Sorption Of Aqueous Uranium(Ⅵ) Onto Red Soil-colloids

Uranium mine waste rock site and the facilities for uranium hydrometallurgy,would necessarily make a large amount of radioactive waste and must bring immenseeffect to environment. Uranium（Ⅵ） inuranium waste rock leachate could directlythreaten human health and surrounding environment after its entering into soilthrough food chain. It is known that, colloids in soil with the double electrical layerand diversity of adsorption active groups, can interact with uranium to form stablecompounds. In our work, we extract the red soil colloids from the red soil near theuranium mine, which is unaffected by the mining, and research the adsorbedeffectiveness of uranium by the red soil colloids. In addition, the mechanisms ofuranium blocking migration was analyzed, which has great significance for moreeffectively controlling environmental damage of radioactive waste uranium andproposing relevant countermeasures in soil. Meanwhile, this study aims to explore theevaluation plan about the environmental impact assessment of uranium leachate.Through research, the main conclusions reached are as follows for experiments in thispaper:（1） On the basis of present the domestic and foreign researches, this paperreviewed the source and classification of soil colloids, and generalized the interactionbetween uranium（Ⅵ） and soil colloids. The blocking effects of the structure of soilcolloids, the form of uranium ions, Eh and pH value of soil, ionic strength and organicmatters on uranium（Ⅵ） adsorption process were discussed.As well as the applicationprogress of colloid are presented. Moreover, several suggestions are proposed for howto present the breakthrough in long-term affecting the environmental of uranium（Ⅵ）which is in uranium waste rock leachate.（2） The adsorption behavior of uranium（Ⅵ） from aqueous solutions onto red soilcolloids have been studied using a static method. The results show that the adsorptioncapacity for uranium（Ⅵ） onto red soil colloid increases with the decrease of ionicstrength or particle size, and at normal temperature and pH3.5when the ionic strength is0.001mol·L^-1, the saturated adsorption capacity qmaxcould be up to76.76μg·mg^-1by d<1μm red soil colloid with organic matter.（3） The experimental date was detailedly analyzed. Using sorption kinetic models（Psendo-second-order equation） to determine the equation that fits best theexperimental results, R2=0.9966, and the Langmuir models have been applied,R2=0.9968, and the absorption process is a spontaneous endothermic reaction.（4） The red soil composition have been examined using X-ray fluorescencespectrum analysis. The results indicate that the red soils are mainly composed ofFe-Si-Al. The mechanism of red soil colloids was discussed by infraredspectroscopy（FT-IR） spectra and scanning electron micrographs（SEM）. The resultsshowed that surface morphology of red soil colloids was changed for absorbinguranium on colloids. In the course of experiments, uranyl ions often to formcomplexes with hydroxyl, carbonyl, Si-O, Si-O-Fe, etc. Therefore, removalmechanisms mainly performing for surface-complexation.