A method for reconstructing the phase of spodumene ore and extracting lithium by alkali leaching

Abstract

The application provides a method for reconstructing lithium extraction from alkali leaching of spodumene, which comprises the following steps: mixing spodumene and alkali liquor in a pressure reaction kettle and carrying out a hydrothermal alkali leaching reaction, and then carrying out solid-liquid separation on the reaction slurry to obtain alkali leaching residue and filtrate; mixing the alkali leaching residue and a leaching agent in the reaction kettle and carrying out an alkali leaching residue leaching reaction, and then carrying out solid-liquid separation on the reaction slurry to obtain leaching residue and lithium-containing leaching liquor. The method for reconstructing lithium extraction from alkali leaching of spodumene does not need to carry out high-temperature calcination and crystal transformation activation of spodumene, but can obtain lithium-containing leaching liquor through hydrothermal alkali leaching reaction and alkali leaching residue leaching reaction, so that clean production is realized, and the lithium-containing leaching liquor can be used to produce lithium carbonate, lithium hydroxide, lithium chloride, lithium phosphate and other series of lithium salt products with high purity, high value and wide application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ore lithium extraction, and particularly relates to a method for reconstructing lithium extraction of alkali leaching of spodumene. BACKGROUND

[0002] Lithium is an important element for promoting the development of modernization and the technology industry. In recent years, lithium and its compounds are widely used in battery energy, glass ceramics, aerospace and other fields. Especially under the promotion of the new energy vehicle industry, lithium products have great growth space in the future.

[0003] Global lithium ore can be mainly divided into brine type and ore type, that is, lithium mainly exists in two forms in nature: one is in the form of lithium ions in salt lake brine, underground brine, seawater and oil field brine; the other is in the form of lithium-containing ore such as spodumene, lepidolite and petalite in rock and ore. China is rich in lithium resources, especially liquid lithium resources. However, the grade of salt lake brine in China is low, and the magnesium-lithium ratio is high, which brings great challenges to lithium resource mining. Spodumene, as a high-lithium-content lithium ore, is one of the main lithium ore resources used for ore lithium extraction in the industry. Domestic spodumene ore is mainly distributed in Xinjiang (Altai region, Hotan region, Hami region, etc.), Sichuan (Jikeyika ore field in Ganzi, A'ba ore field, etc.) and Ganzhou in Jiangxi, and foreign spodumene ore is mainly distributed in Western Australia, Canada, Zimbabwe, Ireland, Finland, Congo, etc. At present, domestic spodumene mainly depends on imports from Western Australia.

[0004] Spodumene has three crystal forms: monoclinic alpha phase, hexagonal gamma phase and tetragonal beta phase. Among them, the alpha phase is a low-temperature stable phase, the gamma phase is a high-temperature metastable phase, and the beta phase is a high-temperature stable phase. Naturally occurring spodumene is alpha-spodumene. At present, the sulfuric acid method is mainly used for lithium extraction in the industry, that is, alpha-spodumene is first calcined at a high temperature of 950-1100 DEG C to convert to beta-spodumene, then sulfuric acid roasting is carried out at 250-300 DEG C with concentrated sulfuric acid to generate soluble lithium sulfate and insoluble gangue, and then the acidified clinker is leached with water at 90 DEG C to obtain a solution rich in lithium sulfate, and then lithium products are prepared through a series of impurity removal.

[0005] The traditional sulfuric acid method for lithium extraction has been large-scale industrialized production, and the process is mature and has high yield, but it has problems such as high energy consumption of high-temperature calcination, serious environmental pollution and complicated impurity removal process. Therefore, a new type of environmentally friendly spodumene lithium extraction process is provided to solve the problem of high calcination energy consumption in the traditional process, which has great industrialization significance. SUMMARY

[0006] In order to overcome the deficiencies of the prior art, solve the problems of high energy consumption, serious environmental pollution and high impurity content in leaching solution in the high-temperature calcination crystalline transformation process of spodumene, the present application provides a method for lithium extraction from spodumene by alkali leaching and phase reconstruction, which uses alkali leaching to treat spodumene, reconstructs the spodumene phase into lithium salt lithium metasilicate, obtains a lithium-rich solution by secondary leaching of the lithium metasilicate, and prepares lithium salt products by lithium precipitation.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A method for lithium extraction from spodumene by alkali leaching and phase reconstruction, the method comprising the following steps:

[0009] (1) mixing spodumene ore and alkali solution in a pressure reaction kettle and carrying out hydrothermal alkali leaching reaction, and then carrying out solid-liquid separation on the reacted slurry to obtain alkali leaching residue and filtrate;

[0010] (2) mixing the alkali leaching residue obtained in step (1) with a leaching agent in a reaction kettle and carrying out alkali leaching residue leaching reaction, and then carrying out solid-liquid separation on the reacted slurry to obtain leaching residue and lithium-containing leaching solution;

[0011] The present application is further provided that the method further comprises the following steps:

[0012] (3) adding a lithium precipitation agent to the lithium-containing leaching solution obtained in step (2) to prepare lithium salt by reaction crystallization or evaporation crystallization.

[0013] The present application is further provided that the alkali solution in step (1) is NaOH or KOH solution, wherein:

[0014] When the alkali solution in step (1) is NaOH solution, the concentration of the NaOH solution is 5%-50% (mass fraction), the alkali-to-ore ratio, i.e. the mass ratio of alkali to spodumene, is 0.5-8, the hydrothermal alkali leaching reaction temperature is 150-300℃, and the reaction time is 1-30h.

[0015] When the alkali solution in step (1) is KOH solution, the concentration of the KOH solution is 10%-80% (mass fraction), the alkali-to-ore ratio, i.e. the mass ratio of alkali to spodumene, is 0.5-8, the hydrothermal alkali leaching reaction temperature is 150-350℃, and the reaction time is 1-30h.

[0016] The present application is further provided that the solid-liquid separation operation in steps (1) and (2) can adopt centrifugal separation, cyclone separation or filtration separation such as suction filtration and pressure filtration.

[0017] The application is further provided that the filtrate obtained by the solid-liquid separation in the step (1) contains part of lithium elements, which can be recycled to the hydrothermal alkaline leaching reaction as a mother liquor after being re-proportioned with NaOH or KOH concentration to continue to participate in the reaction, or can be reacted with phosphate to prepare lithium phosphate products.

[0018] The application is further provided that the alkali leaching residue obtained by the solid-liquid separation after the water washing is subjected to the leaching reaction of the alkali leaching residue in the step (2), and the washing liquid after the water washing can be mixed with the filtrate as a mother liquor to be recycled to the hydrothermal alkaline leaching reaction after being re-proportioned with NaOH or KOH concentration to continue to participate in the reaction, or can be reacted with phosphate to prepare lithium phosphate products.

[0019] The application is further provided that the leaching agent in the step (2) is dilute acid or alkali, wherein,

[0020] When the leaching agent in the step (2) is dilute acid, dilute sulfuric acid, dilute hydrochloric acid, dilute nitric acid, etc. can be used, the concentration of the dilute acid is 0.2-6 mol / L, the acid dosage is 0.1-2 times of the theoretical dosage, the temperature of the alkali leaching residue leaching reaction is 20-90℃, the time is 1-240 min, when the alkali solution in the step (1) is NaOH solution, the theoretical dosage is calculated according to the molar amount of Li2O and Na2O in the alkali leaching residue, according to the stoichiometry of 1 mol Li-1 mol H and 1 mol Na-1 mol H; when the alkali solution in the step (1) is KOH solution, the theoretical dosage is calculated according to the molar amount of Li2O and K2O in the alkali leaching residue, according to the stoichiometry of 1 mol Li-1 mol H and 1 mol K-1 mol H.

[0021] When the leaching agent in the step (2) is alkali, calcium oxide can be used, the dosage of the calcium oxide is 0.5-10 times of the theoretical dosage, the liquid-solid ratio, i.e. the mass ratio of water and alkali leaching residue is 5-100, the temperature of the alkali leaching residue leaching reaction is 50-200℃, the reaction time is 1-30 h, when the alkali solution in the step (1) is NaOH solution, the theoretical dosage is calculated according to the molar amount of Li2O and Na2O in the alkali leaching residue, according to the stoichiometry of 1 mol Li-1 mol Ca and 3 mol Na-2 mol Ca; when the alkali solution in the step (1) is KOH solution, the theoretical dosage is calculated according to the molar amount of Li2O and K2O in the alkali leaching residue, according to the stoichiometry of 1 mol Li-1 mol Ca and 3 mol K-2 mol Ca.

[0022] The application is further provided that when the leaching agent of step (2) is dilute acid, concentrated acid is supplemented to the lithium-containing leaching solution obtained in step (2) for again alkali leaching residue leaching reaction, and the lithium concentration in the lithium-containing leaching solution is improved by recycling for multiple times; the recycling times are preferably 2-5 times.

[0023] The application is further provided that the leaching residue obtained by solid-liquid separation in step (2) is washed with water to obtain a washing solution, which can be used as a lithium precipitation agent for preparing lithium salt in step (3) or a leaching agent in step (2).

[0024] The application is further provided that calcium oxide is added to the lithium-containing leaching solution obtained in step (2) to remove magnesium and silicon in the lithium-containing leaching solution, and then a carbonate is added to remove calcium in the lithium-containing leaching solution; when the alkali solution in step (1) is NaOH solution, the carbonate is preferably sodium carbonate; when the alkali solution in step (1) is KOH solution, the carbonate is preferably potassium carbonate.

[0025] The application is further provided that the amount of calcium oxide is 0.1-6 times of the theoretical amount, i.e. 0.1-6 times of the total molar amount of magnesium and silicon in the lithium-containing leaching solution, and the amount of the carbonate is 0.1-6 times of the theoretical amount, i.e. 0.1-6 times of the molar amount of calcium in the lithium-containing leaching solution after removing magnesium and silicon, the reaction temperature during the removal of impurities is 20-80℃, and the reaction time is 20-100 min.

[0026] The application is further provided that a lithium precipitation agent is added to the lithium-containing leaching solution in step (3) to prepare lithium salt products by reaction crystallization, wherein:

[0027] A carbonate is added to the lithium-containing leaching solution to prepare lithium carbonate precipitate by reaction crystallization;

[0028] A phosphate is added to the lithium-containing leaching solution to prepare lithium phosphate precipitate by reaction crystallization;

[0029] When the alkali solution in step (1) is NaOH solution, the carbonate is preferably sodium carbonate, and the phosphate is preferably sodium phosphate; when the alkali solution in step (1) is KOH solution, the carbonate is preferably potassium carbonate, and the phosphate is preferably potassium phosphate.

[0030] When the leaching agent in step (2) is alkali, CO2 is introduced into the lithium-containing leaching solution to prepare lithium carbonate precipitate by reaction crystallization.

[0031] The application is further provided that the temperature of reaction crystallization is 20-100℃, the reaction time is 10-120 min, and the amount of the lithium precipitation agent is 1-5 times of the theoretical amount, i.e. 1-5 times of the molar amount of lithium in the lithium-containing leaching solution.

[0032] The application is further provided that when the leaching agent of the step (2) is alkali, the lithium-containing leaching solution in the step (3) is prepared into lithium hydroxide precipitate through evaporation crystallization; the temperature of the evaporation crystallization is preferably 30-90 DEG C, and the evaporation temperature difference is preferably 5-20 DEG C.

[0033] The application is further provided that when the leaching agent of the step (2) is dilute sulfuric acid, the step (3) is prepared into lithium salt through reaction crystallization, and then solid-liquid separation is carried out, and the obtained mother liquor is prepared into sulfate byproduct through freeze crystallization; when the alkali solution of the step (1) is NaOH solution, the sulfate byproduct is sodium sulfate tenhydrate; when the alkali solution of the step (1) is KOH solution, the sulfate byproduct is potassium sulfate; preferably, the temperature of the freeze crystallization is-20--10 DEG C.

[0034] The application is further provided that when the leaching agent of the step (2) is dilute sulfuric acid, the step (3) is prepared into lithium salt through reaction crystallization, and then solid-liquid separation is carried out, and the obtained mother liquor is prepared into sulfate byproduct through freeze crystallization; when the alkali solution of the step (1) is NaOH solution, the sulfate byproduct is sodium sulfate tenhydrate; when the alkali solution of the step (1) is KOH solution, the sulfate byproduct is potassium sulfate; preferably, the temperature of the freeze crystallization is-20--10 DEG C.

[0035] The application is further provided that when the leaching agent of the step (2) is dilute sulfuric acid, the step (3) is prepared into lithium salt through reaction crystallization, and then solid-liquid separation is carried out, and the obtained mother liquor is prepared into sulfate byproduct through freeze crystallization; when the alkali solution of the step (1) is NaOH solution, the sulfate byproduct is sodium sulfate tenhydrate; when the alkali solution of the step (1) is KOH solution, the sulfate byproduct is potassium sulfate; preferably, the temperature of the freeze crystallization is-20--10 DEG C.

[0036] The application has the following beneficial effects:

[0037] (1) The method for extracting lithium from alkali leached spodumene ore can realize clean production without high-temperature calcination of spodumene, and can obtain lithium-containing solution through hydrothermal alkali leaching reaction and alkali leaching residue leaching reaction;

[0038] (2) The conversion rate of Li2O in the single hydrothermal alkali leaching reaction is more than 95%, and the leaching rate of Li2O in the single alkali leaching residue leaching reaction is more than 95%;

[0039] (3) The lithium can be selectively leached through the two-step reaction of hydrothermal alkali leaching and alkali leaching residue leaching, and the lithium-containing leaching solution rich in lithium and low in impurity content is obtained, and a large amount of silicon and aluminum elements are converted into leaching residue rich in silicon and aluminum elements, which can be used in the fields of cement and building materials, and the spodumene resources are efficiently utilized;

[0040] (4) Lithium-containing leachate can be used to produce a series of lithium salt products with high purity, high value and wide application, such as lithium carbonate, lithium hydroxide, lithium chloride and lithium phosphate, through various methods.

[0041] (5) The filtrate and washing liquid after the hydrothermal alkaline leaching reaction can be recycled as mother liquor to continue participating in the hydrothermal alkaline leaching reaction; the washing liquid after the alkaline leaching residue leaching reaction can be used as a solvent to prepare the required lithium precipitation agent or leaching agent, thus realizing the comprehensive utilization of resources and reducing the loss of lithium resources. Attached Figure Description

[0042] Figure 1 A process flow diagram for lithium extraction from spodumene minerals through alkaline leaching and phase reconstruction.

[0043] Figure 2 XRD patterns of spodumene ore and alkaline leaching residue under the conditions of Example 1;

[0044] Figure 3 SEM images of spodumene ore (a), alkaline leaching residue (b) and leaching residue (c) under the conditions of Example 1;

[0045] Figure 4 XRD patterns of spodumene ore and alkaline leaching residue under the conditions of Example 8;

[0046] Figure 5 SEM images of spodumene ore (a), alkali leaching residue (b), and leaching residue (c) under the conditions of Example 8. Detailed Implementation

[0047] The present invention will be further described in detail below with reference to embodiments. It should be understood that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0048] The technical concept of this invention is as follows: Alkali leaching is used to treat spodumene, reconstructing and decomposing the α-spodumene mineral phase into lithium metasilicate, a lithium salt. The alkali leaching residue containing the lithium metasilicate is then subjected to a second leaching to obtain a lithium-rich solution, and lithium is precipitated to prepare the lithium salt product. The method includes the following steps:

[0049] (1) Lithium spodumene ore and alkaline solution are mixed in a pressure reactor and a hydrothermal alkaline leaching reaction is carried out. The slurry after the reaction is separated into solid and liquid to obtain alkaline leaching residue and filtrate.

[0050] (2) The alkaline leaching residue obtained in step (1) is mixed with the leaching agent in a reactor and an alkaline leaching reaction is carried out. The slurry after the reaction is separated into solid and liquid to obtain leaching residue and lithium-containing leachate.

[0051] (3) adding a lithium precipitating agent to the lithium-containing leaching solution obtained in step (2) to prepare a lithium salt by reaction crystallization or evaporation crystallization.

[0052] Example 1

[0053] Lithium feldspar ore with a Li2O content of 5.3% (mass fraction) was subjected to hydrothermal alkali leaching reaction with NaOH solution at 250°C, a stirring speed of 500 rpm, an alkali / ore ratio of 0.5, an alkali concentration of 25% (mass fraction), and a reaction time of 20 h. After the reaction, the slurry was centrifugally separated to obtain alkali leaching residue.

[0054] 6 mol / L dilute sulfuric acid was mixed with the alkali leaching residue at a theoretical acid dosage of 0.1 times the theoretical amount and allowed to react at 20°C for 240 min to obtain leaching of the alkali leaching residue. Concentrated sulfuric acid was added to the lithium-containing leaching solution obtained after solid-liquid separation to leach new alkali leaching residue. After repeating the process twice, a lithium sulfate-rich leaching solution was obtained.

[0055] Calcium oxide was added to the lithium sulfate-rich leaching solution at 1 times the theoretical amount at 20°C to remove magnesium and silicon, and then sodium carbonate was added at 1 times the theoretical amount to remove calcium.

[0056] Sodium carbonate solution was introduced into the impurity-removed leaching solution at 100°C to reaction crystallize for 10 min. The amount of sodium carbonate used was 2 times the theoretical amount, and lithium carbonate product was obtained.

[0057] The conversion rate of Li2O in the hydrothermal alkali leaching reaction was 53.6%, the single leaching rate of Li2O in the alkali leaching residue leaching reaction was 76.3%, the purity of the lithium carbonate product obtained by reaction crystallization was 85.2%, and the yield was 79.1%. The XRD of the alkali leaching residue and lithium feldspar ore is shown in Figure 2 The SEM images of the lithium feldspar ore (a), alkali leaching residue (b), and leaching residue (c) are shown in Figure 3

[0058] Example 2

[0059] Lithium feldspar ore with a Li2O content of 6.0% (mass fraction) was subjected to hydrothermal alkali leaching reaction with NaOH solution at 150°C, a stirring speed of 500 rpm, an alkali / ore ratio of 1, an alkali concentration of 50% (mass fraction), and a reaction time of 20 h. After the reaction, the slurry was filtered to obtain alkali leaching residue and filtrate. The filtrate was re-dosed and recycled to the hydrothermal alkali leaching reaction.

[0060] 0.2 mol / L dilute hydrochloric acid was mixed with the alkali leaching residue at an acid dosage of 1 times the theoretical amount and allowed to react at 30°C for 10 min to obtain leaching of the alkali leaching residue. Concentrated hydrochloric acid was added to the lithium-containing leaching solution obtained after solid-liquid separation to leach new alkali leaching residue. After repeating the process once, a lithium chloride-rich leaching solution was obtained. ​

[0061] The magnesium and silicon in the lithium chloride-rich leaching solution were removed by adding 1 times theoretical amount of calcium oxide at 50°C for 60 minutes, and then adding 0.1 times theoretical amount of sodium carbonate for 60 minutes.

[0062] The lithium carbonate product was prepared by adding sodium carbonate solution to the impurity-removed leaching solution at 60°C for 60 minutes of reaction crystallization, and the amount of sodium carbonate was 2 times the theoretical amount.

[0063] In the hydrothermal alkali leaching reaction, the conversion rate of Li2O in spodumene was 41.2%, the single leaching rate of Li2O in the alkali leaching residue leaching reaction was 94.5%, and the purity of the lithium carbonate product obtained by reaction crystallization was 91.6% with a yield of 72.5%.

[0064] Example 3

[0065] The spodumene with a Li2O content of 6.0% (mass fraction) was subjected to a hydrothermal alkali leaching reaction with NaOH solution at 300°C, a stirring rate of 100 rpm, an alkali-to-mineral ratio of 8, an alkali concentration of 25% (mass fraction), and a reaction time of 1 hour. After the reaction, the slurry was separated by cyclone and washed with water to obtain alkali leaching residue, and the filtrate and water washing liquid were re-dosed and recycled to the hydrothermal alkali leaching reaction for further reaction.

[0066] The alkali leaching residue was mixed with 2 times theoretical amount of 1 mol / L dilute nitric acid at 90°C for 1 minute to carry out alkali leaching residue leaching reaction, and concentrated nitric acid was added to the lithium-containing leaching solution after solid-liquid separation to leach new alkali leaching residue. After three repetitions, a lithium nitrate-rich leaching solution was obtained.

[0067] The magnesium and silicon in the lithium nitrate-rich leaching solution were removed by adding 6 times theoretical amount of calcium oxide at 50°C for 60 minutes, and then adding 1 times theoretical amount of sodium carbonate for 60 minutes.

[0068] The lithium phosphate product was prepared by adding sodium phosphate solution to the impurity-removed leaching solution at 20°C for 120 minutes of reaction crystallization, and the amount of sodium phosphate was 2 times the theoretical amount.

[0069] In the hydrothermal alkali leaching reaction, the conversion rate of Li2O in spodumene was 65.5%, the single leaching rate of Li2O in the alkali leaching residue leaching reaction was 85.4%, and the purity of the lithium phosphate product obtained by reaction crystallization was 94.1% with a yield of 65.0%.

[0070] Example 4

[0071] The lithium spodumene with 2.4% (mass fraction) Li2O content is reacted with NaOH solution in a hydrothermal alkali leaching reaction at 250℃, stirring rate 900rpm, alkali to ore ratio 1, alkali concentration 25% (mass fraction), reaction time 10h. After reaction, the slurry is separated by centrifugation and washed with water to obtain alkali leaching residue, the filtrate and washing liquid are re-proportioned and recycled to the hydrothermal alkali leaching reaction to continue participating in the reaction.

[0072] The calcium oxide is mixed with the alkali leaching residue at 150℃ for 1h to have a leaching reaction of alkali leaching residue, the liquid to solid ratio is 50, and the leaching solution rich in lithium hydroxide is obtained after solid-liquid separation.

[0073] The leaching solution rich in lithium hydroxide is added with 1 times theoretical amount of calcium oxide at 50℃ to react for 60min to remove magnesium and silicon, and then added with 1 times theoretical amount of sodium carbonate to react for 60min to remove calcium.

[0074] The leaching solution after removal of impurities is evaporated and crystallized at an evaporation temperature of 50℃ and an evaporation temperature difference of 10℃ to prepare lithium hydroxide product.

[0075] In the hydrothermal alkali leaching reaction, the conversion rate of Li2O in the lithium spodumene is 80.6%, in the leaching reaction of alkali leaching residue, the leaching rate of Li2O is 47.5%, and the purity of the lithium hydroxide product obtained by evaporation and crystallization is 98.3% with a yield of 56.2%.

[0076] Example 5

[0077] The lithium spodumene with 6.2% (mass fraction) Li2O content is reacted with NaOH solution in a hydrothermal alkali leaching reaction at 250℃, stirring rate 500rpm, alkali to ore ratio 1, alkali concentration 25% (mass fraction), reaction time 20h. After reaction, the slurry is separated by centrifugation and washed with water to obtain alkali leaching residue, the filtrate and washing liquid are re-proportioned and recycled to the hydrothermal alkali leaching reaction to continue participating in the reaction.

[0078] The calcium oxide is mixed with the alkali leaching residue at 50℃ for 30h to have a leaching reaction of alkali leaching residue, the liquid to solid ratio is 100, and the leaching solution rich in lithium hydroxide is obtained after solid-liquid separation.

[0079] The leaching solution rich in lithium hydroxide is added with 1 times theoretical amount of calcium oxide at 80℃ to react for 60min to remove magnesium and silicon, and then added with 6 times theoretical amount of sodium carbonate to react for 60min to remove calcium.

[0080] The leaching solution after removal of impurities is added with sodium carbonate solution at 60℃ to react and crystallize for 60min, the amount of sodium carbonate is 1 times theoretical amount, and lithium carbonate product is prepared.

[0081] The conversion rate of Li2O in the lithium spodumene in the hydrothermal alkali leaching reaction is 96.0%, the leaching rate of Li2O in the alkali leaching residue is 45.7%, the purity of the lithium carbonate product obtained by reaction crystallization is 88.1%, and the yield is 70.6%.

[0082] Example 6

[0083] The lithium spodumene with a Li2O content of 5.3% (mass fraction) is subjected to a hydrothermal alkali leaching reaction with a NaOH solution at 250°C, a stirring rate of 500 rpm, an alkali / mineral ratio of 1.5, an alkali concentration of 5% (mass fraction), and a reaction time of 30 h. After the reaction, the slurry is subjected to centrifugal separation and water washing to obtain alkali leaching residue, and the filtrate and water washing liquid are re-proportioned and recycled to the hydrothermal alkali leaching reaction to continue participating in the reaction.

[0084] Calcium oxide is mixed with the alkali leaching residue at 150°C for 15 h to carry out an alkali leaching residue leaching reaction, and the liquid / solid ratio is 5. After solid-liquid separation, a leaching liquid rich in lithium hydroxide is obtained.

[0085] 0.1 times the theoretical amount of calcium oxide is added to the leaching liquid rich in lithium hydroxide at 50°C to react for 20 min to remove magnesium and silicon, and then 1 times the theoretical amount of sodium carbonate is added to react for 20 min to remove calcium.

[0086] Carbon dioxide is introduced into the impurity-removed leaching liquid at 60°C to react and crystallize for 60 min, and the amount of carbon dioxide is 5 times the theoretical amount, to prepare a lithium carbonate product.

[0087] The conversion rate of Li2O in the lithium spodumene in the hydrothermal alkali leaching reaction is 70.8%, the leaching rate of Li2O in the alkali leaching residue is 55.9%, the purity of the lithium carbonate product obtained by reaction crystallization is 87.2%, and the yield is 77.4%.

[0088] Example 7

[0089] The lithium spodumene with a Li2O content of 5.3% (mass fraction) is subjected to a hydrothermal alkali leaching reaction with a NaOH solution at 250°C, a stirring rate of 500 rpm, an alkali / mineral ratio of 1, an alkali concentration of 25% (mass fraction), and a reaction time of 20 h. After the reaction, the slurry is subjected to centrifugal separation and water washing to obtain alkali leaching residue, and the filtrate and water washing liquid are re-proportioned and recycled to the hydrothermal alkali leaching reaction to continue participating in the reaction.

[0090] Calcium oxide is mixed with the alkali leaching residue at 200°C for 15 h to carry out an alkali leaching residue leaching reaction, and the liquid / solid ratio is 50. After solid-liquid separation, a leaching liquid rich in lithium hydroxide is obtained.

[0091] The magnesium and silicon in the lithium hydroxide-rich leaching solution are removed by adding 1 times the theoretical amount of calcium oxide at 50°C for 100 minutes, and then adding 1 times the theoretical amount of sodium carbonate for 100 minutes to remove calcium.

[0092] The leaching solution after the impurities are removed is reacted with a sodium phosphate solution at 60°C for 60 minutes to crystallize, and the amount of sodium phosphate is 2 times the theoretical amount, to obtain a lithium phosphate product.

[0093] The conversion rate of Li2O in the lithium spodumene in the hydrothermal alkaline leaching reaction is 96.1%, the leaching rate of Li2O in the alkaline leaching residue leaching reaction is 96.5%, the purity of the lithium phosphate product obtained by reaction crystallization is 96.5%, and the yield is 98.3%.

[0094] Example 8

[0095] The lithium spodumene ore with a Li2O content of 5.5% (mass fraction) is subjected to a hydrothermal alkaline leaching reaction with a KOH solution at 250°C, a stirring rate of 500 rpm, an alkali-to-ore ratio of 0.5, an alkali concentration of 10% (mass fraction), and a reaction time of 20 hours. After the reaction, the alkaline leaching residue is obtained by centrifugal separation and water washing of the slurry, and the filtrate and water washing liquid are re-dosed and recycled to the hydrothermal alkaline leaching reaction.

[0096] The calcium oxide is mixed with the alkaline leaching residue at 0.5 times the theoretical amount at 150°C for 1 hour to obtain the alkaline leaching residue leaching reaction, and the liquid-to-solid ratio is 50. After solid-liquid separation, a lithium hydroxide-rich leaching solution is obtained.

[0097] The magnesium and silicon in the lithium hydroxide-rich leaching solution are removed by adding 1 times the theoretical amount of calcium oxide at 50°C for 60 minutes, and then adding 1 times the theoretical amount of potassium carbonate for 60 minutes to remove calcium.

[0098] The leaching solution after the impurities are removed is evaporated and crystallized at an evaporation temperature of 50°C and an evaporation temperature difference of 10°C to obtain a lithium hydroxide product.

[0099] The conversion rate of Li2O in the lithium spodumene in the hydrothermal alkaline leaching reaction is 43.5%, the leaching rate of Li2O in the alkaline leaching residue leaching reaction is 45.8%, the purity of the lithium hydroxide product obtained by evaporation crystallization is 96.1%, and the yield is 55.5%. The XRD of the alkaline leaching residue and the lithium spodumene ore is shown in Figure 4 The SEM images of the lithium spodumene ore (a), the alkaline leaching residue (b), and the leaching residue (c) are shown in Figure 5 .

[0100] Example 9

[0101] The lithium spodumene ore with 6.4% (mass fraction) of Li2O content is subjected to hydrothermal alkali leaching reaction with KOH solution at 150℃, stirring speed of 500rpm, alkali / ore ratio of 1, alkali concentration of 60% (mass fraction), and reaction time of 20h, and the slurry after reaction is filtered to obtain alkali leaching residue.

[0102] Calcium oxide is mixed with the alkali leaching residue at 10 times of the theoretical amount at 50℃ for 30h to have leaching reaction of alkali leaching residue, and the liquid / solid ratio is 100, and the leaching solution rich in lithium hydroxide is obtained after solid-liquid separation.

[0103] To the leaching solution rich in lithium hydroxide, 1 times of the theoretical amount of calcium oxide is added at 80℃ for 60min to remove magnesium and silicon, and then 6 times of the theoretical amount of potassium carbonate is added to remove calcium.

[0104] Carbon dioxide is bubbled into the leaching solution after impurity removal at 60℃ for 60min to crystallize, and the amount of carbon dioxide is 5 times of the theoretical amount, and the lithium carbonate product is prepared.

[0105] In the hydrothermal alkali leaching reaction, the conversion rate of Li2O in the lithium spodumene ore is 45.8%, and in the leaching reaction of alkali leaching residue, the leaching rate of Li2O is 43.7%, and the purity of the lithium carbonate product obtained by reaction crystallization is 89.1%, and the yield is 71.4%.

[0106] Example 10

[0107] The lithium spodumene ore with 2.4% (mass fraction) of Li2O content is subjected to hydrothermal alkali leaching reaction with KOH solution at 350℃, stirring speed of 500rpm, alkali / ore ratio of 8, alkali concentration of 80% (mass fraction), and reaction time of 1h, and the slurry after reaction is separated by cyclone to obtain alkali leaching residue and filtrate, and the filtrate is re-dosed and recycled to the hydrothermal alkali leaching reaction to participate in the reaction.

[0108] Calcium oxide is mixed with the alkali leaching residue at 5 times of the theoretical amount at 200℃ for 15h to have leaching reaction of alkali leaching residue, and the liquid / solid ratio is 5, and the leaching solution rich in lithium hydroxide is obtained after solid-liquid separation.

[0109] To the leaching solution rich in lithium hydroxide, 0.1 times of the theoretical amount of calcium oxide is added at 50℃ for 20min to remove magnesium and silicon, and then 1 times of the theoretical amount of potassium carbonate is added to remove calcium.

[0110] Carbon dioxide is bubbled into the leaching solution after impurity removal at 60℃ for 60min to crystallize, and the amount of carbon dioxide is 5 times of the theoretical amount, and the lithium carbonate product is prepared.

[0111] The conversion rate of Li2O in the spodumene in the hydrothermal alkali leaching reaction is 73.7%, the leaching rate of Li2O in the alkali leaching residue is 57.6%, the purity of the lithium carbonate product obtained by reaction crystallization is 85.3%, and the yield is 73.4%.

[0112] Example 11

[0113] The spodumene ore with a Li2O content of 5.5% (mass fraction) is subjected to a hydrothermal alkali leaching reaction with KOH solution at 250°C, a stirring rate of 500 rpm, an alkali / ore ratio of 1, an alkali concentration of 60% (mass fraction), and a reaction time of 10 h. After the reaction, the slurry is subjected to centrifugal separation and water washing to obtain alkali leaching residue, and the filtrate and water washing liquid are re-proportioned and recycled to the hydrothermal alkali leaching reaction to continue participating in the reaction.

[0114] Calcium oxide is mixed with the alkali leaching residue at 200°C for 15 h to carry out alkali leaching residue leaching reaction, and the liquid / solid ratio is 50. After solid-liquid separation, a lithium hydroxide-rich leaching solution is obtained.

[0115] To the lithium hydroxide-rich leaching solution, 1 times theoretical amount of calcium oxide is added at 50°C to react for 100 min to remove magnesium and silicon, and then 1 times theoretical amount of potassium carbonate is added to react for 100 min to remove calcium.

[0116] To the impurity-removed leaching solution, potassium phosphate solution is introduced at 60°C to react for 60 min to prepare a lithium phosphate product, and the amount of potassium phosphate is 2 times the theoretical amount.

[0117] The conversion rate of Li2O in the spodumene in the hydrothermal alkali leaching reaction is 67.9%, the leaching rate of Li2O in the alkali leaching residue is 90.6%, the purity of the lithium phosphate product obtained by reaction crystallization is 91.3%, and the yield is 94.6%.

[0118] Example 12

[0119] The spodumene ore with a Li2O content of 5.5% (mass fraction) is subjected to a hydrothermal alkali leaching reaction with KOH solution at 250°C, a stirring rate of 500 rpm, an alkali / ore ratio of 1, an alkali concentration of 60% (mass fraction), and a reaction time of 20 h. After the reaction, the slurry is subjected to centrifugal separation and water washing to obtain alkali leaching residue, and the filtrate and water washing liquid are re-proportioned and recycled to the hydrothermal alkali leaching reaction to continue participating in the reaction.

[0120] 6 mol / L dilute sulfuric acid is mixed with the alkali leaching residue at 20°C for 240 min to carry out alkali leaching residue leaching reaction, and the acid amount is 0.1 times the theoretical amount. Concentrated sulfuric acid is supplemented to the lithium-containing leaching solution after solid-liquid separation to leach new alkali leaching residue, and the process is repeated twice to obtain a lithium sulfate-rich leaching solution.

[0121] The magnesium and silicon in the lithium sulfate-rich leaching solution are removed by adding 1 times the theoretical amount of calcium oxide at 20°C for 60 minutes, and then adding 1 times the theoretical amount of potassium carbonate for 60 minutes to remove calcium.

[0122] The potassium carbonate solution is introduced into the impurity-removed leaching solution at 100°C for 10 minutes of reaction crystallization, and the amount of potassium carbonate used is 2 times the theoretical amount, to obtain a lithium carbonate product.

[0123] In the hydrothermal alkali leaching reaction, the conversion rate of Li2O in spodumene is 86.3%, the single leaching rate of Li2O in the alkali leaching residue leaching reaction is 74.8%, and the purity of the lithium carbonate product obtained by reaction crystallization is 85.8% with a yield of 80.6%.

[0124] Example 13

[0125] The spodumene with a Li2O content of 5.5% (mass fraction) is subjected to a hydrothermal alkali leaching reaction with a KOH solution at 250°C, a stirring rate of 500 rpm, an alkali-to-mineral ratio of 1.5, an alkali concentration of 60% (mass fraction), and a reaction time of 30 hours. After the reaction, the alkali leaching residue is obtained by centrifugal separation and water washing of the slurry, and the filtrate and water washing liquid are re-dosed and recycled to the hydrothermal alkali leaching reaction for further reaction.

[0126] The alkali leaching residue is subjected to a leaching reaction with 0.2 mol / L dilute hydrochloric acid at 30°C for 10 minutes, with an acid amount of 1 times the theoretical amount. Concentrated hydrochloric acid is added to the lithium-containing leaching solution obtained after solid-liquid separation to leach new alkali leaching residue, and the process is repeated once to obtain a lithium chloride-rich leaching solution.

[0127] The magnesium and silicon in the lithium chloride-rich leaching solution are removed by adding 1 times the theoretical amount of calcium oxide at 50°C for 60 minutes, and then adding 0.1 times the theoretical amount of potassium carbonate for 60 minutes to remove calcium.

[0128] The potassium carbonate solution is introduced into the impurity-removed leaching solution at 60°C for 60 minutes of reaction crystallization, and the amount of potassium carbonate used is 2 times the theoretical amount, to obtain a lithium carbonate product.

[0129] In the hydrothermal alkali leaching reaction, the conversion rate of Li2O in spodumene is 97.1%, the single leaching rate of Li2O in the alkali leaching residue leaching reaction is 95.4%, and the purity of the lithium carbonate product obtained by reaction crystallization is 90.3% with a yield of 98.5%.

[0130] Example 14

[0131] The lithium spodumene with 5.5% (mass fraction) Li2O content is subjected to hydrothermal alkali leaching reaction with KOH solution at 250℃, stirring rate 500rpm, alkali / mineral ratio 1, alkali concentration 60% (mass fraction), and reaction time 20h. After reaction, the slurry is centrifuged and washed with water to obtain alkali leaching residue, and the filtrate and washing liquid are re-dosed and recycled to the hydrothermal alkali leaching reaction.

[0132] 1mol / L dilute nitric acid is mixed with the alkali leaching residue at 90℃ for 1min at an acid dosage of 2 times the theoretical amount to carry out alkali leaching residue leaching reaction. Concentrated nitric acid is added to the lithium-containing leaching solution after solid-liquid separation to leach new alkali leaching residue, and the process is repeated three times to obtain a leaching solution rich in lithium nitrate.

[0133] To the leaching solution rich in lithium nitrate, 6 times the theoretical amount of calcium oxide is added at 50℃ for 60min to remove magnesium and silicon, and then 1 times the theoretical amount of potassium carbonate is added to remove calcium.

[0134] To the impurity-removed leaching solution, potassium phosphate solution is introduced at 20℃ for 120min to crystallize lithium phosphate, with the potassium phosphate dosage being 2 times the theoretical amount, to produce lithium phosphate product.

[0135] In the hydrothermal alkali leaching reaction, the conversion rate of Li2O in the lithium spodumene is 86.2%, the single leaching rate of Li2O in the alkali leaching residue leaching reaction is 87.1%, and the purity of the lithium phosphate product obtained by reaction crystallization is 95.1% with a yield of 64.5%.

Claims

1. A method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore, characterized in that, The method includes the following steps: (1) Lithium spodumene ore and alkaline solution are mixed in a pressure reactor and a hydrothermal alkaline leaching reaction is carried out. The slurry after the reaction is separated into solid and liquid to obtain alkaline leaching residue and filtrate. (2) The alkaline leaching residue obtained in step (1) is mixed with the leaching agent in a reactor and an alkaline leaching reaction occurs. The slurry after the reaction is separated into solid and liquid to obtain leaching residue and lithium-containing leachate.

2. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 1, characterized in that, The method further includes the following steps: (3) Add lithium precipitation agent to the lithium-containing leachate obtained in step (2) to react and crystallize or evaporate and crystallize to prepare lithium salt.

3. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 1, characterized in that, The alkaline solution in step (1) is a NaOH solution or a KOH solution.

4. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 3, characterized in that, The concentration of the NaOH solution in step (1) is 5%-50% by mass, the alkali-to-ore ratio is 0.5-8, the reaction temperature is 150-300℃, and the reaction time is 1-30h.

5. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 3, characterized in that, The concentration of the KOH solution in step (1) is 10%-80% by mass, the alkali-to-ore ratio is 0.5-8, the reaction temperature is 150-350℃, and the reaction time is 1-30h.

6. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 1, characterized in that, The solid-liquid separation operations in steps (1) and (2) are performed by centrifugation, cyclone separation or filtration.

7. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 1, characterized in that, The filtrate from step (1) is used as mother liquor and recycled to the hydrothermal alkaline leaching reaction to continue participating in the reaction or to react with phosphate to crystallize and prepare lithium phosphate products.

8. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 1, characterized in that, The alkaline leaching residue in step (1) is washed with water and subjected to solid-liquid separation.

9. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 8, characterized in that, The filtrate from step (1) is mixed with the washing liquid after the alkaline leaching residue is washed and separated into solid and liquid components. This mixture is then used as a mother liquor for re-preparation and recycled to the hydrothermal alkaline leaching reaction to continue participating in the reaction or to react with phosphate to crystallize and prepare lithium phosphate products.

10. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 1, characterized in that, The leaching agent in step (2) is dilute acid or calcium oxide.

11. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 10, characterized in that, The leaching agent is dilute sulfuric acid, dilute hydrochloric acid, or dilute nitric acid. The concentration of the dilute acid is 0.2-6 mol / L, and the amount of acid used is 0.1-2 times the theoretical amount. The leaching reaction temperature of the alkaline residue is 20-90℃, and the time is 1-240 min.

12. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 10, characterized in that, The leaching agent is calcium oxide, and the amount of calcium oxide used is 0.5-10 times the theoretical mass amount. The liquid-solid ratio is 5-100, the leaching temperature of the alkaline leaching residue is 50-200℃, and the reaction time is 1-30h.

13. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 11, characterized in that, Add concentrated acid to the lithium-containing leachate obtained in step (2) for another alkaline leaching reaction, and repeat the process multiple times to increase the lithium concentration in the lithium-containing leachate.

14. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 13, characterized in that, The number of cycles is 2-5.

15. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 2, characterized in that, The leaching residue obtained by solid-liquid separation in step (2) is washed with water and separated to obtain a washing liquid. The washing liquid is used as a solvent to prepare the leaching agent in step (2) or the lithium precipitation agent required for preparing lithium salt in step (3).

16. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 1, characterized in that, Calcium oxide is added to the lithium-containing leachate obtained in step (2) to remove magnesium and silicon from the lithium-containing leachate, and then carbonate is added to remove calcium from the lithium-containing leachate.

17. The method for extracting lithium from spodumene according to claim 16, characterized in that, The amount of calcium oxide used is 0.1-6 times the theoretical amount, the reaction temperature for impurity removal is 20-80℃, and the reaction time is 20-100min.

18. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 16, characterized in that, The amount of carbonate used is 0.1-6 times the theoretical amount, the reaction temperature for impurity removal is 20-80℃, and the reaction time is 20-100min.

19. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 2, characterized in that, The lithium precipitant in step (3) is a carbonate, and lithium carbonate is prepared by reaction crystallization; or The lithium precipitation agent in step (3) is phosphate, which is prepared by reaction crystallization to obtain lithium phosphate.

20. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 19, characterized in that, When the alkaline solution in step (1) is a NaOH solution, the carbonate is sodium carbonate and the phosphate is sodium phosphate; When the alkaline solution in step (1) is a KOH solution, the carbonate is potassium carbonate and the phosphate is potassium phosphate.

21. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 2, characterized in that, In step (2), an alkali is used as the leaching agent. CO2 is introduced into the lithium-containing leaching solution in step (3) as a lithium precipitation agent, and lithium carbonate is prepared by reaction crystallization.

22. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 19 or 21, characterized in that, The reaction crystallization temperature is 20-100℃, the reaction time is 10-120 min, and the amount of lithium precipitation agent used is 1-5 times the theoretical amount.

23. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 2, characterized in that, The leaching agent in step (2) is an alkali, and the lithium-containing leaching solution in step (3) is prepared by evaporation and crystallization to obtain lithium hydroxide.

24. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 23, characterized in that, The evaporation crystallization temperature is 30-90℃, and the evaporation temperature difference is 5-20℃.

25. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 2, characterized in that, The leaching agent in step (2) is dilute sulfuric acid. After preparing lithium salt by reaction crystallization in step (3), solid-liquid separation is performed, and the mother liquor obtained is frozen crystallized to prepare sulfate by-product.

26. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 2, characterized in that, The leaching agent in step (2) is dilute hydrochloric acid. After preparing lithium salt by reaction crystallization in step (3), solid-liquid separation is performed, and the mother liquor obtained is evaporated and crystallized to prepare chloride salt by-product.

27. The method for lithium extraction by alkaline leaching and phase reconstruction of spodumene ore according to claim 2, characterized in that, The leaching agent in step (2) is dilute nitric acid. After preparing lithium salt by reaction crystallization in step (3), solid-liquid separation is performed, and the mother liquor obtained is frozen crystallized to prepare nitrate by-product.

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