Use of soluble bio-based substances isolated from urban biowastes as organic photocatalysts for the degradation of 4-chlorophenol

Natural organic matter (NOM) present in terrestrial waters and soil is known to contain light-absorbing species capable of promoting photochemical reactions that are considered as the major abiotic pathway for the removal of xenobiotics from natural waters. Recently it has been shown that soluble bio-based substances (SBO) isolated from urban biowastes (UBW) have similar chemical composition and photosensitizing properties as NOM. Since SBO may be obtained from easily available cost-effective sources, their performances as organic photocatalysts have been recently considered and encouraging results have been obtained. Moreover the use of urban wastes as source of bio-based photocatalysts is rather appealing in the context of the current issues of waste management. The present work aims to optimize the photodegradation promoted by SBO of 4-chlorophenol, a priority toxic and hardly biodegradable pollutant. Many aspects of the process have been investigated at the laboratory scale using simulated solar light: the effect of SBO concentration, the operative pH, the degradation mechanism, the main reactive species involved and the toxicity evolution. Moreover the effect of added hydrogen peroxide on 4-chlorophenol degradation rate has been considered, since the presence of iron inside SBO structure let envisage synergistic Fenton-like processes; at this purpose design of experiments (DOE) was choosen as methodologic approach to evaluate the influence of irradiation wavelength, hydrogen peroxide, substrate and SBO concentration on the degradation of 4-chlorophenol. Finally the potential of the SBO-based photochemical process to be feasibly scaled up has been evaluated using a pilot plant working under real sunlight irradiation.