Visible-Light-Driven Photocatalytic Degradation of Tetracycline Using Heterostructured Cu₂O–TiO₂Nanotubes, Kinetics, and Toxicity Evaluation of Degraded Products on Cell Lines

Abstract

This study first reports on the tetracycline photodegradation with the synthesized heterostructured titanium oxide nanotubes coupled with cuprous oxide photocatalyst. The large surface area and more active sites on TiO 2 nanotubes with a reduced band gap (coupling of Cu 2 O) provide faster photodegradation of tetracycline under visible light conditions. Cytotoxicity experiments performed on the RAW 264.7 (mouse macrophage) and THP-1 (human monocytes) cell lines of tetracycline and the photodegraded products of tetracycline as well as quenching experiments were also performed. The effects of different parameters like pH, photocatalyst loading concentration, cuprous oxide concentration, and tetracycline load on the photodegradation rate were investigated. With an enhanced surface area of nanotubes and a reduced band gap of 2.58 eV, 1.5 g/L concentration of 10% C-TAC showed the highest efficiency of visible-light-driven photodegradation (∼100% photodegradation rate in 60 min) of tetracycline at pH 5, 7, and 9. The photodegradation efficiency is not depleted up to five consecutive batch cycles. Quenching experiments confirmed that superoxide radicals and hydroxyl radicals are the most involved reactive species in the photodegradation of tetracycline, while valance band electrons are the least involved reactive species. The cytotoxicity percentage of tetracycline and its degraded products on RAW 264.7 (−0.932) as well as THP-1 (-0.931) showed a negative correlation with the degradation percentage with a p -value of 0.01. The toxicity-free effluent of photodegradation suggests the application of the synthesized photocatalyst in wastewater treatment.

Natural degradation of ceftriaxone promoted by direct UVB light in aqueous media. Mechanistic analysis and cytotoxic effects on a eukaryotic cell line and on bacteria

“…More recently, Sharma et al studied the photodegradation of tetracycline with visible light in the presence of titanium oxide nanotubes together with cuprous oxide photocatalysts. 52 The toxicity of the antibiotic and its photoproducts were checked on mouse macrophage and human monocyte cell lines, employing the MTT test to examine the viability of the cells. The results obtained by these authors confirmed that the photoproducts are not cytotoxic.…”

Synthesis of Cu-Doped TiO2 Nanocatalyst for the Enhanced Photocatalytic Degradation and Mineralization of Gabapentin under UVA/LED Irradiation: Characterization and Photocatalytic Activity

“…They concluded that modifying pH is an effective strategy to improve photocatalytic performance. Sharma et al [47] observed that the degradation rate of tetracycline with Cu 2 O-TiO 2 nanotube was complete under acidic, neutral, and alkaline conditions, and it is related to the adsorption of pollutants on the surface catalyst. The number of active sites on the catalyst surface increased, which, in turn, boosted the formation of main reactive species, such as electron-hole pairs or radical hydroxyl during the photo process.…”

“…Additionally, in the presence of an appropriate light source, electrons are excited from the VB to the CB of TiO 2 to create VB holes (positive charge carriers) and CB electrons (negative charge carriers). By scavenging the oxidizing species, these electron-hole pairs produce different reactive oxygen (ROS), further degrading the GBP on the surface of the Cu-TiO 2 [47].…”

“…Sharma et al [47] reported that the main reactive species involved in tetracycline degradation in the photocatalytic process using Cu 2 O-TiO 2 was the superoxide radical (O 2…”

Tailoring Interfacial Physicochemical Properties in Cu2O-TiO2@rGO Heterojunction: Insights from EXAFS and Electron Trap Distribution Analysis

“…Interfacial charge flow generates an internal electric field from TiO 2 to Cu 2 O due to localized regions of Cu 2 O and TiO 2 with surplus negative and positive charges. Finally, electron transfer from Cu 2 O to TiO 2 is facilitated by the p–n heterojunction, which promotes photocatalytic performance. − Furthermore, solid supports, particularly carbonaceous materials, are increasingly used in photocatalytic reactions to prevent aggregation and protect semiconductor photostability . Also as electron mediators, they separate charge carriers in binary heterojunctions, enhancing photocatalytic performance.…”