Microbubble oxidation leaching method for low-valence thallium

Abstract

The invention relates to a microbubble oxidation leaching method for low-valence thallium, in particular to the field of thallium leaching and removing, and the microbubble oxidation leaching method comprises the following steps: leaching slurry containing low-valence thallium by adopting microbubbles, and then carrying out solid-liquid separation to obtain thallium-removed purified solid and thallium-containing liquid. According to the microbubble oxidation leaching method for low-valence thallium, by means of strong shearing force generated in the microbubble generation process and ultra-high-speed microjet and local ultra-high temperature which can be formed by instant pressure release during microbubble breaking, on one hand, lithium smelting slag particles can be crushed into small particles, the contact area between the particles and an aqueous solution medium is increased, and on the other hand, the contact area between the particles and the aqueous solution medium is increased; the efficient dissolution and release rate of the thallium component is improved; and on the other hand, under the action of oxidizing bubbles, the low-valence thallium element can be oxidized into a high-valence thallium component, the thallium component can be efficiently removed, and therefore oxidation leaching of thallium in the lithium smelting slag can be enhanced.

Description

Technical Field

[0001] The invention relates to the field of thallium removal, in particular to a method for microbubble oxidation leaching of low-valent thallium, and in particular to a method for microbubble oxidation leaching of lithium smelting slag containing low-valent thallium. Background Art

[0002] At present, the main industrial raw materials for lithium extraction include lithium ores such as spodumene and lepidolite, but a large amount of lithium smelting slag will be produced during lithium extraction. According to statistics, the amount of smelting slag produced during the process of lithium extraction from spodumene is 8-10 tons / ton of lithium carbonate, and the amount of smelting slag produced during the process of lithium extraction from lepidolite is 30-60 tons / ton of lithium carbonate. At the same time, since lithium ore contains a certain amount of thallium-containing minerals, it is very easy to enter the lithium smelting slag during the smelting process, resulting in the thallium leaching toxicity of the slag far exceeding the national standard concentration of 0.005 mg / L, which is easy to cause major environmental pollution and become a problem that needs to be solved urgently to restrict the high-quality green development of the lithium battery industry.

[0003] Therefore, it is urgent to develop a new technology for the harmless disposal of lithium smelting slag, so as to reduce the leaching toxicity of thallium and realize the large-scale disposal and resource utilization of slag.

[0004] For example, CN117626004A discloses a method for removing thallium from an indium-thallium material, wherein the indium-thallium material is added to an acidic solution for acid dissolution, the pH value is adjusted to 1.0-3.0, and then a sulfide salt solution is added for precipitation to obtain a thallium sulfide precipitate, the thallium sulfide precipitate is immersed in an acidic solution for secondary acid dissolution, and the pH value is adjusted to 1.0-3.5, and then an acidic solution, a stabilizer, and a sulfide salt solution are added to mix and put into a hydrothermal reactor to react for 2-24 hours at a temperature of 150-400°C to obtain a thallium sulfide precipitate. However, the method has a high reaction temperature, a long cycle, a long and complex process, and the acidic solution equipment used is highly corrosive, which limits the cost-reduction and efficiency-enhancing disposal of thallium-containing waste residues.

[0005] CN118289982A discloses a photocatalytic oxidation deep thallium removal device and a thallium removal process, wherein the thallium removal device and the thallium removal process sequentially adjust the pH value of wastewater, perform photocatalytic oxidation and flocculation precipitation using a regulating tank, a sedimentation tank and a temporary storage tank, and the process adjusts the wastewater to a specific pH value and then irradiates it with ultraviolet light to generate hydroxyl radicals to achieve thallium oxidation, and adds a precipitant and an adsorbent to achieve thallium precipitation. The method can achieve real-time monitoring of the thallium oxidation removal process, but the amount of chemical reagents used in the oxidation process of thallium is large, and the photocatalytic oxidation process is inefficient, difficult to control, and costly, resulting in the difficulty of industrial application of thallium oxidation removal.

[0006] In summary, the existing treatment methods for thallium still have the defects of low treatment efficiency and low thallium removal rate. That is, the current removal and treatment of low-valent thallium urgently requires a simple, efficient, green and low-cost method for efficiently removing low-valent thallium in lithium smelting slag. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a microbubble oxidation leaching method for low-valent thallium, which utilizes the strong shear force generated during the microbubble generation process and the rapid mass transfer characteristics of the microbubbles to achieve efficient removal and oxidation of thallium in lithium smelting slag. The thallium leaching toxicity of the treated lithium smelting slag fully meets the national standards, greatly reducing the pollution caused by lithium smelting slag to the ecological environment.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a microbubble oxidation leaching method for low-valent thallium, and the microbubble oxidation leaching method comprises:

[0010] The low-valent thallium-containing slurry is leached with microbubbles, and then the thallium-removed purified solid and thallium-containing liquid are obtained through solid-liquid separation.

[0011] The microbubble oxidation leaching method of low-valent thallium provided by the present invention utilizes the strong shear force generated during the generation of microbubbles and the instantaneous release of pressure when the microbubbles burst to form ultra-high-speed microjets and local ultra-high temperatures. On the one hand, lithium smelting slag particles can be broken into small particles, increasing the contact area between the particles and the aqueous solution medium, and improving the efficient dissolution and release rate of thallium components; on the other hand, under the action of oxidizing bubbles, low-valent thallium elements can be oxidized into high-valent thallium components, which enables the thallium components to be efficiently removed, thereby facilitating the enhanced oxidation leaching of thallium in lithium smelting slag.

[0012] As a preferred technical solution of the present invention, the temperature of the slurry containing low-valent thallium is 25-100°C.

[0013] Preferably, the pH value of the low-valent thallium-containing slurry is 6-9.

[0014] As a preferred technical solution of the present invention, the low-valent thallium-containing slurry is obtained by wet ball milling the low-valent thallium-containing material;

[0015] Preferably, a dissolution aid is added to the wet ball milling.

[0016] Preferably, the dissolution aid comprises one or a combination of at least two of citric acid, acetic acid, oxalic acid or hydrogen peroxide.

[0017] Preferably, the added amount of the dissolution aid is 1-5% of the mass of the low-valent thallium-containing material.

[0018] As a preferred technical solution of the present invention, the low-valent thallium-containing material includes lithium smelting slag.

[0019] As a preferred technical solution of the present invention, the mass ratio of the grinding ball medium to the low-valent thallium-containing material in the wet ball milling is (1-10):1.

[0020] As a preferred technical solution of the present invention, the mass ratio of water to the low-valent thallium-containing material in the wet ball milling is (0.5-5):1.

[0021] As a preferred technical solution of the present invention, the wet ball milling time is 5-360 minutes.

[0022] As a preferred technical solution of the present invention, the gas source used to form microbubbles in the leaching process includes any one of air, oxygen, ozone, fluorine or chlorine, or a combination of at least two of them.

[0023] Preferably, the volume ratio of the slurry containing low-valent thallium to the gas source for forming microbubbles in the leaching is (10-50):1.

[0024] As a preferred technical solution of the present invention, the diameter of the microbubbles formed during the leaching is 1-900 μm.

[0025] Preferably, the flow rate of the gas used to form microbubbles during the leaching is 50-1000 mL / min.

[0026] As a preferred technical solution of the present invention, the leaching time is 30-360 minutes.

[0027] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0028] The microbubble oxidation leaching method provided by the present invention utilizes the strong shear force generated during the generation of microbubbles and the rapid mass transfer characteristics of the microbubbles to achieve efficient removal and oxidation of low-valent thallium in lithium smelting slag, and the thallium leaching toxicity of the treated slag is reduced to 1.79 ppb, which fully meets the national standard limit for leaching toxicity of hazardous wastes, greatly reduces the pollution of the ecological environment caused by lithium smelting slag, has good economic and environmental benefits, and has broad application prospects. DETAILED DESCRIPTION

[0029] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0030] This embodiment provides a microbubble oxidation leaching method for low-valent thallium, and the microbubble oxidation leaching method comprises:

[0031] The low-valent thallium-containing slurry is leached with microbubbles, and then the thallium-removed purified solid and thallium-containing liquid are obtained through solid-liquid separation.

[0032] Specifically, the temperature of the low-valent thallium-containing slurry is 25-100°C, for example, it can be 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Specifically, the pH value of the low-valent thallium-containing slurry is 6-9, for example, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5 or 9.0, etc., and is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Specifically, the low-valent thallium-containing slurry is obtained by wet ball milling a low-valent thallium-containing material;

[0035] Wherein, a dissolution aid is added in the wet ball milling.

[0036] Wherein, the dissolution aid includes one or a combination of at least two of citric acid, acetic acid, oxalic acid or hydrogen peroxide.

[0037] Among them, the addition amount of the dissolution aid is 1-5% of the mass of the low-valent thallium-containing material, for example, it can be 1%, 2%, 3%, 4% or 5%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Specifically, the low-valent thallium-containing material includes lithium smelting slag.

[0039] In the present invention, the lithium smelting slag may be obtained from the lithium extraction process of lithium ores such as spodumene and lepidolite.

[0040] In the present invention, the low-valent thallium-containing material may also be other natural materials containing low-valent thallium or materials containing low-valent thallium produced in industrial processes, and the process of the present invention may be used to achieve efficient removal of thallium from the material.

[0041] Specifically, the mass ratio of the grinding ball medium to the low-valent thallium-containing material in the wet ball milling is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Specifically, the mass ratio of water to low-valent thallium-containing material in the wet ball milling is (0.5-5):1, for example, it can be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Specifically, the wet ball milling time is 5-360 min, for example, it can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 20 min, 40 min, 60 min, 80 min, 100 min, 150 min, 200 min, 250 min, 300 min, 350 min or 360 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In the present invention, before leaching, when the slurry containing low-valent thallium is heated to a specified temperature, stirring can be performed selectively, and the stirring speed is 200-1000r / min, for example, it can be 200r / min, 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min or 1000r / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Specifically, the gas source used to form microbubbles during the leaching includes any one of air, oxygen, ozone, fluorine or chlorine, or a combination of at least two of them.

[0046] Exemplarily, typical but non-limiting combinations include: a combination of air and oxygen, a combination of ozone and fluorine, a combination of ozone, fluorine and chlorine, or a combination of air, oxygen, ozone, fluorine and chlorine, etc.

[0047] Specifically, the volume ratio of the slurry containing low-valent thallium to the gas source for forming microbubbles in the leaching is (10-50):1, for example, it can be 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] Specifically, the diameter of the microbubbles formed in the leaching is 1-900 μm, for example, it can be 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm or 900 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Specifically, the flow rate of the gas used to form microbubbles in the leaching is 50-1000mL / min, for example, it can be 50mL / min, 60mL / min, 70mL / min, 80mL / min, 90mL / min, 100mL / min, 150mL / min, 200mL / min, 250mL / min, 300mL / min, 350mL / min, 400mL / min, 450mL / min, 500mL / min, 550mL / min, 600mL / min, 650mL / min, 700mL / min, 750mL / min, 800mL / min, 850mL / min, 900mL / min, 950mL / min or 1000mL / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are equally applicable.

[0050] Specifically, the leaching time is 30-360 min, for example, it can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 120 min, 140 min, 160 min, 180 min, 200 min, 220 min, 240 min, 260 min, 280 min, 300 min, 320 min, 340 min or 360 min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] Further, in order to illustrate the good treatment effect that can be achieved by the microbubble oxidation leaching method of low-valent thallium provided by the present invention, lithium smelting slag (the thallium content in the slag is in the range of 40-150ug / g, and the valence state is mainly positive monovalent) is used as the treatment object for explanation, and a specific example is as follows:

[0052] Example 1

[0053] This embodiment provides a method for microbubble-enhanced oxidation leaching of thallium in lithium smelting slag, the method comprising the following steps:

[0054] The lithium smelting slag and water are placed in a ball mill for wet grinding, wherein the mass ratio of the grinding ball medium to the lithium smelting slag is 5:1, and the mass ratio of water to the lithium smelting slag is 3:1. After wet grinding for 30 minutes, the ball mill medium is separated from the slurry to obtain a primary mixed slurry;

[0055] The obtained primary mixed slurry is pumped into a stirring tank for heating, the stirring speed is controlled to be 400 r / min, the slurry is heated to a temperature of 60°C and the pH value is controlled to be 8, and then a microbubble generation treatment is performed with a gas source at a volume ratio of the primary mixed slurry to the gas source of 20:1 and a flow rate of the gas source of 200 mL / min. After the treatment for 60 minutes, a microbubble mixed slurry with a pH value of 7.0 is obtained, the diameter of the microbubbles in the microbubble generation treatment is 1-200 μm, and the gas source for forming the microbubbles is composed of 60% of air, 30% of oxygen and 10% of ozone by volume percentage;

[0056] The obtained microbubble mixed slurry is pumped into a solid-liquid separation device for filtration and separation to obtain thallium-removed and purified lithium slag, and then the leaching toxicity of the obtained thallium-removed and purified lithium slag is tested.

[0057] Example 2

[0058] This embodiment provides a method for microbubble-enhanced oxidation leaching of thallium in lithium smelting slag, the method comprising the following steps:

[0059] The lithium smelting slag and water are placed in a ball mill for wet grinding, wherein the mass ratio of the grinding ball medium to the lithium smelting slag is 4:1, and the mass ratio of the water to the lithium smelting slag is 5:1. After wet grinding for 60 minutes, the ball mill medium is separated from the slurry to obtain a primary mixed slurry;

[0060] The obtained primary mixed slurry is pumped into a stirring tank for heating, the stirring speed is controlled to be 300 r / min, the slurry is heated to a temperature of 100° C. and the pH value is controlled to be 9, and then a microbubble generation treatment is performed with a gas source at a volume ratio of 40:1 between the primary mixed slurry and the gas source and a flow rate of 400 mL / min of the gas source. After 120 minutes of treatment, a microbubble mixed slurry with a pH value of 7.5 is obtained, the diameter of the microbubbles in the microbubble generation treatment is 1-400 μm, and the gas source for forming the microbubbles is composed of 50% of air, 40% of oxygen and 10% of ozone by volume percentage;

[0061] The obtained microbubble mixed slurry is pumped into a solid-liquid separation device for filtration and separation to obtain thallium-removed and purified lithium slag, and then the leaching toxicity of the obtained thallium-removed and purified lithium slag is tested.

[0062] Example 3

[0063] This embodiment provides a method for microbubble-enhanced oxidation leaching of thallium in lithium smelting slag, the method comprising the following steps:

[0064] The lithium smelting slag and water are placed in a ball mill for wet grinding, wherein the mass ratio of the grinding ball medium to the lithium smelting slag is 5:1, and the mass ratio of the water to the lithium smelting slag is 4:1. After wet grinding for 90 minutes, the ball mill medium is separated from the slurry to obtain a primary mixed slurry;

[0065] The obtained primary mixed slurry is pumped into a stirring tank for heating, the stirring speed is controlled to be 500 r / min, the slurry is heated to a temperature of 80°C and the pH value is controlled to be 7, and then a microbubble generation treatment is performed with a gas source at a volume ratio of 50:1 between the primary mixed slurry and the gas source and a flow rate of the gas source of 300 mL / min. After the treatment for 90 minutes, a microbubble mixed slurry with a pH value of 6.5 is obtained, the diameter of the microbubbles in the microbubble generation treatment is 1-300 μm, and the gas source for forming the microbubbles is composed of 40% of air, 50% of oxygen and 10% of ozone by volume percentage;

[0066] The obtained microbubble mixed slurry is pumped into a solid-liquid separation device, filtered and separated to obtain thallium-removed and purified lithium slag, and then the leaching toxicity of the obtained thallium-removed and purified lithium slag is tested.

[0067] Example 4

[0068] The difference from Example 1 is that the volume ratio of the microbubble treatment primary mixed slurry to the gas source is adjusted to 5:1, and the rest is the same as Example 1.

[0069] Example 5

[0070] The difference from Example 1 is that the volume ratio of the microbubble treatment primary mixed slurry to the gas source is adjusted to 60:1, and the rest is the same as Example 1.

[0071] Example 6

[0072] The difference from Example 1 is that except that the microbubble treatment temperature is adjusted to 15° C., the rest is the same as Example 1.

[0073] Example 7

[0074] The difference from Example 1 is that except for adjusting the microbubble treatment flow rate to 20 mL / min, the rest is the same as Example 1.

[0075] Example 8

[0076] The only difference from Example 1 is that citric acid, a dissolution aid, is added to the wet ball milling process; the amount of the dissolution aid added is 1% of the mass of the low-valent thallium-containing material.

[0077] Example 9

[0078] The only difference from Example 2 is that oxalic acid, a dissolution aid, is added to the wet ball milling process; the amount of the dissolution aid added is 5% of the mass of the low-valent thallium-containing material.

[0079] Comparative Example 1

[0080] The only difference from Example 1 is that no microbubbles are formed during the leaching, and the corresponding composition gas is directly introduced. The rest is the same as Example 1.

[0081] The thallium removal and purification of lithium slag obtained in Examples 1-7 and Comparative Example 1 were subjected to a thallium leaching toxicity test according to the standard "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method (HJ / T 299-2007)". The test results are shown in Table 1.

[0082] Table 1

[0083] Thallium leaching toxicity (μg / L) Example 1 2.21 Example 2 2.68 Example 3 3.06 Example 4 4.86 Example 5 4.65 Example 6 4.57 Example 7 4.73 Example 8 1.85 Example 9 1.79 Comparative Example 1 10.58

[0084] It can be seen from Table 1 that the method provided by the present invention utilizes mechanical ball milling and microbubble enhanced oxidation leaching to efficiently dissolve, release and oxidize thallium in lithium smelting slag, effectively reducing the leaching toxicity of thallium components in lithium smelting slag, and achieving efficient detoxification of lithium smelting slag.

[0085] By comparing Example 1 with Examples 4 and 5, it can be seen that the proportion of the gas source is too small, the number of microbubbles generated is small, thereby reducing the ability of the microbubbles to break and strip minerals, and the thallium leaching toxicity is increased; when the proportion of the gas source is too large, the bubbles formed are larger, and the bubbles are easily merged into large bubbles, the number of bubbles is greatly reduced, the distribution of bubbles and slurry is uneven, the ability of bubbles to break and strip minerals and the gas-liquid mass transfer efficiency are reduced, thereby increasing the thallium leaching toxicity; by comparing Example 1 with Examples 6 and 7, it can be seen that when the temperature or flow rate is too low during the microbubble generation treatment, the interaction between the bubbles and the particles is weakened, the migration and dissolution of the thallium component is inhibited, and the leaching toxicity of the thallium component is increased.

[0086] By comparing Example 1 with Comparative Example 1, it can be seen that when the lithium smelting slag is not treated with microbubble generation, the leaching toxicity of the thallium component in the treated slag is significantly increased, significantly exceeding the limit value specified in the national standard.

[0087] In summary, the present invention provides a method for enhancing the oxidation leaching of thallium in lithium smelting slag by using microbubbles. The method utilizes the mechanical crushing effect of wet grinding to efficiently dissolve and release the thallium component in the lithium smelting slag. At the same time, the microbubbles are utilized to enhance the oxidation leaching effect, and the thallium component is efficiently dissolved, released and oxidized during the reaction process. The thallium leaching toxicity of the slag after treatment is reduced to 1.79 ppb, which fully meets the national standard for the leaching toxicity of hazardous waste, greatly reduces the pollution caused by lithium smelting slag to the ecological environment, and improves the economic and environmental benefits.

[0088] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0089] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0090] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A microbubble oxidation leaching method for low-valent thallium, characterized in that: The microbubble oxidation leaching method comprises: The low-valent thallium-containing slurry is leached with microbubbles, and then the thallium-removed purified solid and thallium-containing liquid are obtained through solid-liquid separation.

2. The microbubble oxidation leaching method of low-valent thallium according to claim 1, characterized in that: The temperature of the low-valent thallium-containing slurry is 25-100° C.; The pH value of the low-valent thallium-containing slurry is 6-9.

3. The microbubble oxidation leaching method of low-valent thallium according to claim 1, characterized in that: The low-valent thallium-containing slurry is obtained by wet ball milling a low-valent thallium-containing material; The wet ball milling is added with a dissolution aid; The dissolution aid includes one or a combination of at least two of citric acid, acetic acid, oxalic acid or hydrogen peroxide; The added amount of the dissolution aid is 1-5% of the mass of the material containing low-valent thallium.

4. The microbubble oxidation leaching method of low-valent thallium according to claim 3, characterized in that: The low-valent thallium-containing material includes lithium smelting slag.

5. The microbubble oxidation leaching method of low-valent thallium according to claim 3, characterized in that: The mass ratio of the grinding ball medium to the low-valent thallium-containing material in the wet ball mill is (1-10):

1.

6. The microbubble oxidation leaching method of low-valent thallium according to claim 3, characterized in that: The mass ratio of water to the low-valent thallium-containing material in the wet ball milling is (0.5-5):

1.

7. The microbubble oxidation leaching method of low-valent thallium according to claim 3, characterized in that: The wet ball milling time is 5-360 min.

8. The method for microbubble oxidation leaching of low-valent thallium according to claim 1, characterized in that: The gas source used to form microbubbles during the leaching process includes any one of air, oxygen, ozone, fluorine or chlorine, or a combination of at least two of them; The volume ratio of the slurry containing low-valent thallium to the gas source for forming microbubbles in the leaching is (10-50):

1.

9. The method for microbubble oxidation leaching of low-valent thallium according to claim 1, characterized in that: The diameter of the microbubbles formed during the leaching is 1-900 μm; The flow rate of the gas used to form microbubbles during the leaching is 50-1000 mL / min.

10. The method for microbubble oxidation leaching of low-valent thallium according to claim 1, characterized in that: The leaching time is 30-360 minutes.