KR101152382B1 - Manufacturing method of titanium oxide improved whiteness - Google Patents

Abstract

The present invention relates to a method for producing titanium oxide having improved whiteness, and more particularly, to remove white matters contained in titanium oxide obtained from waste sludge resulting from water treatment process of contaminated water such as sewage and wastewater. It relates to a method for producing titanium oxide that can be made.

The method for producing titanium oxide of the present invention comprises the first step of sintering agglomerates formed by adding a hydrolyzable titanium compound as a flocculant to contaminated water to obtain titanium oxide doped with organic / inorganic elements, and adding an aqueous alkali solution to the titanium oxide. The second step of dissolving the organic / inorganic element doped in the titanium oxide, the third step of washing by adding hydrochloric acid to the aqueous alkali solution, and the titanate separated in the third step is heated to 400 to 900 ℃ to the titanium oxide A fourth step of recovery is included.

Titanium oxide, sludge, recovery, whiteness,

Description

Manufacturing method of titanium oxide improved whiteness

The present invention relates to a method for producing titanium oxide having improved whiteness, and more particularly, to remove white matters contained in titanium oxide obtained from waste sludge resulting from water treatment process of contaminated water such as sewage and wastewater. It relates to a method for producing titanium oxide that can be made.

Titanium dioxide powder is thermodynamically stable, non-toxic, and has good whiteness and hiding power, so it is widely used as a raw material for white paints such as paint, plastic, and paper. In particular, rutile titanium dioxide has excellent UV protection ability, so it is used as a UV blocker for cosmetics, UV protection paint for cooling buildings and cars in summer, pigments such as plastics and textiles, and fillers for tires. It has high constant and refractive index, excellent oil adsorption and coloring power, and is chemically stable in strong acidity and strong basicity, so it is used for non-reflective coating film, beam splitter, lens additive of optical equipment.

In addition, recently, due to the ferroelectric properties of titanium dioxide, it is used as a base material of an electronic ceramic device, an oxide semiconductor, an oxygen sensor, and a filter material.

As a method for producing a general titanium dioxide powder, a sulfuric acid method, a chlorine method, a metal alkoxide method and the like are known. Sulfuric acid is a method of producing titanium dioxide by dissolving an ilmenite ore, a titanium-containing mineral, in sulfuric acid, followed by purification, hydrolysis, and calcining. Chlorine is a method using titanium tetrachloride. It is a method of producing titanium dioxide by oxidative decomposition through a reaction.

Since the sulfuric acid method and the chlorine method are excellent in economic efficiency, the most widely commercialized method is currently used in the production of titanium dioxide powders used as raw materials for pigments and cosmetics. However, the titanium dioxide powders produced by the sulfuric acid method and the chlorine method have strong specific aggregates during the heat treatment process by calcination even if the particle size is relatively large or small in particle size of about 100 to 1000 nm. It is known that the characteristics as a photocatalyst, which is greatly affected by particle size and specific surface area because of shrinkage, are not excellent.

Accordingly, in recent years, research has been conducted using a metal alkoxide method to produce titanium dioxide powder having finer particle size and well controlled aggregation state. Such alkoxide method is disclosed in Korean Patent Publication No. 89-8031, Japanese Patent JP96-338671 and the like.

The metal alkoxide method is a method of producing titanium dioxide powder by hydrolyzing an alkoxide (eg, titanium-tetra-ethoxide, etc.), which is an organic substance containing titanium metal (Ti), and then washing, separating, and crystallization. As a method, it has the advantage of producing an ultrafine powder, but on the other hand, there is a problem that the economical efficiency is significantly low because alkoxide, which is a starting material, is expensive.

Currently, commercially available anatase type titanium dioxide powder is the most known P25 from Daegu, and the powder is produced only in limited countries. In addition, some products are sold by dispersing the photocatalyst in water and ethanol for coating, but are sold at a high price because they are manufactured through a complex process as described above.

The present invention was created to improve the above problems, and recovers titanium from flocculant used in the water treatment process of contaminated water, such as sewage and wastewater, as a titanium source, and recycles the sludge resources discarded and doped the recovered titanium oxide. The purpose of the present invention is to provide a method for producing titanium oxide, which is excellent in quality and economically manufactured by removing the organic / inorganic elements that reduce the whiteness, thereby improving whiteness.

A method for producing the titanium oxide of the present invention for achieving the above object comprises the first step of sintering the aggregate formed by injecting a hydrolyzable titanium compound into the contaminated water as a flocculant to obtain a titanium oxide doped with organic / inorganic elements; Adding an aqueous alkali solution to the titanium oxide to dissolve organic / inorganic elements doped in the titanium oxide and heating the same in a reactor; A third step of washing by adding hydrochloric acid to the aqueous alkali solution; And a fourth step of recovering the titanium oxide by heating the titanate separated in the third step to 400 to 900 ° C.

The second step is characterized in that for heating the mixture of the titanium oxide and the alkaline aqueous solution in the reactor at 130 to 190 ℃ for 30 to 70 hours.

The alkaline aqueous solution of the second step is characterized in that any one selected from sodium hydroxide, potassium hydroxide, lithium hydroxide.

The hydrolyzable titanium compound of the first step is characterized in that at least one selected from titanium trichloride, titanium tetrachloride, titanyl sulfate, titanium sulfate, titanium oxysulfate and titanium iron sulfate.

As described above, according to the present invention, titanium dioxide is obtained by sintering titanium recovered from waste sludge generated from a water treatment process of contaminated water such as sewage and wastewater, thereby reducing the amount of waste sludge and recycling waste resources. .

In addition, since titanium dioxide is doped with titanium dioxide to remove various organic / inorganic elements that reduce whiteness, the whiteness is improved, and thus titanium dioxide having excellent quality can be manufactured.

Hereinafter, a method of manufacturing titanium oxide having improved whiteness according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

According to an aspect of the present invention, there is provided a method of preparing titanium oxide, the first step of obtaining a titanium oxide doped with organic / inorganic elements by sintering an aggregate formed by adding a hydrolyzable titanium compound as a flocculant to contaminated water, and the oxidation. An aqueous alkali solution is added to titanium to dissolve the organic / inorganic elements doped in the titanium oxide. A second step of heating in a reactor, a third step of adding hydrochloric acid to the aqueous alkali solution, and a fourth step of recovering titanium oxide by heating the titanate separated in the third step to 300 to 800 ° C. do.

Referring to FIG. 1, contaminated 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 contaminated water. The amount of flocculant added may be selected according to the degree of contamination of the contaminated water.

And an acidic or basic compound for adjusting the pH of the contaminated water may be added before or together with the hydrolyzable 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. By contaminated water herein is meant to include constant, sewage, heavy and waste water and other contaminated water where water treatment is required.

When a hydrolyzable titanium compound is added to contaminated water, it is hydrolyzed to coagulate with an organic compound or colloidal inorganic matter. By this aggregation reaction, precipitated aggregates 2 are formed in the lower portion of the aggregation tank. Agglomerate herein refers to sludge generated in a conventional water treatment process including the precipitation process by the flocculant.

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 oxysulfate and titanium iron sulfate. These hydrolyzable titanium compounds have a high aggregation efficiency of the contaminated water with the 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 separated aggregates are dehydrated to remove moisture. As a dehydration apparatus, a conventional belt press, a filter press, a screw decanter, a centrifuge, or the like can be used. At this time, in order to effectively lower the water content of the sludge can be dehydrated after the addition of a dehydration aid.

Next, dehydrated aggregates are sintered to obtain titanium oxide (TiO ₂ ). According to a preferred embodiment of the present invention, the aggregate provides titanium oxide through sintering, and the sintering temperature is preferably 300 to 800 ° C. If the sintering temperature is less than 300 ℃ sintering is not performed properly. 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.

In the sintering process, excess water and organic compounds are decomposed and removed, and titanium is oxidized to obtain titanium oxide. The titanium oxide obtained at this time is provided in the form doped with various organic / inorganic elements contained in the aggregate. Trace amounts of C, Na, Si, Al, Cr, Fe, P, Cl and the like are present as doped organic / inorganic elements. These organic and inorganic elements differ depending on the type of contaminated water and the type of flocculant.

Organic / inorganic elements doped with titanium oxide act as impurities to reduce the whiteness of the titanium oxide. Therefore, the following steps may be further performed to remove or reduce organic / inorganic elements doped with titanium oxide to improve whiteness.

First, a second step of adding an aqueous alkali solution to titanium oxide, dissolving an organic / inorganic element doped in titanium oxide in an alkaline solution and heating it in a reactor is performed. As the aqueous alkali solution, sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH) which are strongly alkaline are suitable. Since the removal efficiency of organic / inorganic elements varies depending on the concentration of the aqueous alkali solution, the concentration of the alkaline aqueous solution may be appropriately used. For example, it is preferable to apply a concentration of 10 M for aqueous sodium hydroxide and lithium hydroxide, and 14 M for aqueous potassium hydroxide solution.

Titanium oxide and various organic / inorganic elements are present in dissolved form in aqueous alkali solution. The aqueous alkali solution is added to the reaction vessel and then reacted by heating it sufficiently for 30 to 70 hours at a high temperature of 130 to 190 ° C. The reaction with the aqueous alkali solution may be carried out in a conventional autoclave. It is estimated that the titanate which the metal ion of alkaline aqueous solution couple | bonded by this reaction is formed.

The titanate is Na _x Ti _y O _Z when using sodium hydroxide as the aqueous alkali solution, K _x Ti _y O _Z when using potassium hydroxide, Li _x Ti _y O _Z when using lithium hydroxide. In particular, when using sodium hydroxide and potassium hydroxide, it is known that titanium oxide forms a multi-layered tube, an alkali metal is located in the inner space, and a hydroxyl group is located on the outer surface. In addition, various organic / inorganic elements dissolved in the alkaline solution in the second step are present in the inner space or the external solution of the tube, and thus can be easily removed in the washing process of the third step.

The titanate formed by the two step process is present in the form of metal ions in the alkaline aqueous solution combined. Since the metal is not easily removed by high temperature heating, it is preferable to replace the metal with hydrogen ions.

To this end, hydrochloric acid is added to the aqueous alkali solution and washed. The washing is performed by adding about 1 M hydrochloric acid to an aqueous alkali solution in which titanate is present, followed by stirring for a sufficient time. After the addition of hydrochloric acid, the pH can be adjusted to 1-2. By the washing process, a titanate (H _x Ti _y O _Z , typically H ₂ Ti ₃ O ₇ ) in which hydrogen ions of hydrochloric acid are substituted with an alkali metal bonded to titanate can be obtained. When the reaction is completed after washing with hydrochloric acid, wash 2-3 times with deionized water. After washing, the alkali metal and various organic / inorganic elements are separated from the titanate. The titanate may be heated at 300 to 800 ° C. to recover titanium oxide from which hydrogen has been removed, that is, titanium dioxide.

As described above, according to the present invention, titanium oxide having improved whiteness can be easily manufactured by removing organic / inorganic elements doped in titanium oxide separated from sludge. In addition, the titanium dioxide produced according to the present invention is produced in the form of a nano-sized tube, so it seems to have advantageous properties in mechanical strength, material storage, and the like compared to the titanium dioxide of the conventional spherical particles.

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples serve to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1

Contaminated water with a concentration of 10.05mg / L dissolved organic matter was transferred to a coagulation tank, and TiCl ₄ , a coagulant, was added to 10.04 Ti-mg / L to separate and dehydrate the aggregate formed by the coagulation reaction. Sintering for 3 hours at gave a sintered compact (TiO ₂ ) doped with organic / inorganic elements.

Then, the sintered compact was mixed with 10M aqueous sodium hydroxide solution, stirred, heated in an autoclave for 48 hours to form Na-titanate (Na _x Ti _y O _Z ), and then sufficiently stirred by adding 1M aqueous hydrochloric acid solution. Washed by. After washing with acid and washed again with deionized water, the separated H-titanate (H _x Ti _y O _Z ) was heated at 600 ° C. for about 2 hours in an electric furnace to finally prepare titanium dioxide.

Example 2

Titanium dioxide was prepared in the same manner as in Example 1, but K-titanate (K _x Ti _y O _Z ) was formed using an aqueous 14 M potassium hydroxide solution in an aqueous alkali solution, followed by washing with hydrochloric acid and washing with deionized water, followed by an electric furnace. Heated.

Example 3

Titanium dioxide was prepared in the same manner as in Example 1, but Li-titanate (Li _x Ti _y O _Z ) was formed using 10 M lithium hydroxide solution as an aqueous alkali solution, followed by washing with hydrochloric acid and washing with deionized water in an electric furnace. Heated.

Experimental Example 1 Properties of Sintered Body (TiO ₂ )

The XRD pattern of the sintered body obtained by sintering the aggregates at 300 ° C and 700 ° C in addition to 500 ° C in Example 1 was measured and the results are shown in FIG. 2.

In FIG. 2, (a) is a control graph as data of JCPDS of Anatase TiO ₂ , (b) is 300 ° C, (c) is 500 ° C, and (d) is a graph of a sintered body obtained by sintering at 700 ° C. Referring to Figure 2, it can be seen that the sintered body produced at each temperature is consistent with the Anatase TiO ₂ structure.

3 to 5 are SEM images of the sintered body sintered at each temperature. Figure 3 is 300 ℃, Figure 4 is 500 ℃, Figure 5 is a photograph of 700 ℃. As shown in the figure it can be seen that the TiO ₂ prepared in Example 1 are all in the form of uniform spherical particles.

And the results of analyzing the components of the sintered body manufactured at 500 ℃ by EDX (Energy Dispersive X-ray Spectroscopy) is shown in Table 1 below.

division weight% C 3.83 O 50.00 Na 1.15 Si 1.07 S 0.73 Ti 43.23 system 100.00

Looking at the results of Table 1, it can be seen that the main components of the sintered compact are Ti and O and contain trace amounts of organic and inorganic elements such as C, Na, Si, and S. As described above, it was confirmed that the sintered body is consistent with the structure of Anatase TiO ₂ in the graph of FIG. 2, which shows that organic / inorganic elements are doped independently of TiO ₂ without being independently formed in an oxide form. This doping of organic / inorganic elements reduces the whiteness of titanium dioxide.

On the other hand, when the sintering temperature was less than 500 ° C, the color of the sintered body was black, but gradually changed to white with increasing temperature at 500 ° C. This seems to be due to residual organic matter.

Experimental Example 2 Properties of Na, K, and Li-Titanate

Pictures of Na, K and Li-titanate produced in the autoclave in Examples 1 to 3 are shown in FIGS. 6 to 8, respectively.

6 to 8, it can be seen that Na-titanate and K-titanate are formed in a nano-sized tube shape, and Li-titanate is formed in a nano-sized sphere.

And the results of analyzing the components of Na- titanate, K- titanate, Li- titanate by EDX (Energy Dispersive X-ray Spectroscopy) to confirm the reduction rate of organic / inorganic elements are shown in Table 2 below.

weight(%) Ingredient Sintered body Na-titanate K-titanate Li-titanate C 3.83 5.92 14.18 6.17 O 50.00 30.86 47.23 47.60 Na 1.15 0.03 - - Si 1.07 0.03 0.25 0.39 S 0.73 - 0.48 - Ti 43.23 62.86 37.60 45.84 Etc K: 0.27

Looking at the results of Table 2 with the results of Table 1, it can be seen that elements such as Na, Si, S doped in the sintered body is greatly reduced or removed.

Experimental Example 3 Characteristics of Titanium Dioxide

The titanium dioxide finally prepared in Examples 1 and 3 is shown in FIGS. 9 to 11.

9 to 11, the titanium dioxide recovered by heating Na-titanate and K-titanate to a high temperature forms a nano-sized tube form compared to Na-titanate and K-titanate. It can be seen that. It is estimated that the nanotubes are collapsed and progress to the spherical titanium oxide structure. It appears to have a shape that when heated above 800 ° C. will be cut more finely and closer to the spherical shape.

And Li-titanate has a uniform particle shape of nano size.

In addition, nitrogen adsorption was performed to measure the specific surface area and the volume of the pores of titanium dioxide, and the results are shown in FIGS. 12 to 15. 12 is a graph of titanium dioxide obtained by sintering aggregates, and FIGS. 13 to 15 are graphs of titanium dioxide of Examples 1 to 3. FIG.

And the specific surface area and the volume of mesopore (mesopore) calculated by the BET equation is shown in Table 3 below. Control 1 is titanium dioxide obtained by sintering agglomerates, and control 2 is pure titanium dioxide (TiO ₂ , P-25 from Degussa).

division Specific surface area (m ² / g) Mesoporous volume (cm ³ / g) Example 1 368.7 0.534 Example 2 425.8 0.708 Example 3 271.4 0.325 Control 1 59.2 0.266 Control 2 50 0.25

Looking at the results of FIGS. 12 to 15 and Table 3, it can be seen that the titanium dioxide of Examples 1 to 3 has a large difference in the specific surface area and the volume of mesopore compared to the control 1 or 2. The large specific surface area means that the usefulness of titanium dioxide can be further increased.

Meanwhile, XRD patterns were measured to confirm the crystal structure of titanium dioxide, and the results are shown in FIG. 16. The XRD pattern results of Na-titanate, K-titanate and Li-titanate are shown in FIG. 17. 16 and 17, it can be seen that Na-titanate, K-titanate, and Li-titanate before firing have a titanate crystal structure, while titanium dioxide obtained after firing has an Anatase crystal structure.

As described above, the present invention has been described with reference to one embodiment shown in the drawings, which is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. .

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

1 is a view schematically showing a process of obtaining titanium oxide doped with organic / inorganic elements by sintering aggregates,

2 is a graph showing the XRD pattern of the sintered body sintered at each temperature,

3 to 5 are SEM pictures of the sintered body sintered at each temperature,

6 to 8 are SEM pictures of Na, K, Li-titanate,

9 to 11 are SEM pictures showing the titanium dioxide finally prepared in Examples 1 to 3,

12 to 15 are graphs showing nitrogen adsorption isotherms,

 16 and 17 are graphs showing XRD patterns of titanium dioxide.

Claims (4)

delete delete A first step of sintering the aggregate formed by adding TiCl ₄ , a hydrolyzable titanium compound as a flocculant, into contaminated water at 500 ° C. for 3 hours to obtain titanium oxide doped with organic / inorganic elements; An aqueous alkali solution is added to the titanium oxide to dissolve organic / inorganic elements doped in the titanium oxide. A second step of heating in the reactor; A third step of washing by adding hydrochloric acid to the aqueous alkali solution; And a fourth step of recovering titanium oxide by heating the titanate separated in the third step at 600 ° C. for 2 hours. The second step is to heat the mixture of the titanium oxide and the alkali aqueous solution in the reactor at 150 ℃ for 48 hours, The alkali aqueous solution of the second step is a method of producing titanium oxide, the whiteness is improved, characterized in that the aqueous potassium hydroxide solution. 4. The method of claim 3, wherein the titanium oxide recovered in the fourth step is formed in a nano-sized tube shape.

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