铀、钍在改性红壤上的非线性、多参数吸附模型研究

The safe disposal of radioactive waste is paid more and more attention in worldwide, especially actinides (U(VI), Th(IV),etc.), so it is very important to study the sorption activity of radioactive nuclides on environmental mediums. Actinides have the characteristics of long half-life, high toxicity, complex chemical behavior, make the study of sorption and transference on these transuraniums in natural medium be more important. As a clay mineral, red earth has many sorption characteristics such as ion exchange capability, expanding capacity, highly capable of adsorbing pollutants and self-purification functions, therefore clay minerals have the capacity for controlling environmental pollution. While the reports of sorption focused on two-parameters models and linear methods recently. This research project put the focus on the study of nonlinear multiparameter models of actinides sorption on red earth in south China by using dynamic and static adsorption method. While, the elemental speciation analysis will becomme an important means to the study as well. At present, the research on the sorption of uranium and thorium on red earth is relatively broad, but limited to the study of sorption phenomena itself and several linear models. On the contrary,the research on the sorption behavior and mechanism on modified red earth is seldom reported, especially the nonlinear multiparameter sorption model..In this project, The main research contents are: To prepare inorganic and organic modified red earth samples and characterize them using XRD, SEM, XPS and FT-IR, to study the sorption of U(VI) and Th(IV) on red earth as a function of contact time, pH, ionic strength and presence of humic acid (HA); To study the sorption kinetics and thermodynamics of actinides sorption on red earth, describe the sorption isotherms and calculate the distribution coefficients, and to suggest a sorption mechanism of actinides on the modified red earth by the pseudo-second-order rate constant and two or multiple parameter models; To creat a optimized and scientific multiparameter model by the experimental acta and other models to provide experimental basis for the safe disposal of high-level radioactive waste.

本课题针对核燃料利用后高放废物处置和铀、钍等对环境可能造成的风险问题，将核能利用重点地区的红壤作为研究对象，拟采用动态吸附与静态吸附相结合的方法，结合元素的形态分析技术，研究铀、钍在天然红壤及改性红壤上的吸附动力学和热力学，探讨核素在改性红壤上吸附的机理，特别是建立新的非线性、多参数吸附模型，揭示核素在改性红壤中的吸附-迁移规律。目前，国内外对于铀、钍等在土壤上的吸附行为研究较为广泛，但多局限于研究吸附现象本身和几种成熟的线性模型，并且已有的Langmuir等模型不能对吸附过程进行准确描述，而对改性红壤的吸附行为、机理研究，特别是非线性、多参数吸附模型研究少有报道。课题采用无机和有机改性方法对红壤进行改性，研究不同条件下铀、钍的非线性、多参数吸附模型，阐释核素在不同成分红壤上的吸附规律，并通过实验数据，进一步优化吸附理论模型，为高放废物处置中正确选择、优化吸附剂奠定理论和实验基础。

该项目针对我国对高放废物处置技术方法的研究和开发也正处于关键时期的现状，在天然红壤基础上，制备了无机改性、有机改性红壤，以铀、钍在无机改性、有机改性红壤的吸附-迁移等行为研究为重点，通过铀钍在改性红壤介质中的迁移行为研究，进而认识放射性核素在地质材料中的迁移规律，为放射性废物的安全处置以及环境风险评价提供科学依据，具有一定的创新性和现实意义。该项目系统研究了铀钍在改性红壤上的吸附行为，重点考察了pH、共存离子、温度、核素初始活度或浓度等因素对放射性核素在改性红壤表面的吸附性能和机制。创新性地采用线性和非线性方法来探索放射性核素在改性红壤上的动力学和热力学行为，得到了吸附反应的动力学和热力学等重要的相关参数，建立了有效的动力学和热力学模型。项目总结了不同改性方法、不同结构、不同组分、不同影响条件下的放射性核素的吸附规律，概括了吸附反应的特性，为正确选择合理的高放废物处置与处理技术、方法等奠定了一定理论基础，同时为放射性核素对环境的危害评估和风险预测等提供重要的理论支撑。