Semiconductor assisted photodegradation of humic acid using Fe doped TiO2

Abstract

The main objective of this research is to investigate the effect of Fe doping on TiO2 on the photocatalytic degradation of humic acid and its molecular size fractions in aqueous medium in comparison to the use of bare TiO2. The photocatalytic oxidation of humic acid was carried out using bare TiO2 and Fe doped TiO2 as the photocatalyst. The degradation kinetics was assessed based on pseudo first order. Adsorption experiments were conducted to elucidate the surface interactions of the molecular size fractions of humic acid solutions onto oxide surfaces. Bare TiO2 and Fe doped TiO2 in the range of 0.1-1.0 mg mL-1 were used as adsorbents. The adsorption experiments were also evaluated by using appropriate adsorption isotherms. The photocatalytic and adsorption experiments were carried out using various molecular size fractions, namely raw, 0.45 μm filtered fraction, 100 kDa fraction, and 30 kDa fraction of humic acid solution in the presence of bare TiO2 and Fe doped TiO2. The results of adsorption experiments were evaluated using appropriate adsorption isotherms. The spectroscopic properties of each size fraction were characterized and compared by UV-vis spectroscopy and fluorescence spectroscopy in emission and synchronous scan modes. UV-vis spectra recorded for all of the samples displayed a consistent basic declining pattern irrespective of the irradiation period and photocatalyst type. On the other hand, fluorescence spectral profiles exhibited different patterns with respect to both irradiation time and photocatalyst type. Therefore, UV-vis parameters could be used for kinetic evaluation of the photocatalytic degradation of the humic acid and its molecular size fractions whereas fluorescence spectra could only bring a qualitative basis for comparison.