Unveiling the fates of nitro-transformation products in advanced oxidation process: A DFT-based kinetic model

Abstract

Kinetic models are widely employed to investigate the reaction mechanisms and estimate kinetic parameters of advanced oxidation processes (AOPs), which are critical for assessing toxicity variations in these processes. However, conventional models often oversimplify the kinetics related to transformation products (TPs) due to the complex reactions involved in AOPs. Consequently, predicting the concentration profiles of TPs in conventional kinetic models is challenging. In this study, we aimed to overcome this challenge by developing a novel kinetic model that enriches the TPs-related elementary reactions in AOPs. Specifically, we mapped the entire reaction pathways from parent organic compounds through various intermediates to their TPs using density functional theory (DFT). We investigated the formation of nitro-TPs of phenolics, such as salicylic acid, hydroxybenzoic acid, phenol and 4-chlorophenol in sulfated radical-based AOPs in the presence of NO2−. The predicted concentrations of nitro-TPs obtained from our model exhibited a close match with those reported in previous research, thus confirming the accuracy of our predictions. Our research highlights the effectiveness of combining DFT and kinetic modeling, which facilitates a streamlined understanding of the mechanisms governing TP formation and decay in AOPs. This approach holds the potential to advance our comprehension of these complex reactions and may be beneficial in future studies of similar reactions.