Degueldre Claude, Reed Donald, Kropf A Jeremy, Mertz Carol
Nuclear Energy and Safety Division, Paul Scherrer Institute, 5232 Villigen, Switzerland.
J Synchrotron Radiat. 2004 Mar 1;11(Pt 2):198-203. doi: 10.1107/S0909049503024683. Epub 2004 Feb 12.
The sorption of americium, as Am(III), onto groundwater colloids obtained from a marl aquifer was studied in 2 x 10(-2)M sodium bicarbonate groundwater and 2 x 10(-2)M sodium chloride bicarbonate-free solutions. At the in situ groundwater pH of 8.6, the americium was strongly sorbed onto the colloids. XAFS analyses were performed on these sorbed Am species to establish the oxidation state and its near-neighbour bonding. These XAFS data, obtained at 400 mg l(-1) colloid concentrations and total Am concentration of 1.53 x 10(-5)M (dissolved and onto colloids), indicated that Am remains trivalent, and that surface complexes are formed with the colloids without surface precipitation. This conclusion is based on the absence of Am-Am interactions in the second or third shells. The surface complexes generated by the Am(III) sorbed onto active sites are described on the basis of the XAFS data. They include the presence of about seven water molecules around the ternary surface complexes of this trivalent actinide.
研究了在2×10⁻²M碳酸氢钠地下水和2×10⁻²M无碳酸氢根的氯化钠溶液中，三价镅（Am(III)）在从泥灰岩含水层获取的地下水胶体上的吸附情况。在原位地下水pH值为8.6时，镅强烈吸附在胶体上。对这些吸附的镅物种进行了X射线吸收精细结构（XAFS）分析，以确定其氧化态及其近邻键合情况。这些XAFS数据是在胶体浓度为400mg/L且镅总浓度为1.53×10⁻⁵M（溶解态和吸附在胶体上的）条件下获得的，表明镅仍为三价，并且与胶体形成了表面络合物而无表面沉淀。该结论基于第二或第三壳层中不存在镅-镅相互作用。根据XAFS数据描述了吸附在活性位点上的Am(III)产生的表面络合物。它们包括在这种三价锕系元素的三元表面络合物周围存在约七个水分子。
