EVALUATION OF REDOX-ACTIVE TiO2-BASED HYBRID MATERIALS IN THE TREATMENT OF AQUEOUS PHASE FROM HYDROTHERMAL LIQUEFACTION

Metal oxide semiconductors play a central role in the generation of reactive oxygen species (ROS) for the degradation of water contaminants. ROS can be produced at metal oxide surfaces either through photocatalysis, upon energy-intensive pre-treatments, or in the presence of a radical source. Hybrid materials based on TiO2 or ZrO2 coordinated with specific organic ligands can spontaneously generate superoxide radicals (O2•−) and preserve them on their surface owing to the formation of ligand-to-metal charge transfer complexes. The consequent oxidative ability of these materials enables the degradation of various organic pollutants in water without the aid of any light irradiation. Moreover, the visible light absorption of TiO2-β-diketone hybrids allows for the increase of the reaction rate under sunlight. Recently, it was also shown that rosin, mainly composed of abietic acid, can form active complexes with titanium oxide and promote the partial degradation of polyethylene-based microplastics. Here, the possible application of this kind of hybrid materials in the purification of aqueous solutions derived from the hydrothermal liquefaction (HTL) of sewage sludge is proposed. HTL is a thermochemical process able to convert sludges from wastewater treatment plants into bio-oil, suitable for the production of biofuels.