Formulation and characterization of W-doped titania nanotubes for adsorption/photodegradation of methylene blue and basic violet 3 dyes

Abstract Titania nanotubes (TNs) with a 5% tungsten (W) doping content were prepared to improve their reactivity toward the degradation of methylene blue (MB) and basic violet 3 (BV3) under UV radiation. The specific surface areas of the W-doped TNs ranged 224–237 m2 /g with high mesoporous fractions (83–88%). The XPS spectra showed peaks located at 35.5 and 37.6 eV confirming the W6+ species, corresponding to W 4f7/2 and 4f5/2, respectively. The XANES/EXAFS spectra showed that the 5% W-doped TNs with Ti (W) atoms had Ti–O (W–O) bonds with interatomic distances of 1.92 A (1.82 A) and coordination numbers of 2.04 (2.01). The reaction kinetics revealed that MB and BV3 photodegradation were both two-step reactions with two rate constants (MB: k1 / k2 = 68 min-1; BV3: k1 / k2 = 35 min-1). The optimal photocatalytic efficiencies for MB (98.3%) and BV3 (72.58%) were obtained using 5% W-doped TNs.