CN107362780B - Preparation method of straw dye adsorbent with semi-interpenetrating network structure - Google Patents

Abstract

The invention relates to a preparation method of a straw dye adsorbent with a semi-interpenetrating network structure, which comprises the steps of firstly pretreating straws by using ultrasound, then carrying out acrylic acid grafting modification on the straws, finally carrying out graft copolymerization on acrylic acid modified straws and functional monomers to prepare the straw dye adsorbent with the semi-interpenetrating network structure and a plurality of dye adsorption groups, wherein for a dye aqueous solution with the initial concentration of 500-3000 mg/L, the dye adsorption capacity of the straw dye adsorbent with the semi-interpenetrating network structure reaches 200-2000 mg/g, and the adsorption balance is reached within 80-120 min, so that the straw dye adsorbent can be widely applied to dye adsorption separation, dye wastewater pollution control and the like.

Description

Preparation method of straw dye adsorbent with semi-interpenetrating network structure

1. Technical field

The invention relates to a method for preparing a straw dye adsorbent with a semi-interpenetrating network structure. The straw dye adsorbent with a semi-interpenetrating network structure prepared by the invention is suitable for the adsorption and separation of dyes, and can be widely used in dye adsorption, separation and purification And dye environmental pollution control.

2. Background technology

Dye wastewater is colored wastewater containing dyes, mainly from the production industry of dyes and dye intermediates and different industries such as textile, leather, paper, rubber, plastic, cosmetics, pharmaceutical and food. It is one of the more difficult industrial wastewaters to treat due to the characteristics of high concentration, high concentration of COD and BOD, many suspended solids, and many refractory biodegradable substances. In addition, dye wastewater not only has obvious chromaticity, which affects the senses, but also contains pollutants that are toxic and harmful to the water body or human body. If the dye wastewater is directly discharged without treatment, it will cause damage to the ecological environment of the water body, and toxic and harmful substances will enter the food chain. , will affect human health. Therefore, the effective treatment of dye wastewater has become an urgent problem to be solved in today's society.

At present, the methods of treating dye wastewater mainly include chemical, biological and physical methods. The precipitation and flocculation method is simple to operate and low cost, but the large amount of sludge produced increases the operating cost. The electrolytic method consumes a large amount of electricity and metal electrodes when treating wastewater. Photocatalytic oxidation is only effective for low-concentration dye wastewater. The selectivity of biological methods is relatively single, and the microorganisms are sensitive to the environment. The adsorption method has the advantages of simple operation, low cost and good effect, and the adsorbent is easy to recycle. Commonly used adsorbents are activated carbon, minerals, resin adsorbents and so on. Activated carbon has strong adsorption capacity and high removal rate, but high cost. Generally, it is only used for low-concentration printing and dyeing wastewater treatment or advanced treatment. Minerals include natural zeolite, bentonite, etc., which have good ion exchange capacity and adsorption performance, but low activity and difficult regeneration. The resin-based adsorbent has high treatment efficiency, can be regenerated under certain conditions, and can still maintain high efficiency after regeneration, which is suitable for the treatment of dye wastewater.

Superabsorbent resins have the advantages of large adsorption capacity, fast adsorption rate, good cycle adsorption and environmental friendliness. In addition, the three-dimensional cross-linked network structure and functional functional groups of superabsorbent resins make it have high permeability and good ion adsorption. Therefore, the research of superabsorbent resins as dye adsorption resins has gradually attracted people's attention. Wang Yongsheng et al. used the graft copolymerization of modified attapulgite and poly(acrylic acid-acrylamide) to obtain a composite superabsorbent resin for the adsorption of methylene blue dye, and the adsorption amount reached 1273 mg/g at 60 °C. Li Shengfang used amylose composite poly(acrylic acid-acrylamide-methacrylate) resin for the adsorption of crystal violet dye, and concluded that the adsorption process conformed to the Langmuir model and pseudo-second-order kinetic equation. Paulino et al. studied the adsorption performance of modified arabinose and polyacrylic acid-acrylamide graft copolymer composite superabsorbent resin for methylene blue dye, the maximum adsorption capacity was 48mg/g, and the decolorization rate was 98%. Yu Xianglin et al. used acrylic superabsorbent resin to study the adsorption effect of three cationic dyes-malachite green, methylene blue and neutral red. Well, the adsorption rates were all over 90%.

In order to reduce the cost of superabsorbent resin and better build a porous three-dimensional network structure, the research in recent years is mainly based on the graft copolymerization of modified plant cellulose and various polymer monomers into composite superabsorbent resin. Superabsorbent resin has gradually become a research hotspot at home and abroad. Xie et al. pretreated wheat straw with alkali, then grafted it with acrylic acid and attapulgite to form a superabsorbent resin containing nitrogen and boron, and studied the release characteristics of nitrogen and boron. The superabsorbent resin obtained by graft copolymerization of sunflower straw pith with acrylic acid and acrylamide by Feng Zhixin et al. absorbed distilled water at a rate of 293 times, tap water at a rate of 154 times, and absorbed physiological saline at a rate of 31 times. Tan Fengzhi et al. After treatment, it is graft-copolymerized with acrylic acid to prepare super absorbent resin. Wang Dan et al. used wheat straw, acrylic acid, acrylamide and methacryloyloxyethyltrimethylammonium chloride (DMC) as raw materials to obtain amphoteric superabsorbent resin through graft copolymerization, which absorbed distilled water up to 853g/g and absorbed 853g/g of distilled water. Normal saline is 118 g/g. Guo Yan et al. pretreated wheat straw by alkaline cooking, graft copolymerization with acrylic acid and acrylamide into agricultural superabsorbent resin, absorbed deionized water up to 412g/g, absorbed w (compound fertilizer)=0.1% aqueous solution up to 126g /g. Liu Wei et al. used the graft copolymerization of wheat straw and corn straw with acrylic acid to prepare superabsorbent resin. The water absorption ratio of the water absorbent resin prepared from wheat straw was close to 200, while the water absorption ratio of the water absorbent resin prepared from corn straw was close to 150. Fu Zhongxin et al. carried out the graft copolymerization of corn stover with acrylic acid and its sodium salt, and initially explored the optimal conditions for the polymerization reaction, and obtained products with good performance and low price. Wan Tao et al. pretreated corn stalks with acrylic acid, acrylamide and sodium styrene sulfonate for aqueous graft copolymerization to prepare corn stalk composite super absorbent resin, and found that when the straw content was 10%, the straw composite super absorbent resin absorbed water for 10 minutes. The water absorption rate reaches 58% of the equilibrium water absorption rate, and the straw composite superabsorbent resin absorbs water for 50 minutes to reach a balance, and the equilibrium water absorption rate is nearly 350g/g. Wan Tao et al. grafted and copolymerized maleic anhydride-modified straw with acrylic acid and acrylamide to prepare the straw composite superabsorbent resin. The equilibrium water absorption rate and equilibrium salt absorption rate can reach 400 to 1000 times and 30 to 80 times, respectively. The gel strength reaches 5 to 25 Pa.s, and the water retention rate of the water-absorbing gel after drying at 80 to 90° C. for 200 minutes is 15 to 40%.

The preparation method of the straw composite superabsorbent is mainly to gelatinize the straw, treat it with inorganic acid, inorganic base or acid anhydride, and then react with the corresponding functional monomer. At present, there is no report of acrylic acid modified with a semi-interpenetrating network structure at home and abroad. Preparation of dye adsorbents from straw and research on their dye adsorption properties.

3. Content of the Invention

In view of this, the purpose of the present invention is to provide a method for preparing a straw dye adsorbent with a semi-interpenetrating network structure. Firstly, the straw was pretreated by ultrasonic, and then it was modified by acrylic acid grafting, and the acrylic acid modified straw and functional monomers were grafted and copolymerized to prepare straw dyes with semi-interpenetrating network structure and various dye adsorption groups. The adsorbent can adjust the elasticity and extensibility of the polymer network through the semi-interpenetrating network structure. By modifying the straw with acrylic acid, the graft copolymerization of the straw and the functional monomer can be realized, and the compatibility between the straw and the polymer matrix can be improved. Dispersion uniformity of straw in polymer matrix.

According to the purpose of the present invention, a method for preparing a straw dye adsorbent with a semi-interpenetrating network structure is proposed, which is characterized by the following process steps:

a) Wash the straw with deionized water, dry it and then pulverize it, sieve to get 100-200 mesh straw powder, add the straw powder to N,N-dimethylformamide, and place it in an ultrasonic cleaning tank for ultrasonic pretreatment for 1-6 hour, transfer the ultrasonically pretreated straw suspension to a three-necked flask, add acrylic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, heat up to 25-50 °C for 2-6 hours, and cool to room temperature, filtered, washed with ethanol for 3 to 5 times, dried and pulverized to obtain acrylic acid modified straw; the mass ratio of N,N-dimethylformamide, straw and acrylic acid is 100:5～20:2～10, The molar ratio of acrylic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine: 1:0.5～1:0.1～0.5;

b) Dissolve NaOH in 200 mL of deionized water, slowly add acrylic acid dropwise to the NaOH aqueous solution in an ice bath, stir and react for 0.5 to 2 h to obtain a partially neutralized acrylic acid aqueous solution; The linking agent is added to the partially neutralized acrylic acid aqueous solution, stirred evenly, heated to 50-60 °C, added with a redox initiator to initiate the polymerization reaction for 3-5 hours, the product is washed with absolute ethanol for 3-5 times, and dried at 80 °C , pulverized to obtain a straw dye adsorbent with a semi-interpenetrating network structure; the molar ratio of acrylic acid and NaOH is 1:0.5-0.8; the mass ratio of acrylic acid and acrylamide is 1-5:1-5; the cross-linking agent accounts for acrylic acid 0.1-0.8% of the total mass of acrylic acid and acrylamide monomers; redox initiators account for 0.1-2.0% of the total mass of acrylic acid and acrylamide monomers; the molar ratio of oxidizing agent and reducing agent is 1-2:1; Vinylpyrrolidone accounts for 5-20% of the total mass of acrylic acid and acrylamide monomers; acrylic acid modified straw accounts for 5-30% of the total mass of acrylic acid and acrylamide monomers;

c) For the initial concentration of 500-3000 mg/L dye aqueous solution, the dye adsorption capacity of the straw dye adsorbent with semi-interpenetrating network structure reaches 200-2000 mg/g, and the adsorption equilibrium is reached in 80-120 min.

The straw used in the present invention is selected from corn straw, wheat straw, soybean straw, rice straw, sorghum straw and cotton straw.

The frequency of the ultrasonic cleaning tank used in the present invention is 20-80 kHz, and the power is 300-3000 W.

The crosslinking agent used in the present invention is selected from N,N'-methylenebisacrylamide, ethylene glycol diacrylate, ethylene glycol diacrylate, ethylene glycol diacrylate, 1,3 - Propylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, glycidyl methacrylate and polyethylene glycol diacrylate.

The redox initiator used in the present invention includes an oxidizing agent and a reducing agent, the oxidizing agent is selected from ammonium persulfate, potassium persulfate and sodium persulfate, and the reducing agent is selected from sodium hydrogen sulfite, sodium sulfite, sodium thiosulfate and ferrous sulfate.

The dye used in the present invention is selected from methylene blue, cationic blue FGL, cationic orange R, cationic bright yellow 7GL, cationic pink FG, methyl green, crystal violet, methyl orange, reactive black RB5, Congo red, alizarin red, sunset yellow , Alizarin Green, Acid Chrome Blue K, and Eosin Y.

The advantages and effects of the present invention are:

1) The polymerization reaction is directly carried out in an aqueous solution, without environmental pollution, the method is simple and easy to implement, and no nitrogen protection is required, so the nitrogen device is omitted, and the investment cost of the equipment is reduced.

2) By modifying the straw with acrylic acid, the graft copolymerization of the straw and the functional monomer is realized, the compatibility between the straw and the polymer matrix is improved, and the dispersion uniformity of the straw in the polymer matrix is improved.

3) Graft copolymerization of acrylic modified straw and functional monomers to prepare straw dye adsorbents with semi-interpenetrating network structure and various dye adsorption groups, and adjust the elasticity and elasticity of the polymer network through the semi-interpenetrating network structure. Extensibility, through the synergistic effect of various adsorption groups, further improve the dye adsorption performance of straw dye adsorbent;

4) The use of crop straw as a natural material to prepare the crop straw dye adsorbent has the advantages of green environmental protection such as short life cycle chain and natural degradation after disposal, which not only makes full use of inexhaustible renewable resources, but also solves the problem of straw burning. The source of environmental pollution is of great importance to control the current environmental pollution caused by straw burning and dye wastewater in my country, to realize the comprehensive utilization of crop straws and the sustainable development of agriculture, and has huge social, environmental and economic benefits.

The dye adsorption rate and adsorption capacity determination method of the straw dye adsorbent of the present invention is as follows.

Put the dye solution with a concentration of 500-3000mg/L and 0.2g of dry and finely ground straw dye adsorbent into a 250mL conical flask, and then place it in a shaker to oscillate for adsorption, and take samples after shaking for a certain period of time. The spectrophotometer measures the absorbance of the sample at the maximum absorption wavelength of the dye, and each sample is measured 3 times to obtain the average value. The dye adsorption capacity q _t and the adsorption capacity q _e are respectively calculated as follows:

q _t (mg/g)={(C ₀ -C _t )V}/m (1)

q _e (mg/g)={(C ₀ -C _e )V}/m (2)

where C ₀ , C _t , and _Ce are the initial dye concentration, the dye concentration of the oscillating adsorption for a certain time, and the dye adsorption equilibrium concentration (mg.L-1), respectively, V is the solution volume (L), and m is the straw dye adsorbent. Mass (g).

Fourth, the specific implementation

In order to better understand the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

Example 1:

The corn stalk was washed with deionized water, dried and then pulverized, sieved to get 200 mesh corn stalk powder, 15 g of corn stalk powder was added to 100 mL of N,N-dimethylformamide, and placed in an ultrasonic wave with a frequency of 50 kHz and a power of 800 W. The cleaning tank was ultrasonically pretreated for 2 hours, and the ultrasonically pretreated corn stover suspension was transferred to a three-necked flask, and 8g of acrylic acid, 18.34g of N,N'-dicyclohexylcarbodiimide and 4.07g of 4-dimethylaminopyridine were added, The temperature was raised to 25° C. to react for 6 h, cooled to room temperature, filtered, washed with ethanol for 5 times, dried and pulverized to obtain acrylic acid modified corn stover.

Dissolve 7.5g NaOH in 200mL deionized water, slowly add 22g acrylic acid dropwise to the NaOH aqueous solution in an ice bath, stir and react for 2h to obtain a partially neutralized acrylic acid aqueous solution; 4g acrylic acid modified corn stover, 18g acrylamide, 6g polyethylene Pyrrolidone and 0.10g N,N'-methylenebisacrylamide were added to the partially neutralized acrylic acid aqueous solution, stirred uniformly, heated to 50°C, 0.62g ammonium persulfate and 0.21g sodium bisulfite were added, and the polymerization reaction was initiated for 5 hours , the product was washed three times with absolute ethanol, dried at 80°C, and pulverized to obtain a corn stover dye adsorbent with a semi-interpenetrating network structure. and methyl orange aqueous solution, the adsorption capacities of corn stalk dye adsorbents crystal violet, cationic bright yellow 7GL, active black RB5 and methyl orange reached 2000 mg/g, 1682 mg/g, 1459 mg/g and 1386 mg/g, respectively, and the adsorption equilibrium was reached in 80 minutes.

Example 2:

The sorghum straw was washed with deionized water, dried and then pulverized, sieved to obtain 200 mesh sorghum straw powder, 20 g of sorghum straw powder was added to 100 mL of N,N-dimethylformamide, and placed in an ultrasonic wave with a frequency of 50 kHz and a power of 600 W. The cleaning tank was ultrasonically pretreated for 3 hours, the ultrasonically pretreated sorghum straw suspension was transferred to a three-necked flask, 10g of acrylic acid, 28.66g of N,N'-dicyclohexylcarbodiimide and 8.48g of 4-dimethylaminopyridine were added, and the temperature was increased. The reaction was carried out at 40° C. for 3.5 hours, cooled to room temperature, filtered, washed with ethanol three times, dried and pulverized to obtain acrylic acid-modified sorghum straw.

Dissolve 7.2 g of NaOH in 200 mL of deionized water, slowly add 20 g of acrylic acid dropwise to the NaOH aqueous solution in an ice bath, and stir for 0.5 h to obtain a partially neutralized aqueous acrylic acid solution; 10 g of acrylic acid-modified sorghum straw, 20 g of acrylamide, 8 g of polyamide Vinylpyrrolidone and 0.08g of ethylene acetal diacrylate were added to partially neutralize the aqueous acrylic acid solution, stirred evenly, heated to 60°C, added with 0.36g of sodium persulfate and 0.12g of sodium bisulfite, and the polymerization reaction was initiated for 3 hours. The product was washed 5 times with absolute ethanol, dried at 80 °C, and pulverized to obtain a sorghum straw dye adsorbent with a semi-interpenetrating network structure. For methylene blue, methyl green, active black RB5 and alizarin with an initial concentration of 1000 mg/L Red aqueous solution, sorghum straw dye adsorbents methylene blue, methyl green, active black RB5 and alizarin red adsorption capacity reached 994 mg/g, 845 mg/g, 786 mg/g and 646 mg/g, respectively, and the adsorption equilibrium was reached in 110 min.

Example 3:

The soybean straw was washed with deionized water, dried and then pulverized. The 200-mesh soybean straw powder was sieved, and 10 g of soybean straw powder was added to 100 mL of N,N-dimethylformamide. The frequency was 30 kHz and the power was 300 W ultrasonic waves. The cleaning tank was ultrasonically pretreated for 6 hours, and the ultrasonically pretreated soybean straw suspension was transferred to a three-necked flask, and 5g of acrylic acid, 10.03g of N,N'-dicyclohexylcarbodiimide and 2.12g of 4-dimethylaminopyridine were added, The temperature was raised to 50° C. to react for 2 h, cooled to room temperature, filtered, washed with ethanol for 5 times, dried and pulverized to obtain acrylic acid modified soybean straw.

Dissolve 5.4g NaOH in 200mL deionized water, slowly add 16g acrylic acid dropwise to the NaOH aqueous solution in an ice bath, stir and react for 1 h to obtain a partially neutralized acrylic acid aqueous solution; 6g acrylic acid modified soybean straw, 24g acrylamide, 6g polyethylene Pyrrolidone and 0.10g ethylene glycol diacrylate were added to partially neutralized acrylic acid aqueous solution, stirred evenly, heated to 50°C, 0.54g potassium persulfate and 0.18g sodium thiosulfate were added, and the polymerization reaction was initiated for 5 hours. Washed three times with absolute ethanol, dried at 80 °C, and pulverized to obtain a soybean straw dye adsorbent with a semi-interpenetrating network structure. For methylene blue, methyl green, active black RB5 and alizarin red with an initial concentration of 1500 mg/L In aqueous solution, the adsorption capacities of soybean straw dye adsorbents methylene blue, methyl green, active black RB5 and alizarin red reached 994 mg/g, 845 mg/g, 786 mg/g and 646 mg/g, respectively, and the adsorption equilibrium was reached in 110 min.

Example 4:

The wheat straw was washed with deionized water, dried and then pulverized, sieved to obtain 100-mesh wheat straw powder, 8 g of wheat straw powder was added to 100 mL of N,N-dimethylformamide, and placed in an ultrasonic wave with a frequency of 50 kHz and a power of 600 W. The cleaning tank was ultrasonically pretreated for 3 hours, the ultrasonically pretreated wheat straw suspension was transferred to a three-necked flask, 4g acrylic acid, 8.02g N,N'-dicyclohexylcarbodiimide and 1.70g 4-dimethylaminopyridine were added, The temperature was raised to 30° C. to react for 5 h, cooled to room temperature, filtered, washed with ethanol for 3 times, dried and pulverized to obtain acrylic acid modified wheat straw.

9g NaOH was dissolved in 200mL deionized water, 24g acrylic acid was slowly added dropwise to the NaOH aqueous solution in an ice bath, and the reaction was stirred for 2h to obtain a partially neutralized acrylic acid aqueous solution; 8g acrylic acid modified wheat straw, 16g acrylamide, 8g polyvinylpyrrolidone and 0.16g of 1,3-propanediol diacrylate were added to partially neutralized acrylic acid aqueous solution, stirred evenly, heated to 50°C, added 0.60g of potassium persulfate and 0.20g of sodium sulfite to initiate polymerization for 5 hours, and the product was treated with anhydrous ethanol. Washed 5 times, dried at 80 °C, and pulverized to obtain a wheat straw dye adsorbent with a semi-interpenetrating network structure. For the aqueous solutions of cationic bright yellow 7GL, active black RB5, alizarin red and sunset yellow with an initial concentration of 2500 mg/L, wheat The adsorption capacities of straw dye adsorbents cationic bright yellow 7GL, active black RB5, alizarin red and sunset yellow reached 1569 mg/g, 1323 mg/g, 1258 mg/g and 1123 mg/g, respectively, and the adsorption equilibrium was reached in 90 minutes.

Example 5:

Wash the cotton stalks with deionized water, dry them and pulverize them, sieve the 100-mesh cotton stalk powder, add 5 g of the cotton stalk powder to 100 mL of N,N-dimethylformamide, and place it in an ultrasonic wave with a frequency of 50 kHz and a power of 1000 W. The cleaning tank was ultrasonically pretreated for 1 hour, the ultrasonically pretreated cotton straw suspension was transferred to a three-necked flask, 2g acrylic acid, 2.87g N,N'-dicyclohexylcarbodiimide and 0.34g 4-dimethylaminopyridine were added, and the temperature was increased. The reaction was carried out at 25° C. for 6 hours, cooled to room temperature, filtered, washed with ethanol for 5 times, dried and pulverized to obtain acrylic acid modified cotton straw.

Dissolve 9 g of NaOH in 200 mL of deionized water, slowly add 24 g of acrylic acid dropwise to the NaOH aqueous solution in an ice bath, and stir and react for 2 h to obtain a partially neutralized aqueous acrylic acid solution; 12 g of acrylic acid-modified cotton straw, 16 g of acrylamide, 2 g of polyvinylpyrrolidone and 0.12g of ethylene glycol diacrylate were added to the partially neutralized acrylic acid aqueous solution, stirred evenly, heated to 60°C, added with 0.48g of ammonium persulfate and 0.16g of sodium bisulfite, and the polymerization reaction was initiated for 3 hours. Ethanol washed three times, dried at 80°C, and pulverized to obtain a cotton straw dye adsorbent with a semi-interpenetrating network structure. For the aqueous solutions of crystal violet, cationic bright yellow 7GL, sunset yellow and alizarin green with an initial concentration of 500 mg/L, cotton straw dye The adsorption capacities of the adsorbents crystal violet, cationic bright yellow 7GL, sunset yellow and alizarin green reached 495 mg/g, 386 mg/g, 287 mg/g and 200 mg/g, respectively, and the adsorption equilibrium was reached in 120 min.

Claims (5)

1. The application of the straw dye adsorbent with the semi-interpenetrating network structure in dye adsorption is characterized by comprising the following process steps:

washing straws with deionized water, drying and crushing, screening straw powder of 100-200 meshes, adding the straw powder into N, N-dimethylformamide, placing the straw powder into an ultrasonic cleaning tank for ultrasonic pretreatment for 1-6 hours, transferring the straw suspension subjected to ultrasonic pretreatment into a three-neck flask, adding acrylic acid, N' -dicyclohexylcarbodiimide and 4-dimethylaminopyridine, heating to 25-50 ℃, reacting for 2-6 hours, cooling to room temperature, filtering, washing with ethanol for 3-5 times, drying and crushing to obtain acrylic acid modified straws; the mass ratio of the N, N-dimethylformamide to the straw to the acrylic acid is 100: 5-20: 2-10, and the molar ratio of the acrylic acid to the N, N' -dicyclohexylcarbodiimide to the 4-dimethylaminopyridine is as follows: 1: 0.5-1: 0.1-0.5;

dissolving NaOH in 200mL of deionized water, slowly and dropwisely adding acrylic acid into a NaOH aqueous solution in an ice bath, and stirring to react for 0.5-2 h to obtain a partially neutralized acrylic acid aqueous solution; adding acrylic acid modified straws, acrylamide, polyvinylpyrrolidone and a cross-linking agent into a partially neutralized acrylic acid aqueous solution, uniformly stirring, heating to 50-60 ℃, adding a redox initiator, initiating a polymerization reaction for 3-5 hours, washing a product with absolute ethyl alcohol for 3-5 times, drying at 80 ℃, and crushing to obtain a straw dye adsorbent with a semi-interpenetrating network structure; the molar ratio of acrylic acid to NaOH is 1:0.5 to 0.8; the mass ratio of acrylic acid to acrylamide is 1-5: 1-5; the cross-linking agent accounts for 0.1-0.8% of the total mass of the acrylic acid and the acrylamide monomer; the redox initiator accounts for 0.1-2.0% of the total mass of the acrylic acid and the acrylamide monomer; the redox initiator comprises an oxidant and a reducing agent, wherein the molar ratio of the oxidant to the reducing agent is (1-2): 1; the oxidant is selected from ammonium persulfate, potassium persulfate and sodium persulfate, and the reducer is selected from sodium bisulfite, sodium sulfite, sodium thiosulfate and ferrous sulfate; the polyvinyl pyrrolidone accounts for 5-20% of the total mass of the acrylic acid and the acrylamide monomers, and the acrylic acid modified straw accounts for 5-30% of the total mass of the acrylic acid and the acrylamide monomers;

for a dye aqueous solution with the initial concentration of 500-3000 mg/L, the dye adsorption capacity of the straw dye adsorbent with the semi-interpenetrating network structure reaches 200-2000 mg/g, and the adsorption balance is reached within 80-120 min.

2. The application of the straw dye adsorbent with the semi-interpenetrating network structure in dye adsorption according to claim 1 is characterized in that: the straws are selected from corn straws, wheat straws, soybean straws, rice straw straws, sorghum straws and cotton straws.

3. The application of the straw dye adsorbent with the semi-interpenetrating network structure in dye adsorption according to claim 1 is characterized in that: the frequency of the ultrasonic cleaning tank is 20-80 kHz, and the power is 300-3000W.

4. The application of the straw dye adsorbent with the semi-interpenetrating network structure in dye adsorption according to claim 1 is characterized in that: the cross-linking agent is selected from N, N' -methylene bisacrylamide, ethylene glycol diacrylate, monoethylene glycol diacrylate, diethylene glycol diacrylate, 1, 3-propylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, glycidyl methacrylate and polyethylene glycol diacrylate.

5. The application of the straw dye adsorbent with the semi-interpenetrating network structure in dye adsorption according to claim 1 is characterized in that: the dye is selected from methylene blue, cation blue FGL, cation orange R, cation bright yellow 7GL, cation peach red FG, methyl green, crystal violet, methyl orange, reactive black RB5, congo red, alizarin red, sunset yellow, alizarin green, acid chrome blue K and eosin Y.