Adsorption and desorption of uranium (Ⅵ) in aerated zone soil

摘要

In this paper, the adsorption and desorption behaⅥor of uranium (Ⅵ) in aerated zone soil (from Southwest China) was systematically investigated using a static experimental method in order to proⅥde useful information for safety assessment of the disposal of (ultra-)low uraniferous radioactive waste, as well as a potential remediation method for uranium-contaminated soils. The adsorption behaⅥor of uranium (Ⅵ) was firstly studied by batch experiments as functions of contact time, pH, liquid/solid ratio, temperature, colloids, minerals and coexistent ions. The results indicated that the adsorption of uranium (Ⅵ) by natural soil was efficient at an initial concentration of 10 mg/L uranium (Ⅵ) nitrate solution with 100 mg natural soil at room temperature when pH is about 7.0. The adsorption was strongly influenced by the solution pH, contact time, initial concentration and colloids. The adsorption equilibrium for uranium (Ⅵ) in soil was obtained within 24 h and the process could be described by the Langmuir adsorption equation. For uranium (Ⅵ) desorption, EDTA, citric acid and HNO_3 were evaluated under different conditions of temperature, concentration and proportion of liquid to solid. The adsorbed uranium (Ⅵ) on natural soil could be easily extracted by all these agents, especially by HNO_3, implying that the uranium-contaminated soils can be remedied by these reagents.