Electrochemical high-valued method for steel slag

Abstract

The invention relates to the technical field of comprehensive utilization of industrial waste residues, in particular to an electrochemical high-valued method of steel slag. The method comprises the following steps: providing an electrochemical device which comprises a power supply, a cathode, an anode and an electrolyte, and fixing steel slag near the anode in the electrochemical device; the electrochemical device is subjected to water electrolysis treatment, so that the steel slag releases metal cations and forms precipitates through reaction, and calcium cations in the metal cations react with carbon dioxide absorbed by the electrochemical device to form calcium carbonate. The method provided by the invention is carried out in a single reactor, does not need high temperature and high pressure, and does not involve addition of other chemical reagents, so that the existing steel slag carbon sequestration and metal recovery technology is greatly simplified, the efficiency of the existing method is improved, the economic and environmental burden is reduced, and efficient carbon sequestration and metal recovery of the steel slag are realized in the same system.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization of industrial waste slag, and in particular to an electrochemical high-value method for steel slag. Background Art

[0002] As the main by-product of the steel industry, steel slag is considered to be a very promising raw material for carbon dioxide removal. In theory, about 413 kg and 368 kg of carbon dioxide can be removed per ton of basic oxygen furnace (BOF) and electric arc furnace (EAF) slag. In the past, there have been early studies on carbon dioxide sequestration in traditional steel slag, but it is limited by inherent defects such as low utilization rate (due to surface passivation), subsequent difficult treatment of solid waste, and large amount of chemical agents used. For example, patent application CN117865536A discloses the use of water as a medium to generate calcium carbonate using steel slag and introduced carbon dioxide to fix carbon dioxide. However, in this application, the calcium carbonate generated on the surface of the steel slag covers the steel slag, which hinders further carbon dioxide fixation and causes low utilization of the steel slag. In addition, the steel slag after carbon fixation is still solid waste and still needs further disposal. Patent applications CN113979460A and CN115820946A disclose that metal extraction from steel slag is achieved while fixing carbon, but both involve high temperature, high pressure, complex steps and the use of a large number of chemical reagents. For example, in CN113979460A, ammonium chloride solution is first added to steel slag for leaching reaction to obtain a leachate and a filter residue. Carbon dioxide is then introduced into the leachate to obtain calcium carbonate, and a small amount of silicon dioxide and a reducing agent are added to the filter residue and mixed and placed in a high-temperature furnace for melting and separation to obtain metallic iron. Similarly, in CN115820946A, ammonium chloride solution is used to leach free calcium oxide in steel slag to obtain a filter residue and a first leachate, and the first leachate is used for carbon dioxide absorption. Subsequently, the filter residue is leached again with an ammonium chloride solution to obtain a second leaching residue and a mineralized crude liquid. After oxidation, alkali adjustment and solid-liquid separation, the mineralized crude liquid obtains iron-aluminum precipitation and a second mineralized liquid, and the second mineralized liquid is used for carbon dioxide absorption. Finally, sodium hydroxide solution is used to leaching iron and aluminum precipitates to achieve separation of iron and aluminum. It can be seen that most of the existing methods only achieve basic steel slag carbon fixation, ignoring its limited efficiency and the complexity of subsequent solid waste treatment. On this basis, although a few methods have achieved steel slag carbon fixation and metal recovery, their processes are complicated and require a large amount of chemical reagents, which limits the feasibility of their practical application.

[0003] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide an electrochemical high-value method for steel slag, aiming to solve the problems of low efficiency, complex process and requirement of a large amount of chemical reagents in the existing methods for simultaneously achieving steel slag carbon fixation and metal recovery.

[0005] The technical solution of the present invention is as follows:

[0006] The present invention provides a method for electrochemically increasing the value of steel slag, which comprises:

[0007] Providing an electrochemical device, the electrochemical device comprising a power source, a cathode, an anode and an electrolyte, and fixing the steel slag near the anode in the electrochemical device;

[0008] The electrochemical device is subjected to electrolytic water treatment, so that the steel slag releases metal cations and forms precipitation through reaction, and calcium cations in the metal cations react with carbon dioxide absorbed by the electrochemical device to form calcium carbonate.

[0009] Optionally, the steel slag is placed in a porous container, and the porous container is fixed near an anode in the electrochemical device.

[0010] Optionally, a constant current process or a constant voltage process is used to electrolyze water in the electrochemical device.

[0011] Optionally, a constant current process is used to electrolyze water in the electrochemical device, and the constant current in the constant current process is 10 mA to 400 mA.

[0012] Optionally, the steel slag comprises CaO, FeO and Fe2O3.

[0013] Optionally, the material of the anode is a material that can generate hydrogen ions by oxidizing water molecules at the anode.

[0014] Optionally, the material of the anode is an inert metal material or a carbon material.

[0015] Optionally, the material of the cathode is a material that enables the cathode to reduce water molecules to generate hydroxide ions.

[0016] Optionally, the cathode is made of a metal material or a carbon material.

[0017] Optionally, the electrolyte is a sodium salt solution or a potassium salt solution with a concentration of 10 mM to 100 mM.

[0018] Beneficial effects: The present invention provides an electrochemical high-value method for steel slag, which can controllably and efficiently release metal cations (calcium ions, iron ions, etc.) in the steel slag into the system by utilizing the characteristics of acid production at the anode of electrolyzed water in the same electrochemical device, and at the same time utilize the characteristics of alkali production at the cathode of electrolyzed water and the production of a gradient pH of the system to selectively use the released metal cations for carbon dioxide fixation and metal recovery. The electrochemical process involved in the present invention is carried out in a single reactor, and does not require high temperature and high pressure, nor does it involve the addition of other chemical reagents, which greatly simplifies the existing steel slag carbon fixation and metal recovery technology, improves the efficiency of the existing method, reduces the economic and environmental burden, and realizes efficient steel slag carbon fixation and metal recovery in the same system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the device for the electrochemical high-value method of steel slag according to the present invention.

[0020] Figure 2 A schematic diagram of a method for electrochemically increasing the value of steel slag provided by the present invention.

[0021] Figure 3 Figure a in the figure is a graph showing the pH value change of the system after the electrochemical device is energized for 1 hour in Example 1. Figure 3 Figure b shows the Ca content in the solution after the electrochemical device was energized for 1 hour in Example 1. 2+ Concentration and Fe 3+ The concentration change diagram, Figure 3 Figure c in the figure is a graph showing the changes in the concentrations of total inorganic carbon, carbonate and bicarbonate in the solution when the electrochemical device is energized for 1 hour in Example 1.

[0022] Figure 4 Figure a in the figure is a diagram showing the pH value change of the system after the electrochemical device is energized for 8 hours in Example 2. Figure 4 Figure b shows the Ca content in the solution after the electrochemical device was energized for 8 hours in Example 2. 2+ Concentration and Fe 3+ The concentration change diagram, Figure 4 Figure c in the figure is a graph showing the changes in the concentrations of total inorganic carbon, carbonate and bicarbonate in the solution when the electrochemical device is energized for 8 hours in Example 2.

[0023] Figure 5 Figure a in the figure is a schematic diagram of the cathode product in Example 2, Figure 5 Figure b is the X-ray diffraction pattern of the cathode product in Example 2.

[0024] Figure 6 Figure a in the figure is a schematic diagram of the flocculent product in the solution in Example 2, Figure 6 Figure b is the energy dispersive X-ray spectrum result of the flocculent product in the solution in Example 2.

[0025] Figure 7 Figure a in the figure is a graph showing the pH value change of the system after the electrochemical device is energized for 8 hours in Example 3. Figure 7 Figure b shows the Ca content in the solution after the electrochemical device was energized for 8 hours in Example 3. 2+ Concentration and Fe 3+ The concentration change diagram, Figure 7 Figure c in the figure is a graph showing the changes in the concentrations of total inorganic carbon, carbonate and bicarbonate in the solution when the electrochemical device is energized for 8 hours in Example 3.

[0026] Figure 8 Figure a is a schematic diagram of the cathode product in Example 3, Figure 8 Figure b is the X-ray diffraction pattern of the cathode product in Example 3.

[0027] Fig. 9 This is the energy dispersive X-ray spectrum result of the flocculent product in the solution in Example 3. DETAILED DESCRIPTION

[0028] The present invention provides a method for electrochemically increasing the value of steel slag. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Water electrolysis technology can decompose water molecules into hydrogen and oxygen through direct current, and provide hydrogen ions (H + ) and hydroxide ions (OH - ). Water electrolysis technology has been widely used in various scenarios such as hydrogen production, water disinfection and electrochemical induced precipitation. Inspired by its working principle, the present invention innovatively combines water electrolysis technology with steel slag high value technology, and realizes efficient, one-step steel slag carbon fixation and metal recovery based on water electrolysis technology without the need for chemical reagents.

[0030] Specifically, according to one embodiment of the present invention, a method for electrochemically increasing the value of steel slag is provided, which comprises:

[0031] S1. Providing an electrochemical device, wherein the electrochemical device comprises a power source, a cathode, an anode and an electrolyte, and fixing the steel slag near the anode in the electrochemical device;

[0032] S2. Performing electrolytic water treatment on the electrochemical device, so that the steel slag releases metal cations and forms precipitation through reaction, and calcium cations in the metal cations react with carbon dioxide absorbed by the electrochemical device to form calcium carbonate.

[0033] The key innovation of the embodiment of the present invention is that it cleverly utilizes the characteristics of acid production at the anode in electrolyzed water to achieve controllable and efficient extraction of effective components (calcium, iron, etc.) of steel slag. At the same time, combined with the characteristics of alkali production at the cathode in electrolyzed water and the production of gradient pH in the same system, the effective components are selectively used for carbon dioxide fixation and metal recovery and extraction.

[0034] In an embodiment of the present invention, after the electrochemical device is subjected to water electrolysis treatment, the hydrogen ions generated by the electrolysis of water at the anode are used to decompose the steel slag in situ. To ensure the efficient reaction of the steel slag with the hydrogen ions, the steel slag is fixed near the anode. Based on this principle, the main components in the steel slag (such as metal cations such as calcium ions and iron ions) are controllably and continuously released. More importantly, the steel slag is fixed in the anode region that is always acidic, and an acidolysis reaction rather than a carbon fixation reaction occurs on its surface, which avoids the risk of passivation of the steel slag surface, ensures the stable release of metal cations in the steel slag, and improves efficiency. At the same time, due to the full reaction of hydrogen ions with steel slag, the hydroxide produced by the electrolysis of water at the cathode gradually accumulates, and the overall pH of the system in the electrochemical device rises. Since the hydroxide is provided by the electrolysis of water at the cathode, the system presents a gradient pH from low pH at the anode to high pH at the solution, and then to the extremely high pH at the cathode. Under this premise, carbon dioxide is absorbed into the solution due to the alkalinity of the solution, and forms calcium carbonate with the calcium ions released by the steel slag on the cathode surface, thereby achieving the fixation of carbon dioxide. In addition, other metal cations released, such as iron ions, are easily dissolved in an extremely high pH environment (cathode) by the steel slag. 3+ Tends to react with OH at high pH (solution) - Flocculation and sedimentation. In addition, after the removal of Ca 2+ In the absence of interference, the obtained Fe(OH)3 product can be used as a high-quality raw material for steelmaking or other industries.

[0035] After the electrochemical device is subjected to water electrolysis treatment in the embodiment of the present invention, water molecules undergo oxidation reaction at the anode to generate hydrogen ions. At the same time, due to the full reaction of hydrogen ions with steel slag at the anode, the hydroxide produced by the electrolysis of water at the cathode gradually accumulates, and the overall pH of the system in the electrochemical device rises. Since the hydroxide is provided by the electrolysis of water at the cathode, a gradient pH is presented in the electrochemical device, wherein the pH gradually increases from the anode to the electrolyte and then to the cathode, presenting a gradient pH from low pH at the anode to high pH at the solution and then to extremely high pH at the cathode. Under the premise of forming this gradient pH, efficient carbon fixation and metal recovery of steel slag are achieved.

[0036] Compared with the existing carbon fixation and metal recovery technologies (high temperature and high pressure, numerous steps, and the use of a large number of chemical reagents, etc.), the method in the embodiment of the present invention can achieve efficient carbon fixation and metal recovery of steel slag at room temperature and pressure, in one step, without the addition of chemical reagents. Moreover, on the one hand, the method can be used to seal in situ a large amount of carbon dioxide generated by smelting. On the other hand, the metal recovery and extraction products are reused as high-quality raw materials for smelting, which is expected to achieve low-carbon and sustainable production in the steel industry.

[0037] According to one embodiment of the present invention, the power source has a positive electrode and a negative electrode, the positive electrode of the power source is electrically connected to the anode, and the negative electrode of the power source is electrically connected to the cathode.

[0038] According to one embodiment of the present invention, the steel slag is placed in a porous container, and the porous container is fixed near the anode in the electrochemical device.

[0039] The porous container in the embodiment of the present invention fixes the steel slag near the anode, ensuring efficient reaction of the steel slag with hydrogen ions and avoiding the risk of carbon fixation and passivation on the surface of the steel slag. In addition, the multiple holes on the surface of the porous container enable the metal cations released after acid hydrolysis of the steel slag to be transferred to the electrolyte and the cathode, thereby achieving efficient carbon fixation and metal recovery in the steel slag.

[0040] The filling amount of the steel slag in the embodiment of the present invention depends on the volume of the porous container, and it is necessary to ensure that the filling amount of the steel slag is less than the volume of the porous container and that the effective components in the steel slag can be utilized to the maximum extent. Too little steel slag filling amount will lead to the release of too few effective components of iron ions and calcium ions in the steel slag, which directly affects the effect of metallic iron extraction and carbon dioxide fixation. Excessive steel slag filling amount (or the volume of the porous container), although it can ensure the maximum extraction of iron and fixation of carbon dioxide, may cause too many insulators between the anode and cathode, increase resistance and thus lead to excessive energy consumption.

[0041] According to one embodiment of the present invention, the anode is inserted into the porous container so that the slag is fixed near the anode in the electrochemical device.

[0042] According to one embodiment of the present invention, a constant current process or a constant voltage process is used to electrolyze water on the electrochemical device.

[0043] The electrolytic water treatment in the embodiment of the present invention can be carried out by a constant current process or a constant voltage process. Since the electrochemical high-value method of steel slag of the present invention actually involves "the release and re-precipitation / extraction of iron ions in steel slag" and "the release of calcium ions in steel slag and the capture / precipitation of carbon dioxide", the electrolyte composition in the system does not change much, and its conductivity is relatively stable, so the resistance is relatively stable. Therefore, the function of the system can be realized in both constant current and constant voltage modes.

[0044] According to a preferred embodiment of the present invention, a constant current process is used to electrolyze water in the electrochemical device.

[0045] According to a preferred embodiment of the present invention, the constant current in the constant current process is 10 mA to 400 mA. Within this constant current range, the electrochemical device is subjected to electrolytic water treatment, which can well achieve efficient carbon fixation and metal recovery of steel slag.

[0046] According to one embodiment of the present invention, the components of the steel slag include CaO, FeO and Fe2O3. In the present invention, the main components CaO, FeO and Fe2O3 included in the steel slag are utilized to achieve the release and re-precipitation / extraction of iron ions in the steel slag and the release of calcium ions and the capture / precipitation of carbon dioxide, thereby achieving efficient carbon fixation and metal recovery in the steel slag.

[0047] According to one embodiment of the present invention, the material of the anode is a material that can generate hydrogen ions by oxidizing water molecules at the anode. The material of the anode includes but is not limited to inert metal materials or carbon materials, such as platinum, titanium (and its oxides), ruthenium (and its oxides), iridium, glassy carbon, conductive graphite, doped diamond electrodes, etc.

[0048] According to one embodiment of the present invention, the cathode material is a material that can reduce water molecules to generate hydroxide ions. The cathode material includes but is not limited to metal materials or carbon materials, such as platinum, titanium, nickel, aluminum, copper, stainless steel, conductive graphite, doped diamond electrodes, etc.

[0049] In the present invention, the shapes of the anode and cathode are not particularly limited and may be any known shapes of the existing anode and cathode as long as they can form a water electrolysis circuit to achieve the desired effect.

[0050] According to one embodiment of the present invention, the electrolyte is a sodium salt solution or a potassium salt solution with a concentration of 10 mM to 100 mM.

[0051] In this embodiment, the electrolyte uses a neutral sodium salt solution or potassium salt solution, avoiding the use of common acidic or alkaline electrolytes to provide a neutral initial pH environment, which is helpful to form a gradient pH compared to acidic or alkaline electrolytes. And the electrolyte concentration is set at 10mM to 100mM. Too low a concentration will result in too low conductivity of the system, which will lead to higher energy consumption. And too high a concentration may trigger side reactions. For example, the use of sodium sulfate or potassium salt, its concentration is too high will cause calcium ions and sulfate to precipitate to form gypsum, affecting calcium ion carbon fixation.

[0052] According to a preferred embodiment of the present invention, the electrolyte is a sodium sulfate solution with a concentration of 20 mM.

[0053] In this embodiment, the electrolyte selected from 20 mM sodium sulfate solution has the following advantages: (1) Optimized conductivity: A sodium sulfate solution with a concentration of 20 mM has good conductivity, which can effectively improve the conductivity of the electrolyte and reduce the resistance during the electrolysis process. This helps to improve the electrolysis efficiency and reduce energy consumption. (2) Good chemical stability: Sodium sulfate, as the main component of the electrolyte, has good chemical stability. During the electrolysis process, sodium sulfate is not easy to decompose or react, thereby reducing the consumption of the electrolyte and the generation of by-products, and ensuring the stability and sustainability of the electrolysis process. (3) Moderate initial pH value: The use of a neutral sodium sulfate solution can provide a neutral initial pH environment, which helps to form a gradient pH. (4) Reduced side reactions: Sodium sulfate produces fewer side reactions during the electrolysis process, especially compared to some other salts, it does not generate harmful gases such as chlorine, thereby improving the safety and purity of the electrolysis process.

[0054] According to one embodiment of the present invention, the initial pH of the electrolyte is 3-9. Within this pH range, the best gradient pH effect can be achieved in the system.

[0055] The device for the electrochemical high-value method of steel slag of the present invention is schematically shown as follows: Figure 1 As shown, it includes a power supply 1, a cathode 2, an anode 3, a porous container 4, steel slag 5 and an electrolyte 6, wherein the positive electrode of the power supply 1 is electrically connected to the anode 3, the negative electrode of the power supply 1 is electrically connected to the cathode 2, the steel slag 5 is placed in the porous container 4, the porous container 4 is fixed near the anode 3, the anode 3 is inserted in the porous container 4, and the porous container 4 wraps the anode 3, so as to obtain a device 7 for the electrochemical high-value method of steel slag of the present invention.

[0056] Figure 2 The schematic diagram of the electrochemical high-value method of steel slag provided by the present invention is shown in FIG. After the electrochemical device is powered on, water molecules undergo oxidation reaction on the anode to generate H + and O2 (Formula 1). + The main components of steel slag, ferrous oxide (FeO) and ferric oxide (Fe2O3), undergo acidic dissolution, releasing Fe 2+ and Fe 3+ (Formula 2 and Formula 3), where Fe 2+ After release, it is oxidized to generate Fe 3+ (Formula 4) + Reacts with calcium oxide (CaO), the main component of steel slag, to release Ca 2+ (Formula 5).

[0057] The reaction at the anode:

[0058]

[0059] Fe2O3+6H + →2Fe 3+ +H2O (2)

[0060] FeO+2H + →Fe 2+ +H2O (3)

[0061] 4Fe 2+ +O2+4H + →4Fe 3+ +2H2O (4)

[0062] CaO+2H + →Ca 2+ +H2O (5)

[0063] At the same time, water molecules undergo a reduction reaction at the cathode to generate H2 and OH. - (Formula 6). The OH generated thereby - It is released from the cathode into the electrolyte solution, forming a pH gradient from the cathode to the entire solution. This principle provides a theoretical basis for the selective precipitation and separation of CaCO3 and Fe(OH)3.

[0064] The reaction at the cathode:

[0065] 2H2O+2e - →2OH - +H2↑ (6)

[0066] Based on the above reaction equations at the anode and cathode, the slag reacts with the H generated at the anode. + Reaction, H + Therefore, the OH produced at the cathode - The system is retained, and the overall pH of the system shows an upward trend. In this case, the high pH of the system promotes the absorption of external CO2 and the conversion of CO3 2- Although the pH in this system is high, due to the OH - The Ca2+ released by the slag is released into the solution by the cathode, thus a pH gradient is formed from the cathode to the whole solution. 2+ With CO3 2- Combined to form CaCO3 (Formula 9), thereby fixing CO2. Since Fe(OH)3 is easily soluble in an extremely high pH environment (cathode), the Fe released by the slag 3+ Tends to react with OH at high pH (solution) - Flocculation and sedimentation (Formula 10). 2+In the absence of interference, the obtained Fe(OH)3 product can be used as a high-quality raw material for steelmaking or other industries.

[0067] Reaction in solution:

[0068]

[0069]

[0070] Fe 3+ +3OH - →Fe(OH)3 (10)

[0071] In the present invention, by modifying the specific implementation means (such as electrochemical device design, electrochemical treatment steps, etc.), the same principle is still used to finally realize the electrochemical high value of steel slag. For example, by using different types of steel slag to release effective components with the help of in-situ acid generation by electrolysis of water, it can also be used for carbon fixation and recovery of different types of metals in different forms. However, these modifications do not make the essence of the corresponding technical solutions deviate from the scope of each exemplary technical solution of the present invention.

[0072] The present invention will be further described below by means of specific examples.

[0073] Example 1

[0074] This example explores the effectiveness of releasing metal cations and forming a gradient pH in the electrochemical high-value method of steel slag, as follows:

[0075] Provide a device for electrochemical high-value method of steel slag, reference Figure 1 As shown, the anode of the electrochemical device is a titanium rod loaded with rubidium and iridium, the cathode is stainless steel, and the electrolyte is a 20mM Na2SO4 solution. The electrolyte of this embodiment does not contain HCO3 - 40g of steel slag was crushed to a suitable size and placed in a porous container with a volume of 45mL that wrapped the anode. At the same time, the cathode was fixed together in the electrolytic cell to form a loop, and the electrochemical device was sealed to avoid interference from CO2 in the air. When an external constant current (40mA) was provided, the electrochemical device was powered on to electrolyze water for 1 hour.

[0076] Figure 3 The pH value of the system is shown in the figure. 2+ and Fe 3+ The concentration trends of total inorganic carbon, carbonate and bicarbonate concentrations. Figure 3 Figure a shows the pH change of the system after the electrochemical device is energized for 1 hour. According to this figure, the main components of the slag (CaO, FeO and Fe2O3) and the H generated at the anode+ Reaction, H + is consumed, thus raising the overall pH of the system. Figure 3 Figure b shows the Ca content in the solution after the electrochemical device was energized for 1 hour. 2+ Concentration and Fe 3+ The concentration change diagram shows that the main components (CaO, FeO and Fe2O3) in the slag and the H generated at the anode + Reaction, release of Ca 2+ and Fe 3+ , Ca in solution 2+ and Fe 3+ The concentration gradually increased. Figure 3 Figure c is a graph showing the changes in the concentrations of total inorganic carbon, carbonate and bicarbonate in the solution after the electrochemical device was energized for 1 hour. Since the electrolyte in this embodiment does not contain HCO3 - , the system does not contain any inorganic carbon, so the total inorganic carbon, carbonate and bicarbonate concentrations are all zero. This shows that steel slag can react with the H generated by the anode. + reaction, while releasing Ca 2+ and Fe 3+ to the system, and the system is capable of forming a gradient pH.

[0077] Example 2

[0078] This example explores the effectiveness of efficient carbon fixation and metal recovery in the electrochemical high-value method of steel slag, as follows:

[0079] Provide a device for electrochemical high-value method of steel slag, reference Figure 1 As shown, the anode of the electrochemical device is a titanium rod loaded with rubidium and iridium, the cathode is stainless steel, and the electrolyte is a 20mM Na2SO4 solution. 5mM HCO3 is added to the electrolyte of this embodiment. - , used to simulate the HCO3 formed by the external CO2 being absorbed into the system - 40g of steel slag was crushed to a suitable size and placed in a 45mL porous container that wrapped the anode. At the same time, the cathode was fixed together in the electrolytic cell to form a loop, and the electrochemical device was sealed to avoid interference from CO2 in the air. When an external constant current (40mA) was provided, the electrochemical device was powered on to electrolyze water for 8 hours.

[0080] Figure 4 The pH value of the system is shown in the figure. 2+ and Fe 3+ The concentration trends of total inorganic carbon, carbonate and bicarbonate concentrations. Figure 4Figure a shows the pH change of the system after the electrochemical device is energized for 8 hours. According to the figure, the main components of the slag (CaO, FeO and Fe2O3) and the H generated at the anode + Reaction, H + The system pH is constantly increasing as it is consumed. At this pH, CO2 in the external air can be absorbed into the system to form HCO3 - . Figure 4 Figure b shows the Ca content in the solution after the electrochemical device was energized for 8 hours. 2+ Concentration and Fe 3+ The concentration change diagram shows that the main components (CaO, FeO and Fe2O3) in the slag and the H generated at the anode + Reaction, release of Ca 2+ and Fe 3+ , but due to Ca 2+ and Fe 3+ With CO3 2- and OH - The reaction is consumed, resulting in a relatively low Ca 2+ and Fe 3+ concentration. Figure 4 Figure c is a graph showing the changes in the concentrations of total inorganic carbon, carbonate, and bicarbonate in the solution after the electrochemical device was powered on for 8 hours. It can be seen from this graph that due to the formation of a higher system pH, HCO3 - Gradually converted into CO3 2- , due to the extremely high pH at the cathode, CO3 2- With Ca 2+ Calcium carbonate precipitates are formed on the cathode, and the total inorganic carbon shows a downward trend, ultimately achieving efficient carbon fixation.

[0081] Analyze the products on the cathode after electrolysis of water. Figure 5 Figure a is a schematic diagram of the cathode product. Figure 5 Figure b is the X-ray diffraction diagram of the cathode product, and its X-ray diffraction results show that it is calcium carbonate with high crystallinity. In addition, since Fe(OH)3 is easily soluble in an extremely high pH environment (cathode), the Fe released by the steel slag 3+ Tends to react with OH at high pH (solution) - Flocculation and sedimentation, so the flocculent products in the solution are analyzed. Figure 6 Figure a is a schematic diagram of flocculent products in solution. Figure 6 Figure b is the energy dispersive X-ray spectrum result of the flocculent product in the solution. The result shows that the flocculent product in the solution is iron hydroxide, thus realizing the recovery of metal (iron) in steel slag.

[0082] Example 3

[0083] This example explores the effectiveness of high-efficiency air carbon fixation and metal recovery in the electrochemical high-value method of steel slag, as follows:

[0084] Provide a device for electrochemical high-value method of steel slag, reference Figure 1 As shown, the anode of the electrochemical device is a titanium rod loaded with rubidium and iridium, the cathode is stainless steel, and the electrolyte is a 20mM Na2SO4 solution. Air is introduced into the system at a rate of 0.2L / min using an air pump. 40g of steel slag is crushed to a suitable size and placed in a porous container with a volume of 45mL that wraps the anode. At the same time, the cathode is fixed together in the electrolytic cell to form a loop, and the electrochemical device is sealed to avoid interference from CO2 in the air. When an external constant current (40mA) is provided, the electrochemical device is powered on to electrolyze water for 8 hours.

[0085] Figure 7 The pH value of the system is shown in the figure. 2+ and Fe 3+ The concentration trends of total inorganic carbon, carbonate and bicarbonate concentrations. Figure 7 Figure a shows the pH change of the system after the electrochemical device is energized for 8 hours. According to the figure, the main components (CaO, FeO and Fe2O3) in the known steel slag and the H generated by the anode + Under the premise that the reaction can increase the pH of the system, the pH of the system rises sharply to 10 and then stabilizes at 9.5. This phenomenon shows that CO2 in the air reacts with water (Formula 7) and HCO3 - To CO3 2- The conversion (Equation 8) proceeds smoothly, continuously consuming OH - The pH is lowered and eventually becomes a stable pH. Figure 7 Figure b shows the Ca content in the solution after the electrochemical device was energized for 8 hours. 2+ Concentration and Fe 3+ The concentration change diagram shows that the main components (CaO, FeO and Fe2O3) in the slag and the H generated at the anode + Reaction, release of Ca 2+ and Fe 3+ , and due to Ca 2+ and Fe 3+ With CO3 2- and OH - The reaction is continuously consumed, and the Ca in the system 2+ and Fe 3+ The concentration also tends to be stable. Figure 7Figure c shows the changes in the concentrations of total inorganic carbon, carbonate and bicarbonate in the solution after the electrochemical device was powered on for 8 hours. From this figure, it can be seen that the total inorganic carbon in the system continues to increase as CO2 is continuously introduced and reacts with water. - CO3 converted 2- Rapidly with Ca 2+ Calcium carbonate precipitation forms on the cathode, and CO3 in the system 2- The concentration is close to 0mM, achieving efficient air carbon fixation.

[0086] Analyze the products on the cathode after electrolysis of water. Figure 8 Figure a is a schematic diagram of the cathode product. Figure 8 Figure b is the X-ray diffraction diagram of the cathode product, and its X-ray diffraction results show that it is calcium carbonate with high crystallinity. In addition, since Fe(OH)3 is easily soluble in an extremely high pH environment (cathode), the Fe released by the steel slag 3+ Tends to react with OH at high pH (solution) - Flocculation and sedimentation, so the flocculent products in the solution are analyzed. Fig. 9 It is the energy dispersive X-ray spectrum result of the flocculent product in the solution. The result shows that the flocculent product in the solution is iron hydroxide, thus realizing the recovery of metal (iron) in steel slag.

[0087] In summary, the electrochemical high-value method of steel slag provided by the present invention combines the electrolytic water technology with the steel slag high-value technology, and simultaneously realizes efficient carbon fixation and metal recovery of steel slag. The electrochemical high-value method of steel slag provided by the present invention only needs to be carried out in the same electrochemical device, and does not require high temperature and high pressure, nor does it involve the addition of other chemical reagents, which greatly simplifies the existing steel slag carbon fixation and metal recovery technology, improves the efficiency of the existing method, reduces the economic and environmental burden, and realizes the recycling of steel slag.

[0088] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for electrochemically increasing the value of steel slag, characterized in that: include: Providing an electrochemical device, the electrochemical device comprising a power source, a cathode, an anode and an electrolyte, and fixing the steel slag near the anode in the electrochemical device; The electrochemical device is subjected to electrolytic water treatment, so that the steel slag releases metal cations and forms precipitation through reaction, and calcium cations in the metal cations react with carbon dioxide absorbed by the electrochemical device to form calcium carbonate.

2. The electrochemical high-value method of steel slag according to claim 1, characterized in that: The steel slag is placed in a porous container, and the porous container is fixed near an anode in the electrochemical device.

3. The electrochemical high-value method of steel slag according to claim 1, characterized in that: The electrochemical device is subjected to water electrolysis treatment by adopting a constant current process or a constant voltage process.

4. The electrochemical high-value method of steel slag according to claim 3, characterized in that: The electrochemical device is subjected to water electrolysis treatment by adopting a constant current process, wherein the constant current in the constant current process is 10 mA to 400 mA.

5. The electrochemical high-value method of steel slag according to claim 1, characterized in that: The components of the steel slag include CaO, FeO and Fe2O3.

6. The electrochemical high-value method of steel slag according to claim 1, characterized in that: The material of the anode is a material that can generate hydrogen ions by oxidizing water molecules at the anode.

7. The electrochemical high-value method of steel slag according to claim 6, characterized in that: The material of the anode is an inert metal material or a carbon material.

8. The electrochemical high-value method of steel slag according to claim 1, characterized in that: The material of the cathode is a material that can reduce water molecules to generate hydroxide ions.

9. The electrochemical high-value method of steel slag according to claim 8, characterized in that: The cathode is made of metal or carbon.

10. The electrochemical high-value method of steel slag according to claim 1, characterized in that: The electrolyte is a sodium salt solution or a potassium salt solution with a concentration of 10mM to 100mM.

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