Valence Stabilization of Polyvalent Uranium Ions in Presence of Some Organic Additives during Extended Gamma Irradiation of Their Aqueous Acidic Solutions

In gamma irradiated aqueous acidic uranium solutions, tetravalent uranium ions are easily oxidized while U(VI) ions remain unchanged. In general, valence change of polyvalent metallic ions during chemical reprocessing of spent nuclear fuel solutions can lead to undesirable effects under the influence of the existing gamma radiations. Consequently, studies on valence stabilization of Uranium ions during chemical treatment in strong gamma irradiation fields seem to be highly interesting. It has been reported before that some organic compounds proved to be effective in stabilizing the valence of Fe(II) ions during extended gamma irradiation of their acidic solutions. In the present work, valence stabilization of Uranium ions in acidic solutions in presence of different classes of organic compounds has been studied. The results showed that in case of U(IV), methanol or formic acid are capable of providing about 80% protection while ethanol or acetaldehyde can provide about 70% protection. Propanol has the least protective effect i.e. about 54%. On using U(VI) instead of U(IV) in the irradiated solutions, the uranium ions were reduced and the formed U(IV) was protected as follows: formic acid or methanol can provide 69% or 63% protection respectively while ethanol, acetaldehyde or propanol can provide 50%, 35% and 24% respectively. In any case, protection exists as long as the organic additives were not completely consumed.

Sensitivity Enhancement in Uranium Determination by UV-Visible Spectroscopy Using Ion Imprinted Polymer

There is need to determination of uranium concentration at ppb level in environmental matrices.Due to low sensitivity of FAAS,UV-Visible Spectroscopy is generally used as measurement technique.In this study,ion-imprinted polymers(IIP)were prepared for uranyl ion(imprint ion)by formation of ternary(salicylaldoxime and 4-vinylpyridine)complex in 2-methoxy ethanol(porogen)following copolymerization with methacrylic acid(MAA)as a functional monomer and ethylene glycol dimethacrylate(EGDMA)as crosslinking monomer using 2,2-azobisisobutyronitrile as initiator.The synthesized polymers were characterized by FTIR and TGA analysis.ArsenazoⅢin 3M HClO_4 was used as complexing agent in the measurement step.The optimal pH for preconcentration was found to be between 3.5~6.5values.The developed method was applied to uranium(Ⅵ)determination in natural water samples.

Separation Behavior of U(VI) and Th(IV) on a Mixed Ion Exchange Column Using 2,6-Pyridine Dicarboxylic Acid as a Complexing Agent and Determination of Trace Level Thorium in Uranium Matrix Employing High Performance Ion Chromatography

Retention behavior of U(VI) and Th(IV) as their 2, 6-pyridine dicarboxylic acid (PDCA) complexes on reversed phase and ion exchange (cation, anion and mixed ion exchange) columns was studied and based on the results, a simple ion chromatography method for the determination of trace level thorium in uranium oxide using 0.075mM 2, 6-pyridine dicarboxylic acid (PDCA) and 1M KNO3 in 1.2M HNO3 as eluent (flow rate 1 mL/min)was proposed. The advantage of the developed method is that the separation of uranium matrix is not required prior to the ion chromatographic determination of trace Th. Separation was carried out on a mixed ion exchange stationary phase and a 10?4 M arsenazo (III) solution was used as post column reagent for detecting the separated metal ions. The separation of Th from uranium using PDCA in the present investigation is attributed through cation exchange mechanism. A calibration plot was constructed by following the standard addition method over the concentration range of 0.25 to 10 ppm of Th in the presence of uranium matrix, which resulted in a linear regression coefficient of 0.9978. The precision of the method was better than 5% and the LOD for Th was found to be 0.1ppm (S/N=3). The method has been validated by comparing the results with the results obtained from ICP-MS analysis where the This separated from the uranium matrix. The proposed method is simple, rapid, accurate and cost effective compared to techniques like ICP-MS or ICP-AES and is suitable for the routine kind of analysis.

Synthesis, Spectral and Electrochemical Studies of Complex of Uranium(IV) with Pyridine-3-Carboxylic Acid

The investigation of complexation of uranium with biological active ligands is vital for understanding uranium speciation in biosystems. A number of studies have been undertaken for investigating the complexation of uranium in its (VI) oxidation states but similar investigations pertaining to the interaction of uranium, in lower oxidation states, with biological ligands is scarce. The aim of the work is to bridge this gap and studies have been carried out to determine the coordination pattern of pyridine-3-carboxylic acid with uranium(IV). Semi-micro analysis, spectro-analytical techniques, magnetic susceptibility and cyclic voltammetry have been employed for the characterization of the synthesized complex.

Solvent extraction of nitric acid, uranium(VI) and thorium(IV) by N,N,N',N'-tetrahexylsuccinylamide

A new kind of diamide N,N,N’,N’-tetrahexylsuccinylamide（THSA） was synthesized, characterized and used for the extraction of HNO3, U（VI） and TI（IV） in a diluent composed of 0.5 volume fraction 1,2,4-trimethy benzene（TMB） and 0.5 volume fraction kerosene（OK）. Extraction distribution coefficients of U（VI） and TI（IV） as functions of aque- ous nitric acid concentration, extractant concentration, temperature and salting-out agent （LiNO3 ） have been studied, and it is found that THSA as an extractant is superior to TBP for extraction of U（VI） and TI（IV）. Back extraction was also studied. At low acidity, the main adduct of THSA and HNO3 is HNO3.THSA. THSA.（HNO3）2 and THSA.（HNO3）3 are also found at high acidity. The compositions of extracted species, apparent equilibrium constants and enthalpies of extraction reactions have also been calculated.

含铀钍氯化稀土溶液中离子交换法提铀

提出了一种利用铀酰离子与Cl^(-)的络合,从高稀土低铀的含氯体系浸出液中分离提取铀而将大部分的稀土元素和钍留在浸出液中的离子交换法。研究了离子吸附过程中体系pH和氯离子浓度等对吸附效果的影响。结果表明,在反应pH=0~1、Cl^(-)浓度7 mol/L的优化条件下,饱和树脂对铀的吸附量能够达到43.34 mg/g。后续采用7 mol/L HCl溶液酸洗和去离子水淋洗,回收钍和稀土的同时实现了铀的分离提取。该技术不改变传统稀土提取工艺流程,仅增加铀提取工艺技术单元,可实现铀的分离与浓缩,具有工艺流程短、不影响原有稀土提取工艺和矿产最大化利用的特点。

铬(III)离子催化铈(IV)离子氧化四氢糠醇的反应动力学及机理

在酸性介质中用氧化还原滴定法研究了铈(IV)离子在铬(III)离子催化作用下,于25～40℃区间氧化四氢糠醇的反应动力学.结果表明反应对铈(IV)和四氢糠醇均为一级.准一级速率常数kobs随催化剂[Cr(III)]增加而增大,亦随[H+]增加而增大,而随[HSO-4]增加而减小.在氮气保护下,反应不能引发丙烯酰胺聚合,说明在反应中没有自由基产生.提出了催化剂、底物和氧化剂间生成双核加合物的反应机理.通过kobs与HSO-4的依赖关系,并结合Ce(IV)在溶液中的平衡,找到了本反应体系的动力学活性物种是Ce(SO4)2.还计算出一些速率常数及相应的活化参数.

某铀尾矿库渗滤液综合处理工艺研究

针对含铀、锰、氨氮等多种污染物的铀尾矿库渗滤液,采用离子交换法回收铀、电絮凝除重金属和气膜回收氨氮工艺进行综合回收处理。验证了离子交换法回收铀的效果;考察了电絮凝法在不同原水pH、曝气时间和电絮凝时间等条件下,对铀、锰等重金属离子的去除效果;研究了在不同氨氮浓度下,气膜对废水中氨氮的分离效果。结果表明,树脂对铀的一级去除率可达95.7%;在不调整原水pH(pH=7.5)和不曝气的条件下,电絮凝效果较好,电絮凝5 min出水中的铀和锰质量浓度分别降至99.79μg/L和0.06 mg/L;当原水中氨氮质量浓度低于297.00 mg/L时,经过气膜一次处理对氨氮的去除率大于99%,出水氨氮质量浓度降至1.91 mg/L。该渗滤液综合处理工艺可实现铀和氨氮的回收,以及多类污染物的达标。

MOF-808的制备及其对水中铀离子的去除研究

含铀废水不仅污染环境,还会对居民的生命健康带来巨大危害。金属有机骨架(Metal-Organic Framework, MOF)材料具有大的比表面积、可调控的孔隙和丰富的吸附位点,在水体中铀等离子的去除方面前景广阔。本文合成了锆基金属有机骨架材料MOF-808,并用于去除水体中的铀离子;研究了MOF-808用量、初始铀离子浓度、pH和温度等条件对MOF-808吸附铀离子的影响,发现MOF-808吸附铀离子是一个符合Langmuir模型的自发过程;确定在pH=6时,12 h后MOF-808对铀离子的吸附量可达742 mg/g,是目前报道的吸附铀离子的最佳MOF材料之一;通过傅里叶变换红外光谱、X射线光电子能谱等手段对MOF-808进行表征,发现MOF-808对铀离子具有较高的吸附能力是由于铀离子与MOF-808上的Zr-O-C等基团间发生了较强的相互作用。

An Amidoximated-UHMEPE Fiber for Selective and High Efficient Removal of Uranyl and Thorium from Acid Aqueous Solution

High efficient removal and recovery of uranium and thorium from nuclear waste solution are essential for environmental preservation and fuel recycle. A new polymer fiber adsorbent (UHMEPE-g-PAO fiber), prepared by amidoximation of grafted polyacrylonitrile onto Ultra High Molecular Weight Polyethylene (UHMWPE) fiber, was used to remove the uranyl and thorium ions from acid aqueous solutions and its performance was carefully investigated. It was found that uranyl ion can penetrate the fiber through the connected pore structures, forming (UO2) (R-C(NH2)-NO)2 chelates with the amidoxime groups within the fiber. Two amidoxime groups (U-N and U-Oeq) and two water molecules (U-Oeq2) are bound to uranyl ion in the fiber. On the contrary, thorium ions are adsorbed mainly on the fiber surface in the form of Th(OH)4 precipitate that blocks the entrance of Th4+ ion into fiber pores. The maximum included other two capacities of uranyl and thorium ions were estimated to be 262.01 mg/g and 160 mg/g at room temperature with pH 3.0, respectively. The results also indicate that the UHMWPE-g-PAO fiber has higher adsorption selectivity for uranyl ion than thorium ion. Uranium and thorium oxide particles were obtained as the ultimate product after sintering of the fiber adsorbent. This novel and environmentally friendly adsorption process is feasible to extract uranium or thorium from acidic aqueous solution.

Study on charge equilibration time of highly charged ions in carbon foils

Charge state distribution of 0.8MeV/u uranium ions after transmission through a thin carbon foil has been studied. It is observed that the charge state distribution is equilibrated after the uranium ions have passed through a 15μg/cm^2 carbon foil. The equilibrated average charge state is 33.72 and the charge equilibration time of uranium ions in carbon foil is less than 5.4fs.

PHOTOSENSITIVITY OF CERIC ION INITIATED METHYL ACRYLATE POLYMERIZATION

The polymerization of methyl acrylate was sensitive to UV light. Under UV light,the rate of polymerization is 8 times as high as the rate in dark.The overall activation energy was decreased by the UV light (313nm).A tentative explanation is given and the mechanism is discussed.

基于载铀树脂饱和再吸附-淋洗一体化工艺的U型塔设计研究

针对部分酸法地浸铀矿工艺在浸出中后期存在的浸出液铀浓度偏低、HSO_(4)^(-)离子竞争吸附、吸附饱和树脂容量低、固定床淋洗合格液铀浓度低等问题,设计了一种离子交换设备U型塔,研究了采用饱和再吸附与淋洗一体化工艺处理载铀树脂,考察了处理后淋洗液中铀浓度的变化。结果表明:经U型塔一体化工艺处理后,淋洗合格液中铀质量浓度升至43~50 g/L;U型塔运行稳定,树脂运移顺畅,塔内铀浓度梯度分布合理。该设备适用于地浸采铀浸出液处理过程,有一定的推广应用价值。

铀的表面防腐技术研究进展

金属铀因具有优异的放射性能在国防和核能领域具有重要的战略价值。然而,由于铀具有高的反应活性,在大气环境中极易被腐蚀。在众多防腐技术中,表面处理技术被广泛用来提高铀的耐腐蚀性能。聚焦铀表面防腐的需求,重点综述了表面合金化、电镀、离子注入、离子镀等铀的防腐技术的研究进展,并针对不同技术目前面临的难题,展望了其未来的发展。近年来,离子注入、离子镀技术成为铀防腐领域的研究重点,具有很大的发展潜力。然而,金属铀的防腐性能仍需更进一步提高,复合沉积技术可以结合各种技术的优点,有望制备出耐蚀性更好的铀表面防腐涂层。此外,高功率脉冲磁控溅射技术在防腐领域拥有较大的应用潜力,是制备铀表面高性能防腐涂层的潜在方法,值得进一步研究。另一方面,合理利用铀的氢化腐蚀特性,可能使该材料成为一种优秀的储氢材料。

从铀铍浮选尾矿中回收铀的工艺研究

为了回收铀铍浮选尾矿中的铀,同时降低铀产品中铍的含量,采用工艺矿物学方法分析了某铀铍浮选尾矿中铀、铍的赋存状态,采用硫酸浸出工艺浸出尾矿中的铀,考察了酸浓度、浸出时间、浸出温度以及液固体积质量比对铀、铍浸出率的影响,并采用阴离子交换树脂探索了从浸出液中回收铀的可行性。研究表明,铀铍浮选尾矿中的铀较易被硫酸浸出,铍不易被浸出,采用离子交换法能够回收铀并实现铀铍分离。

海水提铀技术研究进展与挑战

铀资源作为核燃料中关键的组成成分,对于保障我国核工业建设和可持续发展至关重要。然而,常规陆地铀资源面临着可开采铀矿相对贫乏、品位较低的问题,而海水铀资源储量却是陆地的近千倍,且我国海域辽阔、海水资源富足。因此,如何能高效地从海水中提取铀资源,进而满足我国核工业发展需求,是亟待探究和解决的重要科学问题。本文系统介绍了国内外海水提铀技术的发展现状,综述了海水提铀材料特别是当前最具发展前景的铀吸附材料的研究概况,并以材料设计和工程应用为切入点,阐晰了海水提铀技术的主要挑战和未来发展展望。

中性地浸采铀水冶工艺淋洗剂的优化

针对内蒙古某铀矿山地浸采铀过程中水冶工艺淋洗合格液铀浓度降低现象,根据吸附-淋洗理论对生产运行数据进行了分析,找出了铀浓度降低的原因;并通过静态淋洗试验,优化了淋洗剂配方,用80 g/L NaCl+18 g/L NaHCO_(3)+18 g/L Na_(2)CO_(3)溶液淋洗,淋洗效果最佳。依据淋洗剂试验结果,对该矿山水冶工艺淋洗剂配制工序进行的优化验证表明,优化后的淋洗剂配制方法更适用于“CO_(2)+O_(2)”地浸采铀矿山。本研究结果可为其他中性地浸铀矿山水冶工艺优化提供技术支撑。

中非含铀铜钴矿湿法提取萃余液除铀工艺研究

针对中非铜钴成矿带上的铜钴伴生矿石采用湿法冶金工艺提取铜和钴时,其产品氢氧化钴存在含铀超标的问题,开展了对含铀铜钴矿湿法冶金提取工艺除铀研究。研究发现:对含铀铜钴矿萃取工艺之后的萃余液进行除铀,是最为适宜和高效的除铀工艺环节,同时,传统除铀工艺存在除铀效果不良、产生二次污染且无法有效回收铀等问题,因此创新将离子交换树脂工艺与圆筒筛和冲洗柱两段冲洗工艺相结合,构建了新型湿法铜钴矿萃余液离子交换树脂法除铀工艺,其除铀效率较传统工艺显著提升,改善了氢氧化钴产品质量,有效综合回收了铀,且无二次污染。