Photocatalytic degradation of indole–4-methylphenol mixture in an aqueous solution: optimization and statistical analysis

Abstract

The photocatalytic degradation of indole and 4-methylphenol mixture, using ZnO, was studied. The optimal conditions for the degradation were determined using response surface methodology. We showed that in, our experimental domain, the quasi-complete degradation of the mixture’s organic constituents is possible. Moreover, we note that the effects of the entire variables are not linear. Indeed, the optimum removal conditions were determined. Thus, the optimal conditions for indole degradation were 1.5 mg/L catalyst concentration, 2.5 L/min airflow, and 7.16 pH. For 4-methylphenol, they were 1.37 mg/L of catalyst concentration, 2.38 L/min airflow, and 6.96 pH. Under optimized conditions, the complete photocatalytic degradation was obtained at 30 μL/L 4-methylphenol and 10 mg/L indole concentration. Similarly, the optimized correlation coefficients R² and for a quadratic model was satisfactorily evaluated as 99.5 and 99.1%, respectively with indole and 99.7 and 99.4%, respectively, with 4-methylphenol. Our results reveal that the tested ZnO photocatalyst can be employed as a powerful tool for the pollutant degradation in wastewater.

Keywords:

• Photocatalysis
• ZnO
• Quadratic model
• Indole
• 4-methylphenol
• Water treatment

Acknowledgment

One of the authors (S.M.) thanks the University of Bejaia (Algeria) for financial support.