Mechanistic Insights into the Markedly Decreased Oxidation Capacity of the Fe(II)/S2O82- Process with Increasing pH.
Mechanistic Insights into the Markedly Decreased Oxidation Capacity of the Fe(II)/S2O82- Process with Increasing pH.
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DOI：
10.1021/acs.est.2c04109
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发表时间：
2022-09
影响因子：
11.4
通讯作者：
D. Rao;Hongyu Dong;Mengfan Niu;Xiaohan Wang;Junlian Qiao;Yuankui Sun;Xiaohong Guan
中科院分区：
文献类型：
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作者：
D. Rao;Hongyu Dong;Mengfan Niu;Xiaohan Wang;Junlian Qiao;Yuankui Sun;Xiaohong Guan
Fe（II）/S_2 O_（82）- [Fe（II）/PDS]体系在pH > 3.0时氧化能力差，限制了其在水处理中的广泛应用。为了揭示潜在的机制，本研究系统地评估了pH 1.0-8.0范围内可能的影响因素，并开发了一个数学模型来量化这些影响。结果表明，在pH 1.0时，产生的Fe（IV）的约82%可用于污染物的降解，而在pH 7.5时，观察到Fe（IV）的贡献可以忽略不计。Fe（IV）的贡献随着pH的增加而急剧下降，这主要是Fe（II）/PDS过程的pH依赖性性能的原因。出乎意料的是，在酸性和近中性条件下，Fe（II）可以消耗约80%的生成的SO 4·-，而在高pH下形成的Fe（III）沉淀物则温和地抑制了SO 4·-的贡献。此外，强的Fe（II）清除作用难以通过减慢Fe（II）给药速率来补偿。在pH ≤ 7.5时，PDS与溶解氧对Fe（II）的竞争不明显，Fe（II）与氧气反应的二级速率常数远低于或与PDS与Fe（II）反应的二级速率常数相当。这些发现可以促进我们对Fe（II）/PDS过程的化学和应用的理解。
The poor oxidation capacity of the Fe(II)/S2O82- [Fe(II)/PDS] system at pH > 3.0 has limited its wide application in water treatment. To unravel the underlying mechanism, this study systematically evaluated the possible influencing factors over the pH range of 1.0-8.0 and developed a mathematical model to quantify these effects. Results showed that ∼82% of the generated Fe(IV) could be used for pollutant degradation at pH 1.0, whereas negligible Fe(IV) contribution was observed at pH 7.5. This dramatic decline of Fe(IV) contribution with increasing pH dominantly accounted for the pH-dependent performance of the Fe(II)/PDS process. Unexpectedly, Fe(II) could consume ∼80% of the generated SO4•- non-productively under both acidic and near-neutral conditions, while the larger formation of Fe(III) precipitates at high pH inhibited the SO4•- contribution mildly. Moreover, the strong Fe(II) scavenging effect was difficult to be compensated for by slowing down the Fe(II) dosing rate. The competition of dissolved oxygen with PDS for Fe(II) was insignificant at pH ≤ 7.5, where the second-order rate constants for reactions of Fe(II) with oxygen were much lower than or comparable to that between Fe(II) and PDS. These findings could advance our understanding of the chemistry and application of the Fe(II)/PDS process.