Factors affecting the catalytic oxidative removal of soluble manganese in natural water by superfine powdered activated carbon and free chlorine
Factors affecting the catalytic oxidative removal of soluble manganese in natural water by superfine powdered activated carbon and free chlorine
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DOI：
10.1016/j.jwpe.2022.103007
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发表时间：
2022-10
影响因子：
7
通讯作者：
S. Saito;Y. Matsui;N. Shirasaki;T. Matsushita
中科院分区：
文献类型：
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作者：
S. Saito;Y. Matsui;N. Shirasaki;T. Matsushita
在微滤之前用游离氯和超细粉状活性炭（SPAC）催化氧化溶解的二价锰离子（Mn2+）已成为一种从天然水中去除锰用于饮用水生产的新技术。然而，在中试实验中，锰尚未被充分去除。本研究阐明了底层去除机制。在天然水中，除了Mn2+之外，可溶性Mn还以氧化形式存在，分子量≥10,000Da的胶体Mn。 Mn2+被SPAC-氯去除，但Ca2+、Mg2+和NOM由于竞争吸附而降低了Mn2+去除率。 SPAC-氯不能去除胶体锰，但可以单独通过混凝和微滤或超滤去除。随着混凝剂（聚氯化铝）的添加，由于局部酸度增加（特别是在低温下）导致沉淀氧化的锰重新溶解，可溶性锰浓度增加，并且由于传质受阻，混凝降低了可溶性锰的去除率。通过使用高强度混合或在 Mn2+ 氧化充分进行后等待添加混凝剂，可以部分减弱这些负面影响。 Mn去除率随温度和混合强度的变化趋势与传质模型预测的趋势相同，但小于预测值。结合 Ca2+、Mg2+ 和 NOM 的影响，看来不仅传质而且吸附过程都是影响总体 Mn 去除率的因素。
Catalytic oxidation of dissolved divalent Mn ion (Mn2+) by free chlorine and superfine powdered activated carbon (SPAC) before microfiltration has been emerged as a new technology to remove Mn from natural water for drinking water production. However, Mn was not sufficiently removed in pilot-plant experiments yet. The present study clarified underlaying removal mechanisms. In natural water, soluble Mn exists as colloidal Mn with a molecular weight ≥ 10,000 Da in the oxidized form in addition to Mn2+. Mn2+was removed by SPAC‑chlorine, but Ca2+, Mg2+, and NOM decreased the Mn2+removal rate as a result of competitive adsorption. The colloidal Mn was not removed by SPAC‑chlorine, but could be removed by coagulation and microfiltration or ultrafiltration alone. With the addition of coagulant (poly‑aluminum chloride), the soluble Mn concentration increased because of redissolution of precipitated-oxidized Mn due an increase in local acidity, in particular at low temperature, and coagulation reduced soluble Mn removal rate due to hindrance of mass transfer. These negative impacts may be partially attenuated by using high-intensity mixing or waiting to add the coagulant after the oxidation of Mn2+has progressed sufficiently. Mn removal rate changed with temperature and mixing intensity in the same trend as predicted by the mass-transfer model, but it was smaller than the prediction. Together with the effects of Ca2+, Mg2+, and NOM, it appears that not only mass transfer but also the process of adsorption is a factor affecting the overall Mn removal rate.