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Diss Factsheets

Environmental fate & pathways

Additional information on environmental fate and behaviour

Currently viewing:

Administrative data

Endpoint:
additional information on environmental fate and behaviour
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
June 25,2004
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No GLP compliant but well described and well conducted

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2004
Report date:
1994

Materials and methods

Test guideline
Qualifier:
no guideline available
Deviations:
not applicable
Principles of method if other than guideline:
The photodegradation of aqueous solutions of C.I. Reactive Orange 16 was investigated under UV irradiation. The degradation was studied by monitoring the change in absorption and relative intensity employing UV-spectroscopic and GC/MS analysis as functions of irradiation time. The rate of degradation of the dye was evaluated. The solution was completely decolorized after 100 min of photooxidation. The generated degradation products were detected by GC/MS. 6-Acetylamino-3-amino-naphthalene-2-sulfonic acid, N-(3,4-bis-hydroxymethyl-phenyl)-acetamide and phthalic acid were found during the degradation of C.I. Reactive Orange 16. The probable pathways for the formation of the degradation products were proposed. GC/MS analysis and degradation
pathways demonstrated that naphthalene and benzene rings were observed during photooxidation.
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
Reactive Orange 16
IUPAC Name:
Reactive Orange 16
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
- Name of test material: Reactive orange 16

Results and discussion

Any other information on results incl. tables

The absorption spectral changes during photooxidation

is observed that the absorption spectrum of C.I. Reactive Orange 16 at pH=10 is characterised by two bands in the UV region, with their maxima located at 235 and 315 nm, and by a band in the visible region located at 480 nm. The absorbance peaks at 235 and 315 nm are due to the benzene and naphthalene rings, and the absorbance peak at 480 nm is due to the azo linkage.It is observed that the absorption of the bands decreases exponentially with time and almost disappears after about 100 min, resulting in complete decolorization of the solution.

The photooxidation reaction is pseudo-first-order with respect to azo dye concentration.

Identification of degradation products

Degradation products were analyzed by GC/MS and identified by interpretation of their fragment ions in the mass spectra. Three main compounds detected in the solution:

6-Acetylamino-3 -aminonaphthalene-2 -sulfonic acid

N-(3,4-Bishydroxymethylphenyl)-acetamide

Phthalic acid

We may find from these results that the photooxidation rate of azo bond is about four times faster than benzene and naphthalene rings.

The primary degradation products undergo successive oxidation steps which lead to formation of aromatic and aliphatic acids. This results in decrease of pH of the solution. GC/MS analysis showed that three degradation products were detected during photooxidation process. The results are comparable with kinetic studies. Although the degradation rate and formation of degradation products depend on the type of the dye, the UV photooxidation technique seems to be applicable to any industrial wastewater containing azo dyes. The results can be taken as a starting step for the next application of the wastewater.

Applicant's summary and conclusion

Conclusions:
It was found that the sulfonated azo dyes can be destroyed by UV photooxidation process. The kinetics of the degradation depends on the azo,benzene and naphthalene groups of the dyes. We found that the first step of the degradation is related to cleavage of azo bond of the molecule and naphthalene ring which leads to further degradation until complete mineralization. Kinetic considerations may allow us to understand the mechanism of the degradation.
Executive summary:

The photodegradation of aqueous solutions of C.I. Reactive Orange 16 was investigated under UV irradiation. The degradation was studied by monitoring the change in absorption and relative intensity employing UV-spectroscopic and GC/MS analysis as functions of irradiation time. The rate of degradation of the dye was evaluated. The solution was completely decolorized after 100 min of photooxidation. The generated degradation products were detected by GC/MS. 6-Acetylamino-3-amino-naphthalene-2-sulfonic acid, N-(3,4-bis-hydroxymethyl-phenyl)-acetamide and phthalic acid were found during the degradation of C.I. Reactive Orange 16. The probable pathways for the formation of the degradation products were proposed. GC/MS analysis and degradation pathways demonstrated that naphthalene and benzene rings were observed during photooxidation.