Chloramide

Additional information on environmental fate and behaviour

Administrative data

Endpoint:

additional information on environmental fate and behaviour

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Data source

Reference

Reference Type:

other: Thesis

Title:

Etude de la décomposition de la monochloramine en milieu aqueux et réactivité avec des composés phénoliques

Author:

Cimetière. N.

Year:

2009

Bibliographic source:

thesis of poier university

Materials and methods

Test guideline

Qualifier:

no guideline followed

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Chloramide

EC Number:

234-217-9

EC Name:

Chloramide

Cas Number:

10599-90-3

Molecular formula:

ClH2N

IUPAC Name:

chloranamine

Results and discussion

Any other information on results incl. tables

The results showed that the rates of decomposition of NH2Cl at a given pH can be described by a kinetic law of order 2 with respect to the concentration of NH2Cl and decomposition reactions are catalyzed by H + ions (kH+ =1,60.107M-².h-¹),by ion H2PO4 -(KH2PO4= 581M-².h-¹) and to a lesser extent by the ions HPO4 ^{2 -}.This work showed that the degradation pathway of monochloramine at basic pH, rarely mentioned in the literature is described by a kinetic law of order1 with respect to each component (M= 0.22,kOH-¹.h-¹).

NH2Cl decomposition is accompanied by the formation of nitrate ion (0.007 to0.033 mole of NO3 -/mole NH2Cl decomposed). The formation yield of the nitrate ion increases with pH and does not appear modified by the presence of phosphate ions.Degradation at alkaline pH of monochloramine led to the formation of hydroxylamine in the presence of oxygen ion can form peroxynitrite (ONOO-)and lead to a significant increase in the rate of degradation of monochloramine.For near neutral pH, the formation of a stable compound with a UV absorption spectrum quite similar to that of NH2Cl was observed.

Experimental speeds decomposition of monochloramine obtained in a wide pH range(5-14) could be properly described using the model of Valentine. This model has, however, been amended to include a new set of constants reflecting disproportionation reactions as well as reactions leading to the degradation of monochloramine in basic medium.The model also allowed to model the speciation chloramines and pH variation during the decomposition in solutions.

The study of the reactivity of monochloramine six simple phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol) showed that monochloramine demands may be higher than those observed during chlorination.. For molar ratioN / Cl equal to 2.0 mol /mol and a reaction time of 48 h, the monochloramine demand (expressed in moles of monochloramine consumed per mole of compound phenolic initial) range between 2.7 mol / mol for phenol to 10.9 mol / mol for phloroglucinol.

The high consumption of monochloramine observed with some phenolic compounds suggest that the chloramination by-products could catalyze the autodecomposition of monochloramine. This degradation pathway, similar to that observed in the absence of compound organic, would also explain the low rate of incorporation of chlorine in AOX observed (0.05 -0.15 mmoleqCl-/mol) ..

Applicant's summary and conclusion

Conclusions:

The study of the autodecomposition of monochloramine in organic-free solutions showed that the rate of decomposition of monochloramine in non-buffered and in phosphate-buffered ultra-pure water could be accurately simulated by a kinetic model. This model could also simulate the concentration-time profiles of monochloramine, dichloramine and free chlorine under a wide range of pH values and N/Cl molar ratios.
The monochloramine demands of six phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol) and of Natural Organic Matter have been determined at neutral pH. The effects of N/Cl on the yields of formation of chloroform, chloroacetic acids and Total Organochlorinated byproducts and on the decay of Total Organic Carbon have been examined.

Executive summary:

The reactivity of monochloramine with model phenolic compounds in aqueous solution has been investigated. Experiments were carried out at ambient temperature, at pH within 5 to 14, and by using ammonia-to-chlorine ratios (N/Cl) ranging from 1.08 to 31.2 mol/mol for the preparation of monochloramine solutions. A preliminary study of the autodecomposition of monochloramine in organic-free solutions showed that the rate of decomposition of monochloramine in non-buffered and in phosphate-buffered ultra-pure water could be accurately simulated by a kinetic model. This model could also simulate the concentration-time profiles of monochloramine, dichloramine and free chlorine under a wide range of pH values and N/Cl molar ratios. The monochloramine demands of six phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol and phloroglucinol) and of Natural Organic Matter have been determined at neutral pH. The effects of N/Cl on the yields of formation of chloroform, chloroacetic acids and Total Organochlorinated byproducts and on the decay of Total Organic Carbon have been examined. The absolute second-order rate constants for the reaction of monochloramine with the three protonated forms of resorcinol and chlororesorcinols were determined. Kinetic modeling of the resorcinol/chlorine/chloramines system evolution underlined the key role played by free chlorine (liberated from monochloramine hydrolysis) in the mechanisms of resorcinol degradation at low N/Cl molar ratios.