JPH0747489B2 - Bi5O7 (NO3) compound represented by formula and process for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel bismuth compound containing (NO ₃ ), and a method for producing the same, which compound is used in various applications such as ion exchange and adsorption, such as nuclear power generation waste liquid and industrial waste liquid. It can be expected for applications such as treatment, adsorption and fixation of harmful ions in gas, and adsorption removal.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
The _{(NO 3) Bi-O- (} NO 3) based bismuth compounds, _{including, Bi 6 O 6 (NO 3} ) 6 is only known.
In general, this is bismuth oxide nitrate such as TiO (NO ₃ ).
It is shown by the formula.

The object of the present invention is to provide a novel bismuth compound containing (NO ₃ ).

[0004]

[Means for Solving the Problems] Conventionally, when bismuth nitrate pentahydrate (Bi (NO ₃ ) ₃ .5H ₂ O) is heated at a high temperature,
It is known that melt decomposition occurs and Bi ₂ O ₃ is produced when the decomposition is completed. However, the present inventor does not proceed with the decomposition until Bi ₂ O ₃ is formed, and the final decomposed product is obtained. When thermally decomposed under the condition that a part of (NO ₃ ) remains, a new compound represented by the formula of Bi ₅ O ₇ (NO ₃ ) was found.

Bi ₅ having a composition similar to this novel compound
A compound having a chemical composition represented by O ₇ I is conventionally known, and this novel compound is a compound of Bi ₅ O ₇ I
It is also considered to be a novel compound having a composition in which (NO ₃ ) is replaced in place of

In order to produce this novel compound, bismuth nitrate (Bi (NO ₃ ) ₃ .5H ₂ O) is heated and pyrolyzed. Complete decomposition of bismuth nitrate (H ₂ O)
And (NO ₃ ) is released, and the presence of (NO ₃ ) makes the atmosphere oxidizing, so that finally Bi ₂ O ₃ is produced. However, the method according to the present invention is
At the stage before becomes ₂ O ₃ is a method of Ru to terminate the thermal decomposition. That is, by heating, all (H
₂ O) and a part of (NO ₃ ) are released, and the decomposition is controlled so that the decomposition product has a composition of Bi ₅ O ₇ (NO ₃ ). Decomposition is controlled by heating temperature and heating time.

First, in the present invention, since it is most important to control the thermal decomposition of the raw material in order to synthesize the target compound, a basic experiment in which the state of the thermal decomposition of bismuth nitrate was investigated in detail is explained. To do.

Information on thermal decomposition was obtained by simultaneous thermogravimetric and differential thermal analysis measurements of bismuth nitrate. The experimental results are shown in FIG. According to this, when the raw material compound is heated from room temperature at a rate of 10 ° C./min, violent decomposition starts at around 60 ° C., transitions to mild decomposition at around 150 ° C., and then completes at around 565 ° C. When the compound after the decomposition was identified by the powder X-ray diffraction method,
It was crystallized Bi ₂ O ₃ .

Further, in parallel with the above measurement, the mass spectrometric apparatus was also used to measure the chemical species released into the atmosphere by thermal decomposition. The experimental results are shown in FIG. According to it, it is understood that the first thing that decomposes and emerges is water contained as crystal water. The release of water ended up to 150 ° C., and H ₂ O was not contained in the sample heated at a temperature higher than this. The release of NO ₃ starts from around 80 ° C. and is continuously and slowly performed up to around 565 ° C. NO
_{When 3} is released, it decomposes and comes out as (NO + O ₂ ) gas. This means that even if the raw material is placed in a reducing atmosphere, it is equivalent to being placed in an oxidizing atmosphere during decomposition, and oxygen is sufficiently supplied. All decomposition is complete near 565 ° C, above which nothing is released.

From the above experimental results, the novel compound Bi ₅ O
Heating temperature suitable for the synthesis ₇ (NO ₃₎ was found to be in the range of at least one hundred fifty to five hundred sixty-five ° C..

Based on the results of this experiment, the thermal decomposition of bismuth nitrate can be represented by a chemical reaction formula as follows. _{5 [Bi (NO 3) 3} · 5H 2 O (s)] → 5 / 2Bi 2 O 3 (s) + 25H 2 O ↑ + 15 (N O) - ↑ + 45 / 4O 2 ↑ ... (1) Here, ( s) represents a solid, and ↑ represents a gas.

The reaction can be divided into two steps.
First, in the first stage, the reaction occurs according to the following equation (2). _{5 [Bi (NO 3) 3} · 5H 2 O (s)] → Bi 5 O 7 (NO 3) (s) + 25H 2 O ↑ + 14 (N O) - ↑ + 21 / 2O 2 ↑ ... (2)

To synthesize the novel compound Bi ₅ O ₇ (NO ₃ ), the compound may be taken out at the stage when the reaction of the formula (2) is completed.

When this compound is further pyrolyzed, the second step reaction proceeds according to the following formula (3). Bi ₅ O ₇ (NO ₃ ) (s) → 5/2 Bi ₂ O ₃ (s) + (NO) ↑ + 3/4 O ₂ ↑ ... (3)

The calculated weight loss of the sample due to this reaction is about 4.4%. In other words, the composition of the decomposition product is the composition of the target compound when the bismuth nitrate shows a weight reduction of 4.4% less than the weight reduction when it is completely decomposed into Bi ₂ O ₃ .

In the experiment shown in FIG. 1, the temperature when the raw material has a composition showing a reduction of 4.4% less than the maximum reduction is about 445 ° C. Near this temperature, the average composition of the decomposition products is Bi ₅ O ₇ (NO ₃ ).

From the above results, the novel compound Bi ₅ O ₇ (N
It has been found that a suitable heating temperature for synthesizing O ₃ ) is preferably around 445 ° C. or lower.

The composition of the above-mentioned thermal decomposition product is Bi ₅ O ₇ (NO
₃ ) was confirmed by the combined use of thermogravimetric analysis and mass spectrometry. After examining the powder X-ray structure diffraction pattern of the obtained thermal decomposition product and further thermally decomposing this compound into Bi ₂ O ₃ , the decomposition reaction is represented by the formula (3). If the compound has the correct composition, then the weight loss should be 4.4%. By observing the chemical species released by mass spectrometry, it was confirmed that the reaction could be described by equation (3).

However, the novel compound Bi ₅ whose thermal decomposition product is
The compositional analysis alone is not sufficient to confirm that it is O ₇ (NO ₃ ). This is because even if the thermal decomposition product is not a single phase but a mixture of compounds having various compositions, the average composition thereof may be Bi ₅ O ₇ (NO ₃ ).

Therefore, it was confirmed by powder X-ray diffraction method that the thermal decomposition product was a single phase. Bi ₅ O
A powder X-ray diffraction pattern of the thermal decomposition product having a composition of ₇ (NO ₃ ) is shown in A of FIG. This diffraction pattern is very similar to that of Bi ₅ O ₇ I shown in FIG. 3B. This indicates that both structures are basically the same.

The structure of Bi ₅ O ₇ I has already been clarified, and it has an orthorhombic structure, and its lattice constant is a = 1.
6.244, b = 5.342, and c = 23.006.

Bi ₅ O ₇ (NO ₃ ) was determined to have an orthorhombic structure, and its lattice constant was determined to be a = 1.
The values were 6.280, b = 5.548, and c = 23.301.

Surface index (hkl) of Bi ₅ O ₇ (NO ₃ ) and surface spacing
Table 1 shows the measured and calculated values of (dÅ) and the measured values of the relative reflection intensity (I%) for X-rays. The measured values and calculated values of all peaks are in good agreement, demonstrating that the results of this structural analysis are correct. Also,
The results also demonstrate that the pyrolysis product with the composition of Bi ₅ O ₇ (NO ₃ ) is a single phase.

[Table 1]

Based on the above experimental results, 150 to 565
As a result of diligent studies on the thermal decomposition reaction conditions in the temperature range of ℃, a new bismuth nitrate thermal decomposition product was successfully synthesized, and this compound has a composition of Bi ₅ O ₇ (NO ₃ ) and structurally Also revealed that it is a single phase having a similar structure to Bi ₅ O ₇ I, and completed the present invention.

The starting material in the method of the present invention is bismuth nitrate [Bi (NO ₃ ) ₃ .5H ₂ O], which is thermally decomposed.
To synthesize the desired compound, when the starting material is pyrolyzed, when it reaches a value about 4.4% less than the maximum weight loss value, when it is completely pyrolyzed to Bi ₂ O _3. Pyrolysis should be completed. It is preferable to quench the sample to complete the pyrolysis.

As mentioned above, since there is a wide range of suitable decomposition temperatures, it is possible to use three temperatures of 450 ° C., 425 ° C. and 400 ° C.
A point was selected as a representative temperature, and pyrolysis was carried out using about 2.0 g of the starting material to synthesize Bi ₅ O ₇ (NO ₃ ). At 450 ° C., about 2 to 3.5 hours, 425 About 5-10 hours at ℃, about 27.5-40 hours at 400 ℃,
Upon heating, the thermal decomposition product contained about 4.4% decomposition components, and in each case the powder X-ray structure diffraction pattern showed to be pure Bi ₅ O ₇ (NO ₃ ). It was The heating time varies depending on the amount of starting material, the shape of the container, the air permeability around the container, and the like.

It is possible to synthesize even if decomposed at a temperature other than this. However, it becomes difficult to control the composition as the temperature becomes higher than 450 ° C. When decomposed at a higher temperature than necessary, rapid decomposition occurs. The rapid decomposition is caused by the compound Bi ₅ O.
_It is not preferable because it interferes with the production of ₇ (NO ₃ ). Because bismuth nitrate usually has five waters of crystallization,
Since it melts at a low temperature, there are no gaps between particles, and when the decomposition is severe, the speed is significantly different between the surface and the inside. For this reason, it becomes difficult for the decomposition to proceed uniformly. Further, when the temperature is lower than 400 ° C., it takes a longer time to complete the reaction.

Next, examples of the present invention will be described.

[0029]

Example 1 About 2.0 grams of bismuth nitrate pentahydrate was placed in a platinum crucible, which was placed in an electric furnace preset at 450 ° C. and heated. After heating for a period of time, the sample was removed and cooled rapidly to room temperature. Since the sample taken out was sintered, it was crushed in a mortar into a powder and used as a sample for X-ray structural analysis and thermogravimetric analysis. Table 2 shows the heating time, weight loss, and analysis results. As is clear from the result, the decomposition product becomes Bi ₅ O ₇ (NO ₃ ) single phase because the weight loss when it is completely decomposed into Bi ₂ O ₃ is 4.25. It is the case of a compound having a composition of ˜4.75% less.

[Table 2]

[0030]

[Example 2] The temperature of the electric furnace was set to 425 ° C, and the thermal decomposition was performed in the same procedure as in Example 1. As is clear from the results shown in Table 3, the decomposition product becomes a Bi ₅ O ₇ (NO ₃ ) single phase because the weight reduction when it is completely decomposed and changed to Bi ₂ O _3. This is when the compound has a composition of 4.39 to 4.68% less.

[Table 3]

[0031]

Example 3 The temperature of the electric furnace was set to 400 ° C. and the thermal decomposition was carried out in the same procedure as in Example 1. As is clear from the results shown in Table 4, the decomposition product becomes the Bi ₅ O ₇ (NO ₃ ) single phase because the weight reduction when the decomposition product is completely decomposed into Bi ₂ O ₃ This is when the compound has a composition of 4.36 to 4.45% less.

[Table 4]

[0032]

As described in detail above, according to the present invention,
A novel compound represented by the formula of Bi ₅ O ₇ (NO ₃ ) can be provided. This compound can be expected to be used for various uses such as ion exchange and adsorption, for example, treatment of nuclear power generation waste liquid and industrial waste liquid, adsorption fixation of harmful ions in gas, and adsorption removal.

[Brief description of drawings]

FIG. 1 is a diagram showing a thermogravimetric analysis curve and a differential thermal analysis curve of bismuth nitrate, where A shows the thermogravimetric analysis curve and B shows the differential thermal analysis curve.

FIG. 2 is a diagram showing a mass spectrometry curve, where A is a curve showing a partial pressure of H ₂ O, B is a curve showing a partial pressure of NO, and C is a curve showing a partial pressure of O ₂ .

FIG. 3 is a diagram showing a powder X-ray diffraction pattern, where A is Bi ₅ O.
_In the case of ₇ (NO ₃ ), B is Bi ₅ O ₇ I.

Claims (2)

[Claims] 1. A compound represented by the formula: Bi ₅ O ₇ (NO ₃ ). 2. Bismuth nitrate [Bi (NO ₃ ) ₃ .5H ₂ O]
A method for producing a compound represented by the formula of Bi ₅ O ₇ (NO ₃ ), characterized in that the compound is represented by the formula of Bi ₅ O ₇ (NO ₃ ), characterized in that the compound is heated to thermally decompose it and the thermal decomposition is terminated before it is converted to Bi ₂ O ₃ .