CN112169766B

CN112169766B - Preparation method of magnetic adsorbent in limited space and application of magnetic adsorbent in cadmium (II) separation

Info

Publication number: CN112169766B
Application number: CN202011023710.8A
Authority: CN
Inventors: 沈丹青; 潘建明
Original assignee: Jiangsu University
Current assignee: Jiangsu University
Priority date: 2020-09-25
Filing date: 2020-09-25
Publication date: 2023-01-17
Anticipated expiration: 2040-09-25
Also published as: CN112169766A

Abstract

The invention belongs to the technical field of separation functional materials, and relates to a preparation method of a magnetic adsorbent in a confined space, which comprises the following steps: fe ₃ O ₄ Dispersing nanoparticles and surfactant in water-phase tris-HCl buffer solution, adding alkane as oil phase dropwise, and stirring at high speed to form HIPEs-Fe ₃ O ₄ (ii) a Subsequently, HIPEs-DA-NTA was prepared using the same method, which replaced MNPs with DA-NTA in the aqueous phase. Then mixing the two high internal phase emulsions under the high-speed stirring of 3000-5000 rpm, wherein the stirring time is 5-15 min, and realizing the new mixed high internal phase emulsion. Placing the mixed high internal phase emulsion at room temperature for 5.0-33 h, extracting the product collected by the neodymium-iron-boron permanent magnet by a Soxhlet extraction method, repeatedly washing the product with ethanol and water to obtain a magnetic adsorbent NAIMSs-E in a confined space, and applying the NAIMSs-E to separation and adsorption of heavy metal Cd ²⁺ . The present invention creates an extensible, time-saving, energy-efficient method of manufacturing monodisperse magnetic adsorbents that solves the problems of the prior art requiring two or more steps and additional vigorous agitation.

Description

Preparation method of magnetic adsorbent in limited space and application of magnetic adsorbent in cadmium (II) separation

Technical Field

The invention belongs to the technical field of separation functional material preparation, relates to preparation of a magnetic adsorbent material, and particularly relates to a preparation method of a magnetic adsorbent in a limited space and application of the magnetic adsorbent in cadmium (II) separation.

Background

Cadmium is one of the most toxic metals because it causes cancer and renal dysfunction, pulmonary insufficiency, bone damage, cancer, anemia, hypertension, itayas disease, weight loss, and the like. And is one of the most common metal pollutants in wastewater discharged from industrial activities such as electroplating, smelting, alloying, pigment, plastic manufacturing, mining, metallurgy, refining and the like. Wherein the cadmium (Cd) is divalent ²⁺ ) Are considered the most dangerous metal ions, their non-biodegradability, bio-accumulation along the food chain and irreversible harm to human health.

Monodisperse magnetic adsorbents (MMSs), in particular core/shell nanostructures containing affinity groups, have a wide application prospect in the aspects of rapid enrichment of blood lead, heavy metal ions, uranium salts, noble metal ions, proteins, polypeptides, dyes and the like. Superparamagnetic and shell-terminal groups (i.e., -COOH, -NH) benefit from an iron oxide core ₂ OH, -SH) and MMSs have excellent specific absorption performance on heavy metal ions, and can be simply collected from a test solution through an external field. The key to its success isHas enough binding units, terminal groups and target molecules/ions compatibility and good shell layer thickness.

Recently, the design and synthesis of size and structure tunable functional absorbents by space-limiting strategies is considered a promising concept. In this theory, the closed space as a reactor can provide the necessary tools for custom design of the microstructure according to the detailed requirements of the separation application. High Internal Phase Emulsions (HIPEs) with high dispersed phase volume fractions are widely used as templates for various porous materials. In addition, their continuous phase films often serve as solid phase walls of spatially confined nanoreactors, with phase equilibrium properties that can be significantly altered.

Disclosure of Invention

In order to solve the problems of the prior art that the synthesis of monodisperse magnetic adsorbents (MMSs) by various strategies often requires two or more steps and additional vigorous agitation, it is necessary to establish a scalable, time-saving, and energy-saving manufacturing method of MMSs.

The invention discloses a preparation method of a magnetic adsorbent in a limited space, which comprises the following steps:

(1) Mixing Fe ₃ O ₄ Dispersing nanometer particles (MNPs) and surfactant in water phase tris-HCl buffer solution, adding alkane as oil phase into water phase drop by drop, stirring at high speed of 5000-8000 rpm for 10-30 min to form O/W HIPEs (HIPEs-Fe) ₃ O ₄ ；

(2) Dispersing 2- (biscarboxymethylamino) -6- {3- [2- (3, 4-dihydroxyphenyl) -ethylcarbamoyl ] -propionylamino } -hexanoic acid (DA-NTA) and a surfactant in an aqueous phase tris-HCl buffer solution, adding the alkane as an oil phase into the aqueous phase drop by drop, and stirring at a high speed of 5000-8000 rpm for 10-30 min to form HIPEs-DA-NTA;

(3) Mixing the HIPEs-Fe prepared in the step (1) ₃ O ₄ Mixing the HIPEs-DA-NTA prepared in the step (2) under the high-speed stirring of 3000-5000 rpm, wherein the stirring time is 5-15 min, and realizing new mixed high internal phase emulsion HIPEs; standing at room temperature for 5.0-33 h, collecting the product with Nd-Fe-B permanent magnetExtracting with ethanol and water repeatedly, collecting product nitrilotriacetic acid fixed magnetic adsorbent NAIMSs-E, vacuum drying, sealing, and storing.

In the step (1), the mass ratio of the MNPs to the surfactant is 10-30mg.

Preferably, the mass ratio of MNPs to surfactant is 10mg.

In the step (2), the mass ratio of DA-NTA to the surfactant is 10-50mg.

Preferably, the mass ratio of DA-NTA to the surfactant is 15mg.

In the step (1) and the step (2), the volume ratio of the water-phase tris-HCl buffer solution to the oil-phase alkane is 3-6 mL, wherein the concentration of the tris-HCl buffer solution is 10mmol/L, and the pH value is 8.5; the alkane is n-decane, dodecane or n-tridecane; the surfactant is sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or Tween 80.

Preferably, the volume ratio of the aqueous-phase tris-HCl buffer solution to the oil-phase alkane is 5mL and 20mL, the alkane is dodecane, and the surfactant is Tween 80.

Preferably, in the step (1) and the step (2), the high-speed stirring speed is 6800rpm;

in step (3), HIPEs-Fe ₃ O ₄ And HIPEs-DA-NTA in a volume ratio of: 1:1.

In the step (3), the high-speed stirring speed is 3000rpm.

In the step (3), the solvent in the Soxhlet extraction method is acetone, and the temperature of vacuum drying is 45-55 ℃.

The magnetic adsorbent in the limited space prepared by the invention is used for heavy metal Cd ²⁺ And (4) adsorption separation.

In the preferred disclosed embodiment of the present invention, the MNPs in step a are synthesized according to the prior art (j.liu, z.k.sun, y.h.deng, y.zou, c.y.li, x.h.guo, l.q.xiong, y.gao, f.y.li, d.y.zhao, high way water-discrete biocompatible magnetic composites with low cytoxicity stabilized by rare group groups, image.chem. int.ed.48 (2009) 5875-5879 htt:// doi.org/10.156/anie.2001002.), which discloses the synthesis method adopted in the present invention:

under ultrasonic treatment, feCl is added ₃ ·6H ₂ O is dispersed in Ethylene Glycol (EG) to form a clear solution. Subsequently, anhydrous sodium acetate (NaAC) and ethylenediamine were added to the solution and stirred vigorously for 20-40 minutes. The mixture was then transferred to a teflon-lined 50mL stainless steel autoclave and held at 200 ℃ for 8h. Finally, the collected black product was washed 3 times with ethanol and dried in a vacuum oven at 40 ℃. Wherein the FeCl ₃ ·6H ₂ The volume mass ratio of the ethylene glycol, the anhydrous sodium acetate and the ethylenediamine is 1.35g.

The present invention provides for the synthesis of sterically constrained nitrilotriacetic acid permanent magnetic adsorbents (NAIMSs-E) in the water continuous phase of a high internal phase emulsion. First, the influence of internal phase ratio volume fraction, reaction time, DA-NTA amount and different surfactants on the structure and morphology of the prepared NAIMSs-E nanoparticles was investigated. Second, NAIMSs-E based on DA-NTA moieties with precisely controlled diameter and shell thickness were prepared and characterized under optimized conditions.

It is still another object of the present invention to apply the nitrilotriacetic acid (NAIMSs-E) immobilized magnetic adsorbent prepared in the method to heavy metal Cd ²⁺ The adsorption separation of (3).

An environment of 25 ℃ was maintained, and 5mg of the prepared magnetic adsorbents (NAIMSs-E) were placed in 10mL of 10mg/L Cd ²⁺ And adsorbing in the solution, taking out after 3h, and testing the concentration of the adsorbed solution.

The adsorption capacity calculation formula is as follows:

wherein C is ₀ (mg L ^-1 ) And C _e (mg L ^-1 ) Are respectively Cd ²⁺ The initial concentration and the equilibrium concentration of (c). V (mL) is the volume of the test solution and m (g) is the mass of the adsorbent.

The adsorption performance evaluation of the present invention was carried out according to the following method:

static adsorption experiment: adding 5mg of the adsorbents (NAIMSs-E) prepared according to the method into 10mL of test solution (the concentration value is 10 mg/L) with the initial pH value of 4-8, measuring the adsorbed content by using an atomic absorption spectrophotometer, and calculating the adsorption capacity according to the result; after saturated adsorption, the adsorption effect of NAIMSs-E is researched through the adsorption quantity of several different concentrations and temperatures; determining the recycling capacity of the adsorbent through an adsorption-desorption experiment; the adsorption effect of NAIMSs-E in the actual environment is researched through the adsorption capacity of three different water qualities.

The method has the beneficial effects that in the water continuous phase of the prepared oil-in-water high internal phase emulsion, the synthesis of the space-limited nitrilotriacetic acid fixed magnetic adsorbent (NAIMSs-E) is carried out in a narrow water continuous phase gap partitioned by liquid drops of an oil phase. The diameter and the shell thickness of the prepared magnetic nanoparticles are controlled by adjusting the internal phase ratio volume fraction, the reaction time, the DA-NTA amount and different surfactants. Cd separation using NAIMSs-E ²⁺ And the application in actual environmental water has great potential.

Drawings

FIG. 1 is a TEM image corresponding to the preparation of MNPs, MPDA and NAIMSs-E in example 1, comparative example and example 4, respectively;

FIG. 2 is a graph of infrared spectra of functional groups of MNPs, MPDA and NAIMSs-E prepared in example 1, comparative example and example 4;

FIG. 3 shows hysteresis loop test spectra of MNPs and NAIMSs-E prepared in example 1 and example 4;

FIG. 4 is a graph showing the effect of pH conditions on the adsorption capacity of NAIMSs-E and the results of the corresponding zeta potentials;

FIG. 5 is a graph showing the results of adsorption capacities of MNPs, MPDA and NAIMSs-E at different water qualities.

FIG. 6 adsorption kinetics and model fitting curves for NAIMSs-E;

FIG. 7 shows the results of the verification of the regenerability of NAIMSs-E.

Detailed Description

The present invention will be described in detail below with reference to examples to enable those skilled in the art to better understand the present invention, but the present invention is not limited to the following examples.

Comparative example

Synthesis of magnetic polydopamine nanoparticles (MPDA)

(1) 10mg of MNPs and 400mg of Tween 80 were dispersed as an aqueous phase in 5mL of tris-HCl buffer solution, and 20mL of dodecane was added dropwise as an oil phase. O/W HIPEs (also known as HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

(2) HIPEs-DA were also prepared by the method described in step (1), but in the aqueous phase, MNPs were replaced with 15mg of dopamine hydrochloride (DA).

(3) Mixing HIPEs-DA and HIPEs-Fe ₃ O ₄ Mixing was carried out at 5000rpm for 5min, and then two emulsion reactors were set to achieve new mixed HIPEs. Placing the mixed HIPEs at room temperature for 6h, extracting the product collected by the NdFeB permanent magnet by a Soxhlet extraction method (using acetone as a solvent), and then repeatedly washing the product by using ethanol and water. The obtained product magnetic poly dopamine nano-particles (MPDA) are dried under the vacuum condition at the temperature of 45 ℃ and are stored in a sealing way.

FIG. 1b is a TEM image of magnetic polydopamine nanoparticles prepared by this comparative example, and it can be found that the shell thickness of the particles is about 2.8 nm.

Example 1

Fe ₃ O ₄ Synthesis of nanoparticles (MNPs)

Under ultrasonic treatment, 1.35g of FeCl ₃ ·6H ₂ O was dispersed in 40mL of Ethylene Glycol (EG) to form a clear solution. Subsequently, 3.6g of anhydrous sodium acetate (NaAC) and 10mL of ethylenediamine were added to the solution and stirred vigorously for 30 minutes. The mixture was then transferred to a teflon-lined 50mL stainless steel autoclave and held at 200 ℃ for 8h. Finally, the collected black product was washed 3 times with ethanol and dried in a vacuum oven at 40 ℃.

FIG. 1a is a TEM image of the magnetic nanoparticles prepared in this example, and it can be found that the diameter of the particles is about 70-100 nm.

Example 2

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg MNPs and 400mg TenSodium dialkyl sulfate was dispersed as an aqueous phase in 5mL of tris-HCl buffer solution, and 20mL of n-decane was added dropwise as an oily phase. O/W HIPEs (also known as HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Subsequently, HIPEs-DA-NTA were also prepared by this method, but in the aqueous phase, MNPs were replaced with 15mg DA-NTA.

Then HIPEs-DA-NTA and HIPEs-Fe ₃ O ₄ Mixing at 5000rpm high speed stirring for 5min to obtain new mixed HIPEs. The mixed HIPEs are placed at room temperature for 6h, the product collected by the NdFeB permanent magnet is extracted by a Soxhlet extraction method (acetone is used as a solvent), and then the product is repeatedly washed by ethanol and water. The obtained product nitrilotriacetic acid fixed magnetic adsorbent (NAIMSs-E) is dried under the vacuum condition of 45 ℃ and sealed for storage.

Example 3

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg of MNPs and 400mg of sodium dodecylbenzenesulfonate as aqueous phase are dispersed in 5mL of tris-HCl buffer solution, and 20mL of n-tridecane as oil phase are added drop by drop. O/W HIPEs (also known as HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Then HIPEs-DA-NTA and HIPEs-Fe ₃ O ₄ Mixing at 5000rpm for 5min to obtain new HIPEs. The mixed HIPEs were left at room temperature for 6h, and the product collected with the Nd-Fe-B permanent magnet was extracted by Soxhlet extraction (acetone as solvent), followed by repeated washing with ethanol and water. The obtained product nitrilotriacetic acid fixed magnetic adsorbent (NAIMSs-E) is dried under the vacuum condition of 45 ℃ and sealed for storage.

Example 4

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg of MNPs and 400mg of Tween 80 as an aqueous phase were dispersed in 5mL of tris-HCl buffer solution, 20mL of dodecane was added drop by drop as the oil phase. O/W HIPEs (also called HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Subsequently, HIPEs-DA-NTA were also prepared by this method, but in the aqueous phase, the MNPs were replaced with 15mg DA-NTA.

Fig. 1c is a TEM image of the magnetic poly-dopamine nanoparticle prepared in this example, and it can be found that the thickness of the shell layer of the particle is about 8.6 nm.

FIG. 2 is an infrared spectrum of the functional groups of MNPs, MPDA and NAIMSs-E analyzed in example 1, comparative example and this example. MNPs, MPDA and NAIMSs-E can be seen at 592cm by using FT-IR ^-1 Obvious characteristic peaks of Fe-O appear at all positions, and for MPDA, except the characteristic adsorption peak of Fe-O bonds, the peak is 1590cm ^-1 And 1496cm ^-1 The absorption peak at (B) is related to the C = C stretching vibration of the aromatic ring, and is at 3400cm ^-1 The broad peak at (a) is the tensile vibration due to OH and NH. And for those at NAIMSs-E, at 1557cm ^-1 And 1405cm ^-1 The absorption peak at (a) is also related to the C = C tensile vibration of the aromatic ring. 1696cm ^-1 And 1601cm ^-1 The absorption peaks at (a) are due to the C = O and N-H bonds of the DA-NTA reagent. COO (carbon organic compound) ^- The symmetric stretching of vibration occurs at 1388cm ^-1 Nearby. These results indicate that the limited space of the HIPE can provide an efficient platform for scalable MPDA and NAIMSs-E synthesis.

FIG. 3 is a magnetic hysteresis plot of magnetization analysis of MNPs and NAIMSs-E of example 1 and this example. It can be concluded that MNP and NAIMSs-E are superparamagnetic with a saturation magnetization (Ms) of 51.5emu g-1 and 35.2emu g, respectively ^-1 . The reason why the Ms of NAIMSs-E is lower than that of MNPs is thatWhich is coated with a non-magnetic coating material on MNPs. However, NAIMSs-E still have strong magnetic response performance in solution.

Example 5

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg of MNPs and 400mg of Tween 80 were dispersed as an aqueous phase in 5mL of tris-HCl buffer solution, and 25mL of dodecane was added dropwise as an oil phase. O/W HIPEs (also known as HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Then HIPEs-DA-NTA and HIPEs-Fe ₃ O ₄ Mixing at 5000rpm high speed stirring for 5min to obtain new mixed HIPEs. The mixed HIPEs were left at room temperature for 6h, and the product collected with the Nd-Fe-B permanent magnet was extracted by Soxhlet extraction (acetone as solvent), followed by repeated washing with ethanol and water. The obtained product nitrilotriacetic acid fixed magnetic adsorbent (NAIMSs-E) is dried under the vacuum condition of 45 ℃ and sealed for storage.

Example 6

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg of MNPs and 400mg of sodium dodecylbenzenesulfonate as aqueous phase are dispersed in 5mL of tris-HCl buffer solution, and 33.3mL of n-decane as oil phase, added drop by drop. O/W HIPEs (also called HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Then HIPEs-DA-NTA and HIPEs-Fe ₃ O ₄ Mixing at 5000rpm high speed stirring for 5min to obtain new mixed HIPEs. The mixed HIPEs were left at room temperature for 6h, the product collected with the neodymium iron boron permanent magnet was extracted by soxhlet extraction (acetone as solvent), then washed repeatedly with ethanol and water. The obtained product nitrilotriacetic acid fixed magnetic adsorbent (NAIMSs-E) is true at 45 DEG CDrying under air condition, sealing and storing.

Example 7

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg of MNPs and 400mg of Tween 80 were dispersed as an aqueous phase in 5mL of tris-HCl buffer solution, and 45mL of dodecane was added dropwise as an oil phase. O/W HIPEs (also called HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Then HIPEs-DA-NTA and HIPEs-Fe ₃ O ₄ Mixing at 5000rpm high speed stirring for 5min to obtain new mixed HIPEs. The mixed HIPEs were left at room temperature for 6h, the product collected with the neodymium iron boron permanent magnet was extracted by soxhlet extraction (acetone as solvent), then washed repeatedly with ethanol and water. The obtained product nitrilotriacetic acid fixed magnetic adsorbent (NAIMSs-E) is dried under the vacuum condition of 45 ℃ and sealed for storage.

Example 8

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg of MNPs and 400mg of Tween 80 as an aqueous phase were dispersed in 5mL of tris-HCl buffer solution, and 20mL of n-decane as an oil phase were added dropwise. O/W HIPEs (also known as HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Subsequently, HIPEs-DA-NTA were also prepared by this method, but in the aqueous phase, the MNPs were replaced with 5mg DA-NTA.

Then HIPEs-DA-NTA and HIPEs-Fe ₃ O ₄ Mixing at 5000rpm for 5min to obtain new HIPEs. The mixed HIPEs were left at room temperature for 23h, and the product collected with the NdFeB permanent magnet was extracted by Soxhlet extraction (acetone as solvent), followed by repeated washing with ethanol and water. The obtained product nitrilotriacetic acid fixed magnetic adsorbing agent (NAIMSs-E) is dried under the vacuum condition of 45 ℃ and sealed for storage.

Example 9

Synthesis of nitrilotriacetic acid immobilized magnetic adsorbents (NAIMSs-E)

10mg of MNPs and 400mg of Tween 80 were dispersed as an aqueous phase in 5mL of tris-HCl buffer solution, and 20mL of dodecane was added dropwise as an oil phase. O/W HIPEs (also called HIPEs-Fe) ₃ O ₄ ) Formed by high speed stirring at 6800rpm for 10 min.

Subsequently, HIPEs-DA-NTA were also prepared by this method, but in the aqueous phase, the MNPs were replaced with 45mg DA-NTA.

Then HIPEs-DA-NTA and HIPEs-Fe ₃ O ₄ Mixing at 5000rpm for 5min to obtain new HIPEs. The mixed HIPEs were left at room temperature for 33h, the product collected with the neodymium iron boron permanent magnet was extracted by soxhlet extraction (acetone as solvent), and then washed repeatedly with ethanol and water. The obtained product nitrilotriacetic acid fixed magnetic adsorbing agent (NAIMSs-E) is dried under the vacuum condition of 45 ℃ and sealed for storage.

Example 10

5mg of nitrilotriacetic acid fixed magnetic adsorbents (NAIMSs-E) prepared as described in example 4 were added to 5.0mL of Cd ions formulated at

pH

4, 5, 6, 7 and 8 ²⁺ Final Cd in the test solution (concentration value 10 mg/L) ²⁺ The concentration was determined by atomic absorption spectrophotometer. And, before the end of the test in each test solution, zeta potential at different pH was measured.

The experiment was performed three times to balance the adsorption capacity.

The results indicate that the adsorption capacity of NAIMSs-E, pH 7>, pH 8, pH 5, pH 4. At the same time, the NAIMSs-E particles were negatively charged in the investigated range and the lowest zeta potential reached-31.4 mV at pH =7.0, indicating the presence of a large number of carboxyl and phenolic hydroxyl groups in the DA-NTA reagent. This indicates that the optimum adsorption condition was achieved at a pH of 7 (the results are shown in FIG. 4).

To further explore the availability of NAIMSs-E, a comparison was used that describes the adsorption capacity of the different materials (i.e., MNP, MPDA and NAIMSs-E). In addition, to evaluate the effect of different water samples on adsorption, test solutions were prepared using deionized water, tap water and river water, respectively. Of the three adsorbents, NAIMSs-E absorbed the highest amount, and the results follow the following sequence: NAIMSs-E > MPDA > MNPs (results are shown in FIG. 5).

The adsorption capacities of NAIMSs-E at different time nodes are investigated, and then the data are fitted by using quasi-primary and quasi-secondary kinetic models, and the dynamics and the fitting curve thereof are drawn (as shown in FIG. 6). The adsorption process of NAIMSs-E can be divided into three steps. The first stage (0 to 60 min) of rapid adsorption, due to the high concentration gradient and sufficient binding sites, large initial Cd ²⁺ Concentration is the main driving force. The next stage is obviously a slow stage, ranging from 60 to 180 minutes. Finally, adsorption equilibrium was reached at 180 minutes.

The regeneration capacity of the NAIMSs-E is tested through five continuous adsorption-desorption cycles, and after 5 regeneration cycle periods, the NAIMSs-E carries out the test on the Cd ²⁺ The adsorption capacity of (2) was 86.7% of the initial adsorption capacity, and the above results show that NAIMSs-E can be reused many times and that the adsorption performance is stable (the results are shown in FIG. 7).

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, or direct or indirect applications in other related fields of technology, which are made by the present specification, are included in the scope of the present invention.

Claims

1. A preparation method of a magnetic adsorbent in a confined space is characterized by comprising the following steps:

(1) Mixing Fe ₃ O ₄ Dispersing nano particles (MNPs) and a surfactant in a water phase tris-HCl buffer solution, taking alkane as an oil phase, adding the oil phase into the water phase one by one, and stirring at a high speed of 5000-8000 rpm for 10-30 min to form O/W HIPEs (HIPEs-Fe) ₃ O ₄ ；

(2) Dispersing 2- (biscarboxymethylamino) -6- {3- [2- (3, 4-dihydroxyphenyl) -ethylcarbamoyl ] -propionylamino } -hexanoic acid (DA-NTA) and a surfactant in an aqueous phase tris-HCl buffer solution, with an alkane as an oil phase, adding the oil phase drop by drop to the aqueous phase, and stirring at a high speed of 5000-8000 rpm for 10-30 min to form HIPEs-DA-NTA;

(3) Mixing the HIPEs-Fe prepared in the step (1) ₃ O ₄ Mixing the HIPEs-DA-NTA prepared in the step (2) under the high-speed stirring of 3000-5000 rpm, wherein the stirring time is 5-15 min, and realizing new mixed high internal phase emulsion HIPEs; standing at room temperature for 5.0-33 h, extracting the product collected by the neodymium iron boron permanent magnet by a Soxhlet extraction method, then repeatedly washing with ethanol and water to obtain a product nitrilotriacetic acid fixed magnetic adsorbent NAIMSs-E, drying in vacuum, sealing and storing.

2. The method for preparing a magnetic adsorbent in a confined space according to claim 1, wherein in step (1), the mass ratio of the MNPs to the surfactant is 10 to 30mg.

3. The method of claim 2, wherein the mass ratio of MNPs to surfactant is 10 mg.

4. The process for producing a magnetic adsorbent in a confined space according to claim 1, wherein in the step (2), the mass ratio of DA-NTA to the surfactant is 10 to 50mg.

5. The process for the preparation of a confined space magnetic adsorbent according to claim 4 wherein the mass ratio of DA-NTA to surfactant is 15mg.

6. The method for preparing the magnetic adsorbent in the limited space according to claim 1, wherein in the step (1) and the step (2), the volume ratio of the water-phase tris-HCl buffer solution to the oil-phase alkane is 3-6 mL; the alkane is n-decane, dodecane or n-tridecane; the surfactant is sodium dodecyl benzene sulfonate, sodium dodecyl sulfate or Tween 80.

7. The method for preparing a confined space magnetic adsorbent according to claim 6, wherein the volume ratio of the aqueous-phase tris-HCl buffer solution to the oil-phase alkane is 5mL, 20mL, the alkane is dodecane, and the surfactant is Tween 80.

8. The method for producing a magnetic adsorbent in a confined space according to claim 1, wherein in the step (1) and the step (2), the high-speed stirring speed is 6800rpm.

9. The method of claim 1, wherein in step (3), HIPEs-Fe ₃ O ₄ And HIPEs-DA-NTA in a volume ratio of: 1; the high-speed stirring speed is 3000rpm; the solvent in the Soxhlet extraction method is acetone, and the temperature of vacuum drying is 45-55 ℃.

10. Use of the confined space magnetic adsorbent prepared by the preparation method of any one of claims 1 to 9 for heavy metal Cd ² ⁺ The use of adsorptive separation according to (1).