Degradation of tris-(2-chloroisopropyl) phosphate initiated by OH and ClO radicals in environment: Mechanisms, kinetics, toxicity and molecular design of substitutes.

Organophosphorus flame retardants (OPFRs) are used widely in industry and chemicals. As one of the representative OPFRs, tris-(2-chloroisopropyl) phosphate (TCIPP) has been detected in the atmospheric and water environment. To remove from environment and reduce the harm to ecosystem, the degradation of TCIPP in the atmosphere and water was investigated using quantum chemical methods. Result showed that in the presence of OH radicals the dominant channel of TCIPP is the H-abstraction with barriers less than 25 kJ/mol in the atmosphere and 34 kJ/mol in water. Subsequent reactions of the main degradation products with NO and O were revealed to assess the environmental chemistry of TCIPP. At 298 K, the total reaction rate constant for TCIPP with OH radicals is 5.07 × 10 cm/(molecule·s) in atmosphere and 3.03 × 10 (M·s) in water, respectively. Therefore, the atmospheric lifetime was estimated to be 0.55 h, and the half-life in wastewater with advanced oxidation processes was estimated to be 0.23-2.29 s. The H-abstraction channels for TCIPP degradation initiated by ClO radicals were studied, as well. The energy barriers are much higher than those with OH radicals, indicating that OH radicals show stronger oxidation capacity than ClO radicals to TCIPP. The ecotoxicity simulation for three aquatic organisms indicates that the acute and chronic toxicity of TCIPP decreases during degradation. Finally, substitutes were designed by introducing nitrogen atoms into TCIPP, and the reaction mechanism and toxicity of the new molecules were predicted to assess its environmental effect.