Efeitos de agentes oxidantes e oxigênio dissolvido na descoloração do azo corante acid orange 7 por fotólise e fotocatálise

Abstract

Recebido em 5/5/08; aceito em 23/1/09; publicado na web em 28/7/09 EFFECTS OF OXIDANT AGENTS AND DISSOLVED OXYGEN ON THE DECOLORIZATION OF ACID ORANGE 7 AZO DYE BY PHOTOLYSIS AND PHOTOCATALYSIS. The decolorization of acid orange 7 azo dye by photolysis and photocatalysis by ZnO was investigated in the presence of oxidants such as NaClO 3 , NaBrO 3 , NaIO 4 , and K 2 S 2 O 8 in an open reactor at 30 ºC. The decolorization was relatively fast at lower oxidants concentrations and slow rate at larger concentrations, except for persulfate in the photocatalysis. Concerning photolysis the rate constant enhanced gradually, except for chlorate, outreaching the obtained values by photocatalysis, at higher concentrations. The air saturation decreased the rate constant in both processes and indicated that the azo dye can be decolorized without dissolved oxygen in persulfate medium.

Remoção do Corante Têxtil Turquesa de Remazol Empregando Aguapé (Eichhornia crassipes) como Adsorvente

“…Ricos em corantes, estes efluentes afetam a atividade fotossintética nos sistemas hídricos, absorvendo e restringindo a penetração da radiação solar, reduzindo o nível de oxigenação do meio, além de serem bioacumulativos, tóxicos, mutagênicos e carcinogênicos. [1][2][3][4][5][6] Com o intuito de minimizar impactos ambientais, várias metodologias estão disponíveis para remover/degredar os corantes dos efluentes têxteis, tais como: processos oxidativos avançados [7], eletrofloculação [8], degradação eletroquímica [9], ozonização [10], degradação fotoeletroquímica [11], fotocatálise [12], degradação biológica [13], fluxo subcrítico [14], e adsorção [15]. A adsorção apresenta vantagens em relação às demais técnicas, em função do custo e praticidade, podendo empregar adsorventes naturais, a exemplo de lignocelulósicos, dando destino a resíduos agrícolas, possibilitando a recuperação do adsorvato e a consequente reutilização do material adsorvente [16,17].…”

Optimization of Photocatalytic Decolorization of the Azo Dye Direct Orange 34 by Statistical Experimental Design

“…Therefore, the reduction step of the air oxygen by photogenerated electrons to produce less O 2 ·-(equation 2) than expected in the conduction band. The effect of dissolved oxygen was investigated also in the decolorization of the monoazo dye Acid Orange 7 (AO7) 29 under photolysis and photocatalysis by ZnO in the presence of 2.5x10 -2 mol L -1 persulfate at 30 o C in saturated medium with O 2 and N 2 , with and without air saturation, respectively. The highest decolorization rate constant was found when the reaction was carried out in oxygen saturated medium, as expected, followed by no air saturation, air saturation in a similar trend of this work and not totally clear so far, and lastly nitrogen saturation.…”