From Biomass Residues to Titania Coated Carbonaceous Photocatalysts: A Comparative Analysis of Different Preparation Routes for Water Treatment Application

This paper investigates on the sustainable ways of associating activated carbon (AC) and titania (TiO₂) into a single material capable of both adsorbing and degrading micropollutants in aqueous solution under UV light. Three main preparation routes were carried out, based on the thermochemical conversion of shea nut shell, an abundant and cost free tropical biomass. N₂ adsorption desorption at 77 K, X-ray diffraction spectroscopy, scanning electron microscopy and energy dispersive spectroscopy were used to assess how each specific preparation route shapes the textural and structural properties of the resulting catalysts. Catalysts obtained from AC impregnation with preformed titania nanoparticles sol (CAT/S) exhibited a regular deposition of TiO₂ nanoparticles in the readily irradiated external macropores providing them with the best performances on phenol photomineralization. Pyrolysis of biomass impregnated with TiO₂ nanoparticles sol leads to catalysts (CAT/SB) with large agglomerates embedded within the AC structure. The third category of catalysts (CAT/G) obtained from the in situ generation of TiO₂ nanoparticles within a titania gel impregnated AC presented a degraded porosity-surface area network, which seems to explain their poor photoactivity. The performances of CAT/S catalysts are maintained after three successive reutilizations and suggest their stability and self regeneration capacity.