A sodium tripolyphosphate-MOF composite nano-adsorbent material, its preparation method and application

Abstract

This invention belongs to the field of inorganic material preparation technology and provides a method for preparing sodium tripolyphosphate-MOF composite nano-adsorbent materials, comprising the following steps: ultrasonically and shearing a sodium tripolyphosphate (Na-TTP) suspension, Co(NO3)2·6H2O, and 2-methylimidazole in methanol to obtain a Na-TTP / ZIF-67 composite solution. The Na-TTP / ZIF-67 nano-adsorbent material prepared by this invention exhibits higher heavy metal adsorption performance than pure ZIF-67 nanoparticles, paving the way for efficient remediation of heavy metal contaminated soil.

Description

Technical Field

[0001] This invention belongs to the field of inorganic material preparation technology and relates to a sodium tripolyphosphate-MOF composite nano-adsorbent material. Background Technology

[0002] With the development of industry and agriculture, soil heavy metal pollution is also increasing. Cadmium (Cd), lead (Pb), and mercury (Hg) are among the most harmful metallic pollutants in soil. Due to their high water solubility, relative mobility, bioaccumulation, and non-degradability, they subsequently pose a potential threat to humans through the food chain. Therefore, the remediation of heavy metal-contaminated soil is a top priority. Remediation methods for heavy metal-contaminated soil can be divided into three categories: chemical, physical, and biological. Physical remediation is efficient, cost-effective, simple to operate, and less destructive. The total content of heavy metals in soil is not the key factor in their mobility and ecotoxicity; it largely depends on the bound state or specific form of the heavy metals. Studies have found that the concentration of metals in plants is closely related to the concentration of metals in exchangeable components. Therefore, the key to remediating heavy metal-contaminated soil is to reduce the mobility and bioavailability of the metals. Nanotechnology has been gradually explored as an ideal alternative to traditional methods for treating and remediating contaminated water with various pollutants. Because of their extremely small size (<100 nm), nanomaterials possess additional chemical, physical, and biological properties and have a larger surface area to volume ratio compared to correspondingly larger nanomaterials, resulting in higher strength of surface reaction sites per unit mass.

[0003] Metal-organic frameworks (MOFs) are a group of porous materials renowned for their diverse structural compositions and remarkable adsorption capabilities. Among them, zeolite imidazolate frameworks (ZIF-67) are particularly popular; they are composed of metal ions (Co... 2+ It is composed of α-cobalt oxide (C₂O₃) and organic molecules (2-methylimidazole). 2-methylimidazole is a linker that participates in the secondary building unit. 2+ The coordination of clusters is crucial. ZIF-67 possesses a highly stable structure due to its cubic crystal symmetry and unit cell characteristics of a=b=c=16.9589 Å. ZIF-67 nanocrystals can be prepared at room temperature using a solvent dispersion method, offering advantages such as low cost, ease of preparation, and wide applicability in environmental protection. The adsorption properties of MOF materials, such as adsorption kinetics, adsorption capacity, adsorption thermodynamics, selectivity, stability, and recyclability, are controlled by their highly ordered framework structure, hydrophilicity, surface area, functionality, pore size, and distribution. Therefore, MOF materials can be modified using appropriate methods to improve their adsorption performance and reduce synthesis costs. Summary of the Invention

[0004] To address the problems existing in the preparation of modified MOFs with heavy metal adsorption function, this invention provides a nano-adsorbent material combining sodium tripolyphosphate (Na-TTP) and MOF (ZIF-67), which improves the adsorption capacity of heavy metals compared with the unmodified MOF material.

[0005] Another object of the present invention is to provide an application of the above-mentioned nano-adsorbent material in the adsorption of heavy metals.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] A method for preparing a sodium tripolyphosphate (Na-TTP)-MOF (ZIF-67) composite nano-adsorbent material includes the following steps:

[0008] Sodium tripolyphosphate (Na-TTP) suspension, Co(NO3)2·6H2O and 2-methylimidazole were ultrasonically and sheared in methanol to obtain Na-TTP / ZIF-67 composite solution.

[0009] In the above method, the mass ratio of Na-TTP to Co(NO3)2·6H2O is 0-0.04:1; more preferably 0-0.03:1; the mass of Na-TTP in the above ratio is not 0; the most preferred mass ratio is 0.02:1.

[0010] In the above method, the mass ratio of water to Na-TTP in the sodium tripolyphosphate (Na-TTP) suspension is 150:1-300:1; preferably 200:1.

[0011] In the above method, the mass ratio of Co(NO3)2·6H2O to 2-methylimidazole is 0.02:1-0.05:1, preferably 0.025:1.

[0012] In the above method, the order of adding the Na-TTP suspension is not affected. It can be added to the ZIF-67 raw material solution, or the ZIF-67 raw material solution can be added to the Na-TTP suspension; preferably, the Na-TTP suspension is added to the ZIF-67 raw material solution.

[0013] The shearing can be provided by any mixing and shearing equipment; preferably, the mixing speed providing the shearing is 2000-10000 rpm, and the mixing time is 45-60 minutes; the ultrasound is provided by an ultrasonic disruptor.

[0014] The present invention also provides sodium tripolyphosphate-MOF composite nano-adsorbent material obtained by the above preparation method.

[0015] Application of the above-mentioned sodium tripolyphosphate-MOF composite nano-adsorbent material in the adsorption of heavy metals.

[0016] The present invention has the following advantages:

[0017] This invention combines Na-TTP inorganic compounds with ZIF-67 nanoparticles via solution blending to prepare nano-adsorbent materials. In the presence of Na-TTP particles, the pore size of the blended nanoparticles decreases and the BET specific surface area increases, resulting in Na-TTP / ZIF-67 nano-adsorbent materials exhibiting higher heavy metal adsorption performance than pure ZIF-67 nanoparticles. This opens a pathway for the efficient remediation of heavy metal-contaminated soils. Attached Figure Description

[0018] Figure 1 These are scanning electron microscope images of ZIF-67 (left) and Na-TTP / ZIF-67 (right) nano-adsorbent materials from Example 1;

[0019] Figure 2 The adsorption capacity q of the prepared pure ZIF-67 nanoparticles and Na-TTP / ZIF-67 nano-adsorbent materials for heavy metals cadmium (Cd), lead (Pb), and mercury (Hg) at different time points is shown. e ;

[0020] Figure 3 The equilibrium adsorption capacity q of the prepared pure ZIF-67 nanoparticles and Na-TTP / ZIF-67 nano-adsorbent materials for the adsorption of heavy metals cadmium (Cd), lead (Pb), and mercury (Hg) is given. e ;

[0021] Figure 4 The adsorption rate R (%) of the prepared pure ZIF-67 nanoparticles and Na-TTP / ZIF-67 nano-adsorbent materials for heavy metals cadmium (Cd), lead (Pb) and mercury (Hg). Detailed Implementation

[0022] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the present invention is not limited to the following embodiments.

[0023] Example 1: Preparation of Na-TTP / ZIF-67 nano-adsorbent materials

[0024] Preparation of Na-TTP suspension: 0.05 parts of inorganic compound were added to a beaker containing 20 parts of deionized water and ultrasonically vibrated for 5 minutes using an ultrasonic disruptor. Then, a magnetic rotor with a length of 1.5 cm was placed in the beaker and stirred at a speed of 2000 rpm for 60 minutes to obtain Na-TTP suspension.

[0025] Preparation of Na-TTP / ZIF-67 nano-adsorbent material: The Na-TTP suspension prepared above was added to a mixture of 20 parts of Co(NO3)2·6H2O and 2-methylimidazolium methanol under stirring; then, the mixture was stirred with a magnetic rotor at 2000 rpm for 10 minutes, and stirred continuously at room temperature for 24 hours; then, the suspension was centrifuged at 10000 rpm, the precipitate was washed with methanol, dried in an oven at 80℃, and then ground into powder in a mortar to obtain Na-TTP / ZIF-67 nano-adsorbent material Na-P / Z-1 containing 1 wt% Na-TTP. Its scanning electron microscope (SEM) results are shown below. Figure 1 As shown in the right figure: Unlike the smooth and regular dodecahedral structure of ZIF-67 nanoparticles, the surface of the modified Na-TTP / ZIF-67 nano-adsorbent material becomes rough and the regular dodecahedral shape formed inside the material is destroyed.

[0026] Example 2: Preparation of Na-TTP / ZIF-67 nano-adsorbent materials

[0027] Preparation of Na-TTP suspension: 0.1 parts of inorganic compound were added to a beaker containing 20 parts of deionized water and ultrasonically vibrated for 5 minutes using an ultrasonic disruptor. Then, a magnetic rotor with a length of 1.5 cm was placed in the beaker and stirred at a speed of 2000 rpm for 60 minutes to obtain Na-TTP suspension.

[0028] Preparation of Na-TTP / ZIF-67 nano-adsorbent material: The Na-TTP suspension prepared above was added to a mixture of 20 parts of Co(NO3)2·6H2O and 2-methylimidazolium methanol under stirring. Then, the mixture was stirred with a magnetic rotor at 2000 rpm for 10 minutes and continued to be stirred at room temperature for 24 hours. The suspension was then centrifuged at 10000 rpm, the precipitate was washed with methanol, dried in an oven at 80℃, and then ground into powder in a mortar to obtain Na-TTP / ZIF-67 nano-adsorbent material Na-P / Z-2 containing 2wt% Na-TTP.

[0029] Example 3: Preparation of Na-TTP / ZIF-67 nano-adsorbent materials

[0030] Preparation of Na-TTP suspension: 0.15 parts of inorganic compound were added to a beaker containing 20 parts of deionized water and ultrasonically vibrated for 5 minutes using an ultrasonic disruptor. Then, a magnetic rotor with a length of 1.5 cm was placed in the beaker and stirred at a speed of 2000 rpm for 60 minutes to obtain Na-TTP suspension.

[0031] Preparation of Na-TTP / ZIF-67 nano-adsorbent material: The Na-TTP suspension prepared above was added to a mixture of 20 parts of Co(NO3)2·6H2O and 2-methylimidazolium methanol under stirring. Then, the mixture was stirred with a magnetic rotor and stirred at 2000 rpm for 10 minutes using a high-speed emulsification shearing device, and stirred continuously at room temperature for 24 hours. The suspension was then centrifuged at 10000 rpm, the precipitate was washed with methanol, dried in an oven at 80℃, and then ground into powder in a mortar to obtain Na-TTP / ZIF-67 nano-adsorbent material Na-P / Z-3 containing 3wt% Na-TTP.

[0032] Comparative Example 1: Preparation of ZIF-67 Nanomaterials

[0033] First, 2.181 parts (5 mmol) of Co(NO3)2·6H2O were dissolved in 60 parts of methanol; then, 1.232 parts (20 mmol) of 2-methylimidazole were dissolved in 40 parts of methanol. The two solutions were mixed and stirred evenly with a magnetic rotor at room temperature for 24 h. The suspension was then centrifuged at 10,000 rpm, the precipitate was washed with methanol, dried in an oven at 80 °C, and then ground into powder in a mortar to obtain ZIF-67 nanoparticles.

[0034] Application Example 1: Adsorption of heavy metals cadmium (Cd), lead (Pb), and mercury (Hg)

[0035] Heavy metal adsorption tests were conducted on the materials prepared in Examples 1-3 and the ZIF-67 prepared in the comparative example:

[0036] Weigh 20 mg of Na-TTP / ZIF-67 nano-adsorbent material or ZIF-67 nano-adsorbent material and add it to 5 mL of 0.5% acetic acid aqueous solution. Dissolve by sonication for later use.

[0037] Obtain approximately 500g of soil from a certified organic farm, wash repeatedly with 10 times its volume of deionized water, and then dry in an oven. Prepare metal ion solutions using lead nitrate, cadmium nitrate, and mercuric nitrate; add these solutions to the soil until the specified concentration (300mg / L) is reached, homogenize, and air dry.

[0038] Add 20g of the above soil to the solutions of each nano-adsorbent material, then place in a shaker and stir at 20℃ for 120min; after centrifugation at 3000rpm, collect the supernatant and use an atomic absorption spectrometer to test the metal concentration.

[0039] The equilibrium adsorption capacity q of nano-adsorbent materials for the adsorption of heavy metals cadmium (Cd), lead (Pb), and mercury (Hg). eThe adsorption rate (R%) can be calculated using equations (1) and (2):

[0040]

[0041] Among them, C0 and C e (mg / L) represent the initial and final concentrations of metal ions, respectively; in this study, M is the mass of the nano-adsorbent material, M=20mg; V is the volume of the supernatant solution after centrifugation of diluted soil during the experiment, V=20 mL.

[0042] Adsorption kinetics analysis of nanomaterials, such as Figure 2 As shown, the adsorption rates of heavy metals cadmium (Cd), lead (Pb), and mercury (Hg) by pure ZIF-67 nanoparticles and Na-TTP / ZIF-67 nanomaterials rapidly increased between 10 and 60 min, then gradually slowed down from 60 to 80 min, finally reaching equilibrium after 80 min. This change in adsorption rate is mainly due to the abundant adsorption sites on the pure ZIF-67 nanoparticles and Na-TTP / ZIF-67 nanomaterials in the early stages, resulting in a high concentration of adsorbed ions in the solution. As the adsorption process progresses, the number of adsorption sites decreases, the ion concentration decreases, and the adsorption rate slows down until equilibrium is reached.

[0043] The maximum adsorption capacity of Na-TTP / ZIF-67 nano-adsorbent material for heavy metal ions cadmium (Cd), lead (Pb), and mercury (Hg) is as follows: Figure 3 The values ​​shown are 246.89 mg / L, 253.87 mg / L, and 252.87 mg / L, respectively.

[0044] like Figure 4 As shown, the Na-TTP / ZIF-67 nano-adsorbent material, as an adsorbent, achieved an adsorption efficiency of over 70% for heavy metal ions cadmium (Cd), lead (Pb), and mercury (Hg). Among them, Na-P / Z-2 exhibited even higher adsorption performance than other materials, with an adsorption efficiency of over 90%.

Claims

1. The application of a sodium tripolyphosphate-MOF composite nano-adsorbent material in the adsorption of heavy metals cadmium, lead, or mercury, characterized in that, The preparation method of sodium tripolyphosphate-MOF composite nano-adsorbent materials includes the following steps: Sodium tripolyphosphate suspension, Co(NO3)2·6H2O and 2-methylimidazole were ultrasonically and sheared in methanol to obtain Na-TPP / ZIF-67 composite solution. The mass ratio of sodium tripolyphosphate to Co(NO3)2·6H2O is 0-0.04:1; in the above ratio, the mass of sodium tripolyphosphate is not 0. The mass ratio of Co(NO3)2·6H2O to 2-methylimidazole is 0.02:1-0.05:

1.

2. The application according to claim 1, characterized in that, The mass ratio of sodium tripolyphosphate to Co(NO3)2·6H2O is 0-0.03:1; in the above ratio, the mass of sodium tripolyphosphate is not 0. The mass ratio of water to sodium tripolyphosphate is 150:1-300:

1.

3. The application according to claim 1, characterized in that, In the sodium tripolyphosphate suspension, the mass ratio of sodium tripolyphosphate to Co(NO3)2·6H2O is 0.02:1; The mass ratio of water to sodium tripolyphosphate is 200:1; The mass ratio of Co(NO3)2·6H2O to 2-methylimidazole is 0.025:

1.

4. The application according to claim 1, characterized in that, The shearing and mixing speed is 2000-10000 rpm, and the mixing time is 45-60 minutes.

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