Combination of photoelectrocatalysis and ozonation: A novel and powerful approach applied in Acid Yellow 1 mineralization

• Photoelectrocatalysis assisted by ozonation (O3 + PEC) was proposed as a novel AOP.
• An applied voltage dramatically improves O3 + PC efficiency.
• O3 + PEC system presented higher mineralization and faster decolorization of AY1 dye.
• O3 flow is the main factor in O3 + PEC treatment and reduces energy treatment cost.
• Ozonation and PEC act synergistically for the improvement of OH generation.

Photoelectrocatalytic oxidation (PEC) is known to be a powerful technique employed with the aim of promoting organic degradation. Its efficiency is nonetheless found to be dramatically decreased when applied in highly concentrated effluent treatment owing to the reduced transparency which minimizes the photons reaching the semiconductor surface. In light of that, the present work seeks to describe a novel combination of photoelectrocatalysis and ozonation (O3 + PEC) techniques, aiming at achieving a faster decolorization of a highly concentrated solution and a higher rate of mineralization. The Acid Yellow 1 dye (AY1), widely used in cosmetics was chosen as a colorful solution model. TiO2 nanotubes electrode was used as photoanode in an annular bubble reactor operating at 2.0 V with UV-B irradiation in the presence of 1.25 × 10−4 mol min−1 of O3. The main factors interfering in the O3 + PEC process were optimized through UV/vis spectrophotometry, total organic carbon (TOC) and mass spectrometry measurements. After 20 min of treatment using the combined system, 100% of decolorization was observed while a total mineralization was seen following 60 min of treatment even in effluents containing 100 ppm AY1. Concomitantly, the combined system (O3 + PEC) showed higher decolorization rate constant and lower energy consumption compared to the other techniques, showing that O3 +  PEC is a successful, efficient and cost-effective alternative for water treatment.

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