Application of response surface methodology for optimization of operational variables in photodegradation of aqueous styrene under visible light

Abstract

In this study, the center composite design in response surface methodology was firstly applied to optimize the photocatalytic degradation of aqueous styrene under visible light. Twenty experiments were done by adjusting three parameters (initial concentration of styrene, concentration of catalyst and initial pH of reaction mixture) at five levels by the method of multiple variable analyses. Based on the experimental design, an empirical expression was firstly established and subsequently applied to predict the photocatalytic degradation efficiency of aqueous styrene under visible light. The results showed that the experimental photocatalytic degradation efficiencies are in accordance with the theoretically predicted values very well with a high correlation. The strongest interaction between the parameters assessed was concentration of catalyst /initial pH of mixture. Optimal experimental conditions for arbitrary aqueous styrene concentration of 115 mg L⁻¹ were found initial pH 6.8 and catalyst loading 2 g L⁻¹. The photocatalytic degradation efficiency of aqueous styrene under this condition reached to about 84%. Furthermore, the main degradation intermediate produced in this process was identified by GC/MS technique. The photocatalytic mineralization of styrene in aqueous solution has been studied by TOC.

Keywords:

• Aqueous styrene
• Photocatalytic degradation
• Visible light
• Design of experiment

Acknowledgement

This project was financially supported by Chemical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Iran. Narjes Keramati is grateful to this University for fundamental research fund. The use of the analytical instrument of university is also acknowledged.