铁负载膨润土对铀(VI)的吸附特性及机理研究

采用膨润土经提纯、钠化及负载铁等过程制备铁负载膨润土,通过静态吸附实验研究了pH、离子强度、吸附剂投加量、U（Ⅵ）初始浓度、阳离子Ca^2＋、Mg^2＋以及阴离子CO3^2-、HCO3^-等对铁负载膨润土吸附模拟废水中U（Ⅵ）的影响,进行了吸附过程动力学、热力学分析,并利用傅里叶红外光谱（FT-IR）、扫描电镜（SEM）探讨了相关吸附机理.试验结果表明,pH值和离子强度是影响吸附效果的重要因素,当溶液pH为6,离子强度为0.01 mol/L NaNO3,U（Ⅵ）初始浓度为19.08 mg/L,铁负载膨润土投加量为0.2 g/L,24 h吸附量达到88.06 mg/g.当pH〈6时,Ca^2＋、Mg^2＋、CO3^2-、HCO3^-的存在分别降低了铁负载膨润土对U（Ⅵ）的吸附效果,而pH〉7时影响作用不大.准二级动力学和Langmuir等温吸附模型对铁负载膨润土吸附U（Ⅵ）的拟合效果较好,SEM和FT-IR分析结果表明铁负载膨润土主要通过羟基络合及离子交换作用结合U（Ⅵ）进入其层间及表面.

Adsorption Characteristics and Mechanism of Uraniumby Fe-immobilized Bentonite

The Fe-immobilized bentonite was prepared by purification,sodium and load of iron compounds. The adsorption properties of U（ Ⅵ） onto Fe-immobilized bentonite was investigated at various conditions of initial solution pH,ionic strength,adsorbent dosage U（ Ⅵ） concentration,as well as adding Ca^2 ＋,Mg^2 ＋,CO3^2-,HCO3^-by batch technique.Conducted adsorption kinetics,thermodynamics analysis,Fe-immobilized before and after adsorption were characterized by Scanning Electrion Microscope（ SEM） and Fourier Transform Infrared Spectra（ FT-IR）. Results indicated that the adsorption capacity were strongly affected by the solution pH and ion strength,the adsorption capacity reached 88. 06 mg /g after 24 h when U（ Ⅵ） concentration was 19. 08 mg /L and Fe-immobilized bentonite dosage was 0. 2 g /L. The common ions of Ca^2 ＋,Mg^2 ＋,CO3^2-,HCO3^-in natural water reduced the adsorption of U（ Ⅵ） by Fe-immobilized bentonite as pH 6,but had no significant effect as pH 7. The adsorption kinetics process was fitted well with the second-order kinetic equation,simultaneously the Langmuir equations could describe the adsorption isotherm of U（ Ⅵ） well. Based on SEM and FT-IR instruments,we found U（ Ⅵ） main entry bentonite layer and surface by hydroxy complex and ion exchange.