Enhanced long-wavelength light utilization with polyaniline/bismuth-rich bismuth oxyhalide composite towards photocatalytic degradation of antibiotics

Abstract

Antibiotics in natural waters have posed serious threats to our ecosystem due to its potent biological toxicity. In the present work, a visible-light-driven PANI/Bi₄O₅Br₂ composite photocatalyst was fabricated and used for the degradation of ciprofloxacin (CIP) and tetracycline (TC) antibiotics under visible light (λ ＞ 420 nm). The PANI/Bi₄O₅Br₂ composite presented a significantly improved ability of CIP and TC photodegradation, which is about 2.2 times and 1.6 times to that of Bi₄O₅Br₂, respectively. The promoted photocatalytic activity results from the interface interaction between PANI and Bi₄O₅Br₂, which contributes to the electron-hole separation. The degradation process of CIP was monitored by mass spectrometry, and a possible degradation pathway was proposed based on the analysis of the product. A microbiological antibacterial experiment was designed, proving that the degraded products of CIP and TC have lower toxicity. Furthermore, long wavelength light irradiated (λ ＞ 550 nm) experiment indicated that the introduction of PANI helps to extend the light absorption region and use the long wavelength light more efficiently, thereby promoting the photocatalytic ability. The optimal composite applied for TC degradation was 0.1% PANI/Bi₄O₅Br₂. Its reaction rate constant was 2.8 times to that of Bi₄O₅Br₂ (λ ＞ 550 nm). Eventually, a possible photocatalytic mechanism over PANI/Bi₄O₅Br₂ composite was proposed.

Keywords: Antibiotic; Bi(4)O(5)Br(2); PANI; Photocatalytic; Toxicity.