Synthesis and characterization of nitrogen-doped TiO₂/AC composite for the adsorption-photocatalytic degradation of aqueous bisphenol-A using solar light

A photocatalytic composite, namely nitrogen-doped titanium dioxide supported on activated carbon, or N-TiO₂/AC, was synthesized using the sol-gel method. This composite was characterized using X-ray diffraction (XRD), N₂ adsorption-desorption isotherm, UV-vis spectrophotometry, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The titania was found to consist predominantly of anatase. The AC-supported N-TiO₂ had a smaller average crystallite size (ca. 5.0 nm) as compared to the unsupported N-TiO₂ (ca. 5.4 nm). XPS revealed that interstitial nitrogen doping occurred in N-TiO₂ and N-TiO₂/AC. Observations under TEM revealed that N-TiO₂ nanocrystals were anchored on the surface of the AC. The dual-functionality properties of N-TiO₂/AC were evaluated using bisphenol-A (BPA) as the target pollutant in the aqueous phase. The effect of pH and influence of excitation wavelengths were investigated. Inhibition of BPA adsorption occurred at pH 11.0, thus resulted in slower kinetics of BPA photodegradation. N-TiO₂/AC was found to be photoresponsive under visible-light (420-630 nm) illumination.