JPS59156911A - Manufacture of a-type zeolite using volcanic glass as principal starting material - Google Patents

Abstract

PURPOSE:To manufacture A-type zeolite contg. practically no iron component and suitable for use as a builder for a detergent by utilizing sodium metasilicate hydrate obtd. by treating volcanic glass by a specified method. CONSTITUTION:8-18N aqueous soln. of sodium hydroxide is added to volcanic glass such as ''Shirasu'', (pumiceous sand produced in Kyushu district in Japan) and they are heat treated at 70-150 deg.C for about 1-4hr to leach 50-70wt% of silica contained in the volcanic glass. Insoluble matter is separated and removed from the resulting liq. after the leaching, and the concn. of sodium metasilicate hydrate to be crystallized in the remaining soln. is adjusted to about 60-95wt%. Sodium metasilicate hydrate is deposited by holding the concd. soln. at about 10-30 deg.C, and an aqueous mixture consisting of the deposited sodium metasilicate hydrate, sodium aluminate, sodium hydroxide and water in molar ratios represented by equations I , II, III is brought into reaction by heating to obtain A-type zeolite.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing type A zeolite from silica using volcanic glass as a main raw material, and in particular to a method for producing type A zeolite suitable for detergent builders that do not substantially contain iron. It is something.

Type A zeolite has the general formula (1,0±0.2)Na20
At203 (2-0±0.2) 5i02 ・nH
It is a hydrous aluminosilicate represented by 2O, and has a specific crystal structure that can be X-ray-distinguished from X-type zeolite, Y-type zeolite, other zeolites, and silicates. Furthermore, type A zeolite has particularly remarkable water softening ability and is useful as a builder for detergents.

However, when manufacturing A-type zeolite using volcanic glass as a raw material, it is difficult to remove the iron contained in the raw material, so the A-type zeolite obtained is unsuitable for use as detergent bilgu. there were. If iron is mixed into a detergent, not only will the detergent itself become colored and reduce its product value, but also, for example, when washing textiles, it will have the opposite effect to the original purpose of coloring the fibers. is a substance that must not be mixed into detergents and is the most undesirable impurity.

Volcanic glass usually contains 12 to 14% by weight of alumina, and when producing sulfur, it is difficult to substantially completely separate and remove the iron content, and the yield of silica is low at 60% or less. Water glass has a quartz ratio (Na20/SiO
It has a composition close to that of sodium metasilicate with □) of about 1.0 and has extremely low alkali efficiency, so it has been difficult to rely on volcanic glass as a starting material for producing silicate compounds.

However, research is being carried out to effectively utilize this unique volcanic glass as a silicate raw material to produce zeolite. For example, volcanic ejecta such as whitebait, which is a typical volcanic glass, is mixed with alkali hydroxide and 33.
Method of increasing reactivity by heating and dissolving at 0℃
5807), a method was proposed in which the reaction process was divided into two stages, first ripening with an alkali at a low temperature, and then raising the temperature to crystallize (Japanese Patent Application Laid-Open No. 110599/1982). This method also cannot satisfactorily separate and remove iron contained as an impurity. In addition, volcanic glass is treated with an alkaline solution to create highly reactive 5i02.
A method for producing synthetic zeolite using a solution in which insoluble matter is separated by selective elution of
7) has also been proposed, but iron oxide (Fe2O3) is contained in the A-type zeolite obtained by this method as well.
The iron content was about 12% by weight, and the iron content was too high to be used as a detergent. Furthermore, a method for producing type A zeolite using natural raw materials such as kaolin and reducing the iron content by adding trialkanolamine during hydrothermal synthesis is also known (West German Patent No. 2, '635, 357). Specification and 2nd.
746,844), the use of such special substances is extremely disadvantageous industrially and is difficult to employ in the production of hD and A-type zeolites.

As described above, it is extremely difficult to industrially produce iron-free silicic acid compounds using volcanic glass containing large amounts of alumina and iron as raw materials. It is an important technical challenge to industrially produce substantially free zeolite and to increase its alkali efficiency.

In view of these circumstances, the inventors of the present invention have conducted extensive research into the effective use of volcanic glass as a raw material for manufacturing various useful industrial products without using expensive special reagents. We have discovered a method for obtaining sodium metasilicate with a low iron content, which is suitable as a raw material for zeolite, and based on this knowledge, we have accomplished the present invention.

That is, in the present invention, volcanic glass is added to an aqueous solution of 8 to 18 N hydroxide and heated to a temperature of 70 to 150°C to dissolve about 50 to 70% by weight of the silica in the volcanic glass.
After removing insoluble matter from the eluate, sodium metasilicate hydrate is crystallized by cooling or adding water, and the required amount of sodium aluminate and sodium hydroxide is added to the obtained sodium metasilicate hydrate. The present invention provides a method for producing type A zeolite using volcanic glass as a main raw material, which is characterized by subjecting an aqueous reaction mixture prepared by adding volcanic glass to a heating reaction.

The raw material used in the method of the present invention is volcanic glass represented by Shirasu, which is a natural raw material containing large amounts of alumina and iron as described above. The alkali to which the volcanic glass is added is a relatively high concentration aqueous sodium hydroxide solution of 8 to 18 normal (N). If the sodium hydroxide concentration of this aqueous solution is less than 8N, it is disadvantageous because it takes time to elute the desired amount of silica by heat treatment, and if it exceeds 18N, the viscosity of the aqueous solution is high and the treatment lacks smoothness. Undesirable. A desirable concentration of the sodium hydroxide aqueous solution is 4 to =N. The mixture of volcanic glass and aqueous sodium hydroxide solution is then heated to a temperature of 70-150°C, reducing the amount of silica in the volcanic glass by about 50-70°C.
Heat treated for a sufficient time to elute the weight. If the heat treatment temperature is less than 70°C, the silica elution rate will be slow and it will take a long time, and if it exceeds 150°C, the impurity removal effect will be reduced, which is not preferable. A temperature range of 90-130°C is preferred. The heat treatment time is usually about 1 to 44 hours, although the higher the concentration of sodium hydroxide in the aqueous solution and the higher the heat treatment temperature, the faster the desired silica elution rate can be obtained.

In the method of the present invention, a high-concentration sodium hydroxide aqueous solution is used to heat and dissolve about 50 to 70% of the tensile strength contained in volcanic glass at about 70% by weight, and the insoluble matter is removed from the solution. The process of precipitating sodium metasilicate hydrate crystals and separating them from other metal compounds is important. When recovering silica from volcanic glass at a higher elution rate, there is a risk that impurities may be mixed into the precipitated sodium metasilicate hydrate, and if the elution rate is less than 50% by weight, the utilization rate is too low to be used industrially. disadvantageous to

The eluate from the highly concentrated alkaline aqueous solution is then separated by filtration or other means to remove insoluble matter, and then the concentration of the sodium metasilicate hydrate Na2SiO39H20 to be crystallized is adjusted to 60 to 95% by weight, and the liquid temperature is cooled. The sample is then held at a temperature of, for example, 10 to 30°C for several hours. When the hydrated salt concentration of the elution filtrate is within the above range, it is cooled as is, but the concentration is usually adjusted by adding water to the elution filtrate. When the solution whose concentration has been adjusted is allowed to stand still, crystals of hydrated salt of metasilicate (IJ) precipitate out as a semi-cloudy sludge.

The lower the temperature at which the liquid is allowed to stand, the more preferable it is. The hydrated salt crystals are then separated by suitable means such as centrifugation or pressure filtration.

The highly purified sodium metasilicate hydrate crystals thus obtained are mixed with the required amounts of sodium aluminate, sodium hydroxide, and water necessary for forming type A zeolite to form an aqueous mixture.

In this case, it is preferable to adjust the molar ratio of the oxides to fall within the following range.

H2O/ Na2O = 20-20O Na20/ (5i02 + At203 ) = 0.
5-4Si02/AA203 = 2±0.5 An aqueous mixture having such a molar ratio range can be obtained by mixing aqueous sodium aluminate solution or sodium hydroxide aqueous solution prepared in advance to an appropriate concentration in the required ratio. It is prepared.

By thoroughly mixing the thus prepared aqueous mixture and reacting at a temperature of 80 to 110° C. for 3 to 20 hours, type A zeolite substantially free of iron can be produced.

At this time, before heating and reacting the aqueous mixture,
By aging at 45° C. for 2 to 48 hours to promote nucleation, the A-type zeolite produced can be made into fine particles. In this case, if the temperature is lower than 15°C, the ripening time will be too long and it is not practical. If the temperature is higher than 45°C, the ripening time will be shortened, but the particle size will become uneven and the effect will be reduced. There is a limit, and particles with a particle size 71% smaller than a certain point cannot be obtained.

Furthermore, instead of ripening, finely pulverized type A zeolite can be added as a seed crystal before the heat treatment, and the resulting type A zeolite can be made into fine particles.

The smaller the particle size, the more effective this seed crystal is, so the particle size 1
A material of μm or less is used. Particle sizes larger than this are hardly effective.

The amount of the seed crystals added is suitably in the range of 0.1 to 10% by weight based on the 71 strength component in the aqueous mixture.

The method of the present invention is an excellent method that does not require expensive special reagents, has high alkaline efficiency, and can industrially advantageously provide type A zeolite suitable for detergent builders from volcanic glass.

Next, the present invention will be explained in more detail with reference to Examples. In addition, the measurement of each performance in an Example was performed by the following method.

l) Crystallinity rate It was calculated using the following formula as the ratio of the peak intensity of the sample to the powder X-ray peak intensity of the standard. Note that A4 size from Toyo Soda ■ was used as the standard product.

The degree of coloring of the A-type zeolite itself was evaluated using the photochromic color i=+.

111) Pour 500 rnl of calcium nitrate solution containing 300 μ as ion exchange capacity CaO into a container equipped with a temperature control and a stirrer, maintain the temperature of the contents at 30°C, and add 0.52 kg of A-type zeolite sample. After 30 minutes, the solution was filtered using a membrane filter. The calcium concentration in the filtrate was measured by atomic absorption, and the exchange amount of zeolite 12 equivalents was converted to CaO (1 ng) to determine the ion exchange capacity. Control: Place in a container with a stirrer, and add 0.1f of zeolite dispersed in 10m of distilled water using ultrasonic waves over time (0.5 minutes, 1 minute, and 2 minutes after adding)
Each sample sampled was filtered through a membrane filter, the calcium concentration was measured by atomic absorption, and the exchange rate in 1 minute of contact with the liquid was determined as the ion exchange rate from the calcium concentration decrease curve.

■) Particle size: 0.2 to 0.2 using a Coulter counter particle size measuring device.
A range of 50 μm was measured.

Example 1 8 Whitebait 5552, ≠N sodium hydroxide aqueous solution 50〇-
Pour 200 cups of water into a reaction vessel equipped with a stirrer, and
After heat treatment at a temperature of 0° C. for 2 hours, the mixture was filtered under pressure to separate insoluble matter. The obtained filtrate was allowed to stand at room temperature for several hours, and the precipitated crystals were centrifuged at 15,000 G to obtain sodium metasilicate hydrate.

An aqueous reaction mixture was prepared by adding sodium aluminate, sodium hydroxide, and water to the obtained sodium metasilicate hydrate to have the following oxide molar ratio.

Na2O/ (5i02 + Al2O2) = 1.
33H20 / Na2O = 40 Si02 / Al2O3 = 2 To this aqueous reaction mixture, 5% by weight of seed crystals obtained by finely pulverizing A-4 manufactured by Toyo Soda ■ in an alumina ball mill for 4 hours was added, and after mixing with a homogenizer for 1 minute, , 90
A heating reaction was carried out at a temperature of 16 hours to precipitate A-type zeolite as crystals.

The various performances of the obtained type A zeolite are shown in Table 1. Table 1 Crystallization rate 92.5 crystal grain size (average) 0.6 μm Ion exchange capacity 123 my/y Ion exchange rate 95 iron content 0.091% Example 2 Using sodium metasilicate hydrate crystals obtained in exactly the same manner as in Example 1, an aqueous mixture prepared to have the following oxide molar ratio was heated once with a homogenizer, and then immediately
Heat treatment was performed at 0°C for 16 hours.

Na2O/ (5i02 +AA203) = 2
, 67H20/Na2O=40 5io2/Az2o3=2 The properties of the obtained type A zeolite are as shown in Table 2.

Table 2 Crystallization degree 78 crystals
Particle size 2.8μm Ion exchange capacity
140/2 Ion exchange rate: 75% Iron content: 0.0742% The conditions for crystallization of water glass obtained by heating the reaction under the same conditions and filtering out insoluble matter, that is, as shown in Table 3. Sodium metasilicate hydrate was crystallized by varying the amount of water added, and type A zeolite was produced under the same conditions as in Example 1 using each hydrate.

In each case, the yield of IJium hydrated ice crystals (weight %), the iron content in the crystals (weight % of Fe2O3 per 5iO2), and the iron content of A-type zeolite in each case. Table 3 shows the reflectance (wt%) and reflectance (ch).

The iron content of water glass before crystallization is 0.5.
62 It was a heavy rice cake.

Table 3 As is clear from this table, adding water to metasilicic acid)
When the IJium hydrate salt is crystallized, the yield is slightly lowered, but the iron content in the crystals and the iron content in the A-type zeolite are significantly reduced, and a high-quality target product can be obtained.

For reference, the iron content and reflectance of several type A zeolites obtained by the method of the present invention, commercially available type A zeolites, and type A zeolites included in commercially available detergents were measured. did.

The figure is a graph plotting the results.

From the figure, it is recognized that the reflectance of type A zeolite is inversely proportional to the iron content, but according to the method of the present invention, it is also possible to produce high purity type A zeolite from shirasu with a lower iron content than commercially available products. Sodium aluminate, sodium hydroxide, and water were added to the metasilicic acid hydrate obtained in the same manner as in Example 1. Additionally, an aqueous mixture was prepared with the following molar ratios:

H2O/ Na2O = 4O Na20 / (5i02 + A7201.) =
2.66Si02/AA203=2 This aqueous mixture was mixed for 1 minute with a homogenizer, aged under the conditions shown in Table 4, and then heat-treated at 90° C. for 16 hours.

The average particle size of the A-type zeolite thus obtained (μ
m) are shown in Table 4.

Table 4 Example 5 After mixing the aqueous mixture prepared in the same manner as in Example 4 for 30 seconds with a homogenizer, various amounts of seed crystals having various average particle sizes as shown in Table 5 were added, The mixture was mixed again using a homogenizer for 30 seconds and heat-treated at 90° C. for 16 hours. The average particle size of the A-type zeolite thus obtained (
μm) are shown in Table 5.

Table 5 Grind for 4 hours.

2) Grind the above pulverized material in an agate mortar for several hours.

[Brief explanation of drawings]

The drawing is a graph showing the relationship between iron content and reflectance of type A zeolite.

Claims (1)

[Claims] 1. Add an 8-18 N aqueous sodium hydroxide solution to volcanic glass and heat it to 70-150°C to elute 50-70% by weight of the silica in the volcanic glass, and remove the insoluble from the eluate. After removing the components, the sodium dimetasilicate hydrate is crystallized and separated by cooling or adding water, and the required amount of sodium aluminate, sodium hydroxide, and water are added to the obtained sodium metasilicate hydrate to form an aqueous mixture. A method for producing A-type zeolite, which is characterized by subjecting it to a heating reaction. 2 Crystallization and separation of sodium metasilicate hydrate with Na2S
The manufacturing method according to claim 1, which is carried out under conditions such that the concentration based on iO3.9H20 is 60-95% by weight. 3 The aqueous mixture has a molar ratio of H2O/IJa20 = 20-20ONa20/
(Si02 + A7203) = 0.5-4Si
The manufacturing method according to claim 1, wherein O□/At, , o3 = 1.5 to 2.5. 4. The manufacturing method according to claim 1 or 3, wherein the aqueous mixture is aged at 15 to 45°C for 2 to 48 hours and then subjected to heating reaction. 5 to the aqueous mixture, based on the silica content therein.
Claim 1: Addition of ~10% by weight of type A zeolite seed crystals finely ground to a particle size of 1 μm or less followed by heating reaction.
The manufacturing method described in item 3 or item 3.