JP5900959B2 - Reverse osmosis membrane filter - Google Patents

Description

  The present invention relates to a reverse osmosis membrane filter.

  A reverse osmosis membrane is a kind of filtration membrane and is a membrane having a property of not allowing impurities other than water such as ions and salts to pass through water, and is used, for example, when pure water is obtained from seawater.

  The biggest problem in the practical application technology of reverse osmosis membranes is fouling caused by organic substances such as proteins and glycoproteins present in raw water passing through membranes such as seawater adsorb on the membranes and block the pores. When the membrane is contaminated with organic matter, a biofilm is formed on the membrane surface, leading to a decrease in salt rejection and permeated water. For this reason, the reverse osmosis membrane is currently washed with chemicals continuously or intermittently, and is mainly treated with a chlorine-based chemical such as sodium hypochlorite.

  At present, most of the reverse osmosis membranes used for seawater desalination and regeneration of treated wastewater are wholly aromatic polyamide membranes. However, in the wholly aromatic polyamide, the amide bond is cleaved and decomposed by chlorine, which causes a decrease in the salt rejection and an increase in the amount of permeated water in a short time. For this reason, in the reverse osmosis process, first, chlorine is injected into the raw water to remove organic substances, and after the raw water is supplied to the reverse osmosis membrane, free chlorine is reduced using a reducing agent and then supplied to the polyamide membrane. It has been broken. This cleaning system contributes to the increase in water production costs.

  Against this background, a reverse osmosis membrane excellent in chemical resistance, oxidation resistance, and heat resistance that does not require the above-described cleaning system is required.

  An inorganic material is a material having the above-mentioned properties, but there has been no example of applying an inorganic material as a reverse osmosis membrane so far. Inorganic membranes have a history of research with attention being paid to their excellent heat resistance, and are applied, for example, as gas separation membranes (for example, Patent Document 1). Non-Patent Document 1 reports on application to separation of n-butanol and water.

JP 2009-233540 A

Hydrostable stable molecular separation membranes from organically linked silica; Castricum, Ashima Sah, Robert Kreiter, Dave H. et al. A. Blank, Jaap F.B. Vente and Johan E. ten Elsof; Journal of Materials Chemistry, 2008, 18, 2150-2158.

  The gas separation membrane of Patent Document 1 is composed of a siloxane network with Si—O bonds. The Si—O bond is hydrolyzed in an aqueous solution. Therefore, this gas separation membrane has low water resistance and cannot be used as it is as a reverse osmosis membrane.

  In Non-Patent Document 1, separation is performed by pervaporation and water is permeated by evacuation of about 1 atm, so that it cannot be directly applied to a reverse separation membrane that requires high pressure.

  The present invention has been made in view of the above matters, and an object thereof is to provide a reverse osmosis membrane filter having excellent water resistance and chemical resistance.

The reverse osmosis membrane filter according to the present invention comprises:
An inorganic-organic hybrid reverse osmosis membrane having a —Si— C ₂ H ₄ —Si— bond or a —Si—C ₂ H ₂ —Si— bond ,
The NaCl blocking rate of the NaCl aqueous solution has a characteristic of 95% or more.
It is characterized by that.
(The NaCl rejection is a value determined by (1−C _p / C _f ) × 100, where C _p represents the NaCl concentration of the permeable NaCl aqueous solution, and C _f represents the NaCl concentration of the supplied NaCl aqueous solution .)

  Moreover, you may provide the said inorganic organic hybrid reverse osmosis membrane on the porous base material.

  Further, the porous substrate may be an inorganic porous substrate.

  Further, an intermediate having a pore smaller than the pore of the inorganic porous substrate and larger than the pore of the inorganic organic hybrid reverse osmosis membrane between the inorganic porous substrate and the inorganic organic hybrid reverse osmosis membrane. A layer may be provided.

  The reverse osmosis membrane filter according to the present invention includes an inorganic-organic hybrid reverse osmosis membrane having —Si—X—Si— bonds. X is a saturated or unsaturated alkyl chain, and the Si—C bond is stable even in an aqueous solution and does not hydrolyze. For this reason, a reverse osmosis membrane filter is excellent in water resistance. In addition, the inorganic-organic hybrid reverse osmosis membrane does not decompose even when subjected to chlorine load, and has excellent chemical resistance. For this reason, the water production cost at the time of obtaining pure water from seawater can be reduced.

It is a schematic diagram which shows schematic structure of an inorganic organic hybrid reverse osmosis membrane. In Example 1, the water permeability and blocking rate of BTESE300 (M1) (reverse osmosis membrane filter provided with an inorganic / organic hybrid reverse osmosis membrane obtained by polymerizing bistriethoxysilylethane and firing at 300 ° C.) for each aqueous solution. It is a graph to show. In Example 1, BTESE300 (M1) and BTESE100 (reverse osmosis membrane filters having an inorganic-organic hybrid reverse osmosis membrane obtained by polymerizing bistriethoxysilylethane and firing at 100 ° C.) for aqueous solutions having different solute molecular weights. It is a graph of a rejection rate. In Example 1, (A) is a graph showing the time-dependent changes in the water permeability and rejection rate of BTESE300 (M1) relative to the NaCl solution, and (B) is the time-dependent change in the water permeability and rejection rate of BTESE100 relative to the NaCl solution. It is a graph. In Example 1, (A) is a graph showing changes over time in the water permeability and rejection of BTESE300 (M1) with respect to the MgSO ₄ solution, and (B) shows changes over time in the water permeability and rejection of BTESE 100 with respect to the MgSO ₄ solution. It is a graph which shows. In Example 1, it is a graph which shows the time-dependent change of the water permeability of BTESE300 (M1) with respect to a glucose solution, and the rejection. In Example 1, it is a graph which shows the time-dependent change of the water permeability of BTESE300 (M1) with respect to an IPA solution, and a rejection. In Example 1, it is a graph which shows the change of the water permeability of BTESE300 (M1) with respect to the temperature change of a NaCl solution, and the rejection. In Example 1, (A) is a graph showing changes in the water permeability and blocking rate of BTESE300 (M1) with respect to changes in the supply pressure of the NaCl solution, and (B) is a water penetration of BTESE100 with respect to changes in the supply pressure of the NaCl solution. It is a graph which shows the change of a rate and a blocking rate. In Example 1, it is a graph which shows the relationship between the chlorine load of BTESE300 (M1), a water permeability, and a rejection. It is a graph which shows the relationship between the chlorine load of a polyamide reverse osmosis membrane and the rejection rate which are put into practical use. In Example 2, it is a graph of the blocking rate of BTESEthy (M1), BTESEthy (M2), and BTESE300 (M2) with respect to each aqueous solution from which the molecular weight of a solute differs. In Example 2, it is a graph which shows the time-dependent change of the water permeability of BTESEthy (M1) with respect to NaCl solution, and the rejection.

The reverse osmosis membrane filter according to the present embodiment is an inorganic material having —Si—X—Si— bonds (in FIG. 1, —Si—C ₂ H ₄ —Si— bonds), as shown in the schematic diagram of FIG. It has an organic hybrid reverse osmosis membrane. As will be described later, the inorganic-organic hybrid reverse osmosis membrane is obtained by hydrolyzing a compound such as bistriethoxysilylethane (hereinafter referred to as BTESE) or bistriethoxysilylethylene (hereinafter referred to as BTESEthy) and polymerizing by dehydration condensation. Water molecules pass through the pores (pore shown in FIG. 1) formed by, thereby preventing the passage of sodium ions, chloride ions, etc. dissolved in water.

The inorganic-organic hybrid reverse osmosis membrane is a membrane provided with -Si-O-, which is an inorganic component, and -X-, which is an organic component (-C ₂ H _4-in the example of FIG. 1), and will be described later. In addition, it has characteristics such as heat resistance and chemical resistance due to inorganic components, flexibility and film formability due to organic components.

  Since the Si—C bond provided in the inorganic / organic hybrid reverse osmosis membrane does not hydrolyze in an aqueous solution, the reverse osmosis membrane filter is excellent in water resistance.

  In addition, the inorganic-organic hybrid reverse osmosis membrane is excellent in thermal stability. There is no problem even through high temperature aqueous solution. Furthermore, when the separation is performed through an aqueous solution at a high temperature, the water permeability is improved without decreasing the blocking rate.

  In addition, the inorganic-organic hybrid reverse osmosis membrane has excellent chemical resistance. As described in Examples below, even when a chlorine load of 35000 ppmh is applied to the reverse osmosis membrane filter, water permeability and solute rejection are maintained. For this reason, when obtaining pure water from salt water, it is not decomposed by chlorine injected to prevent biofouling on the membrane. Therefore, the operation of reducing the free chlorine using a reducing agent after removing the organic substances by injecting chlorine into the raw water becomes unnecessary, so that the water increase cost can be reduced.

  In addition, since the inorganic / organic hybrid reverse osmosis membrane has high heat resistance, it can be used even when the temperature of the liquid to be separated is high, and the membrane can be washed at a high temperature. Furthermore, the higher the temperature of the liquid, the higher the water permeability and rejection.

Note that X in the —Si—X—Si— bond is a saturated or unsaturated alkyl chain in which one or more hydrogens may be substituted. X is preferably a linear saturated hydrocarbon residue, a linear olefinic hydrocarbon residue or a linear acetylene hydrocarbon residue. For example, a linear saturated hydrocarbon residue represented by C _n H _2n , a linear olefinic hydrocarbon residue represented by C _n H _(2n-2) , C _n H _(2n-4) And a linear acetylene hydrocarbon residue represented by the formula: In this case, n of the linear saturated hydrocarbon residue, that is, the number of carbon atoms is preferably 1 or more and 6 or less, more preferably 1 or more and 4 or less. Further, n of the linear olefinic hydrocarbon residue and the linear acetylene hydrocarbon residue is preferably 2 or more and 6 or less, more preferably 2 or more and 4 or less. This is because if the alkyl chain is long, it becomes a bent structure, the pore diameter formed tends to be non-uniform, and may not function as a reverse osmosis membrane.

  It is preferable that a reverse osmosis membrane filter is a form provided with an inorganic organic hybrid reverse osmosis membrane on a porous base material. This is because the inorganic-organic hybrid reverse osmosis membrane is not so high in self-supporting ability, and if it is intended to have self-supporting ability, the film thickness becomes thick and the water permeability may be lowered.

  As the porous substrate, an inorganic porous substrate such as ceramics, an organic porous substrate such as a heat-resistant polymer film, or the like having a mechanical strength that can withstand industrial use is used.

Examples of the inorganic porous substrate include ceramics made of alumina (α-Al ₂ O ₃ (α-alumina), γ-Al ₂ O ₃ (γ-alumina)), mullite, zirconia, titania, or a composite thereof. Can be mentioned. Of these, ceramics based on α-alumina, which is inexpensive and easily available, and has excellent chemical resistance, heat resistance, and strength, are preferred.

  In the case of an inorganic porous substrate, a three-layer structure in which an intermediate layer is provided between the inorganic porous substrate and the inorganic-organic hybrid reverse osmosis membrane is preferable. The pore diameter of the intermediate layer is preferably smaller than the pore diameter of the inorganic porous substrate and larger than the pore diameter of the inorganic-organic hybrid reverse osmosis membrane. Although the substance which comprises an intermediate | middle layer is not limited, A silica zirconia is mentioned as an example. By forming the inorganic-organic hybrid reverse osmosis membrane in this way, the film thickness of the inorganic-organic hybrid reverse osmosis membrane is made uniform, resulting in a reverse osmosis membrane filter exhibiting good performance.

  In addition, when the porous substrate is an organic porous substrate, the reverse osmosis membrane filter is excellent in flexibility and inexpensive compared to the inorganic porous substrate, so that the reverse osmosis membrane filter should be provided at a low cost. Can do. Examples of the organic porous substrate include polysulfone, polyethersulfone, polyimide, and polytetrafluoroethylene. As will be described later in the examples, firing is performed when forming the inorganic-organic hybrid reverse osmosis membrane, but a polymer membrane having heat resistance sufficient to withstand the firing temperature is preferable.

  The reverse osmosis membrane filter mentioned above can be manufactured as follows, for example.

A compound represented by (RO) ₃ SiXSi (OR) ₃ , for example, bisethoxysilylethane, bisethoxysilylbutane, bisethoxysilyloctane represented by (RO) ₃ SiC _n H _2n Si (OR) ₃ , _{(RO) 3 SiC n H (} 2n-2) Si (OR) compounds such as bis triethoxysilyl ethylene represented by _3, Bisuetokishi represented by _{(RO) 3 SiC n H (} 2n-4) Si (OR) 3 A compound such as silylacetylene is added to a solvent containing water to form a sol. Here, R represents an alkyl group. When this compound is added to water, the alkoxy group (OR) is hydrolyzed and adjacent compounds are polymerized by Si—O—Si bonds. More specifically, the above compound is dissolved in a water-containing solvent (such as ethanol), and an acid (hydrochloric acid, nitric acid, etc.) or a base (ammonia) is added as a catalyst, which is sufficient for hydrolysis and polycondensation reactions. The polymer sol can be prepared by stirring for a long time.

  A film-like inorganic-organic hybrid reverse osmosis membrane can be obtained by applying this sol to a glass substrate or the like and baking it. This gas separation membrane can be peeled off from a glass substrate or the like and used as a reverse osmosis membrane filter.

The firing temperature is lower than 400 ° C. This is because the alkyl chain of Si—C _n H _2n —Si disappears at 400 ° C. or higher. A preferable firing temperature is 100 ° C. or higher and 300 ° C. or lower. In this case, it is preferable to set a high firing temperature in the above temperature range. Since dehydration condensation proceeds more and the network becomes denser, the solute rejection rate is improved.

  Moreover, the reverse osmosis membrane filter of the 3 layer structure provided with the above-mentioned inorganic porous base material, an intermediate | middle layer, and an inorganic organic hybrid reverse osmosis membrane can be obtained as follows.

  First, an intermediate layer is formed on an inorganic porous substrate. It is preferable to form the intermediate layer after homogenizing the surface of the inorganic porous substrate. As a material used for homogenization, fine particles of the same material as the inorganic porous substrate may be used. For example, when alumina is used as the inorganic porous substrate, the alumina fine particles of the same material are used as the surface of the inorganic porous substrate. It is good to make it support and homogenize. The alumina fine particles are supported on the inorganic porous substrate by using a sol (for example, silica-zirconia colloidal sol) of the same material as that used for forming the intermediate layer as a binder, and dispersing the alumina fine particles in the binder to form an inorganic porous material. It may be performed by applying to the surface of the porous substrate, drying and firing. Moreover, it is preferable to perform the above-described process a plurality of times to homogenize the surface of the inorganic porous substrate. In this case, it is preferable to gradually reduce the size of the alumina fine particles dispersed in the binder.

  Subsequently, an intermediate layer is formed on the homogenized inorganic porous substrate. The intermediate layer may be formed by a hot coating method as follows. The inorganic porous substrate is heated to about 170 ° C to 180 ° C in advance, and a diluted solution of silica-zirconia colloidal sol is applied to the surface of the homogenized inorganic porous substrate, followed by baking to form an intermediate layer. it can. The silica-zirconia colloidal sol can be applied using a nonwoven fabric or the like. In order to obtain an intermediate layer having a desired thickness, the above process may be repeated a plurality of times.

Then, on the surface of the intermediate _layer, a sol obtained by dissolving a compound represented by _{(RO) 3 SiC n H 2n} Si (OR) 3 in water. The sol can be applied by various methods such as a spin coating method and a non-woven fabric dipped in a solution.

  And by baking with an electric furnace etc., an inorganic-organic hybrid reverse osmosis membrane is formed and the reverse osmosis membrane filter of a 3 layer structure can be obtained.

(Preparation of reverse osmosis membrane)
First, a porous α-alumina tube (length: 100 mm, outer diameter: 10 mm, average pore diameter: 1 μm, empty efficiency: 50%) was prepared as an inorganic porous substrate, and α-alumina as described below. After homogenizing the outer surface of the tube, an intermediate layer and an inorganic-organic hybrid reverse osmosis membrane were sequentially formed.

(Homogenization of porous substrate)
First, the outer surface of the α-alumina tube was homogenized by supporting alumina fine particles on the outer surface of the α-alumina tube. The support of the alumina fine particles was carried out in two steps by varying the average particle size of the alumina fine particles used (1.9 μm, 0.2 μm) as follows.

  Silica-zirconia colloidal sol (average particle size: about 50 nm, concentration: 2.0 wt%) diluted to 4 times with distilled water, alumina fine particles (Sumitomo Chemical Co., Ltd.) with an average particle size of 1.9 μm were about 10 wt. % (Hereinafter referred to as silica-zirconia colloidal sol A). In addition, silica fine particles having an average particle size of 0.2 μm (Sumitomo Chemical Co., Ltd.) were added to silica-zirconia colloidal sol (average particle size of about 50 nm, concentration 2.0 wt%) diluted four times with distilled water. It was dispersed so as to be about 10 wt% (hereinafter referred to as silica-zirconia colloid sol B).

  Silica-zirconia colloidal sol A was applied to the outer surface of the alumina tube using a non-woven fabric (Bencot (registered trademark), Asahi Kasei Co., Ltd.). Then, after drying at room temperature for 20 minutes and 180 ° C. for 10 minutes, it was baked in an electric tubular furnace (EKR-29K, Isuzu Seisakusho Co., Ltd.) at 550 ° C. in air for 15 minutes. This operation was performed twice.

  Subsequently, silica-zirconia colloid sol B was applied to the outer surface of the alumina tube using a nonwoven fabric. Then, after drying at room temperature for 20 minutes and 180 ° C. for 10 minutes, it was baked in an electric tubular furnace (EKR-29K, Isuzu Seisakusho Co., Ltd.) at 550 ° C. in air for 15 minutes. This operation was performed 3 times in total. As described above, the outer surface of the α-alumina tube was homogenized.

(Formation of intermediate layer)
Next, the α-alumina tube having a homogenized outer surface is heated to a high temperature (170 to 180 ° C.) in advance, and a silica-zirconia colloidal sol (average particle diameter of about 50 nm) is formed on the outer surface of the α-alumina tube using a nonwoven fabric. , A concentration of 2.0 wt%) diluted 4 times with distilled water was applied (hot coating method) and baked in air at a temperature of 550 ° C. for 15 minutes. This operation was repeated several times to form an intermediate layer (silica-zirconia) having a pore diameter of about several nm on the outer surface of the separation membrane support.

(Formation of reverse osmosis membrane)
Next, BTESE sol was prepared by adding BTESE to water. The molecular weight of the BTESE sol was about 5000 to 20000 wt / mol as measured by Zetasizer Nano (manufactured by Malverm).

  This BTESE sol was coated on the intermediate layer. And after drying, it baked at 300 degreeC for 30 minute (s) in nitrogen atmosphere, and formed the inorganic-organic hybrid reverse osmosis membrane. In this way, a reverse osmosis membrane filter was produced. Hereinafter, this reverse osmosis membrane filter is referred to as BTESE300 (M1).

  In addition, an inorganic-organic hybrid reverse osmosis membrane was formed under the same conditions as described above except that firing was performed at 100 ° C., and a reverse osmosis membrane filter was produced. Hereinafter, this reverse osmosis membrane filter is referred to as BTESE100.

  When BTESE300 (M1) and BTESE100 were observed with SEM photographs, no cracks could be confirmed. The thickness of the inorganic / organic hybrid reverse osmosis membrane was 100 nm or less.

  The following experiment was performed using BTESE300 (M1) and BTESE100 produced as described above.

(Experimental conditions)
As an aqueous electrolyte solution, an aqueous NaCl solution (2000 ppm) and an aqueous MgSO ₄ solution (2000 ppm), and as an aqueous neutral solute solution, an aqueous methanol solution (500 ppm), an aqueous ethanol solution (500 ppm), an aqueous IPA (isopropyl alcohol) solution (500 ppm), and n-butanol. An aqueous solution (500 ppm) and an aqueous glucose solution (500 ppm) were prepared.

  Each aqueous solution was supplied to BTESE300 (M1) and BTESE100, and crossflow filtration was performed. The supply pressure of each aqueous solution was 1.15 MPa, and the temperature of each aqueous solution was 25 ° C. And the water permeability (Water permeability) with respect to each aqueous solution of BTESE300 (M1) and BTESE100 and the rejection (Rejection) of each solute were calculated | required, and the characteristic was evaluated.

The water permeability L _p (m ³ / (m ² · s · Pa)) was determined by the following formula (1).
Lp = J _v / (ΔP−σΔπ) (1)
J _v is the aqueous solution through a filter flow rate ^{(L / (m 2 · h} )), ΔP-σΔπ is effective transmembrane pressure.
Further, Δπ (osmotic pressure difference) was obtained from the Phantohof equation (the following equation (2)).
Δπ = 2RT (C _f −C _p ) (2)
R is the gas constant, T is the absolute temperature, C _p is the concentration of the permeate liquid, and C _f is the concentration of the aqueous feed solution. C _p and _{C f} were respectively measured by the electric conductivity meter (ES-51, HORIBA Ltd.) and total organic carbon meter (TOC-VE, manufactured by Shimadzu).

The rejection rate R (%) was obtained from the following equation (3).
R (%) = (1−C _p / C _f ) × 100 (3)

(Verification of water permeability and rejection of various aqueous solutions)
FIG. 2 shows the water permeability and blocking rate for each aqueous solution of BTESE300 (M1). The NaCl aqueous solution, MgSO ₄ aqueous solution, isopropanol aqueous solution, and glucose aqueous solution showed a rejection of 95% or more. On the other hand, in the ethanol aqueous solution, the rejection was 76% or less. This is probably because the Stokes diameter of ethanol is 0.4 nm, which is smaller than other neutral solutes (IPA: 0.48 nm, glucose: 0.73 nm). From this result, it is considered that the molecular sieving effect is the main factor in the separation process of BTESE300 (M1).

(Verification of molecular weight cutoff)
Subsequently, FIG. 3 shows the relationship between the molecular weight of each solution and the rejection rate in BTESE300 (M1) and BTESE100. In FIG. 3, SW30HR and ES10 are data of a polyamide reverse osmosis membrane that has been put into practical use. Membr. Sci. 2011, 366, 62-72. "," Y. Kiso, K. Muroshige, T. Oguchi, M. Hirose, T. Ohara, T. Shintani, J. Membr. Sci. 2011, 369, "290-298."

  In FIG. 3, the 90% blocking rate indicated by the broken line is the so-called molecular weight cut-off (MWCO), but in BTESE100, it is about 84 g / mol, which is almost equivalent to a permeable membrane in practical use. , BTESE300 (M1) was about 55 g / mol. Therefore, it can be seen that it has good molecular sieving characteristics equivalent to or better than those of permeable membranes in practical use.

(Verification of stability over time)
A NaCl aqueous solution, a MgSO ₄ aqueous solution, an IPA aqueous solution, and a glucose aqueous solution were continuously supplied to verify the stability of BTESE300 (M1) and BTESE100 over time.

FIG. 4 shows changes with time in water permeability and rejection when an aqueous NaCl solution is supplied (FIG. 4A shows BTESE300 (M1) and FIG. 4B shows BTESE100). Further, FIG. 5 shows a change with time in water permeability and blocking rate when an aqueous MgSO ₄ solution is supplied (FIG. 5A shows BTESE300 (M1), and FIG. 5B shows BTESE100). Further, FIG. 6 shows the temporal change (BTESE300 (M1)) of the water permeability and the rejection when the IPA aqueous solution is supplied. Further, FIG. 7 shows the temporal change (BTESE300 (M1)) of the water permeability and the blocking rate when the glucose aqueous solution was supplied.

  In any case, it can be seen that there is almost no change in water permeability and rejection with time. Therefore, it can be seen that BTESE300 (M1) and BTESE100 can be used without degradation of the separation performance even after continuous use for a long time.

(Verification of thermal stability)
While the supply pressure of the NaCl aqueous solution was kept constant (1.15 Pa), the temperature of the NaCl aqueous solution was raised from 25 ° C. to 90 ° C., and then the temperature was lowered from 90 ° C. to 25 ° C. to verify the thermal stability.

  FIG. 8 shows changes in water permeability and rejection with respect to changes in the temperature of the supplied NaCl aqueous solution in BTESE300 (M1). As shown in FIG. 8, the water permeability improved as the temperature of the NaCl aqueous solution increased. Further, the rejection rate was 97.3% at 25 ° C., but this was also improved to 98.2% at 90 ° C.

  In a general polyamide permeable membrane, the blocking rate tends to decrease as the temperature increases. The reason is considered as follows. At high temperatures, the pore size of the membrane increases and it becomes easy to pass even with large molecules, and Na ions and Cl ions gain energy and easily pass through the membrane, so the water permeability is relatively reduced. As a result, the rejection rate is considered to decrease.

  However, in BTESE300 (M1), as described above, the water permeability and rejection are higher as the temperature is higher. In BTESE300 (M1), it is considered that the pore diameter of the membrane does not change in the above temperature range, and water is more likely to pass through than Na ions and Cl ions due to a decrease in water viscosity. Thus, it can be seen that BTESE300 (M1) has high thermal stability and a wide adaptive temperature range. In addition, since the thermal stability is high, high-temperature film cleaning is also possible.

(Verification of pressure dependence)
Using NaCl aqueous solution, supply pressure was changed in the range of 0.7 MPa to 1.5 MPa, and the pressure dependency of BTESE300 (M1) and BTESE100 was verified.

  FIG. 9 shows changes in water permeability and rejection with respect to changes in the supply pressure of the NaCl aqueous solution (FIG. 9A shows BTESE300 (M1), and FIG. 9B shows BTESE100).

  When the supply pressure is increased, the rejection rate is slightly improved, but the water permeability is maintained at a substantially constant characteristic.

(Verification of chemical resistance)
A commercially available sodium hypochlorite solution (NaClO, active chlorine: 10%) was used to verify the chemical stability of BTESE300 (M1).

The sodium hypochlorite solution was used by adjusting the chlorine concentration to 100 ppm, 500 ppm, and 1000 ppm. Moreover, the pH of the sodium hypochlorite solution was adjusted to 7 using 0.2M KH ₂ PO ₄ buffer.

  BTESE300 (M1) was immersed in the adjusted sodium hypochlorite solution for a predetermined time to give various chlorine loads. Thereafter, BTESE300 (M1) was taken out and washed, and after removing the sodium hypochlorite solution, a NaCl solution (2000 ppm, 1.15 MPa) was supplied in the same manner as described above to obtain water permeability and blocking rate.

  FIG. 10 shows the relationship between chlorine load, water permeability, and rejection. FIG. 11 shows, as a reference example, the relationship between the chlorine load and the rejection rate of a polyamide reverse osmosis membrane (SW30HR, Dow FilmTec) that has been put into practical use. The graph shown in FIG. 11 is quoted from “Ho Bum Park, Benny D. Freeman, Zhong-Bio Zhang, Mehmet Sankir, and James E. McGrath; Angew. Chem. 2008, 120, 6108-6113”.

  Referring to FIG. 11, in the reverse osmosis membrane made of polyamide, after exceeding 5000 ppmh, the rejection rate is significantly reduced as the chlorine load increases. It can be seen that the amide bond is cleaved and decomposed by chlorine, and there is no chemical resistance.

  On the other hand, FIG. 10 shows that in BTESE300 (M1), even when the chlorine load is 35000 ppmh (corresponding to the state of being exposed to a 1 ppm chlorine solution for 4 years), the water permeability and the rejection are almost unchanged and stable. Maintained performance. Therefore, BTESE300 (M1) has excellent chemical resistance, and it is possible to use a disinfectant such as hypochlorous acid, which is impossible with a polyamide permeable membrane.

  An inorganic-organic hybrid reverse osmosis membrane was prepared using BTESEty. First, in the same manner as in Example 1, the outer surface of the α-alumina tube was homogenized.

  An α-alumina tube having a homogenized outer surface is heated to a high temperature (170 to 180 ° C.) in advance, and a silica-zirconia colloidal sol (average particle diameter of about 50 nm, concentration 2 is used on the outer surface of the α-alumina tube using a nonwoven fabric. (0.0 wt%) diluted 4 times with distilled water (hot coating method) was applied and baked in air at a temperature of 550 ° C. for 15 minutes. This operation was repeated 12 times to form an intermediate layer (silica-zirconia) on the outer surface of the homogenized α-alumina tube.

(Formation of reverse osmosis membrane)
Next, BTESEthy, water, ethanol and hydrochloric acid as a catalyst were mixed and stirred at 40 ° C. for 1.5 hours to prepare a BTESEthy sol. The mixing ratio of BTESEthy, water, ethanol, and hydrochloric acid was 1: 60: 122: 0.2 in molar ratio.

  This BTESETY sol was coated on the intermediate layer. And after drying, it baked for 20 minutes at 300 degreeC by nitrogen atmosphere. This operation was performed twice to form an inorganic-organic hybrid reverse osmosis membrane. In this way, a reverse osmosis membrane filter was produced. Hereinafter, this reverse osmosis membrane filter is referred to as BTESEthy (M1).

  In order to confirm reproducibility, a reverse osmosis membrane filter was prepared in the same manner as described above. Hereinafter, this reverse osmosis membrane filter is referred to as BTESEthy (M2).

  Further, a reverse osmosis membrane filter was prepared in the same manner as described above except that BTESEty was replaced with BTESE. Hereinafter, this reverse osmosis membrane filter is referred to as BTESE300 (M2).

  The following experiment was performed using BTESEthy (M1), BTESEthy (M2), and BTESE300 (M2) produced as described above.

(Verification of molecular weight cutoff)
A methanol aqueous solution (500 ppm), an ethanol aqueous solution (500 ppm), an IPA (isopropyl alcohol) aqueous solution (500 ppm), and a glucose aqueous solution (500 ppm) were prepared. Each aqueous solution was supplied to BTESEthy (M1), BTESEthy (M2), and BTESE300 (M2), and crossflow filtration was performed. The supply pressure of each aqueous solution was 1.15 MPa, and the temperature of each aqueous solution was 25 ° C. And the rejection of each solute with respect to each aqueous solution of BTESEthy (M1), BTESEthy (M2), and BTESE300 (M2) was calculated | required. The blocking rate was obtained by the same method as in Example 1.

  FIG. 12 shows the relationship between the molecular weight of each solution and the blocking rate in BTESEthy (M1), BTESEthy (M2), and BTESE300 (M2). In FIG. 12, SW30HR is data of a reverse osmosis membrane made of polyamide that has been put into practical use. “ES Hatakeyama, CJ Gabriel, BR Wiesenauer, JL Lohr, MJ Zhou, RD Noble, DL Gin, J. Membr Sci. 2011, 366, 62-72. "," Y. Kiso, K. Muroshige, T. Oguchi, M. Hirose, T. Ohara, T. Shintani, J. Membr. Sci. 2011, 369, 290- 298. "

  The fractional molecular weights of BTESETHY (M1), BTESETHY (M2), and BTESETHY (M2) (molecular weight with a blocking rate of 90% indicated by the broken line in FIG. 12) are all about 60 g / mol. It can be seen that it has better molecular sieving properties than the membrane (SW30HR).

(Verification of stability over time)
An aqueous NaCl solution (2000 ppm, 25 ° C.) was continuously supplied to BTESEthy (M1) (supply pressure 1.15 MPa), water permeability and rejection were measured over time, and the stability of BTESEthy (M1) over time was improved. Verified. In addition, the water permeability and the blocking rate were obtained by the same method as in Example 1, respectively.

  The result is shown in FIG. It can be seen that the water permeability and rejection with time are almost constant and unchanged. Therefore, it can be seen that the separation function of BTESEthy is not impaired and can be used for continuous use for a long time.

  The reverse osmosis membrane filter can be used for separation of various liquids such as separation of pure water from seawater.

Claims (4)

An inorganic-organic hybrid reverse osmosis membrane having a —Si— C ₂ H ₄ —Si— bond or a —Si—C ₂ H ₂ —Si— bond ,
The NaCl blocking rate of the NaCl aqueous solution has a characteristic of 95% or more.
The reverse osmosis membrane filter characterized by the above-mentioned.
(The NaCl rejection is a value determined by (1−C _p / C _f ) × 100, where C _p represents the NaCl concentration of the permeable NaCl aqueous solution, and C _f represents the NaCl concentration of the supplied NaCl aqueous solution .) Comprising the inorganic-organic hybrid reverse osmosis membrane on a porous substrate;
The reverse osmosis membrane filter according to claim 1 . The porous substrate is an inorganic porous substrate;
The reverse osmosis membrane filter according to claim 2 . An intermediate layer having pores smaller than the pores of the porous substrate and larger than the pores of the inorganic organic hybrid reverse osmosis membrane is provided between the inorganic porous substrate and the inorganic-organic hybrid reverse osmosis membrane. ,
The reverse osmosis membrane filter according to claim 3 .

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