摘要
采用批式法研究了U(Ⅵ)在Na-凹凸棒石黏土上的吸附行为,结果表明,U(Ⅵ)在Na-凹凸棒石黏土上的吸附动力学速度快,且符合假二级动力学方程。探讨了吸附接触时间、离子强度、pH值、富里酸(FA)及温度等因素对吸附的影响。结果发现:在pH<5.5时,随NaCl浓度的增大,U(Ⅵ)在Na-凹凸棒石黏土上的吸附率减小,pH>8.0时,随NaCl浓度的增大,U(Ⅵ)的吸附率反而增大;在pH<6.0时,吸附率随pH值增大而增大,pH>8.0时,吸附率随pH值的增大而减小;在高pH值下,U(Ⅵ)在Na-凹凸棒石黏土上的吸附机理可能主要是表面配合作用,而在低pH值下,其吸附机理可能主要是离子交换作用;高温有利于U(Ⅵ)在Na-凹凸棒石黏土上的吸附,且该吸附是吸热的、自发的过程;FA对吸附有明显的促进作用。
The sorption behavior of radionuclides onto geological media such as rocks,clays or minerals has been an important part in the evaluation of the physicochemical behavior of radionuclides in the environment.Herein,the attapulgite sample was characterized by X-ray diffraction and scanning electronic microscopy,and the sorption of U（Ⅵ） on the Na-attapulgite was investigated as functions of contact time,ionic strength,pH,fulvic acid（FA） and temperature by using a batch technique.The results indicate that the sorption of U（Ⅵ） on Na-attapulgite depends on pH,ionic strength,temperature and humic acid.The sorption of U（Ⅵ） on Na-attapulgite is a kinetically fast process,and the sorption equilibrium can be achieved in about 2-3 h.The sorption of U（Ⅵ） on Na-attapulgite decreases with the increasing concentration of NaCl solution at pH5.5,whereas increases at pH8.0.The sorption of U（Ⅵ） sharply increases with increasing pH at pH6.0,but decreases at pH8.0.Surface complexation may be the main sorption mechanism at high pH values,and ion exchange at low pH values.The sorption of U（Ⅵ） increases with increasing temperature,indicating the sorption process of U（Ⅵ） on Na-attapulgite is endothermic.Enthalpy（ΔH〇-）,entropy（ΔS〇-） and Gibbs free energy（ΔG〇-） were calculated from the temperature-dependent sorption data,the results indicate that the sorption of U（Ⅵ） on Na-attapulgite is a spontaneous process.The presence of fulvic acid enhances the sorption of U（Ⅵ） on Na-attapulgite.
出处
《核化学与放射化学》
CAS
CSCD
北大核心
2012年第5期297-304,共8页
Journal of Nuclear and Radiochemistry
基金
国家自然科学人才培养基金资助项目(J1030932)
