Preparation method of a thallium removal agent and the thallium removal agent

Abstract

The application belongs to the technical field of chemical smelting, and particularly relates to a preparation method of a thallium removal agent and the thallium removal agent. The preparation method of the thallium removal agent comprises the following steps: subjecting a lead ingot to a melting water quenching treatment to obtain lead flowers. The lead flowers are placed in an acidic reaction medium to form a mixed solution, the mixed solution is heated and an oxidizing agent is added to obtain a lead acetate leaching solution. The lead acetate leaching solution is filtered to obtain a filtrate. Seed crystals are added to the filtrate, and the mixture is cooled under insulation conditions to obtain crude lead acetate crystals. The crude lead acetate crystals are mixed with a recrystallization acidic medium and heated, and after cooling and standing, the mixture is filtered to obtain lead acetate crystals used as the thallium removal agent. According to the application, the lead flowers obtained by water quenching of a lead ingot are used to prepare the thallium removal agent. The lead ingot can be obtained from various channels such as primary lead smelting plants, secondary lead enterprises and waste battery recycling, so the raw material source is wide. In addition, the process is simple and has obvious economic and environmental benefits.

Description

Technical Field

[0001] This application belongs to the field of chemical metallurgy technology, specifically relating to a method for preparing a thallium removal agent and the thallium removal agent itself. Background Technology

[0002] In related technologies, the preparation methods of thallium removal agents mostly use high-purity lead or electrolytic lead as raw materials. The source of raw materials is limited, the procurement cost is high, and the process is complicated. Summary of the Invention

[0003] This application aims to address at least one of the technical problems existing in the related art.

[0004] Therefore, the first aspect of this application provides a method for preparing a thallium removal agent.

[0005] A second aspect of this application provides a thallium removal agent.

[0006] According to a first aspect of the embodiments of this application, a method for preparing a thallium removal agent is proposed, comprising the following steps: quenching lead ingots in molten water to obtain lead flowers; placing the lead flowers in an acidic reaction medium to form a mixture; heating the mixture and adding an oxidant to obtain a lead acetate leaching solution; filtering the lead acetate leaching solution to obtain a filtrate; adding seed crystals to the filtrate and cooling it under heat preservation conditions to obtain crude lead acetate crystals; mixing the crude lead acetate crystals with a recrystallization acidic medium and heating the mixture, cooling and allowing it to stand, and then filtering the mixture to obtain lead acetate crystals used as a thallium removal agent; wherein the acidic reaction medium and the recrystallization acidic medium each comprise an acetic acid solution.

[0007] In one possible implementation, the step of molten water quenching lead ingots to obtain lead flowers includes: melting the lead ingots at high temperature to obtain molten lead; and pouring the molten lead into a cooling medium to obtain lead flowers.

[0008] In one possible implementation, the high-temperature melting temperature is 450°C to 670°C, and the temperature of the cooling medium is 7°C to 30°C.

[0009] In one possible implementation, during the step of pouring the molten lead into the cooling medium, the distance from the outlet of the molten lead to the surface of the cooling medium is 500 mm to 600 mm, and the depth of the cooling medium is 300 mm to 400 mm.

[0010] In one possible implementation, the steps of placing the lead fluff in an acidic reaction medium to form a mixture, heating the mixture, and adding an oxidant to obtain a lead acetate leaching solution include: placing the lead fluff in an acidic reaction medium to form a mixture, heating the mixture to a preset temperature, adding an oxidant to the mixture to initiate a reaction, and achieving a density of 1.3 g / cm³ for the mixture.3 Up to 1.6 g / cm 3 When the time is up, stop heating to obtain lead acetate leachate.

[0011] In one possible implementation, the mass ratio of the acidic reaction medium to the lead flower is 2:1 to 5:1, and the concentration of the acidic reaction medium is 2 mol / L to 5 mol / L; the oxidant includes hydrogen peroxide, and the concentration of the oxidant added is 70 ml / L to 200 ml / L; the preset temperature is greater than 95°C.

[0012] In one possible implementation, the step of adding seed crystals to the filtrate and cooling it under heat preservation conditions to obtain crude lead acetate crystals includes: when the filtrate is naturally cooled to 30°C to 35°C, seed crystals are added to the filtrate, and the filtrate is placed in a temperature-controlled chamber for cooling to obtain crude lead acetate crystals; wherein the amount of seed crystals added is 0.2% to 0.5% of the total mass of the filtrate; the initial temperature of the temperature-controlled chamber is 30°C to 35°C, the cooling rate is 3°C / h to 7°C / h, and the final temperature is 10°C to 15°C.

[0013] In one possible implementation, the step of mixing the crude lead acetate crystals with a recrystallization acidic medium and heating, then cooling and allowing it to stand before filtering to obtain lead acetate crystals used as a thallium removal agent includes: mixing the crude lead acetate crystals with a recrystallization acidic medium of 2% to 3% by mass at a mass ratio of 1:1, heating to dissolve, cooling and allowing it to stand before filtering, and drying to obtain lead acetate crystals, which are used as a thallium removal agent.

[0014] In one possible implementation, the drying temperature is 30°C to 40°C.

[0015] According to a second aspect of the embodiments of this application, a thallium removal agent is provided, which is prepared by the aforementioned method for preparing thallium removal agents, and the grade of the thallium removal agent is greater than or equal to 99.5%.

[0016] The preparation method and the thallium detacher provided in this application can achieve at least the following technical effects: The method for preparing the thallium removal agent in this application includes the following steps: Lead ingots are quenched in molten water to obtain lead fluff. The lead fluff is placed in an acidic reaction medium to form a mixture. The mixture is heated and an oxidant is added to obtain a lead acetate leaching solution. The lead fluff is porous and sponge-like with a large specific surface area, allowing for sufficient contact with the acidic reaction medium and improving reaction efficiency. The lead acetate leaching solution is filtered to obtain a filtrate. Seed crystals are added to the filtrate and cooled under heat preservation conditions to obtain crude lead acetate crystals. The seed crystals act as crystallization nuclei, guiding the directional growth of lead acetate molecules to obtain lead acetate crystals. The crude lead acetate crystals are mixed with a recrystallization acidic medium and heated. After cooling and settling, the mixture is filtered to obtain lead acetate crystals used as the thallium removal agent. After recrystallization purification, the purity of the lead acetate crystals is significantly improved. The acidic reaction medium and the recrystallization acidic medium each include an acetic acid solution. This application uses lead flowers generated by water quenching of lead ingots to prepare thallium removal agent. Since lead ingots can be obtained from various channels such as primary lead smelting plants, recycled lead enterprises, and waste battery recycling, the raw material sources are extensive. Furthermore, the process of water quenching to create holes and recrystallization purification is simple and has significant economic and environmental benefits.

[0017] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0018] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein: Figure 1 A flowchart of the preparation method provided in the embodiments of this disclosure; Figure 2 X-ray diffraction pattern of the thallium removal agent provided in the embodiments of this disclosure; Figure 3 Thermogravimetric analysis curve of the thallium removal agent provided in the embodiments of this disclosure. Detailed Implementation

[0019] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0020] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0022] Combination Figure 1 As shown, this application provides a method for preparing a thallium removal agent, comprising the following steps: S11. The lead ingot is subjected to molten water quenching to obtain lead flowers.

[0023] When molten lead is rapidly cooled by a cooling medium, it forms lead flowers. These lead flowers are porous and spongy, and this type of lead flower has a large specific surface area, allowing for sufficient contact with the acidic reaction medium and improving reaction efficiency.

[0024] In some embodiments, the step of molten lead ingots to obtain lead flowers includes: melting the lead ingots at high temperature to obtain molten lead; and pouring the molten lead into a cooling medium to obtain lead flowers.

[0025] Through high-temperature melting and rapid cooling, the molten lead is quickly solidified and broken up in a very short time, forming porous, sponge-like active lead flowers. Dense, large lead ingots are transformed into a malleable liquid state through high-temperature melting, and then their macroscopic and microscopic morphology is changed through water quenching.

[0026] In one possible implementation, the cooling medium could be water.

[0027] In some embodiments, the high-temperature melting temperature is 450°C to 670°C, and the temperature of the cooling medium is 7°C to 30°C.

[0028] Lead has a melting point of 327.5℃, and the temperature range of 450℃ to 670℃ is much higher than its melting point, giving molten lead extremely low viscosity and good fluidity. This allows the molten lead to flow smoothly when poured and to quickly disperse into tiny droplets or flakes upon entering the water. These tiny droplets or flakes solidify rapidly upon cooling, forming lead flowers.

[0029] In some embodiments, during the step of casting molten lead in a cooling medium, the distance from the outlet of the molten lead to the surface of the cooling medium is 500 mm to 600 mm, and the depth of the cooling medium is 300 mm to 400 mm.

[0030] By controlling the pouring height to 500mm to 600mm and the water depth to 300mm to 400mm, the rate of lead molten metal entering the water and the cooling effect can be adjusted, resulting in finer and more uniform lead flakes with higher porosity and lower bulk density. These characteristics significantly increase the specific surface area of ​​the lead flakes, thereby accelerating the reaction rate in the subsequent oxidation leaching steps and ultimately facilitating the acquisition of high-purity lead acetate crystals.

[0031] It should be noted that the outlet of molten lead can refer to the pouring spout of the melting container (such as a quartz crucible).

[0032] Specifically, lead ingots are placed in a quartz crucible and then melted on an induction cooker at a temperature controlled between 450°C and 670°C to obtain molten lead. The molten lead is then poured into water at a temperature between 7°C and 30°C to a height of 500mm to 600mm and a water depth of 300mm to 400mm. The molten lead enters the water rapidly in multiple thin streams or linear rings, causing it to cool and solidify quickly, forming lead flowers.

[0033] It should be noted that the molten lead is broken up by an airflow breaker as it flows down from the pouring spout of the quartz crucible into the water, forming lead flowers. The size of the lead flowers is controlled by adjusting the diameter of the pouring spout of the quartz crucible and the airflow intensity of the airflow breaker; the diameter of the lead flowers ranges from 5mm to 15mm.

[0034] S12. Place lead flowers in an acidic reaction medium to form a mixture, heat the mixture and add an oxidizing agent to obtain lead acetate leaching solution.

[0035] In one possible implementation, the acidic reaction medium includes an acetic acid solution.

[0036] Lead (Pb) reacts very slowly in acetic acid solution, but in the presence of an oxidizing agent, the oxidizing agent first oxidizes lead to lead oxide (PbO) or lead peroxide (PbO2). These oxides will react rapidly with acetic acid solution to generate soluble lead acetate Pb(CH3COO)2.

[0037] In some embodiments, the step of placing lead fluff in an acidic reaction medium to form a mixture, heating the mixture, and adding an oxidant to obtain a lead acetate leaching solution includes: placing lead fluff in an acidic reaction medium to form a mixture, heating the mixture to a preset temperature, adding an oxidant to the mixture to carry out a reaction, and achieving a mixture density of 1.3 g / cm³. 3 Up to 1.6 g / cm 3 When the time is up, stop heating to obtain lead acetate leachate.

[0038] Heating the mixture to a preset temperature initiates the reaction under optimal kinetic conditions, enabling efficient decomposition of the oxidant and rapid reaction. The mixture density reaches 1.3 g / cm³.3 Up to 1.6 g / cm 3 As a signal to stop heating, the reaction endpoint was controlled, and the lead element in the lead flower was fully leached out.

[0039] In some embodiments, the mass ratio of acidic reaction medium to lead fluff is 2:1 to 5:1, and the concentration of the acidic reaction medium is 2 mol / L to 5 mol / L. The oxidant includes hydrogen peroxide, and the concentration of the oxidant added is 70 ml / L to 200 ml / L. The preset temperature is greater than 95°C.

[0040] In one possible implementation, the mass ratio of the acidic reaction medium to the lead flower is 2:1, 3:1, 4:1, or 5:1.

[0041] The mass ratio of acidic reaction medium to lead ions is 2:1 to 5:1 to ensure sufficient acetate ions combine with lead ions. The concentration of the acidic reaction medium is 2 mol / L to 5 mol / L, providing a high concentration of hydrogen and acetate ions to drive the reaction smoothly. The oxidant and high temperature together constitute a highly efficient oxidation system, which accelerates the reaction rate and increases the solubility of lead acetate.

[0042] The main chemical reactions in this embodiment include: Pb + H₂O₂ + 2H₂O + →Pb 2+ +2H2O, Pb 2+ +2CH3COO →Pb(CH3COO)2.

[0043] In one possible implementation, the pH of the lead acetate leaching solution is 5 to 6.

[0044] Specifically, lead flowers are placed in an acetic acid solution with a concentration of 2 mol / L to 5 mol / L to form a mixture, with the mass ratio of acetic acid solution to lead flowers being 2:1 to 5:1. The mixture is heated to above 95°C. An excess of hydrogen peroxide with a concentration of 70 ml / L to 200 ml / L is added dropwise to the mixture to initiate a reaction. The reaction is allowed to proceed for 1 to 3 hours, and the density of the mixture is measured to reach 1.3 g / cm³. 3 Up to 1.6 g / cm 3 When the time is up, stop heating to obtain lead acetate leachate, the pH of which is 5 to 6.

[0045] It should be noted that the density of the mixture is calculated as follows: take 10 ml of the mixture, weigh it, and calculate the density.

[0046] S13. Filter the lead acetate leaching solution to obtain the filtrate.

[0047] The lead acetate leaching solution is filtered to completely separate the liquid from the remaining solid residue. The solid residue, such as impurities, provides a clear and pure lead acetate solution for subsequent crystallization.

[0048] S14. Add seed crystals to the filtrate and cool it under heat preservation conditions to obtain crude lead acetate crystals.

[0049] Seed crystals serve as growth sites, guiding lead acetate molecules to preferentially precipitate and grow on their surface, rather than spontaneously forming numerous small crystal nuclei. Slow cooling under insulated conditions allows the crystals to grow slowly and orderly. During this process, a small amount of dissolved impurity ions in the filtrate are expelled from the crystal lattice and remain in the mother liquor, thus improving the purity of the lead acetate crystallization product.

[0050] In some embodiments, the step of adding seed crystals to the filtrate and cooling it under heat preservation conditions to obtain crude lead acetate crystals includes: naturally cooling the filtrate to 30°C to 35°C, adding seed crystals to the filtrate, and placing it in a temperature-controlled chamber for cooling to obtain crude lead acetate crystals. The amount of seed crystals added is 0.2% to 0.5% of the total mass of the filtrate. The initial temperature of the temperature-controlled chamber is 30°C to 35°C, the cooling rate is 3°C / h to 7°C / h, and the final temperature is 10°C to 15°C.

[0051] Before adding seed crystals, the filtrate is naturally cooled to 30°C to 35°C to create a mild and stable environment for the seed crystals, allowing them to fully and effectively exert their inductive effect. The amount of seed crystals added is 0.2% to 0.5% of the total mass of the filtrate, providing sufficient growth sites to guide all the solute to grow on the seed crystals, resulting in large, uniform crystals. By controlling the cooling rate at 3°C / h to 7°C / h, the slow and uniform cooling process ensures orderly and slow crystal growth. The final temperature is controlled at 10°C to 15°C to ensure that most of the lead acetate in the filtrate is fully precipitated.

[0052] In one possible implementation, the temperature control chamber has an initial temperature of 30°C, a cooling rate of 5°C / h, and an ending temperature of 15°C.

[0053] Specifically, when the filtrate is naturally cooled to 30°C to 35°C, seed crystals are added to the filtrate at a rate of 0.2% to 0.5% of the total mass of the filtrate. Then, the filtrate is placed in a temperature-controlled chamber for cooling. The initial temperature of the chamber is 30°C, the cooling rate is 5°C / h, and the final temperature is 15°C, resulting in crude lead acetate crystals with a grain size of 1cm to 2cm.

[0054] S15. Mix crude lead acetate crystals with a recrystallization acidic medium and heat. After cooling and settling, filter to obtain lead acetate crystals used as a thallium removal agent.

[0055] Mixing crude lead acetate crystals with an acidic recrystallization medium and heating them for recrystallization can improve the purity of lead acetate crystals and remove impurities due to their high solubility in the acidic recrystallization medium.

[0056] In some embodiments, the step of mixing crude lead acetate crystals with a recrystallization acidic medium and heating, cooling and allowing to stand, and then filtering to obtain lead acetate crystals used as a thallium removal agent includes: mixing crude lead acetate crystals with a recrystallization acidic medium of 2% to 3% by mass at a mass ratio of 1:1, heating to dissolve, cooling and allowing to stand, filtering, and drying to obtain lead acetate crystals, which are used as a thallium removal agent.

[0057] A recrystallization acidic medium with a mass fraction of 2% to 3% can provide an acidic environment to inhibit the hydrolysis of lead acetate crystals. Mixing crude lead acetate crystals with the recrystallization acidic medium at a mass ratio of 1:1 can provide sufficient dissolving medium without excessive dilution, allowing the crude lead acetate crystals to dissolve completely while improving the yield of lead acetate crystals.

[0058] In one possible implementation, the acidic medium for recrystallization includes an acetic acid solution.

[0059] In some embodiments, the drying temperature is 30°C to 40°C.

[0060] In this embodiment, the drying temperature is 30°C to 40°C, and low-temperature drying can effectively remove the moisture and residual acetic acid adhering to the surface of lead acetate crystals.

[0061] Specifically, crude lead acetate crystals are mixed with an acetic acid solution of 2% to 3% by mass at a mass ratio of 1:1, heated to dissolve, cooled and allowed to stand, and then filtered to obtain purified lead acetate crystals. The wet lead acetate crystals are dried under vacuum conditions at a temperature of 30°C to 40°C to obtain lead acetate crystals, which are used as thallium removal agents.

[0062] In this embodiment, the lead acetate crystals can be lead acetate trihydrate.

[0063] For example, combining Figure 2 As shown, X-ray diffraction (XRD) analysis was performed on lead acetate crystals. Figure 2 XRD results showed that the phase in the lead acetate crystals was lead acetate trihydrate. Figure 2 The highest characteristic peak appears at a diffraction angle of 10.3817°, which is a characteristic diffraction peak of lead acetate trihydrate, indicating that the main product is lead acetate trihydrate crystal.

[0064] Combination Figure 3As shown, thermogravimetric analysis (TG) results indicate that the lead acetate crystals, analyzed under nitrogen protection, maintained a relatively constant mass after reaching 382℃. During this process, four major weight loss phenomena occurred, with mass changes of 4.72%, 6.65%, 13.05%, and 12.31%, respectively. Simultaneously, the differential scanning calorimetry (DSC) curves showed distinct endothermic peaks corresponding to each weight loss stage. Theoretical calculations show that the theoretical mass loss of each of the three water molecules removed from lead acetate trihydrate is 4.75%, 9.49%, and 12.66%, respectively. That is, the theoretical mass loss of each water molecule is equal to the molecular weight of water divided by the molecular weight of lead acetate trihydrate. Comparing the actual weight loss data from the TG curves with the theoretical values, slight deviations in individual weight loss data are caused by the presence of a small amount of other impurities in the lead acetate crystals, but the overall weight loss trend is basically consistent with the theoretical values. Therefore, combining the phase identification results of XRD and the thermal decomposition weight loss data of TG, it can be inferred that the first three weight losses correspond to the gradual removal of the three waters of crystallization in the lead acetate trihydrate crystal, and the fourth weight loss is mainly the further decomposition process of the anhydrous lead acetate crystal.

[0065] It should be noted that, Figure 3 The DSC curve in the figure is defined using the coordinate system with the endothermic peak pointing upwards.

[0066] This application provides a thallium removal agent, which is prepared by the aforementioned method for preparing thallium removal agents, and the thallium removal agent has a purity greater than or equal to 99.5%.

[0067] In this embodiment, the thallium removal agent has a purity greater than or equal to 99.5% and a total impurity content of ≤2%, which can be used as a high-efficiency thallium removal agent to improve thallium removal efficiency.

[0068] The preparation process of the thallium removal agent will be described below through Examples 1 to 4.

[0069] Example 1 A method for preparing a thallium removal agent includes the following steps: As shown in Table 1, lead ingots were melted at a high temperature of 600℃ to obtain molten lead.

[0070] As shown in Table 1, molten lead was poured into water at a temperature of 7°C to 30°C to obtain lead flowers, with a mass of 150g.

[0071] As shown in Table 1, lead flowers were placed in a 3 mol / L acetic acid solution. The mixture was heated to 97°C, and then an excess of 100 ml / L hydrogen peroxide was added dropwise to initiate the reaction. After 1.5 hours of reaction, the density of the mixture was measured to be 1.46 g / cm³. 3 When the time is up, stop heating to obtain lead acetate leachate.

[0072] The lead acetate leaching solution was filtered to obtain the filtrate.

[0073] When the filtrate is naturally cooled to 30°C to 35°C, seed crystals are added to the filtrate at a rate of 0.2% to 0.5% of the total mass of the filtrate. Then, the filtrate is placed in a temperature-controlled chamber for cooling. The initial temperature of the chamber is 30°C, the cooling rate is 5°C / h, and the final temperature is 15°C, resulting in crude lead acetate crystals with a grain size of 1cm to 2cm.

[0074] Crude lead acetate crystals are mixed with an acetic acid solution of 2% to 3% by mass at a mass ratio of 1:1, heated to dissolve, cooled and allowed to stand, and then filtered to obtain purified lead acetate crystals. These crystals are then dried under vacuum conditions at a temperature of 30°C to 40°C to obtain lead acetate crystals, which are used as thallium removal agents.

[0075] Example 2 As shown in Table 1, the difference between Example 2 and Example 1 is that the lead flowers were placed in a 5 mol / L acetic acid solution, and the density of the mixture was measured to be 1.48 g / cm³. 3 Stop heating when the time is up. The remaining steps are the same as in Example 1.

[0076] Example 3 As shown in Table 1, the difference between Example 3 and Example 1 is that: an excess of hydrogen peroxide with a concentration of 150 ml / L was added dropwise to the mixture for reaction, and the density of the mixture was measured to be 1.51 g / cm³. 3 Stop heating when the time is up. The remaining steps are the same as in Example 1.

[0077] Example 4 As shown in Table 1, the difference between Example 4 and Example 1 is that: the lead flowers were placed in a 5 mol / L acetic acid solution, an excess of 150 ml / L hydrogen peroxide was added dropwise to the mixture for reaction, and the density of the mixture was measured to be 1.52 g / cm³. 3 Stop heating when the time is up. The remaining steps are the same as in Example 1.

[0078] As shown in Table 1, the concentrations of the acetic acid solution in Examples 1 and 2 were 3 mol / L and 5 mol / L, respectively. Under the same preparation conditions, the remaining lead flowers weighed 22.02 g and 19.49 g, respectively, and the specific gravity of the lead acetate leaching solution was 1.46 g / cm³. 3 and 1.48 g / cm 3 All of them meet the crystallization requirements (≥1.4g / cm³). 3 The less lead oxide remains, the higher the specific gravity of the leachate, and the faster the reaction rate, indicating that increasing the acetic acid concentration helps to increase the reaction rate. The specific gravity of the mother liquor after crystallization was measured to be 1.26 g / cm³. 3and 1.24 g / cm 3 The concentrations remained at low levels, indicating that lead acetate crystals were fully precipitated. Furthermore, the lower the specific gravity of the mother liquor after crystallization, the more lead acetate crystals precipitated, resulting in a higher product yield. Calculations showed that the product yields for Examples 1 and 2 were 85.32% and 87.01%, respectively.

[0079] In Examples 3 and 4, the concentrations of the acetic acid solution were 3 mol / L and 5 mol / L, respectively. Under the same preparation conditions, the remaining lead flowers weighed 17.12 g and 15.27 g, respectively, and the specific gravity of the lead acetate leaching solution was 1.51 g / cm³. 3 and 1.52g / cm 3 All of them meet the crystallization requirements (≥1.4g / cm³). 3 The less lead oxide remains, the higher the specific gravity of the leachate, and the faster the reaction rate, indicating that increasing the acetic acid concentration helps to increase the reaction rate. The specific gravity of the mother liquor after crystallization was measured to be 1.21 g / cm³. 3 and 1.20g / cm 3 The concentrations remained at low levels, indicating that lead acetate crystals were fully precipitated. Furthermore, the lower the specific gravity of the mother liquor after crystallization, the more lead acetate crystals precipitated, resulting in a higher product yield. Calculations showed that the product yields for Examples 3 and 4 were 88.59% and 89.82%, respectively.

[0080] In Examples 1 and 3, the hydrogen peroxide concentrations were 100 ml / L and 150 ml / L, respectively. Under the same preparation conditions, the remaining lead flowers weighed 22.02 g and 17.12 g, respectively, and the specific gravity of the lead acetate leaching solution was 1.46 g / cm³. 3 and 1.51 g / cm 3 All of them meet the requirements for crystallization (≥1.4g / cm³). 3 The less lead oxide remains, the higher the specific gravity of the leachate, and the faster the reaction rate, indicating that increasing the hydrogen peroxide concentration helps to increase the reaction rate. The specific gravity of the mother liquor after crystallization was measured to be 1.26 g / cm³. 3 and 1.21 g / cm 3 The levels remained at low levels, indicating that lead acetate crystals were fully extracted.

[0081] In Examples 2 and 4, the hydrogen peroxide concentrations were 100 ml / L and 150 ml / L, respectively. Under the same preparation conditions, the remaining lead flowers weighed 19.49 g and 15.27 g, respectively, and the specific gravity of the lead acetate leaching solution was 1.48 g / cm³, respectively. 3 and 1.52g / cm 3 All of them meet the requirements for crystallization (≥1.4g / cm³). 3The less lead oxide remains, the higher the specific gravity of the leachate, and the faster the reaction rate, indicating that increasing the hydrogen peroxide concentration helps to increase the reaction rate. The specific gravity of the mother liquor after crystallization was measured to be 1.24 g / cm³. 3 and 1.20g / cm 3 The levels remained at low levels, indicating that lead acetate crystals were fully extracted.

[0082] In summary, the less lead fluff remaining and the higher the specific gravity of the lead acetate leaching solution, the faster the reaction rate. A low specific gravity in the mother liquor after crystallization indicates sufficient precipitate of lead acetate crystals, leading to a higher product yield. Maintaining an acetic acid solution concentration of 3 mol / L to 5 mol / L accelerates the reaction rate; further accelerating the reaction rate with a hydrogen peroxide concentration of 100 ml / L to 150 ml / L effectively increases the product yield.

[0083] It should be noted that the product yield is calculated using the following formula: Yield = (Final lead acetate crystal mass / Theoretically, the lead acetate crystal mass that should be obtained after complete conversion) × 100%.

[0084] It should be noted that, based on theoretical calculations, the concentration of the acetic acid solution and the amount of oxidant required are as follows: the solubility of anhydrous lead acetate is 44.3 g / 100 g water, and the solubility is determined when the specific gravity of the solution reaches 1.4 g / cm³. 3 Approximately 400g of lead acetate can be dissolved in each liter of water. The amount of acetic acid solution must be greater than 2.5mol / L. After accounting for volatilization losses, a concentration of 3mol / L to 5mol / L for the acetic acid solution is more appropriate. The amount of hydrogen peroxide used is 100ml / L to 150ml / L.

[0085] Table 1. Preparation conditions and experimental results of lead acetate crystals

[0086] Application examples 1 to 3 illustrate the application of thallium removal agent (lead acetate crystals) in the cadmium removal process of the two-stage purification process of zinc sulfate solution, including the following steps: Adjust the reaction temperature of the zinc sulfate solution before the second-stage purification to 40℃ to 90℃; Add 1 g / L to 5 g / L of zinc powder and 0.1 g / L to 0.5 g / L of thallium removal agent to the zinc sulfate solution before the second stage of purification, and react for 30 min to 90 min.

[0087] The two-stage purification process for zinc sulfate is mainly a cadmium removal process. This process utilizes the property that the standard electrode potential of zinc is more negative than that of cadmium under the conditions of a circulating reactor and a certain temperature. By adding zinc powder to the solution, cadmium is displaced, and by adding a flocculant (polyacrylamide, 0.03 g / L) to control a certain reaction rate, cadmium is separated from the solution, thereby achieving the purpose of purifying the zinc sulfate solution.

[0088] The main chemical reactions are: Zn+Cd 2+ =Zn 2+ +Cd During the cadmium removal process, thallium is also removed by the action of lead acetate crystals.

[0089] The chemical reaction for thallium removal is as follows: 4PbAc+2Tl(SO4)2+4H2O=TlAc2·Tl(OH)4↓+4PbSO4+2H2Ac.

[0090] The experiment used zinc sulfate solution before the second stage of purification (Tl content 0.645 mg / L) as the stock solution, and a combination of zinc powder and thallium removal agent as the thallium removal agent. The experimental scale was 1L / test (each test treated 1L of solution).

[0091] Application Example 1 The effect of temperature on thallium removal: Referring to Table 2, adjust the reaction temperature of the zinc sulfate solution before the second-stage purification to between 40℃ and 90℃. Add 3g / L zinc powder and 0.3g / L thallium removal agent to the zinc sulfate solution before the second-stage purification, and react for 60min.

[0092] Table 2 Thallium removal experiments under different reaction conditions

[0093] As shown in Table 2, the thallium removal rate is above 86% in the temperature range of 40℃ to 90℃. The thallium removal rate first increases and then decreases with increasing temperature. The optimal temperature is 60℃, where the thallium content can be reduced to below 0.05 mg / L and the thallium removal rate is 92.7%.

[0094] Application Example 2 The effect of thallium removal agent dosage on thallium removal: Adjust the reaction temperature of the zinc sulfate solution before the second-stage purification to 60℃; As shown in Table 2, add 3 g / L zinc powder and 0 g / L to 0.5 g / L thallium removal agent to the zinc sulfate solution before the second stage of purification, and react for 60 min.

[0095] As shown in Table 2, without the addition of a thallium removal agent, the thallium removal rate was only 19.8%. After adding the agent, the removal rate reached over 86%, and the thallium content was reduced to below 0.1 mg / L, meeting production requirements. The thallium removal effect increased with the increase of the agent dosage. When the agent dosage reached 0.3 g / L, the thallium content in the solution decreased to 0.029 mg / L, and the removal rate was 95.5%, indicating that the agent significantly enhanced the thallium removal effect of zinc powder.

[0096] Application Example 3 The effect of zinc powder addition on thallium removal: Adjust the reaction temperature of the zinc sulfate solution before the second-stage purification to 60℃; As shown in Table 2, add 0.5 g / L to 5 g / L zinc powder and 0.3 g / L thallium removal agent to the zinc sulfate solution before the second stage of purification, and react for 60 min.

[0097] As shown in Table 2, the thallium removal rate first increases and then decreases with the increase of zinc powder addition. The optimal thallium removal rate is reached when the zinc powder addition is 3 g / L, with a thallium removal rate of 98.9% and a thallium content of 0.007 mg / L. When the zinc powder addition is increased to 5 g / L, the thallium removal effect decreases, with a thallium removal rate of 92.6%.

[0098] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A method for preparing a thallium removal agent, characterized in that, Includes the following steps: Lead ingots are melted and quenched in water to obtain lead flowers; The lead flowers are placed in an acidic reaction medium to form a mixture. The mixture is heated and an oxidant is added to obtain a lead acetate leaching solution. The lead acetate leaching solution was filtered to obtain the filtrate; Seed crystals were added to the filtrate, and the mixture was cooled under heat preservation conditions to obtain crude lead acetate crystals. The crude lead acetate crystals were mixed with a recrystallization acidic medium and heated. After cooling and settling, the mixture was filtered to obtain lead acetate crystals used as a thallium removal agent. The acidic reaction medium and the recrystallization acidic medium each comprise an acetic acid solution.

2. The preparation method according to claim 1, characterized in that, The steps for obtaining lead flowers by molten and water-quenching lead ingots include: Lead ingots are melted at high temperatures to obtain molten lead; The molten lead is poured into a cooling medium to obtain lead flowers.

3. The preparation method according to claim 2, characterized in that, The high-temperature melting temperature is 450°C to 670°C, and the temperature of the cooling medium is 7°C to 30°C.

4. The preparation method according to claim 2, characterized in that, In the step of pouring the molten lead into the cooling medium, the distance from the outlet of the molten lead to the surface of the cooling medium is 500mm to 600mm, and the depth of the cooling medium is 300mm to 400mm.

5. The preparation method according to claim 1, characterized in that, The steps of placing the lead flowers in an acidic reaction medium to form a mixture, heating the mixture and adding an oxidizing agent to obtain a lead acetate leaching solution include: The lead flowers are placed in the acidic reaction medium to form a mixture. The mixture is heated to a preset temperature, and an oxidizing agent is added to initiate the reaction. The density of the mixture reaches 1.3 g / cm³. 3 Up to 1.6 g / cm 3 When the time is up, stop heating to obtain lead acetate leachate.

6. The preparation method according to claim 5, characterized in that, The mass ratio of the acidic reaction medium to the lead flower is 2:1 to 5:1, and the concentration of the acidic reaction medium is 2 mol / L to 5 mol / L. The oxidant includes hydrogen peroxide, and the concentration of the oxidant added is from 70 ml / L to 200 ml / L; The preset temperature is greater than 95℃.

7. The preparation method according to claim 1, characterized in that, The steps of adding seed crystals to the filtrate and cooling it under heat preservation conditions to obtain crude lead acetate crystals include: When the filtrate is naturally cooled to 30°C to 35°C, seed crystals are added to the filtrate and the solution is placed in a temperature-controlled chamber for cooling to obtain crude lead acetate crystals. The amount of seed crystals added is 0.2% to 0.5% of the total mass of the filtrate; the initial temperature of the temperature control chamber is 30°C to 35°C, the cooling rate is 3°C / h to 7°C / h, and the final temperature is 10°C to 15°C.

8. The preparation method according to claim 1, characterized in that, The steps of mixing the crude lead acetate crystals with a recrystallization acidic medium and heating, followed by cooling and filtration to obtain lead acetate crystals for use as a thallium removal agent include: The crude lead acetate crystals are mixed with a recrystallization acidic medium of 2% to 3% by mass at a mass ratio of 1:1, heated to dissolve, cooled and allowed to stand, filtered, and dried to obtain lead acetate crystals, which are used as thallium removal agents.

9. The preparation method according to claim 8, characterized in that, The drying temperature is 30°C to 40°C.

10. A thallium removal agent, characterized in that, The thallium removal agent is prepared using the preparation method of the thallium removal agent as described in any one of claims 1 to 9; The thallium removal agent has a purity greater than or equal to 99.5%.

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