粘土岩对铀(Ⅵ)的吸附特征研究

Study of adsorption characteristic of uranium(Ⅵ)on clay rock

以内蒙古阿拉善粘土岩为研究对象,通过静态吸附实验,探讨接触时间、U(Ⅵ)初始浓度、固液比、pH值、离子类型以及离子浓度等因素对U(Ⅵ)吸附特征的影响.研究结果表明:粘土岩对U(Ⅵ)的吸附速率较快,24h即可达到吸附平衡,最佳吸附固液比为1∶200,最佳吸附初始浓度为160μg·mL-1;随着pH值的增大,粘土岩对U(Ⅵ)的吸附能力不断增强,pH为8时,吸附能力达到最大;溶液中Ca^(2+)、CO_3^(2-)和HCO_3^-对U(Ⅵ)吸附有很强的抑制作用,不利于U(Ⅵ)的吸附,K^+、Na^+、Cl^-、NO_3^-、SO_4^(2-)对U(Ⅵ)的吸附影响较弱,U(Ⅵ)在粘土岩表面吸附主要以内层络合作用为主.因此,开展粘土岩对U(Ⅵ)的吸附研究,对我国高放废物的处置工作开展起到了极其关键的作用.

In this paper, experimental study on static absorption was carried out for Alashan clay rock on Inner Mongolia. To explore the factors which may influence absorption characteristic of U（Ⅵ） on clay rock, including contact time, U（Ⅵ） initial concentration, solid-liquid ratio, pH value, ionic type and i- onic concentration. The following results are obtained. The absorption rate of U（Ⅵ） on Alashan clay rock in Inner Mongolia is quite fast with adsorption equilibrium achieved in 24 hours. The optimum ad- sorption ratio is 1 ： 200, and the optimum adsorption concentration is 160 μg · mL-1. The absorption ca- pacity of clay rock was enlarged with the increasing of pH value. When pH value is at 8, the ability of absorption reaches the best. The absorption capacity of U （VI） is largely hindered by Ca2＋ , CO3^2- and HCO3 , which have a great effect on the absorption ability of U（Ⅵ）. The distribution coefficients of K＋ ,Na＋ ,Cl-,NO3- ,SO4^2- can be changed with the change of ionic concentration, The surface adsorp- tion of U（Ⅵ） on clay rock is dominated by inner-sphere complexation. The studies indicate the adsorp- tion behavior of U（Ⅵ） on clay rock has a great significance on settling high level radioactive waste in China.