Extraction of Uranium from Seawater Using Magnetic Adsorbents

Abstract

A new process for the extraction of uranium from seawater was developed. In the process, uranium adsorption is effected using powdered magnetic adsorbents; the adsorbents are then separated from seawater using magnetic separation technology. This process is superior to a column method using a granulated hydrous titanium oxide adsorber bed in the following ways: (1) a higher rate of adsorption is realized because smaller particles are used in the uranium adsorption; and (2) blocking, which is inevitable in an adsorber bed, is eliminated.

The composite hydrous titanium-iron oxide as a magnetic adsorbent having high uranium adsorption capacity and magnetization can be prepared by adding urea to a mixed solution of titanium sulfate and ferrous sulfate. Adsorption and desorption of uranium and the removal of the adsorbent using a small-scale uranium extraction plant (about 15 m³/d) is reported, and the feasibility of uranium extraction from seawater by this process is demonstrated.     

New and simple synthetic strategy for two-dimensional ultra-microporous aromatic framework for selective uranium capture in liquid

Uranium is a key element to improve nuclear energy demands, and thereby the extraction of uranium from seawater is a strategic way to address uranium sustainability. Herein, a novel two-dimensional porous aromatic framework (AO-PAF), which possesses an ultra-microporous architecture with an ordered structure, excellent stability and selectivity of uranium extraction from a liquid phase. AO-PAF shows excellent uranium adsorption capacities of 637 (mg/g) and 3.22 (mg/g) in simulated and natural seawater attributable to the selective uranium coordinating groups on highly accessible pores on the walls of open channels. In addition, benefiting from the super-hydrophilicity due to the presence of amidoxime groups attributes high selectivity and ultrafast kinetics with an uptake rate of 0.43 ± 0.03 (mg/g·day) and allowing half-saturation within 1.35 ± 0.09 days. This strategy demonstrates the potential of PAF not only recovery of uranium and can be extended for other applications by sensible planning of target ligands.     

乳状液膜法从铀矿的硫酸浸出液中提取铀的研究

本文研究了以双丁二酰亚胺为表面活性剂,三正辛胺为载体,磺化煤油为溶剂,碳酸钠为膜内相组成的乳状液膜体系,从矿石硫酸浸出液中提取铀.考察了各种因素对膜稳定性和铀提取率的影响,提出了适宜的工艺条件.结果表明,此乳状液膜体系对铀具有迁移速度快,提取效率高,选择性和稳定性好的优点.铀的提取率可达99.4%.     

生物质基铀吸附材料的研究进展

铀资源是国家核工业发展的重要战略资源,安全可持续铀资源供应是核电健康发展的关键。除铀矿资源外,绿色海水提铀技术是最有应用潜力的铀资源供应途径。吸附法是海水提铀和含铀废水处理的常见方法,面对复杂的海洋环境,设计和制备吸附量大、选择性高的吸附材料成为解决问题的关键,以高附加值的生物质基材料为铀吸附剂是一种新型的可持续发展策略。本文详细综述了生物质基铀吸附材料的分类、制备方法及其吸附性能,概括了生物质基吸附材料的研究现状和热点,基于研究现状,展望了未来高效生物质基吸附材料在海水提铀方面的发展方向和研究趋势。     

Recovery of uranium by tannin immobilized on matrices which have amino group

Tannin, which contains polyhydroxy groups, has a high affinity for uranium. Various tannin–protein complexes were prepared to develop new adsorbents for uranium recovery from seawater. Albumin tannate has a high ability to adsorb uranium from seawater. Tannin was immobilized on matrices which have multiple active amino groups, such as aminopolystyrene and poly(vinyl-4,6-diamino-s-triazine)—poly VT. Of these complexes, tannin immobilized on poly VT adsorbed uranium most efficiently from seawater and highly selectively from a solution containing various heavy metals; the uranium adsorption was very rapid and was pH dependent. This adsorbent therefore appears to have potential for use in a commercial process for uranium recovery from seawater or from uranium-containing waste water.     

Carbon adsorbents from of shale oils and phenols

The liquid products of shale conversion—shale oil and shale phenols (a mixture of alkylresorcinols) and their solutions in commercial furfural, which are used as a new binding agent—make it possible to form carbon adsorbents with high mechanical strength (to 97%), microporosity (to 0.70 cm³/g), and higher sorption capacity than that of industrial adsorbents. The medium-combustion-loss samples exhibited higher selectivity in the extraction of noble metals from the multicomponent polymetallic solutions than those formed of traditional wood tar. They also outperform industrial adsorbents in these characteristics. It is possible to apply them to the absorption and concentration of aromatic hydrocarbons and to use them at atomic power plants, transport, and air conditioning plants for food and vegetable storage.     

Study of Uranium Removal from Groundwater by Supported Liquid Membranes

The separation of uranium from synthetic Hanford site groundwater by liquid-liquid extraction and by supported liquid membranes (SLM) was atudied. Bis(2,4,4-trimethylpentyl) phosphinic acid, H[DTMPeP], contained in the commercial extractant Cysnex 272, was selected for the membrane carrier because of its selectivity for uranium over calcium and magnesium. n-Dodecane was used as diluent and polypropylene membranea were used as the support. A water soluble complexing agent, 1-hydroxyethane-1,1-diphoaphonic acid, HEDPA, was used as atrlpping agent.

The permeability coefficient of U(V1) was evaluated from a detailed study of the permeation of U(VI) through flat-sheet SLMs as a function of the membrane carrier concentration. The diffusion coefficient of the uranium complex in the organic phase was also evaluated from permeation experiments performed under loading conditions. Experiments were also carried out with Cs(II) and Fe(III) to measure the membrane selectivity for U(VI) over these two cations. A very high selectivity of U(VI) over Cs(II) was obtained, due the very low distribution ratio of Cs(II) with the extractant H[DTMPeP] (thermodynamic selectivity). In the case of Fe(III), a good selectivity was also obtained, due to the slow reaction of Fe(III) species with H[DTMPeP] (kinetic selectivity).

The possibility of concentrating U(VI) in the strip solution by a factor of at least 10³ has been experimentally demonstrated by properly designed distribution experiments.     

吸附法海水提铀材料研究进展

吸附法是海水提铀的最适宜方法之一,选择性好且吸附效率高的吸附材料是从海水中提取铀的最佳材料。本文回顾了到目前为止吸附法海水提铀的无机、有机、无机/有机杂化材料的制备方法、结构、吸附性能和铀吸附机理,介绍了不同海水提铀装置的结构和吸附性能。由于有机/无机杂化材料具有高机械强度、高铀吸附量、低共存离子干扰等优点,是一种理想的海水提铀材料;而且膜式吸附装置由于操作流程简单、可连续化等优点,是一种较佳的吸附方式。开展高铀吸附量、高选择性的吸附剂和处理量大的吸附方式是今后吸附法海水提铀的重要研究方向。     

Extraction of uranium from sea water using biological origin adsorbents

Waste microbial biomass has been shown to be a good adsorbent for uranium. A small scale pilot plant was operated at Woods Hole Oceanographic Institute in collaboration with the Department of Nuclear Engineering of MIT in order to assess the potential use of the two selected types of microbial biomass to sequester uranium from sea water effectively. The experimental results suggest that factors such as the presence of carbonates in the sea water, suppress substantially the uranium adsorptive uptake capacity of the biomass. The selectivity of the biomass for uranium, is not as good as that of other synthetic inorganic or organic adsorbents as, for example, hydrous titanium oxide.     

Adsorption of Uranium from Dilute Aqueous Solution on Inorganic Adsorbents

Abstract

The adsorption of uranium from a dilute aqueous solution by a large number of inorganic adsorbents has been investigated. A mixture of aluminum hydroxide, ferric hydroxide, and activated carbon in the weight ratio 1:3:4 has shown a high adsorbability for uranium. The separation of uranium from a dilute aqueous solution by this mixed adsorbent under various temperatures and pH values has been studied. The adsorbability was found to exhibit a maximum at pH 4.0 to 5.5 and to decrease with increasing temperature. A number of eluting solutions for the desorption of uranium from the mixed adsorbent were also tested; 1 N (NH₄)₂ CO ₃ was found to be the most suitable eluting solution (93% recovery of uranium).     

Carbamoylalkylphosphonates for Dramatic Enhancement of Uranium Extraction from Phosphates Ores

We describe here the full synthesis of a novel family of bifunctional ligands and present a complete study of their extraction properties in regards to an aqueous phosphoric acid solution containing uranium. We developed a high yielding synthesis of amido phosphonate ligands and focused our investigation on the effect of steric hindrance on the methylene bridge between the two functions. These new bifunctional ligands were found to extract selectively hexavalent uranium U(VI) with high distribution coefficient (D) and selectivity towards iron Fe (III) in 5 M phosphoric acid solution. From a structure-activity approach a specific ligand called DEHCNPB has been put forward in regard to the outstanding results obtained for the selective extraction, and quantitative recovery of uranium compared to the URPHOS reference system.     

Preparation of fibrous adsorbents containing amidoxime groups by radiation-induced grafting and application to uranium recovery from sea water

Polypropylene fibers and polyethylene hollow fibers were used as trunk polymers and were irradiated by electron beams with a dose of 200 kGy under N₂ atmosphere. Grafting of acrylonitrile to those irradiated fibers was carried out at 40°C for different periods of time. The degree of grafting was determined as a function of time. The fibrous adsorbents containing amidoxime groups were prepared by the reaction of acrylonitrile-grafted polymers with 3% hydroxylamine in a methanol–water mixture (1 : 1). Distribution of copper ions complexed with amidoxime groups at various adsorption times was obtained by electron-probe X-ray microanalysis. The amidoxime groups are homogeneously distributed in the cross section of fibrous adsorbents. The fibrous adsorbents based upon polypropylene fiber of 40 μm showed a remarkable kinetic behavior for Cu²⁺. Even after 15 min, the adsorption capacity was 2.32 mmol Cu²⁺ per gram of fiber. Also, the functionalization with hydroxylamine was carried out at different conditions to compare the adsorption characteristics of the resultant adsorbents. Despite having superficially different properties (elemental microanalysis, ion-exchange capacities, adsorption capacity for UO), the polypropylene-based fibrous adsorbents showed similar adsorption properties for uranium from sea water. The adsorption tests proved the performance of the polypropylene-based fibrous adsorbents as a promising material for uranium recovery from sea water. In addition, uranium uptake of fibrous adsorbents increased in proportion to the volume of sea water. © 1993 John Wiley & Sons, Inc.     

Ion exchangers and carbon adsorbents from of shale phenols

Ampholytes with a static exchange capacity of 3.5–6.6 mg-equiv/g for 0.1 N H₂SO₄ or 1.3–2.0 mg-equiv/g for 0.1 N NaOH were obtained from shale phenols (a mixture of alkylresorcinols) by polycondensation with polyethylenepolyamines and furfural. The interaction of shale phenols with hexamethylentetramine resulted in polycondensation products, which gave polyfunctional cation exchangers with a capacity of up to 7.5 mg-equiv/g upon a radiation exposure with acrylic acid. Carbon adsorbents based on the polycondensation products of shale phenols (ampholytes) prepared in an industrial process exhibited developed microporosity (V _mi = 0.28–0.30 cm³/cm³) and a considerable concentration of heteroatoms (to 16%). This made it possible to obtain adsorbents whose sorption capacity and selectivity in the extraction of gold from multicomponent solutions are twice as high, as compared with those of a KAD-iodine commercial sorbent.     

Supercritical Carbon Dioxide Extraction of Uranium from Acidic Medium Employing Calixarenes

Various calixarenes were evaluated for the supercritical fluid extraction of uranium from nitric acid medium. The extraction efficiency was found to be affected by various parameters, namely pressure, temperature, CO₂ flowrate, extraction time, and molarity of nitric acid. The addition of HPFOA (pentadecafluoro-n-octanoic acid) for the production of CO₂-phillic fluorinated counter ion enhanced the extraction efficiency. Under optimized conditions (pressure of 200 atm, temperature of 323 K, 30 minutes of static time followed by 30 minutes of dynamic time, CO₂ flowrate of 2 mL min^?1, nitric acid molarity of 0.1 M) for uranium: calixarene: HPFOA mole ratio of 1:5:10, highest extraction efficiency could be obtained with p-tert.-butyl calix[6]arene (79.9%). Solvent extraction study with hexane as the organic phase indicated the formation of [UO₂ (calixarene)]²⁺. In order to assess the suitability of the developed method to extract uranium in the presence of a host of other ions, extraction efficiency for other metal ions was estimated.     

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.     

改性吸附剂去除废水中磷的应用研究进展

去除废水中过量的磷可以减缓水体富营养化。吸附除磷因具有能耗低、容量大、污染少等优点而备受关注，改性吸附剂则可在此基础上提高除磷的靶向性，拓宽操作条件，增大吸附容量。本文分析了改性硅酸盐类、改性金属氧化物类、改性固体废弃物类和聚合物类4类除磷吸附剂的改性方法和吸附性能。硅酸盐类吸附材料以及固体废弃物类材料除磷效果略差，但因来源丰富、价格低廉而具有极大的吸引力。聚合物类吸附剂具有高吸附容量、高选择性，但价格昂贵。金属（氢）氧化物具有出色的磷酸盐吸附性能，且选择性好、吸附速度快，这些化合物已被掺入到沸石、介孔二氧化硅和生物炭等材料中，进一步增强其吸附性能，并在工程材料应用中取得重大突破，主要包括磁性吸附剂和颗粒吸附剂。4类吸附剂的作用机理可归纳为两种：一种是吸附剂上的金属与磷酸盐离子发生配位反应，形成沉淀；另一种是酸性条件下吸附剂上的羟基质子化，使羟基带正电，质子化的羟基通过静电吸引使磷得以去除。通过对不同类别吸附剂的吸附特性进行对比分析，提出将高分子技术运用到吸附剂制备过程中，开发同时具有较强解吸能力的改性吸附剂将成为除磷吸附剂研究的新热点。     

Binding of heavy metal ions by chemically modified woods

Three chemically modified woods were prepared and used for the binding of heavy metal ions. Wood–polythylenimine composite (wood–PEI) was found to be effective for the adsorption of heavy metal ions such as Hg²⁺, Cu²⁺, and other metal ions which tend to form stable ammine complexes. Adsorption of metal ions on a wood–PEI derivative containing dithiocarbamate group (DTC–wood) was higher than that by wood–PEI. Especially, the reactivity of DTC–wood with Hg²⁺ was quite high and the binding capacity of about 5 mmol/g was easily attainable. The rate of adsorption on these wood-based adsorbents was very high, and adsorption of about 70% of total binding capacity was accomplished in the first 1 h. This may be due to a highly porous structure and a hydrophilic nature of the wood which constitutes the skeleton of the adsorbents. Amidoximated wood (AO–wood) prepared by the reaction of cyanoethylated wood with hydroxylamine showed selective adsorptivity for uranium in sea water. More than 53% of uranium in the sea water used was adsorbed by the AO–wood.     

Removal of Residual Uranium in Simulated Radwaste Solution by TBP Extraction

Abstract

The extraction behavior of uranium in a multicomponent system simulated on the basis of high-level liquid waste was examined in order to find effective conditions for the removal of residual uranium in a simulated radwaste solution by the TBP solvent extraction method. While the conventional semiempirical equation for the distribution coefficient of uranium could be used in a system composed of only uranium and nitric acid, it was found to be unsuitable for a multicomponent system where the concentration of uranium is not dominant. Uranium extractability by TBP was found to be limited in multicomponents systems regardless of high TBP concentration, phase ratio, and extraction times because of the presence of neodymium and iron together with uranium in the systems.     

EXTRACTIVE SEPARATION OF URANIUM AND ZIRCONIUM SULFATES BY AMINES

ABSTRACT

This paper describes an amine extraction process for zirconium and uranium separation. The behaviour of an extraction system containing uranium (VI) sulfate, zirconium (IV) sulfate, 0.2 and 0.5 M sulfuric acid (as the original aqueous phase), tertiary amine tri-n-lauryl- amine or primary amine Primene JMT in benzene (as the original organic phase) is discussed on the basis of equilibrium data.

The measured dependences show that the degree of extraction of zirconium at the sulfuric acid concentration of 0.5 M and above is only slightly affected by a presence of uranium in solution. From this surprising behaviour it follows that zirconium may be employed for the displacement of uranium from the organic phase. This effect is more pronounced with the primary amine Primene JMT than with TLA.     

Recovery of Uranium from Seawater

Abstract

Seawater contains various elements in solution. Deuterium, lithium, and uranium are the important ingredients for energy application at present and in the future. This paper deals with the recovery of uranium from seawater, with emphasis on the development of an adsorbent with high selectivity and rate of adsorption for uranium.

Polyacrylamidoxime chelating resins were synthesized from various co-polymers of acrylonitrile and cross-linking agents. The resulting resins with the chelating amidoxime group showed selective adsorption for uranium in seawater. The amount of uranium adsorbed from seawater at room temperature reached 3.2 mg/g resin after 180 days.

Polyacrylamidoxime fiber, which was prepared from polyacrylo-nitrile fiber and hydroxylamine, showed a high rate of adsorption for uranium. The polyacrylamidoxime fiber conditioned with 1 M HCl and 1 M NaOH adsorbed 4 mg U/g fiber from seawater in ten days.