Modified lignin-attapulgite composite material, preparation method and application thereof

Abstract

This invention belongs to the field of environmental industrial water treatment technology, and discloses a modified lignin-attapulgite composite material, its preparation method, and its application. Method: Activated enzymatically hydrolyzed lignin is covalently grafted with a thiol reagent via a nucleophilic substitution reaction under inert gas protection, alkaline conditions, a catalyst, and a polar aprotic solvent system to obtain thiolized enzymatically hydrolyzed lignin. Attapulgite is mixed with an aqueous solution of an active metal component, ultrasonically dispersed, and then an alkaline solution is added dropwise, followed by calcination to obtain Me-ATP. Water, Me-ATP, thiolized enzymatically hydrolyzed lignin, and a penetrant are mixed and subjected to a hydrothermal reaction to obtain S / EHL-Me-ATP. This S / EHL-Me-ATP is dispersed in a spherical polymer molding solution, then added dropwise to water. After phase separation, spherical particles are obtained, and after standing, the composite material is obtained. This invention improves the adsorption selectivity, adsorption capacity, and regeneration performance of the composite material for pollutants. The composite material is less prone to agglomeration, its mechanical strength is significantly improved, and recycling is simpler.

Description

Technical Field

[0001] This invention belongs to the field of environmental industrial water treatment technology, and more specifically, relates to a modified lignin-attapulgite composite material, its preparation method, and its application. Background Technology

[0002] With the development of industrialization and modern agriculture, environmental pollution caused by the emission of heavy metal ions and organic pollutants poses a serious threat to the ecological environment and human health. In particular, heavy metal pollution, due to its non-degradability and bioaccumulation effects, has become an environmental problem that urgently needs to be solved globally.

[0003] Lignin-based composite materials have advantages such as being environmentally friendly and low-cost. Lignin-based adsorbents have certain adsorption effects on heavy metal ions, organic matter and other pollutants. However, they are prone to problems such as agglomeration, poor mechanical strength and unsatisfactory selective adsorption during the adsorption process, which affect the long-term operating performance of the adsorbent in dynamic water flow systems.

[0004] Natural nanostructured attapulgite adsorbents possess strong adsorption properties and potential for multifunctional composite applications, making them versatile tools in environmental protection, agriculture, and chemical industries. They are widely used in wastewater treatment, air purification, soil remediation, feed additives, and slow-release fertilizers. However, they also face challenges such as difficult regeneration, easy loss of powdered form, and difficulties in recycling. Gao Bingying et al. used direct and seed methods to load Silicalite-1 molecular sieves onto the surface of attapulgite, and then modified the composite material with amino groups to improve its hydrophobicity under high humidity conditions and its adsorption capacity for acetaldehyde. Liu Jinju et al. utilized hexadecyltrimethylammonium bromide to modify the surface chemical properties and pore structure of attapulgite, optimizing its adsorption performance for metal elements, with chemisorption as the main mechanism, but did not elaborate on the recycling of the adsorbent material.

[0005] Developing efficient, economical, and environmentally friendly purification materials is an important strategy for addressing environmental pollution. As a residue from biomass energy conversion, enzymatically hydrolyzed lignin has a huge yield, but its utilization rate is low. Enzymatically hydrolyzed lignin retains most of its natural structure and contains abundant functional groups such as phenolic hydroxyl groups, carboxyl groups, and methoxy groups, making it a bio-based resource with high value potential.

[0006] Therefore, there is an urgent need to propose a new modified lignin-attapulgite composite material, its preparation method, and its application. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a modified lignin-attapulgite composite material, its preparation method, and its applications. This invention improves the adsorption selectivity, adsorption capacity, and regeneration performance of the composite material for pollutants. The composite material of this invention is less prone to agglomeration, exhibits significantly improved mechanical strength, and is easier to recycle.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a modified lignin-attapulgite composite material, the method comprising the following steps: S1: Activated enzymatic hydrolysed lignin is covalently grafted with a thiol reagent through nucleophilic substitution reactions (esterification, etherification) in an inert gas protection, alkaline conditions, with a catalyst and a polar aprotic solvent system to obtain thiolized enzymatic hydrolysed lignin; S2: Attapulgite (ATP) is mixed with an aqueous solution of an active metal component and ultrasonically dispersed to obtain an attapulgite impregnation solution; an alkaline aqueous solution is added dropwise to the attapulgite impregnation solution under stirring, and after stirring, standing, filtering, washing, drying and calcining, Me-ATP is obtained; S3: Water, the Me-ATP, the thiolized enzymatically hydrolyzed lignin and the penetrant are mixed and subjected to a hydrothermal reaction. After filtration, washing and drying, S / EHL-Me-ATP is obtained. S4: Disperse the S / EHL-Me-ATP in a spherical polymer molding solution (stirring speed 1500-3500r / min) to form a suspension; add the suspension dropwise to water under stirring, and the organic droplets undergo phase separation, aggregation, and solidification to obtain spherical particles, which are then allowed to stand, washed, and dried to obtain the composite material.

[0009] In this invention, the preparation method of the modified lignin-attapulgite composite material starts from the perspective of compound molecular regulation design. First, thiol groups are introduced into activated enzymatic hydrolyzed lignin (EHL) through a nucleophilic substitution reaction. Then, an active metal is introduced through impregnation (ultrasonic dispersion)-precipitation (alkali addition) to prepare a supported attapulgite adsorbent matrix (Me-ATP). Afterward, thiol-enzymatic hydrolyzed lignin supported attapulgite (S / EHL-Me-ATP) is obtained by hydrothermal reaction. Finally, spherical composite materials are prepared by phase transition method.

[0010] According to the present invention, preferably, the method includes sequentially subjecting enzymatically hydrolyzed lignin to acid treatment and alkali treatment to obtain the activated enzymatically hydrolyzed lignin.

[0011] In this invention: The acid treatment solution used is a hydrochloric acid aqueous solution or a sulfuric acid aqueous solution with a pH of 1-3; The mass ratio of acid treatment solution to enzymatically hydrolyzed lignin is 15-5:1; The alkaline treatment solution used is at least one of the following: sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, sodium carbonate aqueous solution, and sodium bicarbonate aqueous solution with a pH of 9-12. The mass ratio of alkali treatment solution to enzymatically hydrolyzed lignin is 15-5:1.

[0012] In this invention, as a preferred embodiment, the acid treatment process includes: adding enzymatically hydrolyzed lignin to the acid treatment solution, stirring for 10-45 min at a stirring speed of 100-300 r / min and a temperature of 20-45℃; after acid treatment, performing vacuum filtration separation, washing the filter cake with distilled water until the pH of the filtrate is ≥5, and after washing, vacuum drying (temperature 30-60℃, drying time 4-8 h) to obtain acid-treated enzymatically hydrolyzed lignin.

[0013] In this invention, as a preferred embodiment, the alkali treatment process includes: adding acid-treated enzymatically hydrolyzed lignin to the alkali treatment solution, stirring for 45-120 min at a stirring speed of 100-300 r / min and a temperature of 35-75℃; after alkali treatment, performing vacuum filtration separation, washing the filter cake with distilled water until the pH of the filtrate is ≤9, and after washing, vacuum drying (temperature 30-60℃, drying time 4-8 h) to obtain activated enzymatically hydrolyzed lignin, which is then stored anhydrous.

[0014] According to the present invention, preferably, in step S1: The alkaline conditions are provided by at least one alkaline reagent selected from sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate; the mass ratio of the alkaline reagent to the activated enzymatically hydrolyzed lignin is 0.1-1.5:1; The catalyst is anhydrous aluminum trichloride and / or anhydrous zinc chloride; the mass ratio of the catalyst to the activated enzymatically hydrolyzed lignin is 0.01-0.5:1; The polar aprotic solvent is at least one selected from γ-valerol, propylene carbonate, sulfolane, N,N-dimethylformamide, dimethyl sulfoxide, and acetonitrile; the mass ratio of the polar aprotic solvent to the activated enzymatically hydrolyzed lignin is 8-20:1. The thiol reagent is a thiol fatty acid and / or a thiol fatty alcohol; the mass ratio of the thiol reagent to the activated enzymatically hydrolyzed lignin is 0.5-2:1; The nucleophilic substitution reaction is carried out at a temperature of 50-100℃ for a time of 4-10 hours.

[0015] In step S1 of the present invention, the inert gas is nitrogen or argon; in addition, after the nucleophilic substitution reaction is completed, the reaction system is cooled to 20-30°C, an ice-water mixture is added to end the reaction, the precipitate is filtered, and the mixture is washed alternately with ethanol and water 2-3 times, and then vacuum dried (temperature 30-60°C, drying time 4-8h) to obtain thiolized enzymatically hydrolyzed lignin S / EHL.

[0016] According to the present invention, preferably, the thiol reagent is at least one selected from thioglycolic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid and β-mercaptoethanol.

[0017] According to the present invention, preferably, in step S2: The active metal component is at least one of the following: a water-soluble inorganic salt containing titanium (at least one of titanium tetrachloride, titanium sulfate, and titanium nitrate), a water-soluble inorganic salt containing zirconium (at least one of zirconium tetrachloride, zirconium sulfate, and zirconium nitrate), and a water-soluble inorganic salt containing iron (at least one of ferric chloride, ferric sulfate, and ferric nitrate). The mass fraction of the aqueous solution containing the active metal component is 1.5%-10%; the mass ratio of the active metal component to attapulgite is 0.1-1:1. The ultrasonic dispersion time is 0.5-3.5 hours, and the temperature is 20-60℃. The alkaline aqueous solution is at least one selected from sodium hydroxide aqueous solution, ammonia solution, and potassium hydroxide aqueous solution; the mass fraction of the alkaline aqueous solution is 3%-10%. The dripping rate is 1-5 mL / min; the pH of the mixture of the alkaline aqueous solution and the attapulgite impregnation solution is 5-6; The stirring speed is 100-250 r / min, and the temperature is 20-60℃; The settling time is 5-12 hours; The drying temperature is 60-80℃, and the time is 4-6 hours; The calcination conditions include: in an air atmosphere, first heating to 145-155℃ at a heating rate of 5-8℃ / min and holding for 45-90min, then heating to 300-400℃ at a heating rate of 8-10℃ / min and holding for 60-90min, and finally cooling to 15-30℃ at a cooling rate of 8-10℃ / min.

[0018] In this invention, attapulgite is stirred and dispersed in an aqueous solution of an active metal component, and after impregnation-precipitation and calcination, a binary composite material, denoted as Me-ATP, is obtained. Specifically: Impregnation: Add attapulgite to the aqueous solution of the active metal component and disperse it by ultrasonication to obtain an attapulgite impregnation solution; Precipitation: Add an alkaline aqueous solution dropwise to the attapulgite impregnation solution while it is being stirred. After the addition is complete, continue stirring for 10-20 minutes and then stop. Allow the mixture to stand and age, filter the precipitate, wash it with ethanol and distilled water alternately 2-3 times, dry it and calcine it to obtain Me-ATP.

[0019] According to the present invention, preferably, in step S3: The mass ratio of water to Me-ATP is 6-35:1; The mass ratio of the thiolized enzymatically hydrolyzed lignin to Me-ATP is 0.1-1:1; The mass ratio of the permeabilizer to Me-ATP is 1:80-200; The conditions for the hydrothermal reaction include: heating to 100-130℃ at a heating rate of 2-5℃ / min and holding at that temperature for 2-6 hours; The drying temperature is 40-60℃, and the time is 4-8 hours.

[0020] In this invention, the penetrant is a commercially available nonionic penetrant, preferably penetrant JFC and / or penetrant OE-35.

[0021] According to the present invention, preferably, in step S4: The spherical polymer molding solution is formulated from a main solvent, an auxiliary agent, and a solubilizing agent. The main solvent is at least one selected from sulfolane, dimethyl sulfoxide, γ-valerolactone, propylene carbonate, and N-methyl-2-pyrrolidone; the mass ratio of the main solvent to S / EHL-Me-ATP is 5-15:1; The auxiliary agent is polysulfone; the mass ratio of the main solvent to the auxiliary agent is 10-20:1. The solubilizing agent is Tween80 and / or PEG-40; the mass ratio of the solubilizing agent to S / EHL-Me-ATP is 1:100-200. The temperature of the suspension is 40-50℃; The dripping rate was 2-6 mL / min, and the device used was a syringe pump; The stirring speed of the water in the stirred state is 50-150 r / min, and the temperature of the water in the stirred state is 25-50℃; the mass ratio of the water in the stirred state to the suspension is 3-1:1. The settling time is 10-15 hours.

[0022] In this invention, the preparation of the spherical polymer molding liquid includes: heating the main solvent to 40-80°C, adding solubilizing agents and auxiliary agents under stirring conditions, and continuing to stir until completely dissolved to form a uniform and transparent spherical polymer molding liquid.

[0023] In step S4 of the present invention, the water is used as a non-solvent, and the suspension (i.e., the organic liquid droplet phase) is added dropwise to the water in a stirred state, which triggers instantaneous phase separation, and the droplets rapidly agglomerate and solidify into spherical particles.

[0024] The second aspect of the present invention provides a method for preparing the modified lignin-attapulgite composite material.

[0025] The third aspect of the present invention provides the application of the modified lignin-attapulgite composite material as an adsorbent and / or catalyst for treating wastewater containing heavy metal pollutants.

[0026] According to the present invention, preferably, the pH of the wastewater containing heavy metal pollutants is 2-9 and the temperature is 10-80℃.

[0027] In this invention, when the modified lignin-attapulgite composite material is used as an adsorbent for treating wastewater containing heavy metal pollutants, the method for treating wastewater containing heavy metal pollutants includes: (1) Filtering to remove suspended solids from the wastewater containing heavy metal pollutants; (2) The composite material of the present invention is loaded into an adsorption column (or fixed bed); (3) The wastewater treated in step (1) enters the adsorption column in step (2) from bottom to top, and the water effluent from the top is the purified wastewater; (4) When the top effluent does not meet the treatment requirements, the composite material needs to be regenerated.

[0028] In this invention, the regeneration method of the modified lignin-attapulgite composite material is elution, wherein: The eluent (transformation agent) used in the regeneration process can be ethanol, 5-10 wt% sodium hydroxide aqueous solution, 1-5 wt% hydrochloric acid aqueous solution, or 0.5-5 wt% sulfuric acid aqueous solution; Eluent (transformation agent) dosage: 2 BV~8 BV; The flow rate during the regeneration (transformation) process is 0.5-3 BV / h; After regeneration, the clean water rinsing rate is 2-5 BV / h, and the rinsing time is 0.5-2.5h.

[0029] The beneficial effects of the technical solution of this invention are as follows: The composite material of this invention can be used for the adsorption of pollutant ions in wastewater, and also for the degradation of organic pollutants in wastewater. Specifically: (1) In this invention, the activated enzymatic hydrolyzed lignin is introduced with the functional group thiol (-SH) through a nucleophilic substitution reaction. The thiol (-SH) can form a coordination covalent bond with metal ions (such as copper, nickel, cadmium, etc.), which improves the adsorption selectivity, adsorption capacity and regeneration performance of the composite material of this invention for pollutants.

[0030] (2) The present invention prepares an attapulgite matrix loaded with active metals (Me-ATP) by impregnation-precipitation, which effectively avoids the phenomenon of "migration and enrichment" of active metals, achieves uniform distribution of active metals on the inner wall of attapulgite pores, and prevents the agglomeration of active metal particles. After attapulgite is loaded with active metals, the abundant active sites can adsorb heavy metal pollutants through ligand exchange, inner sphere complexation, ion exchange and synergistic coordination.

[0031] (3) While retaining the original pore structure and active sites of attapulgite, an active metal is introduced. With the participation of thiolized enzymatic hydrolysis of lignin, synergistic effect is achieved through electron transfer regulation (attapulgite, active metal, thiolized enzymatic hydrolysis of lignin) and surface microenvironment design. This makes the composite material of the present invention have stable adsorption-regeneration capacity in a wide pH range (2-9), is not easy to agglomerate, and can also catalytically degrade organic pollutants. (4) The composite material particles obtained by the present invention are regular spherical, the mechanical strength is significantly improved, recycling is simpler, and it is suitable for long-term operation in dynamic water flow systems.

[0032] (5) The composite material of the present invention has a simple synthesis method, readily available raw materials, stable finished product performance, obvious advantages in wastewater purification, provides new ideas for pollution control, and has important research value and application prospects in the fields of materials science and environmental engineering.

[0033] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0034] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings.

[0035] Figure 1 The infrared spectra (λ is wavelength) of the structures of enzymatic hydrolyzed lignin (EHL) and thiolated enzymatic hydrolyzed lignin (S / EHL) in Example 1 of the present invention are shown.

[0036] Figure 2 The infrared spectra of the structures of ATP and Zr-ATP in Example 1 of the present invention are shown.

[0037] Figure 3 The present invention illustrates the reaction process of introducing thiol groups through nucleophilic substitution in the preparation method of a modified lignin-attapulgite composite material provided by the present invention.

[0038] Figure 4 This invention illustrates the process of loading active metals onto attapulgite in a method for preparing a modified lignin-attapulgite composite material provided by the present invention.

[0039] Figure 5 The hydrothermal reaction process in the preparation method of a modified lignin-attapulgite composite material provided by the present invention is shown. Detailed Implementation

[0040] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0041] The following embodiments: The enzymatically hydrolyzed lignin was purchased from Wuhan Jiyesheng Chemical Co., Ltd., with a purity of 90%. The attapulgite was purchased from Guangdong Daxiao Chemical Co., Ltd., and its effective ingredient content is 98%.

[0042] Example 1

[0043] This embodiment provides a method for preparing a modified lignin-attapulgite composite material, the method comprising the following steps: (1) Enzymatic hydrolysis of lignin activation The enzymatically hydrolyzed lignin was subjected to acid treatment and then alkali treatment sequentially to obtain the activated enzymatically hydrolyzed lignin; wherein: The acid treatment process includes: adding 260g of hydrochloric acid aqueous solution (pH=2) to a beaker, turning on the stirrer (120r / min), adding 50g of enzymatically hydrolyzed lignin to the beaker, stirring at room temperature for 15min, then filtering and separating by suction, washing with distilled water until the pH of the filtrate is ≥5, and then vacuum drying (50℃, drying for 6h) to obtain 49.6g of acid-activated enzymatically hydrolyzed lignin; The alkaline treatment process includes: adding 300g of sodium hydroxide aqueous solution (pH=10) to a beaker, starting the stirrer (150r / min), heating to 50℃ and keeping it warm, then adding 48g of acid-activated enzymatic hydrolysed lignin to the beaker, stirring at 50℃ for 60min, then filtering and separating, washing with distilled water until the pH of the filtrate is ≤9, and then vacuum drying (temperature 65℃, drying for 8h) to obtain 47.3g of activated enzymatic hydrolysed lignin.

[0044] (2) Nucleophilic substitution to introduce thiol group

[0045] 350 g of N,N-dimethylformamide (polar aprotic solvent), 0.6 g of anhydrous zinc chloride (catalyst), and 4.5 g of potassium carbonate (alkaline reagent) were added to a reactor equipped with a peristaltic pump, a reflux condenser, a magnetic stirrer, and a temperature control. The stirring was turned on, nitrogen protection was applied, and the temperature was raised to 50 °C. 40 g of activated enzymatic hydrolyzed lignin (EHL) was added, and the mixture was stirred until it was evenly dispersed. 40 g of 3-mercaptopropionic acid was added using a peristaltic pump (3 mL / min, added in about 11 min). The mixture was stirred and the temperature was raised to 80 °C. After reacting for 7 h, the system was allowed to cool naturally to room temperature. The nitrogen protection was turned off, and the reaction solution was transferred to an open container. An ice-water mixture (1 / 3 of the reaction solution volume) was added, and a precipitate was formed. The precipitate was filtered, washed 2-3 times alternately with ethanol and water, and then dried under vacuum (40 °C, drying for 6 h) to obtain 60.4 g of thiolized enzymatic hydrolyzed lignin product S / EHL.

[0046] (3) Attapulgite loaded with active metals

[0047] Add 270g of 10% zirconium tetrachloride aqueous solution to a three-necked flask, add 100g of attapulgite, and ultrasonically disperse for 2 hours at a temperature of 40-45℃ to obtain an attapulgite impregnation solution. After sonication, the three-necked flask (containing the attapulgite impregnation solution) was transferred to a water bath with a magnetic stirrer. The stirrer was turned on (120 r / min), and 8% sodium hydroxide aqueous solution was added dropwise (3 mL / min) to adjust the pH of the impregnation solution to about 6. The stirring was continued for 15 min and then stopped. The mixture was allowed to stand for 10 h, and the precipitate was filtered. The precipitate was washed twice with ethanol and distilled water alternately. The precipitate was then transferred to an oven and dried at 60 °C for 6 h. The dried precipitate was transferred to a muffle furnace and heated to 150°C in air at a rate of 5°C / min, held for 60 min, and then heated to 400°C at a rate of 8°C / min, held for 60 min. After that, it was cooled to room temperature at a rate of 5°C / min and calcined to obtain 107.4 g of product, denoted as Zr-ATP.

[0048] (4) Hydrothermal reaction

[0049] Add 400g of distilled water, 0.4g of permeabilizing agent JFC, and 60g of Zr-ATP to a hydrothermal reactor and stir until evenly dispersed. Then add 30g of S / EHL and stir until evenly dispersed. Heat the reaction to 120℃ (heating rate 4℃ / min) and maintain the temperature for 5h. After the reaction is complete, allow it to cool to room temperature naturally. Filter the precipitate and wash it twice with distilled water and ethanol alternately. Dry it under vacuum at 40℃ for 6h to obtain 87.2g of product, denoted as S / EHL-Zr-ATP.

[0050] (5) Phase separation method for making spheres

[0051] Heat 400g of propylene carbonate (main solvent) to 55℃, add 0.8g of Tween80 (solubilizer) and 25g of polysulfone (auxiliary agent) under stirring, and continue stirring until completely dissolved to form a uniform and transparent spherical polymer molding liquid; Add 70g of S / EHL-Zr-ATP to the spherical polymer molding solution and stir at high speed (2000r / min) until it is evenly dispersed to prepare a homogeneous suspension (temperature 40℃). Add 650g of distilled water to a beaker, heat to 45℃ and keep warm, stirring (70r / min). The suspension is added dropwise to the distilled water under stirring using a syringe pump (3mL / min). After the addition is complete, continue stirring for 5min and then stop. Soak the spherical particles in distilled water for 12h. Remove the spherical particles and wash them twice with ethanol and distilled water alternately. Let them air dry at room temperature to obtain 68.2g of spherical particles (i.e., the composite material described in this example), and package them for later use.

[0052] Example 2

[0053] This embodiment provides a method for preparing a modified lignin-attapulgite composite material, the method comprising the following steps: (1) Enzymatic hydrolysis of lignin activation Same as Example 1.

[0054] (2) Nucleophilic substitution to introduce thiol group

[0055] The polar aprotic solvent is γ-valerolactone, 320g; The alkaline reagent is sodium carbonate, 4.2g; The thiol reagent is β-mercaptoethanol, 32g; The process was the same as in Example 1, yielding 48.7 g of thiolized enzymatically hydrolyzed lignin product S / EHL.

[0056] (3) Attapulgite loaded with active metals

[0057] The aqueous solution of the active metal component is 18g of ferric chloride aqueous solution with a mass fraction of 10%; The calcination conditions included: a muffle furnace, an air atmosphere, heating to 150°C at a rate of 5°C / min, holding at that temperature for 60 min, then heating to 350°C at a rate of 10°C / min, holding at that temperature for 90 min; then cooling to room temperature at a rate of 5°C / min for calcination. Everything else was the same as in Example 1, and 124.7 g of product was obtained, denoted as Fe-ATP.

[0058] (4) Hydrothermal reaction

[0059] Add 400g of distilled water, 0.3g of OE-35 penetrant, and 60g of Fe-ATP to a hydrothermal reactor and stir until evenly dispersed. Then add 35g of S / EHL and stir until evenly dispersed. Heat the reaction to 110℃ (heating rate 5℃ / min) and maintain the temperature for 6h. After the reaction is complete, allow it to cool to room temperature naturally. Filter the precipitate and wash it twice with distilled water and ethanol alternately. Dry it under vacuum at 40℃ for 6h to obtain 84.1g of product, denoted as S / EHL-Fe-ATP.

[0060] (5) Phase separation method for making spheres

[0061] Heat 350g of propylene carbonate (main solvent) to 55℃, add 0.7g of PEG-40 (solubilizer) and 25g of polysulfone (auxiliary agent) under stirring, and continue stirring until completely dissolved to form a uniform and transparent spherical polymer molding liquid; Add 70g of S / EHL-Fe-ATP to the spherical polymer molding solution and stir at high speed (2300r / min) until the mixture is evenly dispersed to prepare a homogeneous suspension (temperature 40℃). Add 600g of distilled water to a beaker, heat to 45℃ and keep warm, stirring (70r / min). The suspension is added dropwise to the distilled water while stirring using a syringe pump (5mL / min). After the addition is complete, continue stirring for 5min and then stop. Soak the spherical particles in distilled water for 12h. Remove the spherical particles and wash them twice with ethanol and distilled water alternately. Let them air dry at room temperature to obtain 68.6g of spherical particles (i.e., the composite material described in this example), and package them for later use.

[0062] Test case

[0063] This test example performs infrared spectroscopy analysis on the structures of enzymatically hydrolyzed lignin (EHL) and thiolized enzymatically hydrolyzed lignin (S / EHL) from Example 1, such as... Figure 1 As shown: EHL characteristic absorption peak: 3450 cm⁻¹ -1 The absorption peak near the -OH stretching vibration is at 2944 cm⁻¹. -1 The absorption peaks are for the -CH3 and -CH2- stretching vibrations, at 1500-1700 cm⁻¹. -1 The vicinity is characterized by aromatic ring skeletal vibrations. S / EHL characteristic absorption peak: 3140 cm⁻¹ -1 The nearby area is the -OH absorption peak, 2620 cm⁻¹. -1 2540cm -1 The peak at 1238 cm⁻¹ is a characteristic peak of the -SH stretching vibration. After the successful introduction of -SH, the intensity of the -OH absorption peak weakens, and the absorption peak of the aromatic ring skeleton vibration weakens. -1 CO enhancement of phenolic ethers.

[0064] This test example performs infrared spectroscopy analysis on the structures of ATP and Zr-ATP from Example 1, such as... Figure 2 As shown: ATP characteristic absorption peak: 3560 cm⁻¹ -1 The absorption peak at 1200 cm⁻¹ is the stretching vibration absorption peak of R-OH. -1 -1000cm -1 The range is the (Mg,Al)-Si-O stretching vibration interval; Zr-ATP characteristic absorption peak: R-OH characteristic absorption peak shifted to 3540 cm⁻¹ -1 Location, 3229cm -1 The newly added absorption peak at 1750 cm⁻¹ may be due to the formation of Zr-O-Si or Zr-OH coordination bonds. -1 The absorption peak at 500 cm⁻¹ is presumed to be the stretching vibration of the Zr-O bond in highly dispersed zirconia species. -1 The nearby absorption peaks are presumably the vibrational absorption peaks of the Zr-O-Si bonds.

[0065] Application Example 1

[0066] In a Jiangsu electroplating plant, rinsing water from plated parts accounts for more than 75% of the total electroplating wastewater. The heavy metal content in the rinsing water is directly affected by the type of plating layer. The average concentration of total nickel is 78.2 mg / L, the average concentration of total chromium is 86.7 mg / L, the concentration of total copper is 126.9 mg / L, and the pH is 3-5. The wastewater treatment requirements are: total chromium concentration <0.5 mg / L, total copper concentration <0.5 mg / L, and total nickel concentration <0.1 mg / L.

[0067] This application example uses chemical precipitation-coagulation pretreatment of plating rinse water with a heavy precipitant, followed by deep adsorption treatment of the pretreated effluent using the S / EHL-Zr-ATP composite material from Example 1. The method for detecting the metal content in wastewater is to use the standard HJ 776-2015 "Determination of 32 Elements in Water by Inductively Coupled Plasma Atomic Emission Spectrometry". The water sample processing is based on Part VIII "Samples" and the metal element detection is based on Part IX "Analytical Procedures".

[0068] The pretreated effluent (ICP test) showed the following concentrations: nickel 28.3 mg / L, chromium 42.6 mg / L, copper 26.8 mg / L, and pH ≈ 3.5. In Example 1, the spherical S / EHL-Zr-ATP composite adsorption column was packed to a height of 0.4 m and a volume of approximately 160 mL (96 g). It was washed with clean water until the effluent was clear. The influent was switched to pretreated effluent (flow rate 1 BV / h). When the treated water volume was 202 BV, the nickel concentration was 0.12 mg / L (>0.1 mg / L, breakthrough), the chromium effluent was 0.43 mg / L (<0.5 mg / L), and the copper effluent was 0.16 mg / L (<0.5 mg / L).

[0069] Regeneration of the adsorbent material (spherical S / EHL-Zr-ATP composite material of Example 1): The influent was switched to clean water and rinsed for 1 BV (flow rate 1 BV / h); the influent was switched to 3 wt% hydrochloric acid aqueous solution, with a dosage of 2 BV and a regeneration time of 120 min; then the influent was switched back to clean water and rinsed until pH≈4, and the composite material was regenerated.

[0070] In this application example, the composite material was adsorbed, regenerated, and adsorbed 5 times. The adsorption amount of each pollutant is shown in Table 1. The regenerated composite material does not show significant changes in the adsorption amount of each pollutant element, and has adsorption stability and regeneration value.

[0071] Table 1. Adsorption capacity of each pollutant

[0072] Application Example 2

[0073] This application example treats the effluent from the secondary sedimentation tank of a biopharmaceutical factory in Xinjiang after biochemical treatment. The pH is around 6.5 and the COD is around 210 mg / L, which does not meet the treatment requirement of ≤50 mg / L.

[0074] This application example utilizes the spherical S / EHL-Fe-ATP composite material from Example 2 to further degrade the organic matter in the secondary sedimentation tank effluent via heterogeneous Fenton catalytic oxidation. Specifically: Wastewater COD testing was conducted according to standard HJ828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method"; the method for detecting the leaching of active metal components from composite materials was standard HJ 776-2015 "Determination of 32 Elements in Water - Inductively Coupled Plasma Atomic Emission Spectrometry"; water sample processing was conducted according to Part VIII "Samples"; and metal element detection was conducted according to Part IX "Analytical Procedures".

[0075] (1) Soak the spherical S / EHL-Fe-ATP composite material of Example 2 in an equal volume of 0.05mol / L sulfuric acid aqueous solution, shake on a shaker for 5 min, and then wash the composite material with clean water until the pH of the wash water is ≥5; (2) Add an appropriate amount of the secondary sedimentation tank effluent into the conical flask, adjust the pH to 3, 4, 5, 6 and no pH adjustment respectively with 0.1 mol / L sulfuric acid aqueous solution, add the spherical S / EHL-Fe-ATP composite material treated in step (1) (dosage 0.65 g / L), and shake in a shaker at room temperature for 30 min; (3) Then add 30% hydrogen peroxide to the conical flask, the amount of which is 3wt‰ of the water to be treated in the conical flask. Continue to shake the reaction for 30 minutes and measure the COD of the treated wastewater. (4) Regeneration method of spherical S / EHL-Fe-ATP composite material in Example 2: soaking and shaking with appropriate amount of ethanol - washing with clean water - activation with 0.05mol / L sulfuric acid aqueous solution - washing with clean water until the pH of the wash water is ≥5.

[0076] Table 2 shows the COD and active metal leaching of the effluent after oxidation of wastewater at different pH levels. Table 3 shows the degradation of organic matter by the recycled composite material (with the pH of the secondary sedimentation tank effluent adjusted to 6). The data in Tables 2 and 3 show that the composite material of this invention exhibits stable catalytic performance and maintains high catalytic activity during recycling.

[0077] Table 2. COD and active metal leaching of effluent after oxidation of wastewater at different pH levels

[0078] Table 3. Degradation of organic matter by the recycling of composite materials (pH of secondary sedimentation tank effluent adjusted to 6)

[0079] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing a modified lignin-attapulgite composite material, characterized in that, The preparation method includes the following steps: S1: Activated enzymatic hydrolysed lignin is covalently grafted with a thiol reagent through a nucleophilic substitution reaction under inert gas protection, alkaline conditions, catalyst, and polar aprotic solvent system to obtain thiolized enzymatic hydrolysed lignin; S2: Attapulgite is mixed with an aqueous solution of an active metal component and ultrasonically dispersed to obtain an attapulgite impregnation solution; an alkaline aqueous solution is added dropwise to the attapulgite impregnation solution under stirring, and after stirring, standing, filtering, washing, drying and calcining, Me-ATP is obtained; The active metal component is at least one of a water-soluble inorganic salt containing titanium, a water-soluble inorganic salt containing zirconium, and a water-soluble inorganic salt containing iron. S3: Water, the Me-ATP, the thiolized enzymatically hydrolyzed lignin and the penetrant are mixed and subjected to a hydrothermal reaction. After filtration, washing and drying, S / EHL-Me-ATP is obtained. S4: Disperse the S / EHL-Me-ATP in a spherical polymer molding liquid to form a suspension; add the suspension dropwise to water under stirring, and the organic liquid droplets undergo phase separation, aggregation, and solidification to obtain spherical particles, which are then allowed to stand, washed, and dried to obtain the composite material.

2. The method for preparing modified lignin-attapulgite composite material according to claim 1, wherein, The method includes sequentially subjecting enzymatically hydrolyzed lignin to acid treatment and alkali treatment to obtain the activated enzymatically hydrolyzed lignin.

3. The method of preparing modified lignin-attapulgite composite material according to claim 1, wherein, In step S1: The alkaline conditions are provided by at least one alkaline reagent selected from sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate; the mass ratio of the alkaline reagent to the activated enzymatically hydrolyzed lignin is 0.1-1.5:1; The catalyst is anhydrous aluminum trichloride and / or anhydrous zinc chloride; the mass ratio of the catalyst to the activated enzymatically hydrolyzed lignin is 0.01-0.5:1; The polar aprotic solvent is at least one selected from γ-valerol, propylene carbonate, sulfolane, N,N-dimethylformamide, dimethyl sulfoxide, and acetonitrile; the mass ratio of the polar aprotic solvent to the activated enzymatically hydrolyzed lignin is 8-20:

1. The thiol reagent is a thiol fatty acid and / or a thiol fatty alcohol; the mass ratio of the thiol reagent to the activated enzymatically hydrolyzed lignin is 0.5-2:1; The nucleophilic substitution reaction is carried out at a temperature of 50-100℃ for a time of 4-10 hours.

4. The method for preparing modified lignin-attapulgite composite material according to claim 3, wherein, The thiol reagent is at least one of thioglycolic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid, and β-mercaptoethanol.

5. The method for preparing the modified lignin-attapulgite composite material according to claim 1, wherein, In step S2: The mass fraction of the aqueous solution containing the active metal component is 1.5%-10%; the mass ratio of the active metal component to attapulgite is 0.1-1:

1. The ultrasonic dispersion time is 0.5-3.5 hours, and the temperature is 20-60℃. The alkaline aqueous solution is at least one selected from sodium hydroxide aqueous solution, ammonia solution, and potassium hydroxide aqueous solution; the mass fraction of the alkaline aqueous solution is 3%-10%. The dripping rate is 1-5 mL / min; the pH of the mixture of the alkaline aqueous solution and the attapulgite impregnation solution is 5-6; The stirring speed is 100-250 r / min, and the temperature is 20-60℃; The settling time is 5-12 hours; The drying temperature is 60-80℃, and the time is 4-6 hours; The calcination conditions include: in an air atmosphere, first heating to 145-155℃ at a heating rate of 5-8℃ / min and holding for 45-90min, then heating to 300-400℃ at a heating rate of 8-10℃ / min and holding for 60-90min, and finally cooling to 15-30℃ at a cooling rate of 8-10℃ / min.

6. The method for preparing the modified lignin-attapulgite composite material according to claim 1, wherein, In step S3: The mass ratio of water to Me-ATP is 6-35:1; The mass ratio of the thiolized enzymatically hydrolyzed lignin to Me-ATP is 0.1-1:1; The mass ratio of the permeabilizer to Me-ATP is 1:80-200; The conditions for the hydrothermal reaction include: heating to 100-130℃ at a heating rate of 2-5℃ / min and holding at that temperature for 2-6 hours; The drying temperature is 40-60℃, and the time is 4-8 hours.

7. The method for preparing the modified lignin-attapulgite composite material according to claim 1, wherein, In step S4: The spherical polymer molding solution is formulated from a main solvent, an auxiliary agent, and a solubilizing agent. The main solvent is at least one selected from sulfolane, dimethyl sulfoxide, γ-valerolactone, propylene carbonate, and N-methyl-2-pyrrolidone; the mass ratio of the main solvent to S / EHL-Me-ATP is 5-15:1; The auxiliary agent is polysulfone; the mass ratio of the main solvent to the auxiliary agent is 10-20:

1. The solubilizing agent is Tween80 and / or PEG-40; the mass ratio of the solubilizing agent to S / EHL-Me-ATP is 1:100-200. The temperature of the suspension is 40-50℃; The dropping rate is 2-6 mL / min; The stirring speed of the water in the stirred state is 50-150 r / min, and the temperature of the water in the stirred state is 25-50℃; the mass ratio of the water in the stirred state to the suspension is 3-1:

1. The settling time is 10-15 hours.

8. The modified lignin-attapulgite composite material prepared by the method of any one of claims 1-7.

9. The application of the modified lignin-attapulgite composite material according to claim 8 as an adsorbent and / or catalyst for treating wastewater containing heavy metal pollutants.

10. The application according to claim 9, wherein, The pH of the wastewater containing heavy metal pollutants is 2-9, and the temperature is 10-80℃.

Images