SORPTION BEHAVIOR OF ACTINOIDS ON WEATHERED MINERALS

了解具有长期放射性毒性的核素在地质材料上的吸附行为是放射性废物地下处置安全评估的核心。为了考察各种氧化物和水合氧化物的晶体结构、结晶度和表面条件对金属离子吸附的影响，研究了天然铁铝矿物、合成氧化物粉末和实验室制备的水合氧化物对Np(V)的吸附随pH的变化规律，其吸附能力大小顺序为：氢氧化物和氢氧化物；合成氧化物粉末；矿物(赤铁矿、磁铁矿和刚玉)。这些结果表明，铁和铝的氧化物和水合氧化物的吸附主要受其晶体结构的控制，其次受其比表面积的控制，说明铁和铝的氧化物和水合氧化物的转化发生在自然环境…中。更多的核素将对放射性核素的迁移产生严重影响。在较宽的金属离子浓度范围内，研究了金属离子饱和度对针铁矿、三水铝石和实验室制备的无定形铁铝氧化物吸附Eu(III)和Co(II)的影响。当金属离子浓度较低时，一个简单的Langmuir方程，假设一个结合常数，能够描述吸附在这些水合氧化物上。在较高的金属离子浓度下，针铁矿和三水铝石在这些矿物上的吸附呈现明显的饱和极大值，表明它们的吸附是由金属离子与结合位之间简单的一对一相互作用控制的。相反，在实验室制备的水合氧化物上的吸附即使在高金属离子浓度下也继续增加，这表明在无定形水合氧化物上的吸附是通过一些不同的途径进行的，例如在结合表面形成原酸盐或固溶体。较少

Understanding the sorption behavior of nuclides having long-term radiological toxicity onto geological materials is central to the safety assessment of underground disposal of radioactive waste. In order to see the effect of crystal structure, crystallinity and surface conditions of various oxides and hydrous oxides on the sorption of metal ions, the sorption of tracer concentrations of Np(V) on naturally occurring iron and alumiun minerals, synthetic oxide powders and laboratory-prepared hydrous oxides was studied as a function of pH.The orders of their abilities to sorb Np(V) were hydrous oxides including oxyhydroxides and hydroxides > synthetic oxide powders > minerals (hematite, magnetite and corundum). These results suggest that the sorption of tracer concentrations of actinoids is controlled primarily by their crystal structures and subsidiarily by their surface areas, indicating that the transformation of oxides and hydrous oxides of iron and aluminum occurring in natural enviro … More nments will give a serious influence on the migration of radionuclides. The effects of metal ion saturation on the sorption of Eu(III) and Co(II) on goethite, gibbsite and laboratory-prepared amorphous iron and aluminum oxides were studied as a function of pH over a wide range of metal ion concentrations. When the metal ion concentrations were low, a simple Langmuir equation, assuming a single binding constant, was capable of describing sorption on these hydrous oxides. At high metal ion concentrations, sorption on goethite and gibbsite exhibited clear saturation maxima, indicating that sorption on these minerals was controlled by a simple one-to-one interaction between the metal ion and a binding site. Conversely, sorption on laboratory-prepared hydrous oxides continued to increase even at high metal ion concentrations, indicating that sorption on amorphous hydrous oxides proceeds through a somewhat different pathway, such as the formation of a pricipitate or a solid solution at the binding surface. Less