Preparation method and application of iron-zirconium double-metal modified chitosan alkaline lignin aerogel material

Abstract

The invention discloses a preparation method and application of an iron-zirconium double-metal modified chitosan alkaline lignin aerogel material, and belongs to the technical field of aerogel material preparation. The method comprises the following steps: firstly dissolving chitosan to obtain a chitosan solution, adding alkaline lignin into the chitosan solution, then adding ferric salt and zircon salt to obtain an iron / zirconium / chitosan alkaline lignin mixed solution, and cross-linking the iron / zirconium / chitosan alkaline lignin mixed solution through a cross-linking agent to obtain the iron / zirconium / chitosan alkaline lignin composite material. And finally, freeze-drying to obtain the iron-zirconium double-metal modified chitosan alkaline lignin aerogel material. The method is simple and convenient in process, low in cost, green, environment-friendly and easy for large-scale production. The prepared aerogel material has the characteristics of a mesoporous material, is good in stability and mechanical property, has excellent performance in the aspect of adsorbing heavy metal and metalloid ions, can be regenerated and reused through desorption after adsorption, and can be applied to the fields of environmental governance and the like.

Description

Technical Field

[0001] This invention relates to the field of aerogel material preparation technology, specifically to a method for preparing and applying an iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material. Background Technology

[0002] Chitosan (CS) is a natural polycationic electrolyte with good biocompatibility, biodegradability, and mechanical stability. It is widely available, primarily extracted from the shells of crustaceans such as shrimp and crab. However, when chitosan is used alone to prepare aerogels, it suffers from insufficient structural stability and limited functionality. Alkali lignin (AL) is an abundant biomass resource, a byproduct of the paper industry, and offers advantages such as low cost and renewability. Its molecular structure contains numerous active groups such as phenolic and alcoholic hydroxyl groups. However, alkaline lignin suffers from poor solubility and low reactivity, limiting its application in aerogel materials.

[0003] Aerogel materials have shown great application potential in many fields such as adsorption, catalysis, and energy storage. However, existing research on biomass-based aerogels still lacks efficient, stable, and scalable preparation methods. Traditional aerogel materials suffer from problems such as high raw material costs, limited sources, or environmental unfriendliness, which restrict their large-scale application. Therefore, it is necessary to develop an aerogel that is simple to process, low in cost, and has good performance. Summary of the Invention

[0004] To address the issues of high raw material costs, limited availability, and unstable and inefficient preparation methods for aerogel materials, the present invention aims to provide a method for preparing iron-zirconium bimetallic modified chitosan alkaline lignin aerogel materials. This method is simple, low-cost, and can be mass-produced.

[0005] The preparation method of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material of the present invention specifically includes the following steps: (1) Add chitosan to an aqueous acetic acid solution, seal and stir to obtain a chitosan solution; after sealing and magnetic stirring, the amino exposure of the chitosan molecular chain surface is increased by 30%~50%.

[0006] (2) Add alkaline lignin to the chitosan solution, seal and stir to obtain a chitosan-alkaline lignin mixed solution; after adding alkaline lignin, continue to seal and stir magnetically to increase the content of active groups such as carboxyl and epoxy groups in alkaline lignin molecules by about 40%, thereby enhancing the coordination and binding ability with bimetallic ions.

[0007] (3) Add iron salt and zirconium salt to the chitosan alkaline lignin mixed solution and disperse by ultrasonication to obtain iron / zirconium / chitosan alkaline lignin mixed solution.

[0008] (4) Add the iron / zirconium / chitosan alkaline lignin mixed solution dropwise to the matrix solution, stirring continuously during the dropwise addition. After the dropwise addition is completed, let it stand at room temperature, filter, and wash with water until the pH of the washing solution is neutral to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material. The dropwise addition can make iron and zirconium ions uniformly dispersed and form Fe-O-Zr bonded structure, thereby improving the stability of the material.

[0009] (5) Add a crosslinking agent to the wet iron / zirconium / chitosan alkaline lignin aerogel material, shake to crosslink, filter, wash, freeze dry to obtain iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

[0010] Preferably, in step (1) of the present invention, the degree of deacetylation of chitosan is ≥90%, and the molecular weight is 700 kDa~800 kDa; the mass percentage concentration of the acetic acid aqueous solution is 2%; and the mass percentage concentration of chitosan in the chitosan solution is 2%.

[0011] Preferably, the sealing and stirring conditions in step (1) of the present invention are: magnetic stirring and dissolving for 20 min to 40 min at a temperature of 20℃ to 30℃ and a stirring speed of 120 r / min to 150 r / min.

[0012] Preferably, the alkaline lignin in step (2) of the present invention has an ash content of ≤3% and a molecular weight of 505.01 Da; the sealing stirring conditions are: magnetic stirring and dissolving for 20 min to 40 min at 20℃~30℃ and a stirring speed of 120 r / min~150 r / min.

[0013] Preferably, the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution in step (2) of the present invention is 2%.

[0014] Preferably, in step (3) of the present invention, the iron salt is ferrous chloride and the zirconium salt is zirconium oxychloride.

[0015] Preferably, in step (3) of the present invention, the mass ratio of iron salt to zirconium salt is 0.5~2; the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution is 1%~2%, and the mass percentage concentration of zirconium salt in the iron / zirconium / chitosan alkaline lignin mixed solution is 1%~2%.

[0016] Preferably, the conditions for ultrasonic dispersion in step (3) of the present invention are: power of 300 W to 600 W and time of 10 min to 30 min.

[0017] Preferably, the matrix solution in step (4) of the present invention is a sodium hydroxide aqueous solution with a mass percentage concentration of 5%~10%; the conditions for continuous stirring during the drop addition are: at 20℃~30℃, the drop is added at a rate of 1~2 drops / second, and the magnetic stirring speed is 120 r / min~150 r / min; the standing time is 24h~48h.

[0018] Preferably, in step (5) of the present invention, the crosslinking agent is a glutaraldehyde aqueous solution with a mass percentage concentration of 5%; the volume ratio of the wet iron / zirconium / chitosan alkaline lignin aerogel material to the crosslinking agent is 1:1; the vibration crosslinking conditions are: vibration crosslinking at 150 r / min to 200 r / min for 3 h to 6 h; the washing is performed by washing with deionized water and ethanol aqueous solution 3 to 5 times in sequence, and the volume percentage concentration of the ethanol aqueous solution is 30% to 50%.

[0019] Preferably, the freeze-drying conditions in step (5) of the present invention are: first freeze at -10℃ to -50℃ for 10 h to 18 h, and then vacuum dry at -10℃ to -50℃ for 36 h to 48 h. The present invention avoids the collapse of the pore structure of the gel due to rapid loss of water during the dehydration process by freezing at low temperature first and then vacuum drying.

[0020] The aerogel material prepared by this invention has an iron loading (by mass fraction) of 30%–40% and a zirconium loading (by mass fraction) of 8%–10%, with an average pore size of 23.70 nm and a specific surface area of ​​82.93 m². 2 / g, maintaining structural stability within the pH range of 2 to 10, and significantly enhancing the adsorption capacity for heavy (class) metal pollutants (such as As(III) and Sb(III)).

[0021] Another objective of this invention is to provide an application of an iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material in the adsorption of heavy metals and metalloid ions in wastewater, wherein the aerogel material exhibits excellent performance in adsorbing heavy metals and metalloid ions.

[0022] Mechanism of the invention: This invention uses chitosan and alkaline lignin as a matrix, and introduces Fe and Zr to form immobilized Fe groups (such as FeOOH, Fe(OH)3) and Zr groups (such as ZrO2) to prepare an aerogel material with excellent adsorption properties. The amino, alcoholic hydroxyl, and phenolic hydroxyl groups provided by chitosan and alkaline lignin can selectively adsorb Cu from water through coordination and chelation. 2+ Pb 2+ Cationic heavy metals; while immobilized Fe-based (containing Fe) 2+ / Fe3+ ) and Zr-based (containing Zr) 4+ These sites not only enhance the mechanical and structural stability of the material but also compensate for the insufficient adsorption capacity of the matrix for anionic pollutants. These metal-based sites carry a positive surface charge at suitable pH levels, enabling them to efficiently bind AsO4 through both coordination interactions (metal ions provide empty orbitals, anions provide lone pairs of electrons) and electrostatic attraction. 3- CrO4 2- Anionic contaminants, and the matrix and metal base sites are connected by coordination bonds (e.g., amino-NH2 and Fe). 3+ hydroxyl-OH and Zr 4+ These components are closely integrated, forming a synergistic and complementary whole (not acting independently), jointly achieving the adsorption of heavy metals with different electrical properties. Furthermore, this aerogel material possesses a mesoporous structure (average pore size 23.7 nm) and a medium-low specific surface area (82.93 m²). 2 The adsorption process provides a sufficient reaction interface and smooth mass transfer channel for adsorption processes such as coordination complexation, ion exchange, and electrostatic attraction. For specific pollutants, the adsorption process also involves multiple synergistic mechanisms. For example, when adsorbing Cr(VI), Cr(VI) is first reduced to Cr(III) by immobilized Fe(II) groups. The generated Cr(III) then complexes with the amino groups of chitosan to adsorb Pb. 2+ Simultaneously, the coordination of chitosan and the ion exchange of alkaline lignin are involved. This multi-mechanism parallel process further enhances the adsorption efficiency and capacity, ultimately making the material an adsorbent that can efficiently remove a variety of heavy metals and metalloid pollutants.

[0023] Compared with the prior art, the present invention provides a method for preparing and applying an iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material, which has the following beneficial effects: (1) The iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared by the present invention has mesoporous characteristics, uniform pore size distribution, and high specific surface area, which provides a large number of active sites for adsorbing heavy metals and metalloid ions. It has excellent adsorption performance, high stability and good mechanical properties. The aerogel material prepared by the present invention has a removal rate of 94.16% for Pb(II), 80% for Cu(II), 89.91% for As(III), 95.12% for As(V), 96.28% for Sb(III), and 88.61% for Cr(VI).

[0024] (2) The iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared in this invention has the highest leaching amount of iron and zirconium in the pH range of 3 to 11, which are 0.185 mg / L and 0 mg / L, respectively. In the pH range of 3 to 10, the removal rate of As(III) and Sb(III) by the aerogel material is over 80%, indicating that the prepared aerogel material has good stability and can be used in wastewater solutions with different pH values. At the same time, it will not cause secondary environmental pollution risk due to material leaching and decomposition.

[0025] (3) The preparation method of the present invention is simple and does not require complex equipment and special reaction conditions. It uses chitosan and alkaline lignin, which are widely available and inexpensive, as raw materials. The preparation system is green and environmentally friendly, which can effectively reduce production costs and is easy to achieve large-scale production.

[0026] (4) The preparation method of the present invention does not require the addition of additional complex additives to prepare iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material with a stable composite structure.

[0027] (5) The iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared by the present invention can be reused after desorption and regeneration, which significantly reduces long-term costs and resource consumption, reduces environmental burden and secondary pollution, and is more green and environmentally friendly. Attached Figure Description

[0028] Figure 1 The images show the molecular structure diagram and physical image of chitosan.

[0029] Figure 2 The images show the molecular structure and physical representation of alkaline lignin.

[0030] Figure 3 This is a step-by-step diagram illustrating the preparation stages of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material of the present invention.

[0031] Figure 4 The images shown are physical images and electron microscope images of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material of the present invention. (a) is a physical image of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material, and (b) is a scanning electron microscope image of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

[0032] Figure 5 The removal rates of different heavy (type) metal ions by the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel materials prepared in Example 1 and Comparative Example 1 at pH=4.

[0033] Figure 6 The removal rate of As(III) by the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel materials prepared in Examples 1-4 of this invention at pH=7.

[0034] Figure 7 The removal rate of Sb(III) by the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel materials prepared in Examples 1-4 of this invention at pH=7.

[0035] Figure 8 The removal rates of Pb(II), Cu(II), Cr(VI), As(III), As(V) and Sb(III) of the chitosan alkaline lignin aerogel material prepared for Comparative Example 2 at pH=4 were measured.

[0036] Figure 9 The removal rates of Pb(II), Cu(II), Cr(VI), As(III), As(V) and Sb(III) of the single-iron modified chitosan alkaline lignin aerogel material prepared for Comparative Example 3 at pH=4 were measured.

[0037] Figure 10 The removal rates of Pb(II), Cu(II), Cr(VI), As(III), As(V) and Sb(III) of the single zirconium-modified chitosan alkaline lignin aerogel material prepared for Comparative Example 4 at pH=4 were measured.

[0038] Figure 11 The image shows the adsorption isotherm fitting curve of Sb(III) for the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared in Example 2 of this invention.

[0039] Figure 12 The image shows the adsorption isotherm fitting curve of As(III) for the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared in Example 2 of this invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Unless otherwise specified, the acetic acid aqueous solution used in the embodiments and comparative examples of this invention has a mass percentage concentration of 2%; the chitosan used has a degree of deacetylation ≥90% and a molecular weight of 700 kDa~800 kDa; the alkaline lignin used has an ash content ≤3% and a molecular weight of 505.01 Da.

[0042] Example 1 (1) Add chitosan to an aqueous acetic acid solution and dissolve it by magnetic stirring under sealed conditions at 25°C and a stirring speed of 135 r / min for 30 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0043] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 25°C and stirring speed of 135 r / min, seal and magnetically stir for 30 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0044] (3) Ferrous chloride (FeCl2) and zirconium oxychloride (ZrOCl2) were added to the chitosan alkaline lignin mixed solution (the mass ratio of FeCl2 and ZrOCl2 was 1:1), and ultrasonically dispersed for 20 min at a power of 300 W to obtain an iron / zirconium / chitosan alkaline lignin mixed solution (the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution was 1%, and the mass percentage concentration of zirconium salt was 1%).

[0045] (4) At 25°C, the iron / zirconium / chitosan alkaline lignin mixed solution was added dropwise to a 5% sodium hydroxide aqueous solution at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 135 r / min. After the addition was completed, the mixture was allowed to stand at room temperature for 24 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material.

[0046] (5) Add 5% glutaraldehyde aqueous solution (volume ratio of wet iron / zirconium / chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet iron / zirconium / chitosan alkaline lignin aerogel material, crosslink at 150 r / min for 6 h, filter, wash 5 times with deionized water and ethanol aqueous solution in sequence, the volume percentage concentration of ethanol aqueous solution used is 50%, freeze the washed material at -50℃ for 12 h, and then vacuum dry at -50℃ for 48 h to obtain iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

[0047] like Figure 4 As shown in Figure (a), the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material exists in the form of spherical particles. The particles are brownish-red, with uniform particle size and good overall dispersion. Figure (b) is a scanning electron microscope (SEM) image of the material (magnification 50x). The surface of the material is relatively flat, but there are some cracks.

[0048] Example 2 (1) Add chitosan to an aqueous acetic acid solution and dissolve it by magnetic stirring under sealed conditions at 20°C and a stirring speed of 135 r / min for 40 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0049] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 20°C and stirring speed of 135 r / min, seal and magnetically stir for 40 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0050] (3) Ferrous chloride (FeCl2) and zirconium oxychloride (ZrOCl2) were added to the chitosan alkaline lignin mixed solution (the mass ratio of FeCl2 and ZrOCl2 was 2:2), and ultrasonically dispersed for 30 min under a power of 300W to obtain an iron / zirconium / chitosan alkaline lignin mixed solution (the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution was 2%, and the mass percentage concentration of zirconium salt was 2%).

[0051] (4) At 20°C, the iron / zirconium / chitosan alkaline lignin mixed solution was added dropwise to a sodium hydroxide aqueous solution with a mass percentage concentration of 7% at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 120 r / min. After the addition was completed, the mixture was allowed to stand at room temperature for 36 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material.

[0052] (5) Add 5% glutaraldehyde aqueous solution (volume ratio of wet iron / zirconium / chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet iron / zirconium / chitosan alkaline lignin aerogel material, crosslink at 180 r / min for 3 h, filter, wash 4 times with deionized water and ethanol aqueous solution in sequence, the volume percentage concentration of ethanol aqueous solution used is 50%, freeze the washed material at -50℃ for 10 h, and then vacuum dry at -50℃ for 36 h to obtain iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

[0053] Example 3 (1) Add chitosan to an aqueous acetic acid solution and dissolve it under sealed magnetic stirring at 30°C and a stirring speed of 135 r / min for 20 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0054] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 30°C and stirring speed of 135 r / min, seal and magnetically stir for 20 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0055] (3) Ferrous chloride (FeCl2) and zirconium oxychloride (ZrOCl2) were added to the chitosan alkaline lignin mixed solution (the mass ratio of FeCl2 and ZrOCl2 was 2:1), and ultrasonically dispersed for 10 min under a power of 600 W to obtain an iron / zirconium / chitosan alkaline lignin mixed solution (the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution was 2%, and the mass percentage concentration of zirconium salt was 1%).

[0056] (4) At 30°C, the iron / zirconium / chitosan alkaline lignin mixed solution was added dropwise to a 10% sodium hydroxide aqueous solution at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 150 r / min. After the addition was completed, the mixture was allowed to stand at room temperature for 48 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material.

[0057] (5) Add 5% glutaraldehyde aqueous solution (volume ratio of wet iron / zirconium / chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet iron / zirconium / chitosan alkaline lignin aerogel material, crosslink at 200 r / min for 5 h, filter, wash 3 times with deionized water and ethanol aqueous solution in sequence, the volume percentage concentration of ethanol aqueous solution used is 30%, freeze the washed material at -10℃ for 18 h, and then vacuum dry at -10℃ for 46 h to obtain iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

[0058] Example 4 (1) Add chitosan to an aqueous acetic acid solution and dissolve it by magnetic stirring under sealed conditions at 25°C and a stirring speed of 135 r / min for 30 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0059] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 25°C and stirring speed of 135r / min, seal and magnetically stir for 30 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0060] (3) Ferrous chloride (FeCl2) and zirconium oxychloride (ZrOCl2) were added to the chitosan alkaline lignin mixed solution (the mass ratio of FeCl2 and ZrOCl2 was 1:2), and ultrasonically dispersed for 20 min under a power of 500W to obtain an iron / zirconium / chitosan alkaline lignin mixed solution (the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution was 1%, and the mass percentage concentration of zirconium salt was 2%).

[0061] (4) At 25°C, the iron / zirconium / chitosan alkaline lignin mixed solution was added dropwise to a 5% sodium hydroxide aqueous solution at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 135 r / min. After the addition was completed, the mixture was allowed to stand at room temperature for 24 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material.

[0062] (5) Add 5% glutaraldehyde aqueous solution (volume ratio of wet iron / zirconium / chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet iron / zirconium / chitosan alkaline lignin aerogel material, crosslink at 150 r / min for 6 h, filter, wash 5 times with deionized water and ethanol aqueous solution in sequence, the volume percentage concentration of ethanol aqueous solution used is 50%, freeze the washed material at -50℃ for 12 h, and then vacuum dry at -50℃ for 48 h to obtain iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

[0063] from Figure 6 As can be seen, the material prepared in Example 1 had a removal rate of 81.78% for As(III), the material prepared in Example 2 had a removal rate of 90.52%, the material prepared in Example 3 had a removal rate of 83.38%, and the material prepared in Example 4 had a removal rate of 87.16%. Overall, the material of the present invention has a good adsorption and removal capacity for As(III).

[0064] As can be seen from Figure 7, the material prepared in Example 1 had a removal rate of 88.56% for Sb(III), the material prepared in Example 2 had a removal rate of 95.61%, the material prepared in Example 3 had a removal rate of 92.39%, and the material prepared in Example 4 had a removal rate of 93.89%. Overall, the material of the present invention has a good adsorption and removal capacity for Sb(III).

[0065] 1. Material adsorption performance experiment: The iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared in Example 2 was used to conduct adsorption experiments on Sb(III) solutions with different initial concentrations. Subsequently, the adsorption experimental data were fitted and analyzed using the Langmuir model, Freundlich model, and Sips model, respectively. The adsorption data are shown in Table 1. Under the Sips model fitting, the adsorption capacity of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel for Sb(III) in wastewater can reach 147 mg / g to 185 mg / g.

[0066] Table 1 The iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared in Example 2 was used to conduct adsorption experiments on As(III) solutions with different initial concentrations. Subsequently, the adsorption experimental data were fitted and analyzed using the Langmuir model, Freundlich model, and Sips model, respectively. The adsorption data are shown in Table 2. Under the Sips model fitting, the adsorption capacity of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel for As(III) in wastewater can reach 89 mg / g~144 mg / g.

[0067] Table 2 The adsorption isotherm fitting curve of Sb(III) for iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material is as follows: Figure 11 As shown, the adsorption isotherm fitting curve for As(III) is as follows: Figure 12 It can be seen that the Sips model can fit the experimental data of the adsorption system well, indicating that the adsorption process of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared in this invention may have both homogeneous and heterogeneous adsorption characteristics, and the adsorption sites on the surface of the adsorbent have a certain degree of uniformity.

[0068] 2. Actual wastewater treatment verification experiment: Experimental method: Prepare simulated wastewater solutions of heavy metals (Pb(II), Cu(II), As(III), As(V), Sb(III) and Cr(VI)) with a concentration of 10 mg / L. Weigh 50 mg of the above materials and add them at a dosage of 1 g / L. Shake and adsorb for 48 h at pH=4, 25℃ and 180 r / min. Then filter and separate to obtain the adsorbed materials.

[0069] Treatment effect: Testing showed that the concentration of heavy metal ions (such as Pb(II) and Sb(III)) in the water after adsorption by the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel materials prepared in Examples 1-4 was ≤0.05 mg / L, which is better than the Class A discharge standard limit of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" (GB 18918-2002). This result demonstrates the high efficiency of the material of this invention in purifying low-concentration wastewater at extremely low dosages.

[0070] 3. Material recycling and reuse performance test: The material adsorbed in the actual wastewater treatment experiment was desorbed by shaking with a 15% NaOH aqueous solution at 25°C for 24 hours. After washing and drying, it can be reused 4-5 times, and the adsorption capacity after each regeneration can be maintained at more than 80% of the initial capacity, showing good regenerability.

[0071] Comparative Example 1 (1) Add chitosan to an aqueous acetic acid solution and dissolve it by magnetic stirring under sealed conditions at 25°C and a stirring speed of 135 r / min for 30 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0072] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 25°C and stirring speed of 135 r / min, seal and magnetically stir for 30 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0073] (3) Ferrous chloride (FeCl2) and zirconium oxychloride (ZrOCl2) were added to the chitosan alkaline lignin mixed solution (the mass ratio of FeCl2 and ZrOCl2 was 2:2), and ultrasonically dispersed for 20 min under a power of 500 W to obtain an iron / zirconium / chitosan alkaline lignin mixed solution (the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution was 2%).

[0074] (4) At 25°C, the iron / zirconium / chitosan alkaline lignin mixed solution was added dropwise to a 5% sodium hydroxide aqueous solution at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 135 r / min. After the addition was completed, the mixture was allowed to stand at room temperature for 24 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material.

[0075] (5) Add 5% glutaraldehyde aqueous solution (volume ratio of wet iron / zirconium / chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet iron / zirconium / chitosan alkaline lignin aerogel material, crosslink at 150 r / min for 6 h, filter, wash with deionized water and ethanol aqueous solution 3 times in sequence, and then place in an oven at 45℃ for 36 h to obtain iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

[0076] The material prepared in Example 1 of this invention exhibits good adsorption effects on a variety of metals, such as... Figure 5 As shown, Example 1 (freeze-drying) significantly outperformed Comparative Example 1 (drying) in adsorption. For Pb(II), both the Example and Comparative Examples showed high removal rates, exceeding 90%. For Cu(II), Example 1 achieved a removal rate of 80%, while Comparative Example 1 achieved 45.6%. For As(III), the Example achieved 89.91%, compared to only 27.4% in Comparative Example 1. For As(V), Example 1 achieved 95.12%, compared to only 24.98% in Comparative Example 1. For Sb(III), Example 1 achieved a high removal rate of 96.28%, compared to 66.62% in Comparative Example 1. For Cr(VI), Example 1 achieved 88.61%, compared to only 23.35% in Comparative Example 1. The adsorption effect of Example 1 was significantly better than that of Comparative Example 1.

[0077] Comparative Example 2 (1) Add chitosan to an aqueous acetic acid solution and dissolve it by magnetic stirring under sealed conditions at 25°C and a stirring speed of 135 r / min for 30 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0078] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 25°C and stirring speed of 135 r / min, seal and magnetically stir for 30 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0079] (3) At 25°C, the chitosan alkaline lignin mixed solution was added dropwise to a 5% sodium hydroxide aqueous solution at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 135 r / min. After the addition was completed, the mixture was left to stand at room temperature for 24 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet chitosan alkaline lignin aerogel material.

[0080] (4) Add 5% glutaraldehyde aqueous solution (volume ratio of wet chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet chitosan alkaline lignin aerogel material, crosslink at 150 r / min for 6 h, filter, wash with deionized water and ethanol aqueous solution 3 times in sequence, freeze at -20℃ for 12 h, and then vacuum dry at -20℃ for 48 h to obtain chitosan alkaline lignin aerogel material.

[0081] As shown in Figure 8, the chitosan-based alkaline lignin aerogel material prepared without metal loading in this comparative example showed a removal rate of 50.99% for Pb(II), 60.64% for Cu(II), 21.35% for As(III), 12.69% for As(V), 9.04% for Sb(III), and 76.51% for Cr(VI); significantly lower than the adsorption and removal rates of the above heavy metals in the embodiments of this invention.

[0082] Comparative Example 3 (1) Add chitosan to an aqueous acetic acid solution and dissolve it by magnetic stirring under sealed conditions at 25°C and a stirring speed of 135 r / min for 30 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0083] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 25°C and stirring speed of 135 r / min, seal and magnetically stir for 30 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0084] (3) Add ferrous chloride (FeCl2) to the chitosan alkaline lignin mixed solution and ultrasonically disperse it for 20 min at a power of 500 W to obtain an iron / chitosan alkaline lignin mixed solution (the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution is 1%).

[0085] (4) At 25°C, the iron / chitosan alkaline lignin mixed solution was added dropwise to a 5% sodium hydroxide aqueous solution at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 135r / min. After the addition was completed, the mixture was allowed to stand at room temperature for 24 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet iron / chitosan alkaline lignin aerogel material.

[0086] (5) Add 5% glutaraldehyde aqueous solution (volume ratio of wet iron / chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet iron / chitosan alkaline lignin aerogel material, crosslink at 150 r / min for 6 h, filter, wash 5 times with deionized water and ethanol aqueous solution, freeze at -20℃ for 12 h, and then vacuum dry at -20℃ for 48 h to obtain iron-modified chitosan alkaline lignin aerogel material.

[0087] As shown in Figure 9, the chitosan-based alkaline lignin aerogel material prepared by loading single iron metals achieved a removal rate of 91.33% for Pb(II), 77.69% for Cu(II), 82.3% for As(III), 82.37% for As(V), 95.87% for Sb(III), and 84.5% for Cr(VI); these rates are lower than the adsorption and removal rates of the aforementioned heavy metals in the embodiments of the present invention.

[0088] Comparative Example 4 (1) Add chitosan to an aqueous acetic acid solution and dissolve it by magnetic stirring under sealed conditions at 25°C and a stirring speed of 135 r / min for 30 min to obtain a chitosan solution (the mass percentage concentration of chitosan in the chitosan solution is 2%).

[0089] (2) Add brown powdered alkaline lignin to the chitosan solution, and under the conditions of 25°C and stirring speed of 135 r / min, seal and magnetically stir for 30 min to dissolve, to obtain a chitosan-alkaline lignin mixed solution (the mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution is 2%).

[0090] (3) Zirconium oxychloride (ZrOCl2) was added to the chitosan alkaline lignin mixed solution and ultrasonically dispersed for 20 min under a power of 500 W to obtain a zirconium / chitosan alkaline lignin mixed solution (the mass percentage concentration of iron salt in the zirconium / chitosan alkaline lignin mixed solution was 2%).

[0091] (4) At 25°C, the zirconium / chitosan alkaline lignin mixed solution was added dropwise to a 5% sodium hydroxide aqueous solution at a rate of 1~2 drops / second. The reaction was carried out by continuous stirring during the addition. The magnetic stirring speed was 135r / min. After the addition was completed, the mixture was allowed to stand at room temperature for 24 h, filtered, and washed with water until the pH of the washing solution was neutral to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material.

[0092] (5) Add 5% glutaraldehyde aqueous solution (volume ratio of wet zirconium / chitosan alkaline lignin aerogel material to glutaraldehyde aqueous solution is 1:1) to wet zirconium / chitosan alkaline lignin aerogel material, crosslink at 150 r / min for 6 h, filter, wash 5 times with deionized water and ethanol aqueous solution, freeze at -20℃ for 12 h, and then vacuum dry at -20℃ for 48 h to obtain zirconium modified chitosan alkaline lignin aerogel material.

[0093] As shown in Figure 10, the chitosan-based alkaline lignin aerogel material prepared by loading zirconium metal has a removal rate of 92.65% for Pb(II), 95.64% for Cu(II), 32.91% for As(III), 34.4% for As(V), 83.81% for Sb(III), and 14.78% for Cr(VI); the material has extremely poor sphericity.

[0094] In summary, this invention uses chitosan and alkaline lignin as the matrix and introduces iron and zirconium bimetals to prepare a stable composite structure of iron-zirconium bimetal-modified chitosan alkaline lignin aerogel material. This aerogel material exhibits excellent adsorption performance, high stability, and good mechanical properties. The removal rates for Pb(II) reach 94.16%, Cu(II) 80%, As(III) 89.91%, As(V) 95.12%, Sb(III) 96.28%, and Cr(VI) 88.61%. The preparation method of this invention is simple, the preparation system is green and environmentally friendly, effectively reduces production costs, and is easy to scale up for mass production.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material, characterized in that, Specifically, the following steps are included: (1) Add chitosan to an aqueous acetic acid solution, seal and stir to obtain a chitosan solution; (2) Add alkaline lignin to the chitosan solution, seal and stir to obtain a chitosan-alkaline lignin mixed solution; (3) Add iron salt and zirconium salt to chitosan alkaline lignin mixed solution and disperse by ultrasonication to obtain iron / zirconium / chitosan alkaline lignin mixed solution; (4) Add the iron / zirconium / chitosan alkaline lignin mixed solution dropwise to the matrix solution, stirring continuously during the dropwise addition. After the dropwise addition is completed, let it stand at room temperature, filter, and wash to obtain spherical wet iron / zirconium / chitosan alkaline lignin aerogel material. (5) Add a crosslinking agent to the wet iron / zirconium / chitosan alkaline lignin aerogel material, shake to crosslink, filter, wash, freeze dry to obtain iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material.

2. The preparation method of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, The degree of deacetylation of the chitosan in step (1) is ≥90%, and the molecular weight is 700 kDa~800 kDa; the mass percentage concentration of the acetic acid aqueous solution is 2%; the mass percentage concentration of chitosan in the chitosan solution is 2%.

3. The preparation method of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, The conditions for sealing and stirring in step (1) are: magnetic stirring for 20 min to 40 min at 20℃~30℃ and stirring speed of 120 r / min~150 r / min.

4. The preparation method of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, The alkaline lignin in step (2) has an ash content of ≤3% and a molecular weight of 505.01 Da; the sealing stirring conditions are: magnetic stirring for 20 min to 40 min at 20℃~30℃ and a stirring speed of 120 r / min~150 r / min.

5. The preparation method of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, The mass percentage concentration of alkaline lignin in the chitosan-alkaline lignin mixed solution in step (2) is 2%.

6. The method for preparing the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, In step (3), the iron salt is ferrous chloride, the zirconium salt is zirconium oxychloride, and the mass ratio of iron salt to zirconium salt is 0.5~2; the mass percentage concentration of iron salt in the iron / zirconium / chitosan alkaline lignin mixed solution is 1%~2%, and the mass percentage concentration of zirconium salt in the iron / zirconium / chitosan alkaline lignin mixed solution is 1%~2%.

7. The method for preparing the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, The conditions for ultrasonic dispersion in step (3) are: ultrasonic power of 300 W to 600 W and time of 10 min to 30 min.

8. The method for preparing the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, The matrix solution in step (4) is a sodium hydroxide aqueous solution with a mass percentage concentration of 5%~10%; the reaction conditions during the dropwise addition are: at 20℃~30℃, the dropwise addition is at a rate of 1~2 drops / second, and the magnetic stirring speed is 120 r / min~150 r / min; the standing time is 24 h~48 h; the washing is: washing with water until the pH value of the washing solution is neutral.

9. The method for preparing the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material according to claim 1, characterized in that, The crosslinking agent in step (5) is a glutaraldehyde aqueous solution with a mass percentage concentration of 5%; the volume ratio of the wet iron / zirconium / chitosan alkaline lignin aerogel material to the crosslinking agent is 1:1; the vibration crosslinking conditions are: vibration crosslinking at 150 r / min to 200 r / min for 3 h to 6 h; the washing is washing with water and ethanol aqueous solution 3 to 5 times in sequence, with the volume percentage concentration of ethanol aqueous solution being 30% to 50%; the freeze-drying conditions are: first freezing at -10℃ to -50℃ for 10 h to 18 h, and then vacuum drying at -10℃ to -50℃ for 36 h to 48 h.

10. The application of the iron-zirconium bimetallic modified chitosan alkaline lignin aerogel material prepared by the method according to any one of claims 1 to 9 in wastewater treatment.

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