Method for removing beryllium element in lithium carbonate smelting slag

Abstract

The invention provides a method for removing beryllium in lithium carbonate smelting slag, and relates to the technical field of preparation of lithium carbonate from lepidolite. The invention discloses a method for removing beryllium in lithium carbonate smelting slag. The method comprises the following steps: S1, adding a solvent into the lithium carbonate smelting slag for washing, and filtering to obtain primary leachate and smelting slag subjected to primary impurity removal; s2, a solvent is added into the smelting slag subjected to primary impurity removal, a complex is added, a pH regulator is added to adjust the pH, stirring and filtering are conducted, and secondary leachate and smelting slag subjected to secondary impurity removal are obtained; s3, a solvent is added into the smelting slag subjected to secondary impurity removal, stirring and filtering are conducted, and third-time leaching liquid and smelting slag subjected to third-time impurity removal are obtained; and S4, phosphate and an adsorbent are added into the smelting slag obtained after third-time impurity removal, the mixture is mixed to be uniform, and purified smelting slag is obtained. The level of toxic elements leached from the treated smelting slag meets the standard of common solid waste.

Description

Technical Field

[0001] The invention relates to the technical field of preparing lithium carbonate from lepidolite, and in particular to a method for removing beryllium from lithium carbonate smelting slag. Background Art

[0002] Beryllium is a harmful metal element, listed as a Class I carcinogen, and is excreted from human tissues at an extremely slow rate. Lithium carbonate smelting slag is industrial waste residue produced in the process of preparing lithium carbonate from lepidolite. However, lithium carbonate smelting slag contains highly toxic beryllium, and untreated lithium carbonate smelting slag cannot be identified as general solid waste.

[0003] The methods for removing beryllium generally include precipitation, adsorption, and heat treatment. The precipitation method removes beryllium by adding alkaline substances or other anionic salts to form insoluble precipitates with beryllium ions, which is generally suitable for removing beryllium from water. The adsorption method uses adsorbents to adsorb beryllium ions in solid waste to achieve beryllium removal. The heat treatment method converts beryllium-containing waste slag into stable glassy substances or other stable forms through high-temperature smelting or calcination, reducing the volatilization and leaching of beryllium.

[0004] The traditional method of removing beryllium from smelting slag is mainly aimed at the steel industry, etc., while the smelting slag produced in the lithium extraction process of lepidolite, especially the smelting slag obtained by high-temperature roasting of sulfate formula in tunnel kiln, contains different proportions of alkaline substances and concentration of leached beryllium from the traditional steel industry, lead and zinc industry, etc. Therefore, it is urgent to develop a method to remove beryllium from lithium carbonate smelting slag, which is of great significance for environmental governance and sustainable development in the field of lithium extraction from lepidolite. Summary of the invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a method for removing beryllium element from lithium carbonate smelting slag.

[0006] The present invention provides a method for removing beryllium from lithium carbonate smelting slag, comprising the following steps:

[0007] S1, adding solvent to lithium carbonate smelting slag for washing, filtering to obtain a primary leachate and a primary impurity-removed smelting slag;

[0008] S2, adding a solvent to the smelting slag after primary impurity removal, adding a complex, adding a pH adjuster to adjust the pH, stirring, filtering, and obtaining a secondary leaching solution and a smelting slag after secondary impurity removal;

[0009] S3, adding solvent to the smelting slag after secondary impurity removal, stirring, filtering, and obtaining a tertiary leaching solution and tertiary impurity removal smelting slag;

[0010] S4. Add phosphate and adsorbent to the smelting slag after three times of impurity removal and mix them evenly to obtain purified smelting slag.

[0011] The present invention first utilizes a washing step to remove most of the soluble beryllium ions, and then adds a complex beryllium removal agent to perform deep beryllium removal. The subsequent addition of phosphate and an adsorbent can further solidify the residual soluble beryllium, reduce the dissolution of beryllium under acidic conditions, and after the purified smelting slag is subjected to toxic leaching, the level of leached toxic elements meets the general solid waste standard.

[0012] Preferably, in S1, the mesh size of the lithium carbonate smelting slag is less than 60 meshes.

[0013] Preferably, in S1 and S2, the solvent is water.

[0014] Preferably, in said S1, the mass ratio of lithium carbonate smelting slag to solvent is 1:(1-2).

[0015] Controlling the washing of lithium carbonate smelting slag and solvent within a certain mass ratio range is helpful to preliminarily remove beryllium with the most economical amount of water.

[0016] Preferably, in said S1, the pH of the primary leaching solution is 6.5-10.5.

[0017] The pH of the primary leachate within a certain range is conducive to the subsequent reaction to proceed fully.

[0018] Preferably, in S2, the mass ratio of the solvent to the smelting slag after primary impurity removal is 2:1.

[0019] Preferably, in S2, the complex is selected from one or more of trisodium citrate and sodium tartrate.

[0020] The complex is added for deep beryllium removal. The complex has a strong complexing ability for beryllium ions, and can complex and expose some soluble beryllium ions to the leachate. The generated beryllium ion complex is relatively stable under weak alkaline or neutral conditions.

[0021] Preferably, in the S2, after the complex is added, the reaction is stirred at 20-30° C. for 15-30 min.

[0022] Preferably, in S2, the pH is adjusted to 6-8.

[0023] Preferably, in S2, the pH regulator is selected from one or more of 5% sulfuric acid solution, 3% sulfuric acid solution, and acetic acid-sodium acetate buffer solution.

[0024] Selecting different types of pH adjusters to adjust the pH to 6-8 will help the reaction proceed fully.

[0025] Preferably, in S2, when the beryllium concentration in the primary leaching solution is <100 μg / L, 2-3‰ of the mass of the smelting slag after the primary impurity removal is added; when the beryllium concentration in the primary impurity removal solution is ≥100 μg / L, 4-5‰ of the mass of the smelting slag after the primary impurity removal is added.

[0026] By varying the concentration of beryllium in the primary leaching solution, adding different amounts of complex beryllium removers helps to preliminarily remove the beryllium with the most economical dosage. The amount of complex used is small, which reduces costs, and the complex will not remain in the solid.

[0027] Preferably, in said S2, the concentration of beryllium in the secondary leaching solution is 1000-2000 μg / L.

[0028] Preferably, in S3, when the beryllium concentration in the primary leachate is <100 μg / L, the solvent and the smelting slag after secondary impurity removal are washed at a mass ratio of 1.5:1, and the pH is adjusted to 6.5-10.5; when the beryllium concentration in the primary leachate is ≥100 μg / L, the solvent and the smelting slag after secondary impurity removal are washed at a mass ratio of 2.5:1, and the pH is adjusted to 6.5-10.5, and the solid-liquid separation is repeated once, and a tertiary leachate is obtained after the secondary washing; the beryllium concentration in the tertiary leachate is 10-20 μg / L.

[0029] When the concentration of beryllium in the primary leaching solution is different, washing with solvents of different mass ratios is helpful to preliminarily remove the complexed beryllium with the most economical amount of water.

[0030] Preferably, in the step S3, after adding the solvent, the reaction is stirred at 20-30° C. for 15-30 min.

[0031] Preferably, in S4, the phosphate and the adsorbent are added in the form of solids and need to be crushed to less than 60 meshes.

[0032] Preferably, in the S4, the mass of the phosphate is 4-5‰ of the mass of the smelting slag after the three impurities removal, and the mass of the adsorbent is 8-9‰ of the mass of the smelting slag after the three impurities removal.

[0033] The mass fraction of phosphate and adsorbent can further solidify the residual soluble beryllium within a certain range and reduce the dissolution of beryllium under acidic conditions.

[0034] Preferably, in S4, the phosphate is selected from one or more of sodium phosphate, potassium phosphate, calcium hydrogen phosphate and calcium dihydrogen phosphate.

[0035] Preferably, in S4, the adsorbent is selected from one or more of polyferric sulfate, polyferric chloride, polyaluminum sulfate, and sodium hexametaphosphate.

[0036] Preferably, in said S4, the concentration of beryllium leached in the toxic leaching test of the purified smelting slag is ≤20 μg / L.

[0037] The beneficial effects of the present invention are:

[0038] The method for removing beryllium from lithium carbonate smelting slag provided by the present invention has a high removal depth of beryllium, does not require additional heating and roasting, and after the purified smelting slag is subjected to toxic leaching, the level of leached toxic elements meets the general solid waste standard. The entire process of the present invention realizes rapid impurity removal, generates less secondary pollution, and has low requirements on equipment. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail through specific embodiments.

[0040] Unless otherwise specified, the materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources.

[0041] The steps of toxic leaching are as follows: 1) Dry the solid to be tested, take a 50g sample and dry it at 105℃; 2) Add 5.7ml of glacial acetic acid to 500ml of reagent water, add 64.3ml of 1mol sodium hydroxide, and dilute to 1L. Prepare an extractant with a pH of 4.93. 3) Place the solid to be tested in a 2L extraction bottle, add 1L of extractant, cover the bottle cap tightly, and fix it on a flip-type oscillating device, adjust the speed to 30±2r / min, and oscillate at 23±2℃ for 18±2h.

[0042] The concentration determination method of beryllium element is as follows: 1) For solutions with an estimated concentration greater than 20μg / L, sample 5mL and dilute to a 100mL volumetric flask for the next concentration determination. For solutions with an estimated concentration less than 20μg / L, directly proceed to the next concentration determination; 2) Draw a standard curve at a mass-to-charge ratio of 9.012 on ICP-MS (4 points in total: 0.00μg / L, 5.00μg / L, 10.0μg / L, 20.0μg / L, the linear coefficient is not less than 0.999, and the calibration error of each point does not exceed 2%); the concentration of the standard series solution is 0.00μg / L, 5.00μg / L, 10.0μg / L, 20.0μg / L 2% nitric acid medium beryllium sulfate (II) standard solution. 3) Filter the solution in step 1) with a sand core funnel and measure it on ICP-MS. The radio frequency power of the inductively coupled plasma atomic emission spectrometer was 1000 W, the plasma gas flow rate was 10 L / min, the carrier gas flow rate was 0.90 L / min, the auxiliary gas flow rate was 1.2 L / min, and the spray chamber temperature was 2 ° C. Three parallel measurements were taken and the average value was taken as the final concentration reading.

[0043] Example 1

[0044] A method for removing beryllium from lithium carbonate smelting slag comprises the following steps:

[0045] S1. Add water of equal mass to the lithium carbonate smelting slag with a beryllium concentration of 206.1 μg / L in the leachate after toxic leaching, stir and react for 10 minutes, and filter through a belt filter to obtain a primary leachate and a primary impurity-removed smelting slag; the beryllium concentration in the primary leachate is detected to be 13.3 μg / L;

[0046] S2, mixing water and the smelting slag after the primary impurity removal in a mass ratio of 2:1, adding 2.5‰ trisodium citrate accounting for the mass fraction of the smelting slag after the primary impurity removal, adding 5% sulfuric acid to maintain the pH at 8.0, stirring and reacting for 20 minutes, filtering through a belt filter to obtain a secondary leachate and the smelting slag after the secondary impurity removal; detecting the beryllium concentration in the secondary leachate to be 1055.1μg / L;

[0047] S3, mixing water and the smelting slag after secondary impurity removal in a mass ratio of 1.5:1, stirring for 15 minutes, filtering through a belt filter, and obtaining a tertiary leaching solution and tertiary impurity-removed smelting slag; detecting the beryllium concentration in the tertiary leaching solution to be 16.0 μg / L;

[0048] S4. Add 4‰ calcium dihydrogen phosphate and 8‰ sodium hexametaphosphate to the smelting slag after three times of impurity removal, mix and slurry to obtain purified smelting slag.

[0049] The purified smelting slag in S4 was taken for toxic leaching experiment and the leachate was tested. The results showed that the concentration of beryllium in the leachate was 11.9 μg / L, which indicated that the purified smelting slag was a general solid waste.

[0050] Example 2

[0051] A method for removing beryllium from lithium carbonate smelting slag comprises the following steps:

[0052] S1. Add water of equal mass to the lithium carbonate smelting slag with a beryllium concentration of 455.0 μg / L in the leachate after toxic leaching, stir and react for 10 minutes, and filter through a belt filter to obtain a primary leachate and a primary impurity-removed smelting slag; the beryllium concentration in the primary leachate is detected to be 115.3 μg / L;

[0053] S2, mixing water and the smelting slag after the primary impurity removal in a mass ratio of 2:1, adding trisodium citrate accounting for 4‰ of the mass fraction of the smelting slag after the primary impurity removal, adding acetic acid-sodium acetate buffer solution with a pH of 6 to maintain the pH at 8.0, stirring the reaction for 20 minutes, filtering through a belt filter to obtain a secondary leachate and the smelting slag after the secondary impurity removal; detecting the concentration of beryllium in the secondary leachate to be 1841.0 μg / L;

[0054] S3, mixing water and the smelting slag after secondary impurity removal in a mass ratio of 2.5:1, stirring for 15 minutes, filtering through a belt filter, and obtaining a tertiary leachate and tertiary impurity-removed smelting slag; detecting the beryllium concentration in the tertiary leachate to be 11.1 μg / L;

[0055] S4. Add 5‰ calcium dihydrogen phosphate and 9‰ sodium hexametaphosphate to the smelting slag after three times of impurity removal, mix and slurry to obtain purified smelting slag.

[0056] The purified smelting slag in S4 was taken for toxic leaching experiment and the leachate was tested. The results showed that the concentration of beryllium in the leachate was 14.3 μg / L, which indicated that the purified smelting slag was a general solid waste.

[0057] Example 3

[0058] A method for removing beryllium from lithium carbonate smelting slag comprises the following steps:

[0059] S1. Add water of equal mass to the lithium carbonate smelting slag with a beryllium concentration of 590.7 μg / L in the leachate after toxic leaching, stir and react for 10 minutes, and filter through a belt filter to obtain a primary leachate and a primary impurity-removed smelting slag; the beryllium concentration in the primary leachate is detected to be 177.0 μg / L;

[0060] S2, mixing water and the smelting slag after the primary impurity removal in a mass ratio of 2:1, adding trisodium citrate accounting for 4‰ of the mass fraction of the smelting slag after the primary impurity removal, adding acetic acid-sodium acetate buffer solution with a pH of 6 to maintain the pH at 8.0, stirring the reaction for 20 minutes, filtering through a belt filter to obtain a secondary leachate and the smelting slag after the secondary impurity removal; detecting the concentration of beryllium in the secondary leachate to be 2423.6μg / L;

[0061] S3, mixing water and the smelting slag after secondary impurity removal in a mass ratio of 2.5:1, stirring for 15 minutes, filtering through a belt filter, and obtaining a tertiary leachate and tertiary impurity-removed smelting slag; detecting the beryllium concentration in the tertiary leachate to be 13.2 μg / L;

[0062] S4. Add 5‰ calcium dihydrogen phosphate and 9‰ sodium hexametaphosphate to the smelting slag after three times of impurity removal, mix and slurry to obtain purified smelting slag.

[0063] The purified smelting slag in S4 was taken for toxic leaching experiment and the leachate was tested. The results showed that the concentration of beryllium in the leachate was 15.1 μg / L, which indicated that the purified smelting slag was a general solid waste.

[0064] Comparative Example 1

[0065] A method for removing beryllium from lithium carbonate smelting slag comprises the following steps:

[0066] S1. Add water of equal mass to the lithium carbonate smelting slag with a beryllium concentration of 206.1 μg / L in the leachate after toxic leaching, stir and react for 10 minutes, and filter through a belt filter to obtain a primary leachate and a primary impurity-removed smelting slag; the beryllium concentration in the primary leachate is detected to be 13.3 μg / L;

[0067] S2, mixing water and the smelting slag after primary impurity removal in a mass ratio of 2:1, adding 5% sulfuric acid to maintain the pH at 8.0, stirring and reacting for 20 minutes, filtering through a belt filter to obtain a secondary leachate and the smelting slag after secondary impurity removal; detecting the beryllium concentration in the secondary leachate to be 21.5 μg / L;

[0068] S3, mixing water and the smelting slag after secondary impurity removal in a mass ratio of 1.5:1, stirring for 15 minutes, filtering through a belt filter, and obtaining a tertiary leachate and tertiary impurity-removed smelting slag; detecting the beryllium concentration in the tertiary leachate to be 4.1 μg / L;

[0069] S4. Add 4‰ calcium dihydrogen phosphate and 8‰ sodium hexametaphosphate to the smelting slag after three times of impurity removal, mix and slurry to obtain purified smelting slag.

[0070] The purified smelting slag in S4 was taken for toxic leaching experiment, and the leachate was tested. The results showed that the concentration of beryllium in the leachate was 33.1 μg / L.

[0071] Comparative Example 2

[0072] The difference between Comparative Example 2 and Example 1 is that S4 is different: first, S1-S3 are carried out according to Example 1, and S4 is to add 8‰ sodium hexametaphosphate to the smelting slag after three impurity removals to mix and slurry, so as to obtain purified smelting slag.

[0073] The purified smelting slag in S4 was taken for toxicity leaching experiment, and the leachate was tested. The results showed that the concentration of beryllium in the leachate was 22.7 μg / L.

[0074] Comparative Example 3

[0075] The difference between Comparative Example 3 and Example 1 is that S4 is different: first, S1-S3 are carried out according to Example 1, and S4 is to add 4‰ calcium dihydrogen phosphate to the smelting slag after three impurity removals to mix and slurry, so as to obtain purified smelting slag.

[0076] The purified smelting slag in S4 was taken for toxicity leaching experiment, and the leachate was tested. The results showed that the concentration of beryllium in the leachate was 35.2 μg / L.

[0077] The level of toxic elements leached from the smelting slag treated by the method for removing beryllium from lithium carbonate smelting slag of the present invention meets the general solid waste standards. From the data of comparative example 1 and the embodiment, it can be seen that no complex was added in step S2 of comparative example 1, and the concentration of beryllium in the leaching solution of the purified smelting slag was relatively high, indicating that the addition of the complex in the present invention can promote the beryllium removal effect. From the data of comparative examples 2-3 and the embodiment, it can be seen that the synergistic effect of the use of phosphate and adsorbent in the present invention helps to promote the beryllium removal effect.

[0078] In summary, the method for removing beryllium from lithium carbonate smelting slag provided by the present invention can achieve rapid impurity removal, generate less secondary pollution, and the level of toxic elements leached from the treated smelting slag meets the general solid waste standards.

[0079] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for removing beryllium from lithium carbonate smelting slag, characterized in that: The following steps are involved: S1, adding solvent to lithium carbonate smelting slag for washing, filtering to obtain a primary leachate and a primary impurity-removed smelting slag; S2, adding a solvent to the smelting slag after primary impurity removal, adding a complex, adding a pH adjuster to adjust the pH, stirring, filtering, and obtaining a secondary leaching solution and a smelting slag after secondary impurity removal; S3, adding solvent to the smelting slag after secondary impurity removal, stirring, filtering, and obtaining a tertiary leaching solution and tertiary impurity removal smelting slag; S4. Add phosphate and adsorbent to the smelting slag after three times of impurity removal and mix them evenly to obtain purified smelting slag.

2. The method according to claim 1, characterized in that In the S1, the mass ratio of lithium carbonate smelting slag to solvent is 1:(1-2).

3. The method according to claim 1, characterized in that In the S1, the pH of the primary leaching solution is 6.5-10.

5.

4. The method according to claim 1, characterized in that: In the S2, the complex is selected from one or more of trisodium citrate and sodium tartrate.

5. The method according to claim 1, characterized in that In the S2, the pH regulator is selected from one or more of 5% sulfuric acid solution, 3% sulfuric acid solution, and acetic acid-sodium acetate buffer solution.

6. The method according to claim 1, characterized in that In the S2, when the beryllium concentration in the primary leaching solution is <100 μg / L, 2-3‰ of the mass of the smelting slag after the primary impurity removal is added; when the beryllium concentration in the primary impurity removal solution is ≥100 μg / L, 4-5‰ of the mass of the smelting slag after the primary impurity removal is added.

7. The method according to claim 1, characterized in that In the S3, when the beryllium concentration in the primary leachate is <100 μg / L, the solvent and the smelting slag after secondary impurity removal are washed at a mass ratio of 1.5:1, and the pH is adjusted to 6.5-10.5; when the beryllium concentration in the primary leachate is ≥100 μg / L, the solvent and the smelting slag after secondary impurity removal are washed at a mass ratio of 2.5:1, and the pH is adjusted to 6.5-10.

5.

8. The method according to claim 1, characterized in that: In the S4, the mass of the phosphate is 4-5‰ of the mass of the smelting slag after the three impurities removal, and the mass of the adsorbent is 8-9‰ of the mass of the smelting slag after the three impurities removal.