Ingeniería ambiental

Efecto del pH sobre la oxidación electroquímica de fenol empleando un ánodo dimensionalmente estable de SnO₂-Sb₂O₅-RuO₂

Effect of pH on the electrochemical oxidation of phenol using a dimensionally stable anode of SnO₂-Sb₂O₅-RuO₂

G.C. López-Ojeda*, Ma. R. Gutiérrez-Lara y A. Durán-Moreno

Universidad Nacional Autónoma de México, Facultad de Química, Departamento de Ingeniería Química, Ciudad Universitaria, CP. 04510. México, D.F. *Autor para la correspondencia. E-mail: alfdur@unam.mx, Tel. (+52 55) 56225293, Fax (+52 55) 56225303.

Recibido 15 de Febrero de 2013
Aceptado 19 de Mayo de 2015

Resumen

En el presente trabajo se estudió el desempeño de un ánodo dimensionalmente estable (DSA por sus siglas en inglés) recubierto con capas de SnO₂-Sb₂O₅-RuO₂ para su empleo en la oxidación anódica de soluciones sintéticas de fenol. Las capas de recubrimiento fueron aplicados por depositación catódica sobre una malla metálica de titanio, seguida de una activación térmica a 450 °C. El ánodo se caracterizó por microscopía electrónica de barrido y voltamperometría cíclica. Para las pruebas experimentales se empleó un reactor tubular y concentraciones de fenol de 100, 300, 500 y 1000 mg/L utilizando NaCl como electrolito soporte y valores de pH de 2, 7 y 12. El mecanismo de oxidación fue función del pH, por medio de la generación de oxidantes derivados del cloro sumada a la generación de radicales hidroxilo de la electrólisis del agua. En todos los casos, se obtuvieron porcentajes de remoción mayores al 90% medidos en términos de disminución de fenol, del 80% para la demanda química de oxígeno y del 70% en el carbono orgánico total. En los experimentos realizados con la mayor concentración de fenol en condiciones ácidas, se observó el efecto de polimerización de los subproductos de la oxidación del fenol.

Palabras clave: tratamiento de aguas residuales, oxidación anódica, ánodo dimensionalmente estable, óxido de estaño, fenol.

Abstract

In the present work as been studied the performance of a dimensionally stable anode (DSA) coated with layers of SnO₂-Sb₂O₅-RuO₂ to be used in the anodic oxidation of synthetic solutions of phenol. The coating layers were applied by cathodic deposition on a titanium mesh, followed by thermal activation at 450° C. The anode was characterized by scanning electron microscopy and cyclic voltammetry. In the experimental tests we employed a tubular and phenol concentrations of 100, 300, 500 and 1000 mg/L using NaCl as supporting electrolyte and conducting the experiments at different pH values of 2, 7 and 12. The mechanism of oxidation was function of the pH, through the generation of oxidants chlorine derivatives added to the generation of hidroxyl radicals obtained from the electrolysis of water. In all cases, removal percentages obtained were greater than 90% measured in terms of decrease of phenol, 80% for the chemical oxygen demand and 70% for the total organic carbon. In the experiments with the higher concentration of phenol in acidic conditions, was observed the effect of polymerization of the byproducts of oxidation of phenol.

Key words: wastewater treatment, anodic oxidation, dimensionally stable anode, tin oxide, phenol.

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