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Title: Free Radical Chemistry of Disinfection Byproducts 2: Rate Constants and Degradation Mechanism of Trichloronitromethane (Chloropicrin)

Abstract

Absolute rate constants for the free-radical-induced degradation of trichloronitromethane (TCNM, chloropicrin) were determined using electron pulse radiolysis and transient absorption spectroscopy. Rate constants for hydroxyl radical, OH, and hydrated electron, eaq-, reactions were (4.97 ± 0.28) × 107 M-1 s-1 and (2.13 ± 0.03) × 1010 M-1 s-1, respectively. It appears that the OH adds to the nitro-group, while the eaq- reacts via dissociative electron attachment to give two carbon centered radicals. The mechanisms of these free radical reactions with TCNM were investigated, using 60Co gamma irradiation at various absorbed doses, measuring the disappearance of TCNM and the appearance of the product nitrate and chloride ions. The rate constants and mechanistic data were combined in a kinetic computer model that was used to describe the major free radical pathways for the destruction of TCNM in solution. These data are applicable to other advanced oxidation/reduction processes.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - NE
OSTI Identifier:
912432
Report Number(s):
INL/JOU-05-00866
Journal ID: ISSN 0013-936X; ESTHAG; TRN: US0800386
DOE Contract Number:
DE-AC07-99ID-13727
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 41; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION SPECTROSCOPY; CARBON; CHEMISTRY; CHLORIDES; COMPUTERS; ELECTRON ATTACHMENT; ELECTRONS; HYDRATION; HYDROXYL RADICALS; IRRADIATION; KINETICS; NITRATES; RADIATION DOSES; RADICALS; RADIOLYSIS; SOLVATED ELECTRONS; STERILIZATION; TRANSIENTS

Citation Formats

B. J. Mincher, S. K. Cole, W. J. Cooper, R. V. Fox, P. R. Gardinali, S. P. Mezyk, and K. E. O'Shea. Free Radical Chemistry of Disinfection Byproducts 2: Rate Constants and Degradation Mechanism of Trichloronitromethane (Chloropicrin). United States: N. p., 2007. Web.
B. J. Mincher, S. K. Cole, W. J. Cooper, R. V. Fox, P. R. Gardinali, S. P. Mezyk, & K. E. O'Shea. Free Radical Chemistry of Disinfection Byproducts 2: Rate Constants and Degradation Mechanism of Trichloronitromethane (Chloropicrin). United States.
B. J. Mincher, S. K. Cole, W. J. Cooper, R. V. Fox, P. R. Gardinali, S. P. Mezyk, and K. E. O'Shea. Thu . "Free Radical Chemistry of Disinfection Byproducts 2: Rate Constants and Degradation Mechanism of Trichloronitromethane (Chloropicrin)". United States. doi:.
@article{osti_912432,
title = {Free Radical Chemistry of Disinfection Byproducts 2: Rate Constants and Degradation Mechanism of Trichloronitromethane (Chloropicrin)},
author = {B. J. Mincher and S. K. Cole and W. J. Cooper and R. V. Fox and P. R. Gardinali and S. P. Mezyk and K. E. O'Shea},
abstractNote = {Absolute rate constants for the free-radical-induced degradation of trichloronitromethane (TCNM, chloropicrin) were determined using electron pulse radiolysis and transient absorption spectroscopy. Rate constants for hydroxyl radical, OH, and hydrated electron, eaq-, reactions were (4.97 ± 0.28) × 107 M-1 s-1 and (2.13 ± 0.03) × 1010 M-1 s-1, respectively. It appears that the OH adds to the nitro-group, while the eaq- reacts via dissociative electron attachment to give two carbon centered radicals. The mechanisms of these free radical reactions with TCNM were investigated, using 60Co gamma irradiation at various absorbed doses, measuring the disappearance of TCNM and the appearance of the product nitrate and chloride ions. The rate constants and mechanistic data were combined in a kinetic computer model that was used to describe the major free radical pathways for the destruction of TCNM in solution. These data are applicable to other advanced oxidation/reduction processes.},
doi = {},
journal = {Environmental Science and Technology},
number = 3,
volume = 41,
place = {United States},
year = {Thu Feb 01 00:00:00 EST 2007},
month = {Thu Feb 01 00:00:00 EST 2007}
}
  • Halonitromethanes (HNMs) are byproducts formed through ozonation and chlorine/ chloramine disinfection processes in drinking waters that contain dissolved organic matter and bromide ions. These species occur at low concentration, but have been determined to have high cytotoxicity and mutagenicity and therefore may represent a human health hazard. In this study, we have investigated the chemistry involved in the mineralization of HNMs to non-hazardous inorganic products through the application of advanced oxidation and reduction processes. We have combined measured absolute reaction rate constants for the reactions of chloronitromethane, bromonitromethane and dichloronitromethane with the hydroxyl radical and the hydrated electron with amore » kinetic computer model in an attempt to elucidate the reaction pathways of these HNMs. The results are compared to measurements of stable products resulting from steady-state 60Co y-irradiations of the same compounds. The model predicted the decomposition of the parent compounds and ingrowth of chloride and bromide ions with excellent accuracy, but the prediction of the total nitrate ion concentration was slightly in error, reflecting the complexity of nitrogen oxide species reactions in irradiated solution.« less
  • Halonitromethanes are disinfection-byproducts formed during ozonation and chlorine/chloramine treatment of waters that contain bromide ion and natural organic matter. In this study, the chemical kinetics of the free-radical-induced degradations of a series of halonitromethanes were determined. Absolute rate constants for hydroxyl radical, OH, and hydrated electron, eaq-, reaction with both chlorinated and brominated halonitromethanes were measured using the techniques of electron pulse radiolysis and transient absorption spectroscopy. The bimolecular rate constants obtained, k (M-1 s-1), for eaq-/OH, respectively, were the following: chloronitromethane (3.01 ± 0.40) × 1010/(1.94 ± 0.32) × 108; dichloronitromethane (3.21 ± 0.17) × 1010/(5.12 ± 0.77) ×more » 108; bromonitromethane (3.13 ± 0.06) × 1010/(8.36 ± 0.57) × 107; dibromonitromethane (3.07 ± 0.40) × 1010/(4.75 ± 0.98) × 108; tribromonitromethane (2.29 ± 0.39) × 1010/(3.25 ± 0.67) × 108; bromochloronitromethane (2.93 ± 0.47) × 1010/(4.2 ± 1.1) × 108; bromodichloronitromethane (2.68 ± 0.13) × 1010/(1.02 ± 0.15) × 108; and dibromochloronitromethane (2.95 ± 0.43) × 1010 / (1.80 ± 0.31) × 108 at room temperature and pH ~7. Comparison data were also obtained for hydroxyl radical reaction with bromoform (1.50 ± 0.05) × 108, bromodichloromethane (7.11 ± 0.26) × 107, and chlorodibromomethane (8.31 ± 0.25) × 107 M-1 s-1, respectively. These rate constants are compared to recently obtained data for trichloronitromethane and bromonitromethane, as well as to other established literature data for analogous compounds.« less
  • The halonitromethanes (HNMs) are byproducts of the ozonation and chlorine/chloramine treatment of drinking waters. Although typically occurring at low concentrations HNMs have high cytotoxicity and mutagenicity, and may therefore represent a significant human health hazard. In this study, we have investigated the radical based mineralization of fully-halogenated HNMs in water using the congeners bromodichloronitromethane and chlorodibromonitromethane. We have combined absolute reaction rate constants for their reactions with the hydroxyl radical and the hydrated electron as measured by electron pulse radiolysis and analytical measurements of stable product concentrations obtained by 60Co steady-state radiolysis with a kinetic computer model that includes watermore » radiolysis reactions and halide/nitrogen oxide radical chemistry to fully elucidate the reaction pathways of these HNMs. These results are compared to our previous similar study of the fully chlorinated HNM chloropicrin. The full optimized computer model, suitable for predicting the behavior of this class of compounds in irradiated drinking water is provided.« less
  • Two chlorinated hydroxylated furanones, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) and 3,4-(dichloro)-5-hydroxy-2(5H)-furanone (MA), are bacterial mutagens and they are also byproducts of chlorine disinfection, and frequent contaminants of drinking water. In this work MX is shown to induce nuclear anomalies in the gastrointestinal tract of the B6C3F1 mouse. The other chlorohydroxyfuranone, MA, gives suggestive evidence of activity. In this bioassay MX was approximately equivalent in potency to epichlorohydrin (ECH) but was much less potent than methylnitrosourea (MNU). The latter two chemicals are confirmed rodent gastrointestinal tract carcinogens. The duodenum was the most sensitive tissue responding with both increased numbers of nuclear anomalies per mousemore » and increased incidence of animals presenting the nuclear aberrations 24 h after a single oral dose of 0.37 mmol/kg{sup {minus}1} of MX. MA also induced a significant increase in duodenal nuclear anomalies. The proximal colon and forestomach responded to MX but not MA. This is the first study demonstrating that chlorohydroxyfuranones are capable of inducing nuclear toxicity in vivo. However, it is clear, for MX at least, that its potency in the gastrointestinal tract nuclear anomalies assay is not commensurate with its extreme bacterial mutagenicity.« less
  • The rate constant for the reactions NH{sub 2}({sub x}{sup 2}B{sub 1}) + NH(X{sup 3}{Sigma}{sup -}) and NH{sub 2}({sub x}{sup 2}B{sub 1}) + H({sup 2}S) were measured over a pressure range from 2 to 10 Torr in CF{sub 4}, or Ar gases at 293 {+-} 2 K. The radicals were produced by the 193 nm photolysis of NH{sub 3} dilute in the carrier gas. Both radicals were monitored simultaneously following the photolysis laser pulse using high-resolution time-resolved absorption spectroscopy. The NH{sub 2} radical was monitored using the {sup 1}2{sub 21} {l_arrow} {sup 1}3{sub 31} rotational transition of the (0,7,0){sub A}{sup 2}A{submore » 1} {l_arrow} (0,0,0) {sub x}{sup 2}B{sub 1} vibronic band near 675 nm, and the NH radical was monitored using the {sup 1}R{sub 3}(4) rotational transition on the 1?0 vibrational transition near 3084 nm. The data was analyzed using model simulations of the NH{sub 2} and NH temporal concentration profiles. The rate constants for the NH{sub 2} + NH and NH{sub 2} + H reactions were found to be (9.6 {+-} 3.2) x 10{sup -11} and (7.7 {+-} 14) x 10{sup -15} cm{sup 3} molecule{sup -1} s{sup -1}, respectively, where the uncertainty includes an estimate of both systematic and random errors. The measurements were independent of the nature of the diluents, CF{sub 4} or Ar, and total pressure.« less