Mn(II) Oxidation by Free Chlorine Catalyzed by the Hydrolytic Products of Ferric and Aluminum Species under Drinking Water Conditions.
Mn(II) Oxidation by Free Chlorine Catalyzed by the Hydrolytic Products of Ferric and Aluminum Species under Drinking Water Conditions.
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DOI：
10.1021/acs.est.2c02323
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发表时间：
2022-07
影响因子：
11.4
通讯作者：
Guiwei Li;Yuanyuan Zhao;Guangyu An;Baoyou Shi
中科院分区：
文献类型：
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作者：
Guiwei Li;Yuanyuan Zhao;Guangyu An;Baoyou Shi
水处理厂可采用游离氯氧化法去除Mn(II)。这一反应还会导致饮用水分配系统中颗粒MnOx的形成和积累。研究了在饮用水条件下，Fe(III)和Al(III)的水解产物(主要是沉淀物)对游离氯氧化Mn(II)的影响。结果表明，Fe3+以FeCl3形式加入，Al(III)以数十~数百微克/升聚合氯化铝(PACl)形式加入时，对游离氯氧化Mn(II)有明显的催化作用。在近中性的pH条件下，Fe3+和Al13(PACl中的主要预成铝物种)通过水解沉淀分别生成类Fe(OH)3粒子和Al13聚集体，引发了非均相的Mn(II)氧化。动力学模拟表明，一旦有MnOx生成，MnOx和Fe(OH)3对随后的Mn(II)氧化具有同等程度的催化作用。与相同摩尔浓度的MnOx和Fe(OH)3相比，Al13物种形成的粒子(聚集体)的催化能力较弱。有趣的是，与PACl中的Al13物种不同，Al(III)以AlCl3的形式加入对Mn(II)氧化的影响可以忽略不计，即使在Al(OH)3(Am)沉淀形成的情况下也是如此。用天然水和出厂水实验证实了Fe3+和Al13水解物的催化作用，较低的Mn(II)氧化速率主要是由有机物引起的。
Mn(II) oxidation by free chlorine can be applied to remove Mn(II) at water treatment plants. This reaction also results in particulate MnOx formation and accumulation in drinking water distribution systems. This study investigated the effect of Fe(III) and Al(III) hydrolysis products (mainly precipitates) on Mn(II) oxidation by free chlorine under drinking water conditions. The results showed that Fe3+ added as FeCl3 and Al(III) added as polyaluminum chloride (PACl) at tens to hundreds of micrograms per liter dramatically catalyzed Mn(II) oxidation by free chlorine. Through hydrolytic precipitation at circumneutral pH, Fe3+ and Al13 (the dominant preformed Al species in PACl) generated Fe(OH)3-like particles and Al13 aggregates, respectively, which initiated heterogeneous Mn(II) oxidation. Kinetic modeling indicated that, once some MnOx was formed, MnOx and Fe(OH)3 catalyzed the subsequent Mn(II) oxidation to an equal extent. The particles (aggregates) formed from Al13 species exhibited a weaker catalytic capacity in comparison to MnOx and Fe(OH)3 at equivalent molar concentrations. Interestingly, unlike Al13 species in PACl, Al(III) added as AlCl3 had a negligible influence on Mn(II) oxidation, even when Al(OH)3(am) precipitates were formed. The catalytic effects of Fe3+ and Al13 hydrolysis products were confirmed by experiments with natural water and finished water, and the lower Mn(II) oxidation rate was mainly attributed to organic matter.