Detailed Description
In view of the deficiencies in the prior art, the inventors of the present invention have made extensive studies and extensive practices to provide technical solutions of the present invention. The technical solution, its implementation and principles, etc. will be further explained as follows.
As one aspect of the technical solution of the present invention, there is provided a method for preparing a high flux forward osmosis hollow fiber membrane, comprising:
providing a mixed reaction system at least comprising a polymer, a functional monomer, an initiator, an additive and a solvent, and heating the mixed reaction system in a protective atmosphere to enable the functional monomer to generate polymerization-crosslinking reaction to form a semi-interpenetrating network structure to obtain a spinning solution;
and co-extruding the spinning solution and a core solution containing an acyl chloride monomer through a spinning nozzle, then immersing the spinning solution and the core solution into a coagulating bath containing an amine monomer for solidification to form a hollow fiber membrane, and enabling the acyl chloride monomer and the amine monomer to instantly generate interfacial polymerization on the inner wall and the outer wall of the hollow fiber membrane while solidifying to form a membrane to generate a loose ultrathin polyamide functional layer, thereby obtaining the high-flux forward osmosis hollow fiber membrane.
In some embodiments of the invention, the method of making comprises:
(1) uniformly mixing at least a polymer, a functional monomer and an additive in a solvent in a protective atmosphere, heating to 20-130 ℃, adding an initiator, and reacting at 60-150 ℃ for 0.5-60 hours to enable the functional monomer to perform polymerization-crosslinking reaction to form a semi-interpenetrating network structure, thereby obtaining a spinning solution;
(2) and (2) taking an acyl chloride monomer solution as a core solution, taking an amine monomer solution as a coagulating bath, co-extruding the spinning solution obtained in the step (1) and the core solution through a spinning nozzle, staying in the air for 0.5-60 seconds, then immersing into the coagulating bath for solidification to form a film, and carrying out heat treatment at 60-120 ℃ for 0.5-10 minutes to obtain the high-flux forward osmosis hollow fiber film.
In some embodiments, the mixed reaction system comprises 5 to 35wt% of polymer, 0.5 to 15wt% of functional monomer, 0.1 to 5wt% of initiator, 0.01 to 20wt% of additive, and the balance comprising solvent.
Preferably, the polymer includes any one or a combination of two or more of polysulfone, sulfonated polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyvinylidene fluoride, cellulose acetate, and the like, but is not limited thereto.
Preferably, the functional monomer includes any one or a combination of two or more of acrylic acid, methacrylic acid, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, acrylamide, hydroxyethyl methacrylate, polyethylene glycol methyl ether methacrylate, N-vinyl pyrrolidone, N-isopropyl acrylamide, and the like, but is not limited thereto.
Preferably, the additive includes any one or a combination of two or more of polyethylene glycol, polyoxyethylene, polyethyleneimine, graphene, carbon nanotube, silica nanoparticle, titania nanoparticle, gold nanoparticle, N' -methylenebisacrylamide, and the like, but is not limited thereto.
Preferably, the initiator includes azobisisobutyronitrile, but is not limited thereto.
Preferably, the solvent includes any one or a combination of two or more of dimethyl sulfoxide, N-methylpyrrolidone, N '-dimethylformamide, N' -dimethylacetamide, acetone, trimethyl phosphate, and the like, but is not limited thereto.
In some embodiments of the invention, the bore fluid comprises 0.01 to 10wt% of an acid chloride monomer n-hexane solution (i.e., an organic phase solution).
Preferably, the acid chloride monomer includes any one or a combination of two or more of isophthaloyl chloride, terephthaloyl chloride, phthaloyl chloride, trimesoyl chloride, 5-oxoformyl chloride-isophthaloyl chloride, 5-isocyanate-isophthaloyl chloride, and the like, but is not limited thereto.
In some embodiments, the coagulation bath comprises 0.01 to 10wt% of an aqueous amine monomer solution (i.e., an aqueous phase solution).
Preferably, the amine monomer includes any one or a combination of two or more of m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, piperazine, ethylene diamine, 1, 2-ethylene diamine, 1, 4-cyclohexanediamine, 1, 3-cyclohexanediamine, diethyltriamine, and the like, but is not limited thereto.
Preferably, the preparation method comprises the following steps:
and co-extruding the spinning solution and a core solution (namely an organic phase solution) containing acyl chloride monomers through a spinning nozzle, then immersing the spinning solution into a coagulating bath (namely an aqueous phase solution) containing amine monomers to be solidified to form a hollow fiber membrane, and enabling the organic phase solution and the aqueous phase solution to respectively flow through the inner wall and the outer wall of the hollow fiber membrane while solidifying to form a membrane, so that interfacial polymerization is instantly generated, a loose ultrathin polyamide functional layer is generated, and the large-flux forward osmosis hollow fiber membrane is obtained.
Wherein, as a more specific embodiment, the preparation method may comprise the steps of:
step (1): adding a polymer, a functional monomer, an additive and a solvent into a reaction kettle, introducing nitrogen, continuously stirring at 20-130 ℃ until the functional monomer is completely dissolved, adding azobisisobutyronitrile to initiate the functional monomer to polymerize, and reacting at 60-150 ℃ for 0.5-60 hours to obtain a spinning solution; wherein the mass percentage concentration of the polymer is 5-35%, the mass percentage concentration of the functional monomer is 0.5-15%, the mass percentage concentration of the additive is 0.01-20%, the mass percentage concentration of the azodiisobutyronitrile is 0.1-5%, and the balance is solvent;
step (2): co-extruding the spinning solution prepared in the step (1) and the core solution through a spinning nozzle by a metering pump, staying in the air for 0.5-60 seconds, then immersing in a coagulating bath for curing to form a film, cleaning, performing heat treatment at 60-120 ℃ for 0.5-10 minutes, drying, and rolling to obtain a high-flux forward-osmosis hollow fiber film; wherein the core solution is an oil-phase acyl chloride monomer n-hexane solution with the mass percentage concentration of 0.01-10%, and the coagulating bath is an amine monomer water solution with the mass percentage concentration of 0.01-10%.
As another aspect of the present invention, it also relates to a large-flux forward osmosis hollow fiber membrane prepared by the foregoing method.
Preferably, the high flux forward osmosis hollow fiber membrane comprises:
the hollow fiber membrane body comprises a semi-interpenetrating network structure mainly formed by polymerizing and crosslinking functional monomers;
and loose ultrathin polyamide functional layers at least distributed on the inner wall and the outer wall of the hollow fiber membrane body.
Preferably, the thickness of the ultrathin polyamide functional layer is 5-30 nm;
preferably, the tensile strength of the high-flux forward osmosis hollow fiber membrane is 3.2-6.8 MPa, and the pure water flux is 42.7-93.8 Lm-2h-1The rejection rate of the sodium chloride is 82.5-98.9%.
By the preparation process, the acyl chloride monomer solution and the amine monomer solution are respectively used as a core solution and a coagulating bath, interfacial polymerization is completed in the spinning process, and a loose ultrathin polyamide functional layer is generated by instantaneous reaction, so that the large-flux forward osmosis hollow fiber membrane is obtained. The functional monomer in the hollow fiber membrane prepared by the method is polymerized and crosslinked in a polymer solution to form a stable semi-interpenetrating network structure, the elution rate is low, and the hollow fiber membrane can be endowed with excellent mechanical strength for a long time and durably. The preparation method provided by the invention has the advantages that the interfacial polymerization and the preparation of the hollow fiber membrane are synchronously completed, the efficiency is high, the preparation is simple and easy to implement, and the large-scale production and application are easy.
The technical solution of the present invention is explained in more detail below with reference to several preferred embodiments.
Example 1
(1) Adding 5 g of polysulfone, 0.5 g of acrylic acid, 20 g of polyethylene glycol and 74.5 g of dimethyl sulfoxide into a reaction kettle, introducing nitrogen, continuously stirring at 130 ℃ until the materials are completely dissolved, adding 0.1 g of azobisisobutyronitrile to initiate acrylic acid polymerization, and reacting at 60 ℃ for 60 hours to obtain a spinning solution;
(2) co-extruding the spinning solution and a n-hexane solution of isophthaloyl dichloride with the mass percentage concentration of 0.01 percent through a metering pump through a spinning nozzle, staying in air for 0.5 second, then soaking the spinning solution into a m-phenylenediamine aqueous solution with the mass percentage concentration of 0.01 percent for curing to form a film, cleaning, performing heat treatment at 60 ℃ for 0.5 minute, drying and rolling to obtain the high-flux forward osmosis hollow fiber film.
Through testing, the hollow fiber membrane prepared in the embodimentThe polyamide layer (2) had a thickness of 12nm, a tensile strength of 5.1MPa, and a pure water flux of 42.7L · m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 91.5%.
Example 2
(1) Adding 35 g of sulfonated polysulfone, 15 g of methacrylic acid, 0.01 g of graphene and 49.99 g of N-methyl pyrrolidone into a reaction kettle, introducing nitrogen, continuously stirring at 20 ℃ until the materials are completely dissolved, adding 5 g of azobisisobutyronitrile to initiate methacrylic acid polymerization, and reacting at 150 ℃ for 0.5 hour to obtain a spinning solution;
(2) co-extruding the spinning solution and a normal hexane solution of terephthaloyl chloride with the mass percentage concentration of 10% through a metering pump through a spinning nozzle, staying in the air for 60 seconds, then soaking the spinning solution into an o-phenylenediamine aqueous solution with the mass percentage concentration of 10% to be solidified into a film, cleaning, performing heat treatment at 120 ℃ for 10 minutes, drying and rolling to obtain the high-flux forward osmosis hollow fiber film.
The hollow fiber membrane prepared in this example was tested to have a polyamide layer thickness of 5nm, a tensile strength of 4.4MPa, and a pure water flux of 67.8 L.m. when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 98.9%.
Example 3
(1) Adding 10 g of polyether sulfone, 2 g of dimethylaminoethyl methacrylate, 1 g of polyoxyethylene and 87 g of N, N' -dimethylformamide into a reaction kettle, introducing nitrogen, continuously stirring at 40 ℃ until the materials are completely dissolved, adding 0.2 g of azobisisobutyronitrile to initiate polymerization of the dimethylaminoethyl methacrylate, and reacting at 70 ℃ for 5 hours to obtain a spinning solution;
(2) co-extruding the spinning solution and a phthalic acid chloride normal hexane solution with the mass percentage concentration of 0.1% through a metering pump through a spinning nozzle, staying in the air for 5 seconds, then soaking the spinning solution into a p-phenylenediamine aqueous solution with the mass percentage concentration of 0.1% to solidify into a film, cleaning, performing heat treatment at 70 ℃ for 1 minute, drying and rolling to obtain the high-flux forward osmosis hollow fiber film.
Through testing, the hollow fiber membrane prepared in the example has polymerThe thickness of the amide layer was 22nm, the tensile strength was 3.2MPa, and the pure water flux was 57.1L · m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 86.2%.
Example 4
(1) Adding 15 g of polyacrylonitrile, 4 g of diethylaminoethyl methacrylate, 5 g of polyethyleneimine and 76 g of N, N' -dimethylacetamide into a reaction kettle, introducing nitrogen, continuously stirring at 50 ℃ until the materials are completely dissolved, adding 0.5 g of azobisisobutyronitrile to initiate polymerization of the diethylaminoethyl methacrylate, and reacting at 80 ℃ for 10 hours to obtain a spinning solution;
(2) co-extruding the spinning solution and a n-hexane solution of trimesoyl chloride with the mass percentage concentration of 0.3% through a metering pump through a spinning nozzle, staying in the air for 10 seconds, then soaking the spinning solution into a piperazine water solution with the mass percentage concentration of 0.2% for curing to form a film, cleaning, performing heat treatment at 80 ℃ for 3 minutes, drying and rolling to obtain the high-flux forward-osmosis hollow fiber film.
The hollow fiber membrane prepared in this example was tested to have a polyamide layer thickness of 27nm, a tensile strength of 6.8MPa, and a pure water flux of 88.3L m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 99.1%.
Example 5
(1) Adding 20 g of polyimide, 5 g of acrylamide, 8 g of carbon nano tube and 67 g of N, N' -dimethylformamide into a reaction kettle, introducing nitrogen, continuously stirring at 70 ℃ until the materials are completely dissolved, adding 1 g of azobisisobutyronitrile to initiate acrylamide polymerization, and reacting for 15 hours at 90 ℃ to obtain a spinning solution;
(2) co-extruding the spinning solution and a 5-oxygen formyl chloride-isophthalic acid chloride normal hexane solution with the mass percentage concentration of 1% through a metering pump through a spinning nozzle, staying in the air for 20 seconds, then soaking the spinning solution into an ethylene diamine water solution with the mass percentage concentration of 0.5% to be solidified into a film, cleaning, performing heat treatment at 90 ℃ for 5 minutes, drying and rolling to obtain the high-flux forward osmosis hollow fiber film.
Through testing, the hollow fiber membrane prepared in the example has polymerThe thickness of the amide layer was 30nm, the tensile strength was 5.9MPa, and the pure water flux was 93.8L · m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 82.5%.
Example 6
(1) Adding 25 g of polyvinylidene fluoride, 10 g of hydroxyethyl methacrylate, 1.5 g of silicon dioxide nano particles and 63.5 g of trimethyl phosphate into a reaction kettle, introducing nitrogen, continuously stirring at 80 ℃ until the materials are completely dissolved, adding 5 g of azobisisobutyronitrile to initiate hydroxyethyl methacrylate to polymerize, and reacting at 100 ℃ for 20 hours to obtain a spinning solution;
(2) co-extruding the spinning solution and a 5-isocyanate-isophthaloyl chloride n-hexane solution with the mass percentage concentration of 4% through a metering pump through a spinning nozzle, staying in air for 30 seconds, then soaking the spinning solution into a 6% 1, 2-ethylenediamine aqueous solution with the mass percentage concentration, curing to form a film, cleaning, performing heat treatment at 100 ℃ for 6 minutes, drying, and rolling to obtain the high-flux forward osmosis hollow fiber film.
The hollow fiber membrane prepared in this example was tested to have a polyamide layer thickness of 17nm, a tensile strength of 4.7MPa, and a pure water flux of 61.2L m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 93.6%.
Example 7
(1) Adding 30 g of cellulose acetate, 15 g of polyethylene glycol methyl ether methacrylate, 2.5 g of titanium dioxide nano particles and 52.5 g of acetone into a reaction kettle, introducing nitrogen, continuously stirring at 60 ℃ until the mixture is completely dissolved, adding 2.5 g of azobisisobutyronitrile to initiate polyethylene glycol methyl ether methacrylate, and reacting at 60 ℃ for 25 hours to obtain a spinning solution;
(2) co-extruding the spinning solution and 5-isocyanate-isophthaloyl chloride n-hexane solution with the mass percentage concentration of 5% through a spinning nozzle by a metering pump, staying in air for 30 seconds, then soaking the spinning solution into 5% 1, 4-cyclohexanediamine with the mass percentage concentration of 5% to be solidified into a film, cleaning, performing heat treatment at 105 ℃ for 8 minutes, drying and rolling to obtain the high-flux forward osmosis hollow fiber film.
After testing, the bookThe hollow fiber membranes prepared in the examples had a polyamide layer thickness of 21nm, a tensile strength of 6.3MPa, and a pure water flux of 87.6L m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 90.4%.
Example 8
(1) Adding 12.5 g of polysulfone, 12.5 g of N-vinyl pyrrolidone, 2 g of gold nanoparticles and 73 g of N, N' -dimethylformamide into a reaction kettle, introducing nitrogen, continuously stirring at 100 ℃ until the gold nanoparticles are completely dissolved, adding 3 g of azobisisobutyronitrile to initiate N-vinyl pyrrolidone to polymerize, and reacting at 120 ℃ for 36 hours to obtain a spinning solution;
(2) co-extruding the spinning solution and a phthalic acid chloride n-hexane solution with the mass percentage concentration of 8% through a metering pump through a spinning nozzle, staying in the air for 40 seconds, then soaking the spinning solution into a 6% 1, 3-cyclohexanedimethylamine aqueous solution for curing to form a film, cleaning, performing heat treatment at 100 ℃ for 2 minutes, drying and rolling to obtain the high-flux forward-osmosis hollow fiber film.
The hollow fiber membrane prepared in this example was tested to have a polyamide layer thickness of 28nm, a tensile strength of 5.9MPa, and a pure water flux of 71.3L m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 93.6%.
Example 9
(1) Adding 16 g of polyether sulfone, 9 g of N-isopropylacrylamide, 1 g of N, N '-methylenebisacrylamide and 67 g of N, N' -dimethylacetamide into a reaction kettle, introducing nitrogen, continuously stirring at 120 ℃ until the materials are completely dissolved, adding 0.8 g of azobisisobutyronitrile to initiate N-isopropylacrylamide polymerization, and reacting at 130 ℃ for 50 hours to obtain a spinning solution;
(2) co-extruding the spinning solution and a phthalic acid chloride normal hexane solution with the mass percentage concentration of 2.5% through a metering pump through a spinning nozzle, staying in air for 50 seconds, then soaking the spinning solution into a diethyl triamine aqueous solution with the mass percentage concentration of 2.5% to be solidified into a film, cleaning, then carrying out heat treatment at 120 ℃ for 6 minutes, drying and rolling to obtain the high-flux forward osmosis hollow fiber film.
The hollow fiber membrane prepared in this example was tested to have a polyamide layer thickness of 17nm, a tensile strength of 6.4MPa, and a pure water flux of 79.1L m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 86.7%.
Comparative example 1:
the preparation method of the comparative example includes: firstly, immersing a support membrane into an aqueous solution containing an active monomer or prepolymer, taking out the membrane after a certain time, immersing the sample into an organic solution containing another active monomer, and carrying out an interface reaction to obtain the hollow fiber membrane.
The hollow fiber membrane prepared in this comparative example had a tensile strength of 1.8MPa when a sodium chloride solution having a concentration of 2mol/L was used as the draw solution, and a pure water flux of 20.1L · m when a sodium chloride solution having a concentration of 2mol/L was used as the draw solution-2·h-1The rejection rate for sodium chloride was 50.6%.
Comparative example 2: this comparative example is substantially the same as example 1 except that: and (2) carrying out polymerization-crosslinking reaction without adding a functional monomer in the step (1).
The hollow fiber membrane prepared in this comparative example had a tensile strength of 1.2MPa when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution, and had a pure water flux of 24.6L · m when a sodium chloride solution having a concentration of 2mol/L was used as an extraction solution-2·h-1The rejection rate for sodium chloride was 58.1%.
It was found by comparison that the hollow fiber membranes obtained in comparative examples 1 and 2 were far inferior to those obtained in examples 1 to 9 of the present invention in terms of the tensile strength, pure water flux, and sodium chloride rejection.
In addition, the present inventors have also conducted experiments with other raw materials and conditions and the like listed in the present specification by referring to the manner of examples 1 to 9, and have also produced a large flux forward osmosis hollow fiber membrane having a large forward osmosis water flux and excellent mechanical strength.
It should be understood that the above is only a specific application example of the present invention, and the protection scope of the present invention is not limited in any way. All the technical solutions formed by equivalent transformation or equivalent replacement fall within the protection scope of the present invention.