JP5564680B2 - Glass foam, phosphoric acid adsorbent containing glass foam, plant growth medium containing glass foam, and method for producing glass foam - Google Patents

Description

  The present invention relates to a glass foam used for wastewater treatment and a method for producing the glass foam, and particularly has high phosphoric acid adsorption ability suitable for recovering phosphoric acid in wastewater, and after use for wastewater treatment. In order to facilitate the use of glass foam in plant cultivation, a glass foam rich in pores capable of holding water that can be used in plants, a phosphate adsorbent containing glass foam, and a plant growth medium containing glass foam And a method for producing a glass foam.

  In recent years, global environmental problems have occurred as a result of increased human industrial activities. From the viewpoint of protecting the global environment, regulations on the release of harmful substances in the atmosphere and water have been made, and there is an urgent need for purification of the atmosphere and water. Has been. For example, with regard to water areas, phosphoric acid derived from domestic wastewater, industrial wastewater, and other livestock excreta is a cause of water pollution and eutrophication of water systems, such as significant changes in ecosystems and disruption of food chains. Causes serious problems. In order to deal with this problem, the Water Pollution Control Law, the Lake Water Quality Special Measures Law, etc. have been enacted, and phosphoric acid emission standards have been established. In recent years, in order to more strictly regulate such water pollution, the 6th Total Water Quality Regulation (which sets a target for reducing the pollution load flowing into Tokyo Bay) has further reduced the concentration of phosphoric acid in wastewater. Is required.

Examples of methods for reducing the concentration of phosphoric acid in wastewater include biological treatment methods such as anaerobic and aerobic methods, coagulation precipitation methods, crystallization dephosphorylation methods, and adsorption methods.
The anaerobic / aerobic method has high phosphoric acid removal efficiency, but has the problem of high equipment installation costs. The coagulation sedimentation method is simple and inexpensive, but the reaction efficiency is low because phosphoric acid and the coagulant have a low reaction efficiency, and a large amount of sludge and sludge are generated.

  As for the crystallization dephosphorylation method, the removal efficiency of phosphoric acid is high, but the equipment introduction cost, the adjustment of reaction conditions and the maintenance management cost for removing the scale are expensive. Although the removal efficiency is high and simple, disposal of the adsorbent after use for wastewater treatment is a problem. This is because the existing adsorbent strongly adsorbs phosphoric acid, making it difficult to use it as a fertilizer.

As described above, water quality regulations on wastewater have been strengthened in recent years, and further reduction of the phosphoric acid concentration in the wastewater has been demanded. However, the concentration of phosphoric acid in the actual wastewater (raw water) may fluctuate greatly even at one establishment. Even if one of the above treatment methods is used, the concentration of phosphoric acid in the treated water Fluctuates greatly with acid concentration.
As a result, it is feared that the regulation value (reference value) may be exceeded temporarily, so that it will be used in the subsequent stage of the existing wastewater treatment facility in order to cope with such a transient regulation value excess. There is a need for a simple and simple treatment method with high phosphoric acid removal efficiency.

  As this treatment method, application of the above adsorption method is conceivable, and in Patent Document 3 below, as an adsorbent for phosphoric acid, one or more selected from aluminum, ferrous iron, ferric iron or calcium sulfate and chloride There is disclosed a water-purifying granule that has a mother nucleus containing water and a coating layer formed around the core and has a particle diameter in the range of 0.5 to 40 mm.

JP 2007-169119 A JP-A-2005-97065 JP-A-9-103608

According to the above adsorption method, the existing adsorbent must be treated with sulfuric acid having a high concentration of about 0.2 N in order to desorb and regenerate the adsorbed phosphoric acid, and disposal of the generated waste liquid is a problem. For example, according to Patent Document 3, for reuse of a filter medium in which a metal salt of phosphoric acid is captured, the metal of phosphoric acid is immersed in about 0.5% dilute sulfuric acid or dilute hydrochloric acid for about 2 minutes. It is described that salt can be removed.
Phosphoric acid is a causative substance that causes water pollution and eutrophication of water systems, but is an essential element indispensable for plant growth and is also useful as a fertilizer for plant cultivation. Phosphate ore, the raw material for phosphate fertilizer, is a scarce resource that is in danger of being exhausted, and in recent years resource prices have soared. Therefore, the need for efficient recovery and recycling of phosphoric acid is increasing. Therefore, in order to recycle the adsorbed phosphoric acid as phosphate fertilizer, it is desirable that the adsorbent be easily regenerated / desorbed. Also, from the viewpoint of environmental problems, an adsorbent that can be recycled (recycled) is preferable.

On the other hand, glass foam manufactured by pulverizing glass discharged from ordinary households and business establishments, mixing and firing materials that generate gas at high temperatures, is sold as a recycled glass product. This glass foam is mainly used as civil engineering and building materials, taking advantage of its light weight, porosity and heat insulation.
And the present inventors previously revealed that the glass foam is an adsorbent capable of adsorbing phosphoric acid (hereinafter sometimes referred to as having a phosphate adsorbing ability) (Patent Document 2). However, phosphoric acid adsorption ability of existing glass foams is low, and it was not applicable to wastewater treatment. In this method, glass powder is mixed with calcium carbonate as a foaming agent and heated and cooled. This is because the existing glass foam is limited to the use of lightweight materials such as civil engineering and construction, and is still insufficient from the viewpoint of phosphate adsorption.

  In Patent Document 1, as an improvement of the MAP (magnesium ammonium phosphate) method for removing and collecting phosphate ions in waste water as crystals, glass powder, a powder containing a magnesium component, and a foaming agent are mixed. A technique for efficiently producing a foamed glass material having a small particle diameter is disclosed by a firing step of heating and a rapid cooling step of cooling the fired product. And the invention of the said patent document 1 is made to adsorb | suck the phosphorus (phosphoric acid) of to-be-processed water by exposing a magnesium component to the surface of a foam glass material, and a space | gap inner wall surface.

The MAP method is a method of precipitating phosphoric acid as a double salt of ammonium and magnesium. Although the processing efficiency is high, it is necessary to introduce a processing device for adjusting the reaction conditions, and therefore it takes an initial cost. There is a problem that the maintenance of the apparatus is also expensive. In the invention described in Patent Document 1, it has not been confirmed whether phosphoric acid is actually supported on the adsorbent and the adsorbed phosphoric acid can be dissociated and recovered.
In addition, even if the inside of the foamed glass material is not sufficiently porous, phosphorous acid (phosphoric acid) is only adsorbed on the surface, even if the foamed glass material has a small particle size. I cannot expect much improvement.

  Also, from the viewpoint of energy saving, it is more desirable if it is a multifunctional glass foam that can be used not only for phosphate adsorption but also for other uses. Taking advantage of the characteristics of the glass foam having pores inside, for example, utilization for plant cultivation in rooftop greening and the like can be considered. In this case, a glass foam having high water absorption is desired to promote the elongation of plant roots such as air permeability and water permeability.

  The subject of this invention is solving the said problem, and providing the glass foam which can be applied to waste water treatment, and its manufacturing method. Moreover, the subject of this invention is providing the glass foam which provided the phosphate adsorption ability, and its manufacturing method. Furthermore, the subject of this invention is providing the glass foam which can be applied to plant cultivation, and its manufacturing method.

Specifically, the present invention can be achieved by adopting the following configuration.
The invention according to claim 1 is a glass foam made of two or more kinds of glasses having different softening temperatures, and glass having a softening temperature higher than that of the glass is dispersed in at least one kind of glass. And a glass foam containing a calcium component.
The invention according to claim 2 has a single maximum value in the region where the pore diameter is 0.1 to 2 μm with respect to the pore diameter distribution indicating the relationship between the pore diameter (μm) and the pore volume (cm ³ / g). The glass foam according to claim 1, wherein the maximum value is 0.1 cm ³ / g or more.

The invention described in claim 3 is a phosphate adsorbent for adsorbing phosphoric acid or phosphate radicals contained in the aqueous solution to be treated, including the glass foam according to claim 1 or 2.
Invention of Claim 4 is a culture medium for plant growth containing the glass foam of Claim 2. In the invention according to claim 5, (a) two or more kinds of glass powders having different softening temperatures are mixed with (b) calcium magnesium carbonate or dolomite which is a foaming agent, and the lowest softening temperature of each glass. This is a method for producing a glass foam that is fired and foamed at a temperature that is equal to or higher than the temperature and that does not exceed the highest temperature.
Invention of Claim 6 uses soda-lime glass as glass with the lowest softening temperature among the glass powder, and uses alumina borosilicate glass or alkali barium glass as glass with the highest softening temperature. It is a manufacturing method of this glass foam.

(Function)
As a harmful substance that is contained in domestic wastewater and industrial wastewater and is a treatment target, for example, phosphoric acid, which is a causative substance for water pollution and aqueous eutrophication, is representative.
According to the conventional method of adsorbing phosphoric acid, it is necessary to treat with about 0.2 N sulfuric acid in order to desorb and regenerate the adsorbed phosphoric acid, and disposal of the generated waste liquid is a problem. . This is because the adsorption of phosphoric acid is due to the chemical adsorption of aluminum and iron on the surface of the adsorbent, and these elements and phosphoric acid are strongly adsorbed, so a high concentration of sulfuric acid is required to dissociate. It is thought that.

However, in addition to aluminum and iron, calcium is an element that reacts with phosphoric acid. Chemically, when the solubility of phosphate with each metal ion of aluminum, iron, and calcium is compared, calcium phosphate is about 10 ⁻⁷ mol / liter, iron phosphate is about 10 ⁻⁸ mol / liter, aluminum phosphate Is increased in the order of about 10 ⁻¹¹ mol / liter, and is considered to be strongly bonded to phosphoric acid in the order of aluminum, iron, and calcium. This solubility relationship is a phenomenon related to the interaction between each metal ion and phosphoric acid in an aqueous solution, but when these metals are present on the surface of the adsorbent, the same phenomenon occurs. Inferred.

  Therefore, the present inventors thought that calcium, unlike aluminum and iron, could be dissociated by a low concentration acid that can be easily treated with a waste liquid, by adsorbing slowly with phosphoric acid. The inventors of the present invention believe that the problem of wastewater treatment using the above adsorbent can be solved if a glass foam adsorbent enriched with a calcium component on the surface can be solved. We have intensively studied how to enrich the calcium component on the surface by increasing the surface area of the agent.

That is, the present inventors speculated that the performance of the adsorbent is defined by the abundance of reactive groups (calcium) on the adsorbent surface and the surface area.
For example, when calcium carbonate containing calcium carbonate or dolomite is mixed with glass powder and heated and fired, calcium carbonate releases carbon dioxide at high temperatures, and the bubbles pass through the softened glass. Holes and voids are formed. The manufacturing method of the glass foam which uses typical calcium carbonate and dolomite as a foaming agent goes through the process of mixing calcium carbonate (or dolomite) with glass powder, and heating and cooling.

And the present inventors performed further examination about the glass (glass powder) used as the raw material of a glass foam. As described above, it was presumed that the phosphate adsorption capacity was defined by the surface area of the glass foam, and first, a method for increasing the surface area of the glass foam was studied.
Therefore, the present inventors can increase the surface area of the glass foam by attaching and dispersing particles of other types of glass inside or on the surface of at least one type of glass using a plurality of types of glass. I found out. In other words, instead of a multi-layered structure in which multiple types of uniform glass layers are stacked, another glass having a non-softened particle shape is dispersed on the softened and uniformized glass surface and inside. Thus, the surface area of the glass foam can be increased.

  Conventionally, there is one kind of glass used as a raw material for glass foam. That is, when different types of glass are mixed and fired and foamed, the strength of the glass foam produced by the difference in the degree of thermal shrinkage between the two glasses decreases during the subsequent cooling step, resulting in deterioration of quality. It is. Since glass foam is porous, lack of strength itself becomes a problem. Accordingly, if the strength is further reduced by using a plurality of types of glass, it becomes difficult to use the glass as a civil engineering / building material.

In the case where a multilayer structure is formed by the above-described plurality of types of glass, there is a concern that the strength and quality of the generated glass foam may be deteriorated, but the present inventors do not soften another glass to the softened glass. In the state of being dispersed in the form of particles, the inventors have found that the problem of deterioration of the strength and quality of the glass foam is solved, and have completed the present invention.
Furthermore, from the viewpoint of energy saving, a multifunctional glass foam that can be used not only for phosphoric acid adsorption but also for other uses is more desirable. Taking advantage of the characteristics of the glass foam having pores inside, for example, utilization for plant cultivation in rooftop greening and the like can be considered.

  Since calcium contained in the glass foam is adsorbed slowly with phosphoric acid, it can be dissociated and regenerated by a low-concentration acid that can be easily treated with waste liquid. And when it tries to utilize a glass foam for plant cultivation after reproducing | regenerating in this way or without making it regenerate with the phosphoric acid holding | maintaining to a glass foam, it is generally more water-absorbing that the pore size distribution is uniform. Therefore, the formation of pores with a more uniform pore size distribution is also desired. Furthermore, the larger the pore volume of such uniform pores, the higher the water absorption.

Further, the surface area of the glass foam is closely related to the amount of voids generated by the foaming reaction.
When two or more types of glass powders having different softening temperatures are mixed, baked and foamed, the glass having the lowest softening temperature is first softened to form a uniform layer. At this time, the glass having a softening temperature higher than that of the glass is not yet softened and is in a state of being dispersed in the form of particles inside or on the glass having the lowest softening temperature.

  Furthermore, by raising the maximum temperature to a temperature that does not exceed the softening temperature of the glass having the highest softening temperature and then cooling, a glass having a softening temperature that is substantially the same as the maximum temperature or higher than the maximum temperature has a softening temperature higher than the maximum temperature. Due to the difference in the degree of thermal shrinkage, the voids are generated at the boundary surfaces of these glasses while being dispersed in the form of particles in the low glass interior or on the surface. And while this space | gap increases the surface area of a glass foam, it is anticipated that it contributes to the porosity improvement of a glass foam, the improvement of a phosphoric acid adsorption ability, and the improvement of a water absorption rate. Further, since the size of the voids formed at this time is controlled only by the thermal characteristics of the glass to be used if the glass particle size is controlled, it is expected that a relatively uniform pore size distribution is obtained.

On the other hand, glass (FPD glass) used for liquid crystal panel glass and plasma television glass can save power and resources, and demand is expanding due to dramatic improvements in image quality. Therefore, recycling efforts are being carried out.
As an example of recycling, FPD glass is separated from a product, made into glass cullet, mixed with cement and paint, and used as a non-permeable lightweight material for civil engineering.

  The present inventors paid attention to the fact that these FPD glasses usually have a higher softening point than glass containers (waste glass, bottle glass) discharged from ordinary households. That is, when FPD glass and bottle glass having different characteristics, such as a difference in softening point, are mixed and fired, a mechanism as shown in FIG. 1 can be considered. In FIG. 1, the conceptual diagram of the manufacturing method of the glass foam of this invention is shown.

When the bin glass particles 1 and the FPD glass particles 2 are mixed and fired, the bin glass having a low softening temperature is softened. And in the softened soda-lime glass (a general glass as a bottle glass) 3, the FPD glass particles 2 that are not softened are dispersed, and the surface area of the glass foam compared to the case of using one kind of glass. Will increase. Then, by cooling, due to the difference in thermal shrinkage between the two, a void 4 is formed at the boundary surface between the two, and this void 4 further increases the surface area of the glass foam, making it porous and improving the phosphate adsorption capacity. It is expected to contribute to the improvement of water absorption. Moreover, since the size of the voids 4 formed at this time is controlled only by the thermal characteristics of both types of glass if the glass particle size is controlled, it is expected that a relatively uniform pore size distribution is obtained. .
Examples of the FPD glass include alumina borosilicate glass (also referred to as aluminoborosilicate glass) used as liquid crystal panel glass (referred to as LCD) and alkali barium glass used as plasma television glass (referred to as PDP).

The softening temperature of soda-lime glass is 720-740 ° C., the softening temperature of alumina borosilicate glass is 900-980 ° C., and the softening temperature of alkali barium glass is 850 ° C. or less (Japan Electronics and Information Technology Industries Association, Japan). “Excerpts from“ Issues on TV Recycling ””, page 9 “I-3. (1) Specificity of CRT glass” (April 27, 2007) by the Home Appliances Association), alumina borosilicate glass and alkali barium glass Since the softening temperature of the soda lime glass is about 100 to 200 ° C. higher than the softening temperature of soda lime glass, alumina borosilicate glass or alkali barium glass is used as the high softening temperature, and soda lime glass is used as the low softening temperature glass. do it.
Alumina borosilicate glass and alkali barium glass contain a barium component. Since barium is the same alkaline earth metal as calcium, it is considered that the number of reactive groups that adsorb phosphoric acid increases and the phosphate adsorbing ability further increases.

According to invention of Claim 1, the surface area of a glass foam increases because the glass whose softening temperature is higher than this glass is disperse | distributed to at least 1 type of glass. Thus, there exists an effect | action which the adsorption | suction performance of the substance which can adsorb | suck to Ca component improves because the surface area of the glass foam in which calcium exists increases. As the substance to be adsorbed other than phosphoric acid, organic phosphoric acid, phosphorous acid, polyphosphoric acid and the like that can be adsorbed to the Ca component are conceivable.
According to the invention of claim 2, in addition to the action of the invention of claim 1, the glass foam has a single maximum value and the pore size distribution has a relatively large value of the maximum value. For this reason, the water to be treated containing the substance to be adsorbed easily enters the inside of the glass foam due to the maximum pore diameter, and is easily adsorbed by calcium within the pore diameter, and also improves the water absorption.

According to the invention described in claim 3, since it is a phosphate adsorbent containing calcium and containing a glass foam having a large surface area (or high water absorption) as described in claim 1 or 2, Phosphoric acid or phosphate radicals contained in the treatment aqueous solution can be adsorbed efficiently.
According to the invention described in claim 4, the glass foam having pores capable of retaining moisture that can be absorbed by the plant according to claim 2, allows water retention, water permeability as a plant growth medium, Good air permeability can be maintained.

According to the invention of claim 5, two or more kinds of glasses having different softening temperatures are fired and foamed with the highest temperature being the lowest temperature of the softening temperatures of these glasses and not exceeding the highest temperature. By making it, the state where glass with a high softening temperature disperse | distributes to a glass can be formed in glass with a low softening temperature. Therefore, the surface area of the glass foam can be increased, and the adsorbing substance such as phosphoric acid is efficiently adsorbed to the reactive group (calcium).
According to the invention described in claim 6, in addition to the action of the invention described in claim 5, alumina borosilicate glass or alkali barium glass is used as the glass having a high softening temperature, and soda lime glass is used as the glass having a low softening temperature. As a result, alumina borosilicate glass or alkali barium glass is dispersed in particles in the softened soda-lime glass phase. In addition, since alumina borosilicate glass and alkali barium glass contain a barium component, the number of reactive groups for adsorbing phosphoric acid increases, and phosphoric acid is adsorbed more efficiently.

The present invention is effective in adsorbing and removing harmful substances contained in domestic wastewater and industrial wastewater, and specifically has the following effects.
According to the first aspect of the present invention, the surface area of the glass foam can be increased, and the adsorbing substance is effectively adsorbed on the calcium contained in the glass foam to improve the adsorption performance.
According to the invention described in claim 2, in addition to the effect of the invention described in claim 1, the water to be treated containing the substance to be adsorbed more easily enters the inside of the glass foam, It is easily adsorbed by calcium, and the adsorption performance of phosphoric acid is further improved, and the water absorption is also improved.

According to invention of Claim 3, since phosphoric acid in to-be-processed aqueous solution can be adsorb | sucked efficiently, it can respond easily to the water quality regulation (concentration regulation of the phosphoric acid in waste water) of the phosphoric acid being strengthened. it can.
According to invention of Claim 4, the water | moisture content which a plant can absorb as a culture medium for plant growth can be hold | maintained by the hole of the glass foam of Claim 2, and it is excellent material as a rooftop greening or a soil improvement agent. Become.

According to the invention of claim 5, by mixing inorganic powder foaming agents with different softening temperatures, and further using calcium magnesium carbonate or dolomite as the foaming agent, a glass foam having excellent adsorption performance can be obtained easily and inexpensively. Can be manufactured.
According to the invention described in claim 6, in addition to the effect of the invention described in claim 5, soda lime glass is used as the low softening temperature glass, and alumina borosilicate glass or alkali barium glass is used as the high softening temperature glass. This will promote the recycling of FPD glass and contribute to the formation of a recycling society. Moreover, the glass foam which the adsorption | suction performance of the substance which can adsorb | suck to Ba component improves can be manufactured.

It is a conceptual diagram of the manufacturing method of the glass foam of this invention. It is an external appearance photograph of a LCD mixed glass foam (Example 1). It is an external appearance photograph of a PDP mixed glass foam (Example 1). It is an external appearance photograph of the prototype of LCD mixed glass foam (Example 2). It is an external appearance photograph of the prototype of a PDP mixed glass foam (Example 2). It is the figure which showed the phosphoric acid adsorption rate of the FPD glass foam of the Example of this invention. It is the figure which showed the water absorption of the FPD glass foam of the Example of this invention. It is the figure which showed the pore diameter distribution of the glass foam of the Example of this invention. It is an electron microscope image (x4000) of the glass powder particle | grains which are not softened confirmed on the glass foam surface containing 5% of LCD. It is an electron microscope image (x2000) of the glass powder body which is not softened confirmed on the surface of 75% PDP containing glass foam. It is an external appearance photograph of the glass foam of 100% bottle glass (comparative example of Example 1). It is an external appearance photograph of the prototype of the glass foam of 100% bottle glass (comparative example of Example 2).

Embodiments of the present invention will be described with reference to the drawings.
A glass foam was produced using soda lime glass powder and FPD glass powder as an example of glass used as a raw material for the glass foam. Examples of the glass include quartz glass, 96% silica glass, lead alkali silicate glass, borosilicate glass, and aluminosilicate glass, but are not limited to these types. Moreover, if waste glass is used as a raw material, it promotes the reuse of glass and contributes to the formation of a recycling-oriented society.

  And what is necessary is just to select the kind of glass from these so that it may become a combination from which softening temperature differs. The difference between the softening temperatures of the glass having the lowest softening temperature and the glass having the highest softening temperature is preferably about 100 ° C to 200 ° C. When the difference in softening temperature is small, the glass having the highest softening temperature is also softened and the particle state cannot be maintained. If the difference in softening temperature is large, the glass with the highest softening temperature is difficult to sinter and foaming becomes insufficient, and the mixing ratio of the glass with the highest softening temperature cannot be increased.

And the manufacturing process of a glass foam is divided roughly into mixing processes, such as a foreign material removal process from a glass container or waste FPD glass, a grinding | pulverization process (coarse grinding | pulverization, fine powder), a dolomite (or calcium magnesium carbonate), and a baking process. . Dolomite means calcium and magnesium double carbonate CaMg (CO ₃ ) ₂ or rocks containing this as a main component (Source: Chemical Dictionary Popular Edition, Morikita Publishing Co., Ltd., page 881, January 1985) Issued on the day).
A method for preparing a glass powder (glass pulverized product) and a method for producing a glass foam used in this example and the following comparative examples are shown below.

As a raw material for the glass powder, a glass container (soda lime glass) and waste FPD glass discharged from a general household were used. Foreign substances such as labels and metal crowns were removed from these glass containers and waste FPD glass, washed with water, dried, and then roughly pulverized to a particle size of about 10 mm using a hammer.
In the case of waste FPD glass, a member obtained by peeling off members such as a deflecting plate and a heat sink is used. As waste FPD glass, waste liquid crystal panel glass (LCD) (alumina borosilicate glass) and waste plasma display glass (PDP) are used. ) (Alkali barium glass).

After roughly pulverizing each glass as described above, the glass was pulverized to a particle size of 1000 μm or less using a high-speed stamp mill (ANSC 143 (alumina thin, alumina hammer)). The particle size composition of the prepared soda-lime glass (bin glass) is 16.3% of 1000 to 500 μm, 22.0% of 500 to 250 μm, 14.9% of 250 to 150 μm, 11.3% of 150 to 90 μm, 90 μm or less was 35.5%. The component composition of soda-lime glass was measured by a fluorescent X-ray analysis method (apparatus name: scanning type X-ray fluorescence analyzer, manufactured by Rigaku Co., Ltd., model ZSX Primus II). SiO ₂ : 68.9%, Na ₂ O: 13. 6%, CaO: 13.3%, Al ₂ O ₃ : 1.96%, K ₂ O: 1.42%, and other components were 0.82%. In addition, unless otherwise indicated,% of a component represents weight%.

The composition of waste liquid crystal panel glass (LCD) (alumina borosilicate glass) is SiO ₂ : 58.1%, Al ₂ O ₃ : 17.8%, B ₂ O ₃ : 10.7%, CaO: 8. 4%, SrO: 2.1%, MgO: 1.7%, BaO: 0.3%, and other components were 0.9%. The particle size distribution was less than 100 μm and the center particle size (peak of particle size distribution) was about 50 μm.
The composition of waste plasma display glass (PDP) (alkali barium glass) is SiO ₂ : 50.1%, BaO: 9.3%, SrO: 9.2%, K ₂ O: 7.6%, Al ₂ O ₃ : 7.6%, ZrO ₂ : 4.7%, Na ₂ O: 4.1%, CaO: 2.5%, MgO: 2.0%, and other components were 2.9%. . The particle size distribution was less than 100 μm and the center particle size was about 50 μm.

The dolomite carbonate (Made in Fire Country, limestone lime) and the above ground glass are uniformly mixed, the mixture is transferred to an alumina container, and the electric furnace is a muffle furnace (model FO710 manufactured by YAMATO). And baked.
In addition, bottle glass, LCD glass, PDP glass, and a foaming agent were mixed by the ratio shown in Table 1 (LCD glass) and Table 2 (PDP glass).

  The firing conditions were a temperature increase rate of 10 ° C./min, a maximum temperature of 850 ° C. for 20 minutes, and a temperature decrease rate of 10 ° C./min. And after cooling to room temperature, the presence or absence of sintering and foaming of a baked product was confirmed visually. The reason why the maximum temperature during firing was 850 ° C. is that the softening temperature of soda-lime glass is 720-740 ° C., the softening temperature of alumina borosilicate glass is 900-980 ° C., and the softening temperature of alkali barium glass is 850 ° C. or less. Therefore, the temperature is higher than the softening temperature of soda lime glass having a low softening temperature and does not exceed the softening temperature of alumina borosilicate glass and alkali barium glass having a high softening temperature.

FIGS. 2 (a) to (c) show an appearance photograph of a glass foam mixed with LCD glass, and FIGS. 3 (a) to (d) show an appearance photograph of a glass foam mixed with PDP glass, In FIG. 11, the external appearance photograph of the glass foam only of a bottle glass (and foam) is shown as a comparative example. Tables 3 and 4 show the results of visual confirmation.
As can be seen from FIG. 2, when the mixing ratio of the LCD glass is 30% or more, the structure does not sinter and the structure easily collapses by touch. Further, as can be seen from FIG. 3, when PDP glass was mixed, sintering / foaming was confirmed even at a mixing ratio of 100%, but foaming was insufficient when 100% PDP glass was used as a raw material. .

  Further, in the glass foam according to the present example, the formation of rough voids of several mm units, that is, voids related to plant root elongation such as air permeability and water permeability was confirmed by visual observation. Therefore, in the manufacturing conditions of the glass foam according to the present embodiment, the LCD glass can be mixed up to 20% by weight and the PDP glass can be mixed up to 75%. And the glass foam which has sufficient intensity | strength and quality can be produced by adjusting the mixing ratio of FPD glass in this way.

The reason why LCD glass has a lower mixing weight ratio than PDP glass is that the softening temperature (softening point) of LCD glass is much higher than the softening temperature of bottle glass compared to the softening temperature of PDP glass. This is presumed to be because sintering becomes difficult as the value increases.
In the case of PDP glass, the softening temperature is close to the softening temperature of bottle glass compared to LCD glass, so it is presumed that the glass was sintered and foamed even at a high mixing ratio.

  Next, from the results of Example 1 above, the mixing ratio of LCD glass was limited to 5% and 10%, and the mixing ratio of PDP glass was limited to 25%, 50%, and 75%. Using a large tunnel furnace with an increased amount of use, a glass foam mixed with FPD glass was manufactured by a method of pouring a mixture of glass powder and a foaming agent on a belt conveyor and firing with a gas burner while flowing.

As the material, the LCD glass and PDP glass of Example 1 were pulverized using a high-speed stamp mill (ANS143 manufactured by Nissho Science Co., Ltd.) and sieved to 90 μm or less. About the bottle glass, what crushed the glass container discharged | emitted from a general household similarly to Example 1 was used.
As the foaming agent, the above-described dolomite was used. Firing conditions were prepared in the above-mentioned tunnel furnace under 850 ° C. for 20 minutes. Table 5 shows the mixing conditions of the raw materials.

  4 and 5 show the appearance of the prototype of this embodiment. 4 (a) to 4 (b) show photographs of the appearance of glass foam mixed with LCD glass, and FIGS. 5 (a) to 5 (c) show prototypes of glass foam mixed with PDP glass. The appearance photograph is shown. In addition, FIG. 12 shows a photograph of the appearance of a glass foam prototype made only of bottle glass (and foam) as a comparative example. From FIG. 4 and FIG. 5, sintering and foaming were confirmed in any case. In the case of mixing PDP glass, it was recognized that the mixture became brown and the volume decreased as the mixing rate increased.

The glass foam prepared by the above method was crushed with a hammer and sieved to 2 to 4 mm, and used for evaluation of phosphate adsorption capacity. The phosphoric acid concentration in the supernatant after immersion in 20 mL of 1 mg PO ₄ -P / liter phosphoric acid aqueous solution (prepared with KH ₂ PO ₄ ) per 1 g of glass foam and left at room temperature for 24 hours is the molybdenum blue absorbance. Measurement (colorimetric determination) was performed by a photometric method (according to JIS K0102). When 100% of phosphoric acid in the liquid was adsorbed, it was expressed as phosphoric acid adsorption rate 100%.

Moreover, what cut | disconnected the prepared glass foam with the diamond saw (V-19 by Tecso Co., Ltd.) so that it might be set to about 3 g was used for the water absorption evaluation. The prepared sample was submerged in 100 mL of ultrapure water and allowed to stand at room temperature for 24 hours. The weight before water immersion was also measured in advance, and the change rate of the weight was calculated by the following formula (1) as the water absorption rate.
Water absorption rate (%) = (weight after water absorption−weight before water absorption) / weight before water absorption × 100 (%) (1)

FIG. 6 shows the phosphoric acid adsorption rate of the FPD glass foam, and FIG. 7 shows the water absorption rate of the FPD glass foam. In each figure, (a) shows the measured value of the glass foam when the LCD glass is mixed, and (b) shows the measured value of the glass foam when the PDP glass is mixed. Each measured value represents an average value ± standard deviation.
Phosphoric acid adsorption ability (FIG. 6) was increased by mixing of LCD glass and PDP glass as compared with the case of using only bottle glass as a raw material. As for the mixing ratio, no difference was observed in phosphate adsorption capacity between 5% and 10% of LCD glass. When PDP glass was mixed, the phosphate adsorption capacity was highest when the mixing rate was 25%. The phosphoric acid adsorbed in this way is bound to calcium and barium (derived from LCD glass and PDP glass) in the glass foam, and is considered to be easily eluted and recovered by dilute sulfuric acid.

  As shown in FIG. 1, since the softening temperature is lower than the highest temperature (850 ° C.) during firing, the surface of the bottle glass (soda lime glass) 3 softened and made uniform is almost the same as the highest temperature during firing. The surface area of the glass foam is increased compared to the case of using only bottle glass by dispersing the LCD glass 2 and the PDP glass 2 having a softening temperature higher than the firing temperature and maintaining the unsoftened particle shape. Can do. Therefore, it is considered that phosphoric acid adsorbing ability is improved by effectively adsorbing phosphoric acid to adsorbing groups such as calcium and barium.

As for the water absorption rate (FIG. 7), when LCD glass was mixed, a tendency to increase as the mixing rate increased was observed. When the PDP glass was mixed, it was optimum at a mixing rate of 25%, which was higher than when only the bottle glass was used. On the other hand, when the mixing ratio of PDP glass was 50% and 75%, the water absorption ratio was rather lowered.
It is surmised that the phosphate adsorption capacity of the glass foam is defined by the degree of contact between the foam and the water to be treated and the amount of adsorbing groups on the surface of the foam. The amount of adsorbing group is defined by the amount of alkaline earth metal such as Ca (derived from foaming agent), Ba, etc., which can react with phosphoric acid, and any test condition is the foaming derived from the Ca component that becomes the adsorbing group Since there is no difference in the addition amount of the agent, the mechanism for improving the phosphate adsorption capacity by adding FPD glass will be discussed below from the viewpoint of the degree of contact between the foam and the water to be treated.

  First, according to the result of the water absorption rate in FIG. 7, it can be seen that the water absorption rate is improved by adding 5%, 10% of LCD glass and 25% of PDP glass. Regarding the phosphate adsorption capacity (FIG. 6), the cases where the mixing ratio of LCD glass was 5% and 10% and the mixing ratio of PDP glass was 25% were improved as compared with the other cases. As a result, it is expected that the water to be treated penetrates into the inside of the glass foam, and the reaction between the phosphate adsorption group on the foam surface and phosphoric acid is promoted. Furthermore, in order to clarify the mechanism of increasing the water absorption rate by adding FPD glass, the pore size distribution and the porosity of the glass foam were measured.

AutoPore IV9500 (manufactured by micrometrics) was used as a measuring device, and the measurement conditions were a contact angle of 140 ° and a surface tension of 485 dynes / cm. The result is shown in FIG. FIG. 8A shows measured values of the glass foam when the LCD glass is mixed, and FIG. 8B shows measured values of the glass foam when the PDP glass is mixed.
As shown in FIG. 8, when the LCD glass is mixed, the distribution of pores having a pore diameter of about 1 μm increases as the addition amount increases. When PDP glass was mixed, an increase in pores having a pore diameter of about 1 μm was observed only when 25% was added, but not when 50% or 75% was added.

The same tendency was observed with respect to the porosity (Table 6 below), and the porosity increased with the addition of 5% LCD, 10% addition, and 25% PDP compared to the case of using only bottle glass as a raw material. Therefore, it is considered that an increase in pores having a pore diameter of about 1 μm causes an increase in porosity and an increase in water absorption.
And the glass foam which is excellent in water absorption is that the maximum value in the region where the pore diameter is around 0.1 to 2 μm is 0.1 cm ³ / g or more, which is larger than the pore volume when only the conventional bottle glass is used. It is thought that a body is obtained.

  Next, the reason why the addition of LCD glass or PDP glass causes an increase in pores with a pore diameter of about 1 μm will be considered. The characteristics of LCD glass and PDP glass are that the softening temperature is higher and the degree of thermal shrinkage is smaller than soda lime glass represented by bottle glass. When glass having different characteristics is mixed and fired, under high-temperature conditions in the firing process, unsoftened FPD glass particles 2 are dispersed in the softened soda-lime glass 3 as shown in FIG. Will be. Thereafter, by cooling, the degree of shrinkage of the soda-lime glass phase is larger than that of the FPD glass particle phase due to the difference in the degree of thermal shrinkage between the two, resulting in the formation of voids 4 at the interface between the two. The voids 4 are expected to increase the surface area of the glass foam, and contribute to making the glass foam porous, improving the phosphate adsorption capacity, and improving the water absorption rate. Since such an effect occurs in a state where the periphery of the FPD glass particles 2 is surrounded by the phase of the soda lime glass 3, the amount of FPD glass added is equal to or more than that of the soda lime glass, that is, PDP 50%, It was inferred that 75% addition conditions did not increase pores with a pore diameter of about 1 μm.

On the other hand, since calcium contained in the glass foam is slowly adsorbed with phosphoric acid, the glass foam after the phosphoric acid adsorption can be dissociated and regenerated by a low-concentration acid that can be easily treated with waste liquid. And also from a viewpoint of energy saving, if the glass foam with phosphoric acid retained and the glass foam after regeneration can be used for plant cultivation in rooftop greening or the like, the use of the glass foam is widened.
When using a glass foam for plant cultivation, the characteristic of the glass foam of a present Example is evaluated from an agricultural viewpoint. When plant roots try to absorb water in the soil, uniform capillaries with a diameter of about 0.6 to 3 μm are considered desirable (“Soil”, Department of Social Communication Education, Tokyo University of Agriculture, 109-114). Page, second edition, second edition, revised April 1, 1990). This is because when the pore diameter range is exceeded, the capillary pressure in the pores is smaller than gravity, so that water is lost to the lower soil layer in a short period of time, and the plant cannot use the moisture. When the pore diameter is narrower than the above range, the capillary pressure is higher than the water suction force of the surface tissue of the plant root, so that the plant cannot absorb and use the moisture.

The pore diameter distribution of the glass foam when adding 5% LCD, 10% LCD and 25% PDP in this example is 1 μm as a maximum and is distributed in a relatively narrow range around 0.1 to 2 μm. Is close to the pore size distribution region where water can be absorbed. When a certain capillary tries to absorb water, it is desirable that its diameter is more uniform. This is because it is difficult for the water once absorbed by the capillary having a small diameter to move to the capillary having a larger diameter that is continuous with the capillary. In this respect, since the glass foam of this example has one maximum value (indicated by an arrow in FIG. 8) in the pore diameter region, the glass foam of this example was suitable for the water absorption capacity of plants. It is also promising as a water retention material. And the glass maximum which is excellent in a water absorption is because the single maximum value of the area | region of 0.1-2 micrometers vicinity is 0.1 cm < ³ > / g or more larger than the pore volume at the time of using only the conventional bottle glass. It is thought that a body is obtained. Therefore, regardless of whether this glass foam is regenerated or not (because its use as a water retention material is a performance not related to whether or not phosphoric acid is retained), if used as a plant growth medium, water retention, water permeability, Good air permeability can be maintained.

FIG. 9 shows an electron microscopic image of a non-softened glass powder particle confirmed on the surface of a glass foam added with 5% LCD glass (× 4000, miniscope TM-1000 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 15 kV). FIG. 10 shows an electron microscopic image (× 2000) of the non-softened glass particles confirmed on the surface of the glass foam added with 75% PDP glass.
FIG. 9 and FIG. 10 indicate the possibility that the added FPD glass particles (powder particles) remain in the glass foam without being softened. In addition, although the softening point of PDP glass (alkali barium glass) is 850 degrees C or less and is substantially the same as a calcination temperature, when it observed with the microscope, it remained without softening.

  Moreover, although the example at the time of mixing two types of glass was shown in the present Example, you may use 3 or more types of glass. In this case, glass particles whose softening temperature is almost the same as the highest temperature during firing or higher than the highest temperature during firing have a softening temperature lower than the highest temperature during firing and are dispersed in the interior or surface of the softened glass. Thus, the same effect can be achieved.

  INDUSTRIAL APPLICABILITY The present invention can be utilized and used for the subsequent treatment of wastewater treatment facilities at business establishments that require wastewater treatment. In addition, glass foam that retains phosphoric acid and recycled glass foam can be used as rooftop greening materials, and can be used in various technical fields such as environmental fields and construction fields other than wastewater treatment. is there.

1 Particles of bottle glass (soda lime glass) 2 Particles of FPD glass 3 Softened soda lime glass 4 Void

Claims (6)

  A glass foam composed of two or more kinds of glasses having different softening temperatures, wherein glass having a softening temperature higher than that of the glass is dispersed in at least one kind of glass and contains a calcium component. Characteristic glass foam. The pore size distribution showing the relationship between the pore size (μm) and the pore volume (cm ³ / g) has a single maximum value in the region where the pore size is 0.1 to 2 μm, and the maximum value is 0.00. It is 1 cm < ³ > / g or more, The glass foam of Claim 1 characterized by the above-mentioned.   A phosphoric acid adsorbent for adsorbing phosphoric acid or phosphate radicals contained in the aqueous solution to be treated, comprising the glass foam according to claim 1.   A plant growth medium comprising the glass foam according to claim 2.   (A) Two or more kinds of glass powders having different softening temperatures and (b) calcium magnesium carbonate or dolomite as a foaming agent are mixed, and the highest temperature is equal to or higher than the lowest temperature among the softening temperatures of the glasses. A method for producing a glass foam, characterized by firing and foaming at a temperature that does not exceed the maximum temperature.   6. The glass foam according to claim 5, wherein among the glass powders, soda-lime glass is used as the glass having the lowest softening temperature, and alumina borosilicate glass or alkali barium glass is used as the glass having the highest softening temperature. Body manufacturing method.

Images