FR2639652A1 - Adsorbent for uranium comprising bacterial cells - Google Patents

Abstract

Adsorbent for uranium comprising bacterial cells from fermentation of the amino acids belonging to the species Brevibacterium or to the species Corynebacterium. The adsorbent according to the invention makes it possible to adsorb and to recover the uranium present in the water released during the extraction and enrichment of nuclear fuels.

Description

 The present invention relates to uranium adsorbents using amino acid fermentation bacteria cells.

Constant progress has been made towards using
Uranium and thorium as sources of nuclear energy. Nuclear power is expected to dominate in the years to come.

 Terrestrial uranium resources are estimated at 5 million tonnes on continents, while huge uranium resources, which amount to 4 billion tonnes, are dissolved in seawater.

 In addition, with the progress of the nuclear industry, the urgent and serious problem of treating and recovering water containing radioactive waste released during the extraction and enrichment of fuel elements has appeared. nuclear such as uranium, thorium, etc., which goes hand in hand with the energizing of these elements. In addition, it is essential for the use of nuclear energy to recover and regenerate the nuclear fuels used and, to do this, it is desirable to have a safer and more economical process.

The present invention makes it possible to adsorb and recover
Uranium from Water containing Uranium released during a series of nuclear fuel element extraction processes to recover and reuse Uranium safely and economically.

 As a process for adsorbing uranium using microorganisms, there is known a process using algae (Japanese patent application open to public inspection No. 50-73810).

 In addition, actinomycetes, bacteria, yeasts and fungi have been studied for their uranium adsorption capacity (Marine Chemistry, 15 (11), 681-686, 1983). In the course of the selection test, bacteria belonging to the genus Bacillus and to the genus E. coli were studied. Among the 4 types of microorganisms mentioned above, actinomycetes have been shown to have an excellent ability to condense uranium.

In addition to uranium, the algae or cells of microorganisms mentioned above such as actinomycetes, bacteria, etc., all largely adsorb heavy metals such as cadmium, cobalt, nickel, copper, etc. As a result, attempts have been made to selectively develop inexpensive adsorbents for uranium. Attempts have also been made to develop adsorbents having a better adsorption capacity for uranium.
To meet this desire, the present invention provides uranium adsorbents and was carried out on the basis of the observation that bacteria cells adsorbing fermentation of determined amino acids can adsorb uranium selectively with an excellent capacity. adsorption.

 More specifically, the present invention relates to uranium adsorbents characterized in that they comprise bacteria bacteria for fermentation of amino acids belonging to the genus Brevibacterium or to the genus Corynebacterium.

There is no particular limitation with regard to the types of amino acid fermentation bacteria, but the bacteria used for the fermentation of glutamic acid and lysine can be widely used and the bacteria used otherwise for fermentation arginine, histidine, glutamine, alanine, lornithine, aspartic acid, citrulline, threonine, etc. Examples of fermentation bacteria include Brevibacterium flavum,
Brevibacterium lactofermentam, Corynebacterium glutamicum, etc. We can cultivate these bacterial cells independently in order to make them proliferate, but we prefer to use the cells constituting waste released during the fermentation of amino acids since they are inexpensive and because 'they are used effectively. The culture supernatant may not be completely eliminated from the cells. To isolate the cells, any method of centrifugation and filtration can be used. Alternatively, the cells can be precipitated beforehand by adding a precipitation agent or the like, before isolation. In the case of the use of a filter aid in the filtration process, the container system
The filter aid to adsorb the uranium in the state. However, it is preferred to proceed by centrifugation because the contaminants are present in less quantity. If necessary and if desired, the cells obtained are washed with water.

 The cells can be used as an uranium adsorbent in the form of a suspension or cake. Furthermore, the cells can also be immobilized using a polyacrylamide gel, etc., and the immobilized cells can be used. Adsorption can be carried out by means of a discontinuous system in which the cells are added to a uranium-containing liquid. In addition, in the case where the cells are immobilized, the immobilized cells can be introduced into a column to allow continuous treatment. In all cases, on an industrial scale, it is desirable to put the waste in which the uranium was recovered by adsorption in contact with fresh cells, thereby increasing the recovery rate. The cells brought into contact with the waste are brought into contact with a fresh liquid containing uranium to increase the amount of uranium adsorbed. Then, we elect uranium from them.

 The elution of uranium can be achieved by bringing the cells into contact with an acid or a base. The acid or base can be in the form of a buffer solution. Mention may be made of sodium carbonate as an example of eluent.

 The cells obtained after uranium uranium can be used again for uranium adsorption.

Or else, we can get rid of the cells by destroying them with fire.

 Furthermore, when the cells are used for the purification of a liquid containing waste, etc., without being intended for the recovery of uranium, they can be solidified using concrete, etc., without Elute the uranium, and the solidified cells can be eliminated.

 There is no particular limitation with regard to the type of liquid containing uranium and this can be, for example, a liquid containing waste released during the enrichment process of a nuclear fuel, a liquid containing waste released during the processing of a nuclear fuel, a liquid containing extraction waste, a liquid containing phosphate, sea water, etc.

 Other advantages and characteristics of the invention will appear better in the following nonlimiting examples.

Example 1
20 mg (dry weight) of wet cells of Brevibacterium flavum (strain deposited on September 9, 1975 at the Japanese Institute for Research on Fermentations under the number FERM-P 3247) which are fermentation bacteria of glutamic acid and 20 mg (dry weight) of Bacillus subtilis wet cells were added to 100 ml of an aqueous solution of U02 (N03) 2 having a uranium concentration of 10 ppm, respectively. Each mixture was stirred at 300C for 1 h. Next, the cells were separated and the uranium concentration of the supernatant was measured using an inductively coupled plasma device to measure the concentration of metal ions (Quantometer ICPQ-100, Shimadzu Seisakusho) to determine the amount of adsorbed uranyl ions. The results obtained are presented in the following table
Uranium adsorption rate
Brevibacterium flavum 99.2 X
Bacillus subtilis 97.3 X
Example 2
20 mg (dry weight) of Brevibacterium flavum (FERM-P nO 3247) were added to different amounts of an aqueous solution of U02 (N03) 2 having a uranium concentration of 20 ppm, respectively. Each mixture was stirred for 30 ° C for 1 h. Then, the cells were separated and the uranium concentration of the supernatant was measured in the same way as in Example 1. The results obtained are presented in the following table
Aqueous solution Adsorption rate Amount of uranium adsorbed uranium ~ uranium in cells
100 ml 98.5 X 99.2 mg / g
300 ml 69.2 X 209.1 mg / g
500 ml 47.3 X 238.2 mg / g
Example 3
20 mg (dry weight) of Brevibacterium wet cells
o flavum (FERM-P n 3247) and 20 mg (dry weight) of Bacillus subtilis were added to an aqueous solution containing 4 x 10 5 M of each of the following: cadmium (cadmium chloride), cobalt (cobalt chloride ), copper (cupric chloride), manganese (manganese chloride), nickel (nickel chloride), zinc (zinc chloride) and uranium (uranyl nitrate) and having a pH of 5.

Each mixture was stirred at 300C for 1 h. Then, the cells were separated and the concentration of metal ions in the supernatant was measured with an inductively coupled plasma device to measure the concentration of metal ions (Quantometer ICPQ-100, Shimadzu Seisakusho) to determine the amount of each adsorbed metal ions. The results obtained are presented in the following table:
Brevibacterium flavum Bacillus subtilis
CD 6.5 X 16.8 X
Co 3.3 7.8
Cu 33.5 63.3
Mn 2.5 9.3
Ni 4.3 90.5
Zn 3.5 9.5
U 93.5 60.8
EXAMPLE 4
The quantity of each of the metal ions adsorbed on Corynebacterium glutamicum (strain deposited on September 9, 1975 at the Japanese Institute for Research on Fermen was determined.
oations under FERM-P 3250). Results similar to those of Examples 1 to 3 were obtained.

 It is thus found that by using the adsorbent according to the present invention, the uranium contained in water can be recovered selectively and efficiently. As a result, the present invention not only makes it possible to extract uranium from new sources such as sea water, etc., but also to treat liquids containing wastes containing uranium.

 Various modifications can be made to the invention without departing from its scope.

Claims (1)

 CLAIM  Uranium adsorbent characterized in that it comprises amino acid fermentation bacteria cells belonging to the genus Brevibacterium or to the genus Corynebacterium.