RU2207393C1 - Method of thorium recovery and concentration from process solutions - Google Patents

Abstract

FIELD: hydrometallurgy; applicable for selective recovery of thorium from solutions containing other metals. SUBSTANCE: method includes sorption of thorium at pH 2.8-3.5 and temperature of 60-95 C on porous sulfacationite with subsequent washing of cationite and desorption of thorium with carbonate-containing solution. In this case, prior to sorption, introduced into initial solution is magnesium chloride in amount of 10-100 mg - equivalent Mg²⁺ per mg-equivalent of ions Th⁴⁺ in initial solution. After sorption, cationite is washer first with water and then with solution of MgCl₂ with concentration of 50-150 g/cu.dm. Filtrate after sorption is combined with washing waters. Introduced successively into combined solution are first potassium iodate, and then barium chloride and sodium sulfate. Pulp is filtered and radioactive iodate-sulfate cake is separated from deactivated solution which is directed for recovery and utilization of rare and trace metals. Thorium-containing eluate is treated with mineral acid, for instance, hydrochloric acid up to pH 0.5-2.0, heated up to 80- 100C, held at elevated temperature for 0.5-2h and alkali reagent, for instance, solution of hydroxide of sodium and/or ammonia up to pH5-8 is introduced. Formed pulp is set and filtered, sediment of thorium hydroxide and hydroxycarbonate is separated from mother liquor, combined with radioactive iodate-sulfate cake and directed for processing or for burial into special waste storage. Besides, magnesium chloride is introduced into initial solution in amount ensuring its content in solution before sorption of 50-150 g/cu.dm. Used for introduction into initial solution of magnesium chloride are natural and/or synthetic bishofite, and/or carnallite, and/or middlings, and/or wastes of carnallite raw material processing selected from carnallite dust of the first stage of carnallite dehydration or slime of carnallite chlorinators. KJO₃ is introduced in form of solution with concentration of 10-50 g/cu.dm in amount of 1.2-1.5 of solutions with concentration of 50-150 g/cu.dm in amount of 1.2-1.5 moles of Na₂SO₄ per mole of BaCl₂. EFFECT: higher degree of thorium recovery from scandium-containing solutions, higher degree of scandium cleaning from thorium and reduced irreversible losses of scandium with thorium in radioactive cakes and sediments. 5 cl, 2 tbl, 3 ex

Description

 The invention relates to hydrometallurgy and can be used for the selective extraction of thorium from solutions containing other metals. The invention can be used, in particular, in the technology for producing scandium oxide from various raw materials - for the selective extraction and concentration of thorium from scandium-containing solutions.

 There is a method of extracting thorium from solutions, which consists in the sorption of thorium ions from chloride-hydrochloric acid solutions followed by desorption of thorium (see. Extraction of thorium from waste from the chlorination process of loparite concentrates // Radiochemistry, 1986, 4. P. 486-489). The disadvantage of this method is the lack of process selectivity when extracting thorium from solutions containing scandium: in this case, scandium is also sorbed simultaneously with thorium. Other known methods of thorium extraction have the same disadvantage (A.S. 1420972 USSR, publ. BIPM 19, 2000, p. 602; A.S. 1485606 USSR, publ. BIPM 2, 2000, p. 593), which include sorption of thorium from solutions with amphosphate ampholytes.

 Of the known analogues, the closest to the proposed invention in terms of purpose, combination of features and the achieved result is a known method for the extraction of thorium from solutions containing scandium (a.s. 703929 USSR with a priority of 10/05/1977. Publ. BI 41, 1983. C. 256; see also: Izvestiya VUZov, Non-ferrous metallurgy, 1984, 4. P. 59-61; Journal of Applied Chemistry, 1986, 4. P. 896-900) - adopted as a prototype.

The prototype method consists in the following: an initial solution containing thorium and scandium with a pH of 2.8-3.5 is passed through a sorption column with porous sulfocathionite in Na form; sorption is carried out at 60-90 ^o C until the “appearance” of thorium in the filtrate, after which the cation exchange resin in the column is washed in 2-3 volumes of water, with a NaCl solution (for desorption of scandium) and then thorium is desorbed 1-3 n. Na ₂ CO ₃ solution. Compared with other previously known methods, the prototype method allows selective extraction of thorium from scandium-containing solutions. The disadvantage of this method is the unsatisfactory degree of separation of scandium and thorium and the relatively low dynamic exchange capacity for thorium - i.e. capacity to "slip" of thorium into the filtrate.

 The claimed invention is aimed at solving the problem of increasing the efficiency of the process by increasing the degree of separation of scandium and thorium; increase in process productivity by increasing DOE in thorium.

 The technical result achieved in this case is to increase the degree of extraction of thorium from scandium-containing solutions, increase the degree of purification of scandium from thorium and reduce the irreversible loss of scandium with thorium - with radioactive cakes and precipitates. In other words, the technical result achieved by the implementation of the developed method consists in increasing the dynamic capacity for thorium and increasing the sorption load for thorium, i.e., increasing the productivity of the process, reducing losses of scandium with thorium-containing radioactive fallout.

The technical result is achieved by the fact that in the method of extracting thorium from technological solutions, including sorption of thorium at a pH of 2.8-3.5 and a temperature of 60-95 ^o With porous sulfocathionite, followed by washing the cation exchange resin and desorption of thorium with carbonate-containing solutions, is new, that magnesium chloride is preliminarily introduced into the initial solution in the amount of Mg ²⁺ mEq per 1 mEq of Th ⁴⁺ ions in the initial solution before sorption, the cation exchange resin is washed first with water, then with a MgCl ₂ solution with a concentration of 50-150 g / dm ³ promvody combine t with the filtrate after sorption sequentially administered solution (10-50 g / ^dm3) of potassium iodate in an amount of 10-100 cm ³ per 1 dm ³ solution, after which the solution is administered (50-150 g / dm ³⁾ of barium chloride and sodium sulphate in the amount of 1.2-1.5 mol of Na ₂ SO ₄ per 1 mol of BaCl ₂ , the radioactive iodate-sulfate cake is separated from the deactivated solution, which is sent to the extraction and disposal of rare and scattered metals (Sc), the thorium-containing eluate is treated with mineral acid, e.g., hydrochloric acid, until pH 0.5-2.0 is heated to 80-100 ^o C, maintained at elevated temperatures within 0.5-2 hours, an alkaline reagent is introduced, for example, a solution of sodium and / or ammonium hydroxide to a pH of 5-8, the resulting pulp is settled and filtered, the precipitate of hydroxide and thorium hydroxocarbonate is separated from the mother liquor, combined with radioactive iodate-sulfate cake and sent for burial in the storage of special waste. In addition, magnesium chloride is introduced into the initial solution in an amount ensuring its content in the solution before sorption. In addition, when magnesium chloride is introduced into the initial solution, prior to sorption of thorium, natural and / or synthetic bischofite and / or carnallite and / or intermediate products and / or carnallite processing waste products selected from the series are used: carnallite dust of the first stage of carnallite dehydration , sludge carnallite chlorinators.

 Ceteris paribus, the proposed method, characterized by new methods of performing actions and a new order of actions, the use of certain substances, without which it is impossible to implement the method itself, with new modes and parameters of the process, provides a technical result in the implementation of the claimed invention.

 Checking the patentability of the claimed invention shows that it corresponds to the inventive step, as it should not be obvious to specialists.

The analysis of the prior art indicates that in the book, journal and patent literature there is no information on the selective extraction of thorium from technological solutions containing scandium by sorption from solutions at pH 2.8-3.5, in which MgCl ₂ is preliminarily introduced before sorption in an amount of 10-100 mEq per 1 mEq Th, a washing of the cation exchange resin after sorption is carried out with a solution of MgCl ₂ with a concentration of 50-150 g / dm ³ , the filtrate after sorption is combined with the promoters, KIO ₃ , Na ₂ are sequentially introduced into the combined solution SO _{4 2} VaSl radioactive iodate -sulfatny precipitate was separated from the solution, which is sent to the extraction of rare metals such as Sc, thorium-bearing eluate carbonate treated with HCl to a pH of 0.5-2.0, is heated to 80-100 ^o C, aged 0.5-2 hours alkaline administered the reagent is up to pH 5-8, the pulp is defended, filtered, the radioactive precipitate is separated from the solution, combined with cake and sent to HCO.

 Therefore, the claimed invention meets the condition of "novelty." It must be emphasized that the technical result of the claimed invention is achieved only if all of the above conditions and process parameters are met.

Failure to perform at least one of the features (known or new) of the claimed method does not allow to increase the dynamic viscosity of thorium and does not make it possible to increase the efficiency of the process of extracting thorium from solutions containing scandium. In particular, when using phosphorus-containing ion exchangers for sorption of thorium (instead of sulfocathionites) and when all other conditions (pH, temperature, concentration of MgCl ₂ , etc.) are met, the technical result is not only not achieved, but generally selective extraction of thorium from scandium-containing solutions not happening. On the other hand, when MgCl ₂ is introduced into the initial solution in amounts differing from the optimal ones (more or less than 50-150 g / dm ³ ), the effect of increasing DOE in thorium disappears. Another important issue is the "fate" of solutions - thorium-containing eluates. In the known methods there are no technical solutions for their processing and disposal.

 Thus, the analysis of the totality of the features of the claimed invention and the result achieved in this case shows that there is a well-defined causal relationship between them, expressed in that the process under the above conditions provides a solution to the problem and the achievement of a technical result. In violation of the above process modes, sequence of actions, etc. the above technical result is not achieved.

 It should be noted that the established causal relationship does not explicitly follow for specialists and does not follow from the literature data on the chemistry and technology of thorium and its compounds.

 Information confirming the implementation of the invention with obtaining the above technical result, as well as a comparison of the effectiveness of the known (prototype) and the proposed technical solutions are given in the examples.

 Example 1

 A comparison is made of the efficiency of extraction of thorium from solutions according to the known and proposed methods.

According to the known method: through a sorption column with 2 g of porous sulfonic cation exchanger KU-23 in Na-form, a solution with a pH of 3.0 is passed, containing 2.4 g / l of scandium and 4.4 g / l of thorium until the “slip” of thorium into the filtrate ("DOE"). Sorption is carried out at 80 ^o C. After sorption, the cation exchange resin in the column is washed with water and desorption is carried out: scandium - 2 N. sodium chloride solution; thorium - 3 n. ammonium carbonate solution.

According to the proposed method: in a stock solution containing 2.7 g / l of scandium and 3.7 g / l of thorium, 100 g / l of magnesium chloride MgCl ₂ (33 mEq per 1 mEq Th) is added. This solution (pH 3.0) is passed at 80 ^{° C.} through a sorption column from 2 g of macroporous sulfocationionite to a “slip” of thorium into the filtrate (DOE). After sorption, the cation exchange resin in the column is washed with water and desorption is carried out: scandium - with a solution of magnesium chloride (100 g / dm ³ ) and then thorium - 3 N. ammonium carbonate solution. The results of the experiments are given in table. 1. The data in table 1 show that the proposed method provides, compared with the prototype, an increase in the sorption load on the cation exchange resin by 1.5 times and, therefore, an increase in the productivity of the process due to the introduction of magnesium chloride into the initial solution and leads to an increase in the volume of the solution passed to "slip" of thorium ions into the filtrate and to increase the sorption capacity of cation exchange resin on thorium.

 At the same time, the degree of separation of scandium and thorium at the sorption stage increases by about 3 times.

 Example 2

In the initial chloride solution with a pH of 3.0, containing 5.0 g / dm ^{3 of} thorium and 4.0 g / dm ^{3 of} scandium, 100 g / dm ^{3 of} MgCl ₂ was introduced in an amount providing an optimal ratio of Mg ²⁺ / Th ⁴⁺ , equal to 24.4 mEq / mEq. Then this solution was passed at 80 ± 5 ^o C through a heated sorption column with macroporous sulfonic cation exchanger KU-23 in salt form. Sorption was carried out before the "slip" - until the appearance of thorium in the filtrate. Under these conditions, thorium was selectively sorbed by sulfocationite, and scandium was displaced into the filtrate. Small amounts of scandium remaining in the intergranular space and the cation exchanger phase — after the “breakthrough” of Th ⁴⁺ were removed by sequential washing with water first (2 volumes with respect to the volume of cation exchanger resin), then with a solution of MgCl ₂ with a concentration of 100 g / dm ³ . All promoters were combined with the filtrate and a solution of KIO ₃ (10 g / dm ³ ) KIO ₃ was first sequentially introduced in an amount of 30 cm ³ per 1 dm ³ , then BaCl ₂ and Na ₂ SO ₄ (in the form of a solution with a concentration of 150 g / dm ³ ) and Na ₂ SO ₄ (in the amount of 1.3 mol of Na ₂ SO ₄ per 1 mol of BaCl ₂ ). The resulting slurry was filtered, a radioactive precipitate containing thorium and its decay products (Ra-228, Ra-224) was separated from the mother-deactivated scandium-containing solution, and then this precipitate was combined with a hydrate-hydroxocarbonate precipitate obtained after processing of the thorium-containing eluate (150 g / dm ³ Na ₂ CO ₃ ), for which it was treated with concentrated HCl to a pH of 1 ± 0.2, heated to 95 ± 5 ^o C, kept at this temperature for 1 hour, after which it was treated with a solution of NaOH (100 g / dm ³ ) to pH 6.0. The precipitated precipitate of thorium oxyhydrates and hydroxocarbonates was separated from the solution by filtration, combined with the iodate-sulfate precipitate, and sent for burial to the repository ("KhSO" - a waste storage facility).

 Example 3

Sorption extraction of thorium from the solutions of example 1 is carried out (according to the proposed method, but the concentration of magnesium chloride in the experiments is 20, 50, 150, 200 g / dm ^3. The results of the experiments are shown in table 2.

From the table. 2 it can be seen that an increase in the sorption load on cation exchanger for thorium (and, consequently, an increase in the productivity of the process) is ensured by the introduction of magnesium chloride in the amount of 50-150 g MgCl ₂ / dm ³ into the initial solution.

 Thus, the implementation of the developed technical solution provides high selectivity (selectivity) for the extraction of Th from scandium-containing solutions, while allowing to increase the productivity of the process by 1.5 times.

Claims (5)

1. The method of extraction and concentration of thorium from technological solutions, including sorption of thorium at a pH of 2.8-3.5 and a temperature of 60-95 ^o With porous sulfacationite, followed by washing the cation exchange resin and desorption of thorium carbonate-containing solution, characterized in that in the initial solution before sorption, magnesium chloride is preliminarily introduced in an amount of 10-100 mg • equiv. Mg ²⁺ per 1 mg • equivalents of Th ⁴⁺ ions in the initial solution, the cation exchange resin is washed first with water, then with a solution of magnesium chloride with a concentration of 50-150 g / dm ³ , the filtrate after sorption combined with promoters, first potassium iodate is subsequently introduced into the combined solution, then barium chloride and sodium sulfate are filtered, the pulp is filtered, the radioactive iodate-sulfate cake is separated from the deactivated solution, which is sent to the extraction and disposal of rare and dispersed metals, the thorium-containing eluate is treated with mineral acid, for example hydrochloric acid, to a pH of 0.5-2.0, heated to 80-100 ^o C, maintained at elevated temperature for 0.5-2 hours, injected with an alkaline reagent, such as a solution of sodium hydroxide and / or ammonia, to pH 5-8, the resulting pulp is sedimented and filtered, the precipitate of thorium hydroxide and hydroxocarbonate is separated from the mother liquor, combined with radioactive iodate-sulfate cake and sent for recycling or disposal in a special waste storage. 2. The method according to claim 1, characterized in that the magnesium chloride is introduced into the initial solution in an amount that ensures its content in the solution before sorption of 50-150 g / DM ³ .  3. The method according to claim 1, characterized in that for the introduction into the initial solution of magnesium chloride using natural and / or synthetic bischofite, and / or carnallite, and / or intermediate products, and / or waste from the processing of carnallite raw materials, selected from among: carnallite dust of the first stage of carnallite dehydration, sludge from carnallite chlorinators. 4. The method according to p. 1, characterized in that the potassium iodate is administered in the form of a solution with a concentration of 10-50 g / dm ¹ in an amount of 10-100 cm ³ per 1 dm ^{3 of the} solution. 5. The method according to claim 1, characterized in that barium chloride and sodium sulfate are introduced in the form of solutions with a concentration of 50-150 g / dm ³ in an amount of 1.2-1.5 mol of sodium sulfate per 1 mol of barium chloride.

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