Optimization of Methyl Orange Removal from Aqueous Solutions Using Sol–Gel Synthesized TiO2-ZnO Nanophotocatalyst: Application of Response Surface Methodology (RSM)

Shahsavari, Sajad; Shafeeyan, Mohammad Saleh

doi:10.22112/jwwse.2026.540204.1459

Optimization of Methyl Orange Removal from Aqueous Solutions Using Sol–Gel Synthesized TiO₂-ZnO Nanophotocatalyst: Application of Response Surface Methodology (RSM)

Document Type : Original Article

Authors

Sajad Shahsavari ¹

Mohammad Saleh Shafeeyan ²

¹ M.Sc., Department of Chemical Engineering, Faculty of Engineering, Golestan University, Aliabad Katoul, Iran.

² Assistant Professor, Department of Chemical Engineering, Faculty of Engineering, Golestan University, Aliabad Katoul, Iran.

10.22112/jwwse.2026.540204.1459

Abstract

In this study, TiO₂–ZnO nanocomposites were synthesized via the sol–gel method in three different weight ratios (1:3, 1:1, and 3:1) to enhance their photocatalytic performance. The synthesized nanocomposites were thoroughly characterized using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), and UV–Vis spectroscopy to evaluate their crystal structure, surface morphology, functional groups, optical band gap, and light absorption characteristics. The photocatalytic activity of the nanocomposites was investigated for the degradation of Methyl Orange (MO) dye in aqueous solution under Ultraviolet (UV) irradiation. Experimental design and statistical modeling were performed using Response Surface Methodology (RSM) based on Central Composite Design (CCD). The four input variables were varied within defined ranges, including UV light intensity (6-18 W), initial dye concentration (10-30 ppm), reaction time (0.2-5.5 hr), and catalyst dosage (0.1-1.9 g/L), and were used to develop the predictive regression model. The degradation of MO occurred predominantly through photocatalytic oxidation by the TiO₂–ZnO nanocomposite, and the pH of all experiments was maintained at a constant value of 4. Analysis of variance (ANOVA) confirmed the statistical significance and robustness of the developed quadratic regression model, with a high coefficient of determination (R² > 0.99) and a p-value below 0.0001, indicating excellent predictive capability and model accuracy. The optimal conditions for achieving the maximum dye removal efficiency of 96.36% were determined to be an initial dye concentration of 13.68 ppm, UVA irradiation at 17.55 W, a reaction time of 2.37 hr, and a catalyst dosage of 0.62 g/L. Enhanced light absorption in the UV region compared to individual TiO₂ or ZnO nanoparticles demonstrated the superior photocatalytic performance of the synthesized TiO₂-ZnO nanocomposite in degrading the target organic pollutant.

Keywords

Nanophotocatalyst

Sol-Gel

TiO₂

ZnO

Methyl Orange

Response Surface Methodology (RSM)

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