Uranium from seawater

Uranium content in seawater very low compared with other deposits seawater 0.003 ppm 

Uranium is present in seawater as uranyl carbonate or carbonato-complexes. 

The average uranium-content in seawater is at 0.003 ppm significantly lower than in conventional uranium ores (350 to 5000 ppm) or in phosphates (100 to 200 ppm). About 27 10- t of uranium is fed annually into the sea via rivers. 

The uranium in seawater is present, depending upon the pH and carbon dioxide concentration, as UO2CO3, [U02(C03)2H20]2- or [U02(C03)3]4-. 

It is technically feasible to extract uranium from seawater. There are, however, sufficient quantities of terrestrial uranium deposits, with extraction costs well below the extraction costs of uranium from seawater. 

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Acrylonitrile fibers treated with hydroxides have been reported to be useful for adsorption of uranium from seawater (105). Tubular fibers for reverse osmosis gas separations, ion exchange, ultrafiltration, and dialysis are a significant new appHcation of acryUc fibers and other synthetics. Commercial acryUc fibers have already been developed by Nippon Zeon, Asahi, and Rhc ne-Poulenc. 

PEI derivatives have proven to be effective carriers of cations in Hquid membrane systems (404). This technology led to the development of ion-exchange resins (405), which are also suitable for extracting uranium from seawater (406). 

The properties of hydrated titanium dioxide as an ion-exchange (qv) medium have been widely studied (51—55). Separations include those of alkaH and alkaline-earth metals, zinc, copper, cobalt, cesium, strontium, and barium. The use of hydrated titanium dioxide to separate uranium from seawater and also for the treatment of radioactive wastes from nuclear-reactor installations has been proposed (56). 

Cellulose. Cellulose or starch xanthate cross-linked by titanates can adsorb uranium from seawater (536). CarboxymethylceUulose cross-linked with TYZOR ISTT is the bonding agent for clay, talc, wax, and pigments to make colored pencil leads of unusual strength (537). 

Hotta, H. (1987). Recoveiy of Uranium from Seawater. Oceanas (Spring) 30. 

Adsorbing colloid flotation has been used to separate uranium from seawater [101]. 

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. 

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. 

Titanates and silico-titanates The oxide and hydroxide of titanium are effectively used in applications of removing metal ions from water. Early studies (since 1955) have shown that hydrous titanium oxide is the most appropriate material for extracting uranium from seawater, whereas titanates and hydrous titanium oxide are suitable for removing strontium. 

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,... 

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... 

Those ion exchangers that reach adequate values for the sorption of uranium from seawater are presented in Table 5. 

Figure 11 Schematic diagram of continuous extraction of uranium from seawater with polyamidoxime/polyhydroxamic acid fiber cloth used as an endless belt" (needs permission from Reactive Polymers).

Tabushi, I., Kobuke, Y., Nakayama, N., Aoki, T., and Yashizawa, A., Chelating resin functionalized with dithiocarbamate for the recovery of uranium from seawater. Ind. Eng. Chem. Prod. Res. Dev., 1984, 23 445 148. 

Research Commitee on Extraction of Uranium from Seawater. The Atomic Energy Soc. of Japan, Energy Developments in Japan, Vol. 3, 67 (1980)... 

Another calixarene, with long alkyl side chains and eight phosphate groups, has been used to recover uranium from seawater in 68-94% yields.71 Seawater contains 3 ppb of uranium. The resin could be recycled several times. 

Although seawater contains oniy 3.34 /rg of uranium/liter, the oceans of the world are so vast that their total uranium content is estimated to be around 4 billion MT [Dl]. Extraction of uranium from seawater is discussed in Sec. 8.8. 

Despite the very low concentration of uranium in seawater, 3.34 mg/m , the large total amount in the world s oceans, around 4 X lO MT of uranium [Dl], has provided incentive for study of means for extracting uranium from this ubiquitous source. To produce 1 MT (1 Mg) of uranium requires processing 10 /3.34X 10" =300 million m of seawater. This enormous volume gives rise to the principal problems in extracting uranium from seawater. These problems are (1) providing at low cost a continual supply of feed water undiluted by depleted... 

In a December 1974 report, Battelle Pacific Northwest Laboratory [B2] summarized the principal processes that had been proposed for extracting uranium from seawater and gave references to more detailed descriptions of these processes. That report concluded that the most promising process was the selective adsorption of uranium from seawater on hydrous titanium oxide (titania). 

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. 

Figure 5.20 Steps in recovering uranium from seawater by adsorption on titania.

It has been proposed that some of the natural uranium needed to fuel a pressurized-water nuclear power plant be obtained by extracting uranium from seawater used to cool the plant. If the seawater temperature rise is lO C and the reactor and fuel-cycle conditions are as given in Frg. 3.31, how many kilograms of uranium per year could be recovered at 80 percent yield from cooling water What fraction is this of the armual fuel requirement of the reactor ... 

K. Saito, T. Hori, S. Furusaki, T. Sugo and J. Okamoto, Porous Amidoxime-Group-Containing Membrane for the Recovery of Uranium from Seawater, Ind. Eng. Chem. Res., 26 (1987) 1977. 

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

M. Kanno, Present Status of Study on Extraction of Uranium from Seawater,... 

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,... 

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