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

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

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

Sorption extraction of REE useful for primary concentration from solutions with low content of REE, especially on the background of significant amounts of salts (iron(III) and Al) in solution. In this case the used ion exchangers should have a high capacity and selectivity relative to REE.

The known method [Temporary production process regulations of polyuranates ammonium, Federal state unitary enterprise "JSC", JSC DALUR, sukstanskii, 2006], in which the recovery of REE from the technological solution pH=0.5÷2.5 is carried out by adsorption on the gel sulfonic cation exchanger KU-2. Obtained after elution and precipitation concentrate contains %: REE - 1; iron - 2,0÷2,2; aluminum - 15÷18; water - 82. This is followed by a stage with resultant deposition rates in order to bring the draft of REM concentrate to commercial products 30-40%.

The main disadvantages of this method is the low sorption capacity and selectivity sulfonic cation exchanger by REE and inefficient operation of bringing the rough concentrate REE to marketable products. These shortcomings lead to neobhodimosti additional equipment - reactors for dissolution of hydrates, filters for filtering a large number of intermediates, as well as to additional consumption rather expensive reagent alkali leaching of aluminum. In addition, the degree of REE extraction this method is sufficiently low output is 60%.

To reduce the influence of iron(III) and Al, on the parameters of the sorption of REE extraction was used way [Smirnov DI, Molchanov T.V., Divers LI, Peganov, VA Sorption extraction of rare earth elements, yttrium and aluminium from red mud. Tsvet, No. 8, 2002, p.64-69.]. In which the sorption of REE were from acidified to pH=1.7 to discharge the pulp obtained after sorption leaching of scandium from red slime, gel-sulfonic cation exchanger KU-2. Removing in a rough concentrate REE, yttrium, and aluminum was 48, 42 and 29%, respectively. After alkaline Department of aluminium was obtained bulk concentrate REE and yttrium, with the total content of oxides of rare-earth elements 18÷25% and yttrium 9÷14%.

However, this method also failed to effectively extract REE due to competitive adsorption on sulfonic cation exchanger iron(III) and aluminium. Stage of finishing the rough concentrate to commercial products is time-consuming and energy-intensive process that makes it economically viable recovery of REE from solutions and slurries of this method.

Closest to the claimed method is (prototype) [Mursalimova M., Stroeva EV Determination of equilibrium parameters of ion sorption of yttrium and lanthanum of mineralized solutions and iron-containing slurries on carboxylic cation exchanger KB-4 gel type. // Vestnik OSU, No. 5, 2006, pp.86-90]in which to increase the capacity of the sorbent by REE uses a carboxylic cation exchanger gel type CB-4, and to increase the selectivity of the extraction process in the presence of iron(III) and Al acidic solution containing REE, neutralized with ammonia to pH of 6.2. Higher capacity carboxylic cation exchange resin in comparison with sulfonic cation exchanger is a consequence of the formation of a strong complex compounds REE with carboxyl groups of the cation KB-4 in contrast to the purely electrostatic interaction REE with sulfo, in the case of sulfonic cation exchanger. Separation from major impurities of iron(III) and aluminum is achieved by translating them into the hydroxide form at pH=6,2.

The disadvantage of this method is the fact that the maximum sobiraemosti by REE on carboxylic cation exchanger is observed at pH of 6.2. This leads to the necessity to neutralize the acidic solution until the pH value that is a result of significant losses REE (up to 25%) as a result of co-precipitation with hydroxides of iron(III) and aluminium.

The best results compared carboxilate cationic for REE extraction from solutions with pH=2.5÷6.5 can be achieved, using ampholytes with iminodiacetate groups. This pH interval is determined by the beginning of the dissociation of functional groups of the ampholyte and the beginning of the precipitation of hydroxides of rare earth elements. Due to the complex formation at pH>2.5, due to the dissociation of functional groups, this class ampholytes allows you to separate the REE from alkali, alkaline earth metals, aluminum and other cations that strongly simplifies further processing of the eluates. Higher capacity iminodiacetate ampholytes compared with carboxyl cation is determined by the formation of more stable complex compounds of rare-earth elements with functional groups ampholytes.

It Is Known [Wenrich, Averilla, Mleczarnia. Sorption extraction of rare earth metals from solutions of complex composition complexing ion // Materials of international conference "Noble and rare metals" BRM occupational-2003, Ukraine, Donetsk, September 22-26, 2003.], what iminodiacetate the ampholytes have a high affinity for transition elements (iron(III), copper, Nickel, cobalt, lead). To eliminate the effect of these interfering ions on the sorption of REE from solutions (slurries) with a pH of>2.5 use their deposition or alkaline complexing agents. This operation, when the sorption of REE from the clarified solution will allow to get a clean e is waty, that will have an impact on reducing future costs of production of marketable concentrates.

The most complete separation of REE ions from iron(III), as the most disturbing impurities can be achieved by introducing into the solution a reducing agent in order to restore ions of iron(III) to iron(II)because it is known that the ampholytes with iminodiacetate functional groups show little affinity for ions of iron(II) [Awhole, Mvenyane, Ichannel, Brasada Separation of trivalent actinides and rare earth elements from iron impurities with the use of some complex compounds. // Radiochemistry. No. 6, T, 2005. s-535].

The difference in sobiraemosti different valence States of iron due to the difference of their electronic configurations. Electronic structure of iron(III) determine the complexation with iminodiacetate functional groups of the ampholyte as due to coordination to the oxygen of the hydroxyl group of the material, and through the coordination of the imine nitrogen group, which is the electron donor.

The absorption of the ampholyte ion iron(II) begins to occur at pH>3, with the beginning of the dissociation of carboxyl groups. Sorption in this case is only through the exchange of iron ions on the hydrogen ion carboxyl group, without the formation of complex compounds.

Depressing effect for the e unequally valence of ions of iron and aluminum on the sorption of REE from solutions iminodiacetate ampholyte suggests, to increase the degree of extraction of REE must strive to reduce the impact of background impurities in the solution by neutralizing, and by adding the reductant.

Object of the invention is the creation of a more effective sorption way of REE extraction from solutions containing iron(III) and Al.

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

Example 1

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

Sorption was carried out in static conditions from acidic solutions of HCl, H₂SO₄, HNO₃(pH=1; 2; 3; 4; 5; 6), containing 1000 mg/DM³Rare earth elements (lanthanum), 1000 mg/DM³iron(III), 1000 mg/DM³aluminum. Sample ampholytes (0.5 g) was contacted with stirring with 50 cm³the above solution in the tip is of 5 hours. The solution after sorption were analyzed by atomic emission method with inductively coupled plasma. Sobiraemosti and the degree of extraction was determined as the difference of the initial and final concentrations of ions in solution.

From table 1 it is seen that with increasing pH of the solution sobiraemosti REE (lanthanum) passes through the peak. The maximum sobiraemosti observed when changing the pH from 4 to 5. Reducing sobiraemosti at lower pH due to the protonation of the carboxyl groups of the ampholyte. Increasing the pH of the solution also reduces sobiraemosti lanthanum, the cause of which is a deep hydrolysis of ions of rare-earth elements (lanthanum) and coprecipitation with iron hydroxides and aluminum. The obtained regularities true for all the investigated acidic environments.

Example 2

Table 2 presents the results of studies on the optimum conditions sorption of REE extraction (lanthanum) depending on the ratio of the ion exchanger: p is LpA.

Sorption was carried out in static conditions from acidic solution of H₂SO₄, neutralized to pH=4, containing 1000 mg/DM³Rare earth elements (lanthanum), 1000 mg/DM³iron(III), 1000 mg/DM³aluminum. Sample ampholytes (0.5 g) was contacted with stirring with obtained after neutralization of the slurry at a ratio of Ionith: pulp 1:10, 1:30, 1:50, 1:80, 1:100, 1:150, 1:200, within 5 hours. The solution after sorption were analyzed by atomic emission method with inductively coupled plasma. Sobiraemosti and the degree of extraction was determined as the difference of the initial and final concentrations of ions in solution.

From table 2 it is seen that with increase in the ratio of the ion exchanger: pulp >150 sobiraemosti REE (lanthanum) increases.

Example 3

Table 3 presents the results of studies on the optimum conditions sorption of REE extraction (lanthanum) depending on the contact time of the phases.

Sorption was carried out in static conditions from acidic solution of H₂SO₄, neutralized to pH=4, with a ratio of Ionith: the pulp of 1:100, containing 1000 mg/DM³Rare earth elements (lanthanum), 1000 mg/DM³iron(III), 1000 mg/DM³aluminum. Sample ampholytes contacted when mixing with the pulp within 0.5, 1, 3, 5, 7, 9 hours. The solution after sorption, were analyzed by atomic emission method with inductively coupled plasma. Sobiraemosti and the degree of extraction was determined as the difference of the initial and final concentrations of ions in solution.

As can be seen from table 3, the most complete extraction of rare-earth elements (lanthanum) is for 3-6 hours.

Example 4

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

Sorption was carried out in static conditions from acidic solution of H₂SO₄, neutralized to pH=4, with a ratio of Ionith:the pulp of 1:100, containing 1000 mg/DM³Rare earth elements (lanthanum), 1000 mg/DM³iron(III), 1000 mg/DM³aluminum. Sample ampholytes contacted when mixed with the pulp at a temperature of 20; 40; 60; 80°C, for 5 hours. The solution after sorption, were analyzed by atomic emission method with inductively coupled plasma. Sobiraemosti and the degree of extraction was determined as the difference of the initial and final concentrations of ions in solution.

From table 4 it follows that the temperature holding process of adsorption of lanthanum no significant impact on the degree of extraction from acidic solutions.

Example 5

Table 5 presents the results of research on the influence of addition of various reducing agents on the completeness and selectivity of extraction of rare earth elements (lanthanum).

Sorption was carried out in static conditions from acidic solution of H₂SO₄, neutralized to pH=2, 3, 4, 5, 6 when the ratio of Ionith: the pulp of 1:100, containing 1000 mg/DM³Rare earth elements (lanthanum), 1000 mg/DM³iron(III), 1000 mg/DM³aluminum. After adjusting the pH of the pulp to the desired values, the slurry was injected reducing agent (iron shavings, sodium sulfite, urea) with a sixfold excess of the stoichiometric content of ions of iron(III). Next sample ampholytes contacted when mixed with the pulp for 5 hours. The solution after sorption, were analyzed by atomic emission method with inductively coupled plasma. Sobiraemosti and the degree of extraction was determined as the difference of the initial and final concentrations of ions in solution.

From table 5 it follows that the introduction of the acid solution reductant bring the to a sharp increase in the capacity of iminodiacetate amplite by REE (lanthanum) and reduced capacity for iron(III).

Thus, the technical result of the proposed method of REE extraction from solutions is determined by the high efficiency of this method due to the greater sorption capacity and selectivity iminodiacetate material on REE in the presence of iron(III) and Al, while neutralization or acidification of the solution to pH=4-5 and the process of sorption in the presence of a reducing agent.

The method for extracting rare earth elements from solutions containing iron(III) and aluminum, including sorption of rare earth elements on the sorbent, characterized in that the sorbent use Ippolit with iminodiacetate functional groups and sorption was carried out after prior neutralization or acidification of the solution to pH=4÷5 any alkaline or acidic agent with the further introduction of material into the resulting slurry without separation of the solid part, with a ratio of alfalit:pulp 1:50 to 1:150, the contact time between phases 3÷6 h in the presence of a reducing agent.