Optimization synthesis of carbon nanotubes-anatase TiO2 composite photocatalyst by response surface methodology for photocatalytic degradation of gaseous styrene

Abstract

In present study, the center composite design in response surface methodology (RSM) was firstly applied to optimize the synthesis of multi-wall carbon nanotubes (MWCNTs)–TiO2 composite photocatalyst. Twenty-eight composite photocatalysts were prepared by adjusting four operating parameters (amount of MWCNTs, amount of TiF4, hydrothermal temperature and hydrothermal time) at five levels by the method of multiple variable analysis. The structural, optical and morphological properties of the prepared composite photocatalysts were characterized by X-ray diffraction, UV–visible absorption spectra and scanning electron microscopy, respectively. Based on the experimental design, a semi-empirical expression was firstly established and subsequently applied to predict the photocatalytic degradation activity of the prepared composite photocatalysts to gaseous styrene in a cubic flow-through reactor. The results showed that the experimental photocatalytic degradation efficiencies using the differently prepared MWCNTs–TiO2 composite photocatalysts matched with the theoretically predicted values very well with a high correlation (R2=0.9790). Based on the theoretical and experimental results, the optimum synthesis parameters for the composite photocatalyst within the experimental ranges were 0.01g MWCNTs, 0.14g TiF4, and 120°C hydrothermally treated for 87.2h. The photocatalytic degradation efficiency of gaseous styrene using the MWCNTs–TiO2 composite photocatalyst synthesized under the optimum parameters reached 74.4%. All these demonstrates that the experimental design and theoretical prediction methods used in this work would have great significance in designing and developing high performance photocatalysts for environmental remediation and solar energy conversion.