Multi-cycle performance and solar-driven degradation of crystal violet dye using ZnO integrated rGO photocatalyst

• Facile fabrication of Zinc oxide/reduced graphene oxide nanocomposites via chemical reduction method. • Utilization of advanced analytical tools e.g. XRD, SEM, & EDX for the characterization of ZnO-rGO nanocomposite. • Exploring photocatalytic efficacy of ZnO-rGO nanocomposite for the degradation of crystal dye. • Successive degradation of CV dye up to 98.3% by usage minute dosage 7.0 mg of ZnO/rGO nanocomposite. The present study reports the synthesis, characterization, and photocatalytic application of zinc oxide reduced graphene oxide (ZnO/rGO) nanocomposite for the effective degradation of crystal violet (CV), a tenacious organic dye commonly found in industrial wastewater. The nanocomposite was synthesized using a facile chemical method and broadly characterized to confirm its structural, morphological, and elemental properties. X-ray diffraction (XRD) analysis confirmed the hexagonal wurtzite structure of ZnO and the successful integration with rGO sheets. Scanning electron microscopy (SEM) showed a uniform distribution of ZnO nanoparticles over the crumpled surface of rGO, while energy-dispersive X-ray spectroscopy (EDX) confirmed the elemental configuration and purity of the nanocomposite. Photocatalytic degradation trials were conducted under sunlight using sodium borohydride (NaBH 4 ) as a proton source. The effects of catalyst dose and NaBH 4 volume on degradation efficacy were thoroughly examined. A maximum degradation of 98.3% was attained with 7.5 mg of ZnO/rGO and 45 µL of NaBH 4 under optimal environments. Kinetic studies showed that the degradation followed a pseudo-second-order model, signifying strong chemisorptive interactions. Stability trials demonstrated a gradual decline in activity over five successive cycles, with the efficiency reducing to 64%, indicating reasonable recyclability. The improved performance is attributed to the synergistic effect of ZnO photocatalytic activity and rGO excellent electron mobility, which minimizes recombination of photo-induced charge carriers. The findings confirm that the ZnO/rGO nanocomposite is a promising aspirant for eco-friendly, solar-driven wastewater treatment applications.