Preparation method of nano-pore stainless steel alloy hollow fiber membrane

Abstract

The invention relates to a preparation method of a porous stainless steel alloy hollow fiber membrane, in particular to a preparation method of a nano-pore stainless steel alloy hollow fiber membrane. The method comprises the following steps: 1, preparing a spinning solution containing four components, namely 316L stainless steel powder, copper powder, a polymer adhesive and an organic solvent; 2, preparing the spinning solution into hollow fibers through a non-solvent induced phase separation (NIPS) process by adopting a solution spinning method, and airing the hollow fibers in air to obtain a polymer hollow fiber precursor containing metal components; and step 3, putting the dried hollow fiber precursor into a tubular furnace, and calcining in a gas atmosphere by adopting a programmed heating method to obtain the nano-porous stainless steel / copper alloy hollow fiber membrane. The defects that an existing porous stainless steel hollow fiber membrane is large in apparent aperture and rough in surface are overcome.

Description

Technical Field

[0001] The present invention relates to a method for preparing a porous stainless steel alloy hollow fiber membrane, and more specifically to a method for preparing a nano-porous stainless steel alloy hollow fiber membrane. Background Art

[0002] Metal materials have characteristics such as high electrical conductivity, high mechanical strength, corrosion resistance, high temperature resistance, and high pressure resistance. Therefore, porous separation membranes made of metals have broad application prospects and great commercial value in the field of special separation under extreme environments. Currently, the apparent pore sizes of metal hollow fiber membranes reported in China are generally in the micron level, and the surface roughness is relatively high. For example, the stainless steel hollow fibers disclosed in patent documents CN103933866A and CN 108970417 B, and the nickel hollow fibers disclosed in patent document CN105126640 A, all have pore sizes in the micron level and a relatively wide distribution, and can only be used in a few fields such as the filtration of larger particles and oil-water separation, severely restricting the application and development of metal hollow fiber membranes. Although the current porous metal hollow fiber membranes all adopt the method of powder sintering, they all use single metal powders and lack research on hollow fiber membranes in alloy systems. In patent document CN 112295414 A, a method of preparing a layer of TiO2 on the surface of a macroporous stainless steel hollow fiber is used to reduce the pore size, but the research on in-situ preparation of nano-porous stainless steel hollow fiber membranes is still blank. Summary of the Invention

[0003] The purpose of the present invention is to solve the disadvantages of the existing porous stainless steel hollow fiber membranes with relatively large apparent pore sizes and rough surfaces, and to provide a method for preparing a nano-porous stainless steel alloy hollow fiber membrane.

[0004] A method for preparing a nano-porous stainless steel alloy hollow fiber membrane of the present invention includes the following steps:

[0005] Step 1: Prepare a spinning solution containing four components: 316L stainless steel powder, copper powder, polymer binder, and organic solvent.

[0006] The average particle size of the 316L stainless steel powder in Step 1 is 0.5 - 3.0 μm, and the average particle size of the copper powder is 0.3 - 1.0 μm.

[0007] The polymer binder in Step 1 is polyethersulfone (PES) or polyetherimide (PEI).

[0008] The organic solvent described in Step 1 is at least one or a mixed solvent of two in any proportion selected from solvents such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), etc. The organic solvent is a good solvent for PES and PEI. Only a good solvent can effectively dissolve PES and PEI to form a uniform polymer solution. Since it is miscible with water and water is not a poor solvent for PEI and PES, the NIPS process can occur.

[0009] The mass ratios of the components in the spinning solution described in Step 1 are as follows: 1) at least one stainless steel powder accounts for 42% - 54%; 2) at least one copper powder accounts for 6% - 18%; 3) at least one polymer binder accounts for 6% - 10%; 4) at least one organic solvent accounts for 30% - 34%. The sum of the components is 100%. The components within this range can ensure that the viscosity of the spinning solution is above 4000 cps, making it easy to spin, and the components within this range can control the pore diameter of the final alloy fiber to be around 100 nm.

[0010] In Step 2, solution spinning is adopted. Through the non-solvent induced phase separation (NIPS) process, the spinning solution is made into hollow fibers, and after air drying, a polymer hollow fiber precursor containing metal components is obtained. The non-solvent induced phase separation (NIPS) process is as follows: non-solvent induced phase separation means dissolving the polymer in a solvent to form a homogeneous solution, then adding a reagent with stronger miscibility with the solvent (referred to as an extractant, mostly water) to extract the solvent, forming a two-phase structure with the polymer as the continuous phase and the solvent as the dispersed phase, and then removing the solvent to obtain a polymer with a certain pore structure.

[0011] The solution spinning method described in Step 2 is a well-known solution spinning process. Using mechanical power or compressed gas as the driving force, at a certain speed, the spinning solution is extruded from a hollow spinneret, enters a water or aqueous solution coagulation bath after passing through a 0 - 15 cm air bath, the core liquid is water or aqueous solution, and after 24 - 48 h of solvent exchange (NIPS), a solidified polymer hollow fiber precursor is obtained. The size of the spinneret is not limited, and a corrosion-resistant metal spinneret with an inner diameter of 1.0 - 1.5 mm, an outer diameter of 2.0 - 3.0 mm, and an inner core diameter of 0.5 - 0.9 mm is preferably used.

[0012] In Step 3, the dried hollow fiber precursor is placed in a tubular furnace. The dried hollow fiber precursor needs to be placed in a 10 mm diameter corundum tube and then placed in the tubular furnace. Sintering is carried out under a gas atmosphere using a programmed heating method to obtain a nano-porous stainless steel alloy hollow fiber membrane.

[0013] The temperature programming range described in Step 3 is 25°C to 1100°C, the heating rate is 5 to 15°C / min, and the sintering time at the highest temperature is 10 min to 120 min. 15°C is the upper limit of the heating rate of a general tubular furnace. A rate below 5°C is too slow, wasting time and being unhelpful for the final result. A sintering time above 10 min ensures the basic strength of the fibers, while a sintering time above 120 min results in too low a fiber porosity.

[0014] The gas atmosphere described in Step 3 is a reducing gas at 50 to 200 mL / min, and carbon monoxide or hydrogen with a purity of 99.999% can be selected. The reducing gas can remove polymers more effectively than ordinary inert gases.

[0015] Compared with the prior art, the positive effects of the present invention are:

[0016] The present invention can be used to prepare a nano-porous stainless steel alloy hollow fiber membrane. By sintering a hollow fiber precursor containing 316L stainless steel and copper in pure hydrogen, the pore diameter on the surface of the metal hollow fiber is successfully reduced to less than 100 nm, and at the same time, the surface roughness is greatly reduced. The obtained porous hollow fiber membrane has excellent gas-liquid permeation performance, broadening the application scope of porous metal membranes and having great application prospects in the fields of energy, environment, biomedicine, electronics, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The following further describes the present invention in detail with reference to the drawings and specific implementation methods.

[0018] Figure 1 SEM image of the surface of the alloy hollow fiber prepared in Example 1;

[0019] Figure 2 Pore size distribution of the alloy hollow fiber prepared in Example 1. SPECIFIC EMBODIMENTS

[0020] A method for preparing a nano-porous stainless steel alloy hollow fiber membrane according to the present invention includes the following steps:

[0021] Step 1: Prepare a spinning solution containing four components: 316L stainless steel powder, copper powder, polymer binder, and organic solvent.

[0022] The average particle size of the 316L stainless steel powder described in Step 1 is 0.5 to 3.0 μm, and the average particle size of the copper powder is 0.3 to 1.0 μm.

[0023] The polymer binder described in Step 1 is polyethersulfone (PES) or polyetherimide (PEI).

[0024] The organic solvent described in Step 1 is at least one or a mixed solvent of two solvents in any proportion selected from solvents such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).

[0025] The mass ratios of the components in the spinning solution described in Step 1 are as follows: 1) at least one stainless steel powder accounts for 42% to 54%; 2) at least one copper powder accounts for 6% to 18%; 3) at least one polymer binder accounts for 6% to 10%; 4) at least one organic solvent accounts for 30% to 34%. The sum of the components is 100%.

[0026] In Step 2, solution spinning is adopted. Through the non-solvent induced phase separation (NIPS) process, the spinning solution is made into hollow fibers, and then dried in the air to obtain a polymer hollow fiber precursor containing metal components.

[0027] The solution spinning method described in Step 2 is a well-known solution spinning process. Using mechanical power or compressed gas as the driving force, the spinning solution is extruded from a hollow spinneret at a certain speed, enters a water or aqueous solution coagulation bath after passing through a 0 - 15 cm air bath, with the core liquid being water or an aqueous solution. After 24 - 48 hours of solvent exchange (NIPS), a solidified polymer hollow fiber precursor is obtained. The size of the spinneret is not limited, and a corrosion-resistant metal spinneret with an inner diameter of 1.0 - 1.5 mm, an outer diameter of 2.0 - 3.0 mm, and an inner core diameter of 0.5 - 0.9 mm is preferably used. The obtained fiber has a diameter of more than 1 mm and a thickness of more than 0.2 mm to ensure strength.

[0028] In Step 3, the dried hollow fiber precursor is placed in a tube furnace and sintered under a gas atmosphere using a programmed heating method to obtain a nano-porous stainless steel / copper alloy hollow fiber membrane.

[0029] The programmed heating range described in Step 3 is 25°C to 1100°C, the heating rate is 5 - 15°C / min, and the sintering time at the highest temperature is 10 min to 120 min.

[0030] The gas atmosphere described in Step 3 is a reducing gas at 50 - 200 mL / min, and carbon monoxide or hydrogen with a purity of 99.999% can be selected.

[0031] The present invention can be used to prepare a nano-porous stainless steel alloy hollow fiber membrane. By sintering a hollow fiber precursor containing 316L stainless steel and copper in pure hydrogen, the pore diameter on the surface of the metal hollow fiber is successfully reduced to less than 100 nm, and at the same time, the surface roughness is significantly reduced. The obtained porous hollow fiber membrane has excellent gas-liquid permeation performance, broadening the application scope of porous metal membranes, and has great application prospects in the fields of energy, environment, biomedicine, electronics, etc.

[0032] Where the present invention is not described, it is applicable to the prior art.

[0033] Specific embodiments of the present invention are given below. These embodiments only specifically illustrate the present invention and do not limit the protection scope of the claims of the present invention application.

[0034] Embodiment 1:

[0035] Step 1: Prepare the spinning solution. Add 6 g of PES to 34 g of N-methylpyrrolidone (NMP), stir and mix at room temperature for 3 h, add 54 g of 316L stainless steel powder and 6 g of copper powder, and continuously mechanically stir for 3 h to obtain a spinning solution with a total mass of 100 g. The mass ratio of the four components of 316L stainless steel powder, copper powder, PES, and N-methylpyrrolidone (NMP) is 54:6:6:34, and the sum of the four components is 100% in any case.

[0036] Step 2: Make the spinning solution into a polymer hollow fiber precursor. Place the spinning solution in a ball mill and continuously ball mill for 10 h to further evenly disperse the metal powder and ensure the uniformity of the spinning solution. Then transfer it to a stainless steel syringe and degas for 10 h under a vacuum of 0.005 MPa. Using solution spinning, use an injection pump to spray the spinning solution from the syringe through a spinneret, and through the non-solvent (water) induced phase separation (NIPS) process, make the spinning solution into hollow fibers. Soak the obtained hollow fibers in water at room temperature for 24 h and air dry to obtain a polymer hollow fiber precursor containing two metal powders.

[0037] Step 3: Place the dried hollow fiber precursor in a tubular furnace and calcine it in a pure hydrogen atmosphere using a programmed heating method. The heating rate is 10 °C / min, the final sintering temperature is 1100 °C, the sintering time is 30 min, and the hydrogen supply is 50 mL / min. After natural cooling, a nano-porous stainless steel / copper alloy hollow fiber membrane is obtained.

[0038] Using a pore size analyzer, its average pore size is measured to be 70 nm, and the N2 flux at 1 atm pressure is 12700 GPU. The pore size on the surface of the metal hollow fiber is successfully reduced to less than 100 nm, and at the same time, the surface roughness is greatly reduced. Membranes with a pore size less than 100 nm have a wider application range than membranes with a micron-sized pore diameter. The cut-off size is smaller, and smaller substances can be filtered. At the same time, it can be used as a support membrane to load nano-materials with a size of dozens to hundreds of nanometers. The N2 gas flux can prove the mass transfer ability of the hollow fiber, which is positively correlated with its pore size and porosity to a certain extent.

[0039] Example 2: The difference between this example and Example 1 is that the sintering time described in step 3 is 10 min, and the remaining steps are the same as those in Embodiment 1. The measured average pore size is 102 nm, and the N2 flux under 1 atm pressure is 43950 GPU

[0040] Example 3: The difference between this example and Example 2 is that the sintering time described in step 3 is 60 min, and the remaining steps are the same as those in Embodiment 1. The measured average pore size is 62 nm, and the N2 flux under 1 atm pressure is 2050 GPU.

[0041] Example 4: The difference between this example and Example 2 is that the hydrogen supply described in step 3 is 25 mL, and the remaining steps are the same as those in Embodiment 1. The measured average pore size is 116 nm, and the N2 flux under 1 atm pressure is 34610 GPU.

[0042] Example 5: The difference between this example and Example 2 is that the hydrogen supply described in step 3 is 75 mL, and the remaining steps are the same as those in Embodiment 1. The measured average pore size is 61 nm, and the N2 flux under 1 atm pressure is 5785 GPU.

[0043] Example 6: The difference between this example and Example 2 is that the hydrogen supply described in step 3 is 100 mL, and the remaining steps are the same as those in Embodiment 1. The measured average pore size is 57 nm, and the N2 flux under 1 atm pressure is 1832 GPU.

Claims

1. A preparation method of a nanoporous stainless steel alloy hollow fiber membrane, characterized in that, It includes the following steps: Step 1: Prepare a spinning solution containing four components: stainless steel powder, copper powder, polymer binder, and organic solvent. Step 2: Using the solution spinning method, through the non-solvent induced phase separation (NIPS) process, the spinning solution is made into hollow fibers, and dried in air to obtain a polymer hollow fiber precursor containing metal components. Step 3: Place the dried hollow fiber precursor in a tubular furnace, and calcine it under a gas atmosphere using a programmed heating method to obtain a nano-porous stainless steel alloy hollow fiber membrane.

2. The preparation method of a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The stainless steel powder described in Step 1 is 316L stainless steel powder, and the average particle size of the 316L stainless steel powder is 0.1 - 10.0 μm.

3. The preparation method of a nanochannel stainless steel alloy hollow fiber membrane according to claim 1, wherein: The average particle size of the copper powder described in Step 1 is 0.05 - 3.0 μm.

4. The preparation method of a nanochannel stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The polymer binder described in Step 1 is polyethersulfone (PES) or polyetherimide (PEI).

5. The preparation method of a nanoporous stainless steel alloy hollow fiber membrane according to claim 4, characterized in that: The organic solvent described in Step 1 is a good solvent for PES and PEI, and is miscible with water, including at least one of solvents such as N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), or a mixed solvent of any two in any proportion.

6. The preparation method of a nanochannel stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The mass ratio of each component in the spinning solution described in Step 1 is: 1) at least one stainless steel powder accounts for 42% - 54%; 2) at least one copper powder accounts for 6% - 18%; 3) at least one polymer binder accounts for 6% - 10%; 4) at least one organic solvent accounts for 30% - 34%; the sum of each component is 100%.

7. The preparation method of a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: For the solution spinning method described in Step 2, the spinning solution is continuously ball-milled in a ball mill, then transferred to a stainless steel syringe, degassed under vacuum, and quantitatively extruded from the hollow spinneret using mechanical power or compressed gas as the driving force. After passing through a 0 - 15 cm air bath, it enters a water or aqueous solution coagulation bath, with the core liquid being water or aqueous solution, and then undergoes solvent exchange (NIPS) for 24 - 48 h to obtain a solidified polymer hollow fiber precursor.

8. The preparation method of a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The programmed heating range described in Step 3 is 25°C - 1100°C, and the heating rate is 5 - 15°C / min; the sintering time at the highest temperature is 10 min - 120 min.

9. The preparation method of a nanoporous stainless steel alloy hollow fiber membrane according to claim 1, characterized in that: The gas atmosphere described in Step 3 is 99.999% reducing gas at 50 - 200 mL / min, and carbon monoxide or hydrogen with a purity of 99.999% can be selected.

10. The preparation method of a nanochannel stainless steel alloy hollow fiber membrane according to claim 7, characterized in that: The spinneret is a corrosion-resistant metal spinneret with an inner diameter of 1.0 - 1.5 mm, an outer diameter of 2.0 - 3.0 mm, and an inner core diameter of 0.5 - 0.9 mm.

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