Method for precipitating iron from wet-process zinc smelting leachate and application of method

Abstract

The invention discloses a method for precipitating iron from wet-process zinc smelting leachate and application of the method, and relates to the technical field of wet-process metallurgy. The invention specifically discloses a method comprising the following steps: carrying out a semi-acid oxidation neutralization iron precipitation reaction on a leaching solution containing zinc sulfate and ferrous sulfate produced by wet-process zinc smelting, an oxidizing agent and a first neutralizer in a reactor; the mass ratio of zinc in the first neutralizer to iron in the hematite slag obtained by iron precipitation is (0.4-0.6): 1; the iron precipitation reaction contains at least five stages of sub-reactions; the dosage of the neutralizer in the first-stage sub-reaction, the dosage of the neutralizer in the second-stage sub-reaction, the third-stage sub-reaction, the fourth-stage sub-reaction and the fifth-stage sub-reaction is 20wt%-35wt%, 55wt%-70wt% and 5wt%-10wt% of the dosage of all the neutralizers respectively. By means of the method, reduction control over sulfur in the iron slag produced in the iron precipitation process can be effectively achieved.

Description

Technical Field

[0001] This invention relates to the field of chemical metallurgy, and in particular to a method for precipitating iron from wet zinc smelting leachate and its application. Background Technology

[0002] Hydrometallurgical zinc refining has become the mainstream method in modern zinc smelting due to its advantages such as high metal recovery rate, high product purity, low energy consumption, and ease of mechanization and automation. In the hydrometallurgical zinc refining process, the removal of iron from the zinc-containing solution is crucial.

[0003] Common wet zinc smelting methods for iron precipitation include the jaundice process, the goethite process, and the hematite process. The jaundice process yields a sulfate solution suitable for electrolysis and achieves high recovery rates of valuable metals such as copper and cadmium. However, this method produces a large amount of slag with high sulfur and low iron content (the actual iron content in the slag is only about 30 wt%). The goethite process produces iron precipitation slag with an iron content of about 40 wt%, higher than that of the jaundice process. However, the acid-base balance is difficult to control during the precipitation process. The hematite process achieves a high recovery rate of valuable metals, and the resulting hematite slag has a high iron content and low slag volume, making it suitable for sale as an iron-containing material. However, the hematite slag obtained from the hematite process has a sulfur content exceeding 4%, which is unfavorable for subsequent sales. For example, the patent "A method for mineralizing iron precipitate from wet zinc smelting leaching solution" (application number 202210262813.2) proposes to add zinc oxide slurry during the hematite precipitation process of wet zinc smelting leaching solution, and mineralize iron precipitate by controlling the final pH value of 0.2~2.0 through a first-order reaction. However, the sulfur content of the obtained iron precipitate product is high (up to 1.5 wt%). Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for precipitating iron from the leaching solution of wet zinc smelting.

[0005] The present invention also provides the application of the above method in the field of hydrometallurgy.

[0006] A method for removing iron from a wet zinc smelting leaching solution according to a first aspect of the present invention includes the following steps: The leachate containing zinc sulfate and ferrous sulfate produced by hydrometallurgical zinc smelting undergoes a semi-acid iron precipitation reaction with an oxidant and a first neutralizing agent in a reactor, followed by solid-liquid separation to obtain hematite slag and iron-removed liquid. The first neutralizing agent comprises zinc oxide; the mass ratio of zinc in the first neutralizing agent to iron in the hematite slag is (0.4-0.6):1; The semi-acid iron precipitation reaction contains at least five sub-reactions; The amount of the first neutralizing agent used in the first-order sub-reaction is 20wt%-35wt% of all the first neutralizing agents; The sum of the amounts of the first neutralizing agent used in the second to fourth stage sub-reactions is 55wt%-70wt% of all the first neutralizing agents. The amount of the first neutralizing agent in the fifth-order sub-reaction is 5 wt%-10 wt% of all the first neutralizing agents; The sum of the amounts of the first neutralizing agent used in all sub-reactions is 100%.

[0007] The method according to embodiments of the present invention has at least the following beneficial effects: The method described in this embodiment regulates the acidity of the system during the iron precipitation process by controlling the amount of neutralizing agent. This neutralizes approximately half of the sulfuric acid produced during the iron precipitation process. The multi-stage reaction can effectively enhance the reactivity of the neutralizing agent. Under high residual acid conditions, the zinc leaching rate of the neutralizing agent is high, reducing the amount of neutralizing agent required and decreasing the amount of hematite slag and its sulfur content. This produces low-sulfur and low-zinc hematite slag (Fe≥55wt%, Zn≤1.5wt%, S≤0.9wt%), which is convenient for subsequent sale. This method has a promising application prospect in achieving efficient recovery of valuable metals and high-value utilization of hematite slag.

[0008] The semi-acid precipitation reaction refers to the precipitation reaction carried out during the hematite precipitation process by adding a neutralizing agent to neutralize about half of the acid produced.

[0009] According to some embodiments of the present invention, the amount of the first neutralizing agent in the first-stage sub-reaction is 20wt%-35wt% of all the first neutralizing agents. For example, it can be 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, or 35wt%.

[0010] According to some embodiments of the present invention, the sum of the amounts of the first neutralizing agents used in the second to fourth stage sub-reactions is 55wt%-70wt% of all the first neutralizing agents. For example, it can be 55wt%, 56wt%, 57wt%, 58wt%, 59wt%, 60wt%, 61wt%, 62wt%, 63wt%, 64wt%, 65wt%, 66wt%, 67wt%, 68wt%, 69wt%, or 70wt%.

[0011] According to some embodiments of the present invention, the amount of the first neutralizing agent in the fifth-order sub-reaction is 5wt%-10wt% of all the first neutralizing agents. For example, it can be 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, or 10wt%.

[0012] According to some embodiments of the present invention, the mass ratio of zinc in the first neutralizing agent to iron in the hematite slag is (0.4-0.6):1. The mass of iron in the hematite slag refers to the mass of iron in the hematite slag produced after the iron precipitation reaction, that is, the amount of iron removed during the iron precipitation reaction, which is the expected value for those skilled in the art. For example, the mass ratio can be 0.4:1, 0.41:1, 0.42:1, 0.43:1, 0.44:1, 0.45:1, 0.46:1, 0.47:1, 0.48:1, 0.49:1, 0.5:1, 0.51:1, 0.52:1, 0.53:1, 0.54:1, 0.55:1, 0.56:1, 0.57:1, 0.58:1, 0.59:1, or 0.6:1.

[0013] According to some embodiments of the present invention, the zinc concentration of the leachate is 80 g / L-100 g / L. For example, it can be 80 g / L, 81 g / L, 82 g / L, 83 g / L, 84 g / L, 85 g / L, 86 g / L, 87 g / L, 88 g / L, 89 g / L, 90 g / L, 91 g / L, 92 g / L, 93 g / L, 94 g / L, 95 g / L, 96 g / L, 97 g / L, 98 g / L, 99 g / L, or 100 g / L.

[0014] According to some embodiments of the present invention, the iron concentration of the leachate is 15 g / L-45 g / L. For example, it can be 16 g / L, 22 g / L, 28 g / L, 36 g / L, or 45 g / L.

[0015] According to some embodiments of the present invention, the pH value of the leachate is 1.0-3.0. For example, it can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.

[0016] According to some embodiments of the present invention, the zinc oxide includes at least one of zinc oxide and zinc calcinate.

[0017] According to some embodiments of the present invention, the mass ratio of the first neutralizing agent in the second-order sub-reaction, the third-order sub-reaction, and the fourth-order sub-reaction is 1: (0.9-1.1): (0.9-1.1).

[0018] According to some embodiments of the present invention, the mass ratio of the first neutralizing agent in the second-level sub-reaction, the third-level sub-reaction, and the fourth-level sub-reaction is 1:1:1.

[0019] According to some embodiments of the present invention, the oxidant includes oxygen.

[0020] According to some embodiments of the present invention, the oxidant comprises oxygen, and the method comprises the following steps: The leachate containing zinc sulfate and ferrous sulfate produced by hydrometallurgical zinc production undergoes a semi-acid precipitation reaction with oxygen, steam, and a first neutralizing agent.

[0021] According to some embodiments of the present invention, the method is carried out in a reactor comprising at least five sequentially connected reaction chambers; along the flow direction of the leachate, each reaction chamber sequentially carries out a series of sub-reactions of the semi-acid iron precipitation reaction. The first-stage sub-reaction, the second-stage sub-reaction, the third-stage sub-reaction, the fourth-stage sub-reaction, and the fifth-stage sub-reaction occur in sequence.

[0022] According to some embodiments of the present invention, the reaction temperature is 185℃-200℃. For example, it can be 185℃, 186℃, 187℃, 188℃, 189℃, 190℃, 191℃, 192℃, 193℃, 194℃, 195℃, 196℃, 197℃, 198℃, 199℃, or 200℃.

[0023] According to some embodiments of the present invention, the pressure of the reaction is 1.6 MPa-1.7 MPa. For example, it can be 1.6 MPa, 1.61 MPa, 1.62 MPa, 1.63 MPa, 1.64 MPa, 1.65 MPa, 1.66 MPa, 1.67 MPa, 1.68 MPa, 1.69 MPa or 1.7 MPa.

[0024] According to some embodiments of the present invention, the reaction time is 3 h to 4 h. For example, it can be 3 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h, 3.5 h, 3.6 h, 3.7 h, 3.8 h, 3.9 h or 4 h.

[0025] According to some embodiments of the present invention, the method for preparing the leachate includes the following steps: S1. Roast the zinc concentrate to obtain roasted sand; S2. The calcined sand is subjected to neutral leaching in an acid solution to separate the intermediate leaching residue; S3. The intermediate leaching residue is subjected to hot acid reduction leaching treatment to separate the hot acid reduction leaching solution. S4. The hot acid reduction leachate is pre-neutralized and the liquid phase is separated to obtain the leachate.

[0026] According to some embodiments of the present invention, the calcination temperature is 880℃-920℃.

[0027] According to some embodiments of the present invention, the acid solution is a solution containing sulfuric acid.

[0028] According to some embodiments of the present invention, the acid solution includes waste electrolyte and iron-removed liquid produced from semi-acid iron precipitation.

[0029] According to some embodiments of the present invention, the sulfuric acid concentration in the waste electrolyte is 160 g / L-180 g / L.

[0030] According to some embodiments of the present invention, the temperature of the neutral leaching is 60°C-70°C.

[0031] According to some embodiments of the present invention, the neutral leaching time is 1 h to 2 h.

[0032] According to some embodiments of the present invention, the endpoint pH of the neutral leaching is 4.8-5.4.

[0033] According to some embodiments of the present invention, the temperature of the hot acid reduction leaching treatment is 85-95°C.

[0034] According to some embodiments of the present invention, the hot acid reduction leaching treatment time is 2 h-3 h.

[0035] According to some embodiments of the present invention, the final acid concentration of the hot acid reduction leaching treatment is 40 g / L-60 g / L.

[0036] According to some embodiments of the present invention, the pre-neutralization temperature is 55°C-65°C.

[0037] According to some embodiments of the present invention, the pre-neutralization time is 0.5 h to 1 h.

[0038] According to some embodiments of the present invention, the endpoint pH value of the pre-neutralization is 1.0 to 3.0.

[0039] According to some embodiments of the present invention, the second neutralizing agent used in the pre-neutralization includes zinc oxide.

[0040] According to some embodiments of the present invention, the solid-liquid separation includes at least one of filtration, vacuum filtration, and centrifugation.

[0041] According to some embodiments of the present invention, the iron content of the hematite slag is not less than 55 wt%. For example, it can be 55 wt%, 56 wt%, 57 wt%, 58 wt%, 59 wt%, 60 wt%, 61 wt%, or 62 wt%.

[0042] According to some embodiments of the present invention, the zinc content of the hematite slag is not higher than 1.5 wt%. For example, it can be 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, or 1.5 wt%.

[0043] According to some embodiments of the present invention, the sulfur content of the hematite slag is not higher than 0.9 wt%. For example, it can be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, or 0.9 wt%.

[0044] Application of the method described in the first aspect of the second aspect of the present invention in the field of hydrometallurgy.

[0045] According to some embodiments of the present invention, the hydrometallurgical field is the field of hydrometallurgical zinc smelting.

[0046] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0047] Figure 1 This is a process flow diagram of the hydrometallurgical zinc smelting of the present invention. Detailed Implementation

[0048] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0049] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0050] In the description of this invention, the use of terms such as "first," "second," etc., is for the purpose of distinguishing technical features only and should not be construed as indicating or implying relative importance, or implicitly indicating the number of technical features indicated, or implicitly indicating the order of the technical features indicated.

[0051] In the description of this invention, it should be noted that, unless otherwise explicitly limited, terms such as "setup" and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0052] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0053] The term "not higher than" means less than or equal to, and should be understood to include the number itself.

[0054] The term "not less than" means greater than or equal to, and should be understood to include the number itself.

[0055] In the embodiments of the present invention, the waste electrolyte comes from the electrolysis workshop, and the sulfuric acid concentration is 160 g / L-180 g / L.

[0056] In an embodiment of the present invention, the steps of the method for preparing the leachate are as follows: (1) Fluidized bed roasting: Zinc concentrate is roasted in a fluidized bed furnace at a temperature of 900°C to produce roasted sand; the flue gas produced is sent to produce sulfuric acid.

[0057] (2) Neutral leaching: Waste electrolyte and iron removal solution are added to the calcined sand for neutral leaching. The leaching temperature is 60°C, the leaching time is 1 h, and the final pH value is 5.0. The intermediate leaching residue and intermediate leaching solution are separated. The intermediate leaching solution is sent for purification, electrolysis, and casting to produce electrolytic zinc.

[0058] (3) Hot acid reduction leaching: Waste electrolyte and zinc concentrate are added to the intermediate leaching residue for hot acid reduction leaching. The leaching temperature is 90°C, the leaching time is 3 h, and the final acid content is 50 g / L. The hot acid reduction leaching solution and leaching residue are separated. The leaching residue is sent to the pyrometallurgical slag treatment.

[0059] Zinc ferrite (ZnO·Fe2O3) in the intermediate leaching residue can only dissolve to form zinc sulfate and ferric sulfate under high temperature and high acid conditions (reaction as shown in Formula I). ​​An appropriate amount of zinc concentrate (mainly ZnS) can be used as a reducing agent to reduce ferric sulfate to ferrous sulfate (reaction as shown in Formula II), thereby achieving the purpose of zinc ferrite leaching and iron reduction.

[0060] ZnO·Fe2O3+4H2SO4=ZnSO4+Fe2(SO4)3+4H2O (Formula I); ZnS + Fe2(SO4)3 = ZnSO4 + 2FeSO4 + S 0 (Formula II).

[0061] Using zinc concentrate as a reducing agent avoids the increase in sulfuric acid content in the system due to SO2 reduction, saves production costs, maintains the acid balance of the system, and avoids the generation of large amounts of gypsum slag that would result from adding lime for neutralization. High-acid leaching is combined with Fe... 3+ The reduction reaction is integrated, reducing the process flow and equipment investment.

[0062] (4) Pre-neutralization: The hot acid reduction leachate is pre-neutralized by adding calcined sand or zinc oxide at a temperature of 60°C for 0.5 h and a final pH of 2.0. The pre-neutralization residue and pre-neutralization liquid are then separated. The pre-neutralization residue is returned to the neutral leaching process, and the pre-neutralization liquid is the leachate.

[0063] It is understandable that due to the differences in elements in different batches of zinc concentrate, the zinc and iron content of the leachate obtained under the same preparation method will vary.

[0064] In hydrometallurgical zinc production, the leachate containing zinc sulfate and ferrous sulfate is subjected to oxygen at temperatures of 185℃-200℃ and pressures of 1.6℃-1.7 MPa, where oxygen slowly decomposes the Fe in the leachate. 2+ Oxidized to Fe 3+ The reaction shown in Formula III occurs. Specifically, when the acidity is high, the Fe in the leachate... 3+ It will preferentially hydrolyze to form yellow basic ferric sulfate, as shown in Formula IV; while when the acidity is low, the Fe in the leachate... 3+ It will hydrolyze to form a reddish-brown Fe2O3 precipitate, as shown in formula V.

[0065] 4FeSO4 + O2 + 2H2SO4 = 2Fe2(SO4)3 + 2H2O (Formula III); Fe2(SO4)3+2H2O=2FeOHSO4+H2SO4 (Formula IV); Fe2(SO4)3+3H2O=Fe2O3+3H2SO4 (Formula V).

[0066] This invention utilizes a semi-acid iron precipitation technique to treat leachate containing zinc sulfate and ferrous sulfate. A neutralizing agent neutralizes approximately half of the sulfuric acid produced during the iron precipitation process (i.e., semi-acid iron precipitation), thereby promoting iron precipitation reaction V and inhibiting iron precipitation reaction IV. This achieves reduced sulfur content in the hematite slag produced during the iron precipitation process. By using a neutralizing agent to leach zinc and reduce acidity, low-sulfur, low-zinc hematite slag (Fe≥55wt%, Zn≤1.5wt%, S≤0.9wt%) is obtained during the iron precipitation process. Because the neutralizing agent (such as zinc oxide, zinc calcined sand, etc.) is added in multiple reaction chambers, its reactivity is enhanced, resulting in a more uniform and thorough iron precipitation process. This allows for timely neutralization of some of the acid produced during iron precipitation. The amount of neutralizing agent added is controlled to participate only in the semi-acid neutralization reaction. At the end of the semi-acid neutralization iron precipitation reaction, approximately half of the residual acid remains, ensuring that most of the zinc in the neutralizing agent is leached out during the semi-acid neutralization process. Therefore, excessive neutralizing agent is not required, resulting in a smaller amount of iron slag produced and improved sulfur reduction efficiency. If a neutralizing agent is added after the semi-acid iron precipitation is completed, the residual acid at the reaction endpoint will be reduced, and an excessive amount of neutralizing agent will need to be added subsequently. This is because the lower the residual acid at the reaction endpoint, the lower the zinc leaching rate of the neutralizing agent will be, and the larger the amount of neutralizing agent needed to be added. Adding an excessive amount of neutralizing agent will increase the amount of iron slag, and the resulting hematite slag will have a low iron content and a high zinc and sulfur content.

[0067] Insufficient pressure and low temperature hinder crystal growth into large particles or may lead to the formation of colloidal precipitates, making subsequent solid-liquid separation difficult and increasing zinc loss with the hematite slag. Conversely, prolonged reaction time and excessively high temperatures increase energy consumption and equipment requirements, have little effect on promoting the reaction, and increase costs.

[0068] In an embodiment of the present invention, the zinc calcined sand slurry is prepared by mixing zinc calcined sand and water at a solid-liquid ratio of 1 g: (2-3) mL; the zinc oxide slurry is prepared by mixing zinc oxide and water at a solid-liquid ratio of 1 g: (2-3) mL.

[0069] In the embodiments of the present invention, the reaction apparatus consists of a 6 L vertical reactor (with one 6 L reaction chamber) and a 24 L horizontal reactor (with four 6 L reaction chambers connected in sequence), with a total reaction volume of 30 L. The leachate flows sequentially through the vertical and horizontal reactors, and the five reaction chambers are numbered 1#, 2#, 3#, 4#, and 5# according to the flow direction of the leachate.

[0070] Those skilled in the art may also set up another 6 L vertical reactor (with a reaction chamber of 6 L volume) as needed, and use it alternately with the 6 L vertical reactor in the above-mentioned reaction device, and clean the iron slag regularly to prevent scaling.

[0071] Example 1 This example provides a method for removing iron from the leaching solution of a wet zinc smelting process, the steps of which are as follows: Leaching solution (containing 90 g / L zinc, 16 g / L iron, pH 2.0) was added to the reaction apparatus at a flow rate of 10 L / h. Simultaneously, steam, oxygen, and zinc calcinate slurry (115 g / h, containing 55 wt% zinc and 8 wt% iron) were introduced into each reaction chamber. After reacting at 185℃ and 1.6 MPa for 3 h, the mixture was cooled and depressurized by flash evaporation, and then filtered to separate the iron-removed solution (10 L / h, containing 96 g / L zinc, 2 g / L iron, and 15 g / L sulfuric acid) and hematite slag (271 g / h, containing 1.1 wt% zinc, 55 wt% iron, and 0.8 wt% sulfur). The iron-removed solution can be returned to neutral leaching.

[0072] In this process, after zinc calcined sand is slurried, it is fed into chambers 1, 2, 3, 4, and 5 at rates of 23 g / h, 26.83 g / h, 26.83 g / h, 26.83 g / h, and 11.5 g / h, respectively. The mass ratio of zinc in the zinc calcined sand to iron in the hematite slag is 0.45.

[0073] Example 2 This example provides a method for removing iron from the leaching solution of a wet zinc smelting process, the steps of which are as follows: Leaching solution (containing 85 g / L zinc, 22 g / L iron, pH 2.0) was added to the reaction apparatus at a flow rate of 8.8 L / h. Simultaneously, steam, oxygen, and zinc calcinate slurry (152 g / h, containing 58 wt% zinc and 6 wt% iron) were introduced into each reaction chamber. After reacting at 190℃ and 1.65 MPa for 3.4 h, the mixture was cooled and depressurized by flash evaporation, and then filtered to separate the iron-removed liquid (8.8 L / h, containing 95 g / L zinc, 2 g / L iron, and 20 g / L sulfuric acid) and hematite slag (339 g / h, containing 1.2 wt% zinc, 55 wt% iron, and 0.7 wt% sulfur). The iron-removed liquid can be returned to neutral leaching.

[0074] In this process, after zinc calcined sand is slurried, it is fed into chambers 1, 2, 3, 4, and 5 at rates of 38 g / h, 33.95 g / h, 33.95 g / h, 33.95 g / h, and 12.15 g / h, respectively. The mass ratio of zinc in the zinc calcined sand to iron in the hematite slag is 0.5.

[0075] Example 3 This example provides a method for removing iron from the leaching solution of a wet zinc smelting process, the steps of which are as follows: Leaching solution (containing 80 g / L zinc, 28 g / L iron, pH 2.0) was added to the reaction apparatus at a flow rate of 8.3 L / h. Simultaneously, steam, oxygen, and zinc oxide slurry (180 g / h, containing 60 wt% zinc) were introduced into each reaction chamber. After reacting at 190℃ and 1.65 MPa for 3.6 h, the solution was cooled and depressurized by flash evaporation, and then filtered to separate the iron-removed solution (8.3 L / h, containing 93 g / L zinc, 2 g / L iron, and 26 g / L sulfuric acid) and hematite slag (390 g / h, containing 1.0 wt% zinc, 56 wt% iron, and 0.7 wt% sulfur). The iron-removed solution can be returned to neutral leaching.

[0076] In this process, after zinc oxide is slurried, it is fed into chambers 1, 2, 3, 4, and 5 at rates of 54 g / h, 38.4 g / h, 38.4 g / h, 38.4 g / h, and 10.8 g / h, respectively. The mass ratio of zinc in zinc oxide to iron in hematite slag is 0.5.

[0077] Example 4 This example provides a method for removing iron from the leaching solution of a wet zinc smelting process, the steps of which are as follows: Leaching solution (containing 80 g / L zinc, 36 g / L iron, pH 2.0) was added to the reaction apparatus at a flow rate of 7.5 L / h. Simultaneously, steam, oxygen, and a zinc oxide slurry (216 g / h, containing 65 wt% zinc) were introduced into each reaction chamber. After reacting at 195℃ and 1.7 MPa for 4 h, the mixture was cooled and depressurized by flash evaporation, and then filtered to separate the iron-removed liquid (7.5 L / h, containing 98 g / L zinc, 2 g / L iron, and 31 g / L sulfuric acid) and hematite slag (456 g / h, containing 1.1 wt% zinc, 56 wt% iron, and 0.6 wt% sulfur). The iron-removed liquid can be returned to neutral leaching.

[0078] In this process, after zinc oxide is slurried, it is fed into chambers 1, 2, 3, 4, and 5 at rates of 75.6 g / h, 43.2 g / h, 43.2 g / h, 43.2 g / h, and 10.8 g / h, respectively. The mass ratio of zinc in the zinc oxide to iron in the hematite slag is 0.55.

[0079] Comparative Example 1 This example provides a method for precipitating iron from a wet zinc smelting leaching solution, which is basically the same as the steps in Example 4, except that the distribution ratio of zinc oxide in each reaction chamber is different. Specifically, after zinc oxide is slurried, zinc oxide is added to chamber #1 at a mass of 216 g / h, while no zinc oxide slurry is added to chambers #2, #3, #4, and #5.

[0080] The resulting liquid after iron removal contained 98 g / L zinc, 2 g / L iron, and 28 g / L sulfuric acid, while the hematite slag contained 1.3 wt% zinc, 55 wt% iron, and 3 wt% sulfur. This may be due to the excessive residence time of zinc oxide, which easily leads to surface passivation and reduced reactivity, resulting in a high sulfur content in the hematite slag.

[0081] Comparative Example 2 This example provides a method for precipitating iron from a wet zinc smelting leachate, which is basically the same as the steps in Example 4, except that the distribution ratio of zinc oxide in each reaction chamber is different. Specifically, after zinc oxide is slurried, it is introduced into chambers 1#, 2#, 3#, 4#, and 5# at masses of 86.4 g / h, 32.4 g / h, 32.4 g / h, 32.4 g / h, and 32.4 g / h, respectively.

[0082] The resulting liquid after iron removal contained 96 g / L zinc, 2 g / L iron, and 30 g / L sulfuric acid, while the hematite slag contained 1.2 wt% zinc, 55 wt% iron, and 2.6 wt% sulfur. This may be due to an unreasonable distribution ratio of zinc oxide in each reaction chamber, resulting in an excessively long residence time of zinc oxide, easy surface passivation, and weakened reactivity, thus leading to a high sulfur content in the hematite slag.

[0083] Comparative Example 3 This example provides a method for removing iron from the leaching solution of a wet zinc smelting process. The steps are essentially the same as in Example 4, except that the mass ratio of zinc in the zinc oxide to iron in the leaching solution is different. Specifically, the mass ratio of zinc in the zinc oxide to iron in the hematite slag is 1.1. After the zinc oxide is slurried, it is introduced into chambers 1#, 2#, 3#, 4#, and 5# at rates of 151.2 g / h, 86.4 g / h, 86.4 g / h, 86.4 g / h, and 21.6 g / h, respectively.

[0084] The resulting liquid after iron removal contained 112 g / L zinc, 2 g / L iron, and 5 g / L sulfuric acid. The hematite slag contained 7.1 wt% zinc, 45 wt% iron, and 1.8 wt% sulfur. This may be due to the zinc-to-iron ratio being greater than 0.6, resulting in a reduction in residual acid at the reaction endpoint, a decrease in the zinc leaching rate of the neutralizing agent, and an excess of zinc oxide added. After neutralizing the acid, some zinc oxide remains insoluble and enters the slag phase, leading to a large amount of iron slag produced, a significant amount of sulfur carried over, a decrease in iron grade, and an increase in zinc and sulfur content.

[0085] Comparative Example 4 This example provides a method for precipitating iron from a wet zinc smelting leaching solution, which is basically the same as the steps in Example 4, except that zinc oxide is not added. Specifically, the zinc oxide slurry is replaced with water.

[0086] The resulting liquid after iron removal contained 79 g / L zinc, 2 g / L iron, and 54 g / L sulfuric acid, while the hematite slag contained 1.1 wt% zinc, 58 wt% iron, and 4 wt% sulfur. This may be because the absence of zinc oxide during the iron precipitation process leads to an increase in solution acidity, which easily produces basic ferric sulfate, resulting in a high sulfur content in the iron slag.

[0087] The embodiments of the present invention have been described in detail above with reference to the examples. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for precipitating iron from a wet zinc smelting leaching solution, characterized in that, Includes the following steps: The leachate containing zinc sulfate and ferrous sulfate produced by hydrometallurgical zinc smelting undergoes a semi-acid iron precipitation reaction with an oxidant and a first neutralizing agent in a reactor, followed by solid-liquid separation to obtain hematite slag and iron-removed liquid. The first neutralizing agent comprises zinc oxide; the mass ratio of zinc in the first neutralizing agent to iron in the hematite slag is (0.4-0.6):1; The semi-acid iron precipitation reaction contains at least five sub-reactions; The amount of the first neutralizing agent used in the first-order sub-reaction is 20wt%-35wt% of all the first neutralizing agents; The sum of the amounts of the first neutralizing agent used in the second to fourth stage sub-reactions is 55wt%-70wt% of all the first neutralizing agents. The amount of the first neutralizing agent in the fifth-order sub-reaction is 5 wt%-10 wt% of all the first neutralizing agents; The sum of the amounts of the first neutralizing agent used in all sub-reactions is 100%.

2. The method according to claim 1, characterized in that, The zinc oxide includes at least one of zinc oxide and zinc calcinate.

3. The method according to claim 1, characterized in that, The oxidant includes oxygen.

4. The method according to claim 1, characterized in that, The method is carried out in a reactor comprising at least five sequentially connected reaction chambers; each reaction chamber sequentially carries out the various stages of the semi-acid iron precipitation reaction along the flow direction of the leachate.

5. The method according to claim 3, characterized in that, The reaction temperature is 185℃-200℃.

6. The method according to claim 3, characterized in that, The reaction was carried out at a pressure of 1.6 MPa to 1.7 MPa.

7. The method according to claim 3, characterized in that, The reaction time is 3-4 hours.

8. The method according to claim 1, characterized in that, The sulfur content of the hematite slag is not higher than 0.9 wt%; the iron content of the hematite slag is not lower than 55 wt%; and the zinc content of the hematite slag is not higher than 1.5 wt%.

9. The method according to claim 1, characterized in that, The method for preparing the leachate includes the following steps: S1. Roast the zinc concentrate to obtain roasted sand; S2. The calcined sand is subjected to neutral leaching in an acid solution to separate the intermediate leaching residue; S3. The intermediate leaching residue is subjected to hot acid reduction leaching treatment to separate the hot acid reduction leaching solution. S4. The hot acid reduction leachate is pre-neutralized and the liquid phase is separated to obtain the leachate.

10. The application of the method according to any one of claims 1 to 9 in the field of hydrometallurgy.

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