JP3097928B2 - Cation adsorbent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cation adsorbent comprising an amorphous composite oxide composed of aluminum, magnesium and silicon, the constituent elements of which are three-dimensionally polymerized via oxygen atoms. More specifically, the present invention relates to a cation adsorbent having characteristics in which elution of adsorbed metal ions is hardly recognized.

[0002]

2. Description of the Related Art Conventionally, as a method for adsorbing and removing cations in an aqueous solution, it is known to use organic and inorganic ion exchange substances. As an example of using an organic ion exchange material, a method of using a cation exchange resin such as a phenol sulfonic acid type, a polystyrene sulfonic acid type, and a phenol carboxylic acid type is known. Examples of use are natural or synthetic,
It is known to use montmorillonite, illite, bentonite, vermiculite, zeolite and the like.

[0003] Generally, the organic cation exchange resin is
It has a high ion exchange capacity and a cation exchange capacity (hereinafter C
EC (abbreviated as EC) up to about 400 meq / 100 g. However, due to its high cost, its use is limited to small-scale use such as packing for ion-exchange chromatography and use as an ion exchanger for pure water production. It is not used in any processing steps.

On the other hand, the above-mentioned inorganic ion exchange materials are inexpensive, but their CECs are, for example, 100 meq / 100 g for montmorillonite and 150 m for zeolite.
eq / 100 g. However, since these conventional cation exchange agents exhibit reversible ion exchange ability, when a cation having problems in terms of toxicity and safety, such as a specific radioactive substance, is adsorbed, There is a problem that considerable attention has to be paid to the elution with time.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel cation adsorbent in which the adsorbed cation is hardly eluted with time and has no problem in terms of safety. The purpose is to:

[0006]

Means for Solving the Problems The present inventors have found that when amorphous magnesium silicate is added to an aqueous solution of a weakly acidic metal salt, the polymerized skeleton in the magnesium silicate is reduced. Based on the finding that at the same time that a part of magnesium is eluted as an ion, the metal ion is adsorbed as a metal oxide ion on the part where the magnesium is eluted, as a result of intensive studies to solve the above problems,
The present inventors succeeded in providing a novel adsorbent in which almost no elution of the adsorbed cation with the passage of time was observed, and which had no problem in terms of safety.

The present invention provides a novel cation adsorbent comprising an amorphous composite oxide comprising aluminum, magnesium and silicon, and these constituent elements are three-dimensionally polymerized via oxygen atoms. It is. The amorphous composite oxide used in the present invention has a general formula: Al ₂ O ₃ / a
MgO / bSiO ₂ .nH ₂ O (where a = 0.3 to
3, b = 0.3-5). For example,
Magnesium aluminate silicate (Al ₂ O ₃ / 2MgO
/ SiO ₂ .nH ₂ O, trade name Neusilin A ^(R) ),
Magnesium aluminate metasilicate (Al ₂ O ₃ / Mg
O / 1.7SiO ₂ · nH ₂ O, trade name Neusilin
^(R) ) and the like. The specific surface area of these composite oxides is 100 to 300 m ² / g.

The method for producing the composite oxide of the present invention and its use as a cation adsorbent will be described in detail below.

The amorphous composite oxide used in the present invention is usually prepared by reacting an aqueous solution of a water-soluble aluminum salt with caustic soda and an aqueous solution of an alkali silicate or a magnesium salt. The solution is obtained by filtering, washing with an appropriate amount of water, drying and pulverizing. Examples of the water-soluble aluminum salt include sodium aluminate,
Or aluminum chloride and aluminum sulfate, and the like.As the alkali silicate, for example, sodium silicate can be mentioned, and as the magnesium salt,
Mention may be made of magnesium chloride and magnesium sulfate. In the above production method, methods such as washing, filtration, drying, and pulverization are not particularly limited.

The amorphous composite oxide of the present invention may be used as it is, but may be fired if desired.
The calcination temperature at this time is preferably 100 to 600 ° C. because the adsorption ability decreases when the amorphous composite oxide crystallizes. The specific surface area of the amorphous composite oxide is 100 to 3
00 m ² / g, which is equivalent to the conventional one.

In order to use the amorphous composite oxide of the present invention as a cation adsorbent, it is added directly to an aqueous solution containing a cation, and preferably used with stirring.
Cations can be efficiently adsorbed and removed. Further, if desired, it is also possible to fill and use a column or the like. Further, the pH range of the aqueous solution containing a cation, preferably when contacted with an aqueous solution containing a cation,
The pH is preferably in the range of 3.5 to 7 at which the aluminum in the skeleton is not eluted, so that magnesium in the skeleton can be easily eluted.

The above cations include Ca, Cu, F
e, Sr, Y, Cr, Mn, Ni, Zn, Ag, Co,
Rb, Ru, Cs, Ce and the like can be exemplified.

The fact that the adsorbent of the present invention suppresses the elution of the cation substituted in the portion from which magnesium was eluted is that after adsorbing an appropriate cation to these adsorbents,
When filtered and washed, the corresponding cation is not detected in the filtrate and the washing solution, and the filtered solid is added to an aqueous solution such as NaCl or KCl. Even after stirring for ~ 72 hours, it can be confirmed from the fact that the corresponding cation is not detected at all in the supernatant obtained by centrifuging the suspension.

The amount of metal ions in the above-mentioned filtrate, washing solution and supernatant can be measured using an atomic absorption spectrometer.
In addition, the CEC of the adsorbent used in the present invention is obtained by an ordinary method, specifically, by calculating the amount of cations adsorbed per 1 g of the adsorbent by the number of equivalents of ions, and converting it into the weight per adsorbent. be able to. For example, in the example of the adsorbent described in Example 5 of the present invention, the CEC is 364 (meq /
100 g).

The adsorbent of the present invention has a completely different adsorbing mechanism from zeolite and the like, and adsorbed metal ions are incorporated into the skeleton of the adsorbent. Can be completely suppressed.

Hereinafter, the present invention will be described in detail with reference to embodiments.

[0017]

【Example】

Example 1 (Production method) Sodium aluminate (Al ₂ O ₃ : 18.7)
%) 80.4 g of water was added to make a total volume of 500 ml, which was designated as solution A. No. 3 sodium silicate (SiO ₂ : 29.
5%) 124.8 g of water was added to make a total volume of 250 ml,
This is designated as solution B. Magnesium chloride hexahydrate (MgO:
41.7 g) and aluminum sulfate (Al ₂ O)
₃ : 17.2%) 34.0 g was dissolved in water and the total amount was 250.
ml, and use this as solution C. Solution A was put into the reaction tank, and solution B was added at a rate of 10 ml / minute while stirring. Solution C was then added at about 25 ml / min. After adding C solution,
After aging for 30 minutes, the product was filtered and washed with water. 9
After drying at 0 ° C. for about 20 hours, the mixture was pulverized in a mortar and sieved with a 100-mesh sieve to obtain an amorphous inorganic powder substance as a white powder. The result of the composition analysis showed that MgO was 1.15 mol and SiO ₂ was 2.84 mol with respect to 1 mol of Al ₂ O ₃ .

(Adsorption test) Cupric chloride dihydrate 1.34
g in 50 ml of ion-exchanged water and put into a reaction vessel.
To this solution, 5 g of the inorganic powdery substance obtained by the above method was added and stirred for 6 hours. After stirring, the suspension was filtered, and the solid content was washed with ion-exchanged water until no chloride ion was detected. The solid content was dried at 60 ° C. for about 20 hours to obtain a bluish-white inorganic powder material. The filtrate and the washing solution were all collected, and copper ions in the solution were measured. As a result, no copper ions were detected in the filtrate and the washing solution.

(Dissolution Test) 2 g of each of the blue-white inorganic powder materials obtained by the above-mentioned adsorption test was suspended in 50 ml of a 1% aqueous NaCl solution, and stirred at room temperature for 24, 48 and 72 hours. After the stirring, the suspension was centrifuged, and the copper ion in the obtained supernatant was measured. As a result, no copper ion was detected in each supernatant.

Example 2 (Dissolution test) 2 g of the bluish-white inorganic powder obtained in the adsorption test of Example 1 was added to 50 ml of a 1% aqueous NaCl solution, and the mixture was stirred at 60 ° C. for 20 hours. Thereafter, treatment was performed in the same manner as in the dissolution test of Example 1, and copper ions were measured. As a result, no copper ions were detected in the supernatant.

Example 3 (Dissolution test) 2 g of the bluish-white inorganic powder obtained in the adsorption test of Example 1 was added to 50 ml of a 1% aqueous NaCl solution, and the mixture was stirred at 95 ° C. for 4 hours. Thereafter, treatment was performed in the same manner as in the dissolution test of Example 1, and copper ions were measured. As a result, no copper ions were detected in the supernatant.

Example 4 (Production method) Sodium aluminate (Al ₂ O ₃ : 18.7)
%) Add water to 138.1 g to make a total volume of 500 ml,
This is designated as solution A. No. 3 sodium silicate (SiO ₂ : 2
(9.5%) 76.4 g of water was added to make a total volume of 250 ml, which was designated as solution B. Magnesium chloride hexahydrate (Mg
O: 19.8%) 25.5 g and aluminum sulfate (Al
(2O3: 17.2%) 74.4 g was dissolved in water to give a total amount of 2
Make up to 50 ml, and use this as solution C. Thereafter, the same treatment as in Example 1 was performed to obtain an amorphous white powder. The result of the composition analysis showed that MgO was 0.37 mol and SiO ₂ was 1 mol with respect to 1 mol of Al ₂ O ₃ .

(Adsorption Test) Cobalt chloride hexahydrate 1.8
0 g is dissolved in 50 ml of ion-exchanged water and put into a reaction tank. 5 g of the inorganic powdery substance obtained by the above-mentioned production method was added to this solution.
Was added and stirred for 24 hours. Thereafter, the same treatment as in Example 1 was performed to obtain a pale pink inorganic powder material. When the cobalt ion in the filtrate and the washing solution was measured in the same manner as in the adsorption test of Example 1, no cobalt ion was detected in the filtrate and the washing solution.

(Dissolution test) 2 g of the pale pink inorganic powder substance obtained in the above adsorption test was added to 50% of a 1% KCl aqueous solution.
and stirred at 60 ° C. for 24 hours. Thereafter, the treatment was carried out in the same manner as in Example 1, and the elution of cobalt ions was measured. As a result, no cobalt ions were detected in the supernatant.

Example 5 (Adsorption test) To a solution prepared by dissolving 1.80 g of manganous chloride tetrahydrate in 50 ml of ion-exchanged water was added 5 g of the inorganic powdery substance obtained in Example 4, and the mixture was stirred for 20 hours. did.
Thereafter, the same treatment as in Example 1 was performed to obtain a pale yellow inorganic powdery substance. When the manganese ions in the filtrate and the washing solution were measured in the same manner as in the adsorption test of Example 1, no manganese ions were detected in the filtrate and the washing solution.

(Dissolution Test) 2 g of the pale yellow inorganic powdery substance obtained in the above adsorption test was added to 50 ml of a 1% KCl aqueous solution, and the mixture was stirred at 60 ° C. for 24 hours. Thereafter, the treatment was carried out in the same manner as in Example 1, and the elution of manganese ions was measured. As a result, no manganese ions were detected in the supernatant. In addition, when CEC was obtained based on the above results, 364
(Meq / 100 g).

Example 6 (Adsorption test) 1.04 g of zinc chloride was added to 50 parts of ion-exchanged water.
5 g of the inorganic powdery substance obtained in Example 4 was added to a solution of the inorganic powdery substance dissolved in ml and an appropriate amount of diluted hydrochloric acid, followed by stirring for 17 hours. Thereafter, the same treatment as in Example 1 was performed to obtain a white inorganic powdery substance. When the zinc ion in the filtrate and the washing solution was measured in the same manner as in the adsorption test of Example 1, no zinc ion was detected in the filtrate and the washing solution.

(Dissolution Test) 2 g of the white inorganic powdery substance obtained in the above-mentioned adsorption test was added to 50 ml of a 1% KCl aqueous solution, followed by stirring at 60 ° C. for 17 hours. Thereafter, the treatment was carried out in the same manner as in Example 1, and the elution of zinc ions was measured. As a result, no zinc ions were detected in the supernatant.

Example 7 The inorganic powdery substance obtained by the method of Example 1 was calcined at 500 ° C. for about 1 hour, and an adsorption test and a dissolution test were carried out in the same manner as in Example 1. No copper ions were detected.

[0030]

According to the present invention, it is possible to provide a cation adsorbent capable of effectively adsorbing cations and suppressing elution of the adsorbed cations over time. This is extremely advantageous for the use of heavy metals and radioactive substances in the field of wastewater treatment and the like, in which elution and contamination to the external environment poses a problem in terms of safety and toxicity.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01J 20/12-20/18 B01D 15/04 B01J 39/10

Claims (2)

(57) [Claims] 1. A compound of the general formula: Al ₂ O ₃ / aMgO / bSi
O ₂ · nH ₂ O (where a = 0.3-3, b = 0.3-
5) consisting of aluminum, magnesium and silicon, whose constituent elements are amorphous composite oxides three-dimensionally polymerized via oxygen atoms, and have a pH in the range of 3.5 to 7. A cation adsorbent characterized by being used in: 2. The amorphous composite oxide is obtained by reacting an aqueous solution of an alkali silicate and an aqueous solution of a magnesium salt with an aqueous solution obtained by adding caustic soda to a water-soluble aluminum salt. A cation adsorbent according to the above.