Effective photocatalytic degradation of tetracycline antibiotic using novel TiO_2–slag nanocomposite: Optimization using response surface model

Numerous economically disadvantaged countries face substantial challenges in water purification due to the absence of centralized wastewater treatment systems. Consequently, this study investigates the optimal degradation of the antibiotic contaminant tetracycline from wastewater utilizing a TiO₂–slag nanocomposite synthesized via an ex situ method under simulated solar irradiation. The morphology and crystalline structure of the synthesized hybrid material were characterized through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FTIR) was employed to analyze the elemental composition and functional groups. To evaluate photocatalytic performance, a Box–Behnken design (BBD), integrated with response surface methodology, was used to determine the influence of three operational variables: pollutant concentration (20–40 ppm), catalyst loading (10–50 mg/L), and pH level (3–11), with a fixed reaction duration of 60 minutes. The experimental matrix, comprising 17 runs, was designed to capture the interactive effects among these variables on degradation efficiency. A reduced quadratic regression model was established, demonstrating strong predictive capability aligned with empirical results. The coefficient of determination (R²) values for the analysis of variance (ANOVA) were 0.99 and 0.98, indicating statistical significance (p < 0.05) of the proposed model.

Among the tested parameters, catalyst dosage emerged as the most influential factor, exerting a notable effect on the photocatalytic reaction, whereas the synergistic interaction between pollutant concentration and pH showed a positive contribution, culminating in a maximum degradation efficiency of 99.92%. Furthermore, an economic assessment revealed the treatment cost to be $0.9438 per cubic meter, signifying a cost-effective solution. These findings highlight the potential application of TiO₂–slag nanocomposites as an efficient and low-cost material for industrial wastewater remediation, thereby reducing dependence on expensive chemical reagents.