Method and system for conveniently extracting metal ions from solid waste

Abstract

The invention relates to the technical field of carbon dioxide utilization and alkaline solid waste treatment, and particularly discloses a method and a system for conveniently extracting metal ions from solid waste, and the method comprises the following steps: dissolving carbon dioxide in seawater containing a calcium carbonate source to generate a DIC solvent rich in bicarbonate radicals and carbonate ions; and then the DIC solvent is contacted with alkaline solid waste to carry out single-step extraction reaction so as to synchronously extract four metal ions of calcium, magnesium, silicon and aluminum. The system comprises a carbon dioxide dissolving system and a solid waste dissolving system. By utilizing the unique pH buffer characteristic of DIC, hydrogen ions or hydroxyl ions can be automatically released under different acid-base conditions, so that overall efficient extraction of various metal ions can be realized without adding external chemical reagents or adjusting pH. The method is low in cost, environment-friendly and suitable for various solid wastes such as recycled concrete fine aggregate, steel slag and fly ash, and has the effects of carbon dioxide fixation and resource utilization.

Description

Technical Field

[0001] This invention relates to the fields of carbon dioxide utilization and alkaline solid waste treatment, and in particular to a method and system for the convenient extraction of metal ions from solid waste. Background Technology

[0002] Alkaline solid wastes, such as recycled concrete fine aggregates, steel slag, fly ash, and cement kiln ash, typically have low reactivity in their raw state and require treatment before they can be effectively used in building materials and other fields. Currently, chemical activation is the preferred method to enhance their reactivity, mainly by breaking the chemical bonds in the solid waste to extract valuable metal ions (such as calcium (Ca), magnesium (Mg), silicon (Si), and aluminum (Al)) for the production of green adhesives or high-purity carbonates.

[0003] Existing chemical activation methods are mainly divided into two categories: acid activation and alkali activation. Acid activation uses strong acids such as hydrochloric acid (HCl) and sulfuric acid (H2SO4), which can effectively extract Ca and Mg minerals, but have low extraction efficiency for Si and Al minerals. Conversely, alkali activation uses strong bases such as sodium hydroxide (NaOH), which can effectively extract Si and Al minerals, but have poor extraction effect on Ca and Mg minerals.

[0004] To achieve the overall extraction of all four key metal ions, existing techniques typically require the alternating use of acids and bases, inducing significant pH fluctuations in the system. This method is not only cumbersome and costly, but also consumes large amounts of chemical reagents, is environmentally unfriendly, and does not meet the requirements of sustainable development.

[0005] Therefore, there is an urgent need in this field to develop a new method that can extract multiple metal ions such as Ca, Mg, Si, and Al from alkaline solid waste in a single step without relying on external chemical reagents or adjusting pH. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for the convenient extraction of metal ions from alkaline solid waste that is simple to operate, low in cost, and environmentally friendly, so as to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides a method for convenient extraction of metal ions from solid waste, comprising the following steps:

[0008] Prepare a DIC solvent containing bicarbonate ions and carbonate ions;

[0009] The DIC solvent is contacted with alkaline solid waste to extract metal ions in a single step, wherein the metal ions include calcium, magnesium, silicon and aluminum;

[0010] The extraction process does not require the addition of external chemical reagents. It releases hydrogen ions or hydroxide ions through the buffering mechanism of DIC solvent to achieve overall metal ion extraction.

[0011] Preferably, the step of preparing the DIC solvent includes:

[0012] Carbon dioxide gas is passed into seawater to form carbonic acid;

[0013] The carbonic acid is reacted with a calcium carbonate source to generate a DIC solvent containing calcium ions, bicarbonate ions, and carbonate ions.

[0014] Preferably, the calcium carbonate source is selected from seashells, limestone, or a combination thereof.

[0015] Preferably, the alkaline solid waste is selected from recycled concrete fine aggregate, steel slag, fly ash, cement kiln ash, or a combination thereof.

[0016] Preferably, when generating the DIC solvent, the flow rate of carbon dioxide gas to seawater has a gas-liquid ratio G / L of 10-50.

[0017] Preferably, the solid-liquid ratio of the alkaline solid waste to the DIC solvent is 1:10.

[0018] Preferably, the extraction process is carried out under stirring conditions, with a stirring speed of 200-300 RPM and an extraction time of 0.5-2 hours.

[0019] A system for implementing the above method includes:

[0020] A carbon dioxide dissolving system is used to generate DIC solvent; the carbon dioxide dissolving system includes a carbon dioxide gas source, a pressure regulator, a gas flow meter, an absorption tower and a first water pump; the carbon dioxide gas source, the pressure regulator, the gas flow meter and the absorption tower are connected in sequence through pipelines, and the first water pump is connected to the absorption tower and is used to pump seawater into the absorption tower.

[0021] A solid waste dissolution system is used to mix DIC solvent with alkaline solid waste and extract metal ions; the solid waste dissolution system includes a second water pump, a dissolution tank, a stirring device, and a pH monitoring device; the second water pump is used to pump the DIC solvent in the absorption tower into the dissolution tank, and the stirring device and the pH monitoring device are both installed in the dissolution tank.

[0022] Preferably, the absorption tower is a packed tower, the ratio of the height to the diameter of the packing bed in the packed tower is 5-6, and the packing material in the packed tower is a calcium carbonate source.

[0023] Preferably, the stirring device includes a magnetic stirring rod and a magnetic stirring plate, the dissolving tank is disposed on the magnetic stirring plate, and the magnetic stirring rod is disposed in the dissolving tank.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] 1. The method for convenient extraction of metal ions from solid waste provided by this invention utilizes the unique buffering capacity of DIC solvent to simultaneously and efficiently extract four key metal ions, Ca, Mg, Si and Al, in one step, overcoming the limitation of traditional methods that require pH swinging.

[0026] 2. The entire process uses only seawater, shells (or limestone), and CO2 as raw materials, without consuming expensive strong acids or alkalis, which significantly reduces costs and environmental footprint.

[0027] 3. The DIC solution can automatically release H⁺ or OH⁻ according to the ambient pH, so that the extraction process can be carried out stably and effectively in a wide pH range, with a wide operating window and strong robustness.

[0028] 4. This invention converts industrial CO2 and solid waste into valuable metal extracts that can be used to produce green building materials, achieving "waste treatment with waste" and carbon dioxide fixation, with significant environmental and economic benefits.

[0029] 5. All equipment used in this invention is standard chemical equipment, the system is simple to construct and operate, and has good prospects for industrial scale-up and application. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the metal ion extraction system of the present invention;

[0032] Figure 2 This is a comparison of the XRD characterization results of RCF samples extracted under different solvents and conditions according to the present invention;

[0033] Figure 3 This represents the cumulative extraction amount of Ca, Al, and Si ions from the RCF sample after 1 hour according to the present invention.

[0034] In the diagram: 1. 99.9% pure carbon dioxide cylinder; 2. Pressure regulator; 3. Gas flow meter; 4. Absorption tower; 5. First water pump; 6. Second water pump; 7. Dissolving tank; 8. Magnetic stirring rod; 9. Magnetic stirring plate; 10. pH meter. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] This invention provides a method for convenient extraction of metal ions from solid waste, comprising the following steps:

[0037] Prepare a DIC solvent containing bicarbonate ions and carbonate ions;

[0038] The DIC solvent is contacted with alkaline solid waste to extract metal ions, including calcium, magnesium, silicon and aluminum, in a single step.

[0039] The extraction process does not require the addition of external chemical reagents. It releases hydrogen ions or hydroxide ions through the buffering mechanism of DIC solvent to achieve overall metal ion extraction.

[0040] This invention extracts metal ions from solid waste using dissolved inorganic carbon (DIC) generated by dissolving carbon dioxide in seawater. Utilizing the pH buffering properties of DIC, the extraction can be carried out effectively under different initial pH conditions, achieving overall extraction independent of pH value.

[0041] Further optimization of the scheme, the steps for preparing DIC solvent include:

[0042] Carbon dioxide gas is passed into seawater to form carbonic acid;

[0043] The carbonic acid reacts with the calcium carbonate source to produce a DIC solvent containing calcium ions, bicarbonate ions, and carbonate ions.

[0044] This invention generates DIC using only inexpensive and abundant resources, such as seawater, seashells, and carbon dioxide. The process can be broken down into two simple reactions: carbon dioxide dissolution and seashell dissolution.

[0045] Carbon dioxide dissolution reaction: CO2 + H2O ↔ H2CO3;

[0046] Seashell dissolution reaction: CaCO3 + H2CO3 ↔ Ca²⁺ + 2HCO3⁻.

[0047] The process begins with carbon dioxide dissolving in seawater to form carbonic acid (H₂CO₃), which then dissolves seashells (the source of CaCO₃). The dissolution of the seashells produces calcium ions (Ca²⁺) and HCO₃⁻, the latter of which can further dissociate to form CO₃²⁻. The resulting DIC-rich solvent can then be transferred to a reaction chamber for the extraction of metal ions from alkaline solid waste.

[0048] Dissolved organic compounds (DICs) such as bicarbonate ions (HCO3⁻) and carbonate ions (CO3²⁻) can release key dissolved ions (OH⁻ and H⁺) through a buffering mechanism. In a high-pH environment where H⁺ ions are scarce, HCO3⁻ will release H⁺ ions into a buffer system: HCO3⁻ ⁻ ↔CO3²⁻+H + Conversely, under low pH conditions, CO3... 2- The ions can react with H2O to produce OH- - The reaction CO3²⁻ + H2O ↔ HCO3⁻ + OH⁻ achieves system buffering.

[0049] To further optimize the scheme, the calcium carbonate source is selected from seashells, limestone, or a combination thereof.

[0050] The scheme was further optimized by selecting alkaline solid waste from recycled concrete fine aggregate, steel slag, fly ash, cement kiln ash, or combinations thereof.

[0051] Further optimization of the scheme resulted in a gas-liquid ratio (G / L) of 10⁻⁵ for carbon dioxide gas and seawater during the generation of DIC solvent.

[0052] The scheme was further optimized so that the solid-liquid ratio of alkaline solid waste to DIC solvent was 1:10.

[0053] The extraction process was further optimized by conducting the extraction under stirring conditions at a speed of 200-300 RPM for 0.5-2 hours.

[0054] like Figure 1 As shown, the present invention provides a system for implementing the above method, comprising:

[0055] A carbon dioxide dissolving system is used to generate DIC solvent. The carbon dioxide dissolving system includes a 99.9% pure carbon dioxide cylinder 1, a pressure regulator 2, a gas flow meter 3, an absorption tower 4, and a first water pump 5. The carbon dioxide gas source, pressure regulator 2, gas flow meter 3, and absorption tower 4 are connected in sequence through pipelines. The first water pump 5 is connected to the absorption tower 4 and is used to pump seawater into the absorption tower 4.

[0056] A solid waste dissolution system is used to mix DIC solvent with alkaline solid waste and extract metal ions. The solid waste dissolution system includes a second water pump 6, a dissolution tank 7, a stirring device, and a pH monitoring device. The second water pump 6 is used to pump the DIC solvent in the absorption tower 4 into the dissolution tank 7. The stirring device and the pH monitoring device are both installed in the dissolution tank 7.

[0057] Further optimization of the scheme: absorption tower 4 is a packed tower, the height-to-diameter ratio of the packing bed inside the packed tower is 5-6, and the packing material of the packed tower is a calcium carbonate source.

[0058] The design is further optimized so that the stirring device includes a magnetic stirring rod 8 and a magnetic stirring plate 9, the dissolving tank 7 is set on the magnetic stirring plate 9, and the magnetic stirring rod 8 is set inside the dissolving tank 7.

[0059] Example

[0060] The steps for operating the above device are as follows:

[0061] 1. Fill the absorption tower 4, which has a packing bed height of 0.24 meters and a diameter of 0.03 meters (height-to-diameter ratio of approximately 5.4), with seashells (102.5 grams).

[0062] 2. Start the first water pump 5 to inject 160 ml of seawater into the packing bed until it is completely submerged.

[0063] 3. After the packed bed is submerged, 99.9% carbon dioxide gas is introduced into the absorption tower 4, and the gas pressure is adjusted to 1 bar through the pressure regulating valve.

[0064] 4. Adjust the gas-liquid flow rate using the gas flow meter 3 and the first water pump 5 respectively to maintain the gas-liquid ratio (G / L) in the range of 10-50.

[0065] 5. The system reaches steady state after running for 10 minutes, and the solvent produced in the initial stage is discarded.

[0066] 6. After steady state is established, the solvent is introduced into the dissolution tank 7 placed on the magnetic stirring plate 9.

[0067] 7. When the solvent volume in dissolving tank 7 reaches 500mL, put 50g of solid waste (solid-liquid ratio 1:10) into the system in a porous bag.

[0068] 8. Place the magnetic stir bar 8 into the dissolving tank 7 and stir the reaction medium at 250 rpm for 1 hour.

[0069] 9. During the operation, the pH value was monitored over time using a pH meter 10. Liquid extract samples were collected every 10 minutes for characterization.

[0070] 10. After 1 hour, collect the residual solid waste sample and dry it in an oven at 80°C for 24 hours.

[0071] 11. After the dried sample has cooled to room temperature, it should be sealed in an airtight bag for storage for subsequent characterization.

[0072] For the preliminary feasibility assessment of the proposed process, three sets of experiments were conducted using the above experimental procedure, with gas-liquid ratios (G / L) of 10, 30, and 50, respectively. For comparison, two additional extraction experiments were conducted using conventional 1 mol / L hydrochloric acid (HCl) and 1 mol / L sodium hydroxide (NaOH).

[0073] Figure 2 XRD characterization results of RCF samples extracted under different solvents and conditions are presented. Based on mineral peak intensities, the expected trend was observed: 1M hydrochloric acid showed the best extraction effect for calcium and magnesium minerals, but was ineffective for silica and alumina minerals; while 1M sodium hydroxide showed the opposite effect, effectively extracting silica and alumina minerals, but ineffective for calcium and magnesium minerals. Notably, the proposed DIC solvent exhibited the most uniform extraction effect among all tested minerals. This indicates that the buffering mechanism of DIC (i.e., HCO3⁻ and CO3²⁻) can simultaneously release OH⁻ and H⁺ ions, thereby achieving a single-step extraction of calcium, magnesium, silica, and alumina minerals.

[0074] Figure 3 The cumulative extraction yields of Ca, Al, and Si ions from the RCF sample after 1 hour are shown. Figure 3 As shown in (a), when the liquid-to-gas ratio (L / G) is 10 to 50, DIC solvent can extract 471.19 to 561.56 mg of calcium, which is equivalent to 25% to 30% of the extraction capacity of conventional 1M hydrochloric acid and significantly higher than that of 1M sodium hydroxide, which extracts only 2.13 mg of calcium. Figure 3 (b) The results show that DIC solvent has a significant aluminum extraction capacity, surpassing 1M hydrochloric acid and 1M sodium hydroxide at an L / G ratio of 10, and achieving comparable performance at L / G ratios of 30 and 50. Finally, Figure 3 (c) It shows that DIC solvent can extract 7.90 to 19.01 mg of silicon, with performance comparable to 1M hydrochloric acid and about 31% to 75% of the extraction capacity of conventional 1M sodium hydroxide.

[0075] This invention utilizes the buffering mechanism of dissolved inorganic carbon (DIC) to extract calcium, magnesium, silicon, and aluminum ions from alkaline solid waste for the production of sustainable building materials.

[0076] DIC's buffering capacity exhibits pH-responsive characteristics, releasing H⁺ ions at high pH and OH⁻ ions at low pH—a capability unattainable by traditional single-step extraction processes. This makes it possible to develop pH-independent extraction processes, eliminating the expensive and chemically demanding pH fluctuation steps while enabling the overall extraction of key metal ions from solid waste.

[0077] This process utilizes only cost-effective and naturally abundant resources such as seawater, shells, and carbon dioxide to prepare DIC solvents. By converting carbon dioxide into DIC solvents, the process promotes carbon dioxide sequestration, which can then be used for the sustainable extraction of metal ions from alkaline solid waste, while simultaneously achieving the efficient utilization of solid waste. Overall, this process establishes an environmentally friendly, low-cost, and scalable extraction route, particularly suitable for low-carbon and marine engineering construction.

[0078] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for convenient extraction of metal ions from solid waste, characterized in that, Includes the following steps: Prepare a DIC solvent containing bicarbonate ions and carbonate ions; The DIC solvent is contacted with alkaline solid waste to extract metal ions in a single step, wherein the metal ions include calcium, magnesium, silicon and aluminum; The extraction process does not require the addition of external chemical reagents. It releases hydrogen ions or hydroxide ions through the buffering mechanism of DIC solvent to achieve overall metal ion extraction.

2. The method for convenient extraction of metal ions from solid waste according to claim 1, characterized in that, The steps for preparing the DIC solvent include: Carbon dioxide gas is passed into seawater to form carbonic acid; The carbonic acid is reacted with a calcium carbonate source to generate a DIC solvent containing calcium ions, bicarbonate ions, and carbonate ions.

3. The method for convenient extraction of metal ions from solid waste according to claim 2, characterized in that, The calcium carbonate source is selected from seashells, limestone, or a combination thereof.

4. The method for convenient extraction of metal ions from solid waste according to claim 1, characterized in that, The alkaline solid waste is selected from recycled concrete fine aggregate, steel slag, fly ash, cement kiln ash, or a combination thereof.

5. The method for convenient extraction of metal ions from solid waste according to claim 1, characterized in that, When the DIC solvent is generated, the flow rate of carbon dioxide gas to seawater has a gas-liquid ratio G / L = 10-50.

6. The method for convenient extraction of metal ions from solid waste according to claim 1, characterized in that, The solid-liquid ratio of the alkaline solid waste to the DIC solvent is 1:

10.

7. The method for convenient extraction of metal ions from solid waste according to claim 1, characterized in that, The extraction process is carried out under stirring conditions, with a stirring speed of 200-300 RPM and an extraction time of 0.5-2 hours.

8. A system for implementing the method of claim 1, characterized in that, include: A carbon dioxide dissolving system is used to generate DIC solvent; the carbon dioxide dissolving system includes a carbon dioxide gas source, a pressure regulator, a gas flow meter, an absorption tower and a first water pump; the carbon dioxide gas source, the pressure regulator, the gas flow meter and the absorption tower are connected in sequence through pipelines, and the first water pump is connected to the absorption tower and is used to pump seawater into the absorption tower. A solid waste dissolution system is used to mix DIC solvent with alkaline solid waste and extract metal ions; the solid waste dissolution system includes a second water pump, a dissolution tank, a stirring device, and a pH monitoring device; the second water pump is used to pump the DIC solvent in the absorption tower into the dissolution tank, and the stirring device and the pH monitoring device are both installed in the dissolution tank.

9. The system according to claim 8, characterized in that, The absorption tower is a packed tower, and the ratio of the height to the diameter of the packing bed inside the packed tower is 5-6. The packing material in the packed tower is a calcium carbonate source.

10. The system according to claim 8, characterized in that, The stirring device includes a magnetic stirring rod and a magnetic stirring plate, the dissolving tank is disposed on the magnetic stirring plate, and the magnetic stirring rod is disposed in the dissolving tank.

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