KR20180089153A - Photocatalytic degradation method of urea using titanium dioxide - Google Patents

Abstract

Provided is an effective urea decomposition method intended to decompose urea in a urea-containing solution using a titanium dioxide photocatalyst and ultraviolet in the presence of oxygen. It is more preferable to use the titanium dioxide photocatalyst on which platinum is supported on a surface thereof. As the urea-containing solution, it is more efficient in the urea decomposition to use a solution containing phosphate ion together such as artificial urine instead of using an aqueous solution solely containing urea.

Description

TECHNICAL FIELD The present invention relates to a photocatalytic degradation method using a titanium dioxide photocatalyst,

The present invention relates to a urea decomposition method using a titanium dioxide photocatalyst.

Wastewater from fertilizers, explosives, pharmaceuticals, cosmetics and plastics plants contains a large amount of elements. In addition, the element is a major constituent of the urine of humans and animals, and the concentration of the element in the domestic sewage is very high. Elements contained in the pool water become nitrogenous disinfection byproducts which are highly toxic during the purification of the swimming pool water, and when the urea is introduced into the coast, it acts as a nutrient of the algae and causes algal reproduction. Therefore, development of element decomposition method is important.

Titanium dioxide photocatalyst is a variety of oxidizing substances under UV {valence band holes (valence band hole, h _VB ^+), OH radicals ^(and OH), superoxide radical (O ₂ ^{and -)}} produces, on the oxide materials The pollutants are decomposed. In addition, by supporting platinum (Pt) on the surface of titanium dioxide, the photocatalytic decomposition efficiency can be improved. The platinum supported on the titanium dioxide surface prevents the conduction band electron (e _CB ^- ) of the titanium dioxide conduction band from recombining with the valence band hole (h _VB ⁺ ) of the valence band, thereby promoting the production of the oxide And improves the decomposition efficiency of pollutants.

The present invention seeks to provide a more effective method of decomposing elements.

In order to solve the above-mentioned problems, the present inventor has established an effective method for decomposing urea and completed the present invention.

The present invention

a) Titanium dioxide (TiO ₂ ) Dispersing the titanium dioxide solution in a solvent to prepare a titanium dioxide solution;

b) adding a solution containing the element to the titanium dioxide solution;

and c) irradiating ultraviolet rays while stirring the titanium dioxide solution containing the element in the presence of oxygen in the presence of the ultraviolet ray and the titanium dioxide.

The present invention also relates to a method of ellipsometry using ultraviolet rays and titanium dioxide, wherein the surface area of the titanium dioxide is 30 to 500 m ² / g.

The present invention also relates to a method of urea decomposition using ultraviolet light and titanium dioxide, wherein the concentration of the urea is 1 to 1000 μM.

The present invention also relates to a method of element decomposition using ultraviolet rays and titanium dioxide, characterized in that the solution containing the element is derived from wastewater generated in a fertilizer, explosives, pharmaceutical, cosmetic or plastic production plant or urine of human and animal. .

Further, the present invention relates to a method of urea decomposition using ultraviolet rays and titanium dioxide, wherein phosphate ions are further contained in a solution containing the element.

Further, the present invention relates to a method of decomposing an element using ultraviolet rays and titanium dioxide, wherein the wavelength of the ultraviolet ray to be irradiated is 400 nm or less, preferably 300 to 380 nm.

The present invention also relates to a method for decomposing urea using ultraviolet rays and titanium dioxide, wherein platinum is supported on the surface of titanium dioxide.

In addition, the present invention relates to a method of urea decomposition using ultraviolet rays and titanium dioxide, wherein the weight of the platinum is 0.1 to 5 wt% with respect to titanium dioxide.

The method for decomposing urea using ultraviolet rays and titanium dioxide according to the present invention will be described in more detail. First, It is put into distilled water and dispersed by ultrasonic treatment. At this time, the titanium dioxide has a surface area of 30 m ² / g or more, more preferably 30 to 500 m ² / g, because it is excellent in OH radical production ability, which is the main oxidation substance of urea decomposition.

Also, put the urea solution in the titanium dioxide solution. There is no particular limitation on the concentration of the element, but decomposition of the element is more effective in the range of 1 to 1000 μM.

In addition, element decomposition occurs more effectively when the solution containing the element further contains phosphate ions.

Next, ultraviolet rays are irradiated to the solution containing the urea solution and titanium dioxide. The ultraviolet ray is 400 nm or less, preferably 300 nm to 380 nm. If the range is satisfied, element decomposition can be efficiently performed.

In addition, titanium dioxide is more effective in element decomposition by using titanium dioxide carrying platinum on its surface.

In addition, when the weight of the platinum supported on the titanium dioxide surface is in the range of 0.1 to 5 wt% with respect to the titanium dioxide, the titanium dioxide photocatalytic action can be maximized.

When the urea decomposition method using the ultraviolet ray and the titanium dioxide of the present invention is used, the element can be effectively decomposed by a simple method. Therefore, it can be used for purification of factory waste water, industrial waste water, contaminated water, urine and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the concentration of nitrate ions and ammonium ions produced by the decomposition of water in urea and decomposition of urea using (a) titanium dioxide and (b) titanium dioxide on which surface of platinum is supported. Experimental conditions: [Titanium dioxide] or [Titanium dioxide supported on platinum surface] = 15 mg / 30 mL, [Element] = 860 μM, wavelength of ultraviolet ray = 320 nm or more.
FIG. 2 is a graph showing the removal efficiencies of total organic carbon when decomposing urea aqueous solution using (a) titanium dioxide and (b) titanium dioxide on which surface of platinum is supported. Experimental conditions: [Titanium dioxide] or [Titanium dioxide supported on the surface of platinum] = 15 mg / 30 mL, [Element] = 860 μM, wavelength of ultraviolet ray = 320 nm or more, ultraviolet irradiation time = 3 hours.
FIG. 3 is a graph showing concentrations of nitrate ions and ammonium ions produced by urea decomposition and urea decomposition in artificial urine using (a) titanium dioxide and (b) titanium dioxide on which surface of platinum is supported. Experimental conditions: [Titanium dioxide] or [Titanium dioxide coated with platinum on the surface] = 15 mg / 30 mL, [Element of artificial urine] = 860 μM, wavelength of ultraviolet ray = 320 nm or more.
FIG. 4 is a graph showing the removal efficiency of total organic carbon during artificial urine decomposition using (a) titanium dioxide and (b) titanium dioxide on the surface of which platinum is supported. Experimental conditions: [Titanium dioxide] or [Titanium dioxide supported on the surface of platinum] = 15 mg / 30 mL, [Element of artificial urine] = 860 μM, wavelength of ultraviolet ray = 320 nm or more,
FIG. 5 is a graph showing the water element decomposition according to the presence or absence of phosphate ions. FIG. Test conditions: [Titanium dioxide] = 15 mg / 30 mL, [Phosphate ion] = 64.3 μM, [Element] = 860 μM, wavelength of ultraviolet light = 320 nm or more.

Hereinafter, the configuration of the present invention will be described in more detail with reference to specific embodiments. However, it should be apparent to those skilled in the art that the scope of the present invention is not limited to the description of the embodiments.

Materials and Chemicals

Materials and chemicals used in the present invention are available as follows.

Titanium dioxide _{(Titanium dioxide, TiO 2, Degussa} P25, specific surface area = 50 m ² / g), urea _{(Urea, NH 2 CONH 2,} Sigma-Aldrich), a first potassium phosphate _{(Potassium phosphate monobasic, KH 2 PO} 4, Sigma Aldrich), sodium sulfate (Na ₂ SO ₄ , Sigma-Aldrich), sodium citrate tribasic dihydrate (HOC (COONa) (CH ₂ COONa) ₂ .2H ₂ O, Sigma-Aldrich) (Sigma-Aldrich), creatinine (C ₄ H ₇ N ₃ O, Sigma-Aldrich), sodium oxalate (NaOOCCOONa, Sigma-Aldrich), potassium chloride ₄ Cl, Sigma-Aldrich), magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O, Sigma-Aldrich), sodium chloride (NaCl, Sigma-Aldrich), calcium chloride dihydrate , CaCl ₂ .2H ₂ O, Sigma-Aldrich), urease from Canavalia ensiformis (Jack bean, type III, Sigma), chloroplatinic acid hydrate (H ₂ PtCl ₆ .xH ₂ O, Aldrich), methanol (methanol, CH ₃ OH, Wako). Ion-free ultra-pure water (18.3 MΩ · cm) was used, which was manufactured by Human-Power I + ultra-pure water manufacturing equipment (Human corporation). Artificial urine was made using various chemicals, and its composition is shown in Table 1.

Platinum on the surface Supported  Titanium dioxide synthesis method

Titanium dioxide photocatalyst supported on the surface of platinum was prepared by photodeposition method. Titanium dioxide (0.5 g / 500 mL) was added to an aqueous solution containing chloroplatinic acid hydrate (24.4 μM) as a platinum precursor and methanol (1 M) as an electron donor and dispersed. A 300-W xenon arc lamp (Xe arc lamp, > 295 nm, Oriel). The titanium dioxide photocatalyst was plated with 0.45 μm PVDF disk filter (Pall), washed with distilled water, and then dried in an oven at 70 ° C. The concentration of chloroplatinic acid hydrate remaining after filtration was analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES, Spectro). As a result, the amount of platinum supported on the titanium dioxide surface was about 0.5 wt% Respectively.

Experimental Method

15 mg of titanium dioxide (TiO ₂ ) or titanium dioxide (Pt / TiO ₂ ) on which platinum was supported on the surface was put into distilled water and ultrasonicated for 1 minute in an ultrasonic generator to disperse. A high concentration of urea aqueous solution or artificial urine was put into a solution of titanium dioxide dispersed to set the initial concentration of urea. The initial concentration of urea was 860 μM. The volume of the final solution was 30 mL.

Titanium dioxide or titanium dioxide on which platinum was supported on the surface was stirred for 30 minutes in the state that the urea and urine components were adsorbed and equilibrated until the light was blocked. A 300-W Xen arc lamp (Oriel) was used as the light source. The light emitted from the light source was blocked by infrared rays generated by a 5 cm IR water filter, and only light of 320 nm or longer (λ> 320 nm) was transmitted using a cutoff filter . The focus of the transmitted light was directed to a cylindrical glass reactor (volume = 35 mL). Stirring was continued while irradiating light, and the lid of the reactor was opened so that oxygen was not depleted. Samples were taken 1 mL each while light was irradiated and titanium dioxide or platinum supported on its surface was removed with a 0.45 μm PTFE syringe filter (Millipore) and the results were analyzed. All experiments were performed at least twice.

Concentration of urea

The concentration of urea was measured by analyzing the concentration of ammonium ion (NH ₄ ⁺ ) converted by hydrolysis of urea by urease. In other words, [urea concentration] = {[ammonium ion concentration when urease is present] - [ammonium ion concentration without urease]} / 2. 0.6 g of urease was dissolved in 500 mL of distilled water to prepare an urease solution. 0.1 mL of the urease solution was dispensed into a container containing 0.5 mL of the sample. After the vessel was stirred, it was boiled in warm water at 50 DEG C for 20 minutes and then cooled at room temperature for 30 minutes. The concentration of ammonium in the sample was then measured.

The concentration of ammonium ions produced by enzymatic hydrolysis of nitrate ions and ureas produced by photocatalytic decomposition of urea or photocatalytic decomposition of urea was analyzed by ion chromatography (IC, Dionex ICS-1100). Conductivity detector was used. The column was a Dionex IonPac AS14 column (4 mm x 250 mm, for nitrate ion analysis) and a Dionex IonPac CS12A column (4 mm x 250 mm, for ammonium ion analysis). A 20 mM methanesulfonic acid solution and 3.5 mM sodium carbonate / 1 mM sodium bicarbonate solution were used as eluent to measure ammonium and nitrate ions, respectively. The initial ammonium ion concentration originally contained in the artificial urine was removed from the ammonium ion production concentration.

Analysis of Total Organic Carbon Concentration

The total organic carbon concentration was analyzed using an organic analyzer (TOC analyzer, Shimadzu TOC-L _CPH ). A non-dispersive infrared sensor (NDIR) was used as the carbon dioxide detector. The total organic carbon concentration was calculated by subtracting the inorganic carbon concentration from the total carbon concentration.

Result 1: Titanium dioxide and platinum on the surface Supported  Concentration of nitrate and ammonium ions produced by decomposition of urea and decomposition of urea using titanium dioxide

FIG. 1 shows the concentrations of nitrate ions and ammonium ions produced by decomposition of water and degradation of urea using titanium dioxide coated with titanium dioxide and platinum on its surface. In the case of titanium dioxide, the concentration of urea was reduced by 115 μM after 3 hours of ultraviolet irradiation, and the concentration of urea was decreased by 425 μM in the case of titanium dioxide coated with platinum. In other words, the urea decomposition efficiency of titanium dioxide supported on the surface of platinum was 3.7 times higher than that of titanium dioxide. Similar to these results, the concentration of nitrate and ammonium ions produced by the decomposition of urea was also higher in titanium dioxide coated with platinum than on titanium dioxide.

Result 2: Titanium dioxide and platinum on the surface Supported  Removal efficiency of total organic carbon during decomposition of water element using titanium dioxide

2 is a graph showing the removal efficiencies of the total organic carbon during the decomposition of water in the urea using titanium dioxide and platinum supported on its surface. In the case of titanium dioxide, 12.6% of the total organic carbon in the urea solution was removed after 3 hours of UV irradiation, and 36.1% of the total organic carbon in the urea solution of titanium dioxide supported on the surface of platinum. In other words, the elementalization efficiency of the elemental aqueous solution of titanium dioxide supported on the surface of platinum was 2.9 times higher than that of titanium dioxide.

Result 3: Titanium dioxide and platinum on the surface Supported  Concentrations of nitrate and ammonium ions produced by urea decomposition and urea decomposition in artificial urine using titanium dioxide

FIG. 3 shows the concentrations of nitrate ions and ammonium ions produced by urea decomposition and urea decomposition in artificial urine using titanium dioxide on which titanium dioxide and platinum are supported on the surface. In the case of titanium dioxide, the concentration of urea was reduced by 230 μM after 3 hours of ultraviolet irradiation, and the concentration of urea was reduced by 356 μM in the case of titanium dioxide coated with platinum. That is, the urea decomposition efficiency of titanium dioxide coated with platinum on the surface was 1.5 times higher than that of titanium dioxide. Similar to these results, the concentration of nitrate and ammonium ions produced by the decomposition of urea was also higher in titanium dioxide coated with platinum than on titanium dioxide.

Result 4: Titanium dioxide and platinum on the surface Supported  Removal efficiency of total organic carbon during artificial urine decomposition using titanium dioxide

FIG. 4 is a graph showing the removal efficiencies of total organic carbon during artificial urine decomposition using titanium dioxide and platinum supported on its surface. In the case of titanium dioxide, 25.4% of the total organic carbon in the artificial urine was removed after 3 hours of UV irradiation, and 32.0% of the total organic carbon in the artificial urine was removed in the case of titanium dioxide coated with platinum on the surface. In other words, the artificial uranium mineralization efficiency of titanium dioxide coated with platinum on the surface was 1.3 times higher than that of titanium dioxide.

Result 5: Influence of phosphoric acid ion on decomposition of urea in water using titanium dioxide

FIG. 5 shows the results of water element decomposition according to presence or absence of phosphate ions. The concentration of urea was decreased by 108 μM when phosphoric acid ion was not present after UV irradiation for three hours, and by urea concentration was decreased by 274 μM when phosphate ion of 64.3 μM was present. In the presence of phosphate ions, the urea decomposition efficiency was increased 2.5 times. This is because the phosphoric acid ion adsorbed on the titanium dioxide surface improved the ability of the titanium dioxide to produce OH radicals.

Table 1 below shows the composition of the artificial urine used in the urea decomposition experiment using the titanium dioxide photocatalyst of the present invention.

chemical name dose (g / 500 mL) concentration (mM) urea 12.5 416.25 포터륨 assium monobasic 2.1 30.86 sodium sulfate 1.15 16.19 sodium citrate tribasic dihydrate 0.325 2.21 creatinine 0.55 9.72 Sodium oxalate 0.01 0.15 포터 키라이드 0.8 21.46 공연 시금 0.5 18.70 magnesium chloride hexahydrate 0.325 3.20 sodium chloride 2.3 78.71 calcium chloride dihydrate 0.325 4.42

Claims (8)

a) Titanium dioxide (TiO ₂ ) Dispersing the titanium dioxide solution in a solvent to prepare a titanium dioxide solution;
b) adding a solution containing the element to the titanium dioxide solution;
c) irradiating ultraviolet rays while stirring the titanium dioxide solution containing the element in the presence of oxygen in the presence of oxygen.
The method according to claim 1,
Wherein the titanium dioxide has a surface area of 30 to 500 m ² / g.
The method according to claim 1,
Wherein the concentration of said element is between 1 and 1000 μM.
The method according to claim 1,
Wherein the solution containing the element is derived from wastewater generated in a fertilizer, explosive, pharmaceutical, cosmetic or plastic production plant, or urine of human and animal.
The method according to claim 1,
Wherein the solution containing the element further comprises phosphate ions. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to claim 1,
Wherein the wavelength of ultraviolet light to be irradiated is 300 to 380 nm.
The method according to claim 1,
Wherein the titanium dioxide is platinum supported on the surface thereof.
The method of claim 7,
Wherein the weight of the platinum is 0.1 to 5 wt% with respect to the titanium dioxide.

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