Effect of nitrate on the reduction of Reactive Red 2 by mesophilic anaerobic sludge

2008 ◽  
Vol 57 (7) ◽  
pp. 1067-1071 ◽  
Author(s):  
A. B. Dos Santos ◽  
C. H. C. Braúna ◽  
S. Mota ◽  
F. J. Cervantes
Keyword(s):  
Azo Dye ◽  
Catalytic Properties ◽  
Redox Mediator ◽  
Anaerobic Sludge ◽  
Redox Mediators ◽  
Anaerobic Conditions ◽  
Anaerobic Reactors ◽  
Nitrate Addition ◽  
Dye Reduction ◽  
Reactive Red 2

This research aimed to evaluate the effect of nitrate on anaerobic azo dye reduction by using mesophilic bioreactors, in the absence (reactor R2) and in the presence (reactor R1) of redox mediators. The azo dye Reactive Red 2 (RR2) and the redox mediator anthraquinone-2,6-disulphonate (AQDS) were selected as model compounds. The results showed that the bioreactors were efficient on RR2 reduction, in which ethanol showed to be a good electron donor to sustain dye reduction under anaerobic conditions. The redox mediator AQDS increased the rates of reductive decolourisation, but its effect was not so remarkable compared to the previous experiments conducted. Contrary to the raised hypothesis that the nitrate addition could decrease decolourisation rates and catalytic properties of the redox mediators, no effect of nitrate was observed in the bioreactors, suggesting that the presence of nitrate in textile wastewaters will not decrease the capacity of anaerobic reactors supplemented or not with redox mediators to decolourize azo dyes.

The contribution of biotic and abiotic processes during azo dye reduction in anaerobic sludge

2003 ◽  
Vol 37 (13) ◽  
pp. 3098-3109 ◽  
Author(s):  
Frank P van der Zee ◽  
Iemke A.E Bisschops ◽  
Valérie G Blanchard ◽  
Renske H.M Bouwman ◽  
Gatze Lettinga ◽  
...  
Keyword(s):  
Azo Dye ◽  
Anaerobic Sludge ◽  
Dye Reduction

The role of sulphate reduction on the reductive decolorization of the azo dye reactive orange 14

2006 ◽  
Vol 54 (2) ◽  
pp. 171-177 ◽  
Author(s):  
F.J. Cervantes ◽  
J.E. Enriquez ◽  
M.R. Mendoza-Hernandez ◽  
E. Razo-Flores ◽  
J.A. Field
Keyword(s):  
Electron Donor ◽  
Azo Dye ◽  
Redox Mediator ◽  
Sulphate Reduction ◽  
Anaerobic Sludge ◽  
Biological Mechanisms ◽  
Azo Reduction ◽  
Reactive Orange ◽  
The Impact

The aim of this study was to investigate the impact of a broad range of sulphate concentrations (0–10 g SO4−2 L−1) on the reduction of an azo dye (reactive orange 14 (RO14)) by an anaerobic sludge. An increase in the sulphate concentration generally stimulated the reduction of RO14 by sludge incubations supplemented with glucose, acetate or propionate as electron donor. Sulphate and azo dye reductions took place simultaneously in all incubations. However, there was a decrease on the rate of decolorization when sulphate was supplied at 10 g SO4−2 L−1. Abiotic incubations at different sulphide concentrations (0–2.5 g sulphide L−1) promoted very poor reduction of RO14. However, addition of riboflavin (20 μM), as a redox mediator, accelerated the reduction of RO14 up to 44-fold compared to a control lacking the catalyst. Our results indicate that sulphate-reduction may significantly contribute to the reduction of azo dyes both by biological mechanisms and by abiotic reductions implicating sulphide as an electron donor. The contribution of abiotic decolorization by sulphide, however, was only significant when a proper redox mediator was included. Our results also revealed that sulphate-reduction can out-compete with azo reduction at high sulphate concentrations leading to a poor decolorising performance when no sufficient reducing capacity is available.

scholarly journals Thermal modification of activated carbon surface chemistry improves its capacity as redox mediator for azo dye reduction

2010 ◽  
Vol 183 (1-3) ◽  
pp. 931-939 ◽  
Author(s):  
L. Pereira ◽  
R. Pereira ◽  
M.F.R. Pereira ◽  
F.P. van der Zee ◽  
F.J. Cervantes ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Surface Chemistry ◽  
Azo Dye ◽  
Thermal Modification ◽  
Redox Mediator ◽  
Carbon Surface ◽  
Dye Reduction

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.

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