JP2017189730A - Method for producing silver phosphate-carrying porous carbon material and silver phosphate-carrying porous carbon material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a silver phosphate-carrying porous carbon material that allows silver phosphate to be carried on the surface of a porous carbon material.SOLUTION: A method for producing a silver phosphate-carrying porous carbon material includes immersing a porous carbon material in a phosphate ion-containing solution, evaporating and drying it to obtain a coagulum, bringing the coagulum into contact with a silver ion-containing solution, and thereafter, subjecting it to solid-liquid separation.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a silver phosphate-supporting porous carbon material and a silver phosphate-supporting porous carbon material.

It is known that silver phosphate (Ag ₃ PO ₄ ) exhibits a high oxidative degradation power under visible light irradiation and can decompose organic substances (Patent Document 1). On the other hand, woody biomass is a renewable biomass resource, and porous carbonized material obtained by carbonizing woody biomass is used as an adsorbent.

In Patent Document 2, as a method of supporting a silver phosphate compound represented by Ag ₃ PO ₄ or Ag ₄ P ₂ O ₇ in the pores of a porous inorganic support containing activated carbon, a granular silica support is prepared by phosphoric acid. Immerse in an aqueous solution of ammonium dihydrogen, remove the excess aqueous solution of ammonium dihydrogen phosphate by suction to obtain a precursor complex sample, immerse the obtained precursor complex sample in an aqueous solution of silver nitrate, and add an aqueous solution of excess ammonium dihydrogen phosphate Is specifically disclosed that a particulate composite bactericidal sample comprising a silver phosphate (Ag ₃ PO ₄ ) -silica carrier was obtained by suction removal.

  Patent Document 3 specifically discloses that, as a method of coexisting a silver-containing compound and a phosphoric acid-containing compound, activated charcoal and a silver nitrate solution are reacted to carry silver, and dried and mixed with ammonium phosphate. Has been.

Japanese Patent Laid-Open No. 10-033990 JP 2002-104909 A JP 03-038504 A

However, in the methods described in Patent Documents 2 and 3, silver phosphate (Ag ₃ PO ₄ ) could not be supported on the surface of the porous carbonized material.

An object of the present invention, the porous preparation and silver phosphate supported porous carbon material silver phosphate supported porous carbon material capable of carrying a silver phosphate (Ag 3 _{PO 4)} to the surface of the carbon material Is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-described problems can be solved by the following, and have reached the present invention.

  In the method for producing a silver phosphate-supporting porous carbon material of the present invention, the porous carbon material is immersed in a phosphate ion-containing solution and evaporated to dryness to obtain a solidified product, and the solidified product is contacted with the silver ion-containing solution. After that, solid-liquid separation is performed.

  In the method for producing a silver phosphate-supporting porous carbon material of the present invention, it is preferable to heat-treat woody biomass at 400 to 1000 ° C. to obtain the porous carbon material.

  In the method for producing a silver phosphate-supporting porous carbon material of the present invention, the phosphate ion-containing solution is preferably a disodium hydrogen phosphate aqueous solution, and the concentration thereof is preferably 3 to 20 g / l.

  In the method for producing a silver phosphate-supporting porous carbon material of the present invention, the silver ion-containing solution is preferably a silver nitrate aqueous solution, and the concentration thereof is preferably 3 to 5 g / l.

  The silver phosphate-supporting porous carbon material of the present invention includes a support containing a porous carbon material and a photocatalytic component containing silver phosphate supported on the support.

The silver phosphate-supporting porous carbon material of the present invention preferably has a BET specific surface area of 100 to 1000 m ² / g.

  In the silver phosphate-supporting porous carbon material of the present invention, the supported amount of silver phosphate is preferably 5 to 25% by mass in terms of silver.

According to the present invention, a silver phosphate-supporting porous carbon material in which silver phosphate (Ag ₃ PO ₄ ) is supported on the surface of the porous carbon material is obtained.

FIG. 1 is a graph showing the results of measurement of powder X-ray diffraction patterns of samples of Example 1 and Comparative Examples 1 to 3. The vertical axis represents the diffraction intensity, and the horizontal axis represents the diffraction angle (2θ / degree). FIG. 2 is a scanning electron micrograph of the sample of Example 1 taken at a magnification of 500 times. FIG. 3 is a scanning electron micrograph of the sample of Example 1 taken at a magnification of 10,000. FIG. 4 is a graph showing the results of measurement of powder X-ray diffraction patterns of the samples of Example 1, Example 2, and Example 3. The vertical axis represents the diffraction intensity, and the horizontal axis represents the diffraction angle (2θ / degree). FIG. 5 is a diagram showing the results of a methylene blue decomposition experiment (Example 5) of the sample of Example 1. FIG. The vertical axis represents the methylene blue concentration (μmol / l), and the horizontal axis represents the visible light irradiation time (minutes).

  Hereinafter, modes for carrying out the present invention will be described.

[Method for Producing Silver Phosphate-Supporting Porous Carbon Material According to First Embodiment]
In the method for producing a silver phosphate-supporting porous carbon material according to the first embodiment, the porous carbon material is immersed in a phosphate ion-containing solution and evaporated to dryness to obtain a solidified product (hereinafter referred to as “evaporation drying process”). The solidified product is brought into contact with a silver ion-containing solution, and then solid-liquid separation is performed (hereinafter, solid-liquid separation step).

Thus, in the manufacturing method according to the first embodiment, the porous carbon material is immersed in the phosphate ion-containing solution and the silver ion-containing solution in this order, and the porous carbon material is immersed in the phosphate ion-containing solution. Evaporate to dryness. Therefore, a silver phosphate-supporting porous carbon material in which silver phosphate (Ag ₃ PO ₄ ) is supported on the surface of the porous carbon material, which could not be produced by the conventional manufacturing method, is obtained. This is because in the evaporating and drying process, by evaporating and drying the phosphate ion-containing solution without filtering, a porous carbon material whose surface is mostly covered with inorganic phosphate is obtained, and solid-liquid separation is achieved. In the process, by bringing this into contact with a silver ion-containing solution, the inorganic phosphate covering the surface of the porous carbon material reacts with silver ions to produce silver phosphate (Ag ₃ PO ₄ ). It is guessed.

<Evaporation to dryness process>
In the evaporation / drying step, the porous carbon material is immersed in a phosphate ion-containing solution, and the solvent is evaporated to dryness to obtain a solidified product. That is, a porous carbon material and a phosphate ion-containing solution are mixed to obtain a phosphate ion mixed solution, and the resulting phosphate ion mixed solution is evaporated to dryness to obtain a solidified product.

In the manufacturing method according to the first embodiment, it is important to evaporate and dry the phosphate ion mixture. For example, when the phosphate ion mixed liquid is solid-liquid separated by filtration or decantation, a porous carbon material carrying metal silver (Ag) instead of silver phosphate (Ag ₃ PO ₄ ) on the surface is obtained. This is because when a phosphate ion mixture is solid-liquid separated by filtration or decantation, a porous carbon material almost free of inorganic phosphate is obtained. When this is brought into contact with a silver ion-containing solution, silver ions are obtained. It is presumed that most of the silver ions (Ag ⁺ ) in the containing solution are reduced to metallic silver (Ag) on the surface of the porous carbon material. Further, when the phosphate ion mixed solution is not solid-liquid separated and the silver ion-containing solution is added to the phosphate ion mixed solution, silver phosphate (Ag ₃ PO ₄ ) is generated in the phosphate ion mixed solution. In addition, a porous carbon material supported by silver phosphate (Ag ₃ PO ₄ ) may not be obtained.

(Porous carbon material)
The porous carbon material is composed mainly of carbon. Therefore, the porous carbon material has higher heat resistance, acid resistance, and base resistance than the case where inorganic oxides such as silica (SiO ₂ ), alumina (Al ₂ O ₃ ), and titania (TiO ₂ ) are used as the support. Excellent. Examples of the porous carbon material include charcoal such as black charcoal and white charcoal; and nanospace carbon such as activated carbon, activated carbon fiber, and mesoporous carbon.

The porous carbon material has innumerable pores. Therefore, it is suitable for dispersing silver phosphate (Ag ₃ PO ₄ ) having a large specific surface area and exhibiting high oxidative decomposition ability under irradiation with visible light.

BET specific surface area of the porous carbon material is preferably 100~1000m ² / g, more preferably 300~700m ² / g. The total pore volume of the porous carbon material is preferably 0.05 to 0.50 mL / g. The BET specific surface area and the total pore volume of the porous carbon material can be measured in the same manner as described in the examples.

(Phosphate ion-containing solution)
The phosphate ion-containing solution may be a solution containing phosphate ions, and the solute and the solvent are not limited as long as phosphoric acid is dissolved as ions. Especially, it is preferable to use disodium hydrogenphosphate aqueous solution as a phosphate ion containing solution.

The concentration of the phosphate ion-containing solution is preferably 3 to 20 g / l, more preferably 3 to 5 g / l. If the concentration of the phosphate ion-containing solution is within the above range, the formation of white precipitates not supported on the porous carbon material in the phosphate ion mixed solution can be suppressed, and the supported amount of metallic silver (Ag) is The silver phosphate-supporting porous carbon material in which silver phosphate (Ag ₃ PO ₄ ) is more dispersed and supported can be obtained.

What is necessary is just to adjust the quantity of the phosphate ion containing solution to be used suitably according to the density | concentration etc. of a phosphate ion containing solution. When using a disodium hydrogen phosphate aqueous solution as the phosphate ion-containing solution, the amount of disodium hydrogen phosphate contained in the disodium hydrogen phosphate aqueous solution is porous as the mass of Na ₂ HPO ₄ · 12H ₂ O. Preferably it is 0.6-4.0 g / g with respect to the gross mass of a carbon material.

When using a disodium hydrogen phosphate aqueous solution as the phosphate ion-containing solution, as a method for preparing the disodium hydrogen phosphate aqueous solution, for example, disodium hydrogen phosphate · 12 hydrate (Na ₂ HPO ₄ · 12H ₂ O ) Can be prepared by dissolving in pure water. An anion in the aqueous solution of disodium hydrogen phosphate is mainly composed of HPO ₄ ^2- .

(Evaporation to dryness)
As a method for evaporating and drying, for example, a phosphate ion mixture is heated on a hot plate to evaporate water, and after the water is almost gone, the first method is to dry; A second method of evaporating the solvent of the phosphate ion mixture by leaving it under pressure; first evaporating the solvent of the phosphate ion mixture by heating the phosphate ion mixture to a temperature at which the solvent does not boil; There are three methods. In the first method, the set temperature of the hot plate may be adjusted as appropriate according to the size of the hot plate and the heating container, and is preferably adjusted to a temperature that does not boil the phosphate ion mixture. Is preferably 80 to 200 ° C. The drying method in the first method is, for example, heat drying; air drying; allowing the coagulant to stand in a vacuum desiccator equipped with a desiccant and reducing the pressure in the vacuum desiccator with an oil rotary vacuum pump. And a method of drying under reduced pressure. In the third method, for example, an evaporator or the like can be used as a method of heating the phosphate ion mixed solution.

  After evaporating the phosphate ion mixture to dryness, the solidified product may be dried if necessary. As a method for drying the coagulated product, for example, heat drying; air drying; the coagulant is left in a vacuum desiccator equipped with a desiccant, and the coagulant is depressurized by reducing the pressure in the vacuum desiccator with an oil rotary vacuum pump. The method of drying etc. are mentioned.

<Solid-liquid separation process>
In the solid-liquid separation step, the solidified product is brought into contact with a silver ion-containing solution and then solid-liquid separated. That is, a solidified product and a silver ion-containing solution are mixed to obtain a silver ion mixed solution, and the resulting silver ion mixed solution is subjected to solid-liquid separation. Thereby, the silver phosphate carrying | support porous carbon material is obtained.

(Silver ion-containing solution)
The silver ion-containing solution may be a solution containing silver ions, and the solute and the solvent are not limited as long as silver is dissolved as ions. Of these, an aqueous silver nitrate solution is preferably used as the silver ion-containing solution. The silver ion-containing solution may be a solution using a solvent different from the phosphate ion-containing solution. For example, a combination of an aqueous solution of disodium hydrogenphosphate and an ethanol solution of silver nitrate can be used as the phosphate ion-containing solution and the silver ion-containing solution.

What is necessary is just to adjust suitably the density | concentration of a silver ion containing solution according to the density | concentration of a phosphate ion containing solution, Preferably it is 3-5 g / l. If the concentration of the silver ion-containing solution is within the above range, the supported amount of metallic silver (Ag) is less, and the silver phosphate-supporting porous carbon material in which silver phosphate (Ag ₃ PO ₄ ) is more dispersed and supported It can be. The concentration of the silver ion-containing solution is preferably 0.5 to 1.0 times, more preferably 0.8 to 1.0 times the concentration of the phosphate ion-containing solution. If the concentration of the phosphate ion-containing solution and the concentration of the silver ion-containing solution are within the above range, and the concentration of the silver ion-containing solution is within the above range with respect to the concentration of the phosphate ion-containing solution, it is not supported on the coagulum Generation of silver phosphate or the like can be further suppressed.

  The silver ion-containing solution to be used is preferably adjusted to pH 3-8. If the pH is less than 3, silver phosphate may not be generated.

  What is necessary is just to adjust the quantity of the silver ion containing solution to be used suitably according to the density | concentration etc. of a silver ion containing solution. Moreover, when using silver nitrate aqueous solution as a silver ion containing solution, the quantity of silver nitrate contained in silver nitrate aqueous solution becomes like this. Preferably it is 0.6-1.0 g / g with respect to the gross mass of a porous carbon material.

(contact)
The method for bringing the coagulated product into contact with the silver ion-containing solution is not particularly limited as long as it can be brought into contact with the silver ion so that an ion exchange reaction is possible, and examples thereof include a method of immersing the coagulated product in an aqueous silver nitrate solution.

  It is preferable to keep the silver ion-containing solution at 15 to 25 ° C. for several minutes or more after the solidified product is brought into contact with the silver ion-containing solution and before the silver ion mixed solution is solid-liquid separated. That is, it is preferable to keep the ion exchange reaction between the phosphate cation and silver existing on the surface of the coagulum, that is, for several minutes or more.

(Solid-liquid separation)
The method for solid-liquid separation is not particularly limited, and examples thereof include known methods such as filtration, centrifugation, precipitation separation, and vacuum concentration.

  After the silver ion mixed liquid is subjected to solid-liquid separation, the silver phosphate-supporting porous carbon material may be dried as necessary. As a method for drying the coagulated product, for example, heat drying; air drying; the coagulant is left in a vacuum desiccator equipped with a desiccant, and the coagulant is depressurized by reducing the pressure in the vacuum desiccator with an oil rotary vacuum pump. The method of drying etc. are mentioned.

[Method for Producing Silver Phosphate-Supporting Porous Carbon Material According to Second Embodiment]
In the method for producing a silver phosphate-supporting porous carbon material according to the second embodiment, in the first embodiment, before the evaporation to dryness step, the woody biomass is heat-treated at 400 to 1000 ° C. to obtain the porous carbon material. Other than having the process (henceforth heat processing process) to obtain, it is the same as that of 1st embodiment. That is, the manufacturing method according to the second embodiment performs the heat treatment step, the evaporation to dryness step, and the solid-liquid separation step in this order. Hereinafter, description of the evaporation to dryness step and the solid-liquid separation step is omitted.

<Heat treatment process>
In the heat treatment step, the woody biomass is heat-treated at 400 to 1000 ° C. to obtain a porous carbon material. If a porous carbon material obtained by this heat treatment is used, a silver phosphate-supporting porous carbon material having a larger amount of silver phosphate (Ag ₃ PO ₄ ) and a smaller amount of metal silver (Ag) supported can do.

(Woody biomass)
Woody biomass is renewable organic organic resources (excluding fossil fuels) and made of wood. Specific examples of woody biomass include tree residues from branches and leaves generated during tree felling and lumbering, bark and sawdust from lumber mills, etc., as well as demolishing houses and street trees. The pruned branch of can be mentioned. Such woody biomass is preferably previously dried at 100 to 120 ° C. for 8 to 48 hours to remove moisture. The treatment time for the heat treatment is preferably 0.5 to 3.0 hours.

  A heat-treated product obtained by heat-treating woody biomass may be adjusted to a predetermined size by allowing it to cool and then passing through a sieve.

(Heat treatment)
The temperature of the heat treatment of the woody biomass is 400 to 1000 ° C, preferably 550 to 850 ° C. The time for the heat treatment of the woody biomass is not particularly limited as long as the temperature of the heat treatment of the woody biomass reaches a desired temperature. Examples of the method for heat treating woody biomass include a method using an electric furnace, a method using a charcoal kiln, a method using an industrial furnace equipped with a burner and the like.

[Porous carbon material carrying silver phosphate]
The silver phosphate-supporting porous carbon material according to the present embodiment includes a support containing the porous carbon material and a photocatalytic component containing silver phosphate supported on the support. That is, the silver phosphate-supporting porous carbon material has the adsorption performance of the porous carbon material and the oxidative decomposition power (photocatalytic performance) of silver phosphate (Ag ₃ PO ₄ ) under visible light irradiation. Therefore, for example, volatile organic compounds that cause photochemical oxidants can be removed.

BET specific surface area of the silver phosphate supported porous carbon material is preferably 100~1000m ² / g, more preferably 300~700m ² / g. When the BET specific surface area of the silver phosphate-supporting porous carbon material is within the above range, the silver phosphate-supporting porous carbon material exhibiting excellent adsorption performance derived from the porous carbon material can be obtained.

The amount of silver phosphate supported on the silver phosphate-supporting porous carbon material is preferably 5 to 25% by mass and more preferably 5 to 10% by mass in terms of silver. If the amount of silver phosphate supported is within the above range, a silver phosphate-supporting porous carbon material that can more easily exhibit the oxidative decomposition ability of silver phosphate (Ag ₃ PO ₄ ) under visible light irradiation can be obtained. . The amount of silver phosphate supported on the silver phosphate-supporting porous carbon material can be measured in the same manner as described in the examples.

  The support including the porous carbon material is not particularly limited as long as it includes the porous carbon material described above. The photocatalytic component is not particularly limited as long as it contains silver phosphate. Since the photocatalyst component contains silver phosphate, it exhibits high oxidative decomposition ability under irradiation with visible light, decomposes almost all organic substances, and finally becomes carbon dioxide and water. Therefore, the silver phosphate-supporting porous carbon material can be used as a deodorant, an antibacterial agent, a harmful gas removal agent, a water purification agent, and the like. Visible light refers to light in a wavelength region of 380 nm to 830 nm. The visible light may be, for example, a general illumination such as a white fluorescent lamp, sunlight, a white LED, a light bulb, a halogen lamp, or a xenon lamp; a blue light emitting diode; a light having a blue laser as a light source.

  Hereinafter, the present invention will be specifically described by way of examples.

[Example 1]
(Heat treatment process)
Cedar sawdust dried at 115 ° C. for 24 hours was placed in a crucible and heat-treated in an electric furnace (“EPDS-7.2R” manufactured by Isuzu Seisakusho Co., Ltd.). After heat-processing at 700 degreeC for 1 hour, it stood to cool in a furnace and the heat-processed material was obtained. The obtained heat-treated product was sieved to obtain a porous carbon material having a particle size of 106 to 1000 μm. The total pore volume of the obtained porous carbon material was 0.24 mL / g as determined from the nitrogen adsorption amount at a relative pressure of 0.98.

(Evaporation and drying process)
Disodium hydrogen phosphate.12 hydrate (Na ₂ HPO ₄ · 12H ₂ O) 2 g dissolved in 100 ml of pure water, disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution (concentration: 20 g / l) (hereinafter, (Sometimes referred to as a phosphate ion-containing solution).

0.5 g of the obtained porous carbon material is placed in a 200 mL Erlenmeyer flask, and 100 ml of a disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution (concentration: 20 g / l) is added thereto to obtain a phosphate ion mixed solution. It was. After the phosphate ion mixture is stirred for 24 hours, it is heated on a hot plate set to 200 ° C. to evaporate the moisture in a state where the phosphate ion mixture is not boiling, and the moisture is almost gone. (ONW-450S, manufactured by ASONE CORPORATION) was dried (evaporated to dryness) to obtain a powdery solidified product.

(Solid-liquid separation process)
0.5 g of the obtained coagulum is placed in a 200 ml Erlenmeyer flask, and 100 ml of a silver nitrate (AgNO ₃ ) aqueous solution (concentration: 5 g / l) (hereinafter sometimes referred to as a silver ion-containing solution) is added to the flask. The sample was kept at normal pressure for 60 minutes, filtered, washed with pure water, and dried at 115 ° C. for 24 hours to obtain a sample.

<Powder X-ray diffraction measurement>
Powder X-ray diffraction measurement of the obtained sample was performed under the following measurement conditions. The measurement results are shown in FIG.
Measurement condition:
Measuring device: X-ray diffractometer (manufactured by Rigaku Corporation, “RINT-UltimaIII”)
X-ray irradiation source: Cu-Kα ray Tube voltage: 40 kV
Tube current: 40 mA
Scanning speed: 0.4 degree / min
Measurement range: Diffraction angle 2θ = 20 to 90 ^o
<Scanning electron microscope observation>
Samples obtained using an electrolytic emission scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, “SU8000”) were observed. A scanning electron micrograph of the sample taken at 500 times magnification is shown in FIG. A scanning electron micrograph of the sample taken at a magnification of 10,000 is shown in FIG.

<BET specific surface area measurement>
Using a BET specific surface area measuring device (manufactured by Quantachrome, "AUTOSORB-1-C"), an adsorption isotherm of nitrogen is created in the range of an adsorption temperature of 77.4K and a relative pressure of 0.01 to 1.0, and a BET plot. Thus, the BET specific surface area of the obtained porous carbon material and the sample was measured. The measurement results are shown in Table 1.

<Ag content measurement>
Using an energy dispersive X-ray fluorescence analyzer (“EDXL 300” manufactured by Rigaku Corporation), the Ag content of the obtained sample was measured by X-ray fluorescence elemental analysis. The measurement results are shown in Table 1.

[Comparative Example 1]
20 g of cedar sawdust dried at 115 ° C. for 24 hours, 1.7 g of disodium hydrogen phosphate hydrate (Na ₂ HPO ₄ · 12H ₂ O), 2.4 g of silver nitrate (AgNO ₃ ), balls (diameter: 10 mm and 20 mm) were mixed in a ball mill container, and mixed and stirred for 5 hours under a condition of 100 rpm using a table-top ball mill apparatus (“PM-001” manufactured by As One Co., Ltd.) to obtain a mixture.

  The obtained mixture was put into a crucible and heat-treated in an electric furnace (Isuzu Seisakusho, “EPDS-7.2R”). After heat-processing at 700 degreeC for 1 hour, it stood to cool in a furnace and the heat-processed material was obtained. The obtained heat-treated product was sieved to obtain a sample having a particle size of 106 to 1000 μm.

  Powder X-ray diffraction measurement of the obtained sample was performed in the same manner as in Example 1. The measurement results are shown in FIG.

[Comparative Example 2]
A porous carbon material and a disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution (concentration: 20 g / l) were obtained in the same manner as in Example 1.

0.5 g of the obtained porous carbon material is placed in a 200 mL Erlenmeyer flask, and 100 ml of an aqueous silver nitrate (AgNO ₃ ) solution (concentration: 5 g / l) is added to the flask and kept at 20 ° C. under normal pressure for 24 hours and filtered. The carbon material was obtained by washing with pure water and drying at 115 ° C. for 24 hours.

Next, 0.5 g of the obtained carbon material is placed in a 200 mL Erlenmeyer flask, and 100 ml of a disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution (concentration: 20 g / l) is added thereto, and the mixture is added at 20 ° C. and normal pressure. It was kept for a minute, filtered, washed with pure water, and dried at 115 ° C. for 24 hours to obtain a sample.

  Powder X-ray diffraction measurement of the obtained sample was performed in the same manner as in Example 1. The measurement results are shown in FIG.

[Comparative Example 3]
A porous carbon material and a disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution (concentration: 20 g / l) were obtained in the same manner as in Example 1.

0.5 g of the obtained porous carbon material is placed in a 200 mL Erlenmeyer flask, and 100 ml of an aqueous solution of disodium hydrogen phosphate (Na ₂ HPO ₄ ) (concentration: 20 g / l) is added thereto, and the mixture is stirred at 20 ° C. under normal pressure. It was kept for a time, filtered, washed with pure water, and dried at 115 ° C. for 24 hours to obtain a carbon material.

Next, 0.5 g of the obtained carbon material is placed in a 200 mL Erlenmeyer flask, and 100 ml of an aqueous silver nitrate (AgNO ₃ ) solution (5 g / l) is added thereto, and the mixture is kept at 20 ° C. under normal pressure for 60 minutes, filtered, and purified. The sample was washed with water and dried at 115 ° C. for 24 hours to obtain a sample.

  Powder X-ray diffraction measurement of the obtained sample was performed in the same manner as in Example 1. The measurement results are shown in FIG.

[Example 2]
A sample was obtained in the same manner as in Example 1 except that the heat treatment of cedar sawdust was changed from 700 ° C to 400 ° C. The BET specific surface area of the porous carbon material was 141 m ² / g, and the total pore volume was 0.074 ml / g. And the powder X-ray-diffraction measurement of the obtained sample was performed similarly to Example 1. FIG. The measurement results are shown in FIG.

[Example 3]
A sample was obtained in the same manner as in Example 1 except that the heat treatment of cedar sawdust was changed from 700 ° C to 1000 ° C. The BET specific surface area of the porous carbon material was 944 m ² / g, and the total pore volume was 0.47 ml / g. And the powder X-ray-diffraction measurement of the obtained sample was performed similarly to Example 1. FIG. The measurement results are shown in FIG.

[Comparative Example 4]
A porous carbon material and a disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution (concentration: 20 g / l) were obtained in the same manner as in Example 1.

0.5 g of the obtained porous carbon material was placed in a 200 mL Erlenmeyer flask, and 100 ml of a disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution (concentration: 20 g / l) was added thereto, followed by stirring for 24 hours.

Subsequently, when 100 ml of an aqueous silver nitrate (AgNO ₃ ) solution (5 g / l) was added dropwise thereto, yellow crystals were formed in the solution simultaneously with the dropwise addition. Only the produced yellow crystals were filtered, washed and dried, and powder X-ray diffraction measurement was performed in the same manner as in Example 1. As a result, it was confirmed that the yellow crystals were silver phosphate (Ag ₃ PO ₄ ). .

In Examples 1 to 3, since the porous carbon material was immersed in a phosphate ion-containing solution and evaporated to dryness to obtain a solidified product, the solidified product was brought into contact with a silver ion-containing solution, and then solid-liquid separation was performed. 1. As shown in FIG. 4, several diffraction peaks attributed to silver phosphate (Ag ₃ PO ₄ ) were detected in the measurement result of the powder X-ray diffraction measurement of the obtained sample. From this result, it was confirmed that silver phosphate (Ag ₃ PO ₄ ) was present on the surface of the porous carbon material. Furthermore, as shown in FIG. 2 and FIG. 3, by observing the sample with a scanning electron microscope, it can be confirmed that particles aggregated to several tens to several μm are supported on the surface of the porous carbon material. It was. From these results, it is considered that the particles that are carried on the surface of the porous carbon material and aggregated to about several tens nm to several μm are particles of silver phosphate (Ag ₃ PO ₄ ).

On the other hand, in Comparative Examples 1 to 3, the porous carbon material is immersed in a phosphate ion-containing solution, evaporated to dryness to obtain a solidified product, the solidified product is brought into contact with the silver ion-containing solution, and then solid-liquid separation is performed. Therefore, as shown in FIG. 1, in the measurement result of the powder X-ray diffraction measurement of the obtained sample, a diffraction peak attributed to silver phosphate (Ag ₃ PO ₄ ) was not detected. This result, or silver phosphate on the surface of the porous carbon material (Ag 3 _{PO 4)} is not present, even silver phosphate on the surface of the porous carbon material (Ag 3 _{PO 4)} is present, silver phosphate It was confirmed that the mass concentration of the crystal of (Ag ₃ PO ₄ ) was extremely lower than the mass concentration of the crystal of silver (Ag). Thereby, it can be evaluated that silver phosphate (Ag ₃ PO ₄ ) is not substantially present on the surfaces of the porous carbon materials of Comparative Examples 1 to 3. On the other hand, in the measurement result of the powder X-ray diffraction measurement of the obtained sample, several diffraction peaks attributed to metallic silver (Ag) were detected. From this result, it was confirmed that metallic silver (Ag) was present on the surface of the porous carbon material.

In Comparative Example 1, the diffraction peak attributed to silver phosphate (Ag ₃ PO ₄ ) was not detected because of the gas (CO, CO ₂ , CH ₄ etc.) generated during the heat treatment of the mixture. This is probably because most of (Ag ₃ PO ₄ ) was reduced to metallic silver (Ag).

In Comparative Example 2, the diffraction peak attributed to silver phosphate (Ag ₃ PO ₄ ) was not detected when silver nitrate (AgNO ₃ ) aqueous solution was added and silver nitrate (AgNO ₃ ) on the surface of the porous carbon material. Silver ions (Ag ⁺ ) in the aqueous solution are reduced to metallic silver (Ag) to obtain a carbon material having metallic silver (Ag) supported on the surface. Thereafter, the carbon material is converted to disodium hydrogen phosphate (Na _2). It is considered that even when immersed in the HPO ₄ ) aqueous solution, the metal silver (Ag) supported on the surface of the carbon material hardly reacted with hydrogen phosphate ions (HPO ₄ ²⁻ ).

In Comparative Example 3, the diffraction peak attributed to silver phosphate (Ag ₃ PO ₄ ) was not detected because when a disodium hydrogen phosphate (Na ₂ HPO ₄ ) aqueous solution was added, phosphorous was largely present on the surface. carbon material disodium hydrogen _(Na 2 HPO ₄₎ is hardly carried is obtained, then, when immersing the carbon material silver nitrate (AgNO ₃₎ solution, silver nitrate (AgNO ₃₎ most of the silver in the aqueous solution This is probably because ions (Ag ⁺ ) were reduced to metallic silver (Ag) on the surface of the carbon material, and metallic silver (Ag) was supported on the surface of the carbon material.

In Comparative Example 4, when the aqueous solution of silver nitrate (AgNO ₃ ) was added as it was without solid-liquid separation of the phosphate ion mixture, most of the silver ions (Ag ⁺ ) in the aqueous solution of silver nitrate (AgNO ₃ ) were converted to the surface of the carbon material. Before reaching the pH, it reacted with disodium hydrogen phosphate in a solvent to produce silver phosphate.

On the other hand, in Examples 1 to 3, some diffraction peaks attributed to silver phosphate (Ag ₃ PO ₄ ) were detected without filtering the disodium hydrogen phosphate (Na ₂ HPO ₄ ) solution. By evaporating to dryness, a porous carbon material in which most of the surface was covered with disodium hydrogen phosphate (Na ₂ HPO ₄ ) was obtained, and then the porous carbon material was converted into an aqueous silver nitrate (AgNO ₃ ) solution. By soaking, disodium hydrogen phosphate (Na ₂ HPO ₄ ) and silver phosphate (AgNO ₃ ) covering the surface of the porous carbon material reacted to produce silver phosphate (Ag ₃ PO ₄ ). it is conceivable that.

  And from the result of the powder X-ray diffraction of FIG. 4, the sample of Example 1 (heating temperature of carbonization is 700 ° C.) among Examples 1 to 3 has the highest peak intensity of silver phosphate, and silver phosphate. Seems to generate the most.

In Example 1, as shown in Table 1, the BET specific surface area of the silver phosphate-supporting porous carbon material was smaller than the BET specific surface area of the porous carbon material. This is presumably because the pores of the porous carbon material were covered with silver phosphate (Ag ₃ PO ₄ ) as shown in FIG.

[Example 4]
The concentration of the aqueous solution of disodium hydrogen phosphate (Na ₂ HPO ₄ ) is changed from 20 g / l to 3 g / l, 5 g / l or 10 g / l, and the concentration of the aqueous silver nitrate (AgNO ₃ ) solution is changed to 5 g / l or 3 g / l. A sample was obtained in the same manner as in Example 1 except that And the powder X-ray-diffraction measurement of the obtained sample was performed similarly to Example 1. FIG.

As a result, in all cases, several diffraction peaks attributed to silver phosphate (Ag ₃ PO ₄ ) were detected. From this result, it was confirmed that silver phosphate (Ag ₃ PO ₄ ) was present on the surface of the porous carbon material.

Among them, there are cases where (concentration of aqueous solution of disodium hydrogenphosphate (Na ₂ HPO ₄ ), concentration of aqueous solution of silver nitrate (AgNO ₃ )) = (5 g / l, 5 g / l), (10 g / l, 5 g / l). It was confirmed that silver phosphate was produced without producing metallic silver. Furthermore, (concentration of aqueous solution of disodium hydrogenphosphate (Na ₂ HPO ₄ ), concentration of aqueous solution of silver nitrate (AgNO ₃ )) = (5 g / l, 5 g / l) indicates that silver phosphate is most often produced. It could be confirmed.

[Example 5]
0.1 g of the sample obtained in Example 1 and 30 ml of methylene blue aqueous solution were placed in a 100 mL Erlenmeyer flask and allowed to stand in a dark room at 20 ° C. After the change in the color of the aqueous solution disappeared and the adsorption to the sample was saturated, the aqueous solution was sampled and the absorbance was measured. Thereafter, using a halogen lamp (Schott, “MegaLight100”), the sample was irradiated with visible light, an aqueous solution sample was taken at regular intervals, and the absorbance was measured to measure the degradation of methylene blue. . The result is shown in FIG. In FIG. 5, the time when the adsorption to the sample is saturated and the irradiation of the halogen lamp is started is set to 0 minutes. The horizontal axis indicates the halogen lamp irradiation time, and the vertical axis indicates the concentration of methylene blue in the aqueous solution. In FIG. 5, −30 minutes means 30 minutes before the start of halogen lamp irradiation, and −60 minutes means 60 minutes before the start of halogen lamp irradiation.

  The concentration of methylene blue is calculated from a calibration curve obtained in advance for the absorbance and the concentration of ethylene blue in the aqueous solution. As shown in FIG. 5, the sample obtained in Example 1 is irradiated with visible light to lower the concentration of methylene blue, that is, methylene blue is decomposed by a halogen lamp, and the visible light photocatalytic effect of silver phosphate is confirmed. I was able to.

Claims (7)

  A porous carbon material is immersed in a phosphate ion-containing solution and evaporated to dryness to obtain a coagulated product. The coagulated product is contacted with a silver ion-containing solution, and then solid-liquid separated. Production method.   The manufacturing method of the silver phosphate carrying | support porous carbon material of Claim 1 which heat-processes woody biomass at 400-1000 degreeC, and obtains the said porous carbon material.   The method for producing a silver phosphate-supporting porous carbon material according to claim 1 or 2, wherein the phosphate ion-containing solution is a disodium hydrogen phosphate aqueous solution and the concentration thereof is 3 to 20 g / l.   The method for producing a silver phosphate-supporting porous carbon material according to any one of claims 1 to 3, wherein the silver ion-containing solution is an aqueous silver nitrate solution, and the concentration thereof is 3 to 5 g / l.   A silver phosphate-carrying porous carbon material comprising a carrier containing a porous carbon material and a photocatalyst component containing silver phosphate carried on the carrier. The silver phosphate-supporting porous carbon material according to claim 5, wherein the BET specific surface area is 100 to 1000 m ² / g.   The silver phosphate-supporting porous carbon material according to claim 5 or 6, wherein the supported amount of silver phosphate is 5 to 25 mass% in terms of silver.