A lignin / polyethyleneimine magnetic composite material and a one-step method for preparing the same

Abstract

The present application provides a one-step method for preparing a lignin / polyethyleneimine magnetic composite material, comprising the following steps: step (1): selecting a reactant composed of polyethyleneimine, lignin and ethylene glycol, adding the reactant into a reaction container, heating to 70 DEG C to dissolve and obtaining a brown clear solution; step (2): adding a ferric salt and an alkali into the brown clear solution obtained in step (1), magnetically stirring to dissolve, then transferring into a hydrothermal reaction kettle, reacting at a certain temperature for a certain time, and obtaining a black suspension; step (3): naturally cooling the black suspension obtained in step (2) to room temperature, obtaining a black product, washing the black product with deionized water and ethanol in sequence until clear, and vacuum drying at 60 DEG C for 12h to obtain the lignin / polyethyleneimine magnetic composite material; the present application also provides a lignin / polyethyleneimine magnetic composite material prepared by the above preparation method.

Description

Technical Field

[0001] This invention relates to the field of polymer environmental materials technology, and in particular to a lignin / polyethyleneimine magnetic composite material and its one-step preparation method. Background Technology

[0002] Based on the types of pollutants in the wastewater, electroplating wastewater can be classified into: general wastewater, cyanide-containing wastewater, and heavy metal-containing wastewater, etc. The main pollutants in electroplating wastewater are heavy metal ions, including copper, zinc, nickel, chromium, and lead. Because the electroplating process has pH requirements, strong acids or alkalis are added, making the wastewater highly acidic / alkaline. Cyanides are also added as complexing agents in the electroplating process, further complicating the types of electroplating wastewater and making it more difficult to treat. In addition, the large amounts of heavy metal ions and cyanides in electroplating wastewater are highly hazardous and difficult to treat. Many methods exist for treating water pollution problems, including adsorption, chemical precipitation, ion exchange, and membrane filtration. Among these, adsorption is widely used due to its advantages of low secondary pollution, high treatment efficiency, and regenerable adsorbents.

[0003] Polyethylene imine is a water-soluble polymer and a cationic polyelectrolyte. Its numerous primary, secondary, and tertiary amine functional groups can specifically bind to various pollutants through electrostatic interactions, ion exchange, chelation, and coordination, making it promising for the treatment of wastewater containing heavy metals and dyes. However, polyethylene imine is also readily soluble in water, and its direct use for adsorbing heavy metal ions in water makes it difficult to recycle, thus limiting its application scope.

[0004] Lignin is an important byproduct of the sulfite pulping industry, possessing advantages such as abundant resources, low price, and environmental friendliness, and has broad market prospects. Lignin is a high-molecular-weight polymer with a three-dimensional network structure, containing numerous oxygen-containing functional groups such as hydroxyl, carboxyl, and sulfonate groups. It exhibits strong electronegativity and hydrophilicity, demonstrating excellent dispersion and adsorption properties in aqueous solutions. Therefore, it is used as a dye dispersant, chelating agent, surfactant, and water treatment agent.

[0005] Magnetic iron oxide nanoparticles possess advantages such as high saturation magnetization, large specific surface area, and ease of surface functionalization, leading to their widespread application in pharmaceuticals, water treatment, and other fields. Magnetic iron oxide nanoparticles are easy to prepare, exhibit paramagnetism, and can undergo solid-liquid separation under the influence of a magnetic field, often serving as a composite matrix for adsorbents. However, they are easily oxidized and prone to aggregation, necessitating composite modification to protect their magnetic properties and improve their dispersion stability.

[0006] Chinese patent application No. 201710261211.4 discloses a simple process for preparing magnetic polyethyleneimine, which connects polyethyleneimine to the surface of magnetic iron oxide (Fe3O4). This process allows for both adsorption and rapid separation of pollutants, and the material is stable and easily recyclable. Chinese patent application No. 201310551818.8 discloses a method for preparing a heavy metal ion adsorbent using polyethyleneimine-modified sodium lignosulfonate. This method involves attaching polyethyleneimine to sodium lignosulfonate using electrostatic or chemical cross-linking methods, resulting in a stable polyethyleneimine-sodium lignosulfonate heavy metal ion adsorbent. The adsorbent material synthesized using this method has abundant active adsorption groups such as hydroxyl, sulfonic acid, and amino groups on its surface, and possesses advantages such as simple preparation process, low cost, and good stability. Summary of the Invention

[0007] The purpose of this invention is to provide a lignin / polyethyleneimine magnetic composite material and a one-step preparation method thereof to solve the above problems.

[0008] This invention provides a one-step method for preparing lignin / polyethyleneimine magnetic composite materials, comprising the following steps:

[0009] Step (1): Select reactants consisting of polyethyleneimine, lignin and ethylene glycol, add the reactants to a reaction vessel, heat to 70°C to dissolve and obtain a clear brown solution;

[0010] Step (2): Add ferric salt and alkali to the brown clear solution obtained in step (1), stir magnetically to dissolve, and then transfer to a hydrothermal reactor. React at a certain temperature for a certain time to obtain a black suspension.

[0011] Step (3): The black suspension obtained in step (2) is naturally cooled to room temperature to obtain a black product. The black product is washed with deionized water and ethanol in sequence until it is clear. It is then vacuum dried at 60°C for 12 hours to obtain a lignin / polyethyleneimine magnetic composite material.

[0012] Preferably, the lignin is at least one of sodium lignin sulfonate, calcium lignin sulfonate, and water-soluble lignin.

[0013] Preferably, in step (2), the trivalent iron salt is at least one of FeCl3·6H2O, Fe(NO3)3·9H2O or Fe2(SO4)3·H2O.

[0014] Preferably, in step (2), the alkali is one of sodium acetate trihydrate or sodium oxalate trihydrate.

[0015] Preferably, the weight ratio of polyethyleneimine, lignin and ferric salt in step (1) is 0.1-1.5:0.1-1.5:2.7.

[0016] Preferably, the weight ratio of the ferric salt in step (2) to the ethylene glycol in step (1) is 1.35-2.7:3.6-7.2:60.

[0017] Preferably, in step (2), the temperature of the hydrothermal reactor is 200℃-240℃, and the reaction time is 8-36h.

[0018] The present invention also provides a lignin / polyethyleneimine magnetic composite material prepared by the above preparation method.

[0019] Preferably, the particle size of the lignin / polyethyleneimine magnetic composite material is 100-200 nm.

[0020] Preferably, the lignin / polyethyleneimine magnetic composite material is composed of magnetic iron oxide, polyethyleneimine, and lignin.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. The preparation method of the lignin / polyethyleneimine magnetic composite material of the present invention has the following advantages: simple process, convenient separation, energy saving, easy industrial operation, and good production safety;

[0023] 2. The magnetic lignin / polyethyleneimine composite material prepared by this invention is stable and not easily lost. Attached Figure Description

[0024] Figure 1 This is an electron microscope image of Embodiment 1 of the present invention;

[0025] Figure 2 This is an electron microscope image of Embodiment 2 of the present invention;

[0026] Figure 3 This is an electron microscope image of Embodiment 3 of the present invention;

[0027] Figure 4 This is an electron microscope image of Embodiment 4 of the present invention;

[0028] Figure 5 This is an electron microscope image of Embodiment 5 of the present invention. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] A one-step method for preparing lignin / polyethyleneimine magnetic composite materials includes the following steps:

[0031] (1) A reaction mixture consisting of polyethyleneimine, lignin, and ethylene glycol was selected. The reaction mixture was added to a reaction vessel and heated to 70°C to dissolve, resulting in a clear brown solution. Polyethyleneimine, as an electrolyte, has high conductivity. Adding a certain amount of ions, such as chloride ions or lithium ions, to polyethyleneimine can increase its conductivity. Polyethyleneimine (PEI) molecules contain a large number of amino functional groups. These functional groups can accept protons to form positively charged ions. The charge of the amino functional group is determined by the nitrogen atom and the surrounding electronic environment. The electron cloud of the nitrogen atom contains a lone pair of electrons, which can accept protons to form positively charged ions. When an amino functional group accepts a proton, the lone pair of electrons on the nitrogen atom combines with the received proton to form a positively charged amino ion. Therefore, a lignin-containing amino functional group can form a positively charged amino ion. Molecules or compounds with functional groups usually have positive charges. In polyethyleneimine, due to the large number of amino functional groups in its molecules, polyethyleneimine molecules carry a large number of positive charges, thus PEI has strong positive charge properties. Lignin is a natural high-molecular-weight organic compound containing a variety of charged functional groups, the most common of which are the hydroxyl (-OH) and methoxy (-OCH3) functional groups on the benzene ring. The oxygen atoms in these functional groups and the electron clouds on the benzene ring can participate in redox reactions and protonation reactions, thus giving lignin molecules a negative charge. In addition, there are some carbon atoms in lignin that are connected to oxygen atoms. The valence electron pairs of these carbon atoms may also participate in the electron transfer process, further enhancing the charge of lignin molecules. In subsequent steps, polyethyleneimine and lignin attract each other on the surface of the intermediate product to form a shell-like encapsulation structure, which becomes the adsorption surface layer.

[0032] (2) Add ferric salt and alkali to the obtained brown clear solution, stir magnetically to dissolve, and then transfer to a hydrothermal reactor. React at 200℃-240℃ for 8-36 hours to obtain a black suspension. Ferric salt is transformed into magnetic microparticles during the hydrothermal reaction. The positive and negative charges of polyethyleneimine and lignin are attracted by the magnetic microparticles during the hydrothermal reaction. The positive and negative charges of polyethyleneimine and lignin attract each other on the surface of the magnetic microparticles, thus forming a coating layer on the surface of the microparticles. The coating layer formed by the cross-linking of polyethyleneimine and lignin has adsorption properties. The microparticles are magnetic, and the two form a bipolar material through the shell-core structure.

[0033] (3) The black suspension was naturally cooled to room temperature to obtain a black product. The black product was washed with deionized water and ethanol until it became clear. It was then vacuum dried at 60°C for 12 hours to obtain a lignin / polyethyleneimine magnetic composite material.

[0034] In some optional embodiments, the lignin is at least one of sodium lignin sulfonate, calcium lignin sulfonate, and water-soluble lignin.

[0035] In some optional embodiments, in step (2), the ferric salt is at least one of FeCl3·6H2O, Fe(NO3)3·9H2O or Fe2(SO4)3·H2O.

[0036] In some optional embodiments, in step (2), the base is one of sodium acetate trihydrate and sodium oxalate trihydrate.

[0037] In some optional embodiments, the weight ratio of polyethyleneimine, lignin and ferric salt in step (1) is 0.1-1.5:0.1-1.5:2.7.

[0038] In some optional embodiments, the weight ratio of the ferric salt in step (2) to the alcohol in step (1) is 1.35-2.7:3.6-7.2:60.

[0039] In some optional embodiments, the firing temperature in step (2) is 200℃-240℃ and the reaction time is 8-36h.

[0040] The present invention also provides a lignin / polyethyleneimine magnetic composite material prepared by the above preparation method.

[0041] In some optional embodiments, the particle size of the magnetic composite material is 100-200 nm.

[0042] In some alternative embodiments, the magnetic composite material is composed of magnetic iron oxide, polyethyleneimine, and lignin.

[0043] Example 1:

[0044] 0.2 g of polyethyleneimine, 0.2 g of sodium lignosulfonate, and 10 mL of ethylene glycol were added to a reaction vessel and heated to 70 °C to dissolve, resulting in a clear brown solution. Then, 0.54 g of ferric chloride (FeCl3·6H2O) and 1.44 g of sodium acetate trihydrate were added, and the solution was magnetically stirred and then transferred to a 50 mL hydrothermal reactor. The reaction was carried out at 200 °C for 10 h to obtain a black suspension. After naturally cooling to room temperature, the obtained black product was washed several times with deionized water and ethanol, and the water was removed by magnetic adsorption. The product was then vacuum dried at 60 °C for 12 h to obtain the sample, which is the lignin / polyethyleneimine magnetic composite material with an average particle size of 115 nm.

[0045] Example 2:

[0046] 0.4 g of polyethyleneimine, 0.4 g of calcium lignosulfonate, and 20 mL of ethylene glycol were added to a reaction vessel and heated to 70 °C to dissolve, resulting in a clear brown solution. Then, 1.08 g of ferric nitrate (Fe(NO3)3·9H2O) and 2.88 g of sodium acetate were added, and the solution was magnetically stirred and then transferred to a 50 mL hydrothermal reactor. The reaction was carried out at 210 °C for 8 hours. After natural cooling to room temperature, the resulting black product was washed several times with deionized water and ethanol, and the water was removed by magnetic adsorption. The product was then vacuum dried at 60 °C for 12 hours to obtain the sample, which is the magnetic lignin / polyethyleneimine magnetic composite material with an average particle size of 107 nm.

[0047] Example 3:

[0048] 0.6 g of polyethyleneimine, 0.6 g of water-soluble lignin, and 40 mL of ethylene glycol were added to a reaction vessel and heated to 70 °C to dissolve, resulting in a clear brown solution. Then, 1.62 g of ferric sulfate (Fe2(SO4)3·H2O) and 4.32 g of sodium hydroxide were added, and the solution was magnetically stirred and then transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 220 °C for 12 hours. After naturally cooling to room temperature, the resulting black product was washed several times with deionized water and ethanol, and the water was removed by magnetic adsorption. The product was then vacuum dried at 60 °C for 12 hours to obtain the sample, which is the magnetic lignin / polyethyleneimine magnetic composite material with an average particle size of 107 nm.

[0049] Example 4:

[0050] 0.8 g of polyethyleneimine, 0.8 g of sodium lignosulfonate, and 50 mL of ethylene glycol were added to a reaction vessel and heated to 70 °C to dissolve, resulting in a clear brown solution. Then, 2.16 g of ferric chloride (FeCl3·6H2O) and 5.76 g of sodium hydroxide were added, and the solution was magnetically stirred and then transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 225 °C for 16 hours. After naturally cooling to room temperature, the resulting black product was washed several times with deionized water and ethanol, and the water was removed by magnetic adsorption. The product was then vacuum dried at 60 °C for 12 hours to obtain the sample, which is the magnetic lignin / polyethyleneimine magnetic composite material with an average particle size of 119 nm.

[0051] Example 5:

[0052] 1.0 g of polyethyleneimine, 1.0 g of water-soluble lignin, and 60 mL of ethylene glycol were added to a reaction vessel and heated to 70 °C to dissolve, resulting in a clear brown solution. Then, 2.7 g of ferric nitrate (Fe(NO3)3·9H2O) and 3.6 g of potassium hydroxide were added, and the solution was magnetically stirred and then transferred to a 100 mL hydrothermal reactor. The reaction was carried out at 230 °C for 18 hours. After naturally cooling to room temperature, the resulting black product was washed several times with deionized water and ethanol, and then vacuum dried at 60 °C for 12 hours to obtain the sample, which is the magnetic lignin / polyethyleneimine magnetic composite material with an average particle size of 116 nm.

Claims

1. A one-step method for preparing lignin / polyethyleneimine magnetic composite materials, characterized in that: Includes the following steps: Step (1): Select reactants consisting of polyethyleneimine, lignin and ethylene glycol, add the reactants to a reaction vessel, heat to 70°C to dissolve and obtain a clear brown solution; Step (2): Add ferric salt and alkali to the brown clear solution obtained in step (1), stir magnetically to dissolve, and then transfer to a hydrothermal reactor. React at a certain temperature for a certain time to obtain a black suspension. Step (3): The black suspension obtained in step (2) is naturally cooled to room temperature to obtain a black product. The black product is washed with deionized water and ethanol in sequence until it is clear. It is then vacuum dried at 60°C for 12 hours to obtain a lignin / polyethyleneimine magnetic composite material. The weight ratio of polyethyleneimine, lignin and ferric salt in step (1) to that in step (2) is 1:1:2.

7. In steps (2) and (3), polyethyleneimine and lignin attract each other on the surface of the intermediate product to form a shell-like encapsulation structure, which becomes the adsorption surface layer. The lignin / polyethyleneimine magnetic composite material has a particle size of 100-200 nm. The lignin / polyethyleneimine magnetic composite material is composed of magnetic iron oxide, polyethyleneimine, and lignin. In step (2), the temperature of the hydrothermal reactor is 200℃-240℃, and the reaction time is 8-36h.

2. The method for preparing lignin / polyethyleneimine magnetic composite materials in one step according to claim 1, characterized in that: The lignin is at least one of sodium lignin sulfonate, calcium lignin sulfonate, and water-soluble lignin.

3. The method for preparing lignin / polyethyleneimine magnetic composite materials in one step according to claim 1, characterized in that: In step (2), the ferric salt is at least one of FeCl3·6H2O, Fe(NO3)3·9H2O or Fe2(SO4)3·H2O.

4. The method for preparing lignin / polyethyleneimine magnetic composite materials in one step according to claim 1, characterized in that: In step (2), the alkali is either sodium acetate trihydrate or sodium oxalate trihydrate.

5. The lignin / polyethyleneimine magnetic composite material prepared by any one of the preparation methods of claims 1-4.

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