RU2360986C2 - TREATMENT METHOD OF CONCENTRATE OF β-SPODUMENE - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes sulphation of concentrate by sulfuric acid, water leaching of sulphited concentrate and neutralisation of leaching pulp. After neutralisation it is implemented separation of neutralised pulp on filter cake and sulphate solution, sedimentation from sulphate solution of admixtures with evaporation of current solution and separation of admixtures of evaporated sulphate solution. From treated and evaporated sulphate solution it is implemented sedimentation of lithium carbonate, separation of lithium carbonate from mother solution and sedimentation of lithium hydro-oxide aluminate from mother solution. Then it is implemented separation of lithium hydro-oxide aluminate pulp on lithium hydro-oxide aluminate and solution, caustification of lithium hydro-oxide aluminate, separation of caustification pulp on solution of lithium hydroxide and caustification cake. Additionally leaching pulp is neutralised up to pH 6.0-6.5 by solution of lithium hydroxide from the caustification stage.

EFFECT: increasing of lithium extraction from concentrate of β-spodumene into lithium carbonate and volume reduction of solid wastes during receiving of lithium carbonate from the concentrate of β-spodumene.

1 tbl, 1 ex

Description

The invention relates to metallurgy of lithium, in particular to the extraction of lithium from spodumene concentrates with obtaining lithium carbonate.

Spodumene (Li ₂ O · Al ₂ O ₃ · 4SiO ₂ ) is one of the main industrial lithium minerals. In mining operations, spodumene is extracted from ores into spodumene concentrates.

The natural α-modification of spodumene is a chemically resistant compound to the action of sulfuric acid. To increase the chemical activity of spodumene, its concentrate is subjected to decrypting roasting at 1100 ° С, which ensures the conversion of the spodumene lattice into an acid-opening β-modification.

To extract lithium from β-spodumene concentrate, the method can be used [Ostroushko Yu.I., Buchihin P.I., Alekseeva V.V. et al. Lithium, its chemistry and technology. M .: Atomizdat, 1960. - S.143-149; Plyushchev V.E., Stepin B.D. Chemistry and technology of compounds of lithium, rubidium and cesium. M .: Chemistry, 1970. - P.234-240], adopted for the analogue and providing for sulfatization of the concentrate with 93% sulfuric acid at 250 ÷ 300 ° C. The interaction of β-spodumene with acid proceeds with the formation of water-soluble lithium sulfate and insoluble aluminosilicate cake:

The β-spodumene concentrate thus sulfated in such a way is subjected to aqueous leaching to obtain a solution of lithium sulfate and insoluble cake. Next, the leach pulp is neutralized with calcium carbonate to a pH of 6.0 ÷ 6.5 and filtered, obtaining a solution of lithium sulfate. The filtered mixture of aluminosilicate cake and calcium sulfate is washed with water, returning the wash water to leach a new portion of the sulfated concentrate. The mixture of aluminosilicate cake and calcium sulfate washed from lithium sulfate is dumped into a dump. Obtained by the analogous method, a solution of lithium sulfate is subjected to purification from impurities Mg, Ca, Fe, Al, using chemical methods of precipitation of these impurities in the form of hydroxides and CaCO ₃ . The purified lithium sulfate solution is used to precipitate poorly soluble lithium carbonate by the action of sodium carbonate. Since lithium carbonate has a noticeable solubility, it is impossible to sufficiently precipitate it from the diluted solutions of lithium sulfate obtained by the analogous method (~ 12.7 g / l Li). Therefore, before the deposition of lithium carbonate, the sulfate solution is evaporated to a Li content of ~ 25.5 g / L.

The disadvantages of the analogue method are the low extraction of lithium from β-spodumene concentrate into lithium carbonate (85-90%) and large volumes of lithium-containing dump aluminosilicate cake from the stage of opening the concentrate. The cake is heavily contaminated with gypsum and cannot be used for the production of lithium ceramics and ceramic materials [Starshov V.A., Tyumentseva S.I., Kolmagorova I.V., Samoilov V.I. The use of lithium in the production of ceramics and ceramic materials // Problems of integrated development of ore and non-metallic deposits of the East Kazakhstan region: Sat. Mater. I Intern. scientific - tech. conf. - Ust-Kamenogorsk: EKSTU, 2001. - S.129-131].

The closest set of features to the claimed method is a method of processing a concentrate of β-spodumene [Samoilov V.I. Research of modern and development of promising methods for the extraction of lithium from mineral raw materials into technical compounds. - Ust-Kamenogorsk: Media Alliance, 2005. - P.150-170], which, unlike the analogue method, allows lithium to be extracted from the mother liquor from the stage of lithium carbonate precipitation in the form of lithium hydroxide.

According to the prototype method, the β-spodumene concentrate is processed according to the analogous method to obtain lithium carbonate and dump mother liquor from the lithium carbonate precipitation stage. Further, unlike the analogue method, insoluble lithium hydroxodialuminate is precipitated from the mother liquor by the action of sodium aluminate solution with the extraction of at least 90% lithium:

.

.

Then lithium hydroxodialuminate is separated from the solution and treated with milk of lime with the extraction of 98.4% of lithium in the solution:

.

.

At the final stage of the prototype method, insoluble calcium aluminate is separated from the lithium hydroxide solution. The resulting alkaline solution is characterized by a lithium content of 11 g / l and could be recommended for crystallization of lithium hydroxide monohydrate (after evaporation of the solution).

The prototype method creates the prerequisites for increasing the extraction of lithium from β-spodumene concentrate into technical lithium compounds, due to the additional extraction of lithium from the dump mother liquor from the stage of lithium carbonate deposition. However, the prototype method has a significant drawback - large volumes of lithium-containing dump aluminosilicate cake from the stage of opening the concentrate. Cake is heavily contaminated with gypsum and cannot be used for the production of lithium ceramics and ceramic.

The technical result of the claimed invention is to increase the extraction of lithium from β-spodumene concentrate into lithium carbonate and to obtain aluminosilicate cake (from the stage of opening the concentrate) without gypsum impurity in order to use cake for the production of lithium ceramics and ceramic and to reduce the volume of solid production waste on this basis.

The technical result is achieved by the fact that in the method of processing β-spodumene concentrate with lithium extraction into lithium carbonate, including sulfatization of the concentrate with sulfuric acid, aqueous leaching of sulfated concentrate, neutralization of the leaching pulp, separation of the neutralized leaching pulp into cake and sulfate solution, precipitation from sulfate with evaporation of this solution, separation of impurities from one stripped off sulfate solution, precipitation of lithium carbonate from purified and one stripped off o sulfate solution, separation of lithium carbonate from the mother liquor, precipitation of lithium hydroxodialuminate from the mother liquor, separation of the pulp of lithium hydroxodialuminate into lithium hydroxodialuminate and the solution, caustification of lithium hydroxodialuminate, separation of the caustification pulp into the lithium hydroxide solution and causticization cake, pH 6 0-6.5 lithium hydroxide solution from the causticization stage.

The use of a lithium hydroxide solution from the causticization stage of lithium hydroxodialuminate to neutralize leach pulp to a pH of 6.0-6.5 eliminates the loss of lithium during processing of this solution, for example, lithium hydroxide. In the inventive method, the cake from the stage of neutralizing the leach pulp does not contain gypsum and is suitable for the production of lithium ceramics and ceramic, i.e. cake is not a dump, but a target product of technology. On this basis, in the inventive method eliminated the loss of lithium with cake from the stage of neutralization of the leach pulp and radically reduced volumes of solid waste production.

Example. The initial β-spodumene concentrate contained 6.42% Li ₂ O. According to the claimed method, the concentrate is treated with 93% sulfuric acid (0.12 ml of acid per 1 g of concentrate) at 250 ° C for 1.0 ÷ 1.5 h The concentrate thus sulfated in such a way is leached with water for 30 minutes at T: W = 1: 5 (by concentrate) and a temperature of 95 ° C. The resulting pulp is neutralized to pH 6.0 ÷ 6.5 with a solution of lithium hydroxide from the stage of caustification of lithium hydroxodialuminate (see below). The neutralized pulp is filtered to obtain a lithium sulfate solution and aluminosilicate cake. The latter is subjected to a 2-fold filter-repulpative water washing from a solution of lithium sulfate for 20 min at T: W = 1: 7 (by concentrate) and a temperature of 90 ° C. Washed cake is used to produce lithium ceramics and ceramic. The resulting lithium sulfate solution, the first and second wash water are combined. The combined solution is subjected to purification from magnesium, neutralizing the solution with lime to a pH of 12 ÷ 14 and precipitating magnesium in the form of hydroxide. Then the solution is treated with sodium carbonate (12 g / l of solution) to purify it from calcium with the formation of insoluble calcium carbonate. Next, the precipitate of impurities is filtered off from a solution of lithium sulfate, which is subjected to purification from aluminum and iron (in the form of their hydroxides), neutralizing the solution with sulfuric acid to pH 7. The purification of the sulfate solution from aluminum and iron is combined with the evaporation of this solution to a lithium content of ~ 25 g / l At the end of the evaporation of the solution, it is filtered off from the precipitate Al (OH) ₃ and Fe (OH) ₃ . The lithium sulfate solution thus purified is treated with a sodium carbonate solution (conc. 300 g / l) to precipitate lithium carbonate at 90 ° C. Then lithium carbonate is filtered off from the mother liquor. The mother liquor is treated with a solution of sodium aluminate (conc. 150 g / l for aluminum; free alkali 85 g / l) at a temperature of 20 ° C for precipitation from a solution of insoluble lithium hydroxodialuminate (a solution of sodium aluminate is added to calculate the mass ratio of Li: Al in the pulp lithium hydroxodialuminate 1: 8.5). After precipitation of lithium hydroxodialuminate, it is filtered off from the solution and causticized with milk of lime with a content of calcium oxide of 46.5 g / l (consumption of milk of lime is 7.6 g of CaO per 1 g of lithium in lithium hydroxodialuminate). The resulting causticization pulp is separated into sparingly soluble calcium aluminate and a lithium hydroxide solution. This solution is used to neutralize leaching pulp (see above).

For comparison with the claimed method perform the processing of β-spodumene concentrate according to the prototype method. For this purpose, the β-spodumene concentrate is treated with 93% sulfuric acid (0.12 ml of acid per 1 g of concentrate) at 250 ° C for 1.0 ÷ 1.5 hours. The concentrate thus sulfated is leached out with water for 30 minutes at T: W = 1: 5 (in concentrate) and a temperature of 95 ° C. The resulting pulp is neutralized to pH 6.0 ÷ 6.5 with calcium carbonate. The neutralized pulp is filtered to obtain a lithium sulfate solution and a dump mixture of aluminosilicate cake and gypsum. This mixture is subjected to a 2-fold filter-repulpative washing from a solution of lithium sulfate for 20 min at T: W = 1: 7 (in concentrate), a temperature of 90 ° C and dumped into a dump as unsuitable for producing lithium ceramics and ceramic. The resulting lithium sulfate solution, the first and second wash water are combined. The combined solution is subjected to purification from magnesium, neutralizing the solution with lime to a pH of 12 ÷ 14 and precipitating magnesium in the form of hydroxide. Then the solution is treated with sodium carbonate (12 g / l of solution) to purify it from calcium with the formation of insoluble calcium carbonate. The precipitate of magnesium hydroxide and calcium carbonate is filtered off from a solution of lithium sulfate. Aluminum and iron impurities (in the form of their hydroxides) are removed from the obtained lithium sulfate solution, neutralizing the solution with sulfuric acid to pH 7. The purification of the sulfate solution from aluminum and iron is combined with the evaporation of this solution to a lithium content of ~ 25 g / l. At the end of the evaporation of the solution, it is filtered off from the precipitate Al (OH) ₃ and Fe (OH) ₃ . The lithium sulfate solution thus purified is treated with a sodium carbonate solution (conc. 300 g / l) to precipitate lithium carbonate at 90 ° C. Then lithium carbonate is filtered off from the mother liquor. The mother liquor is treated with a solution of sodium aluminate (conc. 150 g / l on aluminum; free alkali 85 g / l) at a temperature of 20 ° C for precipitation from a solution of sparingly soluble lithium hydroxodialuminate (a solution of sodium aluminate is added based on obtaining the mass ratio of Li: Al in the pulp lithium hydroxodialuminate 1: 8.5). After precipitation of lithium hydroxodialuminate, it is filtered off from the solution and causticized with milk of lime with a calcium oxide content of 46.5 g / l (consumption of milk of lime is 7.6 g of CaO per 1 g of lithium in lithium hydroxodialuminate). The resulting causticization pulp is separated into sparingly soluble calcium aluminate and a solution of lithium hydroxide. This solution according to the prototype method, it is advisable to use for the production of crystalline lithium hydroxide monohydrate.

The table shows the comparative indicators obtained during the implementation of the proposed method and the prototype method.

Table Data on the loss of lithium and the amount of solid waste (dry cake) in the present method and the prototype method. Example No. Implementation Method Loss of Li,% of its initial load with β-spodumene concentrate Li extraction of β-spodumene concentrate in Li ₂ CO _3, in% The mass of cake from the stage of neutralization of the leach pulp, in% of the total number of cakes cake from the stage of leaching pulp neutralization cakes from the stages of cleaning the solution of Li ₂ SO ₄ (combined) cake from the stage of precipitation of hydroxodialuminate Li cake from the causticization stage one Way- 2.5 1,5 0.5 0.5 95.0 85.0 2 prototype 5,0 1,0 2.0 1,0 91.0 90.0 3 5,0 1,0 1,5 2.5 90.0 86.0 four The inventive method 0 1,0 1,5 1,0 96.5 85.0 5 0 1,0 0.5 0.5 98.0 90.0 6 0 1,5 2.0 2.5 95.0 87.0

As follows from the table, in the inventive method, the extraction of lithium from β-spodumene concentrate in lithium carbonate is 95 ÷ 98% against 90-95% by the prototype method. Using the proposed method instead of the prototype method can simultaneously reduce the volume of solid waste production of lithium carbonate by 85 ÷ 90% (table).

Claims (1)

A method of processing a β-spodumene concentrate with the extraction of lithium into lithium carbonate, including sulfatization of the concentrate with sulfuric acid, water leaching of a sulfatized concentrate, neutralization of the leach pulp, separation of the neutralized leach pulp into cake and a sulfate solution, precipitation of impurities from the sulfate solution, separation of impurities from the evaporation from one stripped off sulfate solution, precipitation of lithium carbonate from purified and one stripped off sulfate solution, separation of carbonate lithium hydroxodialuminate, precipitation of lithium hydroxodialuminate from the mother liquor, separation of lithium hydroxodialuminate pulp into lithium hydroxodialuminate and solution, caustification of lithium hydroxodialuminate, separation of causticization pulp into lithium hydroxide solution and caustification cake, characterized in that the leaching pulp has a pH of 6.0 6.5 with lithium hydroxide solution from the causticization step.