Comparative study of zirconium phosphate nanoparticles synthesized by two methods and optimization of methylene blue photocatalytic degradation using Response Surface Methodology

Water quality represents a key concern in the management of available water resources, particularly in relation to the presence of persistent organic contaminants. Among advanced treatment technologies, photocatalysis has attracted considerable attention due to its efficiency, sustainability, and environmental compatibility for degrading pollutants in aqueous systems. In this work, zirconium phosphate materials were synthesized via two distinct preparation routes, and the resulting samples were designated as ZPR and ZPC depending on the synthesis method. The structural, morphological, and physicochemical properties of the obtained catalysts were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) surface area measurements, UV–visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the prepared materials was evaluated through the degradation of methylene blue (MB) in aqueous solution under UV irradiation. To optimize the process parameters, Response Surface Methodology (RSM) based on a Box–Behnken design (BBD) was applied, considering the effects of pH, catalyst dosage, and irradiation time. Statistical analysis using ANOVA at a 95% confidence level was used to determine the significance of each factor. The optimization results indicated that the highest degradation efficiency was achieved under alkaline conditions, with an optimal pH of 11, a catalyst dosage of 1.3 g/L, and an irradiation time of 120 min, leading to a maximum removal efficiency of 96%. Finally, reactive species involved in the photocatalytic mechanism were identified, and a plausible degradation pathway was proposed.