Ultrasonic assisted anchoring of Yb2O3 nanorods on In2S3 nanoflowers for norfloxacin degradation and Cr(VI) reduction in water: Kinetics and degradation pathway

Abstract

The design and fabrication of environmentally benign, visible light-responsive heterojunction photocatalysts remain a viable route towards sustainable exploitation of photocatalysis for water treatment. In this contribution, binary nanostructures consisting of varying ratios of In2S3 and Yb2O3 (In2S3/Yb2O3) were obtained via a two-step method involving hydrothermal synthesis and ultrasonic treatment. The prepared materials were characterised extensively to reveal information about their morphology, optical properties, phase composition, chemical states and electrochemical properties. Subsequently, the nanocomposite photocatalysts were investigated for their dual role of photooxidation of the emerging pollutant; norfloxacin (NFX) and photoreduction of the toxic heavy metal; Cr(VI) in spiked water samples. The photocatalytic activity of the nanocomposites was found to be dependent on the photocatalyst composition (ratio of In2S3:Yb2O3) and dose, contact time and initial concentration of the pollutant. Under optimised conditions, Cr(VI) reduction efficiency reached 96.4% in just 45 min of visible light irradiation and the degradation rate is 28.84 times and 3.90 times higher than that of Yb2O3 and In2S3, respectively. Equally, over 95.0% NFX degradation was achieved in 50 min, under optimal conditions. The enhanced activity is credited to efficient visible light absorption, remarkable charge separation and transfer, leading to increased lifetime of the photogenerated charge carriers. Moreover, the possible degradation route for NFX was crafted based GC-MS analysis. Finally, the photostability and recyclability of the composite photocatalyst was probed and a plausible charge transfer mechanism was proposed. This work demonstrates the effectiveness of the ultrasonication method for preparing binary nanostructures and the versatility of the photocatalysts towards detoxification of both organic and inorganic pollutants in water.