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Evaluation of color removal and toxicity of azo dyes by the use of microbiological, adsorptive and advanced oxidative processes

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Author(s):
Erica Janaina Rodrigues de Almeida
Total Authors: 1
Document type: Doctoral Thesis
Press: Rio Claro. 2018-03-13.
Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro
Defense date:
Advisor: Carlos Renato Corso; Adalgisa Rodrigues de Andrade
Abstract

Water quality has deteriorated globally and provision of clean water is one of most important worldwide issues. Nowadays, various toxic organic and inorganic compounds have been detected at critical levels in waste water, ground and surface waters. The intense use of synthetic dyes is an environmental problem, considering that constantly these compounds are discharged into water bodies by industrial effluents. Azo dyes represent the by far most important class of textile dyes. Their biotransformation by microorganisms (fungi, bacteria, yeasts) may release aromatic amines that have genotoxic and/or carcinogenic properties, and can induce serious damage in aquatic organisms and humans. In addition, the disposal of azo dyes from dyestuff textile processing industries directly into the water resources causes a reduction in water transparency, oxygen solubility and photosynthesis in aquatic plants. Many approaches have been proposed to remove dyes from textile wastewaters, including chemical coagulation/precipitation, physical adsorption, electrochemical oxidation, chemical oxidation. Recently, advanced oxidation processes (AOPs) have been proposed as promising technique for wastewater treatment. These techniques as are able to oxidise a wide range of compounds that are difficult to degrade, disadvantages of these processes include mainly high energy cost. The biological processes also have received attention because of the advantages of low operating cost, less sludge and environmental friendliness compared with chemical or physical methods. Disadvantages the biological process is long treatment period. To circumvent these limitations, a combination of AOP’s treatments to obtain partial dye degradation followed by a biological treatment has been shown to have potential to achieve effective decolorization and mineralization of azo dyes. The main purpose of this study was to remove the dyes Acid Blue 161 e Procion Red MX-5B in simple and binary aqueous solutions using biological and electrochemical/biological decolorization treatments. To perform the biological treatments were used the fungus Aspergillus terreus and the yeast Saccharomyces cerevisiae. Intense molecular changes after decolorization treatments were demonstrated by the HPLC and FTIR analysis. Mutagenicity was determined by the Salmonella/microsome assay (Ames test), and the acute toxicity by the Lactuca sativa seeds. At the end of the decolorization treatment were performed adsorption treatment with white clay 8 immobilized in alginate for removal the highly toxic metabolites formed after the degradation of the dye molecules. After analyzing all the systems tested, we can verify that the electrochemical/biological/clay system was what presented highest adsorption, degradation and/or mineralization capacity of the dye molecules, because occurred reduction of acute toxicity for Lactuca sativa seeds in all solutions tested. For the binary solution the electrochemical/A. terreus/clay system was able to transform an initially mutagenic solution into non-mutagenic after treatment. (AU)

FAPESP's process: 13/25535-4 - Bioremediation of textile azo dyes using microbiological treatments and advanced oxidation processes
Grantee:Érica Janaina Rodrigues de Almeida
Support Opportunities: Scholarships in Brazil - Doctorate