Photocatalytic Degradation of Some Typical Antibiotics: Recent Advances and Future Outlooks

Abstract

The existence of antibiotics in the environment can trigger a number of issues by fostering the widespread development of antimicrobial resistance. Currently, the most popular techniques for removing antibiotic pollutants from water include physical adsorption, flocculation, and chemical oxidation, however, these processes usually leave a significant quantity of chemical reagents and polymer electrolytes in the water, which can lead to difficulty post-treating unmanageable deposits. Furthermore, though cost-effectiveness, efficiency, reaction conditions, and nontoxicity during the degradation of antibiotics are hurdles to overcome, a variety of photocatalysts can be used to degrade pollutant residuals, allowing for a number of potential solutions to these issues. Thus, the urgent need for effective and rapid processes for photocatalytic degradation leads to an increased interest in finding more sustainable catalysts for antibiotic degradation. In this review, we provide an overview of the removal of pharmaceutical antibiotics through photocatalysis, and detail recent progress using different nanostructure-based photocatalysts. We also review the possible sources of antibiotic pollutants released through the ecological chain and the consequences and damages caused by antibiotics in wastewater on the environment and human health. The fundamental dynamic processes of nanomaterials and the degradation mechanisms of antibiotics are then discussed, and recent studies regarding different photocatalytic materials for the degradation of some typical and commonly used antibiotics are comprehensively summarized. Finally, major challenges and future opportunities for the photocatalytic degradation of commonly used antibiotics are highlighted.

Keywords: antibiotics; degradation mechanism; photocatalysts; photocatalytic degradation.

Figure 1

Sources of different emerging antibiotics pollutants in daily life. (Reproduced with permission from [19], copyright 2021, Elsevier).

Figure 2

General photocatalytic mechanism on the degradation of antibiotics by the formation of photo-induced charge carriers (e⁻/h⁺) on the photocatalysts’ surface.

Figure 3

Band energy gaps of selected semiconductors. (Reproduced with permission from [43], copyright 2017, Springer Nature).

Figure 4

The mechanism of coupled processes with bismuth-based compounds for antibiotic degradation. (Reproduced with permission from [26], copyright 2021, Elsevier).

Figure 5

Crystal structure and optical properties of graphitic carbon nitride: (a) Schematic diagram of a perfect graphitic carbon nitride sheet constructed from melem units, (b) Experimental XRD pattern of the polymeric carbon nitride, revealing a graphitic structure with an interplanar stacking distance of aromatic units of 0.326 nm and (c) Ultraviolet-visible diffuse reflectance spectrum of the polymeric carbon nitride. Inset: Photograph of the photocatalyst. (Reproduced with permission from [72], copyright 2009, Springer Nature).

Figure 6

The illustration of commonly investigated antibiotics in photocatalytic processes. (a) Ciprofloxacin. (b) Tetracycline. (c) Norfloxacin. (d) Amoxicillin. (Reproduced with permission from [1], copyright 2021, Elsevier).

Figure 7

(a) The schematic diagram of the photocatalytic mechanism for the Zn-doped Cu₂O (b) Photocatalytic activity of R₂-Cu₂O with different scavenges, inset is degradation rate of ciprofloxacin. (Reproduced with permission from [80], copyright 2019, Elsevier) (c) Diagram of band gap structure of bulk and exfoliated g-C₃N₄ (d) Photocatalytic degradation of ciprofloxacin over g-C₃N₄ as well as exfoliated g-C₃N₄. (Reproduced with permission from [81], copyright 2019, Springer Nature).

Figure 8

(a) Proposed heterojunction differences between TCN and TCN(mix) (b) Photocatalytic degradation efficiencies of tetracycline by employing TiO₂, TCN, TCN (mix), and g-C₃N₄ as the photocatalysts under the xenon lamp irradiation. (Reproduced with permission from [87], copyright 2017, Elsevier). Schematic Illustration of the Mechanism for the Photocatalytic Degradation of tetracycline under Visible Light Irradiation over AgI/BiVO₄ Nanocomposite: (c) Traditional Model and (d) Z-Scheme Heterojunction System. (Reproduced with permission from [88], copyright 2016, American Chemical Society).

Figure 9

(a) Photocatalysis Mechanism of {001} Faceted TiO₂/Ti Film. (Reproduced with permission from [92], copyright 2016, American Chemical Society) (b) Possible mechanism diagram on Z-scheme Ag/FeTiO₃/Ag/BiFeO₃ system (c) Effect of mass ratio of FeTiO₃ and BiFeO₃ and (d) degradation reaction kinetics on photocatalytic activity (2.0 wt.% Ag; 5.0 mg/L norfloxacin; 1.0 g/L catalyst). (Reproduced with permission from [93], copyright 2018, Elsevier).

Figure 10

(a) Possible mechanism of amoxicillin degradation at GO/TiO₂ surface. (Reproduced with permission from [97], copyright 2021, Springer Nature). Photocatalytic degradation kinetics of amoxicillin by the synthesized materials under (b) visible light and (c) simulate solar light. (d) amoxicillin degradation rate constants under solar and visible light. (Reproduced with permission from [99], copyright 2021, Elsevier).