Modified coal gangue carbon adsorption material as well as preparation method and application thereof
By preparing modified coal gangue carbon adsorption materials and utilizing the synergistic effect of biochar, nano-magnesium oxide and graphene oxide, the problem of ineffective utilization of coal gangue was solved, and the effects of efficient CO2 capture and cost reduction were achieved.
Patent Information
- Application Number
- CN202510829790.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-20
- Publication Date
- 2025-09-19
AI Technical Summary
In existing technologies, coal gangue has not been effectively utilized, resulting in environmental pollution and waste of resources. At the same time, traditional carbon adsorption materials are expensive and have insufficient adsorption performance, making them unable to efficiently capture CO2.
By modifying the preparation method of coal gangue carbon adsorption material, the synergistic effect of biochar, nano-magnesium oxide and graphene oxide is utilized to form a multi-level pore structure and chemical adsorption sites, thereby enhancing the physical and chemical adsorption capacity of CO2.
It achieves efficient capture of CO2, reduces material costs, and improves adsorption performance. It is suitable for the adsorption of CO2 in coal-fired flue gas, reducing carbon emissions and improving resource utilization efficiency.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of coal gangue adsorption, and in particular to a modified coal gangue carbon adsorption material, a preparation method and an application thereof. Background Art
[0002] Coal gangue, a solid waste from coal mining and washing, is emitted in excess of 700 million tons annually, with my country's stockpiles exceeding 6 billion tons. Traditional disposal methods, mainly through open-air dumping or landfilling, present two major pain points:
[0003] Environmental pollution: oxidation of sulfur-containing minerals in coal gangue releases CO2 and SO x Greenhouse gases such as GHGs are generated, and spontaneous combustion of open-air storage is a common phenomenon. The annual carbon emissions of a single storage yard can reach tens of thousands of tons.
[0004] Waste of resources: The pore structure of coal gangue is not utilized, and the existing landfill technology only provides covering treatment and cannot actively capture CO2.
[0005] Current carbon adsorption materials (such as activated carbon and molecular sieves) are expensive (>$50 / kg), and research on coal gangue modification focuses on building materials applications (ceramsite and cement). Their specific surface area (<100m2 / g) and CO2 adsorption capacity (<1mmol / g) are far from meeting carbon capture requirements. Summary of the Invention
[0006] Based on the above problems, the present invention provides a modified coal gangue carbon adsorption material and its preparation method and application, which can utilize the pore structure of coal gangue to actively capture CO2, so that coal gangue can be effectively used as solid waste in the field of carbon emission reduction, and the economic value and environmental benefits can be fully tapped.
[0007] The first invention point of the present invention is: a modified coal gangue carbon adsorption material, comprising coal gangue, biochar, nano-magnesium oxide and graphene oxide; the mass ratio of the biochar to the coal gangue is 1:(3-12), the nano-magnesium oxide loading amount is 3-8wt%, and the graphene oxide coating amount is 0.1-1.5wt%.
[0008] The hierarchical pore structure (micropores + mesopores) of modified coal gangue captures CO2 molecules through van der Waals forces.
[0009] The π-π conjugated structure of graphene oxide enhances the selective adsorption of CO2, fixes MgO particles through π-π forces, and inhibits the loss of active components caused by high-temperature desorption.
[0010] Furthermore, the specific surface area of the biochar is 300-600m 2 / g, produced by oxygen-limited pyrolysis of agricultural straw at 450-600℃.
[0011] Biochar, produced by pyrolysis of biomass, has a high specific surface area (300-600 m2 / g) and a rich microporous structure, which complements the pores of coal gangue and provides more physical adsorption sites for CO2. Oxygen-containing functional groups (such as carboxyl and hydroxyl groups) on the surface of biochar can enhance its adsorption affinity for CO2 through hydrogen bonding.
[0012] Rice husk / wheat straw has a high silicon content (SiO > 15%), and after pyrolysis, it forms a Si-O skeleton to enhance mechanical strength (compressive strength ≥ 8MPa)
[0013] Furthermore, the nano magnesium oxide has a particle size of 20-50 nm and is distributed on the pore surface of the material in the form of particles.
[0014] MgO reacts with CO2 to form magnesium carbonate (MgCO3), with a stoichiometric adsorption capacity of up to 24 mmol / g, significantly improving the material's adsorption performance in high-temperature or high-concentration CO2 environments. MgO's alkaline surface preferentially adsorbs acidic CO2 molecules, enhancing selectivity.
[0015] Mg was prepared by ultrasonic impregnation 2 +Preferentially adsorbed on oxygen-containing functional groups (-COOH) of biochar and grew in a localized manner after calcination.
[0016] Furthermore, the specific surface area of the material is ≥1000m 2 / g, and the CO2 adsorption capacity at 25℃ and 1atm is ≥5.8mmol / g.
[0017] Because the biochar and acid-washed coal gangue compound produce a pore superposition effect, the specific surface area of the material is ≥1000m 2 / g.
[0018] Furthermore, the gangue matrix is pre-treated by acid washing, and the pH value is adjusted to 6.5-7.5.
[0019] Through acid washing activation and composite loading of nanomaterials, coal gangue is converted into a carbon adsorption material with high specific surface area and high adsorption capacity, significantly improving its adsorption performance for CO2.
[0020] Preferably, the acid used in the pickling includes at least one of hydrochloric acid (HCl), nitric acid (HNO3), and sulfuric acid H2SO4, with a concentration range of 1-4 mol / L and a treatment temperature of 50–70°C. After pickling, ammonia water is used to adjust the pH to 6.5-7.5.
[0021] The second invention of the present invention is a method for preparing a modified coal gangue carbon adsorption material, comprising the following steps:
[0022] (1) The acid-washed coal gangue and biochar are mixed in proportion, impregnated with KOH solution, dried, and calcined at 600-800°C for 1-3 hours under nitrogen protection to obtain a composite matrix;
[0023] (2) immersing the composite matrix prepared in step (1) in a magnesium nitrate solution, ultrasonically treating for 0.5-2 hours, and then calcining at 350-450° C. for 1.5-3 hours to form a nano-magnesium oxide supported structure;
[0024] (3) Immersing the nano-magnesium oxide supported structure obtained in step (2) in a graphene oxide suspension, and drying the suspension to obtain a final material.
[0025] The alkaline sites (such as KCO) generated by KOH activation react with CO to form stable carbonates.
[0026] Furthermore, the concentration of the KOH solution in step (1) is 2-4 mol / L, and the solid-liquid ratio during immersion is 1 g:5-15 mL.
[0027] Furthermore, the concentration of the magnesium nitrate solution in step (2) is 0.05-0.2 mol / L, and the calcination heating rate is 3-5°C / min.
[0028] Furthermore, in step (3), the concentration of the graphene oxide suspension is 0.3-0.8 wt %, and the drying temperature is 50-80° C.
[0029] The third invention of the present invention is the application of a modified coal gangue carbon adsorption material in the adsorption of CO2 in coal-fired flue gas, with a flue gas temperature of 25-120°C, a CO2 volume concentration of 5-20%, and an adsorption-desorption cycle number of ≥15 times.
[0030] Beneficial effects
[0031] The present invention uses biochar and coal gangue pore synergy (specific surface area ≥ 1000m 2 / g) and nano-MgO chemical adsorption site loading, achieving physical-chemical dual-mode adsorption, the room-temperature CO adsorption capacity is improved compared with pure coal gangue, and the adsorption capacity is still maintained at 3.2-3.5mmol / g at high temperature (100°C); graphene oxide (GO) coating inhibits the sintering of nano-MgO, the capacity retention rate after adsorption-desorption cycles is greater than 90%, and the desorption temperature is reduced to 200°C.
[0032] The raw material cost of the present invention is reduced, the biochar is derived from agricultural straw waste, the nano-MgO loading is only 3-8wt%, and the overall cost is 40% lower than that of activated carbon materials; the carbon emission reduction and efficiency improvement of the present invention are that 30 tons of CO3 can be sealed per 10,000 tons of materials, and the carbon footprint of the entire life cycle is reduced by 35%; the present invention is adapted to coal-fired flue gas working conditions, the penetration time is extended to 180 minutes, and the investment payback period is shortened.
[0033] Specific implementation methods
[0034] To make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below. However, it should be understood that the description herein is only used to explain this application and is not intended to limit the scope of this application.
[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended solely for the purpose of describing specific embodiments and are not intended to limit this application. The reagents and instruments used herein are commercially available, and the characterization methods involved can be found in the relevant descriptions in the prior art and will not be further elaborated herein.
[0036] In order to further understand the present application, the present application is further described in detail below in conjunction with the best embodiment.
[0037] Example 1
[0038] A modified coal gangue carbon adsorption material comprises 97.2 g of coal gangue, 17.5 g of biochar, 5 g of a nano-magnesium oxide loading, and 0.5 g of a graphene oxide coating; (the amount of magnesium nitrate Mg(NO3)2·6H2O used is 31.8 g, because the amount of magnesium nitrate is converted according to a target MgO loading (the conversion rate of Mg(NO3)2·6H2O to MgO is 15.72%; the coal gangue pickling loss rate is 10%, and 87.5 g of pickled coal gangue is obtained after the raw coal gangue is pickled).
[0039] The preparation method comprises the following steps:
[0040] (1) Acid washing treatment: 97.2 g of coal gangue was sieved through an 80-mesh sieve, immersed in 200 mL of 2 mol / L HCl solution, stirred in a 65 °C water bath for 3 h, washed with ammonia water until the filtrate pH = 6.8, and dried at 105 °C for 12 h to obtain 87.5 g of acid-washed coal gangue.
[0041] (2) Biochar preparation: 17.5 g of wheat straw was pyrolyzed at 500 °C for 2 h in oxygen-limited conditions and crushed through a 200-mesh sieve (specific surface area 580 m 2 / g), mixed with the acid-washed coal gangue prepared in step (1), and then added with 3mol / LKOH (the solid-liquid ratio during KOH impregnation is 1g:10mL); then ultrasonically dispersed for 30min, dried at 65°C, and calcined at 700°C for 1.5h under nitrogen protection to obtain a composite matrix.
[0042] (3) Nano-MgO loading: 31.8 g of 0.1 mol / L Mg(NO3)2 solution was used to impregnate the composite matrix prepared in step (2). After ultrasonication for 1 h, the composite matrix was filtered and then calcined at 400°C for 2 h at a heating rate of 4°C / min to achieve a MgO loading of 5 g, thereby forming a nano-MgO loading structure.
[0043] (4) Graphite oxide coating: 0.5 wt% graphene oxide suspension was used to impregnate the nano-magnesium oxide supported structure prepared in step (3), ultrasonicated for 1 h, and vacuum dried at 65° C. to obtain 0.5 g of graphene oxide coating, thereby obtaining 100 g of the modified coal gangue carbon adsorption material of the present invention.
[0044] Example 2
[0045] A modified coal gangue carbon adsorption material comprises 108.5 g of coal gangue, 9.8 g of biochar, 3 g of a nano-magnesium oxide loading, and 0.3 g of a graphene oxide coating; (the amount of magnesium nitrate Mg(NO3)2·6H2O used is 19.1 g, because the amount of magnesium nitrate is converted according to a target MgO loading (the conversion rate of Mg(NO3)2·6H2O to MgO is 15.72%; the coal gangue pickling loss rate is 10%, and 97.7 g of pickled coal gangue is obtained after the raw coal gangue is pickled).
[0046] The preparation method is basically the same as that of Example 1, wherein the solid-liquid ratio during KOH impregnation in step (2) is 1g:5mL; the concentration of the graphene oxide suspension in step (4) is 0.3wt%; and 100g of the modified coal gangue carbon adsorption material of the present invention is obtained.
[0047] Example 3
[0048] A modified coal gangue carbon adsorption material comprises 84.4 g of coal gangue, 25.3 g of biochar, 8 g of a nano-magnesium oxide loading, and 0.8 g of a graphene oxide coating; (the amount of magnesium nitrate Mg(NO3)2·6H2O used is 50.9 g, because the amount of magnesium nitrate is converted according to a target MgO loading (the conversion rate of Mg(NO3)2·6H2O to MgO is 15.72%; the coal gangue pickling loss rate is 10%, and 76.0 g of pickled coal gangue is obtained after the raw coal gangue is pickled).
[0049] The preparation method is basically the same as that of Example 1, wherein the solid-liquid ratio during KOH impregnation in step (2) is 1g:15mL; the concentration of the graphene oxide suspension in step (4) is 0.8wt%; and 100g of the modified coal gangue carbon adsorption material of the present invention is obtained.
[0050] Example 4
[0051] Comparative Example 1
[0052] A coal gangue carbon adsorption material comprises 97.2g of coal gangue, a coal gangue pickling loss rate of 10%, and 87.5g of pickled coal gangue obtained after pickling the raw coal gangue.
[0053] The preparation method comprises the following steps:
[0054] (1) The same as step (1) of Example 1;
[0055] (2) Then, 3 mol / L KOH (the solid-liquid ratio during KOH impregnation is 1 g:10 mL) is added to the acid-washed gangue obtained in step (1); ultrasonic dispersion is then performed for 30 min, dried at 65° C., and calcined at 700° C. for 1.5 h under nitrogen protection to obtain 78.75 g of gangue carbon adsorption material.
[0056] Comparative Example 2
[0057] A coal gangue carbon adsorption material comprises 73.3 g of coal gangue, 33 g of biochar, 10 g of a nano-magnesium oxide loading, and 1 g of a graphene oxide coating; (wherein the amount of magnesium nitrate Mg(NO3)2·6H2O used is 63.6 g, because the amount of magnesium nitrate used is converted according to a target MgO loading (Mg(NO3)2·6H2O→MgO conversion rate is 15.72%; the coal gangue pickling loss rate is 10%, and 66 g of pickled coal gangue is obtained after the raw coal gangue is pickled).
[0058] The preparation method is the same as that in Example 1, and 100 g of coal gangue carbon adsorption material is obtained.
[0059] Comparative Example 3
[0060] A coal gangue carbon adsorption material comprises 105 g of coal gangue, 5 g of a nano-magnesium oxide loading, and 0.5 g of a graphene oxide coating; (the amount of magnesium nitrate Mg(NO3)2·6H2O used is 31.8 g, because the amount of magnesium nitrate is converted according to a target MgO loading (the conversion rate of Mg(NO3)2·6H2O to MgO is 15.72%; the coal gangue pickling loss rate is 10%, and 94.5 g of pickled coal gangue is obtained after the raw coal gangue is pickled).
[0061] The preparation method comprises the following steps:
[0062] (1) Acid washing treatment: 105 g of coal gangue was taken and passed through an 80-mesh sieve, immersed in 200 mL of 2 mol / L HCl solution, stirred in a 65 °C water bath for 3 h, washed with ammonia water until the filtrate pH = 6.8, and dried at 105 °C for 12 h to obtain 94.5 g of acid-washed coal gangue.
[0063] (2) Nano-MgO loading: 31.8 g of 0.1 mol / L Mg(NO3)2 solution was used to impregnate the acid-washed coal gangue prepared in step (1). After ultrasonic treatment for 1 h, the mixture was filtered and then calcined at 400°C for 2 h at a heating rate of 4°C / min to achieve a MgO loading of 5 g, thereby forming a nano-MgO loading structure.
[0064] (3) Graphite oxide coating: 0.5 wt% graphene oxide suspension was used to impregnate the nano-magnesium oxide supported structure prepared in step (3), ultrasonicated for 1 h, and vacuum dried at 65° C. to obtain 0.5 g of graphene oxide coating, thereby obtaining 100 g of coal gangue carbon adsorption material.
[0065] Comparative Example 4
[0066] A modified coal gangue carbon adsorption material comprises 87.5 g of un-acid-washed raw coal gangue, 17.5 g of biochar, 5 g of nano-magnesium oxide loading, and 0.5 g of graphene oxide coating; (the amount of magnesium nitrate Mg(NO3)2·6H2O used is 31.8 g, because the amount of magnesium nitrate is converted according to the target MgO loading (Mg(NO3)2·6H2O→MgO conversion rate is 15.72%).
[0067] The difference between the preparation method and Example 1 is that step (1) of pickling treatment is omitted, and the raw coal gangue is directly used. The remaining steps are the same as those of Example 1, and 100 g of coal gangue carbon adsorption material is obtained.
[0068] Example 5 Effect Test
[0069] The following effect tests were performed on the samples in Examples 1-3 and Comparative Examples 1-4.
[0070] 1. Specific surface area test: Using a Micromeritics ASAP 2460 specific surface area analyzer, the sample was vacuum degassed at 200°C for 6 h to remove adsorbates. The N2 adsorption-desorption isotherm was measured in a liquid nitrogen environment at -196°C. The specific surface area was calculated using the BET model. Three parallel experiments were performed with a relative deviation of <3%. The specific experimental results are shown in Table 1.
[0071] 2. CO2 adsorption capacity test: Custom fixed-bed adsorption reactor (10mm inner diameter); Conditions: ① 25°C test: 15% CO2 + 85% N2 mixture, flow rate 200mL / min; ② 100°C test: same mixture, reactor constant temperature control. Specific process: First, fill 1.0g sample (40-60 mesh), then adsorb to the breakthrough point (CO2 concentration at the outlet reaches 5% of the inlet), and finally calculate the adsorption capacity using a mass spectrometer (MS). The calculation formula is:
[0072]
[0073] (Q: adsorption capacity; F: flow rate; m: sample mass). Specific experimental results are shown in Table 1.
[0074] 3. Cyclic stability test: Adsorption conditions: 25°C, 15% CO / N, 200 mL / min; Desorption conditions: 200°C, vacuum (10-3 Pa) for 1 hour. Specific process: First record the first saturated adsorption amount Q, then repeat the adsorption-desorption cycle 15 times, and finally calculate the retention rate: Retention rate (%) = Q 15 / Q1*100.
[0075] Table 1 Specific surface area, adsorption capacity and cycle retention rate of samples
[0076]
[0077]
[0078] As shown in Table 1, Examples 1-3 of the present invention are significantly superior to the comparative examples in terms of specific surface area (1000-1080 m2 / g), adsorption capacity at 25°C (5.3-6.1 mmol / g), adsorption capacity at 100°C (2.8-3.5 mmol / g), and cyclic stability (>90%). The lack of biochar in comparative example 3 leads to a decrease in adsorption capacity at 25°C, confirming the dominant role of micropore physical adsorption. The absence of acid washing in comparative example 4 reduces the cycle retention rate by 26%, highlighting the necessity of removing metal impurities. Comparative example 2 (biochar 1:2, MgO 10wt%) has a 26% decrease in specific surface area and a 40% decrease in adsorption capacity at 100°C due to pore blockage. The adsorption capacity at 100°C (3.2 mmol / g) of Example 1 is four times that of comparative example 1, indicating that the chemical adsorption mechanism of nano-MgO plays a key role.
[0079] The industrial value of the present invention: The breakthrough time of Example 1 under coal-fired flue gas conditions is greater than 180 min (at 100° C. and 15% CO 2 ), meeting the economic threshold for carbon capture in power plants (greater than 2.5 mmol / g).
[0080] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements or improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.
Claims
1. A modified coal gangue carbon adsorption material, characterized in that: The invention comprises coal gangue, biochar, nano-magnesium oxide and graphene oxide; the mass ratio of the biochar to the coal gangue is 1:(3-12), the loading amount of the nano-magnesium oxide is 3-8wt%, and the coating amount of the graphene oxide is 0.1-1.5wt%.
2. The carbon adsorption material according to claim 1, characterized in that The specific surface area of the biochar is 300-600m 2 / g, produced by oxygen-limited pyrolysis of agricultural straw at 450-600℃.
3. The carbon adsorption material according to claim 1, characterized in that The nano magnesium oxide has a particle size of 20-50 nm and is distributed on the pore surface of the material in the form of particles.
4. The carbon adsorption material according to claim 1, characterized in that The specific surface area of the material is ≥1000m 2 / g, and the CO2 adsorption capacity at 25℃ and 1atm is ≥5.8mmol / g.
5. The carbon adsorption material according to any one of claims 1 to 4, characterized in that: The coal gangue matrix is pre-treated by acid washing, and the pH value is adjusted to 6.5-7.
5.
6. A method for preparing the modified gangue carbon adsorption material according to any one of claims 1 to 5, characterized in that: The following steps are involved: (1) The acid-washed coal gangue and biochar are mixed in proportion, impregnated with KOH solution, dried, and calcined at 600-800°C for 1-3 hours under nitrogen protection to obtain a composite matrix; (2) immersing the composite matrix prepared in step (1) in a magnesium nitrate solution, ultrasonically treating for 0.5-2 hours, and then calcining at 350-450° C. for 1.5-3 hours to form a nano-magnesium oxide supported structure; (3) Immersing the nano-magnesium oxide supported structure obtained in step (2) in a graphene oxide suspension, and drying the suspension to obtain a final material.
7. The method according to claim 6, characterized in that The concentration of the KOH solution in step (1) is 2-4 mol / L, and the solid-liquid ratio during immersion is 1 g:5-15 mL.
8. The method according to claim 6, characterized in that The concentration of the magnesium nitrate solution in step (2) is 0.05-0.2 mol / L, and the calcination heating rate is 3-5°C / min.
9. The method according to claim 6, characterized in that The concentration of the graphene oxide suspension in step (3) is 0.3-0.8wt%, and the drying temperature is 50-80°C.
10. Use of the modified gangue carbon adsorption material according to any one of claims 1 to 5 in adsorption of CO2 from coal-fired flue gas, characterized in that: The treated flue gas temperature is 25-120°C, the CO2 volume concentration is 5-20%, and the number of adsorption-desorption cycles is ≥15 times.