Utilisation of lignin as a model biomass component for preparing a highly active photocatalyst under UV and visible light

Lignin-based carbonaceous material (LBC) with graphitic/semi-graphitic skeleton and oxygenated surface functionalities was prepared by hydrothermal carbonization (HTC) method. Thanks to these properties, LBC becomes a strong candidate as a semiconductor support in photocatalytic applications. In this study, LBC was used as a support material for widely known photocatalyst TiO2 and results showed that a chemical interaction occurred between carboxyl groups of LBC and metallic center of TiO2. TiO2 nanoparticles were also synthesized by the hydrothermal method without LBC support (s-TiO2). Effects of LBC- TiO2, s-TiO2 and commercial TiO2 (c-TiO2) on the removal of methylene blue (MB) as a cationic dye and phenol were compared under different irradiations (UVA and visible light). X-ray photoelectron (XPS), Brunauer–Emmett–Teller (BET), UV–Vis diffuse reflectance (UV-DRS) and raman spectroscopy techniques, as well as x-ray diffraction (XRD), scanning electron microscopy energy dispersive spectrometry (SEM-EDX) mapping and scanning and high resulation transmission electron microscopy (HRTEM) analyses, were performed in order to collect valuable information about the material. LBC-TiO2 presented superior apparent first-order rate constants for MB and phenol removal than those obtained on c-TiO2 and s-TiO2 under visible light. It can be concluded that the photocatalytic performance of LBC-TiO2 was definitely higher than that of bare and commercial TiO2 thanks to sensitization and activation effect of LBC. This study reports an economical and environmentally friendly alternative for preparing catalyst supports from lignin.