Soluble bioorganic substances from compost as photosensitizers for a sustainable homogeneous and heterogeneous photocatalysis

Abstract Soluble bioorganic substances (SBOs) are soluble macromolecular substances isolated from residual biomasses, featuring physical–chemical properties analogous to natural organic matter present in soils, in particular humic acids. SBO’s structure possesses different functionalities, able to chelate metal ions, as well as absorb light in the ultraviolet–visible (UV–vis) spectral interval, showing a certain photoactivity. These properties have been exploited for environmental purposes, in particular the photodegradation of aqueous pollutants. Herein, several examples of the photoactivity of different SBOs are reported, with a focus on the nature of the reactive species generated by SBO upon UV–vis irradiation. Due to their capability to form complexes with Fe(III), SBOs have been demonstrated to be interesting auxiliaries in photo-Fenton-like processes for the degradation of pollutants in aqueous solutions at near-neutral pH. A further development of SBO is their use in heterogeneous photocatalysis to favor the recovery and reuse of the photoactive agent. For this purpose, different materials have been synthesized, having an oxide core and a SBO shell. A detailed characterization of these materials is reported together with their performances in the photodegradation of organic pollutants.