JPH0559045B2 - - Google Patents

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 particularly to a method for producing type A zeolite suitable for use in detergent builders, which does not substantially contain iron. Type A zeolite has the general formula (1.0±0.2) Na ₂
A hydrated aluminosilicate represented by O・A ₂ O ₃ (2.0±0.2)SiO ₂・nH ₂ O, which can be X-ray distinguished from X-type zeolite, Y-type zeolite, and other zeolites and silicates. It has a specific crystal structure that allows for Furthermore, type A zeolite has particularly remarkable water softening ability and is useful as a builder for detergents. However, in the production of type A zeolite using volcanic glass as a raw material, it is difficult to remove the iron contained in the raw material, so the type A zeolite obtained is unsuitable for use as a detergent builder. Ta. If iron gets mixed into detergent,
Iron must not be mixed into detergents because it not only colors the detergent itself and reduces its product value, but also causes the opposite effect to the original purpose of coloring the fibers when washing textiles, for example. substance and is the most undesirable impurity. Volcanic glass usually contains 12 to 14% by weight of alumina and 2 to 4% by weight of iron, and when producing water glass using this as a raw material, it is difficult to substantially completely separate and remove the iron content. The yield of silica is also 60
In addition, the water glass produced has a composition close to sodium metasilicate with a silica ratio (Na ₂ O / SiO ₂ ) of about 1.0, and has extremely low alkali efficiency. It was difficult to rely on volcanic glass as a starting material. However, research is being carried out to effectively utilize this unique volcanic glass as a silicate raw material to produce zeolite. For example, there is a method in which volcanic ejecta such as whitebait, which is a typical volcanic glass, is heated and dissolved in advance at 330°C with alkali hydroxide to increase its reactivity (Japanese Patent Publication No. 38-5807), and the reaction process is divided into two stages. A method was proposed (Japanese Unexamined Patent Publication No. 110599/1983) in which the iron is first aged with an alkali at a low temperature, and then the temperature is raised to crystallize it. It cannot be separated and removed. In addition, volcanic glass is treated with an alkaline solution to make it highly reactive.
A method of producing synthetic zeolite using a solution in which SiO ₂ is selectively eluted and insoluble components are separated has also been proposed (Japanese Patent Application Laid-open No. 1983-91597); Type A zeolite contained about 0.12% by weight of iron oxide (Fe ₂ O ₃ ), and the iron content was too high to be used as a detergent builder. Furthermore, there is also known a method for producing A-type zeolite that uses natural raw materials such as carrion and lowers the iron content by adding trialkanolamine during hydrothermal synthesis (West German Patent Nos. 2,635,357 and 2,746,844). The use of such a special substance is extremely disadvantageous industrially, and it is difficult to employ it in the production of type A zeolite. As described above, it is extremely difficult to industrially produce silicic acid compounds, especially those that do not contain iron, using volcanic glass containing large amounts of alumina and iron as raw materials. It is an important technical challenge to industrially produce zeolites that are substantially free of iron and to increase their alkaline 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 8-18 N aqueous sodium hydroxide solution and heated to a temperature of 70-150°C to dissolve approximately 50-70% of the silica in the volcanic glass.
After removing insoluble matter from the eluate, the sodium metasilicate hydrate is crystallized by cooling or adding water, and the required amount of sodium aluminate and water is added to the obtained sodium metasilicate hydrate. The present invention provides a method for producing A-type zeolite using volcanic glass as a main raw material, which is characterized by subjecting an aqueous reaction mixture prepared by adding sodium oxide 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 a large amount of alumina and iron as described above. Also,
The alkali treated with this volcanic glass is 8
It is an aqueous sodium hydroxide solution with a relatively high concentration of ~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 through 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 8 to 12N. The mixture of volcanic glass and sodium hydroxide solution is
It is then heated to a temperature of 70-150° C. and heat treated for a time sufficient to dissolve about 50-70% of the silica in the volcanic glass. If the heat treatment temperature is less than 70℃, the silica elution rate will be slow and it will take a long time.
If the temperature exceeds 150°C, the impurity removal effect decreases, which is not preferable. A temperature range of 90-130°C is preferred.
Further, the heat treatment time is usually about 1 to 4 hours, although the higher the concentration of sodium hydroxide in the aqueous solution and the higher the heat treatment temperature, the shorter the desired silica elution ratio can be obtained. In the method of the present invention, approximately 50 to 70% by weight of silica, which is contained in volcanic glass at approximately 70% by weight, is eluted by heating using a fairly highly concentrated sodium hydroxide aqueous solution, and metasilicic acid is extracted from the solution after removing the insoluble matter. The process of precipitating sodium 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 from insoluble matter by filtration or other means.
Crystallized sodium metasilicate hydrate Na ₂
The concentration of SiO ₃ .9H ₂ O is adjusted to 60 to 95% by weight, and the liquid temperature is cooled and maintained 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. If the solution whose concentration has been adjusted is allowed to stand still, crystals of sodium metasilicate hydrate will precipitate. 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 =20-200 _Na2O /( _SiO2 + _{A2O3 )} =0.5-4 _SiO2 / _A2O3 =2±0.5 An aqueous mixture having such _a molar ratio range is
It is prepared by mixing an aqueous sodium aluminate solution or an aqueous sodium hydroxide solution prepared in advance to an appropriate concentration in the required ratio. By thoroughly mixing the aqueous mixture thus prepared 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, the A-type zeolite produced can be made into fine particles by aging the aqueous mixture at 15 to 45° C. for 2 to 48 hours to promote nucleation prior to the heating reaction. In this case, the aging time would be too long to be practical at temperatures lower than 15°C.
Furthermore, if the temperature is higher than 45°C, the ripening time will be shortened, but the particle size will inevitably become non-uniform, and there will be a limit to the effectiveness, making it impossible to obtain particles with a smaller size than a certain level. Furthermore, instead of ripening, finely ground A-type zeolite can be added as a seed crystal before the heat treatment, and the produced A-type zeolite can be made into fine particles.
The smaller the particle size of this seed crystal, the more effective it is, so use one with a particle size of 1 μm or less. If the particle size is larger than this, almost no effect will be observed. The amount of seed crystals added is suitably in the range of 0.1 to 10% by weight based on the silica component in the aqueous mixture. The method of the present invention is an excellent method that does not require expensive special reagents and can industrially advantageously provide type A zeolite suitable for detergent builders from volcanic glass with high alkaline efficiency. Next, the present invention will be explained in more detail with reference to Examples. Note that each performance in the Examples was measured by the following method. Crystallization rate Calculated as the ratio of the peak intensity of the sample to the powder X-ray peak intensity of the standard using the following formula. Note that A4 from Toyo Soda Co., Ltd. was used as the standard product. Crystallinity = I (sample peak intensity) / I ₀ (standard peak intensity) × 100 (%) Reflectance Using a color difference meter, the degree of coloration of the A-type zeolite itself was evaluated. Pour 500ml of calcium nitrate solution containing 300mg of ion exchange capacity CaO into a container equipped with a temperature control and stirrer, maintain the temperature of the contents at 30℃, add 0.5g of A-type zeolite sample, and after 30 minutes, dissolve the solution. was filtered using a membrane filter. The calcium concentration in the filtrate was measured by atomic absorption, and the exchange amount per 1 g of zeolite was converted into CaO (mg) to determine the ion exchange capacity. Ion exchange rate 250ml of 1mM calcium nitrate solution was placed in a temperature-controlled container with a stirrer, and 0.1g of zeolite dispersed in 10ml of distilled water using ultrasonic waves was added to the container over time (0.5 minutes after addition,
Each sample sampled at 1 minute and 2 minutes was filtered using a membrane filter, the calcium concentration was measured by atomic absorption, and the exchange rate at 1 minute of contact with the liquid was determined as the ion exchange rate from the calcium concentration decrease curve. I asked for it. Particle size Using a Coulter Counter particle size measuring device,
The range of 0.2 to 50 μm was measured. Example 1 Whitebait 555g, 18N sodium hydroxide aqueous solution 500g
ml and 200ml of water into a reaction container equipped with a stirrer,
After heat treatment at a temperature of 100°C for 2 hours, insoluble matter was separated by pressure filtration. 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. Na ₂ O / (SiO ₂ + A ₂ O ₃ ) = 1.33 H ₂ O / Na ₂ O = 40 SiO ₂ /A ₂ O ₃ = 2 To this aqueous reaction mixture, A-4 manufactured by Toyo Soda Co., Ltd. was added to an alumina ball mill. After pulverizing for 4 hours, 5% by weight of the seed crystals were added, mixed for 1 minute using a homogenizer, and reacted by heating at 90° C. for 16 hours to precipitate A-type zeolite as crystals. Table 1 shows the various performances of the obtained type A zeolite. Table 1 Crystallization rate 92.5% Grain size (average) 0.6 μm Ion exchange capacity 123 mg/g Ion exchange rate 95% Iron content 0.091% Example 2 Sodium metasilicate hydrate obtained in exactly the same manner as Example 1 Using crystals, an aqueous mixture prepared to have the following oxide molar ratio was mixed with a homogenizer for 1 minute, and then immediately heat-treated at 90° C. for 16 hours. Na ₂ O / (SiO ₂ + A ₂ O ₃ ) = 2.67 H ₂ O / Na ₂ O = 40 SiO ₂ /A ₂ O ₃ = 2 The properties of the obtained type A zeolite are as shown in Table 2. . Table 2 Crystallinity 78% Grain size 2.8 μm Ion exchange capacity 140 mg/g Ion exchange rate 75% Iron content 0.0742% Example 3 Obtained by heating and reacting under the same conditions as Example 1 and filtering out insoluble matter. Sodium metasilicate hydrate was crystallized by changing the crystallization conditions of water glass, that is, the amount of water added as shown in Table 3, and type A was obtained using each hydrate salt under the same conditions as in Example 1. produced zeolite. In each case, the yield (wt%) of sodium metasilicate hydrous crystals based on water glass, the iron content in the crystals (wt% of Fe ₂ O ₃ per SiO ₂ ), and the iron content of A-type zeolite. The content (weight %) and reflectance (%) are summarized in Table 3. Note that the iron content of the water glass before crystallization was 0.562% by weight.

[Table] As is clear from this table, when water is added to crystallize sodium metasilicate hydrate, the yield slightly decreases, but the iron content in the crystals and the iron content in A-type zeolite is significantly reduced, resulting in a high-quality object. 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 contained in commercially available detergents were measured. . 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. It can be seen that it can be suitably used as a detergent builder. Example 4 Sodium aluminate, sodium hydroxide, and water were added to sodium metasilicate hydrate obtained in the same manner as in Example 1 to prepare an aqueous mixture having the following molar ratio. H ₂ O / Na ₂ O = 40 Na ₂ O / (SiO ₂ + A ₂ O ₃ ) = 2.66 SiO ₂ /A ₂ O ₃ = 2 After mixing this aqueous mixture with a homogenizer for 1 minute, the conditions shown in Table 4 were applied. aged under and then
Heat treatment was performed at 90°C for 16 hours. Table 4 shows the average particle size (μm) of the A-type zeolite thus obtained.

【table】

[Table] 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, Mix again with a homogenizer for 30 seconds, then 90
Heat treatment was performed at ℃ for 16 hours. A obtained in this way
Table 5 shows the average particle diameter (μm) of the type zeolite.

【table】 [Brief explanation of the drawing]

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

Claims (1)

[Claims] 1 Add an 8-18N 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 metasilicate 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
The manufacturing method according to claim 1, which is carried out under conditions where the concentration based on Na ₂ SiO ₃ .9H ₂ O is 60 to 95% by weight. _3. The aqueous mixture has _a molar ratio of _H2O / _Na2O =20-200 _Ha2O /( _SiO2 + _A2O3 )=0.5-4 _SiO2 / _A2O3 =1.5-2.5 A manufacturing method according to claim 1. 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.
0.1 to 10% by weight of A finely ground to a particle size of 1 μm or less
The manufacturing method according to claim 1 or 3, wherein the zeolite seed crystals are added and then subjected to a heating reaction.