Method for utilizing zeolite related to PFAS and apparatus directly used for its implementation, and method for manufacturing amorphous materials related to PFAS and apparatus directly used for its implementation.

Abstract

This invention provides a method for producing amorphous PFAS, an apparatus for directly using this method, and a modified zeolite, all of which can be performed at low cost in a series of steps: dispersing zeolite to adsorb PFAS, transporting the recovered zeolite directly to a furnace, and amorphousizing it at medium to low temperatures. [Solution] The method comprises the steps of: generating modified zeolite from natural or synthetic zeolite having a crystalline structure by pretreatment; dispersing the modified zeolite to adsorb PFAS; recovering the modified zeolite and transporting it to a sealed or exhaust gas treated medium-low temperature furnace, pre-drying it for dehydration; sintering the modified zeolite in the furnace at a temperature where the crystalline structure is destroyed and a temperature lower than the melting temperature of the modified zeolite to form an amorphous body; and cooling after sintering.

Description

Technical Field

[0001] The present invention relates to a method for producing an amorphous body related to PFAS (per- and polyfluoroalkyl substances), which are chemical pollutants difficult to decompose, an apparatus directly used for its implementation, and a modified zeolite.

Background Art

[0002] Patent Document 1 discloses removing PFAS using a first adsorbent material and a second adsorbent material containing zeolite.

[0003] Further, Patent Document 2 discloses taking in radioactive waste as a harmful substance into the pores of natural zeolite or synthetic zeolite and closing the openings of the pores by heating and firing the zeolite surface while maintaining the crystal structure.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, Patent Document 1 does not disclose or suggest transporting zeolite adsorbed with PFAS to a medium- or low-temperature furnace and destroying the crystal structure of zeolite in a medium- or low-temperature furnace to produce an amorphous body.

[0006] Here, a high-temperature furnace at 1500°C to 2000°C is expensive, costing 40 million to 50 million yen for a 1-ton capacity, but a medium- or low-temperature furnace at 900°C to 1100°C is inexpensive, costing 5 million to 10 million yen for a 1-ton capacity. Furthermore, Patent Document 2 not only does not disclose the adsorption of PFAS, but it also does not disclose or suggest in any way that amorphous materials are produced by destroying the crystalline structure of zeolite that has adsorbed PFAS in a medium-to-low temperature furnace. In other words, Patent Document 2 describes sealing the pores of zeolite while maintaining the crystalline structure without destroying it. In Patent Document 2, since the crystalline framework (Al-O-Si) is maintained as the crystalline structure, there is a possibility that the framework will gradually deteriorate over the long term and PFAS may leak out. In addition, there is a possibility that the blocked parts will reopen due to microcracks in the crystalline framework caused by fire, geothermal heat, and chemical changes in the disposal environment, and that the adsorbed PFAS may leak out when new surfaces and pores are exposed due to crushing and abrasion during transport to the furnace.

[0007] This invention utilizes the dual nature of zeolite, which has both a state where the crystalline structure is maintained (adsorption of PFAS) and a state where the crystalline structure is destroyed (production of amorphous material), and controls the temperature in a region beyond the temperature range that maintains the crystalline structure during sintering.

[0008] The objective of this invention is to disperse zeolite to adsorb PFAS, transport the recovered zeolite directly to a furnace, and then process it at medium to low temperatures. Sintering Each of these steps can be performed at a low cost. Methods for utilizing zeolites in relation to PFAS and equipment directly used in their implementation, as well as Method for manufacturing amorphous PFAS and for direct use in its implementation Device The objective is to provide. [Means for solving the problem]

[0009] To achieve the above objective, the method of using zeolite related to PFAS according to the present invention is: The process involves the steps of: producing a modified zeolite having a crystalline structure by subjecting a natural or synthetic zeolite having a crystalline structure to a pretreatment including at least an acid treatment; recovering the modified zeolite after it has been dispersed and adsorbed PFAS, and transporting it to a sealed or exhaust gas treatment type medium-low temperature furnace, pre-drying it at 80-120°C for dehydration; and transporting the modified zeolite that has adsorbed PFAS to the transported medium to low temperature The process includes the step of sintering the modified zeolite in a furnace, The temperature of the aforementioned medium- and low-temperature furnace is in the range of 900 to 1100°C. It is characterized by the following: Furthermore, the apparatus used directly for implementing the method of using zeolite for PFAS according to the present invention comprises a pre-processing unit for performing the pre-treatment, a recovery unit for recovering the modified zeolite that has adsorbed PFAS, and a drying unit for pre-drying the recovered modified zeolite for dehydration. The aforementioned medium- and low temperature range is 900 to 1100°C It has a furnace. Furthermore, the method for producing amorphous PFAS according to the present invention includes the steps of: producing a modified zeolite having a crystalline structure by subjecting a natural zeolite or synthetic zeolite having a crystalline structure to a pretreatment including at least an acid treatment; recovering the modified zeolite on which PFAS has been adsorbed by dispersing the modified zeolite and transporting it to a sealed or exhaust gas treatment type medium-low temperature furnace, and pre-drying it at 80-120°C for dehydration; and transporting the modified zeolite on which PFAS has been adsorbed to the same medium to low temperature The process involves: sintering the modified zeolite in a furnace at a temperature controlled to break down the crystalline structure and lower than the temperature at which the modified zeolite melts, thereby forming an amorphous body; and cooling the amorphous body after sintering. death, The temperature of the aforementioned medium- and low-temperature furnace is characterized by being in the range of 900 to 1100°C.

[0010] Preferably, the modified zeolite is a natural zeolite mainly composed of clinoptilolite that has undergone the aforementioned pretreatment, and the temperature-controlled temperature is in the range of 900 to 1100°C, which is lower than the 1200°C at which the modified zeolite melts.

[0011] Also preferably, the modified zeolite is obtained by subjecting a natural zeolite mainly composed of clinoptilolite to the pretreatment, and the temperature controlled temperature is in the range of 1000 to 1100 °C, which is lower than 1200 °C at which the modified zeolite melts.

[0012] Also preferably, the modified zeolite is dispersed and arranged in any one of the environments of water, soil, and air for adsorbing PFAS, and after being recovered after adsorption, it is directly transported to the furnace after being pre-dried.

[0013] Also preferably, the medium to low temperature In the furnace, CaO or MgO is added to promote fluorine fixation during the sintering.

[0015] Also preferably, the medium to low temperature In the furnace, the temperature is controlled to be a constant temperature.

[0016] Also preferably, the medium to low temperature The temperature of the furnace is detected using a two-color thermometer measurement method.

[0017] Also preferably, as the pretreatment Furthermore amine modification treatment is include.

[0018] Also preferably, the acid treatment is a treatment using hydrochloric acid.

[0019] Also preferably, when using the natural zeolite, the natural zeolite includes clinoptilolite in which the composition ratio of silica to alumina is 4.5 or more and 5.5 or less.

[0020] Also preferably, when using the natural zeolite, the natural zeolite is shredded into pieces of 3 mm or more and 5 mm or less to expand the specific surface area and is directly supplied to the pretreatment. 。 Furthermore, the present invention is an apparatus directly used in the implementation of a method for producing an amorphous body related to the above PFAS, including a pretreatment unit for performing the pretreatment, a recovery unit for recovering the modified zeolite adsorbed with PFAS, and a drying unit for pre-drying the recovered modified zeolite for dehydration. The aforementioned medium- and low temperature range is 900 to 1100°C It includes those having a furnace.

Advantages of the Invention

[0021] According to the present invention, a series of steps such as adsorbing PFAS by dispersing and arranging zeolite, transporting the recovered zeolite directly to the furnace, and amorphizing at medium and low temperatures can be carried out at low cost respectively.

Brief Description of the Drawings

[0022] [Figure 1] It is a diagram showing the flow according to an embodiment of the present invention. [Figure 2] It is a photograph showing natural zeolite (white-gray).

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0024] (First Embodiment) When the object adsorbed by zeolite is PFAS, hereinafter, it will be described in the order of natural zeolite having a crystal structure as a raw material, modified zeolite obtained by modifying natural zeolite through pretreatment, transportation (transfer) of the recovered zeolite to the furnace, sintering by a medium and low temperature furnace, and generation of an amorphous body.

[0025] (Natural Zeolite with Crystal Structure) The natural zeolite used in this embodiment has a silica composition ratio of 4.5 to 5.5 to alumina, and contains mordenite in addition to clinoptilolite as the main component. The mixing ratio of clinoptilolite to mordenite is 9:1. It is then cut into pieces of 3 mm to 5 mm in size to increase its specific surface area, and supplied directly to the pretreatment described below. Here, a photograph of the natural zeolite (white-gray) used in this embodiment is shown in Figure 2. (Modified zeolite) Modified zeolites, which retain their crystalline structure, are produced by pretreatment from natural zeolites that possess a crystalline structure. The pretreatment can be either acid treatment alone, or acid treatment combined with amine modification. Here, amine modification is a type of organic modification in which amines (-NH2, -R-NH-, -NR2, etc.), which are functional groups belonging to organic compounds, are introduced to the surface of the zeolite using amine-based reagents (APTES, PEI, EDA, etc.). In aqueous environments where PFAS exists as anions, amine modification treatment can directly enhance the adsorption driving force (charge interaction), making it easier to improve removal capacity (and potentially selectivity). Acid treatment is performed to remove impurities using 0.01-0.1 M HCl (hydrochloric acid) or 0.01-0.1 M HNO3, followed by neutralization by rinsing with water at room temperature for a short period of 30-120 minutes. Regarding the acid treatment, the BET specific surface area before acid treatment was 129.4781 m². 2 The value was / g, and after acid treatment, the value was 236.5362m 2 Expanded to / g By increasing the Si / Al ratio through such acid treatment to slightly improve hydrophobicity, and then further performing cationic organic modification (surfactant / amine) as an amine modification, hydrophobicity and electrostatic attraction functions are imparted. More specifically, as a mild acid treatment, surface impurities are removed with 0.05-0.2M HCl for a short time to slightly increase the Si / Al ratio (to increase hydrophobicity). Then, a polyamine (such as PEI) is used as a cationic modification to attract the anion PFAS. In general, it is preferable to have a pH range of neutral to weakly basic. (Transportation of recovered zeolite to a medium-to-low temperature furnace) Modified zeolite, dispersed in one of the following environments—water, soil, or air—to adsorb PFAS, is recovered and transported to the furnace described later. Before transport, it is pre-dried at 80-120°C to dehydrate it. This recovered modified zeolite can then be transported directly to the furnace, thus reducing transportation costs.

[0026] (Sintering in a medium-to-low temperature furnace) 1) Decomposition and volatilization of PFAS PFAS adsorbed onto zeolite is highly likely to decompose and volatilize before the zeolite's crystalline structure is destroyed and it becomes amorphous. Therefore, a sealed furnace or an exhaust gas treatment furnace with measures to prevent HF and fluorocarbons generated by decomposition from leaking outside the furnace is necessary. In such a furnace, it is preferable to control the temperature by setting a sufficient residence time so as to ensure a slow rise in temperature to avoid promoting the volatilization of PFAS. 2) Amorphization of zeolites (amorphous material with fluorine fixed after PFAS decomposition) Modified zeolite with adsorbed PFAS requires a temperature-controlled medium-to-low temperature furnace (which can be either a sealed or exhaust gas treatment type furnace as described below) for processing, as described below. In such a furnace, the zeolite is sintered, fixing the fluorine inside after PFAS decomposition. That is, sintering destroys the crystalline structure of the zeolite, making it amorphous (non-crystalline), and producing an amorphous body with fluorine fixed inside. During such sintering, it is preferable to add CaO or MgO to promote fluorine fixation.

[0027] Regarding specific temperature control, the temperature is detected using a two-color thermometer, and heating and non-heating are controlled so that the temperature range is between a first temperature (the minimum temperature at which the crystalline structure of the modified zeolite in this embodiment is destroyed, i.e., the amorphous temperature) as the lower limit and a second temperature (the minimum temperature at which the modified zeolite in this embodiment melts, i.e., the melting temperature) as the upper limit.

[0028] In this embodiment, for the modified zeolite using the natural zeolite mainly composed of clinoptilolite described above, the upper limit, the second temperature, was set to 1100°C, and the lower limit, the first temperature, was set to 900°C.

[0029] By controlling two points in this way—an upper limit (second temperature) and a lower limit (first temperature)—the temperature range can be controlled to 900-1100°C, and even further to 1000-1100°C. However, it is also possible to control the temperature to a single point within this temperature range, that is, a constant temperature in the temperature range between the first and second temperatures (for example, 1000°C or 1050°C). In this case, temperature control becomes simpler.

[0030] (Amorphous form related to PFAS) After cooling, the amorphous zeolite containing fluorine fixed inside after PFAS decomposition is collected as general waste (recyclable waste). (Analysis of PFAS adsorption using simulated samples) Here, we present an analysis of PFAS adsorption by modified zeolite using a simulated sample containing PFAS, and the results are shown below. In order to investigate the PFAS removal performance of modified zeolite in water storage tanks installed in apartment buildings and other similar structures, an analysis of the PFAS removal (adsorption) performance of modified zeolite was conducted using simulated samples (test solutions to which PFAS had been added). Here, the cases of using natural zeolite, specifically natural zeolite without acid treatment, and modified zeolite (natural zeolite pre-treated with acid) were compared with the case of not using natural zeolite. Here, regarding PFAS, the following two representative substances were quantified.

[0031] • Perfluorooctanesulfonic acid (PFOS) • Perfluorooctanoic acid (PFOA) The method for preparing the test solution and the specific analysis are as follows. Regarding the PFOS and PFOA concentrations in the test solution, since the target value for tap water is 0.00005 mg / L (50 ng / L), the solution was prepared at the following concentrations, which are 10 times that value.

[0032] PFOS: 0.00025 mg / L (250 ng / L) PFOA: 0.00025 mg / L (250 ng / L) Total: 0.0005mg / L (500ng / L) Here, the standard stock solutions used to prepare the test solutions were methanol solutions of three types of organic fluorine compound mixed standard solutions (PFHxS, PFOS) and PFDA, each at a linear concentration of 2 μg / ml, manufactured by Fujifilm Wako Pure Chemical Industries.

[0033] Then, 60 g of modified zeolite was added to 1 L of the test solution containing PFOS and PFOA, and the mixture was gently shaken at room temperature. After shaking for 1 hour, the supernatant was dispersed by centrifugation, and the concentrations of PFOS and PFOA were measured.

[0034] Quantitative analysis of PFOS and PFOA was performed using the method described below. <Analysis method> Regarding the measurement of the Ministerial Ordinance concerning Water Quality Standards, amendments to the Enforcement Regulations of the Waterworks Act, etc., and points to note in water quality management (October 10, 2003) (Kensuihatsu No. 1010001) Attachment 4: Solid-phase extraction-liquid chromatography-mass spectrometry as defined in Objective 31. <Analysis results for 3 types of test solutions> Test solution 1: Test solution + natural zeolite (untreated with acid) Test solution 2: Test solution + modified zeolite (acid treated) Test solution 3: Test solution + no zeolite While there was no difference in concentration between test solution 1 and test solution 3, the concentration of test solution 2 decreased to about half that of test solution 3. In other words, PFAS adsorption in the modified zeolite was demonstrated by the analytical results.

[0035] [Table 1] (Second embodiment) In the first embodiment described above, modified zeolite obtained by pre-treating natural zeolite was used, but synthetic zeolite can be used instead of natural zeolite, and modified zeolite obtained by pre-treating synthetic zeolite can also be used. Synthetic zeolites, like natural zeolites, are crystalline materials with a three-dimensional aluminosilicate (Al-Si-O) framework. This framework contains regularly arranged pores, channels, and cages, and these structures give rise to ion exchange and adsorption properties. Natural zeolites have advantages such as low cost, easy mass supply, relatively high mechanical strength and durability, and low environmental impact due to their natural origin. However, they also have disadvantages such as non-uniform crystal structure and chemical composition, unoptimized Si / Al ratio and pore size, and the presence of impurities. Synthetic zeolites overcome these disadvantages. Specifically, synthetic zeolites allow for arbitrary design of Si / Al ratio, pore size, and crystal form, enabling them to exhibit performance optimized for specific pollutants. Furthermore, they have a larger surface area and higher adsorption capacity than natural zeolites, as well as higher ion exchange capacity. In addition, as industrial products, their quality and performance are uniform. Moreover, their performance can be enhanced according to the purpose through organic modification (amine modification), metal ion exchange, acid treatment, etc. In this embodiment, where synthetic zeolites are used instead of natural zeolites, representative synthetic zeolites that can be used include zeolite Y(FAU), zeolite X(FAU), and zeolite A(LTA). In this embodiment, a modified zeolite derived from synthetic zeolite can be used to adsorb the PFAS described in the first embodiment, sinter it in a medium-to-low temperature furnace with a controlled temperature of 900°C to 1100°C, and then cool it to produce an amorphous body related to PFAS. (Apparatus used directly in the implementation of a method for manufacturing amorphous materials related to PFAS) This apparatus comprises at least a pre-treatment section for pre-treating natural or synthetic zeolite, a recovery section where the pre-treated modified zeolite is dispersed and recovered after adsorbing PFAS, and a drying section for pre-drying the recovered modified zeolite for dehydration, and may further include a medium-to-low temperature furnace. (modified version) Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. For example, the modified zeolite derived from natural zeolite described in the first embodiment and the modified zeolite derived from synthetic zeolite described in the second embodiment may be mixed and used together.

Claims

1. A step of producing a modified zeolite that has the crystalline structure by subjecting a natural or synthetic zeolite having a crystalline structure to a pretreatment that includes at least an acid treatment, The modified zeolite is dispersed and PFAS is adsorbed onto it. The modified zeolite is then recovered and transported to a sealed or exhaust gas treatment type medium-low temperature furnace, in which case it is pre-dried at 80-120°C for dewatering. The modified zeolite on which the PFAS has been adsorbed is transported to a medium-to-low temperature furnace, and the modified zeolite is sintered in the furnace. It has, A method for utilizing zeolite related to PFAS, characterized in that the temperature of the medium- and low-temperature furnace is in the range of 900 to 1100°C.

2. An apparatus for direct use in implementing the method of using zeolite related to PFAS as described in claim 1, A pre-processing unit that performs the aforementioned pre-processing, A recovery section from which the modified zeolite that has adsorbed PFAS is recovered, A drying section for pre-drying the recovered modified zeolite for dehydration, The aforementioned medium-to-low temperature furnace, having a temperature in the range of 900 to 1100°C, An apparatus characterized by having the following features.

3. A step of producing a modified zeolite that has the crystalline structure by subjecting a natural or synthetic zeolite having a crystalline structure to a pretreatment that includes at least an acid treatment, The modified zeolite is dispersed and PFAS is adsorbed onto it. The modified zeolite is then recovered and transported to a sealed or exhaust gas treatment type medium-low temperature furnace, in which case it is pre-dried at 80-120°C for dewatering. In the medium-to-low temperature furnace to which the modified zeolite having adsorbed the PFAS has been transported, the modified zeolite is sintered by controlling the temperature to a temperature at which the crystalline structure is destroyed and which is lower than the temperature at which the modified zeolite melts, thereby forming an amorphous body. The steps include: cooling the amorphous body after the sintering, It has, A method for manufacturing amorphous bodies related to PFAS, characterized in that the temperature of the medium- and low-temperature furnace is in the range of 900 to 1100°C.

4. The method for producing amorphous PFAS according to claim 3, characterized in that the modified zeolite is a natural zeolite mainly composed of clinoptilolite that has undergone the aforementioned pretreatment, and the temperature controlled is in the range of 900 to 1100°C, which is lower than the 1200°C at which the modified zeolite melts.

5. The method for producing amorphous PFAS according to claim 3, characterized in that the modified zeolite is a natural zeolite mainly composed of clinoptilolite that has undergone the aforementioned pretreatment, and the temperature controlled is in the range of 1000 to 1100°C, which is lower than the 1200°C at which the modified zeolite melts.

6. The method for producing amorphous PFAS according to claim 3, characterized in that the modified zeolite is dispersed in one of the following environments—water, soil, or air—to adsorb PFAS, is recovered after adsorption, and is transported as is to the medium- or low-temperature furnace after the pre-drying.

7. The method for producing amorphous PFAS according to claim 3, characterized in that CaO or MgO is added during sintering in the medium-to-low temperature furnace to promote fluorine fixation.

8. The method for manufacturing amorphous bodies related to PFAS according to claim 3, characterized in that the temperature of the medium- and low-temperature furnace is controlled to maintain a constant temperature.

9. The method for manufacturing amorphous bodies related to PFAS according to claim 3, characterized in that the temperature of the medium- and low-temperature furnace is detected using a two-color thermometer.

10. A method for producing amorphous PFAS according to claim 3, characterized in that the aforementioned pretreatment further includes an amine modification treatment.

11. The method for producing amorphous PFAS according to claim 3, characterized in that the acid treatment is performed using hydrochloric acid.

12. The method for producing amorphous PFAS according to claim 3, characterized in that, when using the aforementioned natural zeolite, the aforementioned natural zeolite comprises clinoptilolite having a silica composition ratio of 4.5 to 5.5 with respect to alumina.

13. The method for producing amorphous PFAS according to claim 12, characterized in that, when the aforementioned natural zeolite is used, the aforementioned natural zeolite comprises mordenite in addition to the aforementioned clinoptilolite as the main component.

14. The method for producing amorphous PFAS according to claim 3, characterized in that when the natural zeolite is used, the natural zeolite is cut into pieces of 3 mm to 5 mm in size to increase its specific surface area and supplied as is to the pretreatment.

15. An apparatus for direct use in carrying out a method for manufacturing an amorphous body relating to PFAS as described in any one of claims 3 to 14, A pre-processing unit that performs the aforementioned pre-processing, A recovery section from which the modified zeolite that has adsorbed PFAS is recovered, A drying section for pre-drying the recovered modified zeolite for dehydration, The aforementioned medium-to-low temperature furnace, having a temperature in the range of 900 to 1100°C, An apparatus characterized by having the following features.

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