Method for recovering lead, iron and zinc step by step from zinc hydrometallurgy acid leaching residues

Abstract

The embodiment of the invention discloses a method for recycling lead, iron and zinc from zinc hydrometallurgy acid leaching residues step by step. The method comprises the steps that the zinc hydrometallurgy acid leaching residues and concentrated sulfuric acid are mixed and subjected to a curing reaction, and then sulfuric acid curing residues are obtained; carrying out water leaching treatment on the sulfuric acid curing slag to obtain a mixed solution, and carrying out solid-liquid separation on the mixed solution to obtain a zinc-iron-containing leachate and lead-containing filter residues; adding a phosphate ion solution into the zinc-iron-containing leachate for reaction to obtain a reacted solution, and filtering the reacted solution to obtain iron phosphate and an iron-removed solution; and the iron-removed liquid is put into an electrolysis device to be subjected to electrolysis treatment, so that metal zinc is generated at a cathode of the electrolysis device. According to the embodiment of the invention, the process method combining concentrated sulfuric acid curing, water leaching treatment and phosphate ion solution precipitation is adopted, so that the step-by-step recovery of lead, iron and zinc from the zinc hydrometallurgy acid leaching residues can be directly realized, and the method has the advantages of simple operation, short process flow, high metal recovery rate and the like.

Description

Technical Field

[0001] The present invention relates to the field of resource recovery, and particularly to a method for stepwise recovering lead, iron, and zinc from acid leaching residues in zinc hydrometallurgy. Background Art

[0002] As a by-product of the zinc hydrometallurgy process, the treatment of acid leaching residues in zinc hydrometallurgy has long restricted the sustainable development of the industry. In traditional processes, after zinc concentrate is leached with sulfuric acid, about 10% - 15% of the zinc is solidified in the slag phase in the form of zinc ferrite (ZnFe₂O₄), and at the same time, valuable metals such as lead and silver and toxic components such as arsenic and cadmium are associated. However, the spinel structure of zinc ferrite has stable chemical properties, the zinc leaching rate by conventional acid leaching methods is low, and the separation efficiency of the multi-metal symbiotic system is low, and secondary waste residues are easily generated.

[0003] In current recovery processes for acid leaching residues in zinc hydrometallurgy, the commonly used high-temperature roasting - acid leaching method is to roast the acid leaching residues in zinc hydrometallurgy at a high temperature of 800 - 1000 °C. The spinel structure of zinc ferrite is destroyed by thermal decomposition. After roasting and cooling, it is mixed and stirred with concentrated sulfuric acid for leaching, so that metals such as zinc and iron are converted into sulfates and enter the solution. The leaching solution is separated from iron and arsenic by neutralization precipitation and then zinc is extracted by electrolysis. The leaching residues need to be further processed to recover metals such as lead and silver. However, roasting flue gas and acid leaching waste gas will be generated during the production process, and dust removal and desulfurization devices and alkali liquor need to be configured to absorb and treat the waste gas, resulting in a high cost for waste gas treatment and high energy consumption at the same time. Summary of the Invention

[0004] In view of at least some of the problems and deficiencies in the prior art, embodiments of the present invention disclose a method for stepwise recovering lead, iron, and zinc from acid leaching residues in zinc hydrometallurgy, which is simple to operate and has a high recovery rate of metal resources.

[0005] A method for stepwise recovering lead, iron, and zinc from acid leaching residues in zinc hydrometallurgy provided by embodiments of the present invention includes: mixing and aging the acid leaching residues in zinc hydrometallurgy with concentrated sulfuric acid to obtain sulfuric acid aged slag. The sulfuric acid aged slag is subjected to water leaching treatment to obtain a mixed solution, and the mixed solution is subjected to solid-liquid separation to obtain a zinc and iron-containing leaching solution and a lead-containing filter residue. A phosphate ion solution is added to the zinc and iron-containing leaching solution for reaction to obtain a reaction solution, and the reaction solution is filtered to obtain iron phosphate and a solution after iron removal. The solution after iron removal is put into an electrolysis device for electrolysis treatment to generate metallic zinc at the cathode of the electrolysis device.

[0006] In an embodiment of the present invention, in the step of mixing and aging the acid leaching residues in zinc hydrometallurgy with concentrated sulfuric acid to obtain sulfuric acid aged slag: the mass ratio of the acid leaching residues in zinc hydrometallurgy to the concentrated sulfuric acid is 1:0.8 - 1, the reaction temperature in the aging reaction is 180 - 220 °C, and the reaction duration is 1 - 2 h.

[0007] In an embodiment of the present invention, in the step of subjecting the sulfuric acid matured slag to water leaching treatment to obtain a mixed leachate and performing solid-liquid separation on the mixed solution to obtain a zinc-iron-containing leachate and a lead-containing filter residue: the solid-liquid ratio of the sulfuric acid matured slag to water is 1:10, the leaching temperature in the water leaching treatment is 23-27 °C, and the leaching time is 1-3 h.

[0008] In an embodiment of the present invention, in the step of adding a phosphate ion solution to the zinc-iron-containing leachate and stirring to react to obtain a post-reaction solution and performing filtration treatment on the post-reaction solution to obtain iron phosphate and a de-ironed solution: the addition amount of the phosphate ion solution is such that the molar ratio of phosphate ions to ferric ions in the post-reaction solution is 1:1.

[0009] In an embodiment of the present invention, putting the de-ironed solution into an electrolysis device for electrolysis treatment to generate metallic zinc at the cathode of the electrolysis device, specifically including: mixing the de-ironed solution with the concentrated sulfuric acid to obtain an electrolytic solution and putting the electrolytic solution into the electrolysis device for electrolysis treatment. Among them, the control conditions for the electrolysis treatment are that the current density is 200-400 A / m² and the temperature of the electrolytic solution is 34-38 °C.

[0010] In an embodiment of the present invention, the dosage of the concentrated sulfuric acid satisfies that the mass ratio of zinc ions in the de-ironed solution to the concentrated sulfuric acid is 1:3.

[0011] In an embodiment of the present invention, lead elements are recovered in the form of the lead-containing filter residue. Zinc elements are recovered in the form of the metallic zinc.

[0012] In an embodiment of the present invention, iron elements are recovered in the form of the iron phosphate.

[0013] In an embodiment of the present invention, the mass concentration of the concentrated sulfuric acid is ≥98%, and the concentration of the phosphate ion solution is 0.5-1.5 mol / L.

[0014] In an embodiment of the present invention, the pH of the zinc-iron-containing leachate is 1-2; the pH of the de-ironed solution is 1-2.

[0015] As can be seen from the above, the above technical features of the present invention can have one or more of the following beneficial effects: In the embodiments of the present invention, the spinel structure of zinc ferrite in the acid leaching residue of zinc hydrometallurgy is destroyed through the curing reaction with concentrated sulfuric acid. During the curing reaction process, mainly water vapor is generated. Compared with the waste gas generated by high-temperature roasting, the composition of the waste gas is simple and the output is small, reducing the waste gas treatment facilities and processes and effectively reducing the waste gas treatment cost. Secondly, compared with the traditional high-temperature roasting method, the reaction temperature of the concentrated sulfuric acid curing is lower, reducing the consumption of coke. After being treated by concentrated sulfuric acid curing, the structures of minerals such as zinc ferrite are destroyed. In the water leaching step, valuable metals such as zinc and iron can be more fully dissolved into the solution, with a high leaching rate. Further, through the precipitation of phosphate ions and electrodeposition, the separation of lead, iron, and zinc is achieved, thereby improving the recovery efficiency of valuable metals. At the same time, it has the advantages of a simple process flow and mild operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a schematic flow chart of a method for stepwise recovering lead, iron, and zinc from the acid leaching residue of zinc hydrometallurgy provided by the embodiments of the present invention.

[0018] Figure 2 For Figure 1 Another flow schematic diagram of the method for stepwise recovering lead, iron, and zinc from the acid leaching residue of zinc hydrometallurgy.

[0019] Figure 3 It is a graph showing the change of Gibbs free energy of the curing reaction with temperature.

[0020] Figure 4 It is a phosphate solubility product diagram.

[0021] Figure 5 It is an XRD diagram of the solid products of each step. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the specific embodiments and corresponding drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0023] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0024] It should also be noted that the division of multiple embodiments in the present invention is only for the convenience of description and should not constitute a special limitation. The features in various embodiments can be combined and cross-referenced without conflict.

[0025] Referring to Figure 1 and Figure 2 As shown, a method for stepwise recovering lead, iron and zinc from acid leaching residues of hydrometallurgical zinc smelting provided by an embodiment of the present invention may, for example, include the following steps:

[0026] S10, mixing and maturing the acid leaching residues of hydrometallurgical zinc smelting with concentrated sulfuric acid to obtain sulfuric acid matured residues.

[0027] S20, subjecting the sulfuric acid matured residues to water leaching treatment to obtain a mixed solution, and performing solid-liquid separation on the mixed solution to obtain a zinc and iron-containing leaching solution and a lead-containing filter residue.

[0028] S30, adding a phosphate ion solution to the zinc and iron-containing leaching solution for reaction to obtain a post-reaction solution, and performing filtration treatment on the post-reaction solution to obtain iron phosphate and an iron-removed solution.

[0029] S40, putting the iron-removed solution into an electrolysis device for electrolysis treatment to generate metallic zinc at the cathode of the electrolysis device.

[0030] Specifically, Figure 2The zinc smelting slag in this invention is the acid leaching slag from hydrometallurgical zinc smelting, the aging slag is the sulfuric acid aging slag, and the lead-containing waste residue is the lead-containing filter residue. The acid leaching slag from hydrometallurgical zinc smelting is obtained in the hydrometallurgical zinc smelting process where zinc concentrate is leached with acid solutions such as sulfuric acid, enabling zinc to enter the solution in ionic form. Meanwhile, some impurities in the ore will also dissolve or form insoluble residues. After solid-liquid separation, the solid part obtained is the acid leaching slag. The main components of the acid leaching slag in this embodiment include ZnFe2O4 (zinc ferrite) and various elements such as O (oxygen), Fe (iron), Zn (zinc), Si (silicon), Pb (lead), etc. Among them, ZnFe2O4 is a spinel-type compound. During the hydrometallurgical zinc smelting process, elements such as zinc and iron in the zinc concentrate will form zinc ferrite under specific conditions. It has relatively stable chemical properties. Under conventional acid leaching conditions, zinc ferrite is difficult to be completely decomposed by sulfuric acid, so a large amount of it remains in the acid leaching slag. In the embodiment of this invention, lead is recovered in the form of lead-containing filter residue. Exemplarily, the lead-containing filter residue can be sent to a lead smelter for recovery in the form of lead sulfate. Iron is recovered in the form of iron phosphate. The iron phosphate generated by the reaction of adding a phosphate ion solution to the zinc-iron leaching solution can be used for the preparation of lithium iron phosphate batteries. Meanwhile, zinc is recovered in the form of metallic zinc.

[0031] In the embodiment of this invention, the spinel structure of zinc ferrite in the acid leaching slag from hydrometallurgical zinc smelting is destroyed through a concentrated sulfuric acid aging reaction. During the aging reaction process, mainly water vapor is generated. Compared with the waste gas generated by high-temperature roasting, the composition of the waste gas is simple and the output is small, reducing the waste gas treatment facilities and processes and effectively reducing the waste gas treatment cost. Secondly, compared with the traditional high-temperature roasting method, the reaction temperature of concentrated sulfuric acid aging is lower, reducing the consumption of coke. After being treated by concentrated sulfuric acid aging, the structures of minerals such as zinc ferrite are destroyed. In the water leaching step, valuable metals such as zinc and iron can be more fully dissolved into the solution, with a relatively high leaching rate. By adding a phosphate ion solution to the zinc-iron leaching solution to selectively precipitate iron phosphate, this step has a simple process and is easy to operate. The electrolysis treatment can be, for example, a zinc electrodeposition process, which has a simple operation and does not require complex equipment and multiple processes.

[0032] In step S10: The mass ratio of the acid leaching slag from hydrometallurgical zinc smelting to concentrated sulfuric acid is 1:0.8 - 1. The reaction temperature in the aging reaction is 180 - 220 °C, and the reaction duration is 1 - 2 h.

[0033] Specifically, the concentrated sulfuric acid selected is concentrated sulfuric acid with a mass concentration ≥ 98%. The acid leaching residue of zinc hydrometallurgy and the concentrated sulfuric acid are mixed at a mass ratio of 1:0.8 - 1, and a paste-like mixture is obtained through a corrosion-resistant stirring and mixing device. Then, the paste-like mixture is sent to a muffle furnace, and the temperature of the muffle furnace is controlled at 180 - 220 °C for a ripening reaction for 1 - 2 h to destroy the spinel structure, and the sulfuric acid-ripened residue is obtained upon completion of the reaction. The muffle furnace can be, for example, a vacuum muffle furnace, which effectively avoids the oxidation of the paste-like mixture by oxygen in the air and reduces the occurrence of side reactions. During the reaction, the concentrated sulfuric acid in the paste-like mixture reacts with zinc ferrite, and the hydrogen ions in the sulfuric acid molecule gradually replace the zinc and iron ions in the crystal structure of zinc ferrite, destroying the spinel structure of zinc ferrite, and the valuable metals such as zinc and iron are converted into soluble sulfates. At the same time, the strong oxidizing property of the concentrated sulfuric acid reacts with impurities such as sulfides in the acid leaching residue, further promoting the leaching of valuable metals.

[0034] The sulfuric acid molecule concentration in the concentrated sulfuric acid with a mass concentration ≥ 98% selected is large and the reaction activity is strong. For example, experiments have shown that within the same reaction time, the leaching rate of zinc by the concentrated sulfuric acid with a mass concentration ≥ 98% is higher than that of low-concentration sulfuric acid. In the temperature range of 180 - 220 °C, the reaction rate is appropriate, which accelerates the reaction rate between the concentrated sulfuric acid and substances such as zinc ferrite, and reaches a relatively high reaction degree in a relatively short time. At the same time, this temperature range is conducive to destroying the spinel structure of zinc ferrite, enabling the hydrogen ions in the sulfuric acid molecule to more effectively replace the zinc and iron ions in the crystal structure of zinc ferrite, and promoting the conversion of valuable metals such as zinc and iron into soluble sulfates. The reaction time is controlled within the range of 1 - 2 h, taking into account the production efficiency while ensuring the full progress of the reaction.

[0035] After the acid leaching residue of zinc hydrometallurgy and the concentrated sulfuric acid are mixed and ripened, the sulfuric acid-ripened residue is obtained. The specific reaction can be, for example, the following equation:

[0036] ZnFe2O4 + 4H2SO4 = ZnSO4 + Fe2(SO4)3 + 4H2O

[0037] As can be seen from the above, in this embodiment, the acid leaching residue of zinc hydrometallurgy and the concentrated sulfuric acid are mixed and ripened to mainly produce water vapor. Compared with the waste gas generated by high-temperature roasting, the composition of the waste gas is simple and the output is small, reducing the waste gas treatment facilities and processes and effectively reducing the waste gas treatment cost. The reaction conditions for sulfuric acid ripening are mild, relatively easy to achieve and control compared with high-temperature and high-pressure reaction conditions, the requirements for equipment are relatively low, and it has good adaptability to acid leaching residues of zinc hydrometallurgy with different compositions and properties.

[0038] In step S20: the solid-liquid ratio of the sulfuric acid-ripened residue to water is 1:10, the leaching temperature in the water leaching treatment is 23 - 27 °C, and the leaching time is 1 - 3 h.

[0039] Specifically, the sulfuric acid matured slag is mixed with water in a reaction kettle at a solid-liquid ratio of 1:10 to obtain a mixed solution. Here, the solid-liquid ratio is the ratio of the mass of the solid to the volume of the liquid, that is, 1 unit mass of sulfuric acid matured slag is mixed with 10 unit volumes of water. The leaching is carried out at a temperature of 23 - 27 °C for 1 - 3 h. During the leaching process, the mixed solution can be continuously stirred. After the leaching is completed, the solid-liquid separation of the mixed solution is carried out. For example, a vacuum filter can be used to filter the mixed solution to obtain a zinc and iron-containing leaching solution and a lead-containing filter residue. During the leaching process, substances such as soluble zinc and iron sulfates in the sulfuric acid matured slag will gradually dissolve into the water to form a zinc and iron-containing leaching solution. Exemplarily, the water can be, for example, deionized water or distilled water. The reaction kettle can be, for example, a glass reaction kettle. It should be noted that the leaching temperature can also be, for example, room temperature.

[0040] The solid-liquid ratio of 1:10 enables the water to be fully mixed with the sulfuric acid matured slag, and the soluble components in the sulfuric acid matured slag, such as sulfates of zinc and iron, can more fully contact and dissolve with the water, thereby increasing the leaching rate of valuable metals. Compared with leaching with concentrated sulfuric acid, in this embodiment, water is used for leaching in the leaching reaction. Its properties are stable and it can be operated at room temperature, effectively avoiding the strong corrosiveness of concentrated sulfuric acid to equipment. Moreover, in the water leaching treatment process of this embodiment, the generation of waste gas is effectively reduced, and the environmental pollution and waste gas treatment cost are reduced. Secondly, the valuable metals in the sulfuric acid matured slag have good selective dissolution characteristics under water leaching conditions, and can effectively separate iron and zinc from other impurities, improving the recovery rate and purity of valuable metals.

[0041] In step S30: the addition amount of the phosphate ion solution is such that the molar ratio of phosphate ions to ferric ions in the solution after the reaction is 1:1.

[0042] Specifically, in the embodiment of the present invention, the phosphate ion solution is a solution formed by directly ionizing phosphate ions through the dissolution of phosphate salts in water. Exemplarily, the phosphate ion solution can be, for example, an ammonium phosphate solution. The concentration of the phosphate ion solution is 0.5 - 1.5 mol / L. Within this range, the phosphate ions in the phosphate ion solution can react with the ferric ions in the zinc and iron-containing leaching solution relatively quickly and fully to form iron phosphate precipitate, ensuring its reaction efficiency and iron removal effect. The preset addition amount of the phosphate ion solution can be calculated according to the content and molar ratio of ferric ions in the zinc and iron-containing leaching solution to calculate the volume of the required phosphate ion solution, and it is accurately added to the zinc and iron-containing leaching solution by a metering pump. Among them, chemical analysis methods, such as spectrophotometry, titration method, etc., can be used to accurately measure the concentration of ferric ions in the zinc and iron-containing leaching solution. The phosphate ion solution is added to the zinc and iron-containing leaching solution according to the required volume and stirred to react to obtain a solution after the reaction. During the reaction process, phosphate ions and ferric ions will combine to form iron phosphate. After the reaction is completed, the solution after the reaction is filtered to obtain iron phosphate and the iron-removed solution.

[0043] The phosphate ion solution is added to the zinc-iron leaching solution for reaction. The specific reaction can be, for example, the following equation:

[0044]

[0045] Adding the phosphate ion solution according to a molar ratio of phosphate ions to ferric ions of 1:1 can maximize the conversion of ferric ions into precipitates, thereby efficiently removing ferric ions from the solution and achieving a better iron removal effect. At the same time, it avoids the problem of the decrease in the purity of iron phosphate caused by the excess phosphate ions introducing extra phosphate precipitates mixed in the iron phosphate.

[0046] Preferably, the pH of the zinc-iron leaching solution is 1-2, and the pH of the solution after iron removal is 1-2. Under acidic conditions, the reaction equilibrium between phosphate ions and ferric ions in the zinc-iron leaching solution is more favorable for shifting towards the direction of forming iron phosphate precipitates. At this time, ferric ions can be more completely converted into iron phosphate, thereby improving the iron removal efficiency and reducing the iron content in the solution after iron removal. Secondly, both the zinc-iron leaching solution and the solution after iron removal are at a low pH value, and the hydrogen ion concentration in the solution is relatively high to inhibit the combination of zinc ions and hydroxide ions, thereby avoiding the loss of zinc ions during the iron removal process, ensuring the zinc recovery rate, and being beneficial to the subsequent recovery and utilization of zinc.

[0047] In step S40: The solution after iron removal is mixed with concentrated sulfuric acid to obtain an electrolyte solution, and the electrolyte solution is placed in an electrolysis device for electrolysis treatment; wherein, the control conditions for the electrolysis treatment are that the current density is 200-400 A / ㎡, and the temperature of the electrolyte solution is 34-38 °C.

[0048] Specifically, the electrolytic treatment can be, for example, zinc electrodeposition. The electrolytic apparatus includes, for example, an electrolytic cell made of, for example, PVC (polyvinyl chloride). PVC has excellent corrosion resistance, making it suitable for the construction of the electrolytic cell and helping to improve the durability and safety of the electrolytic cell. Concentrated sulfuric acid and iron-removed solution are mixed as an electrolyte, which is placed in a PVC electrolytic cell. Zinc electrodeposition is performed at a current density of 200 to 400 A / m² and an electrolyte temperature of 34 to 38°C, with metallic zinc deposited directly on the cathode. The electrolytic cell is equipped with a cathode and an anode. The anode is used for oxidation during the electrolytic treatment, while the cathode is used for reduction. As the reaction proceeds, zinc ions in the solution continuously receive electrons at the cathode to generate elemental zinc, which gradually deposits on the cathode surface to form a metallic zinc layer. The cathode is a rolled aluminum plate. Using rolled aluminum plate as the cathode can lower the hydrogen ion deposition potential, making the hydrogen ion deposition potential lower than that of zinc ions. This makes zinc ions more likely to be deposited at the cathode than hydrogen ions, ultimately achieving the electrodeposition of zinc ions to obtain metallic zinc. The anode is a lead-silver alloy plate, which has the characteristics of high oxygen evolution overpotential, good corrosion resistance, excellent conductivity, and excellent mechanical properties.

[0049] The cathode electrode reaction can be expressed as follows:

[0050] Zn 2+ +2e - =Zn

[0051] Among them, by optimizing the temperature and current density of electrolysis treatment to 34-38℃ and 200-400A / m 2 , which is beneficial to improving electrolysis efficiency and product quality. When the electrolysis temperature is 34-38℃, the chemical reaction rate can be accelerated, thereby improving the overall efficiency of the electrolysis process. The increase in temperature usually increases the mobility of ions and reduces the resistance during the electrolysis process. The current density is 200-400A / m 2 This helps speed up the reduction rate of metal ions at the cathode, which in turn helps speed up the deposition rate. During the electrolytic deposition process of zinc metal recovery, zinc ions receive electrons on the cathode surface and are directly reduced to metallic zinc, which is then deposited. This process effectively separates zinc from other impurities and, by effectively controlling the electrolysis conditions, can achieve a high level of zinc purity.

[0052] Preferably, the dosage of concentrated sulfuric acid is such that the mass ratio of zinc ions to concentrated sulfuric acid in the solution after iron removal is 1:3. Adding concentrated sulfuric acid in this ratio can bring the concentration of sulfate ions in the electrolyte to an appropriate level, forming a good match with the zinc ion concentration, which is conducive to maintaining the ion balance in the electrolyte and promoting the smooth progress of the reduction reaction of zinc ions on the cathode surface. The addition of concentrated sulfuric acid can adjust the pH value of the solution after iron removal to an acidic environment suitable for zinc electrodeposition, which helps the dissolution and migration of zinc ions and improves the conductivity of the electrolyte. There are also other metal impurity ions in the solution after iron removal, such as copper, cadmium, nickel, etc. The acidic environment can inhibit the discharge of these impurity ions and reduce the possibility of their co-deposition with zinc on the cathode, thereby improving the purity of the electrodeposited zinc. Specific embodiments:

[0054] In this specific embodiment, 20 g of acid leaching residue from zinc hydrometallurgy is taken, and its partial component composition is shown in Table 1.

[0055] Table 1 Partial component composition of acid leaching residue from zinc hydrometallurgy

[0056] Element Name Content / % Element Name Content / % O 32.6 S 2.1 Fe 24.99 Mn 1.304 Zn 14.77 Al 0.703 Si 11.15 Cu 0.652 Pb 7.77 Na 0.425

[0057] Mix 20 g of acid leaching residue from zinc hydrometallurgy with concentrated sulfuric acid with a concentration ≥ 98% at a mass ratio of 1:1, and react at a temperature of 200 °C for 2 h. After the reaction is completed, 32 g of sulfuric acid matured residue is obtained. Mix 32 g of sulfuric acid matured residue with water at a solid-liquid ratio of 1:10 to obtain a mixed solution, stir and leach at a temperature of 25 °C for 2 h. After the leaching is completed, perform solid-liquid separation on the mixed solution to obtain 292 mL of zinc-iron-containing leaching solution and 3.3 g of lead-containing filter residue. Then add a 1 mol / L ammonium phosphate solution to the zinc-iron-containing leaching solution to obtain a reaction solution. Among them, the addition amount of the ammonium phosphate solution is such that the molar ratio of phosphate ions to ferric ions in the reaction solution is 1:1. Filter the reaction solution to obtain 4.8 g of iron phosphate and 220 mL of solution after iron removal. Finally, add concentrated sulfuric acid to the solution after iron removal and mix it at a dosage ratio of 1:3 to obtain an electrolyte. Put the electrolyte into an electrolysis device and perform zinc electrodeposition under the conditions of an electrolyte temperature of 36 °C and a current density of 400 A / m 2 to finally recover and precipitate metallic zinc at the cathode. Among them, in the electrodeposition and precipitation of metallic zinc, the current efficiency is above 85%.

[0058] In this embodiment, the contents of zinc, iron, and lead in 292 mL of zinc-iron-containing leaching solution and 220 mL of solution after iron removal are shown in Table 2.

[0059] Table 2 Contents of zinc, iron, and lead in zinc-iron-containing leaching solution and solution after iron removal

[0060] Ion Zinc-Iron Leaching Solution (V) Solution after Iron Removal (V) <![CDATA[Zn 2+ > 3.2 3.01 <![CDATA[Fe 3+ > 3.89 0.1279 <![CDATA[Pb 2+ ]]> 0.0034 0.00226

[0061] According to Table 1 and Table 2, it can be seen that for Zn 2+ the recovery rate = the content of zinc ions in the solution after iron removal / the content of zinc ions in the zinc-iron leaching solution, that is, for Zn 2+ =(3.01 / 3.2)×100% ≈ 94.06%. For Fe 3+ the recovery rate = (the content of iron ions in the zinc-iron leaching solution - the content of iron ions in the solution after iron removal) / the content of iron ions in the zinc-iron leaching solution, that is, for Fe 3+ =[(3.89 - 0.1279) / 3.89]×100% ≈ 96.71%. For Pb 2+ the recovery rate = (the content of lead ions in 20 g of acid leaching residue for zinc hydrometallurgy - the content of lead ions in the zinc-iron leaching solution) / the content of lead ions in 20 g of acid leaching residue for zinc hydrometallurgy. Among them, the content of lead ions in 20 g of acid leaching residue for zinc hydrometallurgy = 20 g × 7.77% = 1.554 g, that is, for Pb 2+ =[(1.554 - 0.0034) / 1.554]×100% ≈ 99.78%. As can be seen from the above, the method provided by the embodiment of the present invention effectively improves the recovery of zinc, iron and lead metals in the acid leaching residue for zinc hydrometallurgy, realizes the recycling of resource value, and reduces the environmental governance cost.

[0062] Referring to Figure 3 as shown, within the temperature range of 50°C to 200°C, the Gibbs free energy ΔG < 0, and the ripening reaction can proceed spontaneously. In this specific embodiment, the temperature is selected as 200°C, that is, on the premise of ensuring that the ripening reaction can proceed spontaneously, its reaction rate can reach the expected level faster within a certain time, improving the production or experimental efficiency. Referring to Figure 4 as shown, it can be seen from the figure that as the concentration of increases from 0 to 1.0 gradually, the value of lg Fe n+ decreases continuously from about -19 to about -21, indicating that as the phosphate concentration increases, the concentration of Fe n+ ions in the solution decreases continuously. As the concentration of increases from 0 to 1.0 gradually, the value of lgZn n+ decreases continuously from about -5 to about -7, indicating that as the phosphate concentration increases, the concentration of Zn n+ ions in the solution decreases continuously. It can be seen from Figure 4 that the tendency of Fe ions to form phosphate precipitates is stronger than that of Zn ions, and it is easier to form phosphate precipitates. In this specific embodiment, the characteristic of using ammonium phosphate solution with a concentration of 1 mol / L to preferentially precipitate Fe ions is used to achieve the separation of Fe and Zn. The ammonium phosphate solution with this concentration is more conducive to the formation of phosphate precipitates of Fe ions, which helps to improve the recovery efficiency of Fe ions. Zn ions are basically retained in the solution, which helps to purify Zn from the solution containing multiple metal ions.

[0063] Referring toFigure 5 As shown, the raw material slag is the acid leaching slag provided by the embodiment of the present invention for hydrometallurgical zinc smelting, the ripening slag is the sulfuric acid ripening slag provided by the embodiment of the present invention, and the water leaching slag is the lead-containing filter residue provided by the embodiment of the present invention. It can be seen from the figure that there is a peak corresponding to the standard diffraction peak position of ZnFe2O4 (zinc ferrite) in the raw material slag, indicating that the raw material slag contains the ZnFe2O4 phase. There are diffraction peaks corresponding to ZnSO4 (zinc sulfate) and Fe2(SO4)3 (iron sulfate) in the ripening slag, indicating that the substances in the raw materials have changed during the ripening process, generating phases such as ZnSO4 and Fe2(SO4)3. Comparing the spectra of the raw material slag and the ripening slag, the phase composition has changed significantly. The original stable crystal structure of ZnFe2O4 has completely decomposed after the high-temperature sulfuric acid ripening reaction and transformed into two soluble sulfates, Fe2(SO4)3 and ZnSO4·2H2O (zinc sulfate dihydrate). There is a peak corresponding to the standard diffraction peak position of PbSO4 (lead sulfate) in the water leaching slag, indicating that the water leaching slag has the PbSO4 phase. Comparing the spectra of the ripening slag and the water leaching slag, the soluble sulfates in the ripening slag enter the liquid phase through water leaching, and insoluble substances such as lead sulfate enter the slag phase; and comparing with the spectrum of the raw material slag, there is no ZnFe2O4 crystal in the water leaching slag, indicating again that in the ripening stage, ZnFe2O4 has completely transformed into two soluble sulfates, Fe2(SO4)3 and ZnSO4·2H2O.

[0064] In summary, a method for stepwise recovering lead, iron, and zinc from the acid leaching slag of hydrometallurgical zinc smelting provided by the embodiment of the present invention can effectively improve the recovery rates of lead, iron, and zinc in the acid leaching slag, and has the characteristics of simple process flow and mild operating conditions, effectively solving the problems of low recovery rates of multiple metals, resource waste, and heavy metal pollution in the acid leaching slag of hydrometallurgical zinc smelting.

[0065] It can be understood that the foregoing various embodiments are only exemplary descriptions of the present invention. On the premise that there is no conflict in technical features, no contradiction in structure, and no violation of the invention purpose of the present invention, the technical solutions of each embodiment can be arbitrarily combined and used.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present invention.

Claims

1. A method for stepwise recovering lead, iron, and zinc from acid leaching residues of hydrometallurgical zinc smelting, characterized in that, Comprising: Mixing the acid leaching residue of zinc hydrometallurgy with concentrated sulfuric acid for a ripening reaction to obtain a sulfuric acid ripened residue; Performing water leaching treatment on the sulfuric acid ripened residue to obtain a mixed solution, and performing solid-liquid separation on the mixed solution to obtain a zinc-iron containing leachate and a lead-containing filter residue; Adding a phosphate ion solution to the zinc-iron containing leachate for reaction to obtain a post-reaction solution, and performing filtration treatment on the post-reaction solution to obtain iron phosphate and an iron-removed solution; Putting the iron-removed solution into an electrolysis device for electrolysis treatment to generate metallic zinc at the cathode of the electrolysis device.

2. The method for stepwise recovering lead, iron and zinc from acid leaching residues of zinc hydrometallurgy according to claim 1, characterized in that, In the step of mixing the acid leaching residue of zinc hydrometallurgy with concentrated sulfuric acid for a ripening reaction to obtain a sulfuric acid ripened residue: The mass ratio of the acid leaching residue of zinc hydrometallurgy to the concentrated sulfuric acid is 1:0.8 - 1, the reaction temperature in the ripening reaction is 180 - 220°C, and the reaction duration is 1 - 2 h.

3. The method for stepwise recovering lead, iron, and zinc from acid leaching residues of hydrometallurgical zinc smelting according to claim 1, wherein, In the step of performing water leaching treatment on the sulfuric acid ripened residue to obtain a mixed solution, and performing solid-liquid separation on the mixed solution to obtain a zinc-iron containing leachate and a lead-containing filter residue: The solid-liquid ratio of the sulfuric acid ripened residue to water is 1:10, the leaching temperature in the water leaching treatment is 23 - 27°C, and the leaching time is 1 - 3 h.

4. The method for stepwise recovering lead, iron, and zinc from acid leaching residues of hydrometallurgical zinc smelting according to claim 1, wherein, In the step of adding a phosphate ion solution to the zinc-iron containing leachate for stirring reaction to obtain a post-reaction solution, and performing filtration treatment on the post-reaction solution to obtain iron phosphate and an iron-removed solution: The addition amount of the phosphate ion solution is such that the molar ratio of phosphate ions to ferric ions in the post-reaction solution is 1:

1.

5. The method for stepwise recovering lead, iron and zinc from acid leaching residues of hydrometallurgical zinc smelting according to claim 1, characterized in that, The step of putting the iron-removed solution into an electrolysis device for electrolysis treatment to generate metallic zinc at the cathode of the electrolysis device specifically includes: Mixing the iron-removed solution with concentrated sulfuric acid to obtain an electrolyte solution, and putting the electrolyte solution into an electrolysis device for electrolysis treatment; wherein, the control conditions for the electrolysis treatment are that the current density is 200 - 400 A / m² and the temperature of the electrolyte solution is 34 - 38°C.

6. The method for stepwise recovery of lead, iron and zinc from acid leaching residues of zinc hydrometallurgy according to claim 5, wherein, The dosage of the concentrated sulfuric acid is such that the mass ratio of zinc ions in the iron-removed solution to the concentrated sulfuric acid is 1:

3.

7. The method for stepwise recovering lead, iron, and zinc from acid leaching residues of hydrometallurgical zinc smelting according to claim 1, wherein Recovering lead element in the form of the lead-containing filter residue; recovering zinc element in the form of the metallic zinc.

8. The method for stepwise recovering lead, iron, and zinc from acid leaching residues of hydrometallurgical zinc smelting according to claim 1, wherein Recovering iron element in the form of the iron phosphate.

9. The method for stepwise recovering lead, iron, and zinc from acid leaching residues of zinc hydrometallurgy according to claim 1, wherein, The mass concentration of the concentrated sulfuric acid is ≥98%, and the concentration of the phosphate ion solution is 0.5 - 1.5 mol / L.

10. The method for stepwise recovering lead, iron, and zinc from acid leaching residues of zinc hydrometallurgy according to claim 1, wherein, The pH of the zinc-iron containing leachate is 1 - 2; the pH of the iron-removed solution is 1 - 2.

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