WO2017215682A1

WO2017215682A1 - A polymeric matrix for the preparation of membranes and a membrane made of the polymeric matrix

Info

Publication number: WO2017215682A1
Application number: PCT/CZ2017/050024
Authority: WO
Inventors: Lukáš DVORÁK; Jan DOLINA
Original assignee: Technická univerzita v Liberci
Priority date: 2016-06-13
Filing date: 2017-06-13
Publication date: 2017-12-21
Also published as: CZ2016351A3; CZ306870B6

Abstract

The polymeric matrix for the preparation of membranes contains a solution of polyethersulfone, N-methyl-2-pyrrolidone and polyvinylpyrrolidone and further an organic additive selected from the group consisting of 1-([1,2,4]triazolo[1,5-c]quinazoline-2-ylthio)-3-(2-methoxyphenoxy) propan-2-ol, potassium 2-(furan-3-yl)-[1,2,4]triazolo[1,5-c]quinazoline-5-thiolate, 1-(4-chloro-2-(1H-tetrazol-5-yl)phenyl)-3-(3-(trifluoromethyl)phenyl) urea and 2-(3-(furan-2-yl)-1H-1,2,4-triazol-5-yl) aniline.

Description

A polymeric matrix for the preparation of membranes membrane made of the polymeric matrix

Field of the invention

The invention relates to a polymeric matrix for the preparation of membranes and a membrane made of the polymeric matrix. The membranes are suitable for application in the filtration of water containing microorganisms, for example in the filtration of surface water or wastewater.

Prior Art

Membranes are currently used in a wide range of industries, for example in the processing of technological liquids, drink water, seawater, utility water and wastewater.

One of the major problems associated with the application of membranes is the fouling of the membrane surface; this represents the greatest limitation of membrane technologies in general. This negative effect occurs not only when filtering biologically contaminated water (surface water or wastewater), but across all applications of membrane technologies. Membrane fouling is caused by mutual interaction between the membrane surface and the biological, organic, and inorganic compounds present in the suspension being filtered. The membrane fouling leads to a decrease in permeability (volume flowing through the membrane per unit area, per unit time and per unit driving pressure) . This results in a reduction of the economic efficiency of membrane processes, on one hand caused by the increase of operating costs (pressure increase, smaller volume of filtered water resulting in need of larger membrane areas and bigger tanks etc.), on the other hand by requiring more frequent chemical cleaning of membranes in order to remove fixed foulants.

Existing options used for mitigation of membrane fouling can be divided into two basic groups. The first one lies in a modification of the original surfaces of existing membranes. The second one is based on the principle of using new materials, and modified matrix compositions, from which the membranes are subsequently prepared. a) Surface modifications of existing membranes

Membrane surfaces have been modified, for example, by chemical or physico-chemical processes, thereby substantially altering their final properties in favour towards fouling resistance. For instance, plasma of nitrogen (Tang et al . , 2009), ammonia and carbon dioxide (Yu et al . , 2005a, b) or air plasma (Yu et al . , 2008) was used to modify existing membrane surfaces resulting in formation of new functional groups. Such modified surfaces exhibit higher resistance towards fouling. Surface modification performed by UV radiation also leads to the membranes exhibiting a lower tendency to the fouling (Mansourpanah et al . , 2013) .

Another possibility of membrane surface modification is so- called "molding" or "immobilization" technique. This allows preparation of thin films on the surface of the original membrane. For these purposes, polyvinyl alcohol, zirconium compounds, magnesium oxide, titanium dioxide and silver are typically used. Such modified surfaces exhibit greater fouling resistance compared to unmodified surfaces (Asatekin et al . , 2006) .

Other methods of surface modification include for example covalent crosslinking/binding which is based on formation of covalent bonding between the polymers. To initiate this reaction, heat, change of pH value or pressure is needed. The resulting properties are strongly dependent on the density of the crosslinking (Tripathi et al . , 2014, Ma et al . , 2007, Zhao et al . , 2011) .

Aforementioned techniques of the membrane surface modification have, however, a lot of disadvantages. Above all, they are consuming considerable energy, making the final membranes almost inapplicable in the commercial sphere. Another disadvantage are very complex reactions occurring on the surface of the modified membranes during their modification, so the course of reactions (modification) cannot be accurately controlled (Yu et al . , 2007) . b) Mixed matrix polymer membranes/additives incorporation

Preparation of membranes made of mixed matrix is another possibility of membrane modification. An example may be the incorporation of inorganic metallic nanoparticles into the polymer matrix, which results in lower tendency to fouling of the membrane surface (Yin and Deng, 2015) . A weak bond between incorporated metal nanoparticles and their compounds with the surrounding polymer matrix is, however, the main limitation of this method. It subsequently leads to leaching of particles and loss of the improved surface properties during membrane use .

Another possibility for the preparation of mixed matrix membranes is the subsidy of organic additives (Ghaemi et al . , 2012) . The advantage of organic additives is often their chemical affinity with the polymeric matrix. It enables to adjust the properties of the final membrane which are influenced by chemical and structural properties of those organic additives.

Polyethersulfone (PES) membranes have been modified by various inorganic and organic additives to date (Ahmad et al . , 2013) . Example of PES matrix modification lying on the boundary between inorganic and organic additives is modification by silica nanoparticles coated by poly ( 2-hydroxyethyl methacrylate ) (Zhu et al . , 2014) . Membranes doped by this additive prepared by phase inversion method showed an increase in permeability with clean water and a lower tendency to surface fouling. Another example is the use of N-halamines for modifying silica nanoparticles and their subsequent incorporation into the PES matrix (Yu et al . , 2013) . These membranes showed a higher hydrophilicity, a lower tendency to fouling, and antimicrobial properties towards pure culture of E. coli. Silica was also modified by polyvinylpyrrolidone (PVP, compound forming pores in membranes) and subsequently incorporated into the PES matrix (Sun et al . , 2009) . The results showed more porous membrane surface (higher porous density) compared to membrane with the addition of PVP alone.

From the organic additives, e.g. cellacefate (cellulose acetate phthalate) was used in the PES matrix (Rahimpour and Madaeni, 2007) . Mansourpanah et al . (2011) tested the use of organic additives in the form of multi-walled carbon nanotubes which were modified by polycaprolactone . After incorporation of these nanotubes into the PES matrix, an increase in hydrophilic properties and a lower tendency to surface fouling was observed. Balamurali and Preetha (2014) tested the addition of polyethylene glycol (PEG, 600 g -mol^-1) to the PES matrix. This additive resulted in an increase in surface hydrophilicity, pore size, and surface pore density of the active layer of the membrane. Rahimpour and Madaeni (2010) used hydrophilic monomers in the form of acrylic acid and 2- hydroxyethyl methacrylate. Their results showed that the presence of hydroxyl groups of both monomers led to an increase in membrane surface hydrophilicity.

Polyamide-imide (PAI) polymers have also been used to modify PES membranes (Rahimpour et al . , 2008) . The presence of amide and amine polar groups resulted in increased surface hydrophilicity . Increasing PAI/PES ratio led to an increase in the flow intensity through the membranes. Moreover, these membranes simultaneously showed a lower tendency to fouling.

Hydrophobic copolymers as poly ( 1-vinylpyrrolidone-co-styrene ) with different contents of 1-vinylpyrrolidone resulted in a homogeneous solution with PES matrix (Kim and Kim, 2005) . The results confirmed increased surface hydrophilicity and increased permeability of the membranes prepared from this mixed matrix.

Zhu et al . (2007) tested a styrene-based copolymer with maleic anhydride. As the additive increases, the hydrophilicity and roughness of the top layer of the membrane increased. Addition of amphiphilic copolymer of polystyrene and polyethylene glycol to PES membranes was subject of a study performed by Ma et al . (2007) . The results showed an increase in surface hydrophilicity and a lower tendency to fouling caused by proteins as parts of the polyethylene glycol molecules were present above the membrane surface.

Although the aforementioned organic additives have improved the surface properties of the PES membranes (usually increased hydrophilicity) , the resulting surfaces did not exhibit antimicrobial properties (or were not evaluated in those studies) in contrast to membranes doped by the organic additives, which are the subject of this invention.

Based on literature and patent survey, it is clear that the newly added organic additives from the group consisting of derivatives of heterocyclic aromatic compounds based on alcohols, diphenyl urea, esters and amines, and in particular derivates of [ 1 , 2 , 4 ] triazolo [ 1 , 5-c] quinazoline and derivates of 2- ( lff-tetrazol-5-yl ) aniline into the PES matrix are neither identical nor structurally identical with the organic compounds used as additives for the preparation of mixed PES membranes .

Thus, there is a clear need for further solutions in this filed, which would, on the one hand, satisfy the condition of significantly improved surface properties of the membranes, and which would be relatively easy to carry out under favourable economic conditions.

Summary of the invention

The inventors of the present invention have now unexpectedly found that to significantly eliminate the aforementioned problems with membrane fouling, the matrix used as standard for membrane preparation, containing a solution of polyethersulfone (PES), N-methyl-2-pyrrolidone (NMP) and polyvinylpyrrolidone (PVP) in the right ratio, is to be enriched with organic additive selected from the group consisting of certain derivatives of heterocyclic aromatic compounds based on alcohols, diphenyl urea, esters or amines, in particular an organic additive selected from the group consisting of derivates of [ 1 , 2 , 4 ] triazolo [ 1 , 5-c] quinazoline and derivates of 2- ( lff-tetrazol-5-yl ) aniline .

The sub ect-matter of the invention is a polymeric matrix for the preparation of membranes comprising a solution of polyethersulfone, N-methyl-2-pyrrolidone and polyvinylpyrrolidone and an organic additive selected from the group consisting of: 1- ( [l,2,4]triazolo[l,5-c] quinazoline-2-ylthio ) -3- ( 2- methoxyphenoxy) propan-2-ol (LA 178) of the formula

potassium 2- ( furan-3-yl ) - [1, 2, 4] triazolo [1, 5-c] quinazoline-5- thiolate (BK 55) of the formula

1- (4-chloro-2- ( lH-tetrazol-5-yl ) phenyl ) -3- (3- (trifluoromethyl) phenyl) urea (KB 213) of the formula

(3- (furan-2-yl) -lH-1, 2, 4-triazol-5-yl ) aniline (BK

.e formula

In one preferred embodiment, the polymeric matrix contains from 8 to 20 wt% of polyethersulfone, from 70 to 90 wt% of N- methyl-2-pyrrolidone, from 2 to 10 wt% of polyvinylpyrrolidone, always related to the total weight of the matrix, and further from 0.5 to 20 wt% of the additive, related to the weight of the polyethersulfone .

In a further preferred embodiment, the polymeric matrix contains from 8 to 12 wt% of polyethersulfone, from 80 to 88 wt% of N-methyl-2-pyrrolidone, from 4 to 8 wt% of polyvinylpyrrolidone, always related to the total weight of the matrix, and from 2 to 5 wt% of the additive, related to the weight of the polyethersulfone .

In a yet more preferred embodiment, the polymeric matrix contains 10 wt% of polyethersulfone, 83.8 wt% of N-methyl-2- pyrrolidone and 6 wt% of polyvinylpyrrolidone, related to the total weight of the matrix, and 2 % by weight based on the weight of the polyethersulfone, of the additive, or 10 wt% of polyethersulfone, 83.5 wt% of N-methyl-2-pyrrolidone, 6 wt% of polyvinylpyrrolidone, based on the total weight of the matrix, and 5 % by weight, based on the weight of the polyethersulfone, of the additive.

Most preferably, the additive is 1- ( [ 1 , 2 , 4 ] triazolo [ 1 , 5- c] quinazoline-2-ylthio) -3- (2-methoxyphenoxy) propan-2-ol of the formula

A further object of the invention is a membrane prepared from a polymeric matrix containing a solution of polyethersulfone, N-methyl-2-pyrrolidone and polyvinylpyrrolidone and an organic additive selected from the group consisting of 1- ( [l,2,4]triazolo[l,5-c] quinazoline-2-ylthio ) -3- ( 2- methoxyphenoxy) propan-2-ol, potassium 2- ( furan-3-yl ) - [ 1 , 2 , 4 ] triazolo [ 1 , 5-c] quinazoline-5-thiolate, 1- (4-chloro-2-

(lff-tetrazol-5-yl) phenyl ) -3- (3- ( trifluoromethyl ) phenyl ) urea and 2- ( 3- ( furan-2-yl ) -lH-1 , 2 , 4-triazol-5-yl ) aniline.

Incorporation of organic additive into the base polymer solution results in new properties of membrane surface (both outer and inner structure) prepared from this mixed polymeric matrix. Improved surface properties are positively reflected by increase in flow characteristics of the membranes compared to the membranes without incorporation of these organic additives, particularly when the membrane is in contact with biologically contaminated water or wastewater, i.e. in the presence of microorganisms. Moreover, the membranes prepared from the doped polymeric matrix retain high selectivity (separation properties) , internal structure and mechanical properties, such as membranes prepared from the polymer solution without the incorporation of the organic additive.

Clarification of drawings

Figures la and lb represent a comparison of the permeability over time for the reference and modified membranes in the test with activated sludge: a) 2 wt% of additive LA 178, b) 5 wt% of additive LA 178, always related to the weight of PES.

Figure lc displays a percentage comparison of the difference in the permeabilities of membranes doped by additive LA 178 and the reference membrane during filtration of activated sludge . Figures 2a and 2b represent a comparison of the permeability over time for the reference and modified membranes in the test with activated sludge: a) 2 wt% of additive BK 55, b) 5 wt% of additive BK 55, always related to the weight of PES.

Figure 2c displays a percentage comparison of the difference in the permeabilities of membranes doped by additive BK 55 and the reference membrane during filtration of activated sludge.

Figures 3a and 3b represent a comparison of the permeability over time for the reference and modified membranes in the test with activated sludge: a) 2 wt% of additive KB 213, b) 5 wt% of additive KB 213, always related to the weight of PES.

Figure 3c displays a percentage comparison of the difference in the permeabilities of membranes doped by additive KB 213 and the reference membrane during filtration of activated sludge .

Figures 4a and 4b represent a comparison of the permeability over time for the reference and modified membranes in the test with activated sludge: a) 2 wt% of additive BK 31; b) 5 wt% of additive BK 31, always related to the weight of PES.

Figure 4c displays a percentage comparison of the difference in the permeabilities of membranes doped by additive BK 31 and the reference membrane during filtration of activated sludge.

Examples of embodiments of the invention

It is to be understood that the examples described below are for illustrative purposes only and are not intended to limit the invention to these examples. Certainly, a person skilled in the art will be able to prepare equivalents to the specific embodiments of the invention described herein by means of routine experimentation. These equivalents are also included within the scope of protection defined by the following patent claims .

Example 1

The polymeric matrix according to the composition described in Table 1 below was prepared by the below mentioned process. As additive, 1- ( [1, 2 , 4] triazolo [1, 5-c] quinazoline-2-ylthio) -3- (2- methoxyphenoxy) propan-2-ol (LA 178) was used.

Table 1: Composition of polymeric matrix (weights of individual compounds are expressed in grams to prepare 30 g of polymeric matrix)

Compound PES PVP NMP Additive

Reference membrane 3 .00 1. ί 30 25. 20 -

Membrane with 2 wt%* dose of

3 .00 1. ί 30 25. 14 0. 06 additive

Membrane with 5 wt%* dose of

3 .00 1. ί 30 25. 05 0. 15 additive

weight of additive is related to the weight polyethersulfone (PES)

First, the additive was dissolved in N-methyl-2-pyrrolidonine (NMP) and mixed on a horizontal stirrer at 150 rpm. After 24 hours and subsequent sonication of the mixture for 20 minutes at 65 °C, polyvinylpyrrolidone (PVP) as pore-forming agent was added. The resulting solution was stirred for additional 24 hours at the same rpm. This was followed again by sonication (at the same conditions as above) , addition of the polyethersulfone (PES) and mixing on a horizontal stirrer at 150 rpm for another 24 hours. At the end, the resulting solution was again sonicated for 20 minutes at 65 °C. Such prepared matrix was used to prepare relevant membrane through the phase inversion method.

Example 2

The membranes prepared according to Example 1 were subjected to filtration tests with broad-spectrum of microorganism' s consortia. The activated sludge (mixed culture of various groups of micro-organisms) taken from the municipal wastewater treatment plant was used as the filtration medium. Testing was carried out by placing the membrane prepared according to Example 1 into a continuously stirred filtration cell. The fresh activated sludge taken from the aerobic part of the activation tank was diluted five times. Water from a stainless storage vessel at a constant pressure of 0.3 bar was pumped to the stirred filtration cell, so the volume of the medium, therefore both concentration of microorganisms and suspended solids, was kept constant throughout the test. The filtration cell was continuously stirred on a magnetic stirrer (100 rpm) during the test. During relaxation process, the filtration cell was depressurised and faster stirring (200 rpm) was simultaneously applied to clean fouled membrane surface more effectively. The process of relaxation was performed after 2, 4, 6 and 23 hours. At the same time, a filtration test with the reference membrane (without organic additive) was performed under identical conditions as the test with modified membrane .

The permeability of the membrane over time was compared to the permeability of reference membrane, and the results being recorded in Figures la and lb. It is clear from these figures that both membranes with additives showed higher permeabilities than unmodified membranes. Apparent difference was observed in both cases already after the third relaxation as both modified membranes showed a clearly higher permeability .

The percent permeability difference for reference membrane and membranes prepared according to Example 1 is shown in Figure lc. From the data shown above, it is clear that the additive had a significant positive effect and led to a significant improvement of the membrane properties against the fouling of its surface.

The separation properties of the modified membranes were not changed, as shown in Table 2.

Table 2: Results of retention of organic compounds (COD - chemical oxygen demand) - separation properties of membrane

COD [mg-1 ^χ]

Membrane Filtrate

Feed

(e luent)

Reference (2 wt%) 1298 19, 2

2 wt% of additive LA

1312 21,7

178

Reference (5 wt%) 987 12,3

5 % of additive LA

1108 2,76

178

Example 3

The polymeric matrix with composition described in Table 1 was prepared as described in Example 1 while using potassium 2- ( furan-3-yl ) - [1, 2, 4] triazolo [1, 5-c] quinazoline-5-thiolate (BK 55) , as the additive, and membranes were prepared from the matrix . Example 4

The membranes prepared according to Example 3 were subjected to the filtration tests in accordance with Example 2, the permeability (volume flowing through the membrane per unit area, per unit time and per unit driving pressure) over time was compared with the permeability of the reference membrane. The results are recorded in Figures 2a and 2b. The percent permeability difference for the reference membranes and membranes prepared according to Example 3 is shown in Figure 2c .

Example 5

The polymeric matrix with composition described in Table 1 was prepared as described in Example 1 while using 1- ( 4-chloro-2- (lff-tetrazol-5-yl) phenyl ) -3- (3- ( trifluoromethyl ) phenyl ) urea (KB 213) as the additive, and membranes were prepared from the matrix .

Example 6

The membranes prepared according to Example 5 were subjected to the filtration tests in accordance with Example 2, the permeability (volume flowing through the membrane per unit area, per unit time and per unit driving pressure) over time was compared with the permeability of the reference membrane. The results are recorded in Figures 3a and 3b. The percent permeability difference for reference membranes and membranes prepared according to Example 5 is shown in Figure 3c. Example 7

The polymeric matrix with composition described in Table 1 was prepared as described in Example 1 while using 2- ( 3- ( furan-2- yl ) -lH-1 , 2 , 4-triazol-5-yl ) aniline (BK 31) as the additive, and membranes were prepared from the matrix.

Example 8

The membranes prepared according to Example 7 were subjected to the filtration tests in accordance with Example 2, the permeability (volume flowing through the membrane per unit area, per unit time and per unit driving pressure) over time was compared with the permeability of the reference membrane. The results are recorded in Figures 4a and 4b. The percent permeability difference for reference membranes and membranes prepared according to Example 7 is shown in Figure 4c.

Industrial applicability

Polymeric membranes made of the aforementioned polymeric matrix and prepared by the phase inversion method showed much better flow properties/lower tendency to surface fouling during the test with biologically contaminated water than the reference membranes, i.e. the membranes without additive, consisting of PES, NMP and PVP only. Additionally, besides the positive effect on the membrane surface properties, incorporation of additives did not affect any other properties of the membrane, i.e. did not reduce its selectivity (separation ability), did not affect the internal structure or mechanical properties. The additive in the polymer matrix also did not influence the membrane preparation process. The membranes can be used especially for water filtration, including water with high concentrations of microorganisms, e.g. for the separation of biomass and treated wastewater in wastewater treatment plants, thus producing very high-quality water with economical operation of the whole technology.

References :

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Claims

PATENT CLAIMS

1. A polymeric matrix for the preparation of membranes containing a solution of polyethersulfone, N-methyl-2- pyrrolidone and polyvinylpyrrolidone, characterized in that it further contains an organic additive selected from the group consisting of 1- ([ 1 , 2 , 4 ] triazolo [ 1 , 5-c] quinazoline-2-ylthio ) - 3- (2-methoxyphenoxy) propan-2-ol, potassium 2- ( furan-3-yl ) - [1,2, 4] triazolo [1, 5-c] quinazoline-5-thiolate, 1- (4-chloro-2- (lff-tetrazol-5-yl) phenyl ) -3- (3- ( trifluoromethyl ) phenyl ) urea and 2- (3- ( furan-2-yl ) -lH-1, 2, 4-triazol-5-yl) aniline .

2. A polymer matrix according to claim 1, characterized in that it contains from 8 to 20 wt% of polyethersulfone, from 70 to 90 wt% of N-methyl-2-pyrrolidone, from 2 to 10 wt% of polyvinylpyrrolidone, all related to the total weight of the matrix, and further from 0.5 to 20 wt% of the additive related to the weight of polyethersulfone .

3. A polymer matrix according to claim 1, characterized in that it contains from 8 to 12 wt% of polyethersulfone, from 80 to 88 wt% of N-methyl-2-pyrrolidone, from 4 to 8 wt% by of polyvinylpyrrolidone, all related to the total weight of the matrix, and further from 2 to 5 wt% of the additive related to the weight of polyethersulfone .

4. A polymer matrix according to claim 1, characterized in that it contains 10 wt% of polyethersulfone, 83.8 wt % of N- methyl-2-pyrrolidone, 6 wt % of polyvinylpyrrolidone, all related to the total weight of the matrix, and further 2 wt% of the additive related to the weight of the polyethersulfone .

5. A polymer matrix according to claim 1, characterized in that it contains 10 wt% of polyethersulfone, 83.5 wt % of N- methyl-2-pyrrolidone, 6 wt% of polyvinylpyrrolidone, all related to the total weight of the matrix, and further 5 wt% of the additive related to the weight of the polyethersulfone .

6. A polymeric matrix according to any one of claims 1 to 5 characterized in that the additive is 1- ( [ 1 , 2 , 4 ] triazolo [ 1 , 5- c] quinazoline-2-ylthio ) -3- (2-methoxyphenoxy) propan-2-ol .

7. A membrane characterized in that it is prepared from a polymeric matrix according to any one of claims 1 to 6.