A novel electro-catalytic ozonation process for treating Rhodamine B using mesoflower-structured TiO2-coated porous titanium gas diffuser anode

A combined heterogeneous catalytic ozonation (CATAZONE) and electrochemical oxidation (EO) process (E-CATAZONE) for a quick and effective oxidation of refractory organic pollutants (i.e. Rhodamine B) (RhB) was developed. In this process, a porous Ti gas diffuser (PTGD) coated with mesoflower-structured TiO2 was fabricated and simultaneously acted as anodes, ozone (O-3) gas diffusers and catalysts for E-CATAZONE process. Results showed that E-CATAZONE presented a unique synergy between heterogeneous catalytic ozonation and electrochemical oxidation on hydroxyl radical ((OH)-O-center dot) production and RhB mineralization. Owing to the unique 3-D porous structure, novel morphology, as well as its multi catalytic capabilities for both the CATAZONE and EO reactions, mesoflower-structured TiO2 coated porous Ti gas diffusers (MFT-PTGDs) exhibit higher catalytic activity than PTGDs alone for the E-CATAZONE process, thus a high COD (chemical oxygen demand) removal rate of 95.7% was achieved at 2.5 h, showing an apparent pseudo-first-order kinetics with a rate constant of 0.96 h(-1). According to different operation conditions, results also show that the O-3 sparging mode and the electrochemical role of MFT-PTGD significantly affects COD removal. It is found that flow-through mode for O-3 sparging and use of MFT-PTGD as the anode were particularly beneficial for the E-CATAZONE oxidation of Rhodamine B. Thus, the proposed E-CATAZONE presents significantly high oxidation ability than sole CATAZONE and EO processes by using MFT-PTGDs. (C) 2016 Elsevier B.V. All rights reserved.