Nanofiber ball for treating nickel-containing wastewater and preparation method thereof

Abstract

This invention discloses a nanofiber sphere for treating nickel-containing wastewater and its preparation method. A heterogeneous structure is achieved through rapid quenching of a polymer emulsion, resulting in high-porosity nanofiber spheres (>85%), which are then used for nickel adsorption. The specific steps include: dissolving a characteristic polymer in a mixed solvent of tetrahydrofuran and water, adding inorganic fillers for dispersion and grinding to achieve uniformity; slowly adding a viscous oil to the grinding fluid and emulsifying at high speed to form a uniform emulsion; rapidly placing the emulsion into liquid nitrogen to form a colloidal mass, adding an ice / water mixture for solvent exchange; washing the reaction product with distilled water, and freeze-drying to obtain the nanofiber spheres. The nanofiber sphere adsorbent prepared by this invention uses traditional chemical raw materials, which are abundant; the preparation method is simple, requires no high temperature or high pressure, and is easy to scale up industrially; the microspheres have high porosity (>85%) and contain abundant pores; and they exhibit fast adsorption response and high capacity for nickel-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of adsorbent preparation technology, and in particular to a nanofiber ball for treating nickel-containing wastewater and its preparation method. Background Technology

[0002] Among numerous heavy metals, nickel, as a transition metal, is widely used in the production of industrial products such as instruments, medical devices, and automotive parts due to its wear resistance and corrosion resistance. However, this has resulted in nickel-containing wastewater, a significant problem. Nickel pollutants entering water bodies partially enter riverbed sediments and can be released under certain conditions, posing a potential threat. The remaining portion exists in dissolved form, combining with suspended solids in the water and migrating with the current. High concentrations of nickel, once absorbed by aquatic organisms, cannot be degraded by the organisms themselves. They can only be transformed and dispersed in different forms, accumulating to high concentrations through the food chain, with enrichment factors reaching thousands of times. Ultimately, this contamination enters the human body through drinking water and the food chain, harming human health. According to the World Health Organization, the maximum acceptable concentration of nickel in drinking water is 0.02 mg / L. my country's "Electroplating Pollutant Discharge Standard" (GB 21900—2008) also clearly stipulates that the permitted nickel concentration discharged into water bodies cannot exceed 0.50 mg / L. Therefore, the problem of nickel-containing wastewater urgently needs to be addressed.

[0003] Adsorption methods are widely used due to their advantages of simple operation, high efficiency, economy, and environmental friendliness. Currently, the main types of adsorbents extensively studied include iron ore, clay zeolite, activated carbon, industrial solid waste, and agricultural and forestry waste. However, these adsorbents lack suitable and sufficient pores as adsorption sites for nickel capture, resulting in small adsorption capacity and low adsorption rate. For example, the porosity of clay zeolite is generally no more than 25%, which cannot provide strong excess surface energy, resulting in an adsorption capacity generally no more than 20 mg / g, indicating limited adsorption capacity. To improve the adsorption capacity of adsorbents for nickel, it is necessary to develop nanofiber spheres with high porosity (>85%) to increase the exposure of adsorption sites and thus increase the adsorption capacity.

[0004] Nanofibers are typically prepared using methods such as electrospinning, template methods, and quantitative stretching, and often contain large pores. Polylactic acid (PLA) solutions, when quenched and cooled, readily form a two-phase structure; conventional cooling temperatures are above -50°C, resulting in PLA nanofibers. Other polymers, such as polyamides, polyesters, and polyvinyl alcohol, form clustered structures above -50°C, making nanofiber formation difficult. This invention increases the cooling temperature to -196°C, inducing extreme Mullins–Sekerka instability, causing the solvent to form a linear structure. This induces the formation of nanofibers in common polymers (such as polyamides, polyesters, and polyvinyl alcohol), thereby increasing the porosity of the nanofibers. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a nanofiber ball for treating nickel-containing wastewater and a method for its preparation.

[0006] To achieve the above objectives, the present invention provides a method for preparing nanofiber microspheres, the method comprising the following steps: S1. Dissolve the characteristic polymer in a mixed solvent of tetrahydrofuran and water, add inorganic filler, disperse and grind evenly; S2. Slowly add a certain amount of viscous oil to the grinding fluid and emulsify at high speed to form a uniform emulsion; S3. Quickly place the emulsion into liquid nitrogen to form a gel-like block, and then add an ice / water mixture for solvent exchange. S4. Wash the reaction product with distilled water and freeze-dry the product to obtain nanofiber spheres.

[0007] As one embodiment of the present invention, the characteristic polymer is selected from at least one of polyamide, polyester and polyvinyl alcohol.

[0008] In one embodiment of the present invention, the mass ratio of tetrahydrofuran to water in the mixed solvent is 20.0–1.0:1.0. In the system of the present invention, tetrahydrofuran is used as the polymer solvent and water is used as a poor polymer solvent. By increasing the cooling temperature to -196°C, Mullins–Sekerka instability is induced, causing the solvent to form a linear structure.

[0009] As one embodiment of the present invention, the inorganic filler is selected from at least one of goethite, ferrihydrite, magnetite, zeolite, diatomite, titanium dioxide, and fly ash.

[0010] As one embodiment of the present invention, the grinding zirconium beads used in the grinding process have a diameter of 0.4-3.0 mm, and the grinding fineness is that the particle diameter is controlled between 10.0-500.0 nm.

[0011] As one embodiment of the present invention, the viscous oil is selected from at least one of glycerol, diethanol, castor oil, glyceryl diacetate, and dimethyl silicone oil.

[0012] In one embodiment of the present invention, the total amount of viscous oil is 2-5 times that of the mixed solvent.

[0013] In one embodiment of the present invention, in step S2, the emulsification stirring time is 0.5-3.0 hours.

[0014] In one embodiment of the present invention, in step S3, the temperature before quenching is controlled at 0-100 degrees Celsius, and the liquid nitrogen quenching time is 10-60 minutes. Polyamides, polyesters, and polyvinyl alcohols, etc., form cluster structures above -50 degrees Celsius, making it difficult to form nanofibers. Figure 1 This invention induces extreme Mullins–Sekerka instability by increasing the cooling temperature to -196°C, causing the solvent to form a linear structure, which induces the formation of nanofibers from common polymers (such as polyamides, polyesters, and polyvinyl alcohol), thereby increasing the porosity of the nanofibers.

[0015] In one embodiment of the present invention, the solvent exchange time is 10-48 hours.

[0016] As one embodiment of the present invention, the freeze-drying time is 48-72 hours and the cooling temperature is -52±5℃.

[0017] This invention also provides the use of the nanofiber microspheres prepared by the aforementioned method for the treatment of nickel-containing wastewater. The nanofiber microsphere adsorbent of this invention has a maximum adsorption capacity of 367.5 mg / g for nickel.

[0018] Compared with existing technologies, the mesoporous nanofiber microspheres prepared by this invention have the following beneficial effects: 1) The raw materials are traditional chemical raw materials with abundant sources; the preparation method is simple, without high temperature and high pressure, and is easy to scale up industrially; the microspheres have high porosity (greater than 85%) and contain abundant pores; they have a fast adsorption response and high capacity for nickel-containing wastewater; 2) By increasing the cooling temperature to -196°C, this invention induces extreme Mullins–Sekerka instability, causing the solvent to form a linear structure. This can induce the formation of nanofibers in common polymers other than polylactic acid (such as polyamide, polyester, and polyvinyl alcohol), thereby increasing the porosity of the nanofibers and making the cooling method for preparing common nanofibers universal. Attached Figure Description

[0019] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 It is a clustered polymer generated by cooling polyamide at -45 degrees Celsius, and other experimental conditions are the same as in Example 1; Figure 2 This is a scanning electron microscope image of the nanofiber spheres in Example 1 of the present invention; Figure 3 This is an adsorption kinetic diagram of nickel adsorption by nanofiber spheres in Example 1 of the present invention, wherein... q t This refers to the adsorption capacity.t The adsorption time is denoted as . Detailed Implementation

[0020] 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.

[0021] Example 1 (1) Dissolve 2.0 g of polyamide polymer in a mixed solvent of 100 g tetrahydrofuran and water (mass ratio of 5:1), and add 0.5 g of goethite to disperse and grind evenly. The diameter of the zircon beads is 2.0 mm and the particle size is 300 nanometers. (2) Add 300 g of glycerol to the grinding liquid and emulsify it evenly. The emulsification stirring time is 0.5 hours to form a uniform emulsion. (3) Place the emulsion in liquid nitrogen, control the temperature to 25 degrees Celsius before quenching, quench for 10 minutes to form a gel-like block, and then add an ice / water mixture for solvent exchange for 24 hours. (4) The reaction product was washed with distilled water and then freeze-dried at -52°C for 48 hours to obtain nanofiber balls.

[0022] The porosity of the microspheres, as determined by mercury porosimetry, was 89%. Figure 2 In the adsorption experiment, 400 mL of nickel-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 nickel ion concentration was measured to calculate the adsorption capacity. Figure 3 The results showed that the adsorption capacity of the nanofiber spheres for nickel was 367.5 mg / g.

[0023] Example 2 (1) Dissolve 2.0 g of polyethylene terephthalate polymer in a mixed solvent of 100 g of tetrahydrofuran and water (mass ratio of 5:1), and add 0.5 g of goethite to disperse and grind evenly. The diameter of the zircon beads is 2.0 mm and the particle size is 300 nanometers. (2) Add 300 g of diethanol to the grinding liquid and emulsify it evenly. The emulsification stirring time is 0.5 hours to form a uniform emulsion. (3) Place the emulsion in liquid nitrogen, control the temperature to 25 degrees Celsius before quenching, quench for 10 minutes to form a gel-like block, and then add an ice / water mixture for solvent exchange for 24 hours. (4) The reaction product was washed with distilled water and then freeze-dried at -52°C for 48 hours to obtain nanofiber balls.

[0024] In the adsorption experiment, 400 mL of nickel-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 nickel ion concentration was measured to calculate the adsorption capacity. The results showed that the adsorption capacity of the nanofiber spheres for nickel was 263.7 mg / g.

[0025] Example 3 (1) Dissolve 2.0 g of polyvinyl alcohol polymer in a mixed solvent of 100 g of tetrahydrofuran and water (mass ratio of 5:1), and add 0.5 g of goethite for dispersion. Grind evenly, and the diameter of the zircon beads is 2.0 mm and the particle size is 300 nanometers. (2) Add 300 g of glycerol to the grinding liquid and emulsify it evenly. The emulsification stirring time is 0.5 hours to form a uniform emulsion. (3) Place the emulsion in liquid nitrogen, control the temperature to 25 degrees Celsius before quenching, quench for 10 minutes to form a gel-like block, and then add an ice / water mixture for solvent exchange for 24 hours. (4) The reaction product was washed with distilled water and then freeze-dried at -52°C for 48 hours to obtain nanofiber balls.

[0026] In the adsorption experiment, 400 mL of nickel-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 nickel ion concentration was measured to calculate the adsorption capacity. The results showed that the adsorption capacity of the nanofiber spheres for nickel was 169.1 mg / g.

[0027] Example 4 (1) Dissolve 2.0 g of polyamide polymer in a mixed solvent of 100 g of tetrahydrofuran and water (mass ratio of 5:1), and add 0.5 g of goethite to disperse and grind evenly. The diameter of the zircon beads is 2.0 mm and the particle size is 300 nanometers. (2) Add 400g of glycerin to the grinding liquid and emulsify it evenly. The emulsification stirring time is 0.5 hours to form a uniform emulsion. (3) Place the emulsion in liquid nitrogen, control the temperature to 25 degrees Celsius before quenching, quench for 10 minutes to form a gel-like block, and then add an ice / water mixture for solvent exchange for 24 hours. (4) The reaction product was washed with distilled water and then freeze-dried at -52°C for 48 hours to obtain nanofiber balls.

[0028] In the adsorption experiment, 400 mL of nickel-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 nickel ion concentration was measured to calculate the adsorption capacity. The results showed that the adsorption capacity of the nanofiber spheres for nickel was 342.9 mg / g.

[0029] 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 nanofiber microspheres, characterized in that, The method includes the following steps: S1. Dissolve the characteristic polymer in a mixed solvent of tetrahydrofuran and water, add inorganic filler, disperse and grind evenly; S2. Slowly add a certain amount of viscous oil to the grinding fluid and emulsify at high speed to form a uniform emulsion; S3. Place the emulsion into liquid nitrogen to form a gel-like block, and then add an ice / water mixture for solvent exchange. S4. Wash the reaction product with distilled water and freeze-dry the product to obtain nanofiber spheres.

2. The method for preparing nanofiber microspheres as described in claim 1, characterized in that, The characteristic polymer is selected from at least one of polyamide, polyester and polyvinyl alcohol; the mass ratio of tetrahydrofuran to water in the mixed solvent is 20.0 to 1.0:1.

0.

3. The method for preparing nanofiber microspheres as described in claim 1, characterized in that, The inorganic filler is selected from at least one of goethite, ferrimagnetite, magnetite, zeolite, diatomite, titanium dioxide, and fly ash.

4. The method for preparing nanofiber microspheres as described in claim 1, characterized in that, The grinding process uses zirconium beads with a diameter of 0.4-3.0 mm, and the grinding fineness is controlled to have a particle diameter of 10.0-500.0 nm.

5. The method for preparing nanofiber microspheres as described in claim 1, characterized in that, The viscous oil is selected from at least one of glycerol, diethanol, castor oil, glyceryl diacetate, and dimethyl silicone oil.

6. The method for preparing nanofiber microspheres as described in claim 1 or 5, characterized in that, The total amount of viscous oil used is 2-5 times the mass of the mixed solvent.

7. The method for preparing nanofiber microspheres as described in claim 1, characterized in that, In step S2, the emulsification stirring time is 0.5 - 3.0 hours.

8. The method for preparing nanofiber microspheres as described in claim 1, characterized in that, In step S3, the temperature before quenching is controlled at 0-100 degrees Celsius, the liquid nitrogen quenching time is 10-60 minutes, and the solvent exchange time is 10-48 hours.

9. The method for preparing nanofiber microspheres as described in claim 1, characterized in that, The freeze-drying time is 48-72 hours, and the cooling temperature is -52±5℃.

10. Use of nanofiber microspheres prepared by the method according to any one of claims 1-9, characterized in that, The nanofiber microspheres are used for the treatment of nickel-containing wastewater.

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