Photoinduced transformation of waste-derived soluble bio-based substances

Abstract

Waste-derived, soluble bio-based substances (SBO), are effective low-cost photosensitizers that couldfind application in pollutant photodegradation. For this reason, it is important to understand if and towhat extent irradiation could modify their properties. The exposure of SBO to simulated sunlight inducedimportant spectral and structural modifications. Both the whole material and its acid-soluble fractionwere characterized, highlighting several properties in common with humic and fulvic substances, includingabsorption spectra, specific absorbance and fluorescence behavior. The latter was described with athree-component model using PARAFAC analysis. Irradiation induced SBO photobleaching, but the absorbanceof the acid-soluble fraction increased with irradiation. This finding suggests a progressivephotochemical solubilization of SBO, which is confirmed by the increase of the carboxylic groups. In additionto absorbance, the fluorescence of whole SBO was also decreased by irradiation, thereby suggestingthat both chromophores and fluorophores were photodegraded. The increasingly hydrophilic charactergiven to SBO by irradiation also accounted for the photoinduced decrease of the surfactant propertiesof the material.