CN107151039B - Water treatment method using stainless steel nanotube array - Google Patents
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- CN107151039B CN107151039B CN201610120527.7A CN201610120527A CN107151039B CN 107151039 B CN107151039 B CN 107151039B CN 201610120527 A CN201610120527 A CN 201610120527A CN 107151039 B CN107151039 B CN 107151039B
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 122
- 229910001220 stainless steel Inorganic materials 0.000 title claims abstract description 106
- 239000010935 stainless steel Substances 0.000 title claims abstract description 106
- 239000002071 nanotube Substances 0.000 title claims abstract description 97
- 238000011282 treatment Methods 0.000 title claims abstract description 82
- 238000000034 method Methods 0.000 title claims abstract description 50
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 91
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- 229940012189 methyl orange Drugs 0.000 description 6
- 230000001590 oxidative effect Effects 0.000 description 6
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 5
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- 239000000460 chlorine Substances 0.000 description 5
- 239000010408 film Substances 0.000 description 5
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- 150000002894 organic compounds Chemical class 0.000 description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
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- 239000002245 particle Substances 0.000 description 3
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- 239000000126 substance Substances 0.000 description 3
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- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
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- -1 iron ions Chemical class 0.000 description 2
- 238000007726 management method Methods 0.000 description 2
- 244000005700 microbiome Species 0.000 description 2
- 238000010979 pH adjustment Methods 0.000 description 2
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 2
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- 229910052697 platinum Inorganic materials 0.000 description 2
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- 239000000758 substrate Substances 0.000 description 2
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- QDHHCQZDFGDHMP-UHFFFAOYSA-N Chloramine Chemical class ClN QDHHCQZDFGDHMP-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000003905 agrochemical Substances 0.000 description 1
- 238000002048 anodisation reaction Methods 0.000 description 1
- 230000004071 biological effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004061 bleaching Methods 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
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- 238000000349 field-emission scanning electron micrograph Methods 0.000 description 1
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- 239000012535 impurity Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000010842 industrial wastewater Substances 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N iron (II) ion Substances [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 231100000518 lethal Toxicity 0.000 description 1
- 230000001665 lethal effect Effects 0.000 description 1
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- 238000012423 maintenance Methods 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000002085 persistent effect Effects 0.000 description 1
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- 238000011084 recovery Methods 0.000 description 1
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- 239000002341 toxic gas Substances 0.000 description 1
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Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/30—Treatment of water, waste water, or sewage by irradiation
- C02F1/32—Treatment of water, waste water, or sewage by irradiation with ultraviolet light
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/722—Oxidation by peroxides
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/74—Treatment of water, waste water, or sewage by oxidation with air
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/02—Specific form of oxidant
- C02F2305/026—Fenton's reagent
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2305/00—Use of specific compounds during water treatment
- C02F2305/10—Photocatalysts
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- Chemical & Material Sciences (AREA)
- Water Supply & Treatment (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Physical Water Treatments (AREA)
- Treatment Of Water By Oxidation Or Reduction (AREA)
- Catalysts (AREA)
Abstract
Water treatment apparatus and methods using stainless steel nanotube arrays are disclosed. According to the water treatment apparatus and method, a stainless steel nanotube array having an increased specific surface area, which is stable in pH and temperature, is used as a photocatalyst. Unlike using existing photocatalysts, the use of stainless steel nanotube arrays eliminates the need to limit external environmental factors. The stainless steel nanotube array was used in combination with UV light and hydrogen peroxide. This combination is very effective in efficiently degrading the contaminants. The water treatment apparatus and method do not require additional equipment and contribute to a reduction in initial equipment costs. The stainless steel nanotube array is substantially free from loss and damage during oxidation. Thus, continuous water purification is possible and can greatly reduce the costs of production, management and water treatment. In addition, stainless steel nanotube arrays are much less corrosive and toxic than conventional photocatalysts, and prevent the possibility of secondary contamination. Thus, the apparatus and method achieve environmentally friendly water treatment.
Description
Technical Field
The invention relates to a high-efficiency water treatment method using a stainless steel nanotube array. More particularly, the present invention relates to a water treatment method for effectively removing contaminants from a water system using a stainless steel nanotube array prepared by anodizing a stainless steel surface to form nanotubes.
Background
With recent rapid industrial development, environmental pollution has become a serious problem. Various solutions have been developed to provide solutions to the problem of environmental pollution. In particular, increased household waste and industrial waste water is responsible for the release of large amounts of persistent pollutants into the water system. Such persistent pollutants cause serious pollution of water resources, making it difficult to provide clean water. Under these circumstances, there is a growing demand for water treatment facilities that can effectively prevent water resource pollution.
Some of the water treatment processes developed to date involve the use of microorganisms. Such biological water treatment methods do not cause secondary pollution and do not destroy the ecosystem due to their environmental friendliness. Despite these advantages, biological water treatment processes have limited utility in degrading pollutants present in water systems and require significant treatment, maintenance and management costs to meet increasingly stringent effluent quality requirements.
The water treatment process using chlorine chemicals can achieve the goals of bleaching and disinfection. However, chlorine chemicals readily react with organic compounds in water to produce carcinogens, such as chloramines, which can cause secondary pollution. In the case where chlorine-containing water is released into a river, the residual chlorine component in the treated water may cause many problems. For example, residual chlorine components are lethal to various kinds of microorganisms inhabiting a river region, thereby destroying the ecosystem.
In order to overcome the limitations of the above water treatment methods, various advanced oxidation methods using strong oxidizing Ultraviolet (UV) light, hydrogen peroxide, ozone, and a photocatalyst without causing secondary pollution have been proposed.
Advanced oxidation processes refer to more advanced water treatment technologies in which ozone/hydrogen peroxide, hydrogen peroxide/UV light, etc. are used to generate strongly oxidizing hydroxyl radicals (OH.) as a vehicle for oxidizing and degrading organic contaminants in contaminated water. Advanced oxidation processes have been developed to degrade persistent contaminants (e.g., synthetic detergents and agrochemicals) that are not readily degraded by typical treatment methods or to treat high concentrations of contaminants in a short period of time.
The water treatment using ozone alone is effective in suppressing THM generation, improving taste, preventing aggregation or precipitation, and enhancing biological activity. In addition, the strong oxidizing power of ozone can be expected. However, the slow reaction of ozone with most organic compounds leads to an increase in the capacity of the ozone supply of the treatment device. Ozone does not react with some organic compounds, which are therefore still not removed. That is, ozone reacts very selectively with organic compounds. This selectivity makes the use of ozone alone unsuitable for water treatment.
Ozone can produce carcinogens in the presence of bromine in raw water and is highly corrosive and toxic. In addition, ozone gas has limited solubility in water. For these reasons, water treatment using ozone is limited and causes many problems.
In a water treatment method using ozone and hydrogen peroxide, strongly oxidizing hydroxyl radicals are generated in a simple and efficient manner by irradiating UV light onto hydrogen peroxide as an oxidizing agent. However, an excess of hydrogen peroxide is required to obtain hydroxyl radicals in an amount sufficient to degrade organic contaminants present in raw water, which poses an economic burden.
The Fenton method is based on the use of iron (II) ions (Fe)2+) Incorporation of hydrogen peroxide (H) as catalyst2O2). The catalyst increases the oxidizing power of the hydrogen peroxide. The Fenton method is effective in a pH range of 3 to 5, and thus requires additional equipment or steps for pH adjustment, for example, equipment or steps for pH adjustment of raw water, equipment or steps for readjusting pH to a higher level to remove iron ions after oxidation is completed, and steps for removing precipitates generated from iron ions. Such additional equipment or steps complicate the process, which imposes a huge economic burden in terms of processing cost and time.
[ Prior Art document ]
[ patent documents ]
(patent document 1) Korean patent publication No. 10-2012-0048420
(patent document 2) Korean patent publication No. 1997-0065435
Disclosure of Invention
The present invention has been made keeping in mind the problems of the prior art, and an object of the present invention is to provide a water treatment apparatus, which is stable to external environmental factors and uses a stainless steel nanotube array having an exponentially increased specific surface area to effectively treat various types of pollutants present in a water system.
It is another object of the present invention to provide a water treatment method which does not generate by-products such as precipitates while achieving high degradation efficiency without controlling the conditions (e.g., pH and temperature conditions) of raw water and a reactor.
An aspect of the present invention provides a water treatment apparatus including a hollow reactor having a predetermined capacity, a feed pump for feeding raw water into the reactor, a transfer pump for transferring treated water from the reactor to the outside, at least one stainless steel nanotube array installed in the reactor to be at least partially in contact with the raw water, Ultraviolet (UV) irradiation means for irradiating UV light onto the stainless steel nanotube array, and hydrogen peroxide supply means for supplying hydrogen peroxide to the reactor.
The stainless steel nanotube array is attached to the inside of the reactor or spaced apart from the inside of the reactor by a predetermined distance.
The UV irradiation device is in the form of a cylinder rotatably mounted and axially arranged in the central part of the reactor.
The UV irradiation device includes at least one UV lamp axially disposed in a cylinder, blades attached at upper and lower ends of the cylinder, and a variable speed motor connected to a hollow rotary shaft integrally attached to the upper end of the cylinder to provide a rotational force.
The stainless steel nanotube array is prepared by anodizing a stainless steel thin film.
The stainless steel nanotubes have an outer diameter of 10nm to 500nm and an average length of 1nm to 100 nm.
Another aspect of the present invention provides a water treatment method comprising I) feeding raw water into a reactor by a feed pump, II) treating the raw water in the reactor with UV light, hydrogen peroxide and a stainless steel nanotube array, and III) transferring the treated water to the outside of the reactor.
In step II), the stainless steel nanotube array is irradiated with UV light of a wavelength of 200nm to 400 nm.
The stainless steel nanotubes have an outer diameter of 10nm to 500nm and an average length of 1nm to 100 nm.
According to the water treatment apparatus and method of the present invention, a stainless steel nanotube array having an increased specific surface area, which is stable in pH and temperature, is used as a photocatalyst. Unlike using existing photocatalysts, the use of stainless steel nanotube arrays eliminates the need to limit external environmental factors. The stainless steel nanotube array was used in combination with UV light and hydrogen peroxide. This combination is very effective in efficiently degrading the contaminants.
In addition, the water treatment apparatus and method of the present invention do not require additional apparatuses such as an apparatus for precipitate separation, an apparatus for photocatalyst supply, and an apparatus for photocatalyst recovery, which contribute to a reduction in initial equipment cost. The stainless steel nanotube array is substantially free from loss and damage during oxidation. Thus, continuous water purification is possible and can greatly reduce the costs of production, management and water treatment.
In addition, stainless steel nanotube arrays are much less corrosive and toxic than conventional photocatalysts, and prevent the possibility of secondary contamination. Thus, the apparatus and method of the present invention enable environmentally friendly water treatment.
Drawings
These and/or other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a cross-sectional view illustrating the structure of a water treatment apparatus according to a first embodiment of the present invention;
fig. 2 is a cross-sectional view illustrating the structure of a UV irradiation device installed in a water treatment apparatus according to a second embodiment of the present invention;
FIG. 3 is an FE-SEM photograph showing the surface morphology of the stainless steel nanotube array prepared in preparation example 1;
fig. 4 is a graph showing experimental results obtained when organic contaminants are degraded by treatment with the stainless steel nanotube array prepared in preparation example 1, hydrogen peroxide, UV light, or a combination thereof;
FIG. 5 is a graph comparing experimental results obtained when organic contaminants are degraded by treatment with a combination of UV light and hydrogen peroxide using a raw stainless steel thin film as a photocatalyst with experimental results obtained when the same type of organic contaminants are degraded by treatment with a combination of UV light and hydrogen peroxide using a stainless steel nanotube array as a photocatalyst; and
fig. 6 is a graph showing life characteristics of the stainless steel nanotube array prepared in preparation example 1 when repeatedly used in combination with UV light and hydrogen peroxide according to the present invention.
Detailed Description
The objects, specific advantages and novel features of the invention will become apparent from the following detailed description of the preferred embodiment when considered in conjunction with the drawings. It should be noted that wherever possible, the same elements are indicated by the same reference numerals even though they are depicted in different drawings. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. In the description of the present invention, a detailed explanation of the related art is omitted when it is considered that it may unnecessarily obscure the essence of the present invention.
Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
Fig. 1 is a cross-sectional view illustrating the structure of a water treatment apparatus according to a first embodiment of the present invention. With respect to fig. 1, the water treatment apparatus includes a hollow reactor 100 having a predetermined capacity, a feed pump 200 for feeding raw water into the reactor 100, a transfer pump 300 for transferring treated water from the reactor 100 to the outside, at least one stainless steel nanotube array 400 installed in the reactor 100 to be at least partially in contact with the raw water, a UV irradiation device 500 for irradiating UV light onto the stainless steel nanotube array 400, and a hydrogen peroxide supply device 600 for supplying hydrogen peroxide to the reactor 100.
A feed pump 200 is provided in the pipeline to feed external raw water into the reactor 100.
The UV irradiation apparatus 500 is installed in the reactor 100, and may take, as an example, a light irradiation lamp, particularly a high-pressure mercury lamp.
At least one light irradiation lamp as the UV irradiation device 500 may be installed at the top, side or bottom of the reactor 100. The size of the light irradiation lamp can be appropriately adjusted.
The hydrogen peroxide supplier 600 is connected to a hydrogen peroxide storage tank and has a pipe line connected at one end to the top, side or bottom of the reactor 100. Hydrogen peroxide is fed into the reactor 100 through the hydrogen peroxide supply device 600.
Preferably, the stainless steel nanotube array 400 is in close contact with the inside of the reactor 100 or is spaced apart from the inside of the reactor 100 by a certain distance. It is desirable to maintain a distance of 0.1cm to 30 cm.
Preferably, the stainless steel nanotubes have an outer diameter of 10nm to 500nm and an average length of 1nm to 100 nm. Stainless steel nanotubes having dimensions smaller than those defined above are complex to produce, require complex production conditions that are difficult to achieve, and may be unsatisfactory in strength. Meanwhile, stainless steel nanotubes of a size larger than the above-defined size cannot provide sufficient surface area for degrading organic pollutants, resulting in lower organic pollutant degradation efficiency than the conventional titania-based method or the Fenton method. It is most preferable that the size of the stainless steel nanotube is appropriately selected within the range defined above in consideration of the raw water state and the like.
The shape of the stainless steel nanotube array 400 is not particularly limited and may be appropriately determined according to the position of the nanotube array 400 in the reactor. The stainless steel nanotube array 400 is preferably rectangular in shape except when it is attached to the inside of the reactor. The rectangular shape is advantageous in maximizing the contact area of the stainless steel nanotube array 400 with raw water and hydrogen peroxide.
The rectangular stainless steel nanotube array 400 may have an aspect ratio of 1 to 3. In consideration of the amount of contaminated water or the size of the reactor, it is most preferable to appropriately select the length and width of the stainless steel nanotube array 400 within the range defined above.
Titanium dioxide as a representative photocatalyst exists in two forms: powder and an immobilized phase. Titanium dioxide powder has proven to be highly effective in water treatment due to its large specific surface area. However, titanium dioxide powder is difficult to separate and recover from water. In order to reuse the photocatalyst and obtain clean water, the titanium dioxide needs to be completely recovered. For this reason, an expensive technique is additionally required. Fine powder particles of titanium dioxide tend to agglomerate into larger particles during water treatment. As the aggregation proceeds, the separation efficiency of titanium dioxide gradually decreases. The dose rate decreases rapidly as the distance of the fine powder from the light source increases. For these reasons, the titanium dioxide powder is difficult to apply to high-capacity water treatment equipment.
Techniques for immobilizing photocatalysts such as titanium dioxide on a substrate or support have been developed. However, the stability of the immobilized photocatalyst attached to a substrate or a support is decreased with increasing frequency of water treatment, resulting in loss of the photocatalyst. This loss results in poor degradation efficiency.
The stainless steel nanotube array 400 is prepared by anodizing a stainless steel thin film to form nanotubes on the surface of the stainless steel thin film. Unlike conventional photocatalysts, the stainless steel nanotube array 400 is not present in the form of a powder, but is provided in the form of a thin film. Thus, the stainless steel nanotube array 400 experiences less degradation in adhesion stability during processing. As a result, the stainless steel nanotube array is free from loss or damage despite long-term use, so that it can be prevented from floating in a water system. Even when the stainless steel nanotube array 400 is attached to the inside of the reactor 100, it can be replaced with a new stainless steel nanotube array during processing without stopping the operation of the reactor 100. Therefore, the form of the stainless steel nanotube array 400 installed in the reactor 100 is not particularly limited.
The stainless steel nanotube array 400 is stable to external environmental factors such as pH, temperature and heat, which achieves high degradation efficiency without controlling the conditions of raw water fed into the reactor 100.
Unlike water treatment apparatuses using ozone or an oxychlorinating agent, the water treatment apparatus using the non-toxic stainless steel nanotube array 400 does not cause secondary pollution, and thus is environment-friendly.
The water treatment apparatus of the present invention may further include a rotating shaft 110 to provide a rotating force in the reactor 100. The rotation shaft 110 may be disposed at a central portion of the reactor 100. It is preferable that the rotation axis 110 is spaced apart from the stainless steel nanotube array 400 installed in the reactor 100. The distance is preferably 1cm to 20 cm. The movement of the rotary shaft 110 makes raw water entering the reactor 100 flowable, resulting in an increase in contact area of raw water with hydrogen peroxide, UV light and a stainless steel nanotube array. This increased contact area shortens the time it takes to treat the raw water.
The combination of the stainless steel nanotube array 400, the UV irradiation device 500, and the hydrogen peroxide supply device 600 in the water treatment apparatus according to this embodiment of the present invention increases the possibility that a large amount of hydroxyl radicals may be generated, which contributes to a significant reduction in the time taken to treat raw water, as compared to the use of hydrogen peroxide and UV light in the conventional water treatment method.
The water treatment method of the present invention is cost-effective compared to the conventional water treatment method because a large amount of radicals can be generated by the stainless steel nanotube array even when a small amount of hydrogen peroxide is supplied.
Hereinafter, a water treatment apparatus according to a second embodiment of the present invention will be described with reference to fig. 2. Fig. 2 is a cross-sectional view of the water treatment apparatus.
The water treatment apparatuses according to the first and second embodiments of the present invention are similar as a whole, but are different in that the water treatment apparatus according to the second embodiment is configured such that UV light and rotational force are more effectively provided to the reactor 100', as shown in fig. 2. Specifically, the stainless steel nanotube array 400 ' is in the form of a cylinder 401 ' rotatably installed and axially arranged at a central portion of the reactor 100 ', blades 402 ' are attached at upper and lower ends of the cylinder 401 ', a variable speed motor 404 ' is connected with a rotation shaft 403 ' to provide a rotation force, and the rotation shaft 403 ' is integrally attached to the upper end of the cylinder 401 '.
Repeated explanation of the same components in the water treatment apparatuses of the first and second embodiments is omitted herein.
Another aspect of the present invention relates to a water treatment method comprising I) feeding raw water into a reactor by a feed pump, II) treating the raw water in the reactor with UV light, hydrogen peroxide and a stainless steel nanotube array, and III) forcibly transferring the treated water to the outside of the reactor.
The stainless steel nanotube array is prepared by forming nanotubes on the surface of a stainless steel thin film. The nanotubes did not peel off from the stainless steel film during water treatment.
The stainless steel nanotube array is prepared by anodic oxidation. Specifically, anodic oxidation is performed by immersing a stainless steel thin film and another conductive material such as platinum or copper in an electrolyte solution and applying a voltage to the thin film and the conductive material. As a result of the anodic oxidation, nanotubes having a uniform size are formed on the entire surface of the stainless steel thin film.
In the water treatment method, a stainless steel nanotube array prepared by anodic oxidation is used as a photocatalyst.
According to the water treatment method, first, raw water is fed into a reactor by a feed pump.
Thereafter, a stainless steel nanotube array was installed in the reactor and hydrogen peroxide and UV light were supplied to the reactor. In the reactor, organic contaminants present in the raw water are disposed of by oxidation. After the reaction is complete, the treated water is transferred to the outside of the reactor.
Preferably, the stainless steel nanotubes have an outer diameter of 10nm to 500nm and an average length of 1nm to 100 nm. Stainless steel nanotubes having dimensions smaller than those defined above are complex to produce, require complex production conditions that are difficult to achieve, and may be unsatisfactory in strength. Meanwhile, stainless steel nanotubes of a size larger than the above-defined size cannot provide sufficient surface area for degrading organic pollutants, resulting in lower organic pollutant degradation efficiency than the conventional titania-based method or the Fenton method. It is most preferable to appropriately select the size of the stainless steel nanotube within the range defined above in consideration of the state of raw water.
In step II), the stainless steel nanotube array is preferably irradiated with UV light of a wavelength of 200nm to 400 nm. The use of full band UV lamps for UV irradiation is inefficient because the amount of hydroxyl radicals produced is not significantly related to energy consumption.
The water treatment method may further include removing suspended matters having a large particle size from the raw water fed into the reactor. This pretreatment ensures faster water treatment by the water treatment method of the present invention compared to that by the existing UV light/hydrogen peroxide based water treatment method and Fenton method, and allows continuous water treatment without loss of degradation efficiency due to external environmental factors such as pH and temperature.
Stainless steel nanotube arrays can be used semi-permanently, avoiding the need to stop processing and exchange the photocatalyst or use additional equipment for continuously feeding the photocatalyst. That is, the water treatment method of the present invention does not have the problems encountered in the existing water treatment methods. Therefore, the water treatment method of the present invention is very advantageous from the viewpoint of economic efficiency.
The present invention will be described in more detail with reference to the following examples. However, these examples should not be construed as limiting or restricting the scope and disclosure of the present invention. It is understood that one skilled in the art can easily implement other embodiments of the present invention not explicitly provided by the experimental results based on the teachings of the present invention including the following examples. It is also to be understood that such modifications and variations are intended to be included within the scope of the appended claims.
<Preparation example 1>
Stainless steel (304L) film was cut to a size of 10mm by 10mm, which facilitated anodic oxidation and electroreduction. Possible impurities, such as organic substances, are removed from the surface of the stainless steel thin film by physical/chemical etching. The etched stainless steel film was cleaned with distilled water and ethanol. Physical etching was performed using sandpaper, and chemical etching was performed using a solution of hydrofluoric acid, nitric acid, and distilled water (1:4:5, v/v/v). The chemical etching is performed within 30 seconds to prevent the formation of metal defects and the generation of toxic gases due to hydrogen embrittlement. Nanotubes were formed on the stainless steel surface pretreated using an anodic oxidation system. A 5% by volume solution of perchloric acid (70%) in ethanol was used as an electrolyte for the anodic oxidation. The anodization was carried out under constant voltage conditions using a power supply system (EP1605, PNCYS). A stainless steel film was arranged as an anode, and a 95% platinum or copper film or wires wound at 5cm uniform intervals were arranged as a cathode. A cooler was used to maintain a constant temperature of 5 ℃. The anodizing time is 10 minutes to 20 minutes. The anodized stainless steel was then rinsed with distilled water and ethanol and stored in a desiccator before being used in the next experiment.
FIG. 3 is an FE-SEM image showing the surface topography of a stainless steel nanotube array. The figure shows that the nanotubes are formed uniformly over the entire surface of the stainless steel thin film. The nanotubes were observed to have an outer diameter of about 100 nm.
The following experiment was conducted to evaluate the efficiency of the water treatment method of the present invention for degrading methyl orange as an organic pollutant in an artificially contaminated solution. The pH of the artificially contaminated solution is about 6 to 8.
The artificially contaminated solution was treated with an array of stainless steel nanotubes as catalyst, hydrogen peroxide (30%) at a fixed concentration of 1% and a UV lamp at a power of 5W.
Fig. 4 is a graph showing experimental results obtained when organic contaminants are degraded by treatment with a stainless steel nanotube array, hydrogen peroxide, UV light, or a combination thereof. In this figure, SSNT, H2O2And UV refers to treatment with stainless steel nanotube arrays, hydrogen peroxide, and UV light, respectively.
The concentration of methyl orange, the organic contaminant remaining in the artificially contaminated solution, was measured after treatment with hydrogen peroxide alone. As a result, methyl orange remains unremoved. About 5% to 7% of the methyl orange was removed after treatment with UV light alone or with a combination of stainless steel nanotube arrays and hydrogen peroxide. Only about a 1% to 4% increase in methyl orange removal was observed after treatment with a combination of UV light and stainless steel nanotube arrays.
In contrast, removal efficiencies of about 80% and 99% were achieved 10 and 20 minutes after treatment with UV light/hydrogen peroxide without the addition of the stainless steel nanotube array, respectively.
In particular, when treated simultaneously with stainless steel nanotube array/UV light/hydrogen peroxide, 99% of methyl orange was removed in the first 10 minutes, which demonstrates that the water treatment method of the present invention is excellent in degradation efficiency and reduction of the time taken for treatment by half or more compared to the conventional advanced oxidation method using UV light/hydrogen peroxide.
Fig. 5 is a graph comparing experimental results obtained when organic contaminants are degraded by treatment with a raw stainless steel thin film as a photocatalyst in combination with UV light and hydrogen peroxide, with experimental results obtained when the same type of organic contaminants are degraded by treatment with a stainless steel nanotube array as a photocatalyst in combination with UV light and hydrogen peroxide. As a control, no photocatalyst was added.
As shown in fig. 5, the use of a stainless steel nanotube array as a photocatalyst results in a reduction of the treatment time by half or more compared to the use of UV light and hydrogen peroxide in conventional advanced oxidation processes.
Fig. 6 is a graph showing the lifetime characteristics of a stainless steel nanotube array when the water treatment method according to the present invention is repeatedly used in combination with UV light and hydrogen peroxide.
As shown in fig. 6, the degradation performance of the stainless steel nanotube array remained unchanged even when the stainless steel nanotube array was repeatedly used 1 to 100 times, and no weight loss of the stainless steel nanotube array was observed. Based on these findings, it was concluded that the water treatment method of the present invention using stainless steel nanotube arrays could be used continuously and consistently.
Claims (6)
1. A water treatment apparatus comprising a hollow reactor having a predetermined capacity, a feed pump for feeding raw water into the reactor, a transfer pump for transferring treated water from the reactor to the outside, at least one stainless steel nanotube array installed in the reactor to be at least partially in contact with raw water, Ultraviolet (UV) irradiation means for irradiating Ultraviolet (UV) light onto the stainless steel nanotube array, and hydrogen peroxide supply means for supplying hydrogen peroxide to the reactor, wherein the stainless steel nanotubes have an outer diameter of 10nm to 500nm and an average length of 1nm to 100 nm.
2. The apparatus of claim 1, wherein the array of stainless steel nanotubes is attached to the inside of the reactor or is spaced a predetermined distance from the inside of the reactor.
3. The apparatus of claim 1, wherein the UV irradiation means is in the form of a cylinder rotatably installed and axially disposed at a central portion of the reactor, and includes at least one UV lamp axially disposed in the cylinder, blades attached at upper and lower ends of the cylinder, and a variable speed motor connected to a hollow rotation shaft integrally attached to an upper end of the cylinder to provide a rotation force.
4. The apparatus of claim 1, wherein the array of stainless steel nanotubes is prepared by anodizing a thin film of stainless steel.
5. A method of water treatment comprising: I) feeding raw water into a reactor by a feed pump, II) treating the raw water in the reactor with UV light, hydrogen peroxide and a stainless steel nanotube array, and III) forcibly transferring the treated water to the outside of the reactor, wherein the stainless steel nanotubes have an outer diameter of 10nm to 500nm and an average length of 1nm to 100 nm.
6. The method according to claim 5, wherein in step II), the stainless steel nanotube array is irradiated with UV light of a wavelength of 200nm to 400 nm.
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