Separation membrane, method for preparing the same and unit for purification

Abstract

A separation membrane for removing contaminants comprises: a hydrophobic membrane; and a graphene oxide layer formed to cover the hydrophobic membrane partially or wholly, wherein one surface of the hydrophobic membrane facing the graphene oxide layer has been hydrophilic-processed. The separation membrane is capable of enhancing removal efficiency on volatile contaminants, while maintaining a performance of the conventional separation membrane. The separation membrane is useful as a separation membrane for water treatment. Further, the separation membrane may be comprised in a membrane distillation apparatus, or may be utilized as a filter of a humidifier or a water purifier.

Claims

1. A method for preparing a separation membrane for removing contaminants, the method comprising: a hydrophilic-processing step of preparing a hydrophobic membrane having one hydrophilic-processed surface; and a graphene oxide layer forming step of forming a graphene oxide layer by applying a graphene oxide coating liquid containing graphene oxide particles onto the hydrophilic-processed surface of the hydrophobic membrane.

2. The method of claim 1, wherein the hydrophilic-processing step comprises a process of forming a hydrophilic-processed layer by applying a hydrophilic coating liquid containing a hydrophilic polymer, onto the hydrophobic membrane.

3. The method of claim 2, wherein at least one of a process of forming a graphene oxide layer by applying a graphene oxide coating liquid onto the hydrophilic-processed hydrophobic membrane, and a process of forming a hydrophilic-processed layer by applying a hydrophilic coating liquid onto the hydrophobic membrane is performed by a micro spray method selected from a group consisting of an air brush, a nebulizer, an atomizer, an electro-spray and combinations thereof.

4. The method of claim 1, wherein at least one of the hydrophilic-processing step, and the graphene oxide layer forming step is performed in a state where a temperature of the hydrophobic membrane is 20 C.50 C.

5. The method of claim 1, wherein the graphene oxide coating liquid comprises a solvent and graphene oxide particles, and wherein the solvent comprises one selected from a group consisting of water, ethylene glycol, dimethylformamide (DMF), methylpyrrolidone (NMP) tetrahydrofuran (THF) and combinations thereof.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a sectional view of a separation membrane for removing contaminants according to an embodiment of the present invention;

(2) FIG. 2 is a conceptual view illustrating an example where a unit for removing contaminants according to an embodiment of the present invention comprises an air gap as a gap portion, and a condenser as a cooling portion;

(3) FIG. 3 is a conceptual view illustrating an example where a unit for removing contaminants according to an embodiment of the present invention comprises an air gap as a gap portion, and cooling water as a cooling portion;

(4) FIG. 4 is a conceptual view of a humidifier according to an embodiment of the present invention;

(5) FIG. 5(a) is a frontal view of an evaporator used in experiments according to Example 1, and FIG. 5(b) is an upper view of the evaporator;

(6) FIG. 6 is a graph illustrating results on efficiency of removing ethanol measured in Experimental Example 1 of the present invention; and

(7) FIG. 7 is a graph illustrating results on evaporation rates on water and ethanol measured in Experimental Example 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

(8) Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. It will also be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

PREPARATION EXAMPLES

(9) 1. Preparation of Hydrophilic Coating Liquid and Graphene Oxide Coating Liquid

(10) 1 g of hydrophilic polymer, Polyvinyl alcohol (PVA, prepared by Aldrish Inc., 99+% hydrolyzed product, weight-average molecular weight of 89,00098,000 g/mol) was mixed with 1,000 g of water serving as a solvent. Then, the mixture was heated at a temperature of 90 C. or more than, thereby preparing a hydrophilic coating liquid containing 0.1 wt. % hydrophilic polymer.

(11) 2 g of graphene oxide was mixed with 1,000 g (or mol) of water serving as a solvent, thereby preparing 0.2 wt. % graphene oxide coating liquid.

(12) 2. Preparation of Separation Membrane for Removing Contaminants

(13) FIG. 1 is a sectional view of a separation membrane for removing contaminants 100. The separation membrane for removing contaminants 100 may include a graphene oxide layer 10, a hydrophilic-processed layer 30, and an hydrophobic membrane 20. FIG. 2 is a conceptual view illustrating an example where a unit for removing contaminants 500 comprises an air gap portion 400 and a condenser 310. The condenser 310 may be provided over the gap portion 400 and the separation membrane for removing contaminants 100 may be provided under the gap portion 400. A supplying portion 200 may be provided under the separation membrane for removing contaminants. FIG. 3 is a conceptual view illustrating an example where a unit for removing contaminants 500 comprises an air gap portion 400 and cooling water 320. The cooling water 320 may be provided over the gap portion 400. FIG. 4 is a conceptual view of a humidifier according to one embodiment including the unit for removing contaminants 500 as illustrated in FIGS. 2 and 3.

(14) Polytetrafluoroethylene (PTFE, prepared by Milipore Inc., having a diameter of 47 mm), a hydrophobic membrane 20 was fixed onto a heating plate, and the temperature of heating plate was maintained as 50 C. 1-2 ml of hydrophilic coating liquid was applied onto the hydrophobic membrane 20 using an air brush, and then was dried for 10 minutes, thereby forming a hydrophilic-processed layer 30 on the hydrophobic membrane.

(15) The graphene oxide coating liquid was applied onto the hydrophilic-processed layer 30 using an air brush, and then was dried for 30 minutes, thereby forming a graphene oxide layer 10. As a result, a separation membrane for removing contaminants 100 according to Example 1 was prepared.

EXPERIMENTAL EXAMPLES

(16) 1. Test for Removal of Volatile Materials by the Separation Membrane for Removing Contaminants according to Example 1

(17) FIGS. 5(a) and 5(b) are conceptual views of an evaporator used in Experimental Examples according to the present invention. Referring to FIGS. 5(a) and 5(b), the separation membrane 100 according to Example 1 was arranged so that one surface 110 of a hydrophilic membrane exposed to outside can be positioned at a supplying portion 200 of a reactor. Then, ethanol, a volatile organic solvent, is injected into the supplying portion 200, thereby measuring an evaporation amount of the volatile organic solvent according to time. The results, on whether volatile contaminants have passed through the separation membrane for removing contaminants 100 according to Example 1, were shown in FIG. 6.

(18) In Comparative Example 1, ethanol was injected into an evaporator having no separation membrane, in the same manner as in Example 1. The results thereof were shown in FIG. 6.

(19) In Comparative Example 2, experiments were conducted in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE, prepared by Milipore Inc.) serving as a hydrophobic membrane was used as a separation membrane. The results thereof were shown in FIG. 6.

(20) In Comparative Example 3, experiments were conducted in the same manner as in Example 1, except that a separation membrane obtained by forming only a PVA coating layer on the hydrophobic membrane according to Comparative Example 2 was used. The results thereof were shown in FIG. 6.

(21) FIG. 6 exhibits the results on Comparative Example 1 where no separation membrane has been installed, the results on Comparative Example 2 where only a hydrophobic membrane has been used, and the results on Comparative Example 3 where a PVA coating layer, a hydrophilic polymer has been formed on a hydrophilic membrane. Referring to FIG. 6, it could be verified that volatile contaminants were scarcely removed in Comparative Embodiments 2 and 3, because all of the ethanol (volatile material) was transmitted with the same ratio.

(22) 2. Test for Performance to Collect Water by the Separation Membrane for Removing Contaminants according to Example 1

(23) A test for a performance to collect vapor was conducted in Example 1 and Comparative Embodiments 13 in the same manner as in Experimental Example 1, using the same reactor. However, water rather than ethanol (volatile material) was supplied to the supplying portion of the reactor. And the results of a collect rate (evaporation rate) on water were shown in FIG. 7.

(24) Referring to FIG. 7, the separation membrane according to Example 1 exhibited an inferior collection rate on vapor per hour, than the separation membranes according to Comparative Embodiments 2 and 3. However, it could be verified that vapor was collected with a prescribed rate despite a formed graphene oxide layer.