放射性废物因其在地质处置中可能会引发二次污染而备受关注。Sr是放射性废物中的典型组分之一，是地质处置中需要重点关注的元素。黏土岩是我国放射性核废物地质处置库围岩的主要类型之一，胶体是地下水中的常见组分，会直接影响黏土岩对核素吸附和阻滞效果。因此，在黏土岩处置库类型中，开展胶体作用于黏土岩对Sr吸附行为研究具有较强的应用价值。本研究选取核素Sr作为研究对象，以内蒙古苏宏图地区的黏土岩为吸附介质，采用静态吸附实验分析影响吸附过程的关键因素，通过拟合吸附动力学模型，采用多种光谱技术表征和水文地球化学模拟，揭示不同种类胶体作用下，黏土岩对Sr的吸附反应类型、吸附机理以及水-岩作用机制和Sr的赋存形态。

（1）通过静态吸附实验研究无胶体、针铁矿胶体、膨润土胶体、复合胶体作用下黏土岩对Sr的吸附作用，并探讨了胶体加入量、反应时间、吸附介质量、pH值、温度以及伊利石（黏土岩主要黏土矿物组分）对Sr吸附效果。结果表明：不同胶体作用下黏土岩对Sr的吸附过程分为两个阶段。实验前期（＜120 min），针铁矿胶体和膨润土胶体单独作用下，未体现出对吸附体系明显的作用，而复合胶体对Sr在黏土岩上的吸附呈现出轻微的抑制作用。实验时间t＞120 min时，针铁矿胶体和膨润土胶体单独作用时对吸附体系呈现出一定的促进作用，其中膨润土胶体的促进作用更加明显，吸附率增加约3.13%~7.55%；而复合胶体体系由于自身的复杂性对吸附过程呈现出轻微的抑制作用。胶体加入量和吸附介质量对吸附体系的影响均呈现吸附率随着胶体加入量和吸附介质量的增加先快速增大后趋于稳定。pH的影响则体现为酸碱性条件下吸附率差异大，碱性条件有利于吸附。温度的增高可以使黏土岩对Sr的吸附率呈现先增大后减小趋势。对Sr在伊利石上的吸附前期（＜120 min），膨润土胶体有轻微的抑制作用；平衡阶段膨润土胶体和复合胶体抑制吸附，其中膨润土胶体的抑制作用更加明显，吸附率降低3.93%。

（2）采用吸附动力学模型拟合及其特征参数分析，揭示不同胶体作用下Sr-黏土岩以及Sr-伊利石之间的吸附反应模式和吸附类型。Sr-黏土岩体系中：无胶体和针铁矿胶体作用下黏土岩对Sr的吸附行为遵循准一级、准二级和双曲正切吸附动力学模型，表明吸附过程受初始阶段扩散作用和化学吸附共同控制；膨润土胶体作用下的吸附过程遵循一般吸附（GO）动力学模型，表明吸附机制以表面吸附为主；复合胶体作用时的吸附过程可由Elovich、准一级、准二级和一般吸附动力学模型准确描述，表明该过程为包括静电、表面络合、离子交换等作用的复杂机制。伊利石对Sr的吸附行为在四种体系中均遵循准一级和准二级模型，说明其机制包含物理吸附与化学吸附；一般吸附动力学模型表明针铁矿胶体作用下Sr在伊利石上的吸附作用为表面吸附。

（3）通过SEM、EDS、XRD、FTIR和XPS光谱表征技术分析吸附前后黏土岩和伊利石的微观结构、元素含量、晶体结构和官能团种类、元素价态及电子结构的变化及吸附机制推测。SEM图谱显示膨润土胶体作用下黏土岩表面粗糙度和微孔结构量变化最多，吸附点位明显增多，是促进Sr吸附的重要机制；而复合胶体作用下黏土岩变化特征与之相反，吸附率降低。XRD结果表现出膨润土胶体使黏土岩衍射峰位移量大，峰形变化剧烈，对Sr的吸附率显著提高；但使伊利石衍射峰位移量最小，吸附率降低。FTIR图谱变化特征表明膨润土胶体通过提高黏土岩中官能团的环境电负性而促进吸附，但对伊利石影响较小。XPS结果表明，膨润土胶体中的Si、Al等和针铁矿胶体中的Fe可与黏土岩键合生成官能团从而促进吸附。因此，膨润土胶体对Sr在黏土岩上的吸附过程有一定促进作用，而对伊利石吸附Sr的过程产生抑制。

Radioactive waste raises great concern because of its possible secondary contamination in geological disposal. Sr, as one of the typical components of radioactive waste, should be paid attention to in geological disposal. Claystone is one of the main types of surrounding rock in the geological disposal of radioactive nuclear waste reservior in China. Colloid is a common component in groundwater, which will directly affect the adsorption and blocking effect of claystone on nuclides. Therefore, in the type of claystone disposal reserviore, it is of great application value to study the adsorption behavior of Sr by colloid acting on claystone. This study selected the nuclide Sr as the research object, and used the claystone in Suhongtu area of Inner Mongolia as the adsorption medium. Furthermore, the batch experiments were performed to analyze the key factors affecting the adsorption process. Through fitting the adsorption kinetic models, a variety of spectral characterizations and hydrogeochemical simulations were used for research. Meanwhile, under the action of different types of colloid, the types of adsorption reaction, the mechanisms of adsorption, the mechanisms of water-rock reaction and the form of occurrence of Sr in claystone were studied.

(1) In order to study the adsorption of Sr by claystone, the batch experiments were made under the action of colloid free, goethite colloid, bentonite colloid and composite colloid. And the adsorptioon effect of the amount of colloid, reaction time, adsorption medium mass, pH value, temperature and illite (the main clay mineral component of claystone) on Sr were discussed. The results showed that the adsorption process of Sr by claystone with different colloid could be divided into two stages. One was the early stage of adsorption (<120 min). The goithite colloid and bentonite colloid alone did not show a significant effect on the adsorption while the composite colloid showed a slight inhibition effect on the adsorption of Sr on claystone. In the adsorption stage t>120 min, goethite colloid and bentonite colloid separately promoted the adsorption more obviously, and the adsorption rate increased by about 3.13%~7.55%. However, the composite colloid had a slight inhibition effect on the adsorption process due to its complexity. The amount of colloid and the mass of adsorption medium on the adsorption system suggested that the adsorption rate increased rapidly first and then stabilized with the increase of the amount of colloid and the mass of adsorption medium. And the effect of pH was reflected by the different rate of adsorption under acid and alkaline conditions that were favorable for adsorption. With the increase of temperature, the adsorption rate of Sr by claystone increased firstly and then decreased. The early stage of adsorption of Sr by illite (<120 min), bentonite colloid had a slight inhibition; In equilibrium stage, bentonite colloid and the composite colloid inhibited the adsorption, and bentonite colloid indicated that a more obvious inhibition effect, reducing the adsorption rate by 3.93%.

(2) By fitting the adsorption kineic models and analyzing the characteristic parameters, this study reveals the adsorption reaction modes and types of Sr-claystone and Sr-illite (the main clay mineral components in claystone) under the action of different colloids. In the Sr-claystone system, the adsorption behavior of the claystone for Sr without colloid and goethite colloid followed pseudo-first-order, pseudo-second-order, and hyperbolic-tangent adsorption kinetic models, which indicated that the adsorption process was controlled by diffusion and chemical adsorption; The adsorption process under the action of bentonite colloid followed the general adsorption kinetic model, indicating that the adsorption mechanism was mainly surface adsorption; The adsorption process under the action of the composite colloid can be accurately described by Elovich, pseudo-first-order, pseudo-second-order and the general adsorption kinetic models, indicationg that the process was a complex mechanism including electrostatic, surface comolexation and ion exchange. The adsorption behavior of illite for Sr in colloid free, goethite colloid, bentonite colloid and composite colloid all followed the pseudo-first-order and pseudo-second-order, indicating that the physical adsorption and chemical adsorption mechanism coexisted. The general adsorption kinetic model showed that the adsorption of Sr on illite under goethite colloid was surface adsorption.

(3) SEM, EDS, XRD, FTIR and XPS spectral characterization techniques were used to characterize changes of the microstructure, element content, crystal structure, functional group types, valence and electronic structure of claystone and illite. The SEM spectrum showed that the surface roughness and microporous structure of the claystone under the action of the bentonite colloid had the most changes, and the adsorption sites were significantly increased, which was an important mechanism to promote the adsorption rate of Sr. On the contrary, the adsorption rate of claystone decreased under the action of the composite colloid. The XRD results showed that bentonite colloid made the displacements of diffraction peaks of claystone change greatly, the peak shape change drastically, and the adsorption rate of Sr is significantly increased. However, the displacements of the drffraction peaks of illite was the smallest and the adsorption rate was reduced. The changes of the FTIR specturm indicated that the bentonite colloid promoted adsorption rate by increasing the environmental electronegativity of functional groups in claystone, while it had little influence on illite. The XPS results showed that Si and Al in bentonite colloid and Fe in goethite colloid can bond with claystone to form functional groups to promote adsorption. Therefore, the bentonite colloid had a certain promotion effect on the adsorption process of Sr on the claystone, while inhibiting the adsorption process of Sr on the illite.

(4) The hydrogeochemical simulation software (The Geochemist’ s Workbench, GWB) was used to simulate and analyze the chemical form characteristics of Sr in aqueous solution during the adsorption process. The results showed that the chemical forms of Sr in the claystone/illite system were all mainly Sr²⁺、SrCl⁺、SrOH⁺, as well as SrCO₃(aq)、SrSO₄(aq)、SrHPO₄(aq)、SrH₂PO₄⁺、SrP₂O₇^2-、SrCH₃COO⁺ and Sr(CH₃COO)₂(aq).