缓冲回填材料膨润土胶体的提取与分析

Optimization of Extraction Methods and Basic Properties Research of GMZ Bentonite Colloids

我国拟建造的高放废物地质处置库计划使用膨润土作为缓冲回填材料。有效提取膨润土在处置库地下水中形成的胶体,检测其各项物理化学参数,对理解胶体对关键放射性核素在处置库近场的吸附、扩散和迁移行为的影响具有重要意义。本工作分析了原状高庙子膨润土的矿物组成及其元素含量。对原状高庙子膨润土胶体预处理、提取方法进行了优化,建立了稳定、可靠获取膨润土胶体的实验方法。结果表明:超声振荡或沸热分散后再离心分离的方法不仅能在较短的时间内获得尺寸在100nm左右的膨润土胶体,且有较好的单体分散性,此外,不同批次胶体样品的zeta电位均大于-60mV,显示其良好的稳定性。能量色散X射线光谱分析结果表明,膨润土胶体主要成分为SiO_2。

China plans to construct a high-level radioactive waste geological repository using bentonite as backfilling material. It is great significance for understanding the effect of colloid on the sorption, diffusion and migration behavior of key radio nuclides in the near field of the repository that effectively extract bentonite colloids formed in the groundwater at the repository condition and measure the various physical and chemical parameters. In this paper, analysis of undisturbed Gaomiaozi bentonite by X-ray diffraction and X-ray fluores- cence shows that the content of montmorillonite is about 52~//oo and the main elements are Si and A1. A simplified and optimized soil colloid extraction method was set up. This method was used to extract bentonite colloids and to examine the properties of colloids. Our experi- mental results indicate that ultrasonic oscillation or boil up dispersion method can obtain ben-tonite colloids of about 100 nm in a shorter time and with better monodispersity. The zeta potential of the colloids are greater than -60 mV suggesting good stability. Analysis by energy dispersive X-ray spectroscopy shows that the main component of the colloids is SiO2.