Method for producing composite modified membranes for removing dyes

Abstract

FIELD: membrane technology.SUBSTANCE: invention can be used for the preparation of composite membranes by the physical adsorption method for the purpose of using them for purification and separation of industrially significant process liquid media required for the chemical, food, pharmaceutical, petrochemical and other industries. A method for producing composite modified membranes for removing dyes involves applying a selective layer based on carboxymethyl cellulose onto a porous substrate based on polyphenylene isophthalamide, manufactured by a phase inversion method, by immersion in a coagulation bath with distilled water. As a selective layer, 0.5 wt.% carboxymethyl cellulose in distilled water is used, to which 5 wt.% modifier is added by introducing a dispersion of the modifier with a concentration of 20 g / l. The modifier is selected from graphene oxide, or graphene oxide modified with titanium dioxide, or graphene oxide functionalized with an amino group.EFFECT: increased efficiency in the production of composite modified membranes with higher productivity and a wider range of applications.1 cl, 1 tbl, 3 ex

Description

[0001] The invention relates to the field of membrane technology and can be used to prepare composite membranes by the physical adsorption method for use in the purification and separation of industrially significant process liquid media required for the chemical, food, pharmaceutical, petrochemical and other industries.

[0002] The state of the art in this area is presented on the basis of an analysis of patent information sources and scientific literature over the past 20 years, according to the results of which the closest analogues of methods for producing composite membranes were identified and selected [1-3].

[0003] A known method [1] for producing a composite polymer membrane, in which an ultrafiltration (porous) layer based on polysulfone or polyethersulfone is applied to a non-woven material, the surface of which is sequentially treated with an aqueous solution of piperazine with a concentration of 1-5% for 6-10 minutes, then with a solution of a mixture of trimesoyl chloride and isophthaloyl chloride, taken in a ratio of 1: 1 (weight), in an organic solvent medium with a concentration of 0.15-0.6% for 6-10 minutes, the treatment is carried out at 18-25 ° C. After forming an ultra-thin polymer selective layer, the resulting composite polymer membrane is dried at a temperature of 25-40 ° C for 8-15 minutes. The disadvantage of the known method is the use of a large number of reagents, which complicates the process of producing composite membranes.

[0004] A known method [2] for producing a composite nanofiltration membrane from a polymer mixture by interfacial polymerization (IP) occurring between polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and 1,6-hexamethylene diisocyanate (HDI) at ambient temperature. In this method, a porous substrate based on polysulfone (PS) was immersed in an aqueous solution of PVA / CMC, which was prepared in a 1 / 1 weight ratio of different concentrations (from 0.5 to 2.5 wt.%) and to which sodium dodecyl sulfate and NaOH (0.2 wt.%) were added, for 30 min, followed by drying in air for 40 minutes. Next, the membrane surface was rolled with a soft rubber roller to remove small bubbles. After this, the membrane was immersed in a solution of HDI in n-hexane (concentration 1.0 vol.%) for interfacial polymerization at room temperature for a certain time (from 5 to 40 min).The membrane was then heat-treated in an oven at a specific temperature (50 to 80°C for 30 minutes, or at 80°C for 15 or 30 minutes). A disadvantage of this method is the use of a toxic component, hydrochloric acid (HDI), which can irritate the skin, eyes, and respiratory tract. When heated, it decomposes, forming toxic and corrosive vapors and gases containing nitrogen oxides and hydrogen cyanide.

[0005] A method for preparing composite membranes is known, in which a selective layer based on carboxymethyl cellulose modified with metal-organic framework structures based on Zn (Zn(SEB), Zn(BDC)Si, Zn(BIM)) is applied to a porous substrate based on cellulose acetate (CA), polyphenylene isophthalamide (PA) and polyacrylonitrile (PAN) [3]. The composite membranes were prepared by the physical adsorption method by applying a 1 wt.% CMC solution, which was prepared by dissolving the polymer in distilled water at 40 °C with constant stirring, followed by ultrasonic treatment, onto porous membranes (substrates) made of CA, PA and PAN, followed by evaporation of the solvent at ambient temperature for 12 hours to form a thin, dense selective layer. Porous substrates of AC, PA and PAN were prepared without using polyester or non-woven substrate by the phase inversion method.To use the composite membranes in the nanofiltration of aqueous solutions, crosslinking of the CMC polymer chains was performed by immersing the composite membranes in an aqueous solution containing 1 wt.% glutaraldehyde (GA) and 0.5 wt.% sulfuric acid (H2SO4) for 1 min. The membranes were then air-dried for 30 min and then dried in a drying oven at 60°C for 10 min, followed by rinsing with distilled water. To prepare the modified composite membranes, 5 and 15 wt.% of Zn(SEB), Zn(BDC)Si, or Zn(BIM) were added to the CMC solution based on the polymer weight. This method is closest to the claimed invention in terms of its intended purpose and achievable technical result and is accepted as a prototype.

[0006] The disadvantage of the known method adopted as a prototype is the high concentration of metal-organic framework structures, the optimal amount of which is 15 wt.%. In addition, the composite membranes based on CMC obtained by this method showed insufficient water permeability of 0.04-0.43 kg / (m) during nanofiltration. 2 ⋅h⋅atm).

[0007] The technical result of the claimed method for producing composite modified membranes consists in increasing the efficiency of their production with higher productivity and a wide range of uses, for example, for removing organic dyes with high selectivity and permeability.

[0008] The specified technical result is achieved by applying a composite layer to a PA-based substrate, which is obtained by the phase inversion method, an aqueous solution of 0.5 wt.% CMC with the addition of 5 wt.% graphene oxide (GO) nanoparticles or GO modified with titanium dioxide (GO-TiO2) or GO functionalized with an amino group (GO-NH2). The method is characterized in that the CMC solution is used at a concentration of 0.5 wt.%.

[0009] The claimed invention was tested in laboratory conditions at the St. Petersburg State University, and its implementation is confirmed by the specific examples below.

[0010] Example 1. For the composite membrane with a CMC-based selective layer, a porous PA substrate was used, which was formed from a 15 wt.% PA solution in dimethylacetamide (DMA) (the PA solution in DMA was prepared by stirring at 90°C for 4 hours) using the phase inversion method by applying a thin layer of the PA solution to glass, followed by stretching it with a spinneret with a 200 μm gap and immersion in a coagulation bath with distilled water. After at least 12 hours, the porous substrate was ready for the application of the selective CMC layer. To do this, the PA porous substrate was stretched over an iron ring with the selective layer facing inward, secured with rubber bands, and left vertically in air for 30 minutes. Next, a 0.5 wt.% solution of CMC in distilled water (which was prepared by stirring at 40 °C for 6 hours) was applied to the substrate for 15 seconds, poured off and left to dry vertically in air.To use the membranes for water purification, cross-linking of polymer chains was used. For this purpose, the finished composite membrane was immersed in a solution of 1 wt.% GA with the addition of 0.5 wt.% H2SO4 in a water / isopropanol mixture (10 / 90 vol.%) for 5 min, followed by drying at 40 °C for 5 min. The resulting composite membrane is then ready for use. For a composite membrane with a selective layer based on CMC, modified with 5 wt.% GO, a dispersion of GO in water with a concentration of 20 g / L, which was prepared by dissolution using ultrasound for 3 hours, was added to the finished 0.5 wt.% CMC solution in distilled water.

[0011] Example 2. For a composite membrane with a selective layer based on CMC, modified with 5 wt% GO-TiO2, a porous PA-based support was used. A thin layer was applied via physical adsorption according to the procedure described in Example 1. To prepare a modified CMC solution, a dispersion of GO-TiO2 in water with a concentration of 20 g / L, prepared by dissolution using ultrasound for 3 hours, was added to a prepared 0.5 wt% CMC solution in distilled water.

[0012] Example 3. For a composite membrane with a selective layer based on CMC, modified with 5 wt% OG-NH2, a porous PA-based support was used. A thin layer was applied by physical adsorption according to the procedure described in Example 1. To prepare a modified CMC solution, a dispersion of OG-NH2 in water with a concentration of 20 g / L, prepared by dissolution using ultrasound for 3 hours, was added to a prepared 0.5 wt% CMC solution in distilled water.

[0013] The transport properties of composite membranes consisting of a thin CMC layer on a PA substrate, prepared according to the methods described in Examples 1-3, were determined in the process of nanofiltration of aqueous solutions of dyes with a concentration of 0.01 g / l: sunset yellow (SY), congo red (CR), brilliant blue (BS).

[0014] Permeability (J) kg / (m 2 ⋅h⋅atm) for membranes is calculated using the following equation: J = , where m is the mass of permeate (kg), A is the effective area (m 2 ), t is the time interval of nanofiltration (h), P is the pressure (atm).

[0015] The retention coefficient (R) characterizes the selective properties of the membrane and is calculated using the equation: R = (1 - )⋅100%, where c f - concentration of the initial solution and c p - permeate concentration.

[0016] Flow Recovery Rate (FRR) allows to evaluate the antifouling properties of membranes (fouling resistance) and is calculated using the equation: FRR = ( )⋅100%, where J w - the permeability of pure water before contact with the dye solution, and J R - permeability of pure water after passing a dye solution during a nanofiltration experiment.

[0017] The table presents the results of experiments (transport properties of the obtained membranes in the process of nanofiltration of water and dye solutions) using the example of 4 samples, including an unmodified CMC membrane and membranes modified with GO, or GO-TiO2, or GO-NH2.

[0018] Table

[0019] Transport properties of composite membranes in nanofiltration of water and dye solutions.

[0020] Composition of the composite layer Transport characteristics Initial solution water Housing and communal services KK BS CMC+OG J, kg / (m2⋅h⋅atm) 3,80 2,88 1,29 1,05 R,% - 99,9 99,3 95,7 FRR, % - 86 84 80 CMC+OG-TiO2 J, kg / (m2⋅h⋅atm) 1,26 1,11 1,06 1,00 R,% - 99,9 99,9 96,7 FRR, % - 92 91 90 CMC+OG-NH2 J, kg / (m2⋅h⋅atm) 3,30 1,73 1,00 0,86 R,% - 97,1 90,0 89,7 FRR, % - 50 42 42 KMC J, kg / (m2⋅h⋅atm) 1,64 1,40 0,78 0,67 R,% - 97,2 95,4 92,3 FRR, % - 90 85 86

[0021] As shown by the results of studies conducted in real time, and specific examples of the implementation of the claimed method, the obtained data on the transport properties of composite membranes confirm the qualitatively new possibilities of the claimed production method, and also, which is very important, high efficiency, productivity (water permeability of more than 1.26 l / (m 2 ⋅h⋅atm), dyes more than 0.67 l / (m 2⋅h⋅atm), selectivity (dye retention greater than 89%), and antifouling properties (flow recovery greater than 42%). The best transport properties were observed with the addition of GO to the thin selective layer. This method for producing composite membranes enables the production of membranes that are particularly in demand for the purification and separation of various process liquids in industries such as food, chemical, petrochemical, pharmaceutical, and other industries. Furthermore, the claimed method for producing composite modified membranes, compared to similar methods, offers greater productivity and a wider range of applications, for example, for the removal of organic dyes with high selectivity.

[0022] List of sources of information used:

[0023] 1) Patent RU 2492916C1, publ. 09 / 20 / 2013

[0024] 2) Miao J, Zhang R, Bai R. Poly (vinyl alcohol) / carboxymethyl cellulose sodium blend composite nanofiltration membranes developed via interfacial polymerization. Journal of Membrane Science. 2015; 493: 654-663. https: / / doi.org / 10.1016 / j.memsci.2015.07.031

[0025] 3) Dmitrenko M, Kuzminova A, Zolotarev A, Selyutin A, Ermakov S, Penkova A. Nanofiltration Mixed Matrix Membranes from Cellulose Modified with Zn-Based Metal-Organic Frameworks for the Enhanced Water Treatment from Heavy Metal Ions. Polymers. 2023; 15(6):1341. https: / / doi.org / 10.3390 / polym15061341 - (Прототип).

Claims

A method for producing composite modified membranes for removing dyes, comprising applying a selective layer based on carboxymethyl cellulose onto a porous substrate based on polyphenylene isophthalamide, manufactured by a phase inversion method, by immersion in a coagulation bath with distilled water, characterized in that 0.5 wt.% carboxymethyl cellulose in distilled water is used as the selective layer, to which 5 wt.% of a modifier selected from graphene oxide, or graphene oxide modified with titanium dioxide, or graphene oxide functionalized with an amino group is added, by introducing a dispersion of the modifier with a concentration of 20 g / l, obtained in water by dissolution using ultrasound for 3 hours.