TWI428183B - Preparation of Modified Titanium Dioxide with Better Degradation Efficiency - Google Patents

Description

Process for improving modified titanium dioxide with better degradation efficiency

The invention relates to a method for preparing modified titanium dioxide, in particular to a method for preparing modified titanium dioxide with a specific proportion of metal and having better degradation efficiency.

In recent years, the industry and commerce have flourished, and the environmental pollution problems have become more and more serious. Among them, organic matter is a major source of pollution. Although there are environmentally friendly treatment procedures for degradable organic matter, the existing treatment procedures are mainly carried out by adsorption and sedimentation. It is easy to produce a lot of waste, which causes a burden on the treatment.

Photocatalyst is a substance that can be driven by light energy. If a photocatalyst that can directly use visible light such as solar energy can be produced, it will be closer to the "green earth" target. Due to its high photoactivity, stable chemical properties, thermal properties, corrosion resistance and non-toxicity, titanium dioxide has opened up the study of using semiconductors as photocatalysts and effectively decomposing organic pollutants. After the n-type semiconductor titania is irradiated with incident light having an energy greater than the energy band gap, the valence band electrons can transition to the conduction band to generate electron/hole separation. Due to the action of the space charge layer, the hole moves toward the interface, and the hole can interact with the adsorbed water molecules or hydroxide ions to generate a highly oxidizing hydroxyl radical (OH‧), which is extremely oxidizing. Strong hydroxyl radicals (OH‧) oxidatively decompose organic matter in water. Since the electrons located in the conduction band cannot cross the space energy difference of the space charge layer, the reduction reaction cannot occur, and therefore the organic matter oxidized by the hole does not reversely react with electrons, thereby achieving the purpose of effectively decomposing harmful organic substances in the water.

However, the main absorption wavelength of titanium dioxide photocatalyst is concentrated in the ultraviolet region, and the proportion of ultraviolet light in sunlight is only about 5%, which is harmful to the human body, and thus is not an ideal source of light energy. In order to enhance the practicality and economic value of titanium dioxide as a photocatalyst, many studies have developed titanium dioxide having visible light absorbing ability. The "Method for Producing Metal Implanted Titanium Dioxide Nanotubes" disclosed in the Patent Application No. 096144718 of the Republic of China, the "Metal/TiO2 Slurry and Photocatalyst Material Manufacturing Method" disclosed in No. 97140988, and the Invention No. 951158135 The "TiO2 visible light photocatalyst and its manufacturing method" disclosed in the patent application respectively have a function of absorbing visible light by implanting or adding metal in titanium dioxide by different manufacturing methods. In addition, the existing literature, for example, "Zhu J., Chen F., Zhang J., Chenb H., Anpo M. (2006) "Fe ³⁺ -TiO ₂ photocatalysts prepared by combining sol-gel method with hydrothermal treatment and their Characterization", Journal of Photochemistry and Photobiology A: Chemistry Vol. 180,196-204." and "Karthik, K., Kesava Pandian, S., Victor Jaya N., (2010) Effect of nickel doping on structural, optical and electrical properties Applied TiO ₂ nanoparticles by sol-gel method. Applied Surface Science 256, 6829-6833" also discloses the preparation of a titanium dioxide photocatalyst containing iron or nickel by a sol-gel method, and having a content capable of absorbing visible light for degradation. As described above, although titanium dioxide photocatalyst capable of absorbing visible light has been successfully produced, in view of the demand for processing a large amount of organic pollutants, there is still a need to continuously develop a modified titanium dioxide photocatalyst having better visible light degradation efficiency. Practical needs and economic benefits of rapidly processing large amounts of organic pollutants.

Accordingly, it is an object of the present invention to provide a process for producing modified titanium dioxide having improved degradation efficiency which is capable of improving the visible light absorption value and having stable quality while meeting practical needs and economical benefits.

Thus, the method for preparing modified titanium dioxide having better degradation efficiency of the present invention comprises the following steps:

(A) mixing anhydrous ethanol with deionized water and adding a polyvinyl alcohol compound to form a premix;

(B) adding a monoprotic acid aqueous solution, a metal salt compound containing a doping metal, and a titanium dioxide precursor to the premix, mixing and stirring uniformly to obtain a pre-gelling mixture, wherein the doping The metal is iron or nickel, and when the doping metal is iron, the doping metal is used in an amount of 0.05 to 0.5 parts by weight based on 100 parts by weight of titanium in the titanium dioxide precursor, when the doping metal is In the case of nickel, the doping metal is used in an amount of 5 to 15 parts by weight based on 100 parts by weight of titanium in the titanium dioxide precursor;

(C) subjecting the pre-molecule mixture to a heating step to obtain a jelly;

(D) subjecting the gum to a high temperature sintering step to obtain a metal-doped modified titanium dioxide crystal.

The invention has the beneficial effects that the present invention utilizes a sol-gel method to produce modified titanium dioxide having visible light absorbing ability, and by limiting the type of doping metal and the ratio of the amount of the doping metal to titanium in the manufacturing process, The modified titanium dioxide produced can produce excellent degradation efficiency under the visible light of different light sources, thereby enabling more efficient and rapid processing efficiency when actually applied to the treatment of organic pollutants, and thus the present invention The method of preparation helps to obtain high-performance modified titanium dioxide products, which not only meets market demand and economic benefits, but also is very suitable for the development of industrially mass-produced and modified titanium dioxide, and thus has practical value.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Referring to Figure 1, a preferred embodiment of the process for producing modified titanium dioxide having preferred degradation efficiency of the present invention comprises the steps of: step 101 is mixing anhydrous ethanol with deionized water, and adding a polyvinyl alcohol compound to form a premix. Things.

Step 102 is: adding a monoprotic acid aqueous solution, a metal salt compound containing a doping metal, and a titanium dioxide precursor to the premix, mixing and stirring uniformly to obtain a pre-molten mixture, wherein the doping The metal is iron or nickel, and when the doping metal is iron, the amount of the doping metal is preferably 0.05 to 0.5 parts by weight based on 100 parts by weight of titanium in the titanium dioxide precursor, and most preferably 0.1 parts by weight, when the doping metal is nickel, the amount of the doping metal is preferably 5 to 15 parts by weight, and most preferably 10 parts by weight, based on 100 parts by weight of titanium in the titanium dioxide precursor. . The metal salt compounds used in this example were respectively iron nitrate and nickel nitrate.

Among them, the monobasic acid aqueous solution is preferably selected from an aqueous hydrochloric acid solution, an aqueous acetic acid solution or an aqueous solution of nitric acid. In the present embodiment, an aqueous hydrochloric acid solution is selected. The titania precursor is preferably selected from titanium isopropoxide (titanium (IV) isopropoxide), Titanium tetrachloride (TiCl _4, titanium tetrachloride) titanium or tetra-propyl alcohol oxygen (titanium tetraisopropoxide, simply referred to as TTIP), in In this embodiment, titanium isopropoxide is used as the titanium dioxide precursor.

In step 103, the pre-gelatinized mixture is subjected to a heating step to obtain a gel. In this embodiment, the oil bath is heated by using eucalyptus oil, and the pre-gel mixture is heated at a temperature of 60 ° C / hour, and heating is continued at the temperature when the temperature is raised to 110 ° C until the pre-heating The gelation mixture is gelled to obtain the gel, and heating can be stopped.

In step 104, the gel is subjected to a high temperature sintering step to obtain a metal-doped modified titanium dioxide crystal. Wherein, in order to obtain a titanium dioxide crystal having a preferred photocatalytic activity, high temperature sintering of the jelly is preferably carried out at a temperature of 400 ° C to 600 ° C, and in this embodiment, at a temperature of 400 ° C. The high temperature sintering is performed thereon, and the time for high temperature sintering is preferably 4 hours.

In step 105, the modified titanium dioxide crystal is subjected to a grinding step to obtain a doped metal modified titanium dioxide powder.

Hereinafter, the modified titanium dioxide produced by the process of the present invention will be described in a number of specific examples, and compared with unmodified pure titanium dioxide and commercially available commercial titanium dioxide (P-25, Degussa Co.), respectively, and further illustrated. The modified titanium dioxide obtained by the method of the present invention differs in appearance morphology, adsorption capacity and photocatalytic ability to organic pollutants, and degradation of organic matter under visible light source with pure titanium dioxide.

In the following specific examples, salicylic acid is selected as the target of pollution. Salicylic acid is an organic pollutant that appears in industrial wastewater such as papermaking, cosmetics, incineration ash and effluent, because of its chemical structure. The aromatic ring is not easy to be decomposed, and intermediate products such as catechol and polyhydroxy sanitizer are produced in the process of photocatalytic degradation. Therefore, when the degradation experiment is carried out, the salicylic acid removal rate and salicylate are simultaneously applied. The acid mineralization rate is evaluated. Wherein, the mineralization rate refers to the ratio of the organic compound to the inorganic compound in the salicylic acid, and the salicylic acid is determined by measuring the concentration of the dissolved organic carbon remaining in the test solution. Mineralization rate. Among them, the salicylic acid concentration is measured by using an ultraviolet/visible spectrophotometer (λ=298 nm) and the salicylic acid calibration line is prepared, and the dissolved organic carbon concentration is determined by the method of the inspection method number NIEA W531.51C. The method is tested. The calculations related to the degradation efficiency of salicylic acid in the following specific examples are calculated according to the formulas (21) to (24):

SA degradation efficiency:

SA residual percentage:

Percentage of intermediate product generation:

Mineralization percentage:

Wherein C ₀ : initial concentration of salicylic acid (mgL ^-1 );

C _t : residual concentration of salicylic acid at time t (mgL ^-1 );

C _{0 (as C)} : initial concentration of salicylic acid expressed as the concentration of organic carbon (mgL ^-1 );

C _{t(as C)} : the residual concentration of SA at time t, expressed as the concentration of organic carbon (mgL ^-1 );

DOC _t : residual organic carbon concentration (mgL ^-1 ) at time t.

In addition, referring to FIG. 2, a schematic diagram of a constant temperature light box device 3 used for illuminating a light source in the following specific examples, all tests are performed at a temperature of 25 ° C. The constant temperature light box device 3 has a configuration for accommodating. a quartz reaction tank 31 of a predetermined concentration of salicylic acid solution, and eight tubes 32 disposed at equal intervals around the quartz reaction tank 31, each of the tubes 32 and the quartz reaction tank 31 are maintained at equal intervals, and the lamps are The light source of the tube 32 can be replaced with a visible light tube or a fluorescent tube, respectively, depending on the purpose of the experiment.

< Specific Example-1 Comparison of Photocatalytic Ability of Pure Titanium Dioxide Prepared by the Process of the Present Invention and Commercially Available Titanium Dioxide P-25 >

(1-1) Background experiment of oxidizing salicylic acid by light source alone: preparing a solution with salicylic acid concentration of 10 mgL ^-1 and pH=4, and its temperature is 25 °C, with UV-A (365 nm) light source Irradiation, the reaction time is 0-180 min, no added titanium dioxide, the experimental results show that the salicylic acid concentration in the solution does not decrease, so the removal rate is 0, it can be seen that the salicylic acid alone is not degraded by ultraviolet light irradiation. Occurred, it showed that salicylic acid was extremely stable after being irradiated by ultraviolet light. Therefore, the photodegradation of salicylic acid was neglected in the subsequent experiments.

(1-2) Preparation of pure titanium dioxide: 14 ml of absolute ethanol is mixed with 1 ml of deionized water, and 1 g of polyvinyl alcohol compound is added to be mixed as a premix, and the premix is subjected to oil bath with eucalyptus oil (30 ° C Then, add 2.5 ml of HCl to mix, then add 5 ml of titanium isopropoxide, and stir for 30 minutes, then take out the magnet, then gradually raise the temperature to 110 ° C in an oil bath, and continue heating until a dry white gum is obtained. The gum was placed in a high temperature furnace and heated at 400 ° C for 4 hours to form titanium dioxide crystals, and finally pure titanium dioxide powder p was obtained by grinding.

(1-3) Comparison of adsorption capacity : Prepare 2 parts of salicylic acid concentration 10 mgL ^-1 and pH=4, and the temperature is 25 °C, respectively (1-2) prepared titanium dioxide powder p and commercial Titanium dioxide P-25 was added to the above solution, the addition amount was 0.5 gL ^-1 , the adsorption reaction time was 0-180 minutes, and neither of them was irradiated with ultraviolet light. The results showed that salicylic acid in the solution increased with time. There are cases of reduction, and the measurement shows that the salicylic acid removal rates of titanium dioxide p and commercial titanium dioxide P-25 prepared by the method of the present invention are 30.1% and 18.2%, respectively, that is, both kinds of titanium dioxide have adsorption conditions, The adsorption capacity of the pure titanium dioxide p produced by the process of the invention is superior to that of the commercial titanium dioxide P-25.

(1-4) Comparison of photocatalytic ability : the same as (1-3), only the ultraviolet light source is irradiated with the salicylic acid solution during the reaction time, and the result shows that the pure titanium oxide p produced by the method of the present invention Commercial titanium dioxide P-25 completely destroyed salicylic acid within 120 min. From the comparison results of (1-3) and (1-4), it is known that the titanium dioxide produced by the process of the present invention has the adsorption capacity and photocatalytic ability comparable to commercially available commercial titanium dioxide, and accordingly, the process of the present invention is Titanium dioxide conforming to commercial specifications is produced, and has practical value for industrial manufacturing.

< Specific Example-2 Comparison of Appearance and Specific Surface Area of Pure Titanium Dioxide and Modified Titanium Dioxide Prepared by the Process of the Present Invention >

(2-1) Preparation of pure titanium dioxide: It is exactly the same as that described in (1-2), and will not be described again here, and finally pure titanium oxide powder p can be obtained.

(2-2) Preparation of modified titanium dioxide doped with iron: 14 ml of absolute ethanol is mixed with 1 ml of deionized water, and 1 g of polyvinyl alcohol compound is added to be mixed as a premix, and the premix is oiled with eucalyptus oil. Bath (30 ° C), add HCl 2.5ml mixed, and add doped metal, here is the addition of ferric nitrate (Fe (NO ₃ ) ₃ ‧9H ₂ O, purity 99%, Merck) mixed, then, add 5 ml of titanium isopropoxide, after stirring for 30 minutes, the magnet was taken out, and then gradually heated to 110 ° C in an oil bath, and heating was continued until a dry white gum was obtained, and then the gel was placed in a high temperature furnace and heated at 400 ° C. It was shaped into titanium dioxide crystals in 4 hours, and finally, iron-doped modified titanium dioxide powder was obtained by grinding. The amount of iron nitrate added is equivalent to 0.01, 0.05, 0.1, 0.5 parts by weight, respectively, based on the amount of titanium in titanium isopropoxide, and a1, a2, respectively. A3 and a4 four modified titanium oxynitride powders. In the present example, 5 ml of titanium isopropoxide has a weight equivalent to 5 g, and accordingly, the amount of titanium can be calculated by matching the purity of the titanium isopropoxide, and the amount of iron to be added can be calculated from the amount of titanium. Then, the amount of iron, the purity of iron nitrate and the proportion of iron in iron nitrate can be used to obtain the amount of ferric nitrate to be added separately. This calculation process is well known to those skilled in the relevant art, and is not detailed here. Said.

(2-3) Preparation of modified titanium dioxide doped with nickel: the same method as (2-2) except that the ferric nitrate was changed to nickel nitrate (Ni(NO ₃ ) ₂ ‧6H ₂ O, 98%, Alfa Aesar) . Wherein the amount of nickel added is 100 parts by weight of titanium in titanium isopropoxide, and the amount of nickel added is equivalent to 1, 5, 10, and 15 parts by weight, respectively, and b1 and b2 are respectively prepared. , b3 and b4 four modified titanium oxide powder. The calculation process is also well known to those skilled in the art and is easy to be extrapolated, and will not be described in detail herein.

Result analysis:

(2-4) The pure titanium dioxide prepared by (2-1), (2-2), and (2-3) and the modified titanium dioxide a1, a2, a3, and a4 doped with iron are modified by doping nickel. Titanium dioxide b1, b2, b3 and b4 were observed by SEM microscopy (here, using field emission electron scanning microscopy with EDS function, FE-SEM/EDS, model JSM-7401F, brand JEOL), and respectively The specific surface area was calculated using a BET surface analyzer (model ASAP2020, branded micromeritic).

As shown in Fig. 3, the iron-modified titanium dioxide a1, a2, a3 and a4 can be observed from the SEM image, and the particle size is the same as that of the unmodified pure titanium dioxide p, which is about 15-20 nm, and the particles are approximately round. Spherical. The nickel-doped modified titanium dioxides b1, b2, b3 and b4 have the same particle size as the unmodified pure titanium dioxide, and there is no significant difference from the iron-modified titanium dioxide photocatalyst, and the particle size is also 15- Around 20 nm, the particles are approximately spherical. Although the SEM image shows that the particle size of the unmodified and doped metal modified titanium dioxide photocatalyst does not change significantly, comparing the image of FIG. 3, it can be seen that the metal-doped modified titanium dioxide has a particle aggregation phenomenon that is not modified. The titanium dioxide is obvious. In order to further confirm that the modified titanium dioxide produced by the above method does contain a doping metal, the modified titanium dioxide a4 and b4 doped with iron and nickel are further analyzed by an energy dispersive spectrometer (EDS), and the result is shown in FIG. 4(I). As shown in (II), the peak signal of the added metal appears on the two EDS maps, and it can be seen that the modified titanium dioxide a4 and b4 catalysts are indeed embedded with iron and nickel. From this, it was confirmed that the modified titanium oxide produced by the process of the present invention was doped with an added metal, respectively.

As shown in Table-1 below, it can be seen that the modified titanium dioxide photocatalyst with iron has a specific surface area of about 90-95 m ² /g, and the modified titanium dioxide photocatalyst with nickel has a specific surface area of about 98-103 m ² / g, according to this, compared with the titanium dioxide p without added metal, the modified titanium dioxide photocatalysts a1~a4 and b1~b4 added with iron and nickel have a slight increase in the comparative surface area, and in addition, the specific surface area of commercial titanium dioxide P-25 It is only 50 m ² /g. It is obvious that the specific surface area of the modified titanium dioxide photocatalyst added with iron or nickel prepared by the present invention is much higher than that of the commercial P-25.

(2-5) Analysis by X-ray powder diffractometer (model Rigaku-TTR AXIII, manufacturer: Japan) (2-1), (2-2), (2-3) The obtained pure titanium dioxide and iron-doped modified titanium oxides a1, a2, a3 and a4 are doped with nickel-modified titanium dioxides b1, b2, b3 and b4.

Before referring to the results of the analysis, it should be added that titanium dioxide has three common crystal structures, namely anatase, rutile and brookite. Because of its unstable structure, brookite is a metastable phase and is rarely used. Rutile and anatase are widely used. Although the two are of the same crystal system, the former has a denser structure, relative density and refractive index. High, so rutile has good shielding properties against ultraviolet light, and is often used in anti-ultraviolet light materials. Among the three crystal structures, the photocatalytic activity of anatase is better. Therefore, if the XRD analysis results show anatase The more pronounced the crystal phase of the ore, the better the photocatalytic activity of the titanium dioxide product should provide better degradation efficiency.

The results are shown in the XRD patterns of Fig. 5 and Fig. 6. The XRD pattern is indicated by A, which is the position where the main peak of the anatase crystal phase appears. It can be seen that the preparation at the sintering temperature of 400 °C has not been changed. The quality or modification of titanium dioxide photocatalyst, the crystal phase analysis at 2 deg / min scanning rate, and then with the JCPDS database in the XRD instrument (this database is a database for collecting various crystal phases of titanium dioxide, can be used as It is confirmed that the titanium dioxide powder produced by the method only exhibits a single crystal phase of anatase, and no rutile is found. (rutile) crystal phase, according to which the modified titanium dioxide produced at a sintering temperature of 400 ° C has a crystal phase which is mainly anatase. In addition, the results of the EDS spectrum indicate that the transition metal ions added in the present invention have been doped in the modified titanium dioxide, and the diffraction peaks of any transition metal oxides are not found in the XRD pattern, further illustrating that The transition metal oxides such as iron and nickel do not aggregate on the surface of the modified titanium dioxide photocatalyst to form crystal grains of the metal oxide, and it is explained that the transition metal should be highly embedded in the internal structure of the titanium dioxide crystal, or even replace the part. Titanium position.

<Specific Example-3 Degradation Experiment of Modified Titanium Dioxide with Different Doped Iron Ratios>

(3-1) Background experiment of oxidizing salicylic acid by different light sources separately: preparing a solution with salicylic acid concentration of 10 mgL ^-1 and pH=4, and the temperature is 25 °C, without adding titanium dioxide, respectively The visible light, fluorescent lamp and sunlight are used as the light source, and the reaction time is 0-180 min. The experimental results show that the salicylic acid concentration in the solution does not decrease regardless of the light source used, so the removal rate is 0. It can be seen that the salicylic acid alone is not degraded by different light sources, indicating that the salicylic acid is different. The light source is extremely stable after irradiation, so the photodegradation of salicylic acid can be ignored in the subsequent experiments.

(3-2) Background experiment of adsorbing salicylic acid with iron-doped modified titanium dioxide alone: preparing 5 parts of salicylic acid concentration 10 mgL ^-1 and pH=4, and the temperature is 25 °C, respectively <Specific Example-1> The titanium dioxide powder p prepared in (1-2) and the four modified titanium dioxide powders a1 and a2 doped with different ratios of iron prepared in (2-2) of <Specific Example-2> A3 and a4 were respectively added to the above solution, and the addition amount was 0.5 gL ^-1 , and the adsorption reaction time was 0 to 180 minutes, and no light source irradiation was provided.

The results showed that the salicylic acid in the solution decreased with the increase of time, and there was no significant difference in the salicylic acid removal rate between the pure titanium dioxide and the modified titanium dioxide powder doped with different proportions of iron, all of which were 32%. This shows that the modified titanium dioxide doped with iron has no significant improvement in its adsorption capacity compared to pure titanium dioxide without undoped metal.

(3-3) Experiment of degrading salicylic acid under the visible light of modified titanium dioxide doped with iron: Prepare 5 parts of salicylic acid with a concentration of 10 mgL ^-1 and pH=4, and the temperature is 25 °C, respectively (1-2) The prepared titanium dioxide powder p and the four kinds of modified titanium dioxide powders a1, a2, a3 and a4 doped with different proportions of iron prepared by (2-2) are respectively added to the above solution, and the addition amount thereof is For 0.5 gL ^-1 , the reaction time was 9 hours, and the constant temperature illumination device 3 as shown in Fig. 2 was used to continuously provide visible light irradiation during the reaction. Among them, the visible light lamp label used is DiDai, the model is PL-S, the specification is 13W/BLUE, the wavelength range is 400 nm~500 nm, and the illumination intensity of a single tube is 5.2 W/m ² , which is used in this embodiment. The constant temperature light box device 3 is provided with 8 lamps, each of which has a distance of 5 cm from the quartz reaction tank 31 and an average light intensity of 30 W/m ² .

The results are shown in Fig. 7 (I). After the pure titanium dioxide p and the modified iron oxides a1, a2, a3 and a4 of different iron ratios degrade the salicylic acid under visible light for 9 hours, the residual ratio of salicylic acid with the reaction time Gradually, after removing the residual rate by 100%, the removal rate of salicylic acid was obtained, which were 58.8%, 63%, 75.9%, 100%, and 78.8%, respectively. Among them, the removal rate of a3 (that is, the modified titanium dioxide prepared by the weight ratio of iron to titanium is 0.1:100) is the best, up to 100%, and it is obvious that the amount of titanium in the titanium precursor is 100 weight. In the case where the amount of iron in the iron salt compound to be added is controlled to 0.1 part by weight, the modified titanium oxide having the best degradation efficiency can be obtained, and in addition, the removal rates of salicylic acid are superior to a1, a2 and a4. p, the modified titanium dioxide exhibiting iron-doped degradation of salicylic acid is better than unmodified titanium dioxide. Among them, when the weight ratio of iron to titanium is increased to 0.5:100, the salicylic acid removal rate is decreased, indicating that although the appropriate amount of modified metal will capture the electrons generated by the excitation of titanium dioxide, reduce electrons and holes. The probability of combination makes it effectively separate, thereby enhancing the catalytic activity of the titanium dioxide photocatalyst, but the excessive metal addition may cause the metal to deposit on the surface of the catalyst and become the center of recombination of the electron hole, which in turn causes the catalytic activity of the titanium dioxide photocatalyst to decrease.

Further analysis of the mineralization rate of the salicylic acid solution with different titanium dioxide added in 0-9 hours, the results show that the dissolved organic carbon residues detected in the salicylic acid solution are shown in Fig. 7 (II). The concentration (DOC) decreased with time, and the mineralization rates of pure titanium dioxide p and different iron ratios of modified titanium dioxide a1, a2, a3 and a4 after degrading salicylic acid under visible light for 9 hours were 48.43%, 53.76% and 66.61, respectively. %, 92.98%, 71.94%. Among them, the mineralization rate of a3 (the modified titanium dioxide prepared at a weight ratio of iron to titanium of 0.1:100) is also the best.

(3-4) Experiment of degrading salicylic acid with fluorescent modified titanium dioxide under fluorescent lamp: The experimental method is exactly the same as (3-3), and the test is also carried out using the constant temperature light box device 3 shown in Fig. 2, The lamps 32 were replaced with fluorescent tubes, and the illumination and reaction time were extended to 24 hours. Among them, the fluorescent tube label used is PHILIPS, the model is PL-S, 13W/865, the wavelength range is 400 nm~700 nm, and the illumination intensity of a single tube is 12 W/m ² , and the quartz reaction tank 31 is subject to such The average light intensity of the tube 32 was 46.5 W/m ² .

As a result, as shown in (I) of FIG. 8, the removal rate of salicylic acid was 67.83% after pure titanium dioxide p and modified iron oxides a1, a2, a3 and a4 of different iron ratios were degraded by salicylic acid for 24 hours under fluorescent lamps, respectively. , 73.77%, 90.79%, 100%, 86.89%. Among them, the removal rate of a3 (the modified titanium dioxide prepared by the weight ratio of iron and titanium is 0.1:100) is the best, up to 100%, and the removal of salicylic acid by a1, a2 and a4 The rate is also better than p, indicating that the modified titanium dioxide-doped titanium dioxide has better degradation efficiency for salicylic acid than unmodified titanium dioxide.

Further analysis of the mineralization rate of salicylic acid solution with different titanium dioxide added in 0-24 hours, the results show that the dissolved organic carbon detected in the salicylic acid solution is shown in Fig. 8 (II). The residual concentration (DOC) decreased with time, and the mineralization rates of pure titanium dioxide p and different iron ratios of modified titanium dioxide a1, a2, a3 and a4 after degrading salicylic acid under fluorescent lamp for 24 hours were 44.86% and 55.60%, respectively. 78.79%, 89.64%, 70.07%. Among them, the mineralization rate of a3 is still the best, similar to the removal rate.

(3-5) Experiment of degrading salicylic acid by modified titanium dioxide in sunlight: preparing 5 parts of salicylic acid concentration 10 mgL ^-1 and pH=4, and the temperature is 25 °C, respectively The titanium dioxide powder p prepared in (1-2) and the four modified titanium dioxide powders a1, a2, a3 and a4 doped with different ratios of iron prepared in (2-2) are respectively added to the above solution, and then They were respectively poured into a quartz reaction tank and placed directly outdoors for sunlight. During the experiment, the sunlight intensity was recorded by the solar light intensity meter. The measurement results showed that the average light intensity during the experiment was about 880~. 950 W/m ² .

As a result, as shown in (I) of Fig. 9, the removal rate of salicylic acid was 59 after pure titanium dioxide p and modified iron oxides a1, a2, a3 and a4 of different iron ratios were degraded by salicylic acid for 3 hours under sunlight. %, 78.6%, 96.80%, 100%, 97.8%. Among them, the removal rate of a3 (the modified titanium dioxide prepared by the weight ratio of iron and titanium is 0.1:100) is the best, up to 100%, and the removal of salicylic acid by a1, a2 and a4 The rate is also better than p, according to which it is better to modify the salicylic acid than the unmodified titanium dioxide.

Further analyzing the mineralization rate of salicylic acid solution with different titanium dioxide added in 0-24 hours, the results show that the dissolved organic carbon detected in the salicylic acid solution is shown in Fig. 9 (II). The residual concentration (DOC) decreased with time, and the mineralization rates of pure titanium dioxide p and different iron ratios of modified titanium dioxide a1, a2, a3 and a4 after degrading salicylic acid under sunlight for 3 hours were 45.51% and 66.95%, respectively. , 90.03%, 94.07%, 93.26%. Among them, the mineralization rate of a3 is still the best.

(3-6) Comprehensive comparison of salicylic acid degradation efficiency of modified titanium dioxide doped with different light sources: four kinds of unmodified titanium dioxide powders measured by (3-3)~(3-5) The salicylic acid removal rate and mineralization rate of the modified titanium dioxide powders a1, a2, a3 and a4 doped with different proportions of iron under different light sources for 3 hours were arranged into Fig. 10(I), (II). ) to understand the photocatalytic degradation of salicylic acid under different light sources. It can be seen from Fig. 10(I) that under the sunlight as the light source, the photocatalytic salicylic acid can achieve 100% removal rate within 3 hours of removal rate, and the fluorescent lamp and visible light removal rate are lower than the sun. Light. Among them, the removal rate of modified titanium dioxide a3 under different light sources is the best, it is obvious that the ratio of iron to titanium in a3 is the ratio with the best degradation efficiency, while the other modified titanium dioxide a1, a2 and a4 are added to the water. The degradation efficiency of salicylic acid is better than that of unmodified titanium dioxide p. It can be seen from (II) of Fig. 10 that the mineralization rate of the modified titanium dioxide a3 under photocatalytic salicylic acid for 3 hours under sunlight is 94.1%, and the removal rate and mineralization rate of degraded salicylic acid under different light sources are A3 is the best. In addition, the above results also indicate that when the modified titanium dioxide is produced, when the metal in the metal salt compound is iron, and the amount of titanium in the titanium precursor is 0.1:100, the optimum degradation efficiency can be obtained. Modified titanium dioxide

<Specific Example-4 Degradation Experiment of Modified Titanium Dioxide with Different Nickel Ratios>

(4-1) Background experiment of adsorbing salicylic acid with nickel-doped modified titanium dioxide alone: Prepare 5 parts of salicylic acid concentration 10 mgL ^-1 and pH=4, and the temperature is 25 °C, respectively (1-2) The prepared titanium dioxide powder p and the four kinds of modified titanium dioxide powders b1, b2, b3 and b4 doped with different ratios of nickel (2-3) are respectively added to the above solution, and the addition amount is 0.5 gL ^-1 , adsorption reaction time is 0-180 minutes, and no light source is provided.

The results showed that the salicylic acid in the solution decreased with time, and the salicylic acid removal rate of pure titanium dioxide and modified titanium dioxide powder doped with different proportions of nickel did not differ significantly, both were 32%. This shows that the modified titanium dioxide doped with nickel has no significant improvement in adsorption capacity compared to pure titanium dioxide without undoped metal.

(4-2) Experiment of degrading salicylic acid under visible light with modified titanium dioxide: The experimental conditions and methods are the same as those described in (3-3) of <Specific Example-3> , but will be added a modified titanium dioxide photocatalyst acid solution were changed to <specific Example-1> of the (1-2) prepared and four kinds of titanium dioxide powder doped p <specific Example-2> of (2-3) prepared in Modified titanium dioxide powders b1, b2, b3 and b4 of different proportions of nickel.

The results are shown in Fig. 11 (I). After the modified titanium dioxide b1, b2, b3 and b4 of different titanium ratios degraded salicylic acid under visible light for 9 hours, the salicylic acid removal rate was 58.8%. 66.70%, 73.29%, 91.1%, 81.3%. Among them, the removal rate of b3 (that is, the modified titanium dioxide prepared when the weight ratio of nickel to titanium is 10:100) is the best, up to 100%, and it is obvious that the amount of titanium in the titanium precursor is 100 weight. When the amount of nickel in the nickel salt compound to be added is controlled to 10 parts by weight, the modified titanium oxide having the best degradation efficiency can be obtained, and in addition, the removal rates of salicylic acid are excellent for b1, b2 and b4. At p, it is shown that the modified titanium dioxide-doped titanium dioxide has better degradation efficiency for salicylic acid than unmodified titanium dioxide. Among them, when the weight ratio of nickel to titanium is increased to 15:100, the salicylic acid removal rate is decreased, indicating that adding an appropriate amount of modified metal can capture the electrons generated by the excitation of titanium dioxide, thereby reducing electrons and holes. Recombining the probability and effectively separating it, thereby enhancing the catalytic activity of the titanium dioxide photocatalyst, but excessive metal addition may cause the metal to deposit on the surface of the catalyst and become the center of recombination of the electron hole, which may cause the catalytic activity of the titanium dioxide photocatalyst. reduce.

Further analysis of the mineralization rate of the salicylic acid solution with different titanium dioxide added in 0-9 hours, the results show that the dissolved organic carbon residues detected in the salicylic acid solution are shown in Fig. 11 (II). The concentration (DOC) decreased with time, and the mineralization rates of pure titanium dioxide p and different nickel ratios of modified titanium dioxide b1, b2, b3 and b4 after degrading salicylic acid under visible light for 9 hours were 48.43%, 53.92%, 57.81, respectively. %, 78.09%, 68.05%. Among them, the mineralization rate of b3 is also the best. Comparing the foregoing results with the results of (I) of Fig. 11, it can be seen that after 9 hours of the reaction, although b3 has destroyed most of the salicylic acid (salitar acid removal rate of 91.1%).

(4-3) Experiment of degrading salicylic acid under fluorescent lamp with modified nickel-doped titanium dioxide: The experimental method is exactly the same as (3-4) of <Specific Example-3> except that the addition is added to the salicylic acid solution. The modified titanium dioxide photocatalyst type is b1, b2, b3 and b4 doped with nickel, so it will not be described again. The results are shown in Fig. 12 (I). After the modified titanium dioxide p and the different nickel ratios of the modified titanium oxides b1, b2, b3 and b4 degraded salicylic acid under fluorescent lamps for 24 hours, the salicylic acid removal rates were 67.83%. , 82.02%, 75.82%, 98.50%, 93.81%. Among them, the removal rate of b3 is still the best, up to 98.50%, and the removal rate of salicylic acid by b1, b2 and b4 is also better than p, indicating that the degradation efficiency of salicylic acid is improved by the modified titanium dioxide. It is preferred over unmodified titanium dioxide.

Further analyze the mineralization rate of salicylic acid solution with different titanium dioxide added for 0-24 hours. As shown in Fig. 12(II), the dissolved organic carbon detected in salicylic acid solution can be known. The residual concentration (DOC) decreased with time, and the mineralization rates of pure titanium dioxide p and different iron ratios of modified titanium dioxide b1, b2, b3 and b4 after degradation of salicylic acid under fluorescent lamp for 24 hours were 44.86% and 53.63%, respectively. 59.05%, 84.86%, 76.65%. Among them, the mineralization rate of b3 is still the best, similar to the removal rate.

(4-4) Experiment of degrading salicylic acid by modified titanium dioxide doped with sunlight in sunlight: The experimental method is exactly the same as (3-5) of <Specific Example-3> except that the change is added to the salicylic acid solution. The modified titanium dioxide photocatalyst type is b1, b2, b3 and b4 doped with nickel, so it will not be described again.

As a result, as shown in (I) of FIG. 13, after the purified titanium dioxide p and the different nickel ratios of the modified titanium oxides b1, b2, b3 and b4 degraded salicylic acid under sunlight for 3 hours, the salicylic acid removal rates were 65, respectively. %, 88.5%, 92.10%, 100%, 95.70%. Among them, the removal rate of b3 is still the best, up to 100%, and the removal rate of salicylic acid by b1, b2 and b4 is also better than p, according to the degradation of salicylic acid by the modified titanium dioxide doped with nickel. The efficiency is better than the unmodified titanium dioxide.

Further analysis of the mineralization rate of salicylic acid solution with different titanium dioxide added in 0-24 hours, the results show that the dissolved organic carbon detected in the salicylic acid solution is shown in Fig. 13 (II). The residual concentration (DOC) decreased with time, and the mineralization rates of pure titanium dioxide p and different nickel ratios of modified titanium dioxide b1, b2, b3 and b4 after degrading salicylic acid under sunlight for 3 hours were 45.51% and 71.88%, respectively. 7,4.67%, 86.17%, 81.75%. Among them, the mineralization rate of b3 is still the best.

(4-5) Comprehensive comparison of salicylic acid degradation efficiency of modified titanium dioxide doped with nickel under different light sources: four kinds of unmodified titanium dioxide powders measured by (4-2)~(4-4) The salicylic acid removal rate and mineralization rate of the modified titanium dioxide powders b1, b2, b3 and b4 doped with different proportions of nickel under different light sources for 3 hours were arranged into Fig. 14(I), (II). ) to understand the photocatalytic degradation of salicylic acid under different light sources. It can be seen from Fig. 14(I) that under the sunlight as the light source, the photocatalytic salicylic acid can achieve 100% removal rate within 3 hours, and the fluorescent lamp and visible light removal rate are lower than the sun. Light. Among them, the removal rate of modified titanium dioxide b3 under different light sources is the best, it is obvious that the ratio of nickel to titanium in b3 is the ratio with the best degradation efficiency, while the other modified titanium dioxide added b1, b2 and b4 to water The degradation efficiency of salicylic acid is better than that of unmodified titanium dioxide p. It can be seen from (II) of Fig. 14 that the mineralization rate of the modified titanium dioxide b3 under photocatalytic salicylic acid for 3 hours under sunlight is 86.2%, and the removal rate and mineralization rate of degraded salicylic acid under different light sources are B3 is the best, according to the description, when the modified titanium dioxide is produced, when the metal in the metal salt compound is nickel, and the ratio of the amount of titanium to the titanium precursor is 10:100, the best degradation efficiency can be obtained. The modified titanium dioxide.

<Specific Example-5 Degradation Experiment of Modified Titanium Dioxide Doped with Different Sintering Temperatures>

(5-1) Preparation of modified iron-doped titanium dioxide: Preparation of iron-doped modified titanium dioxide by the method described in ( Example 2-2) (2-2), and titanium in titanium isopropoxide The amount of iron nitrate added is 100 parts by weight, and the amount of iron is equal to 0.1 parts by weight. Four white gums are prepared according to the above doping ratio, and then the gel is placed. The high-temperature furnace is heated at 400 ° C, 500 ° C, 600 ° C, and 700 ° C for 4 hours to form titanium dioxide crystals. Finally, the iron-doped modified titanium dioxide powders c1, c2, and c3 having different sintering temperatures can be obtained by grinding. , c4.

According to the test methods described in <Specific Example-3> and <Specific Example-4> , the removal rates of degraded salicylic acid under different light sources such as visible light, fluorescent lamp and sunlight are measured respectively. The mineralization rate and the conditions of various light sources are the same as those described in the above specific examples. The results are shown in Table 2 below:

It can be seen from the results in Table-2 that the modified iron-doped titanium dioxide prepared at a sintering temperature of 400 ° C to 600 ° C can degrade the salicylic acid at different light sources and the mineralization rate can reach 50% or more. Among them, the modified titanium dioxide prepared at a sintering temperature of 400 ° C has the best removal rate and mineralization rate, and can exhibit the best degradation efficiency, according to which the sintering temperature also affects the degradation of the modified titanium dioxide. Efficiency, therefore, in order to obtain a photocatalytic product with better photocatalytic ability, in addition to controlling the ratio of the amount of titanium in the doping metal to the titanium precursor, it is still necessary to limit the sintering temperature.

(5-2) Comprehensively compare the salicylic acid degradation efficiency of the modified titanium dioxide at different sintering temperatures under different light sources: further, the modified titanium dioxide powders c1, c2, c3 and c4 of different sintering temperatures are different The salicylic acid removal rate and mineralization rate under degradation of salicylic acid for 3 hours under light source were compiled into Fig. 15(I) and (II), respectively, to understand the photocatalytic degradation of salicylic acid under different light sources. It can be seen from (I) of Fig. 15 that the modified titanium dioxide prepared at a sintering temperature of 400 ° C can remove 100% of photocatalytic salicylic acid in sunlight for 3 hours, and has a low removal rate by using fluorescent lamps and visible light as a light source. In the sun. Among them, the removal rate of titanium dioxide with sintering temperature of 400 °C under different light sources is the best, showing that the sintering temperature of 400 °C is the best preparation condition. The result shown in (II) of Fig. 15 is similar to (I), and it is shown that the titanium oxide prepared at a sintering temperature of 400 ° C has an optimum mineralization ratio.

<Specific Example-6 Degradation Experiment of Nickel-Doped Modified Titanium Dioxide Prepared at Different Sintering Temperatures>

(6-1) Preparation of modified titanium dioxide doped with nickel: Preparation of nickel-doped modified titanium dioxide by the method described in < 2-3 of the specific example-2> , and titanium in titanium isopropoxide The amount of nickel nitrate added is 100 parts by weight, and the amount of nickel is equal to 10 parts by weight. Four white gums are prepared according to the above doping ratio, and then the gel is placed. The high-temperature furnace is heated at 400 ° C, 500 ° C, 600 ° C, and 700 ° C for 4 hours to form titanium dioxide crystals. Finally, the iron-doped modified titanium dioxide powders d1, d2, and d3 at different sintering temperatures can be obtained by grinding. , d4.

According to the test methods described in <Specific Example-3> and <Specific Example-4> , the removal rates of degraded salicylic acid by d1, d2, d3, and d4 under different light sources such as visible light, fluorescent lamp, and sunlight are measured, respectively. The mineralization rate and the conditions of various light sources are the same as those described in the above specific examples. The results are shown in Table-3 below:

It can be seen from the results in Table-3 that the removal rate and mineralization rate of salicylic acid degraded by different nickel-doped modified titanium dioxide prepared at a sintering temperature of 400 ° C to 600 ° C can reach 50% or more. The modified titanium dioxide prepared at a sintering temperature of 400 ° C has the best removal rate and mineralization rate, and can exhibit the best degradation efficiency, and accordingly confirms that the sintering temperature affects the degradation of the modified titanium dioxide. In terms of efficiency, and in order to obtain a photocatalytic product with better photocatalytic ability, in addition to controlling the ratio of the amount of titanium in the doped metal to the titanium precursor, it is still necessary to limit the sintering temperature.

(6-2) Comprehensive comparison of salicylic acid degradation efficiency of modified titanium dioxide at different sintering temperatures under different light sources : Further, the modified titanium dioxide powders d1, d2, d3 and d4 of different sintering temperatures are different The salicylic acid removal rate and mineralization rate under degradation of salicylic acid for 3 hours under light source were compiled into Fig. 16(I) and (II), respectively, to understand the photocatalytic degradation of salicylic acid under different light sources. It can be seen from (I) of Fig. 16 that the modified titanium dioxide prepared at a sintering temperature of 400 ° C can remove 100% of photocatalytic salicylic acid in sunlight for 3 hours, and has a low removal rate by using fluorescent lamps and visible light as a light source. In the sun. Among them, the removal rate of titanium dioxide with sintering temperature of 400 °C under different light sources is the best, showing that the sintering temperature of 400 °C is the best preparation condition. The result shown in (II) of Fig. 16 is also similar to (I), and it is shown that the titanium oxide prepared at a sintering temperature of 400 ° C has an optimum mineralization ratio.

In summary, the method for preparing modified titanium dioxide having better degradation efficiency of the present invention can attain the following effects and advantages, so that the object of the present invention can be achieved:

1. It can be seen from the results of <Specific Example-1> that the titanium dioxide produced by the method of the present invention has an adsorption capacity and a photocatalytic ability comparable to those of commercially available commercial titanium dioxide, and accordingly, the method of the present invention can be produced. It meets the commercial specifications of titanium dioxide, so it has practical value for industrial production.

2. It can be seen from the results of <Specific Example-2> that the unmodified or modified titanium dioxide photocatalyst prepared at a sintering temperature of 400 ° C can be used to indicate that the transition metal ions can be doped by the method of the present invention by the EDS spectrum. In the modified titanium dioxide, the XRD pattern showed that the prepared titanium dioxide powder showed only a single crystal phase of anatase, and no rutile crystal phase was found, which was explained at 400 ° C. The modified titanium dioxide produced at the sintering temperature still has an anatase phase, and the doping metal does not affect the crystal phase of pure titanium dioxide. No transition metal oxide is formed in the XRD pattern. The peak of the shot indicates that the transition metal such as iron or nickel should be highly embedded in the internal structure of the titanium dioxide crystal, or even replace the position of a part of the titanium metal. Therefore, the method of the present invention can produce a modified titanium dioxide product with stable quality.

3. It can be seen from the results of <Specific Example-3> and <Specific Example-4> that the present invention can contribute to different production by limiting the range of the ratio of the doping metal to the amount of titanium in the titanium precursor. The modified titanium dioxide product which performs photocatalysis under visible light source and has better degradation efficiency makes the product prepared by the invention can improve the performance of the photocatalyst and has practical value and economic benefit.

4. From the results of <Specific Example-5> and <Specific Example-6> , it can be seen that, in addition to limiting the range of the ratio of the doping metal to the amount of titanium in the titanium precursor, the sintering temperature in the manufacturing process is further limited, and there are also Helping to produce modified titanium dioxide with high degradation efficiency, the method of the present invention can produce a photocatalytic product having the best degradation efficiency by limiting the proportion of the main raw materials and the sintering temperature, and applying the modified titanium dioxide light touch product. In the treatment of organic pollutants, the intermediate products degraded by organic matter can be further decomposed into non-toxic inorganic compounds, and the environmental protection performance is better, thereby indicating that the method of the present invention not only has the practical value of being developed into an industrial process. The economic benefits, according to the products produced can also effectively reduce organic pollutants, and can meet environmental protection needs.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

3‧‧‧ thermostat light box device

31‧‧‧Quartz reaction tank

32‧‧‧Light tube

1 is a flow chart of a preferred embodiment of the process for producing modified titanium dioxide having better degradation efficiency of the present invention; and FIG. 2 is a schematic diagram of salicylic acid degradation experiments using the modified titanium dioxide produced by the preferred embodiment. A schematic view of a thermostatic light box device; FIG. 3 is an SEM image showing the appearance of modified titanium dioxide of different metal doping ratios produced by the preferred embodiment; (I) and (II) of FIG. It is an EDS spectrum, which illustrates the case where the modified iron and nickel modified titanium dioxide produced by the preferred embodiment contains a doped metal; and FIG. 5 is an XRD pattern illustrating the doped iron produced by the preferred embodiment. The crystal phase of the modified titanium dioxide and the pure titanium dioxide; FIG. 6 is an XRD pattern illustrating the crystal phase of the nickel-doped modified titanium dioxide and the pure titanium dioxide produced in the preferred embodiment; (I), (II) of FIG. ) is a graph showing the residual rate and mineralization rate of salicylic acid degraded by visible iron in different proportions of iron modified titanium dioxide; (I) and (II) of Fig. 8 are graphs respectively showing the residual rate and mineralization rate of salicylic acid degraded by different proportions of iron-modified titanium dioxide under fluorescent lamps; (I) and (II) of Fig. 9 are graphs. , respectively, indicating the residual rate and mineralization rate of salicylic acid degraded by different proportions of iron-modified titanium dioxide in sunlight; (I) and (II) in Figure 10 are bar graphs, respectively indicating different ratios of iron-modified titanium dioxide in different Degradation rate and mineralization rate of salicylic acid under light source; (I) and (II) of Fig. 11 are graphs showing the residual rate and mineralization rate of salicylic acid degraded by visible light in different proportions of nickel modified titanium dioxide. ; Fig. 12 (I) and (II) are graphs showing the residual rate and mineralization rate of salicylic acid degraded by different proportions of nickel-modified titanium dioxide under fluorescent lamps; (I) and (II) of Fig. 13 are graphs. , respectively, indicate the residual rate and mineralization rate of salicylic acid degraded by different proportions of nickel-modified titanium dioxide under sunlight; (I) and (II) of Fig. 14 are bar graphs, respectively indicating different ratios of nickel-modified titanium dioxide in different Degradation rate and mineralization rate of salicylic acid under light source; (I) and (II) of Fig. 15 are bar graphs showing the removal rate of salicylic acid degraded by iron-modified titanium dioxide with different sintering temperatures under different light sources. And the mineralization rate; and (I) and (II) of Fig. 16 are bar graphs, respectively illustrating the removal rate and mineralization rate of salicylic acid degraded by nickel modified titanium dioxide at different sintering temperatures under different light sources.

Claims (9)

A method for preparing modified titanium dioxide with better degradation efficiency, comprising the steps of: (A) mixing anhydrous ethanol with deionized water, and adding a polyvinyl alcohol compound to form a premix; (B) premixing the premix Adding a monoprotic acid aqueous solution, a metal salt compound containing a doping metal, and a titanium dioxide precursor, mixing and stirring uniformly to obtain a pre-gelling mixture, wherein the doping metal is nickel and titanium dioxide is used. The amount of titanium in the precursor is 100 parts by weight, the doping metal is used in an amount of 5 to 15 parts by weight; (C) the pre-gluing mixture is subjected to a heating step to obtain a jelly; D) subjecting the gum to a high temperature sintering step to obtain a metal-doped modified titanium dioxide crystal. The method for preparing modified titanium dioxide having better degradation efficiency according to the first aspect of the patent application, wherein the gel of the step (D) is sintered at a high temperature at a temperature of 400 ° C to 600 ° C. The method for preparing modified titanium dioxide having better degradation efficiency according to claim 2, wherein the gel of the step (D) is sintered at a high temperature at a temperature of 400 °C. The method for producing modified titanium dioxide having better degradation efficiency according to the second aspect of the patent application, wherein the step (D) is performed at a high temperature for 4 hours. The modification with better degradation efficiency according to item 2 of the patent application scope The method for producing titanium dioxide, wherein, in the step (B), the amount of the doping metal is 10 parts by weight based on 100 parts by weight of the titanium in the titanium dioxide precursor. The method for producing modified titanium dioxide having a preferred degradation efficiency according to claim 1, wherein the aqueous solution of the monoprotic acid in the step (B) is selected from the group consisting of aqueous hydrochloric acid solution, aqueous acetic acid solution or aqueous nitric acid solution. The method for preparing modified titanium dioxide having better degradation efficiency according to claim 1, wherein the titanium precursor compound in the step (B) is selected from titanium isopropoxide, titanium tetrachloride or tetra Titanyl oxypropoxide. The method for preparing modified titanium dioxide having better degradation efficiency according to the first aspect of the patent application, wherein the pre-gel mixture of the step (C) is heated at a temperature of 60 ° C / hour, and is heated to a temperature. Heating at this temperature was continued at 110 ° C until the gum was obtained. The method for preparing modified titanium dioxide having better degradation efficiency according to claim 1 of the patent application, further comprising a step (E) after the step (D), wherein the step (E) is to make the modified titanium dioxide crystal A grinding step is performed to obtain a metal-doped modified titanium dioxide powder.