Green synthesized cerium oxide nanorods using Curcuma longa extract for response surface methodology-based photocatalytic degradation application

In this study, green fabrication of cerium oxide (CeO₂) nanoparticles (CNRs) was achieved by utilizing Curcuma longa extract. The fabricated CNRs were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-VIS), and Fourier transform infrared spectroscopy (FTIR). It was observed that the CNRs exhibited a rod-like morphology with a mean length and width of ∼13.1 nm and 4.9 nm (assessed via TEM micrograph), respectively. The presence of the characteristic diffraction peak of (111) in the XRD analysis also validated the successful fabrication of CNRs. The surface functionalization of the CNRs confirmed that several functional moieties were available on the surface of the CNRs, which enhances the application potential of the CNRs. The synthesized CNRs were utilized for performing the photocatalytic degradation (PD) of norfloxacin (NFX; antibiotic pollutant) by using the response surface methodology (RSM) technique. The reaction was analyzed by utilizing statistical key regressive parameters for the development of a reaction-specific central composite design (CCD)-based model. The CCD model was further tested and validated by using the analysis of variance (ANOVA), normal probability, actual vs predicted PD% value plots, etc. The diagnostics and validity revealed that the quadratic model (with a p-value of <0.0001 and an R² value of 0.9285) exhibited the best fit for representing the PD of NFX. The reaction was optimized considering several criteria. The degradation value of 92.31% was acquired using a CCD-based quadratic model with the optimized parameters of reaction time = 36.31 min, CNR dose = 39.56 mg L⁻¹, NFX dose = 54.52 ppm, and pH = 5.26. The current study underscores the significance of green methodologies for synthesizing morphology-specific nanomaterials and using RSM for analyzing the underlying reactions in detail.