阅读说明：本技术 一种磁铁矿中稀土元素的检测方法 (Method for detecting rare earth elements in magnetite ) 是由 刘艳红 薛丁帅 张丹萍 于 2020-05-18 设计创作，主要内容包括：本发明公开了一种磁铁矿中稀土元素的检测方法,所述方法利用改性聚氨酯泡沫对磁铁矿中铁基质进行吸附,通过ICP-OES测定改性聚氨酯泡沫对铁基质的吸附效率,再通过ICP-MS检测稀土元素含量。本发明所述的改性聚氨酯泡沫是指经过异硫氰酸酯和氨基硫醇改性的聚氨酯泡沫,对磁铁矿中铁基质的吸附率达到99.2±0.7％,有利于磁铁矿中稀土元素回收,稀土元素的回收率为98-102％。本发明提供的改性聚氨酯泡沫具有对铁基质特异性吸附效果,而且吸附量大,耐酸,从而实现快速、准确、精确检测磁铁矿中稀土元素的目的。(The invention discloses a method for detecting rare earth elements in magnetite, which comprises the steps of adsorbing an iron substrate in the magnetite by modified polyurethane foam, measuring the adsorption efficiency of the modified polyurethane foam on the iron substrate by ICP-OES, and detecting the content of the rare earth elements by ICP-MS. The modified polyurethane foam is modified by isothiocyanate and amino mercaptan, the adsorption rate of the modified polyurethane foam on iron substrates in magnetite reaches 99.2 +/-0.7%, recovery of rare earth elements in the magnetite is facilitated, and the recovery rate of the rare earth elements is 98-102%. The modified polyurethane foam provided by the invention has a specific adsorption effect on an iron substrate, is large in adsorption capacity and is acid-resistant, so that the aim of quickly, accurately and precisely detecting the rare earth element in the magnetite is fulfilled.)

1. A method for detecting rare earth elements in magnetite comprises the following steps: (1) digesting magnetite; (2) adsorbing an iron matrix in the acid liquor by using a modified PUF (physically unclonable function), wherein the concentration of hydrochloric acid in the acid liquor is 6-8.5M; (3) detecting the content of the rare earth elements by ICP-MS; characterized in that the modified PUF is a polyurethane foam modified with isothiocyanates and aminothiols.

2. The detection method according to claim 1, wherein the magnetite sample to be detected has a weight of 10-20mg, and the hydrochloric acid concentration in the acid solution of step (2) is 8-8.5M.

3. The detection method according to claim 1, wherein the modified PUF is prepared by foaming an A component and a B component in a polyurethane foaming machine, wherein the A component comprises polyether polyol, amino mercaptan, a foaming agent and a crosslinking agent, and the B component comprises a combination of isothiocyanate and one of Toluene Diisocyanate (TDI), 4-diphenylmethane diisocyanate (MDI) and polyphenyl polymethylene polyisocyanate (crude MDI).

4. The detection method as claimed in claim 3, wherein the polyether polyol is at least one selected from polyoxypropylene glycol, polyether triol and polytetrahydrofuran, the molecular weight is 2000-4800, the crosslinking agent is one selected from 1, 4-Butanediol (BDO) and ethylene glycol, and the foaming agent is water.

5. The detection method according to claim 3, wherein the isothiocyanate is selected from the group consisting of phenyl isothiocyanate and p-toluenesulfonyl isothiocyanate, and the aminothiol is selected from at least one of mercaptoethylamine, p-aminophenol, m-aminophenol, o-aminophenol, mercaptoacetamide, and 3-mercapto-1-propylamine.

6. The detection method according to claim 5, wherein the modified PUF is prepared by: putting 80-85 parts of polytetrahydrofuran, 5-15 parts of mercaptoethylamine, 5-15 parts of 3-mercapto-1-propylamine, 3-5 parts of cross-linking agent 1, 4-butanediol and 1-2 parts of water which comprise the following raw materials in parts by weight into a foaming machine, stirring to obtain a component A, and adding a component B comprising the following raw materials in parts by weight into the component A: 50-80 parts of MDI, 40-50 parts of crude MDI and 20-30 parts of tosyl isothiocyanate, stirring, and carrying out foaming reaction at 30-40 ℃ for 2-4 hours to obtain the modified PUF.

7. The assay according to any one of claims 1-6, wherein the modified PUF is based on a modified PUF and the peptidoglycan is coupled to the surface of the modified PUF by glutaraldehyde to form a modified PUF/peptidoglycan complex.

8. The detection method according to claim 7, wherein the modified PUF/peptidoglycan complex is prepared by: (1) heating the modified PUF in hydrochloric acid with concentration of 4-5moL/L at 70-90 deg.C for 3-4 hr to expose amino group on surface to form modified PUF-NH₂(ii) a (2) Will modify PUF-NH₂Placing the mixture into a peptidoglycan aqueous solution, dropwise adding glutaraldehyde, and heating and reacting at 37-40 ℃ for 24-36 hours; (3) and washing the reaction product with clear water for 3-5 times, and drying to obtain the modified PUF/peptidoglycan complex.

9. The detection method according to claim 8, wherein the volume-to-mass ratio of the hydrochloric acid solution to the modified PUF in step (1) is 80-100:1mL/g, the concentration of the aqueous peptidoglycan solution in step (2) is 40-60g/L, and the aqueous peptidoglycan solution to the modified PUF-NH is₂The volume-mass ratio of the glutaraldehyde is 80-100:1mL/g, and the dropping volume of the glutaraldehyde is 5-15% of the volume of the reaction system.

10. Use of a method of detection of rare earth elements in magnetite according to any one of claims 1 to 9 for rare earth element analysis of small iron-rich samples in geochemistry, cosmic chemistry and environmental studies.

Technical Field

The invention belongs to the technical field of geochemistry, and particularly relates to a method for removing an iron matrix in magnetite through modified polyurethane foam and detecting rare earth elements in the magnetite through an ICP-MS method.

Background

Rare Earth elements (REE Earth, REE) are a group of elements with similar chemical properties, and mostly have consistent behaviors in various geological processes, so that analysis of Rare Earth elements can provide critical data for diagenetic history of geological samples. The striped iron construction (BIF) is a very unique and important sedimentary rock, most common during precambrian sedimentary succession. Although many aspects of their origin remain unresolved, it is widely believed that long-term changes in their depositional forms are related to the earth's environment and the geochemical evolution. Thus, BIF provides data support for a comprehensive insight into the significant changes in earth evolution. Rare earth systems have long been used as corresponding chemical tools to understand the origin of BIF and the ancient ocean. However, many of the early studies of rare earth elements with respect to BIF led to ambiguous conclusions, in part, due to limitations in the analysis and sampling from the drastically changing elements. Accurate determination of magnetite (Fe) in iron build micro-strips₃O₄) The rare earth element content of the single mineral can provide strong evidence for the material source of BIF, the oxidation state of ancient seawater and atmospheric changes on land. In order to understand the geological processes more clearly and correctly, one skilled in the art must obtain high resolution rare earth data from each BIF microstrip slice by means of micro-sample analysis.

Because the detection method is simple, the dynamic range is wide, multiple elements can be detected, and the detection limit is low, inductively coupled plasma mass spectrometry (ICP-MS) has been proved to be the most appropriate technology for determining rare earth elements in geological materials. For iron-rich minerals, some researchers have attempted rare earth element determination using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to achieve in situ analysis of micro samples. However, the relatively high detection limits (ranging from μ g/g to sub μ g/g), the limited matrix matching standards and the large standard deviation make the data less accurate.

For example, non-patent literature, "quantitative method for determining values of 15 rare earth elements in standard substances of gallium, germanium, indium and thallium ores, geology of Chenhaiying and Jilin; 2014, 02 ", discloses that 15 rare earth elements in gallium, germanium, indium and thallium ores are measured by microwave digestion-inductively coupled plasma mass spectrometry (ICP-MS), the detection limit of the method is (0.003-0.015) mu g/g, the relative standard deviation is between 1.11 and 2.92 percent, and the normalized recovery rate is between 95.5 and 105.9 percent.

For the solution mode, the rare earth element concentration of the iron-rich material sample is very low, generally between ng/g-mug/g, and if the dilution factor is 1000, the detection limit of ICP-MS is approached. In addition, the deposition of high concentrations of iron can cause severe physical damage to the cone as the iron is deposited, resulting in a narrowing of the orifice and increased memory effects in ICP-MS induction systems. The ICP-MS sensitivity is rapidly reduced due to the influence, the detection limit is higher, 2-3 orders of magnitude can be improved, and the stability of the instrument is reduced. Therefore, the prior art generally pre-concentrates the rare earth elements prior to detection in order to obtain reliable data on the iron-rich ore samples. For example, there is a report in the literature that rare earth elements can be accurately measured in iron-rich geological samples after separation from a strong iron matrix by ion exchange resin or co-precipitation. However, the methods using ion exchange resins or coprecipitation are cumbersome, time consuming and relatively expensive.

Polyurethane foam (PUF) has the characteristics of elasticity, porosity, controllable cell structure, adjustable shape, simple preparation process, high stability, high adsorption/desorption rate and the like, and is widely applied to the aspect of enriching/separating metal ions recently. Since 1970, researchers have used porous solid organic urethane foam (PUF) as an adsorbent to adsorb iron (iii) element in a solution. Compared with other separation and concentration technologies, the PUF preconcentration process is simple, efficient, environment-friendly and economical. However, it is not clear whether PUFs can be used as special adsorbents of iron to separate rare earth elements from magnetite. Furthermore, a method for detecting rare earth elements in iron-rich geological samples after removal of the matrix by PUF has not been reported before.

The invention provides a method for quickly and accurately detecting rare earth elements in a magnetite sample after removing iron matrix in the magnetite by using PUF. In order to obtain the best iron separation effect, the inventor further modifies the PUF, and the obtained modified PUF has a better adsorption effect on an iron matrix. The invention carries out the accuracy evaluation of the detection method by using the reference materials 15mag-11 and 15mag-13, and the detection method provided by the invention is considered to be capable of accurately determining the detection of the rare earth elements with low concentration in the iron-rich monominerals and can be easily reproduced in most geochemistry laboratories.

Disclosure of Invention

The invention aims to provide a method for detecting rare earth elements in magnetite, which comprises the steps of adsorbing an iron substrate in the magnetite by using modified polyurethane foam (modified PUF), measuring the adsorption efficiency of the modified polyurethane foam to the iron substrate by ICP-OES, and detecting the content of the rare earth elements by ICP-MS.

A method for detecting rare earth elements in magnetite comprises the following steps: (1) digesting magnetite; (2) adsorbing an iron matrix in the acid liquor by using a modified PUF (physically unclonable function), wherein the concentration of hydrochloric acid in the acid liquor is 6-8.5M; (3) and detecting the content of the rare earth elements by ICP-MS, wherein the modified PUF is polyurethane foam modified by isothiocyanate and amino mercaptan.

Preferably, the weight of the sample to be detected of the magnetite is 10-20mg, and in the best embodiment of the invention, the method can realize accurate detection of rare earth elements in the sample with the weight of 10 mg.

The higher the concentration of hydrochloric acid, the better the binding force between iron and the PUF, so that the iron adsorption rate of the PUF is higher. Preferably, the hydrochloric acid concentration in the acid solution in the step (2) is 8-8.5M, and in the best embodiment of the invention, the modified PUF can adsorb the iron matrix in HCl with the concentration of 8.5M without decomposition or dissolution.

The modified PUF is prepared by a component A and a component B through a foaming reaction in a polyurethane foaming machine, wherein the foaming reaction temperature is 35-37 ℃, the component A comprises polyether polyol, amino mercaptan, a foaming agent and a crosslinking agent, and the component B comprises a combination of one of Toluene Diisocyanate (TDI), 4-diphenylmethane diisocyanate (MDI) and polyphenyl polymethylene polyisocyanate (crude MDI) and isothiocyanate.

The polyether polyol used in the present invention is a polyether polyol having a molecular weight of 2000-4800, and specifically, one of polyoxypropylene diol, polyether triol and polytetrahydrofuran is preferable.

The amino mercaptan is one or the combination of more than two of mercaptoethylamine, p-aminophenol, m-aminophenol, o-aminophenol, mercaptoacetamide and 3-mercapto-1-propylamine.

The cross-linking agent is 1, 4-Butanediol (BDO), and the foaming agent is water.

The isothiocyanate provided by the invention is phenyl isothiocyanate or p-toluenesulfonyl isothiocyanate.

In a preferred embodiment of the invention, the modified PUF is prepared by: putting 80-85 parts of polytetrahydrofuran, 5-15 parts of mercaptoethylamine, 5-15 parts of 3-mercapto-1-propylamine, 3-5 parts of cross-linking agent 1, 4-butanediol and 1-2 parts of water into a foaming machine, stirring to obtain a component A, adding 50-80 parts of MDI, 40-50 parts of crude MDI and 20-30 parts of p-toluenesulfonyl isothiocyanate, stirring, and carrying out foaming reaction at 37 ℃ for 2-4 hours to obtain the modified PUF.

Unless otherwise specified, the term "parts" in the present invention means parts by weight.

The inventor of the application finds that the modified PUF prepared by adding the amino mercaptan and the isothiocyanate on the basis of the conventional polyurethane foam preparation raw material has stronger adsorption capacity on iron element, only selectively adsorbs iron, but hardly adsorbs the rare earth element, has high recovery rate of the rare earth element, and ensures the aim of accurately detecting the rare earth element. The reason for the analysis may be that the polyurethane foam prepared by adding the amino mercaptan and the isothiocyanate has exposed sulfur atoms and nitrogen atoms, and lone-pair electrons on the exposed sulfur atoms and nitrogen atoms can form coordination bonds with iron atoms which are abundantly present in the magnetite solution. Therefore, the PUF modified by adding the amino mercaptan and the isothiocyanate has stronger adsorption capacity on iron.

Secondly, the higher the concentration of hydrochloric acid, the better the binding force between iron and the PUF, which leads to a higher adsorption rate of the PUF to iron, but the conventionally used PUF is not stable in a strong acid solution, usually when the concentration of hydrochloric acid is high>Decomposition and dissolution occurred at 6.5M (m.drtil, J.and t.braun, fresenius.j.ana.chem., 1990,338, 50-53.). On the basis, the inventor couples the peptidoglycan to the surface of the modified PUF through glutaraldehyde on the basis of the modified PUF to form a modified PUF/peptidoglycan complex, so that the acid resistance of the modified PUF is greatly improved. The peptidoglycan used by the invention is a multi-layer reticular macromolecular structure formed by polymerizing acetylglucosamine, acetylmuramic acid and four to five amino acid short peptides, in particular to a macromolecule formed by cross-linking heteropolysaccharide formed by alternately linking N-acetylglucosamine and N-acetylmuramic acid and different peptides. Peptidoglycan is a major component of many bacterial cell walls, and the inventors of the present invention have found that coupling of peptidoglycan to conventional PUFs or to the surface of the modified PUFs provided by the present invention can greatly increase the acid stability of the PUFs. In general, because PUF is unstable, the hydrochloric acid concentration of magnetite digestion reaction does not exceed 6.5M, and the modified PUF/peptidoglycan complex provided by the invention is still stable under the condition that the hydrochloric acid concentration is 8.5M.

In a preferred embodiment of the invention, the modified PUF/peptidoglycan complex is prepared by the following method: (1) heating the modified PUF in hydrochloric acid with concentration of 4-5moL/L at 70-90 deg.C for 3-4 hr to expose amino group on surface to form modified PUF-NH₂(ii) a (2) Will modify PUF-NH₂Placing the mixture into a peptidoglycan aqueous solution, dropwise adding glutaraldehyde, and heating and reacting at 37-40 ℃ for 24-36 hours; (3) and washing the reaction product with clear water for 3-5 times, and drying to obtain the modified PUF/peptidoglycan complex.

Preferably, the volume-to-mass ratio of the hydrochloric acid solution to the modified PUF in step (1) is 80-100:1mL/g, and more preferably, the volume-to-mass ratio is 90-100:1 mL/g.

Preferably, the concentration of the aqueous solution of peptidoglycan in the step (2) is 40-60g/L, and the aqueous solution of peptidoglycan is mixed with the modified PUF-NH₂The volume-mass ratio of the glutaraldehyde is 80-100:1mL/g, and the dropping volume of the glutaraldehyde is 5-15% of the volume of the reaction system.

In the invention, the modified PUF is heated in hydrochloric acid to hydrolyze the original connecting bond between amino and isocyanate group to release amino, so as to form modified PUF-NH with free amino on the surface₂Modifying PUF-NH with glutaraldehyde as coupling agent under heating state₂The amino groups exposed on the surface are connected with the hydroxyl groups on the peptidoglycan, and the glutaraldehyde has two aldehyde groups, and the peptidoglycan has a multilayer net structure, so that the connected peptidoglycan has an acid resistance protection effect on the modified PUF, and the finally formed modified PUF/peptidoglycan complex can not be decomposed or dissolved under the environment with the hydrochloric acid concentration of 8.5M.

The feasibility and reliability of the detection method provided by the invention are verified and evaluated by taking magnetite samples 15mag-11 and 15mag-13 as reference materials. In the most preferred embodiment of the present invention, the method for detecting rare earth elements in magnetite comprises accurately weighing about 10-20mg of magnetite (to 0.01mg) into a reaction flask, adding 0.2-0.4mL of 22MHF, 0.9-2.0mL of 16M HCl and 0.3-0.6mL of 14M HNO₃The acidic mixture of (3) was heated to dissolve at 150 ℃ for 24 hours, cooled and slowly heated to evaporate HF, then 3-6mL of 8-8.5M HCl was added and heated at 120 ℃ for 30 minutes. After cooling, the sample solution was transferred to a centrifuge tube, the sample volume was replenished with 8-8.5M HCl to 10-20mL and accurately weighed. . Adding the modified PUF or the modified PUF/peptidoglycan complex into the sample solution, shaking for 30-40 min, and taking out the modified PUF or the modified PUF/peptidoglycan complex. The treated sampleThe solution was transferred to a Savillex PFA vial, evaporated to dryness at 120 deg.C, and the sample residue was dried at 120 deg.C with 4-8mL of 2% HNO₃And (4) re-dissolving, cooling, transferring the final solution into a centrifugal tube, accurately weighing, and detecting iron and rare earth elements in the sample solution by ICP-OES and ICP-MS.

On the other hand, the invention provides an application of the detection method of the rare earth elements in the magnetite in rare earth element analysis of a small amount of iron-rich samples in geochemistry, cosmic chemistry and environmental research.

The invention has the following beneficial effects: (1) provides a simple and rapid chemical method for detecting the rare earth elements in the magnetite, and realizes the accurate determination of the rare earth elements in a small amount (10-20mg) of iron-rich samples; (2) according to the invention, the PUF is modified by amino mercaptan and/or isothiocyanate, so that the modified PUF has a better adsorption effect on iron substrates in magnetite, the removal rate of iron can reach 99.2 +/-0.4% under the optimal extraction condition, and the recovery rate of rare earth elements is between 98 and 102%; and (3) the compound formed by compounding the modified PUF and the peptidoglycan can effectively increase the acid resistance of the PUF, so that the PUF is still stable in an environment with the hydrochloric acid concentration of 8.5M. According to the invention, 10mg of magnetite is used as a reference material for detection, and experimental results prove that the detection result obtained by the detection method disclosed by the invention is very consistent with the detection value of an anion resin method, and meanwhile, the detection precision of the detection method is not significantly different from the result of using a 100mg sample. All the results show that the detection method of the rare earth elements in the magnetite provided by the invention provides an effective method for accurately determining multiple rare earth elements in the iron-rich monomineral, and the method has great potential for trace element analysis of a small amount of iron-rich samples in geochemistry, cosmic chemistry and environmental research.

Drawings

FIG. 1 is a schematic diagram of the procedure for detecting rare earth elements in magnetite samples

FIG. 2 shows the results of rare earth recovery

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Experimental instrument and experimental material

All chemical synthesis and separation, spectroscopy and mass spectrometry presented in this invention were performed at the institute of geological and geophysical institute of the Chinese academy of sciences, and the chemical processes were performed in a class 100 flow hood in a class 10000 clean room environment.

The ultrapure water used in the present invention was obtained from a Milli-Q water purification system (Elix-Millipore, USA) with a resistivity of 18.2MU cm^-1Ultrapure water, nitric acid (HNO)₃) Hydrofluoric acid (HF) and hydrochloric acid (HCl) (grade BV-III, Peking chemical research institute) were purified using a Savillex DST-1000 Teflon ultra-boiling distillation system (Minitonca, Minn., USA). The present invention uses round bottom Savillex PFA screw bottles (Savillex Corporation, usa) for sample digestion experiments and drying step after sample separation, centrifuge tubes (5mL and 50 mL; Haimen Dabo experimental facilities limited, china corning) to hold the final solution, and in the process of adsorbing iron matrix using modified PUF, THZ-C-1 horizontal vibration bath (china tai-bin instrument factory) is used for shaking.

Magnetite reference materials 15mag-11 and 15mag-13 from the laboratory, the external calibrant for REE was prepared by appropriate dilution of 100 μ g/mL mixed standard solution (NCS, China test technologies, Inc.). To correct for instrument drift, the internal standard concentration of Rh in ICP-MS samples, calibration solutions and blank solutions was kept constant at 10 ng/g.

Inductively coupled plasma emission spectrometry (ICP-OES, IRIS Advantage, Thermo Scientific) is used to determine high concentrations of the major element (Fe), the spectrometer used in the present invention is equipped with a concentric atomizer and a rotating atomizer chamber, and the instrument optimization should be performed according to standard procedures before use. The ICP-OES used in the present invention have the following instrument operating parameters.

TABLE 1 ICP-OES Instrument operating parameters

Inductively coupled plasma mass spectrometer (HR-ICP-MS, Element I, Thermo Fisher) is used to determine rare earth elements, clean the sample introduction system components before use, adjust the instrument with 10ng/mL solution containing Li, Rh and U to maximize sensitivity covering low and medium mass ranges, measured under conventional experimental conditions for MO of Ce⁺/M⁺The ratio is kept below 2 per mill, and the washing time between samples is 3% v/v HNO₃For 1 minute. The HR-ICP-MS used in the present invention has the following instrument operating parameters as shown in the table.

TABLE 2 Instrument operating parameters for HR-ICP-MS

Preparation example 1 preparation of modified PUF

Putting 85g of polytetrahydrofuran, 15g of mercaptoethylamine, 15g of 3-mercapto-1-propylamine, 5g of 1, 4-butanediol and 2g of water into a foaming machine, stirring to obtain a component A, adding 75g of MDI, 50g of crude MDI and 25g of p-toluenesulfonyl isothiocyanate, uniformly stirring, and carrying out foaming reaction at 37 ℃ for 4 hours to obtain the modified PUF.

Preparation example 2 preparation of modified PUF/peptidoglycan Complex

S1: 1g of the modified PUF prepared in preparation example 1 was put into 100mL of hydrochloric acid having a concentration of 4moL/L, and the mixture was heated at 90 ℃ to react for 4 hours, so that the bond between the amino group and the isocyanate group was hydrolyzed to release the amino group, and the amino group on the surface was exposed to form a modified PUF-NH₂Drying for later use;

s2: preparing 60g/L aqueous solution of peptidoglycan with ultrapure water, and preparing the modified PUF-NH prepared in the previous step₂About 1g of the mixture is put into 100mL of aqueous solution of peptidoglycan, heated to 40 ℃, 15mL of glutaraldehyde solution with the mass concentration of 25 percent is added dropwise,continuously heating and reacting for 24 hours;

s3: and (3) squeezing the PUF prepared in the previous step to remove water, repeatedly washing with clear water for 5 times, and drying to obtain the modified PUF/peptidoglycan complex.

Comparative preparation example 1

115g of polytetrahydrofuran, 5g of 1, 4-butanediol and 2g of water are put into a foaming machine and stirred to obtain a component A, 75g of MDI75g, 50g of crude MDI and 25g of tosyl isothiocyanate are added and stirred uniformly, foaming reaction is carried out at 37 ℃ for 4 hours to obtain a modified PUF without amino thiol, and then the preparation of the PUF/peptidoglycan complex is carried out according to the same method as the preparation example 2.

Comparative preparation example 2

85g of polytetrahydrofuran, 15g of mercaptoethylamine, 15g of 3-mercapto-1-propylamine, 5g of 1, 4-butanediol and 2g of water are put into a foaming machine and stirred to obtain a component A, 75g of MDI and 75g of crude MDI are added and stirred uniformly, foaming reaction is carried out at 37 ℃ for 4 hours to obtain a modified PUF without isothiocyanate, and then the preparation of the PUF/peptidoglycan complex is carried out according to the same method as the preparation example 2.

Comparative preparation example 3

Putting 115g of polytetrahydrofuran, 5g of 1, 4-butanediol and 2g of water into a foaming machine, stirring to obtain a component A, adding g g of MDI and 75g of crude MDI, uniformly stirring, carrying out foaming reaction at 37 ℃ for 4 hours to obtain a conventional PUF, and then preparing the PUF/peptidoglycan complex according to the same method as the preparation example 2.