Aqueous OH Radical Reaction Rate Constants for Organophosphorus Flame Retardants and Plasticizers: Experimental and Modeling Studies

摘要

Aqueous ·OH reaction rate constants ( k _(OH)) for organophosphate esters (OPEs) are essential for assessing their environmental fate and removal potential in advanced oxidation processes (AOPs). Herein experimental and in silico approaches were adopted to obtain k _(OH) values for a variety of OPEs. The determined k _(OH) for 18 OPEs varies from 4.0 × 10~(8) M~(–1) s~(–1) to 1.6 × 10~(10) M~(–1) s~(–1). Based on the experimental k _(OH) values, a quantitative structure–activity relationship model that involves molecular structural information on the number of heavy atoms, content index, and the most negative charge of C atoms was developed for predicting k _(OH) of other OPEs. Furthermore, appropriate density functional theory (DFT) and solvation models were selected, which together with transition state theory were employed to predict k _(OH) of three representative OPEs. The deviation between the DFT calculated and the experimental k _(OH) values ( k _(cal)/ k _(exp)) is within 2. Half-lives of the OPEs were estimated to be 0.5–22791.3 days in natural waters and 0.044–19.7 s in AOPs, indicating the OPEs are potentially persistent in natural waters and can be quickly eliminated by AOPs. The determined k _(OH) values and the in silico methods offer a scientific base for assessing OPEs fate in aquatic environments.