锌镍铁三元水滑石的制备及其对铀的吸附性能研究

Preparation of Zn-Ni-Fe Ternary Hydrotalcite and its Adsorption Properties for Uranium

用水热法成功制备了蜂窝状的锌镍铁三元水滑石(ZnNiFe-LDH),并将其用于吸附含铀废水中的铀。考察了溶液pH、吸附剂投加量、铀初始质量浓度等因素对ZnNiFe-LDH吸附U(Ⅵ)的影响,结合吸附前后材料的微观表征,探究了ZnNiFe-LDH对U(Ⅵ)作用机理。实验结果表明:当温度为25℃、pH为5、固液比为0.10 g/L时,ZnNiFe-LDH对10 mg/L铀的去除率为97.57%。吸附动力学和热力学实验表明:准二级动力学模型和Langmuir等温吸附模型的相关系数R^(2)更接近于1,表明ZnNiFe-LDH对铀的吸附是以化学吸附为主的单分子层吸附,且该反应是一个容易进行的自发吸热反应。反应前后材料的原子价态和晶相结构未发生明显变化,表明ZnNiFe-LDH吸附U(Ⅵ)的主要机理为表面络合。25℃时,ZnNiFe-LDH对U(Ⅵ)平衡吸附量高达689.66 mg/g,在处理低浓度含铀废水方面有一定的应用前景。

The honeycomb-shaped zinc-nickel-iron ternary hydrotalcite(ZnNiFe-LDH)was successfully prepared by hydrothermal method and used to adsorb uranium from uranium-containing wastewater.The effects of solution pH,adsorbent dosage,initial mass concentration of uranium and other factors on the adsorption of U(Ⅵ)by ZnNiFe-LDH were investigated.The mechanism of ZnNiFe-LDH on U(Ⅵ)was explored by combining the microscopic characterization of the materials before and after adsorption.The results show that the removal rate of 10 mg/L uranium by ZnNiFe-LDH is 97.57%when the temperature is 25℃,pH is 5 and the solid-liquid ratio is 0.10 g/L.The adsorption kinetics and thermodynamic experiments show that the correlation coefficient R^(2) of the quasi-second-order kinetic model and the Langmuir isotherm adsorption model is closer to 1,indicating that the adsorption of uranium by ZnNiFe-LDH is a monolayer adsorption based on chemical adsorption,and the reaction is a spontaneous endothermic reaction that is easy to proceed.After adsorption,the atomic valence and crystal structure of the material did not change significantly,indicating that the main mechanism of ZnNiFe-LDH on U(Ⅵ)is surface complexation.The saturated adsorption capacity can reach 689.66 mg/g at 25℃,which has great application prospects in the treatment of low-concentration uranium-containing wastewater.