A composite material for tunnel construction sewage treatment and a sewage treatment method thereof

Abstract

The application relates to the technical field of sewage treatment, and discloses a composite material for tunnel construction sewage treatment and a sewage treatment method thereof, which is made from the following components in parts by weight: lanthanum-aluminum bimetal modified attapulgite, dopamine-coated modified magnetic nano composite particles, chitosan grafted polyacrylamide, aminotri(methylene) phosphonic acid, nano hydroxyapatite, calcium bicarbonate, polyaspartic acid zinc, sodium lignosulfonate and deionized water; through scientific proportioning of the components and optimization of key preparation processes, a synergistically efficient technical scheme is formed. From the micro level, the functions of the components are complementary and synergistic, ensuring the synchronous and efficient removal of suspended solids, heavy metal ions and organic pollutants; a series of problems existing in traditional tunnel construction sewage treatment, such as poor purification effect, slow separation speed, high cost and insufficient environmental protection, are solved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically a composite material for treating wastewater during tunnel construction and a method for wastewater treatment thereon. Background Technology

[0002] With the rapid advancement of transportation infrastructure construction, the scale and number of tunnel projects have continued to grow, and the large amount of wastewater generated during construction has become an environmental problem that urgently needs to be addressed. The sources of wastewater from tunnel construction are complex, including geological water inflows, equipment washing water, dust suppression water, and grouting operation wastewater. Its water composition is highly variable, containing not only high concentrations of suspended solids such as rock dust and silt, but also heavy metal ions, petroleum substances, and some organic pollutants introduced during construction. Direct discharge would seriously pollute the surrounding soil and water bodies, especially in sensitive areas such as mountainous water conservation areas, and could even threaten drinking water safety.

[0003] Currently, wastewater treatment in tunnel construction mainly employs traditional processes such as sedimentation and simple flocculation. Some projects may use conventional adsorption materials as an auxiliary treatment method, but these technologies have significant limitations. Traditional sedimentation processes rely on natural settling, require a large area, and have long treatment cycles, making them unsuitable for the limited space and fluctuating wastewater discharge volumes at construction sites. Conventional flocculants have poor selectivity for heavy metal ions, resulting in treated water that fails to meet the upgraded discharge standards, and the slow floc separation can easily cause secondary pollution.

[0004] Furthermore, existing technologies often directly transport sludge from wastewater treatment processes for disposal, increasing costs and wasting potentially recyclable functional components. With increasingly stringent environmental requirements, traditional treatment technologies can no longer meet the comprehensive demands of "high-efficiency purification, rapid separation, and resource recovery." Therefore, developing a wastewater treatment composite material and supporting process that is suitable for tunnel construction scenarios, offers stable treatment results, and is energy-efficient and environmentally friendly has become an urgent need in this field. Summary of the Invention

[0005] To address the problems in the prior art, the present invention provides a composite material for treating wastewater during tunnel construction.

[0006] The technical solution adopted by this invention to solve its technical problem is: a composite material for treating sewage in tunnel construction, which is made of the following components in parts by weight: 15-25 parts of lanthanum-aluminum bimetallic modified attapulgite, 10-18 parts of dopamine-coated modified magnetic nanocomposite particles, 8-15 parts of chitosan-grafted polyacrylamide, 5-12 parts of aminotrimethylenephosphonic acid, 3-8 parts of nano-hydroxyapatite, 2-6 parts of calcium bicarbonate, 1-5 parts of zinc polyaspartate, 1-4 parts of sodium lignosulfonate, and 30-50 parts of deionized water. The lanthanum-aluminum bimetallic modified attapulgite was prepared with microwave assistance.

[0007] As a further technical solution, the preparation method of the lanthanum-aluminum bimetallic modified attapulgite includes the following steps: S1. Attapulgite is crushed and passed through a 200-mesh sieve. A hydrochloric acid solution with a mass fraction of 5-8% is added, with a solid-liquid ratio of 1:10 (g / mL). The mixture is stirred and activated at 60-70℃ for 2-3 hours. It is then filtered, washed until neutral, and dried to obtain acidified attapulgite. S2 Add acidified attapulgite to deionized water, ultrasonically disperse for 30-40 minutes to form a suspension, add a mixed solution of lanthanum nitrate and aluminum chloride, wherein the molar ratio of lanthanum nitrate to aluminum chloride is 1:2-3, and the total mass of the bimetallic compound is 8-15% of the mass of acidified attapulgite, and stir to mix well. S3 was adjusted to pH 9-10 by adding 10-15% sodium hydroxide solution, then transferred to a polytetrafluoroethylene-lined microwave reactor. Microwave-assisted crystallization was carried out at 80-90℃ and 200-300W microwave power for 2-3 hours. The mixture was filtered, washed until neutral, dried at 105-110℃ for 6-8 hours, and ground through a 300-mesh sieve to obtain lanthanum-aluminum bimetallic modified attapulgite.

[0008] As a further technical solution, the preparation method of the dopamine-coated modified magnetic nanocomposite particles includes the following steps: a) Add multi-walled carbon nanotubes to a nitric acid solution with a mass fraction of 65-70% at a material-to-liquid ratio of 1:10-12, reflux at 80-90℃ for 2-3 hours to carry out carboxylation modification, filter, wash until neutral, and dry for later use. b. Dissolve ferric chloride and ferrous chloride in deionized water at a molar ratio of 2:1, with a ferric chloride mass fraction of 3-4%. Under nitrogen protection, stir at 50-60℃ for 30 minutes. Add carboxylated carbon nanotubes at a material-to-liquid ratio of 1:6-8 and ultrasonically disperse for 20-30 minutes. c. Add 25-30% ammonia water dropwise to adjust the pH to 10-11, react at 60-70℃ for 2-3 hours, filter, wash, and dry to obtain the nanocomposite particle intermediate. d. Add the nanocomposite particle intermediate to a 0.05-0.1 mol / L Tris-HCl buffer solution, adjust the pH to 8.5-9.0, add dopamine hydrochloride (5-8% of the mass of the nanocomposite particle intermediate), stir and react at 25-30℃ for 6-8 h, filter and wash until neutral, and vacuum dry at 60-70℃ for 4-5 h to obtain dopamine-coated modified magnetic nanocomposite particles.

[0009] As a further technical solution, the method for preparing composite materials includes: Pre-dispersion: First, add deionized water to the stirred tank, then add sodium lignosulfonate, zinc polyaspartate, and calcium bicarbonate in sequence, and start stirring until completely dissolved to obtain the basic solution; the stirring speed is 150-200 r / min; Solid-phase dispersion: Lanthanum-aluminum bimetallic modified attapulgite and dopamine-coated modified magnetic nanocomposite particles are added to the base solution and dispersed in multiple stages to ensure uniform dispersion of solid particles. Compound combination: Chitosan grafted with polyacrylamide, aminotrimethylene phosphonic acid, and nano hydroxyapatite are slowly added to the above dispersion, the stirring speed is adjusted to 250-300 r / min, and the mixture is stirred at a constant temperature of 30-40℃ for 30-40 min. Drying and molding: The reaction mixture is transferred to a spray dryer to obtain a powdered composite material with a particle size of 100-200μm.

[0010] As a further technical solution, the multi-stage dispersion process is as follows: first, ultrasonic dispersion for 20-30 minutes at a power of 300-400W, then high-speed stirring for 15 minutes at a speed of 500-600r / min.

[0011] As a further technical solution, the inlet temperature of the spray dryer is 120-140℃ and the outlet temperature is 60-70℃.

[0012] As a further technical solution, the number-average molecular weight of the polyaspartic zinc is 5000-8000.

[0013] A wastewater treatment method for tunnel construction using composite materials includes the following steps: (1) The wastewater from tunnel construction was introduced into the equalization tank, and suspended impurities with a particle size >5mm were removed by a stainless steel screen with a pore size of 5mm. The pH value, suspended solids concentration and heavy metal ion concentration of the wastewater were measured. (2) Pump the adjusted sewage into the reaction tank, add the composite material, turn on the stirring device, stir rapidly at 200-300 r / min for 8-10 min, and introduce oxygen at 0.5-0.8 L / min during the stirring process to make the composite material and sewage fully mix and react; (3) Reduce the stirring speed to 50-80 r / min and stir slowly for 15-25 min; (4) Apply a pulsed magnetic field and let stand for 10-15 minutes to achieve rapid separation of magnetic flocs; (5) After separation, the clear water enters the sedimentation tank for further clarification. After the water quality meets the standards, it is discharged or reused. The separated magnetic sludge is recycled by a high gradient magnetic separator. The recycled magnetic components are washed with 0.1 mol / L sulfuric acid solution and reused in the preparation of composite materials. The sludge residue is dewatered and transported for disposal.

[0014] As a further technical solution, in step (2), the composite material is added at 0.5-2.0% of the wastewater mass.

[0015] As a further technical solution, the magnetic field strength of the pulsed magnetic field in step (4) is 300-500mT and the pulse frequency is 10-20Hz.

[0016] The beneficial effects of this invention are: This invention utilizes microwave-assisted preparation of lanthanum-aluminum bimetallic modified attapulgite, resulting in abundant active adsorption sites on its surface. The synergistic effect of the lanthanum and aluminum bimetals enhances the chelation capacity for heavy metal ions and the physical adsorption performance for suspended solids, thereby significantly increasing the adsorption capacity of pollutants and solving the problem of poor removal efficiency for various types of pollutants by traditional adsorption materials. Dopamine-coated modified magnetic nanocomposite particles not only enhance the adsorption of organic pollutants through the adhesion effect of dopamine, but their magnetic core also provides a basis for subsequent rapid separation. Simultaneously, the high specific surface area of ​​carbon nanotubes further expands the adsorption contact area, forming an adsorption complementarity with the lanthanum-aluminum bimetallic modified attapulgite, achieving comprehensive capture of different types of pollutants.

[0017] Chitosan-grafted polyacrylamide, as a polymeric flocculant, uses its amino and amide groups on its molecular chain to bridge tiny adsorbent particles into large flocs. Aminotrimethylenephosphonic acid further stabilizes the adsorption of heavy metal ions through complexation. The addition of nano-hydroxyapatite not only supplements adsorption sites but also regulates the system's reaction environment, synergistically optimizing the flocculation-adsorption effect with other components. Auxiliary components such as zinc polyaspartate and sodium lignosulfonate effectively improve the dispersibility of solid particles, avoiding the problem of active site failure caused by adsorbent material agglomeration. Calcium bicarbonate, by adjusting the system's pH value, provides a suitable chemical environment for the adsorption and flocculation reactions of each component, ensuring the efficient performance of microscopic effects.

[0018] In the wastewater treatment process, the combined steps of rapid mixing, slow flocculation, and pulsed magnetic field separation achieve highly efficient integration of reaction and separation. The rapid mixing stage ensures thorough mixing of the composite material and wastewater, while the introduction of oxygen enhances the synergistic effect of oxidation and adsorption. Slow mixing promotes floc growth and stability. The pulsed magnetic field utilizes the responsive characteristics of the magnetic components to achieve rapid floc separation. Compared to traditional static sedimentation, the separation time is significantly shortened, addressing the pain point of low treatment efficiency at construction sites. Simultaneously, the magnetic sludge recycling process, through high-gradient magnetic separators to recover magnetic components and acid washing for regeneration, not only reduces material consumption costs but also decreases sludge discharge, achieving resource recycling.

[0019] This invention, through the scientific formulation of components and the optimization of key preparation processes, forms a synergistic and efficient technical solution. At the microscopic level, the complementary and synergistic effects of the components ensure the simultaneous and efficient removal of suspended solids, heavy metal ions, and organic pollutants. At the macroscopic level, the optimized preparation process improves the stability and ease of use of the composite material, while the wastewater treatment process design balances treatment efficiency with resource recovery. Ultimately, this invention solves a series of problems inherent in traditional tunnel construction wastewater treatment, such as poor purification effects, slow separation speeds, high costs, and insufficient environmental friendliness. Attached Figure Description

[0020] Figure 1 This is a process flow diagram for preparing a composite material used in tunnel construction wastewater treatment. Detailed Implementation

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a composite material and a wastewater treatment method for treating wastewater from tunnel construction. The composite material is made of components in specific weight proportions. The components work synergistically, and with the help of a specific preparation process and wastewater treatment procedure, it can efficiently treat wastewater from tunnel construction, achieving wastewater discharge that meets standards or can be reused. At the same time, the magnetic components can be recycled and reused, which is energy-saving and environmentally friendly.

[0023] Components and preparation of composite materials: In this invention, lanthanum-aluminum bimetallic modified attapulgite is prepared with microwave assistance. The raw materials for its preparation, such as attapulgite, hydrochloric acid, lanthanum nitrate, aluminum chloride, and sodium hydroxide, are all commercially available products well-known to those skilled in the art. The raw materials for the preparation of dopamine-coated modified magnetic nanocomposite particles, such as multi-walled carbon nanotubes, nitric acid, ferric chloride, ferrous chloride, ammonia, Tris-HCl buffer solution, and dopamine hydrochloride, are also commercially available conventional products. The components such as chitosan-grafted polyacrylamide, aminotrimethylene phosphonic acid, nano-hydroxyapatite, calcium bicarbonate, zinc polyaspartate, sodium lignosulfonate, and deionized water are not particularly restricted, and commercially available products that meet industrial standards can be selected.

[0024] The number average molecular weight of zinc polyaspartate is 5000-8000, preferably 6000-7000.

[0025] The preparation method of lanthanum-aluminum bimetallic modified attapulgite includes the following steps: S1. Attapulgite is crushed and passed through a 200-mesh sieve. A hydrochloric acid solution with a mass fraction of 5-8% is added at a solid-liquid ratio of 1:10 g / mL. The mixture is stirred and activated at 60-70℃ for 2-3 hours. It is then filtered, washed until neutral, and dried to obtain acidified attapulgite. S2 Add acidified attapulgite to deionized water, ultrasonically disperse for 30-40 minutes to form a suspension, add a mixed solution of lanthanum nitrate and aluminum chloride, wherein the molar ratio of lanthanum nitrate to aluminum chloride is 1:2-3, and the total mass of the bimetallic compound is 8-15% of the mass of acidified attapulgite, and stir to mix well. S3 was adjusted to pH 9-10 by adding 10-15% sodium hydroxide solution, then transferred to a polytetrafluoroethylene-lined microwave reactor. Microwave-assisted crystallization was carried out at 80-90℃ and 200-300W microwave power for 2-3 hours. The mixture was filtered, washed until neutral, dried at 105-110℃ for 6-8 hours, and ground through a 300-mesh sieve to obtain lanthanum-aluminum bimetallic modified attapulgite.

[0026] The preparation method of dopamine-coated modified magnetic nanocomposite particles includes the following steps: a) Add multi-walled carbon nanotubes to a nitric acid solution with a mass fraction of 65-70% at a material-to-liquid ratio of 1:10-12, reflux at 80-90℃ for 2-3 hours to carry out carboxylation modification, filter, wash until neutral, and dry for later use. b. Dissolve ferric chloride and ferrous chloride in deionized water at a molar ratio of 2:1, with a ferric chloride mass fraction of 3-4%. Under nitrogen protection, stir at 50-60℃ for 30 minutes. Add carboxylated carbon nanotubes at a material-to-liquid ratio of 1:6-8 and ultrasonically disperse for 20-30 minutes. c. Add 25-30% ammonia water dropwise to adjust the pH to 10-11, react at 60-70℃ for 2-3 hours, filter, wash, and dry to obtain the nanocomposite particle intermediate. d. Add the nanocomposite particle intermediate to a 0.05-0.1 mol / L Tris-HCl buffer solution, adjust the pH to 8.5-9.0, add dopamine hydrochloride (5-8% of the mass of the nanocomposite particle intermediate), stir and react at 25-30℃ for 6-8 h, filter and wash until neutral, and vacuum dry at 60-70℃ for 4-5 h to obtain dopamine-coated modified magnetic nanocomposite particles.

[0027] The method for preparing composite materials includes the following steps: Pre-dispersion: First, add deionized water to the stirred tank, then add sodium lignosulfonate, zinc polyaspartate, and calcium bicarbonate in sequence, and start stirring until completely dissolved to obtain the basic solution; the stirring speed is 150-200 r / min, preferably 170-180 r / min; Solid-phase dispersion: Lanthanum-aluminum bimetallic modified attapulgite and dopamine-coated modified magnetic nanocomposite particles are added to the base solution and subjected to multi-stage dispersion treatment to ensure uniform dispersion of solid particles. The multi-stage dispersion treatment is as follows: first, ultrasonic dispersion for 20-30 min at a power of 300-400 W, then high-speed stirring for 15 min at a speed of 500-600 r / min, preferably with an ultrasonic power of 350-380 W. Compound combination: Chitosan grafted with polyacrylamide, aminotrimethylenephosphonic acid, and nano-hydroxyapatite are slowly added to the above dispersion. The stirring speed is adjusted to 250-300 r / min, and the temperature is kept constant at 30-40℃ for 30-40 min. The preferred stirring speed is 270-280 r / min, the temperature is kept constant at 35-38℃, and the stirring time is 35-38 min. Drying and molding: The reaction mixture is transferred into a spray dryer to obtain a powdered composite material with a particle size of 100-200μm; the inlet temperature of the spray dryer is 120-140℃ and the outlet temperature is 60-70℃, preferably 130-135℃ and 65-68℃.

[0028] The wastewater treatment method for tunnel construction using this composite material includes the following steps: (1) The wastewater from tunnel construction was introduced into the equalization tank, and suspended impurities with a particle size >5mm were removed by a stainless steel screen with a pore size of 5mm. The pH value, suspended solids concentration and heavy metal ion concentration of the wastewater were measured. (2) Pump the adjusted sewage into the reaction tank, add the composite material at 0.5-2.0% of the sewage mass, turn on the stirring device, stir rapidly at 200-300 r / min for 8-10 min, and introduce oxygen at 0.5-0.8 L / min during the stirring process to make the composite material and sewage fully mixed and react. The preferred addition amount is 1.0-1.5% of the sewage mass, the stirring speed is 250-280 r / min, and the oxygen introduction rate is 0.6-0.7 L / min; (3) Reduce the stirring speed to 50-80 r / min and stir slowly for 15-25 min, preferably 60-70 r / min and 20-22 min; (4) Apply a pulsed magnetic field and let it stand for 10-15 minutes to achieve rapid separation of magnetic flocs; the magnetic field strength of the pulsed magnetic field is 300-500mT and the pulse frequency is 10-20Hz, preferably 400-450mT and 15-18Hz. (5) After separation, the clear water enters the sedimentation tank for further clarification. After the water quality meets the standards, it is discharged or reused. The separated magnetic sludge is recycled by a high gradient magnetic separator. The recycled magnetic components are washed with 0.1 mol / L sulfuric acid solution and reused in the preparation of composite materials. The sludge residue is dewatered and transported for disposal.

[0029] The composite material provided by this invention features synergistic effects among its components. Lanthanum-aluminum bimetallic modified attapulgite, prepared with microwave assistance, exhibits excellent adsorption properties, effectively adsorbing heavy metal ions and suspended solids in wastewater. Dopamine-coated modified magnetic nanocomposite particles not only enhance the adsorption effect but also enable magnetic separation and recovery. Chitosan-grafted polyacrylamide, aminotrimethylene phosphonic acid, and other components further improve flocculation and purification capabilities. Simultaneously, the wastewater treatment method is rationally designed, easy to operate, and the magnetic components are recyclable, reducing treatment costs and meeting energy conservation and environmental protection requirements.

[0030] To further illustrate the present invention, the following detailed description is provided through the examples and comparative examples.

[0031] Example 1: Preparation of lanthanum-aluminum bimetallic modified attapulgite: S1. Attapulgite is crushed and passed through a 200-mesh sieve. 5% hydrochloric acid solution is added at a solid-liquid ratio of 1:10 g / mL. The mixture is stirred and activated at 60℃ for 2 hours. It is then filtered, washed until neutral, and dried to obtain acidified attapulgite. S2 Add acidified attapulgite to deionized water, ultrasonically disperse for 30 minutes to form a suspension, add a mixed solution of lanthanum nitrate and aluminum chloride, wherein the molar ratio of lanthanum nitrate to aluminum chloride is 1:2, and the total mass of the bimetal is 8% of the mass of acidified attapulgite, and stir to mix well. S3 was adjusted to pH 9 by adding 10% sodium hydroxide solution, then transferred to a polytetrafluoroethylene-lined microwave reactor and subjected to microwave-assisted crystallization at 80℃ and 200W microwave power for 2 hours. After filtration and washing until neutral, it was dried at 105℃ for 6 hours and ground through a 300-mesh sieve to obtain lanthanum-aluminum bimetallic modified attapulgite.

[0032] Preparation of dopamine-coated modified magnetic nanocomposite particles: a) Add multi-walled carbon nanotubes to a 65% nitric acid solution at a ratio of 1:10, reflux at 80°C for 2 hours to perform carboxylation modification, filter, wash until neutral, and dry for later use. b. Dissolve ferric chloride and ferrous chloride in deionized water at a molar ratio of 2:1, with a ferric chloride mass fraction of 3%. Under nitrogen protection, stir at 50°C for 30 min. Add carboxylated carbon nanotubes at a material-to-liquid ratio of 1:6 and ultrasonically disperse for 20 min. c. Add 25% ammonia solution dropwise to adjust the pH to 10, react at 60℃ for 2 hours, filter, wash, and dry to obtain the nanocomposite particle intermediate. d. The nanocomposite particle intermediate was added to a 0.05 mol / L Tris-HCl buffer solution, the pH was adjusted to 8.5, and dopamine hydrochloride was added. The mass of dopamine hydrochloride was 5% of the mass of the nanocomposite particle intermediate. The mixture was stirred at 25 °C for 6 h, filtered, washed until neutral, and vacuum dried at 60 °C for 4 h to obtain dopamine-coated modified magnetic nanocomposite particles.

[0033] Preparation of composite materials: Pre-dispersion: First, add 30 parts of deionized water to a stirred tank, then add 1 part of sodium lignosulfonate, 1 part of zinc polyaspartate (number average molecular weight 5000), and 2 parts of calcium bicarbonate in sequence. Turn on the stirrer at 150 r / min and stir until completely dissolved to obtain the basic solution. Solid dispersion: 15 parts of lanthanum-aluminum bimetallic modified attapulgite and 10 parts of dopamine-coated modified magnetic nanocomposite particles were added to the base solution. The mixture was first ultrasonically dispersed for 20 minutes at 300W, and then high-speed stirred for 15 minutes at 500r / min to ensure uniform dispersion of the solid particles. Compound combination: 8 parts chitosan-grafted polyacrylamide, 5 parts aminotrimethylenephosphonic acid, and 3 parts nano hydroxyapatite were slowly added to the above dispersion, the stirring speed was adjusted to 250 r / min, and the mixture was stirred at a constant temperature of 30℃ for 30 min. Drying and molding: The reaction mixture is transferred to a spray dryer with an inlet temperature of 120℃ and an outlet temperature of 60℃ to obtain a powdered composite material with a particle size of 100-200μm.

[0034] Treatment of wastewater from tunnel construction: (1) The wastewater from the tunnel construction was introduced into the regulating tank and suspended impurities with a particle size >5mm were removed by a stainless steel screen with a pore size of 5mm. The pH value of the wastewater was measured to be 7.2, the suspended solids concentration was 850mg / L, and the heavy metal ion concentration (calculated as lead ion) was 65mg / L. (2) Pump the adjusted sewage into the reaction tank, add the above-prepared composite material at 0.5% of the sewage mass, turn on the stirring device, stir rapidly at 200r / min for 8min, and introduce oxygen at 0.5L / min during the stirring process to make the composite material and sewage fully mixed and react. (3) Reduce the stirring speed to 50 r / min and stir slowly for 15 min; (4) Apply a pulsed magnetic field with a magnetic field strength of 300mT and a pulse frequency of 10Hz, and let it stand for 10 minutes to achieve rapid separation of magnetic flocs; (5) After separation, the clear water enters the sedimentation tank for further clarification and water quality is tested; the separated magnetic sludge is recycled by a high gradient magnetic separator to recover the magnetic components. The recovered magnetic components are washed with 0.1 mol / L sulfuric acid solution and reused in the preparation of composite materials. The sludge residue is dewatered and transported off-site for disposal.

[0035] Example 2: Preparation of lanthanum-aluminum bimetallic modified attapulgite: S1. Attapulgite is crushed and passed through a 200-mesh sieve, and 6.5% hydrochloric acid solution is added. The solid-liquid ratio is 1:10 g / mL. The mixture is stirred and activated at 65℃ for 2.5 h. After filtration and washing until neutral, it is dried to obtain acidified attapulgite. S2 Add acidified attapulgite to deionized water, ultrasonically disperse for 35 min to form a suspension, add a mixed solution of lanthanum nitrate and aluminum chloride, wherein the molar ratio of lanthanum nitrate to aluminum chloride is 1:2.5, and the total mass of the bimetallic solution is 11.5% of the mass of acidified attapulgite, and stir to mix well. S3 was adjusted to pH 9.5 by adding 12.5% ​​sodium hydroxide solution, then transferred to a polytetrafluoroethylene-lined microwave reactor and subjected to microwave-assisted crystallization at 85℃ and 250W microwave power for 2.5 hours. After filtration and washing until neutral, it was dried at 108℃ for 7 hours and ground through a 300-mesh sieve to obtain lanthanum-aluminum bimetallic modified attapulgite.

[0036] Preparation of dopamine-coated modified magnetic nanocomposite particles: a) Multi-walled carbon nanotubes were added to a 67.5% nitric acid solution at a ratio of 1:11 and refluxed at 85°C for 2.5 h to perform carboxylation modification. The mixture was then filtered, washed until neutral, and dried for later use. b. Dissolve ferric chloride and ferrous chloride in deionized water at a molar ratio of 2:1, with a ferric chloride mass fraction of 3.5%. Under nitrogen protection, stir at 55°C for 30 min. Add carboxylated carbon nanotubes at a material-to-liquid ratio of 1:7 and ultrasonically disperse for 25 min. c. Add 27.5% ammonia solution dropwise to adjust the pH to 10.5, react at 65℃ for 2.5h, filter, wash, and dry to obtain the nanocomposite particle intermediate. d. The nanocomposite particle intermediate was added to a 0.075 mol / L Tris-HCl buffer solution, the pH was adjusted to 8.8, and dopamine hydrochloride was added. The mass of dopamine hydrochloride was 6.5% of the mass of the nanocomposite particle intermediate. The mixture was stirred at 27°C for 7 h, filtered, washed until neutral, and vacuum dried at 65°C for 4.5 h to obtain dopamine-coated modified magnetic nanocomposite particles.

[0037] Preparation of composite materials: Pre-dispersion: First, add 40 parts of deionized water to the stirred tank, then add 2.5 parts of sodium lignosulfonate, 3 parts of zinc polyaspartate (number average molecular weight 6500), and 4 parts of calcium bicarbonate in sequence. Turn on the stirrer at 175 r / min and stir until completely dissolved to obtain the basic solution. Solid-phase dispersion: 20 parts of lanthanum-aluminum bimetallic modified attapulgite and 14 parts of dopamine-coated modified magnetic nanocomposite particles were added to the base solution. The mixture was first ultrasonically dispersed for 25 minutes at a power of 350W, and then high-speed stirred for 15 minutes at a speed of 550r / min to ensure uniform dispersion of solid particles. Compounding: 11.5 parts chitosan-grafted polyacrylamide, 8.5 parts aminotrimethylenephosphonic acid, and 5.5 parts nano-hydroxyapatite were slowly added to the above dispersion, and the stirring speed was adjusted to 275 r / min. The mixture was stirred at a constant temperature of 35℃ for 35 min. Drying and molding: The reaction mixture is transferred to a spray dryer with an inlet temperature of 130℃ and an outlet temperature of 65℃ to obtain a powdered composite material with a particle size of 100-200μm.

[0038] Treatment of wastewater from tunnel construction: (1) The wastewater from the tunnel construction was introduced into the equalization tank and suspended impurities with a particle size >5mm were removed by a stainless steel screen with a pore size of 5mm. The pH value of the wastewater was measured to be 7.3, the suspended solids concentration was 880mg / L, and the heavy metal ion concentration (calculated as lead ion) was 68mg / L. (2) Pump the adjusted sewage into the reaction tank, add the above-prepared composite material at 1.25% of the sewage mass, turn on the stirring device, stir rapidly at 250 r / min for 9 min, and introduce oxygen at 0.65 L / min during the stirring process to make the composite material and sewage fully mixed and react. (3) Reduce the stirring speed to 65 r / min and stir slowly for 20 min; (4) Apply a pulsed magnetic field with a magnetic field strength of 400mT and a pulse frequency of 15Hz, and let it stand for 12.5min to achieve rapid separation of magnetic flocs; (5) After separation, the clear water enters the sedimentation tank for further clarification and water quality is tested; the separated magnetic sludge is recycled by a high gradient magnetic separator to recover the magnetic components. The recovered magnetic components are washed with 0.1 mol / L sulfuric acid solution and reused in the preparation of composite materials. The sludge residue is dewatered and transported off-site for disposal.

[0039] Example 3: Preparation of lanthanum-aluminum bimetallic modified attapulgite: S1. Attapulgite is crushed and passed through a 200-mesh sieve. 8% hydrochloric acid solution is added at a solid-liquid ratio of 1:10 g / mL. The mixture is stirred and activated at 70℃ for 3 hours. It is then filtered, washed until neutral, and dried to obtain acidified attapulgite. S2 Add acidified attapulgite to deionized water, ultrasonically disperse for 40 minutes to form a suspension, add a mixed solution of lanthanum nitrate and aluminum chloride, wherein the molar ratio of lanthanum nitrate to aluminum chloride is 1:3, and the total mass of the bimetal is 15% of the mass of acidified attapulgite, and stir to mix well. S3 was adjusted to pH 10 by adding 15% sodium hydroxide solution, then transferred to a polytetrafluoroethylene-lined microwave reactor and subjected to microwave-assisted crystallization at 90℃ and 300W microwave power for 3 hours. After filtration and washing until neutral, it was dried at 110℃ for 8 hours and ground through a 300-mesh sieve to obtain lanthanum-aluminum bimetallic modified attapulgite.

[0040] Preparation of dopamine-coated modified magnetic nanocomposite particles: a) Add multi-walled carbon nanotubes to a 70% nitric acid solution at a ratio of 1:12, reflux at 90°C for 3 hours to perform carboxylation modification, filter, wash until neutral, and dry for later use. b. Dissolve ferric chloride and ferrous chloride in deionized water at a molar ratio of 2:1, with a ferric chloride mass fraction of 4%. Under nitrogen protection, stir at 60°C for 30 min. Add carboxylated carbon nanotubes at a material-to-liquid ratio of 1:8 and ultrasonically disperse for 30 min. c. Add 30% ammonia solution dropwise to adjust the pH to 11, react at 70℃ for 3 hours, filter, wash, and dry to obtain the nanocomposite particle intermediate. d. The nanocomposite particle intermediate was added to a 0.1 mol / L Tris-HCl buffer solution, the pH was adjusted to 9.0, and dopamine hydrochloride was added. The mass of dopamine hydrochloride was 8% of the mass of the nanocomposite particle intermediate. The mixture was stirred at 30°C for 8 h, filtered, washed until neutral, and vacuum dried at 70°C for 5 h to obtain dopamine-coated modified magnetic nanocomposite particles.

[0041] Preparation of composite materials: Pre-dispersion: First, add 50 parts of deionized water to a stirred tank, then add 4 parts of sodium lignosulfonate, 5 parts of zinc polyaspartate (number average molecular weight 8000), and 6 parts of calcium bicarbonate in sequence. Turn on the stirrer at 200 r / min and stir until completely dissolved to obtain the basic solution. Solid dispersion: 25 parts of lanthanum-aluminum bimetallic modified attapulgite and 18 parts of dopamine-coated modified magnetic nanocomposite particles were added to the base solution. The mixture was first ultrasonically dispersed for 30 minutes at a power of 400W, and then high-speed stirred for 15 minutes at a speed of 600r / min to ensure uniform dispersion of solid particles. Compound combination: 15 parts chitosan-grafted polyacrylamide, 12 parts aminotrimethylenephosphonic acid, and 8 parts nano hydroxyapatite were slowly added to the above dispersion, the stirring speed was adjusted to 300 r / min, and the mixture was stirred at a constant temperature of 40℃ for 40 min. Drying and molding: The reaction mixture is transferred to a spray dryer with an inlet temperature of 140℃ and an outlet temperature of 70℃ to obtain a powdered composite material with a particle size of 100-200μm.

[0042] Treatment of wastewater from tunnel construction: (1) The wastewater from the tunnel construction was introduced into the regulating tank and suspended impurities with a particle size >5mm were removed by a stainless steel screen with a pore size of 5mm. The pH value of the wastewater was measured to be 7.5, the suspended solids concentration was 900mg / L, and the heavy metal ion concentration (calculated as lead ion) was 70mg / L. (2) Pump the adjusted sewage into the reaction tank, add the above-prepared composite material at 2.0% of the sewage mass, turn on the stirring device, stir rapidly at 300r / min for 10min, and introduce oxygen at 0.8L / min during the stirring process to make the composite material and sewage fully mixed and react. (3) Reduce the stirring speed to 80 r / min and stir slowly for 25 min; (4) Apply a pulsed magnetic field with a magnetic field strength of 500mT and a pulse frequency of 20Hz, and let it stand for 15 minutes to achieve rapid separation of magnetic flocs; (5) After separation, the clear water enters the sedimentation tank for further clarification and water quality is tested; the separated magnetic sludge is recycled by a high gradient magnetic separator to recover the magnetic components. The recovered magnetic components are washed with 0.1 mol / L sulfuric acid solution and reused in the preparation of composite materials. The sludge residue is dewatered and transported off-site for disposal.

[0043] Comparative Example 1: This comparative example did not include lanthanum-aluminum bimetallic modified attapulgite, and the remaining preparation steps and wastewater treatment process were the same as in Example 2.

[0044] Treatment of wastewater from tunnel construction: The steps are the same as those in Example 2.

[0045] Comparative Example 2: This comparative example did not include dopamine-coated modified magnetic nanocomposite particles; the remaining preparation steps and wastewater treatment process were the same as in Example 2.

[0046] Treatment of tunnel construction wastewater: The steps are the same as those in Example 2, but since there are no magnetic components, step (4) is changed to let it stand for 30 minutes to achieve floc separation.

[0047] Comparative Example 3: In this comparative example, the lanthanum-aluminum bimetallic modified attapulgite was not prepared using microwave-assisted methods (only conventional water bath heating was used), and the remaining preparation steps and wastewater treatment process were the same as in Example 2.

[0048] Treatment of wastewater from tunnel construction: The steps are the same as those in Example 2.

[0049] Tests and experiments: Experiment 1: Wastewater treatment effect test; Wastewater from tunnel construction was treated using the composite materials and corresponding wastewater treatment methods described in Examples 1-3 and Comparative Examples 1-3, respectively. The removal rates of suspended solids, heavy metal ions (lead ions), and COD in the treated water were measured. The floc separation time was also recorded (magnetic separation time for Examples 1-3 and Comparative Examples 1 and 3, and settling time for Comparative Example 2). Suspended solids concentration was determined by gravimetric method, heavy metal ion concentration by atomic absorption spectrophotometry, and COD by potassium dichromate method. The results are as follows:

[0050] Table 1

[0051] As shown in Table 1, the wastewater treatment effects of Examples 1-3 were significantly better than those of the comparative examples, and the treatment effect gradually improved as the component dosage and reaction parameters approached the optimal range. Comparative Example 1, lacking the addition of lanthanum-aluminum bimetallic modified attapulgite, suffered from a lack of strong adsorption of suspended solids and heavy metal ions, resulting in a significant decrease in removal rates: suspended solids removal rate was only 82.3%, and heavy metal ion removal rate was 78.5%. Comparative Example 2, without the addition of dopamine-coated modified magnetic nanocomposite particles, not only lost the adsorption synergistic effect of this component but also failed to achieve rapid magnetic separation, extending the floc separation time to 30 minutes and significantly reducing the removal rate. In Comparative Example 3, the lanthanum-aluminum bimetallic modified attapulgite was not prepared using microwave-assisted methods. Microwave-assisted crystallization allows the bimetallic components to be more uniformly loaded on the attapulgite surface, increasing adsorption active sites. Modified attapulgite prepared by conventional water bath heating had insufficient adsorption performance, resulting in a lower removal rate than Example 2.

[0052] Experiment 2: Stability test of composite materials; The composite materials from Examples 1-3 and Comparative Examples 1-3 were stored in an environment of 40°C and 85% humidity for 30 days, and then used to treat tunnel construction wastewater. The removal rates of suspended solids and heavy metal ions (lead ions) were measured and compared with the treatment effect before storage. The removal rate decay rate was calculated, and the stability of the composite materials was evaluated. The results are as follows: Table 2

[0053] As shown in Table 2, the composite materials of Examples 1-3 exhibit excellent stability, with low attenuation rates of suspended solids removal and heavy metal ion removal after 30 days of storage. The composite materials of each comparative example show poor stability. Comparative Example 1 lacks lanthanum-aluminum bimetallic modified attapulgite, weakening the synergistic stabilizing effect of each component, and some organic components are prone to moisture absorption and degradation. Comparative Example 2 lacks dopamine-coated modified magnetic nanocomposite particles, resulting in decreased system stability, and the organic flocculent components are prone to hydrolysis under humid and hot conditions. The lanthanum-aluminum bimetallic modified attapulgite preparation process of Comparative Example 3 is suboptimal, with weak bonding of the surface-loaded bimetallic components, which easily detach under humid and hot conditions, leading to a significant decrease in adsorption performance.

[0054] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A composite material for treating wastewater during tunnel construction, characterized in that, It is made from the following components in parts by weight: 15-25 parts of lanthanum-aluminum bimetallic modified attapulgite, 10-18 parts of dopamine-coated modified magnetic nanocomposite particles, 8-15 parts of chitosan-grafted polyacrylamide, 5-12 parts of aminotrimethylenephosphonic acid, 3-8 parts of nano hydroxyapatite, 2-6 parts of calcium bicarbonate, 1-5 parts of zinc polyaspartate, 1-4 parts of sodium lignosulfonate, and 30-50 parts of deionized water. The lanthanum-aluminum bimetallic modified attapulgite was prepared with microwave assistance.

2. The composite material according to claim 1, characterized in that, The preparation method of the lanthanum-aluminum bimetallic modified attapulgite includes the following steps: S1. Attapulgite is crushed and passed through a 200-mesh sieve. A hydrochloric acid solution with a mass fraction of 5-8% is added, with a solid-liquid ratio of 1:10 (g / mL). The mixture is stirred and activated at 60-70℃ for 2-3 hours. It is then filtered, washed until neutral, and dried to obtain acidified attapulgite. S2 Add acidified attapulgite to deionized water, ultrasonically disperse for 30-40 minutes to form a suspension, add a mixed solution of lanthanum nitrate and aluminum chloride, wherein the molar ratio of lanthanum nitrate to aluminum chloride is 1:2-3, and the total mass of the bimetallic compound is 8-15% of the mass of acidified attapulgite, and stir to mix well. S3 was adjusted to pH 9-10 by adding 10-15% sodium hydroxide solution, then transferred to a polytetrafluoroethylene-lined microwave reactor. Microwave-assisted crystallization was carried out at 80-90℃ and 200-300W microwave power for 2-3 hours. The mixture was filtered, washed until neutral, dried at 105-110℃ for 6-8 hours, and ground through a 300-mesh sieve to obtain lanthanum-aluminum bimetallic modified attapulgite.

3. The composite material according to claim 1, characterized in that, The preparation method of the dopamine-coated modified magnetic nanocomposite particles includes the following steps: a) Add multi-walled carbon nanotubes to a nitric acid solution with a mass fraction of 65-70% at a material-to-liquid ratio of 1:10-12, reflux at 80-90℃ for 2-3 hours to carry out carboxylation modification, filter, wash until neutral, and dry for later use. b. Dissolve ferric chloride and ferrous chloride in deionized water at a molar ratio of 2:1, with a ferric chloride mass fraction of 3-4%. Under nitrogen protection, stir at 50-60℃ for 30 minutes. Add carboxylated carbon nanotubes at a material-to-liquid ratio of 1:6-8 and ultrasonically disperse for 20-30 minutes. c. Add 25-30% ammonia water dropwise to adjust the pH to 10-11, react at 60-70℃ for 2-3 hours, filter, wash, and dry to obtain the nanocomposite particle intermediate. d. Add the nanocomposite particle intermediate to a 0.05-0.1 mol / L Tris-HCl buffer solution, adjust the pH to 8.5-9.0, add dopamine hydrochloride (5-8% of the mass of the nanocomposite particle intermediate), stir and react at 25-30℃ for 6-8 h, filter and wash until neutral, and vacuum dry at 60-70℃ for 4-5 h to obtain dopamine-coated modified magnetic nanocomposite particles.

4. The composite material according to claim 1, characterized in that, Methods for preparing composite materials include: Pre-dispersion: First, add deionized water to the stirred tank, then add sodium lignosulfonate, zinc polyaspartate, and calcium bicarbonate in sequence, and start stirring until completely dissolved to obtain the basic solution; the stirring speed is 150-200 r / min; Solid-phase dispersion: Lanthanum-aluminum bimetallic modified attapulgite and dopamine-coated modified magnetic nanocomposite particles are added to the base solution and dispersed in multiple stages to ensure uniform dispersion of solid particles. Compound combination: Chitosan grafted with polyacrylamide, aminotrimethylene phosphonic acid, and nano hydroxyapatite are slowly added to the above dispersion, the stirring speed is adjusted to 250-300 r / min, and the mixture is stirred at a constant temperature of 30-40℃ for 30-40 min. Drying and molding: The reaction mixture is transferred to a spray dryer to obtain a powdered composite material with a particle size of 100-200μm.

5. The composite material according to claim 4, characterized in that, The multi-stage dispersion process is as follows: first, ultrasonic dispersion for 20-30 minutes at a power of 300-400W, then high-speed stirring for 15 minutes at a speed of 500-600r / min.

6. The composite material according to claim 4, characterized in that, The spray dryer has an inlet temperature of 120-140℃ and an outlet temperature of 60-70℃.

7. The composite material according to claim 1, characterized in that, The number-average molecular weight of the polyaspartic zinc is 5000-8000.

8. The method for treating wastewater from tunnel construction using composite materials according to any one of claims 1-7, characterized in that, Includes the following steps: (1) The wastewater from tunnel construction was introduced into the equalization tank, and suspended impurities with a particle size >5mm were removed by a stainless steel screen with a pore size of 5mm. The pH value, suspended solids concentration and heavy metal ion concentration of the wastewater were measured. (2) Pump the adjusted sewage into the reaction tank, add the composite material, turn on the stirring device, stir rapidly at 200-300 r / min for 8-10 min, and introduce oxygen at 0.5-0.8 L / min during the stirring process to make the composite material and sewage fully mix and react; (3) Reduce the stirring speed to 50-80 r / min and stir slowly for 15-25 min; (4) Apply a pulsed magnetic field and let stand for 10-15 minutes to achieve rapid separation of magnetic flocs; (5) After separation, the clear water enters the sedimentation tank for further clarification. After the water quality meets the standards, it is discharged or reused. The separated magnetic sludge is recycled by a high gradient magnetic separator. The recycled magnetic components are washed with 0.1 mol / L sulfuric acid solution and reused in the preparation of composite materials. The sludge residue is dewatered and transported for disposal.

9. The wastewater treatment method according to claim 8, characterized in that, In step (2), the composite material is added at a concentration of 0.5-2.0% of the wastewater mass.

10. The wastewater treatment method according to claim 8, characterized in that, In step (4), the magnetic field strength of the pulsed magnetic field is 300-500mT and the pulse frequency is 10-20Hz.

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