酰胺基两性分子对二硫化钨吸附铀容量的影响机制

Influence mechanism of amide-based amphoteric molecules on uranium adsorption capacity of WS_(2)

含铀废水中铀的回收主要是基于材料与[UO_(2)(H_(2)O)_(5)]^(2+)中UO_(2)(^(2+))之间的络合,但H_(2)O的电偶极矩对络合有显著弱化作用。采用酰胺基两性分子N,N-二甲基-9-癸烯酰胺(NADA)氢键作用与[UO_(2)(H_(2)O)_(5)]^(2+)形成UO_(2)[(H_(2)O)_(x)C_(12)H_(2)3NO]_(n)^(*)(x<5,UO_(2)-Coordination Compound,简称UO_(2)-CC),选取惰性物质WS_(2)为吸附材料,通过静态吸附试验(不同pH、接触时间、浓度和温度)分别研究其对UO_(2)^(2+)和UO_(2)-CC的吸附量。动力学拟合结果表明,二者的吸附反应是化学吸附过程,UO_(2)+经NADA重构后,吸附时间从240 min缩短至180 min,准二级动力学吸附常数提高1.35倍。等温吸附研究结果表明,WS_(2)与UO_(2)-CC络合过程符合Langmuir吸附等温模型,且NADA的加入使吸附由自发吸热过程转变为自发放热过程,吸附反应过程有序度增加。NADA原位重构[UO_(2)(H_(2)O)_(5)]^(2+)后,WS_(2)对UO_(2)^(2+)的平衡吸附量由45.03 mg/g(WS_(2)/UO_(2)^(2+)体系)提高到122.14 mg/g(WS_(2)/UO_(2)-CC体系)。采用光谱分析(X射线光电子能谱法)从分子水平深入研究NADA原位重构[UO_(2)(H_(2)O)_(5)]^(2+)后在WS_(2)上的吸附机制,揭示静电、氢键和U—S共价键等作用力对吸附的贡献,特别是NADA的氢键作用。

The recovery of uranium from uranium-containing wastewater is mainly based on the complexation between the material and UO_(2)^(2+)in[UO_(2)(H_(2)O)_(5)]^(2+),but the electric dipole moment of H_(2)O has a significant weakening effect on the complexation.The amide-based amphoteric molecule N,N-dimethyl-9-decenyl amide(NADA)was used for hydrogen bonding with[UO_(2)(H_(2)O)_(5)]^(2+)to form UO_(2)[(H_(2)O)_(x)C_(12)H_(2)3NO]_(n)^(*)(x<5,UO_(2)-Coordination Compound was named UO_(2)-CC),Inert tungsten disulfide(WS_(2))was selected as the adsorption material,and the adsorption capacities of UO_(2)^(2+)and UO_(2)-CC were studied by static adsorption experiments(different pH,contact time,concentration and temperature).The kinetic fitting results showed that the adsorption reaction was a chemisorption process.After NADA reconstruction,the adsorption time of UO_(2)^(2+)was shortened from 240 min to 180 min,and the quasi-second-order kinetic adsorption constant was increased by 1.35 times.The results of the isothermal adsorption study showed that the complexation process of WS_(2)and UO_(2)-CC conformed to the Langmuir adsorption isothermal model,and the addition of NADA made the adsorption change from spontaneous endothermic process to spontaneous exothermic process,and the order degree of the adsorption reaction process increased.After in situ reconstruction of[UO_(2)(H_(2)O)_(5)]^(2+)by NADA,the equilibrium adsorption capacity of UO_(2)^(2+)by WS_(2)increased from 45.03 mg/g(WS_(2)/UO_(2)^(2+)system)to 122.14 mg/g(WS_(2)/UO_(2)-CC system).Spectroscopic analysis by X-ray photoelectron spectroscopy was used to deeply study the adsorption mechanism of NADA on WS_(2)after in situ reconstruction of[UO_(2)(H_(2)O)_(5)]^(2+)at the molecular level,and to reveal the contribution of various forces(electrostatic,hydrogen bond and U-S covalent bond)to adsorption,especially the hydrogen bond of NADA.