RU2484162C2 - Method of extracting rare-earth metals from technological and productive solutions and pulps - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method of extracting rare-earth metals from solutions containing iron (III) and aluminium comprises sorption of rare-earth metals on sorbent. Ampholyte with iminodiacetic functional groups is used as said sorbent. Sorption is carried out after preliminary neutralisation or acidification of solution to pH 4-5 by whatever alkaline or acid agent to add ampholyte in obtained pulp with separation of solid fraction. Sorption is conducted at ampholyte:pulp ratio of 1:50-1:150, phase contact time of 3-6 h and in the presence of reducing agent.

EFFECT: higher selectivity.

5 tbl, 5 ex

Description

The invention relates to hydrometallurgy of rare metals, in particular to the field of extraction of rare earth elements (REE) in the complex processing of technological and productive solutions, and can be used in the technology of obtaining REE concentrates.

It is advisable to use sorption extraction of REEs for primary concentration from solutions with a low REE content, especially against the background of a significant amount of salts (iron (III) and Al) in solution. In this case, the ion exchangers used should have high capacity and selectivity with respect to REE.

The known method [Temporary, technological regulation of the production of ammonium polyuranates, FSUE "VNIIHT", CJSC "DALUR", Uksyanskoye, 2006], in which the extraction of REE from the technological solution pH = 0.5 ÷ 2.5 is carried out by sorption on gel sulfocationite KU-2. The concentrate obtained after elution and precipitation contains%: REE - 1; iron - 2.0 ÷ 2.2; aluminum - 15 ÷ 18; water - 82. Next, a reprecipitation stage is proposed with the aim of bringing the rough concentrate of rare-earth metals to marketable products of 30-40%.

The main disadvantages of this method is the small sorption capacity and selectivity of sulfocationionite in REE and the inefficient operation of bringing the rough concentrate of rare-earth metals to marketable products. These shortcomings lead to the need to use additional equipment - reactors for dissolving hydrates, filters for filtering a large number of intermediate products, as well as to the additional consumption of a rather expensive reagent - alkali during aluminum leaching. In addition, the degree of REE extraction by this method is quite low - the yield is 60%.

To reduce the effect of iron (III) and Al on the parameters of REE sorption extraction, the method was used [Smirnov DI, Molchanova TV, Vodolazov LI, Peganov VA Sorption extraction of rare earth elements, yttrium and aluminum from red mud. // Non-ferrous metals, No. 8, 2002, p. 64-69.]. In which REE sorption was carried out from acidified pulp acidified to pH = 1.7, obtained after sorption leaching of scandium from red mud, on KU-2 gel sulfocationite. The recovery of REE, yttrium, and aluminum into rough concentrate was 48, 42, and 29%, respectively. After alkaline separation of aluminum, a collective REE and yttrium concentrate was obtained with a total content of REE oxides of 18–25% and yttrium of 9–14%.

However, in this method, it was also not possible to efficiently extract REEs due to competitive sorption on iron (III) and aluminum sulphocationite. The stage of bringing the crude concentrate to marketable products is a labor-intensive and energy-intensive process, which makes it economically unprofitable to extract REE from solutions and pulps in this way.

Closest to the claimed is the method (prototype) [Mursalimova M.L., Stroeva E.V. Determination of the equilibrium sorption parameters of yttrium and lanthanum ions from mineralized solutions and iron-containing pulps on gel type KB-4 carboxyl cation exchanger. // Vestnik of OSU, No. 5, 2006, pp. 86-90], in which KB-4 gel type carboxyl cation exchange resin is used to increase the sorbent capacity for REE, and an acid solution is used to increase the selectivity of the extraction process in the presence of iron (III) and Al containing REE is neutralized by ammonia to pH = 6.2. The higher capacity of carboxylic cation exchange resin compared to sulfation cation exchange resin is the result of the formation of strong REE complex compounds with the carboxyl groups of KB-4 cation exchange resin, in contrast to the purely electrostatic interaction of REE with sulfo groups, in the case of sulfation cationite. Separation from the main impurities of iron (III) and aluminum is achieved by converting them to the hydroxide form at pH = 6.2.

The disadvantage of this method is the fact that the maximum adsorption by REE on carboxylic cation exchange resin is observed at pH = 6.2. This leads to the need to neutralize the acid solution to this pH value, which is a consequence of significant REE losses (up to 25%) as a result of coprecipitation with iron (III) and aluminum hydroxides.

Better results compared to carboxylic cation exchangers for the extraction of REE from solutions with pH = 2.5–6.5 can be achieved using ampholytes with iminodiacetate groups. This pH range is determined by the onset of dissociation of ampholyte functional groups and the onset of precipitation of rare earth hydroxides. Due to complexation at pH> 2.5, due to the dissociation of functional groups, this class of ampholytes allows one to separate REE from impurities of alkali, alkaline earth metals, aluminum, and a number of other cations, which drastically simplifies the further processing of eluates. The higher capacity of iminodiacetate ampholytes in comparison with carboxylic cation exchangers is determined by the formation of stronger REE complex compounds with functional groups of ampholytes.

It is known [V.N. Rychkov, E.V. Kirillov, M.L. Cherny. Sorption separation of rare-earth metals from complex solutions by complexing ion exchangers // Materials of the International Conference "Noble and Rare Metals" BRM-2003, Ukraine, Donetsk, September 22-26, 2003.] that iminodiacetate ampholytes are characterized by high affinity for transition elements (iron (III ), copper, nickel, cobalt, lead). To eliminate the effect of these interfering ions on the sorption of REEs from solutions (pulps) with pH> 2.5, they are precipitated with alkaline or complexing agents. This operation, during the sorption of REE, from the clarified solution, will make it possible to obtain cleaner eluates, which will affect the reduction of further costs in the production of commodity concentrates.

The maximum complete separation of REE from iron (III) ions, as the most interfering impurity, can be achieved by introducing a reducing agent into the solution to reduce iron (III) ions to iron (II), because Ampholytes with iminodiacetate functional groups are known to exhibit a slight affinity for iron (II) ions [A.V. Gogolev, M.V. Nikonov, I.G. Tananaev, B.F. Myasoedov Separation of trivalent actinides and rare-earth elements from iron impurities using some complex compounds. // Radiochemistry. No. 6, T.47, 2005. S. 534-535].

The difference in the adsorbability of different valence states of iron is explained by the difference in their electronic configurations. The electronic structure of iron (III) determines the complexation with the functional groups of the iminodiacetate ampholyte due both to the coordination of the hydroxyl group of the ampholyte to oxygen and to the coordination of the imine group, which is an electron donor, to nitrogen.

Ampholyte absorption of iron (II) ions begins to appear at pH> 3, with the onset of dissociation of carboxyl groups. Sorption in this case is only due to the exchange of iron ions for hydrogen ion of the carboxyl group, without the formation of a complex compound.

The depressing effect of multivalent iron and aluminum ions on the sorption of REE from solutions by iminodiacetate ampholyte suggests that in order to increase the degree of REE extraction, it is necessary to strive to reduce the effect of background impurities in the solution both by neutralization and by introducing a reducing agent in the system.

The objective of the invention is to provide a more efficient sorption method for the extraction of REE from solutions containing also iron (III) and Al.

The problem is achieved according to the method, which consists in the sorption extraction of rare earth elements from solutions on an ampholyte containing iminodiacetate functional groups. For this, the solution is subjected to preliminary neutralization or acidification to pH = 4 ÷ 5 with any alkaline or acidic agent, with the further introduction of ampholyte into the formed pulp, without separation of the solid part, with the ratio of ion exchanger: pulp 1: 50-1: 150, phase contact time 3 -6 hours, in the presence of a reducing agent.

Example 1

Table 1 presents the results of studies on the selection of optimal conditions for the sorption extraction of REE (lanthanum) depending on the pH of the solution.

Sorption was carried out under static conditions from acidic solutions of HCl, H ₂ SO ₄ , HNO ₃ (pH = 1; 2; 3; 4; 5; 6) containing 1000 mg / dm ³ REE (lanthanum), 1000 mg / dm ³ iron (III), 1000 mg / dm ^{3 of} aluminum. Samples of ampholytes (0.5 g) were contacted with stirring with 50 cm ^{3 of the} above solution for 5 hours. Solutions after sorption were analyzed by an inductively coupled plasma atomic emission method. Sorbability and the degree of extraction were determined by the difference between the initial and final concentration of ions in solution.

Table 1 The degree of extraction of lanthanum,% pH = 1 pH = 2 pH = 3 pH = 4 pH = 5 pH = 6 Hcl H ₂ SO ₄ HNO ₃ Hcl H ₂ SO ₄ HNO ₃ Hcl H ₂ SO ₄ HNO ₃ Hcl H ₂ SO ₄ HNO ₃ Hcl H ₂ SO ₄ HNO ₃ Hcl H ₂ SO ₄ HNO ₃ Amph olite 1,5 1.3 1.3 2 1.7 1,5 twenty 17 fifteen 32 28.6 28 31 27.1 28 22 eighteen 19

From the data of table 1 it is seen that with an increase in the pH of the solution, the sorbability of REE (lanthanum) passes through the peak. The maximum sorbability is observed when the pH changes from 4 to 5. A decrease in sorbability at a lower pH is associated with the protonation of the carboxyl groups of the ampholyte. An increase in the pH of the solution also leads to a decrease in the adsorbability of lanthanum, which is caused by deep hydrolysis of REE ions (lanthanum) and coprecipitation with iron and aluminum hydroxides. The obtained laws are true for all studied acidic media.

Example 2

Table 2 presents the results of studies on the selection of optimal conditions for the sorption extraction of REE (lanthanum) depending on the ratio of ion exchanger: pulp.

Sorption was carried out under static conditions from an acidic solution of H ₂ SO ₄ , neutralized to pH = 4, containing 1000 mg / dm ³ REE (lanthanum), 1000 mg / dm ³ iron (III), 1000 mg / dm ³ aluminum. Samples of ampholytes (0.5 g) were contacted with stirring with the pulp obtained after neutralization at an ion exchanger: pulp ratio of 1:10, 1:30, 1:50, 1:80, 1: 100, 1: 150, 1: 200, within 5 hours. Solutions after sorption were analyzed by an inductively coupled plasma atomic emission method. Sorbability and the degree of extraction were determined by the difference between the initial and final concentration of ions in solution.

table 2 capacity, mg / g 1:10 1:30 1:50 1:80 1: 100 1: 150 1: 200 Ampholyte 2 5 fourteen 28 thirty 33 35

From the data of table 2 it is seen that with an increase in the ratio of ion exchanger: pulp> 1:50, the adsorption of REE (lanthanum) increases.

Example 3

Table 3 presents the results of studies on the selection of optimal conditions for the sorption extraction of REE (lanthanum) depending on the phase contact time.

Sorption was carried out under static conditions from an acidic solution of H ₂ SO ₄ , neutralized to pH = 4, with an ion exchanger: pulp ratio of 1: 100 containing 1000 mg / dm ³ REE (lanthanum), 1000 mg / dm ³ iron (III), 1000 mg / dm ³ aluminum. Samples of ampholytes were contacted with stirring with pulp for 0.5, 1, 3, 5, 7, 9 hours. After sorption, the solutions were analyzed by an inductively coupled plasma atomic emission method. Sorbability and the degree of extraction were determined by the difference between the initial and final concentration of ions in solution.

Table 3 % capacity of maximum 0.5 hours 1 hour 3 hours 5 o'clock 7 o'clock 9 hours Ampholyte twenty 40 85 95 96 99

As can be seen from table 3, the most complete extraction of REE (lanthanum) occurs in 3-6 hours.

Example 4

Table 4 presents the results of studies on the selection of optimal conditions for the sorption extraction of REE (lanthanum) depending on the temperature of the process.

Sorption was carried out under static conditions from an acidic solution of H ₂ SO ₄ , neutralized to pH = 4, with an ion exchanger: pulp ratio of 1: 100 containing 1000 mg / dm ³ REE (lanthanum), 1000 mg / dm ³ iron (III), 1000 mg / dm ³ aluminum. Samples of ampholytes were contacted with stirring with pulp at a temperature of 20; 40; 60; 80 ° C, for 5 hours. After sorption, the solutions were analyzed by an inductively coupled plasma atomic emission method. Sorbability and the degree of extraction were determined by the difference between the initial and final concentration of ions in solution.

Table 4 % capacity of maximum 20 ° C 40 ° C 60 ° C 80 ° C Ampholyte 85 87 87 89

From the data of table 4 it follows that the temperature of the process of sorption of lanthanum does not significantly affect the degree of extraction from acidic solutions.

Example 5

Table 5 presents the results of studies on the effect of additives of various reducing agents on the completeness and selectivity of the extraction of REE (lanthanum).

Sorption was carried out under static conditions from an acidic solution of H ₂ SO ₄ , neutralized to pH = 2, 3, 4, 5, 6 with an ion exchanger: pulp ratio of 1: 100 containing 1000 mg / dm ³ REE (lanthanum), 1000 mg / dm ³ iron (III), 1000 mg / dm ³ aluminum. After adjusting the pH of the pulp to the required value, a reducing agent (iron chips, sodium sulfite, urea) was introduced into the pulp with a six-fold excess of the stoichiometric content of iron (III) ions. Next, samples of ampholytes were contacted with stirring with pulp for 5 hours. After sorption, the solutions were analyzed by an inductively coupled plasma atomic emission method. Sorbability and the degree of extraction were determined by the difference between the initial and final concentration of ions in solution.

Table 5 Reducing agent The degree of extraction,% pH = 2 pH = 3 pH = 4 pH = 5 pH = 6 La Fe (III) A1 La Fe (III) A1 La Fe (III) Al La Fe (III) Al La Fe (III) Al Without reducing agent 1.7 2,5 one 17 twenty 5 28.6 10 10 27.1 7 3 eighteen 2 0.5 Iron shavings 3 0,07 1.3 24 0,07 6 fifty 0.1 8 49 0.01 four 27 0.05 0.4 Sodium sulfite 3.3 0,055 1,5 24.5 0,075 5 47.6 0.2 8 49.1 0.09 2 25 0.06 0.4 Urea 3,1 0.05 1.4 23 0.06 5 fifty 0.15 7 51 0,07 2 28 0.04 0.3

From the data of table 5 it follows that the introduction of a reducing agent in an acidic solution leads to a sharp increase in the capacity of iminodiacetate amphlite according to REE (lanthanum) and a decrease in capacity for iron (III).

Thus, the technical result of the proposed method for extracting REE from solutions is determined by the high efficiency of this method due to the greater sorption capacity and selectivity of iminodiacetate ampholyte in REE in the presence of iron (III) and Al, when the solution is neutralized or acidified to pH = 4-5 and sorption process in the presence of a reducing agent.

Claims (1)

The method of extracting rare earth elements from solutions containing iron (III) and aluminum, including sorption of rare earth elements on a sorbent, characterized in that the ampholyte with iminodiacetate functional groups is used as a sorbent and sorption is carried out after preliminary neutralization or acidification of the solution to pH = 4 ÷ 5 any alkaline or acidic agent with the further introduction of ampholyte into the resulting pulp without separation of the solid part, with the ratio of ampholyte: pulp 1: 50 ÷ 1: 150, phase contact time 3 ÷ 6 hours, in the presence of stanovitelya.