KR20020043386A - Dry Preparative Method of A Type Zeolite with Waste Water Treatment From Fly Ash Containing Highly Unburned Carbon - Google Patents

Abstract

PURPOSE: A dry preparation method of A-type zeolite for wastewater adsorbent using fly ash containing highly unburned carbon is provided. CONSTITUTION: The preparation method comprises: mixing 100 wt.% of fly ash or furnace slag with 10-50 wt.% of CaO and Na2CO3 in their mole ratio of 0.3-4 and carrying out hydrothermal reaction by heating at 20-200°C for 1-8 hours; and putting into molds, drying for 7 hours at room temperature or drying and reacting at 50-200°C for more than 24 hours in order to prepare molded A-type zeolite for treatment of polluted and wastewater.

Description

Dry Preparative Method of A Type Zeolite with Waste Water Treatment From Fly Ash Containing Highly Unburned Carbon}

The present invention relates to a dry production method of a zeolite of an A type zeolite adsorbent for wastewater treatment using high carbon flyash.

Recently, with the increase of industrial activities and the increase of energy consumption, air and water pollutants such as sulfurous acid gas, nitrogen oxide, and ammonia have deepened the pollution level, threatening environmental standards. Therefore, there is a need to reduce the NHx and toxic organic compounds contained in the wastewater, and to develop technologies and processes for the flue gas desulfurization and denitrification in the air.

In coal-fired power plants, coal, which is a raw material, contains inorganic powder, and thus, mineral powder remains as fly ash after combustion. Currently, much of Korea's power supply is relied on thermal power plants, and as a result, the amount of coal ash produced after combustion increases according to the use of coal used in thermal power plants. In view of this, various treatment methods for using coal ash have been proposed. Since coal ash has properties similar to clay, it has been applied to cement additives, building bricks, zeolite manufacturing, pigments, insulating materials, and polymer fillers. In particular, coal ash is composed mainly of SiO ₂ and Al ₂ O ₃ , and only low-carbon coal ash containing up to 5% of unburned carbon can be used as the recycled material, and containing 5% or more of unburned carbon. Highly unburned carbon coal ash has not been developed at all, so the entire amount of landfill is being disposed of. In particular, coal ash has been known for a long time that zeolite can be reacted with sodium hydroxide, and research has shown that it can be recycled as an adsorbent. Synthetic zeolites or natural zeolites prepared from water glass have excellent adsorption and ion exchange characteristics, and thus are used for drying, ion exchange, wastewater treatment, and various additives. The technology of synthesizing zeolite using coal ash is mainly produced by reacting with NaOH aqueous solution for a certain time at high temperature. However, NaOH contains harmful toxicity. There is this. In addition, zeolites obtained only in powder form have many limitations in the application process. The powder zeolite may be mixed with various binders such as polyvinyl alcohol and water glass, and then heat-treated at 100 ° C. or higher in various (N ₂ , Ar, atmospheric) atmospheres to produce a molded article.

The present invention relates to a method for preparing a zeolite adsorbent for wastewater treatment using high carbon flyash, which has been landfilled to date, and more specifically, it is possible to manufacture A-type zeolite by a dry method with no wastewater generation. Instead, it was molded into a powder or a specific form and used as an adsorbent for various water treatments, thereby recycling coal ash into an adsorbent for high value-added water treatment in a simple and environmentally friendly manner.

The present invention has been derived from the above-mentioned concept, and is a method for producing a zeolite molded body by a dry method in which coal ash is mixed with a lime binder. It can be used as a substitute for existing activated carbon and synthetic zeolite which is currently used in various industries and environmental fields by reusing it as a functional resource, and it solves the problem of coal ash processing drastically, and the raw material, coal ash, has no cost burden. Its purpose is to secure economic feasibility by making the most of it. Compared to the conventional wet manufacturing method of treating coal ash with sodium hydroxide solution, the present invention is not only an environmentally friendly process, but also an excellent method in that it can be molded into various shapes to be suitable for the final application field. Can be. In addition, by utilizing other industrial wastes such as blast furnace slag as a lime binder, the added value was increased.

The zeolite prepared according to the present invention is capable of replacing various materials currently used as deodorization, reodorization, drying, waste oil treatment, heavy metal, ammonia nitrogen adsorption and catalytic function, soil improvement, waste water treatment agent, etc. Since it is manufactured by the process, the economics are excellent.

1 is a comparative view of the dry manufacturing process of the molded zeolite according to the present invention and the wet manufacturing process of the conventional powder zeolite.

Figure 2 (a) (b) (c) (d) (e) (f) is a scanning electron microscope (Scanning Electron Microscope, SEM) analysis photograph of the zeolite prepared by dry method using coal ash.

3 is a zeolite of the present invention molded into a mold.

Figure 4 shows the results of X-ray diffraction analysis of the zeolite prepared by the dry method.

A type high-strength zeolite manufacturing process for wastewater treatment of the present invention is a hydrothermal reaction process for producing a high viscosity slurry mixture by hydrothermally reacting coal ash with a lime raw material and an alkaline component at 50-200 ° C. for 1 hour to 8 hours, and in a particular form It is configured to produce a high-strength zeolite through a reaction and drying process, which is put in a mold to be molded at 50-200 ° C. for at least 24 hours or at room temperature for at least 7 days.

Hereinafter, each manufacturing process illustrated in FIG. 1 will be described in detail.

(1) hydrothermal reaction process

100 parts by weight of coal ash, 10 to 50 parts by weight of a mixture of lime and an alkali component are added to 200 ml of water and subjected to hydrothermal reaction at a temperature of 50 to 200 ° C. for 1-8 hours. At this time, CaO may be used as the lime raw material, and Na ₂ CO ₃ may be used as the alkali component, and their molar ratio is preferably 0.3 to 4. In addition, by utilizing the blast furnace slag containing both calcareous and alkali components, it is possible to recycle another waste resources.

(2) reaction and drying process

In order to obtain a molded zeolite of a certain form, a slurry mixture subjected to hydrothermal reaction is put into molds of various sizes, and then solidified through a reaction and drying process for at least 24 hours at a temperature of 50 to 200 ° C. or at least 7 days at room temperature. At this time, by controlling the viscosity it can be produced in a variety of forms by various extrusion and injection molding techniques.

The above-mentioned (1) and (2) soft dry process enables the production of molded zeolites of various shapes without any generation of waste water, and the strength of the manufactured zeolite molded body (based on 5 × 5 × 5 cm ³ ) is 100 to It has a high compressive strength of 360 kgf / cm 2.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited by the following examples.

<Representative Composition and Thermal Properties of Coal Ash>

The coal ash used in the present invention is produced at Seocheon Thermal Power Plant, and contains SiO ₂ (41.23%), Al ₂ O ₃ (27.99%), Fe ₂ O ₃ (4.10%), and K ₂ O (3.50%). . It can be seen that only inorganic materials exist as main components SiO ₂ and Al ₂ O ₃ . In order to determine the change according to the temperature of the ash, it was measured up to 1,000 ° C. (10 ° C./min) under a nitrogen atmosphere using a thermogravimetric analyzer (TGA 2050, TA Instruments). It was confirmed that the coal ash used in this experiment contained 5% of unburned carbon content. However, the composition and physical properties of coal ash may vary depending on the location of coal production and the combustion conditions of thermal power plants.

<Example 1>

100 parts by weight of the coal ash, 1 mol of CaO, and 1 mol of Na ₂ CO ₃ are added to 200 ml of water, followed by hydrothermal reaction at a temperature of 500 to 200 ° C for 5 hours. A slurry mixture subjected to hydrothermal reaction was placed in a 5 × 5 × 5 cm size stainless steel mold, and then reacted and dried at 100 ° C. for 24 hours to cause solidification to prepare a zeolite molded body (FIG. 5). The compressive strength of the zeolite prepared as described above was generally 100 kgf / ㎠, BET surface area and pore size showed a slight difference depending on the hydrothermal reaction temperature (see Table 1). In addition, the surface area was very low compared to the activated carbon, but showed a similar value to commercial zeolites. The crystal phases were analyzed by scanning electron microscopy (FIG. 4) and X-ray diffractometer. It was confirmed that A-type zeolite was mainly produced. This was consistent with the crystal phase of the zeolite prepared by the conventional wet method.

On the other hand, Figure 2 is a scanning electron microscope (Scanning Electron Microscope, SEM) analysis photograph of the zeolite prepared by dry method using coal ash, Figure 2 (a) is a hydrothermal reaction temperature of 100 ℃ (x2000), Figure 2 (b) Is 120 ° C (x2000), FIG. 2 (c) is 140 ° C (x750), FIG. 2 (d) is 160 ° C (x750), and FIG. 2 (e) is 180 ° C (x2000). 2 (f) is a photograph in the case of 200 ° C (x1000).

Table 1. Specific surface area by BET method and mean pore analysis by BJH method

Sample name Surface Area (m ² / g) Pore Size (Å) Fly ash 5.9 36.6 100 ℃ * 12.3 103.2 120 ℃ 6.3 66.4 140 ℃ 18.1 85.9 160 ℃ 27.1 95.4 180 ℃ 8.3 90.2 200 ℃ 28.6 97.7 Zeolite (4A) 7.0 41.4 Activated Carbon 10009.5 23.0

* Zeolite according to temperature during hydrothermal reaction

<Example 2>

Except for using blast furnace slag instead of CaO and the same as in Example 2, it was confirmed that the A-type zeolite was produced as a result of the X-ray diffraction analysis of the crystal phase thus prepared. At this time, the compressive strength of the zeolite molded body was 150kgf / cm 2.

<Example 3>

100 parts by weight of coal ash, 2 mol of CaO, 2 mol of Na ₂ CO ₃ was hydrothermally reacted at 100 ° C. for 5 hours, and then dried at 100 ° C. for 24 hours to prepare a zeolite molded body in the same manner as in Example 1. At this time, the compressive strength was 300 kgf / cm 2, and the obtained crystal phase confirmed that the A-type zeolite and the liquid crystal (Quartz) phase existed through the results of X-ray diffraction analysis (FIG. 4).

<Example 4>

In Example 1, the strength of the zeolite prepared by adding only three times the amount of CaO and four times, respectively, was measured. When 3 times CaO was added, the strength increased to 360 kgf / cm 2, but when 4 times CaO was added, the strength did not increase any more, indicating 360 kgf / cm 2.

<Test Example 1>; NH ₄ -N Adsorption Characteristics

The standard solution was prepared by diluting 10 ml in 1000 ml using a 1000 ppm ammonia standard solution to prepare a 10 ppm standard solution. 2 g of the zeolite prepared in Examples 1 and 2 (the same conditions for the entire ammonia adsorption) were put into a 250 ml Erlenmeyer flask with 100 ml of a standard ammonium solution (concentration of 10 ppm), and then kneaded at a stirring speed of 250 min ⁻¹ for 30 minutes. After 6 hours of adsorbing at intervals, the resultant was filtered with a 0.45 μm membrane filter, and the filtrate was collected and measured by an ultraviolet absorber by the Nessler method (see Table 2). The (blast furnace slag) zeolite prepared as in Example 2 maintained a pH of 10 and exhibited a maximum removal rate of 87% when the removal rate was 2 hours. Afterwards, the desorption process proceeded to maintain a removal rate of more than 50%. Compared with natural zeolites, natural zeolites had a maximum removal rate of 77% at 3 hours and 64% at 12 hours. The (CaO) zeolite prepared in Example 1 was maintained at pH 11 and the removal rate was 51 to 71%, showing a maximum removal rate of 71% at 30 minutes. On the other hand, the zeolite prepared by the conventional wet method using high carbon coal ash maintained pH 12 and the removal rate was 15-22%, which was relatively low.

Table 2. NH ₄ -N adsorption (%) of Examples 1 and 2

Adsorption time Example 1 Sample Example 2 Sample 0.5 hours 71 20 1 hours 65 45 2 hours 68 87 3 hours 60 60 4 hours 51 50

<Test Example 2> ; Adsorption Characteristics of Total Organic Carbon (TOC)

The zeolite prepared by the dry method was added to a sewage treatment plant having a total organic carbon (TOC) concentration of 300 ppm or 0.3 g of humic acid in 1 L of water to measure the adsorption capacity. At this time, 1 to 7 g of zeolite powder sample ground to a size of about 150 ml was put in 250 ml Erlenmeyer flasks and stirred for 3 hours at 250 min ⁻¹ using an automatic stirrer (see Table 3). In order to analyze the adsorption performance, the mixed solution was filtered through a 0.45㎛ membrane filter and then diluted 100-fold to measure total organic carbon (TOC). When 7 g of (blast furnace slag) zeolite powder prepared in Example 2 was added, the removal rate was 53%.

Table 3. Example 2 Total Organic Carbon Adsorption of Samples

Sample weight Example 2 Sample 1 g 33 3 g 47 5 g 50 7 g 53

<Test Example 3> ; Heavy metal measurement

100 ml of 1000 ppm Pb and 10 ppm diluted Cd were added to a 250 ml Erlenmeyer flask with 2 g of zeolite prepared by the dry method, and then kneaded at 250 min ⁻¹ for 4, 8 and 24 hours using an autostirrer at room temperature. After the adsorption, each pH was measured, and the filtrate was collected and the residual concentration was measured by an atomic analyzer (AA). At this time, the zeolites prepared in Examples 1 and 3 all exhibited excellent removal rates of 90% or more.

Table 4. Heavy metal adsorption (%) of Examples 1 and 3

Adsorption time Pb ²⁺ Cd ²⁺ Example 1 Sample Example 3 Sample Example 1 Sample Example 3 Sample 4 hours 95 95 95 95 8 hours 95 95 90 90 24 hours 95 95 95 95

<Test Example 4>; Cation exchange capacity

The cation exchange capacity of the zeolite prepared by the dry method was tested by the Harada method. After completely replacing 2 g of the sample with calcium ions, the calcium ions remaining in the crystal gap were removed with 80% ethyl alcohol, and then replaced with ammonium ions having high ion selectivity, and the amount of calcium was analyzed by ICP (Inductively Coupled Plasma Spectroscopy). Ion exchange capacity was evaluated . The coal ash itself showed 1 meq / 100 g, the zeolite prepared in Example 1 was 38 meq / 100 g, the zeolite prepared in Example 2 was 41.2 meq / 100 g, and the commercial 5A zeolite was 82.4 meq / g.

It can be seen that the A-type molded zeolite of the present invention is excellent in heavy metal and ammonia nitrogen adsorption characteristics. This proves that economic efficiency can be secured by recycling coal ash, replacing material of existing activated carbon and synthetic zeolite, which is currently used in various industries and environmental fields, and making full use of the cost-free cost of coal ash, which is a basic raw material. have. In addition, the present invention is more environmentally friendly than the conventional wet manufacturing method for treating coal ash with sodium hydroxide solution, which is not only an environmentally friendly process, but also more excellent in that it can be molded into various shapes suitable for the final application. It can be called a method. In addition, by utilizing other industrial wastes such as blast furnace slag as a lime binder, the added value was increased.

Claims (3)

A step of obtaining a slurry mixture by mixing the calcined raw material and the alkaline component with coal ash and hydrothermally reacting at a temperature of 50 to 200 ° C. for 1 to 8 hours; A method for producing A-type molded zeolite for wastewater treatment using coal ash, wherein the slurry mixture is put into a mold and reacted and dried at 50-200 ° C. for at least 24 hours or at room temperature for 7 hours. The method for producing A-type molded zeolite for wastewater treatment according to claim 1, wherein the calcined raw material and 10 to 50 parts by weight of an alkali component are mixed with 100 parts by weight of coal ash or blast furnace slag is mixed to hydrothermally react. The calcined raw material is CaO, and the alkali component is Na ₂ CO ₃ , wherein the molar ratio of the calcareous raw material and the alkaline component is 0.3 to 4. Manufacturing method.