Utilization of biomass waste derived carbon quantum dots intercalated ZnO for effective photocatalytic degradation of methylene blue

Abstract

This study investigates the photocatalytic degradation of methylene blue (MB) dye using a novel ZnO/shrimp shell-derived carbon quantum dots (SS-CQDs) composite under UV light irradiation. The ZnO, SS-CQDs, and their composite were synthesized via a hydrothermal process and extensively characterized through X-ray diffraction (XRD), UV–visible spectroscopy (UV–Vis), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), elemental mapping, transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. TEM analysis provided detailed insights into the morphology and particle size of the composite, confirming the uniform distribution of SS-CQDs on the ZnO surface. The incorporation of SS-CQDs into the ZnO matrix was found to reduce the composite's band gap, significantly enhancing its photocatalytic activity. Using a low catalyst dosage of 20 mg in a 10 ppm MB solution, the ZnO/SS-CQDs composite demonstrated a remarkable degradation efficiency of 94 % within 90 min under UV light irradiation, following a pseudo-first-order kinetic model equation with a rate constant of K = 0.0278 min −1 . These findings highlight the potential of the ZnO/SS-CQDs composite as an efficient and sustainable material for photocatalytic dye degradation, offering a promising solution for environmental remediation and wastewater treatment. • Synthesis of novel ZnO/Shrimp Shell Carbon Quantum Dots (SS-CQDs) composite. • CQDs enhances photocatalytic efficiency, offering potential for novel materials discovery. • SS-CQDs reduces composite's band gap, enhancing photocatalytic activity. • Low catalyst dosage (20 mg) of ZnO/SS-CQDs achieves 94 % degradation of dye. • Degradation kinetics follow a pseudo-first-order model with rate constant of k = 0.0278 min −1 .

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