Thallium-containing lithium slag treatment method and device based on chemical leaching and biological mineralization

Abstract

The invention discloses a thallium-containing lithium slag treatment method and device based on chemical leaching and biological mineralization, and the method comprises the following steps: carrying out ore blending on thallium-containing lithium slag and a leaching agent, grinding in a sampling machine, uniformly mixing, and carrying out ball milling to obtain blended slag; leaching the prepared slag in water to obtain water-leached ore pulp; carrying out solid-liquid separation on the water-leached ore pulp to obtain elution residues and leachate; refluxing the leachate for cyclic utilization; inoculating a thallium-fixing microbial inoculum into the leachate with the thallium concentration higher than 20mg / L, and carrying out biochemical mineralization reaction to obtain biochemical ore pulp; carrying out solid-liquid separation on the biochemical ore pulp to obtain solid thallium slag and leaching tail liquid; and leaching tail liquid is subjected to membrane filtration. By the adoption of the method and device, the ecological environment risk caused by migration of thallium in the lithium slag is relieved, and enrichment and extraction of thallium are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium slag treatment, and in particular to a method and device for treating thallium-containing lithium slag based on chemical leaching and biological mineralization. Background Art

[0002] Lithium slag is an industrial solid waste produced by lithium extraction processes such as calcination of spodumene or lepidolite with sulfuric acid / calcium carbonate-water leaching. With the rapid development of the new energy industry, the growing demand for lithium raw materials such as lithium carbonate and lithium hydroxide has led to an intensification of lithium smelting activities, and about 600,000 tons of lithium slag are produced annually worldwide. Thallium is a rare heavy metal element associated with lithium, sodium and other elements in spodumene and lepidolite. It is highly toxic, mobile and latent. Thallium is often found in aluminosilicate structures in lithium ore. It is enriched in lithium slag during the lithium smelting process. As the dense structure of lithium slag dissociates, its environmental migration risk increases significantly, which can cause human health and ecological pollution crises.

[0003] At present, the main treatment methods for lithium slag are landfill or open-air storage, and only a very small amount is recycled, such as as cement admixture, concrete admixture, zeolite synthesis raw material, etc. These treatment methods also face health and ecological risks caused by the migration of heavy metal thallium pollution. Therefore, it is a necessary prerequisite for further resource utilization of lithium slag to efficiently separate thallium from thallium-containing lithium slag and eliminate the ecological and environmental risks caused by the migration of thallium in lithium slag. The existing technology lacks such process methods. Summary of the invention

[0004] Based on the technical problems raised in the background technology, the purpose of the present invention is to provide a method and device for treating thallium-containing lithium slag based on chemical leaching and biomineralization, so as to eliminate the ecological and environmental risks caused by the migration of thallium in lithium slag and realize the enrichment and extraction of thallium.

[0005] The present invention proposes a method for treating thallium-containing lithium slag based on chemical leaching and biomineralization, comprising the following steps:

[0006] (1) blending the thallium-containing lithium slag with a leaching agent, grinding and uniformly mixing in a sample preparation machine, and then ball milling to obtain blended slag;

[0007] (2) leaching the slag obtained in step (1) into water to obtain a water-leached slurry;

[0008] (3) separating the solid and liquid of the water-leached slurry obtained in step (2) to obtain eluted slag and leachate;

[0009] (4) returning the leachate from step (3) to step (2) for recycling until the thallium concentration in the leachate is higher than 50 mg / L;

[0010] (5) inoculating a thallium-fixing bacterial agent into the leaching solution with a thallium concentration higher than 20 mg / L obtained in step (4), and obtaining a biochemical slurry through a biochemical mineralization reaction;

[0011] (6) separating the solid and liquid of the biochemical slurry obtained in step (5) to obtain solid thallium slag and leaching tailings;

[0012] (7) The leaching tail liquid obtained in step (6) is filtered through a -0.22 μm membrane.

[0013] Furthermore, the leaching agent described in step (1) includes at least one of citric acid, oxalic acid, lactic acid and acetic acid.

[0014] Furthermore, the ball milling conditions described in step (1) are: ball to material ratio 2.5 to 4:1, rotation speed 300 to 600 rpm / min, and ball milling time 0.5 to 3 h.

[0015] Furthermore, the mass ratio of the substances in the slag blend described in step (1) is: lithium slag: leaching agent = 14 to 24:1.

[0016] Furthermore, the water immersion conditions in step (2) are as follows: a liquid-to-solid ratio of 5 to 15 mL / g, a leaching temperature of 20 to 60° C., and a leaching time of 30 to 90 min.

[0017] Furthermore, the leaching solution obtained in step (3) is returned to step (2) for recycling when the thallium concentration is not greater than 50 mg / L.

[0018] Furthermore, the community composition of the thallium-fixing bacteria agent described in step (5) mainly includes Baccilus substilus, Baccilus cohnni, Baccilus cereus, Sporosarcina pasteurii, and Baccilus sphaericus.

[0019] Furthermore, the biochemical reaction conditions in step (5) are as follows: temperature 15-35°C, microbial concentration 10 8 ~10 9 / mL, stirring speed 120~210rpm, dissolved oxygen concentration 0.5~4.5mg / L, pH 3.0~8.0.

[0020] Furthermore, the bacterial sludge obtained in step (7) is returned to step (5) for recycling; and the obtained filtrate is returned to (2) for recycling.

[0021] The invention discloses a device for treating thallium-containing lithium slag based on chemical leaching and biological mineralization, comprising a sample preparation machine, a slag water leaching device, a water leaching slurry solid-liquid separation device, a leaching liquid inoculation device, a biochemical slurry solid-liquid separation device and a tail liquid membrane filtration device.

[0022] The slag preparation of the present invention is a uniform mixture of lithium slag containing thallium and a leaching agent, which is ball-milled to activate the mineral lattice in the lithium slag and react with the leaching agent, and water-leached to release heavy metals such as thallium in the lithium slag into the liquid phase.

[0023] The eluted residue obtained after solid-liquid separation was tested through HJ / T299 "Toxicity Leaching Method for Solid Waste" and simulated acid rain leaching experiments to verify that the mobility of thallium was significantly reduced and the long-term stability of the eluted residue was verified.

[0024] The leachate obtained by solid-liquid separation is circulated into step (2) to leach the slag; when the thallium concentration in the leachate is higher than 50 mg / L, a thallium-fixing bacterial agent is inoculated therein. After the microorganisms adsorb thallium and form a shell on the surface (the microorganisms use the leaching agent as a carbon source, and calcium is dissolved in the leachate to mediate carbonate deposition), thallium is adsorbed and included in the carbonate shell or embedded in the carbonate shell, thereby achieving thallium enrichment and solidification.

[0025] The leaching liquid of the solid thallium slag is separated by solid-liquid filtration, and the obtained bacterial sludge can be refluxed for recycling.

[0026] When blending ores, the type of leaching agent needs to be regulated to ensure that the leaching agent can efficiently reduce, replace and complex thallium and promote the dissolution of thallium.

[0027] When blending the ore, the mass ratio of lithium slag: leaching agent needs to be regulated, and the mass ratio of the material is required to be: lithium slag: leaching agent = 14-24:1, so as to ensure that there is enough leaching agent to participate in the reduction, replacement and complexation of thallium, so that thallium can be efficiently dissolved. When the mass ratio of lithium slag: leaching agent exceeds 24:1, the excessive leaching agent will lead to increased dissolution of other heavy metal ions, inhibit the activity of thallium-fixing bacteria, and reduce the fixation rate of thallium.

[0028] During ball milling, the ball-to-material ratio, rotation speed and ball milling time need to be regulated. The ball-to-material ratio is required to be 2.5-4:1, the rotation speed is 300-600rpm / min, and the ball milling time is 0.5-3h to ensure that the microstructure of the thallium-containing lithium slag can be activated and destroyed, and the leaching agent and the thallium-containing lithium slag can be fully mixed and pre-reacted.

[0029] In the process of slag leaching, it is necessary to control the solid-liquid ratio, leaching temperature and leaching time. The solid-liquid ratio and leaching temperature are regulated to improve the thallium dissolution performance, avoid thallium residue in the lithium slag, and ensure the stabilization efficiency and extraction rate of thallium in the lithium slag.

[0030] During the biochemical treatment of the leachate, the temperature, stirring speed, dissolved oxygen concentration, pH, and microbial inoculation concentration need to be regulated. The pH and temperature are regulated to promote the adsorption of thallium by microorganisms, control the crystal form of microbially mediated carbonate sediments to be dense calcite, avoid the formation of loose aragonite carbonate shells on the surface of microbial cells and the inability of the cell surface to effectively adsorb thallium; regulate the microbial inoculation concentration and dissolved oxygen concentration to promote the efficiency of microbially mediated carbonate deposition, increase the thickness and chemical stability of the carbonate shell, and enhance the long-term stabilization performance of thallium. These regulatory measures can ensure the removal rate of thallium from the leachate and the long-term stability of thallium in the solid thallium slag.

[0031] The beneficial effects of this method are as follows:

[0032] Control the appropriate ingredient ratio to fully activate and complex the thallium in the lithium slag, improve the leaching performance of thallium, control the appropriate solid-liquid ratio, leaching temperature and leaching time, so that thallium can be efficiently dissolved; it is conducive to the harmless treatment of lithium slag and eliminate the environmental risks of thallium dissolution.

[0033] The thallium accumulated in the circulating leaching solution is adsorbed on the surface of the bacteria through the biochemical treatment process mediated by the thallium-fixing bacteria agent, and is wrapped by the carbonate shell layer, or embedded in the carbonate shell layer. Controlling the appropriate temperature, stirring speed, dissolved oxygen concentration, pH, and microbial inoculation concentration to form a dense calcite carbonate shell layer on the surface of the microorganism is conducive to obtaining a long-term and stable thallium-fixing slag.

[0034] In summary, the present invention can eliminate the thallium environmental pollution risk of lithium slag, and enrich and solidify thallium for a long time. The long-term harmless treatment process of thallium-containing lithium slag based on chemical leaching-biological mineralization involved in the present invention has the advantages of simple process, green and efficient, closed-loop circulation of leached water, and avoids secondary pollution of thallium. Considering the huge amount of lithium slag produced each year, this invention has huge market application prospects and environmental and ecological significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0036] Figure 1 The present invention is a process flow chart of the method for treating thallium-containing lithium slag based on chemical leaching and biological mineralization.

[0037] Figure 2 Schematic diagram of leaching for toxicity identification of lithium slag and solid thallium slag hazardous waste and simulation of 100-year acid rain leaching results.

[0038] Figure 3 Schematic diagram of the device of the present invention. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of description and simplified description of the present invention, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0042] On the one hand, this embodiment provides a method for treating thallium-containing lithium slag based on chemical leaching and biomineralization, referring to Figure 1 , including the following steps:

[0043] (1) blending the thallium-containing lithium slag with a leaching agent, grinding and uniformly mixing in a sample preparation machine, and then ball milling to obtain blended slag;

[0044] (2) leaching the slag obtained in step (1) into water to obtain a water-leached slurry;

[0045] (3) separating the solid and liquid of the water-leached slurry obtained in step (2) to obtain eluted slag and leachate;

[0046] (4) returning the leachate from step (3) to step (2) for recycling until the thallium concentration in the leachate is higher than 50 mg / L;

[0047] (5) inoculating a thallium-fixing bacterial agent into the leaching solution with a thallium concentration higher than 20 mg / L obtained in step (4), and obtaining a biochemical slurry through a biochemical mineralization reaction;

[0048] (6) separating the solid and liquid of the biochemical slurry obtained in step (5) to obtain solid thallium slag and leaching tailings;

[0049] (7) The leaching tail liquid obtained in step (6) is filtered through a -0.22 μm membrane.

[0050] The leaching agent described in step (1) includes at least one of citric acid, oxalic acid, lactic acid and acetic acid.

[0051] The ball milling conditions described in step (1) are: ball to material ratio 2.5 to 4:1, rotation speed 300 to 600 rpm / min, and ball milling time 0.5 to 3 h.

[0052] The mass ratio of the substances in the slag blend described in step (1) is: lithium slag: leaching agent = 14 to 24:1.

[0053] The water immersion conditions in step (2) are: liquid-to-solid ratio of 5 to 15 mL / g, leaching temperature of 20 to 60° C., and leaching time of 30 to 90 min.

[0054] The leaching solution obtained in step (3) is returned to step (2) for recycling when the thallium concentration is not greater than 50 mg / L.

[0055] The community composition of the thallium-fixing bacterial agent described in step (5) mainly includes Baccilus substilus, Baccilus cohnni, Baccilus cereus, Sporosarcina pasteurii, and Baccilus sphaericus.

[0056] The biochemical reaction conditions in step (5) are: temperature 15-35°C, microbial concentration 10 8 ~10 9 / mL, stirring speed 120~210rpm, dissolved oxygen concentration 0.5~4.5mg / L, pH 3.0~8.0.

[0057] The bacterial sludge obtained in step (7) is returned to step (5) for recycling; and the filtrate obtained is returned to (2) for recycling.

[0058] Figure 2 This is a schematic diagram of the toxicity identification of lithium slag and solid thallium slag hazardous wastes and the results of 100-year simulated acid rain leaching. It shows that solid thallium slag is less harmful.

[0059] like Figure 3As shown, on the other hand, this embodiment provides a device used in the above-mentioned method for treating thallium-containing lithium slag based on chemical leaching and biological mineralization, including a sample preparation machine 100, a slag water leaching device 200, a water leaching slurry solid-liquid separation device 300, a leaching liquid inoculation device 400, a biochemical slurry solid-liquid separation device 500 and a tail liquid membrane filtration device 600.

[0060] In order to highlight the technical problems, technical solutions and advantages to be solved by the present invention, specific embodiments are described in detail below.

[0061] In the embodiments of the present invention and the comparative examples, thallium-containing lithium slag is selected, and its main chemical composition is shown in Table 1.

[0062] Table 1 Chemical composition of thallium-lithium slag elements

[0063]

[0064] Comparative Example 1

[0065] The thallium-containing lithium slag and citric acid were prepared and ground at a mass ratio of lithium slag: leaching agent = 24:1, and ball milled at a ball-to-material ratio of 3:1, a rotation speed of 400rpm, and a ball milling time of 2h. The obtained slag was leached in water with a liquid-solid ratio of 5mL / g and a leaching time of 60min. After 31 cycles of leaching, the thallium concentration in the leachate was 20.3mg / L, and the thallium dissolution rate was 65.6%. After solid-liquid separation, the eluted slag was subjected to HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and a simulated 100-year acid rain leaching test. The thallium leaching concentrations were 31.5μg / L and 27.8μg / L, respectively, which were much higher than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB31573-2015). The leachate was treated with thallium-fixing bacteria at a reaction temperature of 25 °C, a stirring speed of 180 rpm, a dissolved oxygen concentration of 3 mg / L, a pH of 8.0, and an inoculation concentration of 5 × 10 8 / mL, the solidification rate of thallium in the leaching solution is 92.7%, that is, the solidification rate of total thallium in the thallium-containing lithium slag is 60.7%. The solid thallium slag has been tested by HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations are 3.2μg / L and 3.5μg / L respectively, which are lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). It can be seen that too little leaching agent will seriously affect the experimental results.

[0066] Comparative Example 2

[0067] The thallium-containing lithium slag and citric acid were prepared and ground at a mass ratio of lithium slag: leaching agent = 22:1, and ball milling was performed under the conditions of ball-to-material ratio of 3:1, rotation speed of 400rpm, and ball milling time of 2h. The obtained slag was leached in water with a liquid-solid ratio of 5mL / g and a leaching time of 60min. After 21 cycles of leaching, the thallium concentration in the leachate was 20.1mg / L, and the thallium dissolution rate was 95.7%. After solid-liquid separation, the eluted slag was subjected to HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations were 2.5μg / L and 2.8μg / L, respectively, which were lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). The leachate was treated with thallium-fixing bacteria at a reaction temperature of 15 °C, a stirring speed of 180 rpm, a dissolved oxygen concentration of 3 mg / L, a pH of 4.0, and an inoculation concentration of 5 × 10 8 / mL, the solidification rate of thallium in the leaching solution is 79.4%, that is, the solidification rate of total thallium in the thallium-containing lithium slag is 76.0%. The solid thallium slag has been tested by HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the leaching concentrations of thallium are 8.2μg / L and 9.5μg / L respectively, which are higher than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). It can be seen that too low biochemical treatment temperature and pH will seriously affect the experimental results.

[0068] Comparative Example 3

[0069] The thallium-containing lithium slag and citric acid were prepared and ground at a mass ratio of lithium slag: leaching agent = 24:1, and ball milling was performed under the conditions of ball-to-material ratio of 3:1, rotation speed of 400rpm, and ball milling time of 2h. The obtained slag was leached in water with a liquid-solid ratio of 5mL / g and a leaching time of 60min. After 21 cycles of leaching, the thallium concentration in the leaching solution was 20.2mg / L, and the thallium dissolution rate was 96.2%. After solid-liquid separation, the eluted slag was subjected to HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations were 1.4μg / L and 2.3μg / L, respectively, which were lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). The leachate was treated with thallium-fixing bacteria at a reaction temperature of 25 °C, a stirring speed of 180 rpm, a dissolved oxygen concentration of 3 mg / L, a pH of 9.0, and an inoculation concentration of 5 × 10 8 / mL, the solidification rate of thallium in the leaching solution is 56.5%, that is, the solidification rate of total thallium in the thallium-containing lithium slag is 54.4%. The solid thallium slag has been tested by HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations are 13.5μg / L and 12.3μg / L respectively, which are much higher than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). It can be seen that too high pH of biochemical treatment will also seriously affect the experimental results.

[0070] Example 1

[0071] The thallium-containing lithium slag and oxalic acid were prepared and ground at a mass ratio of lithium slag: leaching agent = 22:1, and ball milling was performed under the conditions of ball-to-material ratio of 3:1, rotation speed of 300rpm, and ball milling time of 2h. The obtained prepared slag was leached in water with a liquid-solid ratio of 5mL / g and a leaching time of 30min. After 24 cycles of leaching, the thallium concentration in the leaching solution was 20.5mg / L, and the thallium dissolution rate was 85.4%. After solid-liquid separation, the eluted slag was subjected to HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations were 3.6μg / L and 4.1μg / L, respectively, which were lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). The leachate was treated with thallium-fixing bacteria at a reaction temperature of 20 °C, a stirring speed of 180 rpm, a dissolved oxygen concentration of 3 mg / L, a pH of 5.0, and an inoculation concentration of 5 × 10 8 / mL, the solidification rate of thallium in the leaching solution is 95.9%, that is, the solidification rate of total thallium in the thallium-containing lithium slag is 81.9%. The solid thallium slag has been tested by HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations are 1.7μg / L and 2.1μg / L respectively, which are lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015).

[0072] Example 2

[0073] The thallium-containing lithium slag and lactic acid were prepared and ground at a mass ratio of lithium slag: leaching agent = 24:1, and ball milled at a ball-to-material ratio of 4:1, a rotation speed of 300rpm, and a ball milling time of 2h. The obtained slag was leached in water with a liquid-to-solid ratio of 5mL / g and a leaching time of 60min. After 23 cycles of leaching, the thallium concentration in the leaching solution was 20.9mg / L, and the thallium dissolution rate was 90.8%. After solid-liquid separation, the eluted slag was subjected to HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and a simulated 100-year acid rain leaching test. The thallium leaching concentrations were 2.1μg / L and 2.5μg / L, respectively, which were lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). The leachate was treated with thallium-fixing bacteria at a reaction temperature of 20°C, a stirring speed of 180 rpm, a dissolved oxygen concentration of 3 mg / L, a pH of 4.5, and an inoculation concentration of 10 9 / mL, the solidification rate of thallium in the leaching solution is 97.2%, that is, the solidification rate of total thallium in the thallium-containing lithium slag is 88.3%. The solid thallium slag has been tested by HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations are 4.2μg / L and 4.8μg / L respectively, which are lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015).

[0074] Example 3

[0075] The thallium-containing lithium slag and citric acid were prepared and ground at a mass ratio of lithium slag: leaching agent = 24:1, and ball milling was performed under the conditions of ball-to-material ratio of 4:1, rotation speed of 300rpm, and ball milling time of 2h. The obtained slag was leached in water with a liquid-solid ratio of 5mL / g and a leaching time of 60min. After 21 cycles of leaching, the thallium concentration in the leachate was 20.5mg / L, and the thallium dissolution rate was 97.6%. After solid-liquid separation, the eluted slag was subjected to HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations were 0.8μg / L and 1.4μg / L, respectively, which were lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015). The leachate was treated with thallium-fixing bacteria at a reaction temperature of 30°C, a stirring speed of 180 rpm, a dissolved oxygen concentration of 2 mg / L, a pH of 5.0, and an inoculation concentration of 10 9 / mL, the solidification rate of thallium in the leaching solution is 98.6%, that is, the solidification rate of total thallium in the thallium-containing lithium slag is 96.2%. The solid thallium slag has been tested by HJ / T299 "Solid Waste Leaching Toxicity Leaching Method" and simulated 100-year acid rain leaching test, and the thallium leaching concentrations are 1.3μg / L and 0.9μg / L respectively, which are lower than the limit value of 5μg / L in the "Inorganic Chemical Industry Pollutant Emission Standard" (GB 31573-2015).

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for treating thallium-containing lithium slag based on chemical leaching and biomineralization, characterized in that: The following steps are involved: (1) blending the thallium-containing lithium slag with a leaching agent, grinding and uniformly mixing in a sample preparation machine, and then ball milling to obtain blended slag; (2) leaching the slag obtained in step (1) into water to obtain a water-leached slurry; (3) separating the solid and liquid of the water-leached slurry obtained in step (2) to obtain eluted slag and leachate; (4) returning the leachate from step (3) to step (2) for recycling until the thallium concentration in the leachate is higher than 50 mg / L; (5) inoculating a thallium-fixing bacterial agent into the leaching solution with a thallium concentration higher than 20 mg / L obtained in step (4), and obtaining a biochemical slurry through a biochemical mineralization reaction; (6) separating the solid and liquid of the biochemical slurry obtained in step (5) to obtain solid thallium slag and leaching tailings; (7) The leaching tail liquid obtained in step (6) is filtered through a -0.22 μm membrane.

2. A method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The leaching agent described in step (1) includes at least one of citric acid, oxalic acid, lactic acid and acetic acid.

3. A method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The ball milling conditions described in step (1) are: ball to material ratio 2.5-4:1, rotation speed 300-600 rpm / min, and ball milling time 0.5-3h.

4. The method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The mass ratio of the substances in the slag blend described in step (1) is: lithium slag: leaching agent = 14 to 24:

1.

5. A method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The water immersion conditions in step (2) are: liquid-to-solid ratio of 5 to 15 mL / g, leaching temperature of 20 to 60° C., and leaching time of 30 to 90 min.

6. A method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The leaching solution obtained in step (3) is returned to step (2) for recycling when the thallium concentration is not greater than 50 mg / L.

7. The method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The community composition of the thallium-fixing bacteria agent described in step (5) mainly includes Bacillus subtilis, Bacillus cohnii, Bacillus cereus, Sporosarcina pasteurianum, and Bacillus sphaericus.

8. A method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The biochemical reaction conditions in step (5) are: temperature 15-35°C, microbial concentration 10 8 ~10 9 / mL, stirring speed 120~210rpm, dissolved oxygen concentration 0.5~4.5mg / L, pH 3.0~8.

0.

9. A method for treating thallium-containing lithium slag based on chemical leaching and biomineralization according to claim 1, characterized in that: The bacterial sludge obtained in step (7) is returned to step (5) for recycling; and the filtrate obtained is returned to (2) for recycling.

10. A device used in the method for treating thallium-containing lithium slag based on chemical leaching and biomineralization as claimed in claim 1, characterized in that: It includes a sample preparation machine, a slag water leaching device, a water leaching slurry solid-liquid separation device, a leaching liquid inoculation device, a biochemical slurry solid-liquid separation device and a tail liquid membrane filtration device.

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