Wastewater treatment agent for sulfate resource recovery and preparation method thereof

Abstract

The application discloses a kind of sulphate resource recycling wastewater treatment agent and preparation method thereof, belong to wastewater treatment field.Sulphonating agent and alkali lignin are mixed and stirred to obtain sulphonated lignin;Sulphonated lignin and nano cellulose are mixed and treated by ultrasonic to obtain hybrid sol;Hybrid sol and 25wt% glutaraldehyde aqueous solution are stirred to obtain composite gel;Composite gel, ammonium persulfate and urea-based functional ionic liquid are mixed and stirred to obtain the wastewater treatment agent.The wastewater treatment agent of the application is electrostatically attracted to sulfate by quaternary ammonium salt cation, is locked by multiple hydrogen bonds through three urea groups, and hydrophilic transport channel is formed by sulfonic group;Synergistic effect of the three realizes efficient adsorption and recovery of sulfate in wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wastewater treatment, in particular to a wastewater treatment agent for sulfate resource recycling and a preparation method thereof. BACKGROUND

[0002] The existing technology pays insufficient attention to the resource utilization potential of the sulfate contained in the wastewater. Its treatment focus is still on the removal of pollutants, rather than the recycling and value mining of resources. In the Ca(OH)2 precipitation process, the sulfate is usually precipitated in the form of gypsum, generating a large amount of solid waste residue. Although the sulfate is removed from the main body of the wastewater, these gypsums are usually considered as low-value by-products or secondary pollutants, which need further storage or disposal. This not only increases the environmental burden of the treatment chain, but also fails to convert waste into resources with economic value. In addition, although anaerobic reduction can reduce the concentration of sulfate, the sulfides (such as hydrogen sulfide) produced often need additional treatment facilities for removal, rather than efficient capture and conversion into high-value sulfur resource products. This treatment concept of "treating pollution without increasing efficiency" cannot meet the new requirements of society for economic and environmental benefits under the current background of emphasizing sustainable development and resource recycling. The existing complex process has encountered insurmountable bottlenecks in seeking economic, efficient and green treatment solutions due to its high operating cost and lack of consideration for sulfate resource utilization.

[0003] Patent CN102190411B discloses a method for treating high-COD and high-solubility sulfate-containing acid organic chemical wastewater. A method combining Ca(OH)2 precipitation, anaerobic consumption and two-stage aerobic aeration is invented to treat acid sulfate-containing organic chemical wastewater. This method is suitable for treating sulfate-containing wastewater with a wider range of solubility and can overcome the influence of sulfate reduction inhibition. However, the process is complex, the hydraulic retention time is long, the operation is difficult, and there is a lack of consideration for the comprehensive utilization of sulfate in wastewater.

[0004] Patent CN102260014B discloses a method for treating high-sulfate organic wastewater. The sulfate in the wastewater is recovered and utilized by cooling crystallization and solid-liquid separation, and then the desalted effluent is sequentially subjected to Fenton oxidation and sulfate-resistant SBR method to remove organic matter in the wastewater. The advantages of this method are good operability and strong adaptability. However, in the case where the organic matter in the wastewater is not fully degraded, the sulfate recovered by cooling crystallization may contain a large amount of toxic organic matter, which poses a great safety hazard to the subsequent comprehensive utilization. In addition, the use of Fenton method to degrade organic matter in wastewater will produce a large amount of iron sludge, which is difficult to dispose.

[0005] Therefore, providing a new wastewater treatment agent capable of efficiently removing sulfate in wastewater and realizing resource recycling of sulfate has become an important problem to be solved in the field. SUMMARY

[0006] To solve the problems in the prior art, the present application provides a wastewater treatment agent for resource recycling of sulfate and a preparation method thereof, which can efficiently adsorb and enrich sulfate ions in wastewater, and can realize resource recycling of sulfate ions in the form of high-purity ammonium sulfate crystals after elution treatment. Specifically, the technical scheme of the present application includes the following contents:

[0007] A preparation method of a wastewater treatment agent for resource recycling of sulfate, the preparation method comprising the following steps:

[0008] mixing and stirring the sulfonating agent and alkali lignin to obtain sulfonated lignin;

[0009] mixing and stirring the sulfonated lignin and nanocellulose and then performing ultrasonic treatment to obtain a hybrid sol;

[0010] stirring the hybrid sol and a 25wt% glutaraldehyde aqueous solution to obtain a composite gel;

[0011] mixing and stirring the composite gel, ammonium persulfate and urea-based functionalized ionic liquid to obtain the wastewater treatment agent.

[0012] Further, the sulfonating agent is obtained by mixing amino sulfonic acid and urea at a weight ratio of 4.8:15.2.

[0013] Further, the mixing conditions of the amino sulfonic acid and urea include a mixing temperature of 75-85℃ and a mixing time of 30-40min.

[0014] Further, the weight ratio of the sulfonating agent and alkali lignin is 20-30:10.

[0015] Further, the mixing and stirring reaction conditions of the sulfonating agent and alkali lignin include stirring at 100-120℃ for 1-2h, and then increasing the temperature to 120-150℃ and stirring for 4-6h.

[0016] Further, the weight ratio of the sulfonated lignin, nanocellulose and 25wt% glutaraldehyde aqueous solution is 1.5-2.5:1.8-2.2:0.7-0.9.

[0017] Further, the ultrasonic treatment conditions include an ultrasonic power of 200-250W and an ultrasonic time of 10-15min.

[0018] Further, the conditions of the stirring reaction of the hybrid sol and the 25wt% glutaraldehyde aqueous solution include a reaction pH of 9~9.5, a reaction temperature of 23~25℃, and a reaction time of 30~40min.

[0019] Further, the preparation method of the urea-based functionalized ionic liquid comprises the following steps:

[0020] 2-imidazole-1-ethylamine, acryloyl chloride and triethylamine are mixed and stirred to react to obtain olefinated imidazole;

[0021] Tri(2-aminoethyl)amine and 3-chloropropyl isocyanate are mixed and stirred to react to obtain a urea-based complex;

[0022] The olefinated imidazole and the urea-based complex are mixed and stirred to react to obtain the urea-based functionalized ionic liquid.

[0023] Further, the weight ratio of the 2-imidazole-1-ethylamine, acryloyl chloride and triethylamine is 4.5~6.5:5.5~7.5:4.5~5.5.

[0024] Further, the conditions of the stirring reaction of the 2-imidazole-1-ethylamine, acryloyl chloride and triethylamine include a reaction temperature of 23~25℃ and a reaction time of 12~16h.

[0025] Further, the weight ratio of the tri(2-aminoethyl)amine and 3-chloropropyl isocyanate is 1.3~1.7:3.4~3.8.

[0026] Further, the conditions of the stirring reaction of the tri(2-aminoethyl)amine and 3-chloropropyl isocyanate include a reaction temperature of 23~25℃ and a reaction time of 12~24h.

[0027] Further, the weight ratio of the olefinated imidazole and the urea-based complex is 2.58~2.98:2.32~2.72.

[0028] Further, the conditions of the stirring reaction of the olefinated imidazole and the urea-based complex include a reaction temperature of 80~100℃ and a reaction time of 24~48h.

[0029] Further, the weight ratio of the composite gel, ammonium persulfate and the urea-based functionalized ionic liquid is 1:0.05~0.1:1.5~3.

[0030] Further, the conditions of the stirring reaction of the composite gel, ammonium persulfate and the urea-based functionalized ionic liquid include a reaction temperature of 60~70℃ and a reaction time of 12~24h.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] (1) In the present application, 2-imidazole-1-ethylamine and acryloyl chloride are reacted to obtain olefinated imidazole with an olefin at the end, tris(2-aminoethyl)amine is reacted with 3-chloropropyl isocyanate to form a urea-based complex with multiple urea-based sites, and the olefinated imidazole and the urea-based complex are reacted by quaternization to obtain a urea-based functional ionic liquid containing a quaternary ammonium salt; sulfamic acid and urea are mixed as a sulfonating agent to sulfonate alkaline lignin to obtain sulfonated lignin, and then glutaraldehyde is used as a crosslinking agent to crosslink the sulfonated lignin and nanocellulose to form a three-dimensional network structure, and the urea-based functional ionic liquid is fixed on the composite gel by graft copolymerization to prepare a wastewater treatment agent.

[0033] (2) The wastewater treatment agent provided by the present application can efficiently remove sulfate through the synergistic effect of the urea-based functional ionic liquid and the hybrid gel skeleton; the sulfonic acid group forms a hydrophilic channel, which promotes the rapid diffusion of sulfate ions to the internal active sites; the quaternary ammonium salt cation on the urea-based functional ionic liquid preferentially adsorbs sulfate through electrostatic interaction, and then the urea-based functional group strongly anchors the sulfate through multiple hydrogen bonds, significantly improving the selectivity and binding force, so that the sulfate can be selectively recovered from a complex wastewater system; the urea-based functional ionic liquid is fixed in the sulfonated lignin-nanocellulose composite gel skeleton, which not only ensures the efficient use of the ionic liquid functional component, but also overcomes the problem of ionic liquid recovery, making the wastewater treatment agent easy to separate and recycle from wastewater, reducing the operating cost and the risk of secondary pollution; the composite gel as a carrier provides good specific surface area and pore structure, which is beneficial to the rapid mass transfer and adsorption of sulfate; in addition, for the saturated wastewater treatment agent, the sulfate can be recovered by simple desorption and regeneration operation, and the waste in wastewater is converted into valuable resources. DETAILED DESCRIPTION

[0034] The technical solutions of the present application will be described clearly and completely below through the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0035] Unless otherwise specified, the raw materials and reagents used in the present application below are commercially available or can be prepared by known methods.

[0036] Performance test method:

[0037] Sulfate removal rate test: The same batch of wastewater was used for testing, with a sulfate ion concentration of 568 mg / L and pH=4.5. 1 g of the wastewater treatment agent prepared in Examples 1-5 and Comparative Examples 1-6 was weighed and placed into clean containers. 1 kg of wastewater was added to each container. After sealing the containers, they were shaken at 25°C for 24 h. The supernatant was collected, filtered through a 0.45 μm filter membrane, and the sulfate concentration was measured. The sulfate removal rate was calculated.

[0038] Desorption and regeneration performance test: Ammonia water with a mass fraction of 25% and saturated ammonium carbonate solution were mixed at a volume ratio of 9:1 and stirred evenly to obtain the eluent; the wastewater treatment agent that had reached adsorption saturation in the above adsorption capacity test was collected by filtration, and first rinsed quickly with a small amount of deionized water to remove the residual solution attached to the surface, and then soaked in the eluent. After shaking treatment at 25°C for 5 hours, the desorbed wastewater treatment agent and eluent were separated by filtration. The desorbed wastewater treatment agent was washed with deionized water and freeze-dried to obtain the regenerated wastewater treatment agent. The above adsorption capacity test was repeated for the regenerated wastewater treatment agent to complete one "adsorption-desorption" cycle. The cycle was repeated 5 times, and the capacity loss rate of the wastewater treatment agents prepared in Examples 1-5 and Comparative Examples 1-6 was calculated; the eluent was evaporated and crystallized at 70°C to obtain ammonium sulfate crystals, and the purity of the ammonium sulfate crystals was tested.

[0039] Nanocellulose was purchased from Nanjing Tianlu Nanotechnology Co., Ltd., with a solid content of 1.5%~3.0%.

[0040] Preparation Example 1:

[0041] The preparation method of urea-functionalized ionic liquids includes the following steps:

[0042] 4.5 parts by weight of 2-imidazol-1-ethylamine were dispersed in 80 parts by weight of anhydrous dichloromethane and placed in a reaction flask. Under a nitrogen atmosphere, the mixture was stirred and dispersed at 0°C for 10 min. Then, 4.5 parts by weight of triethylamine and 5.5 parts by weight of acryloyl chloride dispersed in 20 parts by weight of anhydrous dichloromethane were slowly added dropwise to the reaction flask. After the addition was complete, the temperature was raised to 23°C and the mixture was stirred and reacted for 12 h. After the reaction was completed, the organic phase was washed three times with saturated sodium carbonate solution and collected. The organic phase was then washed with deionized water until neutral and dried with anhydrous sodium sulfate. The dichloromethane was removed by vacuum distillation to obtain a white solid, which was the olefinized imidazolium.

[0043] 1.3 parts by weight of tris(2-aminoethyl)amine were dispersed in 100 parts by weight of anhydrous dichloromethane. Under nitrogen protection, 3.4 parts by weight of 3-chloropropyl isocyanate were slowly added dropwise at 0°C. After the addition was completed, the temperature was raised to 23°C and the mixture was stirred for 12 h. After the reaction was completed, the white precipitate was collected by filtration, washed three times with cold diethyl ether, and then dried under vacuum at 50°C for 12 h to obtain the urea complex.

[0044] 2.58 parts by weight of olefinic imidazole and 2.32 parts by weight of ureoyl complex were dispersed in 50 parts by weight of anhydrous acetonitrile. The mixture was heated to 80°C under a nitrogen atmosphere and stirred for 24 h. After the reaction was completed, the mixture was cooled to 23°C to obtain a reaction solution. The reaction solution was poured into a large amount of excess anhydrous diethyl ether, allowed to stand, and the supernatant was discarded. The lower viscous substance was collected, washed three times with diethyl ether, and then dried under vacuum at 50°C for 24 h to obtain a ureoyl functionalized ionic liquid.

[0045] Preparation Example 2:

[0046] The preparation method of urea-functionalized ionic liquids includes the following steps:

[0047] Five parts by weight of 2-imidazol-1-ethylamine were dispersed in 80 parts by weight of anhydrous dichloromethane and placed in a reaction flask. Under a nitrogen atmosphere, the mixture was stirred and dispersed at 1°C for 11 min. Then, 4.7 parts by weight of triethylamine and 6 parts by weight of acryloyl chloride were slowly added dropwise to the reaction flask. After the addition was complete, the temperature was raised to 23.5°C and the mixture was stirred and reacted for 13 h. After the reaction was completed, the organic phase was washed three times with saturated sodium carbonate solution and collected. The organic phase was then washed with deionized water until neutral and dried with anhydrous sodium sulfate. The dichloromethane was removed by vacuum distillation to obtain a white solid, which was the olefinized imidazolium.

[0048] 1.4 parts by weight of tris(2-aminoethyl)amine were dispersed in 100 parts by weight of anhydrous dichloromethane. Under nitrogen protection, 3.5 parts by weight of 3-chloropropyl isocyanate were slowly added dropwise at 1°C. After the addition was completed, the temperature was raised to 23.5°C and the mixture was stirred for 15 h. After the reaction was completed, the white precipitate was collected by filtration, washed three times with cold diethyl ether, and then dried under vacuum at 50°C for 12 h to obtain the urea complex.

[0049] 2.68 parts by weight of olefinic imidazole and 2.42 parts by weight of urea complex were dispersed in 50 parts by weight of anhydrous acetonitrile. The mixture was heated to 85°C under a nitrogen atmosphere and stirred for 30 h. After the reaction was completed, the mixture was cooled to 23.5°C to obtain a reaction solution. The reaction solution was poured into a large amount of excess anhydrous diethyl ether, allowed to stand, and the supernatant was discarded. The lower viscous substance was collected, washed three times with diethyl ether, and then dried under vacuum at 50°C for 24 h to obtain a urea-functionalized ionic liquid.

[0050] Preparation Example 3:

[0051] The preparation method of urea-functionalized ionic liquids includes the following steps:

[0052] 5.5 parts by weight of 2-imidazol-1-ethylamine were dispersed in 80 parts by weight of anhydrous dichloromethane and placed in a reaction flask. Under a nitrogen atmosphere, the mixture was stirred and dispersed at 2°C for 12 min. Then, 5 parts by weight of triethylamine and 6.5 parts by weight of acryloyl chloride dispersed in 20 parts by weight of anhydrous dichloromethane were slowly added dropwise to the reaction flask. After the addition was complete, the temperature was raised to 24°C and the mixture was stirred and reacted for 14 h. After the reaction was completed, the organic phase was washed three times with saturated sodium carbonate solution and collected. The organic phase was then washed with deionized water until neutral and dried with anhydrous sodium sulfate. The dichloromethane was removed by vacuum distillation to obtain a white solid, which was the olefinized imidazolium.

[0053] 1.5 parts by weight of tris(2-aminoethyl)amine were dispersed in 100 parts by weight of anhydrous dichloromethane. Under nitrogen protection, 3.6 parts by weight of 3-chloropropyl isocyanate were slowly added dropwise at 2°C. After the addition was completed, the temperature was raised to 24°C and the mixture was stirred for 18 hours. After the reaction was completed, the white precipitate was collected by filtration, washed three times with cold diethyl ether, and then dried under vacuum at 50°C for 12 hours to obtain the urea complex.

[0054] 2.78 parts by weight of olefinic imidazole and 2.52 parts by weight of urea complex were dispersed in 50 parts by weight of anhydrous acetonitrile. The mixture was heated to 90°C under a nitrogen atmosphere and stirred for 36 h. After the reaction was completed, the mixture was cooled to 24°C to obtain a reaction solution. The reaction solution was poured into a large amount of excess anhydrous diethyl ether, allowed to stand, and the supernatant was discarded. The lower viscous substance was collected, washed three times with diethyl ether, and then dried under vacuum at 50°C for 24 h to obtain a urea-functionalized ionic liquid.

[0055] Preparation Example 4:

[0056] The preparation method of urea-functionalized ionic liquids includes the following steps:

[0057] Six parts by weight of 2-imidazol-1-ethylamine were dispersed in 80 parts by weight of anhydrous dichloromethane and placed in a reaction flask. Under a nitrogen atmosphere, the mixture was stirred and dispersed at 3°C ​​for 13 min. Then, 5.2 parts by weight of triethylamine and 7 parts by weight of acryloyl chloride dispersed in 20 parts by weight of anhydrous dichloromethane were slowly added dropwise to the reaction flask. After the addition was complete, the temperature was raised to 24.5°C and the mixture was stirred and reacted for 15 h. After the reaction was completed, the organic phase was washed three times with saturated sodium carbonate solution and collected. The organic phase was then washed with deionized water until neutral and dried with anhydrous sodium sulfate. The dichloromethane was removed by vacuum distillation to obtain a white solid, which was the olefinized imidazolium.

[0058] 1.6 parts by weight of tris(2-aminoethyl)amine were dispersed in 100 parts by weight of anhydrous dichloromethane. Under nitrogen protection, 3.7 parts by weight of 3-chloropropyl isocyanate were slowly added dropwise at 3°C. After the addition was completed, the temperature was raised to 24.5°C and the mixture was stirred for 21 h. After the reaction was completed, the white precipitate was collected by filtration, washed three times with cold diethyl ether, and then dried under vacuum at 50°C for 12 h to obtain the urea complex.

[0059] 2.88 parts by weight of olefinic imidazole and 2.62 parts by weight of urea complex were dispersed in 50 parts by weight of anhydrous acetonitrile. The mixture was heated to 95°C under a nitrogen atmosphere and stirred for 42 h. After the reaction was completed, the mixture was cooled to 24.5°C to obtain a reaction solution. The reaction solution was poured into a large amount of excess anhydrous diethyl ether, allowed to stand, and the supernatant was discarded. The lower viscous substance was collected, washed three times with diethyl ether, and then dried under vacuum at 50°C for 24 h to obtain a urea-functionalized ionic liquid.

[0060] Preparation Example 5:

[0061] The preparation method of urea-functionalized ionic liquids includes the following steps:

[0062] 6.5 parts by weight of 2-imidazol-1-ethylamine were dispersed in 80 parts by weight of anhydrous dichloromethane and placed in a reaction flask. Under a nitrogen atmosphere, the mixture was stirred and dispersed at 5°C for 15 min. Then, 5.5 parts by weight of triethylamine and 7.5 parts by weight of acryloyl chloride dispersed in 20 parts by weight of anhydrous dichloromethane were slowly added dropwise to the reaction flask. After the addition was complete, the temperature was raised to 25°C and the mixture was stirred and reacted for 16 h. After the reaction was completed, the organic phase was washed three times with saturated sodium carbonate solution and collected. The organic phase was then washed with deionized water until neutral and dried with anhydrous sodium sulfate. The dichloromethane was removed by vacuum distillation to obtain a white solid, which was the olefinized imidazolium.

[0063] 1.7 parts by weight of tris(2-aminoethyl)amine were dispersed in 100 parts by weight of anhydrous dichloromethane. Under nitrogen protection, 3.8 parts by weight of 3-chloropropyl isocyanate were slowly added dropwise at 5°C. After the addition was completed, the temperature was raised to 25°C and the mixture was stirred for 24 h. After the reaction was completed, the white precipitate was collected by filtration, washed three times with cold diethyl ether, and then dried under vacuum at 50°C for 12 h to obtain the urea complex.

[0064] 2.98 parts by weight of olefinic imidazole and 2.72 parts by weight of ureoyl complex were dispersed in 50 parts by weight of anhydrous acetonitrile. The mixture was heated to 100°C under a nitrogen atmosphere and stirred for 48 h. After the reaction was completed, the mixture was cooled to 25°C to obtain a reaction solution. The reaction solution was poured into a large amount of excess anhydrous diethyl ether, allowed to stand, and the supernatant was discarded. The lower viscous substance was collected, washed three times with diethyl ether, and then dried under vacuum at 50°C for 24 h to obtain a ureoyl functionalized ionic liquid.

[0065] Preparation Example 6:

[0066] The preparation method of urea-functionalized ionic liquids includes the following steps:

[0067] 22 parts by weight of 3-bromopropylamine hydrobromide were dispersed in 100 parts by weight of anhydrous acetonitrile. Under an argon atmosphere, a mixed solution prepared by 10 parts by weight of acryloyl chloride and 30 parts by weight of anhydrous acetonitrile was slowly added dropwise at a low temperature of 4°C. After the addition was completed, the system temperature was raised to 25°C and the reaction was continued to be stirred for 14 hours. After the reaction was completed, the mixture was subjected to rotary evaporation at 50°C to obtain a light yellow viscous liquid first intermediate.

[0068] 10.5 parts by weight of allyl isocyanate were dispersed in 50 parts by weight of anhydrous dichloromethane to prepare a homogeneous dispersion. Under low temperature conditions of -5°C, a mixed solution prepared by 9.5 parts by weight of 2-imidazol-1-ethylamine and 30 parts by weight of anhydrous dichloromethane was slowly added dropwise to the above dispersion. After the dropwise addition was completed, the reaction system was heated to 25°C and stirred continuously at this temperature for 8 hours. After the reaction was completed, the dichloromethane was removed by rotary evaporation. Subsequently, the product was purified by recrystallization using ethyl acetate and n-hexane as recrystallization solvents. Finally, the product was dried under vacuum to obtain a white crystalline second intermediate.

[0069] 29.5 parts by weight of the first intermediate and 23.3 parts by weight of the second intermediate were dispersed in 150 parts by weight of anhydrous acetonitrile. The mixture was stirred at 80°C for 38 hours under an argon atmosphere. After the reaction was completed, the system was cooled to 25°C to obtain a reaction solution. The reaction solution was then slowly poured into 500 parts by weight of cold diethyl ether under stirring. After standing, the mixture was filtered. The filter cake was washed three times with cold diethyl ether and then recrystallized in an acetonitrile / diethyl ether mixture. Finally, the mixture was dried under vacuum at 40°C for 24 hours to obtain a white solid product, which is the urea-functionalized ionic liquid.

[0070] Example 1:

[0071] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0072] 4.8 parts by weight of aminosulfonic acid and 15.2 parts by weight of urea were stirred and mixed at 75°C for 30 min to obtain a sulfonating agent. 10 parts by weight of alkali lignin were added to 20 parts by weight of the sulfonating agent. The mixture was stirred at 100°C and 500 r / min for 1 h. The temperature was then raised to 120°C and stirred for 4 h to obtain a mixture. The mixture was poured into 200 parts by weight of ice water to terminate the reaction. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 70°C for 12 h to obtain sulfonated lignin.

[0073] 1.5 parts by weight of sulfonated lignin and 1.8 parts by weight of nanocellulose were dispersed in 100 parts by weight of deionized water and ultrasonically treated at 200W for 10 min at 0℃ to obtain a hybrid sol. The pH of the hybrid sol was adjusted to 9, and 0.7 parts by weight of 25wt% glutaraldehyde aqueous solution was added. The mixture was stirred at 40℃ for 30 min. After the reaction was completed, the solid product was collected by filtration, washed several times with ethanol and deionized water, and then freeze-dried to obtain a composite gel.

[0074] One part by weight of the composite gel was dispersed in 100 parts by weight of deionized water and swollen for 30 min. After the gel was fully swollen, 0.05 parts by weight of ammonium persulfate and 1.5 parts by weight of the urea-functionalized ionic liquid prepared in Example 1 were added. The mixture was heated to 60°C and stirred for 12 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by filtration. After washing with ethanol and deionized water alternately, the product was freeze-dried to obtain the wastewater treatment agent.

[0075] Performance testing showed that the wastewater treatment agent had a sulfate removal rate of 90.5%. After five adsorption-desorption-regeneration cycles, its adsorption capacity decreased by 7.8%. The recovered ammonium sulfate yield was 78%, and the purity was 98.0%.

[0076] Example 2:

[0077] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0078] 4.8 parts by weight of aminosulfonic acid and 15.2 parts by weight of urea were stirred and mixed at 77°C for 32 min to obtain a sulfonating agent. 10 parts by weight of alkali lignin were added to 22 parts by weight of the sulfonating agent, and the mixture was stirred at 105°C and 550 r / min for 1.2 h. The temperature was then raised to 125°C and stirred for 4.5 h to obtain a mixture. The mixture was poured into 200 parts by weight of ice water to terminate the reaction. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 70°C for 12 h to obtain sulfonated lignin.

[0079] 1.7 parts by weight of sulfonated lignin and 1.9 parts by weight of nanocellulose were dispersed in 100 parts by weight of deionized water and ultrasonically treated at 210W for 11 min at 1℃ to obtain a hybrid sol. The pH of the hybrid sol was adjusted to 9.1, and 0.75 parts by weight of 25wt% glutaraldehyde aqueous solution was added. The mixture was stirred at 42℃ for 35 min. After the reaction was completed, the solid product was collected by filtration, washed several times with ethanol and deionized water, and then freeze-dried to obtain a composite gel.

[0080] One part by weight of the composite gel was dispersed in 100 parts by weight of deionized water and swollen for 30 min. After the gel was fully swollen, 0.06 parts by weight of ammonium persulfate and 2 parts by weight of the urea-functionalized ionic liquid prepared in Example 2 were added. The mixture was heated to 62°C and stirred for 15 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by filtration. After washing with ethanol and deionized water alternately, the product was freeze-dried to obtain the wastewater treatment agent.

[0081] Performance testing showed that the wastewater treatment agent achieved a sulfate removal rate of 93.8%, and after five cycles, the adsorption capacity decreased by 6.2%; the recovered ammonium sulfate yield was 81%, with a purity of 98.5%.

[0082] Example 3:

[0083] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0084] 4.8 parts by weight of aminosulfonic acid and 15.2 parts by weight of urea were stirred and mixed at 80°C for 35 min to obtain a sulfonating agent. 10 parts by weight of alkali lignin were added to 25 parts by weight of the sulfonating agent. The mixture was stirred at 110°C and 600 r / min for 1.5 h. The temperature was then raised to 130°C and stirred for 5 h to obtain a mixture. The mixture was poured into 200 parts by weight of ice water to terminate the reaction. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 70°C for 12 h to obtain sulfonated lignin.

[0085] Two parts by weight of sulfonated lignin and two parts by weight of nanocellulose were dispersed in 100 parts by weight of deionized water and ultrasonically treated at 220W for 12 min at 2℃ to obtain a hybrid sol. The pH of the hybrid sol was adjusted to 9.2, and 0.8 parts by weight of 25wt% glutaraldehyde aqueous solution was added. The mixture was stirred at 45℃ for 40 min. After the reaction was completed, the solid product was collected by filtration, washed several times with ethanol and deionized water, and then freeze-dried to obtain a composite gel.

[0086] One part by weight of the composite gel was dispersed in 100 parts by weight of deionized water and swollen for 30 min. After the gel was fully swollen, 0.07 parts by weight of ammonium persulfate and 2.5 parts by weight of the urea-functionalized ionic liquid prepared in Example 3 were added. The mixture was heated to 65°C and stirred for 18 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by filtration. After washing with ethanol and deionized water alternately, the product was freeze-dried to obtain the wastewater treatment agent.

[0087] Performance testing showed that the wastewater treatment agent achieved a sulfate removal rate of 95.1%, and after five cycles, the adsorption capacity decreased by 5.5%; the recovered ammonium sulfate yield was 83%, with a purity of 99.0%.

[0088] Example 4:

[0089] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0090] 4.8 parts by weight of aminosulfonic acid and 15.2 parts by weight of urea were stirred and mixed at 82°C for 37 min to obtain a sulfonating agent. 10 parts by weight of alkali lignin were added to 27 parts by weight of the sulfonating agent, and the mixture was stirred at 115°C and 650 r / min for 1.8 h. The temperature was then raised to 140°C and stirred for 5.5 h to obtain a mixture. The mixture was poured into 200 parts by weight of ice water to terminate the reaction. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 70°C for 12 h to obtain sulfonated lignin.

[0091] 2.2 parts by weight of sulfonated lignin and 2.1 parts by weight of nanocellulose were dispersed in 100 parts by weight of deionized water and ultrasonically treated at 235W for 14 min at 3°C ​​to obtain a hybrid sol. The pH of the hybrid sol was adjusted to 9.4, and 0.85 parts by weight of 25wt% glutaraldehyde aqueous solution was added. The mixture was stirred at 47°C for 50 min. After the reaction was completed, the solid product was collected by filtration, washed several times with ethanol and deionized water, and then freeze-dried to obtain a composite gel.

[0092] One part by weight of the composite gel was dispersed in 100 parts by weight of deionized water and swollen for 30 min. After the gel was fully swollen, 0.09 parts by weight of ammonium persulfate and 3 parts by weight of the urea-functionalized ionic liquid prepared in Preparation Example 4 were added. The mixture was heated to 67°C and stirred for 21 h under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled to room temperature, and the solid product was collected by filtration. After washing with ethanol and deionized water alternately, the product was freeze-dried to obtain the wastewater treatment agent.

[0093] Performance testing showed that the wastewater treatment agent achieved a sulfate removal rate of 96.5%, and after five cycles, the adsorption capacity decreased by 4.8%; the recovered ammonium sulfate yield was 84%, with a purity of 99.3%.

[0094] Example 5:

[0095] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0096] 4.8 parts by weight of aminosulfonic acid and 15.2 parts by weight of urea were stirred and mixed at 85°C for 40 min to obtain a sulfonating agent. 10 parts by weight of alkali lignin were added to 30 parts by weight of the sulfonating agent. The mixture was stirred at 120°C and 700 r / min for 2 h. The temperature was then raised to 150°C and stirred for 6 h to obtain a mixture. The mixture was poured into 200 parts by weight of ice water to terminate the reaction. The precipitate was collected by filtration, washed with deionized water, and dried under vacuum at 70°C for 12 h to obtain sulfonated lignin.

[0097] 2.5 parts by weight of sulfonated lignin and 2.2 parts by weight of nanocellulose were dispersed in 100 parts by weight of deionized water and ultrasonically treated at 250W for 15 min at 5℃ to obtain a hybrid sol. The pH of the hybrid sol was adjusted to 9.5, and 0.9 parts by weight of 25wt% glutaraldehyde aqueous solution was added. The mixture was stirred at 50℃ for 60 min. After the reaction was completed, the solid product was collected by filtration, washed several times with ethanol and deionized water, and then freeze-dried to obtain a composite gel.

[0098] One part by weight of the composite gel was dispersed in 100 parts by weight of deionized water and swollen for 30 min. After the gel was fully swollen, 0.1 parts by weight of ammonium persulfate and 3 parts by weight of the urea-functionalized ionic liquid prepared in Preparation Example 5 were added. The mixture was heated to 70°C and stirred for 24 h under a nitrogen atmosphere. After the reaction was completed, it was cooled to room temperature, and the solid product was collected by filtration. After washing with ethanol and deionized water alternately, the product was freeze-dried to obtain the wastewater treatment agent.

[0099] Performance tests showed that the wastewater treatment agent exhibited excellent performance: the sulfate removal rate was 98.2%, and after five adsorption-desorption-regeneration cycles, its adsorption capacity decreased by only 4.5%, demonstrating excellent regeneration performance; the recovered ammonium sulfate yield was 85%, with a purity of up to 99.5%.

[0100] Comparative Example 1:

[0101] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0102] The sulfonated lignin in Example 5 was replaced with alkali lignin, and all other operations were the same as in Example 5.

[0103] Performance testing showed that the wastewater treatment agent achieved a sulfate removal rate of 52.1%, with an adsorption capacity decrease of 18.5% after five cycles. The recovered ammonium sulfate yield was 45%, with a purity of 80.1%. This may be because unsulfonated alkali lignin lacks sulfonic acid groups, resulting in insufficient hydrophilicity and a significantly reduced adsorption capacity for sulfate ions. Its composite effect with nanocellulose and its grafting efficiency with urea-functionalized ionic liquids were also adversely affected.

[0104] Comparative Example 2:

[0105] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0106] Remove the urea-functionalized ionic liquid from Example 5, and keep all other operations the same as in Example 5.

[0107] Performance testing revealed that the wastewater treatment agent achieved a sulfate removal rate of only 28.5%, and after five cycles, the adsorption capacity decreased by 22.3%. The recovered ammonium sulfate yield was 20%, with a purity of 85.0%. This may be due to the absence of urea-functionalized ionic liquid, which caused the wastewater treatment agent to lose its specific and efficient adsorption sites for sulfate ions. At this point, the adsorption performance may only rely on a small amount of physical adsorption and non-specific ion exchange through the composite gel, thus significantly reducing the adsorption performance.

[0108] Comparative Example 3:

[0109] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0110] Remove the composite gel from Example 5, and keep all other operations the same as in Example 5.

[0111] After removing the composite gel carrier, the particles could not be stably formed into separable particles, making effective solid-liquid separation difficult. The adsorption efficiency was also extremely low, making effective quantitative experiments impossible. This demonstrates the crucial role of the composite gel as a carrier framework, providing stable physical support and a high specific surface area for the urea-functionalized ionic liquid, enabling it to form a stable and recyclable morphology. Removing the composite gel would cause the treatment agent to lose its structural integrity, thus failing to perform its intended function.

[0112] Comparative Example 4:

[0113] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0114] The urea-functionalized ionic liquid prepared in Example 5 was replaced with the urea-functionalized ionic liquid prepared in Example 6, and all other operations were the same as in Example 5.

[0115] Performance testing showed that the wastewater treatment agent achieved a sulfate removal rate of 78.7%, but after five cycles, the adsorption capacity decreased by 8.2%. The recovered ammonium sulfate yield was 68%, with a purity of 93.0%. This may be because the number of urea groups in the urea-functionalized ionic liquid decreased from three to one, resulting in poor matching between the single-point binding mode and sulfate ions, weak and unstable binding force, leading to a decrease in adsorption capacity and removal rate. The weaker binding may also be disordered and less selective, making it susceptible to interference from other anions in the wastewater and resulting in low efficiency during elution and regeneration. Ultimately, this leads to a low ammonium sulfate recovery rate and poorer cycle stability of the adsorbent.

[0116] Comparative Example 5:

[0117] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0118] Replace 3 parts by weight of the urea-functionalized ionic liquid prepared in Example 5 with 0.5 parts by weight of the urea-functionalized ionic liquid prepared in Example 5, and keep all other operations the same as in Example 5.

[0119] Performance testing showed that the wastewater treatment agent achieved a sulfate removal rate of 82.3%, but after five cycles, the adsorption capacity decreased by 10.1%. The recovered ammonium sulfate yield was 70%, with a purity of 97.0%. This may be due to insufficient dosage of urea-functionalized ionic liquid, resulting in insufficient effective adsorption sites on the surface of the wastewater treatment agent and failing to fully utilize its adsorption performance, thus leading to a decrease in both adsorption capacity and removal rate.

[0120] Comparative Example 6:

[0121] A method for preparing a wastewater treatment agent for sulfate resource recovery includes the following steps:

[0122] Replace 3 parts by weight of the urea-functionalized ionic liquid prepared in Example 5 with 6 parts by weight of the urea-functionalized ionic liquid prepared in Example 5, and keep all other operations the same as in Example 5.

[0123] Performance testing showed that the wastewater treatment agent achieved a sulfate removal rate of 85.6%, with an adsorption capacity decrease of 9.5% after five cycles. The recovered ammonium sulfate yield was 72%, with a purity of 96.5%. This may be due to excessive use of urea-functionalized ionic liquid, which may have caused some aggregation on the composite gel matrix, thus reducing the accessibility of active sites. In addition, excessive use also increased the material preparation cost without bringing further significant performance improvement, and may even have slightly reduced the specific surface area due to overloading, resulting in a negligible increase in adsorption efficiency.

[0124] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a wastewater treatment agent for sulfate resource recovery, characterized in that, The preparation method includes the following steps: Sulfonating agent and alkali lignin are mixed and stirred to produce sulfonated lignin; Sulfonated lignin and nanocellulose were mixed and ultrasonically treated to obtain a hybrid sol. A composite gel was obtained by stirring and reacting the hybrid sol with a 25 wt% glutaraldehyde aqueous solution. The wastewater treatment agent was prepared by mixing and stirring a composite gel, ammonium persulfate, and urea-functionalized ionic liquid. The preparation method of the urea-functionalized ionic liquid includes the following steps: 2-Imidazole-1-ethylamine, acryloyl chloride, and triethylamine were mixed and stirred to give olefinic imidazole; Tris(2-aminoethyl)amine and 3-chloropropyl isocyanate were mixed and stirred to obtain a urea complex; The urea-functionalized ionic liquid was prepared by mixing and stirring an olefinic imidazole and a urea complex.

2. The preparation method of the wastewater treatment agent for sulfate resource recovery as described in claim 1, characterized in that, The sulfonating agent is obtained by mixing aminosulfonic acid and urea in a weight ratio of 4.8:15.

2.

3. The preparation method of the wastewater treatment agent for sulfate resource recovery as described in claim 1, characterized in that, The weight ratio of the sulfonated lignin, nanocellulose and 25wt% glutaraldehyde aqueous solution is 1.5~2.5:1.8~2.2:0.7~0.

9.

4. The preparation method of the wastewater treatment agent for sulfate resource recovery as described in claim 1, characterized in that, The conditions for the reaction of the hybrid sol and 25wt% glutaraldehyde aqueous solution include a reaction pH of 9-9.5, a reaction temperature of 23-25℃, and a reaction time of 30-40 min.

5. The preparation method of the wastewater treatment agent for sulfate resource recovery as described in claim 1, characterized in that, The weight ratio of 2-imidazol-1-ethylamine, acryloyl chloride, and triethylamine is 4.5~6.5:5.5~7.5:4.5~5.

5.

6. The method for preparing a wastewater treatment agent for sulfate resource recovery as described in claim 1, characterized in that, The weight ratio of the tris(2-aminoethyl)amine to 3-chloropropyl isocyanate is 1.3~1.7:3.4~3.

8.

7. The method for preparing a wastewater treatment agent for sulfate resource recovery as described in claim 1, characterized in that, The weight ratio of the olefinic imidazole and urea complex is 2.58~2.98:2.32~2.

72.

8. The method for preparing a wastewater treatment agent for sulfate resource recovery as described in claim 1, characterized in that, The weight ratio of the composite gel, ammonium persulfate, and urea-functionalized ionic liquid is 1:0.05~0.1:1.5~3.

9. A wastewater treatment agent for the resource recovery of sulfate, characterized in that, It is prepared by the method described in any one of claims 1 to 8 for preparing a wastewater treatment agent for sulfate resource recovery.