School of Environmental Science and Engineering and Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China.
School of Environmental Science and Engineering and Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China.
Environ Pollut. 2018 Apr;235:660-669. doi: 10.1016/j.envpol.2017.12.118. Epub 2018 Jan 12.
Naturally occurring ferrihydrite often contains various impurities, and Al is one of the most prominent impurities. However, little is known about how these impurities impact the physical and chemical properties of ferrihydrite with respect to metal(loid) adsorption. In this study, a series of Al-containing ferrihydrites were synthesized and exposed to a mixed solution containing As(III) and Cr(VI). The results showed that the two contaminants can be quickly adsorbed onto the surface of Al-containing ferrihydrite under acidic and neutral conditions. With the increase of Al molar percentage in ferrihydrites from 0 to 30, the adsorption capacity of As(III) decreased, whereas it increased for Cr(VI). On the other hand, with the increase of pH value from 3.0 to 11.0, the decreasing rate of As(III) was accelerated first, then slowed down, whereas the Cr(VI) decreasing rate slowed down dramatically. X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis method, transmission electron microscopy (TEM) analysis, energy dispersive spectroscopy (EDS) mapping, Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were employed to characterize Al-containing ferrihydrite. Interestingly, it was found that the redox transformation occurred between As(III) and Cr(VI) after the two contaminants were coadsorbed onto the surface of Al-containing ferrihydrite. The oxidation of As(III) to As(V) and reduction of Cr(VI) to Cr(III) would greatly lower the environmental hazard of the As(III) and Cr(VI).
天然水铁矿通常含有各种杂质，其中 Al 是最主要的杂质之一。然而，对于金属（类）吸附而言，这些杂质如何影响水铁矿的物理化学性质还知之甚少。在本研究中，合成了一系列含 Al 的水铁矿，并将其暴露于含有 As(III)和 Cr(VI)的混合溶液中。结果表明，在酸性和中性条件下，这两种污染物可以迅速被吸附到含 Al 的水铁矿表面。随着水铁矿中 Al 摩尔百分比从 0 增加到 30，As(III)的吸附容量降低，而 Cr(VI)的吸附容量增加。另一方面，随着 pH 值从 3.0 增加到 11.0，As(III)的降低速率先加速后减缓，而 Cr(VI)的降低速率则急剧减缓。采用 X 射线衍射（XRD）、Brunauer-Emmett-Teller（BET）分析方法、透射电子显微镜（TEM）分析、能量色散光谱（EDS）映射、衰减全反射傅里叶变换红外光谱（ATR-FTIR）和 X 射线光电子能谱（XPS）对含 Al 的水铁矿进行了表征。有趣的是，发现当两种污染物共吸附到含 Al 的水铁矿表面后，发生了 As(III)和 Cr(VI)之间的氧化还原转化。As(III)被氧化为 As(V)和 Cr(VI)被还原为 Cr(III)，这将大大降低 As(III)和 Cr(VI)的环境危害。
