腐植酸对叔胺萃取铀的影响

简要叙述了腐植酸的主要性能,论述了腐植酸对叔胺-煤油溶液萃取铀和反萃取铀过程的影响。腐植酸与腐植酸铀酰盐对叔胺-煤油溶液萃取铀将降低萃取效率,并形成乳化。在反萃取铀过程中,实践表明,采用腐植酸脱除剂Na2CO3作为反萃取剂进行反萃取,可以有效把叔胺-煤油溶液中负载的铀、腐植酸铀酰盐以及腐植酸反萃取下来,铀的反萃取率达98%以上,腐植酸的脱除率达99%以上;且两相之间无乳化膜。     

溶剂微胶囊--现代萃取技术发展的核心之一

从溶剂微胶囊的制备及应用两方面较为全面地综述了溶剂微胶囊技术的发展,并总结了其特点,提出技术展望。溶剂微胶囊技术是微胶囊技术与萃取技术相结合而发展起来的新型分离技术,溶剂微胶囊具有萃淋树脂可以有效避免乳化和分相容易等优点,而在萃取剂包覆量和防止萃取剂流失方面,具有更明显的优势。     

新试剂DBPMP用于铀的萃取光度法测定研究

本文将新型螯合萃取剂DBPMP用于铀的萃取光度法研究。提出了一种选择性好,灵敏度高的测定方法。铀浓度在0～5.0mg/25ml范围内符合比尔定律。将本法用于矿石中铀的测定,结果满意。     

铀萃取剂的研究进展

介绍了国内外铀萃取剂的研究进展。     

N235萃取回收某铀矿高压浸出液中的铀

采用N235从某铀矿的高压浸出液中萃取回收铀。研究确定了合适的萃取条件为:萃取剂组成为5%N235+95%磺化煤油溶液,接触相比O/A为3︰2,萃取两相混合时间2 min,负载有机相操作容量为3.8 g/L,4级逆流萃取,铀的萃取率达到99%以上;负载有机相100 g/L碳酸钠溶液3级逆流反萃取,铀反萃取率达到99%以上;制备的重铀酸钠产品达到行业一级品标准。     

单级萃取—反萃取同时分离回收磷酸中铀和稀土

使用单级萃取－反萃取工艺，从湿法磷酸（ＷＰＡ）中回收铀和稀土的新工艺，既简单又易于控制，因为它只涉及酸性介质。该工艺是基于用二（２－乙基己基）磷酸（ＤＥＰＡ）和磷酸三丁酯（ＴＢＰ）和磷酸三丁酯（ＴＢＰ），从湿法磷酸中萃取铀和稀土。发现ＤＥＰＡ是唯一有效的，它稳定并且易于反萃取。其它的有机磷酸酯易水解，并且很难反萃取。用含有酸性氟化物的介质，对稀土和铀进行反萃取。对于铀来说，以六价（Ｕ＾６＋）形成被     

吡啶从硝酸介质中萃取铀(Ⅵ)的研究

研究了新萃取剂吡啶从硝酸介质中萃取铀的机理。考察水相硝酸浓度、萃取剂浓度、盐析剂硝酸钠以及振荡时间和温度对萃取分配比的影响，确定了萃合物的组成。求得萃取硝酸铀酰过程的平衡常数及反应的热力学函数。同时研究了相比的影响，以及稀释剂的影响。发现吡啶萃取能力在不同稀释剂中由弱到强的顺序为：四氯化碳、氯仿、苯、甲苯、环己烷、煤油。     

丁香油的超临界CO2萃取及其微胶囊的制备

在70℃和10 MPa条件下通过对丁香花蕾进行超临界CO2萃取得到丁香油,萃取率达19%～21%.气质联用分析结果表明,丁香油中主要化学成分包括丁香酚、β-石竹烯和乙酰基丁香酚等.以丁香油为囊芯,探讨利用干酵母细胞作为囊壁材料制备微胶囊的可行性.通过正交试验考察了包埋温度、包埋时间、丁香油与干酵母配比(芯材比)对微胶囊化丁香油的影响.结果表明,在包埋温度70℃、包埋时间9 h和芯材比为1∶1(w/w)的条件下,微胶囊中丁香油包埋率达到41.26%.通过扫描电镜观察,丁香油微胶囊呈规则的球形,大小均一,颗粒直径在2.0～4.0 μm.在100℃下对经微胶囊化的丁香油加热20 h,其挥发率只有15.04%,远低于相同条件下丁香油的挥发率(58.29%).这种新型的微胶囊化方法,具有制备过程简单、包埋率高和不引入有机溶剂的优点.     

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%。     

吡啶从硝酸介质中萃取铀(VI)的研究

研究了新萃取剂吡啶从硝酸介质中萃取铀的机理。考察水相硝酸浓度、萃取剂浓度、盐析剂硝酸钠以及振荡时间和温度对萃取分配比的影响 ,确定了萃合物的组成。求得萃取硝酸铀酰过程的平衡常数及反应的热力学函数。同时研究了相比的影响 ,以及稀释剂的影响。发现吡啶萃取能力在不同稀释剂中由弱到强的顺序为 :四氯化碳、氯仿、苯、甲苯、环己烷、煤油。     

交联聚脲囊壁微胶囊的制备

以异佛尔酮二异氰酸酯三聚体和三乙烯四胺为微胶囊壁材原料,在剪切乳化机的分散下通过界面聚合法制备出以交联型聚脲为囊壁结构的微胶囊。研究了有机溶剂种类、乳化剂种类以及剪毋分散速率等因素对微胶囊粒径大小与分布的影响,并分别用光学显微镜和扫描电镜观察分析了微胶囊的形貌。结果表明,微胶囊呈微米级球形结构;水溶性较大的油相介质和HLB很高的乳化剂都不利于微胶囊的形成;影响粒径大小与分布的主要因素是剪切分散速率。     

Microcapsules filled with reactive solutions for self-healing materials

Microcapsules containing a solvent and reactive epoxy resin are a critical component for the development of cost-effective, low toxicity, and low flammability self-healing materials. We report a robust in situ encapsulation method for protection of a variety of oil soluble solvents and reactive epoxy resins surrounded by a thin, polymeric, urea-formaldehyde (UF) shell. Resin-solvent capsules are produced in high yield with diameters ranging from 10 to 300 μm by controlling agitation rates. These capsules have a continuous inner shell wall and a rough exterior wall that promotes bonding to a polymer matrix. Capsules as small as 300 nm in diameter are achieved through sonication and stabilization procedures. The presence of both the epoxy resin and solvent core components is confirmed by differential scanning calorimetry (DSC) measurements, and the relative amount of epoxy and solvent in the liquid core is determined by thermogravimetric analysis (TGA). The capsules are shown to satisfy the requirements for use in self-healing materials including processing survivability, thermal stability, and efficient in situ rupture for delivery of healing agent.     

聚脲硫黄微胶囊的制备与表征

以升华硫为芯材、聚脲为壳材,采用界面聚合法制备聚脲硫黄微胶囊,研究反应时间和乙二胺( EDA)/甲苯二异氰酸酯(TDI)摩尔比对微胶囊产量的影响以及微胶囊包覆率的影响因素.结果表明:反应时间和EDA/TDI摩尔比对微胶囊产量的影响较小,最佳的反应时间为2h,EDA/TDI摩尔比为1.5;当明胶质量分数为0.03、乳化剂OP-10用量为0.5g、水油相比为1.2、搅拌速率为200 r· min-1时,微胶囊的包覆率较高.扫描电子显微镜分析表明,聚脲硫黄微胶囊的形态规则,热稳定性较好.     

Extraction of Uranyl Ion Using 2-Thenoyltrifluoro Acetone (HTTA) in Room Temperature Ionic Liquids

The extraction of UO₂²⁺ ion was studied using six different solvent systems containing 2-thenoyltrifluoroacetone (HTTA) in room temperature ionic liquids such as [C_nmim][X] (where, n = 4, 6, or 8 and X^? = PF₆^? or NTf₂^?) from low to moderate pH solutions for the first time. The extraction kinetics studies indicated rather slow attainment of equilibrium which in some cases improved if the solutions were pre-equilibrated with the aqueous phase prior to the actual experiments. The D_U values were found to increase with increasing pH and leading to a plateau like profile at higher pH values. The D values were quite high as compared to that obtained with molecular diluents. The nature of the extracted species was ascertained by slope analysis method which suggested species of the type: UO₂(TTA)⁺_IL, UO₂(TTA)_2,IL, and UO₂(TTA)₂(HTTA)_IL in different ionic liquid based solvents. Temperature variation studies on UO₂²⁺ ion extraction were also carried out and the thermodynamic parameters were calculated which indicated high endothermicity of the reactions with large positive entropy values.     

Understanding interfacial polycondensation: Experiments on polyurea system and comparison with theory

Interfacial polycondensation, with its multiphase character and the involvement of several rate and equilibrium processes, presents unique challenges to our ability to understand and design processes for achieving desired properties. In a recent study [1], we have presented a detailed model for the process and shown that it explains the salient features as reported in the literature for several interfacial systems. In the present paper, we report extensive experimental studies on the polyurea system and their comparison with the model. Two geometries - the spherical geometry of the microcapsule and the flat-film geometry - have been used to study qualitative and quantitative features of the polycondensation and the nature of the film that forms. While some aspects, such as the manner in which the solvent influences the kinetics, confirm earlier findings, inadequacies have been identified in the sample preparation protocols followed in earlier work, because of which property estimations may carry a large error. Improved protocols have accordingly been developed and used to study the development of film properties in time and as a function of the important preparation variables. Detailed molecular weight distributions have been determined using a GPC technique and used to derive important properties of the polyurea (such as Mark-Houwink parameters) as well as to gain insights into mechanisms. The data have been used to determine the rate parameters in the Dhumal and Suresh [1] model. The predictions of the model, as far as trends are concerned, are shown to be satisfactory given the level of uncertainty about parameter values and the complexity of the system being studied. Where discrepancies exist, the reasons have been established and the areas for improvement of the model identified. The findings reported are of interest to applications such as controlled release and membrane separations, in which permeation rate through the membrane is of importance and depends upon various membrane properties like crystallinity, morphology, etc.     

Solvent extraction, separation of uranium (VI) with crown ether

A solvent extraction separation of uranium with a new crown hydroxamic acid 5, 14-N, N′-hydroxyphenyl-4, 15-dioxo-1,5,14,18-tetraaza hexacosane (NHDTAHA) in the presence of cerium, thorium and lanthanides is described. The uranium is extracted with chloroform solution of NHDTAHA and the extract is directly used for GS-AAS measurements. The detection limit is 0.01 ppm with a sensitivity of 20 ng/0.005 absorbance of uranium. The extraction constants of uranium crown hydroxamic acid complexes are determined. The selectivity factors (K_uranyl/Kⁿ⁺_M) for uranium crown hyrdoxamate evaluated by comparing the K_uranyl with the stability constants for competing metal cations (Kⁿ⁺_M) and anions (Kⁿ_A⁻) and were found to be remarkably large. Uranium is preconcentrated and also determined spectrophotometrically. The molar absorptivity is 1.0×10⁴ l⁻¹ mol⁻¹ per cm at 390 nm and system obeys Beer’s law in the range 2.0–30 ppm of uranium. Uranium has been determined in standard and environmental samples.     

An Improved Correlation of the Mean Drop Size in a Modified Scheibel Extraction Column

The drop size is of fundamental importance in the design of liquid‐liquid extraction columns, the drop size was measured as a function of the geometry, operating conditions, and physical properties of a liquid‐liquid system with no mass transfer in a five‐stage modified Scheibel extraction column. An improved correlation of the mean drop size in the Scheibel extraction column is presented. The correlation was divided into three sections in terms of the Reynolds number. It could be applied in a wide range and could be further used for the study of mass transfer performance of the modified Scheibel extraction column.     

A Simple and Adaptive Methodology to Use a Commercial Solvent Extraction Microsystem as Screening Tool: Validation with the U-TBP Chemical System

The solvent extraction of a U (VI) present at several g.L^?1 from the aqueous phase [HNO₃] = 3 M to the organic one (30% TBP) involves a change of the viscosity of the two phases during the extraction process in microsystem. This shifts the position of the interface between the two phases and then affects the quality of the separation at the outlet of the microsystem. The aim of this study is to present a simple method to stabilize the quality of the separation by controlling the interface position during solvent extraction in microsystem. First, a study at low concentration is operated in order to set flow rates and contact time that allow optimal parallel flows and mass transfer. Second, the influence of the high grade concentration (up to 140 g.L^?1) of solute on the flows and extraction yield is studied.