Carbon dioxide radical anion mediated dehalogenation kinetics and mechanisms of halogenated alkanes,Water Research

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Carbon dioxide radical anion mediated dehalogenation kinetics and mechanisms of halogenated alkanes
Water Research ( IF 11.4 ) Pub Date : 2024-05-23 , DOI: 10.1016/j.watres.2024.121799
Xinran Zhang ₁ , Rui Zhang ₂ , Pengfei Ren ₃ , Jianhua Zhou ₃ , Weiguang Li ₄ , Xin Yang ₂

Affiliation

Carbon dioxide radical anion (CO2•−) recently becomes appreciated in halogenated contaminants elimination; nevertheless, its application has been restricted by insufficient mechanistic understanding. Herein, we provided a quantitative insight into the kinetics and mechanisms of CO2•− mediated dehalogenation of halogenated alkanes. A CO2•− dominated UV254/H2O2/HCOO− system has been successfully established and demonstrated for effective elimination of 7 kinds of halogenated alkanes (71.3 % to 100 % of removal). Using a laser flash photolysis technology, the second-order rate constants of CO2•− (kCO2•−″) reacting with CCl4, CHCl3 and CH2Cl2 were firstly reported, to be 2.5 × 108, 6.2 × 107 and 5.8 × 106 M−1s−1, respectively. kCO2•−″ presented a significant negative correlation with the lowest unoccupied molecular orbital energy (ELUMO) of chlorinated alkanes, proving that the enhanced dehalogenation of CO2•− was attributed by direct electron transfer mechanism. A fitting model was developed accordingly for kCO2•−″ prediction. This study also demonstrated that the CO2•− mediated ARP effectively removed halogenated alkanes regardless of pH condition (6.0∼9.0) and bicarbonate concentrations. These findings are significant in advancing the scientific understanding of CO2•− mediated ARP. This reductive process a promising control strategy for halogenated contaminants, such as polyfluoroalkyl substances (PFAS) and halogenated pharmaceuticals.

中文翻译：

二氧化碳自由基阴离子介导的卤代烷烃脱卤动力学和机制

二氧化碳自由基阴离子 (CO2•−) 最近在消除卤代污染物方面受到重视；然而，其应用却因机制理解不足而受到限制。在此，我们对 CO2•− 介导的卤代烷烃脱卤反应的动力学和机制进行了定量研究。已成功建立并证明以CO2•−为主的UV254/H2O2/HCOO−系统可有效消除7种卤代烷烃（去除率71.3%至100%）。利用激光闪光光解技术，首次报道了CO2•− (kCO2•−")与CCl4、CHCl3和CH2Cl2反应的二阶速率常数，分别为2.5 × 108、6.2 × 107和5.8 × 106 M−1s分别为-1。 kCO2•−"与氯化烷烃的最低未占分子轨道能(ELUMO)呈现显着的负相关，证明CO2•−的脱卤增强是通过直接电子转移机制实现的。相应地开发了用于kCO2•−"预测的拟合模型。这项研究还表明，无论 pH 条件（6.0∼9.0）和碳酸氢盐浓度如何，CO2•− 介导的 ARP 都能有效去除卤代烷烃。这些发现对于推进对 CO2•− 介导的 ARP 的科学理解具有重要意义。这种还原过程是一种很有前途的卤代污染物（例如多氟烷基物质（PFAS）和卤代药物）控制策略。

更新日期：2024-05-23

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