POLYMER MEMBRANES INCORPORATED WITH CARRAGEENAN FOR WATER TREATMENT

Abstract

A polymer member is provided. The polymer membrane includes a polymer layer including a polysaccharide, such as, carrageenan. The polymer layer may further include one or more of polyethersulfone, polysulfone, and polyvilidenefluoride.

Claims

1. A polymer membrane comprising a polymer layer including a polysaccharide.

2. The polymer membrane according to claim 1, wherein the polysaccharide is carrageenan.

3. The polymer membrane according to claim 1, wherein the polymer layer includes one or more of polyethersulfone (PES), polysulfone (PS), and polyvilidenefluoride (PVDF).

4. The polymer membrane according to claim 3, wherein the polymer layer is loaded with carrageenan.

5. The polymer membrane according to claim 4, wherein the polymer membrane contains a bovine serum albumin (BSA).

6. The polymer membrane according to claim 1, wherein the polymer layer is derived from a phase inversion casting process.

7. The polymer membrane according to claim 4, wherein the polymer layer is loaded with 0.1 wt. % to 4 wt. % of the carrageenan.

8. The polymer membrane according to claim 4, wherein the polymer layer is loaded with approximately 0.5 wt. % of the carrageenan and a porosity of the polymer membrane is 60% or greater.

9. The polymer membrane according to claim 4, wherein the polymer layer is loaded with approximately 0.5 wt. % of the carrageenan and a contact angle of the polymer membrane is less than 50 degrees.

10. The polymer membrane according to claim 4, wherein the polymer layer is loaded with 0.5 wt. % to 4 wt. % of the carrageenan and a pure water permeability of the polymer membrane is more than 1200 LMH/bar.

11. The polymer membrane according to claim 5, wherein the polymer layer is loaded with 0.5 wt. % to 4 wt. % of the carrageenan and a BSA rejection is more than 97.5% with 200 ppm BSA solution.

12. The polymer membrane according to claim 5, wherein the polymer layer is loaded with at least 0.5 wt. % of the carrageenan and permeate flux with 200 ppm BSA solution is more than 250 LMH.

13. The polymer membrane according to claim 5, wherein the polymer layer is loaded with at least 0.1 wt. % of the carrageenan and fouling of the polymer membrane with 200 ppm BSA solution is more than 200% lower compared to a polymer membrane without the carrageenan.

14. The polymer membrane of claim 1, wherein the polymer membrane is an ultrafiltration membrane.

15. The polymer membrane of claim 14, wherein the polymer membrane is loaded with carrageenan.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0037] Features and advantages of the present disclosure, including a polymer membrane, described herein may be better understood by reference to the accompanying drawings in which:

[0038] FIG. 1 is an image of the chemical structure of carrageenan, according to an embodiment of the present disclosure.

[0039] FIG. 2(a) is a scanning electron microscope (SEM) image of the surface of a plain PES membrane, according to an embodiment of the present disclosure.

[0040] FIG. 2(b) is a SEM image of the surface of a PES membrane with 4 wt. % carrageenan, according to an embodiment of the present disclosure.

[0041] FIG. 2(c) is a SEM image of the cross-section of a plain PES membrane, according to an embodiment of the present disclosure.

[0042] FIG. 2(d) is a SEM image of the cross-section of a PES membrane with 4 wt. % carrageenan, according to an embodiment of the present disclosure.

[0043] FIG. 3 is a graph illustrating the total porosity of PES membranes incorporated with carrageenan at different loadings in casting solutions, according to an embodiment of the present disclosure.

[0044] FIG. 4 is a graph illustrating the water contact angle of PES membranes incorporated with carrageenan at different loadings of the additive in the casting solution as well as water contact angles of various commercial PES membranes, according to an embodiment of the present disclosure.

[0045] FIG. 5 is a graph illustrating the water fluxes of PES membranes incorporated with carrageenan at different loadings of the additive in casting solutions, according to an embodiment of the present disclosure.

[0046] FIG. 6 is a graph illustrating the BSA rejection of PES membranes incorporated with carrageenan at different loadings of the additive in casting solutions at operating pressure of 1 bar and BSA concentration of 20 ppm, according to an embodiment of the present disclosure.

[0047] FIG. 7 is a graph illustrating the permeate fluxes of PES membranes incorporated with carrageenan at different loadings of the additive in casting solutions during filtration of BSA solution at operating pressure of 1 bar and BSA concentration of 200 ppm, according to an embodiment of the present disclosure.

[0048] FIG. 8 is a graph illustrating the reduction in fouling of PES membranes incorporated with carrageenan at different loadings of the additive in casting solutions after filtration of 200 ppm BSA solution at operating pressure of 1 bar, according to an embodiment of the present disclosure.

[0049] The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of certain non-limiting embodiments of the present disclosure.

DETAILED DESCRIPTION

[0050] The present disclosure is generally related to a polymer membrane. More specifically, the present disclosure relates to a polymer member incorporated with a polysaccharide, such as a carrageenan, and for a number of suitable applications, such as for water treatment. Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are not intended to be drawn to scale.

[0051] As described herein, carrageenan refers to the natural linear sulfated polysaccharide as illustrated in FIG. 1. Carrageenan is highly hydrophilic organic compound bearing negatively charged sulfonic groups. Carrageenan may be sourced from edible red seaweeds. Carrageenan has widespread use in commercial sectors as a gelling, thickening, and stabilizing agent, primarily in food production and condiments. Additionally, it finds applications in experimental medicine, pharmaceutical formulations, cosmetics, and various industrial processes.

[0052] To improve the performance and antifouling resistance of polymer membranes, such as UF polymer membranes, carrageenan is added to a casting solution during the preparation of the polymer membrane.

[0053] To demonstrate the effectiveness of carrageenan as an additive to enhance the membrane properties, polyethersulfone (PES), polysulfone (PS), or polyvinylidene fluoride (PVDF) membranes are cast via a phase inversion method using a flat sheet membrane casting system. In the experiments, the solubility of PES and PS at different polymer loadings of 14-20 wt. % in dimethyl acetamide (DMAc) and dimethyl sulfoxide (DMSO) solvents were tested. DMSO is a better fit for PES membrane preparation because of higher PES solubility.

[0054] For membrane casting, the required PES amount is dissolved in DMSO solvent by stirring at room temperature for 6 hours. The amount of PES varies in the range of 14-20 wt. %. An additional set of the PES membrane is prepared with addition of 0.1 wt. % carrageenan to the PES/DMSO solutions. Prior to adding PES, carrageenan is dissolved with DMSO by sonication.

[0055] An ultrasonic processor by 60% ample with a pulse every 5 seconds is used to facilitate dispersion of carrageenan into the solvent for 45 minutes. Once complete, the 16 wt. % PES is dissolved in DMSO with the carrageenan (which had previously been dissolved by stirring at 60 C. for 5 hours).

[0056] This solution is then cast into a membrane via a phase inversion method on a glass plate by using a Q TQC Sheen Film Applicator. The membrane is cast, at thicknesses 200 m at casting speed of 20 cm/sec at room temperature. The glass plate with the cast membrane film is immersed in distilled water and kept until the membrane was detached from the glass plate. The membranes are then washed and kept in distilled water for 24 hours at room temperature to remove traces of the solvent.

[0057] The fabricated PES membranes incorporated with carrageenan are characterized by using scanning electron microscopy and tested by using contact angle, porosity, and filtration measurements.

[0058] FIGS. 2(a)-2(d) illustrate scanning electron microscope (SEM) images of plain PES without carrageenan and PES with 4 wt. % carrageenan membranes. FIG. 2(a) is a SEM image of the surface of a plain PES membrane, whereas FIG. 2(c) is a SEM image of the cross-section of the plain PES membrane. Similarly, FIG. 2(b) is a SEM image of the surface of a PES membrane with 4 wt. % carrageenan, whereas FIG. 2(d) is a SEM image of the cross-section of a PES membrane with 4 wt. % carrageenan.

[0059] As seen in FIGS. 2(a)-2(d), the top surface and the cross-section of the PES membrane embedded with carrageenan have larger pores than the PES membrane without addition of carrageenan. This could be due to essential increase of hydrophilicity of the casting solution at carrageenan loading. As a result, a sharp increase in solvent/nonsolvent exchange takes place when the cast polymer film is immersed in the coagulation bath, which leads to fast polymer precipitation and formation of the enlarged pores in PES sample incorporated with carrageenan.

[0060] It is found that incorporation of carrageenan in polymer matrix notably improve the total porosity of PES membranes. FIG. 3 displays the total porosity (%) of the fabricated PES/carrageenan membranes at different carrageenan loadings. The total porosity of the membranes is calculated by cutting the membranes to a set measured size before weighing the membranes wet (W.sub.w) (wiping excess deionized water droplets first) and then incubating them overnight at 45 C. The membranes are re-weighed the next day (W.sub.d). Multiple samples were weighed in order to obtain an average set of values. The total porosity () was calculated using the following equation: =((W.sub.wW.sub.d)/Al)*100.

[0061] As shown in FIG. 3, the addition of carrageenan had a profound impact on the total membrane's porosity of the prepared membranes. The PES membrane with 0.5 wt. %. carrageenan shows the highest value of the total porosity of about 60%, indicating a significant increase in the available pathways for water transport enhancing the membrane's filtration capabilities, while the total porosity value for the plain PES membrane without carrageenan is only about 35%. Remarkably, that the total porosity value for PES membrane with 0.5 wt. % carrageenan notably exceed the total porosity for commercial Microdin-Nadir PES 150 kDa membrane.

[0062] The incorporation of carrageenan in the polymer membrane matrix significantly increases the hydrophilicity of the membrane. FIG. 4 illustrates the contact angle values of the water droplet on the membrane's surface at different carrageenan loadings in the casting solutions. As shown in FIG. 4, the PES/carrageenan membrane having a 0.5 wt. % carrageenan loading shows the lowest value of the contact angle with a contact angle lower than 50 degrees. On the other hand, the plain PES without the addition of carrageenan shows the value of the contact angle of 62 degrees. This increased hydrophilicity is pivotal in reducing membrane fouling and ensuring the membrane's continuous operation in water treatment systems. It should be highlighted that water contact angle with PES/0.5 wt. % carrageenan membrane is notably lower compared to water contact angles for commercial Snider (PES 10 kDa) and Microdin-Nadir (PES 50 kDa and PES 150 kDa) membranes as shown in FIG. 4.

[0063] FIG. 5 illustrates the water fluxes of the fabricated PES membranes at different loadings of the carrageenan. The water fluxes are measured by using a Sterlitech HP4750X dead-end stirred cell (USA), and are pressurized under nitrogen gas. The water flux (J) was determined using the following equations: J=Q/AT, where Q is the total permeated volume collected in time T and A represents the effective cross-sectional area of the membrane in the filtration cell in m.sup.2.

[0064] It was found that the PES membranes incorporated with carrageenan exhibited high water flux values. FIG. 5 illustrates the water fluxes of the fabricated PES/carrageenan membranes at different loadings of the additive. As seen in FIG. 5, all PES/carrageenan membranes possess much higher water flux values compared to the plain PES membrane without carrageenan. For example, PES membranes casted at 0.5 wt. % and 4 wt % loading of carrageenan in dope solutions possess the flux values of 1200 and 1400 LMH respectively while the plain PES membrane without carrageenan shows the lowest value of the water flux of 560 LMH.

[0065] The PES membranes are also tested with a BSA solution of 20 ppm concentration. The BSA solution testing results in high rejection rates for unwanted substances, such as the BSA itself, ensuring the effective removal of the contaminant from water. The BSA rejection (R) was calculated by the following formula: R=(1C.sub.p/C.sub.f)*100, where C.sub.p is the concentration of BSA in the permeate and C.sub.f is the concentration of the BSA in the feed solution. A Shimadzu spectrophotometer at 258 nm was used to measure the optical density (OD) of the permeate and feed solutions.

[0066] FIG. 6 illustrates BSA rejection with the fabricated PES/Carrageenan membranes at different loadings of the additive at an operating pressure of 1 bar and at BSA concentration of 20 ppm. As seen in FIG. 6, the prepared PES/carrageenan membranes have BSA rejection values higher than 97.5%, while the BSA rejection with the plain PES membrane without carrageenan was the lowest at 88.5%.

[0067] The PES membranes incorporated with carrageenan exhibited notably higher permeate fluxes during filtration of BSA solutions. FIG. 7 illustrates the permeate fluxes of the fabricated PES/carrageenan membranes at different loadings of the additive at an operating pressure of 1 bar and BSA concentration of 20 ppm. As seen in FIG. 7, permeate flux values for PES/carrageenan membranes are much higher compared to the plain PES membrane without carrageenan. For example, PES membranes having a 0.5 wt. % and 4 wt. % loading of carrageenan in dope solutions possess the permeate flux values of 250 and 350 LMH, respectively, while the plain PES membrane without carrageenan shows the lowest value of the permeate flux of 150 LMH. These findings illustrate the improved efficiency and productivity of carrageenan incorporated membranes in water treatment applications.

[0068] Adding carrageenan to PES membranes plays a pivotal role in reducing membrane fouling which was evaluated using the following equation: Fouling=(1J.sub.f/J.sub.i)*100, where J.sub.f and J.sub.i are the water fluxes after and before filtration of BSA solution, respectively.

[0069] As seen in FIG. 8, the PES membranes incorporated with carrageenan showcased a remarkable reduction in fouling, up to 200% compared to the plain PES membrane without carrageenan. This reduction in fouling is crucial for maintaining the membrane's efficiency over time and minimizing the need for frequent maintenance and cleaning.

[0070] The prepared membranes showed higher resistance to BSA fouling than neat PES membranes, with a remarkable decrease in irreversible fouling while maintaining BSA rejection above 97% demonstrating high potential in treating protein-containing waters, which is of special importance in biotechnology and for treating wastewaters from dairy industry.

[0071] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.