CN210410244U - Aminated graphene oxide and graphite-phase carbon nitride composite modified film - Google Patents
Aminated graphene oxide and graphite-phase carbon nitride composite modified film Download PDFInfo
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Abstract
The utility model relates to an aminationGraphene oxide and graphite phase carbon nitride composite modified film. The composite modified membrane comprises a polysulfone hollow fiber organic ultrafiltration membrane, a lamellar structure distributed on one side surface of the polysulfone hollow fiber organic ultrafiltration membrane and a polyamide skin layer compounded on the side surface of the polysulfone hollow fiber organic ultrafiltration membrane; the lamellar structure comprises aminated graphene oxide lamellae and carbon nitride lamellae. The utility model provides a laminated structure is distributed to compound modified membrane on polysulfone hollow fiber organic milipore filter, then compound one deck polyamide cortex on polysulfone hollow fiber organic milipore filter again, and then forms inseparable SL g-C3N4the/NGO/polyamide composite structure layer greatly improves the hydrophilic performance of the membrane surface, greatly reduces the forbidden bandwidth (Eg) value of the membrane functional layer, and has excellent visible light catalytic capability and organic matter catalytic degradation capability; and the membrane flux is greatly improved, the pollution resistance is obviously improved, and the cost is low.
Description
Technical Field
The utility model belongs to the technical field of the water treatment membrane, concretely relates to amination oxidation graphite alkene and graphite looks carbon nitride composite modification membrane.
Background
The membrane separation technology is a novel high-efficiency water treatment technology. The membrane with selective permeability is used as a separation medium, and under the action of external force of pressure difference or concentration difference, the selective permeability of the membrane to different substances is utilized to enable small micromolecule dissolved substances and solvents in stock solution to pass through membrane pores, and macromolecular dissolved substances are intercepted, so that the purpose of separating and purifying the stock solution is achieved. The membrane separation technology can realize selective separation of target pollutants, has the advantages of high efficiency, low energy consumption, simple operation, energy conservation, environmental protection and the like, and does not need to add any chemical agent in the treatment process. The membrane separation technology has gradually become the most safe and reliable water treatment technology in drinking water treatment, industrial wastewater and sewage advanced treatment. The membrane may be classified into differential pressure driving, concentration difference driving, and potential difference driving according to the driving manner of the separation membrane. The membranes can be subdivided into microfiltration membranes, ultrafiltration membranes, nanofiltration membranes and reverse osmosis membranes according to the pore size of the membranes.
In order to deal with the problem of water resource shortage, sewage recycling has become an effective way for relieving the contradiction between supply and demand of urban water. The recycling of urban sewage usually adopts Microfiltration (MF) or Ultrafiltration (UF) to pretreat secondary discharged water, and Nanofiltration (NF) or Reverse Osmosis (RO) is used as a core process in the recycling of sewage. Zhao (Zhao Y, Li P, Li R, et al. direct filtration for the treatment of the biological sewage use flat-sheet ceramic membranes. chemosphere,2019,223: 383-. Coagulation treatment is adopted before FSCM filtration, so that the pollutant removal rate is improved, and membrane pollution is reduced. This coagulation-FSCM filtration can significantly reduce the pollutant load of downstream processing and concentrate organic and nutrients into the sludge for resource recovery. The process ensures that the removal rates of Chemical Oxygen Demand (COD) and phosphorus (P) in the sewage reach 90 percent and 99 percent respectively, the COD of the effluent is lower than 25.0mg/L, and the long-term operation can still stably keep 41.7L/(m)2H) high throughput. In the Gwell county of America, nanofiltration membrane is used to replace the prior high-pH lime-ozone/GAC process, and the daily water yield reaches 2640m3The total nitrogen and TOC in the secondary effluent can be effectively removed, and the local water quality standards (white T D, Fan A G, A.I) are met.
Nanofiltration:Principles and Applications[J]Journal-American Water Works Association,2005: 121-. The Microfiltration (MF) and Ultrafiltration (UF) can effectively remove colloid, NOM, algae, bacteria, virus and other pollutants difficult to remove in natural water, and have the advantages of simple operation, low energy consumption, high water yield and the like. Although the membrane treatment technology has great potential in water treatment application, the current membrane pollution problem is one of the difficult problems limiting the popularization and application of the membrane treatment technology.
The water yield is reduced due to membrane pollution, the service life of the membrane component is shortened, and the operation energy consumption and the cost are both obviously increased. Membrane fouling is mainly divided into: inorganic pollution, organic pollution and biologyAnd (4) pollution. Among them, organic pollution is a difficult problem in membrane pollution research, and is mainly caused by Natural Organic Matter (NOM). Zularisam et al (Zularisam A W, Ismail A F, Salim M R, et al. the effects of Natural Organic Materials (NOM) reactions on faulting characteristics and flux recovery of ultrafiltration membranes [ J]Desalination,2007,212(1-3):191-208.) the mechanism of membrane fouling by NOMs of different hydrophilicity was studied: concentration polarization (for hydrophobic NOM), cake layer stacking (for neutral NOM), adsorption contamination (hydrophilic NOM). GUO et al found that the effect of Dissolved Organics (DOM) on film fouling was also very severe. The enhancement of membrane fouling is achieved when multiple DOM are present in the raw water (Guo X, Zhang Z, Lin F, et al. study on ultrafiltration for surface water a polyvinylidene chloride fiber membrane [ J]Desalinization, 2009,238(1-3): 183-191). Along with the extension of the membrane filtration time, a large amount of inorganic suspended matters contained in natural water gradually deposit on the membrane surface, small particle suspended matters even enter the interior of membrane pores to cause blockage, the water yield is reduced due to the reduction of the water cross section, and the water yield is reduced mainly by calcium salt, magnesium salt, ferric salt and the like (Al-Amoudi A S]Desalinization, 2010,259(1-3): 1-10.). The biological contamination of the membrane refers to the fact that microorganisms contained in raw water are adsorbed on the membrane surface and continuously grow and propagate on the membrane surface during the membrane filtration process (Vourwenvelder J S, Picioreanu C, Kruithof JC, et al]Journal of Membrane Science,2010,346(1): 71-85.). Babel et al found that the extent of biofouling on the membrane surface is greatly influenced by factors such as different seasons, nutrients, sunlight and the like, and bacteria can grow and propagate on the membrane surface to form a biofilm, and the presence of the biofilm causes the water yield of the separation membrane to be reduced[7]. In order to solve a series of problems caused by membrane pollution, domestic and foreign scholars begin to research on anti-pollution modification of membranes.
The polysulfone hollow fiber organic ultrafiltration membrane has the characteristics of high filling density, simple structure, convenient operation and the like, and has attracted extensive attention and research of people. But still has the problems of reduced membrane flux and weak anti-pollution performance during the use process.
Therefore, the development of a novel composite membrane for improving the membrane flux and the anti-pollution capability has important research significance and economic value.
Disclosure of Invention
The utility model aims to overcome the defect or not enough that current polysulfone hollow fiber organic ultrafiltration membrane has membrane flux decline and antipollution performance weaker in the use, provide an amination oxidation graphite alkene and graphite looks carbon nitride composite modified membrane. The utility model provides a composite modified membrane forms SL g-C through lamellar structure and polyamide cortex3N4the/NGO/polyamide composite structure layer greatly improves the hydrophilic performance of the membrane surface, greatly reduces the forbidden bandwidth (Eg) value of the membrane functional layer, and has excellent visible light catalytic capability and organic matter catalytic degradation capability; and the membrane flux is greatly improved, the pollution resistance is obviously improved, and the cost is low.
In order to realize the utility model discloses a purpose, the utility model discloses a following technical scheme:
an aminated graphene oxide and graphite-phase carbon nitride composite modified membrane comprises a polysulfone hollow fiber organic ultrafiltration membrane, a lamellar structure distributed on the surface of one side of the polysulfone hollow fiber organic ultrafiltration membrane and a polyamide cortex compounded on the surface of the side of the polysulfone hollow fiber organic ultrafiltration membrane; the lamellar structure comprises an aminated graphene oxide lamellar distributed on the surface of the polysulfone hollow fiber organic ultrafiltration membrane and a carbon nitride sheet distributed on the aminated graphene oxide lamellar.
The composite modified membrane provided by the utility model adopts an amination graphene oxide (NGO) layer with electropositivity and a material capable of improving photocatalysis efficiency, namely carbon nitride thin sheet (SL g-C)3N4) The modified layer and the modified layer are combined to modify the surface of the polysulfone hollow fiber organic ultrafiltration membrane, a laminated structure which is stacked layer by layer is formed, then a polyamide skin layer is compounded on the polysulfone hollow fiber organic ultrafiltration membrane, and compact SL g-C is formed on the surface of the polysulfone hollow fiber organic ultrafiltration membrane3N4an/NGO/polyamide composite structure layer. The SL g-C3N4the/NGO/polyamide composite structure layer can bring the following effects:
(1) the surface of the composite modified film has epoxy group (C-O-C), hydroxyl group (-OH), amino group (-NH)2) And vibration absorption peaks of hydrophilic functional groups such as amide (CONH). The hydrophilic performance of the membrane surface is obviously improved, and the static contact angle of the surface is reduced to 28.8 +/-0.8 degrees from 69.0 +/-1.3 degrees of the polysulfone hollow fiber organic ultrafiltration membrane, and is only 40 percent of that of the polysulfone hollow fiber organic ultrafiltration membrane.
(2)SL g-C3N4the/NGO heterojunction is uniformly distributed on the surface of the composite modified membrane in a lamellar structure form, and a criss-cross tubular polyamide skin layer is formed on the surface of the heterojunction, so that a nanometer-sized Tuling structure is presented. The elements are uniformly distributed, the O/C atomic ratio is improved to 0.11 from 0.08 of the polysulfone hollow fiber organic ultrafiltration membrane, and the N/S ratio is improved to 31.03 from 1.27 of the polysulfone hollow fiber organic ultrafiltration membrane.
(3) Compact SL g-C formed on surface of composite modified film3N4the/NGO/polyamide composite structure layer improves the HA interception removal rate of the composite modified membrane surface from 63.08 percent of the polysulfone hollow fiber organic ultrafiltration membrane to 97.23 percent. The pollution resistance of the composite modified membrane is obviously improved, the flux attenuation rate is reduced to 18.44% from 33.93% of that of the polysulfone hollow fiber organic ultrafiltration membrane, and the flux recovery rate after hydraulic cleaning is improved to 90.37% from 76.79%.
(4) The composite modified membrane has obviously improved anti-pollution performance to organic dye. Under the dark state condition, the adsorption capacity of the polysulfone hollow fiber organic ultrafiltration membrane surface is 7 times and 3 times of the adsorption capacity of the modified membrane surface respectively.
(5) The composite modified membrane has stronger visible light catalytic capability, and the maximum absorption band edge is widened from 330nm of the polysulfone hollow fiber organic ultrafiltration membrane to 460 nm. The visible light catalytic degradation rates of the modified film to RhB and MO solutions are respectively 98.2% and 74.6%.
(6) The surface of the composite modified membrane has stronger organic matter catalytic degradation capability and stable performance. Under the condition of visible light irradiation, the flux of the modified membrane is 81.32 percent when the modified membrane is irradiated for 1 hourRecovered 90.42%, and SL g-C3N4The interception rate of the/NGO modified membrane to HA is stabilized at 96% +/-2%.
(7) Preparing an area of 64cm2The cost of the composite modified membrane is 5.17 yuan, which is only 61.56% higher than that of the polysulfone hollow fiber organic ultrafiltration membrane.
Polysulfone hollow fiber organic ultrafiltration membranes, which are conventional in the art, can be used in the present invention.
Preferably, the pore diameter of a filter membrane pore of the polysulfone hollow fiber organic ultrafiltration membrane is 10-50 nm.
Preferably, the thickness of the polysulfone hollow fiber organic ultrafiltration membrane is 0.10-0.11 mm.
Preferably, the loading capacity of the upper sheet structure of the polysulfone hollow fiber organic ultrafiltration membrane is 0.039-0.156 g/cm2。
Preferably, the number of lamellar structures is a plurality of groups (e.g. 2, 4, 5, 8, 12, etc.); the number of the aminated graphene oxide sheets and the carbon nitride sheets stacked in each group may be multiple, for example, 2, 4, 5, 8, 12, and the like, and the number stacked in each group may be the same or different.
Each group of lamellar structures is in a layer-by-layer stacking mode.
Preferably, the number of carbon nitride flakes on the aminated graphene oxide sheet layer is several.
Preferably, the mass fraction of the carbon nitride thin slices in the lamellar structure is 1-5%.
Preferably, the thickness of the aminated graphene oxide sheet layer is 0.8-1.6 nm.
Preferably, the thickness of the carbon nitride thin sheet is 1-2 nm.
Preferably, the thickness of the polyamide skin layer is 100nm to 10 μm.
The utility model provides a preparation method of amination oxidation graphite alkene and graphite phase carbon nitride composite modified membrane, including following step:
s1: the amination graphene oxide NGO and the graphite phase of the monoatomic nano-sheet layerCarbon nitride SL g-C3N4Mixing and dispersing to obtain SL g-C3N4an/NGO heterojunction dispersion.
By adjusting NGO and SL g-C3N4The amount of SL g-C can be adjusted3N4And the mass fraction of the NGO in the/NGO heterojunction, and further adjusting the mass fraction of the carbon nitride sheet in the finally obtained lamellar structure.
S2: soaking a polysulfone hollow fiber organic ultrafiltration membrane in an SDBS solution (1-9 g/L) for 10min to realize activation, and then adding SL g-C3N4Introducing nitrogen from one side of a polysulfone hollow fiber organic ultrafiltration membrane into the/NGO heterojunction dispersion liquid to pressurize the SL g-C by 0.1-0.2 MPa3N4the/NGO heterojunction is uniformly loaded on the surface of the polysulfone hollow fiber organic ultrafiltration membrane.
At the moment, a lamellar structure is obtained, wherein the aminated graphene oxide lamellar layer in the lamellar structure is distributed on the surface of the polysulfone hollow fiber organic ultrafiltration membrane, and the carbon nitride flake is distributed on the aminated graphene oxide lamellar layer.
During the activation process, the pore diameter of the filter membrane pore of the polysulfone hollow fiber organic ultrafiltration membrane is enlarged, and the pore diameter of the filter membrane pore which is generally smaller than 10nm is 10-50 nm after the activation.
S3: soaking the polysulfone hollow fiber organic ultrafiltration membrane in an acyl chloride monomer (such as pyromellitic chloride BTTC, trimesoyl chloride TMC and isophthaloyl chloride IPC) aqueous phase solution (0.5-2.0 wt%) for 1-4 min, taking out, drying, soaking in an amine monomer (such as ethylenediamine DMDA, piperazine PIP and m-phenylenediamine MPD) n-hexane organic phase solution (0.05-0.2%) for 30-75 s, and carrying out interfacial polymerization to obtain a polyamide skin layer; and then carrying out heat treatment at 50-90 ℃, and cleaning to obtain the aminated graphene oxide and graphite-phase carbon nitride composite modified film.
The thickness of the polyamide skin layer is adjusted by adjusting the concentration and the soaking time of the acyl chloride monomer aqueous phase solution and the concentration and the soaking time of the amine monomer n-hexane organic phase solution.
The preparation process of the aminated graphene oxide NGO is as follows:
add 200mg GO to 200mL Dimethylformamide (DMF) and sonicate for 2h to fully disperse GO. Then adding 30g of ethylenediamine and 5g N, N' -dicyclohexylcarbodiimide DCC, carrying out ultrasonic treatment for 20min, and then placing the mixture in a water bath kettle at 60 ℃ for reaction for 6 h. And after the reaction is finished, adding 100mL of absolute ethyl alcohol, standing overnight, removing supernatant, repeatedly centrifuging and cleaning with absolute ethyl alcohol and deionized water, dialyzing for 24 hours with a dialysis bag, and finally placing a sample obtained by dialysis in a freeze dryer for drying to obtain the NGO.
The amount of each raw material and the reaction time can be adjusted to obtain the NGO.
Monoatomic nanosheet graphite phase carbon nitride SL g-C3N4The preparation method comprises the following steps:
grinding a certain amount of urea, placing into an alumina crucible, placing the crucible into a muffle furnace, heating to 550 deg.C at a rate of 5 deg.C/min, and maintaining the temperature for 2 hr to obtain block g-C3N4. Then taking a certain amount of blocks g-C3N4Grinding, placing into a crucible, placing the crucible into a muffle furnace for secondary calcination, heating to 475 deg.C at a rate of 5 deg.C/min, and maintaining for 120min to obtain yellow-white flocculent nanometer lamellar structure NS g-C3N4And (3) powder. Finally, placing the mixture into a certain amount of isopropanol for ultrasonic stripping for 4 hours, and obtaining the SL g-C with the monatomic lamellar structure after centrifugation and drying3N4。
Compared with the prior art, the utility model discloses following beneficial effect has:
the utility model provides a laminated structure is distributed to compound modified membrane on polysulfone hollow fiber organic ultrafiltration membrane, then compound one deck polyamide cortex on polysulfone hollow fiber organic ultrafiltration membrane again, and then forms inseparable SL g-C on polysulfone hollow fiber organic ultrafiltration membrane surface3N4the/NGO/polyamide composite structure layer greatly improves the hydrophilic performance of the membrane surface, greatly reduces the forbidden bandwidth (Eg) value of the membrane functional layer, and has excellent visible light catalytic capability and organic matter catalytic degradation capability; and the membrane flux is greatly improved, the pollution resistance is obviously improved, and the cost is low.
Drawings
Fig. 1 is a schematic structural diagram of an aminated graphene oxide and graphite-phase carbon nitride composite modified film provided in example 1;
FIG. 2 shows SL g-C3N4Infrared spectrum analysis of/NGO heterojunction, polysulfone hollow fiber organic ultrafiltration membrane and composite modified membrane;
FIG. 3 is a surface topography of a polysulfone hollow fiber organic ultrafiltration membrane;
FIG. 4 is a surface topography of a composite modified membrane;
FIG. 5 is a schematic view of an element analysis of a polysulfone and polysulfone hollow fiber organic ultrafiltration membrane;
FIG. 6 is an elemental analysis topography of a composite modified membrane;
FIG. 7 is a UV-VIS absorption spectrum of a composite modified film;
FIG. 8 is a contact angle test chart of the composite modified membrane and a polysulfone hollow fiber organic ultrafiltration membrane;
FIG. 9 shows the effect of the composite modified membrane and polysulfone hollow fiber organic ultrafiltration membrane on the adsorption removal of RhB under dark conditions;
FIG. 10 shows the effect of the composite modified membrane and polysulfone hollow fiber organic ultrafiltration membrane on the removal of RhB under illumination;
FIG. 11 shows the MO removal effect of the composite modified membrane and the polysulfone hollow fiber organic ultrafiltration membrane under the dark state condition;
FIG. 12 shows the effect of the composite modified membrane and polysulfone hollow fiber organic ultrafiltration membrane on the removal of MO under illumination;
FIG. 13 shows the change of the flux recovery rate and HA retention rate of the composite modified membrane under the irradiation of visible light;
wherein, 1 is a polyamide skin layer, 2 is an aminated graphene oxide sheet layer, 3 is a carbon nitride sheet, and 4 is a polysulfone hollow fiber organic ultrafiltration membrane; 5 is a filter membrane pipe hole;
in addition, in fig. 2 to 13 and the analysis and description thereof, the composite film and the composite modified film are both referred to as an aminated graphene oxide and graphite-phase carbon nitride composite modified film; the raw membrane refers to a polysulfone hollow fiber organic ultrafiltration membrane.
Detailed Description
The invention will be further illustrated with reference to the following examples. These examples are provided only for illustrating the present invention and are not intended to limit the scope of the present invention. Experimental procedures without specific conditions noted in the examples below, generally according to conditions conventional in the art or as suggested by the manufacturer; the raw materials, reagents and the like used are, unless otherwise specified, those commercially available from the conventional markets and the like. Any insubstantial changes and substitutions made by those skilled in the art based on the teachings of the present invention are intended to be covered by the present invention.
The aminated graphene oxide NGO used in each example was prepared by the following method:
add 200mg GO to 200mL Dimethylformamide (DMF) and sonicate for 2h to fully disperse GO. Then adding 30g of ethylenediamine and 5g N, N' -dicyclohexylcarbodiimide DCC, carrying out ultrasonic treatment for 20min, and then placing the mixture in a water bath kettle at 60 ℃ for reaction for 6 h. And after the reaction is finished, adding 100mL of absolute ethyl alcohol, standing overnight, removing supernatant, repeatedly centrifuging and cleaning with absolute ethyl alcohol and deionized water, dialyzing for 24 hours with a dialysis bag, and finally placing a sample obtained by dialysis in a freeze dryer for drying to obtain the NGO.
Monoatomic nanosheet of graphitic carbon nitride SL g-C used in the examples3N4The preparation method comprises the following steps: grinding a certain amount of urea, placing into an alumina crucible, placing the crucible into a muffle furnace, heating to 550 deg.C at a rate of 5 deg.C/min, and maintaining the temperature for 2 hr to obtain block g-C3N4. Then taking a certain amount of blocks g-C3N4Grinding, placing into a crucible, placing the crucible into a muffle furnace for secondary calcination, heating to 475 deg.C at a rate of 5 deg.C/min, and maintaining for 120min to obtain yellow-white flocculent nanometer lamellar structure NS g-C3N4And (3) powder. Finally, placing the mixture into a certain amount of isopropanol for ultrasonic stripping for 4 hours, and obtaining the SL g-C with the monatomic lamellar structure after centrifugation and drying3N4。
100mg of SL g-C are taken3N4Adding a certain amount of NGO into a solution prepared from water and ethanol (water: ethanol ratio is 1:1), performing ultrasonic treatment for 4 hr, centrifuging to separate solid product, washing with water and ethanol repeatedly at 80 deg.CDrying under the reduced pressure to obtain SL g-C3N4an/NGO heterojunction. SL g-C with different NGO loading amounts are respectively prepared by controlling the adding amount (1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%) of NGO3N4an/NGO heterojunction.
The polysulfone hollow fiber organic ultrafiltration membrane selected in the preparation method of each example is purchased from Tangshan sea Qingyuan membrane technology Co., Ltd, and has a membrane pore diameter of 0.1 μm and a membrane area of 64cm2The pore diameter of the filter membrane pore is less than 10 nm.
Example 1
Referring to fig. 1, the embodiment provides an aminated graphene oxide and graphite-phase carbon nitride composite modified membrane, which includes a polysulfone hollow fiber organic ultrafiltration membrane 4, a lamellar structure distributed on one side surface of the polysulfone hollow fiber organic ultrafiltration membrane, and a polyamide skin layer 1 compounded on the side surface of the polysulfone hollow fiber organic ultrafiltration membrane 4; the lamellar structure comprises an aminated graphene oxide lamellar layer 2 distributed on the surface of the polysulfone hollow fiber organic ultrafiltration membrane 4 and a carbon nitride sheet 3 distributed on the aminated graphene oxide lamellar layer 2.
Specifically, the aperture of a filter membrane tube hole 5 in the polysulfone hollow fiber organic ultrafiltration membrane 4 is 10-50 nm.
The number of the lamellar structures is multiple, and the loading capacity of the lamellar structures on the polysulfone hollow fiber organic ultrafiltration membrane 4 is 2.5 mg; the aminated graphene oxide sheets 2 and the carbon nitride sheets 3 in each group are sequentially overlapped, the number of the carbon nitride sheets 3 on each aminated graphene oxide sheet 2 is a plurality, the mass fraction of the carbon nitride sheets 3 in the sheet structure is 5%, the thickness of each aminated graphene oxide sheet 2 is 0.8-1.6 nm, the thickness of each carbon nitride sheet 3 is 1-2 nm, and the thickness of each polyamide skin layer 1 is 100 nm.
The composite modified membrane is prepared by the following steps:
s1: taking SL g-C with NGO load of 5wt percent3N4an/NGO heterojunction dispersion.
S2: the polysulfone hollow fiber organic ultrafiltration membrane is placed in SDBS solution (3g/L) to be soaked for 10min to realize activation, then SL g-C3N4/NGO heterojunction dispersion liquid is added, nitrogen is introduced from one side of the polysulfone hollow fiber organic ultrafiltration membrane to pressurize to 0.1MPa, and SL g-C3N4/NGO heterojunction is uniformly loaded on the surface of the polysulfone hollow fiber organic ultrafiltration membrane. At the moment, the aperture of the filter membrane tube hole of the polysulfone hollow fiber organic ultrafiltration membrane is 10-50 nm.
S3: soaking a polysulfone hollow fiber organic ultrafiltration membrane in a metaphenylene diamine MPD aqueous phase solution (2.0 wt%) for 3min, taking out, drying, soaking in a trimesoyl chloride TMC n-hexane organic phase solution (0.2 wt%) for 60s, and carrying out interfacial polymerization to obtain a polyamide skin layer; and then carrying out heat treatment at 50-90 ℃, and cleaning to obtain the aminated graphene oxide and graphite-phase carbon nitride composite modified film.
Example 2
The embodiment provides an aminated graphene oxide and graphite-phase carbon nitride composite modified membrane, which comprises a polysulfone hollow fiber organic ultrafiltration membrane 4, a lamellar structure distributed on the surface of one side of the polysulfone hollow fiber organic ultrafiltration membrane and a polyamide skin layer 1 compounded on the surface of the side of the polysulfone hollow fiber organic ultrafiltration membrane 4; the lamellar structure comprises an aminated graphene oxide lamellar layer 2 distributed on the surface of the polysulfone hollow fiber organic ultrafiltration membrane 4 and a carbon nitride sheet 3 distributed on the aminated graphene oxide lamellar layer 2.
Specifically, the number of the lamellar structures is multiple, and the loading capacity of the lamellar structure on the polysulfone hollow fiber organic ultrafiltration membrane 4 is 10 mg; the aminated graphene oxide sheets 2 and the carbon nitride sheets 3 in each group are sequentially overlapped, the number of the carbon nitride sheets 3 on each aminated graphene oxide sheet 2 is a plurality, the mass fraction of the carbon nitride sheets 3 in the sheet structure is 1%, the thickness of each aminated graphene oxide sheet 2 is 0.8-1.6 nm, the thickness of each carbon nitride sheet 3 is 1-2 nm, and the thickness of each polyamide skin layer 1 is 10 microns.
The preparation method is basically the same as that of example 1, and the difference is that: SL g-C selected in S13N4The loading capacity of NGO in the/NGO heterojunction dispersion liquid is 1 wt%; in S3, the concentration of the metaphenylene diamine MPD aqueous phase solution is 0.5 wt%, and the concentration of the trimesoyl chloride TMC n-hexane organic phase solution is 0.05 wt%.
Example 3
The embodiment provides an aminated graphene oxide and graphite-phase carbon nitride composite modified membrane, which comprises a polysulfone hollow fiber organic ultrafiltration membrane 4, a lamellar structure distributed on the surface of one side of the polysulfone hollow fiber organic ultrafiltration membrane and a polyamide skin layer 1 compounded on the surface of the side of the polysulfone hollow fiber organic ultrafiltration membrane 4; the lamellar structure comprises an aminated graphene oxide lamellar layer 2 distributed on the surface of the polysulfone hollow fiber organic ultrafiltration membrane 4 and a carbon nitride sheet 3 distributed on the aminated graphene oxide lamellar layer 2.
Specifically, the number of the lamellar structures is multiple, and the loading capacity of the lamellar structure on the polysulfone hollow fiber organic ultrafiltration membrane 4 is 10 mg; the aminated graphene oxide sheets 2 and the carbon nitride sheets 3 in each group are sequentially overlapped, the number of the carbon nitride sheets 3 on each aminated graphene oxide sheet 2 is a plurality, the mass fraction of the carbon nitride sheets 3 in the sheet structure is 3%, the thickness of each aminated graphene oxide sheet 2 is 0.8-1.6 nm, the thickness of each carbon nitride sheet 3 is 1-2 nm, and the thickness of each polyamide skin layer 1 is 66 mu m.
The preparation method is basically the same as that of example 1, and the difference is that: SL g-C selected in S13N4The loading capacity of NGO in the/NGO heterojunction dispersion liquid is 3 wt%; in S3, the concentration of the metaphenylene diamine MPD aqueous phase solution is 1.0 wt%, and the concentration of the trimesoyl chloride TMC n-hexane organic phase solution is 0.1 wt%.
Performance testing
The performance of the aminated graphene oxide and graphite-phase carbon nitride composite modified films provided in examples 1 to 3 was measured. The specific test method is as follows:
(1) pure water flux JW1Measurement of
The test method is as follows:
mixing SL g-C3N4Placing the/NGO composite modified polyamide membrane in a dead-end filtering device (room temperature, pressure of 0.25MPa) for prepressing for 30min, and then measuring the compressed SL g-C under the pressure of 0.20MPa3N4the/NGO composite modified polyamide membrane has pure water flux.
Wherein J is the membrane flux (L.m)-2·h-1) (ii) a V is the effluent volume (L) of the membrane; a is the effective filtration area (m) of the membrane2) (ii) a t is the filtration time (h).
(2) Membrane flux attenuation ratio RFDMeasurement of
The test method is as follows:
first, SL g-C is determined3N4Filtering flux J of HA solution by/NGO composite modified polyamide membranet. Then, through a cross-flow filtration device, to SL g-C3N4the/NGO composite modified polyamide membrane is subjected to tangential hydraulic flushing (the water pressure is 0.20MPa), and SL g-C after the flushing is measured again3N4Pure water flux of/NGO composite modified polyamide membrane. The membrane flux attenuation rate and the membrane flux recovery rate are calculated as follows:
wherein R isFD(%) and FRR (%) are respectively the membrane flux attenuation rate and the membrane flux recovery rate; j. the design is a squareW1Initial pure water flux (L.m) for the membrane-2·h-1)、JtIs the transmembrane flux (L.m) of HA-2·h-1)、JW2The pure water flux (L.m) of the membrane after the membrane is subjected to the water washing-2·h-1)。
(3) Membrane filtration HA solution Retention η determination
The test method is as follows:
HA rejection of humic acid HA through the membrane can be used to characterize SL g-C3N4the/NGO composite modified polyamide membrane has the retention performance on organic pollutants in water. After the membrane pre-compression and the pure water flux measurement were completed, an HA solution (10 mg. L) was added to the cuvette-1) Filtering under the pressure of 0.20MPa nitrogen for 20min, measuring the absorbance of the HA solution before and after membrane filtration by using an ultraviolet spectrophotometer, and calculating to obtain the membrane-passing retention rate η of HA.
The test results are shown in Table 1.
Table 1 Performance characterization results for composite modified films provided in examples 1-3
In addition, the properties of the composite modified membrane provided in example 3 were characterized as follows:
characterization of composite modified membranes
1. Characterization of surface chemical structure and functional group of composite modified membrane
The composite modified membrane and the polysulfone hollow fiber organic ultrafiltration membrane are characterized by Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR) (the result is shown in figure 2). It can be observed that:
SL g-C3N4the/NGO heterojunction has the following characteristic peaks: 810. 1074, 1200-1600, 1632, 3000-3500 cm-1. Wherein the thickness is 810, 1200-1600, 3000-3500 cm-1Belong to SL g-C3N4Characteristic peak structure of the above, 810cm-1Corresponding to a characteristic peak of a 3-s-triazine structure, 1200-1600 cm-1A stretching vibration peak corresponding to the C-N bond and an in-plane bending vibration peak corresponding to the N-H bond, wherein the in-plane bending vibration peak is 3000-3500 cm-1Corresponds to g-C3N4-NH and-NH on marginal aromatic rings2Stretching vibration peak of the radical. And epoxy group (C-O-C), carbon-carbon double bond (C ═ C) and hydroxyl group (-OH) on NGO are also consistent with characteristic peaks 1074, 1632 and 3000-3500 cm-1One-to-one correspondence, which indicates that SL g-C has been successfully implemented3N4the/NGO heterojunction is loaded on the surface of the polysulfone hollow fiber organic ultrafiltration membrane. In addition, the characteristic peak value is 1536cm-1Corresponding to characteristic peak (N-H) of amine group on amide group (CONH), indicating interfacial polymerization reaction of MPD and TMCSuccessfully forms a polyamide skin layer on the surface of the film.
As described above, epoxy groups (-O-C), hydroxyl groups (-OH), amino groups (-NH)2) And amide (CONH) which are hydrophilic polar groups are successfully introduced to the surface of the modified membrane, so that the hydrophilicity of the surface of the membrane is effectively improved, and the anti-pollution performance of the surface of the membrane is improved.
2. Surface topography of composite modified membranes
The surface morphology characteristics of the polysulfone hollow fiber organic ultrafiltration membrane and the composite modified membrane are researched by a scanning electron microscope SEM. The polysulfone hollow fiber organic ultrafiltration membrane has a flat and smooth surface (see fig. 3a), and the pores can be clearly observed after being magnified to 10000 times and are uniformly distributed (see fig. 3 b). The surface structure of the composite modified membrane is more complex, and a criss-cross tubular polyamide skin layer (see fig. 4a) is formed on the surface of the composite membrane, so that a nano-sized Tuoling structure has good transmission performance. In addition, it can be observed that the lamellar structure with the lamellar stack, which is uniformly distributed over the surface of the film, is associated with SL g-C3N4the/NGO heterojunction structure is consistent. SL g-C3N4The surface of the/NGO heterojunction also forms a compact polyamide skin layer, SL g-C3N4the/NGO heterojunction is firmly embedded in the polyamide skin (see figure 4b) to ensure SL g-C3N4the/NGO heterojunction is not easy to fall off.
3. Surface element analysis of composite modified film
And performing comparative analysis on the element components and the contents of the surfaces of the polysulfone and polysulfone hollow fiber organic ultrafiltration membrane and the composite modified membrane by X-ray energy spectrum analysis (EDS). As can be seen from FIGS. 5 and 6, the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane and the composite modified membrane have very uniform element distributions such as C, O, N, S on the surface (corresponding to FIG. 5 and four diagrams of FIGS. 6a to 6d, respectively), and SL g-C is considered to be3N4the/NGO heterojunction is loaded on the surface of the membrane very uniformly.
The atomic ratio of each element is shown in table 2, for example, the S element on the surface of the composite modified membrane is reduced to 1.24 percent from 3.55 percent of the polysulfone hollow fiber organic ultrafiltration membrane (membrane)The surface is uniformly covered by modifier substances), the N element is increased to 38.48 percent from 4.53 percent of polysulfone and polysulfone hollow fiber organic ultrafiltration membrane, and the increased N element comes from modifier g-C3N4NGO, was uniformly supported on the polysulfone hollow fiber organic ultrafiltration membrane surface (see fig. 6 c). And the C element and the O element are respectively reduced from 85.09 percent and 6.83 percent to 54.29 percent and 5.99 percent, which further shows that the composite modified layer is uniformly and firmly loaded on the surface of the polysulfone hollow fiber organic ultrafiltration membrane, and the anti-pollution performance of the membrane surface is improved.
TABLE 2 atomic ratio of elements in energy spectrum analysis
4. Analysis of visible light absorption Capacity of composite modified film
The absorption capacity for visible light is an important index for evaluating photocatalytic performance. The visible light absorption characteristics of the modified film are researched by testing ultraviolet-visible light diffuse reflection absorption spectrum (UV-vis) of the composite modified film. As can be seen from FIG. 7, the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane has a maximum absorption band edge of 330nm and no visible light response capability (wavelength. lambda.) in the visible light region>420nm) and the maximum absorption band edge of the composite modified film was 460nm, demonstrating SL g-C3N4the/NGO heterojunction is successfully arranged on the surface of the polysulfone and polysulfone hollow fiber organic ultrafiltration membrane, so that the modified membrane has stronger visible light absorption capacity.
5. Analysis of anti-pollution performance of composite modified membrane
The anti-fouling performance of a membrane is generally expressed in terms of flux decay rate and flux recovery rate. The lower the flux decay rate, the higher the flux recovery rate, demonstrating a lesser degree of irreversible fouling of the membrane.
The membrane flux attenuation rate and the membrane flux recovery rate were calculated as follows:
in the formula, RFD(%) and FRR (%) are respectively the membrane flux attenuation rate and the membrane flux recovery rate; j. the design is a squareW1Initial pure water flux (L.m) for the membrane-2·h-1)、JtIs the transmembrane flux (L.m) of HA-2·h-1)、JW2The pure water flux (L.m) of the membrane after the membrane is subjected to the water washing-2·h-1)。
Through comparative analysis of separation performance parameters of the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane and the composite modified membrane (see table 3), the flux attenuation rate of the modified membrane is reduced from 33.93% to 18.44%, and the flux recovery rate is improved from 76.79% to 90.37%. This shows that the anti-pollution performance of the modified membrane is obviously improved after the modifier with high hydrophilicity is introduced.
TABLE 3 comparison of separation Performance parameters of polysulfone hollow fiber organic Ultrafiltration Membrane and composite modified Membrane
6. Analysis of surface hydrophilic property of composite modified membrane
The hydrophilic energy of a membrane surface is typically expressed in terms of the static contact angle of water at the membrane surface. The water static contact angle of the film surface was measured using a video optical contact angle measuring instrument. The smaller the static contact angle, the more hydrophilic the membrane surface, and the more anti-fouling performance during filtration. By introducing NGO and SL g-C on the surface of the membrane3N4And high hydrophilic substances such as polyamide skin layer, the contact angle of which is reduced from 69.0 +/-1.3 degrees of the polysulfone hollow fiber organic ultrafiltration membrane to 28.8 +/-0.8 degrees (see figure 8), which shows thatThe hydrophilicity and the pollution resistance of the modified membrane are both obviously improved.
(II) comparative analysis of photocatalytic capacity of composite modified membrane and polysulfone hollow fiber organic ultrafiltration membrane
1. Adsorption effect on RhB solution under dark state
The composite modified membrane and the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane are respectively placed in a dark state to be subjected to an adsorption test with the RhB solution, and the change of the concentration of the RhB solution in different adsorption time is researched (see figure 9).
As shown in fig. 9, in the absence of light, the concentration of RhB solution in the reference group without membrane was absent, indicating that RhB stability was good and that no degradation occurred by itself. After the composite modified membrane or the polysulfone hollow fiber organic ultrafiltration membrane is introduced in the experiment, the adsorption effect of the polysulfone hollow fiber organic ultrafiltration membrane on RhB is obvious, and the adsorption removal rate reaches 52.2% when the adsorption time reaches 300min, and the adsorption equilibrium state is not reached yet. The adsorption effect of the composite modified film on RhB is not obvious, the adsorption removal rate is only 8.0% when the adsorption time reaches 300min, and the adsorption time reaches 90min, the adsorption state tends to be in an adsorption equilibrium state. The anti-pollution performance of the composite modified membrane after modification is obviously improved.
2. Photocatalytic degradation effect on RhB solution under visible light irradiation condition
Under the condition of visible light irradiation, the composite modified membrane, the polysulfone hollow fiber organic ultrafiltration membrane and the reference group without the membrane are subjected to a photocatalytic degradation test of the RhB solution (5mg/L), and the change rule of the concentration of the RhB solution under different photocatalytic time conditions is studied (as shown in FIG. 10). As can be seen from fig. 10, under the irradiation of visible light, there was no significant change in the RhB solution concentration in the reference group without film. This further indicates that the RhB solution is stable and unaffected by visible light exposure. For the polysulfone hollow fiber organic ultrafiltration membrane, under the visible light irradiation condition and the dark state condition, the adsorption effect on RhB is the same, the change rule of RhB concentration along with the adsorption time is basically consistent, the action mechanism of the polysulfone hollow fiber organic ultrafiltration membrane on RhB under the visible light irradiation is mainly adsorption action, and the polysulfone hollow fiber organic ultrafiltration membrane has no visible light absorption capacity.
In contrast, in the case of the composite modified film, the RhB concentration rapidly decreased under the irradiation with visible light. When the illumination time reaches 210min, the photocatalytic degradation rate of the modified membrane on RhB reaches 92.6%, which is far higher than the adsorption removal rate (41%) of the polysulfone hollow fiber organic ultrafiltration membrane. This further demonstrates that the composite modified film has a strong absorption capability for visible light. Meanwhile, the anti-pollution performance of the film under the irradiation of visible light is also proved to be good.
3. Adsorption effect on MO solution under dark state
The adsorption effect of the composite modified membrane and the polysulfone/polysulfone hollow fiber organic ultrafiltration membrane on MO solution (5mg/L) under the dark state condition is shown in figure 11.
As can be seen from fig. 11, the concentration of the MO solution in the no-film reference group did not change in the absence of light, indicating good MO stability. After the composite modified membrane or the polysulfone hollow fiber organic ultrafiltration membrane is added in the experiment, the adsorption effect of the polysulfone hollow fiber organic ultrafiltration membrane on MO is obvious, and when the adsorption time reaches 300min, the adsorption removal rate reaches 47.0%, and the adsorption equilibrium state is not reached yet. The adsorption effect of the composite modified membrane on MO is not obvious, the adsorption removal rate is only 18.4% when the adsorption time reaches 300min, and the adsorption time reaches 180min, the adsorption equilibrium state is approached. The anti-pollution performance of the composite modified membrane after modification is obviously improved.
In summary, under the condition of no illumination, when the adsorption time is 300min, the dark state adsorption removal rates of the composite modified film to RhB and MO are 8.0% and 18.4%, respectively. The adsorption effect of the composite modified membrane on the MO solution is improved.
4. Photocatalytic effect on MO solution under visible light irradiation condition
Under the irradiation of visible light, the photocatalytic degradation effect of the composite modified membrane, the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane and the reference group without the membrane on the MO solution (5mg/L) is shown in FIG. 12. As can be seen from fig. 12, the MO solution concentration in the reference group without film was not significantly changed under visible light irradiation. This further indicates that the stability of the MO solution is strong. For the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane, under the visible light irradiation condition and the dark state condition, the adsorption effect of the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane on MO is the same, and the change rule of the MO concentration along with the adsorption time is basically consistent, which can further explain that the action mechanism of the polysulfone-polysulfone hollow fiber organic ultrafiltration membrane on MO under the visible light irradiation is mainly adsorption action and has no visible light absorption capacity.
In contrast, in the case of the composite modified film, the MO concentration rapidly decreases under the irradiation of visible light. When the illumination time reaches 300min, the photocatalytic degradation rate of the modified membrane to MO reaches 74.6%, which is far higher than the adsorption removal rate (45.2%) of the polysulfone hollow fiber organic ultrafiltration membrane. The composite modified film is further proved to have stronger absorption capacity to visible light, and the pollution resistance of the film is improved.
In summary, under the irradiation of visible light, the RhB and MO solutions in the reference group without the membrane are not changed, the polysulfone and polysulfone hollow fiber organic ultrafiltration membrane has only the adsorption effect on the RhB and MO solutions, and the degradation rate of the composite modified membrane on the RhB and MO solutions is as high as 98.2% and 74.6% (when the irradiation time of the visible light is 300 min).
5. Photocatalytic self-cleaning performance of composite modified film
Under the condition of visible light irradiation, the surface photocatalytic self-cleaning performance of the composite modified membrane after filtering and trapping the HA solution is researched by taking the flux recovery rate as an evaluation index.
The membrane after filtering the HA solution was taken out and placed in pure water, and a visible light irradiation static light experiment was performed thereon (the result is shown in fig. 13). As is clear from fig. 13, the recovery rate of the membrane flux after irradiation with visible light was improved. Wherein, the membrane flux is recovered from 81.32% to 90.42% when the illumination time is 1 h. The membrane flux recovery was not significant with continued increase in illumination time. The result shows that the photocatalytic composite modified layer with visible light response can effectively photodegrade organic pollutants on the surface of the film in a short time. In addition, the membrane after photocatalytic self-cleaning was subjected to a filtration rejection test of HA solution (as shown in fig. 13). The HA retention rate is kept at a stable level under different illumination time. This further demonstrates that the increase in membrane flux recovery is due to the degradation of organic contaminants on the membrane surface by the photocatalytic effect. Meanwhile, the composite modified film is also shown to have good chemical stability.
(III) cost analysis
The modifier with high hydrophilicity and visible light response capability is introduced to the surface of the polysulfone hollow fiber organic ultrafiltration membrane, so that the pollution resistance of the membrane surface is effectively improved, and the pollutant removal effect of the separation membrane is remarkably improved. However, the modification cost is often one of the important factors for the popularization and application of the modified membrane in practical engineering. Therefore, cost analysis is performed on the composite modified membrane prepared in the laboratory in this section, and the influence of consumable charge, medicament charge, electricity charge, equipment depreciation charge and the like on the preparation cost of the modified membrane is mainly discussed.
As shown in tables 4 and 5, a composite modified membrane (64 cm area) was prepared in the laboratory2Prepared under the conditions of example 3), the required cost is 5.17 yuan, which is increased by 61.56% compared with the cost of the polysulfone hollow fiber organic ultrafiltration membrane, the proportion of the medicine cost is the largest in the increased cost (55.52% of the cost of the polysulfone hollow fiber organic ultrafiltration membrane), and the electricity cost and the depreciation cost respectively account for 3.25% and 3.03%. And because this experiment belongs to the lab scale experiment, and the medicament that the experiment was bought is small-size medicament, and the unit price is higher. If mass production is carried out in the later period, the medicament cost, the electricity charge and the equipment depreciation charge are all obviously reduced.
TABLE 4 preparation of a composite modified Membrane for Electricity and Equipment depreciation costs (laboratory)
TABLE 5 expense and expense of materials (laboratory) for preparing a composite modified membrane
According to the above, the utility model provides a composite modified membrane distributes lamellar structure on polysulfone hollow fiber organic ultrafiltration membrane, then compounds one deck polyamide cortex on polysulfone hollow fiber organic ultrafiltration membrane again, and then at polysulfone hollow fiberOrganic ultrafiltration membrane surface formation of compact SL g-C3N4the/NGO/polyamide composite structure layer greatly improves the hydrophilic performance of the membrane surface, greatly reduces the forbidden bandwidth (Eg) value of the membrane functional layer, and has excellent visible light catalytic capability and organic matter catalytic degradation capability; and the membrane flux is greatly improved, the pollution resistance is obviously improved, and the cost is low.
The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be equivalent replacement modes, and all are included in the scope of the present invention.
Claims (10)
1. The composite modified membrane is characterized by comprising a polysulfone hollow fiber organic ultrafiltration membrane (4), a lamellar structure distributed on the surface of one side of the polysulfone hollow fiber organic ultrafiltration membrane and a polyamide skin layer (1) compounded on the surface of the side of the polysulfone hollow fiber organic ultrafiltration membrane (4); the lamellar structure comprises an aminated graphene oxide lamellar layer (2) distributed on the surface of the polysulfone hollow fiber organic ultrafiltration membrane (4) and a carbon nitride sheet (3) distributed on the aminated graphene oxide lamellar layer (2).
2. The composite modified membrane as claimed in claim 1, wherein the pore diameter of the filter membrane pore of the polysulfone hollow fiber organic ultrafiltration membrane (4) is 10-50 nm.
3. The composite modified membrane of claim 1, wherein the thickness of the polysulfone hollow fiber organic ultrafiltration membrane (4) is 0.10-0.11 mm.
4. The composite modified membrane of claim 1, wherein the loading amount of the sheet structure on the polysulfone hollow fiber organic ultrafiltration membrane (4) is 0.039-0.156 g/cm2。
5. The composite modified membrane of claim 1, wherein the number of the lamellar structures is a plurality of groups; in each group, an aminated graphene oxide sheet layer (2) and a carbon nitride sheet (3) are sequentially stacked.
6. The composite modified membrane according to claim 1, wherein the number of carbon nitride flakes (3) on the aminated graphene oxide sheet layer (2) is several.
7. The composite modified membrane according to claim 1, wherein the mass fraction of the carbon nitride flakes (3) in the lamellar structure is 1-5%.
8. The composite modified membrane according to claim 1, wherein the aminated graphene oxide sheet layer (2) has a thickness of 0.8 to 1.6 nm.
9. The composite modified film according to claim 1, wherein the carbon nitride sheet (3) has a thickness of 1 to 2 nm.
10. The composite modified film according to claim 1, wherein the thickness of the polyamide skin layer (1) is 100nm to 10 μm.
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| CN113877447B (en) * | 2021-11-18 | 2023-11-10 | 康膜科技有限公司 | Preparation technology of high-efficiency intrinsically stable type wholly aromatic polyamide reverse osmosis membrane with high crosslinking degree |
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