JP2008189946A - Triazine thiol-supported carbide, method for producing triazine thiol-supported carbide, metal ion adsorption method and metal recovery method - Google Patents

Abstract

Provided are a material capable of efficiently recovering metal ions such as silver, a method for producing such a material, a metal ion adsorption method using such a material, and a metal recovery method using such a material. To do.
A triazine thiol represented by Chemical Formula 1 is supported in pores on a surface of a carbide obtained from a wood raw material.
[Chemical 1]

[Selection figure] None

Description

  The present invention relates to a carbide supporting triazine thiol, a method for producing a carbide supporting triazine thiol, a method of adsorbing metal ions to a carbide supporting triazine thiol, and a metal recovered using the carbide supporting triazine thiol. Regarding the method.

In recent years, with the growing awareness of environmental conservation and resource recycling, it has become important to remove metals and recover metals contained in waste liquids from factories and the like.
The main object of metal ion adsorption / recovery is the recovery of metals from waste liquids discharged from various industries (waste catalyst in the chemical industry, metal etching waste liquid in the semiconductor industry, photo waste liquid in pharmaceutical facilities, etc.). It is also an important technology from the standpoint of resource conservation, resource recycling, and environmental conservation, related to the detoxification of industrial hazardous wastewater. Known methods for collecting metal ions include ion exchange, adsorption, coprecipitation, membrane separation, and solvent extraction. However, the range of use is limited, and the creation of new high-performance materials and the development of efficient system technologies are considered in view of the prices of chemicals and materials used, the necessity of post-processing and recovery processes, or the economics of the system. Is desired.

For example, as a technique for recovering silver metal among metals, a technique for reducing silver recovery cost by a mercapto-s-triazine precipitation method has been proposed (for example, see Patent Document 1).
JP-A-11-1726

  Triazine thiol (hereinafter referred to as “RTD” where appropriate) can be used as a metal removing agent, a metal surface treatment agent, and a polymer crosslinking agent. However, when triazine thiol is used as a metal remover, there are the following problems. The first problem is that the amount of triazine thiol used is large. The second problem is that triazine thiol that reacts with metal ions is a fine particle, and therefore triazine thiol after reacting with metal ions cannot be sufficiently separated from the waste liquid.

  Activated carbon can be used as wastewater treatment, precious metal recovery, air purification, and catalyst. However, since activated carbon treatment requires advanced technology, there is a problem that it is costly. Moreover, although the wood carbide can be used for waste water treatment or the like, there is a problem that the metal collecting power is small as compared with activated carbon.

The first feature of the present invention is a triazine thiol-supporting carbide, which is supported by triazine thiol represented by Chemical Formula 1 in the pores of the surface of the carbide obtained from the wood raw material.

  A second feature of the present invention is a method for producing a triazine thiol-supported carbide, which is represented by Chemical Formula 1 in which the carbide is dispersed in water and the pH of the solution in which the carbide is dispersed is maintained acidic. A sodium salt solution of triazine thiol is dropped, and after completion of the dropping, the carbide carrying triazine thiol is separated from the solution and dried.

  A third feature of the present invention is a method for adsorbing metal ions, wherein the metal ion-containing liquid is brought into contact with the triazine thiol-supported carbide having the first feature.

  A fourth feature of the present invention is a metal recovery method, wherein a metal ion-containing liquid is brought into contact with a triazine thiol-supported carbide having the first feature to adsorb metal ions and then adsorb metal ions. Another object is to ash the triazine thiol-supported carbide at 550 to 1000 ° C.

  According to the present invention, a triazine thiol-supported carbide can be produced, and the triazine thiol-supported carbide can efficiently remove metal contained in waste liquid from a factory and recover metal at low cost. .

  The best mode for carrying out the present invention will be described below. The following description is merely an example, and the technical scope of the present invention is not limited to the following description.

[Preparation of triazine thiol-supported carbide]
Since triazine thiol (1,3,5-triazine-2,4,6-trithiol: RTD) dissolves as its sodium salt in basic solution and precipitates as RTD in acidic solution, RTD basic solution Was dropped into an acidic solution in which carbides were dispersed, so that RTD was acidified on the carbide surface in the solution.
Here, the sodium salt of RTD may be a monosodium salt, a disodium salt, a trisodium salt, or a mixture thereof, but preferably it should contain a large amount of a trisodium salt.

[Experimental sample]
The following 1,3,5-triazine-2,4,6-trithiol / trisodium salt aqueous solution, carbide, hydrochloric acid and sodium hydroxide were used for the preparation of RTD-supported carbide.
1,3,5-triazine-2,4,6-trithiol / trisodium salt aqueous solution (18.16 wt%) represented by Chemical Formula 2 (manufactured by Sankyo Kasei Co., Ltd.) MW: 243.3
Cedar thinned wood carbide (manufactured by Green Recycle) Particle size (mesh) 12-14, 20-32, 60-80, 100-115, 200 or less (12-14 mesh was obtained through 12-14 mesh This means carbide, the same shall apply hereinafter.)
Hydrochloric acid HCl Wako Pure Chemical Industries, Ltd. Special grade MW: 36.47
Sodium hydroxide NaOH Special grade MW: 40.00 made by Wako Pure Chemical Industries, Ltd.

[Method for preparing RTD-supported carbide]
<Preparation of RTD solution>
The RTD solution was prepared using 1,3,5-triazine-2,4,6-trithiol / trisodium salt aqueous solution (18.16 wt%). The preparation method was performed by adding an appropriate amount of 1,3,5-triazine-2,4,6-trithiol / trisodium salt aqueous solution to a volumetric flask and diluting to 50 mL with distilled water. The amount of 1,3,5-triazine-2,4,6-trithiol / trisodium salt solution added was 10, 20, 30, 40, 50 when the RTD loading calculated in Equation 1 was 1 g of carbide, respectively. , 60, 70 and 80 wt%.
Each of the prepared RTD solutions is expressed as an RTD solution having a theoretical loading (10-80 wt%).

<Preparation of carbide>
The wood material was cedars of conifers that were cut down in Iwate Prefecture.
(1) Porous and (2) Carbide that has the ability to collect metal ions and is superficially compatible with RTD, the condition for producing carbide is softwood cedar, with a carbonization temperature of 800 ° C. there were. The RTD-supporting carbide was produced with a carbonization temperature of 800 ° C. and a particle size of two types: coarse carbide and pulverized coal (fine particle carbide). Coarse carbides and pulverized coal (fine particle carbides) were used by drying the carbides dried at 105 ° C for 24 hours with a mixer, sieving them into particle sizes of various sizes using a wire mesh sieve, and drying at 105 ° C for 24 hours. . FIG. 1 shows an SEM image of pulverized coal (fine particle carbide).

<Preparation of RTD supported carbide>
1 g of each of the above carbides (particle size 12-14 mesh, 20-32 mesh, 60-80 mesh, 100-115 mesh, 200 mesh or less) was dispersed in 50 mL of distilled water. While measuring the pH of the solution in which the carbide was dispersed, 0.1 M HCl was added dropwise so as to reach pH 2. When the pH of the solution showed 2, the RTD solution (50 mL) of each concentration prepared by the above method was dropped into the solution in which carbide was dispersed at a rate of 2 mL / min. During the dropwise addition of the RTD solution, 0.1 M HCl was added dropwise to prevent the pH from rising, and the pH was adjusted to be maintained at 2. After completion of the dropping, solid-liquid separation of the carbide and the solution was performed. A funnel with filter paper was used for solid-liquid separation, and Toyo Filter Paper Co., Ltd. (diameter: 15 cm, No. 5A) was used for the filter paper. In addition, if RTD is precipitated in the solution while the RTD solution is being dropped, the dropping is terminated when the RTD is precipitated, and the wire mesh sieve (12-14 mesh, 20-32 mesh, 60-80 mesh, 100-115 Using carbide, 200 mesh), carbide and solution / deposited RTD were separated. After solid-liquid separation, RTD-supported carbide was prepared by drying at 105 ° C. for 24 hours. Further, using the above method, RTD was supported on activated carbon (activated carbon Fujiyuki A: particle size 80-100 mesh) manufactured by Cerachem Co., Ltd. as a comparative sample.

[Evaluation of RTD supported carbide]
<Measurement of RTD loading>
The RTD loading rate is measured by measuring the RTD residual concentration in the liquid phase with a total organic carbon meter (TOC-5000 manufactured by Shimadzu Corporation) after solid-liquid separation in the above <Preparation of RTD supported carbide>. RTD loading was determined from the residual concentration.
In addition, when RTD was precipitated during dropwise addition of the RTD solution, NaOH was added to the liquid phase, the RTD was once dissolved, acidified again, and the residual RTD amount was determined from the TOC (total organic carbon) measurement value.

<Method for evaluating physical properties of RTD supported carbide>
The physical properties of the dried RTD-supported carbide were evaluated by pore distribution measurement. For comparison, the pore distribution of unsupported carbide was also measured.
For pore distribution measurement, RTD-supported carbide and carbide were each dried at 105 ° C. for 24 hours and then dried under reduced pressure for 3 hours. 0.6 g each of RTD-supported carbide and carbide was taken and degassed at 120 ° C. for 3 hours under a nitrogen stream. After cooling to room temperature, the automatic specific surface area was measured with a pore distribution measuring device (BELSORP-mini, manufactured by BEL Japan Ltd.). For the evaluation of each pore, the micropore distribution was evaluated by the MP method, and the mesopore distribution was evaluated by the BJH method. Further, a scanning electron microscope (Hitachi, Ltd., S-2250NII type: SEM) was used to observe the surface of the RTD-supported carbide.
FIG. 2 shows the above <Method for preparing RTD-supported carbide> and an evaluation method for the prepared RTD-supported carbide.

[result]
<RTD loading>
Table 1 shows the RTD loading on the carbides of each particle size. With the particle size of 12-14 mesh, 20-32 mesh, and 60-80 mesh, yellow precipitates were observed during the dropwise addition of the RTD solution with a theoretical loading rate of 10 wt%. The dropping was finished. Under RTD loading conditions with a theoretical loading rate of 10 wt% with a particle size of 100-115mesh and a theoretical loading rate of 10-80 wt% with a particle size of 200mesh or less, RTD precipitation into the solution was observed when 50 mL of RTD solution was added dropwise. I couldn't.

<Carbide dispersion solution before and after RTD loading treatment>
FIG. 3 shows the carbide dispersion solution before the RTD carrying treatment and the dispersion solution after the carrying treatment. It can be seen that carbides are dispersed throughout the solution before the treatment, whereas carbides are precipitated after the RTD support treatment. This is thought to be due to the fact that RTD was supported in the carbide porous material and the buoyancy decreased.

<RTD-supported carbide after drying>
FIG. 4 shows the RTD-supported carbide after drying. RTD loading rate
From 6.0 wt% to 41.5 wt%, no change on the surface was observed, but from 50.5 wt% to 74.3 wt%, the surface turned gray. This is probably because RTD is supported on the charcoal surface after being supported in the porous material.

<Measurement results of pore distribution>
FIG. 5 shows micropore distribution analysis by the MP method. The horizontal axis indicates the pore width Dp (nm), and the vertical axis indicates the cumulative distribution dVp / dDp.
At 0 wt% with no RTD supported, a large peak of dVp / dDp = 1205 was observed at around 0.6 nm. However, with RTD supported carbide, the peak of the micropore distribution tended to decrease as a whole. This suggests that RTD is accumulated in the micropores and the micropores are decreasing.

FIG. 6 shows mesopore distribution analysis by the BJH method. The horizontal axis represents the pore radius Rp (nm), and the vertical axis represents the pore volume Vp (mm ³ / g). As shown in FIG. 6, mesopores having a pore radius of 3 nm or less exist at 0 wt% that does not carry RTD, and the peak of mesopore distribution tends to decrease greatly in RTD-supported carbide as a whole. A mesopore distribution of 3 nm to 10 nm was confirmed.
Mesopores with a pore radius of 3 nm or less are present at 0 wt% without RTD support, and the peak of mesopore distribution tends to decrease greatly with RTD supported carbide as a whole, and mesopore distribution between 3 nm and 10 nm is observed. Was confirmed.

<SEM image observation results>
FIG. 7 shows SEM images of carbide and RTD supported carbide. There is no significant change in the SEM image at a relatively low RTD loading ratio of 0wt% (unsupported) or RTD loading of 23.3wt% or less, but there is a slight change on the surface at RTD loading of 33.2wt%. As the RTD loading increased to 41.5 wt% and 50.5 wt%, the increase in the loading on the carbide surface was observed, and at RTD loading of 62.9 wt% or more, the carbide surface was observed. It can be observed that it is completely covered with the support.

FIG. 8 shows SEM images of activated carbon and RTD-supported activated carbon. As in FIG. 7, no change in the surface was observed in the range where the RTD loading rate was low, but a load on the surface was observed when the RTD loading rate was 47.8 wt% or more.
7 and 8 are considered to be those in which RTD is precipitated, and it is considered that the RTD loading on the carbide surface increases as the RTD loading rate increases.

[Summary of preparation of RTD supported carbide]
1. RTD supported carbide with a loading rate of 6.8 wt% or more could not be prepared with carbides of 100 mesh or more.
2. For carbides below 200 mesh, it was possible to prepare RTD-supported carbides with different RTD support rates by adjusting the RTD amount.
3. With RTD supported carbides of 200 mesh or less, RTD was supported in the micropores, and RTD was supported on the carbide surface when the RTD support rate increased further.

[Metal ion adsorption by product complex]
<Adsorption characteristics of batch RTD supported carbide>
The removal of silver from aqueous silver nitrate solution by RTD-supported carbides was examined for effects such as RTD support rate, addition amount of RTD-supported carbides, and initial pH of silver nitrate aqueous solution.

FIG. 9 shows the Freundlich adsorption isotherm, and FIG. 10 shows the Langmuir adsorption isotherm. Qe indicates the equilibrium adsorption amount, and Ce indicates the equilibrium concentration.
9 and FIG. 10, the size and amount of the RTD-supported carbide and the like are as follows.
RTD-supported carbide (200 mesh or less): 3mg added, RTD support rate 23.3wt%
Carbide (200mesh or less), activated carbon: 50mg added
Silver nitrate aqueous solution: solution volume 10mL, silver concentration 100-500ppm, pH5
Reaction time: 3 days The adsorption isotherm of Freundlich and Langmuir showed linearity with carbide and activated carbon, but the linearity was not obtained with Freundlich adsorption isotherm with RTD-supported carbide (RTD loading 23.3 wt%). Linearity was obtained with Langmuir's adsorption isotherm. From this, it is considered that the adsorption of silver is physical adsorption by pores in the carbide and activated carbon, but chemical adsorption by RTD in the RTD-supported carbide. From the adsorption isotherms of Freundlich and Langmuir, it became clear that carbides of 200 mesh or less have better silver adsorption capacity than activated carbon.

FIG. 11 shows the result of removing silver from a photographic waste solution by a batch method.
The amount of activated carbon added is as follows.
Activated carbon, carbide: Addition amount 300 mg
RTD solution (18.16%): addition amount 0.1 mL
RTD supported carbide (200 mesh or less): 100, 150 mg added, RTD supported rate 23.3 wt%
Photo waste solution: 10 mL solution volume; silver concentration 3000 ppm
Reaction time: 30 min.
With RTD-supported carbide (RTD support rate 23.3 wt%), the residual silver concentration was 170 ppm at an addition amount of 100 mg, but the residual silver concentration decreased to 3 ppm at an addition amount of 150 mg. From this result, it was possible to remove silver from photographic waste liquid actually discharged in the industry by RTD supported carbide.

  FIG. 12 shows the removal rate of Pt from the Pt model waste liquid by the batch method. FIG. 12 shows that 10 mL of Pt model waste liquid (initial concentration: 100 ppm) was prepared using a batch-type atomic absorption platinum standard solution (manufactured by Wako Pure Chemical Industries, Ltd.), and RTD loadings of 0 wt%, 10 wt%, and 20 wt% The results of measuring the removal rate of Pt by adding 0.01 g, 0.02 g, and 0.05 g of 30% by weight and 30% by weight carbide (200 mesh or less) are shown. The unsupported carbide was 0.01g and 0.02g, the Pt removal rate was 0%, and even when 0.05g was used, the Pt removal rate was 45%. When 0.05 g of carbide with an RTD loading of 10 wt% was added, the Pt removal rate was 100%. It was also found that Pt can be adsorbed by RTD-supported carbide from a solution prepared from a standard Pt solution for atomic absorption using Wako Pure Chemical Industries, Ltd.

<Adsorption characteristics of column type RTD supported carbide>
The dried RTD-supported carbide was packed in a column tube having an inner diameter of 1 cm, and a silver nitrate aqueous solution having a silver concentration of 500 ppm and a pH of 5 was passed therethrough using a pump.

FIG. 13 shows breakthrough curves of silver ions when using columns packed with RTD-supported carbides having different RTD support rates.
The filling amount of the RTD-supported carbide is as follows.
RTD supported carbide: Filling amount 0.5g, RTD supported rate 0-74.3wt%
Silver nitrate aqueous solution: Silver concentration 500ppm, pH5
Flow rate: 1mL / min.
Contact time: 2min.
Column length: 20mm
When silver ions are adsorbed on an adsorbent such as carbide, the concentration at the adsorbent outlet gradually increases when a certain load is exceeded. This phenomenon is called the breakthrough phenomenon of the adsorbent, and the point at which breakthrough begins is called the breakthrough point. Practically, the adsorption operation is finished at this point. In column experiments using unsupported carbide with RTD and activated carbon, breakthrough was observed immediately after permeation of the aqueous silver nitrate solution, but with RTD-supported carbide, the amount of solution that can be processed while maintaining a residual silver concentration of 1 ppm or less before breakthrough began Increased with increasing RTD loading.

FIG. 14 shows the change in the breakthrough curve of silver ions due to the difference in flow rate.
The filling amount of the RTD-supported carbide is as follows.
RTD-supported carbide: Filling amount 0.5 g, RTD support rate 23.3 wt%
Silver nitrate aqueous solution: Silver concentration 500ppm, pH5
Contact time: 2min., 40sec
Column length: 20mm
At a flow rate of 1 mL / min. (Contact time of 2 min.) And a flow rate of 3 mL / min. (Contact time of 40 sec.), The breakthrough started and the silver nitrate aqueous solution passed through 200 mL. From this result, in the column type, sufficient silver removal is possible with a contact time of 40 seconds, and the silver adsorption removal efficiency does not change even if the contact time is extended to 2 minutes. It was shown to be possible.

  FIG. 15 shows the SEM image and EDX element mapping of the composite after silver ion adsorption removal. The RTD-supported carbide used in the column shows Ag distribution only where S is distributed. This result shows that silver was not removed by reacting with RTD, but silver was removed by adsorbing to the carbide pores.

Table 2 shows the results of EDX elemental analysis.
Since RTD-supported carbide has 100% S, it can be seen that RTD is adsorbed on carbide. It can be seen that 3 mol of Ag is adsorbed to 1 mol of RTD from 47.4 at% S and 52.6 at% of Ag in the column-use carbide after silver ion adsorption removal. The column effluent is a powder desorbed from the carbide in the column, and it is understood that this is a compound in which RTD and Ag are reacted.

<Adsorption characteristics of pressurized column RTD supported carbide>
FIG. 18 shows an example of a pressurized RTD-supported carbide column adsorption device. The apparatus shown in FIG. 18 is equipped with two horizontal RTD-supported carbide columns 11 and 12 in the upper stage, two vertical RTD-supported carbide columns 13 and 14 in the lower stage, a liquid feed pump 15 and an outflow regulator 18. ing. The aqueous silver nitrate solution in the beaker 16 is fed to the upper horizontal columns 11 and 12 by a liquid feed pump, passes through the two vertical RTD-supported carbide columns 13 and 14 in the lower stage, and passes through the silver ions in the columns 13 and 14. Is adsorbed and the solution from which the silver ions have been removed is discharged into the beaker 17.
The pressurized column adsorber was filled with the composite, and typical model and actual waste liquids of Ag and Pt were tested.

FIG. 16 shows a silver ion breakthrough curve by a pressurized column adsorber.
The filling amount of the RTD-supported carbide is as follows.
RTD supported carbide (200 mesh or less): Packing amount 5.0g, RTD supported rate 23.3, 41.5wt%
Trap carbide (200 mesh or less): Filling 10.0 g
Silver nitrate aqueous solution: Silver concentration 500 ppm, pH 5
Flow rate: 10mL / min.
Contact time: 2 min.

  In the pressurized column, the RTD-supported carbides with a loading rate of 23.3 wt% and 41.5 wt% both had a volume of liquid that could be processed by 500 mL before the breakthrough started, and there was no difference depending on the RTD loading rate. In addition, the amount of liquid that could be processed before the start of breakthrough was increased by trapping at RTD loading of 41.5 wt%, but it was not changed at 23.3 wt%.

FIG. 17 shows a breakthrough curve of silver ions in a photographic waste liquid that is disposed of in the actual industry by a pressurized column system.
The filling amount of the RTD-supported carbide is as follows.
RTD supported carbide (200 mesh or less): Packing amount 5.0g, RTD supported rate 23.3wt%
Carbide for traps (200 mesh or less): Filling amount 10g
Photo waste liquid: Silver concentration 3000 ppm
Flow rate: 10mL / min.
Contact time: 2 min.
Column length: RTD supported carbide 8 mm, trap carbide 12 mm

  As shown in FIG. 17, the amount of solution that can be processed before the breakthrough was started was 500 mL. As shown in the figure, it was possible to remove silver from the photographic waste liquid using a “pressurized RTD-supported carbide column adsorption device”.

[Recover metal ions from post-adsorption complex]
When salts of RTD and metal ions (Ag and Pt) were prepared and added to an alkaline aqueous solution and the change was examined, it was found that the solubility was low. In addition, the same treatment was performed in a water-soluble alcohol, acetone, and water &#8212; alcohol mixed system, but almost the same result was obtained.
Therefore, a test was conducted on metal recovery by the incineration method. Under the conditions of incineration temperature 550 to 1000 ° C, air and nitrogen atmosphere, and combustion time 0.5 to 2 h, the weight ratio after incineration and before incineration was 0.19 to 0.22 for RTD supported carbide adsorbed with silver, and 0.63 to 0.70 for RTD. It was. From this result, it became clear that RTD and wood carbide combusted and incinerated, but both Ag and Pt can be recovered in a crude metal state by incineration. That is, it was possible to find a new method in which carbon of carbide used as a carrier acts as a reducing agent for metal ions and can be directly recovered as a crude metal.

An SEM image of pulverized coal is shown. A method for preparing RTD-supported carbide and an evaluation method for the prepared RTD-supported carbide are shown. The carbide dispersion solution before RTD carrying treatment and the dispersion solution after carrying treatment are shown. The RTD carrying | support carbide | carbonized_material after drying is shown. The micropore distribution analysis by MP method is shown. The mesopore distribution analysis by BJH method is shown. SEM images of carbide and RTD supported carbide are shown. SEM images of activated carbon and RTD-supported activated carbon are shown. The Freundlich adsorption isotherm is shown. The adsorption isotherm of Langmuir is shown. The removal result of silver from the photographic waste liquid by a batch type is shown. The removal rate of Pt from the Pt model waste liquid by batch type is shown. The breakthrough curve of silver ions when using columns packed with RTD-supported carbides with different RTD support rates is shown. The change of the breakthrough curve of silver ion by the difference in flow velocity is shown. The SEM image and EDX element mapping of the complex after silver ion adsorption removal are shown. The breakthrough curve of the silver ion by a pressure type column adsorption apparatus is shown. The breakthrough curve of the silver ion in the photographic waste liquid discarded in the actual industry by a pressure column type is shown. An example of a pressurized RTD-supported carbide column adsorption apparatus is shown.

Explanation of symbols

11, 12, 13, 14 RTD-supported carbide column 15 Liquid feed pump 16, 17 Beaker 18 Outflow regulator

Claims (4)

A triazine thiol-supported carbide in which triazine thiol represented by Chemical Formula 1 is supported in pores on the surface of a carbide obtained from a wood raw material.
Carbide is dispersed in water, and while maintaining the pH of the solution in which the carbide is dispersed, the sodium salt solution of triazine thiol represented by Chemical Formula 1 is dropped into the solution, and after completion of dropping, the carbide carrying triazine thiol A method for producing a triazine thiol-supported carbide, which comprises separating from a solution and drying.
  A metal ion adsorption method in which a metal ion-containing liquid is brought into contact with the triazine thiol-supported carbide according to claim 1 to adsorb metal ions.   A metal ion-containing liquid is brought into contact with the triazine thiol-supported carbide according to claim 1 to adsorb metal ions, and then the triazine thiol-supported carbide having adsorbed metal ions is combusted and ashed at 550 to 1000 ° C. Metal recovery method to recover.