JPH10101365A - Alkali-proof low melting point glass and treatment of waste with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain glass having a low m.p. and alkali resistance and useful to treat harmful waste by using vanadium oxide as a base. SOLUTION: This alkali-proof low m.p. glass is based on vanadium oxide, and when it is brought into contact with an alkaline material, a layer having a higher concn. of an alkaline earth metal than the interior of the glass is formed in the surface of the glass. The alkaline material is a solid, soln. or gas contg. the alkaline earth metal. Since the formed surface layer prevents the penetration of the alkaline material into the interior of the glass, the degeneration of the glass and the leaching of glass components are not caused. The thickness of the surface layer is preferably <=1,500nm. The alkaline earth metal is preferably at least one among Ca, Sr and Ba.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkali-resistant low-melting glass and a method for treating hazardous waste using the same.

[0002]

2. Description of the Related Art In many cases, wastes such as toxic substances and radioactive substances with low harm are solidified using cement and disposed. On the other hand, high-hazardous waste disposal is to be solidified using glass that can be densified more than cement in order to further suppress the elution of hazardous waste. It is thought what was said. In this case, when water or seawater enters through the concrete, it is assumed that the very alkaline solution comes into contact with the solidified glass. In order to solidify low melting or volatile volatile hazardous waste with glass, it is necessary to use low melting point glass. However, the alkali resistance of the low-melting glass is poor, and there is a concern that highly alkaline water or seawater that has penetrated through the concrete will erode the low-melting glass, and at the same time, hazardous wastes will elute.
For this reason, low melting point,
In addition, a glass composition having high alkali resistance is required.

As a glass composition having a low melting point and excellent water resistance, a glass composition of V ₂ O ₅ —P ₂ O ₅ —Sb ₂ O ₃ system as described in JP-A-62-72543 is known. The composition is disclosed as a glass composition having a low melting point and high water resistance. Also, JP-A-8-75898 discloses JP-A-62-75898.
-72543 discloses a method for solidifying radioactive waste using a glass composition.

[0004]

The above technique is effective for the treatment of low hazardous waste. However, when highly hazardous waste is vitrified and installed in concrete, As described above, the glass comes into contact with the highly alkaline solution for a long period of time, so that the solidified glass may be dissolved and the waste component may be eluted.

An object of the present invention is to provide a glass composition having both low melting property and excellent alkali resistance, and a method for treating hazardous waste using the glass composition.

[0006]

Means for Solving the Problems The inventors of the present invention examined a glass composition having excellent alkali resistance, and
Based on the glass composition described in JP-A-72543, various additives were examined, and changes in alkali resistance were examined.

As a result, 1. In addition to the above composition, by adding an alkaline earth element, a layer having a higher concentration of the alkaline earth element than the inside of the glass is formed on the glass surface when contacting with the alkaline solution, and this layer is formed inside the glass of the alkali component. Control intrusion into the building. 2. In the case where the alkaline earth element is contained in the alkali solution to be brought into contact, even if the glass matrix contains no alkaline earth element, the above-mentioned 1. A layer having a high alkaline earth element concentration is formed on the glass surface to improve alkali resistance. Was found. The present invention has been made based on such new findings. That is, according to the first aspect of the present invention, there is provided a low-melting glass containing vanadium oxide as a main component. There is provided an alkali-resistant low-melting glass characterized in that a layer having a higher alkaline earth element concentration is formed.

[0008] The alkaline substance refers to a solid, a solution, or a gas containing the alkaline substance. Contact requires a certain amount of time for the alkaline earth material to diffuse through the glass. For example, for an alkaline solution at room temperature, 1 hour to
Two hours are required. This time is affected by the temperature, concentration, etc. of the alkaline substance. In order to confirm that a layer having a higher concentration of the alkaline earth element than the inside of the glass is formed in the vicinity of the glass surface, before contact with the alkali substance, the concentration of the alkaline earth element after the contact, For example, it may be checked by SIMS (secondary ion mass spectrometry), Auger electron spectroscopy, or the like. With these methods, the layer thickness of the alkaline earth element can also be determined. Glass produced by the usual method has a uniform distribution of alkaline earth elements.

According to the above structure, the high concentration layer of the alkaline earth element prevents the alkaline substance from penetrating into the inside of the glass, so that the deterioration of the glass and the elution of the glass component do not occur. Therefore, it is possible to provide a glass composition that can be used stably for a long period of time even in an atmosphere where alkaline substances come into contact. These glass compositions can be used as bonding glass for equipment used in chemical plants using high-concentration alkaline solutions, solidifying agents for disposing and storing industrial waste containing high-concentration alkaline substances, and the like.

In the first invention, the thickness of the layer having a high alkaline earth element concentration is preferably 1500 nm or less.

The thickness of the layer having a high alkaline earth element concentration is more preferably 300 nm or less.

In the first invention, it is preferable that the alkaline earth element is at least one of calcium, strontium and barium.

In the first invention, the alkali-resistant low-melting glass preferably contains phosphorus oxide, antimony oxide, and alkaline earth oxide as essential components.

In the first invention, the alkaline earth oxide is preferably at least one of barium oxide and strontium oxide.

In the first invention, the alkali-resistant low-melting glass preferably contains lead oxide.

In the first invention, the low melting point glass is preferably a basic glass.

Further, according to the second aspect of the present invention, in terms of oxide, V ₂ O ₅ : 40 to 60 mol%, P ₂ O ₅ : 20 to
38mol%, BaO + SrO + Sb 2 O 3: 10~30mol
%, And BaO + SrO ≧ 5 mol%, BaO ≧ 0 mol%,
SrO ≧ 0 mol%, Sb ₂ O ₃ ≧ 0 mol%,
Also provided is an alkali-resistant low-melting glass characterized by having PbO: 0 to 15 mol%.

The above structure is a preferred composition for realizing the first invention of the present invention.

According to a third aspect of the present invention, there is provided a method of treating waste, comprising solidifying waste using the alkali-resistant low-melting glass of the first or second aspect. Provided.

According to the above configuration, since solidification is possible at 450 to 600 ° C., it is effective for treating low melting or easily volatile hazardous waste. Examples of this hazardous waste include toxic cations or compounds thereof, and radioactive cations or compounds thereof.

In the third aspect, the solidified waste may be placed inside the concrete.

When the solidified waste is placed inside concrete and stored in the sea or underground, the solution changes to alkaline while seawater or groundwater permeates the concrete wall. Therefore, when the alkali-resistant glass of the present invention is applied to solidification of waste, the solidified substance does not elute or the like, and can be stably stored for a long period of time.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to embodiments.

Table 1 shows the composition and characteristics of the low-melting glass mainly composed of vanadium oxide.

[0025]

[Table 1]

Glass is based on the composition shown in Table 1,
It was prepared by melting at a temperature of 1000 to 1100 ° C. for 1 hour using an alumina crucible. It should be noted that a part of V ₂ O _{5 as} a compounding component was reduced during glass production. The transition temperature and the softening temperature shown in Table 1 were obtained by turning the produced glass into a powder and using a differential thermal analyzer to increase the temperature in the atmosphere by 5%.
Measured in ° C / min. Note that the softening temperature is the second value of the differential heat curve.
By reading the endothermic peak temperature. In the alkali resistance test, a glass processed into a 1 cm cube was immersed in 40 cc of an alkaline solution at 70 ° C. for 4 hours, and the weight loss rate was measured. In addition, alkaline solution has pH 1
1.5 to 12.5 sodium hydroxide (NaOH) aqueous solution, calcium hydroxide (Ca (OH) ₂ ) aqueous solution and sodium hydroxide-containing calcium hydroxide (NaCl + Ca (O
H) ₂ ) Three types of aqueous solutions were used. Was also evaluated in the same manner with respect to several PbO-SiO ₂ -B ₂ O ₃ based low-melting glass and alkali-resistant borosilicate high melting point glass of the prior art. Table 2 shows the system and characteristics of these glasses.

[0027]

[Table 2]

All of the low-melting-point glasses mainly composed of vanadium oxide shown in Table 1 have a transition temperature of 300 to 400 ° C.
And the softening temperature was as low as 400 to 470 ° C. This is effective for solidifying low melting or volatile volatile harmful waste since sealing, joining, sealing and the like can be sufficiently performed at 450 to 600 ° C. With respect to alkali resistance, Table 2 shows V ₂ O ₅ -P ₂ O ₅ binary glasses of Nos. 1 to 3.
Compared with the PbO-SiO ₂ -B ₂ O ₃ based low-melting glass to D, very large for any alkaline solution weight reduction rate, alkali resistance was very poor. No. 1
It was poor in alkali resistance even at 6-18 _{V 2 O 5 -P 2 O 5} -PbO ternary glass. However, Ca (OH) ₂
With respect to the aqueous solution, the glass having a higher PbO content had a significantly reduced weight loss rate. On the other hand, NaOH aqueous solution and Na
The effect of containing PbO was not so significant for the Cl + Ca (OH) ₂ aqueous solution, and the weight reduction rates for them were similar. No. 4 containing alkaline earth oxides
In the ternary glasses of Nos. 1 to 11, the weight loss rate can be remarkably reduced to less than 0.01% when the alkaline earth oxide content is 5 mol% or more with respect to the NaOH aqueous solution. I surpassed. When the glass after immersion in the NaOH aqueous solution was analyzed, a layer having a higher concentration of the alkaline earth element was formed on the glass surface than inside the glass. That is, the Sr high concentration layer on the glass surface of No. 4-7,
A high Ba concentration layer was formed on the surface of the 11 glass. The thickness of this layer was smaller as the content of alkaline earth oxide was larger, and was in the range of 1500 to 300 nm from the glass surface. In addition, the formation of this layer suppressed the intrusion of cations (Na ions) in the NaOH aqueous solution. The thickness of the cation infiltration layer substantially corresponded to the thickness of the high concentration layer of the alkaline earth element, and was in the range of 1500 nm or less from the glass surface. Glass containing vanadium oxide as a main component is a basic glass and attracts cations in an alkaline solution.

The thickness of the penetration layer of the Na ions in the _{V 2 O 5 -P 2 O 5} -PbO ternary glass No.16~18 alkali resistance was poor for NaOH aqueous solution was also 10000nm more than the glass surface. Therefore, it is considered that the formation of the high concentration layer of the alkaline earth element as described above significantly improved the alkali resistance against the NaOH aqueous solution.

Regarding the alkali resistance of the above No. 4 to 11 glasses to Ca (OH) ₂ aqueous solution, as shown in the No. 9 glass, the alkaline earth oxide content was 10 mol%.
As described above, the weight reduction rate was significantly reduced to less than 0.01%. Also in this regard, the conventional low-melting glasses A to D surpassed. When the glasses of Nos. 6, 9, and 11 having an alkaline earth oxide content of 10 mol% or more were analyzed, a high concentration layer of an alkaline earth element was formed on the glass surface. Unlike the NaOH aqueous solution, the alkaline earth element in this case is not Sr or Ba which is a glass constituent element,
The cation was Ca in the alkaline solution. This C
The high concentration layer a was also observed with a scanning electron microscope, and its thickness was 1500 nm or less from the glass surface. It is considered that the formation of this layer improved the alkali resistance to the Ca (OH) ₂ aqueous solution.

NaCl + Ca of No. 4-11 glass
The weight reduction rate with respect to the (OH) ₂ aqueous solution was almost the same as that with the NaOH aqueous solution. That is,
It showed better alkali resistance to Ca (OH) ₂ aqueous solution. No. 9.1 whose weight loss rate is less than 0.01%
When the glass of No. 0 was analyzed, a high concentration layer of an alkaline earth element was also formed on the glass surface. In this case, Ca, which is a cation in the alkaline solution, was contained, and Ba, which is a glass constituent element, was also slightly higher in concentration than inside the glass. In this layer, Ca ions invaded preferentially, but infiltration of Na ions was remarkably suppressed. FIG. 1 shows the result of analyzing the sample of No. 9 glass after the test by SIMS. The horizontal axis is the time when the sample surface was sputtered,
Indicates the depth from the surface of the sample. The vertical axis is the number of detected ions. As shown in FIG. 1, the depth is 300 nm from the sample surface.
It can be seen that a high concentration layer of Ca exists in the range. In the analysis results of the other samples, the high concentration layer of the alkaline earth element was present from the sample surface to a depth of about 1500 nm. The presence of the alkaline earth element was also observed with a scanning electron microscope as in the case of the Ca (OH) ₂ aqueous solution, and the thickness was 1500 nm or less from the glass surface. on the other hand,
The thickness of the infiltration layer of Na ion is 150 nm from the glass surface.
The following was small. It is considered that the formation of the alkaline earth element high concentration layer improved the alkali resistance to the NaCl + Ca (OH) ₂ aqueous solution.

The No. 12 glass containing both SrO and BaO in an amount of 8 mol% each had a weight reduction ratio of less than 0.01% with respect to any of the alkaline solutions, and showed good alkali resistance. Also, formation of a high concentration layer of an alkaline earth element on the glass surface was observed as described above. Sb ₂ O ₃ alkali resistance against ternary In glass No.13~15 Ca (OH) ₂ aqueous solution containing is good results were obtained, NaO
With respect to the alkali resistance to the H aqueous solution and the NaCl + Ca (OH) ₂ aqueous solution, the weight reduction rate was very large. C
With respect to the a (OH) ₂ aqueous solution, a Ca high concentration layer was formed on the glass surface. Its thickness is 1500 from the glass surface
nm or less. On the other hand, infiltration of Na ions, which are cations in the solution, was observed in other solutions, but such a layer was not confirmed. The contained Sb ₂ O ₃ was changed from trivalent to pentavalent ions at the time of glass production. Sb ₂ O ₃ and No.13~18 containing either the four-component glass No.19~21 containing both PbO
The alkali resistance was improved as compared with the ternary glass. However, although the alkali resistance against the Ca (OH) ₂ aqueous solution is good, the alkali resistance against the NaOH aqueous solution and the NaCl + Ca (OH) ₂ aqueous solution is the same as the conventional PbO—SiO 2.
₂ -B ₂ O ₃ system is substantially equal to the low-melting glass to D, not enough. Note that a Ca high concentration layer was formed on the glass surface for the Ca (OH) ₂ aqueous solution. Further, its thickness was 1500 nm or less from the glass surface.

The quaternary glasses Nos. 22 to 27 containing both BaO and Sb ₂ O ₃ exhibited very good alkali resistance to any alkaline solution, taking advantage of both. The alkali resistance of these glasses is the same as the conventional P
bO-SiO ₂ -B ₂ O ₃ system to surpass significantly that of the low-melting glass A~D, of course, was comparable to that of an alkali-resistant borosilicate high melting point glass E.
This glass E exhibits excellent alkali resistance, but has a very high transition temperature and softening temperature, and requires a working temperature of about 1200 ° C. to solidify hazardous waste. That is,
It is not suitable for solidification of low melting or volatile volatile hazardous waste. The formation of the above-mentioned high concentration layer of alkaline earth element was observed on the glass surfaces of Glass Nos. 22 to 27 for any alkaline solution. However, the thickness of the layer was thin, 300 nm or less from the glass surface. Also, B
Pentagonal glass containing aO, Sb ₂ O ₃ and PbO No. 28
Also obtained the same results as in the above Nos. 22 to 27,
It showed excellent alkali resistance.

Next, a glass was selected from Tables 1 and 2 and subjected to a long-term alkali resistance test. This test is 1cm
Glass processed into a cube of 70 ° C alkaline solution 1
The sample was immersed in 00 cc for 30 days, and each major cation element eluted from the glass was subjected to chemical analysis. In addition, two kinds of aqueous solutions of sodium hydroxide (NaOH) and calcium hydroxide (Ca (OH) ₂ ) having a pH of 12 were used as the alkaline solution. The evaporation of the aqueous solution during the test was dealt with by replenishing water as needed. Table 3 shows the sum of the amounts of the major cation elements eluted from each glass into the alkaline solution per unit surface area of glass and per unit day (mg
/ Cm ² · day).

[0035]

[Table 3]

The V ₂ O ₅ -P ₂ O ₅ binary glass No.2 whereas the two types of alkaline solutions as compared to the PbO-SiO ₂ -B ₂ O ₃ based low-melting glass A from the prior art And a considerable amount of glass components were eluted. As can be seen from the results of the weight loss rates in Table 1, the alkali resistance is very poor. However, in the ternary glasses of Nos. 6, 9, and 11 containing alkaline earth oxides, the elution amount can be significantly reduced to 1 mg / cm ² · day or less for both alkaline solutions.
The alkali resistance of the conventional low melting point glasses A and C surpassed. Although the content of the alkaline earth oxide suppressed the elution of the cation elements constituting all the glasses, the effect of suppressing the elution of the element V as the main component was particularly large. When the glass was analyzed, the intrusion of cations in the alkaline solution was suppressed to 1500 nm or less from the glass surface.

In the ternary glass No. 15 containing Sb ₂ O ₃ , the elution amount into the Ca (OH) ₂ aqueous solution is less than half that of the above-mentioned alkaline earth oxide-containing No. 6, 9, and 11 glasses. Very good results were obtained. However, the elution amount was very large with respect to the NaOH aqueous solution, which was almost the same as that of No. 2 glass. For Ca (OH) ₂ aqueous solution, elution of all glass constituent cation elements is suppressed, and cations (Ca ions) enter glass by 1500n from the glass surface.
m or less. However, a large amount of the cation elements constituting the entire glass eluted with respect to the NaOH aqueous solution, and among them, the elution amount of the Sb element was extremely large. Na
A large amount of cations (Na ions) in the OH aqueous solution
The thickness of the infiltration layer was nearly 10,000 nm from the glass surface. PbO-containing quaternary glass No. 1
Even in the cases of Nos. 9 and 21, the amount eluted into the Ca (OH) ₂ aqueous solution was the above-mentioned No.
Alkali resistance was good, equivalent to 15 glasses. However, although the elution amount into the NaOH aqueous solution is still large, the conventional low melting point glass A, C
It could be reduced to the average. In addition, the amount of cations (Ca ions) permeated into the glass was about 1/3 to 1/2 of that of No. 15 glass because the amount of elution into the NaOH aqueous solution was reduced.

In the quaternary glasses Nos. 22, 24, 25, and 27 containing both BaO and Sb ₂ O ₃ , the elution amount was 0.1 mg / cm ² · day or less for any of the alkaline solutions. It was small and showed excellent alkali resistance. Elution of these glasses was comparable to that of PbO-SiO ₂ -B ₂ O ₃ based low-melting glass A, significantly less than that and C, alkali resistance borosilicate high melting point glass E of the prior art. As described above, this glass E exhibits excellent alkali resistance, but has a very high transition temperature and softening temperature, and requires a working temperature of about 1200 ° C. to solidify hazardous waste. Therefore, it is not suitable for solidification of low melting or volatile volatile waste. Glass No.22,2
At 4, 25, and 27, the intrusion of cations in the solutions was observed for both alkaline solutions. However, the thickness of the infiltration layer was very thin, 300 nm or less from the glass surface. Further, in the pentagonal glass No. 28 containing BaO, Sb ₂ O ₃ and PbO, the sum of the contents of BaO and Sb ₂ O ₃ is at least as high as that of the glasses No. 22, 24, 25 and 27. showed that.

As described above, the alkali-resistant low-melting glass of the present invention is a low-melting glass containing vanadium oxide as a main component, and when exposed to an alkaline solution, a layer having a higher concentration of an alkaline earth element than the inside of the glass is formed on the glass surface. By being formed, the alkali resistance was improved or improved. The thickness of the layer having a high alkaline earth element concentration was 1500 nm or less from the glass surface, and was preferably 300 nm or less. The alkaline earth element contained in this layer was calcium, strontium or barium. The alkali-resistant low-melting glass further contained phosphorus oxide, antimony oxide, and alkaline earth oxide as components in addition to vanadium oxide. Barium oxide and / or strontium oxide was effective as the alkaline earth oxide. Further, lead oxide may be included as a glass component.

Further, the alkali-resistant low-melting glass of the present invention is a low-melting glass having a transition temperature of 300 to 400 ° C., and the amount of the main cation element constituting the low-melting glass eluted into an alkaline solution. The sum was 1 mg / cm ² · day or less. More preferably, the sum of the elution amounts is 0.1 mg.
/ Cm ² · day or less. The alkali-resistant low-melting glass was a basic glass, and had a thickness at which cations contained in the alkaline solution penetrated from the glass surface was 1500 nm or less from the glass surface, and preferably 300 nm or less.

The alkali-resistant low-melting glass of the present invention has the following oxide conversion: V ₂ O ₅ : 40-60 mol% P ₂ O ₅ : 20-38 mol% BaO + SrO + Sb ₂ O ₃ : 10-30 mol% (BaO + SrO ≧ 5 mol%, BaO ≧ 0 mol%, SrO
≧ 0 mol%, Sb ₂ O ₃ ≧ 0 mol%) It was effective that the composition range of PbO: 0 to 15 mol% was effective.

The alkali-resistant low-melting glass of the present invention described above can be effectively used for treating low-melting or easily volatile hazardous wastes in order to have sufficient low-melting properties and excellent alkali resistance. it can. Hazardous waste was treated using the alkali-resistant low-melting glass of the present invention. As toxic waste, highly toxic arsenic ions and their compounds were used. With the content of this hazardous waste being 10 to 30 wt.%, The mixture was mixed with an alkali-resistant low-melting glass while being heated at 550 to 600 ° C., and solidified. No. 9 and 24 glasses shown in Tables 1 and 2 were used as the alkali-resistant low-melting glass. Since the alkali-resistant low-melting glass of the present invention is a basic glass, it has a feature that cations such as arsenic ions are easily trapped stably. In the case of solidification using No. 9 and 24 glasses, arsenic ions were almost completely trapped in the glass. For comparison, solidified similarly used also PbO-SiO ₂ -B ₂ O ₃ based low-melting glass A and C of the prior art. As shown in FIG. 2, each block 1 solidified with each low-melting glass was placed in a concrete container 2 and left in water 3 for 50 days. At this time, the water 3 had penetrated into the concrete container 2. The water inside and outside the concrete container 2 contains Ca eluted from the concrete.
By (OH) ₂ etc., it was changed to an alkaline aqueous solution of about pH 12. After 50 days, water inside and outside the concrete container 2 was collected, and the presence or absence of eluted arsenic ions was confirmed by chemical analysis. PbO-SiO ₂ -B ₂ O ₃ from the conventional
When the system low melting glasses A and C were used, arsenic ions were confirmed in both inside and outside water. The elution amount was a problematic amount in both glasses, but a larger amount was eluted when A glass having lower melting property and poor alkali resistance was used. This suggests that arsenic ions are eluted together with the elution of the glass component into the alkaline aqueous solution. When No. 9 and 24 glasses having good alkali resistance were used, no elution of arsenic ions was observed in the water outside the concrete container. However, trace amounts of arsenic ions were detected in the water inside, although this was not a problem in No. 9 glass. On the other hand, no elution of arsenic ions was observed in the internal water of No. 24 glass, which had better alkali resistance than No. 9 glass. A similar test was conducted using salt water, but good results were obtained for No. 9 and No. 24 glasses as in the case of using water. But,
PbO-SiO ₂ -B ₂ O ₃ based low-melting glass A from the prior art
When C and C were used, the elution amount of arsenic ions increased.

Next, using a highly radioactive molten salt (LiCl-KCl) as a hazardous waste, it was solidified with the alkali-resistant low-melting glass of the present invention and subjected to the same test as described above. Assuming that the content of this hazardous waste is 10 to 30 wt.
While heating at 50 to 550 ° C., the mixture was mixed with the alkali-resistant low-melting glass of the present invention and solidified. The alkali-resistant low-melting glass includes Nos. 11 and 25 shown in Tables 1 and 2.
Glass was used. The alkali-resistant low-melting glass N of the present invention
In those solidified using o. 11 and 25, radioactive cations of Li and K were almost completely trapped in the glass. However, most of Cl was evaporated as chlorine gas (Cl ₂ ) during glass solidification. C
Since l is not radioactive, chlorine gas was recovered during glass solidification and reused when synthesizing a new molten salt. For comparison, a conventional PbO-S
iO ₂ -B ₂ O ₃ based low-melting glass A and B were also solidified similarly using. In this case, almost no gasification of Cl was observed. As shown in FIG. 2, the blocks 1 solidified with each low-melting glass were placed inside a concrete container 2 and left in water 3 for 50 days. At this time, the water 3 had penetrated into the concrete container 2. The water inside and outside the concrete container 2 was changed to an alkaline aqueous solution having a pH of about 12 due to Ca (OH) _{2 and the} like eluted from the concrete.
After 50 days, water inside and outside the concrete container 2 was collected, and the presence or absence of eluted Li and K radioactive cations was confirmed by chemical analysis. Conventional PbO-SiO _2-
When B ₂ O ₃ -based low-melting glasses A and B were used, Li ions and K ions were confirmed in both inside and outside water. The elution amount was large in both glasses, which was a major problem in environmental conservation. On the other hand, when the alkali-resistant low-melting glasses Nos. 11 and 25 of the present invention were used, no elution of Li ions and K ions was observed in the water outside the concrete container. However, in the case of No. 11 glass, trace amounts of Li ions and K ions were detected in the water inside. Since it is necessary to ensure absolute long-term reliability for the treatment of high-level radioactive waste, it is not preferable to dissolve even a minute amount by immersion for about 50 days. After several decades, there is a high possibility that Li ions and K ions flow out to outside water through concrete. No. 25 glass, which has better alkali resistance than No. 11 glass, contains Li
Elution of ions and K ions was not confirmed. A similar test was carried out using salt water. As for No. 25 glass, good results were obtained as in the case where water was used.
However, the elution amount of Li ions and K ions was increased in the case of using a PbO-SiO ₂ -B ₂ O ₃ based low-melting glass A and C of the prior art.

As described above, the method for treating hazardous wastes according to the present invention uses the above-described alkali-resistant low-melting glass of the present invention to reduce low-melting or readily volatile hazardous wastes by 450-450.
Since it is solidified at a low temperature of 600 ° C, there is no problem during solidification, and long-term reliability and safety can be ensured by installing it inside concrete. The present invention can be applied to the treatment of toxic cations or compounds thereof as a low-melting or volatile hazardous waste, and the use of the low-melting glass of the present invention, which is more excellent in alkali resistance, allows the use of radioactive cations or The compound can be treated. Since the alkali-resistant low-melting glass of the present invention is a basic glass, it is particularly suitable for solidifying harmful cations. Furthermore,
The treatment of hazardous wastes of the present invention is particularly effective for treating low melting or volatile volatile wastes, but can also be applied to the treatment of other hazardous wastes.

[0045]

According to the present invention, the alkali resistance of low-melting glass can be significantly improved or improved. In the alkali-resistant low-melting glass of the present invention, conventional PbO—SiO ₂ —B ₂
It is possible to realize low melting property equivalent to O ₃ -based low melting point glass and alkali resistance equivalent to conventional alkali-resistant borosilicate high melting point glass. Further, according to the present invention, the low-melting or easily volatile hazardous waste can be solidified at a low temperature by the invented alkali-resistant low-melting glass, and the solidified one can ensure excellent reliability and safety. . The present invention can be applied to the treatment of toxic cations or compounds thereof as a low-melting or volatile hazardous waste, and the use of the low-melting glass of the present invention, which is more excellent in alkali resistance, allows the use of radioactive cations or The compound can be treated. Since the alkali-resistant low-melting glass of the present invention is a basic glass, it is particularly suitable for solidifying harmful cations.

[Brief description of the drawings]

FIG. 1 is a view showing the presence of an alkaline earth element high concentration layer in the glass of the present invention.

FIG. 2 is a diagram showing a treatment test status of hazardous waste.

[Explanation of symbols]

1. Block made of hazardous waste solidified with low melting glass,
2 ... concrete container, 3 ... water or salt water.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Yamamoto 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. Hitachi 1-1, Hitachi Ltd. (72) Inventor Ken Takahashi 7-1-1, Omika-cho, Hitachi City, Ibaraki Pref. Hitachi Research Laboratory, Hitachi, Ltd. (72) Takashi Nishi Hitachi, Ibaraki, Japan 7-2-1, Mikamachi, Oita City Hitachi Electric Power / Electricity Development Division

Claims (11)

[Claims] 1. A low-melting glass containing vanadium oxide as a main component, which is brought into contact with an alkaline substance,
An alkali-resistant low-melting glass, wherein a layer having a higher alkaline earth element concentration than the inside of the glass is formed near the surface of the glass. 2. The alkali-resistant low-melting glass according to claim 1, wherein the thickness of the layer having a high alkaline earth element concentration is 1500 nm or less. 3. The alkali-resistant low-melting glass according to claim 1, wherein the layer having a high alkaline earth element concentration has a thickness of 300 nm or less. 4. An alkali-resistant low-melting glass characterized in that the alkaline earth element according to claim 1 is at least one of calcium, strontium and barium. 5. An alkali-resistant low-melting glass according to any one of claims 1 to 3, wherein the alkali-resistant low-melting glass contains phosphorus oxide, antimony oxide, and alkaline earth oxide as essential components. . 6. The alkali-resistant low-melting glass according to claim 5, wherein the alkaline earth oxide is at least one of barium oxide and strontium oxide. 7. The alkali-resistant low-melting glass according to claim 5, wherein the glass contains lead oxide. 8. An alkali-resistant low-melting glass, wherein the low-melting glass according to claim 1 is a basic glass. 9. V ₂ in terms of oxide _{O 5: 40~60mol% P 2 O} 5: 20~38mol% BaO + SrO + Sb 2 O 3: 10~30mol% and, BaO + SrO ≧ 5mol%, BaO ≧ 0mol%, S
An alkali-resistant low-melting glass having a relationship of rO ≧ 0 mol% and Sb ₂ O ₃ ≧ 0 mol%, and wherein PbO is 0 to 15 mol%. 10. A method for treating waste, comprising solidifying waste using the alkali-resistant low-melting glass according to any one of claims 1 to 9. 11. The solidified waste according to claim 10,
A waste disposal method characterized by being installed inside concrete.