| In-situ leaching of uranium, after joining leaching solution, the leaching liquidreacted with ore-bearing rock and generated a large number of white colloidalsubstance. The white colloidal substance caused serious jam to seam. The whitecolloidal substance were Al(OH)3and SiO2colloids composition. Al(OH)3and SiO2colloids can adsorb to Zn, Cr, Pb, Cu, Cd etc. In the nuclear industry, uranium wastewater can cause pollution to the environment and be through various channels to enterthe body and cause a harm to human body. This paper studied the Al(OH)3and SiO2colloids for forming conditions and The influence of In-situ leaching of uranium, andthen using the best conditions of Al(OH)3and SiO2colloids adsorbed U(Ⅵ) in thisprocess. In this paper, the main research work are as follows:(1) The preparation of Al(OH)3colloids were prepared by adding NH3·H2O toAl(NO)3·9H2O solution. The paper researched that the mass of Al(OH)3colloidschanged with pH value change. The results showed that the pH value exerted animportant influence in the colloids formation course. The pH value in5to6the mosteasily formed Al(OH)3colloids the pH for5to6, the NH3·H2O consumption weresimilar before pH=7and the pH is greater than8, the NH3·H2O consumption has risensharply. Because of SiO2colloidal stability interval of8-10, SiO2colloids wereprepared by mixing Na2SiO3(8%) and NaCl (15%), and the pH value was controlledby H2SO4(10%) in this process. Finally, the characteristics of colloids were identifiedby SEM, EDS and laser particle size analyzer. Results showed that the purity of theAl(OH)3and SiO2colliods were very high, did not contain other impurities, particlewas less than1000nm.(2) In order to study the impact of colloidal seam blocking and adsorption andmigration of uranyl ion in situ leaching of uranium，aluminum nitrate and ammoniahydrate as the starting materials was used for preparation of Al(OH)3，and theAl(OH)3 of preparation at pH=6was used to adsorb the U(Ⅵ) from solution. The effectfactors on the Al(OH)3adsorption the U(Ⅵ)，such as pH value，initial uraniumconcentration， contact time were investigated and described detailedly;pseudo-first-order, composite-second-order and Elovich dynamic models werecalculated and discussed, on the basis of adsorption kinetics parameter obtained thatthe Elovich dynamic was fitted to describe the adsorption of uranium on Al(OH)3colloids, the adsorption was external surface adsorption; Freundlich and Langmuiradsorption isotherm models were applied to experimental equilibrium data, it wasfound that equilibrium data agreed well with the Langmuir model；The properties ofthe Al(OH)3were determined by SEM and laser particle size analyzer, the resultsshowed that the SiO2colloids were changed.(3) SiO2colliods for uranium adsorption experiments focused on exploring theadsorption mechanism of U(VI) onto SiO2colloids. Adsorption behavior of U(VI)onto SiO2colloids was studied in this work. It was found that contact time, pH valueand initial uranium concentration exerted an important influence in the adsorptioncourse. Furthermore, adsorption of U(VI) kinetics and isotherm were calculated anddiscussed. According to adsorption kinetics equations obtained by pseudo-first-order,pseudo-second-order and Elovich dynamic models, the pseudo-second-order wasfitted to describe the adsorption behavior of U(VI) onto SiO2colloids. Additionally,Langmuir, Freundlich and Temkin isotherm models were programmed toexperimental data fitting. It was found that experimental data was very suitable to theLangmuir model. Finally, the characteristics of the SiO2colloids were identified bySEM and EDS, the results showed that the SiO2colloids were changed. |
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