Method for recovering metallic zinc from solid metallurgical waste

Abstract

To provide a method for recovering metallic zinc from solid metallurgical waste containing zinc and manganese.SOLUTION: A. contacting the solid metallurgical waste with an aqueous leaching solution comprising chloride ions and ammonium ions to produce one or more leachates comprising zinc ions and manganese ions and one or more insoluble solid residues; b. cementing the leachate by adding metallic zinc as a precipitating agent to remove one or more metals other than zinc and manganese present in ionic form in the leachate; B. producing a purified leachate; and c. subjecting the purified leachate to electrolysis in an electrolytic cell comprising one or more cathodes and one or more anodes to deposit metallic zinc on the cathodes and produce one or more effluent leachates. The method comprises, prior to the electrolysis, the step of precipitating manganese ions by oxidation with permanganate ions and subsequently separating the sediment containing MnO2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a process for recovering metallic zinc from solid metallurgical waste. [Background technology]

[0002] In the metallurgical industry, dust containing large amounts of zinc and other metals such as lead and nickel is used. For example, electric arc furnaces (EAFs) generate large amounts of solid waste such as ash and slag. In steel mills that produce secondary steel, the zinc content is relatively high (around 20 to 40% by weight). Dust (EAF dust) is generated in large quantities. Other metallurgical wastes containing zinc, e.g. It is generated in the galvanic industry process. Generally, zinc in metallurgical waste is mixed with lead, cadmium, copper, Along with other elements such as silver, manganese, alkali metals, alkaline earth metals, and halides, They exist in the form of metals, oxides and / or alloys, which can be found in variable concentrations depending on the process of their generation. It exists in degrees.

[0003] At the current state of the art, it is not possible to recover zinc contained in metallurgical waste and use it in industrial processes. There is a strong demand for recycling these materials as secondary raw materials. This allows for a reduction in zinc consumption as a raw material and in the costs of managing metallurgical waste (e.g. waste disposal). and therefore in high temperature or electrolytic zinc coating deposition processes or metal alloy manufacturing The environmental impact of production processes such as the

[0004] Both pyrometallurgical and hydrometallurgical processes are known for recovering zinc from metallurgical wastes. and has been in use for some time.

[0005] The pyrometallurgical process widely used to treat wastes such as EAF dust is the Welz process. In this process, metallurgical waste containing zinc is treated at high temperatures to extract the zinc contained in the waste. The zinc metal is volatilized and recovered in the form of concentrated oxide (ZnO). Zinc, also known as crude zinc oxide (CZO), has a zinc content of approximately 60% by weight and is free of heavy metals. It contains a large amount of pure elements (PB, CD, Mn, etc.) and halides. After that, metallic zinc is obtained by pyrometallurgy (e.g., imperial smelting) or hydrometallurgy ( For example, by leaching with sulfuric acid followed by cathodic electrodeposition.

[0006] The main drawbacks of pyrometallurgy are the high energy requirements and the gaseous streams generated in the process. The problem is that a complex system for collecting and purifying the product is required. The presence of halides in the plant not only causes serious corrosion problems, but also This adversely affects the catalytic electrodeposition process of zinc, reducing its effectiveness. To partially overcome this, before leaching CZO with sulfuric acid, Treatment is typically carried out to remove halides.

[0007] One of the hydrometallurgical processes proposed in the state of the art for the recovery of zinc from metallurgical wastes. One of them is the EZINEX® process. This process is described in, for example, US Pat. 54A, US5534131A, and M. Maccagni, J. Sustai n Metall. (2016) 2:133-140. EZINE The X® process involves leaching metallurgical waste with an ammonium chloride leach solution. and purifying the leachate obtained by the cement treatment. and separating the zinc metal by filtration.

[0008] The leaching step of the EZINEX® process involves leaching metallurgical waste to a neutral pH chloride solution. Zinc and other leachable metals present in metallurgical wastes are leached by contacting them with aqueous ammonium hydroxide. A solution containing the metal and the insoluble residue in ionic form is obtained. The process can be represented diagrammatically by the following reaction: MeO n / 2 + n NH4Cl → Me(NH3) n Cl n + n / 2 H2 O (1) Here, Me is, for example, Zn 2+ , Cd 2+ , Cu 2+ Cu + , Ag + or Mn 2+ where n is equal to 1 or 2.

[0009] Leaching, which is carried out at a neutral pH, dissolves the iron or ions present in the metallurgical waste. Under these pH conditions, the trivalent state is insoluble in the leachate. .

[0010] The step of purifying the leachate containing zinc ions generally involves the use of metallic zinc dust as a precipitant. This is done by cementing metals other than zinc using zinc metal leachate. By adding zinc, metals with a higher (or more positive) reduction potential than that of zinc are precipitated. The precipitated metals are removed from the leachate by filtration.

[0011] The process of cementing metals other than zinc can be represented diagrammatically by the following reaction: do. Me n+ + n / 2 Zn → Me + n / 2 Zn 2+ (2) Here, Me is, for example, Pb 2+ , Cd 2+ , Cu 2+ Cu + or Ag + represents , n equals 1 or 2.

[0012] The leachate containing the purified zinc ions is subjected to electrolysis to obtain elemental zinc. The electrodeposition involves the use of at least one cathode, generally made of titanium, and a few cathodes, generally made of graphite. The process is carried out by continuously feeding the leachate into an electrolytic cell equipped with at least one anode.

[0013] The reactions involved in the electrolysis process are schematically as follows: At the cathode: Zn(NH3)2Cl2+ 2 e - → Zn + 2 NH3 + 2 Cl - (3) At the anode: 2 Cl - → Cl2+ 2 e - (4)

[0014] The chlorine produced in reaction (4) is converted into gaseous nitrogen, as shown in the following reaction diagram: As hydrogen is generated, Cl rapidly increases near the anode. - is converted into an ion. Cl2+ 2 / 3NH3→ 1 / 3N2+ 2 HCl (5)

[0015] Therefore, the overall chemical reaction in the electrolytic cell can be represented diagrammatically by the following reaction: do. Zn(NH3)2Cl2+2 / 3NH3→ Zn + 1 / 3N2+ 2 NH4Cl (6)

[0016] After electrodeposition is complete, the discharged leachate is generally regenerated and the leachate accumulated during the process is recycled. Impurities (e.g., halide ions, alkali metal ions, alkaline earth metal ions, transition metals) and water are removed and recycled to the leaching step. For example, the leachate may be heat treated to drive off water in the form of steam, thereby removing insoluble salts (especially halogenated salts). It is also possible to promote the precipitation of impurities in the form of nitrate salts (e.g., NaCl, KCl). The raw process further includes a carbonation step by the addition of carbonate ions (e.g., Na2CO3). The carbonation process produces relatively insoluble carbonates, for example according to the following reaction: By precipitating the salt, calcium and magnesium ions, as well as The concentration of manganese ions can be sufficiently reduced. Me(NH3) n Cl n + Na2CO3→ MeCO3+ n NH3+ 2 NaCl (7) Here, Me is, for example, Mn 2+ , Ca 2+ or Mg 2+ where n is 1 or Equals 2.

[0017] One of the main advantages of the EZINEX® process is that the CZO is leached and then washed with sulfuric acid. Compared with the method of electrodepositing zinc, zinc-containing metallurgical waste is a preliminary step for halide removal. It can be processed without washing.

[0018] However, the EZINEX® process also has some drawbacks. Manganese and iron ions remain in the leachate, and are oxidized at the anode during electrolysis to become insoluble. The metals may precipitate in the form of reactive oxides (mainly MnO2), where MnO2 is deposited on the cathode. This can be trapped in the extracted metallic zinc, reducing the purity of the zinc and the yield of the electrolysis process. There is a possibility.

[0019] Manganese ions contained in metallurgical wastes are actually released during the regeneration process of discharged leachates (e.g. It is only partially removed during the process (e.g., by carbonation reaction (7)). It tends to accumulate in the exudate.

[0020] On the other hand, iron ions are not only leached from metallurgical waste but also have a significant role in cement processing. Iron is introduced into the leachate in small amounts, and is the main impurity of metallic zinc, which is commonly used as a precipitant. Iron is found in the divalent chloride-ammoniacal complex Fe(NH3), for example. x Cl2 and Some of the iron dissolved in the leachate may be present in soluble form. It can be oxidized by atmospheric oxygen to trivalent iron, for example, by the following reaction: Fe(NH3) x Cl2+ 1 / 2O2 + 5 H2O → 2 Fe(OH) 3+ 4 HCl + 2x NH3(8) where x is an integer ranging from 1 to 6, and the reaction is carried out in the above manner and can be removed by filtration. The dissolved iron residue in the leachate is instead transferred to the electrolytic cell. During electrolysis, manganese and iron ions present in the leachate are generated at the anode. is oxidized by the action of gaseous chlorine (reaction 4), e.g., according to the following reaction: Oxide and hydroxide species (e.g., MnO2 and Fe(OH)3) are formed. Mn(NH3) x Cl2+ Cl2+ 2 H2O → MnO2+ 4 HC l + x NH3(9) 2 Fe(NH3) x Cl2+ Cl2+ 6 H2O → 2 Fe(OH)3 + 6 HCl + 2x NH3(10) where x is an integer ranging from 1 to 6. These insoluble species gradually dissolve in the electrolyte. It may accumulate in the cathode and be incorporated into the metallic zinc particles that deposit on the cathode, reducing the purity of zinc. There is.

[0021] During electrolysis, manganese oxides incorporated into the cathode deposit are converted, for example, according to the following reaction: Soluble Mn redispersed in the electrolyte 2+ Partial electrochemical reduction with the formation of ions It can be restored. MnO2+ m NH4Cl + 2 / 3NH3 → Mn(NH3) m Cl2 + 1 / 3N2+ (m-2) HCl + 2 H2O (11) Here, m is an integer ranging from 1 to 6. In this case, the purity of the deposited metallic zinc is adversely affected. However, if manganese ions are present in the leachate subjected to electrolysis, The current efficiency of the cell is low because the proportion of the cathodic current used for the reduction of cation ions is unavailable for zinc electrodeposition. This results in a lower rate of deposition, which makes the electrodeposition process more energy consuming.

[0022] Furthermore, manganese oxides and manganese hydroxides are formed during electrodeposition, so the active metal The use of anodes (or dimensionally stable anodes) is very costly and in practice this type of anode As is well known, active metal anodes are made of precious metals and related metals. Catalytic cores containing a series of oxides (e.g., ruthenium, iridium, platinum, and related oxides) It consists of a conductive substrate (e.g., titanium metal) covered with a coating layer (active coating). These anodes, also called MMOs (multi-metal oxides), are made of a material with an outer active layer, which is desirable. Electrochemical reactions (evolution of oxygen and chlorine in the case of the EZINEX® process) are obtained. This reduces the potential difference that must be applied to the electrodes to achieve the same applied current density. - consumption, or a higher current density with the same overall process energy consumption. It is now available for use.

[0023] In the EZINEX® process, the formation of manganese oxides is strongly adhesive to the anode surface. In the case of graphite anodes, such deposits are accompanied by the formation of gaseous chlorine. On the other hand, in the case of active metal anodes, the shape of the MnO2 deposits The formation of the active catalyst layer causes deterioration of the active catalyst layer, and therefore, for example, the active catalyst layer must be redeposited over the entire anode. This interrupts the anode regeneration process and reduces the cost of managing the zinc recovery process. This obviously increases the time and complexity involved.

[0024] Patent US5833830 describes the use of manganese ions in the zinc electrodeposition process. A method for reducing the electrochemical formation of MnO2 precipitates from sulfuric acid electrolytes containing O2 is disclosed. The described method measures the oxidation-reduction potential of the electrolyte and calculates the measured value. and comparing the measured value with an optimum reference value, and adjusting the oxidation-reduction potential of the electrolyte to the reference value. The regulation stipulates that an oxidation-reduction agent be added to the electrolyte to correct the According to US 5,833,830, the oxidation-reduction The agents include, for example, peroxide compounds (e.g., H2O2), sodium oxalate, and sucrose. The addition of a redox agent, e.g., H2O2, to the electrolyte can be used to select from soluble Mn 2+ This results in the dissolution of the oxide with the formation of ions and therefore the precipitation of MnO2 on the anode. However, dissolution of MnO2 species can be avoided, resulting in prolonged cell operation. , Mn in the electrolyte 2+ This results in a progressive accumulation of ions, resulting in the concentration of these ions reaching a minimum. When the maximum permissible concentration is reached, the process is stopped. The method described in 830 prevents electrodeposition of MnO2 without removing manganese from the electrolyte, but It is maintained in a soluble form so as not to impair the activity of the anode. Summary of the Invention [Problem to be solved by the invention]

[0025] The object of the present invention is to affect the prior art methods for recovering zinc from solid metallurgical waste. The object of the present invention is to at least partially overcome the drawbacks highlighted above.

[0026] Within this general objective, a specific object of the present invention is to recover zinc from solid metallurgical waste. The object of the present invention is to provide a method for producing a cellulose acetate ester, which is particularly suitable for use in the EZINEX® process. With respect to the production of zinc metal, it is possible to obtain high purity zinc metal at a lower cost than known hydrometallurgical processes. This is what is done.

[0027] A second object of the present invention is a method for recovering zinc from solid metallurgical waste, comprising the steps of: The process is characterized by higher energy efficiency, especially in the electrodeposition step. The purpose is to provide.

[0028] The third object of the present invention is to provide a method for reducing the frequency of electrode maintenance interventions and improving management. The object of the present invention is to provide a method for recovering zinc from solid metallurgical wastes that is simpler than conventional methods.

[0029] The fourth object of the present invention is to provide a method for recovering zinc from solid metallurgical wastes by using an active metal cation. The use of electrodes allows for simple and effective electrolytic deposition of metallic zinc, The object of the present invention is to provide a method capable of reducing energy consumption.

[0030] A further object of the present invention is to provide a method for recovering zinc from solid metallurgical waste, comprising the steps of: It is possible to recover the manganese present in the process in the form of a relatively high purity product, Thus, the object is to provide a method that can be reused in other industrial processes. [Means for solving the problem]

[0031] The applicant has prepared a leachate containing zinc ions and manganese ions containing MnO4 - By treating with ions and removing manganese ions from the leachate, It has been found that the above and other objectives well stated can be achieved.

[0032] In fact, the leachate contains MnO4 - When ions are added, manganese ions and any iron ions present are The oxides and hydroxides of manganese and iron are easily separated from the leachate. The formation of insoluble compounds (e.g., MnO2 and Fe(OH)3) and the dissolution of these two It has been observed that leachates containing very little ions are subjected to electrolysis. This effectively solves the problem of manganese ions and iron ions accumulating in the electrolytic cell. At the same time, the leachate that is substantially free of particles of these two metals can be subjected to electrolysis. Therefore, the purity of the metallic zinc deposited on the cathode can be increased.

[0033] Furthermore, the concentrations of manganese ions and iron ions in the leachate subjected to electrolysis are reduced. This reduces the magnitude of unwanted electrochemical reactions occurring within the cell, thus improving the electrodeposition process. The overall energy consumption of the process is reduced and its current efficiency is improved.

[0034] In addition, the concentrations of manganese ions and iron ions in the leachate subjected to electrolysis are significantly reduced. This has the advantage of reducing the formation of anode deposits, resulting in less active metal anodes. This allows for the use of electrodes, which reduces the frequency of electrode maintenance and enables the plant to operate continuously for long periods of time. This is advantageous in terms of plant production volume.

[0035] In addition, since the active metal anode is thinner than the graphite anode, it is possible to use the active metal anode. Therefore, the size of the electrolytic cell used for electrodeposition can be made smaller than that of an electrolytic cell using a graphite anode. do.

[0036] The method described herein allows the removal of manganese and permanganate already present in soluble form in the leachate. Both the manganese added as an acid and the manganese added as an acid are recovered in the form of MnO2 with high purity. This method allows for the removal of contaminants from the leachate and its reuse in other industrial processes. It can be converted into usable raw materials.

[0037] Furthermore, manganese added in the form of permanganate ions can also be recovered in the form of oxide. Therefore, the method according to the invention does not add further chemical elements or compounds to the leachate circulating in the plant. This offers the particular advantage of removing manganese and iron ions without introducing any additives.

[0038] Thus, according to a first aspect, the present invention provides a method for the production of solid metallurgical waste containing zinc and manganese. 1. A method for recovering metallic zinc from an object, comprising: a. leaching said solid metallurgical waste with an aqueous leach solution containing chloride ions and ammonium ions; and contacting the leachate with at least one leachate containing zinc ions and manganese ions. and another insoluble solid residue. b. cementing the leachate by adding metallic zinc as a precipitant; At least one element other than zinc and manganese that may be present in the leachate in ionic form removing the seed metals to produce a purified leachate; c. at least one cathode and at least one anode immersed in said purified leachate; The purified leachate is electrolyzed in an electrolytic cell containing generating at least one effluent leachate, The method further comprises the step of: prior to the electrolysis, converting manganese ions into manganese ions by oxidation with permanganate ions; and then separating the precipitate containing MnO2. .

[0039] Permanganate ion (MnO4 - ) in the leachate by adding n 2+ The oxidation of (C) can occur at one or more points in the process.

[0040] In one embodiment, permanganate ions are used to precipitate and remove manganese ions, for example. In a dedicated treatment device, it is added to the purified leachate from step b.

[0041] In another embodiment, the leachate used in step a may contain MnO4 - Ions are added. In this case, precipitated manganese oxide MnO2 is mixed with the insoluble residues of the leached metallurgical waste. This embodiment is suitable when the manganese concentration in the leachate is relatively low, preferably 1 g This is particularly advantageous when the concentration is less than 1 / 1. This is because it may be economically inconvenient.

[0042] In one embodiment, MnO4 is added to the effluent leachate from step c. - Ions are It is reused as the leachate in step a.

[0043] In a particularly preferred embodiment, MnO4 - The ions are released into the leachate circulating in the plant. At the time selected for the purpose, the leachate is supplied while maintaining its oxidation-reduction potential at an optimal reference value. The optimum value is determined by a calibration method taking into consideration at least the pH of the leaching solution, preferably the pH and the temperature of the leaching solution. It is obtained by the line.

[0044] Further features of the process according to the invention are defined in the dependent claims 2 to 18.

[0045] As used in this specification and the appended claims, the articles "a / one" and "one" refer to and "the" refer to one or at least one unless it is clear that something else is intended. The singular must be read as including the plural. This is done merely for convenience and to give a general sense of the specification. do.

[0046] Where different from or otherwise indicated in the embodiments, the same shall apply throughout the disclosure and claims. All numerical values ​​expressing amounts of ingredients, reaction conditions, etc. are expressed in all cases as "approximately." "context" shall be understood as modified by the term "context."

[0047] The numerical limits and intervals expressed in this specification and the appended claims are intended to be illustrative and not restrictive. Additionally, all values ​​and sub-ranges of limits or numerical intervals are included. shall not be deemed to be specifically included as if they had been expressly mentioned. It must be.

[0048] The composition according to the present invention comprises the essential ingredients and and optional ingredients may "comprise," "consist," or "consist essentially of."

[0049] For purposes of this specification and the appended claims, the term "consisting essentially of" means The composition or component may contain additional components, but the additional components may be present in the composition or component. This means that the essential characteristics are limited to a range that does not substantially change.

[0050] For purposes of this specification and the appended claims, the concentration of ions of a metal in solution is Unless it is clear that the intention is not to It is expressed as follows. [Brief explanation of the drawings]

[0051] [Figure 1] 1 is a schematic diagram of an embodiment of the method according to the present invention;

[0052] (Figure description) The features and advantages of the process according to the invention are shown in the schematic diagram of one embodiment of the method according to the invention. This will become more apparent from the following description with reference to the accompanying Figure 1. The following example embodiments are provided solely for the purpose of illustrating the present invention and are not intended to be limiting unless otherwise specified. This is not to be understood as limiting the scope of protection defined by the scope of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] (Detailed Description of the Invention) Referring to FIG. 1, a system 100 includes an apparatus 101 for leaching metallurgical waste, a zinc and cement treatment equipment 103 for removing metals other than manganese, precipitate containing MnO2 Mn soluble in the form of precipitates 2+ Oxidation device 105 for removing ions, electrolyte recycling device a tank 107, an electrodeposition device 109 for electrodepositing zinc, a carbonation device 111, and a discharged The method according to the present invention is described below in detail with reference to the accompanying drawings. , and relates to an embodiment in which the method is carried out continuously and in a steady state.

[0054] During the process according to the invention, zinc and manganese-containing metallurgical waste 115 is leached into a leaching unit 1 01, where NH4, provided for example in the form of an ammonium chloride solution 116, + ions and Cl - The material is contacted with a leach solution containing ions.

[0055] Preferably, the metallurgical waste is EAF, CZO dust, and ash, slag, sludge, etc. and other wastes containing zinc in oxidized form generated by metallurgical processes. The metallurgical waste is at least one of EAF, CZO dust and mixtures thereof. Includes.

[0056] Zinc and manganese are present in metallurgical wastes in the form of metal, oxides and / or alloys The zinc content in the metallurgical waste is preferably between 15% and 70% by weight. The Mn content is preferably in the range of 0.1 to 10% by weight. More preferably, it is in the range of 0.5% to 5% by weight.

[0057] In addition to manganese, metallurgical waste contains halides (especially fluorides) and metals (especially P b, CD, Cu, Fe, Ni, AG, alkali metals and alkaline earth metals, especially Na and Metal contaminants in metallurgical wastes and The overall concentration of manganese and fluoride will vary depending on the origin of the waste. The overall concentration of metal contaminants is in the range of 2% to 5% by weight, while the concentration of halogens is The overall concentration is in the range of 2% to 10% by weight (represented as X2, where X is the halogen atoms, e.g., Cl or F), the percentages being based on the weight of the metallurgical waste. be.

[0058] The leaching step produces an insoluble residue 117 and a leaching solution containing zinc and manganese ions. The leachate 119 generates a biphasic reaction product containing the metals dissolved during leaching. It also includes other metal contaminants present in gold waste. Dissolved metals are leached in the form of ions. The chlorine-ammonia complexes present in the solution, in particular those formed, for example, according to reaction 1 shown above, It is the body.

[0059] The ammonium ion and chloride ion are preferably expressed as ammonium chloride. It is contained in the infusion solution at variable concentrations ranging from 100 g / l to 600 g / l.

[0060] Preferably, the pH of the infusion solution is in the range of 5 to 9, more preferably 5.2 to 7.5. The pH range is preferably within the range of 6 to 7. The leaching of iron contained in the waste metallurgical materials is minimized. The pH of the leachate is adjusted by adding NH3 water. It can be controlled by adding a solution.

[0061] The leaching is preferably carried out at a temperature ranging from 50°C to 90°C, more preferably from 60°C to 80°C. It is done at 100 degrees.

[0062] After leaching is complete, the insoluble residue 117 is removed, for example, by decantation and / or filtration. The insoluble residue is separated from the leachate119 by ferrous zinc and iron oxides. The insoluble residue is composed of fluoride ions and calcium present in the treated metallurgical waste. The insoluble residue may further contain CaF2 formed by precipitation of ions. or more advantageously, to an EAF furnace for steel production, or or can be recycled into processes for CZO production.

[0063] In one embodiment, the oxidation of soluble manganese ions and optionally soluble iron ions is , MnO4 in the leaching solution - This is done by adding 118 ions. The soluble residue 117 also contains precipitates of MnO2 and optionally Fe(OH)3. .

[0064] In the cement processing device 103, the leachate 119 would otherwise be present during the electrodeposition step. To remove contaminants consisting of dissolved metals other than zinc that may co-deposit with metallic zinc It is subjected to cement treatment.

[0065] Cementation (or chemical shift precipitation) is the process of adding a first metal in ionic form to a A solution containing an elemental metal having a reduction potential lower (or more negative) than the reduction potential of the first metal is added to the solution. Precipitating the first metal in its elemental state by adding a second metal (precipitant) in its elemental state It is a reaction.

[0066] In cement processing equipment, dissolving agents with a higher reduction potential than zinc in the electrochemical series are used. Metallic zinc is used as the precipitant 123 for precipitating the metal. The chemicals required to precipitate metal ions in excess of the metal, e.g., in the leachate It is added to the leachate in dust form in 30% to 200% excess of the stoichiometric amount. The amount of soluble zinc ions from the leaching of metallurgical waste is very small compared to the amount of zinc ions from the leaching of metallurgical waste. It is small.

[0067] Thus, the metallic zinc used as the precipitant contains significant amounts of zinc in addition to elemental zinc. For example, 1 kg of zinc may contain up to 3 to 4 g of iron as an impurity. Iron contamination can be removed along with manganese, making it particularly suitable for non-high purity metallic zinc. Even zinc metal can be used as a precipitant. %, up to 0.5% by weight, or up to 1% by weight of iron (based on the weight of the precipitant) (Concentration expressed as elemental iron).

[0068] The cement treatment may be carried out in one or more stages depending on the total content and type of metal contaminants to be removed. The floors can be run in order.

[0069] The cement treatment can be carried out by techniques and equipment known to those skilled in the art. In an embodiment, the cement processing is carried out continuously in a rotary reactor. The device and its associated methods of use are known to those skilled in the art.

[0070] The cement processing step is carried out by using the purified leachate 125 and the solid product (cement) 127. The purified leachate 125 generates a biphasic product consisting of zinc ions and the influent leachate. The residual amount of metal ions other than zinc that were initially present in the liquid 119. The cement 127 is , elemental metals other than zinc that have a higher reduction potential than zinc, especially Pb, Cd, and Cu, The purified leachate 125 contains Ag and unreacted metallic zinc precipitated. , under the conditions in which cement treatment is carried out, Mn 2+ The reduction potential of the Zn / Mn couple is 2+ / Zn vs. Therefore, the manganese ion concentration in the leachate is almost the same as that in the influent leachate. The temperature is kept almost the same.

[0071] Preferably, the zinc containing manganese in the leachate 119 flowing into the cement processing device 103 The total concentration of ions of metals other than those mentioned above is within the range of 100 mg / l to 3000 mg / l. Preferably, the ions of metals other than zinc, excluding manganese and iron, in the purified leachate 125 The total concentration is in the range of 0.5 mg / L to 2 mg / L. In 25, the concentration of manganese ions is in the range of 10 mg / l to 2,000 mg / l. and more preferably in the range of 20 mg / L to 1,500 mg / L. In the purified leachate 125, the iron ion concentration ranges from 1 mg / L to 50 mg / L. It is within the enclosure.

[0072] According to the embodiment shown in FIG. 1, the purified percolate 125 is purified by, for example, decantation and / or or separated from the metal cement 127 by filtration and then oxidized in the oxidizer 105 It is subjected to a process that oxidizes manganese ions in solution to form insoluble MnO2. The oxidation of manganese ions is achieved by adding permanganate ions 129 to the purified leachate 125. The addition of permanganate ions 129 in the oxidation unit 105 is This can be done alternately or in combination with the addition of permanganate ions 118 in do.

[0073] The oxidation reaction of manganese ions in solution can be carried out, for example, according to the following scheme: Cut. 3 Mn(NH3) x Cl2+ 2 KMnO4+ 2 H2O → 5 MnO 2+ 4 HCl + 2 KCl + 3x NH3(12) where x is an integer ranging from 1 to 6.

[0074] If soluble iron ions are present in the leachate, the formation of MnO2 ions occurs as MnO4 - stomach with iron ions to form insoluble iron hydroxides, for example according to the following reaction: and with the formation of further MnO2. 3 Fe(NH3) x Cl2+ KMnO4+ 7 H2O → MnO2+ 3 Fe(OH)3+ 5 HCl + KCl + 3x NH3(13) where x is an integer ranging from 1 to 6.

[0075] The oxidation step performed in the apparatus 105 removes the insoluble residue 131 and the influent leachate 125. Treated leachate 133 having reduced concentrations of manganese and iron ions relative to the concentrations of and a biphasic reaction product comprising:

[0076] The insoluble residue 131 consists of precipitated manganese in the form of MnO2 and optionally an oxidation step. This includes iron oxides and hydroxides precipitated in the solution. The iron ion concentration in the leachate subjected to the acidification is relatively low compared to the manganese ion concentration, The resulting MnO2 has a high purity (over 95% by weight, up to 99% by weight), and therefore It can be reused as a raw material in industrial processes.

[0077] In one embodiment, the precipitate 131 containing MnO2 has a pH in the range of, for example, 1.5 to 3. This wash removes the iron oxides and iron oxides from the MnO2 precipitate. Since oxides can be removed, the purity of the resulting MnO2 can be increased.

[0078] The permanganate ions 129 and / or 118 are preferably dissolved in an aqueous solution, e.g., KMn In a preferred embodiment, the added MnO4 is in the form of an aqueous solution of MnO4. - ion The amount of leachate 133 is adjusted to maintain a substantially constant redox potential value for the treated leachate 133 exiting the apparatus 105. It is adjusted so that

[0079] For example, the oxidation-reduction potential of the treated leachate leaving the oxidation unit 105 may be measured periodically or continuously. The oxidizing agent is adjusted so as to maintain the oxidation-reduction potential of the treated leachate within a predetermined range (reference range). By adjusting the amount of MnO4 (manually or automatically), -The amount of ions added The reference range can be adjusted for the particular plant in which the method according to the invention is carried out. The range of values ​​can be determined experimentally by one skilled in the art, and such a range of values ​​is determined mainly by the amount of leachate. It can be affected by factors such as composition, temperature, pH, and the material from which the electrodes are made.

[0080] A leachate 13 leaving the oxidation device 105 that is substantially free of manganese ions and iron ions. 3 is fed to an electrodeposition unit 109 for zinc recovery.

[0081] At the point in the process where manganese ions are precipitated and the precipitated MnO2 is removed, Regardless of the concentration, the residual concentration of manganese ions in the leachate circulating in the cell is preferably 2 mg / Preferably, the residual concentration of iron ions in the leachate circulating in the cell is less than 1 mg / L. It is less than l.

[0082] The addition of permanganate ions may, in some cases, reduce the Mn content in the electrolytic cell. 2+ Ion concentration It is not possible to guarantee ideal conditions, i.e., the concentration of Mn 2+ <2mg / l It was observed that the conditions could not be met and therefore high current efficiencies of the cells could not be guaranteed. This drawback is due to the fact that the addition of permanganate ions is a continuous and automated method. The oxidation-reduction potential of the leachate can be kept constant, or the oxidation-reduction potential can be reduced by permanganate. The ions are in stoichiometric excess relative to the concentrations of manganese and iron ions to be precipitated. This can occur both when the hydroxyl group is added and when the hydroxyl group is added.

[0083] The addition of a stoichiometric excess of permanganate ions is, in principle, sufficient to remove manganese ions from the leachate. The two impurities were essentially completely precipitated without increasing the concentration of the ion. The unreacted permanganate ions actually react with ammonia to form Mn It is converted to O2 and is therefore destined to be removed from the leachate in the form of precipitate. Impurities that oxidize in the presence of manganate ions are leached in varying and unpredictable concentrations. In the presence of ammonia, permanganate ions are converted to MnO2. The slow reaction rate leads to incomplete precipitation of MnO2, resulting in the formation of manganese oxide in the leachate. This can be caused by manganese ions reaching the cell, especially when a metal anode is used. This can have a negative effect on the electrodeposition process.

[0084] The applicant has determined the oxidation-reduction potential of the leachate by measuring the amount of added permanganate ions present in the leachate. The optimum value (hereafter referred to as "precipitation redox") corresponds to the value that completely oxidizes all oxidizable species present in the precipitate. Potential" or "Redox ppt " (also referred to as "). In order to maintain The amount of the compound added can be adjusted to achieve a specific pH value, preferably a specific pH value and temperature value. It has now been discovered that this drawback can be overcome by

[0085] The precipitation redox potential is determined by using a solution of permanganate ions as a titrant to determine the amount of manganese to be removed. A series of redox reactions were performed on aliquots of the leachate containing calcium and / or iron ions. It can be determined experimentally either in the plant or in the laboratory by performing a titration. An aliquot of the leachate can be used to determine the possible changes in the value of this parameter during the process. To take into account the variations, an aliquot of the leachate is subjected to titration to different pH values. The pH of the solution is adjusted by adding a basifying agent (e.g., NH4) or an acidifying agent (e.g., HCl). to reach the desired pH.

[0086] Preferably, at least two, more preferably at least three, and even more preferably at least At least four samples with different pH values ​​are prepared. Typically, the number of samples ranges from two to four. 8. Preferably, titration of these samples is performed at the operating temperature of the process, e.g. This is done by keeping the temperature at 70°C.

[0087] Preferably, aliquots of the leachate are titrated to different pH and temperature values ​​to determine the precipitated oxidation product. The effect of variations in both operating conditions on the reduction potential is considered.

[0088] For this purpose, preferably at least two samples with different pH values ​​are prepared. Each of the samples has at least four experimental values ​​of precipitate redox potential. Preferably, the number of samples prepared is at least At most three, and more preferably at least four. Preferably, each sample contains at least Each sample is titrated at three different temperatures, preferably at least four different temperatures. is titrated to

[0089] Experimental Redox ppt The value is the inflection point of the titration curve, i.e., the oxidation-reduction potential value of the solution. It is obtained by determining the inflection point of the graph reported as a function of the amount of titrant added.

[0090] The experimental redox potential, pH, and optionally temperature were mathematically interpolated to obtain the precipitate redox potential. Calibration curves correlating Redox potential with pH and optionally with temperature (T) of the leachate ppt =f(p Interpolation can be performed using known mathematical methods, for example, a 3-dimensional polynomial function. This can be done by number.

[0091] Using the calibration curve, the pH value of the leachate measured during the process and, in some cases, Based on the temperature, the precipitation redox potential can be calculated. The manganese ions were insufficient, resulting in incomplete precipitation of the manganese ions from the solution. or there is an excess, and the unconverted manganese species are caught in the electrolytic bath as MnO2. To avoid this, Redox ppt By periodically repeating the procedure to find the value, The amount of permanganate ions added was varied to ensure optimal precipitation conditions for manganese ions. It is possible to do this.

[0092] Redox ppt The values ​​are based on plant conduction parameters such as pH, temperature, and composition of metallurgical waste. The pH of the infusion solution, which may vary as a result of different factors and different parameters, is preferred. Redox based on pH and temperature ppt Optimizing the manganese ion It has been observed that this is sufficient to obtain a substantially complete precipitation of

[0093] However, Redox ppt Calibration curves for parameters such as pH and In addition to pH, other parameters of plant conduction were also considered in a similar manner as described above for pH and temperature. parameters, such as the current density applied to the electrodes, the content of iron ions in the leachate, other oxidation Reducing couples (e.g., Au / Au + , Ag / Ag + ) etc. It is possible to determine

[0094] Generally, Redox ppt The values ​​can vary widely. In at least one embodiment, Redox ppt The value is 400 to 650 mV (saturated calomel electrode or AgCl (measured with a Pt-based electrode against a reference electrode such as The temperature preferably varies within the range of 5.2 to 7, more preferably 5.5 to 6.5. Or it varies within the range of 60 to 80°C.

[0095] The addition of permanganate ions is effective regardless of the location in the metallurgical waste treatment process. precipitation of said manganese ions, whether in the leachate, the refined leachate or the discharged leachate. It is possible to apply a method for controlling the conditions.

[0096] Advantageously, the aforementioned method for controlling the precipitation conditions of manganese ions is This can be carried out in combination with a system for automatically and continuously adding acid ions.

[0097] In one embodiment, the dosing system includes a device for dosing permanganate ions (e.g., , pump for supplying KMnO4 solution), for the leachate to be treated with permanganate ions A redox sensor for measuring the redox potential of the leachate to be treated. pH sensor and optionally temperature sensor for measuring parameters (pH and temperature) - connected to sensors to receive and process the measurements of redox potential, pH and temperature The controller also includes a control device (e.g., a programmable logic device, PLC) that controls the Configured Redox ppt Controlling the amount of permanganate ions added in response to the value The logic unit is connected to the dosing device to measure the experimentally determined calibration curve. ppt = f(pH) or f(pH,T) is detected by a sensor during the process Redox to be maintained in the leachate based on the determined pH value and, optionally, temperature value. ppt Value It is programmed to calculate and set it periodically.

[0098] During the process, following the addition of permanganate ions, the sensor measures the amount of reduced oxidation measured in the leachate. The control unit transmits the raw potential, pH, and optionally temperature values ​​to the control unit. The optimum redox concentration was determined based on the calibration curve. ppt Calculate the value and set the value to be maintained in the leachate. The control device then sets the redox potential of the leachate at the set Red ox ppt value (for example, by increasing or decreasing the amount of permanganate ions added). ), and the adding device is controlled to add permanganate ions. The process is repeated periodically, possibly continuously, in an automatic mode.

[0099] In one embodiment, the method according to the present invention comprises the steps of: a. Adding permanganate ions to a leachate containing zinc ions and manganese ions and, b. measuring at least the pH, redox potential, and optionally the temperature of said leachate; c. Periodically correlate the precipitate redox potential with at least the pH value and, optionally, the temperature of the leachate. The precipitate oxidation-reduction potential (Redox ppt ), and , - The redox potential of the leachate is calculated as the redox potential of the precipitate (Redox ppt ) This involves changing the amount of permanganate ions added so as to approximate the above.

[0100] The electrodeposition apparatus 109 comprises at least one cathode immersed in the leachate to be electrolyzed and at least one The electrolytic cell (not shown) includes at least one electrolytic cell and one anode.

[0101] According to the scheme of FIG. 1, the leachate 133 to be electrolyzed is recycled before being fed to the electrolytic cell. The leachate stream 135 is removed from the recycle tank 107. The electrolytic solution is circulated in the electrolytic bath of the electrodeposition device 109. During electrolysis, a potential difference is applied to the electrodes. This reduces the zinc ions present in the leachate, producing metallic zinc particles that adhere to the cathode surface. adhere to.

[0102] The concentration of zinc ions leaving the electrolytic cell in the discharged leachate 1 was reduced compared to the inflowing leachate 133. 37 is recirculated to the recycle tank 107 again, and the leachate flowing in from the oxidation device 105 It is mixed with 133.

[0103] In one embodiment, an aliquot 159 of leachate present in the recycle tank 107 is taken. and recycled to the leaching unit 101, where the zinc recovery process is carried out continuously. As such, it is enriched with zinc ions after further leaching of metallurgical waste.

[0104] When the zinc metal recovery process in continuous mode is at steady state, Preferably, (i) The mass of metallic zinc deposited on the cathode per unit time (current 143) is Zn entering Tank 107 2+ Ion mass per unit time (current 133) and recycling Zn in discharged leachate 137 recycled to tank 1072+ Ion quality per unit time It is preferable that the difference between the amount is approximately equal to the amount of (ii) The volumetric flow rate of the recirculating leachate in the electrolytic cell (streams 135, 137) is The volumetric flow rate of the recirculated leachate 159 to 1 (streams 159, 119, 125, and 133) is approximately the same. In a steady state, the Zn in the tank 107 2+ The concentration of ions is , and is therefore substantially constant.

[0105] Electrolysis is described, for example, in patents US5534131A and US5534131A. The reaction can be carried out in an open cell according to techniques known to those skilled in the art, such as

[0106] Cl - Ions and NH4 + The composition of the electrolyte, which contains ions, allows for the deposition of metallic zinc on the cathode. It is possible to obtain the generation of gaseous chlorine at the anode. The remaining gaseous chlorine reacts rapidly with ammonium ions present in the solution around the anode. The electricity generated during electrolysis generates gaseous nitrogen while regenerating ammonium chloride. The chemical reactions are (3) to (6) shown above. NH3 is consumed by the electrolysis reaction. This is supplied to the electrolytic cell (FIG. 1, arrow 141) in the form of, for example, an aqueous ammonia solution. This allows for optional incorporation into the process.

[0107] The zinc deposited on the cathode is separated from the latter (Fig. 1, arrow 143) and optionally processed, e.g. If necessary, it is melted down and disposed of in the form of ingots. Metallic zinc can also be recovered in the form of dust, and one of the The moiety can be used as a precipitant in the cement processing step.

[0108] In one embodiment, the electrolytic cell includes at least one graphite anode.

[0109] In another embodiment, the electrolytic cell comprises at least one active metal anode. Active metal anodes that can be used are known to those skilled in the art and are commercially available.

[0110] Preferably, the active metal anode comprises one or more noble metals and / or one or more noble metals At least one conductive substrate (e.g., T) covered with a catalytic coating layer comprising an oxide of i, Nb, W and Ta).

[0111] The cathode can be made from a variety of materials, including titanium, niobium, tungsten, and tantalum. Preferably, the cathode is made of titanium.

[0112] In order to control the concentration of impurities in the leachate circulating in the continuous process, The resulting leachate contains, in particular, calcium ions, magnesium ions, halide ions, Removes at least one of alkali metal ions and / or alkaline earth metal ions and water It is preferable to carry out a regeneration treatment.

[0113] By controlling the concentration of these impurities, adhesion to heat exchangers used in plants can be reduced. The formation of compounds (especially calcium and magnesium salts) can be controlled.

[0114] In one embodiment, the leachate regeneration process includes a carbonation step. An aliquot 139 of the infusion solution present in the tank 107 is fed to the carbonator 111. , where alkali metal and / or alkaline earth metal carbonates, alkali metal and / or alkaline earth metal bicarbonates, and mixtures thereof (e.g., Na2CO3 and / or NaHCO3), By this, calcium ions and magnesium ions are removed, and the respective insoluble carbon This results in the formation of precipitates in the form of acid salts and / or bicarbonates (Reaction 7). The resulting insoluble precipitate 147 is separated, for example by filtration, into a supernatant liquid which is sent to tank 107. Separated from 149.

[0115] In another embodiment, the calcium ions and magnesium ions in the leachate circulating in the process The control of the concentration of calcium ions is achieved by controlling the insoluble calcium salts and and / or by adding anions capable of forming magnesium salts. It is possible to implement this.

[0116] Preferably, the anion is selected from sulfate, carbonate, and oxalate.

[0117] Preferably, the anion is sulfate anion SO4 2- This means that in the leaching equipment, e.g. For example, sulfuric acid can be added to the leaching solution in the form of an aqueous solution. The ions are extracted in a leaching apparatus using an aqueous solution of, for example, sodium oxalate or sodium carbonate. Sulfate anions can be added to the leachate in the form of calcium sulfate and sulfur. A precipitate containing magnesium sulfate is formed, which is removed together with the insoluble residue 117. The acid solution may be of a commercially available type, for example with a concentration in the range of 20 to 96% by weight. In view of the composition of the ammonium chloride-based leachate, The addition of sulfuric acid in the amount necessary to precipitate sodium and magnesium ions is It does not significantly change the pH of the solution present in the device 101.

[0118] The carbonation unit in the EZINEX® process according to the state of the art is Mn in the leachate circulating in the process 2+ Note that it also functions to control the concentration of ions. The method according to the present invention involves the removal of ammonium nitrate from the leachate by oxidation with permanganate ions. This results in the virtually complete removal of soluble manganese ions from the calcium and When the control of the concentration of magnesium ions is achieved by their precipitation in the leaching unit, In this case, it is possible to eliminate the carbonator, thus reducing the size of the plant and It is possible to simplify the management of

[0119] In one embodiment, the regeneration process comprises a step of heat treating the leachate. An aliquot 155 of the solution present in the tank 107 is fed to the evaporator 113, where Some of the excess water accumulated during the process (dilution water for reagents, washing water for filtration residue) is used for heat treatment. The removed water is expelled in the form of steam flow 151. Halide salts of alkali metals and / or alkaline earth metals (e.g., NaC HCl and KCl) may precipitate, but these may be separated into the supernatant by settling and / or filtration. The supernatant liquid 157 containing the concentrated leachate is separated from the leachate (arrow 153). Sent to 107. [Example]

[0120] The following experimental examples are provided below to further illustrate the features and advantages of the present invention.

[0121] Example 1 The efficiency of the method described herein was demonstrated in a pilot project carried out according to the scheme of FIG. The productivity of the pilot plant without an oxidizer was 1.2 times that of metallic zinc. It was about 8 kg / h.

[0122] The test was carried out by circulating the leachate in the plant at a flow rate of approximately 600 l / h. was done.

[0123] The oxidation device consists of a tank containing an aqueous solution of KMnO4 (40 g / l) and a and a pump to remove the solution and mix it with the leachate circulating in the oxidation unit. The oxidizer also serves to separate the solid MnO2 particles that form after the addition of KMnO4. It was equipped with a filter press.

[0124] The flow rate of the KMnO4 solution supplied to the leaching solution was adjusted to keep the redox potential of the leaching solution constant. The pump flow rate was adjusted based on the redox potential of the leachate leaving the oxidation unit. The pump control unit automatically regulates the oxidation and reduction of the leachate leaving the oxidation unit. Based on the potential measurements, the redox potential of the leachate was measured to a value of 300 mV (Pt measurement potential). The flow rate of KMnO4 was adjusted to maintain a saturated calomel reference electrode. It was composed of.

[0125] The leachate that flowed into the oxidation device contained 357 mg / l of manganese ions and 6 mg of dissolved iron ions. During the test, the KMnO4 feed flow rate averaged approximately 10.5 L / h. The test duration was 2 hours.

[0126] 1320.5 g of particles were recovered from the oxidizer by pressure filtration, washed with water, and dried. The weight of the particles was 1139.6 g. After drying, the particles contained 98.6% of MnO2. The manganese content was 62.3% by weight and iron oxide / hydroxide 0.91%. The filtered leachate flowing into the Visual inspection showed no significant particle presence in the cell during electrolysis. It was.

[0127] The electrolysis device comprises two electrolytic cells connected in series, each containing five titanium cathodes ( Each 1m 2 1000 W working surface) and six graphite anodes.

[0128] Current density 350A / m 2 After 2 hours of electrolysis, the purity was found to be 99.992%. A total of 16.76 kg of metallic zinc (current efficiency 98.2%) was deposited and recovered at the cathode. It was.

[0129] Current efficiency, i.e., the amount of zinc deposited and the theoretically possible deposition according to Faraday's law The ratio between the amount of zinc and the amount of zinc produced was 94% on average for the process carried out without an oxidizer. 5% (maximum 96%) to a stable value of 98% or more in the presence of the oxidation device according to the present invention. The transition has been made.

[0130] Example 2 The optimum Redox is determined based on the pH and T value of the leachate. ppt The redox potential is The flow rate of the KMnO4 solution to the leaching solution was adjusted to constantly maintain the same level. Test 1 was repeated. For this purpose, three aliquots of the leachate were added to a KMnO4 solution (3.16 g / l) at pH = 5.2, 6.0 and 7.0 and at temperatures of 60°C and 70°C. and 80°C, respectively.

[0131] The experimental Redox obtained for each sample ppt The values ​​(titration end points) are shown in the table below .

[0132] [Table 1]

[0133] Experimental Redox ppt The values ​​are mathematically interpolated by a polynomial function, pp t A calibration curve of f = (pH, T) was obtained and used to program the pump controller. The oxidation-reduction potential value of the solution is ppt The addition of permanganate ions is continuously adjusted to the value By doing this, it was possible to supply leachate with a Mn concentration of approximately 0.2 mg / L to the electrolytic cell. Under these conditions, zinc was electrodeposited with a current efficiency equal to 99.2%. remained completely transparent with no trace of dust.

Claims

1. 1. A method for recovering metallic zinc from solid metallurgical waste containing zinc and manganese, comprising: a. leaching the solid metallurgical waste material with an aqueous leach solution containing chloride ions and ammonium ions. and contacting the leachate with at least one leachate containing zinc ions and manganese ions. and another insoluble solid residue. b. Cementing the leachate by adding metallic zinc as a precipitant, At least one element other than zinc and manganese that may be present in the exudate in the form of an ion removing the metals from the leachate to produce a purified leachate; c. at least one cathode and at least one anode immersed in said purified leachate; The purified leachate is electrolyzed in an electrolytic cell containing zinc to deposit metallic zinc on the cathode, and generating at least one effluent leachate; The method further comprises, prior to the electrolysis, converting manganese ions into manganese ions by oxidation with permanganate ions. is precipitated, and then MnO ２ separating a precipitate comprising: method.

2. The step of precipitating manganese ions is performed after the cement treatment step b.

10. The method of claim 1, wherein the electrolysis step is carried out before step c.

3. The step of precipitating the manganese ions comprises adding manganese ions to the leachate in step a.

3. The method according to claim 1, wherein the permanganate ion is added. The method described in paragraph .

4. At least a portion of the discharged leachate from the c phase is recycled as leachate to the a phase. The method according to any one of claims 1 to 3,

5. The step of precipitating manganese ions is carried out by recycling the manganese ions as leachate in step a. a portion of the discharged leachate after the electrolysis step c and before the leaching step a The method of claim 4, wherein the method is carried out in

6. The permanganate ions are in the form of an aqueous solution, preferably KMnO ４ is an aqueous solution of 6. The method according to any one of claims 1 to 5.

7. The oxidation-reduction potential of the leachate from the step of precipitating manganese ions is set as a reference value. The amount of permanganate ion added in the precipitation step is continuously adjusted to maintain the range of 7. The method according to claim 1, wherein the temperature is adjusted continuously or discontinuously.

8. MnO ２ 8. The method of claim 1, wherein the precipitate comprises at least one iron oxide. The method according to any one of claims 1 to 5.

9. At least MnO ２ The precipitate containing 9. The method according to claim 1, wherein the washing is carried out with

10. The leaching solution has a pH in the range of 5 to 9, preferably in the range of 5.2 to 7.

5.

10. The method according to claim 1, wherein the pH is in the range of 6 to 7. method.

11. The discharged leachate contains calcium ions, magnesium ions, halide ions, At least one of alkali metal ions and / or alkaline earth metal ions, and water and the leaching step (a) is carried out after at least partial removal of the soluble solids.

4. The method according to claim 4.

12. The leaching solution in step a) contains insoluble calcium salts and / or magnesium salts. The anions include anions capable of forming ammonium salts, the anions being preferably sulfate, carbonate, or the like.

12. The method of claim 1, wherein the hydroxybenzoate is selected from the group consisting of hydroxybenzoates and oxalates. 。

13. 13. The method according to claim 1, wherein the at least one anode is an active metal anode. The method described.

14. 13. The method according to claim 1, wherein the at least one anode is a graphite anode. How to do it.

15. The cement treatment step b is carried out continuously in at least one rotary reactor.

15. The method according to claim 1, wherein

16. 16. The method of any one of claims 1 to 15, the step of precipitating manganese ions comprises: a. Adding permanganate ions to the leachate containing zinc ions and manganese ions And, b. measuring at least the pH, redox potential, and optionally the temperature of said leachate; 、 c. A calibration curve correlating the precipitate redox potential to at least the pH value and, optionally, the leachate temperature. periodically calculating the precipitate redox potential value by - the oxidation-reduction potential value of the leachate is adjusted so as to approach the calculated oxidation-reduction potential value of the precipitate. and changing the amount of permanganate ions added. method.

17. The calibration curve is a curve of the acidity of the leachate at two or more different pH values ​​and two or more different temperature values.

17. The method of claim 16, wherein the titration is obtained by redox titration.

18. 17. The method of claim 16, wherein the at least one anode is an active metal anode.

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