Photoelectrocatalytic/photoelectro-Fenton coupling system using a nanostructured photoanode for the oxidation of a textile dye: Kinetics study and oxidation pathway.
In this study, a coupled photoelectrocatalytic/photoelectro-Fenton reactor was designed to enhance the degradation efficiency of organic pollutants and tested using the azo dye Orange G as a model compound. Pt-decorated TiO2 nanotubes were used as a photoanode with an air-diffusion polytetrafluoroethylene cathode for H2O2 generation. The sum of individual effects of coupling the photoelectrocatalytic and photoelectro-Fenton processes was evaluated as a function of the decolorization and mineralization of Orange G solutions. The dye solutions were only completely decolorized in more acidic conditions (pH 3.0). The mineralization of the Orange G solutions increased in the sequence photoelectrocatalytic<electro-Fenton<coupled photoelectrocatalytic/photoelectro-Fenton due to the gradual increase in the production of OH radicals. Total organic carbon reductions of 80% for photoelectrocatalysis, 87% for electro-Fenton and 97% for the coupled processes were obtained when using an applied electric charge per unit volume of electrolyzed solution of 200 mA h L(-1). The Orange G decays for all treatments followed pseudo-first-order kinetics, suggesting the attack of a constant concentration of OH radicals. Aromatics such as naphthalenic and benzenic compounds were formed as by-products and were identified using LC-MS/MS analysis. In addition, the generated aliphatic acids were identified using ion-exclusion high-performance liquid chromatography. The final by-products of oxalic and formic acid were identified as ultimate by-products and formed Fe(III) complexes that were rapidly mineralized to CO2 by UV-Vis irradiation. Then, according to the identified oxidation by-products, a plausible pathway was proposed for the degradation of Orange G dye by the coupled process.
Institute of Chemistry of Araraquara, Department of Analytical Chemistry, UNESP, Rua Francisco Degni, 55, 14800-900 Araraquara, SP, Brazil. Electronic address: luciobonn@gmail.com.
Lucio C
LC
Almeida
Institute of Chemistry of Araraquara, Department of Analytical Chemistry, UNESP, Rua Francisco Degni, 55, 14800-900 Araraquara, SP, Brazil.
Bianca F
BF
Silva
Institute of Chemistry of Araraquara, Department of Analytical Chemistry, UNESP, Rua Francisco Degni, 55, 14800-900 Araraquara, SP, Brazil.
Maria V B
MV
Zanoni
D001391:Azo Compounds; D004396:Coloring Agents / Q000737:chemistry*; D004566:Electrodes; D004572:Electrolysis; D005290:Ferric Compounds / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007220:Industrial Waste; D007501:Iron / Q000737:chemistry; D007700:Kinetics; D010084:Oxidation-Reduction; D053719:Tandem Mass Spectrometry; D013784:Textiles; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D001391:Azo Compounds; D004396:Coloring Agents; D005290:Ferric Compounds; D007220:Industrial Waste; D014874:Water Pollutants, Chemical; C008710:Orange G; D006861:Hydrogen Peroxide; D007501:Iron
Dye degradation pathway; Photoelectro-Fenton; Photoelectrocatalysis; Pt-decorated TiO(2)NT anode; Wastewater treatment