KR100875458B1 - Manufacturing method of sidewalk block using photocatalyst recovered from wastewater - Google Patents

Abstract

A manufacturing method of sidewalk block using an optical catalyst is provided to reuse resources by collecting and using titanium oxide from a by-product generated from a process of treating waste water and to cut down a manufacturing cost. A manufacturing method of sidewalk block(10) using an optical catalyst comprises steps of: collecting oxide titanium sintered powders by sintering an aggregate generated by a coagulant put in to remove an organic compound in waste water; molding a main body(11) by mixing aggregate, cement and water; molding a surface layer(15) on an upper part of the main body by mixing the cement, the sand and the water with the sintered powder; and curing the main body and the surface layer.

Description

Manufacturing method of sidewalk block using photocatalyst recovered from wastewater}

The present invention relates to a sidewalk block using a photocatalyst and a method of manufacturing the same, and more particularly, to continuously remove nitrogen oxides and organic compounds in the air by using titanium oxide powder recovered from a flocculant added to waste water to remove organic compounds. The present invention relates to a removable sidewalk block and a method of manufacturing the same.

Photocatalyst is a compound word of light and catalyst. Literally, light is used as an energy source to promote a catalytic reaction. As the photocatalyst, a semiconducting metal oxide or a sulfur compound is used.

Photocatalysts have been rapidly researched since 1972 when Fujishima and Honda announced that titanium dioxide single crystal electrodes were irradiated with light to separate water into hydrogen and oxygen by photooxidation and photoreduction reactions.

In a semiconductor, when a certain region of energy is applied, electrons are excited from the valence band to the conduction band. In other words, electrons are formed in the conduction band, and holes are formed in the valence band. The electrons and holes thus formed participate in oxidation and reduction reactions, respectively. Types of such photocatalysts include zinc oxide (ZnO), cadmium sulfide (CdS), titanium oxide (TiO 2), and the like, and titanium oxide is known to have the best activity. Zinc oxide and cadmium sulfide have a disadvantage in that the catalyst itself is decomposed to light by absorbing light to generate harmful zinc (Zn) and cadmium (Cd) ions.

On the other hand, titanium oxide can be used semi-permanently because it does not change even when it receives light, and has a higher oxidation power than chlorine (Cl2) or ozone (O3). It has the ability to prevent dirt.

As such, titanium oxide photocatalyst is superior to any other photocatalyst and has high whiteness / coloring ability. It is used to control the glossiness of paint, ink, plastic, paper, rubber and fiber, and to improve durability of chemical fiber and synthetic fiber and cosmetics. In the photocatalyst material such as sunscreen is most widely used.

Recently, photocatalyst coating poles are known to collect and adsorb external pollutants by coating a photocatalyst on concrete poles to reduce environmental pollution by automobile exhaust gas in the city center using the photocatalyst material.

In Korea Patent Publication No. 2001-0074099, a molded product obtained by mixing 50 to 80% of clay, 50 to 20% of clay, and 0.5 to 4% of graphite, and then plastically bonding after molding and drying is repeated 1 to 5 times in a titanium oxide solution. Disclosed is a clay block and a manufacturing method for producing a coating and applied molding by drying or heating the titanium oxide sol solution to a thickness of 1 ~ 3㎛ using a soak coating layer or spray apparatus It is.

However, in the above techniques, the photocatalyst sprayed or applied to the outer surface of the electric pole or the block is weak in durability and is removed within a short period of time, thereby shortening the lifespan and thus reducing the performance of removing automobile exhaust gas.

In addition, there is a problem that the production cost is greatly increased because the price of titanium oxide is expensive.

The present invention was created to improve the above problems, using a photocatalyst that can effectively remove air pollutants such as nitrogen oxides (NOx) by sunlight, but recovers titanium oxide from the by-products generated in the water treatment process of waste water The purpose of the present invention is to provide a sidewalk block and a method of manufacturing the same that can be used to reduce the recycling of resources and manufacturing costs.

Another object of the present invention is to provide a sidewalk block and a method of manufacturing the same, which is easy to work when constructing a sidewalk block on a road surface and can be firmly bound between blocks.

The sidewalk block using the photocatalyst recovered from the wastewater of the present invention for achieving the above object is formed including a titanium oxide sintered powder recovered by sintering agglomerates produced by a flocculant introduced to remove organic compounds in the wastewater. It is characterized by.

The flocculant is characterized in that any one hydrolyzable titanium compound selected from the group comprising titanium trichloride, titanium tetrachloride, titanyl sulfate, titanium sulfate, titanium oxalate and titanium iron sulfate.

The sidewalk block is characterized in that it comprises a main body and a surface layer formed on the upper portion of the main body to a predetermined thickness and containing the sintered powder.

The surface layer has a transverse cross-sectional area equal to the cross-sectional area of the main body, and the surface layer is formed to be eccentric from one side to the center across the transverse cross-section of the main body so that one edge of the surface layer protrudes outward from the side of the main body. The opposite edges of the protruding edges may be formed by being drawn inward from the side surface of the main body.

The side of the sidewalk block is provided with a coupling portion to be coupled to the adjacent sidewalk block facing the curved surface, the body is downward from the edge of the upper surface of the main body to be fitted with the adjacent sidewalk block body It is characterized in that it comprises a recessed portion which is stepped to form a step, and a protrusion formed on the edge opposite the recessed portion and having a shape corresponding to the recessed portion.

Method for producing a sidewalk block using the photocatalyst recovered from the wastewater of the present invention for achieving the above object is a recovery to recover the titanium oxide sintered powder by sintering the aggregate produced by the flocculant to remove the organic compounds in the wastewater Steps; A main body forming step of forming a main body by mixing aggregate, cement and water; A surface layer forming step of forming a surface layer on top of the main body by mixing cement, sand and water in the sintered powder; It characterized in that it comprises a; curing step of curing the main body and the surface layer.

The sintered powder in the recovery step is characterized in that the hydrolyzable titanium compound as a flocculant is added to a flocculation tank containing waste water to separate the aggregate formed by the flocculation reaction from the supernatant, and then the aggregate is recovered by sintering at 500 to 800 ° C. It is done.

As described above, according to the present invention, the photocatalyst photoactivated by the irradiation of sunlight can be contained in the block and adhered to the surface of the block or decompose and decompose harmful organic substances, nitrogen oxides, sulfur oxides, etc. in the air.

In addition, by using the photocatalyst recovered from the titanium compound used as a flocculant in the treatment of waste water, it can prevent secondary environmental pollution, recycle resources and reduce the manufacturing cost of the block.

In addition, the recovered titanium oxide powder is recovered in the form of an organic / inorganic element-doped metal oxide, and thus can be photoactivated under visible light as well as ultraviolet light, thereby greatly increasing the photocatalytic effect under sunlight.

In addition, since the sidewalk block of the present invention is coupled to each other between the adjacent blocks when construction on the road surface, the construction work is very easy and is firmly bound between the blocks.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the sidewalk block and the manufacturing method using a photocatalyst recovered from the waste water according to a preferred embodiment of the present invention.

Figure 1 is a schematic diagram showing a system for recovering titanium oxide applied in the present invention, Figure 2 is a graph showing the X-ray diffraction analysis of the recovered titanium oxide in Figure 1, Figure 3 is one of the present invention 4 is a perspective view illustrating a sidewalk block using a photocatalyst according to an embodiment, FIG. 4 is a perspective view illustrating a sidewalk block according to another embodiment of the present invention, and FIG. 5 is a longitudinal cross-sectional view of the sidewalk block of FIG. 4, FIGS. 6 and 7. Is a perspective view showing a sidewalk block according to another embodiment of the present invention.

The sidewalk block of the present invention uses the titanium oxide recovered from the aggregate produced by the flocculant added to remove the organic compound in the waste water as the photocatalytic material.

For example, the titanium oxide powder, water, sand, and cement may be mixed and molded into a rectangular shape to cure. In addition, water, sand, and cement are mixed to form a rectangle, and then the cured molding is immersed in a titanium oxide solution to form a coating layer on the entire surface of the molding, or a sol in which titanium oxide particles are dispersed using a spray device is formed on the surface of the molding. The block may be made by applying to a thickness of 1 to 3㎛ and then drying or heating.

Preferably, as shown in FIG. 3, a main body 11 and a surface layer 15 having a predetermined thickness on the upper part of the main body 11 are formed. In this case, the surface layer 15 is formed by mixing titanium oxide powder with water, sand, and cement. In addition, the surface layer 15 may be added to the pigment to produce a variety of colors, of course.

As described above, the surface layer 15 containing the photocatalytic material is formed on the block 10 exposed to the ground to improve the durability of the photocatalyst and reduce the manufacturing cost.

The sidewalk block of the present invention, when sunlight is irradiated to the surface layer, the surface layer reacts with moisture, oxygen, etc. in the air to generate active oxygen, the active oxygen is attached to the surface of the block harmful organic substances (VOC), nitrogen oxides (NOx) ), Sulfur oxides (SOx), NH ₃ The back is decomposed into water and carbon dioxide gas. It is possible to oxidize and remove air pollutants such as nitrogen oxides (NOx), which is a major component of automobile exhaust gas, and is effective in purifying automobile exhaust gas in urban air by this reaction.

And the sidewalk block of the present invention may have a shape shown in Figures 4 to 6 so that the construction work is easy during construction and can be firmly bound between the blocks.

4 and 5, the surface layer 25 formed to have a constant thickness on the upper portion of the main body 21 has a lateral cross-sectional area equal to that of the main body 21. The surface layer 25 is formed to be eccentric to one side at the center A of the transverse cross section of the main body 21. Accordingly, one edge 25a of the slope edges of the surface layer 25 protrudes outward from the side of the body 21, and the edge 25b of the surface layer opposite the protruding edge 25a is the side of the body 21. It is formed by drawing inwardly. In the example shown, the surface layer 25 is deflected to the rear side with respect to the center A across the transverse cross section of the main body. In addition, the surface layer may be deflected forward.

As another example, referring to FIG. 6, four sides of the sidewalk block are provided with a coupling part 41 to allow adjacent sidewalk blocks to be opposed to each other in a curved surface. And one side of the upper side of the main block 31 and one side of the upper side adjacent to the upper side of the main block 31 so as to be fitted into the recessed portion 45 is drawn downward from the edge of the upper surface of the main body 31 is formed The protrusion 43 having a shape corresponding to the recess 45 is formed at an edge opposite the recess 45.

Hereinafter, a method of manufacturing a sidewalk block using a photocatalyst according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3.

1. Titanium oxide recovery step

The recovery of titanium oxide, which is the biggest feature of the present invention, is recovered from the aggregate produced by the flocculant added to remove organic compounds in the waste water.

1 is a schematic view showing a system for recovering titanium oxide.

Referring to FIG. 1, sewage or waste water is supplied to the coagulation tank 1, and a hydrolyzable titanium compound is introduced into the coagulation tank 1 as a coagulant that coagulates with various organic substances contained in the waste water. The amount of flocculant added may be selected according to the degree of contamination of the wastewater.

And an acidic or basic compound for adjusting the pH of the waste water to an appropriate range may be added before or together with the titanium compound. Agglomeration tank 1 may be configured in various ways in addition to those shown, which is well known to those skilled in the art.

When a hydrolyzable titanium compound is added to waste water, it is hydrolyzed to coagulate with an organic compound or colloidal inorganic matter. By this aggregation reaction, aggregates 2 are produced.

Hydrolyzable titanium compounds useful as flocculants are usually provided in the form of chlorides, sulfates. Specifically examples of the hydrolyzable titanium compound include titanium trichloride, titanium tetrachloride, titanyl sulfate, titanium sulfate, titanium oxalate and titanium iron sulfate. These hydrolyzable titanium compounds have high cohesive efficiency of the waste water with dissolved organics.

Moreover, an iron coagulant or an aluminum coagulant can be mixed and used for the said titanium compound.

The aggregate and the supernatant are separated from the aggregate liquid in which the aggregate 2 is formed by the treatment of the flocculant.

The obtained aggregate is recovered as titanium oxide doped with organic and inorganic materials through a sintering process. According to a preferred embodiment of the present invention, the aggregate of the hydrolyzable titanium compound and the organic material provides titanium dioxide through sintering, wherein the sintering temperature is preferably 500 to 800 ° C. In particular, it is preferable that sintering temperature is 600 degreeC.

If the sintering temperature is less than 500 ° C., sintering is not performed properly and a black sintered body is obtained. And as the sintering temperature increases, the color of the sintered powder is changed from black to white. However, it is inefficient in terms of energy efficiency to perform sintering at a temperature in which the sintering temperature exceeds 800 ° C.

The titanium oxide sintered powder recovered as described above is used as a photocatalyst material in the present invention.

Photocatalyst is a substance having strong redox ability by ultraviolet light, and can sterilize, antibacterial, decompose, antifouling, and deodorize adhesion substances and air in the surface by photocatalytic action. In particular, anatase type titanium dioxide (TiO ₂ ) has advantages such as excellent photoactivity, light, chemical and durability. In general, when titanium dioxide is excited with light having a wavelength equal to or higher than the N-type semiconductor band gap, the reaction proceeds. The titanium dioxide has a band gap of about 3.2 eV and a wavelength of 380 nm or less, and reacts with ultraviolet light of 380 nm or less.

Particularly, in the present invention, titanium oxide doped with organic / inorganic materials, for example, by adding a small amount of iron, which is a transition metal, reduces the band gap energy of titanium dioxide and thus photocatalytic activity even at low energy wavelengths, that is, 400 nm or more visible light. It has the advantage to represent.

2. Molding Step

First, the body is formed by mixing sand, cement, and water. 100 to 600 parts by weight of sand based on 100 parts by weight of cement is mixed and then water is added to adjust the moisture. The above ratio may be arbitrarily adjusted, and may have a mixing ratio of conventional sidewalk blocks. The mixture is put into a vibratory pressure molding machine and then pressure molded to form a rectangular body.

Next, after the titanium oxide sintered powder obtained in the recovery step is mixed with sand and cement, water is added to adjust moisture. In this case, 100 to 600 parts by weight of sand and 5 to 25 parts by weight of titanium oxide sintered powder are mixed based on 100 parts by weight of cement. In addition to the surface layer may be added to 50 to 100 parts by weight of the pigment to the material to produce a variety of colors.

The mixture of the titanium oxide sintered powder is additionally added to the vibration press molding machine containing the main body and then press-molded to form a surface layer on the upper part of the main body. In this case, the thickness of the surface layer is preferably 6 to 10 mm.

3. Curing stage

When the main body and the surface layer is molded in a combined form in the forming step, it is taken out of the vibratory pressure molding machine and cured.

Curing can be carried out by a conventional curing method. For example, steam curing for 1 to 3 hours, and then naturally dried for 1 to 7 days.

Hereinafter, the manufacturing method of the present invention will be described through examples. However, the following examples are only for illustrating the present invention in detail, and the scope of the present invention is not limited to the following examples.

(Example)

Contaminated water with a concentration of 10.05 mg / L and pH 7.3 was transferred to a coagulation tank, and TiCl ₄ was added as 10.04 Ti-mg / L as a hydrolyzable titanium compound as a coagulant. Sintering was then performed at a temperature of 600 ° C. to recover the sintered powder of titanium oxide.

Then, the mixture for the main body, which mixed 400 parts by weight of sand and 40 parts by weight of water, was put in a mold having a size of 25 × 12.5 cm and vibrated, and then 350 parts by weight of sand based on 100 parts by weight of cement. The mixture for the surface layer mixed with 20 parts by weight of titanium sintered powder was put on the mixture for the main body, and covered with a template, and then press-molded with a pressing force of 0.25 kg / cm ² , a frequency of 3100 rpm, an amplitude of 1.4 mm, and a pressure vibration time of 4 seconds. The molded article was steam cured for 2 hours and then naturally dried for 5 days to prepare a 25 × 12.5 × 8 cm cuboid shaped sidewalk block having a thickness of 8 mm.

(Comparative Example)

A block was prepared in the same manner as in the above example, but pure titanium dioxide (TiO ₂ , P-25 of Degussa) powder was used as a photocatalyst.

Experimental Example 1 X-ray Diffraction Analysis

X-ray diffraction analysis was performed to confirm the crystal structure of the oxide recovered from the aggregates in the above example, and the results are shown in FIG. 2.

2 shows that the titanium oxide obtained by sintering at 600 ° C. is titanium dioxide having a crystal phase of anatase.

Experimental Example 2: Component Analysis

In the above example, the weight ratio of the components of the sintered titanium oxide was measured. Together with the results of the titanium oxide sintered at 200, 400, 500, 800 ℃ is also shown in Table 1 below.

 division  weight% 200 ℃ 400 ℃ 500 ℃ 600 ℃ 800 ℃ C 16.69 14.00 12.17 11.99 7.15 O 52.39 50.21 51.43 52.26 54.03 P 2.24 3.27 3.50 3.78 3.67 Ti 28.68 31.55 31.82 31.97 40.16 Etc Fe, Al, Cr, Cl, V, Si, S, Ca, Na, Ni

In the results of Table 1, the sintered powder of titanium oxide was doped with organic / inorganic elements, and in addition, it can be seen that trace amounts of Fe, Al, Cr, Cl, and V were doped. From this, titanium oxide doped with organic and inorganic materials, for example, by adding a small amount of transition metals such as iron, chromium, and nickel, thereby reducing band gap energy of titanium dioxide and having a low energy wavelength, that is, visible light of 400 nm or more. It can be seen that also has a photocatalytic activity.

The color of the sintered powder was black when the sintering temperature was lower than 500 ° C., but gradually changed to white as the temperature increased at 500 ° C. This seems to be due to residual organic matter.

Experimental Example 3 Photoactivity

NO ₂ to examine the photocatalytic effect of the sidewalk block according to the present invention The removal rate was measured.

The block of the above example was used as a test sphere. The block was placed in a reactor and then supplied with a simulated gas containing ₂ ppm of NO ₂ gas from the inlet. At this time, the 10W ultraviolet lamp was installed and 365 nm UV light was irradiated onto the surface layer of the block. The concentration of NO ₂ contained in the gas from the outlet of the reactor was measured and the results are shown in Table 2 below.

                   division NO ₂ Concentration (ppm)      4 hours later  8 hours later  12 hours later Test  1.292 0.876 0.610

As shown in Table 2, the concentration of NO ₂ , which was ₂ ppm at the beginning of the experiment, decreased to 0.61 ppm after about 12 hours. This is a result of about 70% reduction compared to the initial concentration.

Next, in order to examine the photoactivity of the photocatalyst under visible light, the photoactivity was measured by methylene blue decomposition experiment. As a test sphere, the surface layer of the sidewalk block of the Example was separated, and the surface layer of the sidewalk block of the Comparative Example was separated as a control, and cut to a size of 7.5 × 2.5 cm to prepare specimens. The sample was placed in 50 ml of a methylene blue solution diluted to a concentration of 5 ppm, and then the concentration of methylene blue was measured over time by irradiation with 450 nm ultraviolet light. The results are shown in Table 3 below.

   division              Methylene blue concentration (ppm)      4 hours later  8 hours later  12 hours later  Test 4.4 4.1 3.8 Control 5.0 4.9 4.9

As shown in Table 3, the control containing pure titanium oxide powder has little photoactivity in visible light.

On the other hand, the test zone containing titanium oxide powder doped with a transition metal, such as iron, can be found to be active under visible light, thereby decreasing the concentration of methylene blue. This reduces the band gap energy of titanium oxide, so that the photocatalyst is activated even at a low energy wavelength of 360 nm or less, so that the effect can be much increased compared to the photocatalyst activated only in ultraviolet light.

Although the present invention has been described with reference to the embodiments, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments are possible therefrom.

Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

1 is a schematic view showing a system for recovering titanium oxide applied in the present invention,

Figure 2 is a graph showing the X-ray diffraction analysis of the titanium oxide recovered in Figure 1,

3 is a perspective view illustrating a sidewalk block using a photocatalyst according to an embodiment of the present invention;

4 is a perspective view showing a sidewalk block according to another embodiment of the present invention,

5 is a longitudinal cross-sectional view of the sidewalk block of FIG.

6 and 7 are perspective views showing a sidewalk block according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1: flocculation tank 2: aggregate

11: body 15: surface layer

41: coupling portion 43: protrusion

45: concave

Claims (7)

delete delete delete delete delete A recovery step of recovering the titanium oxide sintered powder by sintering the aggregate produced by the flocculant introduced to remove the organic compound in the waste water; A main body forming step of forming a main body by mixing aggregate, cement and water; A surface layer forming step of forming a surface layer on top of the main body by mixing cement, sand and water in the sintered powder; Curing step of curing the main body and the surface layer; Method of manufacturing a sidewalk block using a photocatalyst comprising a. The method of claim 6, wherein the sintering powder of the recovery step is a coagulant is added to the hydrolyzable titanium compound into a coagulation tank containing waste water to separate the agglomerates formed by the coagulation reaction with the supernatant and then the agglomerates at 500 to 800 ℃ Method for producing a sidewalk block using a photocatalyst, characterized in that sintered and recovered.

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