Enhancing surface corrosion of zero-valent aluminum (ZVAl) and electron transfer process for the degradation of trichloroethylene with the presence of persulfate
Enhancing surface corrosion of zero-valent aluminum (ZVAl) and electron transfer process for the degradation of trichloroethylene with the presence of persulfate
复制标题
过硫酸盐存在下增强零价铝（ZVAl）表面腐蚀和降解三氯乙烯的电子传递过程
DOI：
10.1016/j.cej.2018.04.216
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发表时间：
2018-09-15
影响因子：
15.1
通讯作者：
Zhang, Yixuan
中科院分区：
文献类型：
--
作者：
Ren, Tengfei;Yang, Shiying;Zhang, Yixuan
未改性的零价铝(ZVAl)表面覆盖有致密的氧化膜，但与过硫酸盐(PS)复配后，在较宽的初始pH范围(3.00-10.00)内，ZVAl对三氯乙烯(TCE)的降解表现出显著的协同效应，没有任何诱导期。在ZVAl/PS体系中，存在包括PS、O-2、H2O和目标污染物TCE在内的氧化性物种，它们将争夺ZVAl腐蚀释放的电子。为了真正了解反应机理，本工作深入探讨了三氯乙烯降解过程中复杂的表面腐蚀和电子转移过程。首先，通过扫描电子显微镜、透射电子显微镜、粒度分布、N-2吸附-脱附等温线、X-射线衍射仪和X-射线光电子能谱等表征，我们发现原始的ZVAl是一个核壳结构，在反应过程中，核心被腐蚀并被氧化成Al-(Hydr)氧化物。反应后，氧化膜并没有被直接去除，反而变得更加粗糙，导致ZVAl的颗粒尺寸、比表面积、总孔体积和平均孔径增大。添加PS确实可以活化ZVAl表面，加快ZVAl的腐蚀速度，且酸性环境更有利于腐蚀，而不添加PS的情况正好相反。其次，确定了TCE降解的主要活性物种和电子转移过程。SO4中心点是通过电子从ZVAl直接转移到PS中生成的。在酸性pH条件下，O-2可能通过生成O-2(中心点-)和H_2O_2参与该过程。因此，由于PS的高溶解度和标准氧化还原电位(有更多的机会捕获电子)以及生成的自由基的高度氧化能力，可以实现TCE的完全脱氯和部分矿化，而不是通过ZVAl释放的电子进行还原去除。
Though covered with a compact oxide film, unmodified zero-valent aluminum (ZVAl), showed a significant synergistic effect combined with persulfate (PS) for the degradation of trichloroethylene (TCE) over a wide initial pH range (3.00-10.00) without any induction period. In ZVAl/PS system, there are oxidizing species, including PS, O-2, H2O and the target contaminant TCE, which will compete for electrons released from ZVAl corrosion. In order to really understand the reaction mechanism, in this work, the complicated surface corrosion and electron transfer processes for TCE degradation were deeply explored. Firstly, by the characterizations of SEM-EDS, TEM, size distribution, N-2 adsorption-desorption isotherms, XRD and XPS, we found that pristine ZVAl was a core-shell structure and during the reaction the core was corroded and oxidized to Al-(hydr)oxide. After reaction, the oxide film was not directly removed, but became rougher, causing the increase of particle size, specific surface area, total pore volume and average pore size of ZVAl. The addition of PS can indeed activate ZVAl surface and accelerate ZVAl corrosion rate, and acidic environment is more conducive to the corrosion, which is opposite to the case without PS. Secondly, the dominant active species and electron transfer processes for TCE degradation were identified. SO4 center dot- was generated through electron transfer from ZVAl to PS directly. O-2 may be involved in the process at acidic pH by forming O-2(center dot-) and H2O2. Hence, rather than the reductive removal by electron released from ZVAl, complete dechlorination and partial mineralization of TCE could be achieved, due to the high solubility and standard redox potential of PS which has more chance to capture electron and to the highly oxidative capacity of generated radicals.