Method for efficiently recovering scattered metal indium from jarosite slag

Abstract

The invention discloses a method for efficiently recovering scattered metal indium from jarosite slag, and belongs to the technical field of non-ferrous metallurgy. According to the method for efficiently recovering the scattered metal indium from the iron vitriol slag, aiming at the industrial problem that indium in the iron vitriol slag is difficult to efficiently recover, the iron vitriol slag is subjected to heat treatment, and iron in the iron vitriol slag is directionally converted into iron oxide which is not easy to dissolve by adding an additive; loose metal indium and valuable metal zinc exist in the form of soluble sulfate, indium and zinc can be completely transferred into a solution when roasted sand obtained after heat treatment is leached through weak acid, the main component of leaching residues is ferric oxide and can serve as raw materials for ironmaking, leaching liquid is replaced with zinc powder to obtain a sponge indium product, and the main component of replacement liquid is zinc sulfate and can serve as raw materials for ironmaking. And directly returning to a zinc smelting system to recover zinc. The method for efficiently recovering the scattered metal indium from the jarosite slag has the characteristics of short flow, high efficiency, high comprehensive recovery rate of indium and other valuable metals and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal metallurgy, and more specifically, relates to a method for efficiently recovering scattered metal indium from iron alum slag. Background Art

[0002] Indium is a rare metal with good light permeability and conductivity. The ITO film prepared with it has both light transmittance and conductivity, and plays an irreplaceable role in the fields of liquid crystal display, thin-film solar energy, etc. At the same time, semiconductor materials based on indium compounds (InP, InSb, etc.) and indium-doped semiconductor materials also have important applications in aerospace, new generation information technology, national defense and military industries, etc. In recent years, many countries have listed indium as a key raw material for key protection in their key material strategy documents.

[0003] Indium is a low-abundance substance in the earth's crust, only about 1×10 -7, and the degree of dispersion is high, there is basically no independent ore deposit, and it is mainly distributed in sphalerite and other ores in the form of isomorphism. Therefore, indium is often obtained as a by-product of zinc smelting. At present, the hot acid leaching-iron alum precipitation process is one of the main zinc smelting processes in industry. During the production process, indium enters the iron alum slag lattice in the form of isomorphism when the hot acid leaching solution precipitates iron. Therefore, how to efficiently recover and extract indium from the iron alum slag has become a research hotspot in the industry. The Chinese patent application No. 201810943195.1 discloses a method for acid leaching of iron alum slag to reduce iron and separate indium and zinc. The iron alum slag is roasted at a temperature of 600~670℃, and the roasted sand is further leached with sulfuric acid solution at room temperature, achieving an indium leaching rate of more than 70%. The Chinese patent application No. 201710366491.5 discloses a method for recovering zinc, indium, iron and gallium from iron alum slag. By mixing additives with iron alum slag, grinding, balling, oxidative roasting and desulfurization, high-quality furnace materials can be provided for the efficient separation and extraction of multiple valuable elements by pyrometallurgical methods. The Chinese patent application No. 98112542.5 discloses a process for extracting indium by roasting, leaching and extracting iron alum slag. The iron alum slag is subjected to roasting, acid leaching, extraction, replacement and melting and casting in sequence, and finally metal indium ingots are recovered. The total recovery rate of indium is 80.44%. The academic paper (Experimental Study on Recovery of Indium from Iron Alum Slag, Gansu Metallurgy, 2014, 36(05): 30-31) directly acid-leaches the iron alum slag, and then recovers metal indium through extraction, replacement and other processes. Under the best conditions, the recovery rate of indium reaches more than 90%. Academic paper (Experimental study on ultrasonic-assisted leaching of indium and zinc from ferroxite slag, Hydrometallurgy, 2017, 36(04): 262-266), this study introduced ultrasound into the leaching process of ferroxite slag to enhance the leaching of indium and zinc, and compared the effects of direct sulfuric acid leaching and ultrasound-assisted sulfuric acid leaching of indium and zinc. The results showed that the introduction of ultrasound during acid leaching can accelerate the dissolution of ferroxite slag and effectively improve the leaching rate of indium and zinc. Academic paper (Recovery of indium from ferroxite slag by alkaline roasting and secondary precipitation, Comprehensive Utilization of Minerals, 2021, (02): 33-36), ferroxite slag was alkaline roasted, leached with dilute acid, precipitated again, and the secondary ferroxite slag was roasted, acid leached, and reduced to obtain a sponge indium product, with a direct recovery rate of indium of 85%. The academic paper (Recovery of zinc and indium by roasting and leaching of indium-containing iron alum slag, The Chinese Journal of Nonferrous Metals, 2017, 27(05): 1045-1050) proposed a roasting-water leaching method to recover zinc and indium from indium-containing iron alum slag. The leaching rates of zinc and indium were 72.02% and 78.73%, respectively, achieving effective separation from iron. Summary of the invention

[0004] 1. Problem to be solved

[0005] The purpose of the present invention is to overcome the problem that the content of indium in iron alum slag is low, the content of impurities such as iron is high, and indium and iron are similar in nature and difficult to be separated efficiently, and solve the problem of low recovery rate of valuable elements such as indium in iron alum slag treated by traditional methods, and propose to heat-treat the iron alum slag, and by adding additives, the iron in the iron alum slag is directionally converted into insoluble iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of easily soluble sulfate, and the roasted sand after heat treatment can be leached with weak acid to transfer all indium and zinc into the solution, and the main component of the leached slag is iron oxide, which can be used as a raw material for iron smelting, and the leached solution is replaced by zinc powder to obtain a sponge indium product, and the main component of the replacement solution is zinc sulfate, which can be directly returned to the zinc smelting system to recover zinc. A method for efficiently recovering scattered metal indium from iron alum slag of the present invention has the characteristics of short process, high efficiency, and high comprehensive recovery rate of indium and other valuable metals.

[0006] 2. Technical solution In order to solve the above problems, the technical solution adopted by the present invention is as follows: The invention discloses a method for efficiently recovering scattered metal indium from iron alum slag. The method proposes to heat-treat the iron alum slag, and to add additives to directionally convert the iron in the iron alum slag into insoluble iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of easily soluble sulfate. The heat-treated roasted sand can be leached with weak acid to transfer all the indium and zinc into the solution. The main component of the leached slag is iron oxide, which can be used as a raw material for iron smelting. The leached liquid is replaced by zinc powder to obtain a sponge indium product. The main component of the replacement liquid is zinc sulfate, which can be directly returned to the zinc smelting system to recover zinc.

[0007] Furthermore, the specific process operation is: (1) The iron alum slag is mixed evenly with a certain amount of additives, placed in a roasting furnace and heated to a predetermined temperature, and reacted at a constant temperature for a period of time, so that the iron in the iron alum slag is directionally converted into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate.

[0008] (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) is subjected to weak acid leaching to dissolve all indium and zinc into the solution; the leached slurry is subjected to solid-liquid separation to obtain leached slag whose main component is iron oxide, which can be used as a raw material for iron smelting.

[0009] (3) Under mechanical stirring conditions, an appropriate amount of zinc powder is added to the filtrate obtained in step (2) to carry out a replacement reaction. After a period of constant temperature reaction, solid-liquid separation is carried out to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc, and the filter residue is a sponge indium product.

[0010] Furthermore, in step (1), the additive is one of ferrous sulfide, iron powder, sulfur and sodium sulfide, the added amount is 0.1-1 in molar ratio with respect to the iron element in the iron alum slag, the reaction temperature is 450-700°C, and the reaction time is 1-6 h.

[0011] Furthermore, in the weak acid leaching process in step (2), the mechanical stirring speed is 300-800 rpm, the pH value of the leaching solution is 1.5-6.5, the liquid-to-solid ratio is 1-5, the reaction temperature is 20-95°C, and the reaction time is 1-6 h.

[0012] Furthermore, in the replacement reaction process in step (3), the mechanical stirring speed is 300-800 rpm, the molar ratio of zinc powder added to indium ions in the solution is 1.6-2.2, the reaction temperature is 20-95°C, and the reaction time is 1-6 h.

[0013] 3. Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: (1) The core difficulty of efficiently recovering indium from iron alum slag lies in the efficient separation of indium and iron. Since the properties of indium and iron are similar, if the iron alum slag is directly roasted, indium will enter the iron compound lattice in the form of isomorphous phase, which is difficult to separate; and if hot acid is used to leach the iron alum slag, a large amount of iron ions and a small amount of indium ions will coexist in the solution, and the separation of indium and iron in the solution system is also a major problem. Therefore, this patent proposes to heat treat the iron alum slag, and by adding specific additives (ferrous sulfide, iron powder, sulfur, sodium sulfide), the iron in the iron alum slag is directionally converted into insoluble iron oxide, while the scattered metal indium and valuable metal zinc exist in the form of easily soluble sulfate. Further simple weak acid leaching can achieve efficient separation of valuable elements and iron. In addition, the iron alum slag usually contains a certain amount of zinc ferrite, which is stable in nature and difficult to dissolve effectively by conventional acid leaching processes. The invention adds additives during the heat treatment process, which can effectively destroy the stable lattice of zinc ferrite and release soluble zinc, thereby ensuring a high recovery rate of zinc in the further wet leaching process.

[0014] (2) In roasted sand, iron, indium and zinc exist in the form of iron oxide, indium sulfate and zinc sulfate respectively. After simple weak acid leaching, indium, zinc and the like can be completely dissolved. Not only is the leaching rate of valuable elements high, but the main component of the leached slag is iron oxide, of which the iron content can reach more than 50%, which is a high-quality iron-making raw material; for the zinc powder replacement process of the leaching solution, since it is a weak acid system, the zinc powder replacement process does not need to adjust the acidity of the solution, the two processes can be seamlessly connected, and the replacement process does not introduce new impurities. The replacement slag is a sponge indium product, and the replacement liquid is a zinc sulfate solution, which can be directly incorporated into the mature zinc smelting process to recover zinc. The method of efficiently recovering scattered metal indium from iron alum slag proposed in this patent not only has a short process, high efficiency, and a high comprehensive recovery rate of valuable metals such as indium, but also does not produce wastewater and waste slag, is environmentally friendly, and realizes the transformation of hazardous waste iron alum slag into treasure, which is expected to provide strong support for the green and low-carbon transformation and upgrading of the zinc smelting industry. DETAILED DESCRIPTION

[0015] The present invention provides a method for efficiently recovering scattered metal indium from iron alum slag. In view of the industry problem that indium in iron alum slag is difficult to recover efficiently, it is proposed to heat-treat the iron alum slag, and by adding additives, the iron in the iron alum slag is directionally converted into insoluble iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of easily soluble sulfates. The heat-treated roasted sand can be leached with weak acid to transfer all the indium and zinc into the solution. The main component of the leached slag is iron oxide, which can be used as a raw material for iron smelting. The leachate is replaced by zinc powder to obtain a sponge indium product. The main component of the replacement liquid is zinc sulfate, which can be directly returned to the zinc smelting system to recover zinc. The treatment process of the present invention specifically includes the following steps: (1) The iron alum slag is mixed evenly with a certain amount of additives, wherein the additive is one of ferrous sulfide, iron powder, sulfur and sodium sulfide, and the added amount is 0.1-1 in molar ratio to the iron element in the iron alum slag. The mixture is placed in a roasting furnace and heated to 450-700°C. The mixture is reacted at a constant temperature for 1-6 hours, so that the iron in the iron alum slag is directionally converted into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate.

[0016] (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) is subjected to weak acid leaching, the mechanical stirring speed is 300-800 rpm, the pH value of the leaching solution is 1.5-6.5, the liquid-to-solid ratio is 1-5, the reaction temperature is 20-95°C, and the reaction time is 1-6 h, so that all indium and zinc are dissolved into the solution; the leached slurry is subjected to solid-liquid separation to obtain a leached slag whose main component is iron oxide, which can be used as a raw material for iron smelting.

[0017] (3) Under mechanical stirring conditions, add an appropriate amount of zinc powder to the filtrate obtained in step (2) to carry out a replacement reaction, the mechanical stirring speed is 300-800 rpm, the molar ratio of zinc powder added to indium ions in the solution is 1.6-2.2, the reaction temperature is 20-95°C, the reaction time is 1-6 h, and after the reaction is completed, solid-liquid separation is carried out to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc, and the filter residue is a sponge indium product.

[0018] The present invention is further described below in conjunction with specific embodiments.

[0019] Example 1 The method for efficiently recovering scattered metal indium from iron alum slag of the present embodiment specifically comprises the following steps: (1) The iron alum slag is mixed evenly with a certain amount of ferrous sulfide additive, the amount of the additive added is a molar ratio of 1 to the iron element in the iron alum slag, the mixture is placed in a roasting furnace and heated to 700°C, and the temperature is kept constant for 1 hour to make the iron in the iron alum slag directionally converted into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate.

[0020] (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) is subjected to weak acid leaching, the mechanical stirring speed is 300 rpm, the pH value of the leaching solution is 1.5, the liquid-to-solid ratio is 1, the reaction temperature is 20°C, the reaction time is 1 h, and the leaching rates of indium and zinc are 99.21% and 99.18%, respectively; the leached slurry is subjected to solid-liquid separation to obtain a leached slag whose main component is iron oxide, wherein the iron content is 55.62%, which can be used as a raw material for ironmaking.

[0021] (3) Under mechanical stirring conditions, an appropriate amount of zinc powder is added to the filtrate obtained in step (2) to carry out a replacement reaction. The mechanical stirring speed is 300 rpm, the molar ratio of zinc powder added to indium ions in the solution is 2.2, the reaction temperature is 20°C, and the reaction time is 1 h. After the reaction is completed, solid-liquid separation is carried out to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc. The filter residue is a sponge indium product. The total recovery rate of indium is 97.32%.

[0022] Example 2 The method for efficiently recovering scattered metal indium from iron alum slag of the present embodiment specifically comprises the following steps: (1) The iron alum slag is mixed evenly with a certain amount of iron powder additive, the amount of the additive added is a molar ratio of 0.8 to the iron element in the iron alum slag, the mixture is placed in a roasting furnace and heated to 450°C, and the reaction is carried out at a constant temperature for 6 hours, so that the iron in the iron alum slag is directionally converted into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate.

[0023] (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) is subjected to weak acid leaching, the mechanical stirring speed is 800 rpm, the pH value of the leaching solution is 6.5, the liquid-to-solid ratio is 5, the reaction temperature is 95° C., the reaction time is 6 h, and the leaching rates of indium and zinc are 99.37% and 99.23%, respectively; the leached slurry is subjected to solid-liquid separation to obtain a leached slag whose main component is iron oxide, wherein the iron content is 55.83%, which can be used as a raw material for ironmaking.

[0024] (3) Under mechanical stirring conditions, an appropriate amount of zinc powder is added to the filtrate obtained in step (2) to carry out a replacement reaction. The mechanical stirring speed is 800 rpm, the molar ratio of zinc powder added to indium ions in the solution is 1.6, the reaction temperature is 95° C., and the reaction time is 6 h. After the reaction is completed, solid-liquid separation is carried out to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc. The filter residue is a sponge indium product. The total recovery rate of indium is 97.12%.

[0025] Example 3 The method for efficiently recovering scattered metal indium from iron alum slag of the present embodiment specifically comprises the following steps: (1) The iron alum slag is mixed evenly with a certain amount of sulfur additive, the amount of the additive added is a molar ratio of 0.7 to the iron element in the iron alum slag, the mixture is placed in a roasting furnace and heated to 500°C, and the temperature is kept constant for 5 hours to react so that the iron in the iron alum slag is directionally converted into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate.

[0026] (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) is subjected to weak acid leaching, the mechanical stirring speed is 500 rpm, the pH value of the leaching solution is 3, the liquid-to-solid ratio is 2, the reaction temperature is 40°C, the reaction time is 5 h, and the leaching rates of indium and zinc are 99.03% and 99.26%, respectively; the leached slurry is subjected to solid-liquid separation to obtain a leached slag whose main component is iron oxide, wherein the iron content is 55.19%, which can be used as a raw material for ironmaking.

[0027] (3) Under mechanical stirring conditions, an appropriate amount of zinc powder is added to the filtrate obtained in step (2) to carry out a replacement reaction. The mechanical stirring speed is 500 rpm, the molar ratio of zinc powder added to indium ions in the solution is 1.8, the reaction temperature is 40° C., and the reaction time is 5 h. After the reaction is completed, solid-liquid separation is performed to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc. The filter residue is a sponge indium product. The total recovery rate of indium is 97.05%.

[0028] Example 4 The method for efficiently recovering scattered metal indium from iron alum slag of the present embodiment specifically comprises the following steps: (1) Mix the iron alum slag with a certain amount of sodium sulfide additive, the amount of the additive added is 0.1 in the molar ratio of the iron element in the iron alum slag, place the mixture in a roasting furnace and heat it to 550°C, and react at a constant temperature for 4 hours, so that the iron in the iron alum slag is directionally converted into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate.

[0029] (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) is subjected to weak acid leaching, the mechanical stirring speed is 600 rpm, the pH value of the leaching solution is 4, the liquid-to-solid ratio is 3, the reaction temperature is 60° C., the reaction time is 4 h, and the leaching rates of indium and zinc are 99.57% and 99.82%, respectively; the leached slurry is subjected to solid-liquid separation to obtain a leaching slag whose main component is iron oxide, wherein the iron content is 56.01%, which can be used as a raw material for ironmaking.

[0030] (3) Under mechanical stirring conditions, an appropriate amount of zinc powder is added to the filtrate obtained in step (2) to carry out a replacement reaction. The mechanical stirring speed is 600 rpm, the amount of zinc powder added is 2 in molar ratio to the indium ions in the solution, the reaction temperature is 60° C., and the reaction time is 4 h. After the reaction is completed, solid-liquid separation is carried out to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc. The filter residue is a sponge indium product. The total recovery rate of indium is 98.07%.

[0031] Example 5 The method for efficiently recovering scattered metal indium from iron alum slag of the present embodiment specifically comprises the following steps: (1) The iron alum slag is mixed evenly with a certain amount of iron powder additive, the amount of the additive added is a molar ratio of 0.5 to the iron element in the iron alum slag, the mixture is placed in a roasting furnace and heated to 600°C, and the temperature is kept constant for 3 hours to convert the iron in the iron alum slag into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate.

[0032] (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) was subjected to weak acid leaching, the mechanical stirring speed was 700 rpm, the pH value of the leaching solution was 5, the liquid-to-solid ratio was 4, the reaction temperature was 80°C, the reaction time was 3 h, and the leaching rates of indium and zinc were 99.63% and 99.88%, respectively; the leached slurry was subjected to solid-liquid separation to obtain a leached slag whose main component was iron oxide, wherein the iron content was 56.21%, which could be used as a raw material for ironmaking.

[0033] (3) Under mechanical stirring conditions, an appropriate amount of zinc powder is added to the filtrate obtained in step (2) to carry out a replacement reaction. The mechanical stirring speed is 700 rpm, the molar ratio of zinc powder added to indium ions in the solution is 2.1, the reaction temperature is 80°C, and the reaction time is 3 h. After the reaction is completed, solid-liquid separation is carried out to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc. The filter residue is a sponge indium product. The total recovery rate of indium is 98.25%.

Claims

1. A method for efficiently recovering scattered metal indium from iron alum slag, characterized in that: In view of the industry problem that indium in iron alum slag is difficult to recover efficiently, it is proposed to heat treat the iron alum slag. By adding additives, the iron in the iron alum slag is directionally converted into insoluble iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of easily soluble sulfates. The heat-treated roasted sand can be leached with weak acid to transfer all the indium and zinc into the solution. The main component of the leached slag is iron oxide, which can be used as a raw material for iron smelting. The leachate is replaced by zinc powder to obtain a sponge indium product. The main component of the replacement liquid is zinc sulfate, which can be directly returned to the zinc smelting system to recover zinc.

2. The method for efficiently recovering scattered metal indium from iron alum slag according to claim 1, characterized in that: The specific process operations are: (1) The iron alum slag is mixed evenly with a certain amount of additives, placed in a roasting furnace and heated to a predetermined temperature, and reacted at a constant temperature for a period of time, so that the iron in the iron alum slag is directionally converted into iron oxide, while the scattered metal indium and the valuable metal zinc exist in the form of sulfate; (2) Under mechanical stirring conditions, the roasted sand obtained in step (1) is subjected to weak acid leaching to dissolve all indium and zinc into the solution; the leached slurry is subjected to solid-liquid separation to obtain leached slag whose main component is iron oxide, which can be used as a raw material for iron smelting; (3) Under mechanical stirring conditions, an appropriate amount of zinc powder is added to the filtrate obtained in step (2) to carry out a replacement reaction. After a period of constant temperature reaction, solid-liquid separation is carried out to obtain a filtrate as a zinc sulfate solution, which is directly returned to the zinc smelting system to recover zinc, and the filter residue is a sponge indium product.

3. The method for efficiently recovering scattered metal indium from iron alum slag according to claim 2, characterized in that: The additive in step (1) is one of ferrous sulfide, iron powder, sulfur and sodium sulfide, the added amount is 0.1-1 in molar ratio with respect to the iron element in the iron alum slag, the reaction temperature is 450-700°C, and the reaction time is 1-6 h.

4. The method for efficiently recovering scattered metal indium from iron alum slag according to claim 2, characterized in that: In the weak acid leaching process in step (2), the mechanical stirring speed is 300-800 rpm, the pH value of the leaching solution is 1.5-6.5, the liquid-to-solid ratio is 1-5, the reaction temperature is 20-95°C, and the reaction time is 1-6 h.

5. The method for efficiently recovering scattered metal indium from iron alum slag according to claim 2, characterized in that: In the replacement reaction process in step (3), the mechanical stirring speed is 300-800 rpm, the molar ratio of zinc powder added to indium ions in the solution is 1.6-2.2, the reaction temperature is 20-95°C, and the reaction time is 1-6 h.