Kinetics of anaerobic biodecolourisation of azo dyes

Abstract

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 8C). 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.

Effect of Initial Azo Dye Concentration and Biomass Acclimation on Sludge Digestion and Dye Co‐treatment

“…molecular structure of HRO107, a maximum of two moles of SA can be produced from 1 mole HRO107 reduction. Therefore, further SA biodegradation could not be observed in acclimated culture, which contradicts observations by Kalyuzhnyi et al [51]. The reduction products obtained in the acclimated cultures were higher in peak area than those in the unacclimated culture.…”

Biological decolorization of xanthene dyes by anaerobic granular biomass

“…However, with living organisms higher decolorization of dyes aqueous solutions may be achieved due to the combination of both phenomena: adsorption and enzymatic degradation (Bakshi et al 1999;Aretxaga et al 2001). A saturation type curve of azo dye removal with increasing biomass concentration was also observed by Kalyuzhnyi et al (2006). They have explained that, taking into account a regenerating function of sludge for reducing agents participating in azo dye splitting.…”