Uso de extrato de levedura como fonte de carbono e de mediadores redox, para a degradação anaeróbia de corante azo

Abstract

O trabalho investigou a influência do uso do extrato de levedura, fonte dos mediadores redox riboflavina e nicotinamida, na remoção de cor de solução de corante azo Drimaren Azul HF-RL em condições anaeróbias. O trabalho envolveu a execução de ensaios em batelada, em frascos-reatores mantidos a 25 ºC, incubados com o azo-corante e lodo anaeróbio na presença e ausência de fontes de carbono (extrato de levedura ou glicose) e de mediadores redox (riboflavina ou extrato de levedura). O monitoramento da variação temporal de cor, a demanda química de oxigênio (DQO) e ácidos graxos voláteis (AGV) mostraram que a adição de extrato de levedura (0,5 g/L) resultou em eficiências de remoção de cor de 80 a 85% nas primeiras 24 horas de incubação, e que os produtos da degradação do azo-corante foram tóxicos para todo o consórcio anaeróbio, o que resultou em baixas eficiências de remoção de DQO na presença e ausência do extrato de levedura. Os resultados indicaram, ainda, que as eficiências de remoção de cor foram inferiores a 30% na presença de apenas glicose (fonte de carbono) ou riboflavina (mediador redox), indicando que o extrato de levedura atuou simultaneamente como fonte de carbono e de mediadores redox.

Use of Multivariate Experimental Designs for Optimizing the Reductive Degradation of an Azo Dye in the Presence of Redox Mediators

“…These results confirm the results reported by other authors, 5,20 who showed that the addition of yeast extract enhanced anaerobic degradation of azo dyes in anaerobic reactors, probably because it acted simultaneously as a source of carbon and riboflavin, which is a well-known redox mediator. 21,22 Indeed, yeast extract is largely used as source of vitamins in culture biomedia to boost the culture conditions and enhance microorganism activity.…”

“…The experiments were conducted randomly with the concentration of the Remazol golden yellow RNL azo dye fixed at 50 mg L -1 (estimated on the basis of data provided by the textile company that provided the sample) and using 25 mL of biomedia, whose composition is described elsewhere. 5 The molar absorptivity of the Remazol golden yellow RNL was measured as 7,506.7 mol -1 L cm -1 . To ensure anaerobic conditions in the batch reactors, nitrogen gas (Praxair, industrial grade 3.0) was gently fluxed onto the headspace of the flasks for 2 min before the reactors were closed with rubber caps and sealed with aluminum crimps, as described by Baeta et al 20 The concentration of azo dye in the bulk solution was estimated from its absorbance, which was measured at a wavelength of 410 nm using a spectrophotometer (Biospectro, SP-220), which was the maximum absorbance wavelength for the azo dye.…”

“…3,4 Numerous technologies for textile wastewater treatment have been developed, but biological processes are the most widely used because of their favorable cost-benefit analysis. 5 Although the aerobic--activated sludge process is very popular in the textile industry, it is not very efficient in removing color from textile effluents. Dye removal in such processes occurs only because of their physical adsorption onto activated sludge, which is periodically discharged.…”

Application of cellulose-immobilized riboflavin as a redox mediator for anaerobic degradation of a model azo dye Remazol Golden Yellow RNL

“…Corrêa et al (2009) reported that color removal efficiencies of the azo dye blue Drimarem HF-RL in anaerobic systems varies 39-45% within the first 24 h, with a final degradation efficiency of 91% after 150 h. van der Zee et al (2001a) reported a 30% color removal efficiency in a bench-scale UASB reactor kept at 30 • C without redox mediators and fed with the azo dye reactive red (RR2), while a 95% color removal efficiency was seen for different azo dyes in anaerobic systems in less than 6 days (van der Zee et al, 2001b).…”

“…The textile industry employs several steps to give the fabrics the properties and characteristics desired in the final product, of which dyeing is one of the most important, and it is estimated that 10-15% of dyes used in the dyeing process do not adhere to the fibers and end up in the textile effluent (Corrêa et al, 2009). Apart from their potential toxicity, dyes and pigments are recalcitrant (resistant to degradation) and may remain in the environment for long periods, accumulating in water and soil if not suitably treated before being discharged (dos .…”