Sustainable fabrication of Cu-doped cadmium sulfide nanoparticles for detoxification of methyl blue dye from wastewater via adsorption and photocatalysis

This study reports the green, hydrothermally synthesized copper-doped cadmium sulfide nanoparticles (CdS: Cu) with remarkable tunability and efficiency for dye detoxification. Comprehensive characterization using FTIR, XRD, SEM, EDX, and UV–Vis spectroscopy confirmed the successful doping, revealing precise control over elemental composition, nanostructure, and surface morphology. Unlike conventional CdS materials with a restricted band gap of ~ 2.4–2.8 eV, our Cu-doping strategy enabled band gap modulation from 2.63 to 3.33 eV, accompanied by a clear blue shift in absorption (491 → 460 nm). This band gap engineering enhanced charge separation and improved photocatalytic activity. Under optimized conditions (2 mg catalyst, 10 μM dye, pH 11), the system achieved an impressive 96.76% photodegradation of methyl blue, significantly surpassing many reported efficiencies while requiring a substantially lower catalyst dose, ensuring cost-effectiveness and scalability. Kinetic analysis followed a pseudo-first-order model (k = 0.046 min⁻1), reinforcing the predictability of the process for large-scale applications. Importantly, the study addresses the toxic and non-biodegradable nature of methyl blue, whose industrial discharge poses greater challenges than methylene blue, making its detoxification highly valuable. Beyond demonstrating superior photocatalytic activity, the present work provides a sustainable route to wastewater remediation, bridging the gap between laboratory-scale research and industrial-scale implementation. The eco-friendly synthesis, coupled with enhanced reusability and stability of the catalyst, highlights its potential for commercial water treatment systems. Furthermore, the synergy between adsorption and photocatalysis makes this approach adaptable to diverse classes of pollutants, extending its application beyond synthetic dyes to other organic contaminants. Overall, these findings establish Cu-doped CdS nanoparticles as a next-generation, market-relevant photocatalyst, underscoring the critical role of band gap engineering, surface tailoring, and operational optimization in advancing green nanotechnology for environmental sustainability.