Thin-film composite polyamide reverse osmosis membrane with anti-bacterial and anti-biofouling effects and preparation method thereof

Abstract

A thin-film composite polyamide reverse osmosis membrane with anti-bacterial and anti-biofouling effects and a preparation method thereof are disclosed. The preparation method includes: dissolving a highly water-stable metal organic framework CuBTTri in an n-hexane solution containing trimesoyl chloride by ultrasonic wave, immersing a polyethersulfone ultrafiltration membrane in an aqueous solution of m-phenylene diamine and taking out, and then immersing the ultrafiltration membrane in the trimesoyl chloride-n-hexane solution containing the aforementioned metal organic framework for reaction and modification, so as to obtain the thin-film composite polyamide reverse osmosis membrane. The resulting composite reverse osmosis membrane integrated with the anti-bacterial metal organic framework CuBTTri has a high reverse osmosis membrane permeability and possesses greatly improved and persistent anti-bacterial and anti-biofouling properties. The preparation method is simple and conducive to promotion, and has mild conditions.

Claims

1. A thin-film composite polyamide reverse osmosis membrane with anti-bacterial and anti-biofouling effects, comprising a substrate and a thin film, wherein the substrate is an ultrafiltration membrane, and the thin film is formed by loading an aromatic polyamide film containing a CuBTTri uniformly on a surface of the substrate, wherein the CuBTTri has a molecular formula of H3[(Cu.sub.4C1).sub.3-(BTTri).sub.8] and a structural formula of a backbone of the CuBTTri comprises Cu.sup.2+ and an organic ligand H.sub.3BTTri, the H.sub.3BTTri is 1,3,5-tri(1H-1,2,3-triazol-5-yl)benzene, and the H.sub.3BTTri has a structural formula of ##STR00003##

2. The thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 1, wherein the ultrafiltration membrane comprises at least one membrane selected from the group consisting of a polyacrylonitrile membrane, a polysulfone membrane, and a polyethersulfone membrane, and the ultrafiltration membrane has a molecular weight cutoff of 10-20 kDa.

3. A method for preparing the thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 1, comprising the steps of: i) synthesizing the CuBTTri, comprising the steps in order of: a) dissolving CuC1.sub.2.2H.sub.2O in a first organic solvent to obtain a copper chloride solution having a mass concentration of 3.8%-5.7%; b) dissolving the H.sub.3BTTri in a second organic solvent to obtain a first solution, and adding HC1 dropwise to the first solution to acidify to pH 3.0-4.5, to obtain a triazole solution having a mass concentration of 0.5%-1%; c) mixing the copper chloride solution prepared in step a) and the triazole solution prepared in step b) in a volume ratio of 1:(2-3) at 70-100° C. to react for 48-96 h to obtain a resultant; and d) centrifuging the resultant obtained in step c) at 7500-8500 rpm for 5-10 min to obtain a purple precipitate, and vacuum drying the purple precipitate for 12-24 h to obtain the CuBTTri; ii) preparing an aqueous solution of m-phenylene diamine having a mass concentration of 1.5%-2.5%; iii) ultrasonic dispersing the CuBTTri obtained in step i) in a trimesoyl chloride-n-hexane solution having a mass concentration of 0.1%-0.15%, to obtain an n-hexane solution of CuBTTri having a mass concentration of 0.05%-0.2%; iv) first immersing the ultrafiltration membrane in the aqueous solution of m-phenylene diamine obtained in step ii) to react for 1-2 min and taking out the ultrafiltration membrane, and removing the aqueous solution of m-phenylene diamine on a surface of the ultrafiltration membrane; and then immersing the ultrafiltration membrane in the n-hexane solution of CuBTTri obtained in step iii) to react for 30-60 s to form the thin film on the surface of the ultrafiltration membrane, and removing unreacted trimesoyl chloride on the surface of the ultrafiltration membrane to obtain the thin-film composite polyamide reverse osmosis membrane; and v) heat-treating the thin-film composite polyamide reverse osmosis membrane obtained in step iv) at 50-80° C., and then immersing the thin-film composite polyamide reverse osmosis membrane in deionized water at 4° C.

4. The method for preparing the thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 3, wherein the first organic solvent and the second organic solvent in step i) are identical solvents selected from the group consisting of N,N-dimethylformamide, tetrahydrofuran and N-methyl pyrrolidone.

5. The method for preparing the thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 3, wherein an immersion manner of immersing the ultrafiltration membrane in step iv) is a full immersion and the surface of the ultrafiltration membrane is oriented upward.

6. The method for preparing the thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 3, wherein the ultrafiltration membrane comprises at least one of a polyacrylonitrile membrane, a polysulfone membrane and a polyethersulfone membrane, and the ultrafiltration membrane has a molecular weight cutoff of 10-20 kDa.

7. The method for preparing the thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 6, wherein the first organic solvent and the second organic solvent in step i) are identical solvents or each solvent is selected from the group consisting of N,N-dimethylformamide, tetrahydrofuran and N-methyl pyrrolidone.

8. The method for preparing the thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 6, wherein an immersion manner of immersing the ultrafiltration membrane in step iv) is a full immersion and the surface of the ultrafiltration membrane is oriented upward.

9. A method of using the thin-film composite polyamide reverse osmosis membrane with the anti-bacterial and anti-biofouling effects of claim 1, comprising using the thin-film composite polyamide reverse osmosis membrane in water treatment.

10. The method of claim 9, wherein bacteria die when in contact with the thin-film composite polyamide reverse osmosis membrane, a surface of the thin-film composite polyamide reverse osmosis membrane is uniformly loaded with the aromatic polyamide film containing the CuBTTri to achieve sterilization or bacterial growth inhibition.

11. The method of claim 9, wherein the ultrafiltration membrane comprises at least one of a polyacrylonitrile membrane, a polysulfone membrane and a polyethersulfone membrane, and the ultrafiltration membrane has a molecular weight cutoff of 10-20 kDa.

12. The method of claim 11, wherein bacteria die when in contact with the thin-film composite polyamide reverse osmosis membrane, a surface of the thin-film composite polyamide reverse osmosis membrane is uniformly loaded with the aromatic polyamide film containing the CuBTTri to achieve sterilization or bacterial growth inhibition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing the preparation process and the product structure of a thin-film composite polyamide reverse osmosis membrane of the present invention.

(2) FIG. 2A-FIG. 2D show scanning electron microscope (SEM) images of the TFC, TFN-1, TFN-2 and TFN-3 membranes obtained in Embodiment 1.

(3) FIG. 2E shows the CuBTTri distribution.

(4) FIG. 3 is a graph showing the separation performance of the membranes TFC, TFN-1, TFN-2 and TFN-3 obtained in Embodiment 1.

(5) FIG. 4 is a graph showing the results measured by counting the colony forming units (CFU) after Pseudomonas aeruginosa is in contact with the membranes TFC, TFN-1, TFN-2 and TFN-3 obtained in Embodiment 1 for 24 h.

(6) FIG. 5 is a graph showing the water flux during the process that Pseudomonas aeruginosa is in contact with the TFC and TFN membranes obtained in Embodiment 1 for 24 h in cross-flow filtration cell.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention, not to limit the present invention.

Embodiment 1

(8) CuCl.sub.2.2H.sub.2O (383 mg) was dissolved in 15 mL N,N-dimethylformamide to obtain a copper chloride solution. H.sub.3BTTri (150 mg) was dissolved in 30 mL N,N-dimethylformamide to obtain a triazole solution, and the triazole solution was acidified to pH 3.0-4.5 by adding HC1 dropwise. The copper chloride solution and the acidified triazole solution were sufficiently mixed and reacted at 90° C. for 72 h after ultrasonic treatment for 10 min to obtain a metal organic framework CuBTTri. The CuBTTri was centrifuged at 8000 rpm for 8 min to obtain a purple precipitate, and then vacuum dried for 12 h. The resulting CuBTTri was Soxhlet extracted by deionized water for 24 h, and the organic solvent residual in the CuBTTri framework was removed. An m-phenylene diamine solution was dissolved in deionized water with a mass concentration of 2%. A 20 kDa polyethersulfone ultrafiltration membrane was used as a substrate, and the substrate was immersed in the m-phenylene diamine solution to react at 25° C. for 2 min and then taken out. An excessive m-phenylene diamine solution on the surface of the ultrafiltration membrane was blown away by nitrogen. Trimesoyl chloride was dissolved in n-hexane with a mass concentration of 0.1%. The resulting CuBTTri was dissolved in the trimesoyl chloride-n-hexane solution, and mass concentrations of CuBTTri were respectively 0.00%, 0.05%, 0.10% and 0.20%. An ultrasonic dispersion was performed for 45 min. The membrane was immersed in the n-hexane solutions of different CuBTTri concentrations to react at 25° C. for 45 s, and then an aromatic polyamide layer was formed by interfacial polymerization. The unreacted trimesoyl chloride solution on the membrane surface was removed using excessive n-hexane. The membrane was heat-treated at 70° C. for 5 min, to obtain a thin-film composite polyamide reverse osmosis membrane containing CuBTTri (denoted as TFC, TFN-1, TFN-2 and TFN-3, respectively). The membranes then were immersed in deionized water at 4° C. for at least 24 h for use, referring to FIG. 1.

Embodiment 2

(9) CuCl.sub.2.2H.sub.2O (383 mg) was dissolved in 15 mL N,N-dimethylformamide to obtain a copper chloride solution. H.sub.3BTTri (225 mg) was dissolved in 45 mL N,N-dimethylformamide to obtain a triazole solution, and the triazole solution was acidified to pH 3.0-4.5 by adding HC1 dropwise. The copper chloride solution and the acidified triazole solution were sufficiently mixed and reacted at 90° C. for 72 h after ultrasonic treatment for 10 min to obtain a metal organic framework CuBTTri. The CuBTTri was centrifuged at 8000 rpm for 8 min to obtain a purple precipitate, and vacuum dried for 12 h. The resulting CuBTTri was Soxhlet extracted by deionized water for 24 h, and the organic solvent residual in the CuBTTri framework was removed. An m-phenylene diamine solution was dissolved in deionized water with a mass concentration of 2%. A 10 kDa polysulfone ultrafiltration membrane was used as a substrate, and the substrate was immersed in the m-phenylene diamine solution to react at 25° C. for 2 min and then taken out. An excessive m-phenylene diamine solution on the surface of the ultrafiltration membrane was blown away by nitrogen. Trimesoyl chloride was dissolved in n-hexane with a mass concentration of 0.1%. The resulting CuBTTri was dissolved in the trimesoyl chloride-n-hexane solution, and mass concentrations of CuBTTri were respectively 0.00%, 0.05%, 0.10% and 0.20%. An ultrasonic dispersion was performed for 45 min. The membrane was immersed in the n-hexane solutions of different CuBTTri concentrations to react at 25° C. for 45 s, and then an aromatic polyamide layer was formed by interfacial polymerization. The unreacted trimesoyl chloride solution on the membrane surface was removed using excessive n-hexane. The membrane was heat-treated at 70° C. for 5 min to obtain a thin-film composite polyamide reverse osmosis membrane containing CuBTTri (denoted as TFC, TFN-1, TFN-2 and TFN-3, respectively). The membranes then were immersed in deionized water at 4° C. for at least 24 h for use.

Embodiment 3

(10) Membrane surface morphology test: the composite membranes obtained in Embodiment 1 were tested for the surface topography and the CuBTTri distribution by SEM-(energy dispersive x-ray) EDX, as shown in FIG. 2A-FIG. 2E. According to the test, the membranes TFC, TFN-1, TFN-2 and TFN-3 obtained in Embodiment 1 all presented a “ridge-valley” structure which was typical in reverse osmosis (RO) membranes, illustrating that the addition of CuBTTri did not significantly change the formation of the polyamide membrane, and CuBTTri and the polyamide membrane had high compatibility.

Embodiment 4

(11) Water permeability test: the membranes obtained in Embodiment 1 were chosen to carry out cross-flow filtration by a reverse osmosis cell under conditions of 1.6 MPa and 24° C. The effective membrane area was 20.02 cm.sup.2, the cross-flow rate was 22.0 cm/s, and the inflow was deionized water. The water permeability was recorded and calculated. The water permeability was defined as, under certain operating conditions, the volume of water permeating a unit membrane area in unit pressure and unit time, and the unit of the water permeability was L/(m.sup.2hbar). After the test was completed, the salt rejection rate was tested under the same conditions with 2000 mg/L NaCl solution as inflow. The salt rejection rate was equal to the difference between the salt concentration in the feed and permeatedivided by the salt concentration in the feed under certain operating conditions. The results were shown in FIG. 3.

(12) According to the test, the water permeability of the membranes TFN-1, TFN-2 and TFN-3 obtained in Embodiment 1 was significantly higher than the original membrane TFC, and increased with the increase of the concentration of the metal organic framework. It was demonstrated that the metal organic framework having high porosity can effectively improve the membrane permeability. Meanwhile, the salt rejection rate of TFN-2 reached 98% or more and was in the leading level of the reverse osmosis membrane reported at present. It was demonstrated that the introduction of CuBTTri can effectively improve the separating property of the thin-film composite polyamide membrane.

Embodiment 5

(13) Static anti-bacterial test: the membranes prepared in Embodiment 1 were measured for the anti-bacterial properties against Pseudomonas aeruginosa by using a CFU counting method. The operation was as follows: the membranes TFC, TFN-1, TFN-2 and TFN-3 obtained in Embodiment 1 were washed with a phosphate buffer solution and irradiated under an ultraviolet lamp for 30 min for sterilization. The membranes were immersed in 1 mL suspension of Pseudomonas aeruginosa (10.sup.6 CFU/mL) for 24 h under conditions of 150 rpm and 37° C. The membranes were taken out and the bacteria adsorbed on membrane surfaces were removed by sonication using a predetermined amount of phosphate buffer solution. The bacterial suspensions were diluted, 200 μL of the bacterial suspension was distributed on a LB agar plate, and cultured at a constant temperature of 37° C. for 12 h. The CFU was counted and the result was shown in FIG. 4.

(14) According to the test, the membranes TFN-1, TFN-2 and TFN-3 obtained in Embodiment 1 had significantly anti-bacterial properties compared with the original TFC membrane and had remarkable biocidal effects on Pseudomonas aeruginosa. It was demonstrated that the addition of the metal organic framework can effectively improve the anti-bacterial property of the membrane surface.

Embodiment 6

(15) Dynamic anti-bacterial test: the membranes TFC, TFN-1, TFN-2 and TFN-3 obtained in Embodiment 1 were chosen respectively to carry out cross-flow filtration by a reverse osmosis cell under conditions of 1.6 MPa and 24° C. for 24 h. The effective membrane area was 20.02 cm.sup.2, the cross-flow rate was 22.0 cm/s, and the feed was a Pseudomonas aeruginosa solution (6×10.sup.7 CFU/L). The change of the water flux during operation was monitored, and the result was shown in FIG. 5.

(16) As can be seen from the analysis of membrane permeability, the water flux of the TFN-1, TFN-2 and TFN-3 membranes obtained in Embodiment 1 reduced slowly compared to that of the original TFC membrane, illustrating that the TFN-1, TFN-2, TFN-3 membranes had significant anti-bacterial and anti-fouling effects.

(17) The foregoing descriptions are merely preferred embodiments of the present invention, and all variations and modifications made according to the scope of the present invention should fall into the scope of the present invention.