Preparation method of ternary grafted starch-based hydrogel with high adsorption of organic dyes

Abstract

The application discloses a preparation method of a ternary grafted starch-based hydrogel with high efficiency in adsorbing organic dyes. The method comprises the following steps: taking corn starch (St) and sodium carboxymethyl cellulose (CMC) as raw materials, acrylamide (AM), acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as grafting monomers, and preparing ternary grafted starch-based hydrogel St / CMC / P(AM-AA-AMPS) through an emulsion polymerization reaction. In the reaction system, the introduction of CMC and AMPS increases the number and types of effective adsorption functional groups in the hydrogel, and significantly improves the adsorption capacity. The adsorption capacity of the St / CMC / P(AM-AA-AMPS) hydrogel for methyl orange can reach 1624.49 mg / g at 25 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a method for preparing a ternary grafted starch-based hydrogel that efficiently adsorbs organic dyes. Background Technology

[0002] With the development of the dyeing and printing industry, a large amount of organic dyes are discharged into water bodies, accounting for one-third of the total dye wastewater. The large-scale discharge of dye-containing wastewater has caused serious environmental problems because many dyes are highly toxic, carcinogenic, and resistant to degradation. Unfortunately, compared to the large amount of dyeing and printing wastewater discharged, the wastewater recycling rate is only 7%. As people's awareness of environmental protection increases, new treatment methods and agents for this type of wastewater are attracting more and more attention from researchers.

[0003] Ion exchange, adsorption, membrane separation, and precipitation are typical treatment methods. Ion exchange removes or transforms harmful ions in water through an isopleth exchange reaction between an ion exchanger and the water, thus purifying the water. However, this method suffers from high energy consumption and demanding operational techniques. Membrane separation utilizes the high specific surface area and porosity of membrane materials to filter wastewater for purification; however, oil contamination on the membrane surface is a significant challenge, leading to pore blockage, reduced membrane flux, and frequent physical or chemical cleaning, which impacts membrane lifespan and ultimately increases overall operating costs. Precipitation involves adding flocculants / coagulants to wastewater. These flocculants / coagulants use physical and chemical processes to form flocs from suspended organic matter in the water, facilitating sedimentation or filtration. This technology is effective in treating oily wastewater, but its operation is complex, costs are high, and it generates byproducts, posing a risk of secondary pollution. In contrast, adsorption is simple to operate and maintain, and has low costs, making it superior to existing wastewater treatment methods. The key to this technology is the development of a highly efficient adsorption material.

[0004] Hydrogels are polymers with a three-dimensional network structure containing many hydrophilic groups, such as –OH, –CONH2, –NH2, and –COOH. Compared with traditional adsorbents such as activated carbon and zeolite, hydrogels exhibit better water treatment performance. Firstly, due to their unique three-dimensional structure and abundant internal hydrophilic groups, hydrogels can store large amounts of water without dissolving their structure. Furthermore, the hydrophilic groups can form covalent or coordinate bonds with cationic dye molecules and heavy metal ions, enabling them to rapidly, efficiently, and selectively adsorb dyes and heavy metal ions. Secondly, hydrogels are easy to prepare, and the raw materials are readily available. For example, Xu et al. prepared a grafted gum arabic composite hydrogel, GA-g-PAMPS / AA / ST, using microwave irradiation technology. The maximum adsorption capacity for methyl orange (MO) reached 1146 mg / g. Zhang et al. synthesized Fe3O4 magnetic nanoparticles in situ within a polyacrylamide / chitosan (PAAm / CS) hydrogel network, obtaining a magnetic hydrogel, PAAm / CS / Fe3O4. They found that each gram of this hydrogel could adsorb up to 1603 mg MB. Compared to chitosan and cellulose, starch can improve the biocompatibility and biodegradability of biomass-based hydrogels and reduce production costs. Currently, the main grafting monomers used to synthesize starch-based hydrogels are vinyl monomers, such as acrylic acid (AA) and acrylamide (AM). In these mono- or binary grafted starch-based hydrogels, the main functional group involved in adsorption is the carboxyl group. However, because only one type of functional group is involved, the adsorption capacity of such hydrogels for organic dyes is generally low. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a ternary grafted starch-based hydrogel that efficiently adsorbs organic dyes.

[0006] The method for preparing the highly efficient organic dye-adsorbing ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) provided by the present invention includes the following steps: using corn starch (St) and sodium carboxymethyl cellulose (CMC) as raw materials, and acrylamide (AM), acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as grafting monomers, the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) is prepared by emulsion polymerization reaction.

[0007] In the above reaction system, the introduction of CMC and AMPS increases the number and types of effective adsorption functional groups in the hydrogel, resulting in a significant improvement in adsorption capacity. The St / CMC / P (AM-AA-AMPS) hydrogel exhibits an MB adsorption capacity of 1624.49 mg / g at 25°C.

[0008] Furthermore, a crosslinking agent and an initiator are also added to the emulsion polymerization reaction; The crosslinking agent may be selected from N,N-methylenebisacrylamide.

[0009] The initiator may be selected from at least one of the following: ammonium persulfate, potassium persulfate, or azobisisobutyronitrile.

[0010] Furthermore, in the emulsion polymerization reaction, the feed ratio of corn starch (St), sodium carboxymethyl cellulose (CMC), acrylamide (AM), acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), ammonium persulfate (APS), and N,N-methylenebisacrylamide (NMBA) is 1:(0.1-1.0):(0.5-3.5):(2.5-7.5):(0.5-1.5):(0.01-0.1):(0.05-0.25), and the specific ratio can be 1g:0.5g:3g:5mL:0.06g:1g:0.2g.

[0011] Furthermore, the reaction conditions for the emulsion polymerization reaction are: reacting at 60-90°C for 2-10 hours, specifically reacting at 75°C for 5 hours.

[0012] Further, the method includes the following steps: crushing the obtained ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) and soaking the fragments in an ethanol aqueous solution; then vacuum drying the fragments at 40-70°C to obtain white granules. The volume fraction of ethanol in the ethanol aqueous solution can be 40-70%.

[0013] Furthermore, the specific preparation method of the highly efficient organic dye adsorption ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) is as follows: 1) Disperse corn starch in water to form a white suspension, gelatinize the suspension, and cool it for later use; 2) Dissolve sodium carboxymethyl cellulose powder in water to obtain a transparent, viscous liquid; 3) Prepare an acrylic acid solution with a neutralization degree of 40-80%; add the other two grafting monomers acrylamide and 2-acrylamido-2-methylpropanesulfonic acid and the crosslinking agent to the acrylic acid solution and stir to dissolve; 4) Ammonium persulfate dissolved in water serves as the initiator solution; 5) Pour the solutions from steps 2) and 3) into the gelatinized product prepared in step 1) and stir until homogeneous. Then add the initiator solution and form a homogeneous mixture. After stirring until homogeneous, fill the reactor with nitrogen to purge air, and then seal the opening with plastic wrap. 6) The mixed solution was subjected to emulsion polymerization to obtain a translucent block gel; the hydrogel was crushed with a mixer and the fragments were soaked in water and ethanol. The fragments were then vacuum dried to obtain white particles, namely the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS).

[0014] According to an embodiment of the present invention, 15 mL of water and 1 g of corn starch were uniformly stirred to form a white suspension, and the suspension was gelatinized for 10 minutes under magnetic stirring at 90°C.

[0015] According to an embodiment of the present invention, 0.5 g of sodium carboxymethyl cellulose powder is dissolved in 30 mL of water to obtain a transparent viscous liquid.

[0016] According to an embodiment of the present invention, the preparation method of the acrylic acid solution with a neutralization degree of 60% is as follows: 5 mL of acrylic acid is added to a beaker, and 11.7 g of NaOH solution (15 wt%) is added dropwise while stirring to obtain an acrylic acid solution with a neutralization degree of 60%. The beaker is immersed in an ice bath throughout the entire feeding process to prevent boiling.

[0017] The ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) prepared by the above method also falls within the scope of protection of this invention.

[0018] This invention also provides applications of the above-mentioned ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS).

[0019] The applications provided by this invention are the applications of the above-mentioned ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) in at least one of the following aspects: 1) application in the preparation of adsorbent materials; 2) application in wastewater treatment.

[0020] Furthermore, the adsorbent material is used to adsorb organic dyes, such as methylene blue, from wastewater.

[0021] Furthermore, the wastewater treatment involves adsorbing organic dyes, such as methylene blue, from the wastewater.

[0022] The present invention also provides an adsorbent material.

[0023] The adsorbent material includes the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) provided by the present invention.

[0024] The present invention also provides a wastewater treatment method.

[0025] The wastewater treatment method provided by the present invention includes the following steps: adding ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) to the wastewater to be treated for adsorption.

[0026] The adsorption conditions are as follows: dynamic adsorption for 0.5-2.0 hours under stirring conditions (e.g., 500 r / min), followed by static adsorption for 2-6 hours; the adsorption temperature is 20-45°C.

[0027] The mass-to-volume ratio of the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) to the wastewater to be treated is (0.005-0.025 g) mg: 100 mL.

[0028] Furthermore, the wastewater to be treated contains organic dyes, such as methylene blue.

[0029] Furthermore, the pH of the wastewater to be treated is 5-10; The method further includes a step of desorption of the adsorbed ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) after adsorption. The specific method is as follows: under magnetic stirring at 500 rpm, the organic dye adsorbed in the hydrogel is eluted with 30 mL of HCl solution (0.3 mol / L); the eluted hydrogel is washed with water, immersed in ethanol, and dried under vacuum. The desorbed ternary grafted starch-based hydrogel can be recycled.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects: 1. The ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) of the present invention is obtained by emulsion polymerization using corn starch (St) and sodium carboxymethyl cellulose (CMC) as raw materials, and acrylamide (AM), acrylic acid (AA), and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as graft monomers. The introduction of MC and AMPS into this system increases the number and type of effective adsorption functional groups in the hydrogel, significantly improving the adsorption capacity; the adsorption capacity of MB can reach 1624.49 mg / g. Furthermore, the removal rate of methylene blue can reach up to 91.8%.

[0031] 2. The hydrogel prepared by this invention has enhanced thermal stability with the introduction of CMC; the hydrogel can still maintain a high adsorption capacity (1000-1100 mg / g) in an aqueous system with pH=5-10; and the removal rate of methylene blue can still be maintained above 84.3% after 4 adsorption-desorption cycles. Attached Figure Description

[0032] Figure 1This is a schematic diagram illustrating the preparation of starch-based hydrogels. Figure 2 The TG(a) and DTG(b) curves for St, CMC, and starch-based hydrogels are shown. Figure 3 The effect of hydrogel dosage on adsorption capacity; Figure 4 This represents the adsorption capacity of the hydrogel at different pH values. Figure 5 The regeneration and adsorption properties of St / CMC / P (AM-AA-AMPS) hydrogel; Detailed Implementation The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0034] Example 1: Preparation and performance testing of ternary grafted starch-based hydrogels 1. Preparation of ternary grafted starch-based hydrogels Four 100 mL beakers were labeled 1-4. In beaker 1, 15 mL of water and 1 g of corn starch were stirred evenly to form a white suspension. The suspension was gelatinized for 10 minutes with magnetic stirring at 90°C. Beaker 1 was then removed and cooled. In beaker 2, 0.5 g of sodium carboxymethyl cellulose powder was dissolved in 30 mL of water to obtain a clear, viscous liquid. Additionally, 5 mL of acrylic acid was added to beaker 3, and 11.7 g of NaOH solution (15 wt%) was added dropwise while stirring to obtain an acrylic acid solution with a 60% neutralization degree. Beaker 3 was immersed in an ice bath throughout the addition process to prevent boiling. Then, two additional graft monomers, acrylamide (3.0 g) and 2-acrylamido-2-methylpropanesulfonic acid (1.0 g), and the crosslinking agent N-methylenebisacrylamide (0.2 g), were added to the acrylic acid solution and stirred until dissolved. In beaker 4, ammonium persulfate (0.06 g) was dissolved in 6 mL of water as an initiator solution. The solutions from beakers 2 and 3 were poured into beaker 1 and stirred until homogeneous. Then, the initiator solution was added to form a homogeneous mixture. After stirring, nitrogen gas was introduced into beaker 1 to purge air, and the opening was sealed with plastic wrap. The mixture was reacted at 75°C for 5 hours to obtain a translucent block gel. The hydrogel was crushed using a mixer, and the fragments were soaked in a 60% (v / v) aqueous ethanol solution. The fragments were vacuum dried at 60°C to obtain white granules, namely the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS).

[0035] 2. Adsorption test Prepare 100 mL of an aqueous solution containing 120 mg / L methylene blue beforehand. The initial concentration of methylene blue is denoted as [missing value]. ρ 0 mg / L. Then, under magnetic stirring at 500 rpm, 0.005–0.025 g of St / CMC / P (AM-AA-AMPS) ternary grafted starch-based hydrogel was added for dynamic adsorption for 1 hour, followed by static adsorption for 4 hours after stirring was stopped. The methylene blue concentration in the water sample was then analyzed and detected using a spectrophotometer (wavelength 665 nm). The concentration of methylene blue at any given time was recorded as . ρ e The removal rate (E%) and equilibrium adsorption capacity of methylene blue were measured at mg / L. q e mg / g can be calculated using the following formula.

[0036]

[0037] Where V(L) is the volume of the water sample, m (g) represents the amount of hydrogel added.

[0038] In addition, when the amount of hydrogel added to the control system was 0.01 g, the initial concentration of methylene blue was changed ( ρ The effects of different concentrations (0 = 50, 100, 150, 200, and 250 mg / L) on the adsorption capacity of the hydrogel were investigated. Other procedures were the same as above.

[0039] To investigate the change in methylene blue (MB) concentration in the supernatant with adsorption time, 0.01 g of hydrogel was added to 100 mL of water containing 100 mg / L methylene blue (MB). The supernatant was periodically removed and filtered through a 0.45 μm pore size filter membrane. The adsorption capacity (qt, mg / g) at the corresponding time was calculated using (2).

[0040] 3. Hydrogel Adsorption Cycling Experiment First, methylene blue (MB) adsorbed in the hydrogel was eluted with 30 mL of HCl solution (0.3 mol / L) for 4 hours under magnetic stirring at 500 rpm. The eluted hydrogel was washed with water, soaked in ethanol, dried under vacuum, and then used again to adsorb MB from a simulated water sample. ρ (0=100 mg / L), the operation steps are the same as the above experiment.

[0041] Example 2: Performance Test Results of Ternary Grafted Starch-Based Hydrogel 1. The introduction of sodium carboxymethyl cellulose improves the thermal stability of starch-based hydrogels.

[0042] Thermogravimetric (TG) and thermogravimetric differential (DTG) curves of corn starch (St), sodium carboxymethyl cellulose (CMC), and starch-based hydrogels are shown below. Figure 2 As shown in the figure, the TG curves of the three substances are divided into two mass loss stages. Before 100°C, the small amount of weight loss mainly comes from the loss of various bound and unbound water. In the TG curve of St, the significant weight loss occurs between 290 and 340°C, with a weight loss of 74.9%, mainly due to the decomposition of corn starch and microcrystalline phase transition. For CMC, the same situation occurs between 270 and 307°C, mainly due to the decomposition of the sodium carboxymethyl cellulose backbone and structural damage, with a weight loss of 50.7%. For the starch-based hydrogel, the main weight loss (51.6%) occurs between 320 and 460°C, mainly due to the decomposition of side chains and the decomposition of cross-linked structures in the hydrogel. The final residual masses of St, CMC, and hydrogel are 12.6%, 33.1%, and 30.1%, respectively. In addition, the decomposition temperature of the starch-based hydrogel is higher than that of St and CMC, as shown in the DTG figure. Figure 2(b) The results show that the addition of CMC increased the decomposition temperature of the hydrogel. The total mass loss and mass loss rate of the hydrogel were both less than St, indicating that the hydrogel has high thermal stability.

[0043] 2. In wastewater systems, the removal rate of methylene blue can reach up to 91.8% with the increase in the amount of hydrogel added.

[0044] With increasing hydrogel dosage, the removal rate (E%) of MB increased rapidly, such as... Figure 3 As shown, when the hydrogel dosage is 100 mg / L, E% = 91.8%. With further increases in hydrogel dosage, E% remains stable, while the adsorption capacity (qe) shows a consistent decreasing trend. This is mainly because the number of adsorption sites increases with increasing hydrogel dosage, leading to the absorption of more MB molecules and thus significantly improving the MB removal rate. However, the number of MB molecules in the solution is finite. With a constant total MB content, the occupancy rate of adsorption sites decreases with increasing hydrogel dosage, resulting in a continuous decrease in the hydrogel's adsorption capacity (qe).

[0045] 3. The hydrogel can still maintain a high adsorption capacity (1000-1100 mg / g) in a system with pH=5-10.

[0046] The adsorption capacity of the hydrogel remains at a high level (1000-1100 mg / g) within the pH range of 5–10, such as Figure 4 As shown in the figure, the adsorption capacity decreases significantly as the pH value continues to decrease. This is mainly because when a large amount of H+ is present in the solution... + When –COOH groups are present, stable intramolecular hydrogen bonds form between them, making it difficult for them to ionize into –COO. This leads to a reduction in the number of active adsorption sites and a significant decrease in the q of the hydrogel. e .

[0047] 4. Starch-based hydrogels have good recyclability.

[0048] A regenerated hydrogel was used to adsorb a simulated water sample containing 100 mg / L MB. After four adsorption / desorption cycles, the regenerated hydrogel still achieved a MB removal rate of 84.3%. (See results below.) Figure 5 .

[0049] 5. St / CMC / P (AM-AA-AMPS) hydrogel has excellent adsorption capacity, up to 1624.49 mg / g.

[0050] Table 1 Adsorption properties of different biomass-based hydrogels for methylene blue

[0051] Table 1 shows the adsorption performance of different biomass-based hydrogels for methylene blue. For the preparation of biomass-based hydrogels, AA and AM are commonly used grafting monomers. Since starch molecules contain only one type of active group and lack adsorption properties, the adsorption performance of starch-based hydrogels is generally weaker than that of chitosan-based hydrogels. The addition of CMC and AMPS increases the number and types of effective adsorption functional groups in the hydrogel, significantly improving the adsorption capacity; the adsorption capacity of MB reaches 1624.49 mg / g.

[0052] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. An application of a ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) in at least one of the following aspects: 1) application in the preparation of adsorbent materials; 2) application in wastewater treatment; The adsorbent material is used to adsorb methylene blue from wastewater; the wastewater treatment involves adsorbing methylene blue from wastewater. The preparation method of the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) is as follows: 1) Disperse corn starch in water to form a white suspension, gelatinize the suspension, and cool it for later use; 2) Dissolve sodium carboxymethyl cellulose powder in water to obtain a transparent, viscous liquid; 3) Prepare an acrylic acid solution with a neutralization degree of 60%; add the other two graft monomers acrylamide and 2-acrylamido-2-methylpropanesulfonic acid and the crosslinking agent to the acrylic acid solution and stir to dissolve; The crosslinking agent is selected from N,N-methylenebisacrylamide; 4) Ammonium persulfate dissolved in water serves as the initiator solution; 5) Pour the solutions from steps 2) and 3) into the gelatinized product prepared in step 1) and stir until homogeneous. Then add the initiator solution and form a homogeneous mixture. After stirring until homogeneous, fill the reactor with nitrogen to purge air, and then seal the opening with plastic wrap. 6) The mixed solution was subjected to emulsion polymerization to obtain a translucent block gel; the hydrogel was crushed with a mixer and the fragments were soaked in water and ethanol. The fragments were vacuum dried at 40-70°C to obtain white particles, namely the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS). The feed ratio of corn starch, sodium carboxymethyl cellulose, acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, ammonium persulfate, and N,N-methylenebisacrylamide is 1g:0.5g:3g:5mL:1g:0.06g:0.2g.

2. The application according to claim 1, characterized in that: The reaction conditions for the emulsion polymerization reaction are: reaction at 60-90°C for 2-10 hours.

3. A wastewater treatment method, comprising the following steps: adding a ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) to the wastewater to be treated for adsorption of methylene blue; The preparation method of the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) is as follows: 1) Disperse corn starch in water to form a white suspension, gelatinize the suspension, and cool it for later use; 2) Dissolve sodium carboxymethyl cellulose powder in water to obtain a transparent, viscous liquid; 3) Prepare an acrylic acid solution with a neutralization degree of 60%; add the other two graft monomers acrylamide and 2-acrylamido-2-methylpropanesulfonic acid and the crosslinking agent to the acrylic acid solution and stir to dissolve; The crosslinking agent is selected from N,N-methylenebisacrylamide; 4) Ammonium persulfate dissolved in water serves as the initiator solution; 5) Pour the solutions from steps 2) and 3) into the gelatinized product prepared in step 1) and stir until homogeneous. Then add the initiator solution and form a homogeneous mixture. After stirring until homogeneous, fill the reactor with nitrogen to purge air, and then seal the opening with plastic wrap. 6) The mixed solution was subjected to emulsion polymerization to obtain a translucent block gel; the hydrogel was crushed with a mixer and the fragments were soaked in water and ethanol. The fragments were vacuum dried at 40-70°C to obtain white particles, namely the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS). The feed ratio of corn starch, sodium carboxymethyl cellulose, acrylamide, acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, ammonium persulfate, and N,N-methylenebisacrylamide is 1g:0.5g:3g:5mL:1g:0.06g:0.2g.

4. The wastewater treatment method according to claim 3, characterized in that: The reaction conditions for the emulsion polymerization reaction are: reaction at 60-90°C for 2-10 hours.

5. The wastewater treatment method according to claim 4, characterized in that: The adsorption conditions are as follows: dynamic adsorption for 0.5-2.0 hours under stirring, followed by static adsorption for 2-6 hours; the adsorption temperature is 20-45°C. And / or, the mass-to-volume ratio of the ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS) to the wastewater to be treated is (0.005-0.025) mg: 100 mL; And / or, the wastewater to be treated contains organic dyes; And / or, the pH of the wastewater to be treated is 5-10; And / or, the method further includes: after adsorption, a step of desorbing the adsorbed ternary grafted starch-based hydrogel St / CMC / P (AM-AA-AMPS); the specific method is as follows: under magnetic stirring at 500 rpm, the organic dye adsorbed in the hydrogel is eluted with HCl solution; the eluted hydrogel is washed with water, soaked in ethanol, and dried in vacuum.

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