Reactivity of Dissolved Organic Matter with the Hydrated Electron: Implications for Treatment of Chemical Contaminants in Water with Advanced Reduction Processes
Reactivity of Dissolved Organic Matter with the Hydrated Electron: Implications for Treatment of Chemical Contaminants in Water with Advanced Reduction Processes
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DOI：
10.1021/acs.est.3c00909
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发表时间：
2023-05
影响因子：
11.4
通讯作者：
Benjamin D Fennell;Douglas Fowler;S. Mezyk;G. McKay
中科院分区：
文献类型：
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作者：
Benjamin D Fennell;Douglas Fowler;S. Mezyk;G. McKay
高级还原工艺（阿普）在处理难降解化学污染物，特别是全氟烷基和多氟烷基物质（PFAS）方面越来越受到关注。然而，溶解性有机物（DOM）的水化电子（eaq-），在阿普中形成的关键活性物种的可用性的影响，是不完全了解。利用电子脉冲辐解和瞬态吸收光谱技术，测定了8种水生和陆生腐殖物质和天然有机物的eaq-反应双分子速率常数（kDOM，eaq-），其值为（0.51 ± 0.01）~（2.11 ± 0.04）× 108 MC-1 s-1。在不同温度、pH值和离子强度下kDOM，eaq-测量表明，不同DOM分离物的活化能为1.18 kJ mol-1，且可预期kDOM，eaq-在pH 5和9之间或在0.02至0.12 M的离子强度之间变化小于1.5倍。kDOM，eaq-表现出显着的，正相关的%羰基碳的研究分离物，但其他DOM的物理化学性质的关系是令人惊讶的更分散。24小时的紫外线/亚硫酸盐实验，采用氯乙酸盐作为eaq-探针显示，持续eaq-暴露减弱DOM发色团和eaq-清除能力超过几个小时的时间尺度。总的来说，这些结果表明DOM是一种重要的气体清除剂，将降低阿普中目标污染物降解的速率。这些影响在废水流中可能更大，如膜浓缩物、废离子交换树脂或具有升高的DOM浓度的再生盐水。
Advanced reduction processes (ARP) have garnered increasing attention for the treatment of recalcitrant chemical contaminants, most notably per- and polyfluoroalkyl substances (PFAS). However, the impact of dissolved organic matter (DOM) on the availability of the hydrated electron (eaq–), the key reactive species formed in ARP, is not completely understood. Using electron pulse radiolysis and transient absorption spectroscopy, we measured bimolecular reaction rates constant for eaq– reaction with eight aquatic and terrestrial humic substance and natural organic matter isolates ( kDOM,eaq–), with the resulting values ranging from (0.51 ± 0.01) to (2.11 ± 0.04) × 108 MC–1 s–1. kDOM,eaq– measurements at varying temperature, pH, and ionic strength indicate that activation energies for diverse DOM isolates are ≈18 kJ mol–1 and that kDOM,eaq– could be expected to vary by less than a factor of 1.5 between pH 5 and 9 or from an ionic strength of 0.02 to 0.12 M. kDOM,eaq– exhibited a significant, positive correlation to % carbonyl carbon for the isolates studied, but relationships to other DOM physicochemical properties were surprisingly more scattered. A 24 h UV/sulfite experiment employing chloroacetate as an eaq– probe revealed that continued eaq– exposure abates DOM chromophores and eaq– scavenging capacity over a several hour time scale. Overall, these results indicate that DOM is an important eaq– scavenger that will reduce the rate of target contaminant degradation in ARP. These impacts are likely greater in waste streams like membrane concentrates, spent ion exchange resins, or regeneration brines that have elevated DOM concentrations.