Mechanisms of trichloramine removal with activated carbon: Stoichiometric analysis with isotopically labelled trichloramine and theoretical analysis with a diffusion-reaction model
Mechanisms of trichloramine removal with activated carbon: Stoichiometric analysis with isotopically labelled trichloramine and theoretical analysis with a diffusion-reaction model
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活性炭去除三氯胺的机制：同位素标记三氯胺的化学计量分析和扩散反应模型的理论分析
DOI：
10.1016/j.watres.2014.10.051
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发表时间：
2015
期刊：
影响因子：
12.8
通讯作者：
N.
中科院分区：
文献类型：
--
作者：
Sakuma;M.;*Matsushita;T.;Matsui;Y.;Aki;A.;Isaka;M. and Shirasaki;N.
本研究探讨了活性炭去除水处理副产物三氯胺的机理。实验室制备的15 N标记的三氯胺溶液在活性炭处理前后的15 N化学计量质量平衡清楚地表明，活性炭去除三氯胺的机理不是吸附而是还原分解为氮气。有一个弱的正相关性之间的表面分解速率常数的三氯胺和活性炭颗粒表面上的碱性官能团的浓度，这表明，三氯胺可能已被还原的巯基（-SH）的活性炭表面。将市售粉末活性炭（PAC）粉碎成粒径小于1 μm的超细粉末，制备出超细粉末活性炭（SPAC），用于降解三氯胺。SPAC在水中同时存在三氯胺和游离氯时，仍能选择性地分解三氯胺，说明在有效分解三氯胺后，残余游离氯仍能保持较强的消毒能力。在1-5 °C的低水温下，碳接触后三氯胺的残留率略有增加。在这样的低温下，生物处理，控制主要的三氯胺前体（铵态氮）的传统方法，是低效的。即使在如此低的温度下，SPAC也可以将三氯胺浓度降低到可接受的水平。在本研究中开发的扩散-反应模型的理论分析表明，随着水温的降低，三氯胺残留量的增加是由于还原反应速率的温度依赖性，而不是扩散传质速率的温度依赖性。
This study investigated the mechanism by which activated carbon removes trichloramine, a byproduct of water treatment that has a strongly offensive chlorinous odor. A stoichiometrical mass balance for15N before and after activated carbon treatment of laboratory-prepared15N-labeled trichloramine solutions clearly revealed that the mechanism of trichloramine removal with activated carbon was not adsorption but rather reductive decomposition to nitrogen gas. There was a weak positive correlation between the surface decomposition rate constant of trichloramine and the concentration of basic functional groups on the surface of the carbon particles, the suggestion being that the trichloramine may have been reduced by sulfhydryl groups (–SH) on the activated carbon surface. Efficient decomposition of trichloramine was achieved with super powdered activated carbon (SPAC), which was prepared by pulverization of commercially available PAC into very fine particles less than 1 μm in diameter. SPAC could decompose trichloramine selectively, even when trichloramine and free chlorine were present simultaneously in water, the indication being that the strong disinfection capability of residual free chlorine could be retained even after trichloramine was effectively decomposed. The residual ratio of trichloramine after carbon contact increased somewhat at low water temperatures of 1–5 °C. At these low temperatures, biological treatment, the traditional method for control of a major trichloramine precursor (ammonium nitrogen), is inefficient. Even at these low temperatures, SPAC could reduce the trichloramine concentration to an acceptable level. A theoretical analysis with a diffusion-reaction model developed in the present study revealed that the increase in the trichloramine residual with decreasing water temperature was attributable to the temperature dependence of the rate of the reductive reaction rather than to the temperature dependence of the diffusive mass transfer rate.