Carboxylate-regulated rod-like magnesium oxide adsorbent material, and preparation method and application thereof

Abstract

The application relates to a carboxylate-regulated rod-shaped magnesium oxide adsorption material and a preparation method and application thereof, and belongs to the field of environmental functional materials and water treatment technologies.In the preparation of the magnesium oxide, carboxylate is introduced in a carbonization process with the participation of CO2, the coordination of the carboxylate to Mg 2+ and the regulation of the carboxylate to the interface energy of the crystal are utilized, the traditional carbonization reaction path is changed, the anhydrous magnesium carbonate is changed from disordered nucleation growth to directional growth, the rod-shaped precursor structure with a certain length-diameter ratio is formed, and then calcination is carried out, so that the MgO material with a porous rod-shaped structure is obtained.The rod-shaped magnesium oxide adsorption material prepared by the application can still exhibit excellent selective adsorption capacity and high adsorption capacity for Congo red and other anionic dyes in a complex water system containing a large number of competitive anions, so that the application performance and the application range of the material in actual industrial wastewater treatment are significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and water treatment technology, specifically relating to a carboxylate-regulated rod-shaped magnesium oxide adsorbent material, its preparation method, and its application. Background Technology

[0002] With the rapid development of industries such as printing and dyeing, papermaking, leather, and chemicals, large amounts of industrial wastewater containing synthetic dyes are continuously discharged into the aquatic environment. Among them, anionic azo dyes (such as Congo Red, Acid Orange, and Reactive Black) exhibit strong persistence and accumulation in the natural environment due to their high chroma, stable chemical structure, well-developed aromatic ring conjugated system, and difficulty in biodegradation. These pollutants not only significantly reduce the light transmittance of water bodies and inhibit the photosynthesis of aquatic plants, but may also accumulate through the food chain, posing a potential threat to aquatic ecosystems and human health. Therefore, how to achieve efficient removal of such anionic azo dyes has always been an important research direction in the field of water treatment.

[0003] Currently, the main treatment methods for anionic dye wastewater include adsorption, coagulation and sedimentation, membrane separation, and advanced oxidation methods. Among these, adsorption is considered one of the most promising technologies due to its simple operation, relatively low cost, and wide applicability. Commonly used adsorption materials include activated carbon, natural zeolite, layered bimetallic hydroxides, and some metal oxide materials. However, in complex water systems, these materials generally have limitations in handling coexisting anions (such as SO42-). 2- CO3 2- Cl - The competitive adsorption of dyes is highly sensitive, which can easily lead to a significant decrease in the adsorption capacity and removal efficiency of target dye molecules. At the same time, their surface active sites usually lack targeted design, resulting in limited selective recognition and enrichment capabilities for target pollutants, and they are easily disturbed in complex organic-inorganic coexistence systems. In addition, it is often difficult to achieve synergistic regulation of the material's pore structure characteristics, surface charge properties, and functional group distribution, thus limiting its stable application performance under actual industrial wastewater conditions.

[0004] Magnesium oxide (MgO), as a typical alkaline inorganic metal oxide material, has attracted attention in the field of dye wastewater treatment due to its advantages such as wide availability, low cost, environmental friendliness, and certain surface adsorption activity. However, traditional MgO materials usually suffer from problems such as low specific surface area, single surface active sites, and limited surface charge regulation ability, making it difficult to achieve efficient and stable selective adsorption when facing actual wastewater systems with complex structures and variable compositions.

[0005] Therefore, how to enhance the specific surface area, improve the surface charge regulation capability, and introduce specific action sites for anionic dyes while maintaining the intrinsic advantages of MgO materials has become a key technical problem that urgently needs to be solved. This requires addressing these challenges through structural regulation and surface functionalization to achieve efficient and selective removal of target pollutants. Developing a functionalized MgO adsorbent material with controllable structure, designable surface functions, and suitability for complex water systems is of great significance for improving the treatment efficiency of industrial dye wastewater and promoting the practical application of related water treatment materials. Summary of the Invention

[0006] In this invention, a carboxylate is introduced into the CO2-involved carbonization process to utilize its effect on Mg. 2+ The coordination effect and the regulation of the crystal interface energy alter the traditional carbonization reaction pathway, transforming the disordered nucleation growth of anhydrous magnesium carbonate into a directional growth process, thereby forming a rod-shaped precursor structure with a certain aspect ratio. This structure is inherited during subsequent calcination and transforms into a porous rod-shaped MgO (MgO-C) material.

[0007] Furthermore, during carbonization and calcination, the carboxylates are partially transformed into stable surface coordination structures, forming oxygen-containing functional sites. This allows the material to maintain its structural advantages while achieving tunable surface chemical properties. The synergistic mechanism of "carbonization path regulation—structure-oriented growth—morphology inheritance—surface functionalization" thus constructed enables the obtained material to still exhibit excellent selective adsorption capacity and anti-interference performance for Congo red in complex anion coexistence systems.

[0008] The present invention adopts the following technical solution:

[0009] The first aspect of this invention provides a method for preparing a carboxylate-regulated rod-shaped magnesium oxide adsorbent, comprising the following steps:

[0010] (1) Disperse brucite powder in a solution containing carboxylates and carry out a hydrothermal reaction under CO2 atmosphere to allow the carboxylates to participate in crystal growth regulation and form rod-shaped anhydrous magnesium carbonate precursors. Filter, wash and dry the resulting product.

[0011] (2) The precursor is calcined to transform it into rod-shaped MgO material, while some carboxylate is retained on the surface to form stable functional sites.

[0012] Preferably, the brucite powder has a mesh size of 300-900 mesh, and the solid-liquid ratio of brucite powder to solution is 1g:(10-30)mL, so as to ensure sufficient contact and uniform mass transfer of ions in the reaction system.

[0013] Preferably, the CO2 atmosphere is a pressurized CO2 atmosphere with a pressure of 0.5MPa-3MPa and a rate of 50mL / min-300mL / min.

[0014] Preferably, the hydrothermal temperature is 100℃-200℃, and the hydrothermal time is 1h-10h.

[0015] Preferably, the carboxylate is one or more of acetate and citrate, and the concentration of the carboxylate is 0.01 mol / L-0.3 mol / L, so as to effectively control the crystal growth process and avoid structural inhibition caused by excessive complexation.

[0016] Preferably, the hydrothermal reaction is carried out in a closed reactor with a filling rate of 30%-80% to ensure an effective balance between the CO2 gas space and the liquid phase reaction system.

[0017] Preferably, the calcination time is 1h-6h and the calcination temperature is 400℃-700℃ to ensure that the precursor is completely converted into MgO while maintaining the stability of the rod-shaped structure.

[0018] A second aspect of this invention provides a rod-shaped magnesium oxide adsorbent prepared by the above method. The rod-shaped MgO adsorbent has a porous rod-shaped structure with uniform morphology. The porous MgO has a length of 10 μm-30 μm, a width of 2 μm-6 μm, an aspect ratio of 3-10, and a specific surface area of ​​150 m². 2 / g-220m 2 / g; the surface of the rod-shaped magnesium oxide adsorbent contains carboxylate-derived functional groups, and reacts with Mg 2+ Formation of coordination structures.

[0019] A third aspect of this invention provides an application of the rod-shaped magnesium oxide adsorbent prepared by the above method in the removal of Congo red from anionic dye wastewater;

[0020] The removal process involves adding the rod-shaped magnesium oxide adsorbent material to the anionic dye wastewater containing Congo red and dispersing it fully. The adsorption reaction is carried out under constant temperature and oscillation conditions to achieve the removal of the target pollutant.

[0021] Preferably, the dosage of the adsorbent material is 0.05 g / L to 0.15 g / L to ensure sufficient adsorption sites and mass transfer efficiency in the system.

[0022] Preferably, the initial concentration of Congo red in the anionic dye wastewater is 100 mg / L-200 mg / L.

[0023] Preferably, the adsorption process is carried out at a pH of 5-13 to enhance the electrostatic adsorption of anionic dyes by the material.

[0024] Preferably, the oscillation speed under the isothermal oscillation condition is 150 rpm to ensure uniform dispersion of the system and avoid particle sedimentation.

[0025] Preferably, the adsorption temperature is 20℃-60℃ and the adsorption time is 10min-180min.

[0026] Preferably, the anionic dye wastewater contains coexisting anions, and the coexisting anion is SO42-. 2- CO3 2- Cl - One or more of the following, with each anion concentration of 0.005 mol / L-0.05 mol / L, were used to simulate the ion coexistence environment in a real complex water system and to evaluate the anti-interference performance of the adsorbent;

[0027] The removal rate of Congo red from the anionic dye wastewater is no less than 75%.

[0028] In this invention, carboxylates are introduced as structural regulators and precursors to control the carbonization path and crystal growth behavior during material formation, thereby constructing a rod-shaped MgO structure with a specific aspect ratio. Specific functional groups or active sites are introduced onto its surface to enhance electrostatic interactions, coordination interactions, and interfacial adsorption between the material and anionic dyes. The resulting MgO material not only has a higher specific surface area and more favorable exposed crystal faces in its structure, but also achieves controllable functionalization in its surface chemistry, enabling it to function in environments containing a large number of competing anions (such as SO42-). 2- CO3 2- Cl - In complex water systems where these dyes coexist, they still exhibit excellent selective adsorption capacity and high adsorption capacity for anionic dyes such as Congo Red, thus significantly improving their application performance and scope of application in actual industrial wastewater treatment.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) Using natural solid mineral brucite as the magnesium source, reduce the dependence on high-purity chemical magnesium source, give full play to its advantages of wide availability and low cost, and realize the high-value utilization of natural magnesium mineral resources;

[0031] (2) By introducing carboxylates during the carbonization stage, the growth process of anhydrous magnesium carbonate crystals can be effectively controlled, and their directional growth can be induced to form a rod-shaped structure, thereby giving the material specific morphological advantages.

[0032] (3) The rod-shaped precursor structure formed is well inherited during the calcination process, so that the final MgO material maintains an ordered morphological feature, which is conducive to improving the specific surface area and the degree of exposure of active sites.

[0033] (4) During the material formation and heat treatment process, the carboxylates are transformed into surface-stable coordination structures, thereby enhancing the interfacial interaction and recognition capabilities of the material surface for anionic dye molecules.

[0034] (5) The material obtained by this invention in SO4 2- CO3 2- Cl - It can maintain a high adsorption efficiency even in coexisting anion systems, demonstrating excellent resistance to ion competition interference.

[0035] (6) Through the synergistic effect of structural regulation and surface chemical function regulation, the material morphology advantage and interfacial performance are coupled and improved, thereby significantly improving its selective adsorption performance for anionic dyes and its practical application adaptability. Attached Figure Description

[0036] Figure 1 The XRD patterns of rod-shaped anhydrous magnesium carbonate and MgO-C-1 prepared in Example 1 are shown below.

[0037] Figure 2 The images show SEM images of rod-shaped anhydrous magnesium carbonate, MgO-C-1, and MgO-D-1 prepared in Example 1 and Comparative Example 1, with the upper right corner showing a high-magnification SEM image. Among them, (a) shows anhydrous magnesium carbonate with a rod-shaped morphology, (b) shows MgO-C-1, and (c) shows MgO-D-1.

[0038] Figure 3 The nitrogen adsorption-desorption isotherms of MgO-C-1 and MgO-D-1 prepared in Example 1 are shown below.

[0039] Figure 4 The pore size distribution curves of MgO-C-1 and MgO-D-1 prepared in Example 1 are shown.

[0040] Figure 5 The Zeta potentials of MgO-C-1 and MgO-D-1 prepared in Example 1;

[0041] Figure 6 The FT-IR spectra of MgO-C-1 and MgO-D-1 prepared in Example 1 are shown below.

[0042] Figure 7 XPS spectra of MgO-C-1 and MgO-D-1 prepared in Example 1; where (a) is the O1s fitting result and (b) is the C1s fitting result.

[0043] Figure 8 This is a graph showing the effect of adsorption temperature on the adsorption of pure Congo red solution by MgO-C-1 and MgO-D-1 in Example 1.

[0044] Figure 9 The graph shows the effect of adsorption temperature on the adsorption of interfering ions and Congo red mixed solution by MgO-C-1 and MgO-D-1 prepared in Example 1 and Comparative Example 1.

[0045] Figure 10 The graph shows the effect of MgO-C-1 and MgO-D-1 prepared in Example 1 and Comparative Example 1 of the present invention on the adsorption of interfering ions and Congo red mixed solution after 5 cycles of regeneration.

[0046] Figure 11 The graph shows the effect of adsorption temperature on the adsorption of interfering ions and Congo red mixed solution of MgO-C-2 and MgO-D-2 prepared in Example 2 and Comparative Example 2.

[0047] Figure 12 The graph shows the effect of MgO-C-2 and MgO-D-2 prepared in Example 2 and Comparative Example 2 of this invention on the adsorption of interfering ions and Congo red mixed solution after 5 cycles of regeneration.

[0048] Figure 13 The graph shows the effect of solution pH on the adsorption of interfering ions and Congo red mixed solutions prepared in Example 3 and Comparative Example 3.

[0049] Figure 14 The graph shows the effect of adsorption time on the adsorption of interfering ions and Congo red mixed solutions of MgO-C-4 and MgO-D-4 prepared in Example 4 and Comparative Example 4.

[0050] Figure 15 The graph shows the effect of adsorption temperature on the adsorption of interfering ions and Congo red mixed solutions prepared in Example 5 and Comparative Example 5. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0052] Example 1:

[0053] This embodiment provides a carboxylate-regulated rod-shaped magnesium oxide adsorbent and its preparation method, including the following steps:

[0054] (1) Weigh 10g of 800-mesh brucite powder and add it to 100mL of 0.1mol / L sodium citrate solution (solid-liquid ratio 1g:10mL). Stir magnetically for 30min to ensure thorough dispersion. Transfer the mixed solution to a high-pressure reactor and adjust the reactor filling rate to 60%. Introduce CO2 gas to a reaction pressure of 1MPa and control the gas flow rate at 100mL / min. Perform a hydrothermal reaction at 150℃ for 6h. After the reaction is complete, allow it to cool naturally to room temperature. Separate the product by filtration, wash it three times with deionized water, and then dry it at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0055] (2) The precursor was placed in a muffle furnace and calcined at 600℃ for 3h (heating rate 5℃ / min) to obtain MgO-C-1 adsorbent.

[0056] Comparative Example 1:

[0057] This comparative example provides a method for preparing magnesium oxide, comprising the following steps:

[0058] (1) Weigh 10g of 800-mesh brucite powder and add it to 100mL of deionized water. Stir magnetically for 30min to disperse it fully. Transfer the mixed solution to a high-pressure reactor and adjust the reactor filling rate to 60%. Introduce CO2 gas to a reaction pressure of 1MPa and control the gas flow rate at 100mL / min. Perform a hydrothermal reaction at 150℃ for 6h. After the reaction is complete, allow it to cool naturally to room temperature. Separate the product by filtration, wash it three times with deionized water, and then dry it at 80℃ for 12h to obtain anhydrous magnesium carbonate precursor.

[0059] (2) The precursor was placed in a muffle furnace and calcined at 600℃ for 3h (heating rate 5℃ / min) to obtain MgO-D-1.

[0060] Depend on Figure 1 It can be seen that the diffraction peaks in the XRD patterns of the hydrothermal and calcined products correspond one-to-one with the standard characteristic peaks of anhydrous magnesium carbonate and MgO, respectively, indicating that the prepared precursor is pure-phase anhydrous magnesium carbonate and the calcined product is pure-phase MgO. Figure 2 It can be seen that the obtained anhydrous magnesium carbonate has a rod-like morphology, approximately 20 μm long and 4 μm wide, with an aspect ratio of 5. The calcined MgO retains the intrinsic morphology of the precursor, but exhibits nanopores on its surface, resulting in a porous rod-like morphology. Figure 3 and Figure 4 It can be seen that, compared with MgO-D-1 (specific surface area 49.31 m²), 2 The MgO-C-1 obtained by carboxylate regulation has a larger specific surface area (183.91 m² / g). 2The material exhibits a distinct mesoporous structure, with its nitrogen adsorption-desorption isotherm displaying a typical type IV curve accompanied by an H3-type hysteresis loop, indicating that the material possesses a mesoporous structure dominated by slit-like channels. This structure not only provides abundant surface active sites but also facilitates the diffusion and mass transfer of dye molecules, thereby enhancing its adsorption capacity and selective adsorption performance in complex systems.

[0061] Depend on Figure 5 It can be seen that the surface potential of MgO-C-1 is significantly shifted in the negative direction compared to MgO-D-1, indicating that the introduction of carboxylates increases the negative charge density on the material surface, thereby modulating its interfacial electrical properties and contributing to enhanced selective interaction between the material and the target dye molecules. Figure 6 It can be seen that, combined with FT-IR spectrum analysis, MgO-D-1 at 525 cm⁻¹ -1 The peak at this location is the Mg-O lattice vibration peak. After the addition of carboxylate, the MgO-C-1 peak position shifts significantly to 449 cm⁻¹. -1 Furthermore, the increased strength indicates that the carboxylate reacts with Mg. 2+ Coordination occurs between them, leading to distortion of the local lattice environment and increased vibrational infrared activity. Simultaneously, at 902 cm⁻¹... -1 and 981cm -1 A new strong absorption peak appears at 1438 cm⁻¹, attributed to the Mg-OC⁻¹ coordination structure and the CO vibration of the carboxylate, respectively. The peak intensity is significantly enhanced, indicating that the carboxylate has been extensively introduced and formed a stable coordination structure on the material surface. Furthermore, at 1438 cm⁻¹... -1 The peak position shifted to 1445cm -1 Furthermore, the increased strength indicates that the original surface carbonates have been replaced by carboxylate salts, forming a surface chemical structure dominated by carboxylate groups. 1644cm -1 The peak position shifted slightly to 1653cm -1 The enhancement indicates that the surface polarity of the material is increased after the introduction of carboxylates. These results demonstrate that carboxylates are not only successfully introduced into the material surface, but also construct a stable organic-inorganic interface structure through coordination, thereby significantly regulating the surface chemical properties and structural characteristics of the material. Furthermore, by… Figure 7It can be seen that by combining the fitting results of the C1s and O1s high-resolution spectra in XPS, the regulatory effect of citrate on the surface structure of the material can be further revealed. Magnesium oxide samples without carboxylates show characteristic peaks only at approximately 528.91 eV and 531.23 eV in the O1s spectrum, which are attributed to lattice oxygen (Mg-O) and surface hydroxyl groups (-OH), respectively, indicating that their surface is mainly composed of inorganic oxygen species. However, after the introduction of citrate, the O1s spectrum changes significantly. In addition to retaining the characteristic peak of lattice oxygen at approximately 528.96 eV, new characteristic peaks appear at 530.98 eV, 532.25 eV, and 534.96 eV. Among these, 530.98 eV can be attributed to surface hydroxyl groups or defect oxygen, 532.25 eV corresponds to oxygen in the CO bond, and the high binding energy peak at 534.96 eV can be attributed to the OC=O structure in the carboxylate. The appearance of this high binding energy peak indicates that carboxylic acid organic functional groups have been successfully introduced into the material surface. Simultaneously, in the C1s spectrum, in addition to the CC characteristic peak at 284.8 eV, CO and OC=O characteristic peaks appear at 285.95 eV and 289.83 eV, respectively, further confirming the presence of carboxyl groups. The carboxyl carbon peak corresponding to 289.83 eV indicates that citrate has been stably present on the material surface. It is noteworthy that the appearance of a multi-peak structure and the enhancement of the high binding energy peak in the O1s spectrum suggest that the carboxyl group is not simply physically adsorbed onto the material surface, but rather binds to Mg through the carboxyl group. 2+ The coordination interactions between these components form a stable surface coordination structure, thereby constructing functionalized active sites. This structure not only increases the content of oxygen-containing functional groups on the material surface but also modulates its interfacial charge, which is beneficial for enhancing the material's selective adsorption capacity for anionic dye molecules.

[0062] The MgO-C-1 prepared in Example 1 and the MgO-D-1 prepared in Comparative Example 1 were used to adsorb Congo red from Congo red solutions, respectively, according to the following steps: Two 100 mg / L Congo red solutions were prepared, five portions of 100 mL each, and the pH of the solutions was adjusted to 7. 8 mg of MgO-C-1 and 8 mg of MgO-D-1 were added to each solution, respectively. The systems were placed in a constant-temperature shaker and shaken at 150 rpm for 70 min. The shaker temperatures for different solutions in the two groups were set to 20℃, 30℃, 40℃, 50℃, and 60℃, respectively. After adsorption, samples were centrifuged, and the concentration of Congo red in the supernatant was measured. The results are as follows: Figure 8 As shown.

[0063] Depend on Figure 8It can be seen that the adsorption rate and adsorption capacity of MgO-C-1 adsorbent for Congo red simulated wastewater increase significantly with increasing temperature. The adsorption effect is best at an adsorption temperature of 60℃, with an adsorption efficiency of 92.11% and an adsorption capacity of 1151.32 mg / g. Compared with 40℃ (adsorption efficiency of 91.71% and adsorption capacity of 1145.10 mg / g), the improvement is not significant. Considering energy conservation and environmental protection, the adsorption experiment was conducted under the condition of constant temperature oscillator at 40℃. The overall adsorption effect of MgO-D-1 is not as good as that of MgO-C-1, with a maximum adsorption efficiency of 60.78% and a maximum adsorption capacity of 759.81 mg / g.

[0064] The MgO-C-1 prepared in Example 1 and the MgO-D-1 prepared in Comparative Example 1 were used to adsorb Congo red in a Congo red solution under anion coexistence system, respectively, according to the following steps:

[0065] Two 100 mg / L Congo red solutions were prepared, with five aliquots in each group, each aliquot being 100 mL. 0.426 g of Na₂SO₄ was added to each Congo red solution to achieve a Na₂SO₄ concentration of 0.03 mol / L, in order to construct SO₄²⁻. 2- Coexistence system. The pH of the different solutions in each group was adjusted to 7. 8 mg of MgO-C-1 and 8 mg of MgO-D-1 were added to each solution group, respectively. Each system was placed in a constant-temperature shaker and shaken at 150 rpm for 70 min for adsorption. The shaker temperatures for the different solutions in both groups were set to 20℃, 30℃, 40℃, 50℃, and 60℃, respectively. After adsorption, samples were taken and centrifuged, and the Congo red concentration in the supernatant was measured. The results are as follows: Figure 9 As shown. The results indicate that in SO4 2- Under coexisting conditions, the MgO-C-1 adsorbent maintained a high adsorption efficiency of 87.03% and an adsorption capacity of 1087.85 mg / g, indicating its good anti-competitive adsorption ability for the target anionic dye and its adaptability to temperature changes. In contrast, the overall adsorption effect of MgO-D-1 was inferior to that of MgO-C-1, with an adsorption efficiency of 47.51% and an adsorption capacity of 593.91 mg / g. Figure 10 As shown, after five cycles of regeneration, the MgO-C-1 material maintained a high adsorption removal rate, with an adsorption efficiency of 75.24% and an adsorption capacity of 940.45 mg / g. The adsorption performance showed a slight decrease, indicating that the adsorbent has good stability in recycling and its structure, suggesting high potential for reuse in actual wastewater treatment. In contrast, the adsorption performance of MgO-D-1 decreased significantly after five cycles of regeneration, with the adsorption efficiency dropping to 15.00% and the adsorption capacity decreasing to 187.56 mg / g.

[0066] Example 2:

[0067] This embodiment provides a carboxylate-regulated rod-shaped magnesium oxide adsorbent and its preparation method, including the following steps:

[0068] (1) Weigh 10g of 800-mesh brucite powder and add it to 200mL of 0.1mol / L sodium citrate solution (solid-liquid ratio 1g:20mL). After stirring evenly, transfer the solution to a high-pressure reactor, with the reactor filling rate controlled at 50%. Introduce CO2 to a pressure of 2MPa and control the gas flow rate at 150mL / min. Perform a hydrothermal reaction at 160℃ for 5h. After the reaction is complete, cool and filter the solution, wash it with deionized water, and dry it at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0069] (2) The precursor was placed in a muffle furnace and calcined at 650°C for 2 hours (heating rate 5°C / min) to obtain MgO-C-2.

[0070] Comparative Example 2:

[0071] This comparative example provides a rod-shaped magnesium oxide adsorbent material and its preparation method, including the following steps:

[0072] (1) Weigh 10g of 800-mesh brucite powder, add it to 200mL of deionized water, stir magnetically for 5min until uniform, and then transfer it to a high-pressure reactor. The reactor filling rate is controlled at 50%. Introduce CO2 to a pressure of 2MPa, control the gas flow rate at 150mL / min, and carry out a hydrothermal reaction at 160℃ for 5h. After the reaction is completed, cool and filter, wash with deionized water, and dry at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0073] (2) The precursor was placed in a muffle furnace and calcined at 650°C for 2 hours (heating rate 5°C / min) to obtain MgO-D-2.

[0074] The MgO-C-2 prepared in Example 2 and the MgO-D-2 prepared in Comparative Example 2 were used to adsorb Congo red from a Congo red solution in an anion coexistence system, respectively, according to the following steps: Two groups of 150 mg / L Congo red solutions were prepared, five portions of each group, each portion being 100 mL. 0.106 g of Na2CO3 and 0.142 g of Na2SO4 (concentration 0.01 mol / L) were added to the Congo red solutions to construct CO32-. 2- and SO4 2-Coexistence system. The pH of the different solutions in each group was adjusted to 7. 10 mg of MgO-C-2 and 10 mg of MgO-D-2 were added to each solution group, respectively. Each system was placed in a constant-temperature shaker and shaken at 150 rpm for 70 min for adsorption. The shaker temperatures for the different solutions in both groups were set to 20℃, 30℃, 40℃, 50℃, and 60℃, respectively. After adsorption, samples were taken and centrifuged, and the Congo red concentration in the supernatant was measured. The results are as follows: Figure 11 As shown.

[0075] like Figure 11 As shown, the adsorption rate and amount of Congo red in the anion coexistence system by MgO-C-2 adsorbent increased significantly with increasing temperature. The best adsorption effect was observed at an adsorption temperature of 60℃, with an adsorption efficiency of 88.38% and an adsorption amount of 1325.63 mg / g. Compared with 40℃ (adsorption efficiency reached 86.54%, adsorption amount reached 1298.12 mg / g), the improvement was not significant. Considering energy conservation and environmental protection, the adsorption experiment was conducted under the condition of a constant temperature oscillator at 40℃. The overall adsorption effect of MgO-D-2 was not as good as that of MgO-C-2, with a maximum adsorption efficiency of 51.89% and a maximum adsorption amount of 778.29 mg / g.

[0076] like Figure 12 As shown, after five cycles of regeneration, the MgO-C-2 material maintained a high adsorption removal rate, with an adsorption efficiency of 74.38% and an adsorption capacity of 1115.70 mg / g. The adsorption performance showed a slight decrease, indicating that the adsorbent has good stability in recycling and its structure, suggesting high potential for reuse in actual wastewater treatment. In contrast, the adsorption performance of MgO-D-2 decreased significantly after five cycles of regeneration, with the adsorption efficiency dropping to 18.05% and the adsorption capacity decreasing to 270.75 mg / g.

[0077] Example 3:

[0078] This embodiment provides a carboxylate-regulated rod-shaped magnesium oxide adsorbent and its preparation method, including the following steps:

[0079] (1) Weigh 10g of 400-mesh brucite powder and add it to 200mL of 0.05mol / L sodium citrate solution (solid-liquid ratio 1g:15mL). After stirring evenly, transfer the solution to a reaction vessel with a filling rate of 50%. Introduce CO2 to a pressure of 2MPa and a gas flow rate of 100mL / min. Perform a hydrothermal reaction at 140℃ for 10h. After the reaction is complete, cool and filter the solution, wash it with deionized water, and dry it at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0080] (2) The precursor was placed in a muffle furnace and calcined at 500°C for 6 hours (heating rate 5°C / min) to obtain MgO-C-3.

[0081] Comparative Example 3:

[0082] This comparative example provides a rod-shaped magnesium oxide adsorbent material and its preparation method, including the following steps:

[0083] (1) Weigh 10g of 400-mesh brucite powder, add it to 200mL of deionized water, stir magnetically for 5min until uniform, and then transfer it to a high-pressure reactor. The reactor filling rate is controlled at 50%. Introduce CO2 to a pressure of 2MPa, control the gas flow rate at 100mL / min, and carry out a hydrothermal reaction at 140℃ for 10h. After the reaction is completed, cool and filter, wash with deionized water, and dry at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0084] (2) The precursor was placed in a muffle furnace and calcined at 500℃ for 6 hours (heating rate 5℃ / min) to obtain MgO-D-3.

[0085] The MgO-C-3 prepared in Example 3 and the MgO-D-3 prepared in Comparative Example 3 were used to adsorb Congo red from a Congo red solution in an anion coexistence system, respectively, according to the following steps: Two 150 mg / L Congo red solutions were prepared, two portions of each solution, each 100 mL. 0.106 g of Na₂CO₃ and 0.142 g of Na₂SO₄ (concentration 0.01 mol / L) were added to the Congo red solutions to construct CO₃²⁻. 2- and SO4 2- Coexistence systems. 10 mg of MgO-C-3 and 10 mg of MgO-D-3 were added to each solution group, respectively. Each system was placed in a 40℃ constant-temperature shaker and shaken at 150 rpm for 70 min for adsorption. The pH values ​​of the two solutions were adjusted to 5.5 and 12.5, respectively. After adsorption, samples were taken and centrifuged, and the concentration of Congo red in the supernatant was measured. The results are as follows: Figure 13 As shown.

[0086] like Figure 13As shown, MgO-C-3 exhibits superior adsorption stability and anti-interference ability under both acidic and alkaline pH conditions, maintaining high adsorption rates and capacities for Congo red in anion-coexisting systems. Adsorption efficiencies were 80.35% and 77.19%, respectively, with adsorption capacities of 1205.24 mg / g and 1157.87 mg / g, respectively. In contrast, MgO-D-3 showed adsorption efficiencies of 30.30% and 20.62%, respectively, and adsorption capacities of 454.34 mg / g and 309.22 mg / g, respectively, indicating that its adsorption performance is more sensitive to pH changes and its stability and anti-interference ability in complex coexisting systems are relatively weaker.

[0087] Example 4:

[0088] This embodiment provides a carboxylate-regulated rod-shaped magnesium oxide adsorbent and its preparation method, including the following steps:

[0089] (1) Weigh 10g of 400-mesh brucite powder and add it to 200mL of 0.25mol / L sodium acetate solution (solid-liquid ratio 1g:25mL). After stirring evenly, transfer the solution to a reaction vessel with a filling rate of 60%. Introduce CO2 to a pressure of 2MPa and a gas flow rate of 250mL / min. Perform a hydrothermal reaction at 170℃ for 8h. After the reaction is complete, cool and filter the solution, wash it with deionized water, and dry it at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0090] (2) The precursor was placed in a muffle furnace and calcined at 600℃ for 5h (heating rate 5℃ / min) to obtain MgO-C-4.

[0091] Comparative Example 4:

[0092] This comparative example provides a rod-shaped magnesium oxide adsorbent material and its preparation method, including the following steps:

[0093] (1) Weigh 10g of 400-mesh brucite powder, add it to 200mL of deionized water, stir magnetically for 5min until uniform, and then transfer it to a high-pressure reactor. The reactor filling rate is controlled at 60%. CO2 is introduced to a pressure of 2MPa, and the gas flow rate is controlled at 250mL / min. The hydrothermal reaction is carried out at 170℃ for 8h. After the reaction is completed, the mixture is cooled, filtered, washed with deionized water, and dried at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0094] (2) The precursor was placed in a muffle furnace and calcined at 600℃ for 5h (heating rate 5℃ / min) to obtain MgO-D-4.

[0095] The MgO-C-4 prepared in Example 4 and the MgO-D-4 prepared in Comparative Example 4 were used to adsorb Congo red from a Congo red solution in an anion coexistence system, respectively, according to the following steps: Two 150 mg / L Congo red solutions were prepared, two portions of each solution, each 100 mL. 0.106 g of Na₂CO₃ and 0.142 g of Na₂SO₄ (concentration 0.01 mol / L) were added to the Congo red solutions to construct CO₃²⁻. 2- and SO4 2- Coexistence system. The pH of the different solutions in each group was adjusted to 7. 10 mg of MgO-C-4 and 10 mg of MgO-D-4 were added to each solution, respectively. Each system was placed in a 40℃ constant temperature shaker and shaken at 150 rpm for adsorption. The adsorption times for the eight solutions were set to 10 min, 30 min, 50 min, 70 min, 90 min, 110 min, 130 min, and 150 min, respectively. After adsorption, samples were taken, centrifuged, and the concentration of Congo red in the supernatant was measured. The results are as follows: Figure 14 As shown.

[0096] like Figure 14 As shown, with the extension of adsorption time, the adsorption rate and adsorption capacity of MgO-C-4 adsorbent for Congo red in the anion coexistence system first increased and then remained constant. The adsorption effect was best at an adsorption time of 150 min, with an adsorption efficiency of 88.54% and an adsorption capacity of 1328.17 mg / g. Compared with 70 min, the improvement was not significant. Considering the time cost and the fact that the increase in adsorption rate tends to be gradual with longer adsorption time, the adsorption experiment was conducted under the condition of a preparation time of 70 min. The overall adsorption effect of MgO-D-4 was not as good as that of MgO-C, with a maximum adsorption efficiency of 52.66% and a maximum adsorption capacity of 789.87 mg / g.

[0097] Example 5:

[0098] This embodiment provides a carboxylate-regulated rod-shaped magnesium oxide adsorbent and its preparation method, including the following steps:

[0099] (1) Weigh 10g of 400-mesh brucite powder and add it to 200mL of 0.25mol / L sodium acetate solution (solid-liquid ratio 1g:25mL). After stirring evenly, transfer the solution to a reaction vessel with a filling rate of 60%. Introduce CO2 to a pressure of 1.5MPa and a gas flow rate of 200mL / min, and carry out a hydrothermal reaction at 180℃ for 9h. After the reaction is completed, cool and filter the solution, wash it with deionized water, and dry it at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0100] (2) The precursor was placed in a muffle furnace and calcined at 650°C for 4 hours (heating rate 5°C / min) to obtain MgO-C-5.

[0101] Comparative Example 5:

[0102] This comparative example provides a rod-shaped magnesium oxide adsorbent material and its preparation method, including the following steps:

[0103] (1) Weigh 10g of 400-mesh brucite powder, add it to 200mL of deionized water, stir magnetically for 5min until uniform, and then transfer it to a high-pressure reactor. The reactor filling rate is controlled at 60%. Introduce CO2 to a pressure of 1.5MPa, control the gas flow rate at 200mL / min, and carry out a hydrothermal reaction at 180℃ for 9h. After the reaction is completed, cool and filter, wash with deionized water, and dry at 80℃ for 12h to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0104] (2) The precursor was placed in a muffle furnace and calcined at 650°C for 4 hours (heating rate 5°C / min) to obtain MgO-D-5.

[0105] The MgO-C-5 prepared in Example 5 and the MgO-D-5 prepared in Comparative Example 5 were used to adsorb Congo red from Congo red solution in an anion coexistence system, respectively, according to the following steps: Two 150 mg / L Congo red solutions were prepared, two portions of each solution, each 100 mL. 0.106 g Na₂CO₃, 0.142 g Na₂SO₄, and 0.0584 g NaCl (concentration 0.01 mol / L) were added to the Congo red solutions to construct CO₃²⁻. 2- SO4 2- and Cl - Coexistence system. The pH of the different solutions in each group was adjusted to 7. 10 mg of MgO-C-5 and 10 mg of MgO-D-5 were added to each solution group, respectively. Each system was placed in a constant-temperature shaker and shaken at 150 rpm for 70 min for adsorption. The shaker temperatures for the different solutions in both groups were set to 20℃, 30℃, 40℃, 50℃, and 60℃, respectively. After adsorption, samples were taken and centrifuged, and the concentration of Congo red in the supernatant was measured. The results are as follows: Figure 15 As shown.

[0106] like Figure 15As shown, with increasing temperature, the adsorption rate and adsorption capacity of MgO-C-5 adsorbent for Congo red in the anion coexistence system significantly increased, reaching adsorption equilibrium at an adsorption temperature of 40℃, with an adsorption efficiency of 87.05% and an adsorption capacity of 1305.69 mg / g. In contrast, the overall adsorption performance of MgO-D-5 was inferior to that of MgO-C-5, with a maximum adsorption efficiency of 49.14% and a maximum adsorption capacity of 737.14 mg / g. This indicates that MgO-C-5 not only exhibits good adsorption performance in single-anion systems but also maintains good adsorption capacity in binary or ternary coexisting anion systems.

[0107] Example 6:

[0108] This embodiment provides a carboxylate-regulated rod-shaped magnesium oxide adsorbent and its preparation method, including the following steps:

[0109] (1) Weigh 10g of 800-mesh brucite powder and add it to 300mL of 0.1mol / sodium acetate solution (solid-liquid ratio 1g:30mL). After stirring evenly, transfer the solution to a reaction vessel with a filling rate of 40%. Introduce CO2 to a pressure of 3MPa at a flow rate of 200mL / min and carry out a hydrothermal reaction at 180℃ for 4h. After the reaction is complete, cool, filter, wash, and dry to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0110] (2) The precursor was placed in a muffle furnace and calcined at 700℃ for 1 h (heating rate 5℃ / min) to obtain MgO-C-6.

[0111] Comparative Example 6:

[0112] This comparative example provides a rod-shaped magnesium oxide adsorbent material and its preparation method, including the following steps:

[0113] (1) Weigh 10g of 800-mesh brucite powder, add it to 300mL of deionized water, stir evenly, and transfer it to a reaction vessel with a filling rate of 40%. Introduce CO2 to a pressure of 3MPa and a gas flow rate of 200mL / min, and carry out a hydrothermal reaction at 180℃ for 4h. After the reaction is completed, cool, filter, wash and dry to obtain rod-shaped anhydrous magnesium carbonate precursor.

[0114] (2) The precursor was placed in a muffle furnace and calcined at 700℃ for 1 h (heating rate 5℃ / min) to obtain MgO-D-6.

[0115] The MgO-C-6 prepared in Example 6 and the MgO-D-6 prepared in Comparative Example 6 were used to adsorb Congo red in a Congo red solution under anion coexistence system, respectively, according to the following steps: 100 mL of 200 mg / L Congo red solution was prepared, and 0.212 g of Na2CO3 (concentration of 0.02 mol / L) was added to the Congo red solution to construct CO32-. 2- The coexistence system was prepared, and the pH of the solution was adjusted to 8. 15 mg of MgO-C-6 and 15 mg of MgO-D-6 adsorbents were added to the solution. The system was placed in a constant-temperature shaker and shaken at 150 rpm for 60 min. The shaker temperatures were set to 20℃, 30℃, 40℃, 50℃, and 60℃. After adsorption was complete, samples were centrifuged, and the concentration of Congo red in the supernatant was determined.

[0116] The results showed that in CO3 2- Under coexisting conditions, the MgO-C-6 adsorbent maintained a relatively stable Congo red removal effect without significant performance degradation, indicating its good anti-interference ability in a carbonate-competitive environment. Furthermore, the material exhibited a consistent adsorption trend after five regeneration cycles, demonstrating good stability and repeatability in its adsorption behavior, indicating its good adaptability and application potential in complex anion-coexisting wastewater systems.

[0117] In summary, this invention achieves the controllable preparation of anhydrous magnesium carbonate from disordered growth to a directional rod-like structure by introducing carboxylates as crystal growth regulators during the carbonization process of brucite, and inherits the high specific surface area and porous structure of MgO material during calcination. Compared with traditional MgO materials, this invention achieves synergistic optimization in structural construction and surface function regulation, enabling the material to possess both structural and interfacial functional advantages.

[0118] Furthermore, this invention utilizes the regulatory role of carboxylates during crystal growth and their coordination effect on the material surface to form stable functional sites on the material surface, thereby significantly enhancing its interfacial interaction ability with anionic dyes, and in SO4 2- CO3 2- Cl - It maintains good anti-interference performance and selective adsorption capacity in coexisting ion systems, demonstrating good adaptability to complex systems.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent variations or substitutions made in accordance with the present invention should be covered within the scope of protection of the present invention. The raw materials used in the specific embodiments are all commercially available and can be used directly.

Claims

1. A method for preparing a carboxylate-regulated rod-shaped magnesium oxide adsorbent, characterized in that, Includes the following steps: (1) Disperse brucite powder in a solution with a carboxylate concentration of 0.01 mol / L-0.3 mol / L and carry out a hydrothermal reaction under CO2 atmosphere to form rod-shaped anhydrous magnesium carbonate precursor; filter, wash and dry the obtained product; (2) The precursor is calcined to obtain rod-shaped MgO material; the surface of the rod-shaped MgO material has stable functional sites. The solid-liquid ratio of brucite powder to solution is 1g:(10-30)mL; The CO2 atmosphere is a pressurized CO2 atmosphere with a pressure of 0.5MPa-3MPa and a flow rate of 50mL / min-300mL / min.

2. The method for preparing a carboxylate-regulated rod-shaped magnesium oxide adsorbent according to claim 1, characterized in that, The hydrothermal reaction is carried out in a closed reactor with a filling rate of 30%-80%.

3. The method for preparing a carboxylate-regulated rod-shaped magnesium oxide adsorbent according to claim 1, characterized in that, The hydrothermal reaction temperature is 100℃-200℃, and the reaction time is 1h-10h.

4. The method for preparing a carboxylate-regulated rod-shaped magnesium oxide adsorbent according to claim 1, characterized in that, The carboxylate is one or more of acetate and citrate.

5. The method for preparing a carboxylate-regulated rod-shaped magnesium oxide adsorbent according to claim 1, characterized in that, The calcination time is 1-6 hours, and the calcination temperature is 400℃-700℃.

6. A carboxylate-regulated rod-shaped magnesium oxide adsorbent, prepared by the method according to any one of claims 1 to 5, characterized in that, The magnesium oxide adsorbent material has a length of 10μm-30μm, a width of 2μm-6μm, an aspect ratio of 3-10, and a specific surface area of ​​150m². 2 / g-220m 2 / g.

7. The carboxylate-regulated rod-shaped magnesium oxide adsorbent according to claim 6, characterized in that, The surface of the magnesium oxide adsorbent material contains carboxylate-derived functional groups, and it reacts with Mg... 2+ Formation of coordination structures.

8. The application of a carboxylate-regulated rod-shaped magnesium oxide adsorbent prepared by the method according to any one of claims 1 to 5 in the removal of Congo red from anionic dye wastewater, characterized in that, The rod-shaped magnesium oxide adsorbent was added to anionic dye wastewater containing Congo red at a concentration of 100 mg / L-200 mg / L and fully dispersed. The adsorption reaction was carried out for 10 min-180 min under constant temperature shaking conditions with a pH of 5-13 and a temperature of 20℃-60℃. The dosage of the adsorbent material is 0.05 g / L to 0.15 g / L.

9. The application of a carboxylate-regulated rod-shaped magnesium oxide adsorbent according to claim 8 in the removal of Congo red from anionic dye wastewater, characterized in that, The anionic dye wastewater also contains coexisting anions at a concentration of 0.005 mol / L to 0.05 mol / L; The anion is SO4. 2- CO3 2- Cl - One or more of them.

10. The application of a carboxylate-regulated rod-shaped magnesium oxide adsorbent according to claim 9 in the removal of Congo red from anionic dye wastewater, characterized in that, The removal rate of Congo red from the anionic dye wastewater is no less than 75%.

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