Method for recovering high-purity lead carbonate from lead sulfate slag

Abstract

The invention provides a method for recovering high-purity lead carbonate from lead sulfate slag, which comprises the following steps: (1) mixing and slurrying lead sulfate slag, calcium salt, an activating agent and water, then adding the slurried material into a closed reaction kettle, introducing carbon dioxide gas, heating, stirring, and filtering after the reaction is finished to obtain filtrate and transformation slag; (2) mixing and slurrying the transformation slag and water, and adding the mixture into a centrifugal separator for beneficiation to obtain gravity concentrate and gravity tailings; (3) the gravity concentrate and an acetic acid solution are mixed and pulpified, then the pulpified material is added into a reaction kettle, heating and stirring are conducted, filtering is conducted after the reaction is finished, and lead acetate leaching liquid is obtained; and (4) adding the lead acetate leachate into a closed reaction kettle, introducing carbon dioxide gas, heating, stirring, and filtering after the reaction is finished to obtain high-purity lead carbonate and a regenerated acetic acid solution. Compared with the prior art, the method is low in cost, free of wastewater and good in environmental benefit.

Description

Technical Field

[0001] The present invention relates to the technical field of lead recycling, and particularly to a method for recovering high-purity lead carbonate from lead sulfate slag. Background Art

[0002] The acid leaching residue of hydrometallurgical zinc smelting, also known as lead-silver slag, contains zinc, lead, silver, rare-dispersed metals, etc., and has high recycling value. At present, the rotary kiln high-temperature fuming and volatilization process is generally used to recover lead, zinc, rare-dispersed metals and part of silver in the lead-silver slag. This recycling process will produce secondary zinc oxide fume, and the secondary zinc oxide fume can be returned to the hydrometallurgical zinc smelting process to leach zinc and rare-dispersed metals, and the insoluble metal lead is enriched in the acid leaching residue. Since lead mainly exists in the form of lead sulfate minerals in the acid leaching residue, the acid leaching residue is also called lead sulfate slag.

[0003] The lead content of lead sulfate slag is relatively high, which is an important lead resource and has high recycling value. At present, the smelting methods of lead sulfate slag are mainly divided into two types: pyrometallurgy and hydrometallurgy. Due to the high sulfur content and relatively low lead content, lead sulfate slag can only be added in small amounts as a raw material for pyrometallurgical lead smelting. At the same time, the lead sulfate mineral has good stability, the decomposition temperature of lead sulfate is relatively high, and the smelting temperature is also relatively high. Therefore, there are problems such as high energy consumption, high cost, and serious environmental pollution in the pyrometallurgical smelting of lead sulfate slag. Since lead sulfate is difficult to react with acids, alkalis, and salts in solution, hydrometallurgical smelting of lead sulfate slag usually transforms lead sulfate into lead carbonate or lead oxide that is easy to process. Common transformation agents include carbonates, ammonium salts, organic amines, sodium hydroxide, chloride salts, etc. However, the prices of these transformation agents are relatively high, and there are also problems such as a large amount of sodium sulfate or ammonium sulfate waste liquid generated, difficult to treat, chloride salts corroding equipment, and high costs. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a method for recovering high-purity lead carbonate from lead sulfate slag.

[0005] A method for recovering high-purity lead carbonate from lead sulfate slag according to the present invention includes the following steps:

[0006] (1) Mix lead sulfate slag, calcium salt, activator and water to form a slurry. The volume ratio of the activator and water to the mass ratio of the lead sulfate slag and calcium salt is (2-8):1. Then add the slurried material into a closed reaction kettle, introduce carbon dioxide gas, heat up and stir. After the reaction is completed, filter to obtain a filtrate and a transformation slag;

[0007] (2) After mixing the transformation slag with water to form a slurry, add it to a centrifugal concentrator for beneficiation, and control the drum speed of the centrifugal concentrator to be 170-250 r / min to obtain a gravity separation concentrate mainly composed of lead carbonate and a gravity separation tailing mainly composed of calcium sulfate;

[0008] (3)Mix the reselected concentrate with acetic acid solution for pulping, the volume ratio of the acetic acid solution to the mass of the reselected concentrate is (2-10):1, then add the pulped material into a reaction kettle, heat up and stir, filter after the reaction is completed to obtain a lead acetate leaching solution;

[0009] (4)Add the lead acetate leaching solution into a closed reaction kettle, introduce carbon dioxide gas, heat up and stir, filter after the reaction is completed to obtain high-purity lead carbonate and a regenerated acetic acid solution.

[0010] In one embodiment, the calcium salt is one or more of calcium carbonate, calcium oxide, and calcium hydroxide, and the addition amount of the calcium salt is 1-1.5 times the theoretical amount of the calcium salt consumed by the lead sulfate slag.

[0011] In one embodiment, in step (1), the activator is one or several of acetate salts, ethylenediaminediacetate salts, or one or more of methylamine, ethylamine, ethylenediamine, propylenediamine, and amino acids.

[0012] In one embodiment, the acetate salt is one or several of sodium acetate, potassium acetate, ammonium acetate, and magnesium acetate.

[0013] In one embodiment, the ethylenediaminediacetate salt is one or several of sodium ethylenediaminediacetate, potassium ethylenediaminediacetate, ammonium ethylenediaminediacetate, and magnesium ethylenediaminediacetate.

[0014] In one embodiment, the concentration of the activator is 0.1-2 mol / L.

[0015] In one embodiment, in step (1), the pressure of carbon dioxide in the reaction kettle is 0.1-1.5 MPa, heat up to 20-100 °C, and stir and react for 0.5-6 h.

[0016] In one embodiment, in step (3), heat up to 10-100 °C in the reaction kettle and stir and react for 0.5-2 h.

[0017] In one embodiment, it further includes: in step (4), the pressure of carbon dioxide in the reaction kettle is 0.1-0.8 MPa, heat up to 10-90 °C, and stir and react for 0.5-2 h.

[0018] In one embodiment, it further includes: returning the regenerated acetic acid solution obtained in step (4) to step (3) for recycling.

[0019] The beneficial effects of the present invention are:

[0020] (1)Compared with the transformation agents in the prior art, the present invention uses low-cost calcium salts, with wide raw material sources and low prices.

[0021] (2) The present invention uses a centrifugal concentrator to separate lead carbonate and calcium sulfate in the transformation slag, and then uses acetic acid to leach the reselected concentrate. The leaching solution is weakly acidic, which can avoid the leaching of impurities such as silicon, aluminum, and iron in the transformation slag, achieve selective leaching of lead, and have a high lead leaching rate. At the same time, a regenerated acetic acid solution is obtained after the acetic acid leaching reaction, which can be returned to the leaching reaction, without generating waste water, and has good environmental benefits.

[0022] (3) The present invention adds an activator, which is a lead complexing agent, to improve the solubility of lead sulfate in the solution and greatly increase the transformation rate and conversion rate of lead sulfate. When the activator is added to the transformation treatment of lead sulfate slag, the transformation filtrate is mainly the activator and can be returned to the transformation reaction of lead sulfate without treatment. Thus, the activator can be recycled, with extremely low consumption and low cost. Specific Embodiments

[0023] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0024] Aiming at the problems of high cost, large amount of waste liquid generation, and difficult treatment of waste liquid existing in the existing wet treatment process, the present invention uses a low-cost calcium salt as a transformation agent, introduces carbon dioxide into a closed kettle to first transform the calcium salt into a calcium bicarbonate solution, and then lead sulfate reacts with calcium bicarbonate to form lead carbonate and calcium sulfate precipitates. A centrifugal concentrator is used to separate lead carbonate and calcium sulfate in the precipitate, and then acetic acid is used to leach the reselected concentrate to obtain lead carbonate filter residue and a regenerated acetic acid solution.

[0025] Specifically, the method for recovering high-purity lead carbonate from lead sulfate slag of the present invention includes the following steps:

[0026] (1) Mix lead sulfate slag, calcium salt, activator and water to form a slurry. The volume ratio of the activator and water to the mass ratio of lead sulfate slag and calcium salt is (2-8):1. Then add the slurried material into a closed reaction kettle, introduce carbon dioxide gas, heat up and stir. After the reaction is completed, filter to obtain a filtrate and a transformation slag.

[0027] Among them, the calcium salt is one or more of calcium carbonate, calcium oxide, and calcium hydroxide. The addition amount of the calcium salt is 1-1.5 times the theoretical amount of calcium salt consumed by lead sulfate slag. The calcium salt reacts with carbon dioxide to form calcium bicarbonate, and calcium bicarbonate reacts with lead sulfate to form lead carbonate and calcium sulfate. The reaction equations are as follows:

[0028] CaO + 2CO2 + H2O = Ca(HCO3)2

[0029] Ca(OH)2 + 2CO2 = Ca(HCO3)2

[0030] CaCO3 + CO2 + H2O = Ca(HCO3)2

[0031] Ca(HCO3)2 + PbSO4 = CaSO4 + PbCO3 + CO2 + H2O

[0032] Since calcium bicarbonate is unstable in solution and the concentration of bicarbonate in the solution is relatively low, the reaction between calcium bicarbonate and lead sulfate has problems such as slow reaction rate and low conversion rate. Based on this, an activator is added in the present invention. By using the complexation reaction between the activator and lead, the solubility of lead in the solution is increased, and the original liquid-solid reaction is changed into a liquid-liquid reaction, thereby greatly improving the reaction rate and transformation rate of lead sulfate and calcium bicarbonate. In addition, the filtrate obtained by filtration after the reaction is mainly the activator, which can be returned to the transformation reaction of lead sulfate without treatment.

[0033] Specifically, lead sulfate slag, calcium salt, activator and water are mixed and slurried together. Among them, the activator is one or more of acetate, ethylenediaminediacetate, or one or more of methylamine, ethylamine, ethylenediamine, propylenediamine, amino acid. The acetate is one or more of sodium acetate, potassium acetate, ammonium acetate, magnesium acetate, calcium acetate. The ethylenediaminediacetate is one or more of sodium ethylenediaminediacetate, potassium ethylenediaminediacetate, ammonium ethylenediaminediacetate, magnesium ethylenediaminediacetate. The concentration of the activator is 0.1 - 2 mol / L.

[0034] Preferably, the pressure of carbon dioxide in the reaction kettle is 0.1 - 1.5 MPa, the temperature is raised to 20 - 100 °C, and the reaction is stirred for 0.5 - 6 h.

[0035] (2) After the transformation slag is mixed and slurried with water, it is added to a centrifugal concentrator for ore dressing. The drum speed of the centrifugal concentrator is controlled to be 170 - 250 r / min to obtain a gravity separation concentrate mainly composed of lead carbonate and a gravity separation tailing mainly composed of calcium sulfate.

[0036] The transformation slag obtained in step (1) mainly contains lead carbonate and calcium sulfate. If acetic acid is directly used to leach lead carbonate in the transformation slag, the lead ions dissolved in the solution will react with calcium sulfate to form lead sulfate solution with a smaller solubility product, and the leaching rate of lead is relatively low. The centrifugal concentrator is a device for classifying heavy and light minerals in pulp by the action of centrifugal force. Because the centrifugal force is much larger than the gravity, the gravity separation process is strengthened. The centrifugal concentrator can better separate fine-grained minerals of 10 - 74 μm. According to the characteristics that the density difference between lead carbonate and calcium sulfate is large and the particle size of the filter residue is fine, the present invention uses a centrifugal concentrator to separate the transformation slag to obtain a gravity separation concentrate mainly composed of lead carbonate and a gravity separation tailing mainly composed of calcium sulfate.

[0037] (3) Mix the reselected concentrate with acetic acid solution for pulping. The volume ratio of the acetic acid solution to the mass of the reselected concentrate is (2-10):1. Then add the pulped material into a reaction kettle, heat up and stir. After the reaction is completed, filter to obtain lead acetate leaching solution.

[0038] The main component of the reselected concentrate is lead carbonate. In the present invention, acetic acid is used for leaching to obtain lead acetate leaching solution. The reaction equation is as follows:

[0039] 2CH3COOH + PbCO3 = Pb(CH3COO)2 + CO2 + H2O

[0040] Preferably, the addition amount of acetic acid is 1-1.5 times of the theoretical amount of acetic acid consumed by lead carbonate. Experiments have found that when the addition amount of acetic acid is too small, the leaching of lead carbonate is incomplete; when the addition amount of acetic acid is too large, there will be more residual acetic acid after the reaction ends, and the residual acetic acid will dissolve the precipitated lead carbonate, and high-purity lead carbonate cannot be precipitated when carbon dioxide is introduced subsequently. Therefore, in the present invention, by controlling the addition amount of acetic acid, the pH value of the lead acetate leaching solution can be controlled, so that high-purity lead carbonate can be precipitated when carbon dioxide is introduced into the lead acetate leaching solution.

[0041] Preferably, the temperature in the reaction kettle is raised to 10-100 °C, and the reaction is stirred for 0.5-2 h.

[0042] (4) Add the lead acetate leaching solution into a closed reaction kettle, introduce carbon dioxide gas, heat up and stir. After the reaction is completed, filter to obtain lead carbonate filter residue and regenerated acetic acid solution.

[0043] When carbon dioxide is introduced into the lead acetate leaching solution, lead acetate can react with carbon dioxide to form lead carbonate and acetic acid. Therefore, step (4) can treat the leaching solution in step (3) into lead carbonate precipitate and regenerated acetic acid solution, and the regenerated acetic acid solution can be further returned to step (3) to leach lead from the reselected concentrate. The reaction equation is as follows:

[0044] Pb(CH3COO)2 + CO2 + H2O = 2CH3COOH + PbCO3

[0045] Preferably, the pressure of carbon dioxide in the reaction kettle is 0.1-0.8 MPa, the temperature is raised to 10-90 °C, and the reaction is stirred for 0.5-2 h.

[0046] To further understand the present invention, the following is a detailed description of the method for recovering high-purity lead carbonate from lead sulfate slag provided by the present invention in combination with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0047] Example 1

[0048] This embodiment recovers high-purity lead carbonate from lead sulfate slag (the main components are 15.17% Pb, 3.59% Zn, and 6.84% S by weight percentage), and includes the following steps:

[0049] (1) Mix and pulp the lead sulfate leaching residue, calcium carbonate, and sodium acetate solution. Among them, the calcium carbonate is 1.1 times the theoretical amount, the concentration of the sodium acetate solution is 1.5 mol / L, and the volume ratio of the sodium acetate solution to the mass of the lead sulfate leaching residue and calcium carbonate is 5:1 (unit: mL / g). Add the pulped material into a closed reaction kettle, introduce carbon dioxide gas, keep the pressure in the kettle at 0.4 MPa, start stirring, for a time of 2 h, and a temperature of 70 °C. After the reaction is completed, perform vacuum filtration to obtain a filtrate and a transformed residue.

[0050] (2) Pulp the transformed residue with water and then add it to a centrifugal concentrator for beneficiation. Control the drum speed of the centrifugal concentrator at 170 r / min to obtain a gravity separation concentrate mainly composed of lead carbonate and a gravity separation tailing mainly composed of calcium sulfate.

[0051] (3) Mix and pulp the gravity separation concentrate with acetic acid solution. The volume ratio of the acetic acid solution to the mass of the gravity separation concentrate is 4:1, and the acetic acid dosage is 1.2 times the theoretical amount. Then add the pulped material into a reaction kettle, heat up to 60 °C, stir and react for 1 h. After the reaction is completed, filter to obtain a lead acetate leaching solution.

[0052] (4) Add the lead acetate leaching solution into a reaction kettle, introduce carbon dioxide to remove the air in the kettle, then close the reaction kettle, start stirring, control the carbon dioxide pressure in the reaction kettle at 0.4 MPa, a temperature of 60 °C, and a reaction time of 1 h. After the reaction is completed, filter to obtain a lead carbonate product with a purity of 99.62% and a regenerated acetic acid solution.

[0053] Example 2

[0054] This embodiment recovers high-purity lead carbonate from lead sulfate slag (the main components are 38.17% Pb, 4.26% Zn, and 9.31% S by weight percentage), and includes the following steps:

[0055] (1) Mix and pulp the lead sulfate slag, calcium hydroxide, and calcium acetate solution. Among them, the calcium hydroxide is 1.3 times the theoretical amount, the concentration of the calcium acetate solution is 1 mol / L, and the volume ratio of the calcium acetate solution to the mass of the lead sulfate slag and calcium hydroxide is 3:1 (unit: mL / g). Add the pulped material into a closed reaction kettle, introduce carbon dioxide gas, keep the pressure in the kettle at 0.2 MPa, start stirring, for a time of 1 h, and a temperature of 40 °C. After the reaction is completed, perform vacuum filtration to obtain a filtrate and a transformed residue.

[0056] (2) Pulverize the transformed slag with water and then add it to a centrifugal concentrator for ore dressing. Control the drum speed of the centrifugal concentrator at 200 r / min to obtain gravity separation concentrate mainly composed of lead carbonate and gravity separation tailings mainly composed of calcium sulfate.

[0057] (3) Mix and pulp the gravity separation concentrate with acetic acid solution. The volume ratio of the acetic acid solution to the mass of the gravity separation concentrate is 10:1, and the dosage of acetic acid is 1.5 times the theoretical amount. Then add the pulped material to a reaction kettle at a temperature of 20 °C and stir for 2 h. After the reaction, filter to obtain lead acetate leaching solution.

[0058] (4) Add the lead acetate leaching solution to a reaction kettle. After purging the air in the kettle with carbon dioxide, seal the reaction kettle, start stirring, and control the carbon dioxide pressure in the reaction kettle at 0.8 MPa and the temperature at 20 °C for a reaction time of 0.5 h. After the reaction, filter to obtain lead carbonate product with a purity of 99.71% and recycled acetic acid solution.

[0059] Example 3

[0060] This example recovers high-purity lead carbonate from lead sulfate slag (the main components are 24.84% Pb, 3.17% Zn, and 7.68% S by weight percentage), including the following steps:

[0061] (1) Mix and pulp the lead sulfate slag, calcium hydroxide, and ethylenediaminediacetic acid sodium solution. Among them, the amount of calcium hydroxide is 1.2 times the theoretical amount, the concentration of the ethylenediaminediacetic acid sodium solution is 0.2 mol / L, and the volume ratio of the ethylenediaminediacetic acid sodium solution to the mass of the lead sulfate slag and calcium hydroxide is 4:1 (unit: mL / g). Add the pulped material to a sealed reaction kettle, introduce carbon dioxide gas, keep the pressure in the kettle at 1.5 MPa, start stirring for 6 h at a temperature of 90 °C. After the reaction, perform vacuum filtration to obtain filtrate and transformed slag.

[0062] (2) Pulverize the transformed slag with water and then add it to a centrifugal concentrator for ore dressing. Control the drum speed of the centrifugal concentrator at 250 r / min to obtain gravity separation concentrate mainly composed of lead carbonate and gravity separation tailings mainly composed of calcium sulfate.

[0063] (3) Mix and pulp the gravity separation concentrate with acetic acid solution. The volume ratio of the acetic acid solution to the mass of the gravity separation concentrate is 2:1, and the dosage of acetic acid is 1.0 times the theoretical amount. Then add the pulped material to a reaction kettle at a temperature of 90 °C and stir for 0.5 h. After the reaction, filter to obtain lead acetate leaching solution.

[0064] (4) Add the lead acetate leaching solution to a reaction kettle, introduce carbon dioxide to remove the air in the kettle, then seal the reaction kettle, start stirring, control the carbon dioxide pressure in the reaction kettle to be 0.2 MPa, the temperature to be 90 °C, and the reaction time to be 2 h. After the reaction is completed, filter to obtain a lead carbonate product with a purity of 99.66% and a regenerated acetic acid solution.

[0065] Example 4

[0066] This example recovers high-purity lead carbonate from lead sulfate slag (the main components are 11.35% Pb, 2.18% Zn, and 5.81% S by weight percentage), and includes the following steps:

[0067] (1) Mix and pulp the lead sulfate slag, calcium oxide, and calcium acetate solution. Among them, the calcium oxide is 1.5 times the theoretical amount, the concentration of the calcium acetate solution is 0.5 mol / L, and the volume ratio of the calcium acetate solution to the mass of the lead sulfate slag and calcium oxide is 8:1 (unit: mL / g). Add the pulped material to a sealed reaction kettle, introduce carbon dioxide gas, keep the pressure in the kettle at 0.9 MPa, start stirring, the time is 3 h, and the temperature is 75 °C. After the reaction is completed, perform vacuum filtration to obtain a filtrate and a transformed slag.

[0068] (2) Pulp the transformed slag with water and then add it to a centrifugal concentrator for beneficiation. Control the drum speed of the centrifugal concentrator to be 220 r / min to obtain a gravity separation concentrate mainly composed of lead carbonate and a gravity separation tailing mainly composed of calcium sulfate.

[0069] (3) Mix and pulp the gravity separation concentrate with acetic acid solution. The volume ratio of the acetic acid solution to the mass of the gravity separation concentrate is 6:1, and the acetic acid dosage is 1.3 times the theoretical amount. Then add the pulped material to a reaction kettle, the temperature is 50 °C, stir and react for 1.5 h. After the reaction is completed, filter to obtain a lead acetate leaching solution.

[0070] (4) Add the lead acetate leaching solution to a reaction kettle, introduce carbon dioxide to remove the air in the kettle, then seal the reaction kettle, start stirring, control the carbon dioxide pressure in the reaction kettle to be 0.3 MPa, the temperature to be 50 °C, and the reaction time to be 2 h. After the reaction is completed, filter to obtain a lead carbonate product with a purity of 99.81% and a regenerated acetic acid solution.

[0071] Comparative Example 1

[0072] This comparative example recovers high-purity lead carbonate from lead sulfate slag (the main components are 38.17% Pb, 4.26% Zn, and 9.31% S by weight percentage), and includes the following steps:

[0073] (1) Mix the lead sulfate slag, calcium hydroxide, and calcium acetate solution to form a slurry. Among them, the amount of calcium hydroxide is 1.3 times the theoretical amount, the concentration of the calcium acetate solution is 1 mol / L, and the volume ratio of the calcium acetate solution to the mass of the lead sulfate slag and calcium hydroxide is 3:1 (unit: mL / g). Add the well-slurried material to a closed reaction kettle, introduce carbon dioxide gas, maintain the pressure in the kettle at 0.2 MPa, start stirring, for a time of 1 h, and a temperature of 40 °C. After the reaction is completed, perform vacuum filtration to obtain a filtrate and a transformed slag.

[0074] (2) Mix the transformed slag with acetic acid solution to form a slurry. The volume ratio of the acetic acid solution to the mass of the gravity separation concentrate is 10:1, and the amount of acetic acid used is 1.5 times the theoretical amount. Then add the slurried material to a reaction kettle, at a temperature of 20 °C, stir and react for 2 h. After the reaction is completed, filter to obtain a lead acetate leaching solution.

[0075] (3) Add the lead acetate leaching solution to a reaction kettle, introduce carbon dioxide to remove the air in the kettle, then close the reaction kettle, start stirring, control the carbon dioxide pressure in the reaction kettle at 0.8 MPa, at a temperature of 20 °C, and the reaction time is 0.5 h. After the reaction is completed, filter to obtain a lead carbonate product with a purity of 99.65% and a regenerated acetic acid solution.

[0076] Comparative Example 2

[0077] This example recovers high-purity lead carbonate from lead sulfate slag (the main components are 38.17% Pb, 4.26% Zn, and 9.31% S by weight percentage), including the following steps:

[0078] (1) Mix the lead sulfate slag, calcium hydroxide, and water to form a slurry. Among them, the amount of calcium hydroxide is 1.3 times the theoretical amount, and the volume ratio of water to the mass of the lead sulfate slag and calcium hydroxide is 3:1 (unit: mL / g). Add the well-slurried material to a closed reaction kettle, introduce carbon dioxide gas, maintain the pressure in the kettle at 0.2 MPa, start stirring, for a time of 1 h, and a temperature of 40 °C. After the reaction is completed, perform vacuum filtration to obtain a filtrate and a transformed slag.

[0079] (2) Slurry the transformed slag with water and then add it to a centrifugal concentrator for beneficiation. Control the drum speed of the centrifugal concentrator at 200 r / min to obtain a gravity separation concentrate mainly composed of lead carbonate and a gravity separation tailing mainly composed of calcium sulfate.

[0080] (3) Mix the gravity separation concentrate with acetic acid solution to form a slurry. The volume ratio of the acetic acid solution to the mass of the gravity separation concentrate is 10:1, and the amount of acetic acid used is 1.5 times the theoretical amount. Then add the slurried material to a reaction kettle, at a temperature of 20 °C, stir and react for 2 h. After the reaction is completed, filter to obtain a lead acetate leaching solution.

[0081] (4) Add the lead acetate leaching solution into a reaction kettle, introduce carbon dioxide to remove the air in the kettle, then seal the reaction kettle, start stirring, control the carbon dioxide pressure in the reaction kettle to be 0.8 MPa, the temperature to be 20 °C, and the reaction time to be 0.5 h. After the reaction is completed, filter to obtain a lead carbonate product with a purity of 99.59% and a regenerated acetic acid solution.

[0082] Use the following calculation formulas to calculate the conversion rate of lead sulfate and the lead recovery rate of Examples 1-4 and Comparative Examples 1-2. The results are shown in Table 1.

[0083] Conversion rate of lead sulfate:

[0084] In the formula:

[0085] η —— Conversion rate of lead sulfate, unit %;

[0086] m1 —— Mass of lead sulfate waste, unit g;

[0087] m2 —— Mass of transformation slag, unit g;

[0088] ω1 —— Content of lead sulfate in lead sulfate waste, unit %;

[0089] ω2 —— Content of lead sulfate in transformation slag, unit %;

[0090] Lead recovery rate:

[0091] In the formula:

[0092] α —— Lead recovery rate, unit %;

[0093] m1 —— Mass of lead sulfate waste, unit g;

[0094] m2 —— Mass of transformation slag, unit g;

[0095] β1 —— Content of lead in lead sulfate waste, unit %;

[0096] β2 —— Content of lead in silicon fluoride leaching residue, unit %.

[0097] Table 1 Conversion rate of lead sulfate and lead recovery rate

[0098] Conversion rate of lead sulfate Recovery rate of lead Sulfur content in gravity separation concentrate Lead content in gravity separation tailings Example 1 96.27％ 93.36％ 0.022％ 0.35％ Example 2 97.16％ 93.48％ 0.015％ 0.41％ Example 3 96.45％ 92.93％ 0.013％ 0.45％ Example 4 95.82％ 92.29％ 0.014％ 0.42％ Comparative Example 1 96.12％ 41.46％ - - Comparative Example 2 72.13％ 68.92％ 0.025％ 0.38％

[0099] As can be seen from Table 1, the conversion rate of lead sulfate in Examples 1-4 of the present invention is above 95%, and the lead recovery rate is above 92%. Therefore, the method for recovering high-purity lead carbonate from lead sulfate slag of the present invention can achieve excellent recovery effects.

[0100] Compared with Example 2, Comparative Example 1 does not include the ore dressing step, and directly leaches the transformed slag with acetic acid, resulting in a significant reduction in the recovery rate of lead. Therefore, in the present invention, the transformed slag is first beneficiated by a centrifugal ore dressing machine and then leached with acetic acid, which can greatly improve the recovery rate of lead.

[0101] Compared with adding an activator in Example 2, in Comparative Example 2, only calcium salt is used for transformation, the transformation rate of lead sulfate is relatively low, and the corresponding lead recovery rate is also relatively low, which cannot meet the industry requirements. Therefore, adding an activator in the present invention can greatly improve the transformation rate of lead sulfate. Moreover, the filtrate obtained by filtration after the reaction is mainly the activator and can be returned to the transformation reaction of lead sulfate without treatment. It can be seen that the combination of calcium salt and activator in the present invention can achieve a relatively high transformation rate at a relatively low cost.

[0102] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0103] The above-described embodiments only represent several implementation manners of the present invention, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for recovering high-purity lead carbonate from lead sulfate slag, characterized in that, It includes the following steps: (1) Pulverize lead sulfate slag, calcium salt, activator and water, where the volume ratio of the activator and water to the mass of the lead sulfate slag and calcium salt is (2 - 8):

1. Then add the pulverized material into a closed reactor, introduce carbon dioxide gas, heat up and stir. After the reaction is completed, filter to obtain a filtrate and a transformed residue; (2) After pulverizing the transformed residue with water, add it into a centrifugal concentrator for beneficiation, and control the drum rotation speed of the centrifugal concentrator to be 170 - 250 r / min to obtain a gravity concentration concentrate mainly composed of lead carbonate and a gravity concentration tailing mainly composed of calcium sulfate; (3) Pulverize the gravity concentration concentrate with acetic acid solution, where the volume ratio of the acetic acid solution to the mass of the gravity concentration concentrate is (2 - 10):

1. Then add the pulverized material into a reactor, heat up and stir. After the reaction is completed, filter to obtain a lead acetate leaching solution; (4) Add the lead acetate leaching solution into a closed reactor, introduce carbon dioxide gas, heat up and stir. After the reaction is completed, filter to obtain high-purity lead carbonate and a regenerated acetic acid solution.

2. The method for recovering high-purity lead carbonate from lead sulfate slag according to claim 1, characterized in that, The calcium salt is one or more of calcium carbonate, calcium oxide, and calcium hydroxide, and the addition amount of the calcium salt is 1 - 1.5 times the theoretical amount of calcium salt consumed by the lead sulfate slag.

3. The method for recovering high-purity lead carbonate from lead sulfate slag according to claim 1, characterized in that, In step (1), the activator is one or several of acetate salts, ethylenediaminediacetate salts, or one or more of methylamine, ethylamine, ethylenediamine, propylenediamine, and amino acids.

4. The method for recovering high-purity lead carbonate from lead sulfate slag according to claim 3, characterized in that, The acetate salt is one or several of sodium acetate, potassium acetate, ammonium acetate, and magnesium acetate.

5. The method for recovering high-purity lead carbonate from lead sulfate slag according to claim 3, characterized in that, The ethylenediaminediacetate salt is one or several of sodium ethylenediaminediacetate, potassium ethylenediaminediacetate, ammonium ethylenediaminediacetate, and magnesium ethylenediaminediacetate.

6. The method for recovering high-purity lead carbonate from lead sulfate slag according to claim 3, wherein The concentration of the activator is 0.1 - 2 mol / L.

7. The method for recovering high-purity lead carbonate from lead sulfate slag according to any one of claims 1-6, characterized in that, In step (1), the pressure of carbon dioxide in the reactor is 0.1 - 1.5 MPa, heat up to 20 - 100 °C, and stir and react for 0.5 - 6 h.

8. The method for recovering high-purity lead carbonate from lead sulfate slag according to any one of claims 1-6, characterized in that, In step (3), heat up to 10 - 100 °C in the reactor, and stir and react for 0.5 - 2 h.

9. The method for recovering high-purity lead carbonate from lead sulfate slag according to any one of claims 1-6, characterized in that, It also includes: In step (4), the pressure of carbon dioxide in the reactor is 0.1 - 0.8 MPa, heat up to 10 - 90 °C, and stir and react for 0.5 - 2 h.

10. The method for recovering high-purity lead carbonate from lead sulfate slag according to any one of claims 1-6, characterized in that, It also includes: Return the regenerated acetic acid solution obtained in step (4) to step (3) for recycling.