State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, P. R. China.
Department of Chemical and Environmental Engineering, University of California, Riverside, A235 Bourns Hall, 3401 Watkins Drive, Riverside, California 92521, United States.
Environ Sci Technol. 2022 Sep 20;56(18):13131-13141. doi: 10.1021/acs.est.2c04109. Epub 2022 Sep 6.
The poor oxidation capacity of the Fe(II)/SO [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 SO non-productively under both acidic and near-neutral conditions, while the larger formation of Fe(III) precipitates at high pH inhibited the SO 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.
在 pH 值大于 3.0 的条件下，Fe(II)/SO[Fe(II)/PDS]体系的氧化能力较差，限制了其在水处理中的广泛应用。为了揭示其潜在的机制，本研究系统地评估了在 1.0-8.0 pH 值范围内可能存在的影响因素，并建立了一个数学模型来量化这些影响。结果表明，在 pH 值为 1.0 时，约有 82%的生成的 Fe(IV)可用于污染物降解，而在 pH 值为 7.5 时，几乎观察不到 Fe(IV)的贡献。这种随着 pH 值增加而导致的 Fe(IV)贡献的急剧下降，是 Fe(II)/PDS 工艺的 pH 依赖性性能的主要原因。出乎意料的是，在酸性和近中性条件下，Fe(II)可消耗约 80%的生成的 SO，而在高 pH 值下形成的更多的 Fe(III)沉淀则轻微抑制了 SO 的贡献。此外，高 pH 值下 Fe(III)沉淀的形成强烈抑制了 SO 的贡献。而且，通过降低 Fe(II)投加速率来补偿强的 Fe(II)清除效应是很困难的。在 pH 值≤7.5 时，溶解氧与 PDS 竞争 Fe(II)的作用并不显著，因为 Fe(II)与氧气的二级反应速率常数远低于或与 Fe(II)与 PDS 之间的反应速率常数相当。这些发现可以提高我们对 Fe(II)/PDS 工艺的化学和应用的理解。
