Characterization and electrochemical properties of TiO2-rNTs/SnO2–Sb/PbO2 electrodes for the mineralization of persistent organic pollutants using anodic oxidation coupled Electro-Fenton treatment: Effect of precursor selection.

The present study compares the effect of using different solvents on the electrochemical properties of the reduced TiO 2 nanotubes (TiO 2 -rNTs) layered Ti/TiO 2 -rNTs/SnO 2 –Sb/PbO 2 anodes. The electrodes are prepared using three different solvent-based precursors: (i) isopropanol, (ii) ethylene glycol and citric acid (Pechini method), and (iii) 2-hydroxyethylammonium acetate (2HEAA) ionic liquid (IL) via the thermal decomposition route. The decomposition mechanism of precursor solutions was explored using the thermogravimetric (TGA) analysis. Further, the physicochemical properties of the electrodes are examined using Field emission Scanning Electron microscopy (FE-SEM), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron emission spectroscopy (XPS). The results revealed that solvents with higher viscosity and slower decomposition rates support better film uniformity and higher stability of the electrode. The TiO 2 -rNTs bottom layer and PbO 2 top layer helped obtain higher film stability, increased working potential window (2.2 V vs. SHE) of the electrode, and the repeatability of the results. The performance of different electrodes based on the precursor solution is found as IL ≫ Pechini > Isopropanol. 4-chlorophenol (4-CP) is used as a model pollutant to test the performance of IL-Ti/TiO 2 -rNTs/SnO 2 –Sb/PbO 2 anode in an anodic oxidation (AO) coupled electro-Fenton (EF) treatment. Further, the reliability of the electrode is evaluated by mineralizing other persistent organic pollutants (POPs) like tetracyclin, phenol, 2-chlorophenol (2-CP), and 2,4-dichlorophenol (2,4-DCP). Under the optimized conditions, the proposed system was able to mineralize the tetracyclin, phenol, 2-CP, 2,4-DCP, and 4-CP up to 78.91, 82.07, 74.96, 78.78, and 69.3 %, respectively. Moreover, the degradation mechanism of chlorophenols is proposed. [Display omitted] • Morphology of electrode depends on the viscosity and decomposition rate of precursor solvent. • 2HEAA IL based precursor presented more stable and uniform coating with minimum preparation time. • Ti/TiO 2 -rNTs/SnO 2 –Sb/PbO 2 non-active anode is used for the EF treatment. • More than 80 % of mineralization of persistent organic pollutants is achieved during 240 min of electrolysis. • Mineralization current efficiency, energy consumption and degradationpathway is discussed. [ABSTRACT FROM AUTHOR]