Harnessing MnCdS/AgIn5S8 heterojunction with promoted interfacial charge transfer for ultra-high efficiency photocatalytic degradation of levofloxacin

Abstract

Pharmaceutical pollutants in aquatic environments represent major ecological and health problems owing to their persistence and bioactivity, emphasizing the need of effective degrading solutions. Herein we report a S-scheme MnCdS/AgIn₅S₈ heterojunction synthesized through hydrothermal cum physical mixing that utilizes visible light irradiation to efficiently degrade levofloxacin (LEV) antibiotic. The 20 % MnCdS/AgIn₅S₈ heterojunction demonstrated exceptional photocatalytic efficiency with 94.30 % degradation at neutral pH under 80 min light irradiation. The photocatalytic performance of the heterojunction was optimised by investigating several operational factors such as pH, catalyst dosage and starting levofloxacin concentrations. Optimal degradation occurred at neutral pH, with higher dose (30 mg) of improving the degradation rate owing to the availability of active sites. The improved performance is ascribed to the construction of heterojunction, which effectively separates photogenerated electrons and holes in space, reducing recombination. Scavenging studies using potassium iodide (KI), benzoquinone (BQ) and isopropyl alcohol (IPA) and electron spin resonance (ESR) spectra were used to determine the key active species participating in the degradation process. The heterojunction offers an eco-friendly approach to the breakdown of organic contaminants owing to its exceptional stability and reusability across five cycles. This work advances the technique of photocatalytic pollutant degradation by offering a viable method for the solar-driven degradation of pharmaceutical pollutants.