Theoretical Calculation on the Reaction Mechanisms, Kinetics and Toxicity of Acetaminophen Degradation Initiated by Hydroxyl and Sulfate Radicals in the Aqueous Phase

Abstract

The •OH and SO4•− play a vital role on degrading pharmaceutical contaminants in water. In this paper, theoretical calculations have been used to discuss the degradation mechanisms, kinetics and ecotoxicity of acetaminophen (AAP) initiated by •OH and SO4•−. Two significant reaction mechanisms of radical adduct formation (RAF) and formal hydrogen atom transfer (FHAT) were investigated deeply. The results showed that the RAF takes precedence over FHAT in both •OH and SO4•− with AAP reactions. The whole and branched rate constants were calculated in a suitable temperature range of 198–338 K and 1 atm by using the KiSThelP program. At 298 K and 1 atm, the total rate constants of •OH and SO4•− with AAP were 3.23 × 109 M−1 s−1 and 4.60 × 1010 M−1 s−1, respectively, considering the diffusion-limited effect. The chronic toxicity showed that the main degradation intermediates were harmless to three aquatic organism, namely, fish, daphnia, and green algae. From point of view of the acute toxicity, some degradation intermediates were still at harmful or toxic level. These results provide theoretical guidance on the practical degradation of AAP in the water.

HO● ‐ initiated oxidation of isoleucine amino acid in the aqueous phase

“…In the KiSThelP, the tunneling correction factor was determined by the Wigner correction, χ(T) [ 43,46,47 ] that was calculated based on the imaginary frequency lm( v ‡ ) of the transition states (TSs) as the following equation: [ 43 ] …”

“…The ∆G ‡ values of HT reactions were determined by the Gibbs energy differences between reactants and the transition state (TS), whereas Marcus's theory was applied to calculate ∆G ‡ of the SET reaction. [44,45] In the KiSThelP, the tunneling correction factor was determined by the Wigner correction, χ(T) [43,46,47] that was calculated based on the imaginary frequency lm(v ‡ ) of the transition states (TSs) as the following equation: [43] 𝜒(𝑇…”

Oxidation of l -leucine amino acid initiated by hydroxyl radical: are transition metal ions an enhancement factor?

“…In the KiSThelP, the Wigner correction, χ(T ), is applied to acquire the tunnelling correction factor for all the elementary reactions [33,36,37]. This factor was determined based on the imaginary frequency lm(v ‡ ) of the TSs as follows [33]:…”

“…In the KiSThelP, the Wigner correction, χ ( T ), is applied to acquire the tunnelling correction factor for all the elementary reactions [33,36,37]. This factor was determined based on the imaginary frequency lm( v ‡ ) of the TSs as follows [33]:χfalse(Tfalse)=1+true0124(h normallm(v‡)kbT).The rate of reaction was therefore calculated as the following equation:kfalse(Tfalse)=χfalse(Tfalse)×kTSTfalse(Tfalse).…”

A review on the degradation of acetaminophen by advanced oxidation process: pathway, by-products, biotoxicity, and density functional theory calculation

“…They revealed that ACT had a significant impact on the number of Lemna minor fronds (EC 50 = 446.6 mg L −1 ), but there was no effect on Lemna gibba . Xu et al 106 studied the acute and chronicle effects of ACT onto three different aquatic species (i) fish, (ii) green algae and (iii) daphnia. The acute toxicity values were LC 50 = 63.1 mg L −1 for daphnia and LC 50 = 323 mg L −1 for fish, and EC 50 = 26.3 mg L −1 .…”