Visible light active N, S-Carbon quantum dots@FeVO4 nanocomposite as a photodegradation mechanism for wastewater treatment

Environmental remediation involves various strategies, such as degradation and related techniques to reduce the risks posed by chemical and radiological contaminants to human health and ecosystems. The use of nanomaterials in remediation provides advantages including enhanced efficiency, cost-effectiveness, and rapid pollutant breakdown. In this study, an innovative photocatalyst based on Iron Vanadate and Nitrogen and Sulfur co-doped carbon quantum dots (FeVO₄/N, S-CQDs) was synthesized via a hydrothermal route using varying concentrations of N, S-CQDs. Structural characterization using X-ray diffraction (XRD) confirmed the formation of a pure anorthic phase of FeVO₄ after calcination at 300 °C for 180 min, with no impurity peaks and a crystallite size of 29 nm. Photocatalytic activity was evaluated using Methylene Orange (MO) as a model dye under visible-light irradiation (λ ≥ 400 nm). The sample with 0.05 wt% N, S-CQDs showed the highest degradation efficiency, achieving up to 99 % dye removal. UV–Vis spectroscopy revealed over 80 % MO degradation using a small amount of catalyst, with kinetic analysis indicating a pseudo-first-order reaction. SEM analysis demonstrated a reduction in particle size from 4 µm to 200 nm with N, S-CQD incorporation, while EDX confirmed elemental composition. The nanocomposite also showed high reusability with negligible loss in photocatalytic activity. These findings indicate that FeVO₄/N, S-CQDs nanocomposites are effective, stable, and promising materials for the treatment of organic contaminants in industrial wastewater.