Treatment method for extracting lithium from lepidolite and thallium-containing tailings

Abstract

The invention relates to the technical field of pollution-free treatment of industrial waste residues, in particular to a treatment method of thallium-containing tailings obtained by extracting lithium from lepidolite. The method comprises the following steps: mixing the lepidolite lithium extraction thallium-containing tailings with an acid solution, sequentially carrying out three times of stirring reaction, mixing with nano-iron, adjusting the pH value to 10.0, and carrying out adsorption and solid-liquid separation to realize treatment of the lepidolite lithium extraction thallium-containing tailings. According to the method, efficient removal of thallium in the tailings (the leaching toxicity is smaller than 0.1 mg / L, and the removal rate is larger than 99%) is achieved through the acid rinsing-nano iron adsorption coupling technology, meanwhile, a wastewater closed-loop circulation system is constructed, and the treatment cost of each ton of slag is reduced to 300 yuan or below.

Description

Technical Field

[0001] The present invention relates to the technical field of pollution-free treatment of industrial waste residues, and particularly to a method for treating thallium-containing tailings from lithium extraction from lepidolite. Background Art

[0002] In the process of lithium extraction from lepidolite, 8-12 tons of tailings are generated for every 1 ton of lithium carbonate produced. Thallium (TI + ) is mainly enriched in the tailings in the form of soluble thallium sulfate (TI2SO4). The thallium-containing tailings need to be disposed of as hazardous waste, and the comprehensive treatment cost exceeds 1000 yuan / ton. Solidification and stabilization: adding cement and chelating agents to fix thallium, but the volume increases by 35%, and the long-term stability is poor; sulfide precipitation: adding Na2S to generate TI2S precipitation, but the ORP needs to be strictly controlled < -100 mV, and H2S is generated; iron salt coprecipitation: Fe 3+ competes with TI + for adsorption, and excessive reagents need to be added, resulting in an increase in the amount of sludge. The thallium-containing tailings (thallium leaching concentration reaches 2.5-15 mg / L) generated in the process of lithium extraction from lepidolite are listed as hazardous wastes (the limit value of GB 5085.3-2007 is 0.005 mg / L). The traditional treatment technologies have the following problems: 1. High cost: The solidification and stabilization method needs to add 15%-20% of cement-based materials, and the treatment cost per ton of tailings > 800 yuan; 2. Low efficiency: The thallium removal rate of the conventional iron salt precipitation method is only 60%-75%; 3. Safety hazards: The sulfide precipitation method generates H2S gas, and the operation risk is high. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides a method for treating thallium-containing tailings from lithium extraction from lepidolite. Through the acid rinsing-nano iron adsorption coupling process, the present invention realizes the efficient removal of thallium in the tailings (leaching toxicity < 0.005 mg / L), and at the same time constructs a closed-circuit wastewater recycling system, reducing the treatment cost per ton of tailings to less than 300 yuan.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a method for treating thallium-containing tailings from lithium extraction from lepidolite, comprising the following steps:

[0006] 1) Mix the thallium-containing tailings from lithium extraction from lepidolite with acid solution and carry out a first-stage stirring reaction, then carry out solid-liquid separation to obtain a precipitate and a first-stage waste liquid;

[0007] 2) Mix the precipitate obtained in step 1) with acid solution and carry out a second-stage stirring reaction, then carry out solid-liquid separation to obtain a precipitate and a second-stage waste liquid;

[0008] 3) Mix the precipitate obtained in step 2) with acid solution and carry out a third-stage stirring reaction, then carry out solid-liquid separation to obtain a precipitate and a third-stage waste liquid;

[0009] 4) Mix the primary waste liquid obtained in step 1) and the secondary waste liquid obtained in step 2) to obtain a mixed liquid;

[0010] 5) Mix the mixed liquid obtained in step 4) with nano-iron, adjust the pH value to 10.0, then perform adsorption, and carry out solid-liquid separation to achieve the treatment of the thallium-containing tailings from lepidolite for lithium extraction.

[0011] Further, the acid solution includes one or more of sulfuric acid solution, hydrochloric acid solution and nitric acid solution, and the pH value of the acid solution is 2.0.

[0012] Further, the solid-liquid ratio of the thallium-containing tailings from lepidolite for lithium extraction to the acid solution in step 1) is 1:2;

[0013] The solid-liquid ratio of the precipitate in step 2) to the acid solution is 1:2;

[0014] The solid-liquid ratio of the precipitate in step 3) to the acid solution is 1:2.

[0015] Further, the time of the primary stirring reaction in step 1), the secondary stirring reaction in step 2) and the tertiary stirring reaction in step 3) is all 30 min, and the rotation speed is all 60 - 150 rpm.

[0016] Further, the average particle size of the nano-iron in step 5) is within 100 nm, and the specific surface area is above 12 m 2 / g.

[0017] Further, the addition amount of the nano-iron in step 5) is 0.3 - 0.6 g / L.

[0018] Further, the adsorption time in step 5) is 60 min, and the rotation speed is 60 - 150 rpm.

[0019] Further, the precipitate obtained by solid-liquid separation in step 5) is regenerated by a mixed solution of citric acid and ascorbic acid to obtain nano-iron.

[0020] Further, the mass percentage content of citric acid in the mixed solution is 5%, and the concentration of ascorbic acid is 0.1 mol / L.

[0021] Further, the time of the regeneration treatment is 2 h.

[0022] Beneficial effects:

[0023] Through the acidic rinsing - nano-iron adsorption coupling process, the present invention realizes the efficient removal of thallium in the tailings (the leaching toxicity < 0.005 mg / L, the removal rate > 99%). At the same time, a closed-circuit wastewater recycling system is constructed to reduce the treatment cost per ton of tailings to less than 300 yuan.

[0024] 1. Gradient countercurrent pickling process: Improve the thallium dissolution efficiency and reduce acid consumption through three-stage series rinsing;

[0025] 2. Closed-loop water circulation system: The wastewater reuse rate is 100%, reducing the fresh water consumption by 90%;

[0026] 3. Citric acid - ascorbic acid regeneration method: An environmentally friendly regenerant to avoid the corrosion of equipment by strong acids / alkalis.

[0027] The present invention can also be system-configured as follows:

[0028] Pickling module: A three-stage series reaction tank equipped with an on-line pH monitoring and automatic acid addition system;

[0029] Adsorption tower: Filled with nano-iron materials, and provided with multiple filtering layers to prevent material loss;

[0030] Water circulation pipeline: Integrated with an H2SO4 callback unit and a resin protection unit. Description of the Drawings

[0031] Figure 1 It is the technical route of the present invention.

[0032] Figure 2 It is the surface element distribution of the treated nano-iron material. It can be seen from the figure that a large amount of oxidation appears on the surface of the treated nano-iron material, and the thallium element is evenly distributed on the material surface, indicating that the nano-iron material can effectively remove the thallium element in the wastewater.

[0033] Figure 3 It is the XRD detection and analysis of the treated nano-iron material. It can be seen from the figure that the thallium element mainly exists in the form of TI2O3 and TIFeO2 on the material surface, indicating that its removal is the combined effect of surface physical adsorption and chemical adsorption. A large amount of thallium-containing compounds are detected on the surface of the treated nano-iron material, indicating that a large amount of thallium element in the wastewater has been removed and carried away. Detailed Embodiments

[0034] The present invention provides a method for treating thallium-containing tailings from lithium mica for lithium extraction, including the following steps:

[0035] 1) Mix the thallium-containing tailings from lithium mica for lithium extraction with an acid solution and carry out a primary stirring reaction, then perform solid-liquid separation to obtain a precipitate and a primary waste liquid;

[0036] 2) Mix the precipitate obtained in step 1) with an acid solution and carry out a secondary stirring reaction, then perform solid-liquid separation to obtain a precipitate and a secondary waste liquid;

[0037] 3) Mix the precipitate obtained in step 2) with an acid solution and carry out a tertiary stirring reaction, then perform solid-liquid separation to obtain a precipitate and a tertiary waste liquid;

[0038] 4) Mix the primary waste liquid obtained in step 1) and the secondary waste liquid obtained in step 2) to obtain a mixed liquid;

[0039] 5) Mix the mixed liquid obtained in step 4) with nano-iron, adjust the pH value to 10.0, then perform adsorption, and carry out solid-liquid separation to achieve the treatment of the thallium-containing tailings from lithium mica lithium extraction.

[0040] In the present invention, the thallium-containing tailings from lithium mica lithium extraction are mixed with an acid solution and then subjected to a primary stirring reaction, followed by solid-liquid separation to obtain a precipitate and a primary waste liquid. In the present invention, the acid solution preferably includes one or more of a sulfuric acid solution, a hydrochloric acid solution, and a nitric acid solution, and the pH value of the acid solution is 2.0. In the present invention, the solid-liquid ratio of the thallium-containing tailings from lithium mica lithium extraction to the acid solution is preferably 1:2. In the present invention, the time of the primary stirring reaction is preferably 30 min, and the rotation speed is preferably 60-150 rpm.

[0041] In the present invention, the obtained precipitate is mixed with an acid solution and then subjected to a secondary stirring reaction, followed by solid-liquid separation to obtain a precipitate and a secondary waste liquid. In the present invention, the acid solution preferably includes one or more of a sulfuric acid solution, a hydrochloric acid solution, and a nitric acid solution, and the pH value of the acid solution is 2.0. In the present invention, the solid-liquid ratio of the precipitate to the acid solution is preferably 1:2. In the present invention, the time of the secondary stirring reaction is preferably 30 min, and the rotation speed is preferably 60-150 rpm.

[0042] In the present invention, the obtained precipitate is mixed with an acid solution and then subjected to a tertiary stirring reaction, followed by solid-liquid separation to obtain a precipitate and a tertiary waste liquid. In the present invention, the acid solution preferably includes one or more of a sulfuric acid solution, a hydrochloric acid solution, and a nitric acid solution, and the pH value of the acid solution is 2.0. In the present invention, the solid-liquid ratio of the precipitate to the acid solution is preferably 1:2. In the present invention, the time of the tertiary stirring reaction is preferably 30 min, and the rotation speed is preferably 100 rpm.

[0043] In the present invention, the obtained primary waste liquid and the obtained secondary waste liquid are mixed to obtain a mixed liquid.

[0044] In the present invention, the obtained mixed liquid is mixed with nano-iron, the pH value is adjusted to 10.0, then adsorption is carried out, and solid-liquid separation is carried out to achieve the treatment of the thallium-containing tailings from lithium mica lithium extraction. In the present invention, the average particle size of the nano-iron is preferably within 100 nm, the specific surface area is preferably above 12 m 2 / g, and the surface hydroxyl groups (-OH) react with TI at pH = 9.5-10.5 +Specific complexation. In the present invention, the addition amount of the nano-iron is preferably 0.3 - 0.6 g / L. In the present invention, the adsorption time is preferably 60 min, and the rotation speed is preferably 100 rpm. In the present invention, the precipitate obtained by solid-liquid separation is preferably regenerated by a mixed solution of citric acid and ascorbic acid to obtain nano-iron. In the present invention, the mass percentage content of citric acid in the mixed solution is preferably 5%, and the concentration of ascorbic acid is preferably 0.1 mol / L. In the present invention, the regeneration treatment time is preferably 2 h.

[0045] To further illustrate the present invention, the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0046] Example 1

[0047] 1. Gradient pickling for thallium dissolution

[0048] Acid source preparation: Adjust the pH value of the sulfuric acid solution to 2.0, and set the liquid-solid ratio to 4:1 (that is, 4 tons of acid solution are added per ton of tailings).

[0049] Three-stage countercurrent rinsing:

[0050] First reaction tank: The thallium-containing tailings from lithium mica lithium extraction (thallium concentration is 15.2 mg / L) are mixed with the acid solution at a liquid-solid ratio of 1:2, stirred and reacted at 100 rpm for 30 minutes to dissolve soluble thallium (dissolution rate 70%), then solid-liquid separation is carried out, and the thallium concentration in the first-stage waste liquid is 5.2 mg / L.

[0051] Second reaction tank: After the first-stage reaction, the tailings are transferred to the second tank and mixed with the new acid solution, the liquid-solid ratio is 1:2, and the reaction continues for 30 minutes (the cumulative dissolution rate reaches 85%), and the thallium concentration in the second-stage waste liquid is 0.18 mg / L.

[0052] Third reaction tank: After the second-stage reaction, the tailings are transferred to the third tank and mixed with the new acid solution, the liquid-solid ratio is 1:2, and the final dissolution rate > 95%, and the thallium concentration in the third-stage waste liquid is 0.003 mg / L.

[0053] Solid-liquid separation: After pickling, the tailings are dehydrated by a filter press, and the thallium leaching toxicity is reduced to less than 0.005 mg / L (meeting the standard).

[0054] After solid-liquid separation, the wastewater from the third reaction tank is returned to the first reaction tank for reuse, and the wastewater from the first and second reaction tanks enters the next process and is subjected to nano-iron targeted adsorption.

[0055] 2. Nano-iron targeted adsorption

[0056] Adsorbent dosing: Nano iron particles (nZVI, average particle size 60 nm, specific surface area 22 m2 / g) were dosed into the pickling waste liquid (a mixture of primary wastewater and secondary wastewater, thallium concentration 2.7 mg / L) at 0.5 g / L, and the pH was adjusted to 10.0 (controlled by NaOH solution).

[0057] Reaction adsorption: Stir and react for 60 minutes at 100 rpm. The hydroxyl groups on the surface of nano iron complex with TI + The thallium concentration drops from 2.7 mg / L to 0.005 mg / L, and the removal rate is 99.8%.

[0058] Solid-liquid separation: The wastewater after adsorption passes through a multi-stage filtration tower (containing quartz sand and activated carbon layer) to remove residual nano iron particles, and the concentration of Ti+ in the effluent is 0.0033 mg / L.

[0059] 3. Adsorbent regeneration and wastewater reuse

[0060] Regeneration treatment: Immerse the nano iron material separated by solid-liquid separation in a solution of 5% citric acid + 0.1 M ascorbic acid for 2 hours. The regeneration efficiency is > 85%, and the adsorption performance is still > 80% after repeated use 5 times.

[0061] Table 1 Post-treatment data of regenerated nano iron

[0062]

[0063] Note: This experiment mainly detects the effect of the regenerated material. Relying solely on the regenerated material cannot achieve up-to-standard drainage. Therefore, after the regeneration treatment, 10% of new material will be added to ensure the removal effect

[0064] Wastewater recycling: The pH of the wastewater after adsorption is adjusted back to 2.0 (supplemented with waste sulfuric acid), and it is deeply treated by Lewatit TP260 resin (Tl+ < 0.001 mg / L) and reused in the lithium leaching process to achieve closed-loop circulation.

[0065] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. People can also obtain other embodiments based on these embodiments without creative work, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for treating lithium mica lithium-extracting thallium-containing tailings, characterized in that, It includes the following steps: 1) Mix the thallium-containing tailings from lithium extraction of lepidolite with acid solution and conduct a primary stirring reaction, then perform solid-liquid separation to obtain a precipitate and a primary waste liquid; 2) Mix the precipitate obtained in the step 1) with acid solution and conduct a secondary stirring reaction, then perform solid-liquid separation to obtain a precipitate and a secondary waste liquid; 3) Mix the precipitate obtained in the step 2) with acid solution and conduct a tertiary stirring reaction, then perform solid-liquid separation to obtain a precipitate and a tertiary waste liquid; 4) Mix the primary waste liquid obtained in the step 1) and the secondary waste liquid obtained in the step 2) to obtain a mixed liquid; 5) Mix the mixed liquid obtained in the step 4) with nano-iron, adjust the pH value to 10.0 and then conduct adsorption, and perform solid-liquid separation to achieve the treatment of the thallium-containing tailings from lithium extraction of lepidolite.

2. The processing method according to claim 1, characterized in that, The acid solution includes one or several of sulfuric acid solution, hydrochloric acid solution and nitric acid solution, and the pH value of the acid solution is 2.

0.

3. The processing method according to claim 1, wherein The solid-liquid ratio of the thallium-containing tailings from lithium extraction of lepidolite to the acid solution in the step 1) is 1:2; The solid-liquid ratio of the precipitate to the acid solution in the step 2) is 1:2; The solid-liquid ratio of the precipitate to the acid solution in the step 3) is 1:

2.

4. The processing method according to claim 1, characterized in that, The time of the primary stirring reaction in the step 1), the secondary stirring reaction in the step 2) and the tertiary stirring reaction in the step 3) is all 30 min, and the rotation speed is all 60 - 150 rpm.

5. The processing method according to claim 1, characterized in that, In step 5), the average particle size of the nano-iron is within 100 nm, and the specific surface area is above 12 m 2 / g.

6. The processing method according to claim 1, wherein The addition amount of nano-iron in the step 5) is 0.3 - 0.6 g / L.

7. The processing method according to claim 1, characterized in that, The adsorption time in the step 5) is 60 min, and the rotation speed is 60 - 150 rpm.

8. The processing method according to claim 1, characterized in that The precipitate obtained by solid-liquid separation in the step 5) is regenerated by a mixed solution of citric acid and ascorbic acid to obtain nano-iron.

9. The processing method according to claim 8, wherein The mass percentage content of citric acid in the mixed solution is 5%, and the concentration of ascorbic acid is 0.1 mol / L.

10. The processing method according to claim 8, characterized in that The time of the regeneration treatment is 2 h.

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