Preparation of high porosity amine-oxime microspheres based on thermally induced phase separation method and its application in heavy metal adsorption

Abstract

This invention discloses a method for preparing mesoporous amylopectin-based microspheres based on thermally induced phase separation and their application in heavy metal adsorption. The method includes the following steps: dissolving a linear polymer with nitrile groups and a filler in a diluent to prepare a polymer solution; atomizing the polymer solution and placing it in a low-temperature cold source, followed by quenching, and then solidifying the atomized droplets to form gel-like microspheres; immersing the gel-like microspheres in a mixture of distilled water and ethanol for diluent replacement, followed by washing to obtain a microsphere precursor; mixing the precursor with hydroxylamine, an inorganic salt, and distilled water, stirring, and carrying out amylopectinization reaction; washing and drying the product to obtain high-porosity amylopectin-based microspheres containing mesopores. The mesoporous amylopectin-based microsphere adsorbent prepared by this invention has the following advantages: the raw materials are traditional chemical raw materials with abundant sources; the preparation method is simple and easy for industrial production; the microspheres have high porosity (greater than 90%) and contain a large number of abundant mesopores (pore size 2-50 nm); and the adsorption rate and capacity for heavy metals are fast.

Description

Technical Field

[0001] This invention belongs to the field of water treatment / environment, and relates to the preparation process of adsorbents, specifically to the preparation of mesoporous amine oxime microspheres and their application in heavy metal adsorption, and more particularly to the preparation of high porosity amine oxime microspheres based on thermally induced phase separation and their application in heavy metal adsorption. Background Technology

[0002] Heavy metal pollution typically refers to pollution caused by mercury, lead, chromium, nickel, and antimony, primarily originating from industries such as mining, mineral processing, electrolysis, chemical production, printing and dyeing, and papermaking. When heavy metals enter water bodies, some enter riverbed sediments and can be released under certain conditions, posing a potential threat; others exist in dissolved form, combining with suspended solids in the water and migrating with the current. Once absorbed by aquatic organisms, heavy metals cannot be degraded by organisms and can only transform and disperse between different forms. They can accumulate to high concentrations through the food chain, with enrichment factors reaching thousands of times, ultimately entering the human body and harming human health through drinking water and the food chain. Therefore, the problem of heavy metal pollution urgently needs to be addressed.

[0003] Adsorption methods are widely used due to their advantages of simple operation, high efficiency, economy, and environmental friendliness. Traditional heavy metal adsorbents mainly include biomass, metal oxides, ores, and carbon-based materials. However, these adsorbents lack suitable and sufficient functional groups as adsorption sites to capture heavy metals, resulting in small adsorption capacity and limited adsorption ability. Amine oxime-modified linear polymers (AOPs) possess abundant amine oxime functional groups with strong heavy metal capture capabilities, theoretically exhibiting high adsorption performance for heavy metals. Currently, the preparation methods for AOP porous materials mainly include solution spinning, electrospinning, and non-solvent phase separation. AOP porous materials prepared by solution spinning have micron-sized pores and low porosity; while AOP porous materials prepared by electrospinning and non-solvent phase separation (NIPS) typically have pore sizes of 0.5-5 μm and porosity generally not exceeding 50%. Therefore, existing AOP materials have disadvantages such as low porosity (porosity not exceeding 90%) and lack of mesopores, which cannot support efficient physical adsorption and have limited adsorption effect on heavy metals in water.

[0004] As an emerging pore-forming technology, porous materials prepared by thermally induced phase separation (TIPS) have advantages such as controllable pore size and controllable porosity, which can specifically solve the problems of traditional AOP materials. The driving force for phase separation induced by TIPS is that the polymer / diluent system cools down, causing a decrease in the thermodynamic stability of the polymer solution, which leads to a change in the chemical potential of the polymer solution. The magnitude of the driving force is positively correlated with the supercooling of the system. Some studies have combined TIPS and NIPS. During the TIPS process, the non-solvent of NIPS is released. However, the mass and heat transfer of the solvent easily disrupts the thermodynamic stability of the non-solvent, resulting in a decrease in the supercooling in TIPS. The porous materials prepared by this mixed phase separation method have the following characteristics: (1) Since mass transfer takes precedence over heat transfer, NIPS tends to dominate, resulting in uneven pore size distribution in the porous materials; (2) With the decrease in supercooling, the TIPS process is incomplete and insufficient, and it is impossible to generate solvent crystals at the mesoscale on a large scale. The obtained porous materials are mainly macropores and lack mesopores. Therefore, a single TIPS process without controlling phase separation conditions is more likely to prepare porous materials with controllable pore size and porosity. Since TIPS is a non-equilibrium kinetic process, different cooling methods will affect the phase separation process and the structure of the porous material. For example, a faster cooling rate and a lower cooling temperature are conducive to the formation of smaller diluent droplets, thus forming smaller pores. Low temperatures (or ultra-low temperatures) severely disrupt the thermodynamic stability of polymer solutions, triggering and exacerbating their changes. For example, at liquid nitrogen temperatures, polymer molecular chains cannot freely self-adjust, making them more prone to evolving into a polymer depleted phase and a polymer crystalline phase. Therefore, changing phase separation parameters such as polymer concentration, cooling rate, and minimum cooling temperature has a decisive influence on controlling the pore size and porosity of porous materials. However, conventional TIPS methods are mostly controlled above -10℃, and there are few reports on the preparation of high-porosity AOP materials with abundant mesopores under low-temperature (ultra-low-temperature) cooling conditions.

[0005] To address the aforementioned problems, this invention focuses on preparing high-porosity (porosity greater than 90%) AOP microspheres (AOPS) with abundant mesopores using the TIPS method, and applying them to adsorb heavy metals in water. This invention obtains AOPS with a mesoporous structure by controlling TIPS parameters, including temperature control, diluent selection, and filler ratio. Finally, the AOPS are used to remove mercury, lead, chromium, uranium, nickel, and antimony from water. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the purpose of this invention is to provide a method for preparing mesoporous amine oxime-based polyacrylonitrile microspheres and their application in heavy metal adsorption; the porosity of the microspheres is controlled at more than 90% to improve the adsorption capacity of the adsorbent for heavy metals in wastewater.

[0007] To achieve the above objectives, this invention provides a method for preparing high-porosity amine oxime microspheres based on thermally induced phase separation, comprising the following steps:

[0008] S1. Dissolve the linear polymer with nitrile groups and the filler in a diluent to obtain a polymer solution;

[0009] S2. The polymer solution is atomized and sent to a low-temperature cold source for quenching. During this process, thermal phase separation (TIPS) occurs, and the atomized droplets solidify to form gel-like microspheres.

[0010] S3. The gel-like microspheres were immersed in a mixture of distilled water and ethanol for dilution replacement. After washing, the AOPS precursor of the amylopyridine microspheres was obtained.

[0011] S4. Mix the AOPS precursor with hydroxylamine, inorganic salt and distilled water, stir, and carry out the amylopyroxylation reaction to obtain the amylopyroxylation product.

[0012] S5. The amylopyridine product was washed and dried to obtain amylopyridine microspheres (AOPS).

[0013] As one embodiment of the present invention, the linear polymer with nitrile groups is selected from one or more of styrene-acrylonitrile copolymer, polyacrylonitrile, lactic acid-acrylonitrile copolymer, ethylene-acrylonitrile copolymer, propylene-acrylonitrile copolymer, polyethylene oxide-acrylonitrile copolymer, and acrylonitrile-chlorinated polyethylene-styrene copolymer.

[0014] As one embodiment of the present invention, the filler is selected from any one or more of polylactic acid, polyethylene, polyethylene oxide and sodium polyacrylate.

[0015] As one embodiment of the present invention, the diluent is at least one selected from dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and sulfolane.

[0016] In one embodiment of the present invention, the mass ratio of the filler to the linear polymer with nitrile groups is 0 to 5.0:1.

[0017] As one embodiment of the present invention, the mass ratio of the linear polymer with nitrile groups to the diluent is 0.1 to 20:100.

[0018] As one embodiment of the present invention, the atomization is carried out by spraying, and one of spray gun atomization, rotary atomization and sonic atomization is selected.

[0019] As one embodiment of the present invention, the temperature of the cold source is -10.0 to -197.0℃.

[0020] As one embodiment of the present invention, the quenching time is 0.1 to 30.0 min.

[0021] As one embodiment of the present invention, the temperature of the distilled water and ethanol mixture used in S3 is 0-16°C, and the mass ratio of ethanol to distilled water is 0-10.0:1.

[0022] As one embodiment of the present invention, the inorganic salt in S4) is at least one of sodium carbonate, sodium bicarbonate, magnesium carbonate, calcium carbonate, copper carbonate, and iron carbonate.

[0023] In one embodiment of the present invention, the reaction temperature of the oxime amine in S4) is 50-80°C and the reaction time is 15-120 min.

[0024] As one embodiment of the present invention, in S4), the mass ratio of AOPS precursor and hydroxylamine, inorganic salt and distilled water is 0.1-5.0:6.0-8.0:3.8-6.8:100.

[0025] As one embodiment of the present invention, the washed amylated product is dried in an oven at 50°C for 1.0 to 10.0 h, and then dried in a vacuum atmosphere at 70°C for 12 to 48 h.

[0026] The present invention also provides the use of high-porosity amine oxime microspheres prepared by the above method in the treatment of wastewater containing heavy metals, wherein the adsorption capacity for antimony is 300.0-725.3 mg / g and the adsorption capacity for chromium is 250.3-747.0 mg / g.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The raw materials are traditional chemical raw materials with abundant sources;

[0029] 2. The preparation method is simple and easy to industrialize;

[0030] 3. The microspheres have high porosity (greater than 90%) and contain abundant mesopores (pore size of 2-50 nm);

[0031] 4. It has a fast adsorption rate and high capacity for heavy metals. Attached Figure Description

[0032] The following will further explain the concept, specific structure, and technical effects of the present invention with reference to the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention:

[0033] Figure 1 This is a schematic diagram of the preparation of AOPS in Example 1 of the present invention;

[0034] Figure 2 This is an AOPS scanning electron microscope image of Embodiment 1 of the present invention;

[0035] Figure 3 This is an AOPS aperture distribution diagram of Embodiment 1 of the present invention;

[0036] Figure 4 This is the adsorption isotherm of antimony adsorbed by AOPS in Example 1 of the present invention, wherein q e To balance the adsorption amount, c e To balance the adsorption concentration. Detailed Implementation

[0037] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0038] Example 1

[0039] (1) Dissolve 2.0g of styrene-acrylonitrile copolymer in 100mL of dimethyl sulfoxide to prepare a homogeneous polymer solution.

[0040] (2) The polymer solution was rapidly sprayed into a container filled with liquid nitrogen (-196.0℃) using a mechanical spraying method, and the quenching time was 1 min. During this process, the mist droplets solidified to form gel-like microspheres.

[0041] (3) The gel-like microspheres were immersed in an ice / water mixture for 24 hours. After three washes, the AOPS precursor was obtained.

[0042] (4) Mix 0.2g of AOPS precursor with 6.0g of hydroxylamine hydrochloride, 5.8g of sodium carbonate and 100mL of distilled water, stir, and carry out a amine oxime reaction at a reaction temperature of 65℃ and a reaction time of 30min to obtain AOPS product.

[0043] Figure 1 This is a schematic diagram of the preparation of AOPS according to the present invention. Figure 2 and Figure 3 The images show scanning electron microscope (SEM) images and pore size distribution diagrams of the AOPS of this invention. As can be seen from the figures, the AOPS exhibits a rich mesoporous structure with a porosity of 93.5%.

[0044] In the adsorption experiment, 400 mL of antimony-containing wastewater with a concentration of 50 mg / L was prepared, and then 0.02, 0.05, 0.08, 0.11, 0.14, 0.17, and 0.20 g of microsphere adsorbent were added, mixed well, and placed on a shaker. The mixture was shaken uniformly at 25℃ for 24 h. Samples were taken after adsorption, and the antimony ion concentration was measured to calculate the adsorption capacity. The results are as follows: Figure 4As shown, AOPS exhibits a fast adsorption rate and high adsorption capacity for antimony, with an adsorption capacity as high as 750.4 mg / g.

[0045] Example 2

[0046] (1) Dissolve 2.0g of polyacrylonitrile and 2.0g of filler (polylactic acid) in 100mL of dimethyl sulfoxide to prepare a homogeneous polymer solution.

[0047] (2) The polymer solution was rapidly sprayed into a container filled with liquid nitrogen (-196.0℃) using a mechanical spraying method, and the quenching time was 1 min. During this process, the mist droplets solidified to form gel-like microspheres.

[0048] (3) The gel-like microspheres were immersed in an ice / water mixture for 24 hours. After three washes, the AOPS precursor was obtained.

[0049] (4) Mix 0.2g of AOPS precursor with 6.0g of hydroxylamine hydrochloride, 5.8g of sodium carbonate and 100mL of distilled water, stir, and carry out a amine oxime reaction at a reaction temperature of 65℃ and a reaction time of 30min to obtain AOPS product.

[0050] In the adsorption experiment, 400 mL of chromium-containing (hexavalent chromium) wastewater with a concentration of 50 mg / L was prepared, and then 0.02, 0.05, 0.08, 0.11, 0.14, 0.17, and 0.20 g of microsphere adsorbent were added, mixed well, and placed on a shaker. The mixture was shaken uniformly at 25 °C for 24 h. Samples were taken after adsorption, and the chromium ion concentration was measured to calculate the adsorption capacity. The results showed that AOPS exhibited a rich mesoporous structure with a porosity of 95.0%, and the adsorption capacity of AOPS for chromium was 747.0 mg / g.

[0051] Example 3

[0052] (1) Dissolve 2.0g of ethylene acrylonitrile copolymer and 2.0g of filler (polylactic acid) in 100mL of dimethyl sulfoxide to prepare a homogeneous polymer solution.

[0053] (2) The polymer solution was rapidly sprayed into a container filled with liquid nitrogen (-196.0℃) using an acoustic atomization method, and the quenching time was 1 min. During this process, the atomized droplets solidified to form gel-like microspheres.

[0054] (3) The gel-like microspheres were immersed in an ice / water mixture for 24 hours. After three washes, the AOPS precursor was obtained.

[0055] (4) Mix 0.2g of AOPS precursor with 6.0g of hydroxylamine hydrochloride, 5.8g of sodium carbonate and 100mL of distilled water, stir, and carry out a amine oxime reaction at a reaction temperature of 65℃ and a reaction time of 30min to obtain AOPS product.

[0056] In the adsorption experiment, 400 mL of antimony-containing wastewater with a concentration of 50 mg / L was prepared, and then 0.02, 0.05, 0.08, 0.11, 0.14, 0.17, and 0.20 g of microsphere adsorbent were added, mixed well, and placed on a shaker. The mixture was shaken uniformly at 25 °C for 24 h. Samples were taken after adsorption, and the antimony ion concentration was measured to calculate the adsorption capacity for antimony. The results showed that AOPS exhibited a rich mesoporous structure with a porosity of 92.3%, and the adsorption capacity of AOPS for antimony was 725.3 mg / g.

[0057] Example 4

[0058] (1) Dissolve 2.0g of propylene-acrylonitrile copolymer in 100mL of dimethyl sulfoxide to prepare a homogeneous polymer solution.

[0059] (2) The polymer solution was rapidly sprayed into a container filled with dry ice (-80.0℃) using an acoustic atomization method, and the quenching time was 10 min. During this process, the atomized droplets solidified to form gel-like microspheres.

[0060] (3) The gel-like microspheres were immersed in an ice / water mixture for 24 hours. After three washes, the AOPS precursor was obtained.

[0061] (4) Mix 0.2g of AOPS precursor with 12.0g of hydroxylamine hydrochloride, 11.6g of sodium carbonate and 200mL of distilled water, stir, and carry out a amine oxime reaction at a reaction temperature of 65℃ for 30min to obtain AOPS product.

[0062] In the adsorption experiment, 400 mL of chromium-containing wastewater with a concentration of 50 mg / L was prepared, and then 0.02, 0.05, 0.08, 0.11, 0.14, 0.17, and 0.20 g of microsphere adsorbent were added, mixed well, and placed on a shaker. The mixture was shaken uniformly at 25 °C for 24 h. After adsorption, samples were taken, the chromium ion concentration was measured, and the adsorption capacity for chromium was calculated. The results showed that AOPS exhibited a rich mesoporous structure with a porosity of 91.9%, and the adsorption capacity of AOPS for chromium was 553.2 mg / g.

[0063] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing mesoporous amine oxime-containing microspheres based on thermally induced phase separation, characterized in that, The method includes the following steps: S1. Dissolve the linear polymer with nitrile groups and the filler in a diluent to obtain a polymer solution; S2. The polymer solution is atomized and sent to a low-temperature cold source for quenching. During this process, thermal phase separation (TIPS) occurs, and the atomized droplets solidify to form gel-like microspheres. S3. The gel-like microspheres were immersed in a mixture of distilled water and ethanol for dilution replacement. After washing, the AOPS precursor of the amylopyridine microspheres was obtained. S4. Mix the AOPS precursor with hydroxylamine, inorganic salt and distilled water, stir, and carry out the amylopyroxylation reaction to obtain the amylopyroxylation product. S5. The amylopyridine product was washed and dried to obtain amylopyridine microspheres (AOPS).

2. The method for preparing high-porosity geminal oxime microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The linear polymer with nitrile groups is selected from one or more of styrene-acrylonitrile copolymer, polyacrylonitrile, lactic acid-acrylonitrile copolymer, ethylene-acrylonitrile copolymer, propylene-acrylonitrile copolymer, polyethylene oxide-acrylonitrile copolymer, and acrylonitrile-chlorinated polyethylene-styrene copolymer.

3. The method for preparing high-porosity geminal oxime microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The filler is selected from any one or more of polylactic acid, polyethylene, polyethylene oxide, and sodium polyacrylate.

4. The method for preparing high-porosity amine oxime microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The diluent is at least one selected from dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and sulfolane.

5. The method for preparing high-porosity geminal oxime microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The mass ratio of the filler to the linear polymer with nitrile groups is 0 to 5.0:1; the mass ratio of the linear polymer with nitrile groups to the diluent is 0.1 to 20:

100.

6. The method for preparing high-porosity geminal oxime microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The atomization is achieved by spraying, using one of the following methods: spray gun atomization, rotary atomization, or sonic atomization.

7. The method for preparing high-porosity amine oxime-based microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The temperature of the cold source is -10.0 to -197.0℃, and the quenching time is 0.1 to 30.0 min.

8. The method for preparing high-porosity geminal oxime microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The temperature of the distilled water and ethanol mixture used in S3 is 0-16℃, and the mass ratio of ethanol to distilled water is 0-10.0:

1.

9. The method for preparing high-porosity geminal oxime microspheres based on thermally induced phase separation as described in claim 1, characterized in that, The inorganic salt in S4 is at least one of sodium carbonate, sodium bicarbonate, magnesium carbonate, calcium carbonate, copper carbonate, and iron carbonate; the reaction temperature for the amine oxime is 50–80 °C, and the reaction time is 15–120 min; the mass ratio of AOPS precursor and hydroxylamine, inorganic salt, and distilled water is 0.1–5.0:6.0–8.0:3.8–6.8:

100.

10. The use of high-porosity amine oxime microspheres prepared by any one of claims 1 to 9 in the treatment of wastewater containing heavy metals, wherein the adsorption capacity for antimony is 300.0 to 725.3 mg / g and the adsorption capacity for chromium is 250.3 to 747.0 mg / g.

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