Preparation of carbon-sensitized and Fe–Er codoped TiO2 with response surface methodology for bisphenol A photocatalytic degradation under visible-light irradiation

Abstract

The carbon-sensitized and Fe–Er codoped TiO2 (Fe/Er–TiO2) was synthesized by a facile solvothermal method using titanium isopropoxide both as titanium precursor and carbon source, as well as ferric nitrate and erbium nitrate as dopants source. The response surface methodology (RSM) with central composite design (CCD) model was used to obtain the optimum synthesis conditions for this novel Fe/Er–TiO2. The RSM was also applied to study the main and interactive effects of the parameters (Er concentration [Er], Fe concentration [Fe] and calcination temperature [CT]) investigated. The experimental results indicated an improved photocatalytic activity of Fe/Er–TiO2 for bisphenol A (BPA) degradation compared to the pristine TiO2, Er–TiO2, Fe–TiO2 and Degussa P25 (P25) under visible light irradiation. In addition, the RSM model obtained (R2=0.929) showed a satisfactory correlation between the experimental results and predicted values of BPA removal efficiency. The identified optimum condition for preparing Fe/Er–TiO2 was 1.5mol%, 1.25mol% and 450°C for [Er], [Fe] and [CT], respectively. Moreover, the photocatalytic activity of the optimized Fe/Er–TiO2 was preserved effectively even after ten cycles of use. The possible photocatalytic mechanisms induced by the Fe/Er–TiO2 under visible light irradiation are proposed. The enhanced photocatalytic activity of Fe/Er–TiO2 can be attributed to the synergistic effects of photosensitizing (CO band), narrowed band gap and enhanced e−/h+ separation (Ti–O–Fe linkage), and upconversion luminescence property (Ti–O–Er linkage).