Method for Preparing Antibacterial and Dust-removal Membrane

Abstract

This invention discloses a method for preparing an antibacterial and dust-removal membrane. The method comprises the following steps: depositing a layer of nano-ZnO on the immersed membrane surface as the seed crystal with the atomic layer deposition instrument (ALD instrument); vertically immersing the membrane covered with nano-ZnO layer in a hydrothermal reactor filled with crystal growth solution, heating it for a period of time, taking the membrane out and cooling it to the room temperate, and removing it from the substrate; finally, heating this membrane in a drier, and purging it with nitrogen to remove the paraffin within the membrane pore to obtain the porous membrane with nano-ZnO arrays growing on the surface.

Claims

1. A method for preparing an antibacterial and dust-removal membrane, comprising: (1)performing a pretreatment step including: washing an AAO porous membrane with an ethanol solution, and melting a paraffin solution for future use; (2)performing a pore blocking step including: adhering the pretreated AAO porous membrane on a substrate horizontally to prepare a sample, clamping the sample on a glass slide with a clamping slot, and immersing the glass slide having the sample in the paraffin solution and vibrating, taking the sample out after a period of time, cooling the sample to the room temperature with a surface exposed to the paraffin upward, using a hot smooth iron sheet to remove most of the paraffin on the surface of porous membrane, and removing the residual solid paraffin on the surface through plasma etching; (3)performing a crystal seeding step including: placing the AAO membrane in the reaction chamber of ALD instrument after it is ultrasonically cleaned with acetone, ethanol and deionized water, using the diethylzinc and deionized water as a precursor source respectively to provide zinc and oxygen required for the growth of ZnO, and using high purity nitrogen as a carrier and purging gas, starting deposition after it reaches to 15˜20 Pa, and keeping the deposition for a few hundreds cycles; (4) performing a crystal growth step including: preparing a mixed solution of hexamethylene tetramine and zinc nitrate at certain concentration in proportion as a growth solution, pouring the growing solution into a hydrothermal reactor, vertically placing the substrate with the AAO porous membrane covered with ZnO layer in the hydrothermal reactor, placing the hydrothermal reactor in a drier for treatment for a period of time, cooling naturally, taking the membrane out, washing the membrane-with deionized water, and drying it to obtain the porous membrane with nano-ZnO arrays on the surface; (5) performing a pore cleaning step including: removing the porous membrane obtained in Step (4) from the substrate, horizontally placing the membrane in a drier and ensuring that the side is covered with nano-ZnO arrays upwards, heating for a period of time, purging the membrane with nitrogen, cooling and obtaining a porous membrane with nano-ZnO arrays growing on the surface and having uniform permeable pores.

2. The method for preparing an antibacterial and dust-removal membrane of claim 1, wherein the pore diameter of AAO porous membrane in Step (1) is 0.1-10 μm; and the mass concentration of the ethanol solution is 80˜95%.

3. The method for preparing an antibacterial and dust-removal membrane of claim 1, wherein the immersion temperature in Step (2) is 60˜90° C., the immersion time is 3˜5 h; and the temperature of said hot iron sheet is 60˜70° C. and a gas mixture of CH.sub.4, H.sub.2 and Ar is adopted for said plasma etching, in which the molar ratio of the gases is 1:7:5; the flow of the gas is 26˜78 sccm; a bias power is 80˜90 W; a radio-frequency power is 250˜300 W; the etching speed is 10˜25 nm/min, and the etching time is 1˜2 h.

4. The method for preparing an antibacterial and dust-removal membrane of claim 1, wherein pulse time and washing time of said diethylzinc in Step (3) are 0.1˜0.2 s and 3˜4 s respectively; pulse time and washing time of the deionized water are 0.1˜0.2 s and 4˜5 s respectively; the flows of carrier gas of diethylzinc and deionized water respectively are 100˜150 sccm and 150˜200 sccm; the temperature of the substrate is 200˜280° C.; and the number of times for growing is 100˜200 cycles.

5. The method for preparing an antibacterial and dust-removal membrane of claim 1, wherein the concentrations of hexamethylene tetramine and zinc nitrate in said mixed solution in Step (4) are both 0.003˜0.1 mol/L; the molar ratio of hexamethylene tetramine and zinc nitrate in the solution is 1:1; and the addition dose of the mixed solution is 100˜500 ml.

6. The method for preparing an antibacterial and dust-removal membrane claim 1, wherein the temperature of said drier in Step (4) is 80˜100° C., and the treatment time is 2˜4 h.

7. The method for preparing an antibacterial and dust-removal membrane of claim 1, wherein the temperature of the said drier in Step (5) is 60˜90° C.; the flow rate of nitrogen is 0.4˜0.5 m/s, and the pressure is 0.5˜0.6 MPa.

Description

DESCRIPTION OF THE FIGURES

[0025] FIG. 1 is the process flow for preparing an antibacterial and dust-removal membrane.

[0026] FIGS. 2, 3 and 4 are the scanning electron microscopes of antibacterial and dust-removal membrane under different preparation conditions measured by scanning electron microscope S-4800.

EMBODIMENTS

[0027] The present invention is illustrated in combination with the following embodiments, which are only for illustration, not for limiting the scope of implementation.

Embodiment 1

[0028] (1) Pretreatment: washing the 0.1 μm AAO porous membrane by 80% (w/v) ethanol, and melting the paraffin for future use; [0029] (2) Pore blockage: adhering the pretreated AAO porous membrane on the substrate horizontally and closely, clamping on the glass slide with a clamping slot, and immersing the glass slide in the paraffin solution and vibrating, taking it out after immersing at a temperature of 70° C. for 3 h, cooling it to the room temperature with the surface exposed to paraffin upward, using a 60° C. hot smooth iron sheet to remove most of paraffin on the surface of porous membrane; using the gas mixture of CH.sub.4, H.sub.2 and Ar (with the molar ratio of 1:7:5) as etching gas, and removing the residual solid paraffin on the surface through plasma etching, in which the flow of gas used is 26 sccm; the bias power and radio-frequency power respectively are 80 W and 250 W; the etching rate and time are 10 nm/min and 120 min respectively; [0030] (3) Seeding: placing the AAO membrane in the reaction chamber of an ALD instrument after it is ultrasonically cleaned with acetone, ethanol and deionized water, using the diethylzinc and deionized water as the precursor source respectively to provide zinc and oxygen required for the growth of ZnO, and using the high purity nitrogen as the carrier and purging gas, in which the pulse time and washing time of diethylzinc are 0.1 s and 3 s respectively; the pulse time and washing time of the said deionized water are 0.1 and 4 s respectively; the flows of carrier gas of diethylzinc and deionized water are 100 sccm and 150 sccm respectively; the temperature of substrate is 200° C.; the number of time for growing is 100 cycles; and the deposition is started at the vacuum degree of 20 Pa; [0031] (4) Crystal growth: preparing the mixed solution of hexamethylene tetramine (with the concentration of 0.003 mol/L) and zinc nitrate (with the concentration of 0.003 mol/L) as the growth solution, in which the molar ratio of those substances is 1:1; pouring 100 ml mixed solution in a hydrothermal reactor, vertically placing the substrate with the AAO porous membrane covered with ZnO layer in the hydrothermal reactor, placing the hydrothermal reactor in the 80° C. drier to treat for 4 h, cooling it naturally, taking the membrane out, washing it with deionized water, and making it dry;

[0032] (5) Pore cleaning: removing the porous membrane obtained in Step (4) from the substrate, horizontally placing the membrane in a 60° C. drier and ensuring that the side is covered with nano-ZnO arrays upwards, purging the membrane with nitrogen with a flow rate of 0.4 m/s and pressure of 0.5 MPa, cooling it and obtaining the porous membrane with nano-ZnO arrays growing on the surface and uniform permeable pores.

[0033] The air purification membrane prepared in this Embodiment is measured by scanning electron microscope S-4800, as shown in FIG. 2. The surface of AAO membrane is formed with tapered granular ZnO crystal, and the air purification membrane is 0.2mm thick with a pore size of 0.2˜0.3 um. According to the antibacterial experiment [J. Membr. Sci. 2011, 369, 499], the antimicrobial effect is 96.49%, especially for positive bacteria and non-spore bacteria.

Embodiment 2

[0034] (1) Pretreatment: washing an 1 μm AAO porous membrane by 90% (w/v) ethanol, and melting the paraffin for future use; [0035] (2) Pore blockage: adhering the pretreated AAO porous membrane on the substrate horizontally and closely, clamping on the glass slide with a clamping slot, and immersing the glass slide in the paraffin solution and vibrating, taking it out after immersing at a temperature of 60° C. for 5 h, cooling it to the room temperature with the surface exposed to paraffin upward, using a 65° C. hot smooth iron sheet to remove most of paraffin on the surface of porous membrane; using the gas mixture of CH.sub.4, H.sub.2 and Ar (with the molar ratio of 1:7:5) as etching gas, and removing the residual solid paraffin on the surface through plasma etching, in which the flow of gas used is 39 sccm; the bias power and radio-frequency power respectively are 90 W and 300 W; the etching rate and time are 18 nm/min and 90 min respectively; [0036] (3) Seeding: placing the AAO membrane in the reaction chamber of an ALD instrument after it is ultrasonically cleaned with acetone, ethanol and deionized water, using the diethylzinc and deionized water as the precursor source respectively to provide zinc and oxygen required for the growth of ZnO, and using the high purity nitrogen as the carrier and purging gas, in which the pulse time and washing time of diethylzinc are 0.2 s and 4 s respectively; the pulse time and washing time of the said deionized water are 0.2 and 5 s respectively; the flows of carrier gas of diethylzinc and deionized water are 120 sccm and 170 sccm respectively; the temperature of substrate is 240° C.; the number of time for growing is 150 cycles; and the deposition is started at the vacuum degree of 15 Pa; [0037] (4) Crystal growth: preparing the mixed solution of hexamethylene tetramine (with the concentration of 0.025 mol/L) and zinc nitrate (with the concentration of 0.025 mol/L) as the growth solution, in which the molar ratio of those substances is 1:1; pouring 200 ml mixed solution in a hydrothermal reactor, vertically placing the substrate with the AAO porous membrane covered with ZnO layer in the hydrothermal reactor, placing the hydrothermal reactor in a 90° C. drier to treat for 3 h, cooling it naturally, taking the membrane out, washing it with deionized water, and making it dry; [0038] (5) Pore cleaning: removing the porous membrane obtained in Step (4) from the substrate, horizontally placing the membrane in a drier and ensuring that the side is covered with nano-ZnO arrays upwards, purging the membrane with nitrogen with a flow rate of 0.5 m/s and pressure of 0.6 MPa, cooling it and obtaining the porous membrane with nano-ZnO arrays growing on the surface and uniform permeable pores.

[0039] The air purification membrane prepared in this Embodiment is measured by scanning electron microscope S-4800, as shown in FIG. 3. The surface of AAO membrane is formed with filamentary ZnO crystal, and the air purification membrane is 0.4 mm thick with a pore size of 0.3˜0.4 um. According to the antibacterial experiment [J. Membr. Sci. 2011, 369, 499], the antimicrobial effect is 95.8%, especially for positive bacteria and non-spore bacteria; the membrane is good in inhibition to negative bacteria and spore bacteria.

Embodiment 3

[0040] (1) Pretreatment: washing a 10 μm AAO porous membrane by 95% (w/v) ethanol, and melting the paraffin for future use; [0041] (2) Pore blockage: adhering the pretreated AAO porous membrane on the substrate horizontally and closely, clamping on the glass slide with a clamping slot, and immersing the glass slide in the paraffin solution and vibrating, taking it out after immersing at a temperature of 90° C. for 5 h, cooling it to the room temperature with the surface exposed to paraffin upward, using a 70° C. hot smooth iron sheet to remove most of paraffin on the surface of porous membrane; using the gas mixture of CH.sub.4, H.sub.2 and Ar (with the molar ratio of 1:7:5) as etching gas, and removing the residual solid paraffin on the surface through plasma etching, in which the flow of gas used is 78 sccm; the bias power and radio-frequency power respectively are 90 W and 300W; the etching rate and time are 25 nm/min and 60 min respectively; [0042] (3) Seeding: placing the AAO membrane in the reaction chamber of an ALD instrument after it is ultrasonically cleaned with acetone, ethanol and deionized water, using the diethylzinc and deionized water as the precursor source respectively to provide zinc and oxygen required for the growth of ZnO, and using the high purity nitrogen as carrier gas and purging gas, in which the pulse time and washing time of diethylzinc are 0.2 s and 4 s respectively; the pulse time and washing time of the said deionized water are 0.2 and 5 s respectively; the flows of carrier gas of diethylzinc and deionized water are 150 sccm and 200 sccm respectively; the temperature of substrate is 280° C.; the number of time for growing is 200 cycles; and the deposition is started at the vacuum degree of 15 Pa; [0043] (4) Crystal growth: preparing the mixed solution of hexamethylene tetramine (with the concentration of 0.1 mol/L) and zinc nitrate (with the concentration of 0.1 mol/L) as the growth solution, in which the molar ratio of those substances is 1:1; pouring 500 ml mixed solution in a hydrothermal reactor, vertically placing the substrate with the AAO porous membrane covered with ZnO layer in the hydrothermal reactor, placing the hydrothermal reactor in the 100° C. drier to treat for 4 h, cooling it naturally, taking the membrane out, washing it with deionized water, and making it dry; [0044] (5) Pore cleaning: removing the porous membrane obtained in Step (4) from the substrate, horizontally placing the membrane in a drier and ensuring that the side is covered with nano-ZnO arrays upwards, purging the membrane with nitrogen with a flow rate of 0.5 m/s and pressure of 0.6 MPa, cooling and obtaining the porous membrane with nano-ZnO arrays growing on the surface and uniform permeable pores.

[0045] The air gas purification membrane prepared in this Embodiment is measured by scanning electron microscope S-4800, as shown in FIG. 4. The surface of AAO membrane is formed with even rodlike ZnO crystal, and the air purification membrane is 1 mm thick with a pore size of 0.1˜0.25 um. According to the antibacterial experiment [J. Membr. Sci. 2011, 369, 499], the antimicrobial effect is 97.2%, capable of inhibiting the growth and permeation of various kinds of bacteria.