Degradation of Acid Orange 7 by electrochemically generated •OH radicals in acidic aqueous medium using a boron-doped diamond or platinum anode: A mechanistic study

Fernando Oliveira (SFRH/BD/65254/2009) acknowledges Fundacao para a Cioncia e Tecnologia, Portugal, for its doctoral grant financial support. Andrea Zille (C2011-UMINHO-2C2T-01) acknowledges funding from Programa Compromisso para a Cioncia 2008, Portugal.

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Plasma Treatment in Textile Industry

Degradation and mineralization of methylene blue by dielectric barrier discharge non-thermal plasma reactor

Oxidative degradation of direct orange 61 by electro-Fenton process using a carbon felt electrode: Application of the experimental design methodology

Environmental applications of electric discharges are being considered increasingly more often: they imply the chemical properties of the activated species generated in and by the discharge. An overview of the resulting chemical effects is presented, based on rationalized classification, i.e., acid-base effects, oxidizing properties, complex forming reactions, and radical reactions. The gliding discharge is considered to be a specifically suitable plasma source for the treatment of liquids for pollutant abatement in the scope of sustainable environment, and this justifies an overview of the chemical properties. Special emphasis is devoted to temporal post-discharge reactions (TPDRs), which occur when the target is no longer exposed to the plasma source, and several typical examples are detailed. These recently evidenced TPDRs seem to present some general character. They are the key parameters to estimating the efficiency of a discharge treatment; they also have major technical and economical importance for the application of the plasma treatment to pollutant and/or micro-organism abatement at atmospheric pressure and quasi-ambient temperature.

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Chemical Reactivity of Discharges and Temporal Post-Discharges in Plasma Treatment of Aqueous Media: Examples of Gliding Discharge Treated Solutions

The degradation of aqueous solutions of various dyes (e.g., Orange I, Crystal Violet, and Eriochrome Black T) used for the textile industry was performed by means of a special nonthermal quenched plasma technique (i.e., the gliding arc technique, which results from an electric discharge at atmospheric pressure and ambient temperature). The gaseous species formed in the discharge, and especially the OH radicals, induce strong oxidizing effects in the target solution, so that bleaching of the solution and degradation of the solute result, as evidenced by absorbance and chemical oxygen demand (COD) measurements. The two processes were considered as matching reactions, and overall kinetic data were derived when possible. A tentative mechanism based on literature data is also presented.

and Ahmed Addou

Papers

Bleaching and degradation of textile dyes by nonthermal plasma process at atmospheric pressure