Zinc-iron separation method, application and application of zinc-iron separation device

Abstract

The present invention provides a zinc-iron separation method, comprising the following steps: S1. mixing zinc-iron waste liquid with a complexing agent to obtain a mixed liquid; adding a first hydrogen sulfide to the mixed liquid, causing the first hydrogen sulfide to undergo a first gas-liquid sulfidation reaction with zinc ions in the mixed liquid, and maintaining the pH of the first reaction liquid of the first gas-liquid sulfidation reaction at 2 to 5 during the reaction; the complexing agent having a greater binding capacity for iron than for zinc; S2. performing solid-liquid separation on the first reaction liquid to obtain a zinc-containing precipitate and an iron-containing separated liquid; S3. adding a second hydrogen sulfide to the iron-containing separated liquid, causing the second hydrogen sulfide to undergo a second gas-liquid sulfidation reaction with ferrous ions in the iron-containing separated liquid, and maintaining the pH of the second reaction liquid of the second gas-liquid sulfidation reaction at 6 to 9 during the reaction; and performing solid-liquid separation to obtain an iron-containing precipitate. The present invention can achieve efficient and thorough separation of zinc and iron, has significant effects, and is worthy of promotion.

Description

Technical Field

[0001] The present invention belongs to the field of wastewater treatment, and in particular relates to a zinc-iron separation method, application and application of a zinc-iron separation device. Background Art

[0002] Nonferrous metallurgy, hot-dip galvanizing, electroplating, and other industries generate tens of millions of tons of highly concentrated, acidic zinc-iron mixtures annually during production. These mixtures typically have a low pH and are difficult to separate due to the similar properties of zinc and iron. For example, zinc leachate from nonferrous metallurgy and hot-dip galvanizing wastewater are examples. Currently, over 85% of zinc smelters use hydrometallurgical zinc smelting, which inevitably produces various acidic wastewaters containing zinc and iron. One of the key core technologies for this process is zinc-iron separation. Similarly, in the hot-dip galvanizing process, acidic wastewater from the pickling and rinsing stages is generated, containing iron and zinc ions. Direct discharge would pose a significant environmental risk, and therefore requires separation and treatment before discharge.

[0003] Chemical precipitation is a heavy metal waste liquid treatment process commonly used at home and abroad. The heavy metal concentration in the purified water basically meets the national or industry emission standards. However, the co-precipitation of heavy metals in the treatment process produces a large amount of hazardous waste, the secondary pollution problem is prominent, and the valuable resources in the waste liquid are seriously lost.

[0004] Among commonly used technologies, iron removal from zinc leachate in non-ferrous smelting primarily involves the jarosite, goethite, and hematite methods. The jarosite and goethite methods produce millions of tons of low-grade zinc-containing jarosite and goethite slag annually. These slags have low iron content and pose high environmental risks, making them hazardous solid wastes. While the hematite method produces slag with a higher iron content, the entire process requires high temperature and pressure, strict reaction conditions, and incomplete zinc and iron separation.

[0005] For example, Li Xingbin et al. disclosed a method for mineralizing iron precipitation from hydrometallurgical zinc smelting leachate, patented under CN 114807625 A. The leachate is added to a reactor and reacted in oxygen-containing conditions at 100°C to 170°C. Zinc oxide is introduced during the reaction, and the pH value is controlled at 0.2 to 2.0 at the end of the reaction. Liquid-solid separation yields a mineralized iron precipitation product and a zinc sulfate solution. This method requires pH adjustment in a high-temperature, high-pressure reactor. The operating conditions are harsh and difficult to control, resulting in uneven contact between the materials and uneven acid-base distribution. This results in poor zinc-iron separation, with some zinc ions still being mixed into the iron precipitation product, causing zinc loss. Summary of the Invention

[0006] In order to solve the technical problem of poor zinc-iron separation and zinc loss, the present invention provides a zinc-iron separation method, comprising the steps of:

[0007] S1. Mixing the zinc-iron waste liquid with a complexing agent to obtain a mixed liquid, adding a first hydrogen sulfide to the mixed liquid, and causing the first hydrogen sulfide to react with the zinc ions in the mixed liquid to undergo a first gas-liquid sulfidation reaction, and maintaining the pH of the first reaction liquid of the first gas-liquid sulfidation reaction at 2 to 5 during the reaction;

[0008] The binding capacity of the complexing agent to the iron element is greater than the binding capacity of the complexing agent to the zinc element;

[0009] The concentration of zinc in the zinc-iron waste liquid is 0.3-5 g / L, and the concentration of iron in the zinc-iron waste liquid is 0.3-5 g / L;

[0010] S2. The first reaction solution is separated into a solid-liquid state to obtain a zinc-containing precipitate and an iron-containing separated liquid;

[0011] S3. A second hydrogen sulfide is added to the iron-containing separated liquid, and the second hydrogen sulfide undergoes a second gas-liquid sulfidation reaction with the ferrous ions in the iron-containing separated liquid. During the reaction, the pH of the second reaction liquid of the second gas-liquid sulfidation reaction is maintained at 6 to 9, and solid-liquid separation is performed to obtain an iron-containing precipitate.

[0012] Furthermore, the complexing agent includes one or more of acetylacetone, salicylic acid, and sodium tartrate; and the molar ratio of the complexing agent to the iron ions in the zinc-iron waste liquid is 0.9 to 1.2.

[0013] Furthermore, the molar ratio of the first hydrogen sulfide to the zinc ions in the zinc-iron waste liquid is 1.4-2.0, and the molar ratio of the second hydrogen sulfide to the iron ions in the iron-containing separation liquid is 1.1-1.5.

[0014] Furthermore, the temperature of the first gas-liquid sulfidation reaction is 25°C to 65°C, and the duration of the first gas-liquid sulfidation reaction is 20 to 60 minutes; the temperature of the second gas-liquid sulfidation reaction is 25°C to 65°C, and the duration of the second gas-liquid sulfidation reaction is 20 to 60 minutes.

[0015] Furthermore, in step S1, maintaining the pH of the first reaction liquid of the first gas-liquid sulfidation reaction at 2-5 during the reaction process includes: adding alkali solution to the first reaction liquid to stabilize the pH at 2-5; the alkali solution includes sodium hydroxide.

[0016] Furthermore, the preparation of the first hydrogen sulfide and the second hydrogen sulfide includes: adding dilute acid to a sulfur-containing compound; the sulfur-containing compound includes one or more of sodium sulfide, sodium hydrosulfide, and ferrous sulfide, and the dilute acid includes sulfuric acid with a concentration of 0.1 to 1 mol / L.

[0017] Furthermore, the first reaction solution maintains a circulating flow during the reaction process, a portion of the first reaction solution generates a jet negative pressure during the circulating flow, and the first hydrogen sulfide mixes with the first reaction solution from the negative pressure location; and / or;

[0018] The second reaction solution keeps circulating during the reaction process, and part of the second reaction solution generates jet negative pressure during the circulating flow, and the second hydrogen sulfide is mixed with the second reaction solution at the negative pressure.

[0019] The present invention also provides an application of any of the above-described zinc-iron separation methods in zinc-iron wastewater treatment.

[0020] The present invention also provides an application of a zinc-iron separation device in any of the above zinc-iron separation methods, wherein the zinc-iron separation device comprises:

[0021] a hydrogen sulfide gas source, for providing the first hydrogen sulfide and / or the second hydrogen sulfide;

[0022] The reaction part includes an ejector, a circulation pump 7, a circulation pipeline and a reaction container; the reaction container is used to contain the first reaction solution and / or the second reaction solution;

[0023] The ejector includes a liquid inlet, a liquid outlet and an air inlet. The two ends of the circulation pipeline are connected to the accommodating cavity of the reaction container through the liquid inlet and the liquid outlet respectively. The circulation pump 7 is arranged in the circulation pipeline, and the air inlet is connected to the vulcanizer gas source.

[0024] Furthermore, the reaction container also includes a pH detection device.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The present invention strictly controls the pH uniformity and value range during the two gas-liquid sulfurization reactions. On the one hand, the present invention constructs a gas-liquid reaction system, increases the dispersion and reaction area of ​​sulfur in the reaction system, strengthens the reaction mass transfer process, avoids the concentrated distribution of sulfur ions and the pH unevenness caused by the reaction, and further improves the zinc-iron separation and precipitation effect. Among them, the sources of pH uneven distribution mainly include: the reaction of sulfur ions with metals to generate H + The uneven distribution of sulfur ions causes differences in the pH distribution of zinc-iron wastewater, affecting the rate and process of zinc precipitation. In order to maintain pH stability, NaOH is added to make OH in the reaction system - The concentration increases, causing OH - The local concentration is too high, causing some ferric ions or ferrous ions to be entrained and precipitated.

[0027] On the other hand, the present invention uses pH to regulate the reaction process of sulfide ions and metal ions to achieve selective precipitation of zinc and iron and optimize the separation effect of zinc and iron. The first gas-liquid sulfidation reaction is carried out under the condition of pH 2-5, and zinc reacts with hydrogen sulfide to form sulfide precipitate. The sulfidation reaction is: H2S+Zn 2+ =ZnS+2H + The second gas-liquid sulfidation reaction is carried out under the condition of pH 6-9, iron forms sulfide precipitation under neutral conditions, and the sulfidation reaction is H2S+Fe 2+ =FeS+2H + , 2Fe 3+ +HS - =2Fe 2+ +S+H + .

[0028] Based on the stability constant of the metal-ligand complex, the present invention enhances the stability of iron ions in the mixed solution by complexing the complexing agent with iron, further reducing the competitive binding of iron with sulfur ions, allowing hydrogen sulfide to react with zinc to the maximum extent, thereby improving the separation efficiency of zinc and iron in the sulfurization reaction. In this process, hydrogen sulfide converts zinc into a sulfide precipitate, while the iron remains in the solution in ionic form, thus achieving efficient zinc and iron separation. After adjusting the pH of the iron-containing separation solution, hydrogen sulfide is introduced to form ferrous sulfide. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0030] Figure 1 Schematic diagram of the structure of the zinc-iron separation device in the present invention;

[0031] Among them, 1-protective gas cylinder; 2-liquid storage tank; 3-two-way valve; 4-gas storage tank; 5-sulfur production device; 6-constant temperature water bath; 7-circulation pump; 8-separating funnel; 9-reaction container; 10-ejector; 11-pH detection device;

[0032] Figure 2: is a separation effect diagram of zinc-iron waste liquid in the present invention; wherein, (a) is a separation effect diagram of the liquid obtained after the sulfidation reaction in Example 1, (b) is a separation effect diagram of the liquid obtained after the sulfidation reaction in Example 2, (c) is a separation effect diagram of the liquid obtained after the sulfidation reaction in Example 3, (d) is a separation effect diagram of the liquid obtained after the sulfidation reaction in Comparative Example 1; (e) is a separation effect diagram of the liquid obtained after the sulfidation reaction in Comparative Example 2, and (f) is a separation effect diagram of the liquid obtained after the sulfidation reaction in Comparative Example 3.

[0033] Figure 3 This is a 50,000x scanning electron microscope image of the zinc-containing precipitate in Example 1;

[0034] Figure 4 This is a 50,000x scanning electron microscope image of the zinc-containing precipitate in Example 2;

[0035] Figure 5 This is a 50,000x scanning electron microscope image of the zinc-containing precipitate in Example 3;

[0036] Figure 6 This is a 10,000x scanning electron microscope image of the zinc-containing precipitate in Comparative Example 1;

[0037] Figure 7 This is a 10,000x scanning electron microscope image of the zinc-containing precipitate in Comparative Example 2;

[0038] Figure 8 This is a 10,000-fold scanning electron microscope image of the zinc-containing precipitate in Comparative Example 3. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0040] Moreover, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be used. Unless otherwise defined, all technical and scientific terms used herein are consistent with the prior art as understood by those skilled in the art and the description of the present invention. Any prior art methods, devices, and materials similar or equivalent to those described in the examples of the present invention may also be used to implement the present invention.

[0042] The present invention provides a method for separating zinc and iron, comprising the steps of:

[0043] S1. Mixing zinc-iron waste liquid with a chelating agent to obtain a mixed liquid, adding a first hydrogen sulfide to the mixed liquid, and causing the first hydrogen sulfide to react with the zinc ions in the mixed liquid to undergo a first gas-liquid sulfidation reaction, and maintaining the pH of the first reaction liquid of the first gas-liquid sulfidation reaction at 2 to 5 during the reaction.

[0044] Zinc-iron waste liquid can be a high-concentration acidic zinc-iron mixture generated in the production process of non-ferrous metallurgy, hot-dip galvanizing, electroplating and other industries; in the laboratory, zinc-iron waste liquid with a zinc concentration of 0.3-5g / L and an iron concentration of 0.3-5g / L can be pre-prepared to simulate zinc-iron wastewater.

[0045] The complexing agent has a greater binding capacity for iron than for zinc. The complexing agent may include one or more of acetylacetone, salicylic acid, and sodium tartrate. The molar ratio of the complexing agent to the iron ions in the zinc-iron wastewater is 0.9 to 1.2, ensuring sufficient and effective complexation of the complexing agent with iron while preventing reduced zinc sulfidation efficiency and zinc loss due to excessive complexation of the complexing agent with zinc.

[0046] Due to the difference in the complex stability constants of zinc and iron ions, the iron ion has a greater complex stability constant than the zinc ion. Iron ions preferentially form a more stable complex with the chelating agent, which not only weakens the competition of iron with zinc in the gas-liquid sulfidation process but also effectively avoids iron ion precipitation in the first gas-liquid sulfidation reaction caused by uneven pH distribution (such as excessively high local hydroxide ion concentration). At the same time, during this process, changes in pH do not affect the complexation effect of iron with the chelating agent, thereby ensuring that the chelating agent plays the role of strengthening the separation of zinc and iron.

[0047] The first hydrogen sulfide, i.e., hydrogen sulfide, can be prepared by adding a dilute acid to a sulfur-containing compound; the sulfur-containing compound may include one or more of sodium sulfide, sodium hydrosulfide, and ferrous sulfide, and the dilute acid may include sulfuric acid at a concentration of 0.1 to 1 mol / L. Hydrogen sulfide can efficiently reduce trivalent ferrous ions to divalent ferrous ions while simultaneously precipitating zinc ions, allowing the iron to be precipitated as the more stable ferrous sulfide in the second gas-liquid sulfidation reaction.

[0048] Preferably, the dilute acid can be added in sufficient amount to ensure efficient and high-quantity generation of hydrogen sulfide.

[0049] pH control, a key feature of the present invention, directly impacts zinc and iron precipitation, as its range and distribution uniformity can directly influence the precipitation of zinc and iron. On the one hand, controlling the pH between 2 and 5 allows sulfur ions to selectively bind to zinc ions, while iron ions remain in the liquid phase, achieving a preliminary separation of zinc and iron. Maintaining the pH between 2 and 5 can include adding an alkaline solution to the mixed solution to mitigate acidification caused by hydrogen ion generation during the first gas-liquid sulfidation reaction.

[0050] It should be noted that it is preferred to control the pH of the first reaction liquid to a single value rather than fluctuating within the range of 2 to 5. The reason is that the pH in the reaction will continue to decrease due to the sulfidation reaction. By adding alkaline solution to regulate and maintain the pH so that it is fixed at a single value, the reaction is more stable and more intuitive in the display of the pH meter.

[0051] It should also be noted that, as a preferred embodiment of the present invention, the pH of the first reaction solution can be controlled at 3 to 4. This is because, during the first sulfidation reaction, when the pH is 2, although iron hardly precipitates, the zinc precipitation rate is relatively low, resulting in zinc loss. In contrast, when the pH is within the range of 3 to 4, the zinc precipitation rate is significantly increased.

[0052] Preferably, the pH value during the first sulfurization reaction is controlled to be 3. At this time, the zinc precipitation rate reaches the highest while the iron precipitation can be minimized, thereby effectively improving the zinc-iron separation rate.

[0053] On the other hand, in order to improve the uniformity of pH distribution, the present invention selects hydrogen sulfide as the sulfur source and constructs a gas-liquid two-phase reaction system, which increases the dispersion and reaction area of ​​sulfide ions in the reaction system, strengthens the reaction mass transfer process, avoids the concentrated distribution of sulfide ions and the uneven pH caused by the reaction, and further improves the zinc-iron separation and precipitation effects.

[0054] Among them, the main sources of pH unevenness include: the reaction of sulfur ions with metals to generate H + The uneven distribution of sulfur ions causes differences in the pH distribution of zinc-iron wastewater, affecting the rate and process of zinc precipitation. In order to maintain pH stability, NaOH is added to make OH in the reaction system - The concentration increases, causing OH - The local concentration is too high, causing some iron ions to be entrained and precipitated.

[0055] In some embodiments, the first hydrogen sulfide can be directly blown into the mixed liquid to react with the zinc ions in the mixed liquid to produce a first gas-liquid sulfidation reaction. The reaction formula includes: H2S+Zn 2+ =ZnS+2H +.

[0056] In some preferred embodiments, the first reaction solution maintains a circulating flow during the reaction process, a portion of the first reaction solution generates a jet negative pressure during the circulating flow, and the first hydrogen sulfide mixes with the first reaction solution at the negative pressure; and / or;

[0057] The second reaction solution keeps circulating during the reaction process, and part of the second reaction solution generates jet negative pressure during the circulating flow, and the second hydrogen sulfide is mixed with the second reaction solution at the negative pressure.

[0058] Exemplarily, the zinc-iron separation device of the present invention can be used to implement this preferred embodiment. The first reaction solution is circulated to ensure that the reaction solution is in a mass transfer state. At the same time, the principle of jet negative pressure is used to eject the flowing first reaction solution from the nozzle at a high speed. The high-speed flowing liquid forms a vacuum through the mixing chamber of the ejector. After the hydrogen sulfide gas is sucked into the mixing chamber by the air duct, it is violently mixed with the first reaction solution to form a gas-liquid mixture. The strong water flow is mixed with the hydrogen sulfide gas and ejected to perform efficient material transfer. This process forms a homogeneous liquid phase containing a large number of fine hydrogen sulfide bubbles, which not only ensures the dispersion of hydrogen sulfide in the mixed solution (the first reaction solution is formed after the mixed solution is first contacted with hydrogen sulfide, and the first reaction solution can be contacted with hydrogen sulfide multiple times during the cycle), but also ensures that the first reaction solution can be stirred evenly, making the gas-liquid reaction more sufficient and complete.

[0059] In other embodiments, the first gas-liquid sulfidation reaction may be performed in a closed environment to prevent the escape of hydrogen sulfide gas.

[0060] S2. Separate the first reaction liquid into solid and liquid to obtain a zinc-containing precipitate and an iron-containing separated liquid.

[0061] In other embodiments, solid-liquid separation methods such as filtration can be used to separate the iron-containing separation liquid from the zinc-containing precipitate.

[0062] S3. A second hydrogen sulfide is added to the iron-containing separated liquid, and the second hydrogen sulfide undergoes a second gas-liquid sulfidation reaction with the ferrous ions in the iron-containing separated liquid. During the reaction, the pH of the second reaction liquid of the second gas-liquid sulfidation reaction is maintained at 6 to 9, and solid-liquid separation is performed to obtain an iron-containing precipitate.

[0063] The second hydrogen sulfide is hydrogen sulfide, and its preparation method can be the same as the first hydrogen sulfide.

[0064] Based on the aforementioned reducing effect of the first hydrogen sulfide on iron ions, the iron ions in the iron-containing separation liquid are mostly present in the form of ferrous ions.

[0065] In some embodiments, the present invention conducts the second gas-liquid sulfidation reaction at a pH of 6 to 9, efficiently precipitating ferrous ions and ferric ions to generate an iron-containing precipitate whose main component is ferrous sulfide, further achieving zinc and iron separation.

[0066] The iron ions in the present invention are mainly precipitated in the form of ferrous sulfide. On the one hand, compared with conventional technologies, such as the patent for the reuse method of zinc-iron acid solution with publication number CN 111320300 A, divalent iron ions are oxidized to trivalent iron ions by adding hydrogen peroxide or ozone, and ammonia is added to adjust its pH value so that trivalent iron ions generate ferric hydroxide to remove iron in zinc-iron waste liquid. The ferrous sulfide precipitation stability in the present invention is higher than that of ferric hydroxide precipitation, which ensures the effect of waste liquid treatment. On the other hand, the stability of ferrous sulfide in the present invention is much higher than that of iron complex, which avoids the competitive complexation of chelating agents for ferrous ions and iron ions, and reduces iron loss to the greatest extent.

[0067] In some embodiments, the temperature of the first gas-liquid sulfidation reaction is 25°C to 65°C, and the duration of the first gas-liquid sulfidation reaction is 20 to 60 minutes; the temperature of the second gas-liquid sulfidation reaction is 25°C to 65°C, and the duration of the second gas-liquid sulfidation reaction is 20 to 60 minutes.

[0068] Based on the above, the main principles of the present invention include: hydrogen sulfide dissolves in a zinc-iron mixed solution to form a gas-liquid reaction system, which increases the dispersibility of sulfur. Zinc reacts with hydrogen sulfide under acidic conditions to form a sulfide precipitate. The sulfurization reaction is: H2S+Zn 2+ =ZnS+2H + However, iron can only form sulfide precipitation under neutral conditions, and the sulfide reaction is H2S+Fe 2 + =FeS+2H + , 2Fe 3+ +HS - =2Fe 2+ +S+H + .

[0069] The present invention utilizes the differences in the stability constants of metal-ligand complexes to complex the iron with a complexing agent, thereby retaining the iron in solution while maximizing zinc's reaction with hydrogen sulfide. This improves the separation efficiency of zinc and iron during the sulfidation reaction. Based on the differences in the precipitation properties of metal sulfides, hydrogen sulfide is used to convert zinc into a sulfide precipitate, while the iron remains in solution as an ion, achieving efficient zinc and iron separation. After adjusting the pH of the iron-containing separation solution, hydrogen sulfide is introduced to form ferrous sulfide. Furthermore, the resulting zinc sulfide and ferrous sulfide have excellent precipitation properties and are easily separated from the solid.

[0070] Compared with the prior art, the present invention has the following advantages:

[0071] The present invention can achieve efficient separation of zinc and iron in waste liquid, with a separation rate of more than 99%. It not only avoids the harm of zinc and iron waste liquid to the environment, but also improves the utilization rate of resources; the divalent iron in the waste liquid does not need to be oxidized, and the trivalent iron can be reduced to divalent iron by sulfur and react with hydrogen sulfide, shortening the treatment process. The present invention first uses the complexation reaction of the complexing agent with iron to improve the separation efficiency of zinc and iron in the sulfidation reaction, and then constructs a gas-liquid reaction system through the reaction of hydrogen sulfide with the metal, thereby increasing the dispersibility and reaction area of ​​sulfur in the reaction system, strengthening the reaction mass transfer process, and avoiding the situation where iron precipitation is caused by excessively high local pH. By performing the sulfidation precipitation reaction, zinc is selectively precipitated in the form of sulfide, and iron continues to remain in the liquid. After the separation, the iron-containing separated liquid is adjusted in pH and then sulfided to generate ferrous sulfide precipitate. In addition, the purity of the separated zinc and iron precipitates in the present invention is very high and can be further recycled.

[0072] The present invention also provides an application of any of the above-described zinc-iron separation methods in the treatment of zinc-iron wastewater.

[0073] like Figure 1 As shown, the present invention also provides an application of a zinc-iron separation device in any one of the zinc-iron separation methods described above, the zinc-iron separation device comprising:

[0074] a hydrogen sulfide gas source, for providing the first hydrogen sulfide and / or the second hydrogen sulfide;

[0075] The reaction part includes an ejector 10, a circulation pump 7, a circulation pipeline and a reaction container 9; the reaction container 9 is used to contain the first reaction solution and / or the second reaction solution;

[0076] The ejector 10 includes a liquid inlet, a liquid outlet and an air inlet. The two ends of the circulation pipeline are connected to the accommodating cavity of the reaction container 9 through the liquid inlet and the liquid outlet respectively. The circulation pump 7 is arranged in the circulation pipeline, and the air inlet is connected to the vulcanizer gas source.

[0077] In some embodiments, the hydrogen sulfide gas source may include a fixedly connected protective gas cylinder 1, a liquid storage tank 2, a two-way valve, a gas storage tank 4, and a sulfur production device 5 to prepare the first hydrogen sulfide and the second hydrogen sulfide.

[0078] For example, the protective gas in the protective gas cylinder 1 may be nitrogen that is insoluble in water, so as to achieve the water displacement method for storing hydrogen sulfide.

[0079] The sulfur-producing device 5 and the reaction container 9 can be multi-necked bottles.

[0080] In some embodiments, the reaction container 9 can be placed in a constant temperature water bath to achieve constant temperature conduction of the first gas-liquid sulfidation reaction and the second gas-liquid sulfidation reaction.

[0081] In other embodiments, the reaction container 9 may also be fixedly connected to a pH detection device 11 to constantly monitor the pH of the mixed solution and the iron-containing separation liquid, thereby achieving real-time regulation of the pH and controlling the reaction process.

[0082] Illustratively, the pH detection device 11 may be a pH meter.

[0083] Specifically, the experiment involved reacting sulfur-containing compounds with dilute sulfuric acid to produce H2S gas, which was then collected by the drainage method. First, the two-way valve was closed, and the gas tank 4 was filled with a saturated H2S solution and sealed with paraffin wax. The H2S gas generated in the sulfur production unit 5 was then charged into the gas tank 4. The two-way valve 3 was opened, and the liquid in the gas tank 4 was pressed into the liquid storage tank 2. A nitrogen cylinder was opened, and the cylinder pressure gauge was adjusted to a specified pressure. This was then introduced into the gas tank 4 to produce a specific volume fraction of H2S gas. During the experiment, the temperature and solution pH were controlled, and the H2S gas was introduced into the air inlet of the ejector 10. The prepared mixed liquid was then transported to the liquid inlet of the ejector 10 via a circulation pump 7.

[0084] H2S is sucked into the ejector 10 under the pressure difference formed by the circulation of the mixed liquid in the ejector 10, and the hydrogen sulfide is violently mixed with the mixed liquid to form a gas-liquid mixture carrying a large number of hydrogen sulfide bubbles. The strong water flow and the hydrogen sulfide gas are mixed and ejected from the liquid outlet with a small aperture of the ejector 10 and enter the reaction vessel 9.

[0085] Similarly, after the first gas-liquid sulfidation reaction is complete, the solid and liquid are separated, yielding a zinc-containing precipitate and an iron-containing separated liquid. The iron-containing separated liquid enters the ejector 10 via a circulation pump 7 and a circulation pipeline. The absorbed H2S mixes vigorously with the mixed liquid, and the gas-liquid mixture, containing numerous fine bubbles, is ejected from the liquid outlet and reenters the reaction vessel 9.

[0086] The above process is an improvement based on the gas-liquid two-phase sulfidation in the present invention. The coordination of the circulation pump and the ejector ensures sufficient contact between hydrogen sulfide and the mixed liquid, further strengthens the reaction mass transfer process, effectively avoids the uneven distribution of sulfur ions causing differences in precipitation efficiency and pH distribution, and realizes efficient and thorough separation of zinc and iron.

[0087] The mixed liquid sprayed from the small-diameter liquid outlet can fully stir the mixed liquid in the reaction container 9, further ensuring the reaction efficiency and pH uniformity during the subsequent precipitation reaction in the reaction container 9 and after the addition of alkali solution.

[0088] In some embodiments, a disposable syringe can be used to slowly add an appropriate amount of sodium hydroxide solution to adjust the pH value of the mixed solution.

[0089] In order to facilitate those skilled in the art to further understand the present invention, examples are given below:

[0090] Example 1

[0091] Prepare a solution containing FeSO4 and ZnSO4 to simulate a zinc-iron mixture, where Fe 2+ 、Zn 2+ The concentrations are all 1g / L. Salicylic acid and acetylacetone are added to the zinc-iron wastewater to form a mixed solution with a molar ratio of complexing agent to iron of 1.0. This solution is stirred uniformly by an ejector 10 at a circulation pump 7 at 280 rpm. A fixed amount of sodium hydrosulfide is slowly added to excess dilute acid to generate hydrogen sulfide with a S-Zn ratio of 1.4. This mixture is then mixed and subjected to a sulfide precipitation reaction at 35°C. During this process, sodium hydroxide is added to raise the solution's pH to and stabilize it at 2. The reaction continues for half an hour.

[0092] After the reaction is completed, solid-liquid separation is performed by suction filtration to obtain a zinc-containing precipitate and an iron-containing separated liquid. The iron-containing separated liquid is adjusted to pH = 7 and then hydrogen sulfide is introduced. During the reaction, the pH is stabilized at around 7, the S-Fe ratio is 1.2, the temperature is 35°C, and the sulfidation reaction lasts for half an hour to generate an iron-containing precipitate.

[0093] In this example, after the first sulfidation, the zinc removal rate was 88.98%, the iron removal rate was 0, and the zinc ions in the solution were below the detection limit. The results show that under the same conditions, the metal separation effect of adding a complexing agent is better than that without adding a complexing agent. The scanning electron microscope image of the purified zinc precipitate (i.e., zinc sulfide) is shown in the attached figure. Figure 3 As shown, the zinc-containing precipitate contains only one substance, zinc sulfide, without iron sulfide, and is aggregated into a large number of irregular block-shaped small particles.

[0094] Example 2

[0095] Prepare a solution containing FeSO4 and ZnSO4 to simulate a zinc-iron mixture, where Zn 2+ The concentration is 1g / L, Fe 2+ The concentration is 0.3 g / L. Acetylacetone and sodium tartrate are added to zinc-iron wastewater to form a mixed solution with a molar ratio of complexing agent to iron of 1.1. The solution is stirred uniformly by an ejector 10 at a circulation pump 7 at 300 rpm. A fixed amount of ferrous sulfide and hydrogen sulfide with an S-Zn ratio of 1.6, slowly generated by excess dilute acid, are mixed into the mixed solution and subjected to a sulfide precipitation reaction at 25°C. During this process, sodium hydroxide is added to raise the solution's pH to and stabilize at pH 4. The reaction continues for half an hour.

[0096] After the reaction, solid-liquid separation was performed by suction filtration to obtain a zinc-containing precipitate and an iron-containing separated liquid. The iron-containing separated liquid was adjusted to pH = 8 and then hydrogen sulfide was introduced. During the reaction, the pH was stabilized at around pH = 8, the S-Fe ratio was 1.4, the temperature was 25°C, and the sulfidation reaction lasted for 40 minutes to generate an iron-containing precipitate.

[0097] In this embodiment, after the first sulfidation, the zinc removal rate was 99.99%, the iron removal rate was 1.53%, the zinc ions in the solution were below the detection limit, and the metal separation effect was good. The scanning electron microscope image of the purified zinc precipitate (i.e., zinc sulfide) is shown in the attached figure. Figure 4 As shown, the zinc-containing precipitate only contains zinc sulfide, and a large number of irregular blocky particles are attached to the surface of relatively large blocky particles.

[0098] Example 3

[0099] Prepare a solution containing FeSO4 and ZnSO4 to simulate a zinc-iron mixture, where Zn 2+ The concentration is 1g / L, Fe 2+ The concentration is 3g / L. Sodium tartrate and salicylic acid are added to zinc-iron wastewater to form a mixed solution with a molar ratio of complexing agent to iron of 1.2. The solution is stirred uniformly by an ejector 10 at a circulation pump 7 at 270 rpm. A fixed amount of sodium sulfide and hydrogen sulfide with a S-Zn ratio of 1.8, slowly generated by excess dilute acid, are mixed into the mixed solution and subjected to a sulfide precipitation reaction at 45°C. During this process, sodium hydroxide is added to raise the solution's pH to and stabilize at pH 3. The reaction continues for half an hour.

[0100] After the reaction, solid-liquid separation was performed by suction filtration to obtain a zinc-containing precipitate and an iron-containing separated liquid. The iron-containing separated liquid was adjusted to pH = 7 and then hydrogen sulfide was introduced. During the reaction, the pH was stabilized at around pH = 7, the S-Fe ratio was 1.5, the temperature was 45°C, and the sulfidation reaction lasted for half an hour to generate an iron-containing precipitate.

[0101] In this embodiment, after the first sulfidation, the zinc removal rate was 99.99%, the iron removal rate was 0.05%, the zinc ions in the solution were below the detection limit, and the metal separation effect was good. The scanning electron microscope image of the purified zinc precipitate (i.e., zinc sulfide) is shown in the attached figure. Figure 5 As shown, the zinc-containing precipitate only contains zinc sulfide, and a large number of irregular blocky particles are attached to the surface of relatively large blocky particles.

[0102] Comparative Example 1

[0103] Prepare a solution containing FeSO4 and ZnSO4 to simulate a zinc-iron mixture, where Zn 2+ The concentration is 1g / L, Fe 2+ The concentration is 0.3 g / L. The zinc-iron wastewater is uniformly stirred by an ejector 10 under a circulation pump 7 at 300 r / min. A fixed amount of sodium hydrosulfide is slowly added to excess dilute acid to generate hydrogen sulfide with a sulfur-to-zinc ratio of 1.6. This is then mixed into the zinc-iron wastewater and subjected to a sulfide precipitation reaction at 25°C. During this process, sodium hydroxide is added to raise the solution's pH to and stabilize at 4. The reaction continues for half an hour.

[0104] After the reaction, solid-liquid separation was performed by suction filtration to obtain a zinc-containing precipitate and an iron-containing separated liquid. The iron-containing separated liquid was adjusted to pH = 8 and then hydrogen sulfide was introduced. During the reaction, the pH was stabilized at around pH = 8, the S-Fe ratio was 1.4, the temperature was 25°C, and the sulfidation reaction lasted for 40 minutes to generate an iron-containing precipitate.

[0105] In this comparative example, after the first sulfidation, the zinc removal rate was 98.24%, and the iron removal rate was 4.52%, indicating a good metal separation effect. The scanning electron microscope image of the purified zinc precipitate (i.e., zinc sulfide) is shown in the attached figure. Figure 6 As shown, the precipitate is a mixture of two different substances, namely zinc-containing precipitate and iron-containing precipitate. There are a large number of irregular block-shaped zinc-containing small particles with some iron-containing flaky agglomerates mixed in them, and the surface is relatively rough.

[0106] Comparative Example 2

[0107] Prepare a solution containing FeSO4 and ZnSO4 to simulate zinc-iron mixed wastewater, in which Zn 2+ The concentration is 1g / L, Fe 2+ The concentration is 0.3 g / L. The zinc-iron mixed wastewater is added to a flask, and a sodium sulfide solution with a S-Zn ratio of 1.6 is added. The sulfidation reaction is carried out by stirring with a magnetic stirrer. During the entire sulfidation reaction, the pH of the solution is stabilized at around 4, and the reaction is carried out at 25°C for half an hour.

[0108] After the reaction, solid-liquid separation was performed by suction filtration to obtain a zinc-containing precipitate and an iron-containing separated liquid. The iron-containing separated liquid was adjusted to pH = 8 and then hydrogen sulfide was introduced. During the reaction, the pH was stabilized at around pH = 8, the S-Fe ratio was 1.4, the temperature was 25°C, and the sulfidation reaction lasted for 40 minutes to generate an iron-containing precipitate.

[0109] In this comparative example, after the first sulfidation, the zinc removal rate was 97.98%, and the iron removal rate was 10.41%, indicating poor metal separation. Figure 7 As shown, it can be seen that the precipitate is a mixture of two different substances, namely zinc-containing precipitate and iron-containing precipitate. A large number of irregular block-shaped zinc-containing small particles and flaky iron-containing agglomerates are gathered together, and the surface is relatively rough.

[0110] Comparative Example 3

[0111] Prepare a solution containing FeSO4 and ZnSO4 to simulate a zinc-iron mixture, where Zn 2+ The concentration is 1g / L, Fe 2+The concentration is 3g / L. Sodium tartrate and salicylic acid are added to the zinc-iron wastewater to form a mixed solution with a molar ratio of complexing agent to iron of 1.2. The solution is stirred evenly by a circulating pump at 270 rpm. A fixed amount of sodium hydrosulfide is slowly added to excess dilute acid to generate hydrogen sulfide with a S-Zn ratio of 1.8. This mixture is then mixed and subjected to a sulfide precipitation reaction at 45°C. During this process, sodium hydroxide is added to bring the solution's pH to and stabilize at 3. The reaction continues for half an hour.

[0112] After the reaction is completed, solid-liquid separation is performed by suction filtration to obtain a zinc-containing precipitate and an iron-containing separated liquid. The iron-containing separated liquid is adjusted to pH = 7 and then hydrogen sulfide is introduced. During the reaction, the pH is stabilized at around 7, the S-Fe ratio is 1.5, the temperature is 45°C, and the sulfidation reaction lasts for half an hour to generate an iron-containing precipitate.

[0113] In this comparative example, after the first sulfidation, without the mixed injection effect of the ejector, the zinc removal rate was 97.38%, the iron removal rate was 4.41%, and the metal separation effect was poor. The scanning electron microscope image of the obtained precipitate is shown in the attached figure. Figure 8 As shown, it can be seen that the precipitate is a mixture of two different substances, namely zinc-containing precipitate and iron-containing precipitate, containing a large number of irregular block-shaped zinc-containing small particles and flaky iron-containing agglomerates, and the surface is relatively rough.

[0114] The above technical solutions of the present invention are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A zinc and iron separation method, characterized in that: Including steps: S1. The zinc-iron waste liquid is mixed with a complexing agent to obtain a mixed solution, and a first hydrogen sulfide is added to the mixed solution, and the first hydrogen sulfide undergoes a first gas-liquid sulfidation reaction with the zinc ions in the mixed solution, and the pH of the first reaction solution of the first gas-liquid sulfidation reaction is maintained at 2 to 5 during the reaction process; The binding capacity of the complexing agent with iron is greater than the binding capacity of the complexing agent with zinc; the complexing agent includes one or more of acetylacetone, salicylic acid, and sodium tartrate; by adding alkaline solution to the mixed liquid, alleviating the acidification caused by the generation of hydrogen ions during the first gas-liquid sulfidation reaction; The concentration of zinc in the zinc-iron waste liquid is 0.3-5 g / L, and the concentration of iron in the zinc-iron waste liquid is 0.3-5 g / L; S2. The first reaction liquid is separated into a solid-liquid state to obtain a zinc-containing precipitate and an iron-containing separated liquid; S3. Adding a second hydrogen sulfide to the iron-containing separated liquid, the second hydrogen sulfide and the ferrous ions in the iron-containing separated liquid undergo a second gas-liquid sulfidation reaction, and during the reaction process, the pH of the second reaction liquid of the second gas-liquid sulfidation reaction is maintained at 6~9, and solid-liquid separation is performed to obtain an iron-containing precipitate.

2. The zinc-iron separation method according to claim 1, wherein The molar ratio of the complexing agent to the iron ions in the zinc-iron waste liquid is 0.9-1.

2.

3. The zinc-iron separation method according to claim 1, wherein The molar ratio of the first hydrogen sulfide to the zinc ions in the zinc-iron waste liquid is 1.4-2.0, and the molar ratio of the second hydrogen sulfide to the iron ions in the iron-containing separation liquid is 1.1-1.

5.

4. The zinc-iron separation method according to claim 1, wherein The temperature of the first gas-liquid sulfidation reaction is 25°C~65°C, and the duration of the first gas-liquid sulfidation reaction is 20~60 minutes; the temperature of the second gas-liquid sulfidation reaction is 25°C~65°C, and the duration of the second gas-liquid sulfidation reaction is 20~60 minutes.

5. The zinc-iron separation method according to claim 1, wherein In step S1, maintaining the pH of the first reaction liquid of the first gas-liquid sulfidation reaction at 2-5 during the reaction process includes: adding alkali solution to the first reaction liquid to stabilize the pH at 2-5; the alkali solution includes sodium hydroxide.

6. The zinc-iron separation method according to claim 1, characterized in that The preparation of the first hydrogen sulfide and the second hydrogen sulfide includes: adding dilute acid to a sulfur-containing compound; the sulfur-containing compound includes one or more of sodium sulfide, sodium hydrosulfide, and ferrous sulfide, and the dilute acid includes sulfuric acid with a concentration of 0.1-1 mol / L.

7. The zinc-iron separation method according to claim 1, characterized in that The first reaction liquid keeps circulating during the reaction process, a portion of the first reaction liquid generates jet negative pressure during the circulating flow, and the first hydrogen sulfide mixes with the first reaction liquid at the negative pressure location; and / or; The second reaction liquid keeps circulating during the reaction process, and part of the second reaction liquid generates jet negative pressure during the circulating flow, and the second hydrogen sulfide is mixed with the second reaction liquid at the negative pressure point.

8. Use of the zinc-iron separation method according to any one of claims 1 to 7 in the treatment of zinc-iron wastewater.

9. Use of a zinc-iron separation device in the zinc-iron separation method according to any one of claims 1 to 7, characterized in that: The zinc-iron separation device comprises: a hydrogen sulfide gas source, for providing the first hydrogen sulfide and / or the second hydrogen sulfide; The reaction part comprises an ejector, a circulation pump (7), a circulation pipeline and a reaction container; the reaction container is used to contain the first reaction liquid and / or the second reaction liquid; The ejector comprises a liquid inlet, a liquid outlet and an air inlet, and both ends of the circulation pipeline are connected to the accommodating cavity of the reaction container through the liquid inlet and the liquid outlet respectively. The circulation pump (7) is arranged in the circulation pipeline, and the air inlet is connected to the vulcanizer gas source.

10. The use according to claim 9, characterized in that The reaction container also includes a pH detection device.

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