Study of Kinetics Mechanism of PAHs Photodegradation in Solution

As a typical group of persistent organic pollutants, polycyclic aromatic hydrocarbons (PAHs) are widely distributed and persistent in ecological environment via environmental media (e.g. air, soil, water, suspended solids, organisms, etc.), causing great damage to organisms. Its fate and transportation from surface water to aquifers has attracted more and more attention. As PAHs in surface water or in topsoil will undergo photochemical reactions, a self-designed cylindrical photodegradation reactor has been designed to study the photodegradation of PAHs in aqueous solutions in this study. The results have shown that PAHs degrade rapidly under the lighting conditions. Pseudo-first-order kinetics was observed for degradation of fluorene (FLU), phenanthrene (PHE) and pyrene (PYR), as indicated by linear relations between ln (C0/Ct) and time. The reaction kinetics constants of FLU, PHE and PYR were 0.031, 0.045, 0.017 min-1 respectively, and the photolysis half-lives of PAHs are only several minutes (FLU, 4.17min; PHE, 3.79min; PYR 4.77min). Their photolysis rates following the decreasing order PHE > FLU > PYR is due to their different absorption spectrum and peak values under the UV-light.