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Designing Safer Chemicals
Published in Aidé Sáenz-Galindo, Adali Oliva Castañeda-Facio, Raúl Rodríguez-Herrera, Green Chemistry and Applications, 2020
Cesar Garcias Morales, Armando Ariza Castolo, Mario Alejandro Rodriguez
Sometimes a chemical compound may have low or no toxicity, however, the degradation products through metabolism in humans or bacteria in the environment, can lead to the formation of highly toxic compounds. For example, for a long time it was thought that azo compounds used as dyes or pigments were carcinogenic substances. However, after several studies, it was determined that toxicity is not directly due to the compound, but to the molecules formed during metabolic degradation. The azo bonds of pigments can easily be broken down by chemical compounds or by enzymatic action, via reduction to form free aromatic amines, the aromatic amines can be easily absorbed and are responsible for the toxicity of these compounds (see below). In the textile industry, these types of dyes are widely used, therefore in some cases close by water sources can be contaminated, representing a source of exposure to both humans and animals and the environment (DeVito and Garrett, 1996).
Recent Advancements and Perspectives on Biological Degradation of Azo Dye
Published in M. Jerold, V. Sivasubramanian, Biochemical and Environmental Bioprocessing, 2019
K.S. Rajmohan, C. Ramya, Murali Mohan Seepana
The biggest drawback of degradation of microbial dye is the failure to assess the ecotoxicity of degraded products while using color degrading microbes (Rawat Deepak et al., 2016). Azo compounds, after decolorization and inadequate toxicity assessment, are likely to form more dangerous products. A global priority to achieve cost-efficient techniques, energy needs, reduced environmental efficiency and toxic sludge production remains debatable in dye detoxification efficacy (Esther et al., 2004). Figure 2.6 shows the degradation pathway using microbial sources.
Reduction
Published in Richard A. Larson, Eric J. Weber, Reaction Mechanisms in Environmental Organic Chemistry, 2018
Richard A. Larson, Eric J. Weber
Concern over the environmental fate of aromatic azo compounds arises primarily from their importance in the textile dye industry. Of the dyes available on the market today, approximately 50% are azo compounds (Kulkarni et al., 1985). It is estimated that approximately 12% of the synthetic textile dyes used each year are lost to waste streams during manufacturing and processing operations, and 20% of these losses will enter the environment through effluents from wastewater treatment plants (Clarke and Anliker, 1980). The reductive cleavage of the azo linkage of the dyestuffs in aquatic ecosystems represents a possible pathway for the entry of aromatic amines into these systems. The aromatic amines are considered a hazardous class of compounds because of their mutagenic and carcinogenic properties.
Insight into the adsorptive mechanisms of methyl violet and reactive orange from water—a short review
Published in Particulate Science and Technology, 2023
Azrul Nurfaiz Mohd Faizal, Nicky Rahmana Putra, Muhammad Abbas Ahmad Zaini
Textile and leather sectors trigger environmental concern due to high release of improperly treated colored effluents into streams (Salomón et al. 2020). There are more than 0.1 million commercial dyes available worldwide with an annual production of 0.7 million tons, from which about 2% is eventually discharged into water bodies during the production (Sen, Afroze, and Ang 2011). Dyes are commercially applied in leather, fabric, textile, paper, food, and pharmaceutical products (Esvandi et al. 2020; Chaudhary et al. 2021). However, synthetic dyes are toxic, less biodegradable, and environmentally persistent (Yu et al. 2021). Methyl violet (MV) and reactive orange 16 (RO16) are among the commonly used dyes in industries. MV is a phenylmethane cationic dye that gives intensive violet color as it dissolves in water, while RO16 is an anionic sulfonated reactive azo dye (Foroutan et al. 2022). Azo compound is harmful not only because of the color it imparts that interrupts the esthetic nature of water but the products from its degradation are also toxic and mutagenic (Hasanzadeh, Simchi, and Shahriyari Far 2020).
Gelation-based visual detection of analytes
Published in Soft Materials, 2019
Wangkhem Paikhomba Singh, Rajkumar Sunil Singh
A gelation-based visual sensor for NO2− anion was recently reported by McNeil and co-workers (30). They cleverly modified a previously reported hydrogelating scaffold, azo-sulfonate, to design a new visual sensor for nitrite ion (31,32). Typically, azo-compounds are prepared by the Greiss reaction—the coupling reaction between diazonium ions (produced from aromatic amines in presence of nitrous acid) and aromatic compounds with electron donating substituents. The azo-sulfonate hydrogelator 3b was obtained from the two non-gelators, 3a (3,5-dichloro aniline) and 6-hydroxynapthalene-2-sulfonate through the Greiss reaction (Fig. 1). This was tested with water samples taken from different sources such as tap water, river, and pond water. Sodium nitrite spiked water samples produced gels whereas the non-spiked samples did not, a clear indication that this sensor can be applied to polluted aqueous environmental samples.