Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States.
Environ Sci Technol. 2011 Apr 1;45(7):2783-9. doi: 10.1021/es103793y. Epub 2011 Mar 1.
The photochemistry of an aqueous suspension of the iron oxyhydroxide, ferrihydrite, in the presence of arsenite has been investigated using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray absorption near edge structure (XANES), and solution phase analysis. Both ATR-FTIR and XANES show that the exposure of ferrihydrite to arsenite in the dark leads to no change in the As oxidation state, but the exposure of this arsenite-bearing surface, which is in contact with pH 5 water, to light leads to the conversion of the majority of the adsorbed arsenite to the As(V) bearing species, arsenate. Analysis of the solution phase shows that ferrous iron is released into solution during the oxidation of arsenite. The photochemical reaction, however, shows the characteristics of a self-terminating reaction in that there is a significant suppression of this redox chemistry before 10% of the total iron making up the ferrihydrite partitions into solution as ferrous iron. The self-terminating behavior exhibited by this photochemical arsenite/ferrihydrite system is likely due to the passivation of the ferrihydrite surface by the strongly bound arsenate product.
使用衰减全反射傅里叶变换红外光谱（ATR-FTIR）、X 射线吸收近边结构（XANES）和溶液相分析研究了亚砷酸盐存在下铁水羟氧化物（水铁矿）水悬浮液的光化学。ATR-FTIR 和 XANES 均表明，水铁矿在黑暗中暴露于亚砷酸盐不会改变砷的氧化态，但暴露于与 pH 5 水接触的含亚砷酸盐表面在光照下会导致吸附的亚砷酸盐大部分转化为含砷酸盐（砷酸根）的物种。溶液相分析表明，在亚砷酸盐氧化过程中，亚铁离子被释放到溶液中。然而，光化学反应表现出自终止反应的特征，即在亚铁水铁矿作为亚铁铁进入溶液之前，总铁的 10%左右被氧化成亚铁铁，这种氧化还原化学被显著抑制。这种光化学亚砷酸盐/水铁矿系统表现出的自终止行为可能是由于强结合的砷酸盐产物使水铁矿表面钝化。
