Peroxy-Acid Treatment of Polycyclic Aromatic Hydrocarbons: Degradation Kinetics, Thermodynamics, and Predictive Modeling

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are potentially carcinogenic organic compounds that are persistent in the environment. The peroxy-acid treatment is an advanced oxidation process (AOP) that can effectively degrade recalcitrant organic compounds. In this study, the degradation of four PAH compounds (anthracene, benzo[a]pyrene, phenanthrene, and pyrene) with peroxy-acid treatment was investigated. For each compound, a pseudo-first order rate constant for the peroxy-acid treatment process was determined at three different temperatures (25°C, 32°C, and 40°C) over a 24-h period. Reactions took place in 35 mL centrifuge tubes with volume ratios of 3∶3∶9 (v/v/v) acetic acid/50% hydrogen peroxide/DI water, resulting in a total volume of 15 mL in each reaction vessel. As treatment progressed, the hydrogen peroxide and peracetic acid (PAA) in the solution decreased and increased, respectively. In decreasing order, the overall degradation efficiency using a peroxy-acid treatment was anthracene, benzo[a]pyrene, pyrene, and phenanthrene. The activation energy for the reaction scheme was 139.0 for anthracene, 83.1 for phenanthrene, 126.8 for pyrene, and 133.1 kJ mol−1 for benzo[a]pyrene. In addition, the relationship between the property-encoded surface translator (PEST) molecular descriptors and thermodynamic parameters was investigated. Highly-correlated, linear relationships were found, which can be used to estimate the reactivity of other PAHs using peroxy-acid as a treatment choice. Overall, the peroxy-acid treatment process proved to be effective in treating PAH compounds and achieved results comparable to other AOPs used for PAHs. The developed model based on experimental and computational molecular data can serve as a powerful predictive tool, which will decrease the time and need for expensive experimental work when using peroxy-acid as an AOP for PAHs. Further studies with other matrices (such as sediment and soil) and PAH compounds will strengthen the model and provide wider field application.