Electrochemical high-value utilization method for steel slag

Abstract

The present invention relates to the technical field of the comprehensive utilization of industrial waste slag, and in particular to an electrochemical high-value utilization method for steel slag. The method comprises: providing an electrochemical device comprising a power supply, a cathode, an anode, and an electrolyte, and fixing the steel slag near the anode in the electrochemical device; and performing water electrolysis treatment on the electrochemical device, so that metal cations are released from the steel slag and react to form a precipitate, calcium cations in the metal cations reacting with carbon dioxide absorbed by the electrochemical device to form calcium carbonate. The method provided by the present invention is carried out in a single reactor, without requiring high temperature and high pressure and without adding other chemical reagents, thereby significantly simplifying existing technology for carbon sequestration and metal recovery from steel slag, improving the efficiency of existing methods, reducing economic and environmental burdens, and realizing efficient carbon sequestration and metal recovery from steel slag in a same system.

Description

An electrochemical method for high-value utilization of steel slag Technical Field

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

[0002] Steel slag, a major byproduct of the steel industry, is considered a promising feedstock for carbon dioxide removal. Theoretically, approximately 413 kg and 368 kg of carbon dioxide can be removed per ton of basic oxygen furnace slag (BOF) and electric arc furnace slag (EAF), respectively. Previous studies on traditional steel slag carbon dioxide sequestration have been conducted, but they are limited by inherent drawbacks such as low utilization rates (due to surface passivation), difficulty in subsequent solid waste treatment, and large quantities of chemical reagents used. For example, patent application CN117865536A discloses a method using water as a medium to generate calcium carbonate from steel slag and introduced carbon dioxide, thereby fixing carbon dioxide. However, in this application, the calcium carbonate formed on the slag surface hinders further carbon dioxide fixation, resulting in low utilization of the steel slag. Furthermore, the steel slag after carbon fixation is still solid waste and requires further treatment. Patent applications CN113979460A and CN115820946A disclose methods for extracting metals from steel slag while simultaneously fixing carbon, but both involve high-temperature, high-pressure, and complex steps, as well as the use of large quantities of chemical reagents. For example, in CN113979460A, ammonium chloride solution is first added to the steel slag for a leaching reaction, yielding a leachate and filter residue. Carbon dioxide is then introduced into the leachate to obtain calcium carbonate, and a small amount of silica and a reducing agent are added to the filter residue, which is then mixed and melted in a high-temperature furnace to obtain metallic iron. Similarly, CN115820946A uses ammonium chloride solution to leach free calcium oxide from the steel slag, yielding a filter residue and a first leaching solution, which is then used for carbon dioxide absorption. The filter residue is then leached again with ammonium chloride solution to obtain a second leaching residue and a crude mineralized solution. This crude mineralized solution undergoes oxidation, alkali adjustment, and solid-liquid separation to obtain iron-aluminum precipitates and a second mineralized solution, which is then used for carbon dioxide absorption. Finally, the iron and aluminum precipitate was leached using sodium hydroxide solution to achieve iron-aluminum separation. It is evident that most existing methods only achieve basic steel slag carbon fixation, neglecting their limited efficiency and the complexity of subsequent solid waste treatment. While a few methods have achieved steel slag carbon fixation and metal recovery, their complex processes and the need for large amounts of chemical reagents limit their practical feasibility.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an electrochemical high-value recovery method for steel slag, which aims to solve the problems of low efficiency, complex process and large amount of chemical reagents required in existing methods that simultaneously achieve carbon fixation and metal recovery of steel slag.

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

[0006] This invention provides an electrochemical method for the high-value utilization of steel slag, comprising:

[0007] An electrochemical device is provided, the electrochemical device including a power source, a cathode, an anode and an electrolyte, wherein steel slag is fixed near the anode in the electrochemical device;

[0008] The electrochemical device is used to treat water by electrolysis, which causes the steel slag to release metal cations and form precipitates through reaction. The calcium cations in the metal cations react with the 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 the anode in the electrochemical device.

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

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

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

[0013] Optionally, the anode material is a material capable of generating hydrogen ions from water molecules through anodic oxidation.

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

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

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

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

[0018] Beneficial Effects: This invention provides an electrochemical method for the high-value recovery of steel slag. By utilizing the acid-producing characteristics of the anode in water electrolysis within a single electrochemical device, metal cations (calcium ions, iron ions, etc.) in the steel slag can be released into the system in a controllable and efficient manner. Simultaneously, by utilizing the alkali-producing characteristics of the cathode in water electrolysis and the creation of a pH gradient in the system, the released metal cations can be selectively used for carbon dioxide fixation and metal recovery. The electrochemical process involved in this invention is carried out in a single reactor and does not require high temperature, high pressure, or the addition of other chemical reagents. This greatly simplifies existing technologies for carbon fixation and metal recovery from steel slag, improves the efficiency of existing methods, reduces economic and environmental burdens, and achieves highly efficient carbon fixation and metal recovery from steel slag within a single system. Attached Figure Description

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

[0020] Figure 2 is a schematic diagram of the electrochemical high-value utilization method for steel slag provided by the present invention.

[0021] Figure 3a shows the pH change of the system after 1 hour of electrochemical treatment using the device in Example 1, and Figure 3b shows the Ca content in the solution after 1 hour of electrochemical treatment using the device in Example 1. 2+ Concentration and Fe 3+ The concentration change graph, Figure 3c shows the change in the concentration of total inorganic carbon, carbonate and bicarbonate in the solution after 1 hour of electrochemical treatment using an electrochemical device in Example 1.

[0022] Figure 4a shows the pH change of the system after 8 hours of electrochemical treatment using the electrochemical device in Example 2, and Figure 4b shows the Ca content in the solution after 8 hours of electrochemical treatment using the electrochemical device in Example 2. 2+ Concentration and Fe 3+ The concentration change graph, Figure 4c shows the change in the concentration of total inorganic carbon, carbonate and bicarbonate in the solution after 8 hours of electrochemical treatment with an electrochemical device in Example 2.

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

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

[0025] Figure 7a shows the pH change of the system after 8 hours of electrochemical treatment using the device in Example 3, and Figure 7b shows the Ca content in the solution after 8 hours of electrochemical treatment using the device in Example 3. 2+ Concentration and Fe 3+The concentration change graph, Figure 7c shows the change in the concentrations of total inorganic carbon, carbonate and bicarbonate in the solution after 8 hours of electrochemical treatment using an electrochemical device in Example 3.

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

[0027] Figure 9 shows the energy dispersive X-ray spectroscopy results of the flocculent products in the solution in Example 3. Detailed Implementation

[0028] This invention provides an electrochemical method for the high-value utilization of steel slag. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] Water electrolysis technology can decompose water molecules into hydrogen and oxygen using direct current, and provide hydrogen ions (H+) at the anode and cathode, respectively. + ) and hydroxide ions (OH) - Water electrolysis technology is currently widely used in various scenarios such as hydrogen production, water disinfection, and electrochemically induced precipitation. Inspired by its working principle, this invention innovatively combines water electrolysis technology with steel slag high-value utilization technology, achieving efficient, one-step, and chemical reagent-free steel slag carbon fixation and metal recovery based on water electrolysis technology.

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

[0031] S1. Provide an electrochemical device, the electrochemical device including a power source, a cathode, an anode and an electrolyte, and fix the steel slag near the anode in the electrochemical device;

[0032] S2. Electrolyze water using the electrochemical device to release metal cations from the steel slag and form precipitates through a reaction. The calcium cations in the metal cations react with the carbon dioxide absorbed by the electrochemical device to form calcium carbonate.

[0033] The key innovation of this invention lies in its ingenious utilization of the acid-producing characteristic of the anode in water electrolysis to achieve controllable and efficient extraction of effective components (calcium, iron, etc.) from steel slag. Simultaneously, by combining the characteristics of alkali production at the cathode and the creation of a pH gradient in the same system, the effective components are selectively used for carbon dioxide fixation and metal recovery and extraction.

[0034] In this embodiment of the invention, after the electrochemical device treats water by electrolysis, the hydrogen ions generated by the anode electrolysis are used to decompose steel slag in situ. To ensure efficient reaction between the steel slag and hydrogen ions, the steel slag is fixed near the anode. Based on this principle, the main components of the steel slag (such as calcium ions and iron ions) are released in a controllable and continuous manner. More importantly, the steel slag is fixed in the always acidic anode region, where acidolysis occurs on its surface instead of carbon fixation, avoiding the risk of surface passivation and ensuring the stable release of metal cations from the steel slag, thus improving efficiency. Simultaneously, due to the full reaction of hydrogen ions with the steel slag, hydroxide ions generated by the cathode electrolysis gradually accumulate, causing the overall pH of the system in the electrochemical device to rise. Since hydroxide ions are provided by the cathode electrolysis reaction, the system exhibits a pH gradient from low pH at the anode to high pH in the solution, and then to extremely high pH at the cathode. Under this condition, carbon dioxide is absorbed into the solution due to the alkalinity of the solution and forms calcium carbonate with the calcium ions released from the steel slag on the cathode surface, thus achieving carbon dioxide fixation. In addition, other released metal cations, such as iron ions, are released from steel slag because Fe(OH)3 is easily dissolved in an extremely high pH environment (cathode). 3+ It tends to react with OH- in high pH conditions (solution) - Flocculation and sedimentation. Furthermore, after excluding Ca... 2+ Under conditions of interference, the obtained Fe(OH)3 product can be used as a high-quality raw material for steelmaking or other industries.

[0035] In this embodiment of the invention, after water electrolysis in the electrochemical device, water molecules undergo an oxidation reaction at the anode to generate hydrogen ions. Simultaneously, due to the full reaction of hydrogen ions with the steel slag at the anode, hydroxide ions generated from water electrolysis at the cathode gradually accumulate, causing an overall increase in the pH of the system within the electrochemical device. Since hydroxide ions are provided by the water electrolysis reaction at the cathode, a pH gradient is observed within the electrochemical device. Specifically, the pH gradually increases from the anode to the electrolyte and then to the cathode, exhibiting a gradient from low pH at the anode to high pH in the solution, and finally to extremely high pH at the cathode. Under the premise of this pH gradient, efficient carbon fixation and metal recovery from steel slag are achieved.

[0036] Compared with existing carbon fixation and metal recovery technologies (which involve high temperature and pressure, numerous steps, and the use of large amounts of chemical reagents), the method in this invention can achieve efficient carbon fixation and metal recovery from steel slag in one step at room temperature and pressure without the addition of chemical reagents. Furthermore, on the one hand, this method can be used to in-situ solidify the large amounts of carbon dioxide generated during smelting. On the other hand, the recovered metal extract can be reused as a high-quality raw material in smelting, potentially achieving low-carbon and sustainable production in the steel industry.

[0037] According to one embodiment of the present invention, the power supply has a positive terminal and a negative terminal, the positive terminal of the power supply being electrically connected to the anode and the negative terminal of the power supply being electrically connected to the cathode.

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

[0039] In this embodiment of the invention, the porous container fixes the steel slag near the anode, ensuring the efficient reaction between the steel slag and hydrogen ions and avoiding the risk of carbon passivation on the surface of the steel slag. Furthermore, the multiple pores on the surface of the porous container allow the metal cations released after acid hydrolysis of the steel slag to transfer to the vicinity of the electrolyte and the cathode, thereby achieving efficient carbon fixation and metal recovery from the steel slag.

[0040] In this embodiment of the invention, the amount of steel slag filling depends on the volume of the porous container. It is necessary to ensure that the amount of steel slag filling is less than the volume of the porous container while maximizing the utilization of the effective components in the steel slag. Insufficient steel slag filling will result in the release of too few effective components, iron and calcium ions, directly affecting the extraction of metallic iron and the fixation of carbon dioxide. Conversely, excessive steel slag filling (or the volume of the porous container), while ensuring maximum iron extraction and carbon dioxide fixation, may lead to excessive insulation between the anode and cathode, increasing resistance and resulting in excessive energy consumption.

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

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

[0043] The electrolytic water treatment in this embodiment of the invention can be carried out using a constant current process or a constant voltage process. Since the electrochemical high-value utilization method of steel slag in this invention actually involves "the release and reprecipitation / extraction of iron ions in steel slag" and "the release of calcium ions in steel slag and the capture / precipitation of carbon dioxide", the composition of the electrolyte in the system does not change much, its conductivity is relatively stable, and therefore its resistance is relatively stable. Thus, 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, the electrochemical device is used to perform water electrolysis treatment using a constant current process.

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

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

[0047] According to one embodiment of the present invention, the anode material is a material capable of generating hydrogen ions from anodic oxidation of water molecules. The anode material 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, electrically conductive graphite, and doped diamond electrodes.

[0048] According to one embodiment of the present invention, the cathode is made of a material capable of generating hydroxide ions from water molecules reduced at the cathode. The cathode material includes, but is not limited to, metallic or carbonaceous materials, such as platinum, titanium, nickel, aluminum, copper, stainless steel, electrically conductive graphite, and diamond-doped electrodes.

[0049] In this invention, the shapes of the anode and cathode are not particularly limited and can be any known shape of existing anodes and cathodes, as long as they can form an electrolysis circuit to achieve the desired function.

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

[0051] In this embodiment, a neutral sodium or potassium salt solution is used as the electrolyte, avoiding the use of common acidic or alkaline electrolytes, to provide a neutral initial pH environment. This helps to form a pH gradient compared to acidic or alkaline electrolytes. Furthermore, the electrolyte concentration is set between 10 mM and 100 mM. Too low a concentration will result in excessively low system conductivity, leading to higher energy consumption. Too high a concentration may trigger side reactions; for example, using sodium or potassium sulfate at excessively high concentrations can cause calcium ions to precipitate with sulfate ions, forming gypsum and affecting calcium 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 use of a 20mM sodium sulfate solution as the electrolyte has the following advantages: (1) Optimized conductivity: A 20mM sodium sulfate solution 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 in the electrolyte, has good chemical stability. During the electrolysis process, sodium sulfate is not easily decomposed or reacted, thereby reducing the consumption of electrolyte and the generation of by-products, ensuring the stability and continuity of the electrolysis process. (3) Moderate initial pH value: Using 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. In particular, compared with 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 which the optimal gradient pH effect can be achieved in the system.

[0055] Figure 1 shows a schematic diagram of the apparatus for the electrochemical high-value recovery method of steel slag according to the present invention. It includes a power source 1, a cathode 2, an anode 3, a porous container 4, steel slag 5, and an electrolyte 6. The positive terminal of the power source 1 is electrically connected to the anode 3, and the negative terminal of the power source 1 is electrically connected to the cathode 2. The steel slag 5 is placed in the porous container 4, which is fixed near the anode 3. The anode 3 is inserted into the porous container 4, and the porous container 4 encloses the anode 3, thus obtaining the apparatus 7 for the electrochemical high-value recovery method of steel slag according to the present invention.

[0056] Figure 2 is a schematic diagram of an electrochemical method for the high-value utilization of steel slag provided by this invention. After energizing the electrochemical device, water molecules undergo an oxidation reaction at the anode, generating H₂. + With O2 (Equation 1). H + This causes the main components of steel slag, ferrous oxide (FeO) and ferric oxide (Fe2O3), to undergo acidic dissolution, releasing Fe. 2+ and Fe 3+ (Equations 2 and 3), where Fe 2+ It is oxidized immediately after release, producing Fe. 3+ (Equation 4). H + It reacts with calcium oxide (CaO), the main component of steel slag, to release Ca. 2+ (Equation 5).

[0057] The reaction at the anode: Fe2O3+6H + →2Fe 3+ +H₂O(2) FeO+2H +→Fe 2+ +H₂O(3) 4Fe 2+ +O2+4H + →4Fe 3+ +2H₂O(4) CaO+2H + →Ca 2+ +H2O(5)

[0058] At the same time, water molecules undergo a reduction reaction at the cathode, producing H2 and OH. - (Equation 6). The resulting OH... - The electrolyte solution is released from the cathode, creating a pH gradient from the cathode to the overall solution. This principle provides a theoretical basis for the selective precipitation and separation of CaCO3 and Fe(OH)3.

[0059] The reaction at the cathode: 2H₂O + 2e⁻ - →2OH - +H2↑(6)

[0060] Based on the above-described reactions occurring at the anode and cathode, the steel slag reacts with the H produced at the anode... + The reaction, H in the system + It is consumed. Therefore, the OH produced at the cathode - This allows the system's overall pH to rise. Under these conditions, the higher pH promotes the absorption of external CO2 and the conversion of CO3. 2- The conversion (Equations 7 and 8). Although the pH is high in this system, due to OH... - The slag is released into the solution from the cathode, thus creating a pH gradient from the cathode to the overall solution. On the cathode surface, due to the extremely high pH environment, the calcium released from the steel slag... 2+ With CO3 2- The Fe(OH)3 combines to form CaCO3 (Equation 9), thereby fixing CO2. Since Fe(OH)3 readily dissolves in extremely high pH conditions (cathode), the Fe released from the steel slag... 3+ It tends to react with OH- in high pH conditions (solution) - Flocculation and sedimentation (Equation 10). Furthermore, after excluding Ca... 2+ Under conditions of interference, the obtained Fe(OH)3 product can be used as a high-quality raw material for steelmaking or other industries.

[0061] Reaction in solution: Fe 3+ +3OH - →Fe(OH)3(10)

[0062] In this invention, by modifying specific implementation methods (such as electrochemical device design and electrochemical treatment steps), the same principle is ultimately used to achieve the electrochemical high-value utilization of steel slag. For example, by utilizing different types of steel slag to release effective components with the help of in-situ acid production during water electrolysis, it can also be used for carbon fixation and the recovery of different types of metals in different forms. These modifications do not cause the essence of the corresponding technical solutions to deviate from the scope of the various exemplary technical solutions of this invention.

[0063] The present invention will be further described below through specific embodiments.

[0064] Example 1

[0065] This embodiment explores the effectiveness of the electrochemical high-value recovery method for steel slag in releasing metal cations and forming a pH gradient in the system, as detailed below:

[0066] An apparatus for electrochemical high-value recovery of steel slag is provided, as shown in Figure 1. The anode in the electrochemical apparatus is a rubidium-iridium supported titanium rod, the cathode is stainless steel, and the electrolyte is a 20 mM Na₂SO₄ solution. In this embodiment, the electrolyte does not contain HCO₃⁻. - 40g of steel slag was crushed to a suitable size and placed in a 45mL porous container surrounding the anode. Simultaneously, the cathode was fixed in the electrolytic cell to form a circuit. The electrochemical device was sealed to prevent interference from CO2 in the air. With an external constant current (40mA) supplied, the electrochemical device was energized to electrolyze water for 1 hour.

[0067] Figure 3 shows the pH change of the system and the Ca in the solution. 2+ and Fe 3+ The trends in concentration changes, specifically the trends in total inorganic carbon, carbonate, and bicarbonate concentrations. Figure 3a shows the pH change of the system after 1 hour of electrochemical treatment. According to this figure, the main components of the steel slag (CaO, FeO, and Fe2O3) react with the H2O generated at the anode. + The reaction, H in the system + The calcium is consumed, thus increasing the overall pH of the system. Figure 3b shows the Ca concentration in the solution after 1 hour of electrochemical treatment. 2+ Concentration and Fe 3+ The concentration change graph shows that the main components of the steel slag (CaO, FeO, and Fe2O3) react with the H2 produced at the anode. + The reaction releases Ca 2+ and Fe 3+ Ca in the solution 2+ and Fe 3+The concentration gradually increased. Figure 3c shows the changes in the concentrations of total inorganic carbon, carbonate, and bicarbonate in the solution after 1 hour of electrochemical treatment. Since the electrolyte in this example does not contain HCO3-... - The system contains no inorganic carbon, therefore the concentrations of total inorganic carbon, carbonate, and bicarbonate are all zero. This demonstrates that the steel slag can react with the H₂ produced at the anode. + The reaction simultaneously releases Ca. 2+ and Fe 3+ The system is incorporated into the system, and the system is capable of forming a pH gradient.

[0068] Example 2

[0069] This embodiment explores the efficiency of high-efficiency carbon fixation and metal recovery in the electrochemical high-value utilization method of steel slag, as detailed below:

[0070] An apparatus for electrochemical high-value recovery of steel slag is provided, as shown in Figure 1. The anode in the electrochemical apparatus is a rubidium-iridium supported titanium rod, the cathode is stainless steel, and the electrolyte is a 20 mM Na₂SO₄ solution. In this embodiment, 5 mM HCO₃ is added to the electrolyte. - This is used to simulate the absorption of external CO2 into the system to form HCO3. - 40g of steel slag was crushed to a suitable size and placed in a 45mL porous container surrounding the anode. Simultaneously, the cathode was fixed in the electrolytic cell to form a circuit. The electrochemical device was sealed to prevent interference from CO2 in the air. With an external constant current (40mA) supplied, the electrochemical device was energized for water electrolysis for 8 hours.

[0071] Figure 4 shows the pH change of the system and the Ca in the solution. 2+ and Fe 3+ The trends in concentration changes, specifically the trends in total inorganic carbon, carbonate, and bicarbonate concentrations. Figure 4a shows the pH changes in the system after 8 hours of electrochemical treatment. According to this figure, the main components of the steel slag (CaO, FeO, and Fe2O3) react with the H2O generated at the anode. + The reaction, H in the system + As the system continues to consume CO2, its pH level rises. At this pH, CO2 from the outside air can be absorbed into the system to form HCO3-. - Figure 4b shows the Ca concentration in the solution after 8 hours of electrochemical treatment. 2+ Concentration and Fe 3+ The concentration change graph shows that the main components of the steel slag (CaO, FeO, and Fe2O3) react with the H2 produced at the anode. + The reaction releases Ca 2+ and Fe 3+However, due to Ca 2+ and Fe 3+ respectively with CO3 2- and OH - The reaction consumes the energy, resulting in relatively low Ca concentrations in the system. 2+ and Fe 3+ Concentration. Figure 4c shows the changes in the concentrations of total inorganic carbon, carbonate, and bicarbonate in the solution after 8 hours of electrochemical treatment. According to this figure, 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 precipitate forms on the cathode, and the total inorganic carbon shows a decreasing trend, ultimately achieving efficient carbon fixation.

[0072] The products on the cathode after water electrolysis were analyzed. Figure 5a shows a schematic diagram of the cathode products, and Figure 5b shows the X-ray diffraction pattern of the cathode products. The X-ray diffraction results show that they are highly crystalline calcium carbonate. Furthermore, since Fe(OH)3 is easily dissolved in an extremely high pH environment (cathode), the Fe released from the steel slag... 3+ It tends to react with OH- in high pH conditions (solution) - Flocculation and sedimentation occur, so the floc products in the solution are analyzed. Figure 6a is a schematic diagram of the floc products in the solution, and Figure 6b is the energy dispersive X-ray spectroscopy result of the floc products in the solution. The results show that the floc products in the solution are ferric hydroxide, thus realizing the recovery of metal (iron) from steel slag.

[0073] Example 3

[0074] This embodiment explores the efficiency of high-efficiency air carbon sequestration and metal recovery in the electrochemical high-value utilization method of steel slag, as detailed below:

[0075] An apparatus for electrochemically refining steel slag is provided, as shown in Figure 1. The anode in the electrochemical apparatus is a rubidium-iridium supported titanium rod, the cathode is stainless steel, and the electrolyte is a 20 mM Na₂SO₄ solution. Air is introduced into the system at a rate of 0.2 L / min using an air pump. 40 g of steel slag is crushed to a suitable size and placed in a 45 mL porous container surrounding the anode. Simultaneously, the cathode is fixed in the electrolytic cell to form a circuit. The electrochemical apparatus is sealed to prevent interference from CO₂ in the air. Electrolysis of water is performed for 8 hours with an external constant current (40 mA).

[0076] Figure 7 shows the pH change of the system and the Ca in the solution. 2+ and Fe 3+The trends in concentration changes, specifically the trends in the concentrations of total inorganic carbon, carbonate, and bicarbonate. Figure 7a shows the pH changes in the system after 8 hours of electrochemical treatment. According to this figure, the main components of the known steel slag (CaO, FeO, and Fe2O3) react with the H2O generated at 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 indicates that CO2 in the air reacts with water (Equation 7) and HCO3. - To CO3 2- The conversion (Equation 8) proceeded smoothly, continuously consuming OH-. - The pH was lowered until a stable pH was reached. Figure 7b shows the Ca concentration in the solution after 8 hours of electrochemical treatment. 2+ Concentration and Fe 3+ The concentration change graph shows that the main components of the steel slag (CaO, FeO, and Fe2O3) react with the H2 produced at the anode. + The reaction releases Ca 2+ and Fe 3+ And because of Ca 2+ and Fe 3+ respectively with CO3 2- and OH - The reaction continues to consume Ca in the system. 2+ and Fe 3+ The concentrations also tended to stabilize. Figure 7c shows the changes in the concentrations of total inorganic carbon, carbonate, and bicarbonate in the solution after 8 hours of electrochemical treatment. According to this figure, the total inorganic carbon concentration continuously increased due to the continuous introduction of CO2 and its reaction with water. (The text then abruptly shifts to a seemingly unrelated topic about HCO3.) - CO3 derived from conversion 2- Quickly with Ca 2+ Calcium carbonate precipitate forms on the cathode, and CO3 is present in the system. 2- With a concentration close to 0 mM, efficient air carbon sequestration is achieved.

[0077] The products on the cathode after water electrolysis were analyzed. Figure 8a shows a schematic diagram of the cathode products, and Figure 8b shows the X-ray diffraction pattern of the cathode products. The X-ray diffraction results show that they are highly crystalline calcium carbonate. Furthermore, since Fe(OH)3 is easily dissolved in an extremely high pH environment (cathode), the Fe released from the steel slag... 3+ It tends to react with OH- in high pH conditions (solution) - Flocculation and sedimentation were observed, and the floc products in the solution were analyzed. Figure 9 shows the energy dispersive X-ray spectroscopy results of the floc products in the solution. The results show that the floc products in the solution are ferric hydroxide, thus realizing the recovery of metal (iron) from steel slag.

[0078] In summary, the electrochemical high-value recovery method for steel slag provided by this invention combines water electrolysis technology and steel slag high-value recovery technology, simultaneously achieving efficient carbon fixation and metal recovery from steel slag. This method requires only a single electrochemical apparatus, eliminates the need for high temperature and pressure, and avoids the addition of other chemical reagents, significantly simplifying existing steel slag carbon fixation and metal recovery technologies, improving the efficiency of existing methods, reducing economic and environmental burdens, and enabling the reuse of steel slag.

[0079] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An electrochemical high-value method of steel slag, characterized by, The application relates to a method for treating steel slag, and belongs to the technical field of environmental protection. Providing an electrochemical device, which comprises a power source, a cathode, an anode and an electrolyte, fixing the steel slag near the anode in the electrochemical device; Carrying out electrolytic water treatment on the electrochemical device, 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.

2. The method of electrochemically upgrading steel slag according to claim 1, characterized by, Fixing the steel slag in a porous container, and fixing the porous container near the anode in the electrochemical device.

3. The method of electrochemically upgrading steel slag according to claim 1, characterized in that, Carrying out electrolytic water treatment on the electrochemical device by adopting a constant current process or a constant voltage process.

4. The method of electrochemically upgrading steel slag according to claim 3, characterized by, Carrying out electrolytic water treatment on the electrochemical device by adopting a constant current process, and the constant current in the constant current process is 10 mA-400 mA.

5. The method of electrochemically upgrading steel slag according to claim 1, characterized in that, The components of the steel slag include CaO, FeO and Fe2O3.

6. The method of electrochemically upgrading steel slag according to claim 1, characterized in that, The material of the anode is a material capable of making the anode oxidize water molecules to generate hydrogen ions.

7. The method of electrochemically upgrading steel slag according to claim 6, characterized in that, The material of the anode is inert metal material or carbon material.

8. The method of electrochemically upgrading steel slag according to claim 1, characterized in that, The material of the cathode is a material capable of making the cathode reduce water molecules to generate hydroxyl ions.

9. The method of electrochemically upgrading steel slag according to claim 8, characterized in that, The material of the cathode is metal material or carbon material.

10. The method of electrochemically upgrading 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 10 mM-100 mM.

Images