Microbial conversion of selected azo dyes and their breakdown products

2006 ◽  
Vol 53 (11) ◽  
pp. 163-171 ◽  
Author(s):  
N. Yemashova ◽  
S. Kalyuzhnyi
Keyword(s):  
Methyl Orange ◽  
Activated Sludge ◽  
Azo Dyes ◽  
Anthranilic Acid ◽  
Methyl Red ◽  
Acid Orange 7 ◽  
Microbial Conversion ◽  
Aerobic Conditions ◽  
Acid Orange ◽  
Sulphanilic Acid

Four selected azo dyes (acid orange 6, acid orange 7, methyl orange and methyl red) were completely decolourised in the presence of anaerobic granular sludge, while only methyl red was degraded in aerobic conditions using a conventional activated sludge. Additional experiments with culture broth devoid of cells showed that anaerobic decolourisation of azo dyes was performed by extracellular reducing agents produced by anaerobic bacteria. This was further confirmed by abiotic experiments with sulphide and NADH. The presence of redox mediators such as riboflavin led to dramatic acceleration of the anaerobic biodecolourisation process. The azo dye reduction products were found to be sulphanilic acid and 4-aminoresorcinol for acid orange 6; sulphanilic acid and 1-amino-2-naphthol for acid orange 7; N,N-dimethyl-1,4-phenylenediamine and sulphanilic acid for methyl orange; and N,N-dimethyl-1,4-phenylenediamine and anthranilic acid for methyl red. Anaerobic toxicity assays showed that the azo dyes were more toxic than their breakdown products (aromatic amines), except 1-amino-2-naphthol. In the presence of activated sludge, only anthranilic acid was completely mineralised while sulphanilic acid was persistent. 4-aminoresorcinol, 1-amino-2-naphthol and N,N-dimethyl-1,4-phenylenediamine underwent autooxidation in aerobic conditions yielding coloured polymeric products. On the contrary, in the presence of granular methanogenic sludge, 4-aminoresorcinol, 1-amino-2-naphthol and anthranilic acid were quantitatively methanised, sulphanilic acid was partially (70%) mineralised while N,N-dimethyl-1,4-phenylenediamine was only demethylated producing 1,4-phenylenediamine as an end product.

scholarly journals Synthesis of Gd2O3 Nanoparticles and Their Photocatalytic Activity for Degradation of Azo Dyes

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 742
Author(s):  
Sugyeong Jeon ◽  
Jeong-Won Ko ◽  
Weon-Bae Ko
Keyword(s):  
Methyl Orange ◽  
Photocatalytic Degradation ◽  
Azo Dyes ◽  
Uv Light ◽  
Nitrate Hexahydrate ◽  
Acid Orange 7 ◽  
Pseudo First Order Reaction ◽  
Acid Orange ◽  
Vis Spectroscopy ◽  
Gd2o3 Nanoparticles

Gadolinium oxide (Gd2O3) nanoparticles were prepared via the reaction of gadolinium nitrate hexahydrate (Gd (NO3)3·6H2O) and ethylamine (C2H5NH2), and their surface morphology, particle size, and properties were examined by using scanning electron microscopy, X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and ultraviolet visible (UV-vis) spectroscopy. The Gd2O3 nanoparticles were used as the photocatalyst for the degradation of various azo dyes, such as methyl orange (MO), acid orange 7 (AO7), and acid yellow 23 (AY23) under irradiation with UV light. The effect of the experimental parameters (initial concentration of azo dyes, dosage of catalyst, and wavelength of UV light) on the photocatalytic properties of the Gd2O3 nanoparticles were investigated. At a constant H2O2 concentration, the photocatalytic degradation efficiency of the Gd2O3 nanoparticles for various azo dyes was in the order: methyl orange > acid orange 7 > acid yellow 23. The kinetics study showed that the photocatalytic degradation of azo dyes was followed by a pseudo first-order reaction rate law.

scholarly journals Kinetics of anaerobic biodecolourisation of azo dyes

2006 ◽  
Vol 54 (2) ◽  
pp. 73-79 ◽  
Author(s):  
S. Kalyuzhnyi ◽  
N. Yemashova ◽  
V. Fedorovich
Keyword(s):  
Azo Dyes ◽  
Reaction Medium ◽  
Reduction Peak ◽  
Methyl Red ◽  
Acid Orange 7 ◽  
Acid Orange ◽  
First Order ◽  
Irreversible Reduction ◽  
Reducing Environment ◽  
Kinetics Of

Kinetics of anaerobic biodecolourisation (methanogenic environment) of four azo dyes (Acid Orange 6, Acid Orange 7, Methyl Orange and Methyl Red) was investigated with regard to their electrochemical properties as well as under variation of dye and sludge concentrations, pH and temperature. Cyclic voltammetry revealed a correlation between the potential of irreversible reduction peak of the dye and its first-order decolorisation constant. For each dye tested, this decolourisation constant was adversely proportional to dye concentration (0.086–1.7 mM) and had a saturation (hyperbolic) dependency on sludge concentration (0.04–1.1 g VSS/l), a bell-shape dependency on pH (4.0–9.0) and Arrhenius dependency on temperature (24–40 °C). Transfer from methanogenic to sulphate reducing environment led to an increase of decolorisation constant for all the dyes investigated due to the abundant presence of sulphide as a reducing agent in the reaction medium. Similar transfer to a denitrifying environment resulted in an almost complete decease of decolourisation because nitrate easily outcompetes azo dyes as an electron acceptor.

Phase-controlled synthesis of bismuth oxide polymorphs for photocatalytic applications

2018 ◽  
Vol 2 (9) ◽  
pp. 1664-1673 ◽  
Author(s):  
Thangavel Selvamani ◽  
Sambandam Anandan ◽  
Luis Granone ◽  
Detlef W. Bahnemann ◽  
Muthupandian Ashokkumar
Keyword(s):  
Methylene Blue ◽  
Methyl Orange ◽  
Bismuth Oxide ◽  
Rhodamine B ◽  
Controlled Synthesis ◽  
Acid Orange 7 ◽  
Acid Orange ◽  
Photocatalytic Applications

Bismuth oxide polymorphs (β-Bi2O3 nanoparticles and α-Bi2O3 coral-like morphology) were synthesized and they show an enhanced efficacy for the degradation of rhodamine B and acid orange 7 as compared to that of methylene blue and methyl orange under simulated solar illumination.

Two-fold 2D + 2D → 2D interweaved rhombus (4,4) grid: synthesis, structure, and dye removal properties in darkness and in daylight

2019 ◽  
Vol 48 (3) ◽  
pp. 1095-1107 ◽  
Author(s):  
Meng-Jung Tsai ◽  
Jheng-Hua Luo ◽  
Jing-Yun Wu
Keyword(s):  
Methylene Blue ◽  
Methyl Orange ◽  
Malachite Green ◽  
Dye Removal ◽  
Acid Orange 7 ◽  
High Adsorption ◽  
Acid Orange ◽  
Adsorption Capacities

A rhombus (4,4) grid showing two-fold 2D + 2D → 2D interweaved nets appeared to be a good adsorbent to selectively adsorb and separate anionic methyl orange (MO) and acid orange 7 (AO7) dyes over cationic methylene blue (MB) and malachite green (MG) from water with high adsorption capacities in both darkness and daylight.

scholarly journals Role of pH in the Aqueous Phase Reactivity of Zerovalent Iron Nanoparticles with Acid Orange 7, a Model Molecule of Azo Dyes

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
F. S. Freyria ◽  
S. Esposito ◽  
M. Armandi ◽  
F. Deorsola ◽  
E. Garrone ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Azo Dyes ◽  
Physicochemical Characterization ◽  
Surface Oxidation ◽  
Zerovalent Iron ◽  
Acid Orange 7 ◽  
Shell Nanoparticles ◽  
Acid Orange ◽  
Nanoscale Zerovalent Iron ◽  
Starting Solution

The effect of both pH and surface oxidation of nanoparticles is studied on the interaction between a commercial slurry of Nanoscale Zerovalent Iron (NZVI) and the azo dye Acid Orange 7 (AO7). NZVI is a reducing agent used for the degradation of several pollutants, including azo dyes: during pollutant degradation, it undergoes progressive oxidation and dissolution. Though it is generally acknowledged that NZVI consists of core-shell nanoparticles, where the core of metallic iron is covered by FexOy shell, it still remains a poorly defined system. In this work, the solid fraction recovered by filtration and drying was characterized by means of XRD diffraction with Rietveld refinement, N2 isotherms at 77 K, FE-SEM and TEM observation, EDX analysis, and IR spectroscopy. Powders were obtained from both the parent slurry and the same slurry pretreated with HCl in order to remove FexOy shell, finally reactivating the nanoparticles. The aforementioned physicochemical characterization allowed figuring out some correlations between the properties of the studied nanomaterial and the processes occurring when it is in contact with AO7 in aqueous phase. The type of interaction occurring within the NZVI/AO7 system (adsorption and type of redox reactions) strongly depends not only on the pH of the starting solution, but also on the surface oxidation of the nanoparticles.

scholarly journals Photocatalytic Degradation of Azo Dyes Using Microreactors: Mechanistic Study of its Effects on H2O2 Addition

2021 ◽  
Vol 01 (03) ◽  
pp. 1-1
Author(s):  
Minato Nakamura ◽  
◽  
Yoshinori Murakami ◽  
Keyword(s):  
Photocatalytic Degradation ◽  
Azo Dyes ◽  
Azo Dye ◽  
Glass Plate ◽  
Degradation Efficiency ◽  
Mechanistic Study ◽  
Photocatalytic Reaction ◽  
Acid Orange 7 ◽  
Acid Orange ◽  
H2o2 Addition

The photocatalytic reaction involved in TiO<sub>2</sub> photocatalysis was investigated using a microreactor coated with TiO<sub>2</sub> film on the glass plate attached on one side of the microreactor. It was confirmed that the effect of H<sub>2</sub>O<sub>2</sub> on the photocatalytic degradation efficiency of azo dyes (acid orange 7, acid red 151, and acid yellow 23) was dependent on the polymorphs (anatase and rutile) of TiO<sub>2</sub> coated on the glass plate of the UV-irradiated microreactor. Scavengers of holes (KI) and electrons (p-benzoquinone) were added to the solution of azo dyes, and their effects on the degradation efficiencies of the azo dye (acid orange 7) in the microreactor system were investigated. It was found that the electron scavengers of p-benzoquinone showed much larger effects on the photocatalytic degradation efficiency than the hole scavengers of KI. Based on these results, the mechanism of the photocatalytic degradation of the azo dyes in the presence of H<sub>2</sub>O<sub>2</sub> was proposed.

A novel Fe-containing clinoptilolite for wastewater remediation: degradation of azo-dyes acid orange 7 by H2O2 and ascorbic acid

2019 ◽  
Vol 159 ◽  
pp. 121-129
Author(s):  
M. Dosa ◽  
M. Piumetti ◽  
C. Galletti ◽  
N. Russo ◽  
D. Fino ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Azo Dyes ◽  
Wastewater Remediation ◽  
Acid Orange 7 ◽  
Acid Orange

Wet air and catalytic wet air oxidation of several azodyes from wastewaters: the beneficial role of catalysis

2009 ◽  
Vol 60 (8) ◽  
pp. 1989-1999 ◽  
Author(s):  
A. Rodríguez ◽  
J. García ◽  
G. Ovejero ◽  
M. Mestanza
Keyword(s):  
Azo Dyes ◽  
Oxygen Demand ◽  
Organic Carbon Content ◽  
Reactive Black 5 ◽  
Catalytic Wet Air Oxidation ◽  
Acid Orange 7 ◽  
Air Oxidation ◽  
Wet Air Oxidation ◽  
Acid Orange ◽  
Direct Blue

Degradation of several azo dyes, Acid Orange 7 (AO7), Acid Orange 74 (AO74), Direct Blue 71 (DB71), Reactive Black 5 (RB5) and Eriochrome Blue Black B (EBBB), well-known non-biodegradable mono, di and tri azo dyes has been studied using, wet-air oxidation (WAO) and catalytic wet air oxidation (CWAO). The efficiency of substrate decolorization and mineralization in each process has been comparatively discussed by evolution concentration, chemical oxygen demand, total organic carbon content and toxicity of dyes solutions. The most efficient method on decolorization and mineralization (TOC) was observed to be CWAO process. Mineralization efficiency with wet air and catalytic wet air oxidation essays was observed in the order of mono-azo &gt; di-azo &gt; tri-azo dye. Final solutions of CWAO applications after 180 min treatment can be disposed safely to environment.

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