Optimization of AC/TiO₂-Cu ternary composite preparation with enhanced UV light activity for adsorption–photodegradation of metronidazole via RSM-CCD

Abstract

In this study, a statistical optimization design experiment was conducted using a face-centered central composite design-response surface methodology for the preparation of AC/TiO₂-Cu ternary composite photocatalysts. The influence of preparation variables such as AC/TiO₂ ratio (A = 0.1–0.5), Cu dosage (B = 0.1–0.5 g), irradiation power (C = 400–800 Watts), and irradiation time (D = 10–20 minutes) on the removal efficiency of Metronidazole (MZ) was investigated. From ANOVA analysis, the findings show 89.0% removal of MZ at the optimum preparation variables of A = 0.49, $B$= 0.34 g, C = 482 W, and $D$= 13 minutes. The regression analysis with an R² value of 0.9907 indicates good agreement between the experimental results and the predictive values. Further studies on isotherms and kinetics were well described by the Langmuir model and pseudo second-order model, respectively. The synergetic mechanisms for the adsorption–photodegradation included three possible interactions (electrostatic attractions, π–π stacking interaction, and n–π stacking interactions) and the photogenerated electron-hole pair. From the radicals quenching test, hydroxyl radical (•OH) was found to be the most active radical for the removal of MZ. AC/TiO₂-Cu ternary composite photocatalyst could be preserved up to five consecutive cycles with minor losses in removal (<9%). The results of this study show that the prepared AC/TiO₂-Cu ternary composite photocatalyst substantially enhanced the adsorption–photodegradation of MZ removal in an aqueous solution under UV light irradiation.

Graphical Abstract

Keywords:

• AC/TiO₂-Cu
• adsorption–photodegradation
• RSM-CCD
• metronidazole (MZ)

Funding

The author would like to acknowledge the support from the Fundamental Research Grant Scheme (FRGS) under a grant number of FRGS/1/2019/STG07/UNIMAP/02/2 from the Ministry of Higher Education Malaysia.