Nanometer metal sulfide coated straw biomass aerogel and preparation and application thereof

Abstract

The application discloses a kind of nano metal sulfide coating straw biomass aerogel and its preparation and application.The present application uses non-powdered straw biomass material as substrate, by successively dipping metal salt solution and sodium sulfide solution, in-situ nano metal sulfide coating is generated on straw biomass material, and nano metal sulfide coated straw biomass aerogel is obtained.The straw biomass material described in the present application has high adsorption and biological harmlessness, and the modified straw biomass aerogel can simultaneously adsorb cadmium and lead in water and soil environment.The modified straw biomass aerogel has good mechanical property and floatability, the introduction of metal sulfide nano coating increases the good stability of straw biomass, so that the straw biomass is not easily biodegraded, and can maintain high integrity during the process of adsorbing and immobilizing heavy metals, and is easy to salvage and recover after adsorption, effectively reducing the content of heavy metals in water and soil environment.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization and heavy metal pollution control, specifically relating to a nano-metal sulfide coated straw biomass aerogel and its preparation and application. Background Technology

[0002] Currently, most straw is still disposed of through burning or indiscriminate dumping. This not only leads to a huge waste of valuable resources but also causes serious air pollution and environmental problems due to the large amounts of smoke and harmful gases produced by straw burning. In major sunflower-producing areas, due to the large biomass and rapid turnover of sunflower straw, a huge amount of straw is generated each year, which is often improperly disposed of, becoming a prominent environmental problem.

[0003] Sunflower stalks possess unique structural characteristics, being rich in cellulose, hemicellulose, and lignin. These natural polymers provide them with excellent mechanical strength and a porous structure. This unique porous structure makes sunflower stalks a potential adsorbent material, particularly showing promising applications in adsorbing heavy metal ions from water and soil. Through appropriate pretreatment and chemical modification, the adsorption capacity of sunflower stalks can be significantly enhanced, improving their affinity and selectivity for specific heavy metal ions. Furthermore, the widespread availability and relatively low cost of sunflower stalks make them an economical and efficient material choice. In agricultural production, straw is often considered a byproduct or waste; its resource utilization can effectively reduce agricultural waste while providing a sustainable environmental management solution.

[0004] However, current research on the use of sunflower stalks for heavy metal adsorption is relatively limited. This is mainly because the conversion of sunflower stalks into adsorbent materials requires complex pretreatment processes, such as crushing, which not only increases the complexity of the operation but also raises the cost of subsequent processing. Furthermore, in environmental applications, especially in soil environments, the susceptibility of sunflower stalks to microbial degradation limits their efficiency in heavy metal removal, making it difficult to achieve long-term, stable heavy metal removal effects. To overcome these challenges, developing a simple and economical modified sunflower stalk preparation process for environmental heavy metal removal is a key issue that urgently needs to be addressed in this research field.

[0005] Metal sulfides (M x S y ) is an effective adsorbent because its structure contains M y+ and S 2- It possesses high reducing activity, high specific surface area, and readily forms M(OH). yThese characteristics enable it to provide more active sites for capturing heavy metal ions, efficiently removing heavy metals from water through co-precipitation reactions and adsorption, reducing their toxicity and migration ability, thus making it an important material for the removal of various heavy metals. Furthermore, nano-metal sulfides also exhibit good selectivity and low material cost, making them highly economical in practical applications.

[0006] However, nanotechnology also has some significant drawbacks in heavy metal remediation. First, although nanomaterials exhibit highly efficient pollutant removal capabilities, their environmental impacts and potential ecotoxicity are not fully understood, posing environmental safety risks. Second, the production and application costs of nanomaterials remain high, limiting their application in a wide range of environmental remediation projects. Furthermore, the stability of nanomaterials and potential secondary pollution issues, such as toxic byproducts that may be generated during use, require further research and solutions to ensure the safety and effectiveness of their environmental applications. These challenges require researchers to consider not only efficiency but also environmental and economic sustainability when developing new materials and technologies. Summary of the Invention

[0007] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing nano-metal sulfide-coated straw biomass aerogel.

[0008] This invention uses non-powdered straw biomass material as a substrate, and generates a nano-metal sulfide coating on the straw biomass material in situ by impregnating it with a metal salt solution and a sodium sulfide solution, thus obtaining a straw biomass aerogel coated with nano-metal sulfide.

[0009] Another object of the present invention is to provide a nano-metal sulfide coated straw biomass aerogel prepared by the above preparation method.

[0010] Another object of the present invention is to provide the application of the above-mentioned nano-metal sulfide coated straw biomass aerogel in heavy metal removal.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] A method for preparing nano-metal sulfide-coated straw biomass aerogel includes the following steps:

[0013] (1) Non-powdered straw biomass material was soaked in a metal salt solution for a certain period of time, then removed, washed, and dried to obtain metal ion-loaded M. y+ Straw biomass materials;

[0014] (2) Loading metal ions M y+Straw biomass material was soaked in sodium sulfide (Na2S) solution for a certain period of time, then removed, washed, and dried to obtain straw biomass aerogel coated with nano-metal sulfide.

[0015] Preferably, the shape of the non-powdered straw biomass material in step (1) is at least one of sheet, block and rod; more preferably, the thickness of the sheet, block and rod is 0.01 to 10 cm.

[0016] More preferably, the thickness of the sheet-like, block-like, and rod-like shapes is 0.01 to 1 cm.

[0017] Preferably, the non-powdered straw biomass material in step (1) is subjected to washing, drying and cutting; the washing refers to washing with water; the drying is freeze drying, and the time is 24 to 48 hours.

[0018] Preferably, in step (1), the straw biomass material is at least one of corn straw, sunflower straw, sugarcane bagasse, and wheat straw. More preferably, it is at least one of sugarcane bagasse and sunflower straw, and more preferably, it is sunflower straw.

[0019] Preferably, the metal salt solution in step (1) is prepared by mixing metal salt and water at a mass ratio of 1:(1 to 340), and more preferably, the mass ratio is 1:(12 to 33).

[0020] Preferably, in the metal salt solution of step (1), the metal salt is at least one selected from ferric nitrate nonahydrate, ferric sulfate nonahydrate, ferrous chloride tetrahydrate, ferric chloride hexahydrate, ferrous sulfate heptahydrate, manganese sulfate, and zinc sulfate heptahydrate. More preferably, it is ferrous sulfate heptahydrate.

[0021] Preferably, the mass ratio of the non-powdered straw biomass material to the metal salt solution in step (1) is 1:(14-180). More preferably, the mass ratio is 1:(144-152), and even more preferably, the mass ratio is 1:148.

[0022] Preferably, the soaking time in step (1) is 6 to 48 hours. More preferably, it is 24 to 48 hours. More preferably, it is 24 hours.

[0023] Preferably, the washing in steps (1) and (2) refers to washing with water; the drying is conventional drying in the art.

[0024] Preferably, the sodium sulfide (Na2S) solution in step (2) is prepared by mixing Na2S·9H2O and water at a mass ratio of 1:(2.08 to 208). More preferably, the mass ratio is 1:(2.08 to 20.8). Even more preferably, the mass ratio is 1:20.8.

[0025] Preferably, the mass ratio of sodium sulfide in the sodium sulfide (Na2S) solution in step (2) to the metal salt in the metal salt solution in step (1) is 1:(0.6-20.5). Most preferably, it is 1:(0.6-1.8).

[0026] Preferably, the soaking time in step (2) is 6 to 48 hours. More preferably, it is 24 to 48 hours. More preferably, it is 24 hours.

[0027] Preferably, the metal sulfide in step (2) is at least one selected from ferrous sulfide, triferrosulfide, manganese sulfide, zinc sulfide, and magnesium sulfide. More preferably, it is at least one selected from ferrous sulfide, triferrosulfide, manganese sulfide, and zinc sulfide. More preferably, it is ferrous sulfide.

[0028] A nano-metal sulfide coated straw biomass aerogel was prepared by the above method.

[0029] This invention preserves the original network structure of straw biomass while employing nano-coating technology to in-situ load metal sulfides (M) onto the biomass surface. x S y This further enriches the adsorption sites for heavy metals on the surface of straw biomass, thereby improving the adsorption and removal capacity of straw biomass for heavy metals in the environment.

[0030] The above-mentioned application of a nano-metal sulfide coated straw biomass aerogel in the removal of cadmium and lead from water and / or soil.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) This invention proposes a resource-based reuse strategy for straw waste. It utilizes nano-coating technology to load metal sulfides on the surface of straw in situ to obtain a nano-coating, thereby enriching the heavy metal adsorption sites on the surface of straw, especially sunflower stem core, and improving its adsorption and removal capacity for heavy metals in the environment.

[0033] (2) The straw biomass material described in this invention has high adsorption capacity and is biologically harmless. The modified straw biomass aerogel can simultaneously adsorb cadmium and lead in water and soil environments. The modified straw biomass aerogel has good mechanical properties and buoyancy. The introduction of the metal sulfide nanocoating increases the good stability of the straw biomass, making it less susceptible to biodegradation. It can maintain high integrity during the adsorption of immobilized heavy metals and is easy to retrieve and recycle after adsorption, effectively reducing the content of heavy metals in the water and soil environment. In contrast, straw biomass without the metal sulfide nanocoating is easily degraded, or even completely degraded, during the adsorption of immobilized heavy metals, making it impossible to retrieve and recycle after adsorption. Therefore, it cannot effectively remove and reduce the content of heavy metals in the water and soil environment.

[0034] (3) The composite material described in this invention is widely available, inexpensive, simple to manufacture, highly reproducible, and has promising prospects for industrial application, providing a new approach for the resource recycling of straw waste. Attached Figure Description

[0035] Figure 1 The images show physical pictures of the SFC material, Fe(Ⅱ)@SFC material, and FeS(Ⅱ)@SFC material prepared in this invention.

[0036] Figure 2 The images show the FTIR spectra of the SFC material in Example 1, the Fe(Ⅱ)@SFC material in Comparative Example 1, and the FeS(Ⅱ)@SFC material before and after adsorption of cadmium and lead.

[0037] Figure 3 This is the SEM-EDS-Mapping of the SFC material in Example 1.

[0038] Figure 4 This is the SEM-EDS-Mapping of the FeS(Ⅱ)@SFC material in Example 2.

[0039] Figure 5 This is the SEM-EDS-Mapping of the FeS(Ⅱ)@SFC-(cadmium-lead immobilized) material in Example 5.

[0040] Figure 6 XRD patterns of SFC material and FeS(Ⅱ)@SFC material before and after adsorption of cadmium and lead.

[0041] Figure 7 This is a graph showing the adsorption capacity of FeS(Ⅱ)@SFC material for cadmium and lead in a cadmium-lead binary water system in this invention.

[0042] Figure 8 This is a photograph of the recovered SFC- and adjacent soil and FeS(Ⅱ)@SFC material after the soil heavy metal removal application experiment in Example 5.

[0043] Figure 9 The total cadmium and available cadmium content in the soil after the FeS(Ⅱ)@SFC material and the unmodified SFC material were applied to the soil in Example 7.

[0044] Figure 10 SEM images of the in-situ soil after the application of unmodified SFC materials and SEM-EDS images of the recovered FeS(Ⅱ)@SFC materials. Detailed Implementation

[0045] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0046] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0047] Example 1

[0048] Preparation of straw biomass aerogel materials (SBM materials):

[0049] 1.1 Preparation of sunflower stem core aerogel material (SFC)

[0050] 1) Wash the sunflower stems with purified water and dry them in an oven at 105℃ for 24 hours. After drying, separate the skin and core of the sunflower stems to obtain sunflower stalk skin and sunflower core (SFC).

[0051] 2) Use a ceramic knife to cut the SFC material into uniform cylindrical slices, each cylindrical slice being approximately 1 cm thick.

[0052] 1.2 Preparation of Corn Cob Aerogel (COB)

[0053] 1) Wash the collected corn cob (COB) stalks with purified water and dry them in an oven at 105℃ for 24 hours.

[0054] 2) Use a ceramic knife to cut the COB material into uniform cylindrical slices, each slice being about 1cm thick. Then, cut the COB cylindrical slices into four fan-shaped slices of the same size.

[0055] 1.3 Preparation of sugarcane bagasse aerogel (CC) material

[0056] 1) Wash the collected sugarcane bagasse straw with pure water and dry it in an oven at 105℃ for 24 hours.

[0057] 2) The dried sugarcane bagasse is passed through a 20-mesh sieve. Sugarcane bagasse larger than 20 mesh is collected and each 0.1g of sugarcane bagasse is pressed into a cylindrical tablet with a thickness of about 1.0cm and a diameter of about 2cm by a tablet press, which is denoted as CC.

[0058] Example 2

[0059] Nanometal sulfide coated straw biomass aerogel material (M x S y Preparation of @SBM):

[0060] 1.1 Nanoscale metal sulfide coated sunflower stem core aerogel material M x S y Preparation of @SFC

[0061] 1) At room temperature, 5.850g of ferric sulfate nonahydrate (Fe2(SO4)3·9H2O), 3.893g of ferrous sulfate heptahydrate (FeSO4·7H2O), 2.114g of manganese sulfate (MnSO4), and 4.026g of zinc sulfate heptahydrate (ZnSO4·7H2O) were weighed and placed in different beakers containing 70mL of ultrapure water. The mixture was stirred with a glass rod until dissolved, resulting in four different metal salt solutions.

[0062] 2) Take 0.5g of sunflower stem core aerogel material (SFC) and immerse it in different metal salt solutions for 24h. After rinsing with ultrapure water, remove it and freeze-dry it to obtain M. y+ @SFC materials.

[0063] 3) At room temperature, weigh 3.361g of sodium sulfide nonahydrate (Na2S·9H2O) and add it to a beaker containing 70mL of ultrapure water. Stir with a glass rod until completely dissolved.

[0064] 4) After drying M y+ @SFC material was then soaked in sodium sulfide solution for 24 hours and then freeze-dried to obtain M. x S y @SFC materials.

[0065] 1.2 nm metal sulfide coated corn cob aerogel material M x S y Preparation of @COB

[0066] 1) At room temperature, 5.850g of ferric sulfate nonahydrate (Fe2(SO4)3·9H2O), 3.893g of ferrous sulfate heptahydrate (FeSO4·7H2O), 3.444g of magnesium sulfate heptahydrate (MgSO4·7H2O), 2.114g of manganese sulfate (MnSO4), and 4.026g of zinc sulfate heptahydrate (ZnSO4·7H2O) were weighed and placed in different beakers containing 70mL of ultrapure water. The mixture was stirred with a glass rod until dissolved, resulting in four different metal salt solutions.

[0067] 2) Take 0.5g of corn cob aerogel material (COB) and immerse it in different metal salt solutions for 24h. After rinsing with ultrapure water, remove it and freeze-dry it to obtain M. y+ @COB materials.

[0068] 3) At room temperature, weigh 3.361g of sodium sulfide nonahydrate (Na2S·9H2O) and add it to a beaker containing 70mL of ultrapure water. Stir with a glass rod until completely dissolved.

[0069] 4) After drying M y+ @COB material was then soaked in sodium sulfide solution for 24 hours and freeze-dried to obtain M x Sy @COB materials.

[0070] 1.3 nanometer metal sulfide coating on bagasse aerogel material M x S y Preparation of @CC

[0071] 1) At room temperature, 5.850g of ferric sulfate nonahydrate (Fe2(SO4)3·9H2O), 3.893g of ferrous sulfate heptahydrate (FeSO4·7H2O), 3.444g of magnesium sulfate heptahydrate (MgSO4·7H2O), 2.114g of manganese sulfate (MnSO4), and 4.026g of zinc sulfate heptahydrate (ZnSO4·7H2O) were weighed and placed in different beakers containing 70mL of ultrapure water. The mixture was stirred with a glass rod until dissolved, resulting in 8 different metal salt solutions.

[0072] 2) Take 0.5g of sugarcane bagasse aerogel material (CC) and immerse it in different metal salt solutions for 24h. After rinsing with ultrapure water, remove and freeze-dry to obtain M. y+ @CC materials.

[0073] 3) At room temperature, weigh 3.361g of sodium sulfide nonahydrate (Na2S·9H2O) and add it to a beaker containing 70mL of ultrapure water. Stir with a glass rod until completely dissolved.

[0074] 4) After drying M y+ @CC material was then soaked in sodium sulfide solution for 24 hours and freeze-dried to obtain M. x S y @CC materials.

[0075] Comparative Example 1

[0076] 1) Wash the sunflower stems with purified water and dry them in a vacuum oven at 105℃ for 24 hours.

[0077] 2) The dried sunflower stems are subjected to a peel-core separation process to obtain sunflower stalk peel and sunflower stem core (SFC).

[0078] 3) Use a ceramic knife to cut the SFC material into uniform cylindrical slices, each cylindrical slice being approximately 1 cm thick.

[0079] 4) At room temperature, weigh 3.893g of ferrous sulfate heptahydrate (FeSO4·7H2O) and add it to a beaker containing 70mL of ultrapure water. Stir with a glass rod until completely dissolved.

[0080] 5) Take 0.5g of sunflower stem core (SFC) slices, soak them in ferrous sulfate solution for 24h, and then freeze-dry them to obtain Fe(II)@SFC material, i.e., Fe 2+ @SFC materials.

[0081] Figure 1 The images show physical images of the SFC material, Fe(II)@SFC material, and FeS(II)@SFC material prepared in this invention. (a) is a physical image of the SFC material in Example 1 of this invention, (b) is a physical image of the Fe(II)@SFC material in Comparative Example 1 of this invention, and (c) is a physical image of the FeS(II)@SFC material in Example 2 of this invention. It can be clearly seen from the images that the color of the SFC material after modification by coating with nano-ferrous sulfide has significantly turned black, indirectly indicating that the coating process successfully coated the surface of the SFC material with nano-ferrous sulfide.

[0082] Comparative Example 2

[0083] 1) Wash the sunflower stems with purified water and dry them in a vacuum oven at 105℃ for 24 hours.

[0084] 2) The dried sunflower stems are subjected to a peel-core separation process to obtain sunflower stalk peel and sunflower stem core (SFC).

[0085] 3) Use a ceramic knife to cut the SFC material into uniform cylindrical slices, each cylindrical slice being approximately 1 cm thick.

[0086] 4) At room temperature, weigh 3.361g of sodium sulfide nonahydrate (Na2S·9H2O) and add it to a beaker containing 70mL of ultrapure water. Stir with a glass rod until completely dissolved.

[0087] 5) Take 0.5g of sunflower stem core (SFC) slices, soak them in sodium sulfide solution for 24h, and then freeze-dry them to obtain S@SFC material.

[0088] Comparative Example 3

[0089] 1) Wash the sunflower stems with purified water and dry them in a vacuum oven at 105℃ for 24 hours.

[0090] 2) The dried sunflower stems are subjected to a peel-core separation process to obtain sunflower stalk peel and sunflower stem core (SFC).

[0091] 3) Use a ceramic knife to cut the SFC material into uniform cylindrical slices, each cylindrical slice being approximately 1 cm thick.

[0092] 4) At room temperature, weigh 3.361g of sodium sulfide nonahydrate (Na2S·9H2O) and add it to a beaker containing 70mL of ultrapure water. Stir with a glass rod until completely dissolved.

[0093] 5) Take 0.5g of sunflower stem core (SFC) slices, soak them in sodium sulfide solution for 24h, and then freeze-dry them to obtain S@SFC material.

[0094] 6) At room temperature, weigh 3.893g of ferrous sulfate heptahydrate (FeSO4·7H2O) and add it to a beaker containing 70mL of ultrapure water. Stir with a glass rod until completely dissolved.

[0095] 7) The S@SFC material was immersed in ferrous sulfate solution for 24 hours and then freeze-dried to obtain Fe(Ⅱ)-S@SFC material, i.e., Fe 2+ -S@SFC material.

[0096] Figure 2 The figures show the FTIR spectra of the SFC material in Example 1, the Fe(II)@SFC material in Comparative Example 1, and the FeS(II)@SFC material in Example 2 before and after adsorption of cadmium and lead. The results demonstrate that nano-FeS was successfully loaded onto SFC through the immersion coating treatment. As shown in the figure, compared with the FTIR spectra of the SFC material, the four materials—Fe(II)@SFC and FeS(II)@SFC—before and after adsorption of cadmium and lead show significant differences in FTIR spectra in the 1440-1700 cm⁻¹ region. -1 The OH bond stretching vibration peaks appearing at 1550-1695 cm⁻¹ and at 1550-1695 cm⁻¹ -1 The intensity of the C=O bond stretching vibration peak at 3237 cm⁻¹ is significantly enhanced, and the peak intensity of Fe(Ⅱ)@SFC at 3237 cm⁻¹ is also significantly enhanced. -1 A new OH bond stretching vibration peak appears at 615 cm⁻¹. -1 472cm -1 The presence of Fe-O / Fe-S group peaks indicates that iron treatment imparts Fe-O / Fe-S groups to the SFC, and the added iron may complex with the hydroxyl and carboxylic acid ester groups on the SFC, thereby forming new iron-containing components in the SFC.

[0097] Comparing the FTIR plots of Fe(Ⅱ)@SFC and FeS(Ⅱ)@SFC, it can be found that Fe(Ⅱ)@SFC has a peak value of 3237 cm⁻¹. -1 The OH bond stretching vibration peak at 615 cm⁻¹ and the peak at 615 cm⁻¹ -1 472cm -1 The Fe-O / Fe-S group peaks at that location have shifted to 3235 cm⁻¹ of FeS(Ⅱ)@SFC, respectively. -1 and 617cm -1 474cm -1 Location. And within 1440-1700cm. -1 The peak width of the C=O bond stretching vibration at this point is significantly narrowed, which is because the S ion immersion treatment... 2- The adsorption and chelation of iron ions in sunflower pith straw to form FeS results in the release of the originally chelated -COOH and -OH groups.

[0098] Comparing the FTIR spectra of FeS(Ⅱ)@SFC material before and after adsorption of cadmium and lead, it can be found that adsorption of Cd... 2+ Afterwards, FeS(Ⅱ)@SFC at 3235cm -1 The OH bond stretching vibration peak at 617 cm⁻¹ and the peak at 617 cm⁻¹ -1 474cm -1 The Fe-O / Fe-S group peaks at that location have shifted to 3237 cm⁻¹ of FeS(Ⅱ)@SFC-Cd. -1 and 613cm -1 472cm -1 Adsorption of Pb 2+ Afterwards, FeS(Ⅱ)@SFC at 3235cm -1 The OH bond stretching vibration peak at 617 cm⁻¹ and the peak at 617 cm⁻¹ -1 The Fe-O / Fe-S group peaks at that location have shifted to 3237 cm⁻¹ of FeS(Ⅱ)@SFC-Cd. -1 and 615cm -1 The concentration of cadmium and lead after adsorption was 1440-1700 cm⁻¹. Furthermore, compared to before adsorption, the concentration of cadmium and lead after adsorption was significantly higher. -1 The peak width of the OH bond stretching vibration at this location becomes significantly narrower, at 1617 cm⁻¹. -1 The intensity of the corresponding C=O bond stretching vibration peak also decreased. This indicates that during the immobilization of cadmium in FeS(Ⅱ)@SFC, the Fe-O, C=O, and OH bonds interact with Cd. 2+ Pb 2+ A complexation reaction occurs, where FeS(II)@SFC adsorbs Cd. 2+ Pb 2+ The main adsorption sites.

[0099] Example 3

[0100] M x S y @SBM material application example for cadmium removal in unit water systems:

[0101] Weigh out 10 mg of each SBM material prepared in Example 1 and each M from Example 2. x S yThe @SBM material, Fe(II)@SFC material from Comparative Example 1, S@SFC material from Comparative Example 2, and Fe(II)-S@SFC material from Comparative Example 3 were placed into different 50 mL centrifuge tubes. 30 mL of a 100 ppm Cd(II) solution (prepared from 8.2321 mg Cd(NO3)2·4H2O crystals and ultrapure water) was added to each centrifuge tube. The mixture was shaken at 180 r / min at 25 °C for 24 h. Afterward, 5 mL of the solution was filtered through a 0.45 μm cellulose acetate membrane. The cadmium content in the filtrate was determined using an atomic absorption spectrophotometer (NovAA 350, Analytik Jena).

[0102] Example 4

[0103] M x S y @SBM material application example for lead removal in unit water systems:

[0104] Weigh out 10 mg of each SBM material prepared in Example 1 and each M from Example 2. x S y The @SBM material, Fe(II)@SFC material from Comparative Example 1, S@SFC material from Comparative Example 2, and Fe(II)-S@SFC material from Comparative Example 3 were placed into different 50 mL centrifuge tubes. 30 mL of a 180 ppm Pb(II) solution (prepared from 8.6340 mg Pb(NO3)2 crystals and ultrapure water) was added to each centrifuge tube. The mixture was shaken at 180 r / min at 25 °C for 24 h. Afterward, 5 mL of the solution was filtered through a 0.45 μm cellulose acetate membrane. The lead content in the filtrate was determined using an atomic absorption spectrophotometer (NovAA 350, Analytik Jena).

[0105] Tables 1, 2, and 3 show the SBM material in Example 1 and the M material in Example 2. x S y The adsorption capacities of @SBM materials for cadmium (Cd) and lead (Pb) in cadmium- and lead-only aqueous solutions were compared with those in Tables 1, 2, and 3. The following conclusions can be drawn from these comparisons:

[0106] 1) Considering factors such as adsorption effect and ease of recovery, the most preferred straw biomass material in the preparation method of nano-metal sulfide coated straw biomass aerogel provided by this invention is SFC.

[0107] Data from Tables 1, 2, and 3 show that the COB material's ability to immobilize cadmium and lead is significantly lower than that of the SFC and CC materials, and its corresponding modified material M... x Sy @COB's ability to immobilize cadmium and lead is also significantly lower than that of M. x S y @SFC Materials and M x S y @CC material. This is related to the relatively dense porosity of COB itself. Chemically, COB, CC, and SFC are all rich in cellulose, hemicellulose, and a small amount of lignin. Their molecular structures contain a large number of hydroxyl (-OH) and carboxyl (-COOH) groups, exhibiting significant advantages in heavy metal adsorption. COB has much higher mechanical strength than SFC, and its internal structure is more compact and dense. Sunflower stem core (SFC) itself has a naturally loose and porous structure originally used for water and nutrient transport within the plant. This porous nature makes SFC material lighter and less dense, while also giving it good adsorption properties. CC material and its corresponding modified material M... x S y @CC and SFC materials and their corresponding modified materials M x S y @SFC exhibits comparable cadmium and lead immobilization capabilities. This is related to the fact that bagasse itself is a pulverized, blocky material. Although flaking can relatively fix the shape of bagasse and allow for modification, after being introduced into water bodies, CC materials and their corresponding modifiers M... x S y After absorbing water and swelling, the tablet structure of CC is difficult to maintain stably. Instead, it mostly disperses as pulverized granules in the cadmium and lead solution. This property increases the contact area between the material and cadmium and lead in the solution, thereby increasing the adsorption capacity of the material for cadmium and lead. However, it also makes CC material and its corresponding modified material M... x S y @CC is difficult to recycle. SFC, on the other hand, has good mechanical and buoyancy properties and is relatively easy to recycle. Therefore, in the preparation of the nano-metal sulfide coated straw biomass aerogel provided by this invention, the most preferred straw biomass material is SFC.

[0108] 2) From the data in Tables 1, 2, and 3, we can see that M x S y Nano-coating significantly improves the immobilization capacity of SBM materials for cadmium and lead, with FeS(II) showing a particularly significant effect. Specifically, the SFC material exhibits an adsorption capacity of 96.77 mg·kg⁻¹ for cadmium in a single cadmium aqueous solution. -1 The adsorption capacity of lead in a single-lead aqueous solution was 297.13 mg·kg. -1 And through M x S y M modified with nano-coating x S yThe @SFC material significantly improves the immobilization capacity of cadmium and lead in a single-component aqueous solution. The adsorption capacity of FeS(Ⅱ)@SFC for cadmium in a single-component aqueous solution is 249.72 mg·kg⁻¹. -1 The maximum adsorption capacity for lead in a single-lead aqueous solution is as high as 562.19 mg·kg. -1 .

[0109] Table 4 shows the adsorption capacities of SFC material in Example 1, FeS(Ⅱ)@SFC material in Example 2, Fe(Ⅱ)@SFC material in Comparative Example 1, S@SFC material in Comparative Example 2, and Fe(Ⅱ)-S@SFC material in Comparative Example 3 for cadmium (Cd) and lead (Pb) in cadmium and lead single-system aqueous solutions, respectively. The data in Table 4 indicate that the adsorption capacity of SFC for cadmium and lead is significantly reduced after treatment with divalent ferrous ions. This is because the positive charge on the surface of the pith increases after treatment, and the pith reacts more readily with Cd. 2+ and Pb 2+ The electrostatic repulsion of heavy metal ions is enhanced. Conversely, after SFC treatment with sulfur ions, the adsorption capacities of cadmium and lead increased from 96.77 mg / kg and 297.13 mg / kg to 195.59 mg / kg and 515.88 mg / kg, respectively. This increase is due to the increased negative charge on the surface of the pith caused by sulfur treatment, which enhances its affinity for Cd. 2+ and Pb 2+ On the one hand, there is the electrostatic interaction between them; on the other hand, there is the interaction between sulfide ions and Cd. 2+ and Pb 2+ A precipitation reaction occurs, thereby enhancing the adsorption capacity of SFC for these heavy metal ions. Furthermore, comparing the adsorption effects of FeS(Ⅱ)@SFC and Fe(Ⅱ)-S@SFC on cadmium and lead, the nano-coating technology treated with iron ions followed by sulfur ions is more effective in adsorbing cadmium and lead. This is mainly because the abundant -OH and -COOH groups in the straw structure chelate with iron ions through coordination, which facilitates the coating of a uniform and stable nano-ferrous sulfide coating on the surface of the straw network structure, ultimately increasing the amount of cadmium and lead adsorbed and immobilized.

[0110] In summary, this invention provides a method for preparing nano-metal sulfide-coated straw biomass aerogel. Utilizing the porous structure and abundant metal adsorption sites of SFC material, the optimal solution immersion strategy is as follows: first, metal ions from the metal salt solution are adsorbed into the SFC material; then, metal cations react with S in the sodium sulfide (Na₂S) solution. 2- Anions undergo a precipitation reaction, coating nano-metal sulfides in situ into the interior of the SFC, ultimately yielding M... x S y @SFC.

[0111] Example 5

[0112] Example of cadmium-lead application of FeS(Ⅱ)@SFC material in cadmium-lead binary composite water system:

[0113] 10 mg of the SFC material prepared in Example 1 and the FeS(Ⅱ)@SFC material in Example 2 were weighed into different 50 mL centrifuge tubes. 30 mL of a Cd(Ⅱ)-Pb(Ⅱ) composite solution (Cd(Ⅱ) concentration 100 ppm, Pb(Ⅱ) concentration 180 ppm, prepared from 8.2321 mg Cd(NO3)2·4H2O crystals, 8.6340 mg Pb(NO3)2 crystals, and ultrapure water) was added to the centrifuge tube. The mixture was shaken uniformly at 180 r / min at 25 °C for 24 h. The material was then retrieved, and 5 mL of the solution was filtered through a 0.45 μm cellulose acetate membrane. The cadmium and lead content in the filtrate was determined using an atomic absorption spectrophotometer (NovAA 350, Analytik Jena).

[0114] Figure 3 , Figure 4 , Figure 5 The images show the SEM-EDS mappings of the SFC material in Example 1, the FeS(Ⅱ)@SFC material in Example 2, and the FeS(Ⅱ)@SFC-(after cadmium-lead immobilization) material in Example 5. From the SEM-EDS mapping images, it can be observed that... Figure 3 The SEM images of unmodified SFC material show a rich pore structure and a smooth, flat surface. Similar to other straw biomass materials, SFC material is mainly composed of carbon and oxygen, containing small amounts of silicon and carbon, and almost no elements such as iron, sulfur, cadmium, or lead. Figure 4 SEM images of FeS(Ⅱ)@SFC material after medium-nano ferrous sulfide coating show that its pore structure did not change significantly, but its surface was noticeably rougher. Mapping and EDS results show that the content of iron and sulfur elements on the material surface was significantly increased after nano-ferrous sulfide coating, and the distributions of iron and sulfur elements showed a high degree of overlap, indicating that iron and sulfur elements may have been successfully coated on the material surface in a bound state. SEM images ( Figure 5 In the cadmium-lead composite system, the pore structure of the FeS(II)@SFC- (after cadmium-lead immobilization) material after adsorption and salvage remains relatively intact, and granular crystals exist in the pores. The EDS spectrum shows the content of each element in the core material after adsorption. Compared with the EDS spectra of SFC material and FeS(II)@SFC material, after adsorption, the cadmium and arsenic content on the surface of FeS(II)@SFC material significantly increases, and the lead ion content is significantly higher than the cadmium ion content. Furthermore, a high degree of overlap between the distribution of lead and sulfur is clearly observed. This may be because the sulfur and phosphorus elements in the FeS(II)@SFC material react with each other.2+ A precipitation reaction occurs, forming lead sulfide precipitate.

[0115] Figure 6 XRD patterns of SFC material and FeS(Ⅱ)@SFC material before and after adsorption of cadmium and lead are shown. Peaks in the SFC spectrum correspond well with calcium, aluminum, silicon, minerals, and SiO2. In FeS(Ⅱ)@SFC, the ferrous sulfide phase (FeS) was identified according to the card (PDF#23-1121), and peaks in the FeS(Ⅱ)@SFC spectrum before adsorption correspond to CaSO4, CaO, Al2O, and Fe2O3. Regarding Cd adsorption... 2+ In FeS(Ⅱ)@SFC, cadmium sulfide (CdS) and ferrous sulfide (FeS) phases were identified, respectively, using reference cards (PDF#41-1049 and PDF#23-1121). This was in contrast to the adsorption of Pb. 2+ The lead sulfide phase (PbS) and ferrous sulfide phase (FeS) were identified in FeS(Ⅱ)@SFC by referring to the cards (PDF#05-0592 and PDF#23-1121).

[0116] In summary, the XRD results show that nano-ferrous sulfide coating successfully loaded FeS onto the SFC surface. The FeS(II)@SFC material adsorbs Cd. 2+ Pb 2+ Subsequent XRD results showed the presence of Cd. 2+ Pb 2+ The complexation precipitation reaction occurs because ferrous sulfide (FeS) contains both Fe(II) and S in its structure. 2- It possesses characteristics such as high reducing activity, high specific surface area, and easy formation of Fe(OH)2, which enables it to provide more active sites for the capture of heavy metal ions. Through co-precipitation reaction and adsorption, it can efficiently remove Cd from water. 2+ Pb 2+ .

[0117] Figure 7 This figure shows the adsorption capacity of FeS(Ⅱ)@SFC material for cadmium and lead in a cadmium-lead binary water system. The data in the figure indicate that the material has the capacity to immobilize both cadmium and lead in the cadmium-lead composite system. Compared with the adsorption capacity of FeS(Ⅱ)@SFC material in a cadmium-lead monomeric water system shown in Table 1, the maximum adsorption capacity for both cadmium and lead has decreased, but the adsorption capacity for lead is much higher than that for cadmium. This indicates that under the coexistence of Cd and Pb, FeS(Ⅱ)@SFC material has a strong adsorption and immobilization effect on both Cd and Pb, and its ability to immobilize lead is greater than that for cadmium.

[0118] Example 6

[0119] Examples of the application of FeS(II)SFC materials for cadmium removal in soil:

[0120] A cadmium-contaminated farmland in Zhongshan was selected as the experimental field. Twenty-one experimental plots, each 4.8m x 4.8m in size, were set up, completely separated by ridges. The soil in the experimental fields was tilled, weeded, ridged, and flooded. Seven treatments were set up: a blank control group, SFC (50g, 100g, 200g), and FeS(Ⅱ)@SFC (50g, 100g, 200g) treatments, denoted as CK, SFC-(1-3), and FeS(Ⅱ)@SFC-(1-3). 50g, 100g, and 200g of SFC material from Example 1 and FeS(Ⅱ)@SFC material from Example 2 were taken, and each mass was sealed in four mesh sandbags. These were then applied as surface layer to the soil in the 4.8m x 4.8m experimental farmland plots. Soil samples (0-5cm from the topsoil) and materials were collected after 15 days as specified. The total Cd in the soil was determined according to the method of standard HJ 832-2017. After digestion, 5 mL of the solution was filtered through a 0.45 μm cellulose acetate membrane filter and the cadmium content in the filtrate was determined by atomic absorption spectrophotometer (NovAA 350, Analytik Jena).

[0121] Figure 8 The images show the recovered soil and FeS(Ⅱ)@SFC material after the soil heavy metal removal application experiment in Example 5. Figure 8 As shown in Figure A, the unmodified SFC material was mostly degraded after being placed in the soil for 15 days; the FeS(Ⅱ)@SFC material recovery demonstration figure is as follows. Figure 8 As shown in Figure B, with Figure 1 A comparison of the FeS(Ⅱ)@SFC material images clearly shows that the material surface changed from black to yellow, indicating that the ferrous sulfide nanocoating on the material surface underwent a certain chemical reaction in the soil and was consumed. Meanwhile, the recovered FeS(Ⅱ)@SFC material retained a complete pith structure, indicating that the pith modified with FeS nanomaterials can improve the material's stability and anti-degradation properties, which is beneficial for material recycling and effectively reduces heavy metals in the soil environment.

[0122] Figure 9 The figures show the total cadmium and available cadmium content in the soil after applying FeS(Ⅱ)@SFC material and unmodified SFC material in Example 7. The total cadmium content in the untreated soil was 0.535 mg / kg. After treatment with unmodified pith, the total cadmium content in the soil decreased by 7.48%, and the FeS(Ⅱ)@SFC treatment, at the highest application rate, reduced the total cadmium content in the soil by 26.91%, indicating that the FeS(Ⅱ)@SFC material is significantly effective in practical soil cadmium remediation applications.

[0123] Figure 10The images show SEM images of the in-situ soil after the application of unmodified SFC materials and SEM-EDS images of the recovered FeS(Ⅱ)@SFC materials. The pith still retains a porous layered structure without collapse. Energy dispersive spectroscopy (EDS) analysis shows that the recovered FeS(Ⅱ)@SFC structure contains a small amount of Cd, while no Cd was detected in the surrounding soil, indicating that the cadmium content in the soil did not reach the detection limit. These results also demonstrate that FeS(Ⅱ)@SFC has the ability to adsorb and fix Cd.

[0124] Table 1 SFC and M x S y @SFC material's maximum adsorption capacity for cadmium and lead monomers in water systems

[0125]

[0126] Table 2 COB and M x S y @Maximum adsorption capacity of COB material for cadmium and lead monomers in water systems

[0127] sample COB FeS(Ⅱ)@COB <![CDATA[Fe3S4@COB]]> MnS@COB ZnS@COB Cd adsorption capacity (mg / kg) 31.99 145.52 106.98 132.44 128.75 Pb adsorption capacity (mg / kg) 219.35 293.8 191.29 276.55 251.43

[0128] Table 3 CC and M x S y The maximum adsorption capacity of @CC material for cadmium and lead monomers in water systems

[0129] sample CC FeS(Ⅱ)@CC <![CDATA[Fe3S4@CC]]> MnS@CC ZnS@CC Cd adsorption capacity (mg / kg) 92.02 236.04 173.51 207.96 180.85 Pb adsorption capacity (mg / kg) 283.12 491.5 320.01 420.3 399.79

[0130] Table 4. Maximum adsorption capacity of cadmium and lead monomers in water systems for each comparative example.

[0131] sample SFC Fe(Ⅱ)@SFC S@SFC Fe(Ⅱ)-S@SFC FeS(Ⅱ)@SFC Cd adsorption capacity (mg / kg) 96.77 50.02 195.59 148.94 249.72 Pb adsorption capacity (mg / kg) 297.13 177.67 515.88 327.45 562.19

[0132] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. The use of a nanometal sulfide-coated straw biomass aerogel in the removal of cadmium and lead in water bodies and / or soil, characterized by, The preparation method of the nano-metal sulfide coated straw biomass aerogel comprises the following steps: (1) soaking non-powdered straw biomass material in a metal salt solution for a certain time, washing after taking out, freeze-drying to obtain a metal ion loaded straw biomass material; (2) soaking the metal ion loaded straw biomass material in a sodium sulfide solution for a certain time, washing after taking out, freeze-drying to obtain a nano-metal sulfide coated straw biomass aerogel; In step (1), the straw biomass material is sunflower stem core; In step (1), the metal salt in the metal salt solution is ferrous sulfate heptahydrate; The metal sulfide in step (2) is ferrous sulfide.

2. The use of a nano-metallic sulfide coated straw biomass aerogel for removing cadmium and lead in water bodies and / or soil according to claim 1, characterized in that, The shape of the non-powdered straw biomass material in step (1) is at least one of sheet, block and rod.

3. The use of a nano-metallic sulfide coated straw biomass aerogel for removing cadmium and lead in water bodies and / or soil according to claim 1, characterized in that, The metal salt solution in step (1) is prepared from a metal salt and water in a mass ratio of 1:(1-340); The mass ratio of the non-powdered straw biomass material to the metal salt solution in step (1) is 1:(14-180); The soaking time in step (1) is 6-48 h; The sodium sulfide solution in step (2) is prepared from Na2S•9H2O and water in a mass ratio of 1:(2.08-208); The mass ratio of the sodium sulfide in the sodium sulfide solution in step (2) to the metal salt in the metal salt solution in step (1) is 1:(0.6-20.5); The soaking time in step (2) is 6-48 h.

4. The use of a nano-metallic sulfide coated straw biomass aerogel according to claim 3 for the removal of cadmium and lead in water bodies and / or soil, characterized in that, The metal salt solution in step (1) is prepared from a metal salt and water in a mass ratio of 1:(12-33); The mass ratio of the non-powdered straw biomass material to the metal salt solution in step (1) is 1:(144-152); The soaking time in step (1) is 24-48 h; The sodium sulfide solution in step (2) is prepared from Na2S•9H2O and water in a mass ratio of 1:(2.08-20.8); The mass ratio of the sodium sulfide in the sodium sulfide solution in step (2) to the metal salt in the metal salt solution in step (1) is 1:(0.6-1.8); The soaking time in step (2) is 24-48 h.

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