GB1602341A

GB1602341A - Process and an adsorber material for the adsorptive binding of heavy metals

Info

Publication number: GB1602341A
Application number: GB10522/78A
Authority: GB
Original assignee: Kernforschungsanlage Juelich GmbH
Current assignee: Forschungszentrum Juelich GmbH
Priority date: 1977-03-17
Filing date: 1978-03-16
Publication date: 1981-11-11
Also published as: GB1602342A

Description

(54) IMPROVEMENTS IN OR RELATING TO A PROCESS AND AN ADSORBER MATERIAL FOR THE ADSORPTIVE BINDING OF HEAVY METALS (71) We, KERNFORSCHUNGSANLAGE JULICH GESELLSCHAFT MIT BES CHRANKTER HAFTUNG, of Postfach 1913, 5170 Julich, Federal Republic of Germany, a Body Corporate organised according to the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a process for extracting uranium, from sea water, by treatment with an adsorber material.

Many attempts have been made to extract heavy metals contained in sea water, because there is a substantially unlimited supply of such metals therein. However, so far as the hitherto-known processes for the extraction of heavy metals, more particularly uranium, are based upon such techniques as counter-current extraction, chemical precipitation and ion flotation in sea water, it is necessary to use chemical substances. This has the disadvantage that large quantities of chemicals must generally be employed, with the further disadvantage that the cost of the consumption of materials is relatively high. In addition, pollution of the environment by the chemicals employed can only be prevented, if at all. at great cost.

There is disclosed in German Patent Specification 2,441.479 an adsorber material consisting of cultivable mutants of algae. by which it is possible to extract uranium from sea water without chemical substances having to be employed, so that environmental pollution is avoided. However. in order to obtain with this known adsorber material a sufficiently high daily production for economical operation. huge cultures would be necessary for growing the required quantity of algae. and this is not possible without high expenditure.

The present invention provides an economic process for the extraction of uranium from sea water, which can be readily carried out without danger to the environment, as might be the case if a noxious chemical substance had to be used.

According to the invention there is provided a process for extracting uranium from sea water comprising treating sea water with an adsorber material comprising humic acid to bind the uranium thereto. The humic acid may be supported on a carrier therefor, the carrier representing at most 99^we by weight of the total amount of the adsorber material.

Expedientlv the sea water is treated with an adsorber material comprising black peat. the humic acid component of the black peat constituting the active adsorbing agent and the remainder of the black peat constituting a carrier therefor in situ; the black peat may be in granular form having an average particle size of from 0.1 to 10 mm, the granular black peat having been obtained by drying natural black peat and subsequent comminution.

As disclosed and claimed in our copending application No. 80/28222 serial no. 1602342 the preferred adsorber material comprises humic acid or a carrier-supported source of humic acid which has been adhered to a carrier which is stable to sea water so as to leave a substantial proportion of said humic acid or carrier-supported source thereof exposable to a flow of sea water. The said stable carrier may comprise activated charcoal having an average particle size in a range of 0.1 to 10 mm or brown coal having an average particle size in a range of 0.1 I to 10 mm. The said stable carrier may comprise a natural fibrous substance, e.g. jute. cotton or coconut fibre. The natural fibrous substance may be in the form of a gauze-like structure. A desirable form of adsorber material comprises, as a carriersupported source of humic acid. black peat. the peat being further supported by the said stable carrier and which has been applied to the peat. The black peat may be in granular form having an average particle size of from 0.1 to IOmm, the granular black peat having been obtained by drying natural black peat and subsequent comminution. The black peat may be adhered to a gauze of material, e.g. jute or nylon or like material which constitutes said stable carrier.

The humic acid referred to in the present invention will generally be chosen from biologically recent humic acids, i.e. humic acids which have been produced from humification products formed in periods of up to several thousand years.

Humic acids are insoluble in water except for a minor proportion. Therefore they can be used in an aqueous solution such as sea water for a long time, especially as they are biologically resistant to bacterial decay. Their partition coefficient with respect to sea water and defined as the ratio of the uranium concentration in the humic acid adsorber material to the uranium concentration in sea water, under conditions of equilibrium, is surprisingly high.

In a particular convenient form of process embodying the invention the adsorber material is disposed in an envelope in sea water and subjected to a relative movement with respect to the sea water, the envelope being impervious to the absorber material and pervious to sea water, or the adsorber material may be whirled in a vessel containing sea water the whirling being caused by sea water flowing into the vessel.

An especially favoured process embodying the present invention comprises the following steps: (a) treating the sea water with the said adsorber material by contacting the water with the said adsorber material for a sufficient time to adsorb onto the adsorber material as much uranium as possible; (b) separating the adsorber material from the treated sea water (c) washing the resultant adsorber material with dilute acid having a pH value lower than 3 to elute the adsorbed uranium, and (d) separating the adsorber material from the acid containing the uranium.

Step (d) may be followed by steps comprising: (e) adding an alkaline solution to the acid containing the uranium to form a solution having a pH value in a range of 4 to 8; and (f) contacting the resultant solution from step (e) with a second adsorber material capable of adsorbing the uranium thereon in order to further concentrate the uranium.

If desired the adsorbed uranium obtained from step (f) is further concentrated by the formation of metallic salt(s) thereof. Preferably the dilute acid used for the elution of the uranium is employed for further elution of uranium until the uranium concentration reaches a value which is increased by a factor of 103 to 104 relative to the concentration in the sea water being treated with the first mentioned absorber material, the pH value of the acid being kept below 2 by subsequent addition of concentrated acid. The first mentioned adsorber material containing the uranium may be washed out with hydrochloiric acid which has been prepared by electrolytic decomposition of sodium chloride contained in the sea water being treated. The said alkaline solution (step (e)) may be prepared by decomposition of the sodium chloride referred to above. Preferably the second adsorber material comprises humic acid to bind the said uranium.

Of course, the process according to the invention requires optimisation with a view to the most economical procedure. It may therefore be desirable, in order to save time or by reason of the given adsorption kinetics, not to leave the adsorber material in the sea water until the maximum concentration of uranium has been obtained, but to remove it from the sea water before equilibrium is established and to replace it by fresh adsorber material. On the other hand, the adsorptive charging will be made as high as possible in order that the quantity of adsorber necessary per unit weight of uranium and the acid consumption in a subsequent elution (which is preferably applied) may not become too high.

In a very advantageous embodiment of the process according to the invention, uranium contained in sea water is concentrated on an adsorber material comprising natural black peat, the humic acid component of the black peat constituting the active adsorbing agent and the remainder of the black peat constituting a carrier therefor in situ. The degree of decomposition of the black peat, which is a measure of the relative proportion of humification products in the total substance is generally from 35% to 55%. The coefficient of black peat for uranium in sea water is of the order of magnitude of 10 10.1ntitihOis case, not only may uranium be accumulated on the peat but also one or more other heavy metals such as. for example, vanadium and molybdenum. The extraction of these metals as by-products will increase the economy of the process and will therefore be a cost-saving factor. Since the remaining constituents in the peat as well as the humic acid are resistant to bacterial decay in sea water, the black peat may be used in sea water over a long period of time for the extraction of uranium. For this reason. repeated re-use of the adsorber material after the elution of the heavy metals concentrated on the adsorber material may be envisaged. Due to this fact, and owing to the ready availability of peat at reasonable price, the adsorber material can be used on a large scale, which in principle renders possible a daily production of 1 tonne of uranium, which is aimed at for an economical extraction of uranium. The quantity of peat necessary for this purpose is less than about 5 x 103 tonnes per day with at least tenfold repeated use of the adsorber material.

A further advantage is that the peat can be used as peat coke after its use in the process according to the invention is over.

In an adsorber material having a form especially suitable for use for the concentration of uranium, the black peat is present in the form of a granular mass having a grain size in the range from 0.1 to 10 mm, which has been produced, after drying of natural black peat, by subsequent comminution. For the production of this form of construction of the adsorber material, there may be employed as starting material natural, black moist peat from which the greater part of the water content has been extracted by drying on large surfaces lying in the open air. The dried peat sods, known as fuel peat, still have a residual water content of about 28% to 30%. These sods are then comminuted into the form of fine-grained material.

Before the grains are employed as adsorber material, they are again wetted with water, whereby numerous fine channels and peat grains are filled with water and the grains are caused to swell. This operation may be considerably accelerated by reducing the pressure over the wet peat by about 20 mm. Hg., which expels the air from the channels and pores.

In a further form of construction of the adsorber material comprising black peat, which may be conveniently employed, the black peat is present as a layer which adheres to one or more gauzes consisting of material which is sufficiently stable in sea water, such as jute or nylon. the said layer having been formed by the application of natural black peat to the gauze(s). In this case, the stability of the gauze material is sufficient if it remains stable during its wetting for the period of time for which it is proposed to use it, which may be about one month. In the production of a preferred form of adsorber material natural, moist black peat is applied under sufficient pressure to both sides of suitable gauzes, which have a mesh width of a few mm, so that the peat mass penetrates through the gauzes. In the subsequent drying, the layers of peat on the two sides of the gauzes mat together through the meshes. They are thereafter dimensionally stable when re-used with water and even in a strong current of water.

There may alternatively be employed to carry out the process of the invention a form of adsorber material in which there is employed as the carrier material a material which has a large surface having binding capacity, to which the humic acid material has been applied.

The material employed as carrier material for the humic acid material should be resistant to sea water and render possible re-use of the adsorber material. There may with advantage be employed as such a material activated charcoal having a grain size in a range of 0.1 to 10 mm, which may be produced from fuel peat, for example, or brown coal, having a similar granular structure. Although activated charcoal has the larger surface having binding capacity, the use of brown coal as carrier material for the humic acid material would be preferable for reasons of cost. However, it may be desirable for the material employed as carrier material to consist of fibrous natural substances such as jute, cotton and coconut fibres. In this case, the carrier material may be present in the form of a conglomeration in which the fibres are loosely joined together. However, in a preferred form of the carrier material, the fibrous natural substances are present in the form of a gauze-like structure to which the humic acid material has been applied.

If the use of an adsorber material supported on a carrier is contemplated such may be employed in various fashions, depending on its form of construction. Thus, for example, it may be advantageous to subject the supported adsorber material to movement in relation to the sea water in an envelope which is impervious to the supported adsorber material and pervious to sea water. Such procedures are recommended when the adsorber material is present in the form of a granular mass or as a kind of conglomeration of fibrous substances.

The adsorber material may then desirably be enclosed in gauzes of appropriate mesh width, which may consist, for example, of nylon fibres. For the concentration of the heavy metal(s) comprising uranium. a multiplicity of filter bodies formed in this manner, and preferably disposed parallel to one another and in line with one another, are introduced into the sea current in such manner that the current of sea water is directed along the filter bodies, but a sufficient exchange of sea water through the gauzes is nevertheless ensured.

The adsorber material may be employed in the same general way without any envelope being necessary, if it consists of a humic acid adsorber material layer on carrier gauzes. The flow may then be directed along the gauzes, several of which are disposed parallel to one another. There may be a plurality of parallel gauzes disposed in layers, some of which are substantially in a line but offset from their neighbours. In this way, the sea current, after having passed through the first layer, is split up by the succeeding layer, whereby good intermixing of the water is obtained with comparatively low resistance to flow. The distance between the gauzes and the number of layers are made such that, with velocities of flow of up to Sm/s, the desired uranium depletion in the sea water is achieved.

Since acceleration of the sea water by pumping is unfavourable from the energy viewpoint, it is desirable for the necessary relative movement between the adsorber material of whatever form of construction, and the sea water to be produced by a travelling ship trailing the gauzes. Taking as a basis, for example, daily production of 1 tonne of uranium, about 109 m3 of sea water must be passed through the adsorber material per day for an extraction of 1 ltg of uranium from 1 litre of sea water. If the adsorber material is drawn through the sea at a speed of 20 km/h, its total cross-section may be limited to about 2000 m2. Also, when a ship is employed, the advantage is obtained that the adsorber material can be employed in waters which have low biological production. The danger of any growth being formed on the adsorber material is thereby substantially avoided.

A further very desirable manner of using adsorber material in the form of a granular mass in a process according to the invention, involves whirling the adsorber material in a vessel containing sea water, the whirling being effected by means of sea water flowing into the vessel.

The whirling is preferably carried out with the aid of suitable deflecting devices provided in the vessel. Loss of grains is prevented by the provision of fine-meshed gauzes at the outlet of the vessel. When the adsorber material is used in this fashion, the desired charging thereof with uranium from the sea water is very rapidly achieved owing to the whirling.

After the concentration of the uranium the adsorber material containing it is normally taken from the sea water. For this purpose, it is desirable for those parts of the adsorber material which are charged to the desired degree to be replaced as continuously as possible by fresh or eluted parts of the adsorber material. In cases in which the adsorber material employed is situated in an envelope, or an adsorber material is situated on a gauze therein, the adsorber material can be very simply removed from the sea water. If the adsorber material in the form of a granular mass is whirled in an adsorber tank, the granular mass charged with uranium may be separated off. for example, by a centrifuge, which may take the simple form of a tubular coil having, for example, 10 to 20 turns, through which the sea water containing the granular mass is pumped from the adsorber tank at a rate of, for example, 10 m/s. The separated-off granular mass may be re-used a number of times, while the treated sea water is returned into the sea. The capacity of the centrifuges must be made such that the whole adsorber material is eluted on average once per charging period in the adsorber tank.

After the adsorber material having heavy metal(s) comprising uranium concentrated thereon has been removed from the sea water, it may be washed out with dilute acid, preferably hydrochloric acid or nitric acid, at a pH value of less than 3 for the elution of the adsorbed heavy metal(s). The acid may here serve as a uranium store provided that its pH value is kept low. For this purpose, the dilute acid used for the elution of the heavy metal(s) comprising uranium may be employed for further elution until the uranium concentration therein has reached a value which is greater by a factor of the order of magnitude of 103 or 104 in relation to the sea water, the pH value of the acid being kept below 2 by further addition of concentrated acid. In this way, the volume throughput of solution in the further course of the process can be kept low.

In a particularly advantageous form of the process according to the invention the adsorber material containing the heavy metal(s) comprising uranium is washed out by hydrochloric acid produced by electrolytic decomposition of sodium chloride contained in the sea water. The electrolytic decomposition of sodium chloride is known as alkali-metal chloride electrolysis and is already employed on a large scale. For the production of the hydrochloric acid required for the process of the invention, there is employed a method in which sea water is inspissated by known means to form brine, and then hydrogen. sodium hydroxide solution and chlorine are produced therefrom in accordance with the reaction equation of the alkali-metal chloride electrolysis process.

Energy + 2H2O + 2NaClH2 + 2NaOH + Cl2.

In accordance with the reaction equation H2 + Cl2 < 2HC1 + 43.8 Kcal chlorine may then be burnt in hydrogen to form hydrogen chloride with the release of energy, and the HCI formed introduced into water for the production of hydrochloric acid.

In this case, it is also desirable to add to the hydrochloric acid containing the uranium sodium hydroxide solution produced by decomposition of sodium chloride contained in the sea water, because sodium hydroxide solution is in any case formed in the performance of the alkali-metal. chloride electrolysis.

By the application of the alkali-metal chloride process for producing from sea water the hydrochloric acid required for the performance of the preferred form of process of the invention, no additional cost for transport and the provision of the necessary working means is incurred. This is especially advantageous when the process of the invention is carried out, for example, on a ship at sea. In this case, there may be used as starting material for producing the hydrochloric acid and. sodium hydroxide solution inspissated sea water produced directly at the site of the heavy metal extraction installation by evaporation of sea water by known processes. For the evaporation of the water, there is advantageously employed the waste heat of a nuclear reactor which may be situated, like the other parts of the installation required, on the ship or on a corresponding floating body provided for this purpose.

In a very advantageous form of the process of the invention, elution solution containing the uranium is again brought into contact, for the further concentration of the uranium, with a second adsorber material which contains biologically recent humic acid and in which there is present a proportion of at most 99% by weight of material serving as carrier material for the humic acid. In order to achieve maximum concentration of the uranium, the pH value of the solution may be adjusted to an appropriate level for this purpose (preferably minimum 4 and maximum 8). Since the partition coefficient of the uranium also has substantially the same value in this relatively high concentration range as in the concentration range of the sea water, the uranium concentration in the elution solution may be reduced to about 1/10 of its initial value by introducing the adsorber material into an exchanger column. In this way, there is achieved a further concentration in the adsorber material-by factor of 103 to 104, calculated-on they dry substance of the adsorber material, so that the uranium concentration is increased in all by a factor of about 107 in relation to the sea water. Other heavy metals may be concentrated comparably at. the same time.

The adsorber.material employed for increasing the concentration of the uranium may also be burnt after the adsorption step. Since the ash residues of the adsorber material generally amount to less than 5% by weight of the unburnt dry substance. a further concentration of the uranium by a factor of about 20 may be achieved by the burning. This means that the uranium (and, generally, other heavy metals) is then generally present in the ash residue in a concentration which is higher by substantially a factor of 108 in relation to the sea water, and constitute in respect of weight the main components of the ash residue.

The uranium can be readily isolated from the ash residue by known methods.

Example 1 One gram of air-dried black peat (as adsorber material) was ground and screened and- a granular mass having a grain size distribution in a range between 70 and 10Fm inthe dry state was obtained. After wetting with water, the granular mass, which had then swelled to grain sizes of more than 100cm, was introduced into 10 litres of natural sea water at 200C and at a pH value of 8.3, and containing 3.3 llg of uranium and 2 llg of vanadium per litre, and stirred for 4 hours. After subsequent separation of the granular mass from the sea water, the quantity of uranium adsorbed onto the peat .was found to be 18 ug and that of vanadium was found to be 16 > g. The uranium content of the depleted sea water still amounted-to 1.5 g per litre. This corresponds to a partition coefficient for uranium of 1.2 x 104, calculated on the dry weight of the peat. The vanadium content of the depleted sea water was still 0.3 Fg per litre, corresponding to a partition coefficient for vanadium of 5.3 x 104.

The uranium and vanadium adsorbed on the peat were completely eluted by stirring of the peat grains charged therewith in 200 cc of 1% hydrochloric acid (pH = 0.6). For this purpose, the hydrogen ion content of about 4 cc of this acid was consumed per gram of peat.

The concentration and the subsequent elution were repeated 30 times in the described manner with the same peat. Even after the peat had been used 30 times as adsorber, no reduction of the partition coefficients for uranium and vanadium could be detected.

Example 2 On the open sea off the island of Sylt, 54 litres of sea water at 70C were pumped through a fluidised adsorber bed at a rate of 1 litre per minute. In this adsorber bed, which consisted of a column having a capacity of 2.7 litres and. closed at its ends by a nylon gauze having a pore width of 100 um, 20 g of black peat (as adsorber material) having the grain distribution indicated in Example 1 were continuously whirled.

The sea water contained 3.3 Fg of uranium before the depletion. Of the 178 pg of uranium contained in the 54 litres of sea water before the experiment, 137 ug, i.e. 77% by weight of the total quantity of uranium. were bound onto the adsorber material. The first 3 litres of sea water pumped through the adsorber bed were depleted to 0.1 ug of uranium per litre, and the remaining quantity of sea water was depleted to 0.4 llg of uranium per litre.

Example 3 Natural muddy black peat (as adsorber material) is applied under pressure to both sides of jute gauzes (mesh widths about 2 mm) and nylon gauzes (mesh width 1 mm) held in plastics frames in such manner that the peat slurry penetrates through all the meshes. After the subsequent drying in air and the accompanying interlinking, the layers on the two sides of the gauzes became mutually stabilised through the many unions existing through the meshes. Peat of a total dry weight of 3 g was applied to 1 g of jute gauze and 1 g of nylon gauze in this manner so as to adhere firmly thereto. After re-wetting with water, the layers of peat on the gauzes again swell up somewhat. In a stability test, these matrices were exposed for 4 days to sea water flowing along them at a relative speed of about 2 m/sec. The layers of peat remained dimensionally stable and did not become detached from the gauzes.

Example 4 40 g of naturally moist black peat having a water content of about 80% by weight, which had been taken from the upland moor at Gross Hesepe in Emsland, were shaken for about 15 hours in 120 cc of 0.5-normal sodium hydroxide solution and then centrifuged. The solution centrifuged off was added to 32% hydrochloric acid until a pH value of 1 was reached. The humic acid fraction thus precipitated was centrifuged-off and washed to neutrality with distilled water. The dry weight of the humic acid thus obtained was 1.2 g.

The aforesaid quantity of humic acid (adsorber material) was stirred for 2 hours, without previous air drying, with 10 litres of natural sea water at 200C and having a pH of 8.3 and a uranium content of 3.3 ltg per litre. After subsequent separation of the humic acid from the sea water, the following values were measured: the sea water had been depleted to 0.6 ilg of uranium per litre, the humic acid contained 25 ltg of uranium and the partition coefficient was 3.7 x 104, calculated on the dry weight of the humic acid. The uranium adsorbed onto the humic acid was completely eluted by dilute hydrochloric acid in the same way as in Example 1. The concentration and the elution were repeated 8 times on the same humic acid without detriment to the distribution coefficients.

Example 5 40 g of naturally moist black F eat having the same consistency as in Example 4 were again shaken for about 15 hours in :.20 cc of 0.5-normal sodium hydroxide solution and then centrifuged. There were first added to the centrifuged-off solution 3.6 g of fine-grained activated charcoal (mean grain size 10 clam) and then adjusted to a pH of 1 with 32% hydrochloric acid. The humic acid fraction thus precipitated (adsorber material) adhered to the activated charcoal, which acted as carrier. The dry weight of the humic acid-activated charcoal thus produced was 4.8 g, the humic acid being in a weight ratio of 1:3 to the active charcoal.

This humic acid - activated charcoal was stirred for 2 hours with 10 litres of natural sea water as in Example 4. The uranium content of the sea water was thus reduced from 3.3 Fg per litre to 0.8 llg per litre when the humic acid - actvated charcoal had been air-dried before the contacting with the sea water, and to 0.6 llg per litre when the prior air drying was omitted. The corresponding partition coefficients, calculated on the respective dry weight quantities of the humic acid. wa

Example 7 5g of black peat grains (as adsorber material) (grain size after wetting with water between 100 and 200 Mm) were stirred for three hours in 50 litres of sea water at 200C and have a pH of 8.3 whereby the sea water was depleted to 1.5 fug of uranium per litre. The separated-off grains were completely eluted by stirring with 40 cc of 2% hydrochloric acid (pH = 0.3).

The centrifuged-off elution solution had a uranium content of 2.25 mg per litre after the elution of the peat. Thereafter, 5 g of black peat grains which-had been contacted with sea water in the described manner were eluted for a second time with this elution solution, which had again previously been brought to a pH value of 0.3 with 32% hydrochloric acid and made up to 45 cc with distilled water, whereafter their uranium content rose to 4 mg per litre. a concentration which is higher than that in sea water by a factor of 1.2 x 103.

The elution solution was again centrifuged off, adjust to a pH of 7.4 by the addition of sodium hydroxide solution, made up to 50 cc with distilled water and stirred for three hours with 25 mg of black peat grains having the same grain size as indicated in the foregoing.

After separation of the grains from the solution, the uranium content of the depleted elution solution was found to be 220 Fg per litre, and that of the peat 6760 ppm. This corresponds to a uranium partition coefficient in this concentration range and at a pH value of 7.4 of 3 x 104. calculated on the dry weight of the grains. This means that the humic acid of the peat even in the concentration range raised by a factor of 103 as compared with sea water concentrates uranium at least equally as well as in the sea water itself.

The uranium-charged peat grains were reduced to ash. The ash residue contained 169 llg of uranium. Since the ash content of this peat is 3% by weight, the proportion by weight of uranium in the ash residue was 229. This corresponds to a total concentration factor of 6.7 x it)'.

WHAT WE CLAIM IS: 1. A process for extracting uranium from sea water comprising treating sea water with an adsorber material comprising humic acid to bind the uranium thereto.

2. A process according to claim 1. wherein the humic acid is supported on a carrier therefor, the carrier representing at most 99% by weight of the total amount of the adsorber material.

3. A process according to claim 2, wherein sea water is treated with an adsorber material comprising black peat, the humic acid component of the black peat constituting the active adsorbing agent and the remainder of the black peat constiting a carrier therefor in situ.

4. A process according to claim 3. wherein the black peat is in granular form having an average particle size of from 0.1 to 10 mm.

5. A process according to claim 3 or claim 4, wherein the black peat has been adhered to a gauze of material resistant to sea water.

6. A process according to claim 5, wherein the gauze is made of jute or nylon.

7. A process according to any one of claims 1 to 6, wherein the adsorber material comprises humic acid or a carrier- supported source of humic acid supported or further supported by a carrier made of a material stable to sea water and which has been applied to the humic acid or to the carrier-supported source of humic acid.

8. A process according to claim 7, wherein the said carrier made of a material stable to sea water comprises activated charcoal having an average particle size in a range of 0.1 to 10 mm.

9. A process according to claim 7, wherein the said carrier made of a material stable to sea water comprises brown coal having an average particle size in a range of 0.1 to 10 mm.

10. A process according to claim 7, wherein the said carrier made of a material stable to sea water comprises a natural fibrous substance.

11. A process according to claim 10. wherein the natural fibrous substance comprises jute, cotton or coconut fibre.

12. A process according to claim 10 or claim 11, wherein the natural fibrous substance is in the form of a gauze-like structure.

13. A process according to any preceding claim wherein the adsorber material is disposed in an envelope in sea water and subjected to a relative movement with respect to the sea water. the envelope being impervious to the adsorber material and pervious to sea water.

14. A process according to any one of claims 1 to 12 wherein the adsorber material is whirled in a vessel containing sea water, the whirling being caused by sea water flowing into the vessel.

15. A process according to any preceding claim, comprising the following steps: (a) treating sea water with the said adsorber material by contacting the sea water with the said adsorber material for a sufficient time to adsorb onto the adsorber material as much uranium as possible;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 7 5g of black peat grains (as adsorber material) (grain size after wetting with water between 100 and 200 Mm) were stirred for three hours in 50 litres of sea water at 200C and have a pH of 8.3 whereby the sea water was depleted to 1.5 fug of uranium per litre. The separated-off grains were completely eluted by stirring with 40 cc of 2% hydrochloric acid (pH = 0.3). The centrifuged-off elution solution had a uranium content of 2.25 mg per litre after the elution of the peat. Thereafter, 5 g of black peat grains which-had been contacted with sea water in the described manner were eluted for a second time with this elution solution, which had again previously been brought to a pH value of 0.3 with 32% hydrochloric acid and made up to 45 cc with distilled water, whereafter their uranium content rose to 4 mg per litre. a concentration which is higher than that in sea water by a factor of 1.2 x 103. The elution solution was again centrifuged off, adjust to a pH of 7.4 by the addition of sodium hydroxide solution, made up to 50 cc with distilled water and stirred for three hours with 25 mg of black peat grains having the same grain size as indicated in the foregoing. After separation of the grains from the solution, the uranium content of the depleted elution solution was found to be 220 Fg per litre, and that of the peat 6760 ppm. This corresponds to a uranium partition coefficient in this concentration range and at a pH value of 7.4 of 3 x 104. calculated on the dry weight of the grains. This means that the humic acid of the peat even in the concentration range raised by a factor of 103 as compared with sea water concentrates uranium at least equally as well as in the sea water itself. The uranium-charged peat grains were reduced to ash. The ash residue contained 169 llg of uranium. Since the ash content of this peat is 3% by weight, the proportion by weight of uranium in the ash residue was 229. This corresponds to a total concentration factor of 6.7 x it)'. WHAT WE CLAIM IS:

1. A process for extracting uranium from sea water comprising treating sea water with an adsorber material comprising humic acid to bind the uranium thereto.

6. A process according to claim 5, wherein the gauze is made of jute or nylon.

(b) separating the adsorber material from the treated sea water (c) washing the resultant adsorber material with dilute acid having a pH value lower than 3 to elute the adsorbed uranium; and (d) separating the adsorber material from the acid containing the uranium.

16. A process according to claim 15, wherein step (d) is followed by steps comprising: (e) adding an alkaline solution to the acid containing the uranium to form a solution having a pH value in a range of 4 to 8, and (f) contacting the resultant solution from step (e) with a second adsorber material capable of adsorbing the uranium thereon in order to further concentrate the uranium.

17. A process according to claim 16, wherein the adsorbed uranium obtained from step (f) is further concentrated by the formation of metallic salt(s) thereof.

18. A process according to any one of claims 15 to 17, wherein the dilute acid used for the elution of the uranium is employed for further elution of uranium until the uranium concentration reaches a value which is increased by a factor of 103 to 104 in relation to the sea water being treated with the first mentioned adsorber material, the pH value of the acid being kept below 2 by subsequent addition of concentrated acid.

19. A process according to any one of claims 15 to 17 wherein the first mentioned adsorber material containing the uranium is washed out with hydrochloric acid which has been prepared by electrolytic decomposition of sodium chloride contained in the sea water being treated.

20. A process according to claim 19 when dependent on claim 16 wherein the said alkaline solution is prepared by decomposition of sodium chloride contained in the sea water being treated.

21. A process according to claim 16 or any claim appendant thereto, wherein the second adsorber material comprises humic acid to bind the uranium.

22. A process according to claim 1 substantially as herein described and exemplified.

23. Uranium which has been extracted from sea water by the process claimed in any preceding claim.