A magnetic porous loess organic composite material, its preparation method and application

Abstract

This invention belongs to the field of heavy metal pollution remediation technology in water environments, and provides a magnetic porous loess organic composite material, its preparation method, and its application. The preparation method of the magnetic porous loess organic composite material includes: acid-activating loess material to obtain acid-activated loess material; mixing the acid-activated loess material with an alkaline pore-forming agent in water to form a homogeneous slurry, then adding an acid solution dropwise to form a mixed slurry, and reacting under stirring conditions to obtain porous loess material; assembling the porous loess material with Fe3O4 nanoparticles in the presence of sodium carboxymethyl cellulose to obtain a Fe3O4 / loess magnetic composite material; mixing the Fe3O4 / loess magnetic composite material, an amino compound, and an aldehyde compound, and allowing the amino compound and aldehyde compound to undergo a Schiff base reaction to obtain the magnetic porous loess organic composite material. This invention solves the problems of the limited adsorption effect of natural loess on heavy metal ions and the problems existing in the composite process with Fe3O4 nanoparticles.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal pollution remediation technology in water environment, specifically relating to a magnetic porous loess organic composite material, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of industries such as mining, metallurgy, electroplating, and fine chemicals, large quantities of iron (Fe) have been produced. 2+ ), manganese (Mn) 2+ ), copper (Cu) 2+ ), Zinc (Zn) 2+ ) and mercury (Hg 2+ Wastewater containing heavy metal ions, such as sodium ions, is discharged into the aquatic environment. These heavy metal pollutants are characterized by high toxicity, recalcitrant degradation, bioaccumulation, and persistence, posing a serious threat to ecosystems and human health. Long-term exposure to heavy metal ions may lead to damage to the nervous system, liver and kidney function, and the immune system. Therefore, achieving efficient removal and resource recovery of heavy metal ions from the aquatic environment has become an important research direction in the field of environmental remediation.

[0003] Adsorption is considered one of the most promising technologies for heavy metal pollution control due to its advantages such as simple operation, low cost, high selectivity, minimal secondary pollution, and good renewability. The key to adsorption lies in the design and performance optimization of the adsorbent, aiming to simultaneously achieve high adsorption capacity, high selectivity, excellent stability, and easy recyclability. Among various adsorbents, natural mineral adsorbents have attracted much attention due to their wide availability, low price, and good environmental compatibility. Loess is a typical natural silica-alumina mineral material. Its surface contains active groups such as hydroxyl and carboxyl groups, possessing certain ion exchange and electrostatic adsorption capabilities. Furthermore, its well-developed pores and good permeability give it a natural advantage as a heavy metal adsorbent. Especially in the treatment of regional mining wastewater, loess materials have outstanding advantages such as local availability, low cost, and environmental friendliness. However, powdered loess is easily dispersed in water, difficult to recover, and has poor reusability. Magnetic functionalization technology provides a new approach for the efficient separation and reuse of adsorbents. By introducing magnetic nanoparticles such as Fe3O4 into loess materials, rapid solid-liquid separation can be achieved under an external magnetic field, avoiding filtration and centrifugation and significantly improving the operability of the adsorption process. However, in existing technologies, loess and Fe3O4 nanoparticles are composited via a solvothermal method. This method suffers from problems such as high temperature and pressure, high energy consumption, demanding equipment requirements, and the tendency for Fe3O4 nanoparticles to agglomerate. Furthermore, the solvothermal reaction process is highly sensitive to solvent type, temperature, pressure, and reaction time, making it difficult to control. In addition, natural loess has a low adsorption capacity for heavy metal ions, resulting in limited adsorption effects. Summary of the Invention

[0004] To address the limitations of natural loess's adsorption capacity for heavy metal ions in existing technologies and the problems encountered in its composite process with Fe3O4 nanoparticles, this invention provides a magnetic porous loess organic composite material, its preparation method, and its application.

[0005] This invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a magnetic porous loess organic composite material, comprising:

[0007] S1, acid activation treatment is performed on loess material to obtain acid-activated loess material;

[0008] S2, acid-activated loess material and alkaline pore-forming agent are mixed in water to form a homogeneous slurry, and then acid solution is added dropwise to form a mixed slurry. The reaction is carried out under stirring conditions to obtain porous loess material;

[0009] S3, porous loess material and Fe3O4 nanoparticles were assembled in the presence of sodium carboxymethyl cellulose to obtain Fe3O4 / loess magnetic composite material.

[0010] S4. Fe3O4 / loess magnetic composite material, amine compound and aldehyde compound are mixed, and the amine compound and aldehyde compound are subjected to Schiff base reaction to graft Schiff base functional component onto Fe3O4 / loess magnetic composite material to obtain magnetic porous loess organic composite material.

[0011] Preferably, in S2, the alkaline pore-forming agent is sodium bicarbonate, and the acid solution is hydrochloric acid.

[0012] Preferably, in S2, the pH value of the mixed slurry is 4 to 5.

[0013] Preferably, S3 specifically involves: dispersing Fe3O4 nanoparticles in a sodium carboxymethyl cellulose solution and stirring to obtain a sodium carboxymethyl cellulose-Fe3O4 dispersion; dispersing porous loess material in another sodium carboxymethyl cellulose solution and stirring to obtain a sodium carboxymethyl cellulose-loess dispersion; mixing the sodium carboxymethyl cellulose-Fe3O4 dispersion and the sodium carboxymethyl cellulose-loess dispersion, stirring, and separating the solid product to obtain the Fe3O4 / loess magnetic composite material.

[0014] Preferably, S3 specifically involves: dispersing Fe3O4 nanoparticles in a sodium carboxymethyl cellulose solution, stirring to obtain a sodium carboxymethyl cellulose-Fe3O4 dispersion, separating the solid product to obtain a sodium carboxymethyl cellulose-Fe3O4 precursor material; dispersing porous loess material in another sodium carboxymethyl cellulose solution, stirring to obtain a sodium carboxymethyl cellulose-loess dispersion, separating the solid product to obtain a sodium carboxymethyl cellulose-loess precursor material; dispersing the sodium carboxymethyl cellulose-Fe3O4 precursor material and the sodium carboxymethyl cellulose-loess precursor material in water, stirring, separating the solid product to obtain a Fe3O4 / loess magnetic composite material.

[0015] Preferably, in S4, the amine compound is m-phenylenediamine or ethylenediamine; the aldehyde compound is formaldehyde or terephthalaldehyde.

[0016] Preferably, in S4, the total mass of the amine compound and the aldehyde compound is 37.5% to 44.4% of the total mass of the Fe3O4 / loess magnetic composite material, the amine compound and the aldehyde compound.

[0017] Secondly, the present invention provides a magnetic porous loess organic composite material obtained by the preparation method described above.

[0018] Thirdly, the present invention provides the application of the magnetic porous loess organic composite material described above in the adsorption of heavy metal ions in water.

[0019] The heavy metal ion is Fe. 2+ Mn 2+ and Zn 2+ At least one of them.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] First, the method of this invention constructs a mesoporous structure through acid activation and bubble-forming, thereby optimizing the structure of the loess framework and exposing active sites. Specifically, this invention first uses acid activation to remove carbonate impurities from the loess and activate surface hydroxyl sites; then, an alkaline pore-forming agent reacts with acid to generate bubbles in situ, and the release of these bubbles constructs a mesoporous structure, improving specific surface area and pore connectivity. This method is mild, controllable, and environmentally friendly, providing an ideal framework for subsequent Fe3O4 nanoparticle loading and organic functionalization modification. Second, the method of this invention utilizes sodium carboxymethyl cellulose to achieve green and efficient assembly of porous loess materials and Fe3O4 nanoparticles. Magnetic force testing results show that the resulting magnetic porous loess organic composite material has good magnetic response performance, indicating that Fe3O4 nanoparticles have been successfully introduced into the material system. This invention introduces sodium carboxymethyl cellulose (CMC) as a green biopolymer bridging agent. Through the formation of multiple hydrogen bonds and coordination bonds between its carboxyl and hydroxyl groups and the Si-OH / Al-OH on the surface of porous loess materials and the Fe-OH on the surface of Fe3O4, it achieves a stable combination of porous loess materials and Fe3O4 nanoparticles. Simultaneously, CMC also acts as a dispersant and stabilizer for Fe3O4 nanoparticles, inhibiting their aggregation. Compared to the solvothermal method for preparing magnetically modified loess materials, the preparation method provided by this invention does not require high-temperature, high-pressure, and sealed conditions. The process conditions are milder, the operation is simpler, and it helps reduce energy consumption and equipment requirements. Furthermore, the interfacial regulation effect of CMC helps improve the dispersion stability of Fe3O4 nanoparticles on the surface of porous loess materials, reducing the tendency to aggregate, thus facilitating the effective composite of the two. In addition, the method of this invention avoids organic solvent pollution, demonstrating green, efficient, and environmentally friendly characteristics. Furthermore, this invention generates Schiff base functional components containing C=N functional groups in situ on the surface of the Fe3O4 / loess magnetic composite material via a Schiff base reaction. These Schiff base functional components form multiple high-energy coordination sites on the material surface, enabling strong coordination with heavy metal ions and enhancing the material's adsorption capacity for these ions. Finally, this invention forms a multifunctional synergistic system, achieving a comprehensive performance of high capacity, rapid separation, and recyclability. Specifically, in the composite material prepared by this invention, the porous loess framework provides mechanical strength and diffusion channels, while Fe3O4 nanoparticles impart magnetic response and recyclability. These two components form a stable synergistic structure under the bridging effect of sodium carboxymethyl cellulose. Simultaneously, the Schiff base functional components provide a high density of coordination sites, resulting in a material with high adsorption capacity and rapid equilibrium characteristics for heavy metal ions in the aquatic environment, enabling rapid solid-liquid separation under an applied magnetic field.In summary, this invention successfully constructs a magnetic porous loess organic composite material integrating high specific surface area, mesoporous structure, abundant distribution of active functional groups, strong coordination activity, and recyclable magnetic response through multiple innovative strategies such as acid activation, bubble pore formation, green assembly of sodium carboxymethyl cellulose, and grafting Schiff base functional components. The material preparation process is green and efficient, simple, and uses inexpensive raw materials. The resulting material has excellent adsorption performance and has broad engineering application prospects and promotional value in the treatment of mine wastewater, electroplating wastewater, and other heavy metal pollution.

[0022] Furthermore, the pH value of the mixed slurry was adjusted to 4-5 by adding acid solution, and pore-forming treatment was carried out under this condition. The above conditions are conducive to controlling the gas production process and obtaining porous loess material with a relatively well-developed pore structure.

[0023] Furthermore, the Fe3O4 / loess magnetic composite material of the present invention can be prepared by either liquid-phase assembly or solid-phase assembly. The results of the examples show that the Fe3O4 / loess magnetic composite material prepared by the liquid-phase assembly method exhibits superior adsorption of heavy metal ions. This is presumably because, during the liquid-phase assembly process, the Fe3O4 nanoparticles and porous loess material are more fully dispersed in the liquid system, which facilitates effective contact and composite formation between the two, and provides more surface-available sites for the subsequent Schiff base reaction.

[0024] Furthermore, the amine compound used in the Schiff base reaction is m-phenylenediamine or ethylenediamine, and the aldehyde compound is formaldehyde or terephthalaldehyde. The type of aldehyde compound has a certain influence on the heavy metal ion adsorption performance of the final composite material. When formaldehyde is used as the aldehyde compound, the resulting magnetic porous loess organic composite material has better adsorption performance for heavy metal ions.

[0025] Furthermore, by controlling the feed ratio of precursors used to form Schiff base functional components, an appropriate amount of Schiff base functional components are introduced onto the surface of the Fe3O4 / loess magnetic composite material. The amount of Schiff base functional components introduced affects the surface functionalization degree and structural characteristics of the composite material. A low amount may not provide sufficient coordination sites; a high amount may affect the available sites on the material surface and the mass transfer process. The results of this invention show that when the total mass of the precursors (amine compounds and aldehyde compounds) used to form Schiff base functional components is 37.5%~44.4% of the total mass of the Fe3O4 / loess magnetic composite material, amine compounds, and aldehyde compounds, it is beneficial to improve the coordination of heavy metal ions on the material surface, while also taking into account the maintenance of the pore structure of the porous loess material and the mass transfer process. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 Infrared spectra of the composite materials prepared in Examples 1, 2, 3, 4, Comparative Example 3, and Comparative Example 4.

[0028] Figure 2 The nitrogen adsorption-desorption curves are for the magnetic porous loess organic composite materials prepared in Examples 1, 2, 3 and 4.

[0029] Figure 3 The pore size distribution curves are for the magnetic porous loess organic composite materials prepared in Examples 1, 2, 3 and 4.

[0030] Figure 4 The magnetic force distribution curves of the magnetic porous loess organic composite materials prepared in Examples 1, 2, 3 and 4 are shown.

[0031] Figure 5 SEM image of the Fe3O4 / loess magnetic composite material prepared in Comparative Example 3.

[0032] Figure 6 The image shows a SEM image of the Fe3O4 / loess magnetic composite material prepared in Comparative Example 4.

[0033] Figure 7 The image shows a SEM image of the magnetic porous loess organic composite material prepared in Example 3.

[0034] Figure 8 The image shows a SEM image of the magnetic porous loess organic composite material prepared in Example 4.

[0035] Figure 9 The image shows a SEM image of the magnetic porous loess organic composite material prepared in Example 1.

[0036] Figure 10 The image shows a SEM image of the magnetic porous loess organic composite material prepared in Example 2.

[0037] Figure 11 SEM image of the magnetic porous loess organic composite material prepared in Comparative Example 5.

[0038] Figure 12 To apply the magnetic porous loess organic composite materials in Examples 1-15 to Fe 2+ Mn2+ and Zn 2+ The adsorption capacity; Application Examples 1-5 are Fe 2+ Adsorption, examples 6-10 are Mn 2+ Adsorption, application examples 11-15 are for Zn 2+ Adsorption.

[0039] Figure 13 To apply the magnetic porous loess organic composite materials in Examples 16-30 to Fe 2+ Mn 2+ and Zn 2+ The adsorption capacity; Application Examples 16-20 are Fe 2+ Adsorption, application examples 21-25 are Mn 2+ Adsorption, application examples 26-30 are for Zn 2+ Adsorption.

[0040] Figure 14 To apply the magnetic porous loess organic composite material in Examples 31-45 to Fe 2+ Mn 2+ and Zn 2+ The adsorption capacity; Application Examples 31-35 are Fe 2+ Adsorption, application examples 36-40 are Mn 2+ Adsorption, application examples 41-45 are for Zn 2+ Adsorption.

[0041] Figure 15 To apply the magnetic porous loess organic composite material in Examples 46-60 to Fe 2+ Mn 2+ and Zn 2+ The adsorption capacity; Application Examples 46-50 are Fe 2+ Adsorption, application examples 51-55 are Mn 2+ Adsorption, application examples 56-60 are for Zn 2+ Adsorption.

[0042] Figure 16 For the materials in Application Example 1 and Application Examples 61-65, the effect of Fe 2+ Adsorption capacity. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications in the art, unless otherwise stated.

[0045] The preparation method of the magnetic porous loess organic composite material of the present invention includes:

[0046] S1, acid activation treatment is performed on loess material to obtain acid-activated loess material;

[0047] S2, acid-activated loess material and alkaline pore-forming agent are mixed in water to form a homogeneous slurry, and then acid solution is added dropwise to form a mixed slurry. The reaction is carried out under stirring conditions to obtain porous loess material;

[0048] S3, porous loess material and Fe3O4 nanoparticles were assembled in the presence of sodium carboxymethyl cellulose to obtain Fe3O4 / loess magnetic composite material.

[0049] S4. Fe3O4 / loess magnetic composite material, amine compound and aldehyde compound are mixed, and the amine compound and aldehyde compound are subjected to Schiff base reaction to graft Schiff base functional component onto Fe3O4 / loess magnetic composite material to obtain magnetic porous loess organic composite material.

[0050] This invention involves acid-activating loess materials, thereby generating bubbles in situ through an acid-base reaction. The release of these bubbles creates a mesoporous structure within the acid-activated loess material. This bubble-forming process expands the pore size distribution and improves pore connectivity without disrupting the loess framework. The resulting porous loess material framework possesses abundant mesoporous structures, providing greater surface space and mass transfer channels for the subsequent embedding of Fe3O4 nanoparticles and grafting of Schiff base functional components, thus enhancing the heavy metal ion adsorption performance of the magnetic porous loess organic composite material.

[0051] Simultaneously, this invention enables the effective assembly of Fe3O4 nanoparticles and porous loess materials under the action of sodium carboxymethyl cellulose, thereby forming a Fe3O4 / loess magnetic composite material. In this invention, sodium carboxymethyl cellulose is used as a polymeric bridging agent. On the one hand, the carboxyl and hydroxyl groups of sodium carboxymethyl cellulose facilitate interaction with the hydroxylation sites on the surface of Fe3O4 nanoparticles and the oxygen-containing sites such as Si-OH and Al-OH on the surface of porous loess materials, thereby promoting the two-phase composite. On the other hand, the polymeric chain structure of sodium carboxymethyl cellulose helps improve the dispersion state of Fe3O4 nanoparticles in the system and reduces the tendency of Fe3O4 nanoparticles to agglomerate. Compared with solvothermal composite methods, the assembly method used in this invention does not require a high-temperature and high-pressure reaction environment, and has the advantages of mild process conditions, relatively simple operation, and low environmental impact, and is conducive to obtaining Fe3O4 / loess magnetic composite materials with better composite effect.

[0052] This invention introduces amine compounds and aldehyde compounds to generate a Schiff base functional component containing C=N functional groups in situ on the surface of Fe3O4 / loess magnetic composite material through a Schiff base reaction between the two. This Schiff base functional component forms multiple high-energy coordination sites on the material surface, which can strongly coordinate with heavy metal ions, thereby enhancing the material's adsorption capacity for heavy metal ions.

[0053] In some preferred embodiments of the present invention, S1 specifically involves: drying the loess material, grinding and sieving it, mixing it with an acidification solution, and carrying out an acidification reaction under stirring conditions to dissolve and remove the carbonate and impurity components in the loess material and activate the surface, thereby obtaining acid-activated loess material.

[0054] After acid activation treatment, the density of hydroxyl groups (Si-OH, Al-OH) on the surface of loess materials is significantly increased, and their chemical activity is enhanced, providing active sites for subsequent pore formation and composite processes. Acid activation treatment not only improves the surface energy and wettability of loess particles, but also significantly increases their specific surface area and porosity, thereby enhancing their binding ability with Schiff base functional components.

[0055] The acidification solution can be an inorganic acid solution, preferably hydrochloric acid, with a concentration of 0.8~1.2 mol / L (preferably 1 mol / L). The reaction temperature for the acidification reaction is 50~70℃, preferably 60℃, and the reaction time is 4~8 h. The liquid-to-solid ratio of loess material to acidification solution is controlled at 10~15 mL / g. This condition can effectively remove carbonates, soluble metal impurities, and some exchangeable cations from the loess material without damaging the framework structure, increasing the surface hydroxyl density and specific surface area, and providing stable active sites for subsequent reactions. If the hydrochloric acid concentration or reaction temperature is too low, the impurities will not dissolve sufficiently, and the loess surface will not be sufficiently activated. If the hydrochloric acid concentration or reaction temperature is too high, it may damage the silica-alumina layer structure in the loess framework, leading to pore wall collapse. After the acidification reaction is completed, the mixture is filtered, and the filter cake is washed with distilled water until the pH reaches 7.0±0.2, and then dried.

[0056] In some preferred embodiments of the present invention, in step S2, the alkaline pore-forming agent is sodium bicarbonate, and the acid solution is hydrochloric acid. In some embodiments of the present invention, the mass ratio of the acid-activated loess material to sodium bicarbonate is 5:1, the concentration of hydrochloric acid used is 1 mol / L, the pH value of the mixed slurry is adjusted to 4-5, and the reaction time is 20-40 min. After the reaction is completed, it is washed until neutral and dried at 50-70℃. Using the above conditions for pore-forming treatment is beneficial to obtaining porous loess material with a relatively well-developed pore structure. In addition, the average pore size of the porous loess materials obtained in Examples 1-4 is between 16.5666 and 19.0303 nm, which falls within the mesoporous range, indicating that the material has formed a relatively well-developed mesoporous structure, which is beneficial for the subsequent loading and composite of Fe3O4 nanoparticles.

[0057] In some preferred embodiments of the present invention, the preparation of the Fe3O4 / loess magnetic composite material in S3 can be carried out by liquid phase assembly or solid phase assembly.

[0058] Specifically, the liquid-phase assembly process is as follows: Fe3O4 nanoparticles are dispersed in a sodium carboxymethyl cellulose solution and stirred to obtain a sodium carboxymethyl cellulose-Fe3O4 dispersion. Porous loess material is dispersed in another sodium carboxymethyl cellulose solution and stirred to obtain a sodium carboxymethyl cellulose-loess dispersion. The sodium carboxymethyl cellulose-Fe3O4 dispersion and the sodium carboxymethyl cellulose-loess dispersion are mixed and stirred for 3-4 hours. The solid product is separated, washed, and dried to obtain the Fe3O4 / loess magnetic composite material.

[0059] Specifically, the solid-phase assembly process is as follows: Fe3O4 nanoparticles are dispersed in a sodium carboxymethyl cellulose solution and stirred to obtain a sodium carboxymethyl cellulose-Fe3O4 dispersion. The solid product is separated, washed, and dried to obtain a sodium carboxymethyl cellulose-Fe3O4 precursor material. Porous loess material is dispersed in another sodium carboxymethyl cellulose solution and stirred to obtain a sodium carboxymethyl cellulose-loess dispersion. The solid product is separated, washed, and dried to obtain a sodium carboxymethyl cellulose-loess precursor material. The sodium carboxymethyl cellulose-Fe3O4 precursor material and the sodium carboxymethyl cellulose-loess precursor material are dispersed in water, stirred, and the solid product is separated, washed, and dried to obtain a Fe3O4 / loess magnetic composite material.

[0060] Compared to solid-phase assembly, liquid-phase assembly method for preparing Fe3O 4 / Loess magnetic composites exhibit superior adsorption of heavy metal ions. This is presumably because, during liquid-phase assembly, Fe3O4 nanoparticles and porous loess materials, in a dispersed state, achieve more thorough contact, facilitating the exposure of relevant surface sites and the composite process. This, in turn, improves the assembly uniformity of the resulting Fe3O4 / loess magnetic composite and provides more available sites for subsequent Schiff base reactions.

[0061] In one experiment, Fe3O4 nanoparticles were dispersed in a sodium carboxymethyl cellulose solution, and the pH was adjusted to 6.5–7.5. Similarly, porous loess material was dispersed in another sodium carboxymethyl cellulose solution, and the pH was adjusted to 6.5–7.5. Sodium carboxymethyl cellulose retains the solubility and extensibility of its carboxyl groups more readily under neutral conditions, which is beneficial for its stable adsorption on the surfaces of both Fe3O4 nanoparticles and porous loess material.

[0062] The Fe3O4 nanoparticles used in this invention have a particle size of 15-25 nm. Fe3O4 within this particle size range has a high specific surface area and strong magnetic responsiveness, and can be uniformly dispersed and bonded to the surface of porous loess materials under the stabilizing effect of sodium carboxymethyl cellulose. If the Fe3O4 nanoparticles are too small, the magnetic responsiveness is insufficient and they are easily oxidized; if the Fe3O4 nanoparticles are too large, the dispersibility is poor, they are prone to agglomeration, and the specific surface area is reduced.

[0063] As a specific implementation method, the preparation process of sodium carboxymethyl cellulose-Fe3O4 dispersion is as follows: Fe3O4 nanoparticles are added to deionized water and sonicated for 10-15 min (power 40 kHz). Then, sodium carboxymethyl cellulose solution is added, the pH value is adjusted to 6.5-7.5, and the mixture is stirred to obtain sodium carboxymethyl cellulose-Fe3O4 dispersion.

[0064] In some preferred embodiments of the present invention, in S3, the mass ratio of Fe3O4 nanoparticles to porous loess material is 1:(2.5~3.3) to balance magnetic responsiveness and pore structure stability. The mass ratio of Fe3O4 nanoparticles to sodium carboxymethyl cellulose is 1:(0.75~1).

[0065] In some preferred embodiments of the present invention, S4 specifically involves: dispersing the Fe3O4 / loess magnetic composite material in a solvent, adding a solution containing an amine compound and a solution containing an aldehyde compound, performing a Schiff base reaction under condensation reaction conditions, washing and drying the resulting product to obtain a magnetic porous loess organic composite material.

[0066] The preferred reaction time for the Schiff base reaction is 20–24 h, the preferred reaction temperature is room temperature (25 °C), and the preferred drying time is 20–24 h. Under these conditions, the Schiff base reaction can proceed fully, forming a stable C=N structure. If the reaction time is insufficient, the Schiff base reaction will be incomplete; if the reaction time is too long or the temperature is too high, self-polymerization or cross-linking reactions may occur, leading to pore blockage. Furthermore, the solvent is a mixed solution of water and ethanol (water to ethanol volume ratio 1:1), which is mild and environmentally friendly. No organic solvents or toxic reagents are introduced during the preparation process, conforming to the principles of green chemistry.

[0067] In some preferred embodiments of the present invention, in step S4, the amine compound is m-phenylenediamine or ethylenediamine; the aldehyde compound is formaldehyde or terephthalaldehyde; and the molar ratio of the amine compound to the aldehyde compound is preferably 1:1. When formaldehyde is used as the aldehyde compound, the resulting magnetic porous loess organic composite material exhibits better adsorption performance for heavy metal ions.

[0068] In some preferred embodiments of the present invention, in step S4, the Schiff base functional component is appropriately grafted onto the surface of the Fe3O4 / loess magnetic composite material by controlling the feeding ratio of Schiff base precursors (amine compounds and aldehyde compounds). This control strategy facilitates the construction of organic sites with coordination functions on the surface of the Fe3O4 / loess magnetic composite material, thereby improving the coordination adsorption capacity of the magnetic porous loess organic composite material for heavy metal ions, while also maintaining the pore structure and mass transfer process. By controlling the feeding ratio of Schiff base precursors, it is beneficial to reduce the impact on the openness of the original pore structure of the porous loess material while introducing organic sites with coordination functions. Based on a rough estimate of the feeding amount, the total mass of the precursors (amine compounds and aldehyde compounds) used to form the Schiff base functional component in the examples is 37.5%~44.4% of the total mass of the Fe3O4 / loess magnetic composite material, amine compounds, and aldehyde compounds. Under these feeding conditions, it is beneficial to introduce an appropriate amount of Schiff base functional component onto the surface of the Fe3O4 / loess magnetic composite material while maintaining the good structural characteristics of the composite material. The magnetic porous loess organic composite material prepared by the above method of the present invention has good adsorption performance for heavy metal ions in water and can be used for the remediation of heavy metal pollution in water environment.

[0069] The heavy metal ion is Fe. 2+ Mn 2+ and Zn 2+ At least one of them.

[0070] Example 1

[0071] This embodiment provides a magnetic porous loess organic composite material and its preparation method, including:

[0072] Step 1, Acid Activation of Loess

[0073] First, the loess material was placed in an oven and dried at 60℃ for 24 hours. Then, the dried loess material was ground and sieved (100 mesh). 20g of the sieved loess material was weighed and added to 250mL of 1mol / L hydrochloric acid solution. The resulting solution was placed on a magnetic stirrer and stirred at 60℃ for 6 hours. After the reaction was completed, the mixture was filtered. The filter cake was washed with distilled water until neutral. Then, the product was dried at 60℃ for 24 hours to obtain acid-activated loess material.

[0074] Step 2, creating air bubbles in loess

[0075] Weigh 5g of acid-activated loess material, add 1g of NaHCO3 and 40mL of distilled water, and stir until a homogeneous slurry is formed. While stirring, slowly add 1mol / L HCl solution until the pH of the resulting slurry is about 4.5. The slow addition is to prevent the slurry from splashing due to the explosive release of bubbles. Maintain stirring for 30min to allow the generated carbon dioxide bubbles to escape fully. At the same time, the microstructure of the acid-activated loess material is expanded by the bubbles to form pores. Then, place the mixed slurry in a Buchner funnel for vacuum filtration. Wash the filter cake with distilled water until neutral and dry at 60℃ for 24h to obtain porous loess material.

[0076] Step 3, Preparation of Fe3O4 / Loess Magnetic Composite Material

[0077] (1) Sodium carboxymethyl cellulose-Fe3O4 dispersion: 400 mg of Fe3O4 nanoparticles were added to 100 mL of deionized water and sonicated for 10 min; then 30 mL of 1% sodium carboxymethyl cellulose solution (containing 1 g of sodium carboxymethyl cellulose per 100 mL of solution) was added to adjust the pH of the system to about 7, and the mixture was mechanically stirred at 60 °C for 3 h to obtain sodium carboxymethyl cellulose-Fe3O4 dispersion;

[0078] (2) Sodium carboxymethyl cellulose-loess dispersion: 1g of porous loess material was added to 100mL of 0.5% sodium carboxymethyl cellulose solution (each 100mL of solution contains 1g of sodium carboxymethyl cellulose), the pH of the system was adjusted to about 7, and the mixture was magnetically stirred at 60℃ for 3h to obtain sodium carboxymethyl cellulose-loess dispersion;

[0079] (3) Composite and post-processing: Under stirring conditions, sodium carboxymethyl cellulose-Fe3O4 dispersion was added to sodium carboxymethyl cellulose-loess dispersion and mechanical stirring was continued for 3 hours. After the reaction was completed, the solid product was separated by an external magnetic field and washed with deionized water 3 times and ethanol 2 times in sequence. It was then dried at 60℃ for 12 hours to obtain Fe3O4 / loess magnetic composite material.

[0080] Step 4, Preparation of magnetic porous loess organic composite material

[0081] 0.3 g of Fe3O4 / loess magnetic composite material was weighed and dispersed in 100 mL of distilled water to obtain a Fe3O4 / loess dispersion. Separately, 0.1 g of m-phenylenediamine was dissolved in 100 mL of anhydrous ethanol (heated at 45 °C to promote dissolution) to obtain a solution containing an amine compound. This amine compound solution was added to the aforementioned Fe3O4 / loess dispersion, followed by 0.2 mL of 37% formaldehyde solution. The mixture was stirred at room temperature for 16 h to initiate a Schiff base reaction. After the reaction, the solid product was separated using an external magnetic field, washed three times with deionized water and twice with ethanol, and dried at 60 °C for 12 h to obtain a magnetic porous loess organic composite material. Based on a rough estimate of the feed amount (the density of the 37% formaldehyde solution was calculated as 1.08 g / mL), the total mass of m-phenylenediamine and formaldehyde used to form the Schiff base functional component was 37.5% of the total mass of the Fe3O4 / loess magnetic composite material, m-phenylenediamine, and formaldehyde.

[0082] Example 2

[0083] This embodiment provides a magnetic porous loess organic composite material and its preparation method. The specific preparation process is similar to that of Example 1, except that terephthalaldehyde is used in step 4.

[0084] Step 4: Weigh 0.3g of Fe3O4 / loess magnetic composite material and disperse it in 100mL of distilled water to obtain Fe3O4 / loess dispersion; separately, dissolve 0.1g of m-phenylenediamine in 100mL of anhydrous ethanol (heat at 45℃ to promote dissolution) to obtain a solution containing amine compounds; then dissolve 0.14g of terephthalaldehyde in 100mL of anhydrous ethanol (heat at 45℃ to promote dissolution) to obtain a solution containing aldehyde compounds; then add the above solutions containing amine compounds and aldehyde compounds to the aforementioned Fe3O4 / loess dispersion and react with mechanical stirring at room temperature (approximately 25℃) for 16h; after the reaction is completed, the obtained solid product is rapidly separated by an external magnetic field, and the separated solid product is washed three times with deionized water and twice with ethanol to remove unreacted m-phenylenediamine, terephthalaldehyde, and byproducts. The solid obtained after washing was dried at 60℃ for 12 hours to obtain a magnetic porous loess organic composite material. According to a rough estimate based on the amount of feed, the total mass of m-phenylenediamine and terephthalaldehyde used to form the Schiff base functional component is 44.4% of the total mass of Fe3O4 / loess magnetic composite material, m-phenylenediamine and terephthalaldehyde.

[0085] Example 3

[0086] This embodiment provides a magnetic porous loess organic composite material and its preparation method. The specific preparation process is similar to that of Example 1, except that step 3 uses a solid-phase assembly method to prepare the Fe3O4 / loess magnetic composite material.

[0087] Step 3, Preparation of Fe3O4 / Loess Magnetic Composite Material

[0088] (1) Add 400 mg of Fe3O4 nanoparticles to 100 mL of deionized water and sonicate for 10 min; then add 30 mL of 1% sodium carboxymethyl cellulose solution (containing 1 g of sodium carboxymethyl cellulose per 100 mL of solution) to adjust the pH of the system to about 7, and mechanically stir at 60 °C for 3 h. Then collect the solid product using a magnetic separator, wash the obtained solid product with deionized water 3 times, and then wash it with a small amount of ethanol 2 times to remove free sodium carboxymethyl cellulose, and dry it at 60 °C for 12 h to obtain sodium carboxymethyl cellulose-Fe3O4 precursor material.

[0089] (2) Disperse 1g of porous loess material in 100mL of 0.5% sodium carboxymethyl cellulose solution (each 100mL of solution contains 0.5g of sodium carboxymethyl cellulose), adjust the pH of the system to about 7, stir magnetically at 60℃ for 3h, then filter, wash the obtained solid product with deionized water 3 times, wash with a small amount of ethanol 2 times, and dry at 60℃ for 12h to obtain sodium carboxymethyl cellulose-loess precursor material.

[0090] (3) Weigh 0.5g sodium carboxymethyl cellulose-loess precursor material and 0.2g sodium carboxymethyl cellulose-Fe3O4 precursor material, disperse them in 350mL deionized water, mechanically stir at room temperature for 6h, separate the solid products with an external magnetic field, wash the obtained solid products with deionized water 3 times, wash them with a small amount of ethanol 2 times, and dry them at 60℃ for 12h to obtain Fe3O4 / loess magnetic composite material.

[0091] Example 4

[0092] This embodiment provides a magnetic porous loess organic composite material and its preparation method. The specific preparation process is similar to that of Example 3, except that terephthalaldehyde is used in step 4.

[0093] Step 4: Take 0.3g of the Fe3O4 / loess magnetic composite material prepared according to Example 3 and disperse it in 100mL of distilled water to obtain a Fe3O4 / loess dispersion; separately, take 0.1g of m-phenylenediamine and dissolve it in 100mL of anhydrous ethanol (heated at 45℃ to promote dissolution) to obtain a solution containing amine compounds; then take 0.14g of terephthalaldehyde and dissolve it in 100mL of anhydrous ethanol (heated at 45℃ to promote dissolution) to obtain a solution containing aldehyde compounds; then add the above solutions containing amine compounds and aldehyde compounds to the aforementioned Fe3O4 / loess dispersion, and mechanically stir for 16h at room temperature (approximately 25℃) to carry out a Schiff base reaction; after the reaction is completed, the obtained solid product is rapidly separated by an external magnetic field, and the separated solid product is washed three times with deionized water and twice with ethanol to remove unreacted m-phenylenediamine, terephthalaldehyde, and byproducts. The solid obtained after washing is dried at 60℃ for 12h to obtain a magnetic porous loess organic composite material.

[0094] Comparative Example 1

[0095] Following step 1 of Example 1, acid-activated loess material was obtained.

[0096] Comparative Example 2

[0097] Following steps 1 and 2 of Example 1, porous loess material was obtained.

[0098] Comparative Example 3

[0099] Following steps 1, 2, and 3 of Example 1, Fe3O4 / loess magnetic composite material was obtained by liquid-phase assembly.

[0100] Comparative Example 4

[0101] Following steps 1, 2, and 3 of Example 3, Fe3O4 / loess magnetic composite material was obtained by solid-state assembly method.

[0102] Comparative Example 5

[0103] The only difference between this comparative example and Example 1 is that the amount of precursor used to form the Schiff base functional component is increased in the Schiff base reaction stage, while the other conditions remain the same.

[0104] Step 4: Weigh 0.3g of Fe3O4 / loess magnetic composite material and disperse it in 100mL of distilled water to obtain a Fe3O4 / loess dispersion. Separately, dissolve 0.2g of m-phenylenediamine in 100mL of anhydrous ethanol (heated at 45℃ to promote dissolution) to obtain a solution containing an amine compound. Add the solution containing the amine compound to the above Fe3O4 / loess dispersion, and then add 0.4mL of 37% formaldehyde solution to the reaction system. Stir at room temperature for 16h to carry out the Schiff base reaction. After the reaction is completed, separate the solid product using an external magnetic field. Wash the separated solid product three times with deionized water, and then wash it twice with a small amount of ethanol. Dry the resulting solid at 60℃ for 12h to obtain a magnetic porous loess organic composite material. Based on a rough estimate of the feed amount (the density of the 37% formaldehyde solution is calculated as 1.08 g / mL), the total mass of m-phenylenediamine and formaldehyde used to form the Schiff base functional component in this comparative example is 54.5% of the total mass of Fe3O4 / loess magnetic composite material, m-phenylenediamine, and formaldehyde, which is higher than the feed ratio of approximately 37.5% in Example 1.

[0105] By comparing this comparative example with Example 1, the effect of increasing the proportion of Schiff base precursor on the pore structure characteristics and heavy metal ion adsorption performance of the obtained magnetic porous loess organic composite material can be investigated.

[0106] Application Example 1

[0107] At room temperature, 0.1 g of the magnetic porous loess organic composite material prepared in Example 1 was added to a 250 mL stoppered brown conical flask, followed by 10 mg / L Fe. 2+ 100 mL of pollutant solution was placed in an Erlenmeyer flask and reacted on a temperature-controlled shaker at 3°C ​​for 10 h. The Fe content in the supernatant of the reaction system was then measured. 2+ The concentration of heavy metal ions was analyzed to assess the removal efficiency of magnetic porous loess organic composite materials for heavy metal ions.

[0108] Application Examples 2-5

[0109] Application Examples 2-5 are similar to Application Example 1, the only difference being that Fe in Application Examples 2-5 2+ Fe in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0110] Application Example 6

[0111] This application example is similar to Application Example 1, except that: 10 mg / L Fe 2+ The contaminant solution was replaced with 10 mg / LMn 2+ Contaminant solution.

[0112] Application Examples 7-10

[0113] Application Examples 7-10 are similar to Application Example 6, the only difference being that in Application Examples 7-10, Mn 2+ Mn in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0114] Application Example 11

[0115] This application example is similar to Application Example 1, except that: 10 mg / L Fe 2+ The contaminant solution was replaced with 10 mg / L Zn. 2+ Contaminant solution.

[0116] Application Examples 12-15

[0117] Application Examples 12-15 are similar to Application Example 11, the only difference being that Zn in Application Examples 12-15 2+ Zn in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0118] Application Example 16

[0119] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 2 to a 250mL brown conical flask with a stopper.

[0120] Application Examples 17-20

[0121] Application Examples 17-20 are similar to Application Example 16, the only difference being that Fe in Application Examples 17-20 2+ Fe in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0122] Application Example 21

[0123] This application example is similar to Application Example 16, except that: 10 mg / L Fe 2+ The contaminant solution was replaced with 10 mg / LMn 2+ Contaminant solution.

[0124] Application Examples 22-25

[0125] Application Examples 22-25 are similar to Application Example 21, the only difference being that in Application Examples 22-25, Mn 2+ Mn in contaminant solution2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0126] Application Example 26

[0127] This application example is similar to Application Example 16, the only difference being: 10 mg / L Fe... 2+ The contaminant solution was replaced with 10 mg / L Zn 2+ Contaminant solution.

[0128] Application Examples 27-30

[0129] Application Examples 27-30 are similar to Application Example 26, the only difference being that Zn in Application Examples 27-30 2+ Zn in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0130] Application Example 31

[0131] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 3 to a 250mL brown conical flask with a stopper.

[0132] Application Examples 32-35

[0133] Application Examples 32-35 are similar to Application Example 31, the only difference being that Fe in Application Examples 32-35 2+ Fe in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0134] Application Example 36

[0135] This application example is similar to application example 31, the only difference being: 10 mg / L Fe... 2+ The contaminant solution was replaced with 10 mg / LMn 2+ Contaminant solution.

[0136] Application Examples 37-40

[0137] Application Examples 37-40 are similar to Application Example 36, the only difference being that in Application Examples 37-40, Mn 2+ Mn in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0138] Application Example 41

[0139] This application example is similar to application example 31, the only difference being: 10 mg / L Fe... 2+ The contaminant solution was replaced with 10 mg / L Zn. 2+ Contaminant solution.

[0140] Application Examples 42-45

[0141] Application Examples 42-45 are similar to Application Example 41, the only difference being that in Application Examples 42-45, Zn 2+ Zn in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0142] Application Example 46

[0143] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 4 to a 250mL brown conical flask with a stopper.

[0144] Application Examples 47-50

[0145] Application Examples 47-50 are similar to Application Example 46, the only difference being that in Application Examples 47-50 Fe 2+ Fe in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0146] Application Example 51

[0147] This application example is similar to application example 46, except that: 10 mg / L Fe 2+ The contaminant solution was replaced with 10 mg / LMn 2+ Contaminant solution.

[0148] Application Examples 52-55

[0149] Application Examples 52-55 are similar to Application Example 51, the only difference being that Mn in Application Examples 52-55 2+ Mn in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0150] Application Example 56

[0151] This application example is similar to application example 46, except that: 10 mg / L Fe 2+ The contaminant solution was replaced with 10 mg / L Zn.2+ Contaminant solution.

[0152] Application Examples 57-60

[0153] Application Examples 57-60 are similar to Application Example 56, the only difference being that Zn in Application Examples 57-60 2+ Zn in contaminant solution 2+ The concentrations were 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L, respectively.

[0154] Application Example 61

[0155] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the acid-activated loess material prepared in Comparative Example 1 to a 250mL brown conical flask with a stopper.

[0156] Application Example 62

[0157] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the porous loess material prepared in Comparative Example 2 to a 250mL brown conical flask with a stopper.

[0158] Application Example 63

[0159] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the Fe3O4 / loess magnetic composite material prepared by liquid-phase assembly method in Comparative Example 3 to a 250mL brown conical flask with a stopper.

[0160] Application Example 64

[0161] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the Fe3O4 / loess magnetic composite material prepared by solid-phase assembly method in Comparative Example 4 to a 250mL brown conical flask with a stopper.

[0162] Application Example 65

[0163] This application example is similar to Application Example 1, except that the addition of 0.1g of the magnetic porous loess organic composite material prepared in Example 1 to a 250mL brown conical flask with a stopper is replaced by the addition of 0.1g of the magnetic porous loess organic composite material prepared by Comparative Example 5 with a high Schiff base precursor feed ratio to a 250mL brown conical flask with a stopper.

[0164] To gain a clearer understanding of the changes in surface functional groups during the preparation of the magnetic porous loess organic composite material of this invention, Fourier transform infrared spectroscopy analysis was performed on the materials from different embodiments and comparative examples. Figure 1 In the infrared spectra shown, the infrared spectra of the composite materials prepared in Examples 1, 2, 3, 4, Comparative Example 3, and Comparative Example 4 are all within 594 cm⁻¹. -1 and 698cm -1 The presence of an Fe-O absorption peak at 1517 cm⁻¹ corresponds to the characteristic Fe-O peak within the Fe₃O₄ nanoparticles, indicating that the Fe₃O₄ nanoparticles are effectively loaded onto the loess material. Comparing the infrared spectra of the Fe₃O₄ / loess magnetic composite materials prepared in Comparative Examples 3 and 4, it can be seen that the infrared spectra of Examples 1, 2, 3, and 4 all show an absorption peak at 1517 cm⁻¹. -1 and 1622cm -1 Two characteristic peaks were observed at 1622 cm⁻¹, corresponding to the stretching vibrations of the aromatic carbon ring and the C=N functional group, respectively. This indicates that a condensation reaction occurred between the aldehyde group of the aldehyde compound and the amine group of the amine compound, and the resulting Schiff base functional component was successfully loaded onto the Fe₃O₄ / loess magnetic composite material. Furthermore, the peak at 1622 cm⁻¹... -1 The characteristic peak at 1696 cm⁻¹ shifted slightly in different embodiments, possibly due to the different aldehyde compounds used in those embodiments. In the infrared spectra of the magnetic porous loess organic composite materials of Examples 2 and 4, a peak at 1696 cm⁻¹ was observed. -1 The characteristic peak at this location may be related to the terephthalaldehyde selected in the Schiff base reaction, which further illustrates that the aldehyde compounds selected in the Schiff base reaction have a significant impact on the physicochemical properties of the prepared magnetic porous loess organic composite material.

[0165] To understand the changes in specific surface area and pore structure during the preparation of magnetic porous loess organic composite materials, a specific surface area analyzer was used for testing and characterization. The nitrogen adsorption-desorption curves of the magnetic porous loess organic composite materials prepared in Examples 1, 2, 3, and 4 are shown below. Figure 2 As shown, the specific surface areas of the magnetic porous loess organic composite materials prepared in Examples 2 and 4 are 1.3431 m², respectively. 2 / g and 3.5915m 2 / g, lower than Example 1 (9.7699m) 2 / g) and Example 3 (9.0071m) 2The specific surface area of ​​the magnetic porous loess organic composite material prepared by (g) was measured. The specific surface area values ​​of different examples showed differences, which may be related to the aldehyde compounds selected in the Schiff base reaction. In Examples 1 and 3, formaldehyde was selected as the aldehyde compound in the Schiff base reaction, while in Examples 2 and 4, terephthalaldehyde was selected. When formaldehyde was used, the resulting material exhibited a higher specific surface area, while when terephthalaldehyde was used, the specific surface area of ​​the resulting material decreased significantly. This indicates that the type of aldehyde compound affects the introduction of organic components onto the material surface and the pore structure characteristics. Compared to terephthalaldehyde, formaldehyde has a smaller molecular size and may have a relatively smaller impact on the surface coverage and pore structure openness of the material, thus being more conducive to maintaining a higher specific surface area. Furthermore, the average pore sizes of the magnetic porous loess organic composite materials prepared in Examples 2 and 4 were 19.0303 nm and 16.5666 nm, respectively, while the average pore sizes of the magnetic porous loess organic composite materials prepared in Examples 1 and 3 were 18.2865 nm and 17.1116 nm, respectively. This indicates that the average pore sizes of the materials prepared in different examples have small differences and are all within the mesoporous range. Figure 3 As shown in the pore size distribution curves, the magnetic porous loess organic composite material prepared in Example 4 has a more obvious pore size distribution peak around 50 nm. The peak value of Example 2 in the same pore size range is lower than that of Example 4. The pore size distribution of Examples 1 and 3 is relatively wide, indicating that their pore structure distribution is relatively dispersed.

[0166] To evaluate the feasibility of magnetic separation of different magnetic porous loess-organic composite materials, a vibrating sample magnetometer (VSM) was used to characterize the magnetic force of different samples. The magnetic force distribution curves of the magnetic porous loess-organic composite materials prepared in Examples 1, 2, 3, and 4 are shown below. Figure 4As shown, the magnetic saturation strength values ​​of the magnetic porous loess organic composite materials prepared in Examples 1, 2, 3, and 4 are 42.94 emu / g, 36.71 emu / g, 22.21 emu / g, and 24.06 emu / g, respectively. This indicates that the magnetic porous loess organic composite materials prepared in the above examples all have high magnetic saturation strength, which provides feasibility for magnetic separation after subsequent water treatment. Furthermore, the magnetic saturation strength values ​​of the magnetic porous loess organic composite materials prepared in Examples 1 and 2 are quite similar, as are those prepared in Examples 3 and 4. Examples 1 and 2 used a liquid-phase assembly method (step 3) to prepare the Fe3O4 / loess magnetic composite material, while Examples 3 and 4 used a solid-phase assembly method (step 3). This indicates that the magnetic saturation strength of the magnetic porous loess organic composite material mainly depends on the Fe3O4 / loess magnetic composite material. Compared with the solid-phase assembly method, the Fe3O4 / loess magnetic composite material prepared by the liquid-phase assembly method (step 3) has a stronger magnetic saturation strength, resulting in a stronger magnetic porous loess organic composite material, which is more conducive to subsequent separation and recovery. In addition, the selection of different aldehyde compounds also leads to differences in the magnetic saturation strength of the magnetic porous loess organic composite material, which may be related to the degree of Schiff base reaction.

[0167] To analyze the morphological characteristics of different composite materials, scanning electron microscopy (SEM) analysis was performed on the composite materials. Figure 5 and Figure 6 SEM images of the Fe3O4 / loess magnetic composite materials prepared in Comparative Examples 3 and 4 are shown. It can be seen that nanospheres of Fe3O4 (particle size approximately 15-25 nm) are uniformly and effectively loaded on the outer surface of the porous loess material. This indicates that sodium carboxymethyl cellulose, as a green biopolymer bridging agent, can effectively achieve a stable bond between Fe3O4 nanoparticles and the porous loess material, demonstrating the green, efficient, and environmentally friendly nature of the material assembly method of this invention. Figure 5 and Figure 6As shown, the Fe3O4 / loess magnetic composite materials prepared in Comparative Examples 3 and 4 both exhibit the morphological characteristics of Fe3O4 nanoparticles adhering to the surface of the porous loess matrix. In Comparative Example 3, the distribution of Fe3O4 nanoparticles on the surface of the porous loess material is relatively continuous, and the overall morphology is relatively uniform; in Comparative Example 4, some exposed matrix areas are visible on the surface of the porous loess material, and the distribution of Fe3O4 nanoparticles shows a certain degree of heterogeneity. This indicates that compared with the solid-phase assembly method, the liquid-phase assembly method is more conducive to the dispersion and composite of Fe3O4 nanoparticles on the loess surface. This may be related to the assembly strategy of Fe3O4 and porous loess materials; Comparative Example 3 uses the liquid-phase assembly method, while Comparative Example 4 uses the solid-phase assembly method. Furthermore, the SEM images of the magnetic porous loess organic composite materials prepared in Examples 3 and 4 are shown below. Figure 7 and Figure 8 As shown, compared to the Fe3O4 / loess magnetic composite material prepared in Comparative Example 4, the morphological characteristics of the magnetic porous loess organic composite materials prepared in Examples 3 and 4 show significant changes. In the magnetic porous loess organic composite material prepared in Example 3, micro / nanosheet structures can be clearly observed attached to the outer surface of the Fe3O4 / loess magnetic composite material. Figure 8 The micro- and nano-sheet structures are more prominent in the microstructures shown. This indicates that the Schiff base functional component is effectively generated and loaded onto the Fe3O4 / loess magnetic composite material, and also demonstrates that the composite material preparation method selected in this invention is feasible and efficient. The magnetic porous loess organic composite materials prepared in Examples 3 and 4 show certain differences in surface morphology. For example... Figure 7 As shown, in Example 3, the material surface has a large number of particulate deposits, high surface roughness, and obvious particle accumulation characteristics; Figure 8 As shown, the material surface in Example 4 exhibits a more pronounced lamellar and wrinkled structure, with a relatively continuous surface and localized capping layer characteristics. These results demonstrate that, based on the same solid-phase assembly method, the choice of aldehyde compound used in the subsequent Schiff base reaction affects the introduction of the Schiff base functional components onto the material surface and the final morphological structure. Compared to Example 3, which used formaldehyde, Example 4, which used terephthalaldehyde, more easily formed a relatively continuous surface capping structure. Figure 7 and Figure 8 The differences in microstructure further indicate that the aldehyde compounds selected in the Schiff base reaction have a significant impact on the microstructural characteristics of the magnetic porous loess organic composite material. This corresponds to the differences in the degree of condensation in different Schiff base reactions and the physicochemical properties of the resulting Schiff base functional components. Furthermore, Figure 9 and Figure 10SEM images of the magnetic porous loess-organic composite materials prepared in Examples 1 and 2 are shown respectively. The microstructures of the magnetic porous loess-organic composite materials prepared in Examples 1 and 2 also show significant differences. The micro / nano-sheet structure on the surface of the magnetic porous loess-organic composite material in Example 2 is more pronounced, which may be related to the aldehyde ligand selected in the subsequent Schiff base reaction stage. Furthermore, as... Figure 11 As shown, the Schiff base functional component coverage of the magnetic porous loess organic composite material obtained in Comparative Example 5 is relatively high, and its surface pore structure openness is reduced compared to Example 1. Overall, the differences in the microstructure of the composite materials obtained from different comparative examples and examples to some extent illustrate the assembly process of Fe3O4 nanoparticles and porous loess materials during material preparation, as well as the effectiveness of the Schiff base reaction. Furthermore, there are significant differences in the type and exposure of reaction sites in the magnetic porous loess organic composite materials of different examples, leading to significant differences in the adsorption performance of pollutants by different magnetic porous loess organic composite materials.

[0168] like Figure 12 As shown in Examples 1-15, the magnetic porous loess organic composite material prepared in Example 1 exhibits good performance against different concentrations of Fe. 2+ Mn 2+ and Zn 2+ The adsorption properties exhibited significant differences. The magnetic porous loess organic composite material prepared in Example 1, used in Examples 1-5, showed significant differences in adsorption performance for Fe at concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 17.58 mg / g, 112.55 mg / g, 223.61 mg / g, 323.62 mg / g, and 372.62 mg / g, respectively. The magnetic porous loess organic composite material prepared in Example 1 and used in Examples 6-10 were applied to adsorb Mn at concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 16.1 mg / g, 107.55 mg / g, 207.83 mg / g, 296.93 mg / g, and 335.83 mg / g, respectively. The magnetic porous loess organic composite material prepared in Example 1, used in Examples 11-15, was applied to adsorb Zn at concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 21.93 mg / g, 118.95 mg / g, 230.05 mg / g, 334.15 mg / g, and 393.6 mg / g, respectively. The above experimental results show that the magnetic porous loess organic composite material prepared in Example 1 exhibits significant differences in adsorption performance for different types of heavy metal ions, particularly Zn.2+ Its adsorption performance is better than Fe 2+ , for Fe 2+ Its adsorption performance is better than that of Mn 2+ This may be attributed to Zn 2+ Smaller hydration radius, Zn 2+ It is easier for magnetic porous loess organic composite materials to form stable coordination structures with Schiff base functional components, thereby enhancing their ability to react with Zn. 2+ The adsorption capacity is stronger. In addition, as the initial concentration of heavy metal pollutants increases, the adsorption capacity of the magnetic porous loess organic composite material for heavy metal ions also increases, indicating that the prepared magnetic porous loess organic composite material is also suitable for the remediation of high-concentration heavy metal pollution.

[0169] like Figure 13 As shown in Application Examples 16-20, the magnetic porous loess organic composite material prepared in Example 2 was used to apply Fe concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 16.45 mg / g, 111.93 mg / g, 216.55 mg / g, 313.88 mg / g, and 355.28 mg / g, respectively. In Application Examples 21-25, the magnetic porous loess organic composite material prepared in Example 2 exhibited adsorption capacities of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L for Mn. 2+ The adsorption capacities were 15.33 mg / g, 106.92 mg / g, 206.65 mg / g, 283.87 mg / g, and 326.65 mg / g, respectively. In Application Examples 26-30, the magnetic porous loess organic composite material prepared in Example 2 exhibited adsorption capacities of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L for Zn. 2+ The adsorption capacities were 16.98 mg / g, 113.05 mg / g, 221.95 mg / g, 322.2 mg / g, and 379.48 mg / g, respectively. The magnetic porous loess-organic composite material prepared in Example 2 exhibited similar adsorption performance for different types of heavy metal ions at the same concentration as the magnetic porous loess-organic composite material prepared in Example 1, namely: for Zn... 2+ Its adsorption performance is better than Fe 2+ , for Fe 2+ Its adsorption performance is better than that of Mn 2+However, compared to the magnetic porous loess organic composite material prepared in Example 2, the adsorption performance of heavy metal pollutants was slightly lower. This indicates that the aldehyde compound selected during the Schiff base reaction stage affects the heavy metal ion adsorption performance of the magnetic porous loess organic composite material, and the magnetic porous loess organic composite material prepared using formaldehyde exhibits superior performance.

[0170] like Figure 14 As shown in Application Examples 31-35, the magnetic porous loess organic composite material prepared in Example 3 was used to react with Fe concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 14.48 mg / g, 102.78 mg / g, 200.05 mg / g, 291.1 mg / g, and 330.28 mg / g, respectively. In Application Examples 36-40, the magnetic porous loess organic composite material prepared in Example 3 was used to adsorb Mn at concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 13.05 mg / g, 89.43 mg / g, 185.83 mg / g, 275.28 mg / g, and 306.66 mg / g, respectively. In Application Examples 41-45, the magnetic porous loess organic composite material prepared in Example 3 was used to adsorb Zn at concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+The adsorption capacities were 15.8 mg / g, 107.2 mg / g, 211.9 mg / g, 305.83 mg / g, and 365.55 mg / g, respectively. Compared with the magnetic porous loess organic composite materials prepared in Examples 1 and 2, the magnetic porous loess organic composite material prepared in Example 3 showed a decrease in adsorption performance for different types of heavy metal ions, but still maintained high adsorption performance. Examples 1 and 2 used a liquid-phase assembly method (step 3) to prepare Fe3O4 / loess magnetic composite materials, while Example 3 used a solid-phase assembly method (step 3) to prepare Fe3O4 / loess magnetic composite materials. This indicates that the selection of the preparation method is crucial in the preparation of Fe3O4 / loess magnetic composite materials. Compared with the solid-phase assembly method, the liquid-phase assembly method can improve the adsorption performance of the final magnetic porous loess organic composite material for heavy metal ions. Overall, the magnetic porous loess organic composite material prepared by the liquid-phase assembly method exhibits better adsorption performance for heavy metal ions. This may be because the reaction sites of Fe3O4 and porous loess are more fully exposed during the liquid-phase assembly process, resulting in better homogeneity of the prepared Fe3O4 / loess magnetic composite material and more reactive sites, which is more conducive to the subsequent Schiff base reaction.

[0171] like Figure 15 As shown in Application Examples 46-50, the magnetic porous loess organic composite material prepared in Example 4 was used to apply Fe concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 12.98 mg / g, 100.83 mg / g, 191.1 mg / g, 276.1 mg / g, and 305.05 mg / g, respectively. In Application Examples 51-55, the magnetic porous loess organic composite material prepared in Example 4 was used to adsorb Mn at concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+ The adsorption capacities were 12.38 mg / g, 93.08 mg / g, 185.55 mg / g, 258.33 mg / g, and 272.03 mg / g, respectively. In Application Examples 56-60, the magnetic porous loess organic composite material prepared in Example 4 was used to adsorb Zn at concentrations of 10 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, and 200 mg / L. 2+The adsorption capacities were 14.45 mg / g, 103.9 mg / g, 197.78 mg / g, 292.78 mg / g, and 333.05 mg / g, respectively. Overall, the magnetic porous loess-organic composite material prepared in Example 4 exhibited good adsorption performance for different types and concentrations of heavy metal ions, but its adsorption performance was slightly lower than that of the magnetic porous loess-organic composite materials prepared in Examples 2 and 3. This indicates that the adsorption capacity of the magnetic porous loess-organic composite material is not only related to the preparation method of the Fe3O4 / loess magnetic composite material, but also closely related to the aldehyde compound selected for the subsequent Schiff base reaction.

[0172] like Figure 16 As shown, in Application Examples 61-65, the acid-activated loess material prepared in Comparative Example 1, the porous loess material prepared in Comparative Example 2, the Fe3O4 / loess magnetic composite materials prepared in Comparative Examples 3 and 4, and the magnetic porous loess organic composite material prepared in Comparative Example 5 were used to treat 10 mg / L Fe... 2+ The adsorption capacities were 9.15 mg / g, 11.27 mg / g, 16.38 mg / g, 11.71 mg / g, and 16.56 mg / g, respectively. The comparison shows that the Fe... 2+ The adsorption capacity is superior to that of acid-activated loess, indicating that pore-forming treatment of acid-activated loess can improve the adsorption capacity of the material for heavy metal ions. It can also be seen that the Fe3O4 / loess magnetic composite material prepared by the liquid-phase assembly method has a better adsorption capacity for heavy metal ions than the Fe3O4 / loess magnetic composite material prepared by the solid-phase assembly method, which is consistent with the above analysis. Meanwhile, compared with Application Examples 1 and 16 in Application Example 63, and with Application Examples 31 and 46 in Application Example 64, it can be seen that loading the Schiff base functional component improves the adsorption performance of the composite material for heavy metal ions, demonstrating the necessity of the Schiff base reaction and indicating that the magnetic porous loess organic composite material prepared in this invention can be used in the field of heavy metal pollution remediation technology in water environments. Furthermore, in Comparative Example 5, while keeping the liquid-phase assembly method and formaldehyde system unchanged, the amount of precursor used to form the Schiff base functional component was increased. Performance test results show that the magnetic porous loess organic composite material obtained in Comparative Example 5 has a better adsorption capacity for 10 mg / L Fe3O4 / loess. 2+ The adsorption capacity was 16.56 mg / g, lower than the adsorption capacity of the material in Example 1 (17.58 mg / g), indicating that a higher proportion of Schiff base precursor is not necessarily better. This result suggests that introducing an appropriate amount of Schiff base functional component is more beneficial in balancing the construction of coordination sites on the material surface with the maintenance of the original pore structure and mass transfer process, thereby achieving better adsorption performance. The aforementioned SEM characterization results ( Figure 11The results show that the magnetic porous loess organic composite material obtained in Comparative Example 5 exhibits a more pronounced surface coverage characteristic compared to Example 1. Combined with the adsorption performance test results, it can be seen that an excessively high proportion of Schiff base precursor may negatively impact the openness of the original pore structure of the material, thus hindering the improvement of its adsorption performance.

[0173] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing a magnetic porous loess organic composite material, characterized in that, include: S1, acid activation treatment is performed on loess material to obtain acid-activated loess material; S2, acid-activated loess material and alkaline pore-forming agent are mixed in water to form a homogeneous slurry, and then acid solution is added dropwise to form a mixed slurry. The reaction is carried out under stirring conditions to obtain porous loess material; S3, porous loess material and Fe3O4 nanoparticles were assembled in the presence of sodium carboxymethyl cellulose to obtain Fe3O4 / loess magnetic composite material. S4, Fe3O4 / loess magnetic composite material, amine compound and aldehyde compound are mixed, and the amine compound and aldehyde compound are subjected to Schiff base reaction to graft Schiff base functional component onto Fe3O4 / loess magnetic composite material to obtain magnetic porous loess organic composite material. S3 specifically involves: dispersing Fe3O4 nanoparticles in a sodium carboxymethyl cellulose solution and stirring to obtain a sodium carboxymethyl cellulose-Fe3O4 dispersion; dispersing porous loess material in another sodium carboxymethyl cellulose solution and stirring to obtain a sodium carboxymethyl cellulose-loess dispersion; mixing the sodium carboxymethyl cellulose-Fe3O4 dispersion and the sodium carboxymethyl cellulose-loess dispersion, stirring, and separating the solid product to obtain the Fe3O4 / loess magnetic composite material; Alternatively, S3 specifically involves: dispersing Fe3O4 nanoparticles in a sodium carboxymethyl cellulose solution, stirring to obtain a sodium carboxymethyl cellulose-Fe3O4 dispersion, separating the solid product to obtain a sodium carboxymethyl cellulose-Fe3O4 precursor material; dispersing porous loess material in another sodium carboxymethyl cellulose solution, stirring to obtain a sodium carboxymethyl cellulose-loess dispersion, separating the solid product to obtain a sodium carboxymethyl cellulose-loess precursor material; dispersing the sodium carboxymethyl cellulose-Fe3O4 precursor material and the sodium carboxymethyl cellulose-loess precursor material in water, stirring, separating the solid product to obtain a Fe3O4 / loess magnetic composite material.

2. The method for preparing the magnetic porous loess organic composite material according to claim 1, characterized in that, In S2, the alkaline pore-forming agent is sodium bicarbonate, and the acid solution is hydrochloric acid.

3. The method for preparing the magnetic porous loess organic composite material according to claim 1, characterized in that, In S2, the pH value of the mixed slurry is 4~5.

4. The method for preparing the magnetic porous loess organic composite material according to claim 1, characterized in that, In S4, the amine compound is m-phenylenediamine or ethylenediamine; the aldehyde compound is formaldehyde or terephthalaldehyde.

5. The method for preparing the magnetic porous loess organic composite material according to claim 1, characterized in that, In S4, the total mass of the amine compounds and aldehyde compounds is 37.5% to 44.4% of the total mass of the Fe3O4 / loess magnetic composite material, amine compounds, and aldehyde compounds.

6. A magnetic porous loess organic composite material obtained by the preparation method according to any one of claims 1 to 5.

7. The application of the magnetic porous loess organic composite material according to claim 6 in the adsorption of heavy metal ions in water.

8. The application according to claim 7, characterized in that, The heavy metal ion is Fe. 2+ Mn 2+ and Zn 2+ At least one of them.

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