CN111620430B - Hollow fiber membrane reactor based on metal thin film catalysis, manufacturing method and application - Google Patents
Hollow fiber membrane reactor based on metal thin film catalysis, manufacturing method and application Download PDFInfo
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/34—Organic compounds containing oxygen
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/38—Organic compounds containing nitrogen
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Organic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Catalysts (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
Abstract
The invention discloses a hollow fiber membrane reactor based on metal film catalysis and a manufacturing method thereof, belonging to the field of sewage treatment equipment. The reactor comprises a reactor shell and a hollow fiber membrane component; the hollow fiber membrane assembly is arranged in the reactor shell and comprises a plurality of hollow fiber membrane filaments, one end of each hollow fiber membrane filament is closed, and the other end of each hollow fiber membrane filament is communicated with the air inlet; the outer surface of the membrane body of the hollow fiber membrane yarn is attached with a metal thin film for catalyzing the degradation of pollutants; the reactor shell is provided with a water inlet and a water outlet, and an aeration part is arranged inside the reactor shell. The hollow fiber membrane in the reactor adopts a metal film to replace the traditional biological membrane, so that the long biological enrichment and biological membrane hanging time of the traditional hollow fiber membrane reactor are saved, and the reactor can be quickly started. The preparation method of the metal film is convenient and easy, has universality in principle, and is suitable for various metals. Therefore, the invention can treat various pollutants which can be catalytically degraded by different metals, and has strong practicability.
Description
Technical Field
The invention belongs to the field of sewage treatment equipment, and particularly relates to a hollow fiber membrane reactor based on metal thin film catalysis, a manufacturing method and application thereof.
Background
With the continuous promotion of industrialization in China, various factories generate various pollutants which need to be discharged after reaching standards, so the requirements on water treatment methods are increasingly improved. The refractory organic matters are common pollutants in sewage treatment, the chemical characteristics of the refractory organic matters determine that the refractory organic matters are difficult to biodegrade, and part of the refractory pollutants, such as antibiotics, chlorinated organic matters and the like, have biological toxicity, so that the refractory organic matters cannot be removed by a traditional biological method. Chemical processes, such as ozone oxidation, metal catalyzed oxidation, and the like, are now widely used to treat such contaminants. Compared with a biological method, the chemical method has the advantages of high reaction speed, thorough pollutant removal and the like.
Hollow fiber membrane reactors are a novel water treatment process based on membrane technology. The reactor uses a hollow fiber membrane as a carrier. The huge surface area formed by the outer surfaces of the hollow fiber membranes is used for providing active sites for reaction, gas is introduced into the cavities of the hollow fiber membranes, and the gas diffuses out of the cavities from the membrane walls of the hollow fiber membranes, so that the reaction is carried out on the outer surfaces of the hollow fiber membranes. The gas introduced here may be a reducing gas including, but not limited to, hydrogen, methane, carbon monoxide, etc.; it may also be an oxidizing gas such as air, oxygen, etc., or a gas for adjusting the pH of the water, including but not limited to carbon dioxide, ammonia, etc. The gas diffused through the membrane wall can not form bubbles, thereby ensuring extremely high gas utilization efficiency and simultaneously avoiding the risk of blowing off volatile pollutants in water into the atmosphere.
The outer surface of the membrane of the traditional hollow fiber membrane reactor is usually attached with a layer of biological membrane, and the purification process of sewage is completed by utilizing the degradation capability of organisms on pollutants, namely the membrane biological membrane reactor (MBfR). As mentioned above, the nature of membrane biofilm reactors (MBfR) is a biological process and the types of contaminants that can be treated are limited. In addition, membrane biofilm reactors (MBfR) also have their own drawbacks. For example, chinese patent application No. 200810202126.1, which requires a long time to complete the growth of the biofilm on the hollow fiber membrane, requires a long hydraulic retention time in the treatment process after the growth is completed, and causes uneven diffusion of the hydrogen gas due to on-way resistance during the transport process, resulting in uneven growth of the biofilm on the hollow fiber membrane, and thus poor contaminant removal effect. In addition, biofilm thickness control is a significant challenge facing membrane biofilm reactors (MBfR). Since gas and pollutants diffuse into the biofilm from the inside and outside of the biofilm to undergo degradation reactions, the thicker or thinner biofilm may affect the treatment effect of the membrane biofilm reactor (MBfR). Meanwhile, the types of pollutants which can be treated by the biofilm method are quite limited, and the membrane biofilm reactor (MBfR) has quite limited treatment capacity for some pollutants which are difficult to biodegrade.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a hollow fiber membrane reactor based on metal thin film catalysis, a manufacturing method and application thereof.
The invention adopts the following specific technical scheme:
in a first aspect, the invention provides a hollow fiber membrane reactor based on metal thin film catalysis, which comprises a reactor shell and a hollow fiber membrane component; the hollow fiber membrane assembly is arranged in the reactor shell and comprises a plurality of hollow fiber membrane filaments, one end of each hollow fiber membrane filament is closed, and the other end of each hollow fiber membrane filament is communicated with the air inlet; a metal thin film for catalyzing the degradation of pollutants is attached to the outer surface of the membrane body of the hollow fiber membrane yarn; the reactor shell is provided with a water inlet and a water outlet, the aeration part is arranged inside the reactor shell and used for aerating the hollow fiber membrane yarn, and an air supply path of the aeration part extends out of the reactor shell.
Preferably, in the first aspect of the present invention, the reactor shell is tubular, the hollow fiber membrane filaments are arranged along the axial direction of the tube body, the aeration member is arranged below the hollow fiber membrane filaments, and the aeration member is preferably a porous aeration head.
Furthermore, a tensioning member is suspended at the bottom of the hollow fiber membrane wire and used for tensioning the hollow fiber membrane wire.
Further, the top and the bottom of the reactor shell are respectively sealed in a detachable way through end covers; the end cover at the top is provided with an exhaust hole which can be opened and closed controllably.
Preferably, in the first aspect of the present invention, the metal thin film is a deposited layer of a hydroxide and/or an oxide of a metal, and the metal is preferably manganese or copper.
Preferably, in the first aspect of the present invention, the hollow fiber membrane structure is a composite membrane, a porous membrane, or a dense membrane; preferably, the outer diameter of the hollow fiber membrane is 0.015-5.5 mm, the membrane wall thickness is 0.005-1.5 mm, and the membrane aperture is 0-0.55 μm.
In a second aspect, the present invention provides a method for manufacturing a hollow fiber membrane reactor according to any of the above technical solutions, comprising the steps of:
s1: arranging an original hollow fiber membrane wire in a reactor shell, wherein one end of the hollow fiber membrane wire is closed, and the other end of the hollow fiber membrane wire is communicated with an air inlet; the reactor shell is provided with a water inlet and a water outlet, an aeration piece is arranged inside the reactor shell, and an air supply path of the aeration piece extends out of the reactor shell;
s2: introducing a metal ion solution into the reactor shell from the water inlet to submerge the hollow fiber membrane filaments, and continuously introducing ammonia gas into the hollow fiber membrane filaments through the air inlet to keep the membrane body at positive pressure, so that the ammonia gas in the hollow fiber membrane filaments continuously penetrates through the membrane body to be diffused to the outside without bubbles, and metal ions in the solution are deposited on the surface of the membrane; the hydroxide precipitate of the metal ion is insoluble in water;
s3: after a uniform metal layer is formed on the surface of the hollow fiber membrane wire, stopping introducing ammonia gas, and continuously introducing a cleaning solution into the reactor shell from the water inlet to replace a metal ion solution to clean the hollow fiber membrane;
s4: and after the hollow fiber membrane filaments are cleaned, drying the hollow fiber membrane filaments to enable the metal hydroxide attached to the hollow fiber membrane to be partially dried and dehydrated to be changed into oxide, and obtaining the hollow fiber membrane reactor based on metal thin film catalysis.
Preferably, in the first aspect of the present invention, the original hollow fiber membrane filaments are bundled and arranged in the axial direction of the reactor shell, the bottom end openings of the hollow fiber membrane filaments are sealed with epoxy glue and bonded to the metal block, and the hollow fiber membrane filaments are straightened in the reactor shell by the gravity of the metal block.
In a third aspect, the present invention provides a wastewater tetracycline treatment method using the hollow fiber membrane reactor according to any one of the above first aspects, comprising the steps of:
continuously pumping wastewater containing tetracycline to be treated into a reactor shell through a water inlet so as to submerge hollow fiber membrane filaments; oxygen generated by an external air source is simultaneously introduced into the air inlet and the air supply gas circuit, on one hand, the oxygen entering the hollow fiber membrane filaments through the air inlet penetrates through the membrane body and is diffused into the metal film outside the membrane filaments in a bubble-free diffusion mode, and tetracycline in the wastewater is oxidized and degraded under the catalytic action of the metal film; on the other hand, the oxygen entering the aeration member rises in the form of bubbles, and the wastewater is simultaneously oxygenated and mixed to promote the catalytic oxidation reaction.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention designs a reactor with a metal film attached to a hollow fiber film, the hollow fiber film in the reactor adopts the metal film to replace the traditional biological film, thereby saving the long biological enrichment and biological film hanging time of the traditional hollow fiber film reactor, and being capable of being quickly started and put into operation.
(2) The reactor of the invention also provides a process method for forming the metal film on the hollow fiber membrane by in-situ deposition in the reactor, the method adopts a mode of bubble-free diffusion of alkaline gas to adjust the pH value, has controllable speed, can form gradient distribution of the pH value between the surface of the hollow fiber membrane and a liquid phase of metal solution, and ensures that a large amount of metal ions selectively generate precipitation reaction on the surface of the hollow fiber membrane to form a fine and uniform metal layer.
(3) The preparation method of the metal film is convenient and easy to operate, has universality in principle, and is suitable for various metals. Therefore, the invention can treat various pollutants which can be catalytically degraded by different metals, and has strong practicability.
Drawings
FIG. 1 is a schematic diagram of a hollow fiber membrane reaction structure based on metal thin film catalysis;
FIG. 2 is a cross-sectional electron microscope image of a hollow fiber membrane after completion of attachment of a manganese thin film in the present invention.
FIG. 3 is a spectrum diagram of a manganese thin film on a hollow fiber membrane according to the present invention.
FIG. 4 is an X-ray photoelectron spectrum of a manganese thin film on a hollow fiber membrane in the present invention.
FIG. 5 is a graph showing the operation effect of tetracycline catalytic oxidation using a manganese thin film attached to a hollow fiber membrane according to the present invention.
The reference numbers in the figures are: the device comprises a sleeve 1, an air inlet 2, an end cover 3, a water outlet 4, a reactor shell 5, hollow fiber membrane yarns 6, a tensioning piece 7, an air supply path 8, a water inlet 9 and an aeration piece 10.
Detailed Description
The invention will be further elucidated and described with reference to the drawings and the detailed description. The technical features of the embodiments of the present invention can be combined correspondingly without mutual conflict.
As shown in fig. 1, the present invention provides a hollow fiber membrane reactor based on metal thin film catalysis, the main structure of the reactor comprises a reactor shell 5 and a hollow fiber membrane module. The reactor shell 5 is a relatively sealed shell that provides mounting locations for the remaining components. The hollow fiber membrane module is arranged in a reactor shell 5, the core component of the hollow fiber membrane module is a plurality of hollow fiber membrane filaments 6, and the hollow fiber membrane filaments 6 are generally arranged in parallel in a bundle. One end of each hollow fiber membrane wire 6 is closed, and the other end is communicated with the air inlet 2. The hollow fiber membrane filaments 6 of one hollow fiber membrane module may share one inlet port 2, or a plurality of inlet ports 2 may be provided. The hollow fiber membrane yarn 6 is characterized in that a metal thin film for catalyzing the degradation of pollutants is attached to the outer surface of a membrane body.
In subsequent embodiments of the invention, the metal film is deposited on the hollow fiber membrane filament body, typically as a hydroxide deposit of the metal in its initial state. However, the hydroxide precipitation of the metal has instability, and during the subsequent standing in air, the hydroxide can be dried, dehydrated or oxidized to form oxide, and the metal film can be converted into the mixed state of the hydroxide and the oxide. If the conversion process is complete, the main component of the metal film will become metal oxide. Therefore, in practical applications, the specific morphology of the metal film needs to be selected according to the specific metal species and the catalytic performance of the metal in different morphologies, and the form having the best catalytic performance for the target pollutant is selected. Since metal oxides generally have a higher catalytic oxidation ability, the metal thin film is preferably dehydrated by drying to form an oxide form of the metal or a mixed form of a hydroxide and an oxide of the metal.
The metal species is preferably manganese or copper, but may be other metals, and the specific species should be determined according to the characteristics of the wastewater to be treated, so as to have catalytic degradation capability on pollutants in the wastewater.
The reactor shell 5 is provided with a water inlet 9 and a water outlet 4, and an aeration piece 10 is arranged inside the reactor shell and is used for aerating the hollow fiber membrane yarn 6. The air supply path 8 of the aeration piece 10 extends out of the reactor shell 5 and is connected with an external air supply source. The source of aeration is typically air, or oxygen.
In the reactor, the metal film is adopted to replace the biological film of the traditional hollow fiber film reactor, so that the complex and time-consuming biological film hanging procedure is not needed, and the starting time of the reactor can be greatly shortened.
The reactor shell 5 of the present invention may take different shapes, but in a preferred embodiment the reactor shell 5 is tubular. The top and the bottom of the tubular shell are provided with two pipe orifices which are detachably sealed through end covers 3 respectively so as to be convenient for follow-up disassembly and assembly maintenance. The end cover 3 can be an open-hole plastic screw cover with a rubber gasket for sealing, and a gap between the end cover 3 and a pipeline passing through the end cover 3 can be sealed by using a sealant.
In addition, because the inside of the reactor needs to be aerated, in order to prevent the internal gas from gathering and being unable to be discharged, the end cover on the top is provided with an exhaust hole which can be opened and closed controllably. The tubular shell can conveniently carry out the deposition of metal on the membrane body and the subsequent wastewater treatment. In this embodiment, the hollow fiber membrane wires 6 are arranged along the axial direction of the tube body, and the aeration member 10 can be arranged below the hollow fiber membrane wires 6, so that the bubbles can automatically rise during aeration to oxygenate the membrane wires and stir simultaneously, and the wastewater is driven in the movement process to be in a completely uniform state, and meanwhile, the high dissolved oxygen state of the wastewater is kept, and the catalytic oxidation reaction is promoted. The aeration member 10 is preferably a porous aeration head.
In addition, in order to maintain the stability of the membrane filaments within the housing, the bottom of the hollow fiber membrane filaments 6 may be suspended with a tensioning member 7 for tensioning the hollow fiber membrane filaments 6. The tensioning member 7 may be a metal block with a certain weight, which is suspended below the membrane wires and applies a tensioning force to the membrane wires by its own weight. Of course, other fasteners capable of tensioning the membrane filaments may be used.
The hollow fiber membrane structure in the present invention may be a composite membrane, a porous membrane, or a dense membrane. Further, the dimensions of the hollow fiber membrane filaments are preferably as follows: the outer diameter is 0.015 to 5.5mm, the thickness of the membrane wall is 0.005 to 1.5mm, and the pore diameter of the membrane is 0 to 0.55 μm.
The hollow fiber membrane reactor can be manufactured by the following in-situ deposition method, and the method comprises the following specific steps:
s1: the original hollow fiber membrane filaments 6 are arranged in the reactor shell 5, and one end of the hollow fiber membrane filaments 6 is closed and the other end is communicated with the gas inlet 2. The original hollow fiber membrane wires 6 are generally arranged in the axial direction of the reactor shell 5 in a bundling manner in advance, the bottom end openings of the hollow fiber membrane wires 6 can be sealed by epoxy glue, and are placed in the reactor shell 5 after being bonded with metal blocks, and the hollow fiber membrane wires 6 are in a stretched state in the reactor shell 5 through the gravity of the metal blocks.
A water inlet 9 and a water outlet 4 are arranged on the reactor shell 5 in advance, an aeration piece 10 is arranged inside the reactor shell, and an air supply path 8 of the aeration piece 10 extends out of the reactor shell 5. It should be noted that, in the actual manufacturing process, the aeration member 10 and the gas supply path 8 may be preset before the step S2 is performed, or may be added after the deposition process is completed, which is not limited.
S2: and (2) introducing a metal ion solution into the reactor shell 5 from the water inlet 9 to submerge the hollow fiber membrane filaments 6, and continuously introducing ammonia gas into the hollow fiber membrane filaments 6 through the air inlet 2 to keep the membrane body at positive pressure, so that the ammonia gas in the hollow fiber membrane filaments 6 continuously penetrates through the membrane body to be diffused without bubbles to the outside, and metal ions in the solution are deposited on the surface of the membrane. In the above solutions, the hydroxide precipitation of the metal ions should be rendered sparingly soluble in water to ensure that it can be deposited on the membrane during the process.
S3: and after a uniform metal layer is formed on the surface of the hollow fiber membrane wire 6, stopping introducing ammonia gas, and continuously introducing a cleaning solution into the reactor shell 5 from the water inlet 9 to replace a metal ion solution to clean the hollow fiber membrane.
S4: and after the cleaning is finished, drying the hollow fiber membrane filaments 6 to obtain the hollow fiber membrane reactor based on metal thin film catalysis.
The above-mentioned metal layer automatically formed on the surface of the hollow fiber membrane is mainly composed of hydroxide precipitate particles of metals of different valence states. In the deposition process, the pH is adjusted by adopting a non-bubble diffusion mode of alkaline gas, the speed is controllable, the gradient distribution of the pH value can be formed between the surface of the hollow fiber membrane and a liquid phase of the metal solution, and a large amount of metal ions selectively perform a precipitation reaction on the surface of the hollow fiber membrane to form a fine and uniform metal layer.
In step S2, the metal ions in the metal ion solution are ions of the metal corresponding to the metal thin film desired to be attached to the hollow fiber membrane. The metal ion solution adopts a saturated solution, so that the concentration of metal ions in the solution can be improved, and the deposition rate and effect can be improved. In addition, in the deposition process, the metal saturated solution can be continuously circulated between the water outlet 4 and the water inlet 9, so that the solution is completely mixed in the reactor through internal circulation, and the uniformity of the metal layer is improved. The circulation of the solution is continued until a macroscopic, fine, uniform metal layer is formed on the surface of the hollow fiber membrane. Because the end part of the hollow fiber membrane is closed, ammonia gas is continuously introduced into the hollow fiber membrane, so that the interior of the membrane body can be always in a positive pressure state, and under the pressure inside the membrane, the ammonia gas continuously penetrates through the membrane body and is diffused to the surface of the membrane without bubbles. The ammonia gas forms ionization after contacting with the solution on the surface of the membrane, and combines with metal ions in the solution to form metal hydroxide to deposit on the surface of the membrane. It should be noted that the introduction rate of ammonia gas should be controlled, and the pressure in the film should not be too high, so as to prevent bubbles from appearing on the surface of the film and destroy the continuity and uniformity of the metal film.
In step S3, distilled water may be introduced into the hollow fiber membrane reactor to flush the interior of the reactor, and a suitable indicator is selected to detect metal ions in the cleaning solution until the indicator does not develop color, indicating complete cleaning. For manganese and copper ions, a 0.2% PAN indicator may be used for color development.
After step S3 is completed, the hollow fiber membrane reactor may be dried by placing in air for 12h, and then placed in a refrigerator at 4 degrees celsius for 12h to stabilize the membrane body and the metal layer on the surface.
By the above method, a hollow fiber membrane to which a metal thin film is attached can be prepared. The hollow fiber membrane can replace the traditional hollow fiber membrane with a biological membrane attached to the surface and is used for treating pollutants difficult to degrade. When the treatment is carried out, the sewage of the pollutants which are difficult to degrade and are to be treated can be introduced into the reactor, and the pollutants which are difficult to degrade can be treated by degradation reaction by utilizing the catalytic oxidation performance of the metal film attached to the surface of the hollow fiber membrane wire.
The invention specifically provides a wastewater tetracycline treatment method by using the hollow fiber membrane reactor, which comprises the following steps:
the wastewater to be treated containing tetracycline is continuously pumped into the reactor housing 5 through the water inlet 9 so as to submerge the hollow fiber membrane filaments 6. Oxygen generated by an external air source is simultaneously introduced into the air inlet 2 and the air supply path 8, on one hand, the oxygen entering the hollow fiber membrane wire 6 through the air inlet 2 passes through the membrane body and is diffused into a metal film outside the membrane wire in a bubble-free diffusion mode, and the tetracycline in the wastewater is oxidized and degraded under the catalytic action of the metal film; on the other hand, the oxygen gas introduced into the aeration member 10 rises in the form of bubbles, and the wastewater is simultaneously oxygenated and mixed to promote the catalytic oxidation reaction. In the process, the vent 2 at the top nozzle is always open, allowing excess gas to exit the reactor.
In order to better demonstrate the specific technical effects of the present invention, the following description is made with reference to specific examples.
Example 1
In this example, a conventional double-tube hollow fiber membrane reactor was used as a place for both production and wastewater treatment. The reactor comprises a main reaction tube, and the reaction tube contains 60 hollow fiber membrane filaments which are main sites for catalytic degradation reaction. In addition, a side reaction tube is arranged in the reactor, and the reaction tube contains 10 hollow fiber membranes and is used for sampling and observing the metal thin film. The main reaction tube and the secondary reaction tube are both constructed as shown in FIG. 1. The effective volume of the double-tube hollow fiber membrane reactor is 60 mL. The hollow fiber membrane was a composite membrane (composite membrane) made of polypropylene, and the outer diameter was 260 μm.
The preparation process of the manganese metal film in the reactor and the operation process of the manganese metal film for wastewater treatment are described below by taking the catalytic degradation of tetracycline by the manganese metal film as an example.
Firstly, preparing a manganese film attached to a hollow fiber membrane, comprising the following steps:
(1): a sufficient amount of an analytically pure manganese sulfate reagent is dissolved in 100mL of distilled water at room temperature to form a saturated solution of the metal. And (3) putting the saturated solution with the manganese precipitate into an ultrasonic instrument for ultrasonic treatment for 25 minutes to uniformly distribute manganese ions in the solution for later use.
(2): and (2) introducing ammonia gas into the hollow fiber membrane filaments of the hollow fiber membrane reactor, and introducing the saturated manganese solution obtained in the step (1) into the hollow fiber membrane reactor, wherein the gauge pressure of the ammonia gas is 0.15 Mpa. After the reactor is filled with the saturated manganese solution, the saturated manganese solution is internally circulated in the reactor, the internal circulation flow rate is 0.5mL/min, and the hydraulic retention time is 2 h. After 3d of operation, a macroscopic, fine and uniform metal layer with catalytic degradation capacity is formed on the surface of the hollow fiber membrane filaments, and the main component of the metal layer is manganese hydroxide particles.
(3): therefore, a metal layer is attached to the surface of the hollow fiber membrane wire through in-situ deposition, but a large amount of manganese solution still exists on the surface of the metal layer at the moment, and the metal layer needs to be cleaned. And when cleaning, stopping introducing ammonia gas, discharging the solution in the reactor, and introducing distilled water into the hollow fiber membrane reactor to perform in-situ washing on the interior of the reactor. After the cleaning liquid is discharged from the water outlet, 0.2% PAN indicator is selected to detect manganese ions in the cleaning liquid until the indicator does not develop color, which indicates that the cleaning is finished, water feeding is stopped, and the interior is emptied.
And then, after the prepared hollow fiber membrane reactor is placed in the air for 12 hours, the manganese hydroxide in the metal layer is gradually dehydrated and converted into an oxide form with stronger catalytic capacity, and then the hollow fiber membrane reactor is placed in a refrigerator at 4 ℃ for 12 hours and taken out to degrade the tetracycline. In this embodiment, the simulated wastewater is used for the test, and the specific operation is as follows:
(1): preparing the tetracycline-simulated wastewater, wherein the initial concentration of the tetracycline is 10mg/L for later use.
(2): oxygen gas is introduced into the hollow fiber membrane attached with the manganese thin layer under the pressure of 0.15 Mpa.
(3): and (2) introducing the prepared tetracycline wastewater into the hollow fiber membrane reactor, wherein the water inlet rate is 0.1mL/min, the hydraulic retention time is 10 hours, and simultaneously starting an internal circulation pump, wherein the internal circulation rate is 1mL/min, and the hydraulic retention time is 1 hour. The degradation of the tetracycline can be finished by keeping the continuous operation of the operating conditions.
The manganese thin layer attached to the hollow fiber membrane was subjected to material identification and morphological analysis by transmission electron microscopy, energy spectroscopy and XRD (see fig. 2-4 for details). The results showed that fine manganese particles (containing divalent manganese and tetravalent manganese) were attached to the hollow fiber membrane, and the thickness of the manganese thin layer was about 10 um.
The steady state operation results of the reactor in this example are shown in fig. 5, which shows that this example can achieve effective tetracycline removal in a short hydraulic retention time, and the steady state effluent tetracycline removal rate reaches 30%.
The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.
Claims (9)
1. A hollow fiber membrane reactor based on metal thin film catalysis is characterized by comprising a reactor shell (5) and a hollow fiber membrane component; the hollow fiber membrane module is arranged in the reactor shell (5) and comprises a plurality of hollow fiber membrane filaments (6), one end of each hollow fiber membrane filament (6) is closed, and the other end of each hollow fiber membrane filament is communicated with the air inlet (2); a metal thin film for catalyzing the degradation of pollutants is attached to the outer surface of the membrane body of the hollow fiber membrane wire (6); a water inlet (9) and a water outlet (4) are formed in the reactor shell (5); an aeration piece (10) is arranged in the reactor shell (5) and is used for aerating the hollow fiber membrane yarn (6), and an air supply path (8) of the aeration piece (10) extends out of the reactor shell (5);
the manufacturing method of the hollow fiber membrane reactor comprises the following steps:
s1: arranging an original hollow fiber membrane wire (6) in a reactor shell (5), wherein one end of the hollow fiber membrane wire (6) is closed, and the other end of the hollow fiber membrane wire is communicated with an air inlet (2); a water inlet (9) and a water outlet (4) are formed in the reactor shell (5), an aeration piece (10) is arranged in the reactor shell, and a gas supply path (8) of the aeration piece (10) extends out of the reactor shell (5);
s2: introducing a metal ion solution into a reactor shell (5) from a water inlet (9) to submerge the hollow fiber membrane filaments (6), continuously introducing ammonia gas into the hollow fiber membrane filaments (6) through an air inlet (2) to keep the interior of the membrane body at positive pressure, continuously penetrating the ammonia gas in the hollow fiber membrane filaments (6) through the membrane body to diffuse to the outside without bubbles, and depositing metal ions in the solution on the surface of the membrane; the hydroxide precipitate of the metal ion is insoluble in water;
s3: after a uniform metal layer is formed on the surface of the hollow fiber membrane wire (6), stopping introducing ammonia gas, and continuously introducing cleaning liquid into the reactor shell (5) from the water inlet (9) to replace a metal ion solution to clean the hollow fiber membrane;
s4: and after the hollow fiber membrane filaments (6) are cleaned, drying and dehydrating the metal hydroxide part attached to the hollow fiber membrane to obtain an oxide, thus obtaining the hollow fiber membrane reactor based on metal thin film catalysis.
2. The metal thin film catalyst-based hollow fiber membrane reactor of claim 1, wherein the reactor housing (5) has a tubular shape, the hollow fiber membrane filaments (6) are arranged along the axial direction of the tubular body, the aeration member (10) is arranged below the hollow fiber membrane filaments (6), and the aeration member (10) is a porous aeration head.
3. The metal thin film catalysis based hollow fiber membrane reactor according to claim 2, wherein the bottom of the hollow fiber membrane wires (6) is suspended with a tensioning member (7) for tensioning the hollow fiber membrane wires (6).
4. The metal thin film catalyst based hollow fiber membrane reactor of claim 2, wherein the reactor housing (5) is detachably sealed at the top and bottom by end caps (3), respectively; the end cover at the top is provided with an exhaust hole which can be opened and closed controllably.
5. The metal thin film catalytic based hollow fiber membrane reactor of claim 1 wherein the metal thin film is a hydroxide and oxide deposit of a metal, the metal being manganese or copper.
6. The metal thin film catalysis based hollow fiber membrane reactor according to claim 1, wherein the hollow fiber membrane structure is a composite membrane, a porous membrane, or a dense membrane.
7. The metal thin film catalyst-based hollow fiber membrane reactor of claim 1, wherein the hollow fiber membrane has an outer diameter of 0.015 to 5.5mm, a membrane wall thickness of 0.005 to 1.5mm, and a membrane pore diameter of 0 to 0.55 μm.
8. The metal thin film catalyst-based hollow fiber membrane reactor according to claim 1, wherein the original hollow fiber membrane wires (6) are arranged in a bundle in the axial direction of the reactor housing (5), the bottom openings of the hollow fiber membrane wires (6) are sealed with epoxy glue and bonded to a metal block, and the hollow fiber membrane wires (6) are in a straightened state in the reactor housing (5) by the weight of the metal block.
9. A method for tetracycline treatment of wastewater using the hollow fiber membrane reactor of any of claims 1 to 7, comprising the steps of:
continuously pumping the wastewater to be treated containing tetracycline into a reactor shell (5) through a water inlet (9) to submerge the hollow fiber membrane filaments (6); oxygen generated by an external air source is simultaneously introduced into the air inlet (2) and the air supply path (8), on one hand, the oxygen entering the hollow fiber membrane filaments (6) through the air inlet (2) passes through the membrane body and diffuses into the metal film outside the membrane filaments in a bubble-free diffusion mode, and the tetracycline in the wastewater is oxidized and degraded under the catalytic action of the metal film; on the other hand, the oxygen entering the aeration member (10) rises in the form of bubbles, and the wastewater is oxygenated and mixed simultaneously to promote the catalytic oxidation reaction.
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