Electrochemical degradation of reactive dyes at different DSA® compositions

Abstract

Este trabalho investiga a oxidação eletroquímica dos corantes azul reativo 4 (RB-4) e laranja reativo 16 (RO-16) utilizando ânodos dimensionalmente estáveis de RuO 2 . As eletrólises foram realizadas sob controle galvanostático em função do eletrólito de suporte e composição do material eletródico. As eletrólises feitas na presença ou ausência de NaCl foram capazes de remover totalmente a coloração da solução; no entanto, um aumento significativo da combustão do corante somente foi obtido para na presença de cloreto (valores de 80% de remoção de carbono foram atingido). Concentrações elevadas de cloreto não implicaram em aumento significativo de remoção da cor ou mineralização. A composição do óxido influência na destruição do corante (com ou sem cloreto), observa-se que Ti/Ru 0.30 Ti 0.70 O 2 é o material mais ativo para oxidação dos compostos investigados. A reação de desprendimento de oxigênio é uma reação paralela limitante em ambos os eletrólitos de suporte investigados, NaCl e Na 2 SO 4 , e a competição com a oxidação do composto orgânico ainda é um obstáculo. A análise da formação de compostos organoclorados (AOX) revela que existe um pequeno consumo das espécies formadas nos primeiros minutos de eletrólise, a composição Ti/(RuO 2 ) 0.70 (Ta 2 O 5 ) 0.30 é a composição com melhores características para emprego no tratamento ambientais. Tanto a composição como o eletrólito afetam a formação de compostos indesejáveis. This paper investigates the electrochemical oxidation of the reactive dyes reactive blue 4 (RB-4) and reactive orange 16 (RO-16) on RuO 2 dimensionally stable anode (DSA ® ) electrodes. Electrolysis was achieved under galvanostatic control as a function of supporting electrolyte and electrode composition. The electrolyses, performed in either the presence or absence of NaCl, were able to promote efficient color removal; moreover, at low chloride concentration (0.01 mol L -1 ), total color removal was obtained after just 10 min of electrolysis, and a significant increase in total dye combustion was achieved for all the studied anodes in chloride medium (reaching ca. . No significant enhancement in dye color removal or mineralization was observed upon increasing chloride concentration. The influence of oxide composition on dye elimination seems to be significant in both media (with or without chloride), being Ti/Ru 0.30 Ti 0.70 O 2 , the most active material for organic compound oxidation. The oxygen evolution reaction (OER) was shown to be a limiting reaction in both supporting electrolytes; i.e., NaCl and Na 2 SO 4 , and its competition with organic compound oxidation remained an obstacle. The adsorbable organo halogens (AOX) formation study revealed that there is slight consumption of the undesirable species formed within the first minutes of the electrolysis, being Ti/(RuO 2 ) 0.70 (Ta 2 O 5 ) 0.30 the most environmentally friendly composition. Both anode composition and chloride concentration affect the formation of these undesirable compounds.Keywords: reactive dyes, electrochemical oxidat...

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