Kinetics and Equilibrium of Reaction between Octakis (dimethyl sulfoxide) uranium(IV) and Nitrite Ion in Dimethyl Sulfoxide

The kinetics and equilibrium of the reaction between octakis (dimethyl sulfoxide) uranium (IV), U(dmso)₈ ⁴⁺, and nitrite ion N0₂ ^? were studied in dmso solutions by using stopped-flow, diode-array and UV-visible spectrophotometers. Three different reactions were observed under the condition of an excess NaNO₂, and U(IV) was finally oxidized to U(VI) by N0₂ ^?. The first reaction is the formation of 1: 2 adduct complex [U (dmso₈)(NO₂)₂ ²⁺), the rate of which was so fast that the rate constant k_l obs was not determined accurately even by the stopped-flow method. If the concentration of N0₂ ^? was as low as that of U(IV), 1:1 adduct complex was formed. However, 1:1 complex was inert for further redox process, i.e. U(IV) was not oxidized by N0₂ ^? under this condition. The second reaction represents the substitution of coordinated dmso with N0₂ ^? forming mixed ligand complex [U(dmso) _8-x(N0₂ ^?)_x+2(^{2-x +}) The rate constant k ₂0bs for the second reaction was measured by the conventional method using a diode-array spectrophotometer and k ₂0bs increased linearly with the concentration of free N0₂ ^?. The third reaction coincides with the intra-molecular oxygen transfer from coordinated N0₂ ^? to U(IV) and this process is accompanied by the oxidation of U(IV) to U(VI). The oxygen transfer mechanism was confirmed by ¹⁷O labeled experiments using ¹⁷O-NMR. It was found from acid dependence experiments that only nitrite ion oxidized U(IV) and that nitrous acid was inert as an oxidant for U(IV).     

Separation of Uranyl Ions on Starch-Based Functional Hydrogels: Mechanism and Kinetics

In this article, we report the mechanism and kinetics of adsorption of uranyl ions on starch-based functional hydrogels. The hydrogels were prepared from starch in native or hydrolyzed/oxidized form by crosslinking with N,N-methylenebisacrylamide. The hydrogels synthesized from the oxidized starch have carboxylic groups at C-6 position. The effect of the structure and external environmental factors, i.e., contact time, temperature, ion strength, and simulated seawater (0.55 M NaCl and 3 mM NaHCO₃), was investigated on the uranyl adsorption behavior of hydrogels. The adsorption of uranyl ions was rapid as the highest adsorption was observed after 6 h and at 40°C. The sorbents also exhibited appreciable ion uptake even from the simulated seawater. The equilibrium data was analyzed using Langmuir and Freundlich adsorption isotherms and pseudo-first order and pseudo-second order kinetic models. Evidence of adsorption was obtained by characterization of the uranyl ions-loaded hydrogels by FTIR spectroscopy and also by elution with 0.1 N HCl.     

铀酰-salophen印迹聚合物的合成与性能研究

以一种铀酰配合物为模板,制备了一种用于从水相选择性分离铀酰的新型印迹聚合物。用5-氯甲基水杨醛和3,4-二氨基苯甲酸合成四齿配体salophen,再合成铀酰与salophen的配合物铀酰-salophen。然后以甲基丙烯酸甲酯为功能单体,二甲基丙烯酸乙二醇酯为交联剂,铀酰-salophen为模板,合成铀酰的印迹聚合物。聚合物中的铀酰通过酸浸除去。用平衡吸附法研究了聚合物对铀酰的吸附性能和选择识别能力,且探讨了实验条件对印迹聚合物吸附性能的影响。结果表明,在竞争金属离子存在下,印迹聚合物对铀酰具有较高的吸附能力和选择识别能力,选择性系数大于200,且可以循环使用。     

基于磺基Salophen配位反应荧光法测定铀酰

用5-磺基水杨醛与邻苯二胺反应,合成了水溶性良好的四齿西佛碱配体磺基Salophen。研究了磺基Salophen与铀酰离子发生配位反应生成配合物铀酰-磺基Salophen过程的荧光光谱。结果表明,磺基Salophen与铀酰配位后体系的荧光显著增强,最大发射波长位于428 nm。应用该反应建立了荧光分析法测定水溶液中铀酰离子的新方法。在优化条件下测定铀酰的线性范围为0.03~4.0 nmol/mL,检出限为0.015 nmol/mL。应用建立的荧光法测定了实际水样中的铀酰,回收率为97.0%~104.0%。     

活性污泥胞外聚合物对铀酰离子的吸附性能

用乙酸钠培养驯化了取自污水处理厂的活性污泥,采用NaOH提取法从活性污泥中提取了胞外聚合物(EPS)。用静态法研究了EPS对铀酰离子的吸附行为,探讨了温度、pH、反应时间、EPS投加量和离子强度等因素对铀酰离子吸附效果的影响,进行了吸附热力学、吸附动力学研究,对比了EPS吸附铀酰离子前后的红外谱图。结果表明:最佳吸附温度为25℃,最佳吸附时间为120min,EPS最佳投加量为300mg/L,离子强度对吸附影响较大;吸附热力学和动力学研究表明,吸附过程更符合Freundlich吸附模型和假二级反应动力学模型。     

铀酰在氧化石墨烯和碳纳米纤维上吸附的研究进展

铀是核能利用过程中（包括铀矿开采加工、乏燃料后处理和放射性废物的处置等）存在的重要元素之一。铀酰(UO²⁺₂)具有很好的水溶性易于在环境中扩散、迁移与转化。由于其放射性和化学毒性，铀酰进入环境中将对生物和人类造成潜在的威胁。因此，开发新型的纳米材料对水中铀酰的治理具有非常重要的意义。本论文评述氧化石墨烯(GO)、碳纳米纤维(CNF)及其复合材料对铀酰的吸附过程，为实际含铀废水的治理提供理论依据，为我国核能可持续发展和核环境的保护提供技术支持。     

用于铀酰离子检测的光化学分析传感器研究新进展

随着全球变暖和能源问题的出现,对于核能这种清洁能源的开发和应用越发深入和广泛。铀作为一种核原料非常宝贵,然而以铀为主的核废料因其高放射性和生物毒性对人类的生命健康产生了威胁,因此如何实现对其痕量检测成为了人们关注的焦点。光化学传感器由于分析迅速、灵敏度高,能够及时检测排查铀等放射性元素。因此,研发拥有高选择性、高灵敏度和可重复使用的铀酰光化学检测传感器就显得尤为重要。本文主要阐述了近年来基于光化学技术的铀酰检测传感器的前沿进展,其中光化学技术主要包括紫外可见分光光度法（UV-vis）、荧光（fluorescence）分光光度法、表面增强拉曼散射法（SERS）等,并讨论了其各自检测特性,分析了优势与不足之处,初步探讨了光化学传感技术测铀的发展趋势及方向,为进一步设计铀酰光化学检测传感器提供了参考。     

DCH-18-C-6/乙酸乙酯萃取体系萃取分离铀(Ⅵ)的研究

以二苯并-18-冠醚-6(DCH-18-C-6)作为萃取剂,采用溶剂萃取法萃取分离溶液中的铀(Ⅵ),研究了稀释剂、盐析剂、介质酸度等条件对萃取率的影响,确定了乙酸乙酯为稀释剂,0.1 mol/L的KH2PO4为盐析剂、水杨酸为酸性介质的溶剂萃取体系。该萃取体系在选定的条件下,对1×10-4mol/L的铀酰离子一次萃取率可达82.5%。     

基于事故进程的氟化铀酰溶液临界裂变次数估算方法

氟化铀酰溶液临界事故是核燃料循环设施潜在的一种临界事故,需要做好其相应的事故应急评价,为应急响应提供辅助决策支持。临界裂变次数是核临界事故应急评价的重要内容,也是技术难点之一。它反映了核临界事故的大小和规模,直接影响事故应急防护行动决策。裂变次数估算有多种方法,有各自的适用条件。随着事故发生的时间推移,获取的信息越丰富,选择的评价方法也随之优化。因此提出了基于事故进程的氟化铀酰溶液临界裂变次数估算方法,该方法解决了临界事故应急评价实际应用问题及技术人员选择何种评价方法的困难问题。     

MIPR燃料硝酸铀酰溶液中痕量氟、氯离子的测定

采用水蒸气蒸馏法分离出硝酸铀酰溶液中的痕量F-、Cl-,并用离子色谱对F-、Cl-进行测定,对F-、Cl-分离条件和测定条件进行了讨论。该法的线性范围为0.04~0.3 mg/L,线性相关系数大于0.999,相对标准偏差小于10%,样品的加标回收率为94%~97%。