应用偶氮氯膦-mA分光光度法测定水相中微量铀

目前用于分光光度法测定铀的显色剂不少,常用的有铀试剂Ⅲ,CPAⅢ,PADAP,Br-PADAP及TAR等,而在微量铀分析上应用最广的是铀试剂Ⅲ和Br-PADAP两种。     

偶氮氯膦类试剂与钍、铀(Ⅵ)、铈显色反应的研究

在偶氮氯膦Ⅲ(CPA Ⅲ)基础上发展而成的一类不对称偶氮氯膦类试剂是稀土的灵敏显色剂。如间乙酰基偶氮氯膦,间羧基偶氮氯磷,间硝基偶氮氯膦和对硝基偶氮氯膦已分别用于稀土总量、铈组稀土和钇的光度测定。本文进一步研究了此类试剂与钍、铀(Ⅵ)、铈反应的情况,目的是筛选出用于光度测定钍的优良显色剂。     

氯膦偶氮Ⅲ分光光度法测定谷物灰溶液中微量铀

本文介绍采用TBP—二甲苯萃取,氯膦偶氮Ⅲ反萃显色分光光度法测定谷物灰溶液中微量铀的分析方法。研究了样品共存元素对测定的影响并制定了消除干扰的方法。测定范围为0.5—2.5μgU/3.5 ml。精密度优于±5%,样品分析重加回收率为93.3%。     

偶氮氯膦-mA分光光度法测定水相中微量钍

目前,用于分光光度法测定微量钍的显色剂不少,常用的有钍试剂、偶氮胂Ⅰ、偶氮胂羧、偶氮胂Ⅲ和偶氮氯膦Ⅲ。其中偶氮胂Ⅲ为最常用的显色剂,该显色剂只有在中等酸度下测钍才具有较高的灵敏度。其它显色剂在低酸介质中测钍时灵敏度并不理想。偶氮氯膦-mA是由上海师大于1979年首先合成并应用于稀土元素分析的新型显色剂,它为深紫红色结晶粉末,易溶于水,在酸性介质中与钍形成蓝紫色络合物,其结构式如下:     

在表面活性剂存在下钍与2,3,4—三羟基—4‘—磺酸偶氮苯显色反应的研究

变色酸偶氮类显色剂是目前光度法测定钍的主要试剂。这类试剂的特点是灵敏度高,稳定性好,但不足的是希土、铀的干扰严重,测定范围较窄。本文研究了在阳离子表面活性剂氯化十四烷基吡啶(TPC)存在下,钍与2,3,4-三羟基-4’-磺酸偶氮苯(TSAB)的显色反应条件。三元络合物的形成提高了分析方法的灵敏度,其表观摩尔吸光系数ε_(460)=4.95×10~4,较文献中报道的二元络合物提高了二倍。该法能在1000倍希土和40倍铀存在下光度法测定钍。     

偶氮氯膦6,8-萘二磺酸-氯化+四烷基吡啶光度法测定矿石中的铀

铀(IV)在0.5—1.4 mol/l盐酸中,用氯化十四烷基吡啶(简称TPC)作增溶剂,铀(IV)与偶氮氯膦6,8-萘二磺酸(简称偶氮氯膦G)-TPC形成的三元络合物具有极高的灵敏度(ε_(705nm)=1.6×10~5l·mol~(-1)·cm~(-1)和较好的选择性。从而建立了用P_(350)-DA_(201)树脂柱层析分离,在pH1.6—4.5的铁(II)-EDTA体系中还原铀(VI),以偶氮氯磷6,8一萘二磺酸显色,TPC增溶光度法测定矿石中的铀。当矿样中铀量为5×10~(-4)%时,相对标准偏差为±11.4%。     

测定水中微量铀的高灵敏显色体系的研究

本文介绍了一种用于测定水中微量铀的高灵敏显色体系。水样中加入菸酸、乙基紫和硫酸后,用混合溶剂环己烷+甲基异丁基甲酮(MIBK)(1:1)萃取,分光光度法测定。该方法的表观摩尔吸光系数为1.62×10~(-6)L·mol~(-1)·cm~(-1),回收率为97.8—106.0％,探测下限为2×10~(-9)g/mL,避免了使用有害的溶剂苯;Ca~(2+)、W~(6+)、Cu~(2+)和Hg~(2+)等离子对铀的测定干扰较严重。     

偶氮氯磷Ⅲ双波长分光光度法同时测定铀矿石中钍和铀

对偶氮氯膦Ⅲ和钍、铀在磷酸体系中的显色行为作了研究,提出以TRPO-G.D.X-301萃取色层分离稀土、钛、锆等干扰元素、用双波长分光度法同时测定铀矿石中钍和铀的方法。测定钍和铀时,测量波长、参比波长分别为690nm、608nm和670nm、707nm,工作曲线在0～50μg/25ml内成线性。测定矿石中0.03%～0.5%的钍和铀时,误差小于10%。本法可用于复杂样品中钍和铀的同时测定。     

烷基膦酸二烷基酯萃取铀.钍反应中取代基效应的分子力学研究

在确定烷基膦酸二烷基酯在硝酸体系中萃取铀、钍络合物稳定构型的基础上,根据它们的萃取反应平衡常数,应用分子力学方法对烷基的结构效应作了研究,认为这类结构效应主要源于分子内空间张力能的变化。     

H2气氛中铀金属表面反应的XPS研究

用Ｘ射线光电子能谱分析研究了在Ｈ２气氛中，２５℃和２００℃时的铀金属表面反主尖。     

Sorption of U(VI) on the 4-Mercaptopyridine Self-Assembled Monolayer

The sorption of U(VI) on the 4-mercaptopyridine self-assembled monolayer (4-PyS-SAM) on Au(111) was studied by cyclic voltammetry. Cyclic voltammograms (CVs) of the 4-PyS-SAM working electrode were obtained by contact with 1mM UO₂(NO₃)₂ solution, 1mM UO₂(NO₃)₂ and 50mM acetic acid solution, or 1mM UO₂(NO₃)₂ and 50mM oxalic acid solution for 6 h at pH 4. The reduction current of U(VI) to U(V) was detected in the CV. The CV of the U(VI) associated 4-PyS-SAM after transport to U(VI)-free 0.1M NaClO₄ solution showed that the reduction current was detected in the cases of UO₂(NO₃)₂ and U(VI)-acetate, but not in the case of U(VI)-oxalate solution, indicating that U(VI) was adsorbed on the 4-PyS-SAM from the UO₂(NO₃)₂ and U(VI)-acetate solutions, but not from U(VI)-oxalate solution. These results suggest that stability of U(VI)-4-PyS-SAM is not so high that U(VI)-4-PyS-SAM cannot be formed in the presence of 50mM oxalate.     

Low-Temperature Partitioning of Plutonium with High U(VI)-Loading for Fuel Reprocessing

Measurement of the distribution ratios of Pu(IV), U(VI) and HNO₃ at low temperatures and its treatment with DIST code revealed that a high U (VI)-loading of 30% TBP in n-dodecane splits Pu(IV) down to the aqueous phase more strongly than do at 25°C. Based on these findings, flowsheet conditions to separate Pu(IV) from U(VI) were investigated with EXTRA.M code including the distribution equations obtained above. And tentative flowsheets for non-reductive Pu-splitting process at a temperature of 5°C were proposed for fuel reprocessing mainly based on the effects of U (VI)-loading in the solvent and temperature on distribution ratios of Pu(IV) and U(VI). Distribution ratios of the fission products, Zr, Nb, Ru and Ce were also measured to assess their decontamination from U or Pu products in the above process. Finally behavior of Np, in the proposed partitioning process was discussed by analysis with EXTRA. M code and a redox reaction model.     

Photochemical Reactions of Uranium(VI) in Aqueous Phosphoric Acid Solutions

Photochemical reactions of U(VI) ion with halogen and pseudohalogen anions. I^?, Br^?, Cl^? and NCS^?, were studied in aqueous phosphoric acid solutions under irradiation of nitrogen laser. The formation of U(IV) was observed in the reactions with I^?, Br^? and NCS^?, but not with CI^?. The yield of U(IV) increased in the order Br^?<NCS^?<I^?. This order was the same as the quenching rate constants of the excited U (VI) ion with these anions, but the reverse of their standard redox potentials. These facts are consistent with the electron transfer mechanism between excited U (VI) and these anions. The rates of the formation of U (IV) in the presence of Br^? were measured by the spectrophotometric method. It was found that the rate equation was first order in both U (VI) and Br^?. The results were reasonably interpreted by a series of reaction processes involving U(V) and Br radical. The photo-oxidation of tris(1, 10-phenanthroline)-Fe (II) ion by U (VI) was also studied in the same procedures. Based on the rate law, we proposed a one-electron transfer mechanism involving U(V) as an intermediate.     

Solvent Extraction of Np (V) with CMPO from Nitric Acid Solutions Containing U (VI)

The extraction of Np(V) in the presence of U(VI) or Nd(III) was studied with 0.2 M CMPO- decalin and with 0.2 M CMPO-1.4 M TBP-n-dodecane. Distribution ratios of Np(V) decreased with increasing the concentration of Nd(III), which was considered to be explained by the decrease in the concentration of free CMPO. On the other hand, distribution ratios increased as the concentration of U(VI) increased. The absorption spectrum of Np(V) in organic solution showed a new absorption peak which was probably attributable to the formation of cation-cation complexes of Np(V) and U(VI). Assuming the formation of cation-cation complexes, the dependence of distribution ratio of Np(V) on the concentration of U(VI) was found to be semi-quantitatively explained.     

HBMPPT-DOSO-甲苯体系对铀(Ⅵ)的萃取及铀(Ⅵ)、钍(Ⅳ)之间的分离

以个苯甲酰基－２,４二氢－５－甲基－２－苯基－３Ｈ－吡唑硫酮－３（ＨＢＭＰＰＴ）为萃取剂、二正辛基亚砜（ＤＯＳＯ）为协萃剂,研究其在硝酸介质中对铀（Ⅵ）的萃取行为,以及萃取剂浓度、酸度等各种因素对萃取分配比的影响,以确定两种萃取剂的协同萃取及分离效果。结果表明,ＨＢＭＰＰＴ和ＤＯＳＯ有较好的协同萃取效果,一定条件下,铀（Ⅵ）、钍（Ⅳ）的分离系数可达５２３。     

Precipitation of Thorium or Uranium(VI) Complex Ion with Cobalt(III) or Chromium(III) Complex Cation, (III)

Chloride ion (foreign ion) effect on the precipitation of thorium or uranium (VI) sulfato, carbonato and oxalato complex ions has been studied. The results are in correlation with the chemical species present in the solution.

The precipitation of highly-charged complex ions is affected by chloride ion and the precipitation yield decreases with chloride salt concentration. The precipitation of sulfato complex ion shows only slight dependency on the chloride salt concentration because of the absence of highly-charged sulfato complex ion under the experimental conditions.     

铀尾矿库区浅层地下水中U(Ⅵ)迁移的模拟

在详细分析中国南部某大型铀水冶尾矿库的结构特点、运营情况和库区水文地质条件的基础上，对库区水文地质条件进行概述，运用溶质反应-运移模拟软件PHREEQC-Ⅱ，建立研究区U(Ⅵ)在浅层地下水中迁移的一维溶质反应-输运耦合模型，并分析在不同时间、距离、扩散系数、弥散度等条件下铀在铀尾矿库区浅层地下水中的迁移，即铀浓度随时间及距离的变化。模拟结果与现场观测资料基本吻合，表明该软件能较好地模拟U(Ⅵ)的迁移情况，证明了该模型的可行性。研究还表明，弥散作用对铀迁移有显著影响，弥散度的取值是模拟可靠与否的关键参数，而分子扩散对本模拟的影响可忽略不计。      

A study on selective precipitation of U(VI) by hydrophilic cyclic urea derivatives for development of a reprocessing system based on precipitation method

Selective precipitation ability of 2-imidazolidone (EU) and tetrahydro-2-pyrimidinone (PU) for U(VI) species in HNO₃ solutions containing U(VI), U(IV) (simulant of Pu(IV)), and simulated fission products (FPs) was investigated. As a result, it was found that these compounds precipitate almost quantitatively U(VI) as UO₂(NO₃)₂L₂ (L = EU, PU) from 3.0 M HNO₃ solution. In contrast, these urea derivatives form neither solid precipitates nor oily products with U(IV) in HNO₃ solutions containing only U(IV) species and even in U(VI)–U(IV) admixture system. Therefore, the separation of U(VI) from U(IV) was demonstrated to be achieved in use of EU and PU. Furthermore, EU and PU are capable to remove most of simulated FPs[Sr(II), Ru(III), Rh(III), Re(VII) La(III), Ce(III), Pr(III), Nd(III), and Sm(III)] from U(VI) to give their decontamination factors (DFs) higher than 100, while those values of Zr(IV), Mo(VI), Pd(II), and Ba(II) are necessary to be improved in both systems. From these results, it is expected that EU and PU are the promising precipitants for selective separation of U(VI) from HNO₃ solutions dissolving spent FBR fuels.