Toshifumi Murata

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.

Uranium Extraction from Sea Water with Composite Adsorbents, (II): Uranium Adsorption on Composite Hydrous Titanium (IV)-Iron (II) Oxide

A composite hydrous oxide, prepared from the mixed solution of titanium tetrachloride and ferrous chloride by addition of sodium hydroxide solultion, was investigated because of its rather high uranium adsorption capacity and its magnetic property. Results obtained may lead to easier handling of adsorbent species in the extraction of uranium from sea water. The uranium adsorption capacity of the composite hydrous oxide was measured using sea water to which a small amount of uranyl chloride was added. The initial uranium concentration was 10.1 μg/l. Physical and chemical properties, such as specific surface area, mean pore radius and amount of surface OH groups, were also measured. The composite hydrous oxide was found to be composed mainly of relatively small particles of anatase and large particles of magnetite. Uranium adsorption capacity reaches its maximum when the precipitation temperatures are 50–70°C. The capacity of the composite hydrous oxide was found to be closely related to the mean pore size ...

Uranium extraction from sea water with composite adsorbents. IV. Uranium adsorption on composite hydrous titanium(IV)-iron(II) oxides prepared by precipitation from homogeneous solutions.:Uranium Adsorption on Composite Hydrous Titanium(IV)-Iron(II) Oxides Prepared by Precipitation from Homogeneous Solutions

Composite hydrous titanium(IV)-iron(II) oxides prepared by precipitation from homogeneous solutions were studied with a view to developing magnetic adsorbents for uranium extraction from sea water. Higher uranium adsorption capacity was registered with homogeneous than with heterogeneous solution used for preparing the oxide. The adsorbents for uranium prepared from homogeneous solution moreover were found to require the copresence of urea and a suitable anion such as SO2- 4, in order to provide strongly active adsorption of uranium. The value of saturated magnetization of the composite hydrous oxides decreased with increasing titanium mole fraction up to 0.75, increase of the titanium mole fraction had, on the other hand, the effect of enhancing uranium adsorption capacity, which however saturated beyond 0.75 titanium mole fraction. The change of enthalpy brought by the uranium adsorption on the composite hydrous titanium (IV)-iron (II) oxides was 10 kcal/mol, and the amount of change independent of the ...

Uranium Extraction from Sea Water with Composite Adsorbents, (III): Magnetic Properties of Composite Hydrous Titanium (IV)-Iron (II) Oxides and their Magnetic Separation

Measurements were made of the extent of magnetization shown by composite hydrous titanium (IV)-iron (II) oxide adsorbents for use in uranium extraction from sea water. The possibility of removing the adsorbent by means of high-gradient magnetic separation was demonstrated by calculations based on a force balance model. Removal experiments were also carried out, which demonstrated that the composite hydrous oxide can be trapped effectively: A composite hydrous oxide with 1:1 Ti-to-Fe mole ratio, of 400–625 mesh particle size, proved to be removed to 99.9% by a magnetic field of 2.5 kOe, with the slurry flowing at 20 cm/s through a filter matrix 50 cm long packed to 90% void with 100 μm diameter nickel wire stuffing. Together with the evaluations made of the electric power consumed by the high-gradient magnetic separators, the experimental results indicated the possibility of economically extractng uranium from sea water using these separators in combination with magnetic adsorbents.

Transport and Deposition of Metals in Sodium-Stainless Steel Systems, (V) An Experiment on Thermal Diffusion of Zinc, Antimony and Cesium in Liquid Sodium

Thermal diffusion constants were determined over a temperature range of 400°–700°C in liquid sodium alloyed with trace amounts of zinc, antimony or cesium. Purified sodium containing a radioisotope of one of the three solute metals was filled by suction in a capillary made of stainless steel. The capillary was then carefully seal-welded to prevent the sodium from oxidation; the sealed capillary was placed along the core of a heat conductor rod; a steady linear temperature gradient was produced along its length by heating its head and cooling its foot. After a predetermined period of this thermal diffusion run, the capillary was quickly chilled to solidify the sodium and sectioned into pieces. The specific radioactivity observed in the sodium in the sectioned piece were plotted in log-log scale against the absolute temperature prevailing in the piece during the thermal diffusion run, and the thermal diffusion constant was obtained from the inclination of the straight lines drawn through the plots. All thre...

Identification of Methyl Iodide Formed in Iodine by a Mass Spectrometer

Since radioactive iodine is considered to be the critical isotope from the standpoint of the health hazard induced by fission products released from irradiated fuel, the efforts of the workers have been centred on its effective removal(1). Alkyl iodide, in which methyl iodide is a major component, may be present in the iodine released. This lead some complications in the evaluation choice of filter used in the safety devices to provide against unlikely reactor accidents, because methyl

A Preliminaly Experiment on Radial Distribution of Cs-137, Sr-89-90 and Zr-95 in Sintered Uranium Dioxide Pellet

This paper reports on the determination of the radial distribution of fission products (Cs, Sr and Zr) in neutron irradiated UO2 pellets. The first part gives the reuslts obtained by gradual dissolution of a pellet. In the second part the fission products distribution has been determined by micro-sampling along the cross-sectional surface of a UO2 pellet.