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

Abstract

Aqueous ·OH reaction rate constants ( k) 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 values for a variety of OPEs. The determined k for 18 OPEs varies from 4.0 × 10 M s to 1.6 × 10 M s. Based on the experimental k 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 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 of three representative OPEs. The deviation between the DFT calculated and the experimental k values ( k/ k) 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 values and the in silico methods offer a scientific base for assessing OPEs fate in aquatic environments.

Mass defect filtering for suspect screening of halogenated environmental chemicals: A case study of chlorinated organophosphate flame retardants

“…In natural waters ˙OH free radicals are generated by sunlight‐dependent reactions of dissolved organic matter with anions and transition metal complexes and by sunlight‐independent oxidation reactions of reduced dissolved organic matter and iron . The ˙OH reactions are also expected to be key to assessing the transformation of OPFRs in aquatic environments and to designing advanced oxidation processes for their removal . However, all the reagents and solvents used in this study being of HPLC‐grade and us carrying out the reactions at neutral pH, there are no ready explanations that suggest the occurrence of a cation‐catalyzed redox cycle and the formation of ˙OH free radicals in the experimental solutions.…”

“…[67][68][69][70] The˙OH reactions are also expected to be key to assessing the transformation of OPFRs in aquatic environments and to designing advanced oxidation processes for their removal. 71…”

Dissolved Organophosphate Esters and Polybrominated Diphenyl Ethers in Remote Marine Environments: Arctic Surface Water Distributions and Net Transport through Fram Strait

“…3,23,29 This was expected, as alkyl/aryl-OPEs are more readily degradable than Cl-OPEs by indirect photolysis and/or hydrolysis. [30][31][32][33] Additionally, Sühring et al noted that Cl-OPEs may be more effectively transported via ocean currents, while alkyl/aryl-OPEs are transported primarily through the atmosphere. 3 More effective waterborne transport of Cl-OPEs could also help explain the predominance of Cl-OPEs in deep-water samples.…”

Photodegradation of micropollutants in water by UV/H2O2 and UV/persulfate

“…IC3 refers to the information content index (neighborhood symmetry of 3-order). It is also a structural measurement of the complexity per vertex, as determined by the pairwise equivalent atoms in an H-filled molecule (Li et al, 2018). MLogP refers to the Moriguchi octanol-water partition coefficient.…”

“…The descriptor nHM refers to the number of heavy atoms. The heavy atoms (such as phosphorus, sulfur, and halogen atoms) can cause electron-donating/withdrawing effect that influence the reactivity of the radical (Li et al, 2018;Ye et al, 2017a). HLG, namely…”