JP2000086243A - Bismuth-calcium compound and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a novel bismuth-calcium compound expected to be utilized as an inorg. anion exchanger like a bismuth-lead compd. SOLUTION: A mixture is prepd. from a starting material in which the molar ratio among elemental bismuth, elemental calcium, elemental oxygen and the nitric acid group (NO3) is adjusted to 1:1:2:1. The mixture is allowed to react at a temperature between room temp. and 100 deg.C for a prescribed time and then heated to 200-450 deg.C to synthesize the objective bismuth-calcium compound represented by the formula BiCaO2(NO3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel bismuth calcium compound which is expected to be used as an inorganic anion exchanger as well as a bismuth lead compound, and a method for producing the same. More specifically, new bismuth is expected to be used for removing halogen ions from aqueous solutions, organic solvents, or industrial effluents, and removing and fixing iodide ions from spent nuclear fuel processing solutions and effluents in nuclear power generation. -It relates to a calcium compound and its production method.

[0002]

_2. Description of the Related Art As a compound similar to the novel compound of the present invention, a bismuth-lead compound represented by the formula of BiPbO ₂ (NO ₃ ) is known (Japanese Unexamined Patent Publication (Kokai) No. 9-1990).
No. 52715). It is known that bismuth / lead compounds have a very good exchange capacity for halogen ions as an inorganic ion exchanger, but handling after use is problematic depending on how to use lead due to toxicity of lead.

[0003]

SUMMARY OF THE INVENTION The present invention provides BiCaO ₂
The present invention provides a novel bismuth calcium compound represented by the formula (NO ₃ ), and has a layered structure suitable as an inorganic ion exchanger.
₃ ) The second compound synthesized as a type (M1 and M2 are metal elements) compounds, in which a harmless calcium element is used in place of lead. Further, the present invention uses a mixture prepared so that the molar ratio of bismuth element, calcium element, oxygen element, and nitrate group (NO ₃ ) is 1: 1: 2: 1, and this mixture is used at room temperature to room temperature. A method for producing a novel bismuth calcium compound by reacting at 100 ° C. for a predetermined time and then heating to 200 to 450 ° C. for synthesis.

[0004] The novel compound of the present invention is prepared by a bismuth
The method used for lead compounds is not appropriate, and the present invention has developed a unique method. The production of bismuth / lead compounds required special equipment such as platinum tubes and high pressure vessels. In the present invention, such a special device is not required, and after the sample is allowed to react at room temperature to 100 ° C.
By heating to 450 ° C. for synthesis, the desired compound can be produced without using any special equipment. Since the composition and structure of the bismuth calcium compound according to the present invention are similar to those of the bismuth lead compound, properties as an inorganic ion exchanger can be expected, and there is no toxicity.
No special precautions are required for handling after use.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The production reaction of the compound of the present invention is expected to proceed according to the following simple formula.

[0006]

[Formula 1] _{Bi 2 O 3 + Bi (NO} 3) 3 · 5H 2 O + 3Ca (OH) 2 → 3BiCaO 2 (NO 3) + 8H 2 O (1)

First, it was investigated whether this reaction proceeds at room temperature. Commercially available bismuth oxide Bi ₂ as starting material
O _3, bismuth nitrate pentahydrate _{Bi (NO 3) 3 · 5H} 2
O and calcium hydroxide Ca (OH) ₂ were used. The reaction starts as soon as these compounds are mixed at room temperature. FIG.
FIG. 2 is a view showing a powder XRD (X-ray diffraction) pattern of a raw material. a is the raw material mixture before the reaction, b is the sample 4 hours after mixing the raw materials, c is the sample after 2 days, and d is the sample after 14 days. The pattern d hardly changes even after a longer time. Pattern d is b (BiCa) shown in FIG.
(XRD pattern of O ₂ (NO ₃ )), indicating that the target compound has not been prepared yet.

Next, the starting material was heated to a high temperature to react. The starting material is heated at about 350 ° C.
After heating for 0 minutes, this was quenched and the XRD pattern of the reaction product was measured. The results are shown in a, b, c, d of FIG. Here, the sample before heating was prepared by preliminarily starting the starting material at room temperature.
Time, 2 days, 5 days, and 15 days after the reaction, a is used to heat the sample 4 hours after mixing the raw materials, and b is mixed 2 days after the raw materials are mixed, In the case of heating, the case where c heated the sample 5 days after mixing the raw materials, and the case where d heated the sample 15 days after mixing the raw materials. The patterns of c and d in FIG.
And the product is almost BiCaO
2 (NO3).

From the above experiments, it has been found that in order to produce the desired compound, it is preferable to mix the starting materials at room temperature, react for a predetermined time, and then heat at a high temperature for a predetermined time. In addition, since there is no difference from the reaction at room temperature even when heating at 100 ° C. or lower, the heating may be performed at 100 ° C. or lower instead of room temperature in the production method of the present invention. Then, the reaction time and the heating temperature at an appropriate room temperature were examined. Mix the starting materials and add 4
The samples after time (Sample 1), after 2 days (Sample 2), and after 19 days (Sample 3) were heated from room temperature to 800 ° C. in an Ar gas flow, and TG-MS (thermogravimetric-mass) analysis was performed. And observed. 3A, 3B, and 3C are TG curves obtained for the samples 1, 2, and 3, respectively. a is heating the sample 4 hours after mixing the raw materials, b is heating the sample 2 days after mixing the raw materials, c is 19
This is the case when the sample after day is heated. By analyzing these curves, it is possible to find the optimal heating temperature for the synthesis.
FIG. 3 shows that the sample is decomposed by heating, and the decomposition can be divided into decomposition at about 400 ° C. or lower and decomposition at a higher temperature. Molecular species released upon decomposition were analyzed from MS data.

For example, FIG.
The data of S is shown. The TG curve is also shown for reference. The figure shows a case where a sample (c in FIG. 3) was measured 19 days after mixing the raw materials. According to this, the molecular species released by decomposition at 400 ° C. or less are H
₂ O only. Above 400 ° C., the remaining H ₂ O is released around 400 ° C., but over 450 ° C., H ₂ O
Is almost over and NO ₃ begins to be released instead. At around 700 ° C, the release of NO ₃ also ended,
The disassembly ends. As expected from the reaction formula (1),
No H ₂ O is required for BiCaO ₂ (NO ₃ ),
Temperature at which H ₂ O is released but NO ₃ is released, 250-
It is concluded that 400 ° C. is a suitable temperature for the synthesis. However,
Since this result is an experiment under dynamic conditions (temperature rise),
In experiments under static conditions (constant temperature), the temperature range extends further up and down by about 50 ° C.

Further, this series of experiments shows that even if the heating temperature is appropriate, the target compound cannot be synthesized unless the reaction time of the raw materials at room temperature is sufficient. The appropriate amount of time for mixing and reacting the mixture at room temperature depends on the particle size of the reagent, the stirring time, and the like, but it is usually preferable to hold the mixture for at least about one week or more.

5A and 5B show the compound BiPbO ₂ (NO
₃ ) and the compound BiCaO ₂ (NO ₃ ) powder XRD (X
Line diffraction) pattern. Although the diffraction peaks of the two compounds are slightly shifted, they have the same pattern, suggesting that the structures of the two compounds are basically the same. The structure analysis of BiCaO ₂ (NO ₃ ) was performed using a powder XRD pattern. As a result, this compound has a tetragonal structure and the expected number is a = 3.95.
4, c = 14.131 A, and the surface index (hkl), the calculated value (dl) and the measured value (d2) of the surface spacing (d), and the reflection intensity (I) for all the observed peaks ) Was measured. Table 1 shows the results.

[0013]

[Table 1]

Indexing is possible for all peaks,
In addition, the calculated values and the measured values show very good agreement, indicating that the results of this structural analysis are correct. The thermal stability of BiCaO ₂ (NO ₃ ) was examined by TG. When heated from room temperature to 700 ° C in an oxygen stream,
Decomposition started at around 450 ° C. and ended at around 700 ° C. There is a 16.7% weight loss and BiCaO ₂ (NO
₃ ) Calculated value of 15.7% when NO ₃ is replaced with oxygen
Indicates a good match. From the results of the above structural analysis and gravimetric analysis, the synthesized compound was BiCaO ₂ (NO ₃ ).

[0015]

EXAMPLE A commercially available reagent, Ca (OH) ₂ , about 1.485
Grams _{Bi (NO 3) 3 · 5H} 2 About 3.241 grams of O and about 3.107 grams of Bi ₂ O ₃ were thoroughly mixed in a mortar at room temperature (the ratio of elemental bismuth, calcium, oxygen, and nitrate (NO ₃ ) 1: l in ratio:
2: 1). This was allowed to stand in the air at room temperature for about 2 weeks. Put this in a crucible and in air at 300 ° C, 400 ° C,
After heating at 50 ° C. for 1 hour, it was rapidly cooled. In each case, pure BiCaO ₂ (NO ₃ ) was obtained. As a starting material, CaO can be used instead of Ca (OH) ₂ . The heating atmosphere is air, but may be an inert atmosphere such as Ar.

[0016]

As described above, according to the present invention,
By controlling the reaction of the raw material before heating, BiPbO ₂ (NO ₃ )
A new compound BiCaO ₂ (NO ₃ ) which can be expected as an inorganic ion exchanger can be synthesized.

[Brief description of the drawings]

FIG. 1 is a view showing a powder X-ray diffraction pattern.

FIG. 2 is a view showing a powder X-ray diffraction pattern.

FIG. 3 is a diagram showing a TG (thermogravimetric analysis) curve.

FIG. 4 is a diagram showing an MS (mass spectrometry) curve.

FIG. 5 is a view showing a powder X-ray diffraction pattern.

Claims (2)

[Claims] 1. A bismuth calcium compound represented by the formula BiCaO ₂ (NO ₃ ). 2. The molar ratio of bismuth element, calcium element, oxygen element and nitrate group (NO ₃ ) is 1: 1: 2: 1.
The mixture thus prepared was reacted as a raw material at room temperature to 100 ° C for a predetermined time, and then reacted at 200 to 450 ° C.
2. The method for producing a bismuth calcium compound according to claim 1, wherein the bismuth calcium compound is synthesized by heating.