CN113559825B - Preparation method, product and application of ZIF-8/sodium bentonite composite material - Google Patents

Preparation method, product and application of ZIF-8/sodium bentonite composite material Download PDF

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CN113559825B
CN113559825B CN202110921927.9A CN202110921927A CN113559825B CN 113559825 B CN113559825 B CN 113559825B CN 202110921927 A CN202110921927 A CN 202110921927A CN 113559825 B CN113559825 B CN 113559825B
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bentonite
zif
sodium
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sodium bentonite
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CN113559825A (en
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程道建
杨冬亮
吴登峰
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Beijing University of Chemical Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
    • B01J20/12—Naturally occurring clays or bleaching earth
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/223—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material containing metals, e.g. organo-metallic compounds, coordination complexes
    • B01J20/226—Coordination polymers, e.g. metal-organic frameworks [MOF], zeolitic imidazolate frameworks [ZIF]
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/36—Silicates having base-exchange properties but not having molecular sieve properties
    • C01B33/38—Layered base-exchange silicates, e.g. clays, micas or alkali metal silicates of kenyaite or magadiite type
    • C01B33/40—Clays
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/285—Treatment of water, waste water, or sewage by sorption using synthetic organic sorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/46—Materials comprising a mixture of inorganic and organic materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4806—Sorbents characterised by the starting material used for their preparation the starting material being of inorganic character
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00—Aspects relating to sorbent materials
    • B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
    • B01J2220/48—Sorbents characterised by the starting material used for their preparation
    • B01J2220/4812—Sorbents characterised by the starting material used for their preparation the starting material being of organic character
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds

Abstract

The invention discloses a preparation method, a product and an application of a ZIF-8/sodium bentonite composite material, and belongs to the technical field of surface modification and wastewater treatment of modified bentonite. The preparation method comprises the following steps: (1) purifying the bentonite; (2) performing sodium modification on the purified bentonite prepared in the step (1) to prepare sodium bentonite; (3) and (3) mixing the sodium bentonite prepared in the step (2) with a solvent, adding soluble zinc salt, stirring for dissolving 2-methylimidazole, mixing the two solutions for reaction, centrifuging after the reaction is finished, precipitating and drying to obtain the ZIF-8/sodium bentonite composite material. The ZIF-8/sodium bentonite composite material prepared by the invention makes up the defect of single adsorption, not only saves the cost of the adsorbent, but also improves the adsorption performance, and has simple process, easily obtained raw materials and high sewage purification efficiency, thereby leading the ZIF-8 to be possibly applied to industrialization.

Description

Preparation method, product and application of ZIF-8/sodium bentonite composite material
Technical Field
The invention relates to the technical field of surface modification and wastewater treatment of modified bentonite, in particular to a preparation method, a product and application of a ZIF-8/sodium bentonite composite material.
Background
Bentonite is a natural high-quality clay rock with montmorillonite as main component. Its main component montmorillonite is aluminosilicate mineral with "sandwich" structure formed from two layers of siloxate tetrahedral sheet and one layer of aluminoxy octahedral sheet, and because of the cationic isovalent isomorphism substitution in said structure, Si in siloxate tetrahedral is formed4+Is covered with Al3+Substituted, Al in alumino octahedra3+Is coated with Mg2+Instead, the resulting negative charge between the layers readily adsorbs cations. Montmorillonite has large cation exchange capacity, and large amount of cation such as Na is filled between adjacent crystal layers+、Ca2+、Mg2+、K+And the like. Because the interlayer is electronegative, the heavy metal ions can be easily absorbed and the interlayer cations can replace the heavy metal ions in the wastewater to reduce the concentration of the heavy metal ions, thereby achieving the purpose of purifying the wastewater containing the heavy metal ions. The performance of calcium bentonite is far inferior to that of sodium bentonite, so that the calcium bentonite is frequently subjected to sodium modificationTherefore, the modified bentonite has better adsorption performance and is widely applied in the field of wastewater treatment.
Metal Organic Frameworks (MOFs) are porous crystalline materials formed from inorganic metals and organic ligands by a self-assembly process. The porous material has large specific surface area and porosity, so that the porous material is more and more concerned in the last decade, and has good application prospect in a plurality of fields such as adsorption, separation and the like. The zeolite imidazolate framework material is a metal organic framework material (ZIFs) with a zeolite-like structure, and has potential application value in many aspects due to the structure similar to that of zeolite. ZIF-8, which is the most representative ZIFs, is a material having a small fraction of the ability to adsorb and separate metal ions, since some metal ions have a higher coordination capacity than Zn2+The coordination capacity of the ion exchange adsorbent is strong, so that the heavy metal ions can be adsorbed. It is expensive, thus limiting its application in industry.
In recent years, the global industrialization has been rapidly developed, but a large amount of sewage is generated at the same time, so that the development of a method and a material for efficiently treating wastewater has become an important research direction. The adsorption method is a sewage treatment method with simple and efficient process, and the commonly used adsorption material comprises activated carbon, natural clay minerals and the like. Bentonite is widely used for wastewater treatment as a cheap adsorbent, but the small adsorption capacity of the bentonite is limited for high-concentration wastewater treatment, and the bentonite is easy to expand and disperse in an aqueous solution to cause poor solid-liquid separation effect, so that the problem how to make up the defects of the bentonite adsorbent is an urgent need to be solved.
Disclosure of Invention
The invention aims to provide a preparation method, a product and application of a ZIF-8/sodium bentonite composite material. Using metal ligands Zn2+And the organic ligand 2-methylimidazole are self-assembled on the surface of the sodium modified calcium bentonite to form ZIF-8, so that the porous structure and the adsorption capacity of the surface are increased, the process is simple, and the heavy metal wastewater purification effect is obvious.
In order to achieve the purpose, the invention provides the following technical scheme:
one of the technical schemes of the invention is as follows: the preparation method of the ZIF-8/sodium bentonite composite material comprises the following steps:
(1) purifying the bentonite;
(2) performing sodium modification on the purified bentonite prepared in the step (1) to prepare sodium bentonite;
(3) and (3) mixing the sodium bentonite prepared in the step (2) with a solvent, adding soluble zinc salt, stirring for dissolving 2-methylimidazole, mixing the two solutions for reaction, centrifuging after the reaction is finished, precipitating and drying to obtain the ZIF-8/sodium bentonite composite material.
Preferably, the bentonite in the step (1) is calcium bentonite.
Preferably, the specific preparation steps of the purified bentonite in the step (1) comprise: adding bentonite raw ore and a dispersing agent into water, stirring, standing, removing lower-layer sediment, removing lower-layer flocculate after ultrasonic treatment of upper-layer ore pulp, centrifuging the upper-layer ore pulp at the rotating speed of 1200-11000 r/min, removing sediment after centrifugation, centrifuging the upper-layer ore pulp at the rotating speed of 9000-11000r/min, and drying sediment obtained after centrifugation to obtain the purified bentonite.
More preferably, the mass ratio of the bentonite raw ore to the dispersant is 1 (0.3-0.5%); the dispersant is sodium hexametaphosphate; the mass and volume ratio of the bentonite raw ore to the water is 1g (10-12) mL.
The purified bentonite prepared by the preparation method of the invention has the montmorillonite content of 85-90%.
Preferably, the specific preparation steps of the sodium bentonite in the step (2) comprise: adding water into the purified bentonite prepared in the step (1) to prepare ore pulp, adding a sodium modifying agent, heating for reaction, centrifuging the ore pulp at the rotating speed of 9000-.
More preferably, the mass-to-volume ratio of the purified bentonite to water is 1g (10-12) mL; the mass ratio of the purified bentonite to the sodium modifier is 1 (3-5%); the sodium modifier is sodium carbonate; the heating reaction is carried out at the temperature of 60-80 ℃ for 1-1.5 h.
Preferably, the solvent in the step (3) is a mixed solution of methanol and dimethylformamide; the molar ratio of zinc ions to 2-methylimidazole in the soluble zinc salt is 1 (4-6); the soluble zinc salt is zinc nitrate hexahydrate; the reaction time of the reaction is 15-17 h; the rotation speed of the centrifugation is 9000-11000 r/min.
Preferably, the step of drying the precipitate in the step (3) further comprises a step of washing the precipitate with methanol.
The second technical scheme of the invention is as follows: provides a ZIF-8/sodium bentonite composite material prepared by the preparation method.
The third technical scheme of the invention is as follows: provides an application of the ZIF-8/sodium bentonite composite material in heavy metal wastewater treatment.
The invention has the following beneficial technical effects:
compared with bentonite, the adsorption performance of the ZIF-8/sodium bentonite composite material prepared by the invention is greatly improved. Although bentonite is cheap and easy to obtain, the effect of adsorbing heavy metal ions is limited, and ZIF-8 has a good adsorption effect but is expensive and difficult to apply. Therefore, the ZIF-8/sodium bentonite composite material prepared by the invention makes up the defect of single adsorption, not only saves the cost of the adsorbent, but also improves the adsorption performance, and has simple process, easily obtained raw materials and high sewage purification efficiency, thereby leading the ZIF-8 to be possibly applied to industrialization.
When the ZIF-8/sodium bentonite composite material prepared by the invention is applied to adsorbing heavy metal ions, the ZIF-8 loaded on the bentonite in the ZIF-8/sodium bentonite composite material firstly adsorbs the heavy metal ions on the ZIF-8 through surface complexation, ion exchange, hole adsorption and other modes and gradually reaches saturation, so that a heavy metal ion high-concentration area is formed on the surface of the sodium bentonite. Heavy metal ions in the high-concentration area slowly diffuse to the low-concentration area of the sodium bentonite, and at the moment, the heavy metal ions are adsorbed in the sodium bentonite through surface complexation, pore channel adsorption, ion exchange and other modes by the bentonite. When the bentonite is gradually saturated in adsorption, heavy metal ions can be diffused outwards, and at the moment, the ZIF-8 is loaded on the surface of the bentonite to prevent a part of heavy metal ions from being diffused outwards, so that the adsorption capacity of the bentonite to the heavy metal ions is improved.
Drawings
FIG. 1 is an SEM image of a raw ore of bentonite used in the present invention.
FIG. 2 is an SEM photograph at 400nm of a ZIF-8/sodium bentonite composite prepared in example 1.
FIG. 3 is an SEM photograph of a ZIF-8/sodium bentonite composite material prepared in example 1 at 10 μm.
FIG. 4 is an XRD pattern of ZIF-8/sodium bentonite composite materials prepared in examples 1-2, calcium bentonite, purified bentonite, and sodium bentonite in example 1, and ZIF-8 materials prepared in comparative example 1.
Detailed Description
Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention.
As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.
Example 1
S1: 20g of calcium bentonite raw ore is taken, sodium hexametaphosphate dispersant which is 0.3 percent of the mass of the calcium bentonite raw ore is added into the raw ore and placed into a 250ml beaker, deionized water is added according to the solid-to-liquid ratio of 1:10, a magnetic stirrer is used for stirring for 2 hours, and then the mixture is kept stand for 30min to remove lower-layer precipitate. Pouring the upper layer ore pulp into a new beaker, carrying out ultrasonic treatment on the upper layer ore pulp for 10min by using an ultrasonic cleaner at 40KHZ, standing for 5min to remove lower layer flocculates, centrifuging the upper layer ore pulp for 10min by using a centrifuge at the rotating speed of 1200r/min, removing bottom layer sediments, centrifuging the upper layer pulp for 1min by using the centrifuge at the rotating speed of 11000r/min, taking the lower layer sediments, drying at 105 ℃, and grinding to obtain 2.4g of purified bentonite.
S2: taking 15g of the purified bentonite prepared in S1 to prepare ore pulp according to the solid-to-liquid ratio of 1:10, and then adding Na accounting for 3 percent of the mass of the purified bentonite2CO3Performing sodium modification, heating to 80 deg.C with a constant temperature water bath, stirring for 1h, cooling, pouring out the pulp, centrifuging at 11000r/min for 8min, pouring out the supernatant, collecting the precipitate, oven drying at 105 deg.C, and grinding to obtain 12g sodium bentonite.
S3: dissolving 3g of sodium bentonite prepared in S2 and 2g of zinc nitrate hexahydrate in a beaker filled with a mixed solution of 12ml of methanol and 48ml of dimethylformamide, and stirring for 1 hour by using a magnetic stirrer; 2.2g of 2-methylimidazole was dissolved in a beaker containing a mixed solution of 8ml of methanol and 32ml of dimethylformamide, and stirred for 1 hour with a magnetic stirrer. The two solutions were then mixed and stirred for a further 15h before the reaction was stopped. Centrifuging with a centrifuge at 11000r/min for 10min, collecting precipitate, washing the obtained sample with methanol for 3 times, and drying at 70 deg.C to obtain 3.45g ZIF-8/sodium bentonite composite material. In the prepared ZIF-8/sodium bentonite composite material, the mass fraction of ZIF-8 is 13.05%.
Example 2
The difference from example 1 was that zinc nitrate hexahydrate was added in an amount of 1.5g and 2-methylimidazole was added in an amount of 1.656g in the step S3.
Example 3
S1: 20g of calcium bentonite raw ore is taken, sodium hexametaphosphate dispersant which is 0.5 percent of the mass of the calcium bentonite raw ore is added into the raw ore and placed into a 250ml beaker, deionized water is added according to the solid-to-liquid ratio of 1:12, a magnetic stirrer is used for stirring for 2.5h, and then the mixture is kept stand for 30min to remove lower-layer precipitate. Pouring the upper layer ore pulp into a new beaker, carrying out ultrasonic treatment on the upper layer ore pulp for 15min by using an ultrasonic cleaner at 40KHZ, standing for 5min to remove lower-layer flocculates, centrifuging the upper layer ore pulp for 10min by using a centrifuge at the rotating speed of 1500r/min, removing bottom-layer precipitates, centrifuging the upper layer slurry for 5min by using the centrifuge at the rotating speed of 9000r/min, taking the lower-layer precipitates, drying at 105 ℃, and grinding to obtain 2.3g of purified bentonite.
S2: taking 15g of the purified bentonite prepared in S1 to prepare ore pulp according to the solid-to-liquid ratio of 1:12, and then adding Na which is 5 percent of the mass of the purified bentonite2CO3Performing sodium modification, heating to 60 deg.C with a constant temperature water bath, stirring for 1.5h, cooling, pouring out the pulp, centrifuging at 9000r/min for 10min, pouring out the supernatant, oven drying the precipitate at 105 deg.C, and grinding to obtain 11g sodium bentonite.
S3: dissolving 3g of sodium bentonite prepared in S2 and 2g of zinc nitrate hexahydrate in a beaker filled with a mixed solution of 12ml of methanol and 48ml of dimethylformamide, and stirring for 1 hour by using a magnetic stirrer; 2.2g of 2-methylimidazole was dissolved in a beaker containing a mixed solution of 8ml of methanol and 32ml of dimethylformamide, and stirred for 1 hour with a magnetic stirrer. The two solutions were then mixed and stirred for a further 15h before the reaction was stopped. Centrifuging at 9000r/min for 10min by a centrifuge, collecting precipitate, washing the obtained sample with methanol for 3 times, and drying at 80 deg.C to obtain 3.4g ZIF-8/sodium bentonite composite material.
Comparative example 1
2g of zinc nitrate hexahydrate is dissolved in a beaker filled with 12ml of mixed solution of methanol and 48ml of dimethylformamide, and then stirred for 1 hour by a magnetic stirrer; 2.2g of 2-methylimidazole was dissolved in a beaker containing a mixed solution of 8ml of methanol and 32ml of dimethylformamide, and stirred for 1 hour with a magnetic stirrer. The two solutions were then mixed and stirred for a further 15h before the reaction was stopped. Centrifuging at 11000r/min for 10min with a centrifuge, collecting precipitate, washing the obtained sample with methanol for 3 times, and drying at 70 deg.C to obtain 0.26g ZIF-8 material.
Fig. 1 is an SEM image of raw bentonite ore used in the present invention, and it can be seen from fig. 1 that bentonite has a typical layered structure.
FIG. 2 is an SEM photograph at 400nm of a ZIF-8/sodium bentonite composite prepared in example 1.
FIG. 3 is an SEM photograph of a ZIF-8/sodium bentonite composite material prepared in example 1 at 10 μm.
As can be seen from fig. 2-3, the surface of the bentonite is much longer than the regular particle structure, indicating that ZIF-8 has been loaded on the bentonite, demonstrating that the preparation of the composite material is successful.
FIG. 4 is an XRD pattern of ZIF-8/sodium bentonite composite prepared in examples 1-2, calcium bentonite, purified bentonite, and sodium bentonite in example 1, and ZIF-8 material prepared in comparative example 1, wherein Na-MT @ ZIF-8 represents ZIF-8/sodium bentonite composite, Na-MT represents sodium bentonite, T-MT represents purified bentonite, and Ca-MT represents calcium bentonite.
As can be seen from FIG. 4, the diffraction peak d of montmorillonite, which is the main phase of Ca-MT(001)1.522 nm; after sedimentation and ultrasonic centrifugal purification, (T-MT) zeolite diffraction peaks disappear, cristobalite diffraction peaks are weakened, most impurities are removed, and then the content of montmorillonite is detected to be about 88% by a blue absorption method; from XRD patterns of ZIF-8 and Na-MT @ ZIF-8, the diffraction peaks of ZIF-8 are also found on the basis of the diffraction peaks of montmorillonite, which proves that the preparation of the composite material is successful.
Test example 1
The removal effect of the ZIF-8/sodium bentonite composite materials prepared in examples 1 to 3, the ZIF-8 material prepared in comparative example 1, the calcium bentonite as the raw material in example 1, the purified bentonite and sodium bentonite prepared in example 1, and the adsorption material in which the ZIF-8 material prepared in comparative example 1 was mixed with the sodium bentonite prepared in example 1, on the heavy metal solution was measured, and the measurement results are shown in table 1.
A250 mL Erlenmeyer flask was charged with Pb (NO) at a concentration of 302mg/L3)2Adjusting pH to 5.5 with 0.1moL/L hydrochloric acid and 0.1moL/L sodium hydroxide, placing in water bath, adjusting temperature to 28 deg.C, adding adsorbent after temperature is constant0.1g, stirring with a magnetic stirrer for 120min, filtering with 0.45 μm filter membrane, and detecting Pb with ICP-OES2+The residual concentration of the ions, and then calculating the Pb of the adsorbent according to the formulas (1) and (2)2+Removal rate and adsorption amount of (3).
Figure BDA0003207733240000061
Figure BDA0003207733240000062
In the formulas (1) and (2), R is the adsorption removal rate of heavy metal ions; c0Concentration of the solution before adsorption (mg/L); c is the concentration (mg/L) of the solution after adsorption; v is the volume of solution (mL); m is the mass (g) of the adsorbent; q is the equilibrium adsorption capacity (mg/g) of the adsorbent to the heavy metal ions.
TABLE 1
Figure BDA0003207733240000063
Figure BDA0003207733240000071
As can be seen from Table 1, varying the amounts of zinc nitrate hexahydrate and 2-methylimidazole altered the ZIF-8 loading on the bentonite, which affected Pb2+And (5) removing the effect. Pb removal using ZIF-8/sodium bentonite composites2+And compared with a ZIF-8 material, the ZIF-8/sodium bentonite composite material prepared by the invention can greatly save the cost. Meanwhile, the adsorption effect of the ZIF-8/sodium bentonite composite material prepared by the invention is stronger than that of the ZIF-8 material and sodium bentonite which are simply mixed, because ZIF-8 is loaded on the surface of bentonite, partial Pb is prevented2+The bentonite is diffused outwards, so that the saturated adsorption capacity of the bentonite is increased, and the bentonite generate a synergistic effect after the treatment steps are compounded.
Compared with the ZIF-8/sodium bentonite composite material which is completely loaded by calcium bentonite after purification, sodium modification and ZIF-8, the ZIF-8/sodium bentonite composite material prepared by the invention has more holes, larger specific surface area and stronger adsorption capacity, and can adsorb Pb containing2+The effect of removing heavy metal wastewater is obvious.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims (10)

1. A preparation method of a ZIF-8/sodium bentonite composite material is characterized by comprising the following steps:
(1) purifying the bentonite;
(2) performing sodium modification on the purified bentonite prepared in the step (1) to prepare sodium bentonite;
(3) mixing the sodium bentonite prepared in the step (2) with a solvent, adding soluble zinc salt, stirring for dissolving 2-methylimidazole, mixing the two solutions for reaction, centrifuging after the reaction is finished, precipitating and drying to prepare a ZIF-8/sodium bentonite composite material;
the solvent in the step (3) is a mixed solution of methanol and dimethylformamide; the molar ratio of zinc ions to 2-methylimidazole in the soluble zinc salt is 1 (4-6).
2. The method of manufacturing ZIF-8/sodium bentonite composite material according to claim 1, wherein the bentonite in step (1) is calcium bentonite.
3. The method of manufacturing ZIF-8/sodium bentonite composite material according to claim 1, wherein the specific manufacturing step of the purified bentonite in step (1) includes: adding bentonite raw ore and a dispersing agent into water, stirring, standing, removing lower-layer sediment, removing lower-layer flocculate after ultrasonic treatment of upper-layer ore pulp, centrifuging the upper-layer ore pulp at the rotating speed of 1200-11000 r/min, removing sediment after centrifugation, centrifuging the upper-layer ore pulp at the rotating speed of 9000-11000r/min, and drying sediment obtained after centrifugation to obtain the purified bentonite.
4. The preparation method of the ZIF-8/sodium bentonite composite material according to claim 3, wherein the mass ratio of the bentonite raw ore to the dispersant is 1 (0.3-0.5%); the dispersant is sodium hexametaphosphate; the mass and volume ratio of the bentonite raw ore to the water is 1g (10-12) mL.
5. The method of preparing ZIF-8/sodium bentonite composite material according to claim 1, wherein the specific preparation step of the sodium bentonite in step (2) comprises: adding water into the purified bentonite prepared in the step (1) to prepare ore pulp, adding a sodium modifying agent, heating for reaction, centrifuging the ore pulp at the rotating speed of 9000-.
6. The preparation method of the ZIF-8/sodium bentonite composite material according to claim 5, wherein the mass to volume ratio of the purified bentonite to water is 1g (10-12) mL; the mass ratio of the purified bentonite to the sodium modifier is 1 (3-5%); the sodium modifier is sodium carbonate; the heating reaction is carried out at the temperature of 60-80 ℃ for 1-1.5 h.
7. The method of preparing ZIF-8/sodium bentonite composite material according to claim 1, wherein the soluble zinc salt in step (3) is zinc nitrate hexahydrate; the stirring and dissolving time is 1 h; the reaction time is 15-17 h; the rotation speed of the centrifugation is 9000-11000 r/min.
8. The method of manufacturing ZIF-8/sodium bentonite composite material according to claim 1, wherein the step of washing the precipitate with methanol is further included before the step of drying the precipitate in the step (3).
9. The ZIF-8/sodium bentonite composite material prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the ZIF-8/sodium bentonite composite of claim 9 in heavy metal wastewater treatment.
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