A method for preparing zinc sulfate electrolyte from zinc-containing electric furnace dust

Abstract

The application discloses a method for preparing zinc sulfate electrolyte from zinc-containing electric furnace dust, and belongs to the field of hydrometallurgy. The method uses zinc-containing electric furnace dust as raw material, and performs pre-roasting-acid leaching treatment by adding roasting aid ferrous sulfide (FeS). The steps are as follows: the zinc-containing electric furnace dust is uniformly mixed with FeS according to a certain mass ratio, and then roasted at a certain temperature for a certain time; the roasted product is added into appropriate dilute sulfuric acid for leaching, and then separated into solid and liquid through magnetic stirring and suction filtration to obtain zinc sulfate solution and iron-containing leaching residue. The generated zinc sulfate solution can be used as electrolyte for electrolytic zinc, and can be directly sent to an electrolytic zinc plant for electrodeposition to prepare metal zinc; the iron-containing leaching residue can be returned to an iron smelting plant for iron smelting process. The application ingeniously uses FeS to pre-sulfate Zn in the form of ZnO and ZnFe2O4 in the zinc-containing electric furnace dust into zinc sulfate, and then completely converts it into zinc sulfate through dilute sulfuric acid leaching, so that zinc in the zinc-containing electric furnace dust is simply and efficiently extracted. The leaching rate of zinc is as high as 95.33%, and the leaching rate of iron is only 0.17%, so that most of the iron remains in the leaching residue, and the iron removal step before zinc electrodeposition can be avoided. The application can realize zinc extraction and iron separation from the zinc-containing electric furnace dust through the pre-roasting-acid leaching process, realize resource recycling of zinc and iron, realize full utilization and resource utilization of the zinc-containing electric furnace dust, and is a new method for efficiently disposing the zinc-containing electric furnace dust.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy and describes a method for preparing zinc sulfate electrolyte using zinc-containing electric furnace dust by adding the roasting aid FeS for pre-roasting and acid leaching. Background Technology

[0002] Zinc is a common non-ferrous metal that can be alloyed with various other non-ferrous metals. Zinc and its compounds are mainly used in the steel, machinery, construction, and chemical industries. China is the world's largest producer and consumer of zinc, with an annual output of 5.6 million tons. Adjusting the industrial structure, strengthening technological innovation in the zinc industry, improving comprehensive utilization, and enhancing product quality are inevitable trends for the development of my country's zinc industry. However, China's zinc recycling, regeneration, and utilization levels lag far behind those of advanced countries, resulting in resource and energy waste and environmental pollution. Strengthening the resource utilization of secondary zinc-containing solid waste is a crucial measure to address the gradual depletion of my country's zinc resources.

[0003] Currently, 70% of global zinc production comes from the hydrometallurgical process of zinc concentrate, while the remaining 30% comes from the recycling and comprehensive utilization of secondary zinc resources. Zinc-containing electric furnace dust, hot-dip galvanizing slag / ash, waste zinc alloys and zinc materials, gaseous slag / ash generated during copper and lead smelting, and a small amount of zinc waste generated during zinc alloy production are collectively referred to as secondary zinc resources. Among these, zinc-containing electric furnace dust is the largest source of secondary zinc resources, accounting for 35% of total zinc waste, followed by hot-dip galvanizing slag / ash, accounting for 29%. However, the utilization rate of hot-dip galvanizing slag / ash is 83%, while the utilization rate of zinc-containing electric furnace dust is only 60%. The United States recovers more than 50% of its total zinc production and is a global leader in the utilization of secondary zinc resources. Furthermore, developed countries such as Europe and Japan actively encourage the use of secondary zinc resources in the production of zinc products.

[0004] With the orderly development of electric arc furnace steelmaking, the amount of zinc-containing electric arc furnace dust has been increasing year by year. On average, 10-20 kg of dust is generated for every ton of steel produced. Currently, a large amount of zinc-containing electric arc furnace dust is still being simply piled up, causing serious environmental pollution and resource waste. The composition of zinc-containing electric arc furnace dust from a certain plant is shown in Table 1. The Fe content is 41.15%, the Zn content is as high as 11.11%, and it also contains heavy metals harmful to human health such as Pb and Cr. Therefore, the direct accumulation and landfilling of zinc-containing electric arc furnace dust not only pollutes the soil and water bodies, but also wastes valuable metal elements such as Zn and Fe.

[0005] Therefore, researchers have conducted extensive research on the resource utilization of zinc-containing solid waste, hoping to achieve this and solve the problem of my country's increasingly depleted zinc resources. Zinc-containing electric furnace dust has become one of the main research subjects. Among the various zinc-containing electric furnace dust extraction processes, the Waelz kiln is one of the most widely used pyrometallurgical methods for treating electric furnace dust. However, the Waelz kiln requires high temperatures, large amounts of carbonaceous reducing agents, and significant equipment investment. Furthermore, the product of the Waelz kiln is primarily crude, requiring further processing or purification to obtain high-purity zinc compounds or metallic zinc. The addition of carbonaceous reducing agents also introduces carbon emission problems. Hydrometallurgical processes have the advantages of simple equipment, low investment, and high-grade zinc products, making them particularly suitable for extracting low-grade zinc-containing electric furnace dust. However, the complex purification process, large amounts of waste liquid, and small-scale production hinder the large-scale industrial application of hydrometallurgical processes. Furthermore, how to efficiently extract zinc from zinc-containing electric furnace dust while reducing iron leaching remains a key challenge for metallurgists, and research reports on this topic are scarce. Chinese patent CN108531742B discloses a comprehensive method for the recovery and utilization of lead-zinc-containing dust from electric furnace steelmaking. First, the zinc-containing electric furnace dust is formed into pellets and subjected to reducing roasting at 1150-1250℃. Then, lead-zinc-containing gases and dust are collected, and crude lead oxide and crude zinc oxide powders are obtained through oxidation and cooling. These are then further processed through high-temperature sintering, oxidation, and cooling to obtain high-purity refined lead oxide and refined zinc oxide powders. Finally, they are reacted sequentially with hydrochloric acid and sodium carbonate to obtain lead carbonate and zinc carbonate. This patent exhibits a high lead-zinc recovery rate and overall resource utilization rate, but the process is complex, energy-intensive, and involves numerous steps in separating and purifying lead and zinc. Therefore, achieving resource utilization of zinc-containing electric furnace dust through a simple process with low energy consumption and low carbon emissions remains a serious challenge.

[0006] In summary, this invention ingeniously utilizes the addition of the roasting aid FeS for pre-roasting, pre-sulfating Zn present in zinc-containing electric furnace dust in the form of ZnO and ZnFe2O4, and then completely converting it into zinc sulfate using dilute sulfuric acid. This simple and efficient method achieves the extraction of zinc and the separation of iron from zinc-containing electric furnace dust. The zinc leaching rate is as high as 95.33%, while the iron leaching rate is only 0.17%, with the vast majority of the iron remaining in the leaching residue, which can be directly returned to the steel smelting process as raw material. The dilute sulfuric acid can be prepared from the tail gas of the roasting process, which is energy-saving and environmentally friendly, and allows for the full utilization of sulfur in FeS. The main component of the leachate is zinc sulfate, which can be directly sent to the electrolytic zinc plant for electrodeposition to prepare metallic zinc. Furthermore, because the Fe content in the electrolyte is low, the iron removal step before zinc electrodeposition can be avoided. This method can extract zinc from zinc-containing electric furnace dust and separate it from iron, enabling the resource-based reuse of zinc and iron. It also achieves the full-scale and resource-based utilization of zinc-containing electric furnace dust, making it a new and efficient method for disposing of zinc-containing electric furnace dust. Summary of the Invention:

[0007] This invention employs a simple pre-calcination method, placing a uniformly mixed mixture of zinc-containing electric furnace dust and FeS into a crucible and calcining it in a muffle furnace. After the reaction is complete, an appropriate amount of dilute sulfuric acid is added to the calcined product and stirred. Solid-liquid separation is then achieved through filtration, yielding zinc sulfate electrolyte and iron-containing leaching residue. This method simplifies the complex iron removal process of the leaching solution in traditional wet zinc extraction processes, enabling the efficient preparation of zinc sulfate electrolyte and high-grade ironmaking raw materials from zinc-containing solid waste.

[0008] A method for preparing zinc sulfate electrolyte using zinc-containing electric furnace dust is characterized by pre-sulfating the Zn in the zinc-containing electric furnace dust with FeS, followed by complete conversion to zinc sulfate with dilute sulfuric acid. The main component of the leachate is zinc sulfate, which can be directly sent to an electrolytic zinc plant for electrodeposition to prepare metallic zinc. Furthermore, because the Fe content in the electrolyte is low, the iron removal step before zinc electrodeposition can be avoided. The specific steps are as follows:

[0009] (1) Mix zinc-containing electric furnace dust and FeS in a mass ratio of 1:1-1:5 and place them in a crucible. Then place them in a muffle furnace and calcine at 500-800℃ for 1-5 hours. Then cool to room temperature to obtain the calcined product.

[0010] (2) Place the roasted product obtained in step (1) into a beaker, add a certain amount of dilute sulfuric acid into the beaker, and stir magnetically for a certain time at a certain temperature. Then separate the solid and liquid by filtration to obtain zinc sulfate electrolyte and iron-containing leaching residue.

[0011] The method for preparing zinc sulfate electrolyte using zinc-containing electric furnace dust as described in claim 1 is characterized in that the leaching conditions of the roasted product in step (2) are: sulfuric acid volume: 5-100 mL, temperature: 30-70 °C, magnetic stirring: 10-180 min.

[0012] This invention enables the efficient extraction of valuable zinc and the separation of iron from zinc-containing electric furnace dust. The zinc leaching rate is as high as 95.33%, while the iron leaching rate is only 0.17%, with the vast majority of the iron remaining in the leaching residue. The iron-containing leaching residue can be directly returned to the ironmaking process. The main component of the leaching solution is zinc sulfate, which can be directly sent to an electrolytic zinc plant for electrodeposition to obtain metallic zinc. Furthermore, because the Fe content in the electrolyte is low, the iron removal step before zinc electrodeposition can be avoided.

[0013] This invention uses zinc-containing electric furnace dust as a zinc source, which not only realizes the resource utilization of hazardous solid waste containing zinc-containing electric furnace dust, but also helps to alleviate the problem of increasingly depleted zinc ore resources and increases the production pathways of recycled zinc. This invention employs a pre-roasting method under mild conditions to pre-sulfatate Zn present in the form of ZnO and ZnFe2O4 in the zinc-containing electric furnace dust, and then completely converts it into zinc sulfate electrolyte through dilute sulfuric acid leaching. The process is simple, the dilute sulfuric acid can be prepared from the tail gas of the roasting process, which is energy-saving and environmentally friendly, and can fully utilize the S element in FeS. Attached image description:

[0014] Figure 1 Flowchart of the process for preparing zinc sulfate electrolyte using zinc-containing electric furnace dust.

[0015] Figure 2 XRD patterns of zinc-containing electric furnace dust, pre-baked products, and leaching residue. Detailed implementation method:

[0016] 1. Raw material selection

[0017] The raw material is zinc-containing electric furnace dust. Its chemical analysis results are shown in Table 1, and the phase analysis results are as follows: Figure 2 As shown:

[0018]

[0019] 2. Preparation steps: See Figure 1

[0020] 2.1 Implementation Example 1

[0021] (1) The zinc-containing electric furnace dust and FeS are mixed evenly at a mass ratio of 1:1 and placed in a crucible. Then, the crucible is placed in a muffle furnace and calcined at 650°C for 1 hour. Finally, the mixture is cooled to room temperature to obtain the calcined product.

[0022] (2) Place the calcined product obtained in step (1) into a 100 mL beaker, add 50 mL of dilute sulfuric acid, and stir magnetically at 30 °C for 30 min. Then separate the solid and liquid by suction filtration to obtain zinc sulfate electrolyte and iron-containing leaching residue. The leaching rate of zinc was 74.68% and the leaching rate of iron was 1.52% by titration test.

[0023] 2.2 Implementation Example 2

[0024] (1) The zinc-containing electric furnace dust and FeS are mixed evenly at a mass ratio of 1:3 and placed in a crucible. Then, the crucible is placed in a muffle furnace and calcined at 600℃ for 2 hours. Finally, the product is cooled to room temperature to obtain the calcined product.

[0025] (2) The calcined product obtained in step (1) was placed in a 100 mL beaker, and 20 mL of dilute sulfuric acid was added to the beaker. The mixture was then magnetically stirred at 30 °C for 1 h. The solid and liquid were then separated by filtration to obtain zinc sulfate electrolyte and iron-containing leaching residue. The leaching rate of zinc was 81.18% and the leaching rate of iron was 0.99% by titration.

[0026] 2.3 Implementation Example 3

[0027] (1) The zinc-containing electric furnace dust and FeS are mixed evenly at a mass ratio of 1:3 and placed in a crucible. Then, the crucible is placed in a muffle furnace and roasted at 650°C for 3 hours. Finally, the product is cooled to room temperature to obtain the roasted product.

[0028] (2) Place the calcined product obtained in step (1) into a 100 mL beaker, add 50 mL of dilute sulfuric acid, and stir magnetically at 50 °C for 20 min. Then separate the solid and liquid by filtration to obtain zinc sulfate electrolyte and iron-containing leaching residue. The leaching rate of zinc was 95.24% and the leaching rate of iron was 2.33% by titration test.

[0029] 2.4 Implementation Example 4

[0030] (1) The zinc-containing electric furnace dust and FeS are mixed evenly at a mass ratio of 1:3 and placed in a crucible. Then, the crucible is placed in a muffle furnace and roasted at 650°C for 3 hours. Finally, the product is cooled to room temperature to obtain the roasted product.

[0031] (2) Place the calcined product obtained in step (1) into a 100 mL beaker, add 25 mL of dilute sulfuric acid, and stir magnetically at 30 °C for 30 min. Then separate the solid and liquid by suction filtration to obtain zinc sulfate electrolyte and iron-containing leaching residue. The leaching rate of zinc was 95.33% and the leaching rate of iron was 0.17% by titration test.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention. The present invention is not only applicable to dust waste from steel plants, but also to zinc-containing industrial waste from zinc smelters, electroplating plants, machinery plants, mineral processing plants, etc. Under the guidance of the present invention, those skilled in the art can make various similar modifications without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing zinc sulfate electrolyte from zinc-containing electric furnace dust, characterized in that: (1) the zinc-containing electric furnace dust is uniformly mixed with FeS at a mass ratio of 1:1-1:5, then placed in a crucible and put into a muffle furnace, calcined at a temperature of 500-800℃ for 1-5h, and then cooled to room temperature to obtain a calcined product; (2) the calcined product obtained in step (1) is placed in a beaker, a certain amount of dilute sulfuric acid is added into the beaker, and magnetic stirring is carried out at a certain temperature for a certain time, then the solid-liquid separation is carried out by suction filtration to obtain zinc sulfate electrolyte and iron-containing leaching residue. The leaching conditions of the calcined product in step (2) are: sulfuric acid volume: 5-100mL, leaching temperature: 30-70℃, magnetic stirring: 10-180min. ​ 2. A process for the preparation of zinc sulphate electrolyte from zinc containing electric furnace dust as claimed in claim 1 wherein ​

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