Piezoelectric catalyst using piezoelectric effect induced by fluid flow, and water treatment process using same

Abstract

The subject matter disclosed in the present disclosure are: a piezoelectric catalyst in the form of a composite, comprising a fluorinated polymer (including a homopolymer and a copolymer), a conductive carbon and a water-soluble metal salt that promotes the piezocatalysis of the fluorinated polymer; and a water treatment process of injecting same into a fluid (specifically, an aqueous fluid) that contains organic contaminants, and decomposing the organic contaminants by using piezoelectric potential generated by fluid flow.

Description

Piezoelectric catalyst utilizing piezoelectric phenomenon caused by fluid flow and water treatment process using the same

[0001] The present disclosure relates to a piezoelectric catalyst utilizing a piezoelectric phenomenon caused by fluid flow, and a water treatment process using the same. More specifically, the present disclosure relates to a piezoelectric catalyst in the form of a composite comprising a fluorinated polymer (including a homopolymer and a copolymer), conductive carbon, and a water-soluble metal salt that promotes piezoelectric catalysis of the fluorinated polymer, and a water treatment process in which the piezoelectric catalyst is introduced into an organic pollutant-containing fluid (specifically, an aqueous fluid) to decompose organic pollutants using the piezoelectricity generated by the fluid flow.

[0002] Due to the rise of environmental rights that demand a pleasant environment for human life and the strengthening of policies and institutional regulations to support this, effective control of environmental pollution has emerged as a major issue in urbanized and industrialized societies.

[0003] Not only has the volume of wastewater discharge been increasing recently, but wastewater treatment standards are being strengthened both domestically and internationally. Consequently, the need for efficient wastewater treatment methods is growing.

[0004] Biological treatment technology is recognized as a representative process for conventional wastewater treatment. However, biological treatment technology alone is insufficient to address the ever-increasing regulatory requirements. Therefore, if persistent organic pollutants, such as those not removed by biological treatment, flow into water systems, they can disrupt aquatic ecosystems and cause fatal toxicity within the food chain. In particular, for toxic and persistent organic pollutants, faster and more efficient treatment methods must be developed.

[0005] To overcome the limitations of biological treatment technologies, the Fenton oxidation process is also known. It decomposes recalcitrant pollutants in wastewater based on the strong oxidizing power of hydroxyl (-OH) radicals generated by the reaction between hydrogen peroxide and iron (II) ions. However, the Fenton oxidation process requires a low pH range (i.e., acidic), requiring appropriate pH adjustment. Furthermore, the process requires post-treatment to raise the pH, which is cumbersome. Furthermore, the iron used as a reaction catalyst generates large amounts of sludge in the form of iron hydroxide, necessitating a post-treatment process.

[0006] In addition, various treatment methods such as ion exchange, biotreatment, photocatalytic oxidation, chemical precipitation, membrane filtration, and electrochemical treatment have been developed, and in particular, with regard to photocatalyst-based methods, photocatalytic oxidation using ultraviolet (UV) / hydrogen peroxide (H2O2) and photocatalytic oxidation using ultraviolet (UV) / titania (TiO2)-based photocatalysts are being studied.

[0007] However, in the case of the conventional technology described above, there is still a need for improvement in terms of commercialization, such as the additional operational costs required to activate the catalyst when operating the process.

[0008] Recently, a technology has been developed to decompose and remove organic contaminants in a fluid using piezoelectricity generated from a piezoelectric catalyst due to pressure caused by the flow or movement of a fluid (specifically, an aqueous medium) (e.g., ACS EST Engg. 2022, 2, 101-109, etc.). The materials of these piezoelectric catalysts can be broadly divided into inorganic materials (e.g., zirconium titanate, BaTiO3) and organic materials (e.g., polyvinylidene fluoride (PVdF)). Among them, PVdF has high piezoelectric properties and is attracting much attention due to its inherent formability and lightweight nature. However, in the case of PVdF, a high-voltage poling process (i.e., a treatment process that applies an electric field so that the dipole moments align along the direction of the electric field) is required to electrically express piezoelectricity. This polling process is typically performed by applying high voltage (e.g., 2 to 12 kV) over a long period of time (e.g., 12 to 24 hours), such as through a corona process.

[0009] In this way, a method is required to overcome the technical limitations of conventional water treatment processes that require additional energy such as ultraviolet rays or electricity, or treatment costs due to sludge generation, and to alleviate process inefficiency due to the high-voltage poling process required in water treatment processes that utilize piezoelectric catalysts.

[0010] One specific example of the present disclosure is to provide a piezoelectric catalyst capable of exhibiting piezoelectricity without a high voltage poling process.

[0011] In addition, another specific example of the present disclosure seeks to provide a piezoelectric catalyst that can be manufactured into a desired shape based on the plasticity and ease of molding unique to polymers.

[0012] In another specific example of the present disclosure, it is intended to provide a water treatment process that can not only overcome the technical limitations pointed out in the prior art by using the aforementioned piezoelectric catalyst, but also effectively decompose and remove organic pollutants contained in a fluid such as wastewater.

[0013] According to the first page of this disclosure,

[0014] (i) fluorinated polymers;

[0015] (ii) conductive carbon; and

[0016] (iii) a water-soluble metal salt for inducing chemical polarization of the above fluorinated polymer;

[0017] Includes,

[0018] A piezoelectric catalyst is provided in which the weight ratio of fluorinated polymer: conductive carbon: water-soluble metal salt is controlled in the range of 1:0.05 to 1:0.15 to 1.

[0019] According to an exemplary embodiment, the fluorinated polymer may be a polyvinylidene fluoride copolymer in which at least one comonomer selected from the group consisting of trifluoroethylene (TrFE), hexafluoropropylene (HFP), and chlorotrifluoroethylene (CTFE) is added onto polyvinylidene fluoride and / or vinylidene fluoride.

[0020] According to an exemplary embodiment, the fluorinated polymer may contain at least 50 wt% β-PVdF.

[0021] According to an exemplary embodiment, the molecular weight (M) of the fluorinated polymer w ) can be adjusted in the range of 30,000 to 1,600,000.

[0022] According to an exemplary embodiment, the conductive carbon has at least 5.39×10 -10 It can exhibit a conductivity of S / cm (room temperature) and a band gap of less than 3.15 eV.

[0023] According to an exemplary embodiment, the conductive carbon may be at least one selected from the group consisting of graphene, carbon nanotubes (CNTs), graphite, activated carbon, and fullerene.

[0024] According to an exemplary embodiment, the water-soluble metal salt may be at least one selected from the group consisting of sodium chloride, calcium carbonate, calcium chloride, and magnesium chloride.

[0025] According to the second page of this disclosure,

[0026] a) A step of preparing a mixture or dispersion containing a fluorinated polymer and conductive carbon in an organic solvent;

[0027] b) a step of preparing a metal salt-containing mixed solution or dispersion by adding a water-soluble metal salt to the mixed solution or dispersion;

[0028] c) a step of drying the metal salt-containing mixture or dispersion, and then adding an aqueous medium to form a precipitate containing a fluorinated polymer, conductive carbon, and a water-soluble metal salt; and

[0029] d) a step of recovering the above sediment as a catalyst;

[0030] Including,

[0031] A method for producing a piezoelectric catalyst is provided, wherein the weight ratio of the fluorinated polymer: conductive carbon: water-soluble metal salt in the catalyst is controlled in the range of 1:0.05 to 1:0.15 to 1.

[0032] According to an exemplary embodiment, the method for producing the piezoelectric catalyst may not involve a poling process.

[0033] According to the third page of this disclosure,

[0034] A step of introducing the aforementioned piezoelectric catalyst into an aqueous medium; and

[0035] A step of decomposing organic pollutants contained in an aqueous medium by using piezoelectricity generated from a piezoelectric catalyst by a fluid flow within the aqueous medium;

[0036] A water treatment process using a piezoelectric catalyst including .

[0037] According to specific examples of the present disclosure, the piezoelectricity required for catalytic activity can be provided without the high-voltage poling process performed in the production of conventional fluorinated polymer-based piezoelectric catalysts. Furthermore, the catalyst can be manufactured into a desired shape based on the polymer's unique plasticity and moldability. Furthermore, when treating wastewater (specifically, aqueous wastewater) containing organic pollutants using the aforementioned piezoelectric catalyst, the technological limitations of conventional water treatment processes, such as requiring additional energy such as ultraviolet rays or electricity, or requiring treatment costs due to sludge generation, can be overcome. Therefore, widespread commercialization is anticipated in the future.

[0038] FIG. 1 is a drawing exemplarily showing the reaction and drying process between reactants during the entire manufacturing process of a PVdF / AC-NaCl foam piezoelectric catalyst according to an embodiment;

[0039] FIG. 2a is a drawing showing a post-treatment process for forming a solid precipitate after the reaction and drying process during the entire manufacturing process of a PVdF / AC-NaCl foam piezoelectric catalyst according to an embodiment;

[0040] Figure 2b is a photograph showing the appearance of a solidified PVdF / AC-NaCl foam piezoelectric catalyst according to the inner shape of the beaker during the post-processing process;

[0041] Figure 3a is a photograph showing a state in which a piezoelectric catalyst (PVDF / AC-NaCl) manufactured in an example is attached to a mixer blade;

[0042] Figure 3b is a SEM image of the piezoelectric catalyst (PVdF / AC-NaCl);

[0043] Figure 3c is a SEM image of the piezoelectric catalyst (PVdF / AC-NaCl) with superimposed EDS analysis;

[0044] Figure 4a is the FT-IR spectra of PVdF / AC-NaCl, PVdF / AC, PVdF-NaCl, and pure PVdF, respectively;

[0045] Figure 4b is an XRD graph of PVdF / AC-NaCl, PVdF / AC, PVdF-NaCl, and pure PVdF, respectively;

[0046] Figures 5a to 5e are XPS spectra of Cl 2p, F 1s, C 1s, Na 1s, and Na 2s for the PVdF / AC-NaCl piezoelectric catalyst, respectively;

[0047] Figure 6a is a top view plot of the velocity distribution when the fluid rotates at 200 rpm around a fixed PVdF / AC-NaCl blade form;

[0048] FIG. 6b and FIG. 6c are top view plots of the velocity distribution of water in a beaker when the PVdF / AC-NaCl piezoelectric catalyst is rotated at 200 rpm for rectangular and cylindrical shapes, respectively (cylinder: diameter 75 mm, height 40 mm; and rectangle: 75 mm × 30 mm × 40 mm);

[0049] Figure 6d is a velocity distribution plot within a beaker when a rectangular PVdF / AC-NaCl blade foam piezoelectric catalyst is rotated at 200 rpm;

[0050] Figure 6e is a side view plot of the velocity distribution when the rectangular PVdF / AC-NaCl blade foam piezoelectric catalyst rotates at 200 rpm;

[0051] Figure 6f is a top view plot of the pressure distribution when the fluid rotates at 200 rpm around the fixed PVdF / AC-NaCl blade form;

[0052] FIG. 6g is a side plot of the flow-induced pressure distribution on a rectangular PVdF / AC-NaCl blade foam piezoelectric catalyst when rotated at 200 rpm (PVdF / AC-NaCl blade foam is shown in black);

[0053] Figure 6h is a side plot of the voltage distribution generated on the PVdF / AC-NaCl surface resulting from the pressure formed by the flow;

[0054] Figure 7a is a graph showing the change (difference) in the degradation efficiency of methyl orange (MO; concentration: 100 mg / L) according to the amount of NaCl added during the catalyst manufacturing process;

[0055] Figure 7b is a graph showing the piezoelectric decomposition rate and adsorption rate (organic matter concentration: 100 mg / L) for RhB, 4-NIP (4-nitrophenol), phenol, and TC (tetracycline), respectively, using a PVdF / AC-NaCl catalyst;

[0056] Figure 7c is a graph comparing the decomposition rates of RhB (100 mg / L) when the PVdF / AC-NaCl foam piezoelectric catalyst is directly rotated and when the PVdF / AC-NaCl catalyst is fixed and water is rotated;

[0057] Figure 7d is a pseudo-second-order reaction rate graph for the decomposition rates of RhB, 4-NIP, phenol, and TC, respectively;

[0058] Figure 7e is a bar graph of pseudo-first-order rate constants for RhB, 4-NIP, phenol, and TC, respectively;

[0059] Figure 8a is a reusability graph for a PVdF / AC-NaCl foam piezoelectric catalyst ("Re-cycled" indicates a re-synthesized catalyst that was re-dissolved in DMF and re-manufactured for decomposition experiments, and then subjected to 5 cycle tests (repeated tests);

[0060] Figure 8b is a SEM image of the PVdF / AC-NaCl catalyst before the cycle test;

[0061] Figure 8c is a SEM image of the PVdF / AC-NaCl catalyst after the cycle test;

[0062] Figure 8d is a SEM image of the recycled catalyst after the cycle test;

[0063] Figure 8e is an FT-IR graph of the catalyst before the cycle test;

[0064] Figure 8f is an FT-IR graph of the catalyst after the cycle test;

[0065] Figure 8g is an FT-IR graph of the re-synthesized catalyst before the cycle test;

[0066] Figure 9a is a graph showing the results of an active species trapping experiment (active species trapping experiment conditions: MO=30 mg / L, temperature 15°C, initial pH=6.2);

[0067] Figure 9b is the ESR spectrum of the radical trapped by TEMPO, h + is the TEMPO-trapped ESR spectrum; and

[0068] Figure 9c is an ESR spectrum of a DMPO-trapped radical, that is, a DMPO-trapped ESR spectrum of a hydroxyl radical (·OH).

[0069] The present invention can be fully achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention and is not necessarily limited thereto. Furthermore, the attached drawings are provided to aid understanding and are not intended to limit the present invention. Details regarding individual components can be appropriately understood based on the specific intent of the related descriptions described below.

[0070] The terms used in this disclosure may be defined as follows.

[0071] The "piezoelectric effect" can refer to a physical phenomenon in which a deformed piezoelectric material can mediate the transformation between mechanical energy and electrical energy.

[0072] "Piezoelectric material" can mean a material that can convert mechanical vibrations into electric charges or electric fields, and further into mechanical strain in the fields of sensors, energy harvesting, and actuators, etc., by means of the piezoelectric effect.

[0073] "Piezocatalysis" can refer to a wide range of reactions that are based on the piezoelectric effect generated by a catalyst, such as the decomposition of organic pollutants, sterilization, wound healing, and tissue repair.

[0074] “Fluoropolymer” may mean a polymer containing fluorine groups in the polymer chain.

[0075] "Salt" can broadly mean a compound having a pair of cations and anions, and can typically mean a group of ionic compounds formed from a neutralization reaction between an acid and a base.

[0076] “Water soluble salt” may mean a salt that can be dissolved in 100 g of water (distilled water), for example, at least about 0.1 g, specifically at least about 0.5 g, more specifically about 1 g, and especially specifically at least about 2 g.

[0077] In this specification, terms such as “on” or “upper side” and “lower side” or “below” can be understood to describe the relative positional relationship between components or members, and terms such as “located above” or “located below” can be understood to express the relative positional relationship not only in a state of contact with a specific object but also in a state of not being in contact with it.

[0078] When a numerical range is specified herein with lower and / or upper limits, it is understood that any sub-combination within that numerical range is also disclosed. For example, when "1 to 5" is described, it can include 1, 2, 3, 4, and 5, as well as any sub-combination therebetween.

[0079] Where any component or member in this specification is described as being "connected" to another component or member, unless otherwise stated, it is to be understood that this includes not only the case where it is directly connected to said other component or member, but also the case where it is connected through the intervention of said other component or member.

[0080] Similarly, the term "contact" may be understood to include not only direct contact but also contact under the intervention of other components or absences.

[0081] When we say that something "includes" something, we mean that it may also include other components, unless otherwise stated.

[0082]

[0083] piezoelectric catalyst

[0084] According to one specific example of the present disclosure, a piezoelectric catalyst in the form of a composite is provided, which comprises a fluorinated polymer, a conductive carbon, and a metal salt that promotes piezoelectric catalysis of the fluorinated polymer.

[0085]

[0086] - Fluorinated polymers

[0087] According to one specific example, the composite-based piezoelectric catalyst contains a fluorinated polymer as a component to provide the main piezoelectric properties.

[0088] Examples of such fluorinated polymers may be polyvinylidene fluoride (PVdF), and / or polyvinylidene fluoride copolymers in which at least one comonomer selected from the group consisting of trifluoroethylene (TrFE), hexafluoropropylene (HFP), and chlorotrifluoroethylene (CTFE) is added onto vinylidene fluoride.

[0089] In a specific embodiment, polyvinylidene fluoride (PVdF) can be used as the fluorinated polymer. PVdF is a semi-crystalline piezoelectric polymer having at least five different crystalline structures (phases) and containing crystalline and amorphous phases internally. Furthermore, PVdF is a dielectric polymer with high dielectric breakdown strength characteristics that provide long-term surface charge retention, which is due to its amphiphilic molecular structure having CH2-CF2 monomer repeating units. Among the crystal structures of PVdF, the α-phase is the most stable and non-polar phase, while the β-phase may correspond to the phase exhibiting the greatest piezoelectric behavior. The piezoelectric properties of PVdF are related to the crystalline portion of the polymer. In particular, PVdF may be advantageous for energy conversion such as electromechanical actuation and energy harvesting because it exhibits good flexibility and biocompatibility, as well as low dielectric loss. Furthermore, PVdF exhibits high piezoelectric response voltage, good thermal stability and chemical resistance.

[0090] In this regard, the molecular weight (M) of the fluorinated polymer applicable in the present specific example w) may range from about 30,000 to 1,600,000, specifically from about 300,000 to 1,100,000, more specifically from about 570,000 to 600,000, but is not necessarily limited thereto. However, it may be advantageous to have a molecular weight in the aforementioned range, as an excessively low molecular weight may cause insufficient viscosity, making subsequent processing, such as combination with other components, difficult.

[0091] In an exemplary embodiment, when a PVdF (including a copolymer) polymer is used as the fluoropolymer, the fluoropolymer may include a piezoelectric PVdF polymer, and the piezoelectric PVdF may be β-PVdF. In this case, it may be advantageous to contain a type having an increased proportion of β-PVdF, if possible. In an exemplary embodiment, the fluoropolymer may contain at least about 50 wt%, specifically about 60 wt%, and more specifically at least about 70 wt%, of β-PVdF. In a specific embodiment, the fluoropolymer may contain, for example, about 72 to 90 wt%, specifically about 75 to 85 wt%, of β-PVdF. However, the above-described numerical ranges may be understood to be exemplary in nature.

[0092]

[0093] - Conductive carbon

[0094] According to one specific example, the conductive carbon can function as an auxiliary catalyst component to enhance the piezoelectric effect generated from the fluorinated polymer within the catalyst by the flow of the fluid.

[0095] According to an exemplary embodiment, the conductive carbon has, for example, at least about 5.39×10 -10 S / cm, specifically 5.39×10 -10 2.36×10 -8 S / cm, more specifically at least about 2.36×10 -9 5.39×10 -9S / cm, specifically about 3×10 -9 5×10 -9 It can represent the conductivity (room temperature) of S / cm.

[0096] According to an exemplary embodiment, the conductive carbon may be a type that possesses electrons and holes and thus has a band gap. In this regard, the band gap of the conductive carbon may be, for example, about 3.15 eV or less, specifically about 3.1 eV or less, more specifically about 2.1 to 3.1 eV, and particularly specifically about 2.8 to 3.1 eV. In this respect, carbonaceous materials that do not possess free electrons, such as diamond, would be excluded from the scope of conductive carbon.

[0097] According to an exemplary embodiment, the conductive carbon may be, for example, graphene (graphene oxide or reduced graphene oxide), carbon nanotubes (CNT), graphite, activated carbon, fullerene, etc., and at least one of these may be selected and used.

[0098] In this regard, "graphene oxide" may refer to graphene functionalized with oxygen-containing chemical groups (e.g., epoxy or hydroxyl groups), specifically single-layer graphene oxide (a two-dimensional material derived from graphene by introducing C-O covalent bonds), wherein carbonyl and carboxyl groups are located at the edges of the graphene, which may exhibit polar surface properties. The functional groups on the surface of graphene oxide can act as anchor sites for fixing various active species, and it may have tunable electronic properties. "Reduced graphene oxide (rGO)" is a material with a structure similar to graphene, which may exhibit a high specific surface area, thin film, and conductivity. When graphene oxide is reduced, the sheet resistance of rGO is significantly reduced.

[0099] "Carbon nanotube (CNT)" can mean a one-dimensional nanostructure in which a purely sp2-bonded hexagonal carbon network is rolled (curled) into a tubular or cylindrical structure with a nano-sized diameter. Depending on the number of bonds forming the wall or the number of graphitic layers (single-atom-thick flat sheets of sp2-bonded carbon atoms having a honeycomb crystal lattice structure), they are classified into single-walled carbon nanotubes (SWCNTs), double-walled carbon nanotubes (DWCNTs), and multi-walled carbon nanotubes (MWCNTs). In particular, SWCNTs have a diameter of approximately 1 nm and can have a significantly high length-to-diameter ratio (e.g., 132,000,000 times), DWCNTs have a diameter of approximately 5 to 10 nm and can contain one concentric SWCNT inside a larger nanotube, and MWCNTs can contain two or more concentric CNTs inside a larger outer nanotube. CNTs can be typically manufactured through methods such as arc process (arc discharge), laser ablation, CVD (Chemical Vapor Deposition), and CCVD (Catalytic Chemical Vapor Deposition).

[0100] "Graphite" is a material in which graphene layers are held together by van der Waals forces, and the distance between adjacent graphene layers is approximately 0.335 nm.

[0101] "Carbon black" can mean an aggregate of carbon black crystallites with a hexagonal network structure of carbon atoms formed through a process such as dehydrogenation condensation after a six-membered carbon ring is formed by incomplete combustion or thermal decomposition of hydrocarbons, etc., and then polycyclic aromatic compounds are formed. It has a two-dimensional structure (two-dimensional order) compared to the three-dimensional structure of ordinary graphite. The relative density of carbon black can be approximately 1.76 to 1.9 depending on the grade.

[0102] "Activated carbon" can generally refer to a wide range of carbonaceous materials having high porosity and surface area, and hydrogen, sulfur, oxygen, nitrogen, etc. can combine with carbon to form an activated carbon structure.

[0103] "Fullerene" is a nano-sized, soccer ball-shaped carbon molecule with a hollow structure composed only of carbon atoms (carbon atoms form a spherical network structure), C 60 C 70 , C 82 Examples include:

[0104] According to an exemplary embodiment, the conductive carbon may be activated carbon, which is inexpensive compared to other conductive carbon-based materials, yet has good conductivity and band gap characteristics, and thus can effectively strengthen the electric field generated by the piezoelectric effect.

[0105] In this regard, activated carbon can be manufactured in a form with developed micropores by carbonizing a carbon source and then activating it. For example, the carbonization treatment can typically be performed at a temperature of about 450 to 1200°C, specifically about 500 to 1000°C, under an atmosphere of an inert gas (e.g., argon, helium, nitrogen, etc.). For example, the carbon source can be at least one selected from, for example, bituminous coal, sub-bituminous coal, lignite, anthracite, peat, wood, sawdust, charcoal, palm residue, cellulose fibers, synthetic resins such as phenol resins, petroleum pitch, petroleum coke, coal coke, needle coke, polymers (e.g., polyvinyl chloride and polyimide), etc., but this can be understood as an example. Alternatively, commercially available activated carbon can be used, and product names of such activated carbon include, for example, Calgon.

[0106] According to an exemplary embodiment, the conductive carbon (specifically, activated carbon) may exhibit porosity, and as it has porosity, the amount of organic pollutants adsorbed on the conductive carbon increases, so that the decomposition of organic pollutants due to the piezoelectric effect occurring on the surface of the piezoelectric catalyst may be activated. As an example, the specific surface area (BET) of the conductive carbon may be controlled in a range of, for example, about 700 to 1800 m2 / g, specifically about 800 to 1500 m2 / g, and more specifically about 900 to 1200 m2 / g. In addition, the pore volume of the conductive carbon may be controlled in a range of, for example, about 0.6 to 0.9 cm3 / g, specifically about 0.65 to 0.85 cm3 / g, and more specifically about 0.7 to 0.8 cm3 / g. In addition, the average pore size (diameter) of the conductive carbon may be, for example, in the range of about 1.9 to 2.5 nm, specifically about 2 to 2.4 nm, and more specifically about 2.1 to 2.3 nm. It may be advantageous to use a type of conductive carbon having a pore shape appropriately adjusted within the aforementioned range, but the present invention is not limited thereto.

[0107] Meanwhile, the particle size of the conductive carbon may be, for example, about 100 ㎛ or less, specifically about 80 ㎛ or less, and more specifically about 75 ㎛ or less, and grinding and / or sieving may be performed in advance for this purpose. However, the particle size range of the conductive carbon described above may be understood as an example.

[0108]

[0109] - Water-soluble metal salts

[0110] According to one specific example, the piezoelectric catalyst comprises a water-soluble metal salt for inducing chemical polarization of a fluorinated polymer. That is, even if a fluorinated polymer with low piezoelectric properties is used as a starting material during catalyst production, the water-soluble metal salt promotes polarization (e.g., chemical polarization), thereby increasing the proportion of a fluorinated polymer (e.g., β-PVdF) exhibiting piezoelectric properties.

[0111] In addition, as described below, the production of a piezoelectric catalyst may involve precipitation, and during this process, the cations present in the metal salt are attached to the fluorinated polymer. In order to remove the anions, it may be advantageous to select and use a salt that is soluble in water. According to an exemplary specific example, such a water-soluble metal salt may be, for example, sodium chloride, calcium carbonate, calcium chloride, magnesium chloride, etc., and at least one of these may be selected and used.

[0112] Meanwhile, according to one specific example, the weight ratio of fluorinated polymer: conductive carbon: water-soluble metal salt in the piezoelectric catalyst can be controlled in a range of, for example, 1: about 0.05 to 1: about 0.15 to 1, specifically 1: about 0.1 to 0.8: about 0.2 to 0.9, more specifically 1: about 0.2 to 0.7: about 0.25 to 0.6, and particularly specifically 1: about 0.4 to 0.6: about 0.45 to 0.55.

[0113] In this regard, if the relative amount of conductive carbon is too small compared to the fluorinated polymer, it may be difficult to secure the function as a co-catalyst, and if it is too large, it may be lost during the process of catalyst post-treatment (e.g., washing, etc.) and application. In addition, since the water-soluble metal salt plays a role in polarizing the fluorinated polymer (specifically, PVdF) through chemical interaction without a poling process, if the amount of the water-soluble metal salt compared to the fluorinated polymer exceeds a certain range, it may have an undesirable effect on chemical polarization. Therefore, it may be advantageous to appropriately adjust the ratio of the three components within the aforementioned content range. However, the composition range described above is not necessarily limited thereto, as it can change depending on the type of each of the three components.

[0114] Additionally, according to an exemplary embodiment, the fluorinated polymer forms a matrix among the composite-based piezoelectric catalysts, wherein the conductive carbon as an auxiliary catalyst component may be present in a form at least partially embedded within the matrix.

[0115]

[0116] Method for manufacturing piezoelectric catalyst

[0117] According to one specific example, a piezoelectric catalyst based on a fluoropolymer composite (i.e., a composite comprising a fluoropolymer, a conductive carbon, and a water-soluble metal salt) can be prepared through drying and precipitation of a mixture (or dispersion). A method for preparing a piezoelectric catalyst according to an exemplary specific example can be described as follows.

[0118] First, a step of preparing a mixture or dispersion containing a fluorinated polymer and conductive carbon may be performed. At this time, the fluorinated polymer and the conductive carbon may be prepared in the form of a solution or dispersion using an organic solvent, respectively, and then combined to prepare a mixture or dispersion containing the fluorinated polymer and the conductive carbon. According to an exemplary embodiment, the form of the fluorinated polymer combined with the organic solvent may be, for example, a powder, pellet, film, etc. Alternatively, the solution or dispersion may be prepared by introducing the fluorinated polymer and the conductive carbon together into an organic solvent.

[0119] In this regard, the organic solvent may primarily be a type having a solubility for fluorinated polymers. Such solvents may typically be polar solvents. For example, the organic solvent may be at least one selected from N,N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), and the like. In a specific embodiment, the organic solvent may be DMF, which may be advantageous because it has good solubility for fluorinated polymers, particularly PVdF, under mild conditions such as room temperature.

[0120] According to an alternative specific example, when preparing a fluorinated polymer solution, a mixed solvent may be used in combination with the aforementioned organic solvent and an additional solvent (e.g., a ketone-based solvent, specifically, acetone). As an example, the volume ratio of the organic solvent to the additional solvent in the mixed solvent may be adjusted in a range of, for example, 1: about 0.1 to 1, specifically 1: about 0.4 to 0.8, but is not limited thereto.

[0121] Meanwhile, according to an exemplary embodiment, the concentration of the fluorinated polymer in the mixture or dispersion may be appropriately adjusted depending on the method of manufacturing the catalyst. For example, when manufacturing the catalyst by 3D printing, a relatively high concentration is required, whereas when coating on a substrate, etc., a relatively low concentration may be sufficient. Considering this, the concentration of the fluorinated polymer in the mixture or dispersion may be adjusted in the range of, for example, about 0.01 to 0.3 g / mL, specifically about 0.03 to 0.25 g / mL, and more specifically about 0.05 to 0.2 g / mL, but this may be understood as an exemplary purpose.

[0122] Next, after preparing a mixture or dispersion containing a fluorinated polymer and conductive carbon, a water-soluble metal salt may be added to prepare a metal salt-containing mixture or dispersion. As described above, the water-soluble metal salt may be selected from a type capable of inducing chemical polarization of the fluorinated polymer. Therefore, even if a fluorinated polymer that does not exhibit piezoelectricity or has a low content of a piezoelectric fluorinated polymer (e.g., β-PVdF) as a starting material during catalyst preparation is used, the piezoelectricity may increase due to the increase in chemical polarization caused by the water-soluble metal salt described above during the catalyst preparation process. For example, the fluorinated polymer as a starting material may contain a significant amount of α-phase PVdF, and in some cases, mainly α-phase PVdF may be used, but a significant amount of β-PVdF may be contained in the final catalyst through chemical polarization by a water-soluble metal salt.

[0123] According to an exemplary embodiment, as a subsequent step, a step of drying the prepared water-soluble metal salt-containing mixture or dispersion is performed. Here, "drying" may refer to any treatment that removes at least a portion of the liquid medium within the mixture or dispersion, and may be performed, for example, under elevated temperature conditions. In particular, the drying treatment may remove highly volatile components (e.g., acetone) contained in the water-soluble metal salt-containing mixture or dispersion.

[0124] According to an exemplary embodiment, drying can be performed under elevated temperature conditions, in which case the drying temperature can be controlled in consideration of the type of solvent used in preparing the water-soluble metal salt-containing mixture or dispersion. As an example, the drying temperature can be controlled in the range of, for example, about 60 to 90°C, specifically about 65 to 85°C, and more specifically about 70 to 80°C. In addition, the drying time is not particularly limited, but can be controlled in the range of, for example, about 0.1 to 5 hours, specifically about 0.3 to 2 hours, and more specifically about 0.5 to 1 hour.

[0125] According to an exemplary embodiment, the solvent in the mixture or dispersion into which the water-soluble metal salt is introduced can be removed through the drying treatment, for example, at least about 30 wt%, specifically about 35 to 50 wt%, and more specifically about 40 to 45 wt%.

[0126] After the drying treatment of the mixture or dispersion is performed through the above-described process, an aqueous medium (specifically water, more specifically deionized water) may be subsequently added or injected into the dried product (i.e., the dried metal salt-containing mixture or dispersion) to form a precipitate including the fluorinated polymer, conductive carbon, and metal salt. In this regard, the added aqueous medium may be added in an amount of, for example, about 1 to 3 times, specifically about 1.5 to 2.5 times, more specifically about 1.75 to 2 times (by volume) the amount of the dried product. For example, the aqueous medium may be injected into the dried product using an injection means such as a syringe, in which case pores may be created inside to increase the specific surface area. However, as long as the precipitate or solid can be effectively formed through the injection of the aqueous medium, the present invention is not limited to injecting the aqueous medium through a specific means.

[0127] Optionally, a step may be performed to remove this film prior to addition of the aqueous medium, as a film containing impurities may form on the surface as drying progresses.

[0128] In this specific example, when an aqueous medium is added or injected, the organic solvent (specifically, a polar organic solvent) contained in the dried product floats upward due to the density difference, and in the process, the three aforementioned catalyst components may precipitate. Thereafter, the organic solvent is additionally eluted from the precipitate and moves upward.

[0129] As a post-treatment step, a piezoelectric catalyst can be obtained by performing treatments known in the art, such as water washing and drying.

[0130]

[0131] water treatment process

[0132] According to one specific example, a process for performing water treatment is provided by decomposing and removing organic contaminants in a liquid fluid using the aforementioned piezoelectric catalyst.

[0133] According to an exemplary embodiment, the liquid fluid can typically be derived from various aqueous sources, such as lakes, seas, rivers, etc., as well as wastewater discharged from various facilities, specifically, aqueous wastewater.

[0134] As an example, the organic pollutant may be an organic pollutant having a benzene ring and / or a heterocycle. As an example, the organic pollutant may be at least one selected from, for example, volatile organic compounds (VOCs), nitrogen (N)-containing organic compounds (including azo compounds), aromatic compounds (e.g., diphenyls), etc. Specifically, the types of volatile organic compounds (VOCs) may be, for example, benzene, toluene, phenol (PN), etc. In addition, examples of nitrogen (N)-containing organic compounds include p-nitrophenol (nitro, PNP), p-phenylenediamine (amine, PPD), caffeine (purine, CAF), methylene blue (dye, MB), rhodamine B (dye, RB), methyl orange (azo dye, MO), 2,4,6-trichloroaniline, etc. In addition, bisphenol-A (BPA) is a representative example of diphenyls among aromatic compounds.

[0135] Although the present disclosure is not bound by a specific theory, the mechanism by which organic contaminants in a fluid are effectively decomposed and removed by the piezoelectric effect can be explained as follows:

[0136] First, the electric field generated from the piezoelectric catalyst by the fluidity of the fluid, specifically the electric field generated by the fluorinated polymer, is transmitted to the electrons (e) of the conductive carbon. - ) and hole (h +) causes separation of electrons and holes, and the separated electrons and holes react with oxygen and water on the surface of the piezoelectric catalyst to generate radicals. The radicals thus generated can decompose organic pollutants.

[0137] According to an exemplary embodiment, the amount of the piezoelectric catalyst used can be adjusted depending on the degree of contamination in the liquid medium in contact therewith, specifically, the fluid (aqueous medium) containing organic pollutants. As an example, the amount of the piezoelectric catalyst used relative to the fluid (specifically, the wastewater to be treated) can be adjusted in a range of, for example, about 10 to 60 g / L, specifically about 20 to 50 g / L, more specifically about 25 to 40 g / L, and particularly specifically about 25 to 30 g / L, but this can be understood as an exemplary embodiment.

[0138] According to an exemplary embodiment, the water treatment temperature is not particularly limited and may be, for example, about 20 to 30°C, specifically about 22 to 28°C, and more specifically, room temperature.

[0139] The present invention can be more clearly understood by the following examples, which are provided merely for the purpose of illustrating the present invention and are not intended to limit the scope of the invention.

[0140]

[0141] Example

[0142]

[0143] Example 1

[0144]

[0145] A. Preparation of piezoelectric catalyst (PVdF / AC-NaCl)

[0146]

[0147] A PVdF / AC-NaCl piezoelectric catalyst was prepared according to the procedures shown in FIGS. 1 and 2.

[0148]

[0149] Specifically, 2 g of PVdF powder (M wAbout 534,000 (GPC), Sigma-Aldrich) was placed in a 300 mL beaker containing a mixed solvent of 10 mL of N,N-dimethylformamide (DAEJUNG) and 6 mL of acetone (99.5%, SAMCHUN), and stirred for about 30 minutes until a transparent color was reached (Solution A).

[0150] Separately, 1 g of activated carbon (AC, Calgon) was placed in a 100 mL beaker containing 10 mL of N,N-dimethylformamide and stirred for approximately 10 minutes (solution B). At this time, the activated carbon had a diameter of 75 μm, a specific surface area (BET) of 1026.9 m2 / g, a pore volume of 0.78 cm3 / g, and an average pore size of 2.19 nm.

[0151] Solution B was added to the beaker containing solution A (PVdF:AC weight ratio 2:1), and subsequently NaCl (99.5%, SAMCHUN) was added in amounts of 0 g, 0.5 g, 1 g, 2 g, 3 g, 4 g, 5 g, and 6 g, and stirred for about 10 minutes (solution C). Solution C was dried in a desiccator at 80 °C for 40 minutes.

[0152] The beaker containing solution C was taken out from the desiccator, and the film formed on its surface was removed, especially the hardened band-shaped film formed on the edge between the surface and the beaker. Subsequently, deionized water was filled into the beaker so that the dried solution A was submerged, using a syringe as shown in Fig. 2a. As the deionized water was added (injected), N,N-dimethylformamide floated on the water, and other components precipitated along with it. N,N-dimethylformamide was completely eluted over an additional 30 minutes.

[0153] After the elution of N,N-dimethylformamide was completed, the precipitate (solid) was removed from the beaker as shown in Fig. 2b. The removed precipitate had the same internal shape as the container in which the solution was stored. Afterwards, it was lightly washed with running distilled water, and newly distilled water was added to the beaker for storage.

[0154]

[0155] B. Characterization of piezoelectric catalysts

[0156]

[0157] The PVdF / AC-NaCl piezoelectric catalyst manufactured in this example (when 1 g of NaCl was added) attached to a mixer blade is shown in Fig. 3a. According to the drawing, the piezoelectric catalyst was black in color, which was due to the activated carbon (AC) powder contained within the catalyst, and was identified as a foam.

[0158]

[0159] - SEM analysis

[0160] SEM images of the piezoelectric catalyst and SEM images of the piezoelectric catalyst superimposed with EDS analysis are shown in Figs. 3b and 3c, respectively. The SEM analysis was performed using HITACHI's SU5000 product. In addition, the SEM image of the piezoelectric catalyst superimposed with EDS analysis was obtained using HITACHI's SU5000 product (scale: 50 μm).

[0161] Referring to the above drawing, activated carbon particles having a size of less than about 75 μm are embedded or partially embedded in the catalyst surface, specifically, in the PVdF matrix within the catalyst. In particular, referring to Fig. 3c, the fluorine (F) arrangement of PVdF highlighted in red is indicated in green, which is due to the CF of PVdF, and activated carbon particles and PVdF were observed on the surface.

[0162]

[0163] - FT-IR analysis

[0164] In addition to the PVdF / AC-NaCl piezoelectric catalyst manufactured in the examples, PVdF / AC and PVdF-NaCl were manufactured for comparative purposes, and FT-IR analysis was performed on PVdF / AC-NaCl, PVdF / AC, PVDF-NaCl, and pure PVdF, respectively. The FT-IR analysis was performed using BRUKER's product name LUMOS. The results are shown in Fig. 4a.

[0165] Referring to the above drawing, 840 cm -1 The peak at 763 cm indicates the β-phase, while -1 The peak in indicates the α-phase. Thus, it can be seen that the peak intensity of the β-phase compared to the α-phase is significantly affected by the presence of NaCl in the catalyst. In particular, it is noteworthy that the intensity of the β-phase peak increases when NaCl is contained in the piezoelectric catalyst.

[0166]

[0167] - XRD analysis

[0168] In addition to the PVdF / AC-NaCl piezoelectric catalyst manufactured in the examples, PVdF / AC and PVdF-NaCl were manufactured for comparative purposes, and XRD analysis was performed on PVdF / AC-NaCl, PVdF / AC, PVDF-NaCl, and pure PVdF. The XRD analysis was performed using a Bruker-D8 manufactured by ADVANCE. The results are shown in Fig. 4b.

[0169] According to the above figure, in the case of the PVdF / AC-NaCl piezoelectric catalyst, the binding peaks for the (110) and (200) planes of the β-phase were observed at 20.6˚. On the other hand, in the case of PVdF / AC, PVDF-NaCl, and pure PVdF, the intensities of the binding peaks corresponding to the β-phase were measured to be lower than those of the PVdF / AC-NaCl piezoelectric catalyst. In particular, the crystallinity of the PVdF / AC-NaCl piezoelectric catalyst according to the example was 73.32%, which suggests that the β-phase involved in the crystallinity occupies a high proportion throughout the polymer.

[0170]

[0171] - XPS analysis

[0172] XPS analysis was performed on the PVdF / AC-NaCl piezoelectric catalyst manufactured in the examples. The XPS analysis was performed using a PHI 5000 VersaProbe manufactured by Ulvac-PHI. The XPS spectra of Cl 2p, F 1s, C 1s, Na 1s, and Na 2s, respectively, are shown in Figs. 5a to 5e.

[0173] Referring to the above drawing, a peak corresponding to a C-Cl bond was observed from the Cl 2p spectrum (Fig. 5a), indicating that Cl was bonded to the activated carbon. In addition, referring to the F 1s graph (Fig. 5b), peaks for -FCH-, -FCF-, and -CF3 were observed, indicating that a CF bond and a CH bond of PVdF, and a bond between the activated carbon and the F of PVdF were formed.

[0174]

[0175] - Piezoelectric characteristics analysis

[0176] The piezoelectric coefficient (d33) of each of PVdF / AC, PVDF-NaCl, and pure PVdF, including PVdF / AC-NaCl manufactured in the examples, was measured. For this purpose, a piezoelectric measuring instrument (product name YE2730A, Sinocera) was used, and a portion of the piezoelectric catalyst was cut into 5 x 5 ㎟ sizes, and a specimen with a silver-coated surface was manufactured, and measurements were made under the condition of applying a force of 20 N at 5 Hz.

[0177] As a result of measuring the piezoelectric coefficient (d33), the piezoelectric coefficients (d33) of pure PVdF, PVdF-NaCl, PVdF / AC, and PVdF / AC-NaCl were measured to be approximately 13 pC / N, 16 pC / N, 26 pC / N, and 35 pC / N, respectively. These results suggest that as in the examples, the β-phase content in PVdF increases due to chemical polarization by adding NaCl, resulting in stronger piezoelectric properties.

[0178]

[0179] D. Evaluation of the impact on piezoelectric properties

[0180]

[0181] The velocity distribution when the fluid rotates at 200 rpm around a fixed PVdF / AC-NaCl blade form, and the velocity distribution of water in a beaker when the PVdF / AC-NaCl piezoelectric catalyst in a rectangular shape and a cylindrical shape is rotated at 200 rpm, respectively, were measured. The results are shown in Figs. 6a to 6c, respectively.

[0182] According to the above drawing, in the case of a rectangular parallelepiped-shaped piezoelectric catalyst, the flow velocity near the surface increased compared to a cylinder-shaped piezoelectric catalyst, indicating that a rectangular parallelepiped-shaped piezoelectric catalyst is advantageous.

[0183] In addition, when the rectangular PVdF / AC-NaCl blade foam piezoelectric catalyst rotates at 200 rpm, the velocity distribution plot within the beaker and the side view plot of the velocity distribution are shown in Figs. 6d and 6e, respectively. According to the drawings, the magnitude of the flow velocity increases from the center to the outside, indicating that a continuous flow velocity is applied.

[0184] Meanwhile, the pressure distribution when the fluid rotates at 200 rpm around a fixed PVdF / AC-NaCl blade form and the pressure distribution induced by the flow on the rectangular PVdF / AC-NaCl blade form piezoelectric catalyst when rotating at 200 rpm were analyzed, and the results are shown in Figs. 6f and 6g, respectively. According to the drawings, the pressure increased from the center to the outside, indicating that the pressure was continuous.

[0185] In addition, the voltage distribution generated on the surface of the PVdF / AC-NaCl piezoelectric catalyst by the pressure generated by the flow was analyzed, and the results are shown in Fig. 6h. According to the figure, the magnitude of the voltage generated from the center to the outside increased, showing the same trend as the change in the pressure distribution examined above.

[0186]

[0187] Experimental study on the decomposition of organic pollutants using a PVdF / AC-NaCl foam piezoelectric catalyst.

[0188]

[0189] - Decomposition experiments were conducted under room temperature and pressure conditions for each type of organic pollutant (TC, 4-NIP, Phenol, RhB) in an aqueous solution (concentration: 100 mg / L) containing various organic pollutants using a PVdF / AC-NaCl foam piezoelectric catalyst. At this time, the PVdF / AC-NaCl foam piezoelectric catalyst was attached to the blade of a mixer and stirred (rotated) at 200 rpm to conduct an experiment on decomposition of organic pollutants using the piezoelectric catalytic effect. The results are shown in Figures 7a to 7e, respectively.

[0190]

[0191] - In order to derive the optimal amount of water-soluble metal salt (NaCl) added to the PVdF / AC-NaCl foam piezoelectric catalyst, the degradation efficiency of methyl orange (MO) was measured while changing the amount of NaCl added during the catalyst preparation process. Figure 7a shows the change in MO decomposition efficiency according to the amount of NaCl added during the catalyst preparation process, and as the amount of NaCl added increased, the MO decomposition efficiency also increased (based on 5 minutes).

[0192] Referring to the above drawing, the catalyst without added NaCl showed a decomposition rate of about 81%, but when 0.5 g and 1 g of NaCl were added, the decomposition rates increased to 91% and 87%, respectively. However, as the amount of added NaCl continued to increase, the MO decomposition rate actually decreased, and in particular, when 6 g was added, the MO decomposition rate was approximately 79%. From the above results, it was confirmed that the optimal amount of NaCl, a water-soluble metal salt, to be added when manufacturing a piezoelectric catalyst is 1 g.

[0193]

[0194] - The piezoelectric decomposition rate and adsorption rate over time for aqueous solutions containing RhB, 4-NIP (4-nitrophenol), phenol, and TC (tetracycline) were measured for approximately 60 minutes using a PVdF / AC-NaCl foam piezoelectric catalyst, and the results are shown in Fig. 7b. Referring to the figure, the decomposition rates for RhB, 4-NIP, phenol, and TC were 97.03%, 92.02%, 89.19%, and 94.18%, respectively, while the adsorption rates were relatively low.

[0195]

[0196] - The decomposition rate of RhB (concentration: 100 mg / L) was measured in each case where the PVdF / AC-NaCl foam piezoelectric catalyst was directly rotated and where the PVdF / AC-NaCl foam piezoelectric catalyst was fixed and water was rotated, and the comparison results are shown in Fig. 7c.

[0197] According to the above drawing, it is believed that RhB can be decomposed more quickly due to the higher pressure and generated voltage when the piezoelectric effect is utilized by inducing direct fluid flow.

[0198] - The pseudo-second-order reaction rates for the decomposition of RhB, 4-NIP, phenol, and TC using the PVdF / AC-NaCl piezoelectric catalyst were obtained, and the results are shown in Fig. 7d. Referring to the figure, explosively rapid decomposition occurred initially, and the rate decreased as the amount of organic pollutants being decomposed decreased. These results confirmed the effective decomposition performance of the piezoelectric catalyst.

[0199]

[0200] - The pseudo-first-order rate constants for RhB, 4-NIP, phenol, and TC were obtained using a PVdF / AC-NaCl foam piezoelectric catalyst, and the results are shown in Fig. 7e. Referring to the figure, the constants were different for each organic pollutant.

[0201]

[0202] Ma. Reusability Evaluation of PVdF / AC-NaCl Piezoelectric Catalysts

[0203]

[0204] To evaluate the stability of the PVdF / AC-NaCl foam piezoelectric catalyst, five cycle tests were performed on an aqueous solution containing TC (concentration: 100 mg / L).

[0205] After five cycle tests, the PVdF / AC-NaCl foam piezoelectric catalyst was dissolved again in a mixed solvent of DMF and acetone, and a new blade foam catalyst was resynthesized. The TC decomposition rate was measured using the regenerated PVdF / AC-NaCl foam piezoelectric catalyst, and the results are shown in Fig. 8a. Referring to the figure, the TC decomposition rate was maintained at approximately 84% even after five cycle tests, and the TC decomposition rate recovered to 92.22% after resynthesis.

[0206]

[0207] - SEM analysis was performed on the PVdF / AC-NaCl foam piezoelectric catalyst before and after the cycle test, and on the recycled catalyst after the cycle test, and the results are shown in Figs. 8b to 8d, respectively. According to the drawings, the PVdF / AC-NaCl foam piezoelectric catalyst before the cycle test had activated carbon attached to its surface and visible pore structures, and the same properties were observed after the cycle test.

[0208] Furthermore, the PVdF / AC-NaCl foam piezoelectric catalyst resynthesized after cycle testing exhibited surface-attached activated carbon and visible pore structures. This confirms that the piezoelectric catalyst according to the example possesses excellent reusability and durability.

[0209]

[0210] - FT-IR analysis was performed on the PVdF / AC-NaCl foam piezoelectric catalyst before and after the cycle test, and on the recycled catalyst after the cycle test, and the results are shown in Figs. 8e to 8g, respectively.

[0211] According to the above figure, before FT-IR analysis and cycle test, the ratio of β-phase in the entire polymer was 75.53%, but after cycle test, it showed a ratio of 66.86%. Meanwhile, in the case of PVdF / AC-NaCl foam piezoelectric catalyst resynthesized after cycle test, it showed a ratio of 70.12%. From this, it can be confirmed that the catalyst is stable and has good durability because the ratio of β-phase decreased slightly, but did not cause a large difference. Furthermore, when the decrease in the ratio of β-phase increased, it was possible to recover the catalytic activity through resynthesis, which was a favorable result in terms of reusability.

[0212]

[0213] Ba. Clarification of the decomposition mechanism by PVdF / AC-NaCl piezoelectric catalyst.

[0214]

[0215] In order to elucidate the mechanism by which the PVdF / AC-NaCl foam piezoelectric catalyst manufactured according to this example promotes the decomposition of organic pollutants, an active species trapping experiment was performed. In this case, the trapping experiment was performed by stimulating the decomposition of hydroxyl radicals (·OH) and superoxide radicals (·O2) in the presence of thiourea, benzoquinone, and EDTA-2Na at a concentration of 10 mM each. 2- ) and hole (h + ) was trapped to prevent it from participating in the decomposition of organic pollutants, and methyl orange was used as the organic pollutant. The experimental conditions were set as follows: MO = 30 mg / L, temperature 15 ℃, initial pH = 6.2. The results are shown in Figs. 9a to 9c, respectively.

[0216] Referring to Fig. 9a, when EDTA-2Na was added, the decrease in the decomposition rate was the greatest. This means that when the trapping agent was added, the MO decomposition rate was reduced by EDTA-2Na. + It indicates that the greatest decrease was observed because it inhibited the decomposition of organic pollutants. From the above figure, when the PVdF / AC-NaCl piezoelectric catalyst decomposes organic pollutants, h + This is considered to play the biggest role.

[0217] Also, h as the ESR spectrum of the radical trapped by TEMPO + The TEMPO-trapped ESR spectrum of the hydroxyl radical (·OH) as an ESR spectrum of the radical trapped by DMPO and the DMPO-trapped ESR spectrum of the hydroxyl radical (·OH) are shown in Fig. 9b and Fig. 9c. According to the drawings, h through ESR + And the presence of OH radicals can be confirmed, and from this, the contribution of active radicals in the decomposition process of organic pollutants using the PVdF / AC-NaCl foam piezoelectric catalyst can be confirmed, and in particular, the contribution of holes is judged to be the largest.

[0218]

[0219] 4. Measurement of energy consumption required for decomposition of organic pollutants

[0220]

[0221] The energy consumption required for the decomposition of TC in an aqueous medium using the PVdF / AC-NaCl foam piezoelectric catalyst manufactured according to this example was calculated and compared with decomposition processes based on other mechanisms. The results are shown in Table 1 below.

[0222]

[0223] Catalytic driving force k(min) -1 )P (kW)η(%)EE / O(kWh m -3 order -1)CdS / ZnOUV0.0240.3594.411,258.09C-ZnO / CNUV0.0540.1580.14313.80ZnO@C NUV0.0500.15973846.15MoS2NTs / CuInS2QDsVisible light0.0120.389.016150.00Bi4Ti3O 12 Ultrasonic 0.0100.18826460.00K2Ti6O 13 / TiO2Ultrasonic0.0240.16545168.00Cu2O / MoS2 / rGOUltrasonic0.0180.12662584.00MoS2Ultrasonic0.0250.11931894.93MoS2 / GDYBall milling0.0520.2592.2935.33Fe3O4@MoS2 / PVDF pipeWater flow0.0200.02591.5241.04ZnO / CQDs / PVDFUltrasonic0.0580.397.91162.8ZnO / CQDs / PVDF pipeWater flow0.0440.0495.36176.18PVdF / AC-NaCl foam(Example)Water Water flow 0.0470.0494.18163.53

[0224]

[0225] According to the above table, when using the PVdF / AC-NaCl foam piezoelectric catalyst according to the present embodiment, it can be seen that a significantly lower amount of energy is consumed compared to other decomposition processes. In particular, it is noteworthy that it has a high decomposition reaction rate constant despite the significantly lower power consumption.

[0226] All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Claims

1. (i) Fluorinated polymers; (ii) conductive carbon; and (iii) a water-soluble metal salt for inducing chemical polarization of the above fluorinated polymer; Includes, A piezoelectric catalyst in which the weight ratio of fluorinated polymer: conductive carbon: water-soluble metal salt is controlled in the range of 1:0.05 to 1:0.15 to 1.

2. A piezoelectric catalyst according to claim 1, characterized in that the fluorinated polymer is a polyvinylidene fluoride copolymer in which at least one comonomer selected from the group consisting of trifluoroethylene (TrFE), hexafluoropropylene (HFP), and chlorotrifluoroethylene (CTFE) is added to polyvinylidene fluoride and / or vinylidene fluoride.

3. A piezoelectric catalyst according to claim 2, characterized in that the fluorinated polymer contains at least 50 wt% of β-PVdF.

4. In the first paragraph, the molecular weight (M) of the fluorinated polymer w ) is a piezoelectric catalyst characterized by being controlled in the range of 30,000 to 1,600,000.

5. In the first paragraph, the conductive carbon is at least 5.39×10 -10 A piezoelectric catalyst characterized by a conductivity of S / cm (room temperature) and a band gap of 3.15 eV or less.

6. A piezoelectric catalyst according to claim 1, characterized in that the conductive carbon is at least one selected from the group consisting of graphene, carbon nanotubes (CNT), graphite, activated carbon, and fullerene.

7. A piezoelectric catalyst according to claim 1, characterized in that the conductive carbon has a specific surface area (BET) of 700 to 1800 m2 / g, a pore volume of 0.6 to 0.9 cm3 / g, and an average pore size (diameter) of 1.9 to 2.5 nm.

8. A piezoelectric catalyst according to claim 1, characterized in that the water-soluble metal salt is at least one selected from the group consisting of sodium chloride, calcium carbonate, calcium chloride, and magnesium chloride.

9. A piezoelectric catalyst according to claim 8, characterized in that the water-soluble metal salt is sodium chloride.

10. A piezoelectric catalyst according to claim 1, characterized in that the particle size of the conductive carbon is 100 ㎛ or less. 11.a) A step of preparing a mixture or dispersion containing a fluorinated polymer and conductive carbon in an organic solvent; b) a step of preparing a metal salt-containing mixed solution or dispersion by adding a water-soluble metal salt to the mixed solution or dispersion; c) a step of drying the metal salt-containing mixture or dispersion, and then adding an aqueous medium to form a precipitate containing a fluorinated polymer, conductive carbon, and a water-soluble metal salt; and d) a step of recovering the above sediment as a catalyst; Including, A method for producing a piezoelectric catalyst, wherein the weight ratio of the fluorinated polymer: conductive carbon: water-soluble metal salt in the catalyst is controlled in a range of 1:0.05 to 1:0.15 to 1.

12. A manufacturing method according to claim 11, characterized in that the organic solvent is a polar organic solvent.

13. A manufacturing method according to claim 12, characterized in that the organic solvent is at least one selected from the group consisting of DMF (N,N-Dimethylformamide), DMSO (dimethyl sulfoxide), NMP (N-methylpyrrolidone), and DMAc (dimethylacetamide).

14. A manufacturing method according to claim 11, characterized in that the concentration of the fluorinated polymer in the mixed solution or dispersion is controlled in the range of 0.01 to 0.3 g / mL.

15. A manufacturing method characterized in that in the 11th paragraph, at least 30 wt% of the solvent in the metal salt-containing mixture or dispersion is removed through drying in step c).

16. A manufacturing method according to claim 15, characterized in that the drying is performed at 60 to 90°C for 0.1 to 5 hours.

17. A manufacturing method characterized in that in the 11th paragraph, the amount of the aqueous medium added in step c) is controlled in the range of 1 to 3 times that of the dried metal salt-containing mixture or dispersion.

18. A step of introducing a piezoelectric catalyst according to any one of clauses 1 to 10 into an aqueous medium; and A step of decomposing organic pollutants contained in an aqueous medium by using piezoelectricity generated from a piezoelectric catalyst by a fluid flow within the aqueous medium; A water treatment process using a piezoelectric catalyst including:

19. A water treatment process according to claim 18, wherein the organic pollutant is at least one selected from the group consisting of volatile organic compounds (VOCs), nitrogen (N)-containing organic compounds, and aromatic compounds.

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