Enhancement of Cr(VI) removal by mechanically activated micron-scale zero-valent aluminum (MA-mZVAl): Performance and mechanism especially at near-neutral pH
Enhancement of Cr(VI) removal by mechanically activated micron-scale zero-valent aluminum (MA-mZVAl): Performance and mechanism especially at near-neutral pH
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机械活化微米级零价铝 (MA-mZVAl) 增强 Cr(VI) 去除：性能和机制，尤其是在接近中性 pH 条件下
DOI：
10.1016/j.cej.2018.07.174
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发表时间：
2018-12
影响因子：
15.1
通讯作者：
Xin Jia
中科院分区：
文献类型：
--
作者：
Zhang Yixuan;Yang Shiying;Zhang Yuqi;Wu Sui;Xin Jia
致密的氧化膜极大地限制了微米级零价铝（mZVAl）的强还原性，特别是在近中性pH下。在这项研究中，我们发现，在很宽的pH范围（3.00-11.00）内，通过机械活化的mZVAl（MA-mZVAl）可以大大提高Cr（VI）的去除效率。与mZVAl相比，在初始pH 7.00下，MA-mZVAl以大约292倍的速度去除Cr（VI）。BM参数，包括添加剂NaCl的量，BM速度，BM时间，和BM气氛上的Cr（VI）去除的影响进行了评估。通过测定Cr（VI）的不同价态浓度，监测DO、pH、ORP、Al离子浓度等水化学参数的变化，以及确定Cl-在溶液中的作用，探讨了Cr（VI）的去除机理。通过SEM EDS、BET、XRD、XPS等表征手段，揭示了BM后mZVAl的结构演变以及MA-mZVAl与Cr（VI）反应过程中的表面腐蚀机理。在上述实验的基础上，我们发现MA-mZVAl对Cr（VI）有还原去除作用，生成Cr（OH）3（s）沉淀在MA-mZVAl表面。NaCl对MA-mZVAl的反应性的促进作用不是在腐蚀过程中，而是在BM过程中。BM破坏了致密的氧化膜，腐蚀后形成粗糙的Al-（氢）氧化物膜。MA-mZVAl的可重复使用性受到Al和Cr（氢）氧化物的形成的阻碍，但可以很容易地和完全再生的BM。总体而言，BM不仅可以突破氧化膜的瓶颈，还可以恢复钝化的MA-mZVAl。因此，MA-mZVAl颗粒具有相当大的去除污染物的潜力。
The dense oxide film greatly limits the strong reducibility of micron-scale zero-valent aluminum (mZVAl), especially at near-neutral pH. In this study, we found that the removal efficiency of Cr(VI) can be greatly enhanced over a wide pH range (3.00-11.00) by mechanically activated mZVAl (MA-mZVAl), which was prepared from mZVAl by ball milling (BM) in the presence of additive NaCl. Compared with mZVAl, at initial pH 7.00, MA-mZVAl removed Cr(VI) at a roughly 292-fold faster rate. The effects of BM parameters including the amount of additive NaCl, BM speed, BM time, and BM atmosphere on Cr(VI) removal were first evaluated. Then, the Cr(VI) removal mechanism was explored by measuring the concentration of different valent chromium, monitoring the changes of water chemical parameters including DO, pH, ORP, Al ions concentration, and by ascertaining the role of Cl- in solution. Furthermore, the structure evolution of mZVAl after BM and the surface corrosion mechanism of MA-mZVAl during reaction with Cr(VI) were unveiled through the characterization by means of SEM-EDS, BET, XRD, and XPS. Based on above tests, we found that Cr(VI) was reductively removed by MA-mZVAl to form Cr(OH) 3(s) precipitated on the surface of MA-mZVAl. NaCl promoted the reactivity of MA-mZVAl not in corrosion process but in BM process. The dense oxide film was destroyed by BM, and changed into a rough Al-(hydr) oxide film after corrosion. The reusability of MA-mZVAl was hindered by the formation of Al and Cr (hydr) oxide, but can be easily and completely rejuvenated by BM. Overall, BM can not only break through the bottleneck of oxide film but recover the passivated MA-mZVAl. Therefore, MA-mZVAl particles are of considerable potential for pollutants removal.
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