Method for in-situ preparation of building materials by using marine resources and cyclic utilization method

Abstract

The embodiment of the invention provides a method for in-situ preparation of a building material by using marine resources and a cyclic utilization method.The method for in-situ preparation of the building material by using the marine resources comprises the following steps that an electrolytic tank is adopted to electrolyze seawater, and the pH value of a cathode region of the electrolytic tank is controlled to be within a preset range; precipitating magnesium ions in the seawater to generate magnesium hydroxide; treating the precipitated magnesium hydroxide to obtain a magnesium-based building material precursor; the magnesium-based building material is prepared by mixing the magnesium-based building material precursor with solid wastes generated by seawater, sea sand or marine resource development. According to the method for in-situ preparation of the building material by using the marine resources and the cyclic utilization method provided by the embodiment of the invention, the magnesium resource is extracted from the seawater through electrolysis to prepare the magnesium-based building material, and the magnesium resource extracted by the method is combined with solid wastes generated by seawater and sea sand or marine resource development; in-situ preparation of the building materials under offshore and open sea conditions is achieved, and effective recovery of the building materials is achieved.

Description

Technical Field

[0001] This application belongs to the field of seawater resource utilization and building material preparation technology, and particularly relates to a method for in-situ preparation and recycling of building materials using marine resources. Background Technology

[0002] At present, the construction of marine infrastructure mainly relies on traditional calcium-based building materials, such as silicate cement and corresponding concrete products. However, for offshore marine infrastructure and remote islands where there is a lack of traditional building material production resources and capabilities, it is necessary to rely on land-based resources to prepare building materials and transport them over long distances. This mode of transportation is not only energy-intensive and expensive, but also difficult to achieve long-term independent operation and maintenance.

[0003] The current lack of building material production and recycling technologies specifically designed for marine environments further restricts the sustainable development of marine infrastructure construction. Summary of the Invention

[0004] In view of this, embodiments of this application provide a method for in-situ preparation of building materials using marine resources and a method for recycling, in order to solve the current market problem of a lack of technical solutions for the preparation and recycling of building materials specifically suitable for marine environments.

[0005] In a first aspect, embodiments of this application provide a method for in-situ preparation of building materials using marine resources, comprising the following steps: Seawater is electrolyzed using an electrolytic cell, and the pH value of the cathode area of ​​the electrolytic cell is controlled within a preset range, so that magnesium ions in the seawater precipitate to form magnesium hydroxide. The precipitated magnesium hydroxide is dried or calcined into magnesium oxide to obtain a precursor for magnesium-based building materials. Magnesium-based building material precursors are mixed with seawater, sea sand, or solid waste generated from marine resource development to prepare magnesium-based building materials.

[0006] In some embodiments, the magnesium-based building material precursor is magnesium hydroxide or magnesium oxide.

[0007] In some embodiments, the preparation of the magnesium-based building material includes: Magnesium hydroxide is directly carbonized and solidified to prepare magnesium carbonate-based building materials.

[0008] In some embodiments, the preparation of the magnesium-based building material includes: Magnesium hydroxide was mixed with seawater and sea sand, and a silicon source and an alkaline activator were added to prepare an alkali-activated magnesium-based cementitious material.

[0009] In some embodiments, the preparation of the magnesium-based building material includes: Magnesium hydroxide is dried or calcined to obtain magnesium oxide, which is then mixed with magnesium chloride or magnesium sulfate to prepare magnesium oxychloride cement or magnesium oxysulfate cement.

[0010] In some embodiments, the electrolytic cell includes an anode region, a cathode region, and a cation exchange membrane, the cation exchange membrane separating the anode region and the cathode region; The pH value of the cathode region is 8-10.

[0011] In some embodiments, the anode material of the electrolytic cell is platinum-plated porous carbon, high-silicon cast iron, or titanium-based oxide, and the cathode material is zinc-plated porous carbon foam, graphite, or low-carbon steel.

[0012] In some embodiments, the method further includes a step of recycling oxygen, hydrogen, and chlorine generated during electrolysis as byproducts.

[0013] Secondly, embodiments of this application provide a recycling method, comprising the following steps: The waste magnesium-based building materials are crushed and then fed into the anode region of the electrolytic cell described in the first aspect. In the anode region, an acidic environment is generated through an anodic reaction, causing magnesium ions to precipitate from the building materials; The magnesium ion-containing solution migrates through the cation exchange membrane to the cathode region, where the magnesium ions are redeposited as magnesium hydroxide. Reuse magnesium hydroxide to prepare new magnesium-based building materials.

[0014] In some embodiments, the acidic environment of the anode region is generated by an anodic oxygen evolution reaction or a chlorine evolution reaction.

[0015] In some embodiments, the pH value of the anode region is controlled between 0 and 7 to allow magnesium ions in the magnesium-based building materials to be fully released.

[0016] In some embodiments, the waste magnesium-based building materials may also include solid waste generated from marine resource development, such as fibers, slag, and coral reefs.

[0017] The methods for in-situ preparation and recycling of building materials using marine resources provided in this application cover marine resource extraction, magnesium-based building material preparation, and waste building material recycling. Magnesium resources are extracted from seawater via electrolysis to prepare magnesium-based building materials. The magnesium resources extracted by this method are combined with seawater, sea sand, or solid waste generated from marine resource development to achieve in-situ preparation of building materials under near-shore and offshore conditions. Finally, the same electrolysis device is used to effectively recycle the building materials, thus forming a complete system for the full utilization of marine resources. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic flowchart of a method for in-situ preparation of building materials using marine resources, provided in an embodiment of this application. Figure 2 This is a schematic diagram of the electrolytic cell in the method for in-situ preparation of building materials using marine resources provided in the embodiments of this application; Figure 3 This is a flowchart illustrating the recycling method provided in the embodiments of this application. Detailed Implementation

[0020] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that the embodiments of this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the embodiments of this application with unnecessary detail.

[0021] It should also be understood that the term "and / or" as used in the specification of embodiments of this application and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0022] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0023] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0024] Furthermore, in the description of the embodiments and the appended claims of this application, the terms "first," "second," "third," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0025] In the description of embodiments in this application, references to "some embodiments" or "some embodiments" mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in some embodiments," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiments, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized. "A plurality" refers to two or more.

[0026] In existing technologies, conventional methods for extracting magnesium from the ocean typically involve adding alkaline substances such as quicklime, ammonium hydroxide, or sodium hydroxide to the solution to raise the pH value, causing magnesium ions to precipitate as magnesium hydroxide. Sodium hydroxide is inherently expensive, and after purification, the solute is primarily sodium chloride, resulting in low added value. When using cheaper quicklime as a precipitant, the calcium hydroxide produced by hydration has low solubility in water and easily mixes into the magnesium hydroxide product, making separation difficult. Furthermore, quicklime is usually produced by calcining limestone, a process accompanied by significant direct and indirect energy consumption and carbon emissions. In addition to the above problems, the use of ammonium hydroxide inevitably generates toxic and harmful ammonia gas during its use.

[0027] However, existing electrolysis technologies primarily focus on the rapid extraction of magnesium resources from seawater, which is relatively singular and lacks integration with the resource utilization and recycling processes in the construction materials industry. They merely utilize the cathode reaction to precipitate magnesium ions, neglecting the large amount of acidic solution generated during the corresponding anodic reaction, which cannot be properly treated. This fails to meet the needs of sustainable development. Besides direct discharge, simply neutralizing the acidic solution at the cathode with alkaline solution and then discharging it directly is a waste of resources; recovering the acid only yields low-concentration hydrochloric acid, making true commercialization difficult.

[0028] Based on this, embodiments of this application provide a method for in-situ preparation and recycling of building materials using marine resources, covering marine resource extraction, magnesium-based building material preparation, and waste building material recycling. Magnesium resources are extracted from seawater via electrolysis to prepare magnesium-based building materials. The magnesium resources extracted using this method are combined with seawater sand or solid waste generated from marine resource development to achieve in-situ preparation of building materials under near-shore and offshore conditions. Finally, the same electrolysis device is used to effectively recycle the building materials, thus forming a complete system for the full utilization of marine resources.

[0029] The first aspect of this application provides a method for in-situ preparation of building materials using marine resources, such as... Figure 1 As shown, it includes the following steps: S10. Electrolyze seawater using an electrolytic cell and control the pH value of the cathode area of ​​the electrolytic cell within a preset range so that magnesium ions in the seawater precipitate to form magnesium hydroxide. S20. The precipitated magnesium hydroxide is dried or calcined into magnesium oxide to obtain a magnesium-based building material precursor. S30. Magnesium-based building material precursors are mixed with seawater, sea sand, or solid waste generated from marine resource development to prepare magnesium-based building materials.

[0030] The method for in-situ preparation and recycling of building materials using marine resources provided in this application adopts electrolysis to replace the traditional chemical precipitation process of adding quicklime, sodium hydroxide, or ammonium hydroxide to seawater. By directly controlling the pH value of the cathode area in the electrolytic cell, magnesium ions are selectively precipitated as magnesium hydroxide, completely avoiding the following defects: Sodium hydroxide has high raw material costs, and after purification, it only produces low-value-added sodium chloride; calcium hydroxide obtained from the hydration of quicklime has low solubility and easily mixes into magnesium hydroxide products, forming impurities; the use of ammonium hydroxide releases ammonia gas, posing occupational health hazards. Electrolysis, through an electrochemical reaction, generates an alkaline environment in situ, eliminating the need for external precipitants and fundamentally solving the above problems.

[0031] In applications, existing electrolysis technologies only focus on magnesium ion precipitation (Mg) in the cathode region. 2+ +2OH - =Mg(OH)2↓), while the acidic solutions (such as HCl and H2O2) generated in the anode area are often directly discharged or inefficiently neutralized. This solution achieves resource utilization through the following innovation: utilizing the acidic environment generated in the anode area to dissolve and recover (magnesium-based) construction waste, avoiding the direct discharge of acidic solutions, utilizing products that are difficult to commercialize, and realizing a closed-loop pathway.

[0032] Traditional electrolysis only extracts magnesium, while this solution further converts magnesium hydroxide into building material precursors (such as MgO) and combines it with solid waste generated from marine resource development (such as sea sand and coral reef debris) to prepare magnesium-based cementitious materials or magnesium carbonate-based building materials. Traditional electrolysis stops at extracting magnesium salts or magnesium hydroxide, resulting in low added value; this solution extends it to the manufacture of high-performance building materials, effectively increasing the economic value of each unit of magnesium resource. Through synergy with marine solid waste, a resource-efficient, low-carbon, environmentally friendly, and economically feasible in-situ marine building material manufacturing system is constructed, providing key technological support for the blue economy and sustainable infrastructure construction. In some embodiments, the precursor of magnesium-based building materials is magnesium hydroxide or magnesium oxide. Mg(OH)2 can be directly carbonized and solidified to prepare magnesium carbonate-based building materials; after drying or calcination, Mg(OH)2 is used to prepare magnesium oxychloride cement or magnesium oxysulfate cement, significantly improving the strength of building materials. Both pathways directly utilize Mg(OH)2 generated by electrolysis, avoiding additional chemical treatment and effectively improving the utilization rate of magnesium resources. The magnesium hydroxide pathway reduces high-temperature energy consumption, while the MgO pathway expands the application scenarios of building materials (such as marine engineering and refractory materials), thereby comprehensively reducing the production cost of building materials and reducing carbon emissions.

[0033] In some embodiments, the preparation of magnesium-based building materials includes: directly carbonizing and curing magnesium hydroxide to prepare magnesium carbonate-based building materials.

[0034] The carbonization process is carried out at room temperature and pressure (without the need for high-temperature calcination), effectively reducing energy consumption. No chemical precipitants are added throughout the process, avoiding the risk of ammonia gas escape from ammonium hydroxide; the reaction only produces water, with no waste liquid generated, meeting green building material standards.

[0035] In applications, the carbonization and curing process includes: Raw material pretreatment: The magnesium hydroxide slurry obtained by electrolytic precipitation (after filtration, washing and drying to a moisture content of ≤5%) is placed in a carbonization reactor, and sea sand or marine solid waste (such as coral reef slag) is added as aggregate and mixed evenly.

[0036] Carbonation reaction: CO2 gas (concentration ≥95%, sourced from industrial waste gas or pure CO2) is introduced, and the reaction is stirred for 4-12 hours at room temperature (25℃~40℃) and normal pressure. Basic magnesium carbonate is generated, which is subsequently dehydrated into MgCO3. After solidification and molding, the slurry is pressed into shape (pressure 5MPa~10MPa) and naturally cured for 24-72 hours to form magnesium carbonate-based building materials.

[0037] In some embodiments, the preparation of magnesium-based building materials includes: Magnesium hydroxide is mixed with seawater and sea sand, and a silicon source and alkaline activator are added to prepare alkali-activated magnesium-based cementitious materials. Sea sand tailings (annual output exceeding 50 million tons) are used as aggregate, significantly improving resource utilization and reducing building material costs. Electrolysis byproduct NaOH is used as an activator, eliminating the need for external procurement and reducing overall raw material costs. Marine waste (such as diatomaceous earth) is used as the silicon source, avoiding carbon emissions from silicate production. The entire process is free of ammonia and chloride ion emissions, and 100% of the waste liquid is recycled (the NaOH generated in the reaction can be recycled).

[0038] In applications, the preparation process of alkali-activated magnesium-based cementitious materials includes: Raw material pretreatment: Magnesium hydroxide obtained by electrolytic precipitation is mixed with seawater sand (washed, dried, and sieved to a particle size of 0.5 mm to 5 mm) at a mass ratio of 1:3 to 1:5. A silicon source (such as sodium silicate solution, mass fraction 10% to 20%; the silicon source can also be silica fume or finely ground quartz sand) and an alkaline activator (such as sodium hydroxide solution, mass fraction 5% to 10%) are added in proportion, and the mixture is uniformly mixed in a mixer to form a paste slurry.

[0039] Gelation reaction: The slurry is poured into a mold and placed in a curing room at 25°C and humidity >90% for 24 hours to form magnesium silicate gel. Curing and hardening: Continue curing for 7~28 days, and the gel gradually cross-links to form a dense structure, finally obtaining an alkali-activated magnesium-based cementitious material.

[0040] In some embodiments, the preparation of magnesium-based building materials includes: Magnesium hydroxide is calcined to obtain magnesium oxide, which is then mixed with magnesium chloride or magnesium sulfate to prepare magnesium oxychloride cement or magnesium oxysulfate cement. The process involves a closed-loop flow: magnesium hydroxide obtained from seawater electrolysis → calcination of magnesium oxide → recovery of acid to produce MgCl2 / MgSO4 → preparation of magnesium oxychloride / magnesium oxysulfate cement. This achieves low-cost, zero-purchase, high-strength, durable, and near-zero-carbon building material production, completely solving the industry pain points of high energy consumption, high pollution, and low added value in traditional magnesium-based building materials, and providing an economically feasible technological paradigm for the sustainable utilization of marine resources.

[0041] In application, the preparation process of the above-mentioned cement includes: Calcination of magnesium hydroxide: Magnesium hydroxide obtained by electrolytic precipitation is placed in a calcination kiln and heat-treated at 500℃~700℃ for 2~4 hours to dehydrate and produce magnesium oxide. Key control: The temperature must be strictly controlled within 500℃~700℃ to avoid MgO sintering, which would reduce its activity.

[0042] Mixed pulping: Calcinated MgO (after drying Mg(OH)2) is mixed with magnesium chloride solution or magnesium sulfate solution according to the Mg... 2+ :Cl - Mg 2+Mix MgCl2 / MgSO4 at a molar ratio of 7-9:1 and stir until homogeneous to form a slurry. It is worth noting that MgCl2 / MgSO4 can be directly obtained from the acidic solution recovered from the electrolysis anode area, eliminating the need for external purchase.

[0043] In application, all the magnesium-based building materials mentioned above possess extremely high compatibility. Solid waste that may be generated during construction, such as various fibers, slag, and coral reefs, can be incorporated into magnesium-based building materials as filler aggregates and auxiliary cementitious materials to improve the performance of building materials. This minimizes dependence on external resources and achieves self-sufficiency in building materials under offshore conditions.

[0044] In some embodiments, such as Figure 2 As shown, the electrolytic cell includes an anode region, a cathode region, and a cation exchange membrane, which separates the anode region and the cathode region. The pH value of the cathode zone is 8-10. This scheme achieves selective precipitation of magnesium ions in seawater by precisely controlling the pH value of the cathode zone within the range of 8-10. Its technical principle is based on the difference in pH thresholds for ion precipitation: Magnesium ion precipitation conditions: Solubility product of Mg(OH)₂ (K₂O₂) sp =5.61×10 -12 Precipitation begins at pH > 10, but in practice, efficient precipitation can be achieved at pH 8-10 through electrolysis (due to the generation of OH- ions during electrolysis). - (Local concentration gradient). Calcium ion suppression condition: Kc of Ca(OH)2 sp =5.5×10 -6 Precipitation only occurs at pH > 12.5; therefore, calcium ions do not precipitate at pH 8-10 and remain in the solution. By adjusting the electrolysis current (1-32A) and time (24-72 hours), the rate of hydroxide ion generation in the cathode region is dynamically balanced with the seawater ion concentration, precisely maintaining a pH of 8-10. Specifically, the pH can be 8, 9, 10, etc.

[0045] In application, this design achieves efficient magnesium extraction while retaining calcium ions through precise control of pH 8-10 in the cathode zone, solving the problem of impurity contamination in traditional precipitation methods; it eliminates the need for high-cost precipitants, significantly reducing magnesium extraction costs; the alkaline environment of the cathode naturally neutralizes the acidic solution of the anode, providing a technological basis for resource utilization; the precipitate has high purity and moderate particle size, directly adaptable to subsequent building material preparation (such as carbonization curing, alkali activation, etc.), without the need for additional treatment.

[0046] In some embodiments, the anode material of the electrolytic cell is platinum-plated porous carbon, high-silicon cast iron, or titanium-based oxide, while the cathode material is galvanized porous carbon foam, graphite, or low-carbon steel. Using titanium-based oxide as the anode material provides high catalytic activity for the oxygen evolution reaction (OER) and reduces energy consumption. High-silicon cast iron costs only 40% of titanium-based oxide and exhibits excellent corrosion resistance in seawater environments, avoiding downtime losses due to frequent replacements. Using galvanized porous carbon foam as the cathode provides a specific surface area three times that of ordinary graphite, significantly reducing the hydrogen evolution overpotential and effectively improving current efficiency. Using low-carbon steel with galvanization as the cathode is cost-effective, and the galvanized layer effectively blocks seawater corrosion, preventing efficiency degradation caused by cathode passivation.

[0047] In applications, the anode material can be one of graphite anodes, metal oxide anodes, or noble metal coated anodes. Graphite anodes are formed by pressing petroleum coke, pitch coke, or pitch into shape and then graphitizing at high temperatures. Their main component is carbon, with an ash content of approximately 0.5%. They are relatively inexpensive but have a shorter lifespan. Metal oxide anodes, using titanium as a substrate and coated with oxides such as ruthenium and iridium, are currently the mainstream choice. Ruthenium dioxide exhibits excellent catalytic activity for oxygen evolution and chlorine evolution reactions, can operate at high current densities, has a low cell voltage, good chemical stability, and a lifespan of over 10 years. Iridium alloys perform excellently under acidic conditions and are the preferred anode material for hydrogen production via water electrolysis. Noble metal coated anodes: Adding tin or iridium to the coating can increase the oxygen overpotential and improve anode selectivity; adding platinum can improve electrode stability.

[0048] Cathode materials can include low-carbon steel, nickel-based materials, and platinum-based materials. Low-carbon steel is commonly used in aqueous solution electrolyzers due to its lower cost and higher hydrogen evolution overpotential. Nickel-based materials include pure nickel, porous nickel plating, and high-phosphorus electroless nickel plating. Pure nickel can be used under alkaline conditions. Porous nickel plating has a high specific surface area and catalytic activity, effectively reducing the hydrogen evolution overpotential. High-phosphorus electroless nickel plating exhibits better chemical inertness and catalytic performance under alkaline conditions. Platinum-based materials are commonly used in alkaline water electrolysis for hydrogen production, such as platinum cathodes (graphite matrix), which possess excellent catalytic performance.

[0049] Separator materials include traditional separators, novel separators, and composite separators. Traditional separators include asbestos separators and modified asbestos separators. Polytetrafluoroethylene (PTFE) resin-modified asbestos separators incorporate resin as a reinforcing material into asbestos, improving stability and mechanical strength. Novel separators include polyphenylene sulfide (PPS) separators and polyetheretherketone (PEEK) separators. PPS separators, with their good dimensional stability, creep resistance, and heat resistance, are the mainstream product in the alkaline electrolyzer separator market. PEEK and polysulfone separators exhibit good ionic conductivity and chemical stability. Composite separators utilize a sandwich-like structure formed by coating the surface of PPS fabric with functional coatings (such as zirconium dioxide and polymers), improving hydrophilicity and reducing thickness to below 500 micrometers, achieving higher current density and lower energy consumption. In recent years, novel separator materials developed for chlor-alkali production exhibit selectivity for ion permeation, preventing chloride ions from entering the cathode chamber and producing alkaline solutions with extremely low sodium chloride content.

[0050] In some embodiments, the method further includes a step of recycling oxygen, hydrogen, and chlorine generated during electrolysis as byproducts. This solution achieves closed-loop resource utilization by recycling oxygen, hydrogen, and chlorine generated during electrolysis as byproducts: chlorine is directly converted into high-purity hydrochloric acid for the preparation of magnesium chloride, replacing purchased raw materials and significantly reducing costs; hydrogen is recycled as a clean energy source to power the electrolysis system, greatly reducing energy consumption; and oxygen is used for seawater desalination or aquaculture, expanding application scenarios. This approach avoids direct gas emissions, effectively enhances the value of byproducts, reduces carbon emissions, and forms a closed-loop chain from electrolysis to building materials to byproduct recycling, significantly improving economic efficiency and sustainability, and providing key support for the efficient utilization of marine resources.

[0051] Secondly, embodiments of this application provide a recycling method, such as... Figure 3 As shown, it includes the following steps: S100, The waste magnesium-based building materials are crushed and then fed into the anode zone of the electrolytic cell in the first aspect of the method; S200: In the anode region, an acidic environment is generated through the anode reaction, causing magnesium ions to be released from the building materials; S300: The magnesium ion-containing solution migrates through the cation exchange membrane to the cathode region, where the magnesium ions are redeposited as magnesium hydroxide. S400, Reusing magnesium hydroxide to prepare new magnesium-based building materials.

[0052] This solution achieves closed-loop recycling of waste magnesium-based building materials using an electrolytic cell, demonstrating significant technological advantages. First, the crushed waste building materials are fed into the anode zone. Utilizing anodic reactions (such as oxygen or chlorine evolution) in an acidic environment with a pH of 0-7, magnesium ions are efficiently precipitated. The magnesium ion-containing solution then migrates through a cation exchange membrane to the cathode zone, where it is precisely precipitated into high-purity magnesium hydroxide under conditions of pH 8-10. The magnesium regeneration rate exceeds 95%, far surpassing traditional recycling methods. This process directly avoids the resource waste of landfilling or simple crushing of building materials, improves the comprehensive utilization rate of magnesium resources, and reduces the procurement cost of magnesium sources in building material production.

[0053] Furthermore, in terms of environmental benefits, recycling each ton of waste building materials can reduce carbon emissions by 1.2 tons and avoid the waste liquid generated by acid-base neutralization in traditional recycling processes. Technologically, it seamlessly integrates with the in-situ preparation electrolytic cell, requiring no additional equipment, resulting in low operating energy consumption and high compatibility with in-situ preparation pathways (such as carbonization solidification or alkali activation), ensuring that the recycled magnesium hydroxide can be directly used in building material production with stable product performance. This provides a low-carbon closed-loop chain from extraction to building materials to recycling for marine resource development, significantly promoting sustainable building development.

[0054] In application, building materials prepared based on the method provided in the first aspect can be directly fed into the anode zone of an electrolytic cell after recycling and crushing. Simultaneously, different reactions occur in the anode zone under different potentials or electrode material conditions; at lower potentials, an oxygen evolution reaction occurs, producing O2 and H2. + , 2H2O-4e - =4H + +O2; Or the chlorine evolution reaction at a higher potential: produces Cl2, which is readily soluble in water to produce HCl. 2Cl - -2e - =Cl2; Cl2 + H2O = HCl + HClO; Both reactions lower the pH value of the anolyte, producing an acidic solution. Therefore, this application proposes a method for recovering magnesium-based building materials by dissolving them using the low pH of the anolyte region. + To recycle Mg from building materials 2+ The precipitate is released back into the solution and migrates towards the cathode region and precipitates due to the charge balance of the solution. The study employs a single-membrane separation electrolytic cell, where the cathode and anodic reaction products do not interfere with each other, improving reaction efficiency and enabling simultaneous production and recovery, thus reducing energy consumption. This method makes the recovery process more applicable; especially for Mg in building materials. 2+ It will gradually dissolve and be released in an acidic environment, returning completely to the anode region, migrating through the cation exchange membrane to the cathode region, and re-enacting the above process.

[0055] In some embodiments, the acidic environment in the anode region is generated through an anodic oxygen evolution reaction or a chlorine evolution reaction. Generating the acidic environment in situ through an anodic oxygen evolution or chlorine evolution reaction enables efficient dissolution of magnesium ions in waste magnesium-based building materials without the need for external acid agents, significantly reducing treatment costs.

[0056] The Cl2 produced by the chlorine evolution reaction can be directly recovered to prepare high-purity HCl, which is used to produce magnesium chloride, replacing purchased raw materials. The O2 produced by the oxygen evolution reaction can be reused as clean energy in the electrolysis system, reducing energy consumption. The acidic solution is naturally neutralized by the alkaline environment (pH 8-10) in the cathode area, forming an acid-base closed loop, avoiding waste liquid discharge and significantly improving the comprehensive utilization rate of resources. This design seamlessly integrates with the in-situ preparation process, requires no additional equipment, has low operating energy consumption, and realizes the high-value utilization of magnesium resources from building materials to recycling, providing an efficient and low-carbon technical path for the sustainable development of marine resources.

[0057] In some embodiments, the pH value of the anode zone is controlled between 0 and 7 to allow sufficient precipitation of magnesium ions from the magnesium-based building materials. Specifically, the pH of the anode zone can be any value within the range of 0 to 7, such as 0, 1, 2, 3, 4, 5, 6, or 7. This achieves efficient precipitation of magnesium ions from waste magnesium-based building materials. The acidic environment forms a natural neutralization loop with the pH of 8 to 10 in the cathode zone, preventing wastewater discharge. The precipitated magnesium ions migrate to the cathode zone through a cation exchange membrane and are precisely precipitated as high-purity magnesium hydroxide.

[0058] In some embodiments, waste magnesium-based building materials also contain solid waste generated from marine resource development, such as fibers, slag, and coral reefs. Incorporating these marine solid wastes directly into the electrolytic recycling system achieves high-value utilization of solid waste. Without additional treatment, marine solid waste (annual production exceeding 50 million tons) is used as aggregate or inert component in building materials, simultaneously recovering magnesium ions during electrolysis, effectively improving resource utilization. Simultaneously, solid waste replaces purchased aggregates (such as sea sand), reducing building material costs and avoiding carbon emissions from landfill. The electrolysis process is compatible with waste components, does not affect the purity of magnesium hydroxide precipitation, and ensures stable performance of recycled materials, achieving a closed loop of marine solid waste-building materials-recycling. This design significantly reduces environmental impact, improves economic efficiency, and provides a sustainable solution for marine resource development.

[0059] In applications, nearshore and offshore environments offer abundant green energy sources such as solar, wind, and tidal energy. Since the preparation equipment does not require very high voltage, these clean energy sources are ideally suited as a long-term, stable energy supply. Applying this method to floating marine platforms will not be limited by terrain or environmental constraints, further increasing its applicability. The electrolysis solution can utilize higher concentrations of desalinated seawater brine and other salt solutions, enabling not only efficient resource recovery and utilization but also higher conductivity and improved energy efficiency due to the higher solution concentration.

[0060] Under the same electrolysis conditions, by introducing CO2 through the cathode, the removal of Ca from seawater can be achieved in an alkaline environment. 2+ The precipitation of CaCO3 enriches the production scope of this pathway and enables the synergistic extraction and utilization of magnesium and calcium resources.

[0061] In summary, the embodiments of this application provide a closed-loop method for the preparation and recycling of building materials based on marine resources, which achieves efficient extraction of magnesium resources, preparation of building materials, and high-value recycling of waste materials through seawater electrolysis.

[0062] Specifically, seawater is electrolyzed using an electrolytic cell, with the pH value in the cathode area precisely controlled between 8 and 10. Magnesium ions are selectively precipitated as magnesium hydroxide, avoiding the contamination of impurities such as calcium and sodium. The product purity reaches over 95%, significantly superior to traditional chemical precipitation methods. The electrolysis process simultaneously generates byproducts such as oxygen, chlorine, and hydrogen, which can be recycled for the production of magnesium chloride or reused as clean energy, achieving closed-loop resource utilization. The resulting magnesium hydroxide is used to prepare magnesium-based building materials. These materials possess characteristics such as low density, high compressive strength, and low thermal conductivity, and exhibit excellent compatibility, allowing direct mixing with seawater, sea sand, and marine solid waste (such as coral reef debris and sea sand tailings), significantly reducing dependence on land-based building materials. In offshore construction, this method achieves self-sufficiency in building materials, avoiding carbon emissions and costs associated with long-distance transportation.

[0063] Waste magnesium-based building materials are crushed and fed into the anode zone of an electrolytic cell. Magnesium ions are released in the acidic environment (pH 0-7), then migrate through a cation exchange membrane to the cathode zone and precipitate as magnesium hydroxide. This magnesium recovery rate is significantly higher than traditional recycling processes. This recycling mechanism requires no additional processing, operating directly in a closed-loop electrolysis system. It avoids the high energy consumption and low added value issues of purification processes, forming a sustainable full-chain path from seawater electrolysis to building material preparation and waste recycling. This provides efficient and low-carbon technical support for marine resource development and nearshore infrastructure construction.

[0064] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0065] The above-described embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them. Although the embodiments of this application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of the embodiments of this application.

Claims

1. A method for in-situ preparation of building materials using marine resources, characterized in that, Includes the following steps: Seawater is electrolyzed using an electrolytic cell, and the pH value of the cathode area of ​​the electrolytic cell is controlled within a preset range, so that magnesium ions in the seawater precipitate to form magnesium hydroxide. The precipitated magnesium hydroxide is dried or calcined into magnesium oxide to obtain a precursor for magnesium-based building materials. Magnesium-based building material precursors are mixed with seawater, sea sand, or solid waste generated from marine resource development to prepare magnesium-based building materials.

2. The method as described in claim 1, characterized in that, The precursor of the magnesium-based building material is magnesium hydroxide or magnesium oxide.

3. The method as described in claim 1, characterized in that, The preparation of the magnesium-based building material includes: Magnesium hydroxide is directly carbonized and solidified to prepare magnesium carbonate-based building materials; or Magnesium hydroxide is mixed with seawater and sea sand, and a silicon source and an alkaline activator are added to prepare an alkali-activated magnesium-based cementitious material; or Magnesium hydroxide is dried or calcined to obtain magnesium oxide, which is then mixed with magnesium chloride or magnesium sulfate to prepare magnesium oxychloride cement or magnesium oxysulfate cement.

4. The method as described in claim 1, characterized in that, The electrolytic cell includes an anode region, a cathode region, and a cation exchange membrane, wherein the cation exchange membrane separates the anode region and the cathode region; The pH value of the cathode region is 8-10.

5. The method as described in claim 1, characterized in that, The anode material of the electrolytic cell is platinum-plated porous carbon, high-silicon cast iron, or titanium-based oxide, and the cathode material is zinc-plated porous carbon foam, graphite, or low-carbon steel.

6. The method for in-situ preparation of building materials using marine resources as described in claim 1, characterized in that, The method also includes a step of recycling the oxygen, hydrogen, and chlorine produced during the electrolysis process as byproducts.

7. A method for recycling, characterized in that, Includes the following steps: The waste magnesium-based building materials are crushed and then fed into the anode region of the electrolytic cell in any one of claims 1 to 6. In the anode region, an acidic environment is generated through an anodic reaction, causing magnesium ions to precipitate from the building materials; The magnesium ion-containing solution migrates through the cation exchange membrane to the cathode region, where the magnesium ions are redeposited as magnesium hydroxide. Reuse magnesium hydroxide to prepare new magnesium-based building materials.

8. The recycling method as described in claim 7, characterized in that, The acidic environment in the anode region is generated by the anodic oxygen evolution reaction or the chlorine evolution reaction.

9. The recycling method as described in claim 7, characterized in that, The pH value of the anode zone is controlled between 0 and 7 to allow magnesium ions in the magnesium-based building materials to be fully released.

10. The recycling method as described in claim 7, characterized in that, The discarded magnesium-based building materials also include fibers, slag, and solid waste generated from the development of marine resources such as coral reefs.

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