Zinc recovery method

Abstract

A zinc recovery method comprising: an alkaline melting step 102 for bringing, at a temperature equal to or higher than the melting point of sodium hydroxide, a material (1) and the like into contact with molten sodium hydroxide which is sodium hydroxide (5), (14) in a molten state to break up zinc ferrite contained in the material (1) and the like in the molten sodium hydroxide into zinc oxide components and ferric oxide components; a water dissolution step (103) for bringing, into contact with water and at a temperature not higher than the boiling point of water, the ferric oxide components, the zinc oxide components, and sodium hydroxide obtained as a result of lowering the temperature of the molten sodium hydroxide, and dissolving the zinc oxide components into a sodium hydroxide aqueous solution to obtain a zinc-containing aqueous solution (8) containing zinc components and to obtain an insoluble substance (9) including ferric oxide components that would not be dissolved in the sodium hydroxide aqueous solution; and a zinc recovery step (105), (108) for recovering the zinc components derived from the zinc-containing aqueous solution (8).

Description

[Technical Field]

[0001] The present invention relates to a zinc recovery method, and in particular to a zinc recovery method using, as raw materials, electric furnace dust generated during the melting and smelting of scrap in the electric furnace process, which is one of the iron-making processes, as well as primary or secondary dust such as blast furnace dust, blast furnace / converter dust, or RHF (Rotary Hearth Furnace) dust, and zinc-containing dust such as zinc ore cinders for zinc concentrate. [Background technology]

[0002] In the electric furnace process, which is one of the steelmaking processes, electric furnace dust is generated as industrial waste containing zinc oxide, which accounts for approximately 1.5% to 2.0% of the steel produced during the melting and smelting of scrap. It is said that 8 million tons of electric furnace dust are generated worldwide, and 400,000 tons are generated in Japan.

[0003] Most iron scrap comes from abandoned buildings, discarded home appliances, or discarded automobiles. The paint base of abandoned buildings, discarded home appliances, or discarded automobiles is zinc-plated. Scrap also contains paint, plastic, oil, etc. Therefore, electric furnace dust contains not only heavy metals such as zinc or lead, but also harmful organic substances such as chlorides and dioxins. However, electric furnace dust also contains about 20 to 30% iron and 20 to 30% zinc. Furthermore, crude zinc oxide, such as secondary dust, contains about 10% iron and about 60% zinc. Therefore, electric furnace dust To et al. is a very useful resource.

[0004] Under these circumstances, Patent Document 1 discloses a method for producing zinc bullion, which includes the steps of: producing a zinc-containing aqueous solution containing zinc components using electric furnace dust or the like as a raw material; converting the zinc components in the zinc-containing aqueous solution into a zinc-containing compound in at least one form of carbonate, hydroxide, or oxide, and chlorinating the zinc components of the zinc-containing compound to produce purified zinc chloride containing purified zinc chloride; dehydrating the purified zinc chloride to produce anhydrous molten purified zinc chloride containing dehydrated molten purified zinc chloride; and electrolyzing the anhydrous molten purified zinc chloride to produce zinc bullion as an electrolytic product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-119895 Summary of the Invention [Problem to be solved by the invention]

[0006] However, according to the study by the present inventors, in the configuration disclosed in Patent Document 1, in the zinc extraction step 101, electric furnace dust 1 as a raw material containing zinc-containing compounds such as zinc oxide and iron compounds such as iron oxide is directly contacted with an aqueous solution of an alkaline agent 7, and the zinc component is selectively extracted from the zinc-containing compounds to produce an aqueous alkaline agent solution 30 containing the zinc component as a zinc extract, and solid components that are not dissolved in the aqueous solution of the alkaline agent 7 are left as a residue 20. do However, it was found that there is a certain limit to the filterability when filtering out solids that do not dissolve in the aqueous solution of alkaline agent 7, and that a certain amount of time is required for filtering out the solids. In addition, it was also found that it is difficult to dissolve zinc ferrite (ZnFe2O4), a compound containing iron and zinc components that is often contained in large amounts in steelmaking dust.

[0007] In particular, according to the inventors' investigations, in terms of the quality of electric furnace dust, when the zinc quality is low and the iron quality is high, the zinc ferrite content in electric furnace dust and the like is high, and therefore there has been no opportunity to thoroughly investigate the practical application of a zinc recovery method that does not allow zinc ferrite to be filtered and leached, and as a result, it is believed that the zinc ferrite in electric furnace dust and the like is difficult to dissolve and therefore difficult to leach, even when treated at high temperature and high pressure using a high-concentration aqueous sodium hydroxide solution. In other words, according to the inventors' investigations, it is believed that there has been a long-awaited situation in which a new zinc recovery method that can recover zinc by decomposing zinc ferrite into zinc oxide and iron oxide components, even when the zinc ferrite content in electric furnace dust and the like is high, is desired.

[0008] The present invention has been made based on the above-mentioned studies, and aims to provide a zinc recovery method that can recover zinc contained in electric furnace dust and the like while reliably decomposing zinc ferrite contained in electric furnace dust and the like. [Means for solving the problem]

[0009] In order to achieve the above object, the present inventors have conducted various studies to solve the problem that zinc ferrite contained in electric furnace dust and the like is difficult to dissolve in an aqueous sodium hydroxide solution during an alkaline aqueous solution dissolution treatment of electric furnace dust and the like. As a result, they have found that when electric furnace dust and the like containing zinc ferrite is immersed in molten sodium hydroxide that has been heated to about 320°C in a container and kept in a molten state for about one hour, and then the temperature in the container is lowered to obtain a solidified product after melting, and the solidified product is immersed in water in another container, zinc components dissolved in the aqueous sodium hydroxide solution (zinc-containing aqueous solution) and iron oxide, which is the residue of the solidified product, can be obtained, and the present invention has been completed based on this finding.

[0010] A zinc recovery method according to a first aspect of the present invention includes an alkali melting step of contacting a raw material containing a zinc component and zinc ferrite or a treated raw material obtained by treating the raw material with molten sodium hydroxide at a first temperature equal to or higher than the melting point of sodium hydroxide, thereby decomposing the zinc ferrite contained in the raw material or the treated raw material into a zinc oxide component and an iron oxide component in the molten sodium hydroxide; a water dissolution step of contacting the sodium hydroxide, which is obtained by lowering the temperature of the molten sodium hydroxide, the zinc oxide component, and the iron oxide component with water at a second temperature lower than the boiling point of water, thereby dissolving the zinc oxide component in the aqueous sodium hydroxide solution to obtain a first zinc-containing aqueous solution containing the zinc component and to obtain a hardly-soluble matter containing the iron oxide component that is not dissolved in the aqueous sodium hydroxide solution; and a zinc recovery step of recovering the zinc component derived from the first zinc-containing aqueous solution. In the alkali melting step, hydrogen peroxide or sodium nitrate is added as an oxidizing agent to the sodium hydroxide, or at least one of sodium sulfite, sodium thiosulfate, sodium dithionite and zinc metal is added as a reducing agent. do.

[0012] The present invention also provides the first 1 In addition to the above aspect, the method further comprises a halogen washing step of washing the raw material with an aqueous sodium hydroxide solution having a pH value in the range of 8.5 to 10.5 prior to the alkali melting step to wash away halogen components contained in the raw material. 2 The situation is as follows.

[0013] The present invention also provides the first or 2 In addition to the above aspect, the method further comprises a magnetic separation step, prior to the alkali melting step, of applying a magnetic force to the raw material or the treated raw material via a magnet to separate a first concentrate consisting of components adhered to the magnet from a second concentrate not adhered to the magnet according to the magnetic strength of the components in the raw material or the treated raw material, and an alkaline aqueous solution dissolution step, to which the second concentrate is sent and the zinc component contained in the second concentrate is dissolved in an aqueous sodium hydroxide solution to selectively extract the zinc component and obtain a second zinc-containing aqueous solution containing the zinc component, and the first concentrate is sent to the alkali melting step as the treated raw material, and the zinc ferrite in the first concentrate is decomposed into the zinc oxide component and the iron oxide component. 3The situation is as follows.

[0014] The present invention also provides the first or 2 In addition to the above aspect, the present invention further comprises a purifying step of purifying the first zinc-containing aqueous solution, the purifying step including a deironizing step of bringing potassium permanganate or hydrogen peroxide as an oxidizing agent into contact with the first zinc-containing aqueous solution to remove solidified iron, a desiliconizing, decarbonating, and defluorinating step of bringing slaked lime or quicklime into contact with the first zinc-containing aqueous solution from which the iron has been removed to remove solidified silicates, carbonates, and fluorine, respectively, and a substitution step of bringing metallic zinc into contact with the first zinc-containing aqueous solution from which the iron, the silicates, the carbonates, and the fluorine have been removed, to reduce and precipitate metal impurity components that are nobler than zinc, thereby removing the metal impurity components. 4 The situation is as follows.

[0015] The present invention also provides the first 4 In addition to the above aspect, the zinc recovery step includes an electrolysis step of performing electrolysis using the first zinc-containing aqueous solution or a purified first zinc-containing aqueous solution as an electrolyte to obtain electrolytically produced zinc. 5 The situation is as follows.

[0016] The present invention also provides the first 4 In addition to the above aspect, the zinc recovery step includes a zinc carbonate separation step of separating a zinc component in the first zinc-containing aqueous solution or the purified first zinc-containing aqueous solution as zinc carbonate. 6 The situation is as follows.

[0017] The present invention also provides the first 3In addition to the above aspect, the method further comprises a purifying step of purifying the second zinc-containing aqueous solution, the purifying step including a deironizing step of bringing potassium permanganate or hydrogen peroxide as an oxidizing agent into contact with the second zinc-containing aqueous solution to remove solidified iron, a desiliconizing, decarbonating, and defluorinating step of bringing slaked lime or quicklime into contact with the second zinc-containing aqueous solution from which the iron has been removed to remove solidified silicates, carbonates, and fluorine, respectively, and a substitution step of bringing metallic zinc into contact with the second zinc-containing aqueous solution from which the iron, the silicates, the carbonates, and the fluorine have been removed, to reduce and precipitate metal impurity components that are nobler than zinc, thereby removing the metal impurity components. 7 The situation is as follows.

[0018] The present invention also provides the first 7 In addition to the above aspect, the zinc recovery step comprises performing electrolysis using the second zinc-containing aqueous solution or a purified second zinc-containing aqueous solution as an electrolyte, The first step is to obtain zinc by electrolysis. 8 The situation is as follows.

[0019] The present invention also provides the first 7 In addition to the above aspect, the zinc recovery step includes a zinc carbonate separation step of separating a zinc component in the second zinc-containing aqueous solution or the purified second zinc-containing aqueous solution as zinc carbonate. 9 The situation is as follows.

[0020] The present invention also provides the first 1In addition to the above aspect, the present invention further comprises an alkaline aqueous solution dissolving step, prior to the alkali melting step, of bringing the raw material or the treated raw material into contact with an aqueous sodium hydroxide solution to selectively extract the zinc component contained in the raw material or the treated raw material by dissolving it in the aqueous sodium hydroxide solution to obtain a third zinc-containing aqueous solution containing the zinc component, and obtaining a difficult-to-dissolve substance containing zinc ferrite that is not dissolved in the aqueous sodium hydroxide solution, and the difficult-to-dissolve substance containing zinc ferrite is sent to the alkali melting step as the treated raw material and decomposed into a zinc oxide component and an iron oxide component, and in the water dissolving step, the zinc oxide component is dissolved in the aqueous sodium hydroxide solution to obtain a fourth zinc-containing aqueous solution containing the zinc component. 10 The situation is as follows.

[0021] The present invention also provides the first 10 In addition to the above aspect, the fourth zinc-containing aqueous solution is sent to the alkaline aqueous solution dissolving step, where the zinc component contained in the fourth zinc-containing aqueous solution is selectively extracted and becomes a part of the third zinc-containing aqueous solution. 11 The situation is as follows.

[0022] The present invention also provides the first 10 or 11 In addition to the above aspect, the method further comprises a halogen washing step of washing the raw material with a sodium hydroxide aqueous solution having a pH value in the range of 8.5 to 10.5 prior to the alkaline aqueous solution dissolving step, thereby washing out halogen components contained in the raw material to obtain a treated raw material. 12 The situation is as follows.

[0023] Furthermore, in addition to any one of the tenth to twelfth aspects, the present invention further includes a cleaning step of purifying the third zinc-containing aqueous solution, the cleaning step including a deironization step of bringing potassium permanganate or hydrogen peroxide as an oxidant into contact with the third zinc-containing aqueous solution to remove solidified iron, a desiliconization / decarbonation / defluorination step of bringing slaked lime or quicklime into contact with the third zinc-containing aqueous solution from which the iron has been removed to remove solidified silicates, carbonates and fluorine, respectively, and a substitution step of bringing metallic zinc into contact with the third zinc-containing aqueous solution from which the iron, the silicates, the carbonates and the fluorine have been removed to reduce and precipitate metal impurity components nobler than zinc and remove the metal impurity components. , corresponding to the tenth, eleventh and twelfth aspects, 13th , Nos. 17 and 18 The situation is as follows.

[0024] The present invention also provides the first 13 In addition to the above aspect, the zinc recovery step includes an electrolysis step of performing electrolysis using the third zinc-containing aqueous solution or the purified third zinc-containing aqueous solution as an electrolyte to obtain electrolytically produced zinc. 14 The situation is as follows.

[0025] The present invention also provides the first 13 In addition to the above aspect, the zinc recovery step includes a zinc carbonate separation step of separating a zinc component in the third zinc-containing aqueous solution or the purified third zinc-containing aqueous solution as zinc carbonate. 15 The situation is as follows.

[0026] In addition to the fifth, eighth or fourteenth aspect, the present invention provides a method for producing a molten raw material by allowing sodium hydroxide and zinc to remain in the electrolysis solution of the electrolysis step, evaporating water from the electrolysis solution containing the remaining sodium hydroxide and zinc, and then bringing the molten solution into contact with the raw material or the treated raw material in the alkali melting step. , corresponding to the fifth, eighth and fourteenth aspects, No. 16 , 19th and 20th The situation is as follows. [Effects of the Invention]

[0027] According to a first aspect of the present invention, the zinc recovery method includes an alkali melting step of contacting a raw material or a treated raw material containing a zinc component and zinc ferrite with molten sodium hydroxide, which is sodium hydroxide in a molten state, at a first temperature that is equal to or higher than the melting point of sodium hydroxide, thereby decomposing the zinc ferrite contained in the raw material or the treated raw material into a zinc oxide component and an iron oxide component in the molten sodium hydroxide; a water dissolution step of contacting the sodium hydroxide, zinc oxide component, and iron oxide component, which are obtained by lowering the temperature of the molten sodium hydroxide, with water at a second temperature that is lower than the boiling point of water, thereby dissolving the zinc oxide component in the aqueous sodium hydroxide solution to obtain a first zinc-containing aqueous solution containing the zinc component and obtaining a hardly-soluble matter containing the iron oxide component that is not dissolved in the aqueous sodium hydroxide solution; and a zinc recovery step of recovering the zinc component derived from the first zinc-containing aqueous solution.Therefore, it is possible to efficiently recover zinc contained in electric furnace dust, etc. while reliably decomposing the zinc ferrite contained in electric furnace dust, etc.

[0028] In addition, the present invention 1 According to the zinc recovery method of the above aspect, in the alkali melting step, hydrogen peroxide or sodium nitrate is added as an oxidizing agent to sodium hydroxide, or at least one of sodium sulfite, sodium thiosulfate, sodium dithionite and zinc metal is added as a reducing agent, so that zinc ferrite contained in electric furnace dust and the like can be more reliably decomposed.

[0029] In addition, the present invention 2 According to the zinc recovery method in this aspect, the method further includes a halogen washing step in which, prior to the alkali melting step, the raw material is washed with an aqueous sodium hydroxide solution having a pH value in the range of 8.5 to 10.5 to wash away halogen components contained in the raw material and obtain a treated raw material. Therefore, halogen components contained in electric furnace dust and the like can be reliably eluted and washed.

[0030] In addition, the present invention 3According to the zinc recovery method of this aspect, the method further includes a magnetic separation step in which, prior to the alkali melting step, a magnetic force is applied to the raw material or the treated raw material via a magnet, and the first concentrate is separated from the second concentrate consisting of components that adhere to the magnet depending on the magnetic strength of the components in the raw material or the treated raw material, and an alkaline aqueous solution dissolution step in which the second concentrate is sent and the zinc component contained in the second concentrate is dissolved in an aqueous sodium hydroxide solution to selectively extract it, thereby obtaining a second zinc-containing aqueous solution containing the zinc component.Since the first concentrate is sent to the alkali melting step as the treated raw material, and the zinc ferrite in the first concentrate is decomposed into a zinc oxide component and an iron oxide component, the zinc contained in the electric furnace dust, etc. can be efficiently recovered while more reliably decomposing the zinc ferrite contained in the electric furnace dust, etc., in a manner that reduces energy consumption.

[0031] In addition, the present invention 4 According to the zinc recovery method of the above aspect, the method further comprises a purification step of purifying the first zinc-containing aqueous solution, and the purification step includes a deironization step of contacting the first zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidant to remove solidified iron, a desiliconization / decarbonation / defluorination step of contacting the first zinc-containing aqueous solution from which iron has been removed with slaked lime or quicklime to remove solidified silicates, carbonates, and fluorine, respectively, and a substitution step of contacting the first zinc-containing aqueous solution from which iron, silicates, carbonates, and fluorine have been removed with metallic zinc to reduce and precipitate metal impurity components that are more noble than zinc, thereby removing the metal impurity components.Therefore, zinc with reduced impurity contamination can be recovered.

[0032] In addition, the present invention 5 According to the zinc recovery method of this aspect, the zinc recovery process includes an electrolysis process in which electrolysis is performed using a first zinc-containing aqueous solution or a purified first zinc-containing aqueous solution as the electrolyte to obtain electrolytically produced zinc, so that electrolytically produced zinc with reduced impurity contamination can be recovered stably with good yield.

[0033] In addition, the present invention 6According to the zinc recovery method of the above aspect, the zinc recovery step includes a zinc carbonate separation step of separating the zinc component in the first zinc-containing aqueous solution or the purified first zinc-containing aqueous solution as zinc carbonate, so that zinc carbonate with reduced impurity contamination can be recovered stably with good yield.

[0034] In addition, the present invention 7 According to the zinc recovery method of the above aspect, the method further comprises a purification step of purifying the second zinc-containing aqueous solution, and the purification step includes a deironization step of contacting the second zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidant to remove solidified iron, a desiliconization / decarbonation / defluorination step of contacting the second zinc-containing aqueous solution from which iron has been removed with slaked lime or quicklime to remove solidified silicates, carbonates, and fluorine, respectively, and a substitution step of contacting the second zinc-containing aqueous solution from which iron, silicates, carbonates, and fluorine have been removed with metallic zinc to reduce and precipitate metal impurity components that are more noble than zinc, thereby removing the metal impurity components.Therefore, zinc with reduced impurity contamination can be recovered.

[0035] In addition, the present invention 8 According to the zinc recovery method of this aspect, the zinc recovery step includes an electrolysis step in which electrolysis is performed using a second zinc-containing aqueous solution or a purified second zinc-containing aqueous solution as the electrolyte to obtain electrolytically produced zinc, so that electrolytically produced zinc with reduced impurity contamination can be recovered stably with good yield.

[0036] Furthermore, according to the zinc recovery method of the ninth aspect of the present invention, the zinc recovery step includes a zinc carbonate separation step of separating the zinc component in the second zinc-containing aqueous solution or the purified second zinc-containing aqueous solution as zinc carbonate, so that zinc carbonate with reduced impurity contamination can be recovered stably with good yield.

[0037] In addition, the present invention 10According to the zinc recovery method of the above aspect, the method further comprises an alkaline aqueous solution dissolution step in which, prior to the alkali melting step, the raw material or the treated raw material is brought into contact with an aqueous sodium hydroxide solution, and the zinc component contained in the raw material or the treated raw material is dissolved in the aqueous sodium hydroxide solution and selectively extracted to obtain a third zinc-containing aqueous solution containing the zinc component, and also includes an alkaline aqueous solution dissolution step in which a difficult-to-dissolve material containing zinc ferrite that is not dissolved in the aqueous sodium hydroxide solution is obtained, and the difficult-to-dissolve material containing zinc ferrite is sent to the alkali melting step as the treated raw material and decomposed into a zinc oxide component and an iron oxide component, and in the water dissolution step, the zinc oxide component is dissolved in the aqueous sodium hydroxide solution to obtain a fourth zinc-containing aqueous solution containing the zinc component.Therefore, zinc contained in electric furnace dust, etc. can be efficiently recovered while more reliably decomposing zinc ferrite contained in electric furnace dust, etc., in a manner that reduces energy consumption.

[0038] In addition, the present invention 11 According to the zinc recovery method of this aspect, the fourth zinc-containing aqueous solution is sent to an alkaline aqueous solution dissolution step, and the zinc components contained in the fourth zinc-containing aqueous solution are selectively extracted and become part of the third zinc-containing aqueous solution, so that zinc contained in electric furnace dust, etc. can be recovered more efficiently.

[0039] In addition, the present invention 12 According to the zinc recovery method in this aspect, the method further includes a halogen washing step in which, prior to the alkaline aqueous solution dissolution step, the raw material is washed with an aqueous sodium hydroxide solution having a pH value in the range of 8.5 to 10.5 to wash away halogen components contained in the raw material and obtain a treated raw material. Therefore, halogen components contained in electric furnace dust and the like can be reliably eluted and washed.

[0040] In addition, the 13th aspect of the present invention , 17th or 18thAccording to the zinc recovery method of the above aspect, the method further comprises a purification step of purifying the third zinc-containing aqueous solution, and the purification step includes a deironization step of contacting the third zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidant to remove solidified iron, a desiliconization / decarbonation / defluorination step of contacting the third zinc-containing aqueous solution from which iron has been removed with slaked lime or quicklime to remove solidified silicates, carbonates, and fluorine, respectively, and a substitution step of contacting the third zinc-containing aqueous solution from which iron, silicates, carbonates, and fluorine have been removed with metallic zinc to reduce and precipitate metal impurity components that are nobler than zinc, thereby removing the metal impurity components.Therefore, zinc with reduced impurity contamination can be recovered.

[0041] In addition, the present invention 14 According to the zinc recovery method of this aspect, the zinc recovery step includes an electrolysis step in which electrolysis is performed using a third zinc-containing aqueous solution or a purified third zinc-containing aqueous solution as the electrolyte to obtain electrolytically produced zinc, so that electrolytically produced zinc with reduced impurity contamination can be recovered stably with good yield.

[0042] In addition, the present invention 15 According to the zinc recovery method of the above aspect, the zinc recovery step includes a zinc carbonate separation step of separating the zinc component in the third zinc-containing aqueous solution or the purified third zinc-containing aqueous solution as zinc carbonate, so that zinc carbonate with reduced impurity contamination can be recovered stably with good yield.

[0043] Also, the 16th aspect of the present invention , 19th or 20th According to the zinc recovery method in this aspect, sodium hydroxide and zinc are left in the electrolysis tail solution from the electrolysis step, and after evaporating the water from the electrolysis tail solution containing the remaining sodium hydroxide and zinc, the electrolysis tail solution is turned into a molten state and brought into contact with the raw material or treated raw material in the alkali melting step.This makes it possible to stably recover electrolytically produced zinc with reduced impurity contamination and with a high yield, while reducing the amount of sodium hydroxide consumed. [Brief explanation of the drawings]

[0044] [Figure 1] FIG. 1 is a process diagram of a zinc recovery method according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a process diagram of a zinc recovery method according to a second embodiment of the present invention. [Figure 3] FIG. 3 is a process diagram of a zinc recovery method according to a third embodiment of the present invention. [Figure 4] FIG. 4 is a flow chart of a zinc recovery method according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] Hereinafter, the zinc recovery method according to each embodiment of the present invention will be described in detail with reference to the drawings as appropriate.

[0046] (First embodiment) First, with reference to FIG. 1, a zinc recovery method according to a first embodiment of the present invention will be described in detail.

[0047] FIG. 1 is a diagram showing the steps of the zinc recovery method according to this embodiment.

[0048] 1 , in the zinc recovery method of this embodiment, a dehalogenation washing step 101, an alkali melting step 102, a water dissolution step 103, a cleaning step 104, and an electrolysis step 105 are carried out in this order, and the electrolysis step 105 corresponds to the zinc recovery step. Furthermore, electric furnace dust 1 will be used as a representative raw material for use in this recovery method. However, the raw material may be any raw material that contains at least a zinc compound such as zinc oxide, an iron compound such as iron oxide, and zinc ferrite, which is a compound of iron and zinc. In addition to electric furnace dust, primary or secondary dust such as blast furnace dust, blast furnace / converter dust, or RHF (Rotary Hearth Furnace) dust, or zinc concentrate ore clinker may also be used as the raw material.

[0049] Specifically, first, in the dehalogenation cleaning step 101, electric furnace dust 1, which is a raw material containing zinc compounds such as zinc oxide, iron compounds such as iron oxide, and zinc ferrite, a compound of iron and zinc, is cleaned with cleaning liquid 2, and halogen components such as chlorine and fluorine components adsorbed on the electric furnace dust 1 are eluted and separated from the electric furnace dust 1, thereby obtaining cleaned electric furnace dust 3. The cleaned electric furnace dust 3 is sent to the subsequent alkali melting step 102. Furthermore, as the cleaning liquid 2, an aqueous solution of a strong alkaline agent that is highly effective in eluting halogen components from the electric furnace dust 1 can be suitably used. Specifically, an aqueous solution of sodium hydroxide, which is an aqueous solution of such a strong alkaline agent, can be suitably used as the cleaning liquid 2.

[0050] Typically, electric furnace dust 1, crushed to a predetermined size or smaller, is immersed in the sodium hydroxide aqueous solution used as the cleaning solution 2. The immersed electric furnace dust 1 is then stirred in the sodium hydroxide aqueous solution for a predetermined time to form a slurry. The halogen components adhering to the dust 1 are then eluted from the slurry. If the pH value of the slurry electric furnace dust 1 is less than 8.5, the amount of halogen components eluted from the dust 1 cannot be ensured to be practical. Furthermore, unnecessary elution of zinc and lead components from the dust 1 occurs. Therefore, the pH value is preferably 8.5 or higher. Furthermore, if the pH value of the slurry electric furnace dust 1 exceeds 10.5, zinc components are extracted from the dust 1, reducing the amount of zinc components in the cleaned electric furnace dust 3 to be sent to the next process. Therefore, the pH value is preferably 10.5 or lower. Accordingly, the pH value of the sodium hydroxide aqueous solution used as the cleaning solution 2 is preferably set within the range of 8.5 to 10.5. The electric furnace dust 1 is washed with the cleaning solution 2, and the used cleaning solution 4 containing the eluted halogen components adsorbed on the electric furnace dust 1 may be simply discharged as waste liquid, or may be reused as the cleaning solution 2 to wash the electric furnace dust 1 again, as long as further chlorine components can be eluted. The reason why the dehalogenating cleaning step 101 is provided before the alkali melting step 102 and the water dissolution step 103 is to enable more appropriate decomposition of zinc ferrite in the electric furnace dust 1 and extraction of zinc components. When electric furnace dust 1 in which the adhesion of halogen components such as chlorine components and fluorine components has been reduced in advance is used, the dehalogenating cleaning step 101 may be omitted.

[0051] Next, in the alkali melting step 102, the cleaned electric furnace dust 3 is brought into contact with molten sodium hydroxide prepared by molten sodium hydroxide 5, a strong alkaline agent, in a temperature environment equal to or higher than the melting point of sodium hydroxide 5. The zinc ferrite contained in the electric furnace dust 3 is decomposed into zinc oxide and iron oxide components in the molten sodium hydroxide. The molten sodium hydroxide containing the decomposed zinc oxide and iron oxide components is cooled to obtain a zinc-containing solidified material 6 in which the zinc ferrite has been decomposed. The reason for using sodium hydroxide 5, among the strong alkaline agents, in particular is that the zinc ferrite can be rapidly decomposed by molten sodium hydroxide 5. The zinc-containing solidified material 6 in which the zinc ferrite has been decomposed is sent to the next water dissolution step 103.

[0052] Typically, the cleaned electric furnace dust 3 is immersed in an aqueous sodium hydroxide solution that is an aqueous solution of sodium hydroxide 5, the aqueous sodium hydroxide solution in which the cleaned electric furnace dust 3 is immersed is heated to evaporate the water, and the mixture of the cleaned electric furnace dust 3 and sodium hydroxide 5 is heated above the melting point of the sodium hydroxide 5 to melt the sodium hydroxide 5 into molten sodium hydroxide, and the molten sodium hydroxide is brought into contact with the cleaned electric furnace dust 3 for a predetermined time to decompose the zinc ferrite contained in the electric furnace dust 3 into zinc oxide components and iron oxide components. The chemical formula for this case is shown in Chemical Formula 1 below. [ka]

[0053] In the alkali melting step 102, when electrolysis in the electrolysis step 105 is started and the electrolytic tail solution 14 is usable, it is preferable to use the electrolytic tail solution 14, with or without sodium hydroxide 5, in combination with sodium hydroxide 5 or from the start of the next zinc recovery method, from the viewpoint of reducing the amount of sodium hydroxide 5 used and not wasting the electrolytic tail solution 14, and then bring the evaporated water into contact with the washed electric furnace dust 3.

[0054] In the alkali melting step 102, the mixture of the cleaned electric furnace dust 3 and sodium hydroxide 5 is heated to a temperature exceeding the melting point of sodium hydroxide 5 to bring the cleaned electric furnace dust 3 into contact with the molten sodium hydroxide. The lower limit of the temperature range must be equal to or higher than the melting point of sodium hydroxide 5 (approximately 318°C) in order to reliably maintain the sodium hydroxide 5 in a molten state. Furthermore, taking practical variations into consideration, the upper limit of the temperature range must be equal to or higher than the melting point of sodium hydroxide 5 (approximately 318°C). However, since the boiling point of sodium hydroxide 5 is high (exceeding 1300°C), the upper limit of the temperature range is preferably equal to or lower than 600°C in consideration of the amount of energy applied to decompose zinc ferrite and the decomposition efficiency. In addition to sodium hydroxide 5, examples of alkali agents that can be used to generate a molten salt for decomposing zinc ferrite include potassium hydroxide and sodium carbonate. Examples of oxidizing agents added to the molten salt to promote the decomposition of zinc ferrite include hydrogen peroxide and sodium nitrate. Similarly, examples of reducing agents added to the molten salt include at least one of sodium sulfite, sodium thiosulfate, sodium dithionite, and zinc metal. The alkali agents, oxidizing agents, and reducing agents are selected depending on the impurity levels. From the viewpoint of decomposing zinc ferrite, it is preferable that the weight of sodium hydroxide 5 be at least twice the weight of the zinc and iron in the zinc ferrite. Furthermore, since the alkali melting step 102 is performed in a high-temperature environment at least equal to or higher than the melting point of sodium hydroxide 5, when the aqueous solution of sodium hydroxide 5 or the electrolytic solution 14 is introduced into this step, the water contained therein has evaporated into water vapor. Therefore, it is preferable to pass the water vapor through a heat exchanger to cool and liquefy it back into water, and use the heat obtained in the heat exchanger for heating in the alkali melting step 102 and the alkali aqueous solution dissolving step 106 described in the second embodiment, from the viewpoint of improving the thermal efficiency in the alkali melting step 102 and reducing the amount of energy consumed.

[0055] In the alkali melting step 102, it is preferable to add an organic substance that reacts with chlorine to produce a volatile compound to the aqueous solution of sodium hydroxide 5 or the electrolytic tail solution 14, and then immerse the cleaned electric furnace dust 3 in the solution. When the water in the aqueous solution of sodium hydroxide 5 or the electrolytic tail solution 14 evaporates, the organic substance reacts with the chlorine in the cleaned electric furnace dust 3 and vaporizes the volatile organic chlorine compound. This reduces the concentration of the chlorine component in the cleaned electric furnace dust 3, decomposes the zinc ferrite, and produces a zinc-containing solidified material 6 with a reduced chlorine concentration. A practical example of such an organic substance is ethanol. In this case, the ethanol reacts with the chlorine in the cleaned electric furnace dust 3 to produce chloroform, a volatile organic chlorine compound, which is vaporized.

[0056] In the next water dissolution step 103, water 7 is brought into contact with the zinc-containing solidified material 6 resulting from the decomposition of zinc ferrite in a temperature environment below the melting point of sodium hydroxide, typically below the boiling point of water (100°C), to produce an aqueous sodium hydroxide solution and a difficult-to-dissolve material containing iron oxide components that are not dissolved in the aqueous sodium hydroxide solution. During this process, the zinc oxide components obtained by the decomposition of zinc ferrite and the zinc oxide components originally contained in the electric furnace dust 1 are dissolved in the aqueous sodium hydroxide solution, and this aqueous sodium hydroxide solution becomes a zinc-containing aqueous sodium hydroxide solution 8. The mixture of the zinc-containing aqueous sodium hydroxide solution 8 and the difficult-to-dissolve material containing iron oxide components is then filtered to separate the zinc-containing aqueous sodium hydroxide solution 8 and the difficult-to-dissolve material containing iron oxide components (solid-liquid separation). The zinc-containing aqueous sodium hydroxide solution 8 from which the difficult-to-dissolve material containing iron oxide components has been separated in this way has its zinc concentration increased and is sent to the next cleaning step 104, and the difficult-to-dissolve material containing iron oxide components is discharged as residue 9.

[0057] In the next cleaning step 104, first, potassium permanganate or hydrogen peroxide 10a is brought into contact with the zinc-containing sodium hydroxide aqueous solution 8 as an oxidizing agent to solidify the iron, and the solidified iron 12a is separated from the zinc-containing sodium hydroxide aqueous solution 8 and discharged as a residue, thereby obtaining a zinc-containing sodium hydroxide aqueous solution from which the iron 12a has been removed (iron removal step). Next, the zinc-containing sodium hydroxide aqueous solution from which the iron 12a has been separated is brought into contact with slaked lime or quicklime 10b to solidify the silicate, carbonate, and fluorine 12b, and the silicate, carbonate, and fluorine 12b are further separated from the zinc-containing sodium hydroxide aqueous solution from which the iron 12a has been separated and discharged as a residue, thereby obtaining a zinc-containing sodium hydroxide aqueous solution from which the silicate, carbonate, and fluorine 12b have been separated in addition to the iron 12a (silicon removal, decarbonation, and defluorination step). Next, metallic zinc 10c is brought into contact with the zinc-containing sodium hydroxide aqueous solution from which iron 12a, silicate, carbonate, and fluorine 12b have been removed, thereby reducing and precipitating metal impurity components 12c more noble than zinc in the zinc-containing sodium hydroxide aqueous solution 8, thereby obtaining a zinc-containing sodium hydroxide aqueous solution 11 that is a more purified version of the zinc-containing sodium hydroxide aqueous solution 8, and the precipitated metal impurity components 12c. The final step in the cleaning step 104 is a substitution step (cementation step) in which metallic zinc 10c is applied. The thus-purified zinc-containing sodium hydroxide aqueous solution 11 is sent to the next electrolysis step 105, and the metal impurity components 12c are discharged as residue. Such metallic zinc 10c is typically introduced as metallic zinc powder into the zinc-containing sodium hydroxide aqueous solution 8, and the zinc-containing sodium hydroxide aqueous solution 8 into which the metallic zinc powder has been introduced is heated and stirred at high speed while being maintained at a predetermined temperature, thereby promoting a cementation reaction, and as a result, metal impurity components more noble than zinc in the zinc-containing sodium hydroxide aqueous solution 8 can be rapidly precipitated. On the other hand, metallic zinc 10c may be applied as a metallic zinc plate instead of metallic zinc powder, and in such a case, the zinc-containing sodium hydroxide aqueous solution 8 is caused to flow toward a metallic zinc plate fixed so as to be stationary, and brought into contact with the metallic zinc plate, thereby promoting the cementation reaction in the same manner.When using metallic zinc powder, it is possible that the entire surface of the metallic zinc powder may be covered with precipitated metal impurities during the cementation reaction, preventing the center of the metallic zinc powder from participating in the cementation reaction. However, when using a metallic zinc plate, the contact area between the zinc-containing sodium hydroxide aqueous solution 8 and the plate can be freely set, thereby increasing the contact area and reliably promoting the cementation reaction. This also allows for the rapid replacement of the metallic zinc plate on which the metallic impurities have precipitated. The metallic zinc plate may be rotated relative to the flow of the zinc-containing sodium hydroxide aqueous solution 8. When the deironization process, desiliconization, decarbonation, defluorination process, and substitution process are employed in the cleaning process 104, it is preferable to perform the deironization process, desiliconization, decarbonation, defluorination process, and substitution process in this order. The reason for this is that the deironization process is an oxidation process that removes precipitates of oxides of iron, manganese, etc., produced by the oxidizing agent, while the substitution process is a reduction process. Therefore, theoretically, the oxidation deironization process must always be performed before the reduction substitution process. Furthermore, although it is possible to remove iron in the reduction step, the cost of iron removal in the reduction / substitution step is relatively high compared to the cost of iron removal in the oxidation / deironization step. Therefore, from the viewpoint of cost reduction, it is preferable to perform the deironization step before the substitution step. Furthermore, the desiliconization / decarbonation / defluorination step, which removes silicates, carbonates, and fluorine by adding slaked lime or normal lime, can theoretically be performed in any order relative to the oxidation / deironization step and the reduction / substitution step. However, based on the findings of previous experiments, it has been found that the removal rate of these impurities is most improved when the desiliconization / decarbonation / defluorination step is performed after the oxidation / deironization step and before the reduction / substitution step, i.e., when the deironization step, the desiliconization / decarbonation / defluorination step, and the substitution step are performed in this order in the cleaning step 104. The cleaning step 104 may be omitted if the zinc-containing aqueous sodium hydroxide solution 8 contains small amounts of impurities such as iron, silicon, carbonates, fluorine, and metals nobler than zinc.

[0058] In addition to the above steps, the cleaning step 104 may also employ a demanganizing step in which demanganization is performed by adding an oxidizing agent or the like, or a dechlorination step in which dechlorination is performed by adding copper oxide (I) or silver nitrate, or these steps may be combined as necessary. However, considering that halogen components are reduced in advance in the dehalogenation cleaning step 101 and that chlorine components can be reduced in the alkali melting step 102, it can be said that the demanganizing step has a higher priority than the dechlorination step.

[0059] In the next electrolysis step 105, electrolysis was performed using the purified zinc-containing aqueous sodium hydroxide solution 11 as the electrolyte. The electrolytic product, electrolytically produced zinc 13, was deposited on the cathode and recovered as a solid by solid-liquid separation. The electrolytic tail solution 14, which is the electrolyte after recovery of the electrolytically produced zinc 13, may be discharged as waste liquid. However, because it contains sodium hydroxide, it is more rational and preferable to return the electrolytic tail solution 14 directly to the alkali melting step 102. In this case, the water in the electrolytic tail solution 14 is evaporated, and the molten solution is brought into contact with the cleaned electric furnace dust 3 in the alkali melting step 102. The electrolytic tail solution 14 may be used alone in the alkali melting step 102 without adding new sodium hydroxide 5, from the middle of the current zinc recovery method or from the start of the next zinc recovery method. Alternatively, the zinc component may be left in the electrolytic tail solution 14, and the zinc-containing electrolytic tail solution 14 may be returned directly to the alkali melting step 102. In such a case, the electrolytic solution 14 is used as an electrolyte in the electrolysis step 105 after having undergone at least the alkali melting step 102 and the water dissolving step 103 to increase the zinc concentration. Therefore, in order to ensure reliable electrolysis, it is preferable that the electrolytic solution 14 contains sodium hydroxide at a concentration of 200 g / L or more and zinc at a concentration of 10 g / L or more.

[0060] Experimental Example 1 of this embodiment will be described below.

[0061] (Experimental Example 1) In the alkali melting step 102, electric furnace dust 3 (weight 150 g) after dehalogenation cleaning in the dehalogenation cleaning step 101 and electrolytic solution 14 (volume 1 L) containing NaOH (concentration 400 g / L) and Zn (concentration 50 g / L) were charged into an iron crucible and heated. When the liquid temperature reached approximately 300 °C, water evaporation ceased. The temperature was then further increased and maintained at 450 °C for one hour. After one hour, heating was stopped. In the water dissolution step 103, the melt 6 was cooled, and when the temperature of the resulting solidified material fell below 100 °C, water was poured in to dilute the melt to its original volume of 1 L with water. The mixture was then heated and stirred until the liquid temperature reached 100 °C, resulting in a slurry in which the remaining solidified material had dissolved. This slurry was then filtered to separate the Fe residue 9 and the Zn leachate 8 (Zn concentration 110 g / L). The Fe residue 9 was washed with water and dried. In the purification step 104, the Zn leachate 8 was converted into an oxidation purification solution. An oxidizing agent (KMnO4, HO2) 10a was added, and the mixture was stirred for 1 hour, after which the precipitate was filtered. Next, the leachate was converted into a Ca purification solution. CaO 10b was added, and the mixture was stirred for 1 hour, after which the precipitate was filtered. Furthermore, the leachate was subjected to cementation at 60°C for 24 hours, in which it was contacted with zinc metal (powder or plate-like) 10c, to remove impurities such as Cu, Pb, Cd, and Ni 12c. The leachate 11, which had been purified by cementation, was used as the electrolyte in the electrolysis step 105, in which electrowinning was carried out. The electrowinning conditions were a current density of 600 A per square meter, electrolyte concentrations of 400 g / L NaOH and 50 g / L Zn, and an electrolyte temperature of 40°C. Electrolysis resulted in the production of electrolytically produced zinc 13 with a purity of 99.995%. A circulating supply tank was used to adjust the electrolyte concentration so that the Zn concentration in the electrolysis feed solution was 55 g / L and the Zn concentration in the electrolysis tail solution was 50 g / L. A portion of the electrolysis tail solution 14 was extracted and used as the alkaline aqueous solution before evaporation in the alkali melting step 102, followed by the subsequent water dissolution step 103 to become the leaching solution 8. The Zn concentration in the electrolysis tail solution 14 was increased from 50 g / L to 110 g / L by water dissolution.The analytical values ​​of leachate 11 (purified zinc-containing aqueous sodium hydroxide solution) after purification by cementation are shown below (Table 1), and the concentrations of all analyzed components were below the lower limit of measurement. [Table 1]

[0062] (Second embodiment) Next, with reference to FIG. 2, a zinc recovery method according to a second embodiment of the present invention will be described in detail.

[0063] FIG. 2 is a diagram showing the steps of the zinc recovery method in this embodiment.

[0064] 2, the zinc recovery method according to this embodiment is mainly different from the zinc recovery method according to the first embodiment in that it includes an aqueous alkaline solution dissolution step 106 immediately following the dehalogenation washing step 101. In this embodiment, the explanation will be focused on this difference, and the same components will be denoted by the same reference numerals, and the explanation thereof will be omitted or simplified.

[0065] Specifically, an alkaline aqueous solution dissolving step 106 is provided immediately following the dehalogenating cleaning step 101. The reason for providing the dehalogenating cleaning step 101 before the alkaline aqueous solution dissolving step 106 is to enable more appropriate extraction of the zinc component from the electric furnace dust 1. In the alkaline aqueous solution dissolving step 106, prior to the alkali melting step 102, the cleaned electric furnace dust 3 is brought into contact with an aqueous sodium hydroxide solution, which is an aqueous solution of sodium hydroxide 5, to selectively extract the zinc component contained in the cleaned electric furnace dust 3 by dissolving it in the aqueous sodium hydroxide solution, thereby obtaining a zinc-containing aqueous sodium hydroxide solution 15 containing the zinc component and a poorly soluble matter 16 containing zinc ferrite that is not dissolved in the aqueous sodium hydroxide solution. Sodium hydroxide is used as the strong alkaline agent because it allows efficient extraction of the zinc component and can be shared with the strong alkaline agent used in the alkali melting step 102. The chemical formula for obtaining zinc-containing sodium hydroxide aqueous solution 15 containing zinc components by contacting electric furnace dust 3 with an aqueous sodium hydroxide solution and dissolving the zinc components contained in the washed electric furnace dust 3 in the aqueous sodium hydroxide solution and selectively extracting them is shown in Chemical Formula 2 below. [ka]

[0066] The zinc-containing aqueous sodium hydroxide solution 15 thus obtained is sent to the next cleaning step 104, while the obtained refractory matter 16 containing zinc ferrite is sent to the alkali melting step 102, where the zinc ferrite is decomposed into zinc oxide and iron oxide components. The zinc-containing solidified material 6 from which the zinc ferrite has been decomposed is sent to the next water dissolution step 103, where it becomes a zinc-containing aqueous sodium hydroxide solution 8, and is sent to the alkali aqueous solution dissolution step 106, where the zinc component contained in the zinc-containing aqueous sodium hydroxide solution 8 is selectively extracted and becomes part of the zinc-containing aqueous sodium hydroxide solution 15.

[0067] In the alkaline aqueous solution dissolving step 106, when the treatment in the alkaline melting step 102 progresses and a zinc-containing aqueous sodium hydroxide solution 8 is produced and sent to the alkaline aqueous solution dissolving step 106, the zinc-containing aqueous sodium hydroxide solution 8 may be used in combination with sodium hydroxide 5 or without sodium hydroxide 5, and brought into contact with the washed electric furnace dust 3.

[0068] Here, the alkali melting step 102 is supplemented by the alkali melting step 106, and the zinc-containing solidified material 6 containing zinc ferrite is sent from the alkali melting step 106 to the alkali melting step 102, and the zinc-containing solidified material 6 resulting from decomposition of the zinc ferrite is sent as a zinc-containing sodium hydroxide aqueous solution 8 to the alkali melting step 106 via the subsequent water dissolution step 103. This is a so-called countercurrent two-stage treatment process, and is adopted for the following reason: The alkali melting step 102 requires a higher temperature environment than the alkali melting step 106 and therefore consumes a larger amount of energy. However, by treating the electric furnace dust 1 as a zinc-containing raw material containing zinc ferrite not only in the alkali melting step 102 but also in the alkali melting step 106, the treatment time in the alkali melting step 102 can be shortened, thereby realizing a reduction in energy consumption. For example, if 88% of the zinc content of a certain electric furnace dust 1 is contained in zinc oxide and the remaining 12% is contained in zinc ferrite, it would be unreasonable in terms of energy consumption to treat the zinc oxide, which can be dissolved in the alkaline aqueous solution dissolution step 106, which can be performed in a temperature environment of 100°C or less, in the high-temperature alkaline melting step 102. Therefore, if the extraction of 88% of the zinc content is completed in the alkaline aqueous solution dissolution step 106 before the alkaline melting step 102 (the total weight of the electric furnace dust 3 to be treated is also reduced by about 40%), and the zinc ferrite containing the remaining 12% of the zinc content (which has a weight of 8% of the electric furnace dust 3 to be treated) is decomposed in the alkaline melting step 102, it would be possible to rationalize and improve energy consumption. As with the alkaline melting step 102, the electrolytic tail solution 14 may be returned to the alkaline aqueous solution dissolution step 106 and used alone or together with an aqueous sodium hydroxide solution as the alkaline aqueous solution to contact the cleaned electric furnace dust 3.

[0069] Experimental Example 2 of this embodiment will be described below.

[0070] (Experimental Example 2) In the alkali melting step 102, the post-alkali leaching dust 16 (containing zinc components, of which zinc oxide was dissolved by the alkaline leaching, while the zinc components in zinc ferrite remained; weight 70 g) that had been subjected to the alkali aqueous solution dissolution step 106 and the electrolytic solution 14 (NaOH concentration 450 g / L, Zn concentration 50 g / L; volume 1 L) were charged into a 2 L iron container and heated and stirred. When the liquid temperature reached approximately 300°C, evaporation of water ceased. The temperature was then further increased to 400°C and maintained at this temperature for one hour. After one hour, heating was stopped, and in the water dissolution step 103, the melt 6 was cooled to below 100°C, and water was added to dilute it to the original volume of 1 L. The liquid was heated and stirred until the temperature reached 100°C, and then maintained in this state for several hours. After confirming that the zinc components had dissolved, the slurry was filtered. After filtration, the solid cake (iron residue 9) was washed and analyzed, and it was confirmed that 98% or more of the Zn in the electric furnace dust 1 was dissolved.

[0071] In the alkaline aqueous solution dissolution step 106, the electric furnace dust 3 (weight 175 g) after the completion of the dehalogenation cleaning in the dehalogenation cleaning step 101 and the filtrate 8 (volume 1 L) after the completion of the alkali melting step 102 and the water dissolution step 103 were charged into an iron reaction vessel and heated with stirring until the liquid temperature reached 120°C and was maintained at this temperature for two hours. During this process, water evaporated and the dissolved components concentrated as the liquid temperature reached 120°C. The increased concentration of the dissolved components raised the boiling point, which reached 120°C. After two hours, the solution was filtered to separate the solid and liquid. Approximately 70 g of solid (iron residue) 16 was collected on a dry basis. This solid was used as the primary leaching-completed dust for the subsequent alkali melting step 102. Meanwhile, the Zn concentration of the separated liquid was increased to approximately 450 g / L NaOH and 120 g / L Zn, forming leachate 15. Next, in the purification step 104, this leachate 15 was used as an oxidation purification solution. An oxidizing agent (KMnO4, HO2) 10a was added, and the mixture was stirred for 1 hour, followed by filtration of the precipitate. Next, this leachate was used as a Ca purification solution. CaO 10b was added, and the mixture was stirred for 1 hour, followed by filtration of the precipitate. Furthermore, this leachate was subjected to cementation at 60°C for 24 hours, in which it was contacted with zinc metal (powder or plate-like) 10c to remove impurities such as Cu, Pb, Cd, and Ni 12c. Following this cementation process, the leachate 11 was used as the electrolyte for electrowinning in the electrolysis step 105. The electrowinning conditions were a current density of 600 A per square meter, electrolyte concentrations of 450 g / L NaOH and 55 g / L Zn, and an electrolyte temperature of 40°C. Electrolytically produced zinc 13 with a purity of 99.995% was obtained. A circulating supply tank was used to adjust the electrolyte concentration so that the Zn concentration in the electrolysis feed solution was 55 g / L and the Zn concentration in the electrolysis tail solution was 50 g / L. A portion of the electrolysis tail solution 14 was extracted and passed through an alkaline aqueous solution before evaporation in an alkali melting step 102. It was then used as leachates 8 and 15 in the subsequent water dissolution step 103 and alkaline aqueous solution dissolution step 106. The Zn concentration of 50 g / L was increased to 120 g / L by dissolution in water and alkaline aqueous solution.Regarding the analytical values ​​of the leachate 11 (purified zinc-containing sodium hydroxide aqueous solution) after the cementation purification process was completed, the concentrations of all analyzed components were below the lower limit of measurement, similar to the values ​​shown in Table 1 of Experimental Example 1.

[0072] (Third embodiment) Next, with reference to FIG. 3, a zinc recovery method according to a third embodiment of the present invention will be described in detail.

[0073] FIG. 3 is a diagram showing the steps of the zinc recovery method in this embodiment.

[0074] As shown in Fig. 3, the zinc recovery method according to this embodiment differs from the zinc recovery method according to the second embodiment mainly in that it includes a magnetic separation step 107 between the dehalogenation washing step 101 and the alkaline aqueous solution dissolution step 106. In this embodiment, the explanation will focus on this difference, and the same components are denoted by the same reference numerals, and their explanation will be omitted or simplified. Note that the magnetic separation step 107 can also be performed before the dehalogenation washing step 101 if magnetic separation is possible for the electric furnace dust 3 before washing. Furthermore, such magnetic separation step 107 may also be applied to the zinc recovery method according to the first embodiment.

[0075] Specifically, a magnetic separation step 107 is provided immediately following the dehalogenation washing step 101, and prior to the alkaline aqueous solution dissolution step 106, magnetic separation step 107 applies magnetic force to the washed electric furnace dust 3 using a magnet, typically an electromagnet, and separates the washed electric furnace dust 3 into adhered mineral concentrate 18 consisting of components (mainly zinc ferrite and iron components) that have adhered to the magnet, and residual mineral concentrate 19 that is not adhered to the magnet and is not contained in the washed electric furnace dust 3 but is instead adhered mineral concentrate 18. Note that a commercially available wet high-intensity magnetic separator can be used in the magnetic separation step 107.

[0076] The attached mineral concentrate 18 is sent to an alkali melting step 102 where it is brought into contact with molten sodium hydroxide, whereby zinc ferrite in the attached mineral concentrate 18 is decomposed into zinc oxide and iron oxide components, and the zinc-containing solidified material 6 from which the zinc ferrite has been decomposed is sent to the next water dissolution step 103. In the water dissolution step 103, water 7 is brought into contact with the zinc-containing solidified material 6 from which the zinc ferrite has been decomposed, to obtain a zinc-containing sodium hydroxide aqueous solution 8 and a residue 9 consisting of hardly soluble matter containing iron oxide components. However, if the precision of the ore separation in the magnetic separation step 107 is low and the residue 9 contains a large amount of zinc components, part or all of the residue 9' may be sent to an alkali aqueous solution dissolution step 106 to selectively extract the zinc components.

[0077] The residual concentrate 19 is sent to an alkaline aqueous solution dissolution step 106, where the zinc component contained in the residual concentrate 19 is dissolved in an aqueous sodium hydroxide solution and selectively extracted, thereby obtaining a zinc-containing sodium hydroxide aqueous solution 15 containing the zinc component, and a refractory material 16 that is not dissolved in the aqueous sodium hydroxide solution. The zinc-containing sodium hydroxide aqueous solution 15 thus obtained is sent to the next cleaning step 104, while the refractory material 16 obtained is discharged as residue. However, if the precision of the ore separation in the magnetic separation step 107 is low and the refractory material 16 contains a large amount of zinc ferrite, some or all of the refractory material may be removed. 16’ may be sent to an alkali fusion process 102 to decompose the zinc ferrite into zinc oxide and iron oxide components.

[0078] Hereinafter, Experimental Example 3 of this embodiment will be described.

[0079] (Experimental Example 3) In the alkali melting process 102, the magnetized dust 18 (referring to the components attached to the magnet, weighing 67 g of the total 175 g of electric furnace dust) that had been dehalogenated and washed in the dehalogenation washing process 101 and then magnetic separation process 107 was placed in a 2-L iron container and stirred. The resulting alkaline electrolysis solution 14 (NaOH concentration: 450 g / L, Zn concentration: 50 g / L, volume: 1 L) was heated and stirred until the liquid temperature reached approximately 300 °C, at which point water evaporation ceased. The temperature was then further increased to 400 °C and maintained at this temperature for one hour. After one hour, heating was stopped, and in the water dissolution process 103, the melt 6 was cooled to below 100 °C. Water was then added to the melt to dilute it to the original volume of 1 L. The liquid was heated and stirred until the temperature reached 100 °C. After several hours, the solution was confirmed to have dissolved, and the slurry was then filtered. The solid cake was washed with water to obtain the iron leaching residue 9. The iron leaching residue 9 can also be input to an alkaline aqueous solution dissolution step 106 if zinc dissolution is insufficient.

[0080] In the alkaline aqueous solution dissolution step 106, after the completion of dehalogenation washing in the dehalogenation washing step 101, non-magnetic dust 19 (referring to the components that did not adhere to the magnet, weighing 108 g out of the total weight of 175 g of electric furnace dust) was separated through the magnetic separation step 107. The filtrate 8 (volume 1 L) obtained after the completion of the alkali melting step 102 and the water dissolution step 103 was then placed in an iron reactor and heated with stirring until the liquid temperature reached 120°C. This liquid temperature was maintained for two hours (similar to Experimental Example 2). After two hours, the solution was filtered to separate the solid and liquid, yielding solid 16 (iron residue). Analysis of this solid and iron residue after mixing with the iron residue from the alkali melting step confirmed that more than 98% of the Zn in the electric furnace dust had dissolved. The separated liquid was used as leachate 15, and the Zn concentration was increased to 120 g / L. Next, in the purification step 104, this leachate 15 was used as an oxidation purification solution, and an oxidizing agent (KMnO4, HO2) 10a was added. After stirring for 1 hour, the precipitate was filtered off. Next, this leachate was used as a Ca purification solution, and CaO 10b was added. After stirring for 1 hour, the precipitate was filtered off. Furthermore, this leachate was subjected to cementation at a liquid temperature of 60°C for 24 hours, in which zinc metal (powder or plate-like) 10c was contacted, to remove impurities such as Cu, Pb, Cd, and Ni 12c. After the series of purification steps up to this cementation, the leachate 11 was used as the electrolyte for electrowinning in the electrolysis step 105. The electrowinning conditions were set to a current density of 600 A per square meter, electrolyte concentrations of 450 g / L NaOH and 55 g / L Zn, and an electrolyte temperature of 40°C, resulting in electrolytically produced zinc 13 with a purity of 99.995%. A circulating electrolyte supply tank was used to adjust the electrolyte concentration so that the Zn concentration in the electrolysis feed solution was 55 g / L and the Zn concentration in the electrolysis tail solution was 50 g / L. A portion of the electrolysis tail solution 14 was extracted and passed through an alkaline aqueous solution before evaporation in an alkali melting step 102, and then used as leachates 6 and 8 in the subsequent water dissolution step 103 and alkaline aqueous solution dissolution step 106. The Zn concentration of 50 g / L was increased to 120 g / L by water dissolution and alkaline aqueous solution dissolution. Regarding the analytical values ​​of the leachate 11 (purified zinc-containing sodium hydroxide aqueous solution) after the cementation purification process was completed, the concentrations of all analyzed components were below the lower limit of measurement, similar to the values ​​shown in Table 1 of Experimental Example 1.

[0081] (Fourth embodiment) Next, with reference to FIG. 4, a zinc recovery method according to a fourth embodiment of the present invention will be described in detail.

[0082] FIG. 4 is a diagram showing the steps of the zinc recovery method in this embodiment.

[0083] As shown in Fig. 4, the zinc recovery method according to this embodiment is mainly different from the zinc recovery method according to the third embodiment in that it includes a zinc carbonate separation step 108 instead of the electrolysis step 105 as a zinc recovery step. In this embodiment, the explanation will be focused on this difference, and the same components are denoted by the same reference numerals, and their explanation will be omitted or simplified. Note that the zinc carbonate separation step 108 may be applied instead of the electrolysis step 105 of the zinc recovery methods according to the first and second embodiments.

[0084] Specifically, the zinc carbonate separation step 108 involves bringing carbon dioxide gas 20 into contact with the zinc-containing aqueous sodium hydroxide solution 11 that has been subjected to the cleaning step 104, and separating the zinc component from the zinc-containing aqueous sodium hydroxide solution 11 as zinc carbonate 21.

[0085] Typically, carbon dioxide 20 is blown into the zinc component in a zinc-containing aqueous sodium hydroxide solution 11 to precipitate zinc carbonate, as shown in the following chemical formula (Chemical Formula 3), and the precipitated zinc carbonate is filtered to obtain solid zinc carbonate 21. The zinc carbonate 21 can also be used as a product by washing with water and drying it. Furthermore, the residual liquid 22 from the zinc carbonate separation step 108 contains sodium hydroxide, and is therefore returned to the alkali melting step 102. Furthermore, zinc oxide can also be obtained by roasting the solid zinc carbonate 21. [ka]

[0086] In the zinc recovery method of this embodiment, is waterThe increase in chlorine concentration in the aqueous alkaline oxide solution, the aqueous zinc-containing solution, and the electrolytic solution can be suppressed, and zinc having the required quality characteristics can be produced.

[0087] Experimental Example 4 of this embodiment will be described below.

[0088] (Experimental Example 4) As in Experimental Example 3, the Zn concentration was increased from 50 g / L to 120 g / L by dissolving in an alkaline aqueous solution, and the process was carried out up to the purification step 104. Carbon dioxide gas 20 was blown into the purified leachate 11 to precipitate zinc carbonate 21, which was then filtered and recovered. Furthermore, the analytical values ​​of the leachate 11 (purified zinc-containing aqueous sodium hydroxide solution) after purification by cementation were all below the lower limit of measurement, similar to the values ​​shown in Table 1 of Experimental Example 1.

[0089] In the zinc recovery method of the first to fourth embodiments described above, the process includes an alkali melting step 102 in which the raw material 1 or the treated raw material 3, 16, 18 containing zinc components and zinc ferrite is brought into contact with molten sodium hydroxide, which is molten sodium hydroxide 5, 14, at a first temperature equal to or higher than the melting point of sodium hydroxide, to decompose the zinc ferrite contained in the raw material 1 or the treated raw material 3, 16, 18 into zinc oxide components and iron oxide components in the molten sodium hydroxide, and a second temperature in which the temperature of the molten sodium hydroxide is lowered to a second temperature lower than the boiling point of water. The method includes a water dissolution step 103 in which water is brought into contact with sodium hydroxide, zinc oxide components, and iron oxide components present in the electric furnace dust 1, thereby dissolving the zinc oxide components in the aqueous sodium hydroxide solution to obtain a first zinc-containing aqueous solution 8 containing the zinc components, and obtaining a hardly-soluble substance 9 containing the iron oxide components that are not dissolved in the aqueous sodium hydroxide solution, and zinc recovery steps 105 and 108 in which the zinc components derived from the first zinc-containing aqueous solution 8 are recovered.This makes it possible to efficiently recover zinc 13 and zinc 21 contained in the electric furnace dust 1, etc., while reliably decomposing zinc ferrite contained in the electric furnace dust 1, etc.

[0090] In addition, in the zinc recovery methods of the first to fourth embodiments, in the alkali melting step 102, hydrogen peroxide or sodium nitrate is added as an oxidizing agent to the sodium hydroxide 5, 14, or at least one of sodium sulfite, sodium thiosulfate, sodium dithionite and zinc metal is added as a reducing agent, so that zinc ferrite contained in the electric furnace dust 1, etc. can be more reliably decomposed.

[0091] Furthermore, the zinc recovery methods of the first, third and fourth embodiments further include a halogen washing step in which, prior to the alkali melting step 102, the raw material 1 is washed with a washing solution 2, which is a sodium hydroxide aqueous solution having a pH value in the range of 8.5 to 10.5, to wash away the halogen components contained in the raw material 1 and obtain treated raw material 3. This ensures that the halogen components contained in the electric furnace dust 1, etc. can be reliably eluted and washed.

[0092] Furthermore, the zinc recovery methods of the first, third and fourth embodiments further include a magnetic separation process 107 in which, prior to the alkali melting process 102, a magnetic force is applied to the raw material 1 or the treated raw material 3 via a magnet, and the raw material 1 or the treated raw material 3 is separated into a first concentrate 18 consisting of components that adhere to the magnet and a second concentrate 19 that does not adhere to the magnet, depending on the magnetic strength of the components in the raw material 1 or the treated raw material 3; and an alkali aqueous solution dissolution process 106 in which the second concentrate 19 is sent and the zinc component contained in the second concentrate 19 is dissolved in an aqueous sodium hydroxide solution to selectively extract it, thereby obtaining a second zinc-containing aqueous solution 15 containing the zinc component.Since the first concentrate 18 is sent to the alkali melting process 102 as the treated raw material, and the zinc ferrite in the first concentrate 18 is decomposed into a zinc oxide component and an iron oxide component, zinc 13, 21 contained in the electric furnace dust 1, etc. can be efficiently recovered while more reliably decomposing the zinc ferrite contained in the electric furnace dust 1, etc., in a manner that reduces energy consumption.

[0093] Furthermore, the zinc recovery methods of the first, third and fourth embodiments further include a purification step 104 for purifying the first zinc-containing aqueous solution 8 or the second zinc-containing aqueous solution 15, and the purification step 104 includes a de-ironization step for contacting the first zinc-containing aqueous solution 8 or the second zinc-containing aqueous solution 15 with potassium permanganate or hydrogen peroxide 10a as an oxidizing agent to remove solidified iron, and a de-ironization step for removing the first zinc-containing aqueous solution from which iron has been removed. 8 or second zinc-containing aqueous solution 15 The process includes a desiliconization, decarbonation, and defluorination step in which slaked lime or quicklime 10b is brought into contact with the first zinc-containing aqueous solution 8 or the second zinc-containing aqueous solution 15 from which iron, silicates, carbonates, and fluorine have been removed, thereby removing the solidified silicates, carbonates, and fluorine, and a substitution step in which metallic zinc 10c is brought into contact with the first zinc-containing aqueous solution 8 or the second zinc-containing aqueous solution 15 from which iron, silicates, carbonates, and fluorine have been removed, thereby reducing and precipitating metal impurity components that are more noble than zinc, thereby removing the metal impurity components. Therefore, zinc 13, 21 with reduced impurity contamination can be recovered.

[0094] Furthermore, in the zinc recovery methods of the first and third embodiments, the zinc recovery step includes an electrolysis step 105 in which electrolysis is performed using the first zinc-containing aqueous solution 8, the second zinc-containing aqueous solution 15, or a purified solution 11 of the first zinc-containing aqueous solution 8 or the second zinc-containing aqueous solution 15 as the electrolyte to obtain electrolytically produced zinc 13, so that electrolytically produced zinc 13 with reduced impurity contamination can be recovered stably with good yield.

[0095] Furthermore, in the zinc recovery methods of the first and fourth embodiments, the zinc recovery step includes a zinc carbonate separation step 108 in which the zinc component in the first zinc-containing aqueous solution 8, the second zinc-containing aqueous solution 15, or the purified solution 11 of the first zinc-containing aqueous solution 8 or the second zinc-containing aqueous solution 15 is separated as zinc carbonate 21, so that zinc carbonate 21 with reduced impurity contamination can be recovered stably with good yield.

[0096] Furthermore, the zinc recovery method of the second embodiment further includes an alkaline aqueous solution dissolution step 106 in which, prior to the alkali melting step 102, the raw material 1 or the treated raw material 3 is brought into contact with an aqueous sodium hydroxide solution to selectively extract the zinc component contained in the raw material 1 or the treated raw material 3 by dissolving it in the aqueous sodium hydroxide solution to obtain a third zinc-containing aqueous solution 15 containing the zinc component, and also obtain a difficult-to-dissolve substance 16 containing zinc ferrite that is not dissolved in the aqueous sodium hydroxide solution. The difficult-to-dissolve substance 16 containing zinc ferrite is sent to the alkali melting step 102 as the treated raw material, where it is decomposed into a zinc oxide component and an iron oxide component. In the water dissolution step 103, the zinc oxide component is dissolved in the aqueous sodium hydroxide solution to obtain a fourth zinc-containing aqueous solution 8 containing the zinc component. Therefore, zincs 13 and 21 contained in the electric furnace dust 1 and the like can be efficiently recovered while the zinc ferrite contained in the electric furnace dust 1 and the like is more reliably decomposed, in a manner that reduces energy consumption.

[0097] In addition, in the zinc recovery method of the second embodiment, the fourth zinc-containing aqueous solution 8 is sent to the alkaline aqueous solution dissolution step 106, and the zinc components contained in the fourth zinc-containing aqueous solution 8 are selectively extracted and become part of the third zinc-containing aqueous solution 15, so that zinc 13, 21 contained in the electric furnace dust 1, etc. can be recovered more efficiently.

[0098] Furthermore, the zinc recovery method of the second embodiment further includes a halogen washing step 101 in which, prior to the alkaline aqueous solution dissolution step 106, the raw material 1 is washed with an aqueous sodium hydroxide solution having a pH value in the range of 8.5 to 10.5 to wash away the halogen components contained in the raw material 1 and obtain a treated raw material. This ensures that the halogen components contained in the electric furnace dust 1, etc. can be reliably eluted and washed away.

[0099] In addition, the zinc recovery method of the second embodiment further includes a purification step 104 for purifying the third zinc-containing aqueous solution 15. The purification step 104 includes a deironization step in which potassium permanganate or hydrogen peroxide 10a is brought into contact with the third zinc-containing aqueous solution 15 as an oxidant to remove solidified iron, a desiliconization, decarbonation, and defluorination step in which slaked lime or quicklime 10b is brought into contact with the third zinc-containing aqueous solution 15 from which iron has been removed to remove solidified silicates, carbonates, and fluorine, respectively, and a substitution step in which metallic zinc 10c is brought into contact with the third zinc-containing aqueous solution 15 from which iron, silicates, carbonates, and fluorine have been removed to reduce and precipitate metal impurity components that are more noble than zinc, thereby removing the metal impurity components.Therefore, zinc 13, 21 with reduced impurity contamination can be recovered.

[0100] Furthermore, in the zinc recovery method of the second embodiment, the zinc recovery process includes an electrolysis process 105 in which electrolysis is performed using the third zinc-containing aqueous solution 15 or the purified third zinc-containing aqueous solution 15 11 as the electrolyte to obtain electrolytically produced zinc 13, so that electrolytically produced zinc 13 with reduced impurity contamination can be recovered stably with good yield.

[0101] Furthermore, in the zinc recovery method of the second embodiment, the zinc recovery step includes a zinc carbonate separation step 108 in which the zinc component in the third zinc-containing aqueous solution 15 or the purified third zinc-containing aqueous solution 15 11 is separated as zinc carbonate 21, so that zinc carbonate 21 with reduced impurity contamination can be recovered stably with good yield.

[0102] Furthermore, in the zinc recovery methods of the first to third embodiments, sodium hydroxide and zinc are left in the electrolysis tail solution 14 of the electrolysis step 105, and after evaporating the water from the electrolysis tail solution 14 containing the remaining sodium hydroxide and zinc, the electrolysis tail solution 14 is turned into a molten state and brought into contact with the raw material 1 or the treated raw materials 3, 16, 18 in the alkali melting step 102. Therefore, the amount of sodium hydroxide consumed is reduced, and electrolytically produced zinc 13 with reduced impurity contamination can be recovered stably with good yield.

[0103] It should be noted that the shape, arrangement, number, etc. of the components of the present invention are not limited to those of the above-described embodiment, and such components can of course be appropriately modified within the scope of the gist of the invention, such as by appropriately replacing such components with components that have equivalent effects. [Industrial Applicability]

[0104] As described above, the present invention provides a zinc recovery method that can recover zinc contained in electric furnace dust and the like while reliably decomposing zinc ferrite contained in electric furnace dust and the like. Therefore, due to its versatile and universal nature, it is expected to be widely applicable to zinc recovery methods using as raw materials not only electric furnace dust generated during the melting and smelting of scrap in the electric furnace process, which is one of the steelmaking processes, but also primary or secondary dust such as blast furnace dust, blast furnace / converter dust, or RHF (Rotary Hearth Furnace) dust, and clinker of zinc concentrate. [Explanation of symbols]

[0105] 1...Electric furnace dust 2...Cleaning solution 3...Processed electric furnace dust 4...Used cleaning solution 5...Sodium hydroxide 6...Zinc-containing solidified material 7…Water 8...Zinc-containing sodium hydroxide aqueous solution 9...Residue 10a...oxidizer 10b...Slaked lime or quicklime 10c...metallic zinc 11...Zinc-containing sodium hydroxide aqueous solution 12a...Iron 12b...Silicates, carbonates and fluorine 12c…Metal impurity component 13...Electrolytically produced zinc 14...Electrolytic tailing liquid 15...Zinc-containing sodium hydroxide aqueous solution 16…Hardly soluble material, 18...Mineral deposition 19...Remaining minerals 21...Zinc carbonate 22…Residual liquid 101...Halogen cleaning Process 1 02...Alkali melting process 103…Water dissolution process 104...Cleaning process 105...Zinc recovery process 105...Electrolysis process 106...Alkaline aqueous solution dissolution process 107...Magnetic beneficiation process 108...Zinc carbonate separation process

Claims

1. an alkali melting step of contacting a raw material containing zinc and zinc ferrite or a treated raw material obtained by treating the raw material with molten sodium hydroxide at a first temperature equal to or higher than the melting point of sodium hydroxide, thereby decomposing the zinc ferrite contained in the raw material or the treated raw material into a zinc oxide component and an iron oxide component in the molten sodium hydroxide; a water dissolution step of contacting water with the sodium hydroxide, the zinc oxide component, and the iron oxide component, which is obtained by lowering the temperature of the molten sodium hydroxide, at a second temperature that is lower than the boiling point of water, to dissolve the zinc oxide component in the aqueous sodium hydroxide solution, thereby obtaining a first zinc-containing aqueous solution containing a zinc component, and also obtaining a hardly-soluble matter containing an iron oxide component that is not dissolved in the aqueous sodium hydroxide solution; a zinc recovery step of recovering a zinc component derived from the first zinc-containing aqueous solution; Equipped with In the alkali melting step, hydrogen peroxide or sodium nitrate is added as an oxidizing agent to the sodium hydroxide, or at least one of sodium sulfite, sodium thiosulfate, sodium dithionite and zinc metal is added as a reducing agent. A zinc recovery method.

2. 2. The zinc recovery method according to claim 1, further comprising a halogen washing step of washing the raw material with a sodium hydroxide aqueous solution having a pH value of 8.5 or more and 10.5 or less, prior to the alkali melting step, to wash the halogen components contained in the raw material.

3. a magnetic separation step, prior to the alkali melting step, in which a magnetic force is applied to the raw material or the treated raw material via a magnet, and the raw material or the treated raw material is separated into a first concentrate consisting of components adhered to the magnet and a second concentrate not adhered to the magnet according to the magnetic strength of the components; an alkaline aqueous solution dissolution step in which the second concentrate is sent and the zinc component contained in the second concentrate is dissolved in an aqueous sodium hydroxide solution to selectively extract the zinc component, thereby obtaining a second zinc-containing aqueous solution containing the zinc component; Further provided with 3. The zinc recovery method according to claim 1, wherein the first concentrate is sent to the alkali melting step as the treated raw material, and the zinc ferrite in the first concentrate is decomposed into the zinc oxide component and the iron oxide component.

4. 3. The zinc recovery method according to claim 1 or 2, further comprising a purification step of purifying the first zinc-containing aqueous solution, wherein the purification step comprises: a de-ironization step of contacting the first zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidizing agent to remove solidified iron; a de-siliconization, de-carbonation, and de-fluorination step of contacting the first zinc-containing aqueous solution from which the iron has been removed with slaked lime or quicklime to remove solidified silicate, carbonate, and fluorine; and a substitution step of contacting the first zinc-containing aqueous solution from which the iron, silicate, carbonate, and fluorine have been removed with metallic zinc to reduce and precipitate metal impurities more noble than zinc, thereby removing the metal impurities.

5. The zinc recovery method according to claim 4, wherein the zinc recovery step includes an electrolysis step of performing electrolysis using the first zinc-containing aqueous solution or a purified version of the first zinc-containing aqueous solution as an electrolyte to obtain electrolytically generated zinc.

6. The zinc recovery method according to claim 4, wherein the zinc recovery step includes a zinc carbonate separation step of separating zinc components from the first zinc-containing aqueous solution or the purified first zinc-containing aqueous solution as zinc carbonate.

7. The zinc recovery method according to claim 3, further comprising a purification step of purifying the second zinc-containing aqueous solution, wherein the purification step comprises: a de-ironization step of contacting the second zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidizing agent to remove solidified iron; a de-siliconization, de-carbonation, de-fluorination step of contacting the second zinc-containing aqueous solution from which the iron has been removed with slaked lime or quicklime to remove solidified silicate, carbonate and fluorine; and a replacement step of contacting the second zinc-containing aqueous solution from which the iron, silicate, carbonate and fluorine have been removed with metallic zinc to reduce and precipitate metal impurities more noble than zinc, thereby removing the metal impurities.

8. The zinc recovery method according to claim 7, wherein the zinc recovery step comprises an electrolysis step of performing electrolysis using the second zinc-containing aqueous solution or a purified version of the second zinc-containing aqueous solution as an electrolyte to obtain electrolytically generated zinc.

9. The zinc recovery method according to claim 7, wherein the zinc recovery step includes a zinc carbonate separation step of separating zinc components from the second zinc-containing aqueous solution or the purified second zinc-containing aqueous solution as zinc carbonate.

10. The method further comprises an alkaline aqueous solution dissolving step, prior to the alkali melting step, of contacting the raw material or the treated raw material with an aqueous sodium hydroxide solution, dissolving the zinc component contained in the raw material or the treated raw material in the aqueous sodium hydroxide solution, selectively extracting the zinc component, thereby obtaining a third zinc-containing aqueous solution containing the zinc component, and obtaining a hardly soluble matter containing zinc ferrite that is not dissolved in the aqueous sodium hydroxide solution, 2. The zinc recovery method according to claim 1, wherein the refractory matter containing the zinc ferrite is sent to the alkali melting step as the treated raw material and decomposed into a zinc oxide component and an iron oxide component, and in the water dissolution step, the zinc oxide component is dissolved in the sodium hydroxide aqueous solution to obtain a fourth zinc-containing aqueous solution containing a zinc component.

11. The zinc recovery method according to claim 10, wherein the fourth zinc-containing aqueous solution is sent to the alkaline aqueous solution dissolution process, and the zinc components contained in the fourth zinc-containing aqueous solution are selectively extracted and become part of the third zinc-containing aqueous solution.

12. 12. The zinc recovery method according to claim 10 or 11, further comprising a halogen washing step, in which the raw material is washed with a sodium hydroxide aqueous solution having a pH value of 8.5 or more and 10.5 or less, to wash the halogen components contained in the raw material, and obtain a treated raw material, prior to the alkaline aqueous solution dissolving step.

13. 11. The zinc recovery method according to claim 10, further comprising the cleaning process of purifying the third zinc-containing aqueous solution, and the cleaning process comprises the following steps: the de-ironization process, which is carried out by contacting the third zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidizing agent to remove solidified iron; the de-siliconization, de-carbonation and de-fluorination process, which is carried out by contacting the third zinc-containing aqueous solution from which iron has been removed with slaked lime or quicklime to remove solidified silicate, carbonate and fluorine; and the replacement process, which is carried out by contacting the third zinc-containing aqueous solution from which iron, silicate, carbonate and fluorine have been removed with metallic zinc, to reduce and precipitate metal impurities more noble than zinc, to remove the metal impurities.

14. The zinc recovery method according to claim 13, wherein the zinc recovery process includes an electrolysis process in which electrolysis is carried out using the third zinc-containing aqueous solution or a purified version of the third zinc-containing aqueous solution as an electrolyte to obtain electrolytically generated zinc.

15. The zinc recovery method according to claim 13, wherein the zinc recovery step includes a zinc carbonate separation step of separating zinc components in the third zinc-containing aqueous solution or the purified third zinc-containing aqueous solution as zinc carbonate.

16. 6. The zinc recovery method according to claim 5, wherein sodium hydroxide and zinc are left in the electrolysis tail solution of the electrolysis step, and after evaporating the water from the electrolysis tail solution containing the sodium hydroxide and zinc, the electrolysis tail solution is melted and brought into contact with the raw material or the treated raw material in the alkali melting step.

17. A zinc recovery method as described in claim 11, further comprising a purification step of purifying the third zinc-containing aqueous solution, the purification step comprising: a deironization step of contacting the third zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidizing agent to remove solidified iron; a desiliconization / decarbonation / defluorination step of contacting the third zinc-containing aqueous solution from which the iron has been removed with hydrated lime or quicklime to remove solidified silicates, carbonates and fluorine, respectively; and a substitution step of contacting the third zinc-containing aqueous solution from which the iron, silicates, carbonates and fluorine have been removed with metallic zinc to reduce and precipitate metal impurity components that are more noble than zinc, thereby removing the metal impurity components.

18. A zinc recovery method as described in claim 12, further comprising a purification step of purifying the third zinc-containing aqueous solution, the purification step comprising: a deironization step of contacting the third zinc-containing aqueous solution with potassium permanganate or hydrogen peroxide as an oxidizing agent to remove solidified iron; a desiliconization / decarbonation / defluorination step of contacting the third zinc-containing aqueous solution from which the iron has been removed with slaked lime or quicklime to remove solidified silicates, carbonates and fluorine, respectively; and a substitution step of contacting the third zinc-containing aqueous solution from which the iron, silicates, carbonates and fluorine have been removed with metallic zinc to reduce and precipitate metal impurity components that are more noble than zinc, thereby removing the metal impurity components.

19. A zinc recovery method as described in Claim 8, in which sodium hydroxide and zinc are left in the electrolytic tail solution of the electrolysis process, and after evaporating the water from the electrolytic tail solution containing the remaining sodium hydroxide and zinc, the electrolytic tail solution is made into a molten state and brought into contact with the raw material or the treated raw material in the alkali melting process.

20. A zinc recovery method as described in Claim 14, in which sodium hydroxide and zinc are left in the electrolytic tail solution of the electrolysis process, and after evaporating the water from the electrolytic tail solution containing the remaining sodium hydroxide and zinc, the electrolytic tail solution is made into a molten state and brought into contact with the raw material or the treated raw material in the alkali melting process.

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