Photocatalytic degradation of alachlor by TiO₂ nanoparticles from aqueous solutions under UV radiation

This study aimed to synthesise TiO2 nanoparticles (NPs) in pure rutile structure at moderate temperature without calcination and use them as the catalyst for alachlor removal under UV-C radiation. The crystal structure, composition, and particle size of the synthesised TiO2 NPs were analysed using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). The XRD spectra revealed the production of pure rutile TiO2. The individual and interactive effects of initial alachlor concentration (15–75 mg/L), TiO2 concentration (25–125 mg/L), pH (3–11), temperature (20–40 °C) and reaction time (15–75 min) on alachlor removal were investigated using the central composite design model based on the response surface methodology for experimental design, modelling and process optimization. The analysis of variance and multiple linear regression showed a good fit of the experimental data to the second-order polynomial model, with a coefficient of determination (R2) value of 0.8176 and a model F-value of 19.55975, implying that the model was significant. The results showed that decrease in pH and the initial alachlor concentration and increase in TiO2 concentration resulted in an increase in alachlor removal rate. The maximum rate of alachlor removal (98.44%) at optimum conditions occurred at pH = 5, alachlor = 30 mg/L, TiO2=100 mg, temperature = 35 °C and reaction time = 60 min.