Composite treatment agent for municipal sewage and preparation method thereof
By preparing a composite treatment agent containing industrial solid waste such as sulfur and boron sludge, the problems of single function of traditional sewage treatment agents and land occupation by industrial solid waste are solved, and multiple pollutants in urban sewage are removed simultaneously and efficiently and purified in a low-carbon manner.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KAIPING ZHONGQING ENVIRONMENTAL PROTECTION TECH SERVICE CO LTD
- Filing Date
- 2026-03-20
- Publication Date
- 2026-05-19
AI Technical Summary
Traditional wastewater treatment agents have limited functions and cannot remove multiple pollutants simultaneously. They also have problems such as long treatment cycles and the potential for secondary pollution. Furthermore, the dumping of industrial solid waste occupies land resources and causes environmental pollution.
A composite treatment agent composed of industrial solid wastes such as sulfur, boron mud, magnesite powder, and siderite powder, along with epoxidized soybean oil, composite starch nanocrystals, aminated plant-based porous carbon, and sodium silicate, is prepared by granulation. This agent integrates denitrification, phosphorus removal, heavy metal chelation, and porous carbon adsorption, and utilizes the synergistic effect of thiol groups and amino groups to enhance adsorption capacity.
It achieves simultaneous, low-carbon, and efficient removal of multiple pollutants such as nitrogen, phosphorus, and heavy metals from urban sewage, improving purification efficiency, reducing costs, and decreasing sludge production and carbon dioxide emissions.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of water treatment technology, specifically to a composite treatment agent for urban wastewater and its preparation method. Background Technology
[0002] With the acceleration of urbanization, the amount of urban sewage discharge is increasing year by year, and the composition of water quality is becoming increasingly complex. It not only contains a large amount of suspended solids and organic matter, but is also often accompanied by heavy metal ions, nitrogen and phosphorus nutrients and recalcitrant pollutants.
[0003] Traditional wastewater treatment agents often have a single function and are unable to remove multiple pollutants simultaneously. Simply mixing multiple functional components can easily lead to interference between the components, reducing overall performance and causing disintegration and failure during use. Furthermore, traditional wastewater treatment methods often suffer from long treatment cycles and secondary pollution. For example, the problem of excessive total nitrogen in urban wastewater is becoming increasingly prominent; traditional heterotrophic denitrification processes require the addition of large amounts of organic carbon sources, which is not only costly but also leads to increased sludge production and carbon dioxide emissions.
[0004] With the advancement of industrialization, the subsequent treatment of industrial solid waste has become increasingly important. Traditional dumping not only occupies land resources but also easily causes environmental pollution. How to utilize industrial solid wastes such as boron sludge and fly ash to achieve waste-to-waste treatment is a current research hotspot. Therefore, researching how to utilize solid waste to prepare composite water treatment agents for urban sewage has practical significance and economic value. Summary of the Invention
[0005] The purpose of this invention is to provide a composite treatment agent for urban sewage and its preparation method, so as to solve the problems in the prior art.
[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a composite treatment agent for urban wastewater includes the following steps: S1: Crush sulfur, boron mud, magnesite powder, and siderite powder, mix them, and sieve them to obtain sulfur-containing mixed powder. S2: Starch nanocrystals were treated with stearoyl chloride and acryloyl chloride, and then photoinitiated to graft polyethyleneimine derivatives containing thiol groups to obtain composite starch nanocrystals. S3: Sulfur-containing mixed powder, epoxidized soybean oil, composite starch nanocrystals, aminated plant-based porous carbon, sodium silicate, fly ash, and water are mixed and stirred, then granulated to obtain a composite treatment agent for urban sewage.
[0007] Furthermore, in the preparation of the sulfur-containing mixed powder, the mass ratio of sulfur, boron mud, magnesite powder, and siderite powder is 15:2:2:1, and the particle size of the sulfur-containing mixed powder is 250-300 mesh.
[0008] Furthermore, by mass, the raw material composition of the composite treatment agent is as follows: 25-30 parts of sulfur-containing mixed powder, 3-9 parts of epoxidized soybean oil, 1-3 parts of composite starch nanocrystals, 1-3 parts of aminated plant-based porous carbon, 7-11 parts of sodium silicate, 3-7 parts of fly ash, and 10-23 parts of water; the mass ratio of the sum of the composite starch nanocrystals and the aminated plant-based porous carbon to the mass of epoxidized soybean oil is 2:3.
[0009] Furthermore, the preparation of aminated plant-based porous carbon includes the following steps: Plant-based porous carbon and deionized water were mixed, and diethylenetriamine and epichlorohydrin were added. The mixture was refluxed for 2 hours, washed, dried, and sieved to obtain aminated plant-based porous carbon.
[0010] Furthermore, the plant-based porous carbon is one or a combination of several of the following: ulao-based porous carbon, wheat straw-based porous carbon, soybean straw-based porous carbon, and rice-based porous carbon.
[0011] Furthermore, the preparation of ulagra-based porous carbon includes the following steps: Wash, dry, and pulverize the Ula grass, sieve it, and transfer it to a nitrogen atmosphere for carbonization to obtain Ula grass charcoal. Place the Ula grass charcoal in NaOH solution and soak it at 20-100℃ for 1-4 hours. After removing it, dry it to obtain pretreated Ula grass charcoal. Mix the pretreated Ula grass charcoal with solid NaOH, transfer it to a nitrogen atmosphere, keep it at 790-810℃ for 30-35 minutes, cool it, wash it until the pH value is 7, and dry it to obtain Ula grass-based porous carbon.
[0012] Furthermore, the preparation of composite starch nanocrystals includes the following steps: (1) Mix starch nanocrystals and ethyl acetate, add pyridine, stir at 45-50℃ for 30-35 min, add stearoyl chloride and acryloyl chloride, continue to keep warm for 2 h, cool, filter under reduced pressure, rinse, dry, and obtain double bonded starch nanocrystals. (2) Under a nitrogen atmosphere, double-bonded starch nanocrystals, methanol, and deionized water were mixed, and a mixture of polyethyleneimine derivative containing thiol groups, photoinitiator, and N-methylpyrrolidone was added. The mixture was irradiated at 40-50℃ under 365nm light for 4-6 hours, centrifuged, washed, and dried to obtain composite starch nanocrystals.
[0013] Further, the preparation steps of starch nanocrystals are as follows: glutinous rice starch powder and sulfuric acid solution are mixed, stirred at 200 rpm for 7 days in a 40℃ water bath, the pH value is adjusted to neutral, centrifuged, washed, freeze-dried, ground, and sieved to obtain starch nanocrystals.
[0014] Furthermore, the mass ratio of double-bonded starch nanocrystals to thiol-containing polyethyleneimine derivatives is 2.4:1.1.
[0015] Furthermore, the preparation of polyethyleneimine derivatives containing thiol groups includes the following steps: 1) Mix anhydrous dichloromethane and DL-homocysteine thiolactone hydrochloride, add triethylamine, cool to 0°C, add adipic acid chloride, heat to 18-25°C and stir for 2-3 hours, rotary evaporate, wash with dilute hydrochloric acid and deionized water in sequence, and dry to obtain N,N'-adipoxythiolactone. 2) N,N'-adipic thiolactone is mixed with polyethyleneimine and N-methylpyrrolidone and magnetically stirred at 45-50℃ for 5-6 hours to obtain a polyethyleneimine derivative containing thiol groups.
[0016] Furthermore, the molar ratio of the thiolactone group in N,N'-adipoxythiolactone to the amino group in polyethyleneimine is 1:1.5.
[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a composite treatment agent for urban sewage and its preparation method. Through optimization of composition and process, a green and environmentally friendly, non-fired composite treatment agent with high efficiency in nitrogen and phosphorus removal and heavy metal adsorption is prepared, which can effectively improve the condition of urban sewage and improve purification efficiency.
[0018] In response to the requirements of green production, this invention selects industrial solid waste such as boron mud and fly ash as raw materials for the treatment agent, uses epoxidized soybean oil from biomass as a binder, and uses starch from biomass and plant-based porous carbon as adsorbents. These are mixed with sodium silicate and water and granulated to prepare a non-fired composite treatment agent that integrates multiple functions such as sulfur autotrophic denitrification, phosphorus removal, heavy metal chelation, and porous carbon adsorption. When applied to urban wastewater treatment, it can achieve simultaneous, low-carbon, and efficient removal of multiple pollutants such as nitrogen, phosphorus, and heavy metals. After granulation, the composite treatment agent of this invention can be used as a packing material in a biological filter to support the growth of sulfur autotrophic denitrifying bacteria, or it can be directly added to the pretreatment or advanced treatment unit of a wastewater treatment system.
[0019] To improve the uniformity and stability of starch nanocrystal dispersion in composite treatment agents, starch nanocrystals were treated with stearoyl chloride and acryloyl chloride to obtain double-bonded starch nanocrystals containing long alkyl chains and carbon-carbon double bonds. Then, a polyethyleneimine derivative containing thiol groups was grafted onto the double-bonded thiol group using photogravure, which significantly improved the adsorption and purification properties of the starch nanocrystals. The polyethyleneimine derivative containing thiol groups was prepared by using DL-homocysteine thiolactone hydrochloride and adipic acid chloride as raw materials to prepare N,N'-adipoyl thiolactone, which was then ring-opened with polyethyleneimine to obtain a crosslinking agent containing thiol, amino, and amide bonds. The thiol groups have a strong chelating ability for metal ions such as mercury and lead, while the abundant amino groups in the polyethyleneimine skeleton can synergistically adsorb anionic dyes and heavy metal ions through electrostatic and coordination interactions. The introduction of long-chain alkyl groups improves its water resistance.
[0020] In this invention, inexpensive and readily available plant-based porous carbon is combined with starch nanocrystals as an adsorbent. Using *Ula grass* as raw material, biochar is prepared through carbonization. NaOH is used as an activator for surface desiliconization and alkali activation to prepare *Ula grass* porous carbon. To improve its uniform dispersion in the raw materials, diethylenetriamine and epichlorohydrin are used to aminate it. By controlling the mass ratio between the sum of the mass of plant-based porous carbon and composite starch nanocrystals and epoxidized soybean oil, the complexity of the cross-linked network in the composite treatment agent is increased. This synergistic effect with fly ash improves the mechanical strength and durability of the composite treatment agent. Detailed Implementation
[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0022] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0023] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.
[0024] Example 1: A method for preparing a composite treatment agent for urban wastewater, comprising the following steps: S1: Crush sulfur, boron mud, magnesite powder, and siderite powder, mix them, and sieve them to obtain sulfur-containing mixed powder. In the preparation of sulfur-containing mixed powder, the mass ratio of sulfur, boron mud, magnesite powder, and siderite powder is 15:2:2:1, and the particle size of the sulfur-containing mixed powder is 300 mesh. S2: The preparation steps of composite starch nanocrystals are as follows: (1) Mix 9g starch nanocrystals and 27g ethyl acetate, add 0.45g pyridine, stir at 45℃ for 35min, add 0.54g stearoyl chloride and 0.54g acryloyl chloride, continue to keep warm for 2h, cool, filter under reduced pressure, rinse, dry, and obtain double bonded starch nanocrystals. (2) Under a nitrogen atmosphere, 2.4 g of double-bonded starch nanocrystals, 15 mL of methanol, and 15 mL of deionized water were mixed, and 1.1 g of polyethyleneimine derivative containing thiol groups, 0.07 g of photoinitiator, and 15 mL of N-methylpyrrolidone mixture were added. The mixture was heated to 40 °C and irradiated under 365 nm light for 4 h. After centrifugation, washing, and drying, composite starch nanocrystals were obtained. The preparation of the polyethyleneimine derivative containing a thiol group includes the following steps: 1) Mix 10 mL of anhydrous dichloromethane and 5.03 g of DL-homocysteine thiolactone hydrochloride, add 5.2 mL of triethylamine, cool to 0 °C, add 0.73 g of adipic acid chloride, heat to 18 °C and stir for 3 h, rotary evaporate, wash successively with 30 mL of dilute hydrochloric acid and 80 mL of deionized water, and dry to obtain N,N'-adipoxythiolactone; 2) N,N'-adipoxythiolactone and polyethyleneimine were added in a molar ratio of 1:1.5 between the number of thiolactone functional groups and the amino groups of polyethyleneimine. N-methylpyrrolidone was used as a solvent, and the mixture was stirred at 50°C for 6 hours to obtain a polyethyleneimine derivative containing thiol groups. S3: Mix sulfur-containing mixed powder, epoxidized soybean oil, composite starch nanocrystals, aminated plant-based porous carbon, sodium silicate, fly ash, and deionized water, granulate, and dry to obtain a composite treatment agent for urban sewage. The composite treatment agent, by mass fraction, comprises: 25 parts sulfur-containing mixed powder, 3 parts epoxidized soybean oil, 1 part composite starch nanocrystals, 1 part aminated plant-based porous carbon, 7 parts sodium silicate, 3 parts fly ash, and 10 parts deionized water; the mass ratio of the sum of the composite starch nanocrystals and the aminated plant-based porous carbon to the mass of the epoxidized soybean oil is 2:3. The preparation of the aminated plant-based porous carbon includes the following steps: Mix 2g of plant-based porous carbon with 5mL of deionized water, add 1mL of diethylenetriamine and 2mL of epichlorohydrin, reflux for 2h, wash, dry, and pass through a 100-mesh sieve to obtain aminated plant-based porous carbon. The plant-based porous carbon is Ula grass-based porous carbon, and its preparation includes the following steps: Wash, dry, and pulverize the Ula grass, pass it through an 80-mesh sieve, and then carbonize it at 500℃ for 55 minutes under a nitrogen atmosphere to obtain Ula grass char. Place the prepared Ula grass char in a 5wt% NaOH solution and immerse it at 80℃ for 4 hours. After removal, dry it to obtain pretreated Ula grass char. Mix the pretreated Ula grass char and solid NaOH at a mass ratio of 1:4, grind them together, transfer them to a nitrogen atmosphere, keep them at 800℃ for 30 minutes, cool them, wash them until the pH value is 7, and dry them to obtain Ula grass-based porous carbon.
[0025] Example 2: A method for preparing a composite treatment agent for urban wastewater, comprising the following steps: S1: Crush sulfur, boron mud, magnesite powder, and siderite powder, mix them, and sieve them to obtain sulfur-containing mixed powder. In the preparation of sulfur-containing mixed powder, the mass ratio of sulfur, boron mud, magnesite powder, and siderite powder is 15:2:2:1, and the particle size of the sulfur-containing mixed powder is 300 mesh. S2: The preparation steps of composite starch nanocrystals are as follows: (1) Mix 9g starch nanocrystals and 27g ethyl acetate, add 0.45g pyridine, stir at 48℃ for 33min, add 0.54g stearoyl chloride and 0.54g acryloyl chloride, continue to keep warm for 2h, cool, filter under reduced pressure, rinse, and dry to obtain double bonded starch nanocrystals. (2) Under a nitrogen atmosphere, 2.4 g of double-bonded starch nanocrystals, 15 mL of methanol, and 15 mL of deionized water were mixed, and 1.1 g of polyethyleneimine derivative containing thiol groups, 0.07 g of photoinitiator, and 15 mL of N-methylpyrrolidone mixture were added. The mixture was heated to 45 °C and irradiated under 365 nm light for 5 h. After centrifugation, washing, and drying, composite starch nanocrystals were obtained. The preparation of the polyethyleneimine derivative containing a thiol group includes the following steps: 1) Mix 10 mL of anhydrous dichloromethane and 5.03 g of DL-homocysteine thiolactone hydrochloride, add 5.2 mL of triethylamine, cool to 0 °C, add 0.73 g of adipic acid chloride, heat to 20 °C and stir for 2.5 h, rotary evaporate, wash successively with 30 mL of dilute hydrochloric acid and 80 mL of deionized water, and dry to obtain N,N'-adipoxythiolactone; 2) N,N'-adipoxythiolactone and polyethyleneimine were added in a molar ratio of 1:1.5 between the number of thiolactone functional groups and the amino groups of polyethyleneimine. N-methylpyrrolidone was used as a solvent, and the mixture was stirred at 50°C for 6 hours to obtain a polyethyleneimine derivative containing thiol groups. S3: Mix sulfur-containing mixed powder, epoxidized soybean oil, composite starch nanocrystals, aminated plant-based porous carbon, sodium silicate, fly ash, and deionized water, granulate, and dry to obtain a composite treatment agent for urban sewage. The composite treatment agent, by mass fraction, comprises: 26 parts sulfur-containing mixed powder, 6 parts epoxidized soybean oil, 2 parts composite starch nanocrystals, 2 parts aminated plant-based porous carbon, 9 parts sodium silicate, 5 parts fly ash, and 18 parts deionized water; the mass ratio of the sum of the composite starch nanocrystals and the aminated plant-based porous carbon to the mass of the epoxidized soybean oil is 2:3. The preparation of the aminated plant-based porous carbon includes the following steps: Mix 2g of plant-based porous carbon with 5mL of deionized water, add 1mL of diethylenetriamine and 2mL of epichlorohydrin, reflux for 2h, wash, dry, and pass through a 100-mesh sieve to obtain aminated plant-based porous carbon. The plant-based porous carbon is Ula grass-based porous carbon, and its preparation includes the following steps: Wash, dry, and pulverize the Ula grass, pass it through an 80-mesh sieve, and then carbonize it at 500℃ for 60 minutes under a nitrogen atmosphere to obtain Ula grass char. Place the prepared Ula grass char in a 5wt% NaOH solution and immerse it at 85℃ for 2 hours. After removal, dry it to obtain pretreated Ula grass char. Mix the pretreated Ula grass char and solid NaOH at a mass ratio of 1:4, grind them together, transfer them to a nitrogen atmosphere, keep them at 800℃ for 30 minutes, cool them, wash them until the pH value is 7, and dry them to obtain Ula grass-based porous carbon.
[0026] Example 3: A method for preparing a composite treatment agent for urban wastewater, comprising the following steps: S1: Crush sulfur, boron mud, magnesite powder, and siderite powder, mix them, and sieve them to obtain sulfur-containing mixed powder. In the preparation of sulfur-containing mixed powder, the mass ratio of sulfur, boron mud, magnesite powder, and siderite powder is 15:2:2:1, and the particle size of the sulfur-containing mixed powder is 300 mesh. S2: The preparation steps of composite starch nanocrystals are as follows: (1) Mix 9g starch nanocrystals and 27g ethyl acetate, add 0.45g pyridine, stir at 50℃ for 30min, add 0.54g stearoyl chloride and 0.54g acryloyl chloride, continue to keep warm for 2h, cool, filter under reduced pressure, rinse, dry, and obtain double bonded starch nanocrystals. (2) Under a nitrogen atmosphere, 2.4 g of double-bonded starch nanocrystals, 15 mL of methanol, and 15 mL of deionized water were mixed, and 1.1 g of polyethyleneimine derivative containing thiol groups, 0.07 g of photoinitiator, and 15 mL of N-methylpyrrolidone mixture were added. The mixture was heated to 50 °C and irradiated under 365 nm light for 6 h. After centrifugation, washing, and drying, composite starch nanocrystals were obtained. The preparation of the polyethyleneimine derivative containing a thiol group includes the following steps: 1) Mix 10 mL of anhydrous dichloromethane and 5.03 g of DL-homocysteine thiolactone hydrochloride, add 5.2 mL of triethylamine, cool to 0 °C, add 0.73 g of adipic acid chloride, heat to 25 °C and stir for 2 h, rotary evaporate, wash successively with 30 mL of dilute hydrochloric acid and 80 mL of deionized water, and dry to obtain N,N'-adipoxythiolactone; 2) N,N'-adipoxythiolactone and polyethyleneimine were added in a molar ratio of 1:1.5 between the number of thiolactone functional groups and the amino groups of polyethyleneimine. N-methylpyrrolidone was used as a solvent, and the mixture was magnetically stirred at 50°C for 6 hours to obtain a polyethyleneimine derivative containing thiol groups. S3: Mix sulfur-containing mixed powder, epoxidized soybean oil, composite starch nanocrystals, aminated plant-based porous carbon, sodium silicate, fly ash, and deionized water, granulate, and dry to obtain a composite treatment agent for urban sewage. The composite treatment agent, by mass fraction, comprises: 30 parts sulfur-containing mixed powder, 9 parts epoxidized soybean oil, 3 parts composite starch nanocrystals, 3 parts aminated plant-based porous carbon, 11 parts sodium silicate, 7 parts fly ash, and 23 parts deionized water; the mass ratio of the sum of the composite starch nanocrystals and the aminated plant-based porous carbon to the mass of the epoxidized soybean oil is 2:3. The preparation of the aminated plant-based porous carbon includes the following steps: Mix 2g of plant-based porous carbon with 5mL of deionized water, add 1mL of diethylenetriamine and 2mL of epichlorohydrin, reflux for 2h, wash, dry, and pass through a 100-mesh sieve to obtain aminated plant-based porous carbon. The plant-based porous carbon is Ula grass-based porous carbon, and its preparation includes the following steps: Wash, dry, and pulverize the Ula grass, pass it through an 80-mesh sieve, and then carbonize it at 500℃ for 65 minutes under a nitrogen atmosphere to obtain Ula grass charcoal. Place the prepared Ula grass charcoal in a 5wt% NaOH solution and immerse it at 90℃ for 1 hour. After removal, dry it to obtain pretreated Ula grass charcoal. Mix the pretreated Ula grass charcoal and solid NaOH at a mass ratio of 1:4, grind them together, transfer them to a nitrogen atmosphere, keep them at 800℃ for 30 minutes, cool them, wash them until the pH value is 7, and dry them to obtain Ula grass-based porous carbon.
[0027] Comparative Example 1: Using Example 3 as the control group, the composite starch nanocrystals were replaced with starch nanocrystals, while other processes were normal.
[0028] Comparative Example 2: Using Example 3 as the control group, aminated ulagra-based porous carbon was replaced with ulagra-based porous carbon, while other processes were normal.
[0029] Comparative Example 3: Using Example 3 as the control group, the sum of the mass of the composite starch nanocrystals and the aminated plant-based porous carbon was 2:2 with the mass of the epoxidized soybean oil, i.e., 6 parts of epoxidized soybean oil, and other processes were normal.
[0030] In the examples and comparative examples, the preparation steps of starch nanocrystals are as follows: 5g of glutinous rice starch powder and 50mL of 3.16mol / L sulfuric acid solution are mixed and stirred at 200rpm for 7 days in a 40℃ water bath. The pH value is adjusted to neutral, and the mixture is centrifuged, washed, freeze-dried, ground, and passed through a 200-mesh sieve to obtain starch nanocrystals.
[0031] Sources of raw materials used (for illustrative purposes only): Boron mud (by mass fraction, the main elemental composition is: sulfur trioxide 0.95, calcium oxide 3.41, silicon oxide 16.1, aluminum oxide 1.64, magnesium oxide 38.2, sodium oxide 2.2), magnesite powder (by mass fraction, the main elemental composition is: ferric oxide 0.6, sulfur 0.005, sodium oxide 0.2, silicon oxide 4.15, aluminum oxide 0.54, magnesium oxide 41.2, potassium oxide 0.09), siderite powder (main chemical component is FeCO3), photoinitiator (1173), DL-homocysteine thiolactone hydrochloride (6038-19-3, 98%), Ula grass: commercially available; fly ash A01085: Wuhan Jiyesheng Chemical Co., Ltd.; epoxidized soybean oil E107074, polyethyleneimine E107077, sulfur S106611: Aladdin reagent.
[0032] Performance testing: The composite treatment agents prepared in the examples and comparative examples were tested: A composite treatment agent with spherical particles of 3 mm in size was filled into the reactor, with a bulk density of 0.95 g / cm³. 3 The reactor was fed with water via a peristaltic pump at a stable temperature of 25°C. Activated sludge (residual sludge from the secondary sedimentation tank of a wastewater treatment plant) was inoculated. The hydraulic retention time (HRT) was 4 hours. Simulating urban wastewater influent, the influent flow rate was 1.25 mL / min. Water with COD of 400 mg / L, TN (total nitrogen) of 75 mg / L, and TP (total phosphorus) of 4 mg / L was prepared to simulate urban wastewater. The reactor was run continuously for 15 days, and the removal rates of COD, TN, and TP in the wastewater were tested. TN was determined using the alkaline potassium persulfate digestion-ultraviolet spectrophotometry method, TP was determined using the ammonium molybdate spectrophotometry method, and COD was determined using the dichromate method. Prepare 100 mL of 20 mg / Lb solution respectively 2+ Test solution, 100 mL 40 mg / L Cr 6+ The test solution was subjected to 7 cycles of treatment with the composite agent, with one cycle per day. The removal rates of chromium ions and lead ions were then tested, and the removal rate was calculated as (X0-X1) / X0×100%; (X0 is the initial concentration of COD, TN, TP, and metal ions, and X1 is the concentration of COD, TN, TP, and metal ions after treatment); the results are shown in Table 1. Table 1
[0033] This invention provides a composite treatment agent for urban sewage and its preparation method. Through optimization of composition and process, a green and environmentally friendly, non-fired composite treatment agent with high efficiency in nitrogen and phosphorus removal and heavy metal adsorption is prepared, which can effectively improve the condition of urban sewage and improve purification efficiency.
[0034] A comparison of Example 3 and Comparative Example 1 shows that, in order to improve the uniformity and stability of starch nanocrystal dispersion in the composite treatment agent, starch nanocrystals were treated with stearoyl chloride and acryloyl chloride to obtain double-bonded starch nanocrystals containing long alkyl chains and carbon-carbon double bonds. Then, a polyethyleneimine derivative containing thiol groups was grafted onto the double-bonded thiol group using photogravure, which significantly improved the adsorption and purification properties of the starch nanocrystals. The polyethyleneimine derivative containing thiol groups was prepared by using DL-homocysteine thiolactone hydrochloride and adipic acid chloride as raw materials to prepare N,N'-adipoyl thiolactone, which was then ring-opened with polyethyleneimine to obtain a crosslinking agent containing thiol, amino, and amide bonds. The thiol groups have a strong chelating ability for heavy metal ions such as mercury, lead, and cadmium. The large number of amino groups in the polyethyleneimine skeleton can synergistically adsorb anionic dyes and heavy metal ions through electrostatic and coordination interactions. The hydrophobic microdomains formed by the long-chain alkyl groups can effectively capture hydrophobic organic pollutants.
[0035] Comparing Example 3 with Comparative Examples 2 and 3, it can be seen that in this invention, inexpensive and readily available plant-based porous carbon and starch nanocrystals are combined as adsorbents. Ula grass is used as raw material, and biochar is prepared through carbonization. NaOH is used as an activator to perform surface desiliconization and alkali activation to prepare Ula grass porous carbon. To improve its uniformity of dispersion in the raw materials, diethylenetriamine and epichlorohydrin are used to aminate it. By controlling the mass ratio between the sum of the mass of plant-based porous carbon and composite starch nanocrystals and epoxidized soybean oil, the complexity of the cross-linked network in the composite treatment agent is increased. This synergistic effect with fly ash improves the mechanical strength of the composite treatment agent and enhances its various properties.
[0036] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the present invention's specification under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. A method for preparing a composite treatment agent for urban sewage, characterized in that, Includes the following steps: S1: Crush sulfur, boron mud, magnesite powder, and siderite powder, mix them, and sieve them to obtain sulfur-containing mixed powder. S2: Starch nanocrystals were treated with stearoyl chloride and acryloyl chloride, and then grafted with polyethyleneimine derivatives containing thiol groups to obtain composite starch nanocrystals. S3: Sulfur-containing mixed powder, epoxidized soybean oil, composite starch nanocrystals, aminated plant-based porous carbon, sodium silicate, fly ash, and water are mixed and stirred, then granulated to obtain a composite treatment agent for urban sewage.
2. The method for preparing a composite treatment agent for urban sewage according to claim 1, characterized in that, In the preparation of sulfur-containing mixed powder, the mass ratio of sulfur, boron mud, magnesite powder, and siderite powder is 15:2:2:1, and the particle size of the sulfur-containing mixed powder is 250-300 mesh.
3. The method for preparing a composite treatment agent for urban sewage according to claim 1, characterized in that, The composite treatment agent, by mass parts, comprises: 25-30 parts of sulfur-containing mixed powder, 3-9 parts of epoxidized soybean oil, 1-3 parts of composite starch nanocrystals, 1-3 parts of aminated plant-based porous carbon, 7-11 parts of sodium silicate, 3-7 parts of fly ash, and 10-23 parts of water; the mass ratio of the sum of the composite starch nanocrystals and the aminated plant-based porous carbon to the mass of epoxidized soybean oil is 2:
3.
4. The method for preparing a composite treatment agent for urban sewage according to claim 1, characterized in that, The preparation of the aminated plant-based porous carbon includes the following steps: Plant-based porous carbon and deionized water were mixed, and diethylenetriamine and epichlorohydrin were added. The mixture was refluxed for 2 hours, washed, dried, and sieved to obtain aminated plant-based porous carbon.
5. The method for preparing a composite treatment agent for urban sewage according to claim 4, characterized in that, The plant-based porous carbon is one or a combination of several of the following: ulao grass-based porous carbon, wheat straw-based porous carbon, soybean straw-based porous carbon, and rice-based porous carbon.
6. The method for preparing a composite treatment agent for urban sewage according to claim 5, characterized in that, The preparation of the ulagra-based porous carbon includes the following steps: Wash, dry, and pulverize the Ula grass, sieve it, and transfer it to a nitrogen atmosphere for carbonization to obtain Ula grass char. Immerse the Ula grass char in NaOH solution, remove it, and dry it to obtain pretreated Ula grass char. Mix the pretreated Ula grass char with solid NaOH, transfer it to a nitrogen atmosphere, keep it at 790-810℃ for 30-35 minutes, cool it, wash it until the pH value is 7, and dry it to obtain Ula grass-based porous carbon.
7. The method for preparing a composite treatment agent for urban sewage according to claim 1, characterized in that, The preparation of the composite starch nanocrystals includes the following steps: (1) Mix starch nanocrystals and ethyl acetate, add pyridine, stir at 45-50℃ for 30-35 min, add stearoyl chloride and acryloyl chloride, continue to keep warm for 2 h, cool, filter under reduced pressure, rinse, dry, and obtain double bonded starch nanocrystals. (2) Under a nitrogen atmosphere, double-bonded starch nanocrystals, methanol, and deionized water were mixed, and a mixture of polyethyleneimine derivative containing thiol groups, photoinitiator, and N-methylpyrrolidone was added. The mixture was heated to 40-50℃ and irradiated under 365nm light for 4-6 hours. After centrifugation, washing, and drying, composite starch nanocrystals were obtained.
8. The method for preparing a composite treatment agent for urban sewage according to claim 7, characterized in that, The mass ratio of the double-bonded starch nanocrystals to the thiol-containing polyethyleneimine derivative is 2.4:1.
1.
9. The method for preparing a composite treatment agent for urban sewage according to claim 7, characterized in that, The preparation of the polyethyleneimine derivative containing a thiol group includes the following steps: 1) Mix anhydrous dichloromethane and DL-homocysteine thiolactone hydrochloride, add triethylamine, cool to 0°C, add adipic acid chloride, heat to 18-25°C and stir for 2-3 hours, rotary evaporate, wash with dilute hydrochloric acid and deionized water in sequence, and dry to obtain N,N'-adipoxythiolactone. 2) Mix N,N'-adipoxythiolactone, polyethyleneimine, and N-methylpyrrolidone, and stir at 45-50℃ for 5-6 hours to obtain a polyethyleneimine derivative containing thiol groups.
10. A composite treatment agent for urban sewage, characterized in that, Prepared by the preparation method according to any one of claims 1-9.