KR20200070701A - Geopolymer-supported Hybrid Zeolite-hydrotalcite(LDH) Composite And Method for Manufacturing the Same - Google Patents

Abstract

The present invention relates to a bulk-type heavy metal-adsorbing geopolymer-supported hybrid zeolite hydrotalcite (LDH) composite capable of absorbing a large amount of cations and anions, and a method for manufacturing the same by mixing industrial byproducts, such as fly ash and fine dust of slag, with an activating agent and magnesium oxide (MgO) to produce zeolite and LDH at the same time. The geopolymer-supported hybrid zeolite-LDH composite includes: a binder obtained by mixing slag with fly ash at a predetermined ratio; and magnesium oxide (MgO) powder and an alkali activating agent mixed with the binder, and is obtained by heating the mixture of the binder with magnesium oxide powder and the alkali activating agent to a predetermined temperature to carry out hydrothermal synthesis reaction, and curing the resultant product in the air or water.

Description

Geopolymer-supported Hybrid Zeolite-hydrotalcite (LDH) Composite And Method for Manufacturing the Same}

The present invention relates to a geopolymeric hybrid zeolite-LDH complex that can be used for water quality and environmental purification, and more specifically, by mixing magnesium oxide (MgO) and an alkali activator in industrial by-products such as fly ash and fine slag powder. The present invention relates to a bulk-type heavy metal adsorption type geopolymeric hybrid zeolite-LDH composite capable of adsorbing a large amount of cations and anions by simultaneously generating zeolite and LDH (Hydrotalcite), and a method for manufacturing the same.

As road construction spreads along with the explosive increase in urban traffic demand, the water environment of the city's air and rivers is rapidly deteriorating. For the continuous growth of the construction sector in the 21st century, the demand for functional materials that actively mitigate pollutants in the surrounding environment is increasing.

Recently, river blocks produced by mixing natural or synthetic zeolites into concrete for the purpose of water purification in urban rivers or lakes have been used for water purification. For example, in Patent No. 10-0961564, blast furnace slag cement, fly ash cement, and ordinary Portland cement are used as a binder, and natural zeolite, synthetic zeolite, Ca-type artificial zeolite and active agent are used to maximize environmental pollution and water purification. Carbon is mixed at a predetermined ratio with respect to 100 parts by weight of the binder, and as a admixture, a fluidizing agent and a high-performance AE water reducing agent, and hydrophilic polyamide fibers and polyvinyl vinyl having a length of 3 to 30 mm for improving structural performance and durability of concrete. Manufacturing method of high-performance eco-friendly concrete with excellent water quality and environmental purification performance, excellent physical and mechanical properties, and environmental and soil stabilization by mixing polyvinyl alcohol fiber, release steel fiber, and rustproof mesh as reinforcing materials. This is disclosed.

However, such a conventional water or environmental purification concrete or composite is a method to have a heavy metal adsorption performance by zeolite by mixing synthetic or natural zeolite powder with a certain amount of cement or industrial by-products. Although silver cations can be adsorbed, anions are not adsorbed, which limits the ability to remove heavy metals.

Republic of Korea Registered Patent No. 10-0961564 (registered on May 27, 2010) Republic of Korea Patent Publication No. 10-2016-0125188 (2016.10.31. public) Republic of Korea Registered Patent No. 10-1273444 (2013.06.04. registered)

The present invention is to solve the above problems, the purpose of the present invention is not a method of adding zeolite, zeolite and a mixture of alkali activator and magnesium oxide (MgO) in industrial by-products such as fly ash and slag fine powder and It is to provide a bulk type heavy metal adsorption type geopolymeric hybrid zeolite-LDH composite capable of adsorbing a large amount of cations and anions by simultaneously generating LDH (Hydrotalcite) and a method for manufacturing the same.

In addition, another object of the present invention is a geopolymeric hybrid zeolite-LDH composite having a high compressive strength and a large amount of cation and anion adsorption performance to be used as a concrete block for water quality or air purification or a general precast product, and a method for manufacturing the same Is to provide

The geopolymeric hybrid zeolite-LDH composite according to the present invention for achieving the above object is a binder made by mixing slag and fly ash in a certain ratio; And a magnesium oxide (MgO) powder mixed with the binder and an alkali activator; and a mixture of the binder and the magnesium oxide powder and an alkali activator is heated to a certain temperature range to perform a hydrothermal synthesis reaction, and then in water or It is made by curing in air.

The alkali activator may be incorporated in 50 to 60 parts by weight.

In addition, the weight ratio of the slag to the total weight of the binder (slag/binder) is preferably 0.2 to 0.6.

The magnesium oxide preferably has a molar ratio of magnesium (Mg)/(aluminum (Al)+silicon (Si)) in the range of 0.1 to 1.0.

The alkali activator has a weight ratio of waterglass/sodium hydroxide (NaOH) of 0.4 to 0.6, and an aqueous sodium hydroxide (NaOH) solution may have a molar concentration of 5 to 12M.

The method for preparing the geopolymeric hybrid zeolite-LDH composite according to the present invention includes the following steps.

(S1) Step to make a binder by mixing slag and fly ash in a certain ratio

(S2) adding magnesium oxide (MgO) powder to the binder and mixing it by dry boiling

(S3) adding and mixing an alkali activator to the mixture of the binder and magnesium oxide (MgO) powder

(S4) a step of hydrothermal synthesis of the mixture of the binder, magnesium oxide (MgO) powder and an alkali activator within a certain temperature range

(S5) curing the mixture of the cured binder, magnesium oxide (MgO) powder, and an alkali activator in water or in air.

The magnesium oxide mixed in the step (S2) is preferably a molar ratio of magnesium (Mg) / (aluminum (Al) + silicon (Si) is in the range of 0.1 ~ 1.0.

In addition, the alkali activator mixed in (S3) has a weight ratio of waterglass/sodium hydroxide (NaOH) of 0.4 to 0.6, and an aqueous sodium hydroxide (NaOH) solution preferably has a molar concentration in the range of 5 to 12M.

In the step (S4), it is preferable to perform a hydrothermal synthesis reaction in a temperature range of 100 to 130°C for a predetermined time in the chamber.

In the step (S4), it is preferable to proceed with the hydrothermal synthesis reaction while maintaining the internal vapor pressure in the chamber at 0.15 MPa by maintaining the amount of water relative to the entire capacity of the chamber in the chamber at 0.25 MPa.

The alkali activator is preferably incorporated in 50 to 60 parts by weight.

According to the present invention, a large amount of nanopores are formed using a one-step zeolite synthesis method in which the formation of a zeolite crystal phase and the conversion of an amorphous geopolymer gel to a crystalline zeolite are simultaneously performed, rather than a conventional method of adding zeolite, The LDH crystal layer can be formed in the composite by incorporating magnesium oxide (MgO) powder. Therefore, since anions can be adsorbed together with a large amount of cations, a large amount of heavy metals and contaminants can be adsorbed and removed.

The zeolite-LDH composite of the present invention can be used as a block or precast product for bulk water quality and environmental purification to remove harmful ions from water or air.

In addition, the zeolite-LDH composite of the present invention can not only adsorb a large amount of heavy metal ions, but also has excellent mechanical strength and durability.

1 is a XRD graph showing the comparison of Example 1 and Comparative Examples 1 and 2 of the zeolite-LDH composite according to the present invention.
2 is an XRD graph for Examples 1,2,3 of the zeolite-LDH complex according to the present invention.

Hereinafter, examples of the geopolymeric hybrid zeolite-LDH composite according to the present invention and a method of manufacturing the same will be described in detail.

The geopolymeric hybrid zeolite-LDH composite according to the present invention includes a binder made by mixing slag and fly ash at a certain ratio, and a magnesium oxide (MgO) powder and an alkali activator mixed with the binder, and the binder and It is made by heating a mixture of magnesium oxide powder and an alkali activator to a certain temperature range, performing a hydrothermal synthesis reaction, and curing it in water or air.

The fly ash includes SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ , and some may have a crystalline structure or an amorphous structure. The slag is composed mainly of SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ and CaO, and various other metal oxides such as K ₂ O, Na ₂ O, MgO, and TiO ₂ may be contained in a small amount. The weight ratio of the slag to the total weight of the binder, that is, the slag / binder (slag / binder) is preferably in the range of 0.2 to 0.6.

And the magnesium oxide (MgO) powder reacts with the Al component of the fly ash and the slag fine powder of the binder to form a LDH (Hydrotalcite) (Mg ₆ Al ₂ CO ₃ (OH) ₁₆ · 4 (H ₂ O)) crystal layer. ^{_{SO 2-, PO 4 3-, CN}} - can adsorb anions such as. The magnesium oxide (MgO) powder is preferably mixed in a molar ratio of magnesium (Mg) / (aluminum (Al) + silicon (Si) in the range of 0.1 to 1.0.

The alkali activator is mixed with a binder to produce a geopolymer slurry, which is placed in a mold of a certain type and then heated in a chamber to cause a hydrothermal synthesis reaction, thereby causing zeolite Na-P1 (Na _5.92 Al ₆ Si _10O43.28 ).

The alkali activator is preferably mixed with 50 to 60 parts by weight based on 100 parts by weight of the binder (fly ash + slag). As the alkali activator, a mixture prepared by mixing KS 3 water glass (29% SiO ₂ , 95% Na ₂ O and 615% H ₂ O) with an aqueous sodium hydroxide (NaOH) solution in a constant weight ratio may be used. Here, the weight ratio (waterglass/NaOH) of the waterglass and sodium hydroxide (NaOH) is 0.4 to 0.6, and the sodium hydroxide (NaOH) aqueous solution is preferably prepared in a range of 5 to 12M molar concentration. When the waterglass/NaOH is less than 0.4, the CASH gel does not grow due to lack of silicate, so the compressive strength is lowered, and when it exceeds 0.6, the CASH gel grows excessively, resulting in relatively less zeolite production.

As described above, the geopolymer slurry produced by adding an alkali activator to the binder of fly ash and fine slag powder is CASH having the characteristics of cement by reacting CaO, Al ₂ O ₃ , SiO ₂ present in the slag with water due to the hydrothermal synthesis reaction. A gel (C=CaO, A=Al ₂ O ₃ , S=SiO ₂ , H=H ₂ O) is formed. The formation of CASH gel accelerates the setting time in the initial stage and contributes to the strength development in the later stage.

In one embodiment of the present invention, the hydrothermal synthesis reaction temperature is preferably 100 to 130°C, the pressure is preferably 0.15 MPa, and the reaction time is preferably 24 to 48 hours.

When the hydrothermal synthesis reaction is performed at a curing temperature of less than 100°C, zeolite generation is not smoothly performed, and when the curing temperature is performed at a temperature of 130°C or higher, sufficient strength may not be secured. In addition, it is important to reduce water evaporation during the hydrothermal synthesis reaction and to maintain the pressure at 0.15 MPa, which plays an important role in securing strength and generating zeolite, thus causing a hydrothermal synthesis reaction, for example, an autoclave chamber. It is preferable to proceed with the hydrothermal synthesis reaction while maintaining the amount of water relative to the total volume of the chamber at 0.2, that is, 20 Vol%. When the amount of water is less than 20 Vol%, sufficient moisture evaporation is not achieved, so that the internal vapor pressure may be small, and when it exceeds 20 Vol%, excessive energy consumption may occur compared to zeolite formation.

When performing the hydrothermal synthesis reaction according to these conditions, the geopolymer slurry is phase-converted to a crystalline zeolite, thereby forming a plurality of nano-pores.

When the hydrothermal synthesis reaction is completed, the complex is cured in water or air at a temperature of approximately 25°C to complete the complex.

Preparation Example 1: Preparation of alkali activator

10M sodium hydroxide aqueous solution and KS 3 water glass (29% SiO ₂ , 95% Na ₂ O and 615% H ₂ O) are mixed at a weight ratio of 2:1, and the water glass/sodium hydroxide (NaOH) aqueous solution has an alkali weight ratio of 0.5 Activators were prepared.

Example 1: Preparation of zeolite-LDH complex

80 g of fly ash and 20 g of slag fine powder were dry for 1 minute in a blender. After mixing and drying 70 g of magnesium oxide (MgO) powder in the binder in which the fly ash and the fine slag powder are mixed, the alkali activator prepared in Preparation Example 1 is 50 wt% of the binder (fly ash + slag). 50 g was added and mixed for 15 minutes to prepare a geopolymer slurry.

The geopolymer slurry thus prepared was poured into a Teflon mold, placed in an auto-clave chamber having a capacity of 500 ml, and subjected to a hydrothermal synthesis reaction for 48 hours at 100° C. and 0.15 MPa. At this time, 100ml of water was filled into a 500ml chamber, so that the volume ratio of the water/autoclave chamber was 0.2. Then, it was cured in air at 25° C. for one day to prepare a block-shaped zeolite-LDH composite.

The prepared zeolite-LDH complex was made into a powder for XRD (X-ray diffraction analysis) experiments to perform the experiment. As shown in FIG. 1, it was found that zeolite crystal peaks and LDH were formed before the hydrothermal synthesis reaction.

Example 2: Preparation of zeolite-LDH complex

A zeolite-LDH composite was prepared in the same manner as in Example 1, except that a binder was prepared using 60 g and 40 g of fly ash and fine slag powder, respectively.

Example 3: Preparation of zeolite-LDH complex

A zeolite-LDH composite was prepared in the same manner as in Example 1, except that a binder was prepared using 40 g and 60 g of fly ash and fine slag powder, respectively.

Comparative Example 1: Preparation of zeolite block

80 g of fly ash and 20 g of slag fine powder were dry for 1 minute in a blender. Here, the alkali activator prepared in Preparation Example 1 was added to 90 g, which is 90% by weight of the binder (fly ash + slag), and mixed for 15 minutes to prepare a geopolymer slurry.

The prepared geopolymer slurry was poured into a Teflon mold, placed in an auto-clave chamber having a capacity of 500 ml, and subjected to a hydrothermal synthesis reaction for 48 hours at 100°C and 0.15 MPa, and at 25°C for one day. The zeolite block was prepared by curing in air.

Comparative Example 2: Preparation of zeolite block

Comparative Example 2-1: Preparation of geopolymer block

80 g of fly ash and 20 g of slag fine powder were dry for 1 minute in a blender. 90 g of the alkali activator prepared in Production Example 1 was added thereto. The paste obtained after mixing for 2 minutes was placed in a 1 inch cubic mold. Then, it was cured in an oven at 80° C. for 24 hours. Then, it was cured by cooling to ambient temperature, and demoulded in a mold to prepare a geopolymer block.

Comparative Example 2-2: Preparation of zeolite

After the geopolymer block prepared in Comparative Example 2-1 was placed in an auto-clave chamber having a capacity of 500 ml, a hydrothermal synthesis reaction was performed. At this time, the temperature is 100° C., and 50 ml of water is filled into the chamber so that the block is completely immersed in water, and then the reaction is performed for 24 hours. Then, curing was performed in air at 25° C. for one day to prepare a zeolite block.

1 is an XRD graph of the zeolite-LDH composite of Example 1 and the zeolite block by the one-step zeolite synthesis method of Comparative Example 1, and the zeolite block by the two-step zeolite synthesis method of Comparative Example 2, in this graph Z represents zeolite and H represents LDH (Hydrotalcite). As can be seen through the graph of FIG. 1, in the embodiment of the zeolite-LDH composite of the present invention using a one-step zeolite synthesis method and mixing magnesium oxide (MgO) powder, zeolite and LDH (Hydrotalcite) are formed at the same time. Although it was confirmed that Comparative Example 1 and Comparative Example 2 without mixing magnesium oxide (MgO) powder, only zeolite was formed, and it was confirmed that LDH (Hydrotalcite) was not formed.

FIG. 2 is an XRD graph of Examples 1, 2, and 3 showing comparison of the formation of zeolite and LDH (Hydrotalcite) according to the slag content, wherein the content of slag is 40% by weight compared to the total weight of the binder. It was confirmed that the complex had a maximum of zeolite Na-P1 and LDH (Hydrotalcite).

As described above, the present invention uses a one-step zeolite synthesis method in which the formation of a zeolite crystal phase and the conversion of an amorphous geopolymer gel to a crystalline zeolite are carried out simultaneously, rather than a conventional method of adding zeolite, and magnesium oxide (MgO) powder is incorporated. By doing so, the LDH crystal layer can be formed in the composite.

The zeolite-LDH composite of the present invention manufactured by such a manufacturing method can be used as a mortar or concrete block, and can adsorb negative ions together with positive ions, so it is a bulk type water and environmental purification block that removes harmful ions from water or atmosphere Or it can be used as a precast product.

In addition, as can be seen through the compressive strength test results for Example 2 shown in Figure 3, it was confirmed that the zeolite-LDH composite of the present invention has a high 28-day compressive strength of 20.34 MPa.

The zeolite-LDH composite of the present invention can not only adsorb a large amount of heavy metal ions, but also can be made of a revetment block or precast panel/block product having very good mechanical strength and durability.

In the above, the present invention has been described in detail with reference to examples, but those skilled in the art to which the present invention pertains will be capable of various substitutions, additions, and modifications without departing from the technical spirit described above. Of course, it should be understood that such modified embodiments also belong to the protection scope of the present invention as defined by the appended claims.

Z: Zeolite
H: LDH (Hydrotalcite)

Claims (11)

A binder made by mixing slag and fly ash in a certain ratio; And
Magnesium oxide (MgO) powder mixed with the binder and an alkali activator;
Including,
A geopolymeric hybrid zeolite-LDH composite made by heating a mixture of the binder, magnesium oxide powder and an alkali activator to a certain temperature range and performing a hydrothermal synthesis reaction, followed by curing in water or air. The geopolymeric hybrid zeolite-LDH complex according to claim 1, wherein the alkali activator is incorporated in an amount of 50 to 60 parts by weight. According to claim 1, The weight ratio of the slag to the total weight of the binder (slag / binder) is 0.2 to 0.6 geopolymeric hybrid zeolite-LDH composite. According to claim 1, The magnesium oxide is a geopolymeric hybrid zeolite-LDH composite having a molar ratio of magnesium (Mg)/(aluminum (Al) + silicon (Si) in the range of 0.1 to 1.0. The method of claim 1, wherein the alkali activator is a water glass (waterglass) / sodium hydroxide (NaOH) weight ratio of 0.4 ~ 0.6, sodium hydroxide (NaOH) aqueous solution is a geopolymeric hybrid zeolite having a molar concentration in the range of 5 ~ 12M -LDH complex. A method for producing the geopolymeric hybrid zeolite-LDH composite according to any one of claims 1 to 5,
(S1) mixing the slag and fly ash in a certain ratio to make a binder;
(S2) adding magnesium oxide (MgO) powder to the binder and mixing by drying;
(S3) adding and mixing an alkali activator to the mixture of the binder and magnesium oxide (MgO) powder;
(S4) subjecting the mixture of the binder, magnesium oxide (MgO) powder and an alkali activator to a hydrothermal synthesis reaction in a predetermined temperature range; And,
(S5) curing the mixture of the cured binder, magnesium oxide (MgO) powder and an alkali activator in water or in air;
Method for producing a geopolymeric hybrid zeolite-LDH composite comprising a. The preparation of a geopolymeric hybrid zeolite-LDH composite according to claim 6, wherein the magnesium oxide mixed in the step (S2) has a molar ratio of magnesium (Mg)/(aluminum (Al)+silicon (Si)) in the range of 0.1 to 1.0. Way. The method according to claim 6, wherein the alkali activator mixed in (S3) has a weight ratio of water glass/sodium hydroxide (NaOH) of 0.4 to 0.6, and an aqueous sodium hydroxide (NaOH) solution has a molar concentration in the range of 5 to 12M. Method for producing phosphorus geopolymeric hybrid zeolite-LDH composite. The method of claim 6, wherein the step (S4) is a method of manufacturing a geopolymeric hybrid zeolite-LDH complex that undergoes a hydrothermal synthesis reaction in a temperature range of 100 to 130°C for a predetermined time in a chamber. The geopolymeric hybrid zeolite-LDH composite according to claim 9, wherein the step (S4) proceeds a hydrothermal synthesis reaction while maintaining an internal vapor pressure of 0.15 MPa in the chamber by maintaining the amount of water relative to the entire volume of the chamber in the chamber at 0.2. Method of manufacture. 7. The method of claim 6, wherein the alkali activator is mixed with 50 to 60 parts by weight of a geopolymeric hybrid zeolite-LDH composite.

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