Method for deeply removing arsenic in zinc sulfate solution with high arsenic content

Abstract

The invention relates to a method for deeply removing arsenic from a high-arsenic-content zinc sulfate solution, and belongs to the technical field of zinc hydrometallurgy. The method comprises the following steps: adding reduced iron powder into an arsenic-containing zinc sulfate solution, reacting for 1-1.5 hours at the temperature of 70-80 DEG C to carry out copper precipitation and arsenic removal, adding zinc calcine into the solution after copper precipitation and arsenic removal, introducing oxygen-containing gas to carry out primary neutralization treatment, controlling the pH value of the solution to be 2.8-3.5 during the primary neutralization treatment, and producing neutralized slag and neutralized liquid during the primary neutralization treatment; the method comprises the following steps: performing primary neutralization, returning neutralization slag to an oxygen pressure leaching process to further recover zinc, performing secondary neutralization on liquid after primary neutralization to perform deep iron precipitation and arsenic removal treatment, adding limestone powder into the liquid after primary neutralization, adjusting the pH value of the solution to 5.0-5.2, and simultaneously introducing oxygen-containing gas to reduce arsenic in the solution to 0.2 mg / l or below and reduce iron to 20 mg / l or below. The process is simple and controllable, and industrial application is facilitated.

Description

Technical Field

[0001] The present invention relates to a method for deeply removing arsenic from a high-arsenic zinc sulfate solution, belonging to the technical field of hydrometallurgical zinc smelting. Background Art

[0002] The traditional hydrometallurgical zinc smelting process flow is roasting - leaching (neutral leaching + weak acid leaching) - purification - electrowinning, and zinc leaching residues are produced after weak acid leaching. Among them, the purification of zinc sulfate solution is an extremely crucial process in the whole process.

[0003] Purification of zinc sulfate solution refers to the process of removing harmful impurities in the neutral zinc sulfate leaching solution to meet the requirements of zinc electrodeposition, and it is a component of the hydrometallurgical zinc smelting process. The leaching solution used for zinc electrodeposition is the leaching solution of two-stage oxygen pressure leaching. The qualified zinc sulfate solution for zinc electrowinning is obtained after the leaching solution undergoes copper precipitation - iron removal - purification treatment. Generally, the contents of iron, arsenic, antimony, copper, cadmium, and cobalt in the acid leaching solution exceed the concentrations allowed for zinc electrodeposition. In particular, impurities such as arsenic and antimony need to be deeply removed in the previous process, otherwise harmful gases such as arsine will be generated and burning of the plate and redissolution will occur during the electrowinning process.

[0004] Regarding the technology for removing arsenic from zinc sulfate solution, a large amount of research has been done. For example, in Patent CN118005068A, arsenic in the solution is removed by adding ferrous sulfate and potassium permanganate. After arsenic removal, the concentration of arsenic in the solution is 0.59 - 0.79 mg / L. In Patent CN118726752A, arsenic in the solution is removed by adding a zinc - copper - iron alloy powder, and the arsenic removal rate in this patent is about 90%. Chinese patents CN106396200A and CN103435188A use lime milk as a neutralizing agent to adjust the pH to neutral or weakly alkaline, and arsenic precipitates in the form of calcium arsenate or calcium arsenite. However, this method not only generates a large amount of solid waste but also cannot make the wastewater meet the discharge standards. The solubility of calcium arsenite is much greater than that of calcium arsenate, and the solubility is 0.9 g / L. (2) Sulfide precipitation method: The arsenic sulfide method can effectively remove arsenate and produce less precipitation, but the H 2 S produced in the process is a highly toxic substance, seriously endangering the environment and personal safety. (3) Iron salt precipitation method: This method uses iron salts (such as ferric chloride, ferrous sulfate, polyferric sulfate, etc.) as arsenic precipitation agents. The arsenic precipitation effect of ferric chloride solution is better, but it has strong corrosiveness and requires high anti-corrosion performance for equipment. Chinese patents CN113620464A and CN110745988A use ferrous sulfate as an arsenic precipitation agent and control a certain iron - arsenic ratio to form ferric arsenate precipitation. In the above technologies, arsenic generally exists in the form of salts, resulting in low economic value. Summary of the Invention

[0005] In view of the deficiencies of the prior art, especially the technical problem of low high-value utilization of arsenic, the present invention first proposes a method for deep arsenic removal and realizing the high-value utilization of arsenic. A method for deep removal of arsenic in zinc sulfate solution of the present invention can not only deeply remove arsenic in zinc sulfate solution to the lowest range, prevent the generation of arsine gas during the purification process of zinc sulfate solution, but also realize the high-value utilization of arsenic.

[0006] A method for deep removal of arsenic in high-arsenic-containing zinc sulfate solution of the present invention includes the following steps:

[0007] Add reduced iron powder into the arsenic-containing zinc sulfate solution, control the temperature at 70 - 80 °C, and control the time for 1 - 1.5 h for copper precipitation and arsenic removal. After copper precipitation and arsenic removal, the arsenic in the solution is reduced to 20 - 30 mg / l, and arsenic-containing copper slag is produced. After copper precipitation and arsenic removal, zinc calcine is added to the solution, and in the first neutralization process, oxygen-containing gas is introduced to oxidize Fe 2+ to Fe 3+ , acid-neutralize the solution to a pH value between 2.8 and 3.5. The first neutralization treatment produces neutralization slag and post-neutralization liquid. The neutralization slag is returned to the oxygen pressure leaching process for further zinc recovery, and the post-neutralization liquid of the first neutralization enters the second neutralization for deep iron precipitation and arsenic removal. Limestone powder is added to the post-neutralization liquid of the first neutralization to adjust the pH value of the solution to between 5.0 and 5.2, and at the same time, oxygen-containing gas is introduced to reduce the arsenic in the solution to below 0.2 mg / l and the iron to below 20 mg / l, producing qualified middle supernatant. The arsenic in the arsenic-containing copper slag exists in the zero-valent form, and the zinc sulfate solution contains copper.

[0008] In the present invention, a part of arsenic is stored in the arsenic-containing copper slag in the zero-valent form, realizing its high-value utilization.

[0009] As a preference, in the method for deep removal of arsenic in high-arsenic-containing zinc sulfate solution of the present invention, in the zinc sulfate solution, the concentration of acid is 3 - 5 g / l.

[0010] As a preference, in the method for deep removal of arsenic in high-arsenic-containing zinc sulfate solution of the present invention, in the zinc sulfate solution, the concentration of zinc is 145 - 150 g / l.

[0011] As a preference, in the method for deep removal of arsenic in high-arsenic-containing zinc sulfate solution of the present invention, in the zinc sulfate solution, the concentration of arsenic is greater than or equal to 40 mg / l. As a further preference, in the zinc sulfate solution, the concentration of arsenic is 40 - 60 mg / l.

[0012] As a preference, in the method for deep removal of arsenic in high-arsenic-containing zinc sulfate solution of the present invention, in the zinc sulfate solution, the concentration of copper is 1300 - 1500 mg / l.

[0013] As a preference, in the method for deep removal of arsenic in high-arsenic-containing zinc sulfate solution of the present invention, in the zinc sulfate solution, FeT The total iron concentration is 1~2g / l.

[0014] Preferably, in the method for deep removal of arsenic from a high-arsenic zinc sulfate solution of the present invention, the concentration of copper in the solution after copper precipitation and arsenic removal is 250-300 mg / l, and the concentration of iron powder is 3-5 g / l.

[0015] In industrial applications, when copper is deposited and arsenic is removed, the amount of iron powder added is 1.8-2.0kg / m 3 .

[0016] When used in industry, the copper precipitation and arsenic removal are carried out in a stirring state, which is conducive to the rapid generation of arsenic-containing copper slag.

[0017] In the present invention, the principle of copper precipitation and arsenic removal is as follows: after the arsenic in the zinc concentrate is leached by oxygen pressure, it will exist in the zinc sulfate solution in the form of trivalent or pentavalent arsenic acid. After adding reduced iron powder to the zinc sulfate solution, the reduced iron powder will replace the copper element, and the copper element will undergo a disproportionation reaction with the divalent copper ions in the solution to produce cuprous ions. The cuprous ions will reduce the trivalent or pentavalent arsenic in the solution to elemental arsenic and remove it into the slag. Its chemical formula is as follows:

[0018] Fe+Cu 2+ →Fe 2+ +Cu↓

[0019] Cu+Cu 2+ →Cu +

[0020] Cu + +AsO 4 3- →Cu 2+ +As↓

[0021] In the present invention, a neutralization treatment is performed, zinc roasting sand is added and oxygen (oxygen content is greater than or equal to 98.5%) is introduced, and the amount of zinc roasting sand added is controlled at 45-50 kg / m 3 , the pH value of the solution is controlled at 2.8-3.5, part of the iron is precipitated into the slag, Fe T Reduced to 1.5-2.5g / l.

[0022] In the present invention, a neutralization treatment can achieve acid neutralization and iron precipitation.

[0023] In the present invention, limestone powder is added to the liquid obtained after a neutralization treatment, and oxygen-containing gas (including air and industrial oxygen) is introduced at the same time to achieve deep removal of arsenic while neutralizing and precipitating iron; the pH of the solution is controlled at 5.0-5.2 in this process, and the amount of limestone powder added is 2.3-2.5 kg / m 3 , to achieve deep removal of arsenic and iron. The oxygen content in industrial oxygen is greater than or equal to 98.5%.

[0024] In the present invention, after secondary neutralization treatment, deep removal of arsenic can be achieved. In the liquid after secondary neutralization treatment, the As concentration is reduced to less than 0.2 mg / l; the iron concentration is reduced to less than 20 mg / l. When applied industrially, through the treatment of the present invention, the As concentration in the middle and upper zinc sulfate solution obtained can be reduced to about 0.021 mg / l.

[0025] The reaction principle of secondary neutralization for iron and arsenic removal is as follows: The As ions in the solution react with the oxidized iron ions to form iron arsenate, and then stable FeAsO 4 -2H 2 O precipitate is formed. The main chemical reactions are as follows:

[0026] Fe 2+ +H 3 AsO 4 +O 2 → FeAsO 4 ↓ + H 2 O BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] Example 1:

[0029] Copper precipitation and arsenic removal stage: Reductive iron powder is added to the zinc sulfate solution containing 3 g / l of acid, 140 g / l of zinc, 1 g / l of Fe T : 40 mg / l of As, and 1300 mg / l of Cu. The addition amount of reductive iron powder is controlled at 1.8 kg / m 3 . The solution temperature is controlled at 70 °C; the stirring of the reaction tank is started, and the time is controlled at 1 h. After displacement, copper precipitation and arsenic removal, the liquid contains 20 mg / l of arsenic, 250 mg / l of copper, and 3 g / l of iron.

[0030] Primary neutralization and iron precipitation stage: Zinc calcine is added to the liquid after copper precipitation and arsenic removal, and oxygen is introduced at the same time. The acid radical in the solution is neutralized by zinc calcine roasting, and the pH value of the solution reaches 2.8. At the same time, Fe 2+ is oxidized to Fe 3+ . The addition amount of zinc calcine is 45 kg / m 3 , and Fe T is reduced to 1.5 g / l.

[0031] Secondary neutralization, iron precipitation and arsenic removal stage: Limestone powder is added to the primary neutralized liquid, and air is introduced at the same time to achieve deep removal of arsenic while iron is neutralized and precipitated; the addition of limestone powder neutralizes the release of acid radicals during the iron precipitation process. The pH of the solution is controlled at 5.0 to achieve deep removal of arsenic and iron. The addition amount of limestone powder is 2.3 kg / m3 , finally, the arsenic content is reduced to 0.2 mg / l and the iron content is reduced to 20 mg / l.

[0032] Example 2:

[0033] Copper precipitation and arsenic removal stage: Add reduced iron powder to a zinc sulfate solution containing 4 g / l of acid, 145 g / l of zinc, 2 g / l of Fe T : 45 mg / l of As, and 1400 mg / l of Cu. The addition amount of the reduced iron powder is controlled at 1.9 kg / m 3 . The solution temperature is controlled at 75 °C; start stirring the reaction tank, and the time is controlled at 1.2 h. After displacement, the solution after copper precipitation and arsenic removal contains 25 mg / l of arsenic, 280 mg / l of copper, and 3.5 g / l of iron.

[0034] First neutralization and iron precipitation stage: Add zinc calcine to the solution after copper precipitation and arsenic removal and simultaneously introduce oxygen. The zinc calcine neutralizes the acid radicals in the solution to achieve a solution pH value of 3.0. At the same time, Fe 2+ is oxidized to Fe 3+ . The addition amount of zinc calcine is 48 kg / m 3 , and Fe T is reduced to 1.8 g / l.

[0035] Second neutralization, iron precipitation and arsenic removal stage: Add limestone powder to the first neutralized solution and simultaneously introduce air to achieve deep arsenic removal while iron is neutralized and precipitated; the addition of limestone powder neutralizes the acid radicals released during the iron precipitation process. The solution pH is controlled at 5.1 to achieve deep removal of arsenic and iron. The addition amount of limestone powder is 2.4 kg / m 3 , finally, the arsenic content is reduced to 0.15 mg / l and the iron content is reduced to 15 mg / l.

[0036] Example 3:

[0037] Copper precipitation and arsenic removal stage: Add reduced iron powder to a zinc sulfate solution containing 5 g / l of acid, 150 g / l of zinc, 3 g / l of Fe T : 50 mg / l of As, and 1450 mg / l of Cu. The addition amount of the reduced iron powder is controlled at 2.0 kg / m 3 . The solution temperature is controlled at 80 °C; start stirring the reaction tank, and the time is controlled at 1.5 h. After displacement, the solution after copper precipitation and arsenic removal contains 30 mg / l of arsenic, 300 mg / l of copper, and 5 g / l of iron.

[0038] First neutralization and iron precipitation stage: Add zinc calcine to the solution after copper precipitation and arsenic removal and simultaneously introduce oxygen. The zinc calcine neutralizes the acid radicals in the solution to achieve a solution pH value of 3.5. At the same time, Fe 2+ is oxidized to Fe 3+ . The addition amount of zinc calcine is 50 kg / m 3 , and Fe TReduce to 2.0 g / l.

[0039] Second neutralization and iron and arsenic removal stage: Add limestone powder to the first neutralized solution and introduce air simultaneously to achieve deep arsenic removal while iron is neutralized and precipitated; the addition of limestone powder neutralizes the acid radical released during the iron precipitation process. The pH of the solution is controlled at 5.2 during this process to achieve deep removal of arsenic and iron. The addition amount of limestone powder is 2.5 kg / m 3 , and finally, the arsenic content is reduced to 0.1 mg / l and the iron content is reduced to 18 mg / l.

[0040] Industrial production example:

[0041] Pump a zinc sulfate solution containing 3 - 5 g / l of acid, 140 - 150 g / l of zinc, 1 - 2 g / l of Fe T : 40 - 50 mg / l of As, and 1300 - 1500 mg / l of Cu into two 280 m³ displacement copper precipitation operation tanks arranged in a stepped manner at a flow rate of 220 - 280 m³ / h. Continuously add reduced iron powder at a rate of 0.51 t / h - 0.56 t / h (the converted addition amount of iron powder is 1.8 - 2.0 kg / m 3 ). The solution enters from the bottom and exits from the top. The outflowing solution enters a 300 m 2 chamber filter press for pressure filtration. The filtrate is sent to seven 280 m³ iron removal operation tanks arranged in a stepped manner. Roasted ore is added to the first three operation tanks for the first neutralization treatment. The continuous addition amount of roasted ore is controlled at 12.6 - 14 t / h to ensure that the pH of the solution is controlled between 2.8 - 3.5. After the first neutralization treatment, it enters a thickener for thickening. The thickened underflow is returned to the oxygen pressure leaching process for further treatment. The thickened supernatant flows into the latter four operation tanks for the second neutralization treatment. The total addition amount of limestone powder added to the four operation tanks is controlled between 0.664 - 0.74 t / h (the converted addition amount of limestone powder is 2.3 - 2.5 kg / m 3 ). The pH of the solution is controlled between 5.0 - 5.2. Oxygen is introduced into the operation tank during the neutralization process to slowly and continuously oxidize Fe 2+ into Fe 3+ . After the second neutralization treatment, it enters a thickener for thickening. The thickened underflow is sent to a filter press for pressure filtration. The produced slag is iron - arsenic slag. The thickened supernatant, which is the middle supernatant, is sent to the purification process for further treatment. The arsenic content in the middle supernatant solution produced by the second neutralization treatment is reduced to below 0.2 mg / l, and the iron content is reduced to below 20 mg / l.

[0042] Table 1 shows the analysis data of the supernatant solution during the industrial production process using this invention method from June 2024 to March 2025. It can be seen from the table that the arsenic content in the middle supernatant solution is reduced to below 0.2 mg / l, and the Fe content in the solution TIt has been reduced to below 20 mg / l. From the perspective of the actual production effect, its arsenic removal effect is better than that in the laboratory. At the same time, according to the treatment scale in the industrial production example, 200 - 220 t (dry basis) of copper-arsenic slag is produced every month; after conversion based on the main product electrolytic zinc, 1.55 - 1.57 kg of copper-arsenic slag is produced per ton of zinc in the above industrial production process.

[0043]

Claims

1. A method for deep removal of arsenic from a high arsenic zinc sulfate solution, characterized in that: The method comprises the following steps: The reduced iron powder is added to the arsenic-containing zinc sulfate solution, the temperature is controlled at 70-80°C, and the time is controlled at 1-1.5 hours to carry out copper precipitation and arsenic removal. After copper precipitation and arsenic removal, the arsenic content of the solution is reduced to 20-30 mg / l, and arsenic-containing copper slag is produced. After copper precipitation and arsenic removal, zinc roasted sand is added to the solution for a neutralization treatment. During the neutralization process, oxygen-containing gas is introduced to remove Fe 2+ Oxidized to Fe 3+ The solution is acid-neutralized to a pH value between 2.8 and 3.

5. After the first neutralization treatment, neutralized slag and neutralized liquid are produced. The neutralized slag is returned to the oxygen pressure leaching process to further recover zinc. The first neutralized liquid enters the second neutralization process for deep iron precipitation and arsenic removal. Limestone powder is added to the first neutralized liquid. The pH value of the solution is controlled to between 5.0 and 5.

2. At the same time, oxygen-containing gas is introduced to reduce the arsenic in the solution to less than 0.2 mg / l, and the iron to less than 20 mg / l. The arsenic in the arsenic-containing copper slag exists in a zero-valent form, and the zinc sulfate solution contains copper.

2. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: Arsenic exists in arsenic-containing copper slag at zero valence.

3. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: In the zinc sulfate solution, the acid concentration is 3-5 g / l; in the zinc sulfate solution, the zinc concentration is 145-150 g / l.

4. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: In the zinc sulfate solution, the concentration of arsenic is greater than or equal to 40 mg / l. As a further preferred embodiment, the concentration of arsenic in the zinc sulfate solution is 40-60 mg / l.

5. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: The concentration of copper in the zinc sulfate solution is 1300-1500 mg / l; In the zinc sulfate solution, Fe T The total iron concentration is 1~2g / l.

6. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: The concentration of copper in the solution after copper precipitation and arsenic removal is 250-300 mg / l, and the concentration of iron ions is 3-5 g / l.

7. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: When copper is deposited and arsenic is removed, the amount of reduced iron powder added is 1.8-2.0kg / m 3 .

8. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: Neutralization treatment, adding zinc roasted sand and introducing oxygen at the same time, the amount of zinc roasted sand added is controlled at 45-50kg / m 3 , part of the iron sinks into the slag, Fe T Reduced to 1.5-2.5g / l.

9. The method for deep removal of arsenic from a high arsenic-containing zinc sulfate solution according to claim 1, characterized in that: Add limestone powder to the liquid obtained after the neutralization treatment, and introduce oxygen-containing gas at the same time to achieve deep removal of arsenic while neutralizing and precipitating iron; the solution pH is controlled at 5.0-5.2 during this process, and the amount of limestone powder added is 2.3-2.5kg / m 3 .

10. The method for deep removal of arsenic from a high arsenic zinc sulfate solution according to claim 1, characterized in that: After the secondary neutralization treatment, deep removal of arsenic can be achieved. In the liquid after the secondary neutralization treatment, the As concentration is reduced to below 0.2 mg / l; the iron concentration is reduced to below 20 mg / l.

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