CN112705171A

CN112705171A - Nanofiber adsorbing material and preparation method and application thereof

Info

Publication number: CN112705171A
Application number: CN201911024861.2A
Authority: CN
Inventors: 王镭; 宋小飞; 安婷婷; 钟林
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2019-10-25
Filing date: 2019-10-25
Publication date: 2021-04-27

Abstract

The invention relates to the field of membrane separation, and discloses a nanofiber adsorbing material as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) preparing the polymer solution into a nanofiber membrane by an electrostatic spinning method, wherein the spinning voltage is 1-30 kv; (2) contacting an aqueous dopamine solution with the nanofiber membrane; the pH value of the dopamine aqueous solution is 8-9, and the content of dopamine is 0.5-5g relative to 1L of water. The nanofiber adsorbing material has strong adsorption capacity particularly for heavy metals in wastewater, can be directly taken out of the wastewater after adsorption is completed, and is simple to operate and convenient to use.

Description

Nanofiber adsorbing material and preparation method and application thereof

Technical Field

The invention relates to the field of membrane separation, in particular to a nanofiber adsorbing material and a preparation method and application thereof.

Background

The adsorption method is a low-cost, simple and efficient method for removing harmful substances in water. The ideal adsorbent material needs to satisfy the following conditions: (1) the surface has available functional groups; (2) a large specific surface area is required; (3) easy to separate from the system and does not cause secondary pollution.

At present, the common adsorption materials mainly comprise loose porous materials (such as activated carbon) and various nano particles, microspheres and the like, but the loose porous materials and the various nano particles, the microspheres and the like have some defects. The porous material has smaller specific surface area and poorer adsorption capacity. The preparation process of the materials such as nano particles, microspheres and the like is complex, and the materials need to be separated from a solution system after adsorption is completed during application, so that the operation difficulty is increased; if the column is made as a packed column for processing, a higher pressure is required. Therefore, there is a need for development of a novel adsorbent having a high adsorption capacity and easy handling.

Disclosure of Invention

The invention aims to solve the problems of poor adsorption capacity or complex operation of the existing adsorption material, and provides a novel nanofiber adsorption material and a preparation method and application thereof.

The inventor of the invention finds that the nanofiber membrane prepared by the electrostatic spinning method under certain operating conditions has a large specific surface area, and after the nanofiber membrane is treated by a specific dopamine aqueous solution, the nanofiber membrane has a strong adsorption effect on heavy metal ions in water, is easy to attach to a carrier material to form a membrane, and can be used for preparing a functional layer with the adsorption effect. The present invention has been made based on the above findings.

According to a first aspect of the present invention, there is provided a method of preparing a nanofibre adsorbent material, the method comprising:

(1) preparing the polymer solution into a nanofiber membrane by an electrostatic spinning method, wherein the spinning voltage is 1-30 kv;

(2) contacting an aqueous dopamine solution with the nanofiber membrane; wherein,

the pH value of the dopamine aqueous solution is 8-9, and the content of dopamine is 0.5-5g relative to 1L of water.

According to a second aspect of the present invention, there is provided a nanofiber adsorbent material prepared by the preparation method according to the first aspect of the present invention.

According to a third aspect of the invention, the invention provides the use of the nanofiber adsorbent material for treating electroplating wastewater.

The preparation method can prepare the nanofiber adsorbing material with available functional groups on the surface as amino and hydroxyl. The nanofiber adsorbing material has strong adsorption capacity particularly for heavy metals in wastewater, can be directly taken out of the wastewater after adsorption is completed, and is simple to operate and convenient to use.

Drawings

FIG. 1 is a schematic view of an electrospinning apparatus of the present invention.

Fig. 2 is a schematic view of a feeding unit of an embodiment of the electrospinning apparatus of the present invention.

Description of the reference numerals

1: a collection roller; 2: a first transmission device; 3: a second transmission device; 4: an electrostatic generator; 5 a: a feed liquid container; 5 b: a circular hole member; 5 c: a constant flow pump; 5 d: a pipeline; 6: a power mechanism; 7: an electric brush; 8: a lifting device; 9: a laser.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

According to a first aspect of the present invention, there is provided a method of preparing a nanofiber adsorbent material, the method comprising:

(2) contacting an aqueous dopamine solution with the nanofiber membrane.

In the invention, the pH value of the dopamine aqueous solution is 8-9, and the content of dopamine is 0.5-5g relative to 1L of water. Preferably, the dopamine content is 1-3g relative to 1L of water.

In the present invention, the pH of the dopamine aqueous solution may be adjusted by a pH adjuster (e.g., hydrochloric acid).

In the present invention, it is preferable that the dopamine aqueous solution further contains tris (hydroxymethyl) aminomethane, and the concentration of tris (hydroxymethyl) aminomethane is 1.1 to 1.5 g/L. The tris (hydroxymethyl) aminomethane is used as a buffer, so that the influence of factors such as acidic oxides in the air in the preparation process can be reduced, and the stability of the product performance is improved.

According to the present invention, in the polymer solution in the step (1), the polymer may be selected from various water-insoluble polymers suitable for spinning, for example, may be selected from at least one of polyamide (e.g., PA66, PA56), polyurethane, polyvinyl acetate, polyvinyl chloride, polyethylene terephthalate, polyacrylonitrile, and regenerated cellulose. The polymers of the invention suitable for spinning are all commercially available.

The solvent may be selected from at least one of formic acid, acetone, fatty alcohols, aliphatic hydrocarbons, methyl chloride, methylene chloride, chloroform, carbon tetrachloride, benzene, toluene, xylene, phenol, m-cresol, hexafluoropropane, N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, and dimethylsulfoxide.

Preferably, the polymer content of the polymer solution is 2 to 15% by weight.

According to a preferred embodiment, the polymer is selected from polyacrylonitrile and the solvent is N-methylpyrrolidone or N, N-dimethylformamide. According to another preferred embodiment, the polymer is PA66 or PA56 and the solvent is formic acid. The two preferred embodiments can further improve the adsorption performance of the prepared adsorption material.

In step (1), according to an embodiment, as shown in fig. 1, the electrospinning method uses an electrospinning apparatus including: the device comprises a feeding unit, an electrostatic generator 4, a collecting roller 1, a power mechanism 6, a first transmission device 2 and a second transmission device 3; wherein the feeding unit comprises a feed liquid container 5a and a circular hole member 5b, the circular hole member 5b is made of a conductive material, and the collecting roller 1 is a cylinder with a conductive surface; the electrode of the electrostatic generator 4 is connected with the circular hole member 5b, and the surface of the collecting roller 1 is grounded, for example, by a brush 7; under the action of the power mechanism 6, the collecting roller 1 is driven by the first transmission device 2 to rotate around the shaft thereof, and the feed liquid container 5a is drawn by the second transmission device 3 to do reciprocating linear motion along the direction parallel to the axis of the collecting roller 1.

The step (1) comprises the following steps: under the action of the spinning voltage, the polymer solution in the feed liquid container flies to the collecting roller through the circular hole component to form polymer fibers, and a nanofiber membrane is gradually formed. The collecting roller 1 rotates at a speed of 10-300 rpm.

Preferably, said first transmission means 2 is a detachable shaft connector in order to detach said collecting roller 1.

The feeding unit can quantitatively convey the polymer solution. According to one embodiment, as shown in fig. 2, the circular hole member 5b is an electrically conductive needle tube, the feeding unit comprises a constant flow pump 5c, and the feed liquid container 5a, the constant flow pump 5c and the electrically conductive needle tube are sequentially connected through a pipeline 5 d.

Preferably, the diameter of the circular hole member 5b is 0.1-2 mm.

Preferably, the circular hole member 5b has a minimum distance L (hereinafter also referred to as "air gap") of 5 to 25cm from the surface of the collecting roller 1, so that the polymer in the solution is more easily oriented to become fibrous during flight.

Preferably, the feeding speed is 1-50mL/h, and the reciprocating speed is 200-1000 mm/min.

More preferably, the feeding speed of the feed liquid container is 1-5mL/h, and the reciprocating speed is 400-800 mm/min.

Preferably, the collecting roller 1 has a length of 20 to 300cm and a diameter of 1 to 20 mm.

Preferably, the electrostatic spinning equipment further comprises a laser 9, a support provided with scale marks and a lifting device 8, wherein the support is located at one end of the collecting roller 1, the laser 9 is installed on the support and is adjustable up and down through the lifting device 8, and the laser beam direction of the laser 9 is parallel to the axis of the collecting roller 1 and is used for checking the thickness of the nanofiber film on the collecting roller 1 in real time.

According to the invention, in step (2), the contact is carried out in a constant temperature shaking table, the oscillation speed of the constant temperature shaking table is 50-150r/min, the contact temperature is 20-40 ℃, and the contact time is 3-20 hours. Preferably, the shaking time is 5 to 10 hours.

According to a second aspect of the invention, the invention provides a nanofiber adsorbing material prepared by the preparation method.

Preferably, the average fiber diameter of the nanofiber adsorbent material is 50-250nm, more preferably 80-200 nm; the specific surface area is 10-40m²A/g, more preferably 12 to 35m²/g。

The present invention will be described in detail below by way of examples.

The nanofiber adsorbent and the method for producing the same according to the present invention will be described below with reference to fig. 1 and 2. In fig. 1 and 2, the electrospinning device includes: the device comprises a feeding unit, an electrostatic generator 4, a collecting roller 1, a power mechanism 6, a detachable shaft connector, a second transmission device 3, a bracket provided with scale marks, a lifting device 8 and a laser 9; the feeding unit comprises a material liquid container 5a, a circular hole component 5b, a constant flow pump 5c and a pipeline 5 d; the connection of the devices is as described above and shown in the drawings.

The properties of the nanofiber adsorbent material were tested as follows.

(1) Average fiber diameter

The diameter distribution of the fiber is measured by adopting a scanning electron microscope, and the specific test method comprises the following steps: randomly selecting 5 areas on a non-woven tube, observing and measuring the diameters of all visible fibers in each area under a scanning electron microscope, and then calculating the average diameter and the standard deviation; the smaller the standard deviation, the better the product uniformity.

(2) Specific surface area

The specific surface area of the sample was measured using a nitrogen adsorption specific surface area meter.

(3) The removal rate of Cr (VI) is used to characterize the adsorption capacity of the nanofiber adsorbent material.

Different amounts of nanofiber adsorbent material (specifically 25mg, 50mg, 75mg, 100mg) were immersed in 30mL of potassium dichromate solution with initial concentrations of Cr (VI) (c₀) 200mg/L, then placed in a constant temperature shaker and shaken at a speed of 100r/min at 25 ℃ for 12 hours. The adsorbent was removed again and the concentration (c) of Cr (VI) remaining in the solution was determined spectrophotometrically_e) The removal rate R was calculated according to formula I:

example 1

(1) Dissolving 6g of polyacrylonitrile in 54g N, N-dimethylformamide to obtain a polyacrylonitrile solution, and transferring the polyacrylonitrile solution to a feed liquid container of electrostatic spinning equipment;

(2) under the action of electrostatic voltage, the polyacrylonitrile solution in the material liquid container flies to the collecting roller through the circular hole component to form polymer fiber and gradually form a nanofiber membrane;

the parameters of electrostatic spinning are as follows: the inner diameter of the circular hole component is 0.2mm, the air gap is 10cm, a collecting roller with the diameter of 10cm and the length of 50cm is used, the rotating speed of the collecting roller is 20 r/min, the solution conveying speed is 1.2mL/h, the reciprocating speed of the feed liquid container is 600mm/min, and the static voltage is 5 kV.

Spinning is stopped when the thickness of the nanofiber membrane reaches 0.2mm detected by a laser. Cutting along the axial direction of the collecting roller and taking down;

(3) 0.6g of tris (hydroxymethyl) aminomethane was dissolved in 500mL of water, and then 1g of dopamine was added thereto, and after complete dissolution, the pH was adjusted to 8.5 with hydrochloric acid to obtain an aqueous dopamine solution.

Immersing the nanofiber membrane in the solution, placing the nanofiber membrane in a constant-temperature shaking table at 25 ℃ and 100r/min for contact for 6 hours, taking out the nanofiber membrane, washing the nanofiber membrane with water, and airing the nanofiber membrane at room temperature to obtain the nanofiber adsorbing material.

The properties of the nanofiber adsorbent material are shown in table 1.

Comparative example 1

A nanofiber adsorbent was prepared as in example 1, except that 0.6g of tris (hydroxymethyl) aminomethane and 1g of dopamine were directly mixed with the polyacrylonitrile solution and then spun. The properties of the resulting nanofiber adsorbent material are shown in table 1.

Example 2

A nanofiber adsorbent was prepared according to the method of example 1, except that, in the step (1), the electrostatic voltage was adjusted to 10 kV. The properties of the resulting nanofiber adsorbent material are shown in table 1.

Example 3

A nanofiber adsorbent was prepared as in example 1, except that in step (2), 0.5g of dopamine was added. The properties of the resulting nanofiber adsorbent material are shown in table 1.

Example 4

A nanofiber adsorbent material was prepared as in example 1, except that in step (2), dopamine was added in an amount of 2.5 g. The properties of the resulting nanofiber adsorbent material are shown in table 1.

Example 5

A nanofiber adsorbent was prepared according to the method of example 1, except that in the step (2), the contact time was controlled to 4 hours. The properties of the resulting nanofiber sorber are shown in table 1.

Example 6

(1) Dissolving 9g of PA66 in 51g of formic acid to give a PA66 solution, and transferring the solution to a feed vessel of an electrospinning device;

the parameters of electrostatic spinning are as follows: the inner diameter of the circular hole component is 0.3mm, the air gap is 8cm, a collecting roller with the diameter of 10cm and the length of 50cm is used, the rotating speed of the collecting roller is 100r/min, the solution conveying speed is 3.0mL/h, the reciprocating speed of the feed liquid container is 800mm/min, and the static voltage is 15 kV.

Spinning is stopped when the thickness of the nanofiber membrane reaches 0.2mm detected by a laser. Cutting along the axis of the collecting roller and taking down the collecting roller;

(3) 0.6g of tris (hydroxymethyl) aminomethane was dissolved in 500mL of water, and then 1.5g of dopamine was added thereto, and after complete dissolution, the pH was adjusted to 8.5 with hydrochloric acid to obtain an aqueous dopamine solution.

Immersing the fiber membrane in the solution, placing the fiber membrane in a constant-temperature shaking table at 25 ℃ and 100r/min for contact for 8 hours, taking out the fiber membrane, washing the fiber membrane with water, and airing the fiber membrane at room temperature to obtain the nanofiber adsorbing material.

The properties of the nanofiber adsorbent material are shown in table 1.

Example 7

A nanofiber adsorbent material was prepared as in example 6, except that in step (1), formic acid was replaced with phenol. The properties of the resulting nanofiber adsorbent material are shown in table 1.

Example 8

A nanofiber adsorbent material was prepared as in example 6, except that in step (1), the PA66 solution was replaced with a polyvinyl acetate solution, specifically, 9g of polyvinyl acetate was dissolved in 51g of acetone to give a polyvinyl acetate solution. The properties of the resulting nanofiber adsorbent material are shown in table 1.

Example 9

A nanofiber adsorbent was prepared according to the method of example 6, except that, in the step (2), tris was not added. The properties of the resulting nanofiber adsorbent material are shown in table 1.

Comparative example 2

A nanofiber adsorbent was prepared as in example 6, except that the step (2) was not performed, namely, the fiber membrane obtained in the step (1) was directly washed with water and then dried at room temperature. The properties of the resulting fibrous adsorbent material are shown in table 1.

TABLE 1

Comparing the results in table 1 with the comparative examples 1-2, it can be seen that the adsorbing materials prepared in examples 1-9 have higher removal rate of cr (vi) under the condition of the same amount of the adsorbing material; especially when the feeding amount reaches 100mg, the Cr (VI) removing rate is very high; when the feeding amount is 75mg, the removal rate of Cr (VI) is good.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A preparation method of a nanofiber adsorbing material comprises the following steps:

(2) contacting an aqueous dopamine solution with the nanofiber membrane;

2. The method according to claim 1, wherein the aqueous dopamine solution further contains tris (hydroxymethyl) aminomethane, and the amount of tris (hydroxymethyl) aminomethane is 1.1 to 1.5g per 1L of water;

preferably, the concentration of dopamine in the dopamine aqueous solution is 1-3 g/L.

3. The production method according to claim 1 or 2, wherein, in the polymer solution,

the polymer is selected from at least one of polyamide, polyurethane, polyvinyl acetate, polyvinyl chloride, polyethylene terephthalate, polyacrylonitrile and regenerated cellulose;

the solvent is at least one selected from formic acid, acetone, fatty alcohol, aliphatic hydrocarbon, methane chloride, methylene chloride, chloroform, carbon tetrachloride, benzene, toluene, xylene, phenol, m-cresol, hexafluoropropane, N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide and dimethyl sulfoxide;

preferably, the polymer is polyacrylonitrile, and the solvent is N-methylpyrrolidone or N, N-dimethylformamide;

preferably, the polymer is PA66 or PA56 and the solvent is formic acid.

4. The production method according to any one of claims 1 to 3, wherein the polymer content in the polymer solution is 2 to 15% by weight.

5. The production method according to any one of claims 1 to 4, wherein the electrospinning method uses an electrospinning apparatus comprising: the device comprises a feeding unit, an electrostatic generator, a collecting roller, a power mechanism, a first transmission device and a second transmission device;

the feeding unit comprises a feed liquid container and a circular hole member, the circular hole member is made of a conductive material, and the collecting roller is a cylinder with a conductive surface; the electrode of the electrostatic generator is connected with the circular hole component, and the surface of the collecting roller is grounded; under the action of the power mechanism, the collecting roller is driven by the first transmission device to rotate around the shaft of the collecting roller, and the feed liquid container is drawn by the second transmission device to do reciprocating linear motion along the direction parallel to the axis of the collecting roller;

the step (1) comprises the following steps: under the action of the spinning voltage, the polymer solution in the feed liquid container flies to the collecting roller through the circular hole component to form polymer fibers, and a nanofiber membrane is gradually formed; the collection roller has a rotational speed of 10-300 revolutions per minute.

6. The production method according to claim 5, wherein the minimum distance of the circular hole member from the surface of the collecting roller is 5 to 25 cm.

7. The preparation method according to claim 5 or 6, wherein the feeding speed of the feed liquid container is 1-50mL/h, and the reciprocating speed is 200-1000 mm/min;

preferably, the feeding speed of the material liquid container is 1-5mL/h, and the reciprocating speed is 400-800 mm/min.

8. The process according to claim 1, wherein in the step (2), the contacting is carried out in a constant temperature shaking table, the shaking speed of the constant temperature shaking table is 50 to 150r/min, the contacting temperature is 20 to 40 ℃, and the contacting time is 3 to 20 hours;

preferably, the contact time is 5 to 10 hours.

9. The nanofiber adsorbent material prepared by the preparation method according to any one of claims 1 to 8.

10. The nanofibrous adsorbent material of claim 9, wherein the nanofibrous adsorbent material has a fiber average diameter of 50-250nm and a specific surface area of 10-40m²/g。

11. Use of the nanofiber adsorbent material of claim 9 or 10 for treating electroplating wastewater.