Black TiO₂ Nanotube Array/BiVO₄ Heterojunction Photocatalysts for Tetracycline Removal with High Solution Detoxification Efficiency

Abstract

Pulsed laser deposition was employed to accurately vary the BiVO4 content on the outermost surface of black TiO2 (B-TiO2) nanotube arrays. The optimal B-TiO2(225) led to >80% tetracycline (TC) antibiotic removal, while only 27% TC removal was obtained by bare TiO2 nanotubes after 300 min of photocatalytic reaction under visible-light irradiation. Moreover, the removal rate constant using the optimal heterojunction sample was 0.005 min–1, which was more than 5 times higher than that of bare TiO2 nanotubes. Such an improvement in the performance was attributed to the one-dimensional structure, enhanced light absorption of B-TiO2, formation of a thermodynamically favorable type II heterojunction, and deposition of BiVO4 on the top surface of B-TiO2, which increases the light utilization in front illumination. On the basis of the identification of intermediates and byproducts via high-resolution tandem mass spectrometry analysis and the Fukui index, it was revealed that demethylation and oxidation were the main degradation pathways. The toxicity change after treatment was assessed by using the optical density method and the Ecological Structure Activity Relationship (ECOSAR) program. The results indicate that the mass ratio between B-TiO2 and BiVO4 is a critical parameter for determining the photocatalytic activity, in terms of not only the TC degradation efficiency and kinetics but also the type and quantity of byproducts and, hence, the toxicity of the treated solution.

Mo-BiVO4/Ca-BiVO4 Homojunction Nanostructure-Based Inverse Opals for Photoelectrocatalytic Pharmaceutical Degradation under Visible Light

“…In addition, the PEC activity of ms -BiVO 4 nanomaterials is largely impaired by persistent electron–hole recombination stemming from the low electron mobility (∼10 –2 cm 2 V –1 s –1 ), which reflects the strong electron–phonon coupling that leads to polaron formation around V 4+ sites . Intensive research efforts have been accordingly devoted to alleviate these shortcomings by metal doping , and heterostructuring − in order to improve charge transport and separation of BiVO 4 nanomaterials for water oxidation and environmental remediation.…”

Extrinsic Point Defects in TiO2–Acetylacetone Charge-Transfer Complex and Their Effects on Optical and Photochemical Properties

“…The EPR and XPS measurements (Figures and , respectively) did not reveal the presence of Ti 3+ , which would imply a negative shift in the Ti 2p BE and, as a consequence, an increase in the lattice parameters. ,,, In addition, this result is an indication that charge compensation in the TiO 2 -ACAC CTCs occurs predominantly through electronic compensation, which led to the formation of F + centers (eq and Figure ).…”

“…Around 30% TC abatement was observed for Black-TiO 2 nanotube arrays and a maximum TC photodegradation of ∼70% for a Black-TiO 2 nanotube array/BiVO 4 heterojunction after 6 h under visible-light radiation (300 W xenon lamp light with a 420 nm cutoff filter). 23 Ren et al 24 obtained a TC photocatalytic efficiency of ∼70% for a γ-Fe 2 O 3 /Black-TiO 2 heterojunction and ∼60% TC photocatalytic degradation for α-Fe 2 O 3 /Black-TiO 2 under visible-light excitation (300 W xenon lamp and an AM 1.5 filter) during 50 min. Another study on Black-TiO 2 heterojunctions revealed ∼88% TC degradation for Ag/La-Black-TiO 2 after 90 min of excitation at 300 W using a xenon lamp with a 420 nm cutoff filter (λ > 420 nm).…”

“…Additionally, Mousavi and Ghasemi reported an 82.4% degradation efficiency of TC for the Black-TiO 2 /CoTiO 3 nanocomposite under 50 W light-emitting-diode (LED) lamps (λ = 450–650 nm) for 30 min. Around 30% TC abatement was observed for Black-TiO 2 nanotube arrays and a maximum TC photodegradation of ∼70% for a Black-TiO 2 nanotube array/BiVO 4 heterojunction after 6 h under visible-light radiation (300 W xenon lamp light with a 420 nm cutoff filter) . Ren et al obtained a TC photocatalytic efficiency of ∼70% for a γ-Fe 2 O 3 /Black-TiO 2 heterojunction and ∼60% TC photocatalytic degradation for α-Fe 2 O 3 /Black-TiO 2 under visible-light excitation (300 W xenon lamp and an AM 1.5 filter) during 50 min.…”

Cd-doped Ag2O/BiVO4 visible light Z-scheme photocatalyst for efficient ciprofloxacin degradation

“…Combining a doped semiconductor with another can change the photocatalyst reduction and oxidation driving forces along with the excited species charge separation. [17][18][19][20][21] Hence, a doped Ag 2 O material as a part of a composite should give an improved photocatalyst. There have been a few investigations on Ag 2 O-based composites (or photocatalytic heterostructures).…”