Solid bubble composite material for adsorbing heavy metals

Abstract

The invention provides a solid bubble composite material for adsorbing heavy metals as well as a preparation method and an application method thereof, belongs to the technical field of adsorption separation functional materials, and solves one of the technical problems of poor cycling stability, complex and low-efficiency recovery separation, short service life, weak selective adsorbability and low adsorption capacity of an existing organic adsorbent. The invention discloses a solid bubble composite material for adsorbing heavy metals. The heavy metals comprise cadmium ions, lead ions, mercury ions, copper ions and nickel ions. The composite material is solid bubbles loaded with a sulfydryl-containing adsorption layer on the outer surface, and the mass ratio of the solid bubbles to the sulfydryl-containing adsorption layer is 1: (0.12-1.2); and the density of the composite material is 0.12-0.95 g / cm < 3 In the recovery process, high-energy-consumption solid-liquid separation equipment is not needed, after adsorption, the wastewater can quickly float on the water surface for recovery, and the recovery cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adsorption separation functional materials, and particularly relates to a solid bubble composite material for adsorbing heavy metals and a preparation and application method thereof. BACKGROUND

[0002] With the acceleration of industrial modernization process, the rapid development of mining, electroplating, chemical industry, electronic manufacturing and other industries, a large amount of wastewater containing toxic heavy metals such as lead, cadmium, mercury, chromium and arsenic is discharged in disorder, causing global water pollution crisis. These heavy metals have strong toxicity, non-degradability and bioaccumulation, once entering the water environment, they will be enriched through the food chain, causing serious damage to the stability of the ecological system, and directly threatening human health, causing nerve system damage, organ disease and other diseases.

[0003] Among the many heavy metal wastewater treatment technologies, the adsorption method has become a key technical means in the field of water treatment and is widely used due to its simple operation, high treatment efficiency, relatively low cost, wide application range and other core advantages. However, traditional heavy metal adsorbents still have many performance shortcomings, which limit their industrial application effect. For example, although traditional inorganic adsorbents (such as zeolite, bentonite, activated carbon) are easy to obtain, they have low adsorption capacity, poor selectivity, limited treatment efficiency for low-concentration heavy metal wastewater, and poor regeneration performance, which easily causes resource waste; traditional organic adsorbents (such as ion exchange resin, high molecular polymer) have strong adsorption selectivity, but the preparation cost is high, the chemical stability is insufficient, and they are easy to swell and degrade in acidic or high-salt wastewater systems, with short service life. Although some organic-inorganic hybrid adsorption materials have appeared in recent years, such as covalent organic frameworks and metal organic frameworks, the overall synthesis and preparation process of the materials has defects such as expensive raw materials and complex synthesis process. In addition, some traditional adsorbents have slow mass transfer rate, difficult solid-liquid separation and recovery and regeneration, which leads to prolonged treatment cycle and cannot meet the efficient demand of large-scale wastewater treatment. At the same time, most of the traditional adsorbents lack functional modification design and cannot realize the targeted adsorption of specific heavy metal ions, which further restricts their application efficiency in complex contaminated water bodies, and the density of these adsorption active substances is large, which is easy to settle at the bottom, thereby reducing the adsorption rate. Therefore, it is a technical problem to be solved to find a new type of material with strong selective adsorption, convenient recovery and separation, excellent cycle stability, simple operation and low energy consumption. SUMMARY

[0004] In view of the above-mentioned current technology, the present invention provides a solid bubble composite material for adsorbing heavy metals and its preparation and application method. By grafting thiol groups onto solid bubbles, the solid bubble composite material combines the high-efficiency adsorption characteristics of thiol groups with the floating advantages of a carrier. This can at least solve one of the technical problems of existing organic adsorbents, such as poor cycle stability, complex and inefficient recovery and separation, short adsorbent life, weak selective adsorption, and low adsorption capacity.

[0005] It is mainly achieved through the following technical solutions:

[0006] On the one hand, the present invention provides a solid bubble composite material for adsorbing heavy metals, including cadmium ions, lead ions, mercury ions, copper ions, and nickel ions; the composite material is a solid bubble with a thiol-containing adsorption layer on its outer surface, and the mass ratio of the solid bubble to the thiol-containing adsorption layer is 1:(0.12~1.2).

[0007] Furthermore, the particle size of the composite material is 10–1000 μm, and the compressive strength is between 1 MPa and 200 MPa; the solid bubble is an inorganic material composed of a solid shell surrounding a large number of closed gas cavities inside, and the density of the solid bubble is 0.1–0.9 g / cm³. 3 The compressive strength is between 1MPa and 200MPa.

[0008] Furthermore, the solid bubbles are at least one of hollow glass microspheres, insulated glass microspheres, fly ash cenospheres, and ceramic bubbles.

[0009] Furthermore, the thiol-containing adsorption layer includes at least one of the following: 3-mercapto-2-butanol condensation of 3-isocyanate-propyltriethoxysilane, dithiol condensation of 3-glycidyl ether propyltrimethoxysilane, 2,3-dimercaptosuccinic acid condensation of 3-aminopropyltrimethoxysilane, L-cysteine ​​plus polyvinyltrimethoxysilane, mercaptoacetic acid condensation of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropionic acid condensation of 3-cyanopropyltrimethoxysilane, 3-mercapto-2-butanol condensation of 3-ureopropyltriethoxysilane, 2,3-dimercaptosuccinic acid crosslinked aluminum isopropoxystearate, and 2,3-dimercaptosuccinic acid crosslinked di(acetylacetonyl)isopropoxytitanium.

[0010] On the other hand, the present invention also provides a method for preparing the above-mentioned composite material, comprising the following steps:

[0011] S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles.

[0012] S2 involves grafting a grafting agent onto the solid bubbles obtained in S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials, thereby obtaining solid bubbles with sufficient reaction sites.

[0013] S3 modifies the solid bubbles obtained in S2 by utilizing the specific binding of thiol-containing compounds to the reaction sites, thereby introducing thiol groups and obtaining thiol-based solid bubble composite materials.

[0014] Further, in step 1, the alkaline activation treatment is as follows: solid bubbles are placed in a beaker containing a sodium hydroxide solution with a concentration of 0.5-5 mol / L at a solid-liquid ratio of 10-100 g / L and stirred at 50-300 r / min for 1-8 h. The reaction temperature is 20-80℃. After standing and cooling to separate the solid and liquid, the mixture is washed with deionized water until neutral and then dried.

[0015] Further, in step 2, the grafting is as follows: the solid bubbles obtained in S1 are dispersed in the reaction solvent, a grafting agent is added, and the surface grafting is carried out by reflux reaction at 30-80°C for 1-12 hours under a nitrogen atmosphere. After solid-liquid separation, the solid bubbles are washed three times with water and then three times with ethanol. After vacuum drying at 50-90°C for 4-8 hours, solid bubbles with sufficient reaction sites are obtained.

[0016] The grafting agent is at least one of 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-cyanopropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanate-propyltriethoxysilane (IPTS), vinyltrimethoxysilane, aluminum isopropoxystearate, and di(acetylacetonyl)isopropoxytitanium.

[0017] The reaction solvent is one or more selected from ethanol, isopropanol, water, acetone, toluene, xylene, and ethylene glycol monomethyl ether;

[0018] The ratio of solid bubbles, reaction solvent, and grafting agent is 1g:(10~100)mL:(0.1~5)g.

[0019] Further, in step 3, the modification is as follows: the solid bubbles obtained in S2 are reacted with the mercapto-containing compound in a solvent, and a catalyst is added. The reaction is stirred at 40-80°C for 4-24 hours under a nitrogen atmosphere. After solid-liquid separation, the mixture is washed three times with deionized water, then washed three times with ethanol, and then dried.

[0020] The thiol-containing compound is at least one of 3-mercapto-2-butanol, dithiol, 2,3-dimercaptosuccinic acid, L-cysteine, thioglycolic acid, and 3-mercaptopropionic acid;

[0021] The catalyst is at least one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl), N-hydroxysuccinimide (NHS), p-toluenesulfonic acid (PTSA), triethylamine, azobisisobutyronitrile, and dibutyltin dilaurate (DBTDL);

[0022] The solvent is one or more of ethanol, isopropanol, water, acetone, toluene, xylene, and ethylene glycol monomethyl ether.

[0023] Furthermore, the ratio of solid bubbles, solvent, mercapto-containing compound, and catalyst is 1g:(10~100)mL:(0.5~3)g:(0.1~1)g.

[0024] Finally, the present invention also provides a method for applying the above-mentioned composite material, or the composite material prepared by the above method, in the treatment of heavy metal wastewater, wherein the heavy metal wastewater includes at least one of cadmium ions, lead ions, mercury ions, copper ions, and nickel ions.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. This invention uses low-density solid bubbles as a carrier to give composite materials the ability to float independently. Compared with some adsorbents that are dense and easily settle at the bottom of the solution and are difficult to recover during application, the recovery process of this invention does not require high-energy-consuming solid-liquid separation equipment. After adsorption, it can quickly float to the water surface for recovery, which greatly reduces the recovery cost.

[0027] 2. The solid bubbles used in this invention have high mechanical strength and good chemical stability, can withstand complex wastewater environments, and can be recycled multiple times, thus extending the service life of the composite material.

[0028] 3. The thiol group (-SH) used in this invention has extremely strong complexing selectivity for heavy metal ions such as lead, cadmium, and mercury. It has strong binding force and high adsorption capacity, and can quickly capture target ions in complex water bodies with low concentration and high salinity. It also has excellent desorption and regeneration performance.

[0029] 4. The preparation and application methods of the present invention are simple to operate and have low energy consumption. They can be adapted to large-scale heavy metal wastewater treatment scenarios, and are especially suitable for the treatment of shallow surface polluted water bodies. They have broad application prospects and practical value in the field of environmental water treatment. Attached Figure Description

[0030] Figure 1 The infrared spectrum of the solid bubble composite material in Example 1 is shown below.

[0031] Figure 2 The adsorption capacity of each heavy metal ion initially adsorbed by the adsorption materials of Example 1 and Comparative Example 1 is shown. Detailed Implementation

[0032] The following detailed description, in conjunction with specific embodiments, illustrates a solid bubble composite material for adsorbing heavy metals and its preparation and application methods. These embodiments are for illustrative purposes only, and the present invention is not limited to these embodiments.

[0033] First, this invention proposes a solid bubble composite material for adsorbing heavy metals. This composite material consists of solid bubbles with a thiol-containing adsorption layer on their outer surface. The mass ratio of the solid bubbles to the thiol-containing adsorption layer is 1:(0.12–1.2), and the density of the solid bubble composite material is 0.12–0.95 g / cm³. 3 The particle size ranges from 10 to 1000 μm, and its compressive strength typically ranges from 1 MPa to 200 MPa. Heavy metals include cadmium ions, lead ions, mercury ions, copper ions, and nickel ions, but are not limited to these.

[0034] Solid bubbles are a type of inorganic material composed of a solid shell surrounding a large number of closed gas cavities, such as at least one of hollow glass microspheres, insulated glass microspheres, fly ash cenospheres, and ceramic bubbles; the density of solid bubbles is 0.1–0.9 g / cm³. 3 Its particle size is less than 1000μm, and its compressive strength is usually between 1MPa and 200MPa.

[0035] It should be noted that since solid bubble composite materials are made by attaching a layer of thiol-containing organic matter to the outer surface of solid bubbles in inorganic materials, the compressive strength of solid bubble composite materials is equal to that of solid bubbles, that is, both are between 1MPa and 200MPa.

[0036] The thiol-containing adsorption layer includes at least one of the following: 3-mercapto-2-butanol condensation of 3-isocyanate-propyltriethoxysilane, dithiol condensation of 3-glycidyl ether propyltrimethoxysilane, 2,3-dimercaptosuccinic acid condensation of 3-aminopropyltrimethoxysilane, L-cysteine ​​plus polyvinyltrimethoxysilane, thioacetic acid condensation of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropionic acid condensation of 3-cyanopropyltrimethoxysilane, 3-mercapto-2-butanol condensation of 3-ureopropyltriethoxysilane, 2,3-dimercaptosuccinic acid crosslinked aluminum isopropoxystearate, and 2,3-dimercaptosuccinic acid crosslinked di(acetylacetonyl)isopropoxytitanium.

[0037] It should be noted that in the thiol-containing adsorption layer, the thiol group (-SH) has extremely strong complexing selectivity for heavy metal ions such as lead, cadmium, and mercury. It has strong binding force and high adsorption capacity, and can quickly capture target ions in complex water bodies with low concentration and high salinity. It also has excellent desorption and regeneration performance.

[0038] Secondly, the present invention also provides a method for preparing the above-mentioned solid bubble composite material for adsorbing heavy metals, comprising the following steps:

[0039] S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles.

[0040] S2 uses a grafting agent to graft the product of S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials and obtain solid bubbles with sufficient reaction sites.

[0041] S3 modifies the product of S2 by utilizing the specific binding of a thiol-containing compound to the reaction site, thereby introducing thiol groups and obtaining a thiol-based solid bubble composite material.

[0042] In order to give the adsorbent low density characteristics so that it can float on the water surface for recycling, this invention selects a low-density solid bubble as the matrix material.

[0043] Preferably, the solid bubbles described above are a type of inorganic material consisting of a solid shell surrounding a large number of closed gas cavities inside, and can be at least one of hollow glass microspheres, hollow glass microspheres, fly ash cenospheres, and ceramic bubbles.

[0044] More preferably, the density of the solid bubbles is 0.1–0.9 g / cm³. 3 Its particle size is less than 1000μm, and its compressive strength ranges from 1MPa to 200MPa.

[0045] Solid bubbles are materials with a density lower than water, consisting of a solid shell surrounding numerous closed gas cavities. Their size can range from nanometers to micrometers, and they are selected from at least one of hollow glass microspheres, ceramic bubbles, zeolites, and fly ash cenospheres. Table 1 shows the physical properties of commercially available hollow glass microspheres.

[0046] Table 1 Physical properties of hollow glass microspheres

[0047]

[0048] In step S1, the original solid bubbles are alkaline activated to increase the surface hydroxyl density, thereby achieving interfacial hydroxylation and further enhancing the adjustability of subsequent functions.

[0049] Preferably, in step S1 above, solid bubbles are placed in a beaker containing a sodium hydroxide solution with a concentration of 0.5-5 mol / L at a solid-liquid ratio of 10-100 g / L and stirred at 50-300 r / min for 1-8 h to increase the hydroxyl groups on their surface. The reaction temperature is 20-80 °C. After standing and cooling to separate the solid and liquid, the mixture is rinsed with deionized water until neutral and then dried.

[0050] In step S2, a "molecular bridge" is introduced on the surface of the solid bubble by further reacting with the grafting agent, thereby achieving the combination of organic and inorganic materials and increasing the reaction sites for subsequent reactions.

[0051] Preferably, as described in step S2 above, the surface-hydroxylated solid bubbles are dispersed in the reaction solvent, a grafting agent is added, and the surface grafting is carried out by reflux reaction at 30-80°C for 1-12 hours under a nitrogen atmosphere. After solid-liquid separation, the solid bubbles are washed three times with water and then three times with ethanol. Finally, the solid bubbles are vacuum dried at 50-90°C for 4-8 hours to obtain the surface-grafted solid bubbles.

[0052] Preferably, the grafting rate is controlled at 20% to 60%.

[0053] More preferably, the grafting agent is at least one selected from 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-cyanopropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanate-propyltriethoxysilane (IPTS), vinyltrimethoxysilane, aluminum isopropoxystearate, and di(acetylacetonyl)isopropoxytitanium.

[0054] More preferably, the reaction solvent is one or more selected from ethanol, isopropanol, water, acetone, toluene, xylene, and ethylene glycol monomethyl ether.

[0055] More preferably, the ratio of solid bubbles, reaction solvent, and grafting agent is 1g:(10-100)mL:(0.1-5)g.

[0056] In step S3, by further thiolizing the matrix on which the grafting agent has been introduced, a thiol-containing adsorption layer is obtained, thereby realizing the preparation of a thiol-based solid bubble adsorbent.

[0057] Preferably, step S3 above involves reacting surface-grafted solid bubbles with a thiol-containing compound in a solvent, adding a catalyst, and stirring the reaction at 40–80°C for 4–24 hours under a nitrogen atmosphere to introduce thiol groups. After solid-liquid separation, the mixture is first washed three times with deionized water, then washed three times with ethanol, and finally dried.

[0058] Preferably, the conversion rate of the thiol compound is 50% to 95%.

[0059] More preferably, the thiol-containing compound is at least one selected from: 3-mercapto-2-butanol, dithiol, 2,3-dimercaptosuccinic acid, L-cysteine, thioglycolic acid, and 3-mercaptopropionic acid.

[0060] More preferably, the catalyst is at least one selected from: 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl), N-hydroxysuccinimide (NHS), p-toluenesulfonic acid (PTSA), triethylamine, azobisisobutyronitrile, and dibutyltin dilaurate (DBTDL).

[0061] More preferably, the solvent is one or more selected from ethanol, isopropanol, water, acetone, toluene, xylene, and ethylene glycol monomethyl ether.

[0062] More preferably, the ratio of surface-grafted solid bubbles, solvent, mercapto-containing compound, and catalyst is 1g:(10-100)mL:(0.5-3)g:(0.1-1)g.

[0063] Furthermore, the present invention also provides a method for applying the above-mentioned solid bubble composite material, comprising the following steps:

[0064] Step 1: Place the solid bubble composite material into water containing heavy metal ions;

[0065] Step 2: Recover the solid bubble composite material after adsorption reaches equilibrium, wash off heavy metal ions with dilute HNO3 solution, and then wash the solid bubble composite material with water until neutral.

[0066] Step 3: Repeat steps 1 to 2 until the adsorption capacity of the solid bubble composite material drops to below 90% of the initial adsorption capacity.

[0067] It should be noted that in step 1, heavy metal ions include, but are not limited to, cadmium, lead, mercury, copper, and nickel ions. Since solid bubbles have a lower density than water and possess self-floating properties, they can be added from the bottom of the water via a pipe. Utilizing their self-floating characteristic, the solid bubble composite material fully contacts the wastewater as it rises from the bottom, achieving sufficient adsorption of heavy metal ions. Furthermore, it can spontaneously float to the surface, enriching the heavy metal ions. Specifically, to improve the adsorption rate, the solid bubble adsorbent or functionalized solid bubble adsorbent added to the seawater can be shaken to promote adsorption.

[0068] In step 2, the dilute HNO3 solution has a concentration of 0.1 mol / L.

[0069] In step 3, after several cycles, the adsorption capacity of the solid bubble composite material of the present invention drops to less than 90% of the initial adsorption capacity.

[0070] Specifically, the formula for calculating adsorption capacity is:

[0071] In the formula, Q eC is the adsorption capacity, in mg / g; C0 is the initial concentration of heavy metal ions in the solution, in mg / L; C e ω represents the concentration of heavy metal ions in the solution after adsorption reaches equilibrium, in mg / L; V is the solution volume, in L; m is the mass of the solid bubble composite material, in g; ω is the mass fraction of the effective adsorbent in the solid bubble composite material, in %. The ratio of the adsorption capacity after N cycles to the initial adsorption capacity yields the adsorption capacity retention rate after N cycles.

[0072] Example 1

[0073] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:1.2. The solid bubbles are hollow glass microspheres with a density of 0.20 g / cm³. 3 The solid bubble composite material has a particle size range of 50–100 μm, with a median particle size of 65 μm. The density of the solid bubble composite material is 0.48 g / cm³. 3 The compressive strength is 50 MPa. The thiol-containing adsorption layer is a condensation layer of 2,3-dimercaptosuccinic acid and 3-aminopropyltrimethoxysilane.

[0074] A method for preparing the above-mentioned solid bubble composite material for adsorbing heavy metals includes the following steps:

[0075] S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles.

[0076] Hollow glass microspheres with a density of 0.20 g / cm³ 3 Hollow glass microspheres with a median particle size of 65 μm were placed in a glass beaker, and then 500 mL of deionized water was added. The mixture was stirred thoroughly and allowed to stand for 1 hour for flotation. After separation, 20 g of the upper layer of intact hollow glass microspheres was collected for later use. The flotated hollow glass microspheres were placed in 200 mL of 0.5 mol / L sodium hydroxide solution and stirred at 50 rpm for 1 hour in a 20°C water bath. After solid-liquid separation, the product was washed with deionized water until neutral and then dried in an oven.

[0077] S2 uses a grafting agent to graft the product of S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials and obtain solid bubbles with sufficient reaction sites.

[0078] 10g of hydroxylated solid foam was weighed and dispersed in a 100mL mixture of ethanol and water. 1g of 3-aminopropyltrimethoxysilane was added, and the mixture was refluxed at 30℃ for 1h under a nitrogen atmosphere to perform surface grafting. After solid-liquid separation, the mixture was washed three times with water and then three times with ethanol. Finally, it was vacuum dried at 50℃ for 4h to obtain surface-grafted solid bubbles.

[0079] S3 modifies the product of S2 by utilizing the specific binding of a thiol-containing compound to the reaction site, thereby introducing thiol groups and obtaining a thiol-based solid bubble composite material.

[0080] 10g of surface-grafted solid bubbles were dispersed in 100mL of ethanol, and 5g of 2,3-dimercaptosuccinic acid was added for reaction. 1g of catalyst EDC·HCl was added, and the reaction was stirred at 40℃ for 4h under a nitrogen atmosphere to introduce mercapto groups. After solid-liquid separation, the mixture was washed three times with deionized water and then three times with ethanol before drying to obtain a mercapto-based solid bubble composite material. Figure 1 This is the infrared spectrum of the mercapto-based solid bubble composite material obtained in this embodiment. Figure 1 The vibrational peaks of thiol groups are clearly visible, indicating that thiol groups were successfully loaded onto the surface of hollow glass microspheres.

[0081] A method for applying the above-mentioned solid bubble composite material includes the following steps:

[0082] Step 1: Dispose of the solid bubble composite material in an environment containing 70 ppm Hg. 2+ 70ppm Cd 2+ 70ppmPd 2+ 70ppmCu 2+ 70ppm Ni 2+ Add 100 mL of the solution and shake at 25 °C for 4 h;

[0083] Step 2: Recover the adsorbed solid bubble composite material, elute and regenerate it with 0.1 mol / L HNO3 solution, determine the adsorption capacity of each heavy metal ion, and then wash it with water until neutral.

[0084] Step 3: Repeat steps 1 and 2, but change the cyclic adsorption experiment to one containing 70 ppm Hg. 2+ In 100 mL of the solution, the rest is exactly the same as the first time; at least 10 cycles are performed, and the cycle is stopped when the adsorption capacity drops to less than 90% of the initial adsorption capacity.

[0085] The initial adsorption capacity of each heavy metal ion in the solid bubble composite material of this embodiment is shown in the figure. Figure 2 The cyclic adsorption performance of the solid bubble composite material in this embodiment is shown in Table 2.

[0086] Example 2

[0087] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles carrying a thiol-containing compound, with a mass ratio of thiol-containing adsorption layer to solid bubbles of 1:0.12. The solid bubbles are hollow glass microspheres with a density of 0.10 g / cm³. 3 The solid bubble composite material has a particle size range of 10–50 μm, a median particle size of 35 μm, and a density of 0.12 g / cm³. 3 The compressive strength is 100 MPa. The thiol-containing adsorption layer is a 3-mercaptopropyltrimethoxysilane adsorption layer formed by the condensation of mercaptoacetic acid.

[0088] A method for preparing the above-mentioned solid bubble composite material for adsorbing heavy metals includes the following steps:

[0089] S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles.

[0090] Hollow glass microspheres with a density of 0.10 g / cm³ 3 The median particle size was 35 μm. The microspheres were placed in a glass beaker, and 500 mL of deionized water was added. The mixture was stirred thoroughly and allowed to stand for 1 hour for flotation. After separation, 20 g of the upper layer of intact microspheres was collected for later use. The flotated microspheres were then placed in 2 L of a 5 mol / L sodium hydroxide solution and stirred at 300 rpm for 8 hours in an 80°C water bath. After solid-liquid separation, the product was washed with deionized water until neutral and then dried in an oven.

[0091] S2 uses a grafting agent to graft the product of S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials and obtain solid bubbles with sufficient reaction sites.

[0092] 10g of hydroxylated solid foam was weighed and dispersed in 1L of toluene solution. 50g of 3-mercaptopropyltrimethoxysilane was added, and the mixture was refluxed at 80℃ for 12h under a nitrogen atmosphere to perform surface grafting. After solid-liquid separation, the mixture was washed three times with water and then three times with ethanol. Finally, it was vacuum dried at 90℃ for 8h to obtain surface-grafted solid bubbles.

[0093] S3 modifies the product of S2 by utilizing the specific binding of a thiol-containing compound to the reaction site, thereby introducing thiol groups and obtaining a thiol-based solid bubble composite material.

[0094] 10g of surface-grafted solid bubbles were dispersed in 1L of xylene, 30g of mercaptoacetic acid was added for reaction, and 10g of PTSA catalyst was added. The reaction was carried out under nitrogen atmosphere at 80℃ for 24h to introduce mercapto groups. After solid-liquid separation, the mixture was washed three times with deionized water and then three times with ethanol before drying to obtain mercapto-based solid bubble composite material.

[0095] A method for applying the above-mentioned solid bubble composite material includes the following steps:

[0096] Step 1: Dispose of the solid bubble composite material in an environment containing 70 ppm Hg. 2+ Add 100 mL of the solution and shake at 25 °C for 4 h;

[0097] Step 2: Recover the adsorbed solid bubble composite material by elution and regeneration with 0.1 mol / L HNO3 solution, and determine Hg. 2+ The adsorption capacity was measured, and then the solution was washed with water until neutral.

[0098] Step 3: Repeat steps 1 to 2 for at least 10 cycles, and stop cycling when the adsorption capacity drops below 90% of the initial adsorption capacity.

[0099] The adsorption properties of the solid bubble composite material in this embodiment are shown in Table 2.

[0100] Example 3

[0101] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:0.8. The solid bubbles are hollow glass microspheres with a density of 0.57 g / cm³. 3 The solid bubble composite material has a particle size range of 30–80 μm, a median particle size of 55 μm, and a density of 0.85 g / cm³. 3 The compressive strength is 200 MPa. The mercapto-containing adsorption layer is a 3-mercaptopropionic acid condensation poly(3-cyanopropyltrimethoxysilane) adsorption layer.

[0102] A method for preparing the above-mentioned solid bubble composite material for adsorbing heavy metals includes the following steps:

[0103] S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles.

[0104] Hollow glass microspheres with a density of 0.57 g / cm³ 3Hollow glass microspheres with a median particle size of 55 μm were placed in a glass beaker, and then 500 mL of deionized water was added. The mixture was stirred thoroughly and allowed to stand for 1 hour for flotation. After separation, 15 g of the upper layer of intact hollow glass microspheres was collected for later use. The flotated hollow glass microspheres were then placed in 300 mL of a 3 mol / L sodium hydroxide solution and stirred at 180 rpm for 5 hours in a 50°C water bath. After solid-liquid separation, the product was washed with deionized water until neutral and then dried in an oven.

[0105] S2 uses a grafting agent to graft the product of S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials and obtain solid bubbles with sufficient reaction sites.

[0106] 10g of hydroxylated solid foam was weighed and dispersed in 550mL of xylene solution. 25g of 3-cyanopropyltrimethoxysilane was added, and the mixture was refluxed at 55℃ for 7h under a nitrogen atmosphere to perform surface grafting. After solid-liquid separation, the mixture was washed three times with water and then three times with ethanol. Finally, it was vacuum dried at 70℃ for 6h to obtain surface-grafted solid bubbles.

[0107] S3 modifies the product of S2 by utilizing the specific binding of a thiol-containing compound to the reaction site, thereby introducing thiol groups and obtaining a thiol-based solid bubble composite material.

[0108] 10g of surface-grafted solid bubbles were dispersed in 550mL of ethylene glycol monomethyl ether, 18g of 3-mercaptopropionic acid was added for reaction, and 5g of PTSA catalyst was added. The reaction was carried out under nitrogen atmosphere at 60℃ for 14h to introduce mercapto groups. After solid-liquid separation, the mixture was washed three times with deionized water and then three times with ethanol before drying to obtain mercapto-based solid bubble composite material.

[0109] An application method for the above-mentioned solid bubble composite material is provided, with the steps being exactly the same as in Example 2. The adsorption properties of the solid bubble composite material in this example are shown in Table 2.

[0110] Example 4

[0111] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:0.4. The solid bubbles are fly ash cenospheres with a density of 0.62 g / cm³. 3 The solid bubble composite material has a particle size range of 700–1000 μm, a median particle size of 850 μm, and a density of 0.82 g / cm³. 3 The compressive strength is 1 MPa. The mercapto-containing adsorption layer is a dithiol condensation poly(3-glycidyl etheroxypropyltrimethoxysilane) adsorption layer.

[0112] A method for preparing the above-mentioned solid bubble composite material for adsorbing heavy metals includes the following steps:

[0113] S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles.

[0114] Fly ash cenospheres have a density of 0.62 g / cm³. 3 The median particle size was 850 μm. The fly ash particles were placed in a glass beaker, and 500 mL of deionized water was added. The mixture was stirred thoroughly and allowed to stand for 1 hour before flotation. After separation, 20 g of the upper layer of intact fly ash particles was collected for later use. The flotated fly ash particles were then placed in 800 mL of a 1.8 mol / L sodium hydroxide solution and stirred at 250 rpm for 2 hours in a 30°C water bath. After solid-liquid separation, the product was washed with deionized water until neutral and then dried in an oven.

[0115] S2 uses a grafting agent to graft the product of S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials and obtain solid bubbles with sufficient reaction sites.

[0116] 10g of hydroxylated solid foam was weighed and dispersed in a 300mL mixture of acetone and water. 15g of 3-glycidyl etheroxypropyltrimethoxysilane was added. The mixture was refluxed at 60℃ for 3h under a nitrogen atmosphere to perform surface grafting. After solid-liquid separation, the mixture was washed three times with water and then three times with ethanol. Finally, it was vacuum dried at 60℃ for 7h to obtain surface-grafted solid bubbles.

[0117] S3 modifies the product of S2 by utilizing the specific binding of a thiol-containing compound to the reaction site, thereby introducing thiol groups and obtaining a thiol-based solid bubble composite material.

[0118] 10g of surface-grafted solid bubbles were dispersed in 400mL of ethylene glycol monomethyl ether, 20g of dithiol was added for reaction, and 3g of triethylamine catalyst was added. The reaction was carried out under nitrogen atmosphere at 60℃ for 20h to introduce thiol groups. After solid-liquid separation, the mixture was washed three times with deionized water and then three times with ethanol before drying to obtain thiol-based solid bubble composite material.

[0119] An application method for the above-mentioned solid bubble composite material is provided, with the steps being exactly the same as in Example 2. The adsorption properties of the solid bubble composite material in this example are shown in Table 2.

[0120] Example 5

[0121] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:0.82. The solid bubbles are ceramic bubbles with a density of 0.90 g / cm³. 3 The solid bubble composite material has a particle size range of 500–600 μm, a median particle size of 560 μm, and a density of 0.95 g / cm³. 3 The compressive strength is 30 MPa. The thiol-containing adsorption layer is an L-cysteine ​​and polyvinyltrimethoxysilane adsorption layer.

[0122] A method for preparing the above-mentioned solid bubble composite material for adsorbing heavy metals includes the following steps:

[0123] S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles.

[0124] Ceramic bubbles, with a density of 0.90 g / cm³. 3 The median particle size was 560 μm. The particles were placed in a glass beaker, and 500 mL of deionized water was added. The mixture was stirred thoroughly and allowed to stand for 1 hour before flotation. After separation, 20 g of the upper layer of intact ceramic bubbles was collected for later use. The flotated ceramic bubbles were then placed in 500 mL of a 3.8 mol / L sodium hydroxide solution and stirred at 70 rpm for 7 hours in a 70°C water bath. After solid-liquid separation, the product was washed with deionized water until neutral and then dried in an oven.

[0125] S2 uses a grafting agent to graft the product of S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials and obtain solid bubbles with sufficient reaction sites.

[0126] 10g of hydroxylated solid foam was weighed and dispersed in 500mL of isopropanol. 20g of vinyltrimethoxysilane was added, and the mixture was refluxed at 75℃ for 10h under a nitrogen atmosphere to perform surface grafting. After solid-liquid separation, the mixture was washed three times with water and then three times with ethanol. Finally, it was vacuum dried at 80℃ for 5h to obtain surface-grafted solid bubbles.

[0127] S3 modifies the product of S2 by utilizing the specific binding of a thiol-containing compound to the reaction site, thereby introducing thiol groups and obtaining a thiol-based solid bubble composite material.

[0128] 10g of surface-grafted solid bubbles were dispersed in 700mL of ethylene glycol monomethyl ether, 25g of L-cysteine ​​was added for reaction, and 5g of azobisisobutyronitrile catalyst was added. The reaction was carried out under nitrogen atmosphere at 50℃ for 24h to introduce thiol groups. After solid-liquid separation, the mixture was washed three times with deionized water and then three times with ethanol before drying to obtain thiol-based solid bubble composite material.

[0129] An application method for the above-mentioned solid bubble composite material is provided, with the steps being exactly the same as in Example 2. The adsorption properties of the solid bubble composite material in this example are shown in Table 2.

[0130] Example 6

[0131] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:1. The solid bubbles are hollow glass microspheres with a density of 0.20 g / cm³. 3 The solid bubble composite material has a particle size range of 50–100 μm, a median particle size of 65 μm, and a density of 0.44 g / cm³. 3 The compressive strength is 50 MPa. The thiol-containing adsorption layer is a 3-mercapto-2-butanol condensation 3-ureopropyltriethoxysilane adsorption layer.

[0132] The preparation method of the solid bubble composite material in this embodiment is similar to that in Example 1, except that in step S2: 10g of hydroxylated solid foam is weighed and dispersed in 500mL of pure water solution, 10g of 3-ureidopropyltriethoxysilane is added, and the surface grafting is carried out by reflux reaction at 80°C for 1h under nitrogen atmosphere.

[0133] S3, 10g of surface-grafted solid bubbles were dispersed in 600mL of toluene, 30g of 3-mercapto-2-butanol was added for reaction, and 5g of catalyst NHS was added. The reaction was stirred at 70℃ for 6h under a nitrogen atmosphere.

[0134] An application method for the above-mentioned solid bubble composite material is provided, with the steps being exactly the same as in Example 2. The adsorption properties of the solid bubble composite material in this example are shown in Table 2.

[0135] Example 7

[0136] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:1. The solid bubbles are hollow glass microspheres with a density of 0.20 g / cm³. 3 The solid bubble composite material has a particle size range of 50–100 μm, a median particle size of 65 μm, and a density of 0.49 g / cm³. 3The compressive strength is 50 MPa. The thiol-containing adsorption layer is a 3-mercapto-2-butanol condensation poly(3-isocyanate-propyltriethoxysilane) adsorption layer.

[0137] The preparation method of the solid bubble composite material in this embodiment is similar to that in Example 1, except that in step S2: 10g of hydroxylated solid foam is weighed and dispersed in 600mL of toluene, 8g of 3-isocyanate-propyltriethoxysilane is added, and the surface grafting is carried out by reflux reaction at 80°C for 5h under nitrogen atmosphere.

[0138] S3, 10g of surface-grafted solid bubbles were dispersed in 600mL of toluene, 30g of 3-mercapto-2-butanol was added for reaction, and 1g of catalyst DBTDL was added. The reaction was stirred at 50℃ for 6h under a nitrogen atmosphere.

[0139] An application method for the above-mentioned solid bubble composite material is provided, with the steps being exactly the same as in Example 2. The adsorption properties of the solid bubble composite material in this example are shown in Table 2.

[0140] Example 8

[0141] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:1. The solid bubbles are hollow glass microspheres with a density of 0.20 g / cm³. 3 The solid bubble composite material has a particle size range of 50–100 μm, a median particle size of 65 μm, and a density of 0.51 g / cm³. 3 The compressive strength is 50 MPa. The thiol-containing adsorption layer is a 2,3-dimercaptosuccinic acid crosslinked aluminum isopropoxystearate adsorption layer.

[0142] The preparation method of the solid bubble composite material in this embodiment is similar to that in Example 1, except that in step S2: 10g of hydroxylated solid foam is weighed and dispersed in a mixture of 800mL of ethanol and water, and 50g of aluminum isopropoxystearate is added. The surface grafting is carried out by reflux reaction at 80°C for 12h under a nitrogen atmosphere.

[0143] An application method for the above-mentioned solid bubble composite material is provided, with the steps being exactly the same as in Example 2. The adsorption properties of the solid bubble composite material in this example are shown in Table 2.

[0144] Example 9

[0145] A solid bubble composite material for adsorbing heavy metals is disclosed. The composite material consists of solid bubbles loaded with a thiol-containing compound, with a mass ratio of solid bubbles to a thiol-containing adsorption layer of 1:1. The solid bubbles are hollow glass microspheres with a density of 0.20 g / cm³. 3The solid bubble composite material has a particle size range of 50–100 μm, a median particle size of 65 μm, and a density of 0.53 g / cm³. 3 The compressive strength is 50 MPa. The thiol-containing adsorption layer is a 2,3-dimercaptosuccinic acid crosslinked di(acetylacetonyl)isopropoxy titanium adsorption layer.

[0146] The preparation method of the solid bubble composite material in this embodiment is similar to that in Example 1, except that in step S2: 10g of hydroxylated solid foam is weighed and dispersed in 700mL of ethylene glycol monomethyl ether, and 50g of di(acetylacetonyl)isopropoxy titanium is added. The surface grafting is carried out by reflux reaction at 80°C for 12h under nitrogen atmosphere.

[0147] An application method for the above-mentioned solid bubble composite material is provided, with the steps being exactly the same as in Example 2. The adsorption properties of the solid bubble composite material in this example are shown in Table 2.

[0148] Comparative Example 1

[0149] This comparative example uses commercial... The CH-90Na chelating resin was used to adsorb and treat heavy metal wastewater, following the same steps as in Example 1. The initial adsorption capacity of each heavy metal ion by the chelating resin in this comparative example is shown below. Figure 2 The adsorption properties of the chelating resins in this comparative example are shown in Table 2.

[0150] Comparative Example 2

[0151] This comparative example is a solid bubble composite material similar to that of Example 1. The raw materials used in its preparation are exactly the same. The only difference between this comparative example and Example 1 is that this comparative example is a mercapto-based solid bubble composite material that has not undergone alkaline activation treatment. That is, this comparative example does not have step S1 compared to Example 1, while the other steps are exactly the same.

[0152] The application method of the above-mentioned solid bubble composite material is exactly the same as that in Example 2. The adsorption performance of the comparative example solid bubble composite material is shown in Table 2.

[0153] Comparative Example 3

[0154] This comparative example is a solid bubble composite material similar to that of Example 1. The raw materials used in its preparation are exactly the same. The only difference between this comparative example and Example 1 is that this comparative example is an ungrafted thiolized solid bubble composite material. That is, this comparative example does not have step S2 compared to the example, while the other steps are exactly the same.

[0155] The application method of the above-mentioned solid bubble composite material is exactly the same as that in Example 2. The adsorption performance of the comparative example solid bubble composite material is shown in Table 2.

[0156] Comparative Example 4

[0157] This comparative example is a solid bubble composite material similar to that of Example 1. The raw materials used in its preparation are exactly the same. The only difference between this comparative example and Example 1 is that this comparative example is a solid bubble composite material without mercapto treatment. That is, this comparative example does not have step S3 compared to the example, while the other steps are exactly the same.

[0158] The application method of the above-mentioned solid bubble composite material is exactly the same as that in Example 2. The adsorption performance of the comparative example solid bubble composite material is shown in Table 2.

[0159] Table 2 Adsorption performance of the adsorbents in the examples and comparative examples

[0160]

[0161]

[0162] from Figure 2 It can be seen that the heavy metal ions Hg in Example 1 2+ Cd 2+ Pd 2+ Cu 2+ Ni 2+ The initial adsorption capacities of all of them were higher than those of the chelating resin in Comparative Example 1, especially Hg. 2+ Cd 2+ Pd 2+ Three heavy metal ions, such as Hg in Example 1 2+ Cd 2+ Pd 2+ The initial adsorption capacities were 88.04 mg / g, 77.40 mg / g, and 83.70 mg / g, respectively, while the Hg in Comparative Example 1 was... 2+ Cd 2+ Pd 2+ The initial adsorption capacities were 15.21 mg / g, 21.80 mg / g, and 38.90 mg / g, respectively. This indicates that the adsorption capacity of the thiol-based solid bubble composite material of the present invention is significantly increased compared with commercial wastewater heavy metal adsorbents, especially in the treatment of cadmium, mercury, and lead pollution in wastewater.

[0163] As shown in Table 2, the initial mercury ion adsorption capacity of the embodiments of the present invention is above 80 mg / g, and the adsorption capacity retention rate after ten cycles is above 92%, with the number of cycles where the adsorption capacity retention rate is below 90% between 20 and 30. In contrast, the adsorption capacity retention rate of Comparative Example 1 after ten cycles is 85.32%, and the number of cycles where the adsorption capacity retention rate is below 90% is 8. This demonstrates that the embodiments of the present invention exhibit excellent cycling stability and are suitable for long-term industrial use. The initial mercury ion adsorption capacity, adsorption capacity retention rate after ten cycles, and the number of cycles where the adsorption capacity retention rate is below 90% in Comparative Examples 2-4 are significantly lower than those of the embodiments, indicating that each step in the preparation method of the present invention is indispensable and necessary; the absence of any step will prevent the achievement of the technical effects of the present invention.

[0164] The above description of the present invention represents only some embodiments, but the present invention is not limited to the specific implementations described above. The specific implementations described above are illustrative and not restrictive. All specific extensions using the materials and methods of the present invention, without departing from the spirit and scope of the claims, are within the protection scope of the present invention.

Claims

1. A solid bubble composite material for adsorbing heavy metals, characterized in that, The heavy metals include cadmium ions, lead ions, mercury ions, copper ions, and nickel ions; the composite material is a solid bubble with a thiol-containing adsorption layer on its outer surface, and the mass ratio of the solid bubble to the thiol-containing adsorption layer is 1:(0.12~1.2); the density of the composite material is 0.12~0.95 g / cm³. 3 .

2. The composite material according to claim 1, characterized in that, The composite material has a particle size of 10–1000 μm and a compressive strength between 1 MPa and 200 MPa; the solid bubbles are inorganic materials composed of a solid shell surrounding a large number of closed gas cavities inside, and the density of the solid bubbles is 0.1–0.9 g / cm³. 3 The compressive strength is between 1MPa and 200MPa.

3. The composite material according to claim 2, characterized in that, The solid bubbles are at least one of hollow glass microspheres, insulated glass microspheres, fly ash cenospheres, and ceramic bubbles.

4. The composite material according to claim 1, characterized in that, The thiol-containing adsorption layer includes at least one of the following: 3-mercapto-2-butanol condensation of 3-isocyanate-propyltriethoxysilane, dithiol condensation of 3-glycidyl etheroxypropyltrimethoxysilane, 2,3-dimercaptosuccinic acid condensation of 3-aminopropyltrimethoxysilane, L-cysteine ​​plus polyvinyltrimethoxysilane, thioacetic acid condensation of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropionic acid condensation of 3-cyanopropyltrimethoxysilane, 3-mercapto-2-butanol condensation of 3-ureopropyltriethoxysilane, 2,3-dimercaptosuccinic acid crosslinked aluminum isopropoxystearate, and 2,3-dimercaptosuccinic acid crosslinked di(acetylacetonyl)isopropoxytitanium.

5. A method for preparing the composite material according to any one of claims 1-4, characterized in that, The method includes the following steps: S1, after adding solid bubbles to water and stirring thoroughly, let them stand for a period of time for flotation, and after separation, take the upper layer of intact solid bubbles, and increase the surface hydroxyl density through alkaline activation treatment to obtain interfacial hydroxylated solid bubbles. S2 involves grafting a grafting agent onto the solid bubbles obtained in S1. The grafting agent acts as a "molecular bridge" to achieve the combination of organic and inorganic materials, thereby obtaining solid bubbles with sufficient reaction sites. S3 modifies the solid bubbles obtained in S2 by utilizing the specific binding of thiol-containing compounds to the reaction sites, thereby introducing thiol groups and obtaining thiol-based solid bubble composite materials.

6. The method according to claim 6, characterized in that, In step 1, the alkaline activation treatment is as follows: solid bubbles are placed in a beaker containing a sodium hydroxide solution with a concentration of 0.5-5 mol / L at a solid-liquid ratio of 10-100 g / L and stirred at 50-300 r / min for 1-8 h. The reaction temperature is 20-80℃. After standing and cooling to separate the solid and liquid, the mixture is rinsed with deionized water until neutral and then dried.

7. The method according to claim 6, characterized in that, In step 2, the grafting is performed by dispersing the solid bubbles obtained in S1 in the reaction solvent, adding a grafting agent, and refluxing at 30-80°C for 1-12 hours under a nitrogen atmosphere to perform surface grafting. After solid-liquid separation, the solid bubbles are washed three times with water and then three times with ethanol. After vacuum drying at 50-90°C for 4-8 hours, solid bubbles with sufficient reaction sites are obtained. The grafting agent is at least one of 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-cyanopropyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-isocyanate-propyltriethoxysilane (IPTS), vinyltrimethoxysilane, aluminum isopropoxystearate, and di(acetylacetonyl)isopropoxytitanium. The reaction solvent is one or more selected from ethanol, isopropanol, water, acetone, toluene, xylene, and ethylene glycol monomethyl ether. The ratio of the solid bubbles, reaction solvent, and grafting agent is 1g:(10-100)mL:(0.1-5)g.

8. The method according to claim 6, characterized in that, In step 3, the modification is as follows: the solid bubbles obtained in S2 are reacted with the mercapto-containing compound in a solvent, and a catalyst is added. The reaction is stirred at 40-80°C for 4-24 hours under a nitrogen atmosphere. After solid-liquid separation, the mixture is washed three times with deionized water, then washed three times with ethanol, and then dried. The thiol-containing compound is at least one of 3-mercapto-2-butanol, dithiol, 2,3-dimercaptosuccinic acid, L-cysteine, thioglycolic acid, and 3-mercaptopropionic acid. The catalyst is at least one of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl), N-hydroxysuccinimide (NHS), p-toluenesulfonic acid (PTSA), triethylamine, azobisisobutyronitrile, and dibutyltin dilaurate (DBTDL). The solvent is one or more of ethanol, isopropanol, water, acetone, toluene, xylene, and ethylene glycol monomethyl ether.

9. The method according to claim 8, characterized in that, The ratio of the solid bubbles, the solvent, the mercapto-containing compound, and the catalyst is 1g:(10-100)mL:(0.5-3)g:(0.1-1)g.

10. A method for applying the composite material as described in any one of claims 1-4, or the composite material prepared by the method as described in any one of claims 5-9, in the treatment of heavy metal wastewater, wherein the heavy metal wastewater includes at least one of cadmium ions, lead ions, mercury ions, copper ions, and nickel ions.

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