Photodegradation of Phenol by Silver Doped TiO2; A Comparative Study of the Efficiency of HPLC and UV-Vis Analyses

Abstract

The formation of colored intermediate compounds during photocatalytic degradation of phenol represents the risk of single-handedly employing ultraviolet visible (UV-Vis) spectrophotometry for the determination of residual phenol concentration. Moreover, the widely used titania (TiO2) photocatalyst is hindered by the high recombination rate of electron-hole pairs. In this study, phenol was photodegraded in the presence of sol gel synthesized TiO2 and silver doped titania (Ag-TiO2), under UV illumination. Spectrophotometric determination of residual phenol concentration was done using high performance liquid chromatography (HPLC) and UV-Vis spectrophotometry. Scanning electron microscopy-energy-dispersive X-ray (SEM-EDX) and Fourier transform infrared (FTIR) spectroscopies revealed the successful introduction of the Ag dopant into the TiO2 lattice. The UV-Vis and photoluminescence (PL) spectroscopic analyses revealed restrained electron hole-pair recombination and reduced energy bandgap in Ag-TiO2. Ag-TiO2 showed better photocatalytic efficiency than TiO2, in line with the observed optical properties. Optimal conditions of 3% dopant loading, initial pH of 4 and catalyst loading of 1 g/L were determined for the degradation process. Formation of colored intermediates resulted in higher analytical values for residual phenol obtained from UV-Vis as compared to those obtained from HPLC analyses. For high affirmation of the reproducibility of photodegradation results, UV-Vis spectrophotometry should, therefore, be employed alongside other analytical techniques.