Lignin-based porous adsorption material as well as preparation method and application thereof

Abstract

The invention discloses a lignin-based porous adsorption material as well as a preparation method and application thereof, and belongs to the technical field of adsorption material preparation. The preparation method comprises the following steps: grinding and sieving a pore-foaming agent to obtain a pretreated pore-foaming agent; the preparation method comprises the following steps: uniformly mixing lignosulfonate, a pretreatment pore-foaming agent, a cross-linking agent, a catalyst and water, and carrying out a cross-linking reaction to obtain a cross-linked body; and cleaning, dehydrating and drying the cross-linked body to obtain the product. The invention further discloses the lignin-based porous adsorption material prepared by the method and application of the lignin-based porous adsorption material. Compared with a traditional chemical crosslinking curing adsorption material, the lignin-based porous adsorption material has higher specific surface area and functional group utilization rate; the used pore-foaming agent has good water solubility, does not participate in the reaction in the crosslinking process and can be removed to form pores after crosslinking, the porosity and the pore size of the product can be regulated and controlled by adjusting the dosage and the particle size of the pore-foaming agent, and the application prospect is wide.

Description

Technical Field

[0001] This invention belongs to the field of adsorption material preparation technology, specifically relating to a lignin-based porous adsorption material, its preparation method, and its application. Background Technology

[0002] With the acceleration of industrialization and urbanization, the discharge of wastewater containing heavy metals such as lead, zinc, and cadmium has led to increasingly serious water pollution problems, posing a severe threat to the ecological environment and human health. Adsorption is considered one of the most promising technologies for treating heavy metal wastewater due to its simple operation, high treatment efficiency, and relatively low cost. However, traditional adsorption materials such as activated carbon, although having excellent adsorption performance, are expensive to prepare and difficult to regenerate. Inexpensive adsorbents such as natural minerals and agricultural waste are widely available, but they often suffer from low adsorption capacity, poor selectivity, and insufficient mechanical strength, making it difficult to meet the actual needs of efficient treatment.

[0003] Lignin, a major byproduct of the papermaking industry, is a naturally abundant aromatic polymer with advantages such as wide availability, low cost, high carbon content, and rich active functional groups. It has become a research hotspot for the preparation of biomass-based adsorbent materials. While some progress has been made in the development of adsorbent materials using lignin, several challenges remain: First, when lignin and other raw materials are used directly as adsorbents, their low reactivity and poor accessibility of functional groups limit their adsorption capacity for heavy metal ions. Second, existing lignin-based adsorbent materials are mostly in powder or micro / nano particle form, which is easily lost and difficult to recycle in practical applications, limiting their large-scale application. Third, traditional preparation methods often require high-temperature carbonization or complex chemical modification, which is not only energy-intensive and cumbersome but may also lead to a significant loss of the original active functional groups of lignin.

[0004] How to solve the above problems and realize the high-value utilization of lignin and the development of efficient heavy metal adsorption materials is one of the technical difficulties that those skilled in the art need to solve. Summary of the Invention

[0005] The problem this invention aims to solve is to provide a lignin-based porous adsorbent material, its preparation method, and its application, in order to address the issues of existing cellulose-based adsorbent materials having no pore structure, small specific surface area, and small adsorption capacity.

[0006] The technical solution adopted to solve the technical problem is to provide a method for preparing a lignin-based porous adsorbent material, including the following steps: (1) Grind and sieve the porogen to obtain a pretreated porogen; (2) Mix lignin sulfonate, pretreatment porogen, crosslinking agent, catalyst and water and carry out crosslinking reaction to obtain crosslinked body; (3) The cross-linked material is washed, dehydrated and dried to obtain the lignin-based porous adsorbent material.

[0007] The beneficial effects of the above-mentioned technical solution of the present invention are as follows: In the preparation method of the present invention, the porogen is first ground and sieved to prepare fine particles, and then crosslinked with lignin sulfonate. During the crosslinking process, the porogen can be adsorbed on the surface of the material and wrapped in various parts of the material. After washing, the porogen is removed, thereby forming a rich pore structure. The crosslinking reaction forms a three-dimensional network structure, which gives the material good mechanical strength and chemical stability, and is easy to use repeatedly. At the same time, the pore structure obtained by washing exposes the functional groups (such as sulfonic acid groups and hydroxyl groups) in lignin sulfonate, providing effective metal ion binding sites. The lignin-based porous adsorbent material can show high adsorption capacity for various metal ions.

[0008] Preferably, the porogen in step (1) is at least one of calcium carbonate, sodium carbonate, sodium bicarbonate, sodium chloride, and calcium chloride; the grinding particle size of the pretreated porogen is 500~2000 mesh.

[0009] Preferably, in step (2), the crosslinking agent is at least one of glutaraldehyde, epichlorohydrin, triethylenetetramine, diethylenetriamine, 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, and glycerol triglycidyl ether; and the catalyst is at least one of sodium hydroxide, potassium hydroxide, triethylamine, and tributylamine.

[0010] Preferably, the lignin sulfonate is calcium lignin sulfonate or sodium lignin sulfonate.

[0011] Preferably, in step (2), the mass ratio of lignin sulfonate, pretreatment porogen, crosslinking agent, catalyst and water is 100:(30~100):(10~50):(2~10):(10~100).

[0012] More preferably, in step (2), the mass ratio of lignin sulfonate, pretreatment porogen, crosslinking agent, catalyst and water is 100:(50~100):(30~50):(5~10):(20~30).

[0013] More preferably, in step (2), the mass ratio of lignin sulfonate, pretreatment porogen, crosslinking agent, catalyst and water is 100:50:50:5:20.

[0014] Preferably, the temperature of the crosslinking reaction in step (2) is 50~100℃ and the time is 1~4 h.

[0015] More preferably, the temperature of the crosslinking reaction in step (2) is 60~80℃ and the time is 2~4 h.

[0016] More preferably, the temperature of the crosslinking reaction in step (2) is 80°C and the time is 4 h.

[0017] Preferably, in step (3), the cleaning is performed using a hydrochloric acid solution with a pH of 3 to 4; the dehydration is performed by washing with anhydrous ethanol 2 to 3 times; and the drying temperature is 35 to 45°C.

[0018] The present invention also provides a lignin-based porous adsorbent material prepared by the above preparation method.

[0019] This invention also provides the application of the above-mentioned lignin-based porous adsorbent material in the preparation of metal ion adsorbents.

[0020] This invention also provides the application of the above-mentioned lignin-based porous adsorbent material in the treatment of heavy metal ion wastewater.

[0021] The present invention has the following beneficial effects: (1) The lignin-based porous adsorbent material prepared by the method of the present invention has a higher specific surface area and functional group utilization rate compared with traditional chemical cross-linking and solidification adsorbent materials. The porogen used has good water solubility and does not participate in the reaction during the cross-linking process. After the cross-linking is completed, the porogen can be removed from the product by washing with water, thereby forming pores in the product. Furthermore, the porosity and pore size of the product can be controlled by adjusting the amount and particle size of the porogen.

[0022] (2) The method of the present invention uses lignin sulfonate rich in sulfonic acid groups as raw material, and constructs a rich pore structure by introducing a pore-forming agent, and forms a stable three-dimensional network under the action of a crosslinking agent, which effectively overcomes the defects of low reactivity and few adsorption sites of existing lignin adsorption materials. At the same time, the preparation process is carried out gently in the aqueous phase without high-temperature carbonization, which maximizes the retention of active functional groups in lignin, significantly improves the adsorption capacity and selectivity for heavy metal ions, and the lignin-based porous adsorption material obtained has good adsorption effect on metal ions such as lead, zinc, copper, iron and calcium in water.

[0023] (3) The lignin-based porous adsorbent material of the present invention uses lignin sulfonate, a by-product of the papermaking industry, as raw material, which has good sustainability and can be used as a substitute for traditional polymer materials. Attached Figure Description

[0024] Figure 1 The images shown are scanning electron microscope images of the lignin-based porous adsorbent material prepared in Example 1; where (a) is a full-view image of the lignin-based porous adsorbent material at 500 μm; and (b) is a cross-sectional image of the lignin-based porous adsorbent material at 200 μm. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0026] Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0028] Example 1 A method for preparing a lignin-based porous adsorbent material includes the following steps: (1) Grind sodium bicarbonate and sieve it to a particle size of 1000 mesh to obtain a pretreated pore-forming agent; (2) Calcium lignosulfonate, pretreatment porogen, epichlorohydrin, sodium hydroxide and water were mixed in a mass ratio of 100:50:30:5:30 and cross-linked at 60°C for 4 h to obtain the cross-linked body. (3) The crosslinked material was washed with hydrochloric acid solution with pH 3-4 and then washed three times with anhydrous ethanol for dehydration. It was then dried at 40°C to constant weight to obtain brown spherical lignin-based porous adsorbent material.

[0029] Example 2 A method for preparing a lignin-based porous adsorbent material includes the following steps: (1) Grind calcium carbonate and sieve it to a particle size of 500 mesh to obtain a pretreated pore-forming agent; (2) Sodium lignosulfonate, pretreatment porogen, 1,4-butanediol diglycidyl ether, triethylamine and water were mixed in a mass ratio of 100:100:30:10:25 and cross-linked at 70°C for 2 h to obtain the cross-linked body. (3) The crosslinked material was washed with hydrochloric acid solution with pH 3-4 and then washed three times with anhydrous ethanol for dehydration. It was then dried at 40°C to constant weight to obtain brown spherical lignin-based porous adsorbent material.

[0030] Example 3 A method for preparing a lignin-based porous adsorbent material includes the following steps: (1) Grind sodium carbonate and sieve it to a particle size of 500 mesh to obtain a pretreated pore-forming agent; (2) Sodium lignosulfonate, pretreatment porogen, glycerol triglycidyl ether, triethylamine and water were mixed in a mass ratio of 100:50:50:5:20 and cross-linked at 80°C for 4 h to obtain the cross-linked body. (3) The cross-linked material was washed with hydrochloric acid solution with pH 3~4 and then washed three times with anhydrous ethanol for dehydration. It was then dried at 40℃ to constant weight to obtain brown spherical lignin-based porous adsorbent material.

[0031] Comparative Example 1 A method for preparing a lignin-based porous adsorbent material includes the following steps: (1) Sodium lignosulfonate, glycerol triglycidyl ether, triethylamine and water were mixed in a mass ratio of 100:50:5:20 and cross-linked at 80°C for 4 h to obtain the cross-linked body. (2) The cross-linked material was washed with hydrochloric acid solution with pH 3-4 and then washed three times with anhydrous ethanol for dehydration. It was then dried at 40°C to constant weight and ground through a 100-mesh sieve to obtain brown granular lignin-based porous adsorbent material.

[0032] Comparative Example 2 A method for preparing a lignin-based porous adsorbent material includes the following steps: (1) Alkali lignin, glycerol triglycidyl ether, triethylamine and water were mixed in a mass ratio of 100:50:5:20 and cross-linked at 80°C for 4 h to obtain the cross-linked body. (2) The crosslinked material was washed with hydrochloric acid solution with pH 3~4 and then washed three times with anhydrous ethanol for dehydration. It was then dried at 40℃ to constant weight and ground through a 100-mesh sieve to obtain light yellow granular lignin-based porous adsorbent material.

[0033] Experimental Example 1. Morphological characteristics Scanning electron microscopy analysis was performed on the brown spherical lignin-based porous adsorbent material prepared in Example 1, and the results are as follows: Figure 1 As shown.

[0034] from Figure 1 As can be seen from the above, the lignin-based porous adsorbent material prepared by this invention is a brown porous solid particle with obvious porous characteristics on the particle surface. The pore size distribution range is wide (from micropores to macropores). Macropores provide fast transport channels, while micropores / mesopores provide high specific surface area adsorption sites. This hierarchical pore structure can achieve selective adsorption of molecules of different sizes. At the same time, its pore network has strong interconnection, forming a three-dimensional through structure, which is conducive to the rapid diffusion and transport of adsorbate molecules. The particle surface is uneven and has high roughness, which is beneficial to increasing the specific surface area and improving the adsorption capacity.

[0035] 2. Adsorption performance test The lignin-based porous adsorbent materials prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to metal ion adsorption performance tests. The specific steps were as follows: (1) Using lead nitrate, zinc nitrate, calcium chloride and magnesium chloride as reagents, four working solutions with a concentration of 0.1 mol / L were prepared using distilled water respectively. (2) Add 100 mL of the working solution from step (1) to each of the four 250 mL Erlenmeyer flasks, and add 1 g of sample. Shake in a water bath at 25 °C for 1 h. After shaking, filter the solution and bring the volume of the filtrate to 250 mL. Determine the metal ion content in the filtrate by EDTA titration. The results are shown in Table 1.

[0036] Table 1. Test results of adsorption performance of lignin-based porous adsorbent materials

[0037] As can be seen from Table 1, the lignin-based porous adsorbent prepared by the present invention has good adsorption performance for common metal ions. The adsorption amount of the lignin-based porous adsorbent prepared in Comparative Example 1 without the addition of a porogen is significantly lower than that in Examples 1-3 for all metal ions (lead, zinc, calcium and magnesium), indicating that the addition of a porogen helps to form a porous structure, increase the specific surface area and adsorption sites, thereby significantly improving the adsorption performance.

[0038] Based on Comparative Example 1, replacing lignin sulfonate with other cellulose-based materials (alkali lignin) resulted in Comparative Example 2 exhibiting the lowest adsorption capacity on all metal ions, with an adsorption capacity decrease of over 85% compared to the previous example. This is because the lignin sulfonate used in this invention, containing sulfonic acid groups, is more easily functionalized and cross-linked, resulting in an adsorbent material with a stronger metal ion binding capacity; while alkali lignin has lower reactivity and is difficult to form an effective adsorption structure.

[0039] The present invention has been described according to the above embodiments. It should be understood that the above embodiments do not limit the present invention in any way. All technical solutions obtained by equivalent substitution or equivalent transformation fall within the scope of the present invention.

Claims

1. A method for preparing a lignin-based porous adsorbent material, characterized in that, Includes the following steps: (1) Grind and sieve the porogen to obtain a pretreated porogen; (2) Mix lignin sulfonate, pretreatment porogen, crosslinking agent, catalyst and water and carry out crosslinking reaction to obtain crosslinked body; (3) The cross-linked material is washed, dehydrated and dried to obtain the lignin-based porous adsorbent material.

2. The method for preparing the lignin-based porous adsorbent material as described in claim 1, characterized in that, In step (1), the porogen is at least one of calcium carbonate, sodium carbonate, sodium bicarbonate, sodium chloride, and calcium chloride; the grinding particle size of the pretreated porogen is 500-2000 mesh.

3. The method for preparing the lignin-based porous adsorbent material as described in claim 1, characterized in that, In step (2), the crosslinking agent is at least one of glutaraldehyde, epichlorohydrin, triethylenetetramine, diethylenetriamine, 1,4-butanediol diglycidyl ether, trimethylolpropane triglycidyl ether, and glycerol triglycidyl ether; and the catalyst is at least one of sodium hydroxide, potassium hydroxide, triethylamine, and tributylamine.

4. The method for preparing the lignin-based porous adsorbent material as described in claim 1 or 3, characterized in that, In step (2), the mass ratio of lignin sulfonate, pretreatment porogen, crosslinking agent, catalyst and water is 100:(30~100):(10~50):(2~10):(10~100).

5. The method for preparing the lignin-based porous adsorbent material as described in claim 1, characterized in that, The temperature of the crosslinking reaction in step (2) is 50~100℃ and the time is 1~4 h.

6. The method for preparing the lignin-based porous adsorbent material as described in claim 5, characterized in that, The temperature of the crosslinking reaction in step (2) is 60~80℃ and the time is 2~4 h.

7. The method for preparing the lignin-based porous adsorbent material as described in claim 1, characterized in that, In step (3), the cleaning is performed using a hydrochloric acid solution with a pH of 3-4; the dehydration is performed by washing with anhydrous ethanol 2-3 times; and the drying temperature is 35-45℃.

8. The lignin-based porous adsorbent material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the lignin-based porous adsorbent material according to claim 8 in the preparation of metal ion adsorbents.

10. The application of the lignin-based porous adsorbent material according to claim 8 in the treatment of heavy metal ion wastewater.

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