KR19990014546A - Manufacturing method of artificial gravel and color ceramics using sludge of heavy metal wastewater - Google Patents

Abstract

More particularly, the present invention relates to a method for manufacturing a building material by stabilizing sludge as a by-product after treating wastewater containing heavy metals, and a method for manufacturing a building material using the sludge For example, artificial gravel and color ceramics. The artificial gravels and color ceramics produced according to the present invention have low water absorption, high compressive strength, no heavy metal elution, and excellent black color. Therefore, it is possible to reduce the waste disposal cost by recycling the sludge of the heavy metal wastewater, thereby making it possible to produce artificial gravel and color ceramics having economic properties as well as environmental pollution and having excellent physical properties.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing building materials using sludge of heavy metal wastewater and a method of manufacturing building materials for civil engineering and construction by stabilizing sludge as a byproduct after treating wastewater containing heavy metals And a callacer ball used for making artificial gravel and terra cotta tiles used in place of gravel in concrete composed of such manufactured materials, for example, sand, cement, gravel and the like.

Wastewater discharged from steel plants, special steel plants, plating plants, and non-ferrous metals plants contains a large amount of heavy metals. In order to treat such wastewater and reduce the content of heavy metals to below the statutory limit, iron salts, aluminum salts, caustic soda , Slaked lime, and organic coagulants.

The sludge containing heavy metals as a by-product in the treatment of the heavy metal wastewater is produced by sedimentation and coagulation 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 ceramics, cracks occur, the color is unstable, thermochemically unstable, and the presence of free calcium And it is practically impossible to recycle them as artificial gravel and color sera balls since heavy metals are liable to be eluted. Furthermore, although the amount of heavy metal wastewater discharged is increasing day by day, research on the recycling of sludge has not yet achieved satisfactory results.

Therefore, at present, sludge as a byproduct after treatment of heavy metal wastewater is mostly disposed of in the form of waste. The landfilled sludge is reused and permeates into the soil, becoming a secondary source of pollution not only in soil and groundwater but also in rivers and oceans. In addition, the treatment of such sludge is costly and causes a rise in manufacturing cost. Therefore, there is a need to necessarily recycle the sludge.

The metal components of the representative heavy metal wastewater sludge used in the present invention were measured using an atomic absorption spectrometer.

Metal content of sludge of heavy metal wastewater ingredient Content (wt%) ingredient Content (wt%) Na 1.34 Ca 21.90 Al 0.18 Cr 6.16 Si 1.87 Fe 28.00 K 0.15 Mg 0.51

In Table 1, Si, Cr and Fe are components originating from wastewater in the production of special steels, and Al, Ca, Na, K and Mg originate from precipitants and flocculants added to treat heavy metal wastewater . (OH) ₃ , SiO ( ₂₎ , Cr (OH) ₃ , Fe (OH) ₃ , Na (OH) ₂ and the like can be considered as typical compounds that can be produced from such sludge, ₂ SO ₄ , Mg (OH) ₂ , and K ₂ SO ₄ , which change to the most stable compound form when heated at a high temperature.

Such sludge is produced by causing chemical and physical reaction to the heavy metal-containing wastewater as a precipitant, for example, by adding additives such as calcium hydroxide and a flocculant such as aluminum sulfate, iron salt, and precipitating agent such as polyacrylamide The sludge has a fine particle size 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, too much contraction occurs so that the weight loss is about 30%. As a result, cracks, bending phenomena, and the like occur in the formed body, so that it is not possible to hold the formed body of a certain shape. Therefore, it is practically impossible to manufacture color ceramics and synthetic gravel used for terra cotta by using such sludge alone.

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, and they exist in the form of unstable hydroxides mostly at normal temperature. Therefore, when the sludge is fired to produce black ceramics and artificial gravel, when free calcium (CaO) is present in the sintered body, the sludge reacts with moisture in the air to change into Ca (OH) ₂ , And it is possible that this construction material will cause a disaster when the building material is used in the building. In addition, Cr in the fired product is released from the color ceramics and artificial gravel to change the surface to green, and also causes Cr to be dissolved in water and pollute the environment.

In order to recycle the sludge of heavy metal wastewater using the cola ceramics used for the terrazzo and the artificial gravel used for the building material, the following four conditions are usually required to be satisfied. Since the characteristics are almost the same, the explanation about the artificial gravels is omitted below, and only the color ceramics will be described.

1) When the sludge is molded at a high temperature after molding in the shape of a round and a stripe, no pores should be generated inside the molded body.

2) The color cera ball manufactured should have a small absorption rate and a high compressive strength.

3) The prepared cola cerabol should not contain the calcium used as the precipitant of wastewater as calcium oxide (free calcium).

4) The prepared color ceramics should have good durability and should not release heavy metal ions.

On the other hand, terraced roof tile, which is a construction material for construction, is generally made of cement, aggregate, color gravel, marble sculpture, etc., and color gravel having color is used to give color to such terrazzo tiles. However, due to the scarcity of colored pebbles having color, color sera ball is mainly used now.

At present, Kalasera Ball is manufactured by finely grinding natural ores such as feldspar, stones, and quartz, mixing them with inorganic pigments, molding them into spherical or staggered shapes of various sizes, and firing them at high temperatures. Type color and size. ≪ Desc / Clms Page number 2 > In the case of using terracotta tiles with natural ceramics, natural ore is used, resulting in a high cost of raw materials and fuel because of the high firing temperature. Therefore, terrazzo tiles in which natural ores are used in this way have no advantage in price competition with other building materials such as polymer resin tiles and ceramic tiles used for terra cotta tires.

Therefore, if the sludge of the heavy metal wastewater mentioned in the introduction of the present invention can be recycled to produce black ceramics and terra cotta tiles using them, it can be advantageous in price competition with other construction materials as described above.

The inventors of the present invention have conducted diligent studies to solve these problems, and as a result, they have found that the sludge of heavy metal wastewater, which is excellent in water absorption and compression strength and can be reduced in production cost due to low sintering temperature, The present invention relates to a method for producing color sera balls and artificial gravels of the used black system, and to a method for producing the same.

Accordingly, it is an object of the present invention to provide a method of producing black calla lacra ball and artificial gravel using the sludge of heavy metal wastewater by thermochemically stabilizing the sludge of heavy metal wastewater, and a method of producing callacer ball and artificial gravel will be.

It is still another object of the present invention to provide a terrazzo tile using a black system color ceramics manufactured according to the present invention.

These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram showing a color cerabola colored sterically according to the present invention. Fig.

2 is an X-ray diffraction chart of a sludge sintered product of heavy metal wastewater fired at 1000 ° C for 2 hours.

3 is an X-ray diffraction chart of sludge calcination of fluoric acid wastewater fired at 1000 ° C for 2 hours.

Fig. 4 is an X-ray diffraction chart of a sintered product obtained by adding 40 wt% of sludge of hydrofluoric acid wastewater containing iron oxide to heavy metal wastewater sludge and firing at 1100 캜 for 2 hours.

The present invention relates to a method for producing a color system of black color using a sludge of a heavy metal waste water according to the present invention which satisfies all the requirements for producing a color sera ball using sludge of heavy metal wastewater and then recycling it as a terazotilla .

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

The 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 temperatures to form a stable ferrite having black color, Or sludge of fluoric acid wastewater containing a large amount of iron oxide is added, it is possible to obtain a black system color sera ball not only having a good black color but also eliminating heavy metal ions into water. That is, Ca in the sludge reacts with Fe during heating to form a calcium-iron compound (CaFe ₂ O ₄ , 2CaO.Fe ₂ O ₃ ) having a stable structure, 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 ).

For example, when Ca and Fe are present in a molar ratio of 1: 2, they form calcium ferrite (CaFe ₂ O ₄ ) having the most stable spinel structure. When Cr and Fe are present in a ratio of 1: 1, As shown in Table 1, calcium and iron exist in a molar ratio of about 1: 1 in the sludge of the heavy metal wastewater. Therefore, in order to stabilize calcium and chromium in the sludge, it is possible to produce a sintered body having a stable compound by decreasing the content of calcium and chromium in the sludge or increasing the content of iron.

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 the calcium and chromium elements present in the sludge as described above. When the iron oxide is mixed more than two times based on the molar ratio of the metal contained in the sludge, the color of the ceraser ball is reddish by the extra iron oxide. If the amount of the iron oxide is less than that, Elements such as chromium are unstable and are likely to elute in water. Therefore, the addition amount of iron oxide can be obtained by knowing the concentrations of metals other than iron and iron present in the sludge, and is preferably 10 to 30% by weight based on the weight of the sludge based on 10% by weight of the water content of the sludge . When the added amount of iron oxide is less than 10% by weight, calcium and chromium elements exist alone, while when it exceeds 30% by weight, calcium and chromium are stabilized, but the color of calcerabol is changed to dark red.

The sludge of fluoric acid wastewater used in the present invention is a sludge of fluoric acid wastewater produced as a by-product in the treatment of fluoric acid. The sludge of fluoric acid wastewater used in the present invention is a sludge of an iron tube, a semiconductor factory, a steel factory, a glass factory, And the representative metal components thereof are measured using an atomic absorption spectrometer. The results are shown in Table 2 below. ≪ tb > < TABLE >

Metal content of sludge of fluoric acid wastewater ingredient Content (wt%) ingredient Content (wt%) Si 3.21 K 0.12 Al 4.51 Na 0.99 Fe 21.30 Mg 0.51 Ca 23.90

As described above, the sludge of fluoric acid wastewater used in the present invention must be collected because it generates severe acid pollution by generating fluoric acid when heated. When the sludge of heavy metal wastewater is used, sludge of fluoric acid wastewater is used, and when a small amount of the sludge or calcium hydroxide is used together, the fluoric acid generated when the fluoric acid wastewater is heated reacts with calcium oxide contained in the caustic soda or calcium hydroxide to change into CaF ₂ The generation of fluoric acid can be suppressed. The Fe content 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 addition amount of the sludge of the fluoric acid wastewater is fluoric acid It is preferable that 30 to 50% by weight, based on the weight of the sludge of the heavy metal waste water, is based on 10% by weight of the sludge of the waste water and 10% by weight of the water content of the sludge of the heavy metal waste water. When the addition amount of sludge of fluoric acid wastewater containing iron oxide is less than 30% by weight, a part of calcium and chromium exists alone, and when the addition amount exceeds 50% by weight, the color of cera cerabol changes to a slightly red color.

Further, in the method of the present invention, when the stabilizer such as sludge of fluoric acid wastewater containing a large amount of iron oxide or iron oxide is mixed with the sludge of heavy metal wastewater to increase the strength of color sera ball, feldspar, clay ), At least one material selected from the group consisting of clay, kaolin, tungsten mineral, fly ash, silica, magnesite, bauxite, waste glass, alumina and waste paper sand may be mixed together, Is preferably 10 to 60% by weight based on the weight of the sludge, based on 10% by weight of the water content of the sludge. When the amount of the additive is less than 10% by weight, the refractory of the color ceramic is low, so that the molded article undergoes a melting reaction even at a temperature of 1,100 ° C. When the added amount exceeds 60% by weight, the fire resistance is increased but the strength of black is weakened.

According to the present invention, terra cotta tiles can be produced which are advantageous in price competition with existing other construction materials by using the color ceramics manufactured by the method according to the present invention.

In addition, in order to freely construct the color and pattern of the terazotile using the color ceramics, it is possible to form a spherical or fale-like shape, then coat the desired material on the surface and firing to produce a color ceramics having three- have. Fig. 1 is a schematic view showing a color cerabola colored three-dimensionally according to the present invention. The color ceramics produced by the above method are mixed with cement to form terazo tiles, and then subjected to a curing process to polish the ceramics tiles. As a result, as shown in FIG. 1, three-dimensional colors (for example, Can be produced. For example, when the inside of the color ceramics is black, the molded body is immersed in a solution such as FeCl ₂ or FeSO _4, and then fired, thereby forming iron oxide on the outside and changing to red. In addition, coating the existing glaze used in the ceramics factory, you can freely change the color outside.

In the method according to the present invention, the calcination temperature of the calcined ceramics is preferably from 900 to 1200 ° C. If the calcination temperature is less than 900 ° C., the complete calcination reaction does not occur. If the calcination temperature exceeds 1200 ° C., Is not maintained.

As described above, the color system of the black color system manufactured according to the present invention and the color system ceramic color system having the three-dimensional color are mixed with cement, aggregate, etc., molded, cured and polished to form a three- The choice of color ceramics, the type of cement, the type of additive, and the degree of polish during polishing are also important factors in the production of terazo tiles in the form of tiles.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples.

Example 1

Sludge stabilization confirmation test

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

In order to confirm the presence of Ca and Cr stably, 5 g of sintered calcined at 1000 ° C for 2 hours were taken out to test for Cr elution and presence of free calcium. First, 5 g of the sintered material was placed in 50 ml of 0.1 N hydrochloric acid solution, heated for 30 minutes, and analyzed by atomic absorption spectrometry for Cr eluted in hydrochloric acid solution. As a result, it was confirmed that Cr of 100 ppm was eluted. Further, when the sintered material is placed in ethylene glycol and kept at 65 ° C for 2 hours, 5 g of the sintered material is put into 100 ml of ethylene glycol using the principle that free calcium is dissolved in ethylene glycol, and then kept at 65 ° C for 2 hours and then eluted Analysis of the extracted calcium by atomic absorption spectroscopy confirmed that 300 ppm of calcium was eluted.

Therefore, when the sludge is calcined alone, Ca does not form Ca-ferrite at 100 ° C at 100 ° C, part of Fe is present as Fe ₂ O ₃ , Cr is eluted, and the sludge is not stabilized there was.

In addition, even when the firing temperature was elevated to 1100 ° C, the green color of Cr disappeared and the entire sintered material changed to black. However, since the chrome eluted from the elution test and free calcium was also present, the steel sludge alone was not stabilized Could know.

Example 2

Weight loss test according to heating temperature of sludge

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

Weight reduction according to heating temperature of sludge Heating temperature (℃) 400 500 600 700 800 900 1000 1100 Weight loss (% by weight) 15 18 19 20 21 22 23 23

From Table 3, it can be seen that the decomposition of water and organic matter takes place at a heating temperature of up to 400 ° C, and the decomposition of compounds present in the form of precipitates occurs after that. At 800 ° C, the weight loss of sludge is almost completed, The solid phase reaction of the oxides occurred.

Example 3

Addition test of stabilizer

Heavy metal wastewater sludge having a moisture content of about 50 wt% is dried to a moisture content of 10 wt%, and iron oxide is added to the dried sludge based on the weight of the sludge at 5 wt% to 5 wt% After uniformly mixing, the mixture was molded into a sphere having a diameter of about 2 cm, and then fired at 1000 ° C and 1100 ° C for 2 hours and 4 hours to prepare a color ceramics. In each case, the color ceramics were pulverized to test for the presence of free calcium, which is responsible for the heavy metal release test and disintegration of the building materials.

As a result of the test, when the iron oxide was added at 10% by weight, the free calcium was not present, but the elution of the heavy metal was confirmed in all experiments. When the iron oxide was added at 10% by weight at 1100 ° C. for 2 hours, No free calcium was found. When the iron oxide was added in an amount of 30 wt% or more, the fired product started to show a red color, and when 50 wt% was added, the color of the fired product changed to dark red.

In addition, a color sera ball was prepared in the same manner as above except that sludge of fluoric acid wastewater containing a large amount of iron oxide instead of iron oxide (Table 2) was added. The heavy metal leaching test was carried out at sintering temperatures of 900 ° C., 1000 ° C. and 1100 ° C. for 20, 30, 40 and 50 wt% of the sludge of the fluoric acid wastewater, and for 2 hours and 4 hours for sintering. As a result, heavy metals were not eluted from the sintered product obtained by adding 40 wt% and 50 wt% of fluoric acid wastewater sludge and baking at 1100 캜 for 2 hours and 4 hours. As a result of checking the free calcium present in the sludge, free calcium was not found in the calcined sludge containing 30, 40 and 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 leaching test and the free calcium test, it was found that the most favorable condition was that 40 wt% of fluoric acid wastewater sludge was added and calcined at 1100 ° C for 2 hours. Therefore, in order to confirm the crystal phase of the calcined product calcined at 1100 ° C for 2 hours, the calcined product was pulverized and subjected to an X-ray diffraction test.

FIG. 3 is an X-ray diffraction chart showing the crystal phase of fired fluorinated wastewater sludge containing a large amount of iron oxide at 1000 ° C. for 2 hours, from which it can be seen that the main crystal form is CaF ₂ and Fe ₂ O ₃ .

In order to confirm the crystal form of the calcined sludge by adding 40 wt% sludge of hydrofluoric acid wastewater containing iron oxide to the heavy metal waste sludge discharged from the steel mill and heating at 1100 ° C for 2 hours, the JCPDS (Joint Committee on Power Diffraction Standards) card. It can be seen that Cr _1.3 Fe _0.7 O ₃ is confirmed at almost the same position as Ca-ferrite in FIG. 2. Therefore, it was found that the sintered product obtained by calcining the two kinds of sludge at 1100 ° C for 2 hours was CaF ₂ , Fe ₂ O ₃ , Ca-ferrite and Cr _1.3 Fe _0.7 O ₃ .

Further, by adding 40 wt% of fluoric acid wastewater sludge and 30 wt% of clay to the thus-prepared color serabol and heavy metal wastewater sludge, the compression strength and the water absorption of the color ceramics produced by firing at 1100 ° C for 2 hours The results are shown in Table 4 below.

Physical properties of color ceramics according to manufacturing method Manufacturing method of calacera ball Water absorption (% by weight) Compressive strength (Kg _f / cm ²⁾ Adding 40 wt% of fluoric acid wastewater sludge to heavy metal wastewater sludge, calcining at 1100 ° C for 2 hours 8 370 40 wt% of fluoric acid wastewater sludge and 30 wt% of clay were added to heavy metal wastewater sludge, and sintering was carried out at 1100 캜 for 2 hours 5 390

From the test results in Table 4, it can be seen that the color ceramics having excellent water absorption and compression strength were produced according to the present invention, and the physical properties of the color ceramics obtained by adding 30% by weight of clay and firing at 1100 ° C for 2 hours, It was also found that the physical properties were better than those of the color ceramics prepared without the addition of the coloring agent.

In addition to the above two cases, when 10 to 60% by weight of feldspar, such as feldspar, zircon, stover, kaolin and the like, is added, the physical properties of the color ceramics tends to increase as in the case of adding clay.

Example 4

A method of three-dimensionally coloring ceracella balls

Sludge of heavy metal wastewater and 30 wt% and 50 wt% of sludge (Fe content: 21.30 wt%) of fluoric acid wastewater containing a large amount of iron oxide and iron oxide, respectively, were mixed and molded into spherical and fissured forms, It coated the existing blue glaze used in the factory. These molded products were fired at 1100 ° C and 1000 ° C for 2 hours, respectively, to produce three-dimensional color ceramics having a black color on the inside and a blue color on the outside.

The thus prepared color ceramics were mixed with cement to make terazo tiles and then polished. As shown in FIG. 1, the color ceramics had a three-dimensional pattern with black inside and outside blue.

Example 5

Durability test of calacera ball

In order to test the durability of the two types of coloraser balls prepared in Example 3, the coloraser balls were immersed in water for 10 minutes and then immediately moved at 50 캜 to 60 캜 for 60 minutes And the compressive strength was tested by keeping it for 48 hours. As a result, it was found that the two kinds of color ceramics had no change in compressive strength at all.

According to the present invention, artificial gravel and color ceramics are manufactured using sludge of heavy metal wastewater, and the terra cotta tiles used as building flooring materials can be manufactured using the color ceramics manufactured as described above. According to the present invention The manufactured artificial gravel and color ceramics have low water absorption, high compressive strength, and excellent durability against temperature. In addition, color ceramics having stereoscopic hue and terazotile using them can be prepared. Therefore, it is possible to reduce the waste disposal cost by recycling the sludge of the heavy metal wastewater without using the natural black rock, and it is possible to reduce the environmental pollution economically, and also, it is possible to use the black synthetic artificial gravel, The tile can be manufactured. It has been found that when 10 wt% to 20 wt% of heavy metal wastewater sludge is mixed with limestone as a cement raw material by using the principle of artificial gravel and fired at a high temperature of 1300 ° C, a kling car having excellent physical properties is formed, It was confirmed that the same properties as those of the existing cement were exhibited.

Claims (9)

Mixing heavy metal waste wastewater sludge with fluoric acid wastewater sludge containing iron oxide or iron oxide as stabilizing agent; Molding the mixture into spherical or falcon shapes; And a step of firing the molded product. The method of manufacturing synthetic gravel or color ceramics using the heavy metal wastewater sludge. The method of claim 1, further comprising coating the molded product with a coating solution before firing the molded product. The method according to claim 1 or 2, wherein the stabilizer is iron oxide, and the amount of iron oxide added is 10 to 30% by weight based on the weight of the heavy metal waste wastewater sludge based on 10% by weight of the moisture content of the heavy metal waste wastewater sludge A method for producing artificial gravel or color ceramics using heavy metal wastewater sludge. The fluorinated acid sludge according to claim 1 or 2, wherein the stabilizer is fluoric acid wastewater sludge containing iron oxide, wherein the content of Fe in the fluoric acid wastewater sludge is 20 to 30 And the amount of the fluoric acid wastewater sludge is 30 to 50% by weight based on the weight of the heavy metal wastewater sludge based on 10% by weight of the water content of the heavy metal wastewater sludge. Or a method for producing callacerol. The method for producing artificial gravel or color ceramics using heavy metal waste water sludge according to claim 1 or 2, wherein the calcination temperature is 900 ° C to 1200 ° C. The method according to any one of claims 1 to 3, wherein the mixing of the heavy metal waste wastewater sludge and the stabilizer is carried out by mixing the stabilizer with the heavy metal wastewater sludge, wherein the stabilizer is selected from the group consisting of feldspar, clay, clay, kaolin, tungsten mineral, fly ash, silica, magnesite, By weight based on the weight of the heavy metal wastewater sludge, based on 10% by weight of the water content of the heavy metal waste wastewater sludge, and then mixing the two or more substances selected from the heavy metal wastewater sludge together. Gravel or calla cera ball. An artificial gravel or callacer ball produced by the method according to claim 1 or 2 A terazo tile using the color sera ball according to claim 7 A method for producing a cement clinker at 1200 to 1300 占 폚 by adding 10 to 20% by weight of heavy metal wastewater sludge.