Zero-valent aluminum for reductive removal of aqueous pollutants over a wide pH range: Performance and mechanism especially at near-neutral pH
Zero-valent aluminum for reductive removal of aqueous pollutants over a wide pH range: Performance and mechanism especially at near-neutral pH
复制标题
零价铝可在较宽的 pH 范围内还原去除水体污染物：性能和机制，尤其是在接近中性 pH 的情况下
DOI：
10.1016/j.watres.2017.07.013
复制
发表时间：
2017
期刊：
影响因子：
12.8
通讯作者：
Xin Jia
中科院分区：
文献类型：
--
作者：
Yang Shiying;Zheng Di;Ren Tengfei;Zhang Yixuan;Xin Jia
零价铝（ZVAl）因其强还原性而备受关注。然而，在中性pH条件下，ZVAl对污染物的还原能力仍然受到怀疑，因为形成了致密的Al-（氢）氧化物表面膜。本研究首次将未改性的ZVAl在较宽的pH范围内还原去除水中污染物，并系统研究了其在近中性pH条件下的性能和机理。结果表明，ZVAl具有广泛的pH值范围从2到12，即使在中性环境中的适用性。在初始pH值为7时，典型的硝基化合物硝基苯（NB）、典型的偶氮染料酸性橙子7（AO 7）和典型的无机重金属离子Cr（VI）均能被有效去除。通过对反应液pH、ORP、DO、Al离子和TOC的变化以及NB还原产物的UV-Vis和GC-MS分析，发现ZVAl对NB的去除主要是还原作用。NB首先被还原为亚硝基苯，最后被还原为苯胺。同时，该体系存在吸附现象。其次，通过SEM-EDS、TEM、HRTEM、XRD、XPS等手段对反应前后的ZVAl颗粒进行表征，深入揭示了表面反应机理。结果表明，具有核壳结构的ZVAl粉末参与了氧化还原反应，ZVAl核被腐蚀，生成Al-（H2O）2。ZVAl表面氧化膜没有被直接去除，而是被粗糙化。最后，从电子竞争的角度推测了ZVAl对水体污染物的还原机理。在水环境中，O-2、H2O和污染物都能捕获ZVAl释放的电子，三者之间存在明显的竞争关系。当污染物获得电子的机会增加时，即使在接近中性的pH下，也可以发生有效的还原反应来去除污染物。总之，ZVAl是一种很有前途的材料，可以在很宽的pH范围内去除水溶液中的污染物，即使在中性环境中，这显示出其作为一种有效的和环境友好的去除剂的巨大潜力。(C)2017爱思唯尔有限公司版权所有
Zero-valent aluminum (ZVAl) draws much attention due to its strong reducibility. However, under neutral pH conditions, the reduction ability of ZVAl for pollutant removal has still been suspected because of the formed compact surface film of Al-(hydr)oxide. In this study, unmodified ZVAl was employed to reductively remove aqueous pollutants over a wide pH range, and its performance and mechanism, especially at near-neutral pH, were systematically studied for the first time. Results demonstrated that ZVAl had a wide range of pH applicability from 2 to 12, even in neutral environment. Typical nitro compound nitrobenzene (NB), typical azo dye acid orange 7 (AO7), and typical inorganic heavy metal ion Cr(VI) can be effectively removed at initial pH 7. Based on the changes of pH, ORP, DO, Al ions and TOC of the reaction solution, and the determination of reduction products of NB by UV-Vis and GC-MS, we found that NB removal by ZVAl can be primarily attributed to the reduction role. NB was reduced to nitrosobenzene firstly, and to aniline finally. Meanwhile, the adsorption phenomenon existed in this system. Next, the surface reaction mechanism was deeply revealed through the characterization of ZVAl particles before and after reaction by SEM-EDS, TEM, HRTEM, XRD, and XPS. It was found that ZVAl powders with core/shell structure participated in the redox reaction, and that ZVAl core was corroded, generating Al-(hydr)oxide. ZVAl surface oxide film was not directly removed, instead of a rougher one. Finally, the proposed reductive mechanism of aqueous pollutants by ZVAl was speculated from the angle of electronic competition. In water environment, O-2, H2O and pollutants, with a clear competitive relationship, can capture electrons released from ZVAl. When pollutant's opportunities for getting electrons are enhanced, efficiently reductive reactions for pollutant removal can take place, even at near neutral pH. In a word, ZVAl is a promising material to remove aqueous pollutants over a wide pH range, even in neutral environment, which exhibits its great potential as an effective and environment-friendly agent for pollutant removal from water. (C) 2017 Elsevier Ltd. All rights reserved.