KR100254138B1 - A process for preparing artificial gravels and color ceraballs using sludges of waste water containing heavy metals - Google Patents

Abstract

PURPOSE: A method for preparing an artificial gravel and color cellar ball by using sludge of heavy metal wastewater is provided which reduces the cost for treating waste matters and the environmental contamination by recycling the sludge of heavy metal wastewater and provides the artificial gravel and color cellar ball having excellent physical properties. CONSTITUTION: The method comprises steps of: (i) mixing sludge of heavy metal wastewater with iron oxide as a stabilizing agent or sludge of fluoric acid wastewater containing the iron oxide; (ii) molding the mixture into a globular shape or a broken stone shape; and (iii) calcining the mold of the step (ii) at a temperature of 900-1,200 deg.C.

Description

Manufacturing method of artificial gravel and color ceramic ball using sludge of heavy metal wastewater

The present invention relates to a method for manufacturing building materials using sludge of heavy metal wastewater, and more particularly, to a method for manufacturing construction materials for civil engineering and construction by stabilizing by-product sludge after treating wastewater containing heavy metal. And it relates to a color ceramic ball used to make artificial gravel and terrazzo tiles used in place of gravel in concrete composed of such materials, for example, sand, cement, gravel and the like produced.

Wastewater discharged from steel contributors, special steel mills, plating copper fields, and non-ferrous metal factories contains a large amount of heavy metals.In order to treat such wastewater to reduce the content of heavy metals below the legal limit, iron salts, aluminum salts, and caustic soda are usually used. , Slaked lime, organic flocculant and the like are used.

As such, sludge containing heavy metals by-produced in the treatment of heavy metal wastewater is produced by precipitation and flocculation by the wastewater treatment agent. These sludges are reduced in weight when heated to a high temperature, and when they are used to produce artificial gravel and color ceramic balls, they are thermochemically unstable, such as cracks and color irregularities, and there is free calcium, which causes structural collapse. In addition, since heavy metals are easily eluted, it is virtually impossible to recycle them as artificial gravel and color cerabol. In addition, the discharge of heavy metal wastewater is increasing day by day, but studies on the recycling of sludge have not been satisfactory.

Therefore, at present, the sludge produced by the treatment of heavy metal wastewater is mostly disposed of in the form of waste. The landfilled sludge is redissolved and soaked into the soil, becoming a secondary source of pollution not only soil and groundwater, but also rivers and seas. In addition, the treatment of such sludge involves enormous cost, which causes a rise in manufacturing cost. Therefore, there is a need to recycle sludge.

Thus, the result of measuring the metal component of the sludge of the typical heavy metal wastewater used for this invention using the atomic absorption spectrometer is shown in following Table 1.

TABLE 1

Metal Component Content of Sludge in Heavy Metal Wastewater

In Table 1, Si, Cr and Fe are components originating from wastewater in the manufacturing process of special steel, etc., and Al, Ca, Na, K and Mg are components originating from precipitants and flocculants added to treat heavy metal wastewater. . In the form of a compound that can be produced from such sludge, in view of the conventional wastewater treatment process, Ca (OH) ₂ , Al (OH) ₃ , SiO ₂ , Cr (OH) ₃ , Fe (OH) ₃ , Na ₂ SO ₄ , Mg (OH) ₂ , K ₂ SO ₄ , and the like, which are converted into the form of the most stable compound when heated to a high temperature.

Such sludge causes chemical and physical reactions by adding a precipitant such as slaked lime, a coagulant such as aluminum sulphate, iron salts, and a precipitant such as polyacrylamide to the wastewater containing heavy metals. As the produced sludge, the particle diameter is fine and contains a large amount of water, hydroxide, organic matter and the like. Therefore, when they are heated to a high temperature of about 1000 ° C. or more, the shrinkage occurs so much that the burning loss reaches about 30%. For this reason, since a crack, a bending phenomenon, etc. generate | occur | produce in a molded object, a molded object of a constant shape cannot be maintained. Thus, the use of such sludge alone is virtually impossible to produce color cerabol and artificial gravel for terrazzo tiles.

In addition, as shown in Table 1, the sludge of the heavy metal wastewater contains about 21.9% by weight of Ca and about 6.16% by weight of Cr, most of which are present in the form of an unstable hydroxide at room temperature. Therefore, when the sludge is calcined to form black cera ball and artificial gravel, when free calcium (CaO) is present in the calcined product, the calcined product changes to Ca (OH) ₂ while reacting with moisture in the air. There is a possibility that the collapse of the building will gradually increase, and if such building materials are used in the building, a catastrophic disaster will occur. In addition, Cr in the fired product is released from the color ceramic ball and the artificial gravel to not only change the surface to green, but also cause Cr to elute in water to pollute the environment.

In order to recycle heavy metal wastewater sludge to color ceramic balls used for terrazzo tiles and artificial gravel used for construction materials, the following four conditions must generally be met. Since the characteristics are almost the same, the following description about artificial gravel will be omitted and only the color ceramic ball will be described.

1) When the sludge is formed into round and crushed form, when it is fired at high temperature, no pores should be generated inside the molded body.

2) The manufactured color ceramic ball should have low absorption rate and high compressive strength.

3) The manufactured color cerabol should not be present in the form of calcium oxide (free calcium) used as precipitant of waste water.

4) The manufactured color ceramic ball must have good durability and heavy metal ion should not be eluted.

On the other hand, terrazzo tiles, which are construction materials for construction, are generally made of cement, aggregate, color gravel, marble pieces, and the like, and color shades are used to give color to such terrazzo tiles. However, color cera ball is mainly used because of the shortage of color pebbles.

Currently, color cerabol is manufactured by pulverizing natural ore, for example, feldspar, pottery stone, silica, etc., mixing with inorganic pigment, forming spherical or crushed stone of various sizes, and calcining at high temperature. A color cera ball having a variety of colors and sizes is manufactured. When the terrazotile is manufactured using color ceramic balls prepared using natural ores, natural ores are used, which results in high raw material and fuel costs due to high firing temperatures. Therefore, the terrazzo tile using natural ore can not have an advantage in the price competition with other construction materials such as polymer resin tile, porcelain tile used for the purpose such as terrazzo tile.

Therefore, if the sludge of the heavy metal wastewater mentioned at the beginning of the present invention can be recycled to produce black cera color balls and terrazotiles using the same, it may be superior in price competition with other construction materials as described above.

As a result of intensive research to solve these problems, the inventors have found that the heavy metal wastewater sludge, which has excellent absorption rate and compressive strength and low firing temperature, can reduce the manufacturing cost of the product and reduce environmental pollution. The present invention has been completed by developing a method of manufacturing black cera ball and artificial gravel of a black system and thus prepared colored cera ball and artificial gravel.

Accordingly, it is an object of the present invention to provide a method for producing black cera color balls and artificial gravel of a black system using sludge of heavy metal waste water by thermochemically stabilizing the sludge of heavy metal waste water, and to provide the colored cera ball and artificial gravel produced as described above. will be.

It is another object of the present invention to provide a terrazzo tile using a color-based color cerabol prepared according to the present invention.

The above and other objects, features and advantages of the present invention will be clearly understood by the following detailed description of the present invention.

1 is a schematic diagram showing a three-colored colored cera ball according to the present invention.

2 is an X-ray diffraction diagram of sludge calcined heavy metal wastewater calcined at 1000 ° C. for 2 hours.

3 is an X-ray diffraction diagram of a sludge calcined product of fluoric acid wastewater calcined at 1000 ° C. for 2 hours.

4 is an X-ray diffraction diagram of a fired product in which 40 wt% of the sludge of fluoric acid wastewater containing iron oxide is added to heavy metal wastewater sludge and calcined at 1100 ° C. for 2 hours.

The present invention provides a black-based color cera ball using sludge of heavy metal waste water according to the present invention, which satisfies all the conditions required for preparing color cera ball using sludge of heavy metal waste water and then recycling it to terrazotile. It is about how to.

According to the present invention, black color color balls can be produced by mixing the sludge of heavy metal wastewater with the sludge of fluoric acid wastewater containing a large amount of iron oxide or iron oxide as a stabilizer, and molding the mixture into a spherical or crushed form. have.

Iron oxide (Fe ₂ O ₃ ) used in the present invention reacts with metals such as calcium, aluminum, chromium, magnesium, zinc, and manganese at high temperature to form black and poorly soluble stable ferrite, and thus iron oxide in the sludge of heavy metal wastewater. Alternatively, when the sludge of the fluoric acid wastewater containing a large amount of iron oxide is added, not only the color of black is excellent but also the color-based cera ball of the black system in which heavy metal ions are not eluted in water. That is, Ca in the sludge reacts with Fe when heated to form a calcium-iron compound having a stable structure (CaFe ₂ O ₄ , 2CaO.Fe ₂ O ₃ ), and Cr also reacts with Fe to form a stable chromium-iron compound (( Cr.Fe) ₂ O ₃ , Cr _1.3 Fe _0.7 O ₃ ) to form.

For example, Ca and Fe form calcium ferrite (CaFe ₂ O ₄ ), which has the most stable spinel structure when present in a molar ratio of 1: 2, while Cr and Fe form stable compounds when present in 1: 1, As shown in Table 1, calcium and iron are present in a molar ratio of about 1: 1 in the sludge of heavy metal wastewater. Therefore, in order to stabilize the calcium and chromium in the sludge, it can be seen that the calcined body formed with a stable compound can be produced only by reducing the calcium and chromium content or increasing the iron content.

In the present invention, the iron oxide added to the sludge of the heavy metal wastewater preferably has a molar ratio of 2: 1 with calcium and chromium elements present in the sludge as described above. When iron oxide is mixed more than 2 times based on the molar ratio than the metal concentration contained in the sludge, the color cerabol is colored black red by extra iron oxide, and if the amount of iron oxide is less than this, it is colored black but calcium Elements such as and chromium are unstable and easily soluble in water. Therefore, the addition amount of iron oxide can be obtained by knowing the concentration of iron and metals other than iron present in the sludge, 10 to 30% by weight based on the weight of the sludge based on the water content of the sludge 10% by weight. . When the amount of iron oxide added is less than 10% by weight, calcium and chromium elements are present alone, and when it exceeds 30% by weight, calcium and chromium are stabilized, but the color of the color cerabol is changed to dark red.

The sludge of the fluoric acid wastewater used in the present invention is a sludge of the fluoric acid wastewater which is a by-product when treating fluoric acid, and is an electron tube factory, a semiconductor factory, a steel factory, a glass factory, a fertilizer factory, a light bulb factory which contains a lot of iron components. The by-product during the treatment of the wastewater discharged from the back, and the representative metal components thereof are measured using an atomic spectrometer.

TABLE 2

Metal Component Content of Sludge in Fluoric Acid Wastewater

As such, the sludge of the fluoric acid wastewater used in the present invention must be collected since fluoric acid is generated when the heating causes serious pollution. In case of using sludge of fluoric acid wastewater in sludge of heavy metal wastewater, when a small amount of feldspar or hydrated lime is used together, fluoric acid generated when heating the sludge of fluoric acid wastewater reacts with calcium oxide contained in ileite or hydrated lime to CaF ₂ . As a result, it is possible to suppress the generation of fluoric acid. The content of Fe in the fluoric acid wastewater containing a large amount of iron oxide is preferably 20 to 30% by weight based on 10% by weight of the water content of the sludge of the fluoric acid wastewater, and the amount of the sludge added to the fluoric acid wastewater is fluoric acid. Based on the water content of the sludge of the wastewater 10% by weight, and the water content of the sludge of the heavy metal wastewater 10% by weight, 30 to 50% by weight based on the weight of the sludge of the heavy metal wastewater is preferred. When the amount of sludge added to the fluoric acid wastewater containing iron oxide is less than 30% by weight, a part of calcium and chromium are present alone, and when the amount is more than 50% by weight, the color of the color cerabol becomes slightly red.

In addition, in the process of the present invention, when mixing a sludge of heavy metal wastewater with a stabilizer such as sludge of fluoric acid wastewater containing a large amount of iron oxide or iron oxide in order to increase the strength of the color ceramic ball, feldspar, clay (red clay ), Clay, kaolin, pottery minerals, fly ash, silica, magnesite, bauxite, waste glass, alumina and waste foundry sand, one or more materials selected from the group may be mixed together, the amount of which is added to the sludge of heavy metal wastewater. Preference is given to 10 to 60% by weight, based on the weight of the sludge, based on 10% by weight of moisture. If the amount of these added is less than 10% by weight of the color ceramic ball is low in the refractory degree, the molded body melt reaction occurs at a temperature of 1100 ℃, if the addition amount exceeds 60% by weight, the fire resistance increases but the strength of the black is weakened.

According to the invention, it is possible to produce terrazotiles which are advantageous in price competition with other existing construction materials using the color cerabol balls produced by the method according to the invention.

In addition, in order to freely configure the color and pattern of the terrazzo tile using the color cera ball, it is also possible to manufacture a color cera ball having a three-dimensional color by forming a spherical or crushed form and then coating and firing the desired material on the surface. have. The schematic diagram which shows the three-colored colored cera ball according to this invention is shown in FIG. By mixing the color cera ball prepared in this way with cement to form a terrazzo tile, and then polished through curing process, as shown in Figure 1, the three-dimensional color of the inner (black) and outer (desired color) is different A terrazzo tile having the same can be prepared. For example, the inside of the color ceramic ball is black, so that the molded body is immersed in a solution such as FeCl ₂ or FeSO ₄ and then fired to form iron oxide on the outside, which is changed to red. In addition, coating the existing glaze used in ceramic factories can change the color of the outside freely.

In the method according to the present invention, the calcining temperature of the color cerabol is preferably 900 ° C to 1200 ° C. If the calcining temperature is less than 900 ° C, the complete calcining reaction does not occur. This is not maintained.

As described above, the color-based color cera ball manufactured in accordance with the present invention and the color cera ball having a three-dimensional color are mixed with cement, aggregate, etc., molded, cured, and polished to have various three-dimensional patterns such as marble or porcelain tiles in natural state. When producing terazzo tiles, the choice of color ceramic balls, the type of cement, the type of additives, and the glossiness of polishing are also important factors.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Example 1

Stabilization confirmation test of sludge

Sludge from heavy metal wastewater containing 21.90 wt% Ca, 28.00 wt% Fe, 6.16 wt% Cr, 1.87 wt% Si, 1.34 wt% Na, 0.51 wt% Mg, 0.18 wt% Al and 0.15 wt% K. The crystal phase of the sludge fired material of the heavy metal wastewater calcined at 1000 ° C. for 2 hours was irradiated through an X-ray diffraction test (Rigaku X-ray diffractometer D / Max. II A), The results of testing the CaFe ₂ O ₄ crystals using the embedded Joint Committe on Powder Diffraction Standards (JCPDS) card are shown in FIG. 2. As can be seen from FIG. 2, it can be seen that the heavy metal wastewater sludge exists in the crystalline form of Ca-ferrite, which is a stable compound.

In order to confirm whether Ca and Cr are present stably, 5 g of each fired product calcined at 1000 ° C. for 2 hours was used to test the Cr dissolution test and the presence of free calcium. First, 5 g of the calcined product was put in 50 ml of 0.1 N hydrochloric acid solution, and heated for 30 minutes. After analyzing Cr eluted in the hydrochloric acid solution with an atomic absorption spectrometer, it was confirmed that 100 ppm of Cr was eluted. In addition, when the calcined product was put in ethylene glycol and maintained at 65 ° C. for 2 hours, 5 g of the calcined product was put in 100 ml of ethylene glycol and then maintained at 65 ° C. for 2 hours using the principle that free calcium was dissolved in ethylene glycol. After the eluted calcium was analyzed by atomic absorption spectroscopy, it was confirmed that 300 ppm of calcium was eluted.

Therefore, when the sludge alone was fired, it was found that at 1000 ° C., Ca did not form Ca ferrite 100%, a part of Fe was present as Fe ₂ O ₃ , and Cr was eluted, so that the sludge was not stabilized. .

Furthermore, even when the firing temperature was raised to 1100 ° C, the green color of Cr disappeared and the whole of the fired product turned black, but in the dissolution test, chromium was eluted and free calcium was not stabilized by steel mill sludge alone. Could know.

Example 2

Weight loss test according to the heating temperature of the sludge

The weight loss of the sludge of heavy metal wastewater having a water content of 10% by weight was measured by a thermal analyzer (DTA, TGA (Seico 5200)), and the measurement results are shown in Table 3 below.

TABLE 3

Weight loss according to the heating temperature of the sludge

From Table 3, the decomposition of water and organic matter occurs until the heating temperature is 400 ℃, the decomposition of the compound present in the form of a precipitate thereafter, the weight loss of the sludge is almost completed at 800 ℃, at a temperature thereafter It was found that the solid phase reaction of the oxides occurred.

Example 3

Addition test of stabilizer

The heavy metal wastewater sludge having a water content of about 50% by weight was dried to have a water content of 10% by weight, and 5 to 50% by weight of iron oxide was added to the dried sludge at intervals of 5% by weight based on the weight of the sludge. After uniformly mixing, the mixture was molded into a sphere having a diameter of about 2 cm, and then calcined at 1000 ° C. and 1100 ° C. for 2 hours and 4 hours to prepare a color cera ball. In each case, the color ceramic ball was pulverized to test for the dissolution of heavy metals and the presence of free calcium which caused the collapse of the building materials.

As a result, free calcium was not found when 10 wt% of iron oxide was added at 1000 ° C, but elution of heavy metals was confirmed in all experiments, and heavy metal was not eluted when 10 wt% of iron oxide was added at 1100 ° C and calcined for 2 hours. No free calcium was identified. And, when the iron oxide was added at least 30% by weight, the fired material began to have a red color, and when 50% by weight of iron oxide was added, the color of the fired product was completely changed to a reddish red color.

In addition, color cerabol was prepared in the same manner as described above, except that sludge (Table 2) of fluoric acid wastewater containing a large amount of iron oxide was added instead of iron oxide. Heavy metal dissolution test was carried out with the addition amount of the sludge of the fluoric acid wastewater was 20, 30, 40, 50% by weight, the firing temperature is 900 ℃, 1000 ℃, 1100 ℃, firing time 2 hours, 4 hours. As a result, heavy metals were not eluted from the fired product which 40 weight% and 50 weight% of fluoric acid wastewater sludges were added, and baked at 1100 degreeC for 2 hours and 4 hours. As a result of confirming the free calcium present in the calcined product, free calcium was not found in the calcined product added with 30, 40 or 50 wt% of fluoric acid wastewater sludge and calcined at 1100 ° C. for 2 hours and 4 hours.

From the results of the heavy metal dissolution test and the free calcium test, it was found that the most suitable conditions were the conditions in which 40% by weight of sludge of fluoric acid wastewater was added and calcined at 1100 ° C. for 2 hours. Therefore, to confirm the crystal phase of the fired product fired at 1100 ° C. for 2 hours, the fired product was ground and subjected to an X-ray diffraction test.

FIG. 3 is an X-ray diffractogram of a fluoric acid wastewater sludge containing a large amount of iron oxide at 1000 ° C. for 2 hours, and the crystal phases thereof were investigated. From this, it was found that the main crystal forms were CaF ₂ and Fe ₂ O ₃ . .

In addition, 40% by weight of fluoric acid wastewater sludge containing iron oxide was added to the heavy metal wastewater sludge discharged from the steel plant, and JCPDS (built in an X-ray diffractometer) was used to confirm the crystal form of the fired product fired at 1100 ° C for 2 hours. 4 shows the results of inspecting the fired material using the Joint Committe on Powder Diffraction Standards card. It can be seen that Cr _1.3 Fe _0.7 O ₃ is confirmed at about the same position as Ca-ferrite of FIG. 2. Therefore, it was found that the crystal form of the calcined product mixed with two kinds of sludge and calcined at 1100 ° C. for 2 hours was CaF ₂ , Fe ₂ O ₃ , Ca-ferrite, Cr _1.3 Fe _0.7 O ₃ .

In addition, the compressive strength and water absorption rate of the color cerabol prepared in this way and the color cerabol produced by firing at 1100 ° C. for 2 hours by adding 40% by weight of fluoric acid wastewater sludge and 30% by weight of clay to heavy metal wastewater sludge. The measurement is shown in Table 4 below.

TABLE 4

Physical Properties of Color Cera Ball According to Manufacturing Method

From the test results of Table 4, it can be seen that according to the present invention, a color cera ball having excellent absorption and compressive strength was prepared, and the physical properties of the color cera ball which was added at 30% by weight of clay and calcined at 1100 ° C. for 2 hours were clay. It was also found that the physical properties were superior to that of the colored cerabol prepared without the addition.

In addition, in addition to the above two cases, when the addition of ore, such as feldspar, quartz, pottery stone, kaolin 10 to 60% by weight also showed a tendency to increase the overall physical properties of the color cerabol like clay.

Example 4

How to color Carrasera ball three-dimensionally

Sludge of heavy metal wastewater and 30% and 50% by weight of sludge (Fe content: 21.30 wt%) of fluoric acid wastewater containing a large amount of iron oxide and iron oxide, respectively, are molded into spherical and crushed forms, It is coated with the existing blue glaze used in the factory. The molded product was calcined at 1100 ° C. and 1000 ° C. for 2 hours, respectively, to prepare a three-dimensional color cera ball having an inner black color and an outer blue color.

Thus prepared color cera ball mixed with cement to form a terrazzo tile and polished it, as shown in Figure 1 color cera ball has a three-dimensional pattern with a black color on the outside and a blue color on the outside.

Example 5

Durability Test of Color Cera Ball

In order to test what kind of durability the two color cerabols prepared in Example 3 are resistant to climate change, the color cera ball is soaked in water for 10 minutes and then directly at -50 ° C to 60 ° C at 60 minute intervals. The compressive strength was tested by keeping for 48 hours while moving. As a result, it was found that the two kinds of color ceramic balls had no change in compressive strength.

According to the present invention, it is possible to manufacture artificial gravel and color ceramic balls using sludge of heavy metal wastewater, and to prepare terrazoils used as building flooring materials using the prepared colored cera balls, manufactured according to the present invention. Synthetic gravel and color ceramic ball have low absorption rate, high compressive strength and excellent durability against temperature. In addition, it is also possible to produce a color cera ball having a three-dimensional color and a terrazzo tile using the same. Therefore, the waste treatment cost can be reduced by recycling the sludge of heavy metal wastewater without using natural black rock, which is economical and reduces environmental pollution, as well as color-based color ceramic ball and terrazotile with excellent physical properties. Can be prepared.

Claims (8)

Mixing heavy metal wastewater sludge with fluoric acid wastewater sludge containing iron oxide or iron oxide as a stabilizer, Shaping the mixture into spherical or crushed form, and Firing the molding Method for producing artificial gravel or color cerabol using heavy metal wastewater sludge comprising a. The method of claim 1, further comprising the step of coating the molding with a coating solution prior to firing the molding. 3. The heavy metal wastewater sludge according to claim 1 or 2, wherein the stabilizing agent is iron oxide, and the iron oxide addition amount is 10 to 30% by weight based on the weight of the heavy metal wastewater sludge, based on the water content of the heavy metal wastewater sludge 10% by weight. Method for producing artificial gravel or color cera ball. The fluoric acid wastewater sludge according to claim 1 or 2, wherein the stabilizer is a fluoric acid wastewater sludge containing iron oxide, and the content of Fe in the fluoric acid wastewater sludge is 20 to 30% by weight based on 10% by weight moisture content of the fluoric acid wastewater sludge. Method for manufacturing artificial gravel or color cerabol using heavy metal wastewater sludge having 30 to 50% by weight based on the weight of heavy metal wastewater sludge when the amount of the fluoric acid wastewater sludge is added based on the water content of the heavy metal wastewater sludge 10% by weight. . The method according to claim 1 or 2, wherein the firing temperature is 900 ° C to 1200 ° C. The group according to claim 1 or 2, wherein when the heavy metal wastewater sludge and the stabilizer are mixed, feldspar, clay, clay, kaolin, pottery mineral, fly ash, silica, magnesite, bauxite, waste glass, alumina and waste foundry sand Adding at least one material selected from 10 to 60% by weight, based on the weight of the heavy metal wastewater sludge, based on the water content of 10% by weight of the heavy metal wastewater sludge. Artificial gravel or color cerabol produced by the method according to any one of claims 1 to 6. The terrazzo tile using the color cera ball of Claim 7.