Visible-light-driven Photocatalytic Degradation of Erythrosine using Carbon-doped SnO₂ Quantum Dots
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Abstract
Persistent organic pollutants, particularly synthetic dyes, pose a significant environmental challenge due to their chemical stability, resistance to biodegradation, and potential toxicity. Conventional wastewater treatment methods often fail to achieve complete removal of such contaminants, necessitating the development of more efficient and sustainable approaches. In the present study, carbon-doped SnO₂ quantum dots were synthesised via a hydrothermal method and evaluated as photocatalysts for the visible-light-driven degradation of erythrosine. The synthesised materials were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, high-resolution transmission electron microscopy, and UV–visible spectroscopy, confirming the formation of SnO₂ quantum dots with successful carbon incorporation and reduced band gap. Photocatalytic activity was assessed by monitoring the degradation of erythrosine under visible-light irradiation, and the influence of key operational parameters, including solution pH, dye concentration, catalyst loading, and light intensity, was systematically investigated. The results demonstrated that the degradation process follows pseudo-first-order kinetics and is strongly dependent on experimental conditions, with optimal performance observed under near-neutral pH and specific catalyst and light intensity ranges. Carbon doping significantly enhanced the photocatalytic efficiency compared to undoped SnO₂ QDs, which is attributed to improved light absorption and charge carrier dynamics. A tentative mechanism involving reactive oxygen species, particularly hydroxyl radicals, is proposed based on experimental observations. These findings highlight the potential of carbon-doped SnO₂ quantum dots as effective photocatalysts for dye degradation under visible light and provide insights into the optimisation of photocatalytic processes for wastewater treatment applications.
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