Thin film composite hollow fiber membranes for osmotic power generation

Abstract

Disclosed is a thin film composite hollow fiber that includes an outer support layer having a thickness of 10 to 10000 μm and a polyamide thin film layer having a thickness of 1 to 10000 nm; and has a transmembrane pressure resistance rate of higher than 15 bar and a pure water permeability rate of higher than 0.8 Lm −2 h −1 bar −1 . Also disclosed are methods of preparing the above-described support and composite hollow fiber.

What is claimed is: 
     
         1 . A thin film composite (TFC) hollow fiber comprising:
 an outer support layer that is formed of polyethersulfone, polysulfone, polyphenylsulfone, polyacrylonitrile, polyimide, polyether imide, polyamide-imde, polyvinylidene fluoride, cellulose triacetate, polyetherketone, or polyetheretherketone and has a thickness of 10 to 10000 μm, and   an inner thin film layer that is formed of cross-linked polyamide and has a thickness of 1 to 10000 nm, the inner thin film layer adherent to the outer support layer, wherein the hollow fiber has a transmembrane pressure resistance rate of higher than 15 bar and a pure water permeability rate of higher than 0.8 Lm −2  h −1  bar −1 .   
     
     
         2 . The TFC hollow fiber of  claim 1 , wherein the outer support layer is formed of polyethersulfone. 
     
     
         3 . The TFC hollow fiber of  claim 1 , wherein the hollow fiber has a transmembrane pressure resistance rate of higher than 20 bar and a pure water permeability rate of higher than 3.3 Lm −2  h −1  bar −1 . 
     
     
         4 . The TFC hollow fiber of  claim 2 , wherein the hollow fiber has a transmembrane pressure resistance rate of higher than 20 bar and a pure water permeability rate of higher than 3.3 Lm −2  h −1  bar −1 . 
     
     
         5 . The TFC hollow fiber of  claim 2 , wherein the hollow fiber has a salt permeability rate of lower than 0.5 Lm −2  h −1  and a power density rate of higher than 8 Wm 2 . 
     
     
         6 . The TFC hollow fiber of  claim 5 , wherein the hollow fiber has a power density rate of higher than 20 Wm −2 . 
     
     
         7 . The TFC hollow fiber of  claim 4 , wherein the hollow fiber has a salt permeability rate of lower than 0.5 Lm −2  h −1  and a power density rate of higher than 8 Wm −2 . 
     
     
         8 . The TFC hollow fiber of  claim 7 , wherein the hollow fiber has a power density rate of higher than 20 Wm −2 . 
     
     
         9 . The TFC hollow fiber of  claim 1 , wherein the outer support layer has a thickness of 50 to 1000 μm and the inner thin film layer has a thickness of 20 to 1000 nm. 
     
     
         10 . The TFC hollow fiber of  claim 9 , wherein the outer support layer has a thickness of 100 to 300 μm and the inner thin film layer has a thickness of 50 to 500 nm. 
     
     
         11 . The TFC hollow fiber of  claim 4 , wherein the outer support layer has a thickness of 100 to 300 μm and the inner thin film layer has a thickness of 50 to 500 nm. 
     
     
         12 . A method of preparing a hollow fiber structure, the method comprising:
 dissolving a polymer 5 to 50 wt % in a solvent containing N-methyl-2-pyrrolidone (NMP) 5 to 95 wt %, polyethylene glycol (PEG) 0 to 60 wt %, and water 0 to 60 wt % to obtain a spinning dope, the polymer being polyethersulfone, polysulfone, polyphenylsulfone, polyacrylonitrile, polyimide, polyether imide, polyamide-imde, polyvinylidene fluoride, cellulose triacetate, polyetherketone, or polyetheretherketone;   providing a triple orifice spinneret that has an external orifice, a middle orifice, and an internal orifice; and   extruding the spinning dope through the middle orifice into a coagulation bath and at the same time passing a first solvent and a second solvent through the external orifice and the internal orifice, respectively, wherein the first solvent and the second solvent, independently, is NMP, water, alcohols, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, or a combination thereof, thereby forming a polymeric hollow fiber support having a lumen.   
     
     
         13 . The method of  claim 12 , wherein the polymer is polyethersulfone. 
     
     
         14 . The method of  claim 12 , wherein the polymer is 10 to 40 wt %, the NMP is 20 to 90 wt %, the PEG is 0 to 40 wt %, and the water is 0 to 40 wt %. 
     
     
         15 . The method of  claim 14 , wherein the polymer is 15 to 30 wt %, the NMP is 30 to 70 wt %, the PEG is 10 to 40 wt %, and the water is 10 to 40 wt %. 
     
     
         16 . The method of  claim 14 , wherein the polymer is polyethersulfone. 
     
     
         17 . The method of  claim 15 , wherein the polymer is polyethersulfone. 
     
     
         18 . The method of  claim 16 , wherein the first solvent is NWP and the second solvent is water. 
     
     
         19 . The method of  claim 17 , wherein the first solvent is NWP and the second solvent is water. 
     
     
         20 . A method of  claim 12 , further comprising:
 providing a tube having a proximal end, a distal end, and a lumen diameter the same as that of the hollow fiber support;   reversibly connecting the distal end of the tube to one end of the hollow fiber support;   pumping a first monomer solution from the proximal end of the tube to the hollow fiber support to coat the inner surface of the hollow fiber support with the first monomer solution, wherein the first monomer solution is a solution containing m-phenylenediamine (MPD), p-phenylenediamine, p-xylylenediamine, or branched or dendrimeric polyethylenimine;   blowing air from the proximal end of the tube to the hollow fiber support to remove excess first monomer solution; and   pumping a second monomer solution from the proximal end of the tube to the hollow fiber support to coat the first monomer solution thereby forming a cross-linked polyamide thin film layer, wherein the second monomer solution is a solution containing trimesoyl chloride (TMC), benzene-1,3-dicarbonyl chloride or benzene-1,4-dicarbonyl chloride,   
       whereby a thin-film composite hollow fiber having an outer support layer and an inner polyamide thin film layer is obtained. 
     
     
         21 . The method of  claim 20 , wherein the first monomer solution is an aqueous and/or alcohol solution containing MPD 0.1 to 20 wt % and the second monomer solution is a hexane or heptane solution containing TMC 0.01 to 1 wt %. 
     
     
         22 . The method of  claim 21 , wherein the first monomer solution is an aqueous solution containing MPD 1 to 3 wt % and the second monomer solution is a hexane solution containing TMC 0.05 to 0.2 wt %.