Degradation of Diethyl Phthalate by HO• and SO4•-in the Aqueous Phase: Mechanisms, Kinetics, and Toxicity

The chemical degradation processes of diethyl phthalate (DEP) induced by HO center dot and SO4 center dot- in aqueous solution were studied in a theoretical way. Not only radical addition and H-abstraction reactions but also single-electron transfer processes of DEP were considered. The thermodynamic and kinetic results indicate that the more favorable pathways are the H abstraction occurring in aliphatic side chains for all HO center dot/SO4 center dot--initiated degradation reactions of DEP. Subsequent reaction mechanisms of crucial primary intermediates were taken into account. At 298 K, the total rate constants for DEP degradation reactions induced by HO center dot and SO4 center dot- are 2.34 x 10(9) and 1.24 x 10(8) M-1 s(-1), respectively. They are in accordance with the experimental data. In comparison to SO4 center dot-, HO center dot has higher reactivity toward DEP in the research temperature range of 273-303 K. Considering the impact on the water eco-environment and human health, DEP and its 10 products have no bioaccumulation potential, but most products are developmentally toxic, except for (Z)-ethyl-2,5-dioxopent-3-enoate. Moreover, (Z)-ethyl-2,5-dioxopent-3-enoate is acutely toxic to fish; phthalic acid is mutagenicity positive; and we should pay more attention to them in the future.

Automated summary

In this study, the chemical degradation processes of diethyl phthalate (DEP) induced by HO· and SO4·- were investigated in aqueous solution. The results showed that the H abstraction occurring in aliphatic side chains was the most favorable pathway for all HO·/SO4·--initiated degradation reactions of DEP. The rate constants for DEP degradation reactions induced by HO· and SO4·- were 2.34 x 10(9) and 1.24 x 10(8) M-1 s(-1), respectively, at 298 K. HO· exhibited higher reactivity toward DEP compared to SO4·-. DEP and its products showed no bioaccumulation potential but most of them were developmentally toxic, except for (Z)-ethyl-2,5-dioxopent-3-enoate. Moreover, (Z)-ethyl-2,5-dioxopent-3-enoate was acutely toxic to fish and phthalic acid was mutagenicity positive. These findings highlight the importance of further research in this area.