Evaluation of the Acid Blue 161 dye degradation through electrochemical oxidation combined with microbiological systems
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Synthetic textile dyes have considerable molecular complexity, which makes these compounds highly stable and resistant to different types of treatments. Azo dyes represent the most commonly used group of dyes in textile industry. Azo dye contaminants in wastewater are recalcitrant, and microbiological treatments and oxidative processes have been widely studied to remedy this problem. These treatments can transform recalcitrant substances into substances with low toxicity. Therefore, microbiological and electrochemical/microbiological discoloration treatments were performed with the azo textile dye Acid Blue 161 in aqueous solution. The microbiological discoloration treatments were carried out using the filamentous fungus Aspergillus terreus and the yeast Saccharomyces cerevisiae. Discoloration treatments were performed with and without electrochemical pretreatment. The acute toxicity of the solutions was analyzed before and after the treatments using a vegetable test system (Lactuca sativa seeds). Adsorption treatment with white clay was performed to remove intermediate metabolites with high toxicological potential. At the end, all treatments tested were effective at discoloring the Acid Blue 161 dye solution. Moreover, the systems composed of the fungus A. terreus were more efficient and exhibited lower acute toxicity to L. sativa seeds at the end of 288 h of exposure to fungal biomass before and after adsorption treatment with white clay.