Shewanella xiamenensis G5-03 was observed to decolorize the azo dye Congo red in synthetic wastewater. The influence of some factors on the dye decolorization efficiency was evaluated. The optimal decolorization conditions were temperature 30-35 °C, pH 10.0, incubation time 10 h, and static condition. The kinetic of Congo red decolorization fitted to the Michaelis–Menten model (Vmax = 111.11 mg L-1 h-1 and Km = 448.3 mg L-1). The bacterium was also able to degrade benzidine, a product of azo bond breakage of the Congo red, which contributed to reduce the phytotoxicity. The ability of S. xiamenensis G5-03 for simultaneous decolorization and degradation of Congo red shows its potential application for the biological treatment of wastewaters containing azo dyes.
In this study, baker’s yeast-MnO2 composites, produced by direct oxidation of yeast with KMnO4 under acidic conditions, were used as biosorbent to remove the triphenylmethane dye Malachite green (MG) from an aqueous solution. Parameters that influence the adsorption process, such as pH, contact time, temperature, initial dye concentration and biosorbent dosage, were evaluated in batch experiments. The optimum removal of MG was found to be 86.7 mg g-1 at pH 10, 1.0 g L-1 of biomass dosage and 45°C. The kinetic data of dye removal was better described by the pseudo-second-order model. The adsorption process followed the Langmuir isotherm model and the maximum biosorption capacity was estimated to be 243.9 mg g-1 (at 25°C). The negative values of ∆G° and the positive value of ∆H° indicated that the MG biosorption onto yeast-MnO2 composites is spontaneous and endothermic. Fourier transform infrared spectroscopy (FTIR) indicated that the nano-MnO2 particles deposited on yeast-MnO2 composites surface facilitated the MG adsorption. It was concluded that baker’s yeast-MnO2 composites have potential for application as adsorbent for removal of MG from aqueous solution.
Um sistema constituído de reator biológico, bioenriquecido com a bactéria Shewanella xiamenensis G5-03, e wetland construído, vegetado com Typha domingensis, foi desenvolvido para o tratamento de água residuária sintética contendo o corante vermelho Congo. O sistema combinado removeu 96,5% da cor da água residuária, a qual ocorreu principalmente no reator biológico (83,0%) devido às condições anaeróbicas favoráveis à clivagem redutiva dos grupos cromóforos do corante. Também foram observadas altas taxas de remoção de turbidez e DQO (89,9% e 90,6%, respectivamente), enquanto as taxas de remoção de PO4-P e NH4-N foram de 70,4% e 18,3%, respectivamente. O wetland construído removeu, em média, 95,7% de benzidina, um composto carcinogênico que foi gerado no reator biológico a partir da degradação do vermelho Congo, o que pode ter contribuído para a detoxificação parcial da água residuária sintética tratada pelo sistema. Em síntese, o sistema de tratamento avaliado demostrou boa performance na remoção de poluentes da água residuária têxtil sintética.
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