Spherical lignin-phenolic resin, preparation method thereof and application of spherical lignin-phenolic resin in adsorption of N-containing organic dye

Abstract

The invention provides spherical lignin-phenolic resin, a preparation method thereof and application of the spherical lignin-phenolic resin in adsorption of N-containing organic dye, and belongs to the technical field of adsorption materials. The lignin-phenolic resin with the regular spherical morphology can be prepared through a one-step condensation polymerization reaction by taking lignin, hydroquinone and trioxymethylene as raw materials under an acidic catalysis condition and adopting a reversed-phase suspension polymerization method, the lignin belongs to a renewable resource and has the characteristics of low cost and environmental friendliness, and the lignin-phenolic resin can be used for preparing the lignin-phenolic resin with the regular spherical morphology. The phenolic resin can replace phenols to become a main phenol source, the substitution rate can reach 75%, and the yield of the synthesized phenolic resin reaches up to 60-80%. Besides, abundant phenolic hydroxyl groups, sulfonic acid groups and other oxygen-containing groups can be introduced into the resin by selecting the types of monomers, the cross-linked structure of the resin is changed by regulating and controlling the proportion of the monomers, the adsorption capacity of N-containing organic dyes is effectively improved, and efficient adsorption of rhodamine B and methylene blue can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of adsorption materials, and in particular to a spherical lignin-phenolic resin, a preparation method thereof, and application thereof in adsorbing nitrogen-containing organic dyes. Background Art

[0002] Dyes are widely used in industries such as textiles, printing and dyeing, and cosmetics, and are indispensable chemicals in the production processes of many industries. However, organic dye molecules often have complex aromatic structures and strong biotoxicity, making them difficult to degrade naturally. The large amount of dye wastewater generated during production and use, if not properly treated, can damage the aquatic ecological environment and pose a serious threat to organisms and even human health. Rhodamine B (RhB) and methylene blue (MB) are typical nitrogen-containing dyes that are highly toxic, carcinogenic, and persistent. They can harm aquatic organisms even at low concentrations and can accumulate in the human body through the food chain, leading to multiple organ damage and diseases.

[0003] Among numerous wastewater treatment technologies, adsorption has shown great potential in dye wastewater treatment due to its ease of operation, low cost, high efficiency, stability, and reproducibility. Currently, materials used for dye adsorption primarily include activated carbon, metal-organic frameworks (MOFs), and polymeric materials. Activated carbon has a high specific surface area, enabling high adsorption capacities, but suffers from disadvantages such as poor selectivity, susceptibility to interference from coexisting organic matter, and high regeneration costs. Metal-organic frameworks also possess high specific surface areas and tunable pore structures, but are expensive to synthesize and difficult to regenerate. Polymeric materials, such as resins, offer high designability, allowing precise design of pore structures and adjustment of surface functional groups by varying cross-linking and monomer composition to achieve size-matching and electrostatic / hydrogen bonding. However, these materials often suffer from high synthesis costs or require complex post-processing. Therefore, the development of novel adsorbent materials that are efficient, environmentally friendly, low-cost, and require simple synthesis processes has become a research hotspot.

[0004] In recent years, biomass-based adsorbents have attracted attention due to their renewability and environmental friendliness, but their adsorption capacity is generally low, and their mechanical strength is insufficient, making them difficult to recycle. Designing biomass-based adsorbents with both high adsorption capacity and good appearance and morphology still faces challenges. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a spherical lignin-phenolic resin, a preparation method thereof, and an application thereof in adsorbing N-containing organic dyes. The spherical lignin-phenolic resin provided by the present invention has low cost and high adsorption capacity for N-containing organic dyes.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a spherical lignin-phenolic resin, comprising the following steps:

[0008] mixing sodium lignin sulfonate, phenolic substances, aldehyde substances, aqueous solvents and acid catalysts to obtain a reaction phase;

[0009] mixing an oily dispersion medium with a dispersion stabilizer to obtain a continuous phase;

[0010] The reaction phase and the continuous phase are mixed, and suspension polymerization and thermal curing are carried out under stirring conditions to obtain a spherical lignin-phenolic resin.

[0011] Preferably, the phenolic substance includes hydroquinone;

[0012] The aldehyde substance includes trioxymethylene;

[0013] The molar ratio of the phenolic substance to the aldehyde substance is 1:2-4.

[0014] Preferably, the mass ratio of the phenolic substance to sodium lignin sulfonate is 1:0.5-3.

[0015] Preferably, the aqueous solvent is an aqueous solution of ethylene glycol; the mass ratio of the total mass of the sodium lignin sulfonate, phenolic substances, and aldehyde substances to the aqueous solvent is 1:0.8-2.0;

[0016] The acid catalyst includes concentrated hydrochloric acid; the pH value of the reaction phase is 1-2.

[0017] Preferably, the oily dispersion medium comprises liquid paraffin;

[0018] The dispersion stabilizer includes a compound of span-80 and tween-85, wherein the mass ratio of span-80 to tween-85 is 4 to 8:1;

[0019] Preferably, the dispersion stabilizer is 2 to 3‰ of the mass of the oily dispersion medium.

[0020] Preferably, the volume ratio of the continuous phase to the reaction phase is 3 to 5:1.

[0021] Preferably, the suspension polymerization reaction temperature is 90-100° C., and the holding time is 1-1.5 h;

[0022] The temperature of the thermal curing is 110-115° C., and the heat preservation time is 5-10 hours.

[0023] The present invention provides a spherical lignin-phenolic resin prepared by the above preparation method.

[0024] Preferably, the particle size of the spherical lignin-phenolic resin is 0.1 to 0.8 mm.

[0025] The present invention provides application of the spherical lignin-phenolic resin in adsorbing nitrogen-containing organic dyes.

[0026] The present invention provides a method for preparing a spherical lignin-phenolic resin, comprising the following steps: mixing sodium lignin sulfonate, a phenolic substance, an aldehyde substance, an aqueous solvent, and an acid catalyst to obtain a reaction phase; mixing an oily dispersion medium with a dispersion stabilizer to obtain a continuous phase; mixing the reaction phase and the continuous phase, and carrying out a suspension polymerization reaction and heat curing under stirring to obtain the spherical lignin-phenolic resin. The present invention adopts acidic catalysis conditions, sodium lignin sulfonate, hydroquinone, and trioxymethylene as raw materials, and uses a reverse phase suspension polymerization method to prepare a lignin-phenolic resin (abbreviated as SLHF) with a regular spherical morphology through a single-step condensation polymerization reaction. Sodium lignin sulfonate is a renewable resource with low cost and environmentally friendly characteristics. The present invention uses sodium lignin sulfonate to replace phenols (hydroquinone) as the main phenol source, with a substitution rate of up to 75%. The yield of the synthesized phenolic resin is as high as 60-80%. In addition, the present invention can introduce abundant phenolic hydroxyl groups, sulfonic acid groups and other oxygen-containing groups into the resin through the selection of monomer types, which can effectively improve the adsorption capacity of nitrogen-containing organic dyes. The obtained spherical lignin-phenolic resin has a high bio-based content, a good spherical morphology and an adjustable cross-linking density, and can achieve efficient adsorption of rhodamine B and methylene blue. The adsorption amount for 100-1000 mg / L rhodamine B solution can reach 558-2118 mg / g, and the adsorption amount for 100-500 mg / L methylene blue solution can reach 248-334 mg / g.

[0027] The present invention adopts suspension polymerization to prepare spherical lignin-phenolic resin. The good spherical appearance gives the material good fluidity and properties that are conducive to separation and recovery in actual operation, which is convenient for filling adsorption columns and bed reactors and has excellent industrial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 These are optical microscope images of the spherical lignin-phenolic resins of Examples 1, 2, and 3;

[0029] Figure 2 is the Fourier transform infrared spectrum of the lignin-phenolic resin of Example 1;

[0030] Figure 3 This is a scanning electron microscope photograph of the appearance and internal pore structure of the lignin-phenolic resin of Example 1;

[0031] Figure 4 The adsorption kinetics curves of Example 1 and commercial macroporous sulfonic acid resin D072 (hydrogen type);

[0032] Figure 5 Optical microscope photos of resins obtained with different dispersion stabilizers. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing a spherical lignin-phenolic resin, comprising the following steps:

[0034] mixing sodium lignin sulfonate, phenolic substances, aldehyde substances, aqueous solvents and acid catalysts to obtain a reaction phase;

[0035] mixing an oily dispersion medium with a dispersion stabilizer to obtain a continuous phase;

[0036] The reaction phase and the continuous phase are mixed, and suspension polymerization and thermal curing are carried out under stirring conditions to obtain a spherical lignin-phenolic resin.

[0037] Unless otherwise specified, the raw materials used in the present invention are all commercially available.

[0038] The present invention mixes sodium lignin sulfonate, a phenolic substance, an aldehyde substance, an aqueous solvent, and an acid catalyst to obtain a reaction phase. In the present invention, the phenolic substance preferably includes hydroquinone. In the present invention, the mass ratio of the phenolic substance to sodium lignin sulfonate is preferably 1:0.5-3, more preferably 1:2-3, and most preferably 1:3. In the present invention, the aldehyde substance includes trioxymethylene. In the present invention, the molar ratio of the phenolic substance to the aldehyde substance is preferably 1:2-4, more preferably 1:2-3. By controlling the type and amount ratio of the monomers, the present invention can introduce abundant phenolic hydroxyl groups, sulfonic acid groups, and other oxygen-containing groups into the resin, and by adjusting the monomer ratio to change the cross-linking structure of the resin, the adsorption capacity for rhodamine B can be effectively controlled.

[0039] In the present invention, the aqueous solvent is preferably an aqueous solution of ethylene glycol. In the present invention, the mass concentration of ethylene glycol in the aqueous solution is preferably 80-85%, more preferably 83-84%. In the present invention, the mass ratio of the total mass of the sodium lignin sulfonate, phenolic substances, and aldehyde substances to the aqueous solvent is preferably 1:0.8-2.0, more preferably 1:1.2-1.6, and even more preferably 1:1.6.

[0040] In the present invention, the acid catalyst comprises concentrated hydrochloric acid, and the amount of the acid catalyst is controlled to adjust the pH value of the reaction phase to 1-2.

[0041] In the present invention, the mixing method is preferably: firstly add sodium lignin sulfonate, phenolic substances and aldehyde substances into the aqueous solvent, and then add the acid catalyst.

[0042] The present invention mixes an oily dispersion medium with a dispersion stabilizer to obtain a continuous phase. In the present invention, the oily dispersion medium preferably includes liquid paraffin. In the present invention, the dispersion stabilizer preferably includes a compounded span-80 and tween-85, and the mass ratio of span-80 to tween-85 is preferably 4 to 8:1, more preferably 5 to 7:1. In the present invention, the dispersion stabilizer is preferably 2 to 3‰ of the mass of the oily dispersion medium. By controlling the type and amount of the oily dispersion medium and the dispersion stabilizer, the hydrophilicity and lipophilicity of the system can be adjusted, which is beneficial to the control of spherical shape during the synthesis process.

[0043] The present invention has no special requirements for the mixing method, and any mixing method well known to those skilled in the art can be used.

[0044] The present invention mixes the reaction phase and the continuous phase, performs suspension polymerization and thermal curing under stirring conditions, and obtains a spherical lignin-phenolic resin. In the present invention, the volume ratio of the continuous phase to the reaction phase is preferably 3 to 5:1, more preferably 4:1. In the present invention, the stirring paddle used for stirring is preferably placed at the junction of the reaction phase and the continuous phase. In the present invention, the stirring rate is preferably 150 to 230 rpm. In the present invention, the appropriate stirring speed is adjusted to disperse the reaction phase into small droplets of appropriate and uniform size.

[0045] In the present invention, the temperature of the suspension polymerization reaction is preferably 90 to 100° C., more preferably 95° C., and the holding time is preferably 1 to 1.5 hours. In the present invention, during the suspension polymerization reaction, the reaction occurs as shown in Formula A:

[0046]

[0047] After the suspension polymerization reaction, the present invention preferably directly heats the resulting suspension polymerization reaction solution to perform thermal curing. In the present invention, the thermal curing temperature is preferably 110-115°C, and the holding time is preferably 5-10 hours, more preferably 6-8 hours. In the present invention, the purpose of thermal curing is to achieve more complete crosslinking of the resin.

[0048] After the heat curing, the reaction is stopped and the solid spherical resin is obtained after cooling and filtration, and the following post-processing steps are performed on it:

[0049] The solid product after the reaction is first washed with ethanol for 4 to 5 times, and then washed with distilled water for 5 to 6 times until neutral. The resin is placed in a Soxhlet extractor and extracted with petroleum ether with a boiling range of 60 to 90° C. for 8 hours under heating and reflux to remove residual porogens and unreacted monomers in the resin. The resin is then immersed in a 5% hydrochloric acid solution and shaken in a shaker. The hydrochloric acid solution is replaced every half an hour, and this is repeated 4 to 5 times. After washing until neutral, a product with a diameter of 0.1 to 0.8 mm is obtained through screening and stored in a wet state to obtain a spherical lignin-phenolic resin.

[0050] The present invention provides a spherical lignin-phenolic resin prepared by the above preparation method. In the present invention, the particle size of the spherical lignin-phenolic resin is preferably 0.1 to 0.8 mm.

[0051] The present invention provides the use of the spherical lignin-phenolic resin in adsorbing nitrogen-containing organic dyes. In the present invention, the nitrogen-containing organic dye preferably includes rhodamine B and / or methylene blue. In the present invention, the method of using the resin preferably includes the following steps:

[0052] The spherical lignin-phenolic resin is mixed with a solution containing a nitrogen-containing organic dye, and adsorption is performed. After the adsorption, the spherical lignin-phenolic resin is separated.

[0053] In the present invention, the solution containing the N-containing organic dye can be wastewater containing the N-containing organic dye. In the present invention, when the N-containing organic dye is rhodamine B, the concentration of the N-containing organic dye in the solution containing the N-containing organic dye is preferably 100 to 1000 mg / L, more preferably 1000 mg / L; when the N-containing organic dye is methylene blue, the concentration of the N-containing organic dye in the solution containing the N-containing organic dye is preferably 100 to 500 mg / L. As a specific embodiment of the present invention, the mass (dry weight) of the spherical lignin-phenolic resin to the volume ratio of the solution containing the N-containing organic dye is preferably 10 mg:100 mL, the adsorption temperature is preferably 25°C (±0.5°C), and the adsorption time is preferably 40 to 48 hours.

[0054] The spherical lignin-phenolic resin provided by the present invention, its preparation method and its application in adsorbing N-containing organic dyes are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0055] Example 1

[0056] In this embodiment, the monomers are sodium lignin sulfonate, hydroquinone and trioxymethylene, wherein the mass ratio of hydroquinone to sodium lignin sulfonate is 1:3; the molar ratio of hydroquinone to trioxymethylene is 1:2.1; and the amount of solvent used is 1.6 times the total mass of the monomers.

[0057] Preparation of the reaction phase: Add 9.02g of sodium lignin sulfonate, 3.01g of hydroquinone, 1.72g of trioxymethylene, and 22.07g of 83wt% ethylene glycol aqueous solution as solvent into a three-necked flask. After fully dissolving under mechanical stirring, slowly add concentrated hydrochloric acid to adjust the pH to 1.

[0058] Preparation of the continuous phase: Weigh 0.2 g of span-800, 0.03 g of tween-850, and 104.92 g of liquid paraffin in a beaker and stir with a magnetic stirrer to mix evenly.

[0059] The prepared continuous phase is slowly added to the three-necked flask containing the reaction phase, and the stirring is started and the speed is adjusted to 225 rpm. After the reaction phase is dispersed into small droplets of appropriate size and uniformity, the temperature is raised to 95°C for polymerization reaction, kept warm for 1 hour, and then continued to rise to 110°C for curing and reaction for 5 hours. After the reaction is completed, the spherical resin after cooling and filtration is first washed with ethanol 5 times, and then washed with distilled water 5 times until neutral. The resin is placed in a Soxhlet extractor and heated under reflux for 7 hours with petroleum ether with a boiling range of 60-90°C as the solvent to remove the residual porogen and unreacted monomer in the resin. The resin is then soaked in 5% hydrochloric acid solution and shaken in a shaker. The hydrochloric acid solution is replaced every half hour. This is repeated 4-5 times and washed until neutral. The product of 0.1-0.8 mm is sieved and stored in a wet state to obtain a spherical lignin-phenolic resin.

[0060] The product obtained has good spherical shape, a yield of 74%, and a moisture content of 73.8%.

[0061] Example 2

[0062] In this embodiment, the monomers are sodium lignin sulfonate, hydroquinone and trioxymethylene, wherein the mass ratio of hydroquinone to sodium lignin sulfonate is 1:3; the molar ratio of hydroquinone to trioxymethylene is 1:4; and the amount of solvent used is 1.6 times the total mass of the monomers.

[0063] Preparation of the reaction phase: Add 9.06g of sodium lignin sulfonate, 3.02g of hydroquinone, and 3.27g of trioxymethylene into a three-necked flask, add 24.47g of 83.5wt% ethylene glycol aqueous solution as solvent, and after fully dissolving under mechanical stirring, slowly add concentrated hydrochloric acid to adjust the pH to 1.

[0064] Preparation of the continuous phase: weigh 0.26 g of span-80, 0.04 g of tween-85, and 144.76 g of liquid paraffin in a beaker and stir with a magnetic stirrer to mix evenly.

[0065] The prepared continuous phase was slowly added to the three-necked flask containing the reaction phase, and stirring was started at 165 rpm. After the reaction phase was dispersed into small droplets of suitable size and uniformity, the temperature was raised to 95°C for polymerization, kept at this temperature for 1.5 hours, and then continued to rise to 110°C for curing and reaction for 6 hours. After the reaction, the solid product after cooling and filtration was washed with ethanol four times and then with distilled water six times until neutral. The resin was placed in a Soxhlet extractor and heated under reflux for 8 hours using petroleum ether with a boiling range of 60-90°C as the solvent to remove the residual porogen and unreacted monomer in the resin. The resin was then soaked in 5% hydrochloric acid solution and shaken on a shaker. The hydrochloric acid solution was replaced every half an hour. This was repeated four times and then washed until neutral. The product was sieved to obtain a 0.1-0.8 mm product, which was stored in a wet state to obtain a spherical lignin-phenolic resin.

[0066] The obtained product has good spherical shape, a yield of 62%, and a moisture content of 72.2%.

[0067] Example 3

[0068] In this embodiment, the monomers are sodium lignin sulfonate, hydroquinone and trioxymethylene, wherein the mass ratio of hydroquinone to sodium lignin sulfonate is 1:3; the molar ratio of hydroquinone to trioxymethylene is 1:2.1; and the amount of solvent used is 0.8 times the total mass of the monomers.

[0069] Preparation of the reaction phase: Add 12.15g of sodium lignin sulfonate, 4.05g of hydroquinone, and 2.30g of trioxymethylene into a three-necked flask, add 14.94g of 84wt% ethylene glycol aqueous solution as solvent, and after fully dissolving under mechanical stirring, slowly add concentrated hydrochloric acid to adjust the pH to 1.

[0070] Prepare the continuous phase: weigh 0.23 g of span-800, 0.03 g of tween-850, and 97.70 g of liquid paraffin in a beaker and stir with a magnetic stirrer to mix thoroughly.

[0071] The prepared continuous phase was slowly added to the three-necked flask containing the reaction phase, and stirring was started at 190 rpm. After the reaction phase was dispersed into small droplets of suitable size and uniformity, the temperature was raised to 95°C for polymerization, kept at this temperature for 1 hour, and then continued to rise to 110°C for curing and reaction for 8 hours. After the reaction, the solid product after cooling and filtration was washed with ethanol 5 times and then with distilled water 6 times until neutral. The resin was placed in a Soxhlet extractor and heated under reflux for 6 hours using petroleum ether with a boiling range of 60-90°C as the solvent to remove the residual porogen and unreacted monomer in the resin. The resin was then soaked in 5% hydrochloric acid solution and shaken in a shaker. The hydrochloric acid solution was replaced every half an hour. This was repeated 5 times and washed until neutral. The product was sieved to obtain a 0.1-0.8 mm product, which was stored in a wet state to obtain a spherical lignin-phenolic resin.

[0072] The obtained product has good spherical shape, a yield of 72%, and a moisture content of 58.1%.

[0073] Example 4

[0074] In this embodiment, the monomers are sodium lignin sulfonate, hydroquinone and trioxymethylene, wherein the mass ratio of hydroquinone to sodium lignin sulfonate is 1:3; the molar ratio of hydroquinone to trioxymethylene is 1:3; and the amount of solvent used is 1.2 times the total mass of the monomers.

[0075] Preparation of the reaction phase: Add 48.6 g of sodium lignin sulfonate, 16.2 g of hydroquinone, and 13.25 g of trioxymethylene into a three-necked flask, add 93.7 g of 83.5 wt% ethylene glycol aqueous solution as solvent, and after fully dissolving under mechanical stirring, slowly add concentrated hydrochloric acid to adjust the pH to 1.

[0076] Prepare the continuous phase: weigh 0.98 g of span-80, 0.14 g of tween-85, and 420.02 g of liquid paraffin in a beaker and stir with a magnetic stirrer to mix thoroughly.

[0077] The prepared continuous phase was slowly added to the three-necked flask containing the reaction phase. Stirring was started and the speed was adjusted to 210 rpm. After the reaction phase was dispersed into small droplets of appropriate size and uniformity, the temperature was raised to 95°C for polymerization reaction and kept at this temperature for 1.2 hours. The temperature was then raised to 110°C for curing and the reaction was continued for 7 hours. After the reaction was completed, the solid product after cooling and filtration was washed with ethanol 5 times and then with distilled water 6 times until neutral. The resin was placed in a Soxhlet extractor and extracted with petroleum ether with a boiling range of 60-90°C under heating and reflux for 6 hours to remove the residual porogen and unreacted monomer in the resin. The resin was then soaked in 5% hydrochloric acid solution and shaken on a shaker. The hydrochloric acid solution was changed every half an hour. This was repeated 4 times and washed until neutral. The product was sieved to obtain a 0.1-0.8 mm product and stored in a wet state to obtain a spherical lignin-phenolic resin.

[0078] The product obtained has good spherical shape, a yield of 73%, and a moisture content of 64.9%.

[0079] Example 5

[0080] In this embodiment, the monomers are sodium lignin sulfonate, hydroquinone and trioxymethylene, wherein the mass ratio of hydroquinone to sodium lignin sulfonate is 1:3; the molar ratio of hydroquinone to trioxymethylene is 1:2.5; and the amount of solvent used is 1.6 times the total mass of the monomers.

[0081] Preparation of the reaction phase: Add 9.0 g of sodium lignin sulfonate, 3.0 g of hydroquinone, and 2.05 g of trioxymethylene into a three-necked flask, add 22.50 g of 84 wt% ethylene glycol aqueous solution as solvent, fully dissolve under mechanical stirring, and then slowly add concentrated hydrochloric acid to adjust the pH to 1.

[0082] Prepare the continuous phase: weigh 0.26 g of span-80, 0.04 g of tween-85, and 140.80 g of liquid paraffin in a beaker and stir with a magnetic stirrer to mix thoroughly.

[0083] The prepared continuous phase was slowly added to the three-necked flask containing the reaction phase, and stirring was started at 200 rpm. After the reaction phase was dispersed into small droplets of suitable size and uniformity, the temperature was raised to 95°C for polymerization, kept at this temperature for 1.5 hours, and then continued to rise to 110°C for curing and reaction for 6 hours. After the reaction, the solid product after cooling and filtration was washed with ethanol 4 times and then with distilled water 6 times until neutral. The resin was placed in a Soxhlet extractor and heated under reflux for 8 hours using petroleum ether with a boiling range of 60-90°C as the solvent to remove the residual porogen and unreacted monomer in the resin. The resin was then soaked in 5% hydrochloric acid solution and shaken in a shaker. The hydrochloric acid solution was changed every half an hour. This was repeated 5 times and then washed until neutral. The product was sieved to obtain a 0.1-0.8 mm product, which was stored in a wet state to obtain a spherical lignin-phenolic resin.

[0084] The obtained product has good spherical shape, a yield of 65%, and a moisture content of 71.2%.

[0085] Example 6

[0086] In this embodiment, the monomers are sodium lignin sulfonate, hydroquinone and trioxymethylene, wherein the mass ratio of hydroquinone to sodium lignin sulfonate is 1:3; the molar ratio of hydroquinone to trioxymethylene is 1:2.1; and the amount of solvent used is 1.8 times the total mass of the monomers.

[0087] Preparation of the reaction phase: Add 90.2g of sodium lignin sulfonate, 30.3g of hydroquinone, and 17.23g of trioxymethylene into a three-necked flask, add 248.2g of 83wt% ethylene glycol aqueous solution as solvent, and after fully dissolving under mechanical stirring, slowly add concentrated hydrochloric acid to adjust the pH to 1.

[0088] Prepare the continuous phase: weigh 2.20g span-80, 0.55g tween-85, and 1250.50g liquid paraffin in a beaker and stir with a magnetic stirrer to mix thoroughly.

[0089] The prepared continuous phase was slowly added to the three-necked flask containing the reaction phase, and stirring was started at 220 rpm. After the reaction phase was dispersed into small droplets of suitable size and uniformity, the temperature was raised to 95°C for polymerization, kept at this temperature for 1.5 hours, and then continued to rise to 110°C for curing and reaction for 8 hours. After the reaction, the solid product after cooling and filtration was washed with ethanol 5 times and then with distilled water 6 times until neutral. The resin was placed in a Soxhlet extractor and heated under reflux for 6 hours using petroleum ether with a boiling range of 60-90°C as the solvent to remove the residual porogen and unreacted monomer in the resin. The resin was then soaked in 5% hydrochloric acid solution and shaken in a shaker. The hydrochloric acid solution was replaced every half an hour. This was repeated 5 times and washed until neutral. The product was sieved to obtain a 0.1-0.8 mm product, which was stored in a wet state to obtain a spherical lignin-phenolic resin.

[0090] The product obtained has good spherical shape, a yield of 71%, and a moisture content of 74.5%.

[0091] Structural characterization

[0092] (1) The spherical lignin-phenolic resins of Examples 1, 2, and 3 were characterized by optical microscopy. The results are shown in the following table. Figure 1 As shown, Figure 1 In the embodiment, (a) is the spherical lignin-phenolic resin of Example 1, (b) is the spherical lignin-phenolic resin of Example 2, and (c) is the spherical lignin-phenolic resin of Example 3. Figure 1 It can be seen that the product obtained by the present invention is a spherical resin with good appearance and morphology.

[0093] (2) The lignin-phenolic resin of Example 1 was characterized by Fourier transform infrared spectroscopy, and the results were as follows Figure 2 As shown. Figure 2 It can be seen that sodium lignin sulfonate is successfully introduced into the resin obtained by the present invention.

[0094] (3) Figure 3 The following is a scanning electron microscope photograph of the appearance and internal pore structure of the lignin-phenolic resin of Example 1. Figure 3 It can be seen that the lignin-phenolic resin has a smooth spherical appearance and a rich internal pore structure.

[0095] Performance Testing

[0096] (1) The lignin-phenolic resin obtained in Examples 1 to 4 was used to adsorb a rhodamine B solution with a concentration of 100 to 1000 mg / L. The specific method was as follows: about 10 mg of the resin (equivalent to dry weight) was weighed into a brown conical flask, 100 mL of the adsorption solution was added, and static adsorption was carried out in a constant temperature oscillator at 25°C for 48 h. The concentration of the rhodamine B solution before and after adsorption was measured by ultraviolet spectrophotometry and the adsorption amount was calculated. The results are listed in Table 1.

[0097] Table 1 Adsorption capacity of rhodamine B by lignin-phenolic resin obtained in Examples 1 to 4

[0098]

[0099]

[0100] As can be seen from Table 1, the lignin-phenolic resin obtained in the present invention has a high adsorption capacity for rhodamine B. Its adsorption capacity for 100-1000 mg / L rhodamine B solution can reach 558-2118 mg / g, and its adsorption capacity for 1000 mg / L rhodamine B solution can reach 1714-2118 mg / g.

[0101] (2) The lignin-phenolic resin obtained in Examples 5-6 was used for adsorption of methylene blue solution. The specific method was as follows: 10 mg of resin (equivalent to dry weight) was weighed into a brown conical flask, 100 mL of adsorption solution was added, and static adsorption was carried out in a constant temperature oscillator at 25°C for 48 h. The concentration of the methylene blue solution before and after adsorption was measured by ultraviolet spectrophotometry and the adsorption amount was calculated. The results are listed in Table 2.

[0102] Table 2 Adsorption of methylene blue by lignin-phenolic resin obtained in Examples 5 to 6

[0103] Example Methylene blue solution concentration (mg / L) Adsorption capacity of methylene blue (mg / g) Example 5 100 248 Example 6 500 334

[0104] As can be seen from Table 2, the lignin-phenolic resin obtained in the present invention has a high adsorption capacity for methylene blue, and its adsorption capacity for 100-500 mg / L methylene blue solution can reach 248-334 mg / g.

[0105] (3) According to the adsorption method of (1), the adsorption kinetic curves of Example 1 and commercial macroporous sulfonic acid resin D072 (hydrogen type) were compared under the same adsorption conditions. The results are as follows: Figure 4 As shown. Figure 4 It can be seen that the equilibrium time of the two resins is not much different, but the adsorption capacity of the lignin-phenolic resin in Example 1 is significantly better than that of the commercial resin.

[0106] Comparative Example 1

[0107] Compared with Example 1, the difference is that the types of raw materials are changed, while the preparation method remains unchanged. The ball formation of the obtained resin is observed, and the results are listed in Table 3.

[0108] Table 3 The pelletization of resin after changing the type of raw materials

[0109]

[0110]

[0111] Table 3 shows that the selection of monomers and catalysts is crucial for the spheronization effect. Screening of monomers and catalysts commonly used in phenolic resin synthesis showed that hydroquinone trioxymethylene copolymerization under acidic conditions, with high reactivity, symmetrical tetrafunctionality, and a suitable molecular configuration, produced the best spheronization results.

[0112] Comparative Example 2

[0113] On the basis of Example 1, the types of aqueous solvents were changed, and the comparison of the dissolution and spheroidization conditions of the reaction monomers in different solvents is shown in Table 4.

[0114] Table 4 Comparison of dissolution and spheroidization of reaction monomers in different solvents

[0115]

[0116] As can be seen from Table 4, the choice of solvent must meet the requirements of both monomer solubility and ball-forming properties. Ethylene glycol has poor solubility for sodium lignin sulfonate. Water, as a good solvent, causes stickiness for a long time during the polymerization reaction, resulting in adhesion and agglomeration. After screening, an 80 wt % to 85 wt % ethylene glycol aqueous solution was finally selected as the solvent, which has a better ball-forming effect, and more preferably 83 wt % to 84 wt %.

[0117] Comparative Example 3

[0118] On the basis of Example 1, the mass of the dispersion stabilizer (compounded span-80 and tween-85) was changed to 1.5‰ and 3.5‰ of the mass of liquid paraffin, respectively. The optical microscope photos of the resins obtained with different amounts of dispersion stabilizers are shown in FIG. Figure 5 As shown, the left picture shows a dispersant dosage of 1.5‰, and the right picture shows a dispersant dosage of 3.5‰.

[0119] It can be seen that when the amount of dispersion stabilizer is small (1.5‰), the dispersion effect is poor or the spherical shape is difficult to maintain due to the increase in molecular weight during phase separation, resulting in ellipsoidal shape and droplet sinking and aggregation; when the amount of dispersion stabilizer is large (3.5‰), the spherical shape will be smaller and the adhesion will be serious.

[0120] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a spherical lignin-phenolic resin, characterized in that: The following steps are involved: mixing sodium lignin sulfonate, phenolic substances, aldehyde substances, aqueous solvents and acid catalysts to obtain a reaction phase; mixing an oily dispersion medium with a dispersion stabilizer to obtain a continuous phase; The reaction phase and the continuous phase are mixed, and suspension polymerization and thermal curing are carried out under stirring conditions to obtain a spherical lignin-phenolic resin.

2. The preparation method according to claim 1, characterized in that The phenolic substances include hydroquinone; The aldehyde substance includes trioxymethylene; The molar ratio of the phenolic substance to the aldehyde substance is 1:2-4.

3. The preparation method according to claim 1, wherein the mass ratio of the phenolic substance to sodium lignin sulfonate is 1:0.5-3.

4. The preparation method according to claim 1 or 3, characterized in that The aqueous solvent is an aqueous solution of ethylene glycol; the mass ratio of the total mass of the sodium lignin sulfonate, phenolic substances, and aldehyde substances to the aqueous solvent is 1:0.8-2.0; The acid catalyst includes concentrated hydrochloric acid; the pH value of the reaction phase is 1-2.

5. The preparation method according to claim 1, characterized in that The oily dispersion medium includes liquid paraffin; The dispersion stabilizer includes a compound of span-80 and tween-85, wherein the mass ratio of span-80 to tween-85 is 4 to 8:1; The dispersion stabilizer is 2 to 3‰ of the mass of the oily dispersion medium.

6. The preparation method according to claim 1 or 5, wherein the volume ratio of the continuous phase to the reaction phase is 3 to 5:

1.

7. The preparation method according to claim 1, characterized in that The suspension polymerization reaction temperature is 90-100°C and the holding time is 1-1.5h; The temperature of the thermal curing is 110-115° C., and the heat preservation time is 5-10 hours.

8. The spherical lignin-phenolic resin prepared by the preparation method according to any one of claims 1 to 7.

9. The spherical lignin-phenolic resin according to claim 8, characterized in that The particle size of the spherical lignin-phenolic resin is 0.1-0.8 mm.

10. Use of the spherical lignin-phenolic resin according to claim 8 or 9 in adsorbing nitrogen-containing organic dyes.

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