A method for treating arsenic in an arsenic-containing solution using zinc oxide fume

Abstract

The application discloses a method for treating arsenic in an arsenic-containing solution by using zinc oxide fume, and the method uses the solution after zinc germanium is precipitated from the zinc oxide fume leaching solution as raw material. The method uses zinc oxide fume as a neutralizing agent and potassium permanganate as an oxidizing agent, and adopts a two-stage countercurrent neutralization process to realize the reduction of wet zinc smelting iron slag from the source. Researches show that under the conditions that the dosage of zinc oxide fume is 5 g / L, the reaction temperature is 80 DEG C, and the neutralization reaction time is 1 h, the arsenic content in the solution is reduced from 719.20 mg / L to 8.60 mg / L, the arsenic removal rate reaches 98.83%, and the slag amount is reduced to 8 g / L. The slag is treated by an isasmelt lead smelting system, and the valuable metals of zinc, lead and germanium are recovered, and the arsenic is concentrated and disposed.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for treating arsenic in arsenic-containing solutions using zinc oxide fume. Background Technology

[0002] Zinc oxide dust is an important secondary resource in the zinc smelting process, containing various valuable components such as zinc, lead, germanium, indium, and silver, as well as harmful impurities such as arsenic, fluorine, and chlorine. A classic wet process for treating zinc oxide dust involves a first-stage low-acid leaching followed by a second-stage high-acid leaching. During leaching, readily acid-reactive components such as zinc, germanium, indium, arsenic, fluorine, and chlorine are leached into the solution, while difficult-to-leach components such as lead and silver are deposited in the lead slag. After recovering germanium and indium from the zinc oxide dust leachate, the solution contains a high concentration of arsenic, necessitating arsenic removal treatment. Using lime as a neutralizing agent and adding an oxidizing agent to completely oxidize ferrous iron, followed by neutralization, hydrolysis, and precipitation of ferric iron to remove arsenic, is a commonly used arsenic removal process in production. The resulting slag is called iron slag, with the main components (%) being: Zn 6-8, As 1.5-2.5, and Fe 10-15. This method has advantages such as high arsenic removal rate and thorough removal of impurities from the solution. However, this method produces a large amount of iron slag, has low recycling value, and is classified as hazardous waste. Smelting enterprises often outsource its disposal, which presents drawbacks such as significant safety and environmental hazards during transportation and high disposal costs. Therefore, research on iron slag reduction technology in hydrometallurgical zinc smelting is of significant practical importance to hydrometallurgical zinc smelting enterprises. Summary of the Invention

[0003] The purpose of this invention is to provide a method for treating arsenic in arsenic-containing solutions using zinc oxide fume.

[0004] The objective of this invention is achieved as follows: the method for treating arsenic-containing solutions using zinc oxide fume includes a first-stage neutralization and precipitation of arsenic and a second-stage neutralization and precipitation of arsenic, specifically comprising: A. First-stage neutralization and precipitation of arsenic: An oxidant is added to the arsenic-containing solution, and after reaction, the arsenic-containing slag a and reaction solution b are obtained by liquid-solid separation; B. Second-stage neutralization and arsenic precipitation: Zinc oxide dust is added to the reaction solution b and reacted. After liquid-solid separation, the second-stage residue c and the arsenic-removed solution d are obtained. The second-stage residue is returned to the first-stage neutralization and arsenic precipitation step.

[0005] This invention addresses the arsenic-containing solution after recovering valuable metals such as germanium from zinc oxide flue gas leaching solution. Using zinc oxide flue gas as a neutralizing agent and potassium permanganate as an oxidizing agent, a two-stage countercurrent neutralization process is employed. This significantly reduces slag volume while achieving arsenic removal. The arsenic-containing slag is then processed through a lead smelting system to recover valuable components such as zinc, lead, and germanium. Simultaneously, arsenic is centrally and openly treated from the waste acid in the lead system, avoiding many shortcomings of multi-point dispersed arsenic treatment. Attached Figure Description

[0006] Figure 1This is a process flow diagram of the present invention; Figure 2 A schematic diagram showing the effect of zinc oxide dust dosage on arsenic removal; Figure 3 A schematic diagram showing the effect of potassium permanganate dosage on arsenic removal; Figure 4 This is a schematic diagram illustrating the effect of reaction temperature on arsenic removal. Figure 5 This is a schematic diagram illustrating the effect of neutralization reaction time on arsenic removal. Detailed Implementation

[0007] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0008] The method for treating arsenic in an arsenic-containing solution using zinc oxide fume as described in this invention includes a first-stage neutralization and precipitation of arsenic and a second-stage neutralization and precipitation of arsenic, specifically comprising: A. First-stage neutralization and precipitation of arsenic: An oxidant is added to the arsenic-containing solution, and after reaction, the arsenic-containing slag a and reaction solution b are obtained by liquid-solid separation; B. Second-stage neutralization and arsenic precipitation: Zinc oxide dust is added to the reaction solution b and reacted. After liquid-solid separation, the second-stage residue c and the arsenic-removed solution d are obtained. The second-stage residue is returned to the first-stage neutralization and arsenic precipitation step.

[0009] The amount of oxidant used in step A is 0.8~1.0 g / L.

[0010] The oxidant is potassium permanganate.

[0011] The reaction temperature in step A is 75~85℃.

[0012] The reaction time in step A is 20-40 minutes.

[0013] The arsenic-containing solution is the arsenic-containing solution obtained after recovering valuable metals from zinc oxide flue dust leachate.

[0014] In step B, the zinc oxide fume is high-Pb zinc oxide fume.

[0015] The main components of the zinc oxide fume, by mass percentage, are: Zn 40-50%, Pb 15-25%, Fe 3-8%, Ge 0.02-0.09%, In 0.002-0.01%, Ag 0.02-0.06%, S 3-9%, SiO2 2-6%, CaO 0.3-1.0%, MgO 0.1-0.2%, As 0.5-0.8%, Cl 0.1-0.3%, Cu 0.02-0.06%, F 0.01-0.03%, with the remainder being unavoidable impurities.

[0016] The amount of zinc oxide dust used in step B is 4~6 g / L.

[0017] In step B, the reaction temperature is 75~85℃ and the reaction time is 50~70min.

[0018] The invention will be further illustrated below with specific implementation examples: Example 1 1. Experimental Section 1.1 Test materials The experimental raw material, after germanium precipitation, was an arsenic-containing solution from the zinc oxide flue gas leaching solution of a smelter in Yunnan Province, obtained after recovering valuable metals such as germanium. The solution pH was 2.0–3.0, and the main elemental composition (g / L) was: Zn 110, Fe 110. 2+ 6.70, other lower content components (mg / L): As 719.20, Cd 419.93, Ca 435.50, Ge 20.90, Cu 11.51, Mg 14.14, Fe 3+ 12. It can be seen that the main components of this solution are zinc and iron, with iron mainly existing in the form of ferrous iron. The content of the harmful component arsenic is relatively high, making it a typical zinc oxide flue dust leachate.

[0019] The zinc oxide dust used as a neutralizing agent in the experiment has the following main components (%): Zn 44.54, Pb 19.83, Fe 3.56, Ge 0.066, In 0.0085, Ag 0.029, S 5.09, SiO2 2.46, CaO 0.88, MgO 0.18, As 0.69, Cl 0.13, Cu 0.054, F 0.014. It can be seen that this zinc oxide dust is a typical high-Pb zinc oxide dust. Furthermore, the dust contains 666.70 g / t of Ge and 291.0 g / t of Ag, and the content of rare and dispersed metals is also relatively high, indicating significant comprehensive utilization value. Therefore, the recovery and utilization of valuable components should also be considered for the slag obtained using this dust as a neutralizing agent.

[0020] The experiment used analytical grade potassium permanganate as an oxidant to selectively oxidize and regulate the hydrolysis of iron ions.

[0021] 1.2 Test Methods Arsenic removal is achieved using a two-stage countercurrent process.

[0022] (1) For the first stage of neutralization and precipitation of arsenic, a certain volume of solution is placed in a beaker and kept warm in a constant temperature water bath. A certain amount of oxidant is added and after a certain reaction time, the second stage of neutralization residue is added. After a certain reaction time, the liquid and solid are separated. The wet weight of the residue is recorded. The wet residue is dried at 80℃ for 24 hours and then weighed. The target element is analyzed in the residue. The solution is then subjected to the second stage of neutralization and precipitation of arsenic.

[0023] (2) Two-stage neutralization and precipitation of arsenic: the liquid after the first stage of neutralization is placed in a beaker and kept warm in a constant temperature water bath at a certain temperature. A certain amount of neutralizing agent is added and the liquid and solid are separated after a certain reaction time. The residue is returned to the first stage of neutralization, the volume of the liquid is recorded, the target elements such as arsenic are analyzed, and the arsenic removal rate is calculated.

[0024] 2. Experimental Results and Discussion 2.1 Effect of Zinc Oxide Dust Dosage on Arsenic Removal The effect of zinc oxide fume dosage on arsenic removal was investigated under the experimental conditions of 300 ml solution, reaction temperature of 80℃, potassium permanganate dosage of 0.90 g / L, oxidation time of 30 min, and neutralization reaction time of 2.0 h. The experimental results are shown in [Figure number missing]. Figure 2 As shown.

[0025] from Figure 2 It can be seen that as the amount of zinc oxide dust increases, the arsenic concentration in the solution decreases, and the arsenic removal rate increases. When the amount of zinc oxide dust increases from 1 g / L to 6 g / L, the arsenic content in the solution after arsenic removal decreases from 532.13 mg / L to 5.64 mg / L, the arsenic removal rate increases from 28.48% to 99.26%, and the slag volume increases from 1.75 g / L to 8.23 ​​g / L. Increasing the amount of neutralizing agent results in a higher solution pH, which is beneficial for iron hydrolysis and arsenic precipitation. However, excessive neutralizing agent will lead to a larger slag volume, which is detrimental to subsequent treatment. Therefore, considering actual production control to keep As <10 mg / L, the optimal amount of zinc oxide dust is 5 g / L.

[0026] 2.2 Effect of potassium permanganate dosage on arsenic removal The effect of potassium permanganate dosage on arsenic removal was investigated under the following experimental conditions: 300 ml solution, reaction temperature 80℃, zinc oxide fume dosage 5 g / L, oxidation time 30 min, and neutralization reaction time 2.0 h. The experimental results are shown in [Figure number missing]. Figure 3 As shown.

[0027] from Figure 3It can be seen that as the amount of potassium permanganate increases, the arsenic concentration in the solution decreases, and the arsenic removal rate increases. When the amount of potassium permanganate is below 0.90 g / L wet, the arsenic removal rate increases rapidly with increasing potassium permanganate dosage; when the amount of potassium permanganate reaches above 0.90 g / L, the arsenic removal rate tends to stabilize. This is because in the zinc oxide flue dust leachate, the content of trivalent arsenic ions, which are difficult to precipitate, is about 60%~80%. Although sufficient neutralizing agent is added to make the solution pH reach 5.5, arsenic is still difficult to completely remove. Adding potassium permanganate has two effects: first, it oxidizes the difficult-to-precipitate trivalent arsenate ions into pentavalent arsenate ions that precipitate in the solution. The pentavalent arsenate ions react with trivalent ferric ions to form ferric arsenate precipitate; second, it partially oxidizes divalent ferric ions into trivalent ferric ions. The trivalent ferric ions hydrolyze to form colloids, and the colloids adsorb pentavalent arsenate ions, promoting the deep removal of arsenic. The appropriate amount of potassium permanganate is 0.90 g / L.

[0028] 2.3 Effect of reaction temperature on arsenic removal The effect of reaction temperature on arsenic removal was investigated under the following experimental conditions: 300 ml solution, 10 g / L zinc oxide fume, 0.90 g / L potassium permanganate, 30 min oxidation time, and 2.0 h neutralization reaction time. The results are shown in [Figure number missing]. Figure 4 As shown.

[0029] from Figure 4 It can be seen that increasing the reaction temperature is beneficial to arsenic removal, especially for improving the filtration performance of the slurry. As the reaction temperature increased from 40℃ to 80℃, the arsenic removal rate increased from 96.40% to 98.90%, showing a certain improvement. Simultaneously, the slurry filtration time decreased from 72 minutes at 40℃ to 3 minutes at 80℃, indicating that temperature has a significant impact on slurry filtration performance. This is because, during the neutralization process, iron hydrolysis produces ferric hydroxide colloids, which themselves have poor filtration performance. At higher temperatures, the high temperature can promote the migration and aggregation of ferric hydroxide colloidal ions in the solution, producing larger colloidal aggregates, thereby improving the slurry filtration performance. Therefore, the optimal reaction temperature is 80℃.

[0030] 2.4 Effect of neutralization reaction time on arsenic removal The effect of neutralization reaction time on arsenic removal was investigated under the following experimental conditions: 300 ml solution, reaction temperature 80℃, zinc oxide fume dosage 5 g / L, potassium permanganate dosage 0.90 g / L, and oxidation time 30 min. The experimental results are shown in [Figure number missing]. Figure 5 As shown.

[0031] from Figure 5 It can be seen that when the neutralization reaction time is 1 hour, the arsenic removal rate reaches 98.77%, and further extending the neutralization reaction time does not significantly improve the arsenic removal rate. Therefore, a neutralization reaction time of 1 hour was chosen.

[0032] 2.5 Comprehensive Condition Test The optimal combined conditions obtained through experiments were: a two-stage countercurrent neutralization arsenic removal process, a reaction temperature of 80℃, a zinc oxide dust dosage of 5 g / L, a potassium permanganate dosage of 0.90 g / L, an oxidation time of 30 min, and a neutralization reaction time of 1 h. Under these combined conditions, experiments were conducted, and the results are shown in Table 1.

[0033] Table 1 Results of the comprehensive condition test (%)

[0034] Table 1 shows that, under comprehensive conditions, after four cycles of testing, the average arsenic content in the liquid after arsenic removal was 8.60 mg / L, the average arsenic removal rate was 98.83%, the average slag weight was 7.99 g / L, and the average contents of zinc, arsenic, and lead in the slag were 19.21%, 8.30%, and 24.04%, respectively. A smelting enterprise in Yunnan currently uses lime neutralization and water removal to remove arsenic, resulting in an iron slag weight of approximately 31 g / L and an arsenic content of 1.5-2.5%. This process, however, results in an arsenic-containing slag weight of 8 g / L, a significant reduction in slag weight, and simultaneously, an increase in arsenic grade.

[0035] Based on the slag composition in Table 1, the arsenic-containing slag has high levels of valuable components such as zinc and lead, and germanium in the solution also precipitates into the slag. Therefore, this slag can be incorporated into the lead slag and fed into the Isa furnace lead smelting system. The lead enters the crude lead, while the zinc, germanium, and a small amount of arsenic enter the flue dust. Most of the arsenic enters the waste acid of the lead system, and the arsenic is centrally treated from the waste acid, thereby achieving the recovery of valuable components and the opening of the arsenic pathway.

Claims

1. A method for treating arsenic in an arsenic-containing solution using zinc oxide fume, characterized in that, The method for treating arsenic-containing solutions using zinc oxide fume includes a first-stage neutralization and precipitation of arsenic and a second-stage neutralization and precipitation of arsenic, specifically including: A. First-stage neutralization and arsenic precipitation: In the arsenic-containing solution after recovering valuable metals from zinc oxide flue dust leachate, potassium permanganate oxidant is added. After reacting for a certain period of time, second-stage neutralization slag c is added. After reacting for a certain period of time, arsenic-containing slag a and reaction liquid b are obtained through liquid-solid separation. After analyzing the target elements, arsenic-containing slag a is sent to the lead smelting system for processing, and reaction liquid b undergoes second-stage neutralization and arsenic precipitation. B. Second-stage neutralization and arsenic precipitation: High-Pb zinc oxide dust is added to reaction solution b for reaction, and then liquid-solid separation is performed to obtain second-stage neutralization residue c and arsenic-removed solution d. Second-stage neutralization residue c is returned to the first-stage neutralization and arsenic precipitation step.

2. The method for treating arsenic in an arsenic-containing solution using zinc oxide fume according to claim 1, characterized in that, The amount of oxidant used in step A is 0.8~1.0 g / L.

3. The method for treating arsenic in an arsenic-containing solution using zinc oxide fume according to claim 1, characterized in that, The reaction temperature in step A is 75~85℃.

4. The method for treating arsenic in an arsenic-containing solution using zinc oxide fume according to claim 1, characterized in that, The reaction time in step A is 20-40 minutes.

5. The method for treating arsenic in an arsenic-containing solution using zinc oxide fume according to claim 1, characterized in that, The arsenic-containing solution has a pH of 2.0-3.0 and its main elemental components are Zn 110 and Fe. 2+ 6.70, unit is g / L. Other components with lower content: As 719.20, Cd 419.93, Ca 435.50, Ge 20.90, Cu 11.51, Mg 14.14, Fe 3+ 12, in mg / L.

6. The method for treating arsenic in an arsenic-containing solution using zinc oxide fume according to claim 1, characterized in that, The amount of zinc oxide dust used in step B is 4~6 g / L.

7. The method for treating arsenic in an arsenic-containing solution using zinc oxide fume according to claim 1, characterized in that, In step B, the reaction temperature is 75~85℃ and the reaction time is 50~70min.

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