CEA, DEN, DPC/SEARS/LISL, CEN de Saclay 91191 Gif-sur-Yvette CEDEX, France.
Environ Sci Technol. 2012 Oct 2;46(19):10820-6. doi: 10.1021/es301611e. Epub 2012 Sep 20.
The reduction-oxidation reaction between aqueous selenite (SeO(3)(2-)) and siderite (FeCO(3(s))) was monitored by in situ, time-resolved X-ray absorption near-edge structure (XANES) spectroscopy at the selenium K edge in a controlled electrochemical environment. Spectral evolutions showed that more than 60% of selenite was reduced at the siderite surface after 20 h of experiment, at which time the reaction was still incomplete. Fitting of XANES spectra by linear combination of reference spectra showed that selenite reaction with siderite is essentially a two-step process, selenite ions being immobilized on siderite surface prior to their reduction. A kinetic model of the reduction step is proposed, allowing to identify the specific contribution of surface reduction. These results have strong implications for the retention of selenite by corrosion products in nuclear waste repositories and in a larger extent for the fate of selenium in the environment.
在控制电化学环境下，通过硒 K 边的原位、时间分辨 X 射线吸收近边结构（XANES）光谱法监测亚硒酸盐（SeO(3)(2-））与菱铁矿（FeCO(3(s))）之间的氧化还原反应。光谱演变表明，在 20 小时的实验后，超过 60%的亚硒酸盐在菱铁矿表面被还原，此时反应仍未完全。通过参考光谱的线性组合对 XANES 光谱进行拟合表明，亚硒酸盐与菱铁矿的反应本质上是一个两步过程，亚硒酸盐离子在被还原之前固定在菱铁矿表面。提出了还原步骤的动力学模型，允许识别表面还原的特定贡献。这些结果对核废料库中腐蚀产物对亚硒酸盐的保留以及在更大程度上对环境中硒的归宿具有重要意义。
