KR100516526B1 - Photodegradation method of organic pollutants in water by a photocatalytic reaction using ferric ion - Google Patents

Abstract

The present invention relates to a method for removing organic matter in water using a photochemical catalysis system, and more particularly, to remove organic matter in water efficiently by adding iron trivalent ions (Fe ³⁺ ) to the immobilized photochemical catalyst. It relates to a method for removing organic matter in water. In another aspect, the present invention relates to a method for synthesizing a titanium-based inorganic binder having excellent chemical resistance and binding stability in order to provide an immobilized photochemical catalyst having excellent organic resolution. In addition, the present invention relates to an immobilized photochemical catalyst, wherein the photocatalyst having an average particle size of 5 to 50 nm is fixed to a thickness of 1 to 20 μm using the titanium-based inorganic binder of the present invention.

Decomposition of the organic matter in water with the photochemical catalyst immobilized using the inorganic binder of the present invention showed that the decomposition efficiency of the initial organic matter in the water was not only 90 to 100%, but also the chemical resistance and stability of the photochemical catalyst were excellent. . Accordingly, the present invention proposes a photolysis system and process conditions capable of efficiently decomposing organic matter in water.

Description

Method for removing organic matter from water using iron trivalent ions in photochemical catalysis system {PHOTODEGRADATION METHOD OF ORGANIC POLLUTANTS IN WATER BY A PHOTOCATALYTIC REACTION USING FERRIC ION}

The present invention relates to a method for removing organic matter in water using a photochemical catalysis system, and more particularly, to remove organic matter in water efficiently by adding iron trivalent ions (Fe ³⁺ ) to the immobilized photochemical catalyst. It relates to a method for removing organic matter in water.

Industrial wastewater, which has recently increased rapidly due to industrialization, remains in the ecosystem for a long time or is concentrated in living organisms, causing enormous damage to humans, the surrounding environment and living organisms. Considering the increasing trend of domestic chemical production and consumption, the hazard is expected to be even greater. In particular, considering the social concern about the endocrine disruptors (environmental hormones) from incineration, landfilling and discharge of dyes, pesticides and other plastic products, it is necessary to develop new economic and efficient methods for removing organic matter from water.

Korean Patent No. 0205443 uses cross-flow using microfiltration membrane and ultrafiltration membrane to remove chromaticity, odor, sterilization or chemical contaminants of wastewater by using photocatalyst in pretreatment stage of wastewater treatment step An apparatus for treating wastewater using powdered photocatalysts, which facilitates a catalyst separation process while maintaining a flow in a) method, has been proposed. That is, the wastewater treatment technology using the photocatalyst presented in this document is completely different from the present invention for solving the problems related to the stability of the photocatalyst and the efficiency of organic matter decomposition and its technical configuration.

In addition, the Korean Patent Publication No. 2000-058790 as a catalyst immobilization technology is a method of fixing a photocatalyst on a heat-resistant or non-heat-resistant thin film substrate, by applying and spraying a porous inorganic adhesive and a photocatalyst in turn and pressing the titanium dioxide powder on the upper surface thereof A method for preventing oxidation of a thin film substrate by an adhesive and improving photocatalyst efficiency with titanium dioxide evenly compressed on an outer surface is proposed. That is, in this document, a method of immobilizing a photocatalyst using an inorganic adhesive is proposed, but there is no mention or suggestion regarding the application conditions of the specific inorganic adhesive, minerals and photocatalysts, and thus the photocatalyst stability and decomposition efficiency.

This well-known technique focuses on improving operability and improving photocatalyst separation conditions in suspended state, rather than improving photolysis efficiency and catalyst stability, and is applied at the scale of a laboratory or pilot level as a technology using external light energy. This is possible, but has been limited to large-scale wastewater treatment plants.

Therefore, the present invention can be applied to a large-scale wastewater treatment site to improve this problem, and to improve the photocatalyst immobilization efficiency and organic photocatalytic efficiency and the photocatalyst immobilized by the method, such an immobilized photocatalyst An object of the present invention is to provide a method for removing an organic substance in water and a wastewater treatment apparatus using the photocatalyst.

According to a first aspect of the present invention, a photochemical catalyst is fixed by using an inorganic binder (also called a binder), and the inorganic binder is synthesized in a sol state in such a manner as to improve chemical resistance and bonding stability of the photochemical catalyst. A method of immobilizing a photocatalyst is provided.

As a preferable embodiment of such an immobilization method, the binder used for the photocatalyst immobilization is preferably an inorganic series, and the organic binder cannot be used because it is decomposed by UV light. As the inorganic binder useful in the present invention, any inorganic binder known in the art may be used, but preferably, a titanium-based inorganic binder having excellent chemical resistance and bonding stability is preferable. Particularly preferably, this titanium-based inorganic binder starts the synthesis using a composition volume ratio of alcohol / TTIP (titanium tetraisopropoxide) in the range of 4.5 to 10.5 and then reacts for 0.2 to 1 hour before It is preferable that it is an inorganic binder in the sol state obtained by making it react by addition reaction using the composition volume ratio in the range of 0.5-1.5.

As a specific example of the immobilization method, the content of the photocatalyst added for immobilization to the inorganic binder in the sol state prepared as described above may be added in an amount ranging from 5 to 20 parts by weight based on 100 parts by weight of the inorganic binder. It is suitable.

As the immobilization method, various methods known in the art may be used, and a dip coating method is particularly preferable. The photocatalyst thus coated is dried and sintered to crystallize. The reaction conditions of drying and sintering can be easily set by those skilled in the art, for example, at 100 ° C. for 30 minutes, and sintering is carried out at 500 ° C. for 12 hours, for example. A photocatalyst having a crystal characteristic of titanium (TiO ₂ ) can be obtained.

The thickness of the fixed photocatalyst film is preferably 1 to 20 μm, and 5 to 10 μm is most preferred. When the thickness of the film is less than 1 μm, the light resolution is lowered. When the thickness is 20 μm or more, the absorption amount of UV light is increased and the organic material resolution is decreased.

In addition, in a second aspect, the present invention uses the composition volume ratio of alcohol / TTIP (titanium tetraisopropoxide) in the range of 4.5 to 10.5 to start the synthesis and react for 0.2 to 1 hour, followed by the composition volume ratio of water / hydrochloric acid. It provides a method for producing a titanium-based inorganic binder in a sol state comprising the addition of using in the range of 0.5 to 1.5 and then stirred to form an inorganic binder in the sol state.

In the specific example of such a manufacturing method, alcohol, methanol, ethanol, propanol, octanol, etc. are used, Especially ethanol and propanol are preferable. It is preferable that the alcohol composition volume ratio with respect to TTIP is 4.5-10.5, and especially 5.0-9.0. If the composition volume ratio is less than 4.5, entanglement occurs and cannot be synthesized. After the reaction for 0.2 to 1 hour, the composition volume ratio of water / hydrochloric acid is added and reacted under the condition of 0.5 to 1.5. If it is smaller than 0.5, the crystal proceeds too fast, and the particle size increases. Do not.

In a third aspect, the present invention combines the improved chemical resistance, characterized in that the photochemical catalyst having an average particle size of 5 to 50 nm is fixed to a thickness of 1 to 20 μm using the titanium-based inorganic binder of the present invention. An immobilized photochemical catalyst exhibiting stability is provided.

As a preferred embodiment, the photocatalyst used in the present invention includes, but is not limited to, CdS, TiO ₂ , ZnO, Fe ₂ O ₃ having a large interval energy of 2.0 to 3.0 eV, and generally uses TiO ₂ . The average particle diameter of the photocatalyst is limited to the range of 5 to 50 nm, especially the range of 10 to 20 nm is more preferable. If it is 5 nm or less, agglomeration may occur, resulting in a decrease in photo resolution due to absorption of UV light. If the specific surface area is used, the optical resolution is lowered.

The photocatalyst used in photochemical catalysis is composed of molecular orbital functions consisting of valence band and conduction band, which have energy equal to or greater than their inherent band gap energy. Upon receiving light having a wavelength, electrons in the valence band absorb the light, are excited by the conduction band, and generate holes (hole, h _vb ⁺ ) and electrons (electron, e _cb ⁻ ). Holes are formed in the valence band, and electrons are formed in the conduction band, forming a hole-electron pair. By this action, the electrons generated in the conduction band have strong reducing power and the holes in the valence band have strong oxidizing power. Electrons in the excited conduction band and holes in the valence band may be recombined in the absence of other electron acceptors or hole scavengers to generate thermal energy or to cause different redox reactions. Meanwhile, activated oxygen species such as O ₂ , H ₂ O ₂ , and O ₃ may be used as primary electron acceptors in the environmental applications of most semiconductor photocatalysts. These materials are used to increase the oxidation power of the photocatalyst.

hv

TiO ₂ ---------- e- + h + (1)

h + + OH- ---------- OH (2)

e- + O ₂ ---------- O _2- (3)

O _2- + H + ---------- O ₂ H (4)

H + + O _2- + O ₂ H ---------- H ₂ O ₂ + O ₂ (5)

H ₂ O ₂ + hv ---------- 2 OH (6)

Oxidation of OH radicals generated through the reactions from (1) to (6) gives complete decomposition of organic matter in water into CO ₂ and H ₂ O. Among the photocatalysts having such characteristics, titanium dioxide (TiO ₂ ) has the greatest activity for the photooxidation reaction, is less toxic, insoluble in water, does not occur in its own photolysis reaction, and has a lower cost than other materials.

In a fourth aspect, the present invention provides a method for decomposing organic matter in water, wherein iron trivalent ions (Fe ³⁺ ) are added to the immobilized photochemical catalyst to efficiently decompose organic matter in water.

As a preferred embodiment, the immobilized photochemical catalyst is prepared by using an inorganic binder synthesized in a sol state according to the preparation method of the present invention as described above, and the catalyst powder having an average particle of 5 to 50 nm of 1 to 20 μm as described above. It is fixed in thickness.

In addition, the iron trivalent ions added additionally play a role of enhancing the photolysis effect, and the concentration thereof is appropriately in the range of 10 to 200 mg / L, preferably in the range of 50 to 100 mg / L. The iron compound capable of supplying Fe ³⁺ ions is not limited to a specific material, but the higher the solubility, the better and it should be able to maintain a pH range of 2-3. Examples include, but are not limited to, ferric sulfate, ferric chroride, ferric acetylacetonate, ferric fluoride, and the like. The photodegradation was higher in the acid range than in the basic range, but in the case of a stronger acid than pH 2, the photodegradation was lower. When the concentration of Fe ³⁺ ions is less than 10 mg / L, the effect of addition cannot be obtained. When the concentration of Fe ³⁺ ions is more than 200 mg / L, the concentration of Fe ³⁺ ions aggregates to the iron compound, thereby degrading the photodegradation.

As such, after dispersing the Fe ³⁺ ions and reacting at a pH of 2 to 3 for 4 to 6 hours, an organic matter resolution of 90 to 100% can be obtained. Such a method of decomposing organic matter in water can be usefully used to efficiently remove organic matter in the water, such as endocrine disruptors (environmental hormone) or dyes.

Fe ³⁺ ions added to the water are considered to have high organic decomposition effects due to the increased OH radical concentration by the following reactors (7, 8), but this theory is not absolute.

In a fifth aspect, the present invention is a photochemical catalyst member in which the photochemical catalyst prepared as described above is fixed to a tube in which UV light is emitted using an inorganic binder, and a solution in which iron trivalent ions (Fe ³⁺ ) are dispersed in water. It provides an organic material processing apparatus, such as environmental hormones or dyes, characterized in that it comprises a reactor for holding.

More specifically, the reactor can be any known reactor type and material but using polymethyl-metha-acrylate (PMMA) or pyrex (PMMA) as described in the present invention, and the volume and volume / area ratio of 1.5 L is 0.941. It is more effective to use a cylindrical reactor of 1 / m. UV light emitting tube in the reactor used a glass tube such as (13) as shown in Figure 1, but is not necessarily limited thereto.

The processing apparatus of the present invention may be configured, for example, as shown in FIG. 1, but is not limited thereto. Various possible modifications thereof may be made, and such modifications are also included in the scope of the present invention. will be. In more detail with reference to Figure 1, (2) is a power supply, (3) a support frame and UV light emitted from a black light blue (LBB) lamp (6 W, dominant wavelength 365 nm) (5) Is condensed by the condenser 4, and the high heat generated at this time is radiated to the outside through the fan 1, and the condensed UV light is in the reactor through the optical fiber 14 made of PMMA from the tube 6 made of quartz. Is illuminated by. If the quartz connector 6 is not used, it is difficult to use for a long time because the optical fiber is deformed due to high heat. Various materials are known for the optical fiber, but in the present invention, it is preferable to use PMMA in consideration of workability. UV light transmitted through the optical fiber is supplied into the reactor via the glass tube (13). The glass tube has an outer diameter of 1 mm, and the outer surface is a photocatalyst immobilized using an inorganic binder. The reactor was designed to maintain a constant temperature using the coolant (7) and to allow the inflow of air (9). In addition, the stirrer 10, the pH measuring instrument 11, and the blower 12 are attached to the reactor, and samples can be collected and analyzed at regular intervals through the outlet 8.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the following examples are merely to illustrate the present invention, and the present invention is not limited thereto. The analysis of the samples prepared in Examples and Comparative Examples of the present invention It carried out by the following method.

(1) photo resolution

Photodegradation was tested by measuring the concentration of organics in water using a gas chromatography-mass spectrometer and a UV / VIS spectrometer. The GC-mass spectrometer used HP-6890 from Hewlett-Packard, USA and the UV-VIS spectrometer used UV-160A from Shimadzu, Japan. The resolution was calculated by the formula (9).

(9)

(2) photocatalyst film thickness

The thickness of the photocatalyst film fixed to the glass tube surface was measured using SEM (scanning electron microscopy, XL30 ESEM-FEG, FEI Co., N.Y., U.S.A.).

(3) stability and chemical resistance

The fixed photocatalyst film was treated with a sonicator for 10 minutes and evaluated as having a higher stability than the initial fixed amount of the photocatalyst. The ultrasonic grinder used Sonifier 450 from Branson, USA. In addition, the stability according to pH was evaluated as having excellent chemical resistance (acid resistance). When 90% or more of the weight of the initial fixed photocatalyst remained, the stability was good.

Example 1

Photolysis of bisphenol A dissolved in water was carried out using a cylindrical reactor having a volume of 1.5 L and a volume / area ratio of 0.941 1 / m. The light source was a BLB lamp (6 W, 365 nm wavelength) and 10 glass tubes in the reactor. The photocatalyst used anatase type titanium dioxide and the average particle diameter was 25 nm. Titanium inorganic binder was synthesized as follows. 9.5 mL of TTIP was added to 92.1 mL of ethanol and the reaction was started. After 30 minutes of stirring, 7.5 mL of water and 8.1 mL of hydrochloric acid were added thereto, followed by stirring for 90 minutes. At this time, it is better to add nitrogen to control the fast crystallization rate. 15 parts by weight of titanium dioxide powder used as a photocatalyst was added to 100 parts by weight of the inorganic binder in a sol state, and the mixture was stirred and fixed by a dip coating method. When the coating was repeated three times, the thickness of the fixed film was 5.3 μm as observed in SEM. This was dried for 30 minutes at 100 ° C and then sintered at 500 ° C for 12 hours. The photocatalyst fixed layer thus produced was very excellent in stability.

This photocatalyst-fixed glass tube was installed in the reactor, and 75 mg / L of Fe ³⁺ ions were added thereto to decompose. The initial 10 mg / L of bisphenol A was 1 mg / L after 4 hours and 0.6 hours after 5 hours. After 6 hours, the concentration dropped to 0.3 mg / L, indicating photoreactivity of 90%, 94% and 97%, respectively. In addition, as a result of treatment for 10 minutes using an ultrasonic crusher, the weight of the initially fixed photocatalyst was maintained at 100%, indicating that the stability and chemical resistance of the photocatalyst film were good.

Example 6

Photolysis of reactive black 5 (dye) dissolved in water was carried out using a cylindrical reactor having a volume of 1.5 L and a volume / area ratio of 0.941 1 / m. The light source used a BLB lamp (6 W, dominant wavelength 365 nm) and used 10 glass tubes in the reactor. The photocatalyst used anatase type titanium dioxide and the average particle diameter was 25 nm. Titanium inorganic binder was synthesized as follows. 11.2 mL of TTIP was added to 89.8 mL of propanol, and the reaction was started. After 30 minutes of stirring, 8.9 mL of water and 8.9 mL of hydrochloric acid were added thereto, followed by stirring for 90 minutes. At this time, it is better to add nitrogen to control the fast crystallization rate. 10 parts by weight of titanium dioxide powder used as a photocatalyst was added to 100 parts by weight of the inorganic binder in a sol state, and the mixture was stirred and fixed by a dip coating method. In the case of five repeated coatings, the thickness of the fixed film was 8.5 μm as observed in the SEM. This was dried for 30 minutes at 100 ° C and then sintered at 500 ° C for 12 hours. The photocatalyst fixed layer thus produced was very excellent in stability. This photocatalyst-fixed glass tube was installed in the reactor and decomposed with 60 mg / L of Fe ³⁺ ions. The initial 100 mg / L dye, reactive black 5, was 9 mg / L after 4 hours. The concentration dropped to L, 4 mg / L after 5 hours, and 1 mg / L after 6 hours, respectively, resulting in photodegradations of 91%, 96%, and 99%, respectively. In addition, as a result of treatment for 10 minutes by using an ultrasonic mill, the weight of the initially fixed photocatalyst was maintained at 99%, indicating that the stability and chemical resistance of the photocatalyst film were good.

Examples 2-5, 7-10 and Comparative Examples 1-10

The experiments were carried out in the same manner as in Example 1 and Example 6, and the organic matter photolysis was carried out, and the results were compared while changing the experimental conditions as shown in Table 1 below.

As can be seen from the results of Table 1, when the photocatalyst of the present invention was used without immobilization using an inorganic binder (Comparative Example 1), the resolution, stability, and chemical resistance of the photocatalyst were very poor. Although a smaller amount than the photocatalyst used in Comparative Example 1 is used, the photocatalyst immobilized using the inorganic binder of the present invention is not satisfactory, but shows a much higher resolution, stability, and chemical resistance than Comparative Example 1, and thus the immobilization method presented in the present invention. The efficiency of the In addition, in Comparative Examples 3 to 10, various reaction conditions of the present invention described above, for example, photocatalyst type, content, particle size, composition ratio in preparing inorganic binder, photocatalyst film thickness, Fe ³⁺ concentration, and pH are all Each has proved to be an important factor in the resolution, stability and chemical resistance of organic materials of photocatalysts. In contrast, Examples 1 to 10 using the photocatalyst prepared and treated according to the present invention quickly exhibited excellent efficiency in terms of resolution, stability and chemical resistance.

As described above, the immobilized photocatalyst has been found to be excellent in terms of both organic substance resolution, stability, and chemical resistance. Using the Fe ³⁺ iron catalyst together with the photocatalyst, an organic substance such as an endocrine disruptor (environmental hormone) or a dye It can be usefully used for wastewater and water treatment facilities containing.

1 schematically illustrates a reactor in which photochemical catalysis occurs.

FIG. 2 is a SEM (scanning electron microscope) photograph (X5000) showing the thickness of the photocatalyst film fixed under the conditions set forth in Example 1 according to the present invention.

3 is a SEM (scanning electron microscope) photograph (X5000) showing the thickness of the photocatalyst film fixed under the conditions shown in Example 6 according to the present invention.

<Description of Major Symbols in Drawing>

(2): Power supply (3): Support frame

(4): condenser (5): BLB (black light blue) lamp

(6): optical fiber conversion tube (7): coolant

(13): Glass tube fixed with TiO ₂ 14: Optical fiber

Claims (12)

delete delete A method of immobilizing a photocatalyst for immobilizing a photochemical catalyst used to remove organic matter in water using a titanium-based inorganic binder, wherein the titanium-based inorganic binder has a composition volume ratio of alcohol / TTIP (titanium tetraisopropoxide) of 4.5 to 10.5. It is an inorganic binder in a sol state obtained by starting the synthesis and reacting for 0.2 to 1 hour using the range of and then adding and using the composition volume ratio of water / hydrochloric acid in the range of 0.5 to 1.5, followed by stirring. The amount of the photocatalyst added to the inorganic binder for immobilization is in the range of 5 to 20 parts by weight of the photocatalyst powder with respect to 100 parts by weight of the inorganic binder, The thickness of the fixed photocatalyst film is in the range of 1 to 20 μm. delete delete delete delete delete A method for decomposing organic matter in water using a titanium-based inorganic binder used to immobilize a photochemical catalyst used to remove organic matter in water, wherein the composition volume ratio of alcohol / TTIP (titanium tetraisopropoxide) is used in the range of 4.5 to 10.5. After starting the synthesis and reacting for 0.2 to 1 hour, using the composition volume ratio of water / hydrochloric acid in the range of 0.5 to 1.5, the reaction is added, followed by stirring, using a photosolvent having an average particle of 5 to 50 nm using an inorganic binder in a sol state. A method for decomposing organic matter in water, wherein iron trivalent ions (Fe ³⁺ ) are additionally added to the photochemical catalyst having a thickness of 1 to 20 μm fixed thereto. 10. The method of claim 9, wherein the concentration of the iron trivalent ion is in the range of 10 to 200 mg / L. 10. The method of claim 9, wherein the higher the solubility of the iron trivalent ions, the higher the solubility of iron can be maintained. An organic matter treatment apparatus using a titanium-based inorganic binder used to immobilize a photochemical catalyst used to remove organic matter in water, and synthesized using a composition volume ratio of alcohol / TTIP (titanium tetraisopropoxide) in the range of 4.5 to 10.5. After reacting for 0.2 to 1 hour and then adding and using the composition volume ratio of water / hydrochloric acid in the range of 0.5 to 1.5, the mixture was stirred to prepare a photochemical catalyst having an average particle of 5 to 50 nm using an inorganic binder in a sol state. A reactor having a photochemical catalyst member in which a photochemical catalyst fixed to a thickness of 1 to 20 μm is fixed to a tube in which UV light is emitted using an inorganic binder, and a solution in which iron trivalent ions (Fe ³⁺ ) are dispersed in water. Organic material processing apparatus comprising a.