CN105148852A - Thiohydroxy-modified magnetic MOFs adsorbent and preparation method and application thereof - Google Patents

Abstract

The invention discloses a thiohydroxy-modified magnetic MOFs adsorbent and a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing magnetic Fe3O4 nanospheres with the particle size of 10-20 nm by adopting a coprecipitation method; (2) preparing Fe3O4@SiO2 with a core-shell structure by adopting a Stober silicone coupling method; (3) preparing Fe3O4@SiO2@MOF through a solvothermal in-situ growth method; (4) carrying out thiol-functionalization on Fe3O4@SiO2@MOF synthesized in the step (3) in a solvent auxiliary ligand exchange manner, and preparing the thiol-functionalized magnetic MOFs adsorbent with different proportions through adjusting the proportion of mercaptoacetic acid to Fe3O4@SiO2@MOF. According to the invention, the preparation method is mild in reaction conditions, low in cost, and simple and convenient to operate; the prepared magnetic MOFs adsorbent has the advantages of being high in adsorption speed, large in adsorption capacity and good in selectivity when removing the metal ions in water.

Description

A kind of thiol modified magnetic MOFs Adsorbent and its preparation method and application

technical field

The invention belongs to the field of waste water treatment, and in particular relates to a mercapto-modified magnetic MOFs adsorbent and a preparation method and application thereof.

Background technique

With the rapid development of modern industry, a large amount of heavy metals are discharged into the environment. At present, heavy metal pollution has become one of the major hazards that threaten human health. Removing heavy metal ions in aqueous solution by traditional methods such as precipitation is not only costly and complicated to operate, but also often produces a large amount of toxic waste, forming secondary pollution. Environmental workers and researchers have done a lot of work on the treatment of heavy metal pollution such as low development cost and simple operation.

Mercury, as a highly toxic heavy metal element, especially in the water environment, can enter the human body through direct ingestion, bioaccumulation, and biomagnification, causing various hazards, such as vision and hearing decline, affect human development or even distortion, nervous system damage, etc. Therefore, it is of great significance to develop a simple and efficient technology to remove mercury in water. At present, the methods for removing mercury in water mainly include precipitation, adsorption, membrane separation, etc. Among them, adsorption has been widely used due to its advantages of simple operation, fast separation, low cost, and high recovery rate. Although a variety of materials have been used as adsorbents to remove mercury in water bodies, such as clay, activated carbon, graphene, etc., these materials have relatively poor selectivity, low adsorption capacity, and difficult separation, which limits Its wide application. Therefore, it is of great practical significance to develop new adsorbents that are easy to separate with high selectivity and high adsorption capacity for the target pollutant mercury.

Metal-organic frameworks (MOFs) are a class of porous organic-inorganic hybrid materials that use metal ions or metal clusters as ligand centers to form strong chemical bonds with oxygen- or nitrogen-containing organic ligands. Compared with traditional mesoporous materials, they have been widely used in the field of adsorption and separation due to their advantages such as large specific surface area, simple synthesis method, adjustable pore size, and easy post-functional modification. The magnetic MOFs composites (magnetic MOFs composites, MFCs) prepared by combining MOFs and magnetic materials can combine the advantages of rapid separation of magnetic materials with the advantages of large specific surface area of MOFs, and the prepared MFCs are used in many fields. It has a good application prospect. However, the currently prepared MFCs often lack certain functional units, have weak interactions with mercury, and poor selectivity. Therefore, it is necessary to further post-functionalize MFCs to improve their selectivity and adsorption capacity. On the other hand, most of the current MFCs materials are mainly based on HKUST-1 as the modified material, but HKUST-1 is not particularly stable when in contact with water, and the high concentration of Cu ²⁺ itself is somewhat toxic to organisms, easily Cause secondary pollution, so there are certain limitations in application. Therefore, the development of an environmentally friendly, low-cost, and stable MFCs has a good application prospect.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the existing preparation technology, and provide a mercapto-modified magnetic Zr-MOF solid-phase adsorbent with good selectivity, strong stability and high adsorption capacity, its preparation method and application. The adsorbent prepared by the method has fast adsorption speed, large adsorption capacity, wide applicable pH range, and is suitable for rapid removal of heavy metal ions in polluted water.

The object of the present invention is achieved through the following technical solutions:

A thiol-modified magnetic MOFs adsorbent, comprising a magnetic Fe ₃ O ₄ core and a SiO ₂ layer and a MOF layer wrapped sequentially from the inside to the outside on the Fe ₃ O ₄ core, and the MOF layer is UIO-66 or UIO-66 -NH ₂ , the UIO-66 is functionalized with mercaptoalkylcarboxylic acid.

The particle diameter of the magnetic Fe ₃ O ₄ core is 10-20 nm.

A method for preparing the above-mentioned mercapto-modified magnetic MOFs adsorbent, comprising the steps of:

(1) Using tetraethoxysilane as the coupling agent and magnetic Fe ₃ O ₄ nanospheres with a particle size of 10-20 nm as the core, Fe ₃ O ₄ with a core-shell structure was prepared by the Stöber silica gel coupling method @ _SiO2 ;

(2) Ultrasonic disperse Fe ₃ O ₄ @SiO ₂ prepared in step (1) into N,N-dimethylformamide, add soluble metal salt, and mix ultrasonically to obtain a solution ; Add the organic ligand to N,N-dimethylformamide to dissolve, ultrasonically disperse to obtain a solution ;

(3) Under stirring conditions, the solution add solution , forming a suspension, stirring, heating, washing, activation, and drying to obtain the magnetic MOFs material MFC-O;

(4) Disperse the mercaptoalkylcarboxylic acid in water, add KOH to adjust the pH, then add MFC-O, let stand, heat, wash, and dry to obtain the mercapto-modified magnetic MOFs adsorbent.

The magnetic Fe ₃ O ₄ nanospheres with a particle size of 10-20 nm are prepared by co-precipitation; the mass ratio of Fe ₃ O ₄ @SiO ₂ to soluble metal salt in the step (2) is 1:1 -3; the soluble metal salt is ZrCl ₄ ; the organic ligand is a carboxyl ligand.

The carboxyl ligand is terephthalic acid or 2-aminoterephthalic acid, and the molar ratio to the metal salt is 1:1.

The step (3) is specifically: at room temperature, under the stirring condition of a rotating speed of 400-600 rpm, the solution add solution , to form a suspension, continue to stir for 12-24 hours, heat at 110-150 ^o C, wash with DMF and methanol in turn; activate in methanol at room temperature for 24 hours, repeat the activation 3 times, and dry at room temperature to obtain the magnetic MOFs material MFC -O.

The mercaptoalkylcarboxylic acid described in step (4) is mercaptoacetic acid, mercaptopropionic acid or 2,3-dimercaptosuccinic acid, and the mercaptoalkylcarboxylic acid and UIO-66 contained in MFC-O in step (4) The molar ratio is 1-3:1.

The step (4) is specifically: dispersing the mercaptoalkylcarboxylic acid in water, adding KOH to adjust the pH to 7; then adding MFC-O, standing still, heating to 25-60 ^o C under the protection of Ar gas, and keeping 3- 72 hours; then washed with water and methanol in sequence, and dried at room temperature to obtain the mercapto-modified magnetic MOFs adsorbent.

The application of the above-mentioned thiol-modified magnetic MOFs adsorbent in the treatment of wastewater containing heavy metals.

The heavy metal is Hg ²⁺ .

The preparation method of the magnetic MOFs solid-phase extraction agent provided by the present invention is (the schematic diagram of its synthetic route is shown in Figure 1): (1) adopt the co-precipitation method (Liu, X.; Ma, Z.; Xing, J.; Liu , H., "Preparation and Characterization of Amino–Silane Modified Superparamagnetic Silica Nanospheres". [J] J. Magn. Magn. Mater. 2004, 270 (1), 1-6.) prepared a particle size of 10-20 nm magnetic Fe ₃ O ₄ nanospheres; (2) Using tetraethoxysilane as coupling agent, Fe ₃ O ₄ @SiO ₂ with core-shell structure was prepared by Stöber silica gel coupling method; (3) Using soluble Metal salts are used as raw materials, and the magnetic MOFs adsorbent is prepared by in-situ growth in water at room temperature. By adjusting the ratio of metal salts to Fe ₃ O ₄ @SiO ₂ , the thickness of the shell can be effectively adjusted; (4) through solvent-assisted Ligand exchange post-functionalized the magnetic MOFs obtained in step (3), that is, modified sulfhydryl groups on the MOF.

In the preparation method provided by the present invention, the thickness of the shell layer can be effectively adjusted by adjusting the mass ratio of the metal salt to Fe ₃ O ₄ @SiO ₂ ; by adjusting the ratio of mercaptoalkyl carboxylic acid to MFC-O, the The functional group mercapto ratio is adjusted to optimize the material performance.

Under mild conditions, using water as a solvent, the new nano-MFCs material prepared by solvent-assisted ligand exchange combines the advantages of the magnetic rapid separation of nano-Fe ₃ O ₄ with the high selectivity and large adsorption capacity of MOFs materials. The combination of high capacity and fast adsorption performance, the method is simple to operate, low in cost, and has very good application prospects.

The prepared magnetic MOFs solid-phase adsorbent has good water stability and contains sulfhydryl groups with strong affinity for heavy metals, so it can remove various heavy metals in water, and has a good application prospect in the field of wastewater treatment.

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

(1) The preparation method provided by the present invention has the advantages of mild reaction conditions, low energy consumption, simple synthesis method, low cost, and easy realization of industrial production.

(2) The magnetic Zr-MOFs solid-phase adsorbent prepared by the present invention shows fast adsorption speed, large adsorption capacity, wide application range of solution pH, good selectivity and strong anti-interference ability in removing Hg ²⁺ in the water system and reusable advantages.

Description of drawings

Fig. 1 is the synthetic route schematic diagram of MFCs solid-phase adsorbent of the present invention;

Fig. 2 is the transmission electron microscope picture of _Fe3O4 @ _SiO2 prepared in embodiment ₁ ;

Fig. 3 is the transmission electron microscope figure of the MFC-S-3 prepared by embodiment 3;

Fig. 4 is the scanning electron micrograph of the MFC-S-3 prepared by embodiment 3;

Fig. 5 is the FT-IR spectrogram of the MFC-S-X solid-phase extraction agent prepared by embodiment 1-3;

Fig. 6 is the XRD spectrogram of the MFC-S-X prepared by embodiment 1-3;

Fig. 7 is the hysteresis loop of the MFC-S-3 prepared by embodiment 3;

Fig. 8 is Hg ²⁺ solution pH and prepared MFC-S-3 adsorption property graph in embodiment 3;

FIG. 9 is a graph showing the relationship between the adsorption performance of the MFC-S-3 solid-phase adsorbent prepared in Example 3 for Hg ²⁺ .

Detailed ways

The present invention provides a method for preparing a magnetic Zr-MOFs solid-phase adsorbent. The present invention will be further described below in conjunction with the accompanying drawings and specific examples, but these examples are limited to illustrate the present invention and cannot limit the protection scope of the present invention.

Example 1

Co-precipitation method prepared magnetic Fe ₃ O ₄ nanospheres with a particle size of 10-20 nm: 11.68 g of ferric chloride and 4.30 g of ferrous chloride were dissolved in 200 mL of high-purity water, stirred and heated to 85 ℃ under nitrogen protection. Then 20 mL of 30% NH ₃ ·H ₂ O was added, and the color of the solution changed from orange to black rapidly. After reacting for half an hour, the reaction was stopped and cooled to room temperature. The obtained nanoparticles were washed sequentially with high-purity water and 0.02 mol L ^-1 NaCl until neutral, and finally stored with high-purity water.

Fe ₃ O ₄ @SiO ₂ with a core-shell structure was prepared by Stöber silica gel coupling method: half of the Fe ₃ O ₄ nanoparticles were put into a mixed solvent containing 160 mL of ethanol and 40 mL of high-purity water. 5 mL of 30% NH ₃ ·H ₂ O and 6 mL of tetraethoxysilane (TEOS) were sequentially added dropwise to the mixture, and then mechanically stirred for 12 h at room temperature. After the reaction, wash with high-purity water and ethanol in turn until neutral, and store the obtained Fe ₃ O ₄ @SiO ₂ nanoparticles in high-purity water for future use. Its TEM image is shown in Figure 2.

MFC-O was prepared by solvothermal in situ growth method: 1.0 g Fe ₃ O ₄ @SiO ₂ was added to 150 mL DMF, 1.16 g ZrCl ₄ was added after ultrasonic dispersion, and the mixture was ultrasonically mixed for 20 minutes to obtain solution I ; 0.83 g of terephthalic acid was added to 50 mL of DMF, and ultrasonically dispersed to obtain solution II. At room temperature, under the condition of stirring at a speed of 400 rpm, the solution was add solution , to form a suspension, continue to stir for 12-24 hours, heat at 110-150 ^o C, wash with DMF and methanol in turn; activate in methanol at room temperature for 24 hours, repeat the activation 3 times, and dry at room temperature to obtain the magnetic MOFs material MFC -O.

Disperse 1 mmol of mercaptoglycolic acid in water, add KOH to adjust the pH to 7, then add 400 mg of activated magnetic MOFs, let stand, heat to 60 ^o C under the protection of Ar gas, and keep for 3 hours; then wash with water and methanol in sequence , and dried at room temperature to obtain the mercapto-modified magnetic MOFs adsorbent MFC-S-1.

The schematic diagram of the synthesis of the magnetic nanomaterial adsorbent of the present invention is shown in Figure 1. The method provided by the present invention has the advantages of mild reaction conditions, low energy consumption, simple synthesis method, low cost, environmental friendliness and industrialized production.

Example 2

The difference from Example 1 is: Synthesis of MFC-S-2: Disperse 2 mmol of mercaptoglycolic acid in water, add KOH to adjust the pH to 7, then add 400 mg of activated MFC-O, let it stand, and protect it with Ar gas Heated to 40 ^o C at low temperature and kept for 40 hours; then washed with water and methanol in sequence, and dried at room temperature to obtain the mercapto-modified magnetic MOFs adsorbent MFC-S-2.

Example 3

The difference from Example 1 is: Synthesis of MFC-S-3: Disperse 3 mmol of mercaptoglycolic acid in water, add KOH to adjust the pH to 7, then add 400 mg of activated MFC-O, let it stand, and protect it with Ar gas Heated to 25 ^o C and kept for 72 hours; then washed with water and methanol in sequence, and dried at room temperature to obtain the mercapto-modified magnetic MOFs adsorbent MFC-S-3. The TEM is shown in Figure 3, the SEM is shown in Figure 4, the FT-IR is shown in Figure 5, the XRD is shown in Figure 6, and the magnetic properties are shown in Figure 7.

Performance test: Adsorption performance test of MFC-S-3 adsorbent for Hg ²⁺

Hg ²⁺ was selected as a representative of common heavy metals, and the adsorption performance of the MFC-S-3 adsorbent prepared in Example 3 was tested. The operation steps of the test are as follows:

1) Disperse the dried MFC-S-3 solid-phase adsorbent in water (10 g L ^-1 ) to form a suspension of MFC-S-3 solid-phase adsorbent;

2) Prepare 10 ppm Hg ²⁺ solution by serial dilution method: take 1.5 mL of 1.0 mg/mL Hg ²⁺ stock solution and dilute to 15 mL, then take 4 mL to dilute to 40 mL, repeat dilution to Hg ² The concentration of ⁺ was 10 ppm, and the pH was adjusted to 2, 3, 4, 5, 6, 7 and 8 with _HNO3 solution or ammonia solution;

3) Take 10 mL of 10 ppm Hg ²⁺ solution into a 10 mL centrifuge tube, add 100 μL of MFC-S-3 solid-phase adsorbent suspension, shake on a shaker for 6 h, then magnetically separate, take the supernatant and introduce it into the plasma The concentration of the remaining target analyte in the solution was measured by the bulk atomic emission spectrometer (ICP-OES), and the removal effect was good (as shown in Figure 8).

According to the above method, the removal effect of MFC solid-phase adsorbent on different concentrations of Hg ²⁺ solutions was measured, as shown in Figure 9. The experimental results show that the maximum adsorption capacity of MFC-S-3 at pH 3 is 282 mg g ^-1 .

The prepared MFC-S-3 solid-phase absorbent has a large adsorption capacity, and can quickly realize the rapid separation of mother liquor. The adsorption effect has good reproducibility, and the results are satisfactory.

Claims (10)

1. a sulfhydryl modified magnetic MOFs adsorbent, is characterized in that: comprise magnetic Fe ₃o ₄core and Fe ₃o ₄the SiO that core wraps up from inside to outside successively ₂layer and MOF layer, described MOF layer is UIO-66 or UIO-66-NH ₂, described UIO-66 is through mercaptoalkyl carboxylic acid functional.

2. sulfhydryl modified magnetic MOFs adsorbent according to claim 1, is characterized in that: described magnetic Fe ₃o ₄the particle diameter of core is 10-20nm.

3. prepare a method for the sulfhydryl modified magnetic MOFs adsorbent described in claim 1 or 2, it is characterized in that, comprise the steps:

(1) being coupling agent with tetraethoxysilane, take particle diameter as the magnetic Fe of 10-20nm ₃o ₄nanosphere is core, adopts the preparation of St ber silica gel coupling method to have the Fe of nucleocapsid structure ₃o ₄siO ₂;

(2) by Fe prepared by step (1) ₃o ₄siO ₂ultrasonic disperse, in DMF, adds soluble metallic salt, and ultrasonic mixing, obtains solution ; Organic ligand is added in DMF and dissolves, ultrasonic disperse, obtain solution ;

(3) under agitation, by solution add solution in, form suspension, stir, heating, washing, activation, dry, obtain magnetic MOFs material MFC-O;

(4) mercaptoalkyl carboxylic acid is scattered in water, adds KOH and regulate pH, then add MFC-O, leave standstill, heating, washing, dry, obtain sulfhydryl modified magnetic MOFs adsorbent.

4. the method for the sulfhydryl modified magnetic MOFs adsorbent of preparation according to claim 3, is characterized in that: described particle diameter is the magnetic Fe of 10-20nm ₃o ₄nanosphere is prepared by coprecipitation; Fe in described step (2) ₃o ₄siO ₂be 1:1-3 with the mass ratio of soluble metallic salt; Described soluble metallic salt is ZrCl ₄; Described organic ligand is carboxyl ligand.

5. the method for the sulfhydryl modified magnetic MOFs adsorbent of preparation according to claim 4, is characterized in that: described carboxyl ligand is the amino terephthalic acid (TPA) of terephthalic acid (TPA) or 2-, is 1:1 with the mol ratio of slaine.

6. the method for the sulfhydryl modified magnetic MOFs adsorbent of preparation according to claim 3, is characterized in that: described step (3) is specially: room temperature, under the stirring condition of rotating speed 400-600 rev/min, by solution add solution in, form suspension, continue to stir 12-24 hour, 110-150 ^oc heats, and uses DMF and methanol wash successively; In methyl alcohol, activate 24 hours under room temperature, repetition of activation 3 times, drying at room temperature, obtains magnetic MOFs material MFC-O.

7. the method for the sulfhydryl modified magnetic MOFs adsorbent of preparation according to claim 3, it is characterized in that: the mercaptoalkyl carboxylic acid described in step (4) is TGA, mercaptopropionic acid or 2,3-dimercaptosuccinic acid, in mercaptoalkyl carboxylic acid and step (4), contained by MFC-O, the mol ratio of UIO-66 is 1-3:1.

8. the method for the sulfhydryl modified magnetic MOFs adsorbent of preparation according to claim 3, is characterized in that: described step (4) is specially: be scattered in water by mercaptoalkyl carboxylic acid, adds KOH and regulates pH to be 7; Then add MFC-O, leave standstill, under Ar gas shielded, be heated to 25-60 ^oc, keeps 3-72 hour; Then use water and methanol wash successively, drying at room temperature, obtain sulfhydryl modified magnetic MOFs adsorbent.

9. the sulfhydryl modified magnetic MOFs adsorbent described in claim 1 or 2 is containing the application in heavy metal containing wastewater treatment.

10. sulfhydryl modified magnetic MOFs adsorbent according to claim 9 is containing the application in heavy metal containing wastewater treatment, it is characterized in that: described heavy metal is Hg ²⁺.