Multivariate optimization of methylene blue dye degradation using electro-Fenton process with self-doped TiO2 nanotube anode.

This paper reports the optimization of the electro-Fenton (EF) process using different anode materials for the degradation of Methylene Blue (MB) dye as a model compound. The cathode used was an air-diffusion PTFE, while three different anode materials (Pt, DSA, and self-doped TiO2 nanotubes - SD-TNT) were tested individually. A full factorial design (FFD) with a central point combined with response surface methodology (RSM) was employed to optimize the experimental variables, including solution pH, applied current, and anode material. The optimized EF conditions involved a pH of 4.0, a current of 100 mA, and an SD-TNT anode for 120 min of electrolysis. Under these conditions, the MB solution achieved complete decolorization and 45% of total organic carbon (TOC) removal after 120 min of EF treatment. The findings indicate that the hydroxyl radical (•OH) plays a crucial role as the primary oxidizing agent in the EF process. The decay of MB followed pseudo-first-order kinetics, reflecting a consistent formation of •OH radicals that effectively attacked the MB dye and its subproducts during mineralization. Moreover, the EF process exhibited superior performance in terms of energy consumption (EC) and mineralization current efficiency (ECM) in the initial treatment stages, while the presence of recalcitrant by-products and loss of anode self-doping impacted performance in the later stages. The optimized EF conditions and the understanding gained from this study contribute to the advancement of sustainable wastewater treatment strategies for the removal of organic dyes.

Characterization of Cu2O/TiO2NTs nanomaterials using EDXRF, XRD and DRS for photocatalytic applications.

TiO2 nanotube arrays (TiO2NTs) were decorated with Cu2O nanoparticles by pulse electrochemical deposition. The Cu2O nanoparticles were uniformly distributed onto TiO2NTs surface and with diameter varying between 50 and 200 nm. The effects of the independent variables on the photocatalytic response were simultaneously assessed by a multivariate statistical design. Energy-Dispersive X-Ray Fluorescence, X-Ray Diffraction, FEG-SEM and Diffuse Reflectance Spectroscopy were employed to Cu2O/TiO2NTs characterization. The Cu2O films obtained on TiO2NTs surface were crystalline. DRS analysis confirmed that the modification of TiO2NTs with Cu2O nanoparticles improved the quantum efficiency of the material. The Cu2O/TiO2NTs photoelectrode shows an intense absorption peak in the visible region decreasing the band gap energy from 3.20eV for TiO2NTs to 2.96 eV for Cu2O/TiO2NTs.

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