Targeted chromium adsorption material as well as preparation method and application thereof

Abstract

The invention relates to a chromium-targeted adsorbing material as well as a preparation method and application thereof. The preparation method of the targeted chromium adsorption material comprises the following steps: S1, crushing, sieving and pyrolyzing stems of potassium-rich plants to obtain biomass carbon; s2, dispersing biomass carbon in a solvent, adding Cr < 6 + > template ions, Cr < 3 + > template ions, a functional monomer, a cross-linking agent and an initiator for reaction, and washing and drying after reaction to obtain an ion imprinted polymer; and S3, dissolving a reduction barrier agent in a solvent, adding the ion imprinted polymer, and reacting at room temperature to obtain the chromium-targeted adsorption material, the potassium-rich plants are plants with the total potassium mass content of 5%-8%. The long-acting reduction adsorption material for targeted remediation of heavy metal Cr < 6 + > / Cr < 3 + > polluted soil and underground water is prepared, has extremely high specific selectivity and efficient adsorbability, and has obvious advantages in the aspects of heavy metal treatment efficiency, continuity and acid interference resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heavy metal pollution treatment, and particularly relates to a chromium-targeted adsorption material and a preparation method and application thereof. BACKGROUND

[0002] Heavy metal chromium (Cr) is highly toxic, carcinogenic, teratogenic and bioaccumulative. Chromium mainly exists in the form of hexavalent chromium (Cr 6+ ) and trivalent chromium (Cr 3+ ) in nature. The toxicity of Cr 6+ is about 100 times that of Cr 3+ . It is an ingested poison and inhaled extremely toxic substance. A small amount of contact can cause nasal mucosa ulcer and central nervous system damage. It has a persistent danger to the environment. At present, there are many studies on the remediation of single Cr 6+ pollution, but low-toxicity Cr 3+ can also be easily converted into high-toxicity Cr 6+ under the changes of medium environment pH and oxidation-reduction conditions. Therefore, it is very important to study the coordinated, targeted and reduced treatment of Cr 6+ and Cr 3+ .

[0003] Adsorption is one of the most common and effective technologies in the field of heavy metal pollution treatment. However, when traditional adsorption materials adsorb heavy metal chromium, they generally have problems such as complicated preparation process, high cost, serious secondary pollution and low adsorption efficiency, especially in the core problems of targeted capture, long-term adsorption, stable and durable, Cr 6+ / Cr 3+ coordinated reduction and the like.

[0004] The prior art CN107215964B discloses a method for simultaneously removing Cr 6+ and Cr 3+ in wastewater by applying morel mycelium. The biological adsorbent is prepared by using the fungus Morel as raw material. Since heavy metals are toxic, if the concentration is too high, the activity of microorganisms will be inhibited, and even die of poisoning. Therefore, the adsorbent is only limited to treating low-concentration Cr 6+ and Cr 3+ , and does not have selectivity and cannot remove specific heavy metal ions. In addition, the microbial strain has strict requirements for environmental temperature, humidity, nutrition and the like, and is particularly sensitive to environmental pH. If there are influences such as acid rain leaching, acid wastewater erosion and the like, the strain is likely to be inactivated and the heavy metals are likely to be reactivated, so the applicable scene is very limited.

[0005] The prior art CN 110354822 A provides a preparation method of amine group surface ion imprinting straw-based bioadsorbent, belonging to the field of metal ion separation, comprising the following steps: (1) obtaining pretreated straw powder by acid washing and alkali washing of straw powder; (2) adding the pretreated straw powder and epichlorohydrin to a strong alkali solution to perform etherification reaction, washing and centrifuging, then adding to a weak alkali solution, adding organic amine to perform ring-opening grafting amine reaction, and drying to obtain straw powder with surface amine group; (3) adding the straw powder with surface amine group and heavy metal salt to a solvent to perform adsorption reaction, then adding a crosslinking agent to perform surface imprinting reaction, and then sequentially washing with EDTA solution, and freeze-drying to obtain the amine group surface ion imprinting straw-based bioadsorbent. The present application can realize the separation and enrichment of imprinted heavy metal ions in a complex system by using the coordination effect and imprinting effect of the imprinted straw-based bioadsorbent on heavy metal ions, and can realize the separation of heavy metal ions in wastewater. However, the prior art CN uses ordinary straw (such as wheat straw and sugarcane residue) as raw material (without forming biochar), and the skeleton structure is simple and the pore development is limited, so the pore size structure and specific surface area are limited, which restricts the adsorption capacity and selectivity. Moreover, the present application is designed for imprinting a single target ion (such as Cu 2+ or Pb 2+ ), and cannot cope with complex pollution systems with multiple valence ions coexisting. At the same time, the heavy metal ions are easily desorbed under acidic conditions such as acid rain leaching and acid wastewater erosion, which may cause secondary pollution, and the regeneration and recycling performance are limited.

[0006] The prior art CN108047380B relates to a preparation method of a β-cyclodextrin imprinting polymer: first, β-cyclodextrin and maleic anhydride are reacted to obtain a cyclodextrin derivative, then the cyclodextrin derivative is mixed with St, a solvent and an initiator for a period of time, and then fully mixed with Cu 2+ to obtain a β-cyclodextrin metal ion imprinting polymer, and finally the metal ions are eluted to obtain a β-cyclodextrin imprinting polymer capable of specifically adsorbing Cu 2+ again. However, the present application is designed for imprinting Cu 2+ only, and cannot handle multiple valence heavy metal ions at the same time. The pore size structure and specific surface area are limited by the polymerization conditions, which affects the mass transfer and adsorption capacity. Moreover, the heavy metal ions are easily desorbed under acidic conditions, which may cause secondary release risk, SUMMARY

[0007] The present application aims to provide an adsorption material for targeted repair of heavy metal Cr 6+ / Cr 3+ contaminated soil and groundwater, and a preparation method and application thereof.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0009] A method for preparing a chromium-targeting adsorbent material includes the following steps:

[0010] S1. The stems of potassium-rich plants are crushed, sieved, and pyrolyzed to obtain biomass carbon;

[0011] S2. Disperse the biomass carbon in a solvent and add Cr. 6+ Template ions, Cr 3+ Template ions, functional monomers, crosslinking agents and initiators are reacted, and the mixture is washed and dried after the reaction to obtain ion-imprinted polymers.

[0012] S3. First, dissolve the reducing barrier agent in a solvent, add the ion-imprinted polymer, and react at room temperature to obtain the targeted chromium adsorption material.

[0013] The reducing barrier agent is one or more of β-cyclodextrin, tannic acid, gluconolactone, and ascorbic acid ester.

[0014] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows:

[0015] In one preferred embodiment, in step S1, the pyrolysis temperature is 300-500°C, the pyrolysis heating rate is 5-8°C / min, and the pyrolysis is carried out in an inert gas atmosphere.

[0016] The pyrolysis process of potassium-rich plant stems utilizes the abundant alkali metal activator potassium to etch the carbon skeleton, initiating an in-situ self-activation reaction. The resulting pyrolysis yields biochar (KBC) with a highly porous structure and high specific surface area. The obtained KBC is essentially a highly porous biochar material with a density lower than water, thus facilitating subsequent material recycling and reuse.

[0017] Extensive experiments have shown that the polarity of biochar decreases with increasing pyrolysis temperature, and the lower the polarity, the more favorable it is for the adsorption of heavy metals.

[0018] In one preferred embodiment, the pyrolysis temperature is 480-500°C.

[0019] In one preferred embodiment, the inert gas is nitrogen.

[0020] In one preferred embodiment, the potassium-rich plant is a plant with a total potassium content of 5%-8% by mass.

[0021] Using widely distributed, highly adaptable, and biomass-rich multifunctional wild potassium-rich plants as raw materials, we fully utilize their potassium-rich characteristics to generate an "in-situ self-activation effect" to prepare biomass carbon with well-developed pore structures.

[0022] In one preferred embodiment, the potassium-rich plant is any one of pokeweed, foxtail grass, oxtail grass, amaranth, pearlweed, etc., with pokeweed being the preferred plant with the highest potassium content, having a total potassium content of up to 6.5%-8%.

[0023] In one preferred embodiment, in step S1, the mesh size of the pulverized sample is 40-60 mesh.

[0024] In one preferred embodiment, in step S2, the solvent is a mixed solution of alcohol and water, wherein the alcohol is ethanol or isopropanol, and the volume ratio of alcohol to water is 3:7-7:3.

[0025] In one preferred embodiment, in step S2, Cr 6+ Template ions are derived from Cr-containing 6+ A soluble salt solution, preferably a K2Cr2O7 solution.

[0026] In one preferred embodiment, in step S2, Cr 3+ Template ions are derived from Cr-containing 3+ The soluble salt solution is preferably one or more of the following: chromium trichloride hexahydrate solution (CrCl3·6H2O), chromium sulfate octahydrate solution (Cr2(SO4)3·18H2O), and chromium acetate (Cr(CH3COO)3).

[0027] In one preferred embodiment, in step S2, Cr 6+ Template ions and Cr 3+ The template ion molar ratio is 2:1-5:1.

[0028] In one preferred embodiment, in step S2, the mass ratio of biochar to template ions is 2-10:1; the mass of the template ions is Cr. 6+ Template ions and Cr 3+ The sum of the masses of the template ions.

[0029] In one preferred embodiment, in step S2, the molar ratio of template ions to functional monomers is 1:4-8; the molar ratio of template ions to crosslinking agents is 1:20-24; the molar ratio of template ions to initiators is 1:0.2-0.5; and the molar concentration of template ions is Cr. 6+ Template ions and Cr 3+ The sum of the molar concentrations of the template ions.

[0030] In one preferred embodiment, in step S2, the functional monomer is one or more of chitosan, 4-vinylpyridine, hydroxyethyl methacrylate, or vinylimidazole.

[0031] In ion imprinting, functional monomers (such as vinylpyridine or chitosan) are small molecule compounds with specific functional groups (such as -NH2, -COOH), and their core role is to form the chemical basis for constructing recognition sites. These functional groups can interact with template ions (Cr... 6+ and Cr 3+ They interact through coordination bonds, hydrogen bonds, ionic bonds, etc., to form a "pre-assembled complex"; after polymerization and cross-linking, they are fixed in the network, thus forming cavities that can precisely "memorize" and specifically recognize target ions in terms of size and chemical environment after template ion elution. For Cr 6+ and Cr 3+ In general, monomers containing nitrogen or carboxyl groups are chosen because they have good coordination ability with chromium ions.

[0032] In one preferred embodiment, in step S2, the crosslinking agent is any one of ethylene glycol dimethacrylate, divinylbenzene, and triethylene glycol dimethacrylate.

[0033] In ion imprinting, crosslinking agents (such as N,N'-methylenebisacrylamide or ethylene glycol dimethacrylate) are multifunctional molecules that play a crucial role in "building the framework." Their core function is to connect the functional monomers already bound to the template ions, triggered by an initiator, to form a robust three-dimensional network polymer structure. This structure permanently "freezes" the spatial configuration of the recognition sites, preventing cavity collapse after the template ions are eluted, thus ensuring the stability and specific recognition capability of the imprinted sites.

[0034] In one preferred embodiment, in step S2, the initiator is azobisisobutyronitrile.

[0035] In ion imprinting, the initiator (such as ammonium persulfate or azobisisobutyronitrile) acts as the "start switch" for the polymerization reaction. Its role is to generate free radicals under external stimuli (such as heating or light), thereby triggering the polymerization and crosslinking reaction between the functional monomer and the crosslinking agent. Its core function is to provide the initial reaction motive force, permanently fixing the pre-assembled complex surrounding the template ions into a rigid polymer with a three-dimensional network structure, laying the foundation for the formation of stable imprinted cavities.

[0036] In step S2, taking ion-imprinted polymers with specific recognition sites for target ions as the starting point, surface imprinting technology is used to synthesize Cr with recognition memory function on the surface of biomass nanoporous carbon framework (KBC) solid support. 6 + / Cr 3+ Ion-imprinted polymers, for Cr 6+ and Cr 3+The two target heavy metal ions have very strong specificity and selectivity, and can simultaneously target and efficiently adsorb target heavy metals in soil and groundwater.

[0037] In step S2, Cr 6+ / Cr 3+ The synthesis mechanism of ion-imprinted polymers can be explained as follows: Cr 6+ and Cr 3+ Template ions and functional monomers undergo polymerization under acidic conditions with the aid of crosslinking agents and initiators, forming multiple binding sites with memory function. When the template ions are washed into the eluent, Cr is undetectable. 6+ and Cr 3+ Afterwards, the polymer retained substances related to Cr. 6+ and Cr 3+ Holes with matching ionic configurations and binding sites, thereby affecting Cr 6+ and Cr 3+ It has strong selective recognition properties, and its function is similar to that of enzymes and receptors in biology.

[0038] In one preferred embodiment, in step S2, the detergent used for washing is ethanol or water.

[0039] In one preferred embodiment, in step S3, the mass ratio of the reducing barrier agent to the ion-imprinted polymer is 1:2-5.

[0040] A low mass ratio of reducing barrier agent to ion-imprinted polymer (i.e., a relatively high amount of reducing barrier agent such as β-cyclodextrin) can lead to:

[0041] (1) Excessive reducing barrier agents, such as β-cyclodextrin molecules, will physically cover KBC@Cr 6+ / Cr 3+ IIP ion-imprinted polymer surfaces can even block key imprinted channels and cavities, thus hindering Cr... 6+ and Cr 3+ When ions approach and enter the internal imprinted sites, the high selective adsorption capacity of the ion-imprinted polymer cannot be utilized, resulting in a significant decrease in the total adsorption capacity of the material.

[0042] (2) β-Cyclodextrin is relatively expensive. Excessive use will significantly increase the cost of material preparation, but the resulting performance improvement is limited or even negative, leading to waste and reduced cost-effectiveness.

[0043] (3) The outer surface of reducing barrier agents such as β-cyclodextrin is hydrophilic. Excessive β-cyclodextrin will completely mask the surface properties of the ion-imprinted polymer itself, which will affect the dispersibility and stability of the material in different water environments.

[0044] An excessively high mass ratio of reducing barrier agent to ion-imprinted polymer (i.e., a relatively low amount of reducing barrier agent such as β-cyclodextrin, for example, >5:1) will lead to:

[0045] (1) Reduction barrier agents such as β-cyclodextrin not only participate in the Cr reduction under acidic environment stimulation 6+ The reduction and Cr 3+ The complexation and immobilization also provide a certain degree of physical coating. Insufficient β-cyclodextrin quantity means insufficient available reducing functional groups and subsequent complexation sites, leading to a bottleneck in overall reduction efficiency and immobilization capacity, making it unable to handle high concentrations of Cr. 6+ pollute.

[0046] (2) The amount of reducing barrier agents such as β-cyclodextrin is too small to fundamentally solve the desorption problem under acidic conditions.

[0047] In one preferred embodiment, the solvent in step S3 is one or more of ethanol, propylene glycol, isopropanol, and glycerol.

[0048] In step S3, to further avoid KBC@Cr 6+ / Cr 3+ IIP exhibits heavy metal reactivation behavior under environmental stress such as acid leaching. β-cyclodextrin was modified into KBC@Cr. 6+ / Cr 3+ A protective outer layer forms on the IIP polymer, which, through the hydrolysis of β-cyclodextrin in an acidic environment, slowly releases a reducing hemiacetal, thereby effectively reducing the activated Cr. 6+ This converts it into a low-toxicity, low-activity, and low-migration Cr... 3+ And again, Cr in the ion-imprinted polymer 3+ The target site captures and adsorbs the Cr, which is then absorbed into the KBC pores, anchoring it firmly within the biomass nanopores and making it difficult for it to escape. This achieves the targeting of heavy metal Cr. 6+ and Cr 3+ Targeted, persistent, and reduced-volume repair.

[0049] This invention enhances the overall stabilization effect through a synergistic mechanism of "adsorption-reduction-refixation." The core lies in the outer reducing barrier agent, such as β-cyclodextrin (β-CD), a cyclic oligosaccharide with an inner hydrophobic and outer hydrophilic cavity. Its porous structure allows ions and small molecules to pass through, rather than being a dense, sealed layer. Therefore, Cr in the solution... 6+ It can diffuse smoothly through the β-CD layer and be efficiently captured by the highly selective sites of the internal ion-imprinted polymer (IIP), thus retaining its initial adsorption capacity. Subsequently, in an acidic environment, the reducing substances produced by the slow hydrolysis of β-CD can remove any Cr that might desorb from the IIP sites due to environmental changes (such as acid rain leaching, acidic wastewater erosion, etc.).6+ Instantaneous in-situ reduction to Cr 3+ ; Newly generated Cr 3+ Cr can be immediately pre-set in the adjacent IIP 3+ The imprinted cavities are re-specifically captured and immobilized within the deep pores of the biochar. Thus, the reducing barrier layer acts as a smart "chemical gate," transforming potential desorption risks into a more stable fixed form, achieving a leap from simple adsorption to complete immobilization, and ensuring the durability and safety of the remediation effect.

[0050] In one preferred embodiment, the reaction time in step S3 is 24-48 hours.

[0051] Based on the same inventive concept, the present invention also claims protection for the chromium-targeting adsorbent material prepared by the preparation method.

[0052] Based on the same inventive concept, this invention also claims protection for the adsorbent material targeting chromium in the treatment of heavy metal Cr. 6+ and / or Cr 3+ Applications in polluted water or soil.

[0053] The following attempts to further explain the present invention:

[0054] This invention selects widely distributed, highly adaptable, and biomass-rich wild potassium-rich plants as raw materials, and prepares a novel biomass nanoporous carbon framework-supported Cr through in-situ self-activation, surface-imprinted polymerization, and β-cyclodextrin modification. 6+ / Cr 3+ Long-lasting targeted adsorption material. This adsorption material is rich in Cr. 6+ / Cr 3+ Targeted binding sites for Cr in the medium environment 6+ and Cr 3+ Both target heavy metal ions exhibit both high selectivity and strong adsorption capacity. More importantly, when highly toxic Cr ions are adsorbed and fixed by the material... 6+ Stimulated by external environmental factors such as acid rain leaching, Cr appears 6+ During reactivation, the β-cyclodextrin coated on the outer layer of the material can cleverly utilize the H+ in the acid rain environment. + This triggers its hydrolysis reaction, producing a hemiacetal with reducing power, thereby activating Cr. 6+ Reduced to low toxicity, low activity, and low migration Cr 3+ Cr on the adsorbed material again 3+ It targets and adsorbs heavy metal Cr in soil and groundwater through site recognition and inward absorption under the "confined space effect" of the carbon framework nanopores. 6+ and Cr 3+Highly selective capture and stable, long-lasting adsorption.

[0055] Through the preparation method of this invention, a targeted repair agent for heavy metal Cr was obtained. 6+ / Cr 3+ Long-lasting volume reduction adsorbents for contaminated soil and groundwater and their preparation methods, for Cr 6+ and Cr 3+ The two heavy metal ions exhibit extremely strong specificity and high adsorption efficiency, and can even reactivate Cr under harsh environmental conditions such as acid rain leaching. 6+ Successfully achieved detoxification, deactivation, and re-adsorption. Furthermore, in future practical applications, the adsorbent material can be recovered and recycled using hydraulic flotation technology.

[0056] The material of this invention is effective against Cr 6+ and Cr 3+ The two heavy metal ions possess the dual advantages of high selectivity and long-lasting stable adsorption, and solve the problem of the highly toxic Cr in current heavy metal remediation materials under the influence of acid rain leaching and acidic wastewater corrosion. 6+ It addresses the core technical challenges of reactivation and re-polluting, and is easy to recycle and reuse, thus possessing extremely high application prospects.

[0057] The beneficial effects of this invention are as follows:

[0058] (1) This invention selects Phytolacca acinosa, a multifunctional wild potassium-rich plant with wide distribution, strong adaptability and large biomass, as raw material. It utilizes the "in-situ self-activation effect" generated by its own potassium-rich characteristics to prepare a nanoporous carbon framework carrier material with high specific surface area and well-developed pore structure. It is a new type of high-quality raw material that can be used for the preparation of porous biochar.

[0059] (2) This invention uses the “in-situ self-activation method” to prepare porous biochar materials. Compared with the traditional physical and chemical preparation process, this method does not require the addition of chemical activators and pretreatment. It has multiple potential advantages such as simple process, easy operation, low cost, and green environmental protection. It is expected to explore a new way for the simple and environmentally friendly preparation and industrial production of porous biochar.

[0060] (3) As a manganese hyperaccumulator in nature, the present invention also provides a safe and economical post-treatment scheme for hyperaccumulators: converting heavy metal hyperaccumulators into biochar and using it to treat pollutants in the environment, effectively avoiding the re-entry of a large amount of heavy metal-accumulated plant biochar into the environment and causing serious secondary pollution, which has potential social, economic and ecological benefits.

[0061] (4) The biomass nanoporous carbon framework carrier material KBC prepared by this invention has a high specific surface area and uniform pore size distribution. Based on the unique "confined space effect" of nanopores, it can achieve the storage of heavy metal Cr. 6+ and Cr 3+ It provides sustained adsorption and effectively prevents micron-sized microorganisms in the medium environment from entering the pores and reactivating heavy metals, thus ensuring the biosafety of the carbon skeleton.

[0062] (5) This invention uses the prepared nanoporous carbon framework material KBC as a carrier to synthesize a novel Cr by surface imprinting polymerization and β-cyclodextrin modification. 6+ / Cr 3+ A long-lasting targeted remediation material for contaminated soil and groundwater, based on its specific recognition sites and nanopores, enables it to target Cr. 6+ and Cr 3+ Both heavy metal ions possess the dual advantages of high selectivity and strong adsorption, and can effectively target Cr in various media, including soil and complex polluted water bodies. 6+ and Cr 3+ Specific capture and stable, long-lasting adsorption;

[0063] (6) This invention modifies KBC@Cr with β-cyclodextrin. 6+ / Cr 3+ The outer layer of the IIP ion-imprinted polymer effectively prevents Cr from forming. 6+ Reactivation and Cr under the influence of harsh external environments 3+ The escape behavior of heavy metals solves the problem of Cr in current heavy metal adsorption materials under the influence of acid rain leaching and acidic wastewater corrosion. 6+ The core technical challenge of reactivation and recontamination has been successfully overcome, achieving the reactivation of Cr. 6+ and Cr 3+ Reduced repair;

[0064] (7) The adsorbent material prepared by the present invention is easy to be hydraulically recovered and recycled multiple times, and has broad application prospects. Attached Figure Description

[0065] Figure 1 This is a flow chart of the preparation process of the adsorption material of the present invention;

[0066] Figure 2 This is a scanning electron microscope image of the biomass nanoporous carbon framework carrier material ((KBC)) of the present invention;

[0067] Figure 3 The X-ray energy spectrum of the biomass nanoporous carbon framework carrier material ((KBC)) of the present invention is shown. Detailed Implementation

[0068] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0069] Example 1

[0070] The targeted repair of heavy metal Cr in this invention 6+ / Cr 3+ The long-lasting volume-reducing adsorbent material for polluted soil and groundwater has the following formula:

[0071] Table 1 shows the targeted repair of heavy metal Cr. 6+ / Cr 3+ Content of each component in long-lasting volume reduction adsorbents for contaminated soil and groundwater

[0072]

[0073] The functional monomers are chitosan and hydroxyethyl methacrylate in a molar ratio of 5:1. The crosslinking agent is triethylene glycol dimethacrylate. The initiator is azobisisobutyronitrile.

[0074] according to Figure 1 The process flow diagram of the preparation of adsorption materials for targeted repair of heavy metal Cr 6+ / Cr 3+ The preparation method of long-lasting volume reduction adsorbent for polluted soil and groundwater, with specific implementation steps as follows:

[0075] S1: Preparation of biomass nanoporous carbon framework support materials (KBC)

[0076] One kilogram of wild, potassium-rich pokeweed at its fruiting stage was harvested. The stems were separated, rinsed with tap water to remove surface dirt, and dried in an 80°C oven to constant weight. The dehydrated pokeweed stems were then broken into approximately 2cm long segments and pulverized to 40-60 mesh. Approximately 50g of the pulverized pokeweed was placed in a vacuum tube furnace and pyrolyzed at 500°C for 2 hours under a N2 atmosphere at a heating rate of 8°C / min. After pyrolysis, N2 was continuously introduced until the furnace cooled to room temperature. The resulting pyrolysis material was washed three times with deionized water and dried to constant weight, yielding a biomass nanoporous carbon framework (KBC) material with a well-developed pore structure and high specific surface area. Scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) images of the biomass nanoporous carbon framework (KBC) material were obtained, and the results are shown below. Figure 2 and Figure 3As shown, KBC partially retains the skeleton of the original pokeweed stem during carbonization, exhibiting an overall fibrous structure. The material has well-developed pores, whose distribution and morphology show a layer-by-layer etching characteristic, with relatively regular shapes. EDS analysis reveals that its high potassium (K) residue originates from the inherent potassium-rich characteristics of the original pokeweed, further validating the advantage of endogenous alkali metals such as K as a low-cost, high-quality biochar activator.

[0077] S2: Preparation of KBC-based Cr 6+ / Cr 3+ Ion-targeted imprinted polymer (KBC@Cr) 6+ / Cr 3+ IIP)

[0078] Weigh 5g of the biomass nanoporous carbon framework carrier material (KBC) obtained in step S1 and place it in 50ml of isopropanol / water (volume ratio = 6:4) mixed solvent and sonicate for 20min. Then transfer 10ml (0.1g / ml) of Cr 6+ / Cr 3+ The template ion solution (molar ratio = 3:1, K2Cr2O7 solution, chromium trichloride hexahydrate solution (CrCl3·6H2O)) was added to a three-necked flask containing a KBC mixture and stirred under condensation for 30 min. Then, 5 ml (0.055 mol) of the main functional monomer chitosan and 4.8 ml (0.033 mol) of the comonomer hydroxyethyl methacrylate were added, the solution was adjusted to a weakly acidic state, and stirring continued for 30 min until fully dissolved. Next, 10 ml (0.4 mol) of the crosslinking agent ethylene glycol dimethacrylate and 5 ml (0.008 mol) of the initiator azobisisobutyronitrile were added, and the reaction was carried out at 75 °C for 10 h under N2 atmosphere to allow the KBC, main functional monomer chitosan, comonomer hydroxyethyl methacrylate, and CrCl3·6H2O to combine. 6 + / Cr 3+ The template ions polymerize fully under the action of crosslinking agents and initiators to form an ion-imprinted polymer. Finally, the polymer is repeatedly washed with ethanol and water to remove the template ions until no Cr is detectable in the eluent. 6+ and Cr 3+ It was then washed with distilled water until neutral, and dried under vacuum at 60°C to obtain the template-detemplated KBC-based Cr. 6+ / Cr 3+ Ion-targeted imprinted polymer KBC@Cr 6+ / Cr 3+ IIP.

[0079] S3: Preparation of β-cyclodextrin-modified KBC@Cr 6+ / Cr 3+ IIP

[0080] First, dissolve 1g of β-cyclodextrin (β-CD) in 5ml of ethanol, then add 4g of KBC@Cr obtained in step S2. 6+ / Cr 3+ IIP ion-imprinted polymers were incubated at room temperature with shaking for 48 hours to allow β-cyclodextrin to fully bind with KBC and functional monomers through hydrogen bonding between hydroxyl groups, thereby modifying KBC@Cr 6+ / Cr 3+ The outer layer of the IIP polymer ultimately yields a targeted repair layer for heavy metal Cr. 6+ / Cr 3+ KBC@Cr, a long-lasting adsorbent for reducing the volume of polluted soil and groundwater 6+ / Cr 3+ IIP@CD.

[0081] Example 2

[0082] Based on formula 1, the content of each component is adjusted as follows:

[0083] Table 2 shows the targeted repair methods for heavy metal Cr. 6+ / Cr 3+ Content of each component in long-lasting volume reduction adsorbents for contaminated soil and groundwater

[0084]

[0085]

[0086] The functional monomers are chitosan and hydroxyethyl methacrylate in a molar ratio of 5:1. The crosslinking agent is triethylene glycol dimethacrylate. The initiator is azobisisobutyronitrile.

[0087] The preparation method is the same as in Example 1.

[0088] Example 3

[0089] Based on Formula 1 of Example 1, the types of each component are adjusted, while the content and proportion of the corresponding components remain unchanged, as follows:

[0090] Table 3 shows the targeted remediation of heavy metal Cr. 6+ / Cr 3+ Table of Components of Long-Term Volume Reduction Adsorbents for Polluted Soil and Groundwater

[0091]

[0092]

[0093] The experimental procedure is the same as in Example 1.

[0094] Comparative Example 1

[0095] Based on Formulation 1 of Example 1, this study evaluates its effect on heavy metal Cr in complexly polluted water bodies by comparing it only with step S1 of Example 1. 6+ / Cr 3+ It exhibits targeted, long-lasting, and reduced-volume adsorption effects.

[0096] Comparative Example 2

[0097] Based on Formulation 1 of Example 1, this study evaluates its effect on heavy metal Cr in complexly polluted water bodies by comparing steps S1+S2 of Example 1 only. 6+ / Cr 3+ It exhibits targeted, long-lasting, and reduced-volume adsorption effects.

[0098] Comparative Example 3

[0099] Based on Formulation 1 of Example 1, the pokeweed biochar was replaced with the same mass of morel biosorbent as in Example 1 of CN107215964B. Everything else remained the same as in Example 1.

[0100] Comparative Example 4

[0101] Based on Formula 1 of Example 1, the pokeweed biochar was replaced with the same mass of straw powder as in Example 1 of CN 110354822A. Everything else was the same as in Example 1.

[0102] Comparative Example 5

[0103] Based on Formulation 1 of Example 1, the functional monomer (chitosan + hydroxyethyl methacrylate) was replaced with the same molar amount of organic amine as in Example 1 of CN110354822 A. Everything else remained the same as in Example 1.

[0104] Comparative Example 6

[0105] Based on Formulation 1 of Example 1, the protective layer was replaced with the same mass of cyclodextrin derivative (prepared by reacting β-cyclodextrin and maleic anhydride) as in Example 1 of CN108047380B. This was then mixed with pokeweed biochar, solvent, and initiator and reacted for a period of time, followed by reaction with Cr... 6+ / Cr 3+ After thorough mixing and reaction of template ions, a β-cyclodextrin metal ion-imprinted polymer was obtained. Finally, the metal ions were eluted to obtain a polymer that specifically adsorbs Cr. 6+ / Cr 3+ The β-cyclodextrin imprinted polymer was processed using the same steps as in Example 1.

[0106] The effects of Examples 1-3 (Formulas 1-19) and Comparative Examples 1-6 were compared and analyzed. The experimental process is as follows:

[0107] The experiment used groundwater from a non-ferrous metal industrial park in Hunan Province as the substrate, simulating a severe heavy metal pollution scenario through artificial spiked treatment. Potassium dichromate (K₂Cr₂O₇) and chromium trichloride hexahydrate (CrCl₃·6H₂O) were used as standard substances to measure the hexavalent chromium (Cr) in the experimental water sample. 6+ ) and trivalent chromium (Cr 3+ The initial concentration of the adsorbent was prepared at 5.0 mg / L. To ensure fair comparison of the performance of each formulation, the adsorbent dosage ratio in all examples and comparative examples was uniformly set at 0.5% (w / v), i.e., 0.5 g of adsorbent was added per liter of experimental water sample. Each formulation was repeated three times, and the average value was taken. The reaction was carried out in a constant-temperature shaking incubator with a rotation speed of 80 rpm to simulate mild water flow conditions. Samples were taken at regular intervals on days 1, 5, and 10 after the reaction, and the supernatant was used to detect Cr. 6+ and Cr 3+ Concentration was used to monitor its dynamic removal effect.

[0108] To investigate the stability of the material in a real acidic environment, an acid interference experiment was conducted after the reaction ended on day 10. A 1 mol / L dilute hydrochloric acid (HCl) solution was slowly added dropwise to the reaction system using a micropipette to adjust the pH to 3.0 ± 0.5. The reaction was then continued with low-speed shaking in a shaker for 12 hours. After the reaction, samples were taken again to analyze the changes in heavy metal concentrations after the acid shock, thereby assessing the material's resistance to interference and its stability.

[0109] Hexavalent chromium (Cr) 6+ Concentrations were determined using the standard "Water Quality - Determination of Hexavalent Chromium - Diphenylcarbazide Spectrophotometric Method" (GB 7467-87). Total chromium concentration was determined using ICP-OES according to the standard "Water Quality - Determination of 32 Elements - Inductively Coupled Plasma Atomic Emission Spectrometry" (HJ776-2015). Trivalent chromium (Cr...) 3+ The concentration is calculated using the difference method, i.e.: [Cr] 3+ ] = [Total Chromium] - [Cr] 6 + ].

[0110] The experimental comparison results are shown in Table 1:

[0111] Table 1. Results of the Examples and Comparative Examples (mg / L)

[0112]

[0113]

[0114] Examples 1 (Formulas 1-11) and 3 (Formulas 17-19) of the present invention address the heavy metal Cr... 6+ / Cr 3+It showed a significant advantage in the removal of Cr. The formulations in Example 1 showed significant advantages in Cr removal. 6+ / Cr 3+ The concentration remained consistently low (mostly below 0.3 mg / L) and remained stable or even decreased further over time, indicating good heavy metal reduction and removal effects and persistence. Although the concentration in Example 3 was slightly higher than in Example 1, it was still significantly lower than the comparative example, with Cr... 6+ / Cr 3+ When the concentration was controlled below 0.41 mg / L, the removal rate was above 90%, demonstrating its effectiveness.

[0115] In contrast, some components in Example 2 (Formulas 12-16) were not within the effective proportion range, and residual Cr was found in the reaction solution. 6+ / Cr 3+ The concentrations were generally high (0.87-3.54 mg / L), and their performance was close to or even inferior to some comparative examples. Comparative examples 1–6 contained Cr... 6+ / Cr 3+ The concentrations were all high (most exceeding 2.5 mg / L, with the highest reaching 4.33 mg / L), and generally increased further under the interference of acid addition, indicating poor stability.

[0116] Examples 1 and 3 maintained low concentration fluctuations even under acid interference (e.g., formulation 10 only 0.16 mg / L), highlighting their excellent acid resistance. Simultaneously, the low residue achieved with low dosage demonstrates the "reduced dosage, high efficiency" characteristic. In summary, in the effective embodiments of the present invention, Examples 1 and 3 are significantly superior to Example 2 and the comparative examples in terms of high efficiency, durability, and acid interference resistance, possessing outstanding potential for practical application.

[0117] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A method for preparing a chromium-targeting adsorbent material, characterized in that, Includes the following steps: S1. The stems of potassium-rich plants are crushed, sieved, and pyrolyzed to obtain biomass carbon; S2. Disperse the biomass carbon in a solvent and add Cr. 6+ Template ions, Cr 3+ Template ions, functional monomers, crosslinking agents and initiators are reacted, and the mixture is washed and dried after the reaction to obtain ion-imprinted polymers. S3. First, dissolve the reducing barrier agent in a solvent, add the ion-imprinted polymer, and react at room temperature to obtain the targeted chromium adsorption material. The reducing barrier agent is one or more of β-cyclodextrin, tannic acid, gluconolactone, and ascorbic acid ester; The potassium-rich plants are those with a total potassium content of 5%-8% by mass.

2. The preparation method according to claim 1, characterized in that, In step S1, the pyrolysis temperature is 300-500℃, the pyrolysis heating rate is 5-8℃ / min, and the pyrolysis is carried out in an inert gas atmosphere.

3. The preparation method according to claim 1, characterized in that, The potassium-rich plants are any one of the following: pokeweed, foxtail grass, oxtail grass, amaranth, and pearlwort.

4. The preparation method according to claim 1, characterized in that, In step S2, the solvent is a mixed solution of alcohol and water, wherein the alcohol is ethanol or isopropanol, and the volume ratio of alcohol to water is 3:7-7:3; the functional monomer is one or more of chitosan, 4-vinylpyridine, hydroxyethyl methacrylate or vinylimidazole.

5. The preparation method according to claim 1, characterized in that, In step S2, Cr 6+ Template ions are derived from Cr-containing 6+ A soluble salt solution, preferably a K₂Cr₂O₇ solution; Cr 3+ Template ions are derived from Cr-containing 3+ A soluble salt solution, preferably one or more of chromium trichloride hexahydrate solution, chromium sulfate octahydrate solution, and chromium acetate; Cr 6+ Template ions and Cr 3+ The template ion molar ratio is 2:1-5:

1.

6. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of biochar to template ions is 2-10:1; the mass of the template ions is Cr. 6+ Template ions and Cr 3+ The sum of the masses of template ions; the molar ratio of template ions to functional monomers is 1:4-8; the molar ratio of template ions to crosslinking agents is 1:20-24; the molar ratio of template ions to initiators is 1:0.2-0.5; the molar concentration of template ions is Cr. 6+ Template ions and Cr 3+ The sum of the molar concentrations of the template ions.

7. The preparation method according to claim 1, characterized in that, In step S2, the crosslinking agent is any one of ethylene glycol dimethacrylate, divinylbenzene, and triethylene glycol dimethacrylate; The initiator is azobisisobutyronitrile.

8. The preparation method according to any one of claims 1-7, characterized in that, In step S3, the mass ratio of the reducing barrier agent to the ion-imprinted polymer is 1:2-5.

9. The chromium-targeting adsorbent material prepared by the preparation method according to any one of claims 1-8.

10. The chromium-targeting adsorption material according to claim 9 for the treatment of heavy metal Cr 6+ and / or Cr 3+ Applications in polluted water or soil.

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