SERDP project was to evaluate in situ and ex situ biological remediation options for the treatment of NDMA.…”