Catalytic effects of different redox mediators on the reductive decolorization of azo dyes

2006 ◽  
Vol 54 (2) ◽  
pp. 165-170 ◽  
Author(s):  
A.A. Encinas-Yocupicio ◽  
E. Razo-Flores ◽  
F. Sánchez-Díaz ◽  
A.B. dos Santos ◽  
J.A. Field ◽  
...  
Keyword(s):  
Azo Dyes ◽  
Granular Sludge ◽  
Order Rate Constant ◽  
Anaerobic Treatment ◽  
Redox Mediator ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Direct Blue ◽  
Reactive Orange ◽  
Catalytic Effects

The catalytic effects of redox mediators, with distinct standard redox potentials (E′0), were evaluated on the first-order rate constant of decolorization (Kd) of recalcitrant azo dyes by an anaerobic granular sludge. The dyes studied included mono-azo (Reactive Orange 14, RO14), di-azo (Direct Blue 53, DB53), and tri-azo (Direct Blue 71, DB71) compounds. Toxicity and auto-catalytic aspects seemed to play a role in determining the rate of decolorization. Addition of riboflavin, anthraquinone-2,6-disulphonate (AQDS) or lawsone as a redox mediator, increased the Kd value for all dyes studied, although their impact varied in every case. Kd values were increased from 1.1-fold up to 3.8-fold depending on the redox mediator applied. Moreover, catalysts with moderately similar E′0 value caused distinct stimulation on the rate of decolorization. These results should be considered for selecting the proper redox mediator to be applied during the anaerobic treatment of textile wastewaters and effluents containing electron-withdrawing pollutants, such as nitro-aromatic and polychlorinated compounds.

Potentials of high-temperature anaerobic treatment and redox mediators for the reductive decolorization of azo dyes from textile wastewaters

2006 ◽  
Vol 54 (2) ◽  
pp. 151-156 ◽  
Author(s):  
A.B. Dos Santos ◽  
F.J. Cervantes ◽  
J.B. van Lier
Keyword(s):  
High Temperature ◽  
Azo Dyes ◽  
Environmental Problem ◽  
Granular Sludge ◽  
Anaerobic Treatment ◽  
Health Concern ◽  
Redox Mediators ◽  
Reductive Decolorization ◽  
Made In ◽  
Textile Wastewaters

The discharge of dye-colored wastewaters in surface water represents a serious environmental problem because it may decrease the water transparency, therefore having an effect on photosynthesis, and a public health concern because dyes and their reducing products are carcinogenic. In recent years, big achievements have been made in the use of anaerobic granular sludge not only on colored wastewaters but also on the detoxification of other xenobiotics compounds. This paper compiles some important findings related to the potentials of high-temperature anaerobic treatment and redox mediators on the reductive decolorization of azo dyes from textile wastewaters.

Riboflavin as a redox mediator accelerating the reduction of the azo dye Mordant Yellow 10 by anaerobic granular sludge

2003 ◽  
Vol 48 (6) ◽  
pp. 187-193 ◽  
Author(s):  
J.A. Field ◽  
J. Brady
Keyword(s):  
Textile Industry ◽  
Azo Dye ◽  
Granular Sludge ◽  
Anaerobic Treatment ◽  
Redox Mediator ◽  
Maximum Increase ◽  
Zero Order Kinetics ◽  
Redox Active ◽  
Dye Reduction ◽  
Enzyme Cofactors

Azo dyes are important persistent pollutants of textile industry effluents. Reduction of these dyes to their corresponding aromatic amines under anaerobic conditions can be used to initiate biodegradation. Since electron transfer is suggested to be rate limiting, redox mediators are being considered to improve dye reduction kinetics. This study evaluates the use of riboflavin, the redox active moiety of common occurring enzyme cofactors, as a redox mediator to accelerate the reduction of the azo dye, mordant yellow 10 (MY10). Dye reduction was found to follow zero order kinetics, the total rate constant (Vtotal) could be separated into two components: the rate of reduction due to direct contact between enzymes in the sludge with the dye (Vdirect); and the rate of reduction mediated by riboflavin (Vmediated). Riboflavin increased the Vtotal by 61% at extremely sub-stoichiometric concentrations of 9.1 μmol l-1, which corresponded to a molar riboflavin:dye ratio of 1:60. The accelerating effect of riboflavin displayed saturation kinetics at higher concentrations, with a maximum increase of Vtotal of approximately 2-fold. A model is presented which assumes that Vmediated depends on the activity of riboflavin reductase (RR) and thus follows Michaelis-Menton kinetics with respect to the riboflavin concentration. The half-velocity constant (Km) was very low (6.3 μmol l-1), indicating a high affinity of the sludge RR for riboflavin. Both Vdirect and Vmediated were found to be proportional to the assay sludge concentration. The results taken as a whole indicate that vitamin levels of riboflavin can be utilized to improve the kinetics of azo dye reduction during anaerobic treatment.

Decolorization and biogas production by an anaerobic consortium: effect of different azo dyes and quinoid redox mediators

2015 ◽  
Vol 72 (5) ◽  
pp. 794-801 ◽  
Author(s):  
L. H. Alvarez ◽  
R. Valdez-Espinoza ◽  
R. B. García-Reyes ◽  
D. Olivo-Alanis ◽  
M. T. Garza-González ◽  
...  
Keyword(s):  
Azo Dyes ◽  
Biogas Production ◽  
Inhibitory Effect ◽  
Redox Mediators ◽  
Direct Blue ◽  
Anaerobic Consortium ◽  
The Impact ◽  
Direct Blue 71

The inhibitory effect of azo dyes and quinoid compounds on an anaerobic consortium was evaluated during a decolorization process and biogas production. In addition, the impact of quinoid compounds such as lawsone (LAW) and anthraquinone-2,6-disulfonate (AQDS) on the rate of decolorization of Direct Blue 71 (DB71) was assessed. The anaerobic consortium was not completely inhibited under all tested dye concentrations (0.1–2 mmol l−1), evidenced by an active decolorization process and biogas production. The presence of quinoid compounds at different concentrations (4, 8, and 12 mmol l−1) also inhibited biogas production compared to the control incubated without the quinoid compounds. In summary, the anaerobic consortium was affected to a greater extent by increasing the quantity of azo dyes or quinoid compounds. Nevertheless, at a lower concentration (1 mmol l−1) of quinoid compounds, the anaerobic consortium effectively decolorized 2 mmol l−1 of DB71, increasing up to 5.2- and 20.4-fold the rate of decolorization with AQDS and LAW, respectively, compared to the control lacking quinoid compounds.

scholarly journals Laccases: Versatile Biocatalysts for the Synthesis of Heterocyclic Cores

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3719
Author(s):  
Ana Catarina Sousa ◽  
Lígia O. Martins ◽  
M. Paula Robalo
Keyword(s):  
Membered Ring ◽  
Low Molecular Weight ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Multicopper Oxidases ◽  
Phenothiazine Derivatives ◽  
Ph Values ◽  
Electron Shuttles ◽  
Specific Oxidation ◽  
Optimal Ph

Laccases are multicopper oxidases that have shown a great potential in various biotechnological and green chemistry processes mainly due to their high relative non-specific oxidation of phenols, arylamines and some inorganic metals, and their high redox potentials that can span from 500 to 800 mV vs. SHE. Other advantages of laccases include the use of readily available oxygen as a second substrate, the formation of water as a side-product and no requirement for cofactors. Importantly, addition of low-molecular-weight redox mediators that act as electron shuttles, promoting the oxidation of complex bulky substrates and/or of higher redox potential than the enzymes themselves, can further expand their substrate scope, in the so-called laccase-mediated systems (LMS). Laccase bioprocesses can be designed for efficiency at both acidic and basic conditions since it is known that fungal and bacterial laccases exhibit distinct optimal pH values for the similar phenolic and aromatic amines. This review covers studies on the synthesis of five- and six-membered ring heterocyclic cores, such as benzimidazoles, benzofurans, benzothiazoles, quinazoline and quinazolinone, phenazine, phenoxazine, phenoxazinone and phenothiazine derivatives. The enzymes used and the reaction protocols are briefly outlined, and the mechanistic pathways described.

Anaerobic treatment of thermal sludge conditioning liquor with granular sludge

1993 ◽  
Vol 65 (1) ◽  
pp. 6-14 ◽  
Author(s):  
Takashi Kimata ◽  
Takehiko Kawai ◽  
Minoru Tada ◽  
Kazuhiro Tanaka ◽  
Kazuhiro Shinabe ◽  
...  
Keyword(s):  
Granular Sludge ◽  
Anaerobic Treatment ◽  
Sludge Conditioning

scholarly journals Electrolyte Composition in Li/O2 Batteries with LiI Redox Mediators: Solvation Effects on Redox Potentials and Implications for Redox Shuttling

2018 ◽  
Vol 122 (3) ◽  
pp. 1522-1534 ◽  
Author(s):  
Azusa Nakanishi ◽  
Morgan L. Thomas ◽  
Hoi-Min Kwon ◽  
Yuki Kobayashi ◽  
Ryoichi Tatara ◽  
...  
Keyword(s):  
Electrolyte Composition ◽  
Redox Potentials ◽  
Redox Mediators ◽  
Solvation Effects

Fine-tuning the coordination atoms of copper redox mediators: an effective strategy for boosting the photovoltage of dye-sensitized solar cells

2019 ◽  
Vol 7 (20) ◽  
pp. 12808-12814 ◽  
Author(s):  
Yawei Zhao ◽  
Junyu Shen ◽  
Ze Yu ◽  
Maowei Hu ◽  
Chong Liu ◽  
...  
Keyword(s):  
Solar Cells ◽  
Copper Complexes ◽  
Dye Sensitized Solar Cells ◽  
Redox Mediator ◽  
Fine Tuning ◽  
Effective Strategy ◽  
Redox Mediators ◽  
New Class ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

Herein, we report a new class of copper complexes bearing a tetradentate polythioether ligand, [(S4)Cu]2+/+ (12+/+, S4 = 1,4,8,11-tetrathiocyclotetradecane), as a redox mediator in dye-sensitized solar cells (DSCs).

Granular sludge bed anaerobic treatment systems for resource recovery

2020 ◽  
pp. 107-124
Author(s):  
Hamidreza Mojab ◽  
Eldon Raj ◽  
Santiago Pacheco-Ruiz
Keyword(s):  
Granular Sludge ◽  
Resource Recovery ◽  
Anaerobic Treatment

scholarly journals Identification of Quinoide Redox Mediators That Are Formed during the Degradation of Naphthalene-2-Sulfonate by Sphingomonas xenophaga BN6

2002 ◽  
Vol 68 (9) ◽  
pp. 4341-4349 ◽  
Author(s):  
Andreas Keck ◽  
Jörg Rau ◽  
Thorsten Reemtsma ◽  
Ralf Mattes ◽  
Andreas Stolz ◽  
...  
Keyword(s):  
Azo Dyes ◽  
High Performance ◽  
Wild Type Strain ◽  
Gene Replacement ◽  
Redox Mediators ◽  
Liquid Chromatography Mass Spectrometry ◽  
Anaerobic Conditions ◽  
Dioxygenase Gene ◽  
Sphingomonas Xenophaga ◽  
Culture Supernatants

ABSTRACT During aerobic degradation of naphthalene-2-sulfonate (2NS), Sphingomonas xenophaga strain BN6 produces redox mediators which significantly increase the ability of the strain to reduce azo dyes under anaerobic conditions. It was previously suggested that 1,2-dihydroxynaphthalene (1,2-DHN), which is an intermediate in the degradative pathway of 2NS, is the precursor of these redox mediators. In order to analyze the importance of the formation of 1,2-DHN, the dihydroxynaphthalene dioxygenase gene (nsaC) was disrupted by gene replacement. The resulting strain, strain AKE1, did not degrade 2NS to salicylate. After aerobic preincubation with 2NS, strain AKE1 exhibited much higher reduction capacities for azo dyes under anaerobic conditions than the wild-type strain exhibited. Several compounds were present in the culture supernatants which enhanced the ability of S. xenophaga BN6 to reduce azo dyes under anaerobic conditions. Two major redox mediators were purified from the culture supernatants, and they were identified by high-performance liquid chromatography-mass spectrometry and comparison with chemically synthesized standards as 4-amino-1,2-naphthoquinone and 4-ethanolamino-1,2-naphthoquinone.

A new thin layer cell for battery related DEMS-experiments: the activity of redox mediators in the Li–O2 cell

2018 ◽  
Vol 20 (33) ◽  
pp. 21447-21456 ◽  
Author(s):  
P. P. Bawol ◽  
P. Reinsberg ◽  
C. J. Bondue ◽  
A. A. Abd-El-Latif ◽  
P. Königshoven ◽  
...  
Keyword(s):  
Thin Layer ◽  
Underlying Mechanism ◽  
Redox Mediator ◽  
Redox Mediators ◽  
Layer Cell ◽  
Thin Layer Cell ◽  
The Stability

The activity of four different redox mediators was investigated with DEMS. The paper provides information about the underlying mechanism of Li2O2 oxidation by a redox mediator as well as about the stability of the redox mediator.

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