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.

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.

Effect of dye auxiliaries on the kinetics of advanced oxidation UV/H2O2of Acid Orange 7 (AO7)

2008 ◽  
Vol 83 (10) ◽  
pp. 1339-1346 ◽  
Author(s):  
Ángela Anglada ◽  
María J. Rivero ◽  
Inmaculada Ortíz ◽  
Ane Urtiaga
Keyword(s):  
Advanced Oxidation ◽  
Acid Orange 7 ◽  
Acid Orange ◽  
Kinetics Of

scholarly journals Study of C.I. Acid Orange 7 removal in contaminated water by photo oxidation processes

2013 ◽  
Vol 10 (1) ◽  
pp. 16-23 ◽  
Keyword(s):  
Removal Efficiency ◽  
Uv Irradiation ◽  
Rate Constant ◽  
Dye Removal ◽  
Irradiation Time ◽  
Inhibitory Effect ◽  
Textile Dye ◽  
Acid Orange 7 ◽  
Acid Orange ◽  
First Order

C.I. Acid Orange 7 (AO7) commonly used as a textile dye and could be degraded by UV/ZnO, UV/H2O2 and UV/H2O2/Fe (III) (photofenton) processes. In the photocatalytic degradation of dye by UV/ZnO process, effect of some parameters such as UV irradiation time, presence of ZnO and UV irradiation, pH, concentrations of ZnO, dye, H2O2 and ethanol was examined and first order reaction rate constant was calculated equal to 2.39×10-2 min-1 at experimental condition. The semi-log plot of dye concentration versus time was linear, suggesting first order reaction. Efficiency of photodegradation process in the absence of ZnO photocatalyst and UV light was small. Increasing the UV irradiation time increased AO7 removal. Ethanol had inhibitory effect on this process. Maximum AO7 removal was seen at neutral pH area. In the UV/H2O2 process, effect of some parameters such as presence of H2O2 and UV irradiation, amount of H2O2, effect of pH and addition of bicarbonate on the efficiency of dye removal were examined. Absence of each of UV irradiation or H2O2 decreased AO7 removal efficiency near to zero. Increasing H2O2 concentration increased dye removal to some extent but at higher H2O2 concentrations, dye removal efficiency did not increase. Increasing pH to value about 9 increased the AO7 removal efficiency and increasing bicarbonate anion concentration decreased it. Rate constant of AO7 removal by this process was calculated to be equal to 4.221×10-1 min-1 at experimental condition. Also, the order of UV/ H2O2/Fe (III) > UV/ H2O2 > UV/Fe (III) > H2O2/Fe (III), was seen for AO7 removal efficiency of these processes. Increasing Fe (III) and oxalate concentration increased dye removal efficiency.

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 Kinetics and Mechanism of the Oxidation of Naphthol Green B by Peroxydisulphate Ion in Aqueous Acidic Medium

2014 ◽  
Vol 2014 ◽  
pp. 1-4
Author(s):  
B. Myek ◽  
S. O. Idris ◽  
J. F. Iyun
Keyword(s):  
Acidic Medium ◽  
Reaction Medium ◽  
Intermediate Complex ◽  
Kinetic Investigation ◽  
Hydrogen Ions ◽  
First Order ◽  
Order Dependence ◽  
Naphthol Green B ◽  
Kinetics Of ◽  
Aqueous Acidic Medium

The kinetics of the oxidation of naphthol green B (NGB3−) by peroxydisulphate ion has been carried out in aqueous acidic medium at λmax of 700 nm, T=23±1°C, and I=0.50 mol dm−3 (NaCl). The reaction shows a first-order dependence on oxidant and reductant concentration, respectively. The stoichiometry of the NGB—S2O82- reaction is 1 : 2. Change in hydrogen ions concentration of the reaction medium has no effect on the rate of the reaction. Added cations and anions decreased the rate of the reaction. The results of spectroscopic and kinetic investigation indicate that no intermediate complex is probably formed in the course of this reaction.

Modeling of the Acid Orange 7 anaerobic biodegradation

2003 ◽  
Vol 48 (6) ◽  
pp. 133-139 ◽  
Author(s):  
D. Méndez-Paz ◽  
F. Omil ◽  
J.M. Lema
Keyword(s):  
Experimental Data ◽  
Redox Mediator ◽  
Order Kinetic ◽  
Acid Orange 7 ◽  
Fed Batch ◽  
Acid Orange ◽  
First Order ◽  
Autocatalytic Model ◽  
Whole Process ◽  
First Feeding

It was found that 1-amino-2-naphthol, an intermediate generated during the anaerobic degradation of Acid Orange 7, is a redox mediator which plays a significant role in the transport of electrons to the dye, thus giving to the whole process an autocatalytic nature. Evidences of the autocatalytic behaviour were observed in experimental data previously obtained under batch and fed-batch conditions. In this paper, a kinetic model considering all these factors is proposed and validated. In batch assays, this model agrees satisfactorily with the experimental data. In the case of fed-batch assays, the autocatalytic model only can be applied satisfactorily after the first feeding, since the degradation of Acid Orange 7 after the second and third feedings followed a first-order kinetic. This fact can be explained due to the presence of the redox mediator previously generated during the reactions that took place after the first feeding.

scholarly journals Kinetics and Mechanism of Oxidation of Glutamic Acid byN-Bromophthalimide in Aqueous Acidic Medium

2011 ◽  
Vol 8 (4) ◽  
pp. 1472-1477
Author(s):  
N. M. I. Alhaji ◽  
S. Sofiya Lawrence Mary
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Glutamic Acid ◽  
Acidic Medium ◽  
Reaction Medium ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Mechanism Of Oxidation ◽  
Kinetics Of ◽  
Aqueous Acidic Medium

The kinetics of oxidation of glutamic acid (Glu) withN-bromophthalimide (NBP) was studied in perchloric acid medium at 30°C by potentiometric method. The reaction is first order each in NBP and glutamic acid and is negative fractional order in [H+]. Addition of KBr or the reaction product, phthalimide had no effect on the rate. Similarly variation of ionic strength of the medium did not affect the rate of the reaction. Also the rate increased with decrease in dielectric constant of the reaction medium. The thermodynamic parameters were computed from Arrhenius and Eyring plots. A suitable mechanism consistent with the kinetic results has been proposed.

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
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