Photochemistry for pollution abatement
Sunlight is a clean, cheap, and abundant reagent. Many light-initiated reactions can be carried out in water, making photochemistry an ideal tool for pollution abatement and/or elimination. We studied the photoreactivity of different families of common organic micropollutants: light-initiated processes in the absence or presence of co-oxidants, and photocatalyzed reactions using different photocatalysts and composites. Based on the experimental evidences found, detailed transformation mechanisms have been proposed that help understand the reactivity of organic micropollutants and predict their environmental fate. Our approach includes the study of the photophysics for each family of compounds, its reactivity upon direct photolysis, adsorption onto photocatalysts, photocatalytic reactivity, thermodynamics, and kinetics of the processes involved (pKa, Eº, rate constants, etc.), product analysis, and ecotoxicological assessment. Different commonly overlooked problems, related to the kinetics of the process, are reported, and a model is proposed that includes the possibility of adsorption on different types of active sites, leading to different reactivities.