多级结构Ni-Co-LDH的制备及其吸附U(Ⅵ)的行为与机理

Preparation of Hierarchical Structure Ni-Co-LDH and Its Adsorption Behaviour and Mechanism for U(Ⅵ)

以ZIF-67为模板,原位水解制备多级结构Ni-Co-LDH。研究了吸附时间、溶液pH值、温度及U(Ⅵ)初始浓度对吸附U(Ⅵ)性能的影响,并分析了吸附U(Ⅵ)前后Ni-Co-LDH微观结构、表面形貌和含氧基团的变化情况,阐明了Ni-Co-LDH对U(Ⅵ)的吸附机理。结果表明:pH值是影响吸附的主要因素,吸附最佳pH值为5.0,在该条件下,饱和容量最大的吸附剂为Ni-Co-LDH-180,其吸附容量达到1135.30 mg/g。Ni-Co-LDH-180吸附U(Ⅵ)过程与假二级动力学模型及Langmuir吸附等温线模型吻合,且该吸附过程是一个自发吸热过程。Ni-Co-LDH-180在含Ca^(2+)、Mg^(2+)、Ni^(2+)、Cu^(2+)、Zn^(2+)、Pb^(2+)、CO^(2)_(-3)等杂质离子的混合溶液中对U(Ⅵ)具有较好的选择性。Ni-Co-LDH-180高效吸附U(Ⅵ)主要归功于其表面的Ni—OH、Co—OH和Ni—O—Co基团。

Ni-Co-LDH with multistage structure was prepared via in situ hydrolysis using ZIF-67 as template.The effects of adsorption time,solution pH values,temperature and initial concentration of U(Ⅵ)on the adsorption performance of U(Ⅵ)were studied.The changes of microstructure,surface morphology and oxygen-containing groups of Ni-Co-LDH before and after adsorption of U(Ⅵ)were analyzed.The adsorption mechanism of Ni-Co-LDH on U(Ⅵ)was elucidated.The results show that pH value change is the main factor affecting the adsorption,and the optimum pH is 5.0,in which Ni-Co-LDH-180 has the largest saturated capacity for U(Ⅵ),up to 1135.30 mg/g.The adsorption process of U(Ⅵ)on Ni-Co-LDH-180 is consistent with pseudo second order kinetic model and Langmuir isotherm model,and the adsorption process is a spontaneous endothermic process.Ni-Co-LDH-180 has good selectivity for U(Ⅵ)in the mixed solution containing Ca^(2+),Mg^(2+),Ni^(2+),Cu^(2+),Zn^(2+),Pb^(2+),and CO^(2)_(-3).Ni-Co-LDH-180 can effectively adsorb U(Ⅵ)due to the Ni—OH,Co—OH,and Ni—O—Co groups on its surface.