Uranium recovery from seawater

The real boom in uranium from sea projects arose in the mid-1970s when concerted efforts to develop uranium specific sorbents and to evaluate processes based on their use for uranium recovery from seawater were undertaken in Japan and West Germany. The research in Japan, conducted by the Metal Mining Agency of Japan, was sponsored by the Ministry of International Trade and Industry [166,167]. In West Germany, the studies were carried out at the Nuclear Research Center (KFA) injlilich [168]. 

The economic aspects of uranium recovery from seawater, using Xi02 tiH20 sorbents have been discussed in a number of publications [166, 181-183]. They were based on project production scales of 100 to 1000 tons of U2O8 per year, 500 t/year [182], and 180 ty ear [183] the most detailed economic analysis was given by Hirai et al. [166]. 

Technical Devices for Uranium Recovery from Seawater The facilities known to exist for uranium extraction are of two types. The first type requires an external energy source. The second uses seawater motion (waves, tides, streams, etc.) as the natural source of energy. In the first type, the rate of energy expenditure per 1 ton of product (uranium or any other microelement with a concentration level in seawater of around 10 g/L) was 3x 10 kWh [229]. 

A number of additional original technical devices for the second type of uranium recovery from seawater has also been described recently [237-239]. 

FIGURE 31.17 Schemes of the highly selective ligand for uranium recovery from seawater, (a) The hexacarboxylate Ugand (b) after reaction with tri-octyl methyl ammonium chloride. (Reproduced from Tabushi, I., Kobuke, Y., Nakayama, N., Aoki, T., and Yashizawa, A., Ind. Eng. Chem. Prod. Res. Dev., 23, 445, 1984. With permission.)... 

Figure 21 Experimental apparatus for uranium recovery from seawater in the submerged mode of operation at the ocean site.

K. Sekiguchi, K. Saito, S. Konishi, S. Furusaki, T. Sugo and H. Nobukawa, Effect of Seawater Temperature on Uranium Recovery from Seawater Using Amidoxime Adsorbents, Ind. Eng. Chem. Res., 33 (1994) 662. 

Das, S., Pandey, A.K., Athavale, A., Kumar, V, Bhardwaj, Y.K., Sabharwal, S. Manchanda, VK. (2008) Chemical aspects of uranium recovery from seawater by amidoximated electron-beam-grafled polypropylene membranes. Desalination, 232 (1-3), 243-253. 

Numerous publications in the 1960s and 1970s dealt in detail with the description of the mechanism, equilibrium, and kinetics of the uranium sorption reaction on titanium hydroxide [163]. Scaled-up testing of uranium sorption from seawater was carried out in the Soviet Union, United States of America, Great Britain, and Germany. The results were used in the design and construction of units for uranium recovery approximately 10-100 g of uranium were produced per year [180,181]. 

Detailed information on the research carried out in the field of uranium extraction from seawater up to 1984 are given in reviews [ 164, 191-198]. The most intensive investigations are being carried out in Japan in institutes dedicated to uranium recovery firom seawater [196]. 

Table 1 gives the average metal content of the earth s cmst, ore deposits, and concentrates. With the exceptions of the recovery of magnesium from seawater and alkaU metals from brines, and the solution mining and dump or heap leaching of some copper, gold, and uranium (see Uranium and uranium compounds), most ores are processed through mills. Concentrates are the raw materials for the extraction of primary metals. 

Dissolved Minerals. The most significant source of minerals for sustainable recovery may be ocean waters which contain nearly all the known elements in some degree of solution. Production of dissolved minerals from seawater is limited to fresh water, magnesium, magnesium compounds (qv), salt, bromine, and heavy water, ie, deuterium oxide. Considerable development of techniques for recovery of copper, gold, and uranium by solution or bacterial methods has been carried out in several countries for appHcation onshore. These methods are expected to be fully transferable to the marine environment (5). The potential for extraction of dissolved materials from naturally enriched sources, such as hydrothermal vents, may be high. 

Another potentially vast resource is seawater. Uranium resources associated with the oceans are estimated at around 4000 million tonnes however, the uranium concentration in seawater is only around 0.003 ppm. The recovery of uranium from seawater is still subject to basic research. Considerable technological developments as well as significant improvements of economics (or drastic increases in uranium prices) are crucial for the commercial use of this resource, which is unlikely in the foreseeable future. As the energy demand for uranium extraction increases with lower concentrations, the net energy balance of the entire fuel cycle is also critical. 

The concentration of uranium contained in phosphate rocks (50 200 ppm) is higher than that in seawater (see section 12.3.5). Even though economic recovery of uranium from phosphate rock is difficult, several phosphoric acid plants include operation of uranium recovery facilities. 

Lead hydroxide is used in making porous glass in electrical-insulating paper in electrolytes in sealed nickel-cadmium batteries in recovery of uranium from seawater and as a catalyst for oxidation of cyclododecanol. 

Hotta, H. Recovery of Uranium from Seawater, Oceams. 30 (Spring 19871. Lewis, R.J. and N.l. Sax Sax x Dangerous Properties of Industrial Materials, 10th Edition, John Wiley Sons, Inc., New York. NY, 2000,... 

According to the latest estimates of Skinner [18], elements potentially recoverable from seawater are sodium, potassium, magnesium, calcium, strontium, chlorine, bromine, boron, and phosphorus because of their practically unlimited presence in the ocean. After improving respective technologies, recovery of the following elements is expected to become profitable as well lithium, rubidium, uranium, vanadium, and molybdenum. Additional profit can be gained since desalinated water will probably be obtained as a by-product. This could be important for countries with a very limited number of freshwater sources (e.g., Israel, Saudi Arabia). 

During the past 30 years, investigations of the recovery of uranium from seawater have intensified as a result of expectations that land-based uranium deposits will be exhausted by the turn of the century [164, 165]. The... 

From Table 4, it is apparent that almost all uranium in seawater exists in the form of a highly stable tricaibonate complex U02(C03) (its stability constant is approximately 10 ). This fact and its very low concentration in seawater dictates the choice of sorbent most suitable for uranium recovery. The sorbent must be available on a large scale and at low... 

RECOVERY OF MINERALS FROM SEAWATER Table 5 Uranium Selective Ion-Exchange Materials... 

The principal steps in the process proposed by the UKAEA for recovery of uranium from seawater are shown in Fig. 5.20. The titania recovery system consists of 60 beds, 1.3 ft (0.4 m) deep, each with a flow area of 188,000 ft (17,500 m ), filled with hydrous titanium oxide supported on an inert carrier. The inventory of the entire system is 71 million lb (32.2 million kg) of Ti, valued at 71 million in 1966. 

N. Ogata, Review on Recovery of Uranium from Seawater. HI, Nippon Kaisui Gakkaishi, 34 (1980) 3. 

H. J. Schenk, L. Astheimer, E. G. Witte and K. Schwochau, Development of Sorbents for the Recovery of Uranium from Seawater. 1 Assessment of Key Parameters and Screening Studies of Sorber Materials, Sep. Sci.TechnoL,... 

T. Kato, T. Kago, K. Kusakabe, S. Morooka and H. Egawa, Preparation of Amidoxime Fibers for Recovery of Uranium from Seawater, J. Chem. Eng. Japan, 23 (1990) 744. 

K. Uezu, K. Saito, T. Hori, S. Furusaki, T. Sugo and J. Okamoto, Performance of Fixed-Bed Charged with Chelating Resin of Capillary Fiber Form for Recovery of Uranium from Seawater, J. Atom. Energy Soc. Jpn., 30 (1988) 359. 

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