Hybrid water treatment agent of β-manganese dioxide nanoparticles and carbon nanotube, preparation method therefor, water treatment apparatus using same, and underground water in situ treatment apparatus

Abstract

The present invention relates to a water treatment agent, a preparation method therefor, a water treatment apparatus using the same, and an in-situ groundwater treatment apparatus and, more specifically, to: a water treatment agent comprising a carbon nanotube support, and -manganese dioxide nanoparticles adsorbed on the carbon nanotube support and having a particle size of 1,000 nm or less; a preparation method therefor; a water treatment apparatus using the same; and an in-situ groundwater treatment apparatus.

Claims

1. A water treatment agent comprising: a carbon nanotube support; and -manganese dioxide nanoparticles immobilized on the carbon nanotube support, in which the -manganese dioxide nanoparticles have a particle size less than or equal to 1,000 nm.

2. The water treatment agent according to claim 1, wherein the -manganese dioxide nanoparticles have a size of from 1 nm to 100 nm.

3. The water treatment agent according to claim 1, wherein the -manganese dioxide nanoparticles are formed singularly, or by agglomerating at least two particles.

4. The water treatment agent according to claim 1, wherein the water treatment agent further comprises an oxidant.

5. The water treatment agent according to claim 4, wherein the oxidant is any one selected from the group consisting of hydrogen peroxide (H.sub.2O.sub.2), ozone (O.sub.3), and sodium hypochlorite (NaOCl), or mixtures thereof.

6. A water treatment apparatus comprising a reaction tank, wherein the reaction tank is filled with a water treatment agent according to claim 1.

7. An in-situ groundwater treatment apparatus comprising a permeable reactive barrier, wherein the permeable reactive barrier is filled with a water treatment agent according to claim 1.

8. A method of preparing a water treatment agent, comprising: (S1) mixing potassium permanganate, distilled water, alcohol and a carbon nanotube support to prepare a mixed solution; and (S2) heat-treating the mixed solution at 120 to 200 C. for 15 to 36 hours, to form a carbon nanotube support having -manganese dioxide nanoparticles of a particle size less than or equal to 1,000 nm immobilized thereon.

9. The method of preparing a water treatment agent according to claim 8, after the step (S2), further comprising: (S3) heat-treating the carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon at 250 to 500 C. for 2 to 8 hours.

10. The method of preparing a water treatment agent according to claim 8, wherein a weight ratio of the potassium permanganate and the distilled water is from 1:50 to 1:200.

11. The method of preparing a water treatment agent according to claim 8, wherein a volume ratio of the distilled water and the alcohol is from 1:20 to 1:150.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings illustrate a preferred embodiment of the present disclosure, and together with the foregoing disclosure, serve to provide further understanding of the technical spirit of the present disclosure, and thus, the present disclosure is not construed as being limited to the drawings.

(2) FIG. 1 shows a scanning electron microscope (SEM) image of a carbon nanotube support according to one embodiment of the present disclosure.

(3) FIG. 2 shows a SEM image of a carbon nanotube support having needle-shaped -manganese dioxide nanoparticles immobilized thereon according to one embodiment of the present disclosure.

(4) FIG. 3 is a graph showing X-Ray Diffraction (XRD) analysis results of carbon nanotubes (CNTs) and a carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon (CMO/CNT) according to one embodiment of the present disclosure.

(5) FIG. 4 is a graph showing removal test results of an endocrine disrupting chemical 17-ethinylestradiol (EE2) using carbon nanotubes (CNTs), a water treatment agent (CMO/CNT) according to one embodiment of the present disclosure, and a mixture of the water treatment agent and hydrogen peroxide (CMO/CNT+HP).

(6) FIG. 5 is a flowchart showing a method of preparing a water treatment agent according to one embodiment of the present disclosure.

(7) FIG. 6 is an outline diagram showing a water treatment apparatus including a reaction tank filled with a water treatment agent according to one embodiment of the present disclosure.

(8) FIG. 7 is an outline diagram showing an in-situ groundwater treatment apparatus including a permeable reactive barrier filled with a water treatment agent according to one embodiment of the present disclosure.

(9) TABLE-US-00001 Description of Numerals 100: Water treatment apparatus 110: Water collection tank 120: Pump 130, 230: Chemicals tank 140, 240: Chemicals pump 150: Reaction tank 151, 251: Water treatment agent 160: Treated water tank 200: In-situ groundwater treatment apparatus 250: Permeable reactive barrier

BEST MODE

(10) Hereinafter, the present disclosure is described in detail. It should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present disclosure on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation.

(11) Furthermore, the disclosure depicted in the embodiments described herein are just one most preferred example of the present disclosure, not intended to represent all the technical aspects of the present disclosure, so it should be understood that alternatives, other equivalents and modifications would be made thereto at the time the present application is filed.

(12) FIG. 1 shows a scanning electron microscope (SEM) image of a carbon nanotube support according to one embodiment of the present disclosure, and FIG. 2 shows a SEM image of a carbon nanotube support having needle-shaped -manganese dioxide nanoparticles immobilized thereon according to one embodiment of the present disclosure.

(13) Hereinafter, referring to FIGS. 1 and 2, a water treatment agent of the present disclosure includes a carbon nanotube support; and -manganese dioxide nanoparticles immobilized on the carbon nanotube support, in which the -manganese dioxide nanoparticles have a particle size less than or equal to 1,000 nm.

(14) The water treatment agent of the present disclosure includes a carbon nanotube support having needle-shaped -manganese dioxide nanoparticles immobilized thereon as shown in FIG. 2.

(15) On the other hand, FIG. 3 is a graph showing X-Ray Diffraction (XRD) analysis results of carbon nanotubes (CNTs) and a carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon (CMO/CNT) according to one embodiment of the present disclosure.

(16) Referring to FIG. 3, a peak appears in the carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon (CMO/CNT), while no peak appears in the carbon nanotubes (CNTs), and it is a characteristic peak of -manganese dioxide nanoparticles, which signifies that the -manganese dioxide nanoparticles are immobilized and supported on the carbon nanotubes.

(17) Also, the following Table 1 shows Energy Dispersive X-ray Spectroscopy (EDS) results of carbon nanotubes (CNTs) and the carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon (CMO/CNT) according to one embodiment of the present disclosure. It can be seen that the CMO/CNT of the present disclosure includes a large amount of manganese.

(18) TABLE-US-00002 TABLE 1 CNT CMO/CNT Element Weight % Atomic % Weight % Atomic % C 91.11 93.59 61.91 80.98 O 7.96 6.14 11.68 11.47 S 0.2 0.08 Cl 0.3 0.1 Fe 0.43 0.1 Mn 26.41 7.55 Total 100 100 100 100

(19) On the other hand, as compared to particles at micro and larger scales, the manganese oxide nanoparticles have a large specific surface area and rich reactive sites and adsorption sites on the surface, so adsorptive removal performance of heavy metals and adsorption and oxidative removal performance of organic pollutants is far superior.

(20) According to earlier studies, metal oxide nanoparticles are known as having a far higher pollutant removal speed than micro-sized particles (Zhang, 2003). Particularly, because manganese oxide nanoparticles have a high oxidation-reduction potential, they show outstanding performance in the oxidation and degradation of organic pollutants (Zhao et al., 2006).

(21) However, laboratory-scale studies have been conducted in the related field until now, and in spite of outstanding pollutant removal performance as described above, manganese oxide nanoparticles have a problem with a loss in a real reactor, so they could not be used in a practical water treatment process.

(22) In this context, the present disclosure solved the problem with a loss in a reactor by immobilizing and supporting -manganese dioxide nanoparticles on a carbon nanotube support to easily separate -manganese dioxide nanoparticles from water to be treated.

(23) Because -manganese dioxide has higher specific surface area and higher average oxidation states than other manganese dioxide (-manganese dioxide and -manganese dioxide), it has higher catalytic activity than other manganese dioxide (Zhang et al., 2009).

(24) Also, -manganese dioxide nanoparticles are better than hydrogen peroxide at removing refractory organic pollutants, dyes, and when used with an oxidant (hydrogen peroxide, etc.), dye removal rates are greatly improved (Zhang et al, 2006). In addition, -manganese dioxide nanoparticles do not change in properties even though an oxidant (hydrogen peroxide, etc.) exists (Wang et al., 2006), and even after reused five times, they do not reduce in catalytic activity (Zhang et al., 2006), so they can be used for a long time, which gives an advantage to them.

(25) According to the present disclosure, -manganese dioxide nanoparticles are immobilized on a carbon nanotube support capable of adsorbing organic pollutants, so adsorptive removal and oxidative removal can be achieved at the same time, thereby improving removal rates of organic pollutants in water.

(26) Particularly, carbon nanotubes are light and highly adaptable in their application, are chemically and thermally stable, and have excellent mechanical and electrical properties, so they are far superior in the immobilization of nanoparticles.

(27) On the other hand, the size of the -manganese dioxide nanoparticles may be from 1 nm to 100 nm. When the numerical range is satisfied, adsorption performance of heavy metals or organic pollutants is further improved.

(28) Also, the -manganese dioxide nanoparticles may be formed singularly, but may be formed by agglomerating at least two particles.

(29) Further, when the water treatment agent further includes an oxidant, the pollutant removal performance by catalytic oxidation can be further improved.

(30) In this instance, the oxidant may be any one selected from the group consisting of hydrogen peroxide (H.sub.2O.sub.2), ozone (O.sub.3), sodium hypochlorite (NaOCl), ultraviolet light, electron beam, -ray, hydrodynamic cavitation and sonication, or mixtures thereof.

(31) On the other hand, FIG. 4 is a graph showing removal test results of 17-ethinylestradiol (EE2) which is one of the highly toxic endocrine disruption chemicals (EDCs), using carbon nanotubes (CNTs), a water treatment agent (CMO/CNT) according to one embodiment of the present disclosure, and a mixture (CMO/CNT+HP) of the water treatment agent and hydrogen peroxide (HP).

(32) Referring to FIG. 4, the carbon nanotubes having -manganese dioxide nanoparticles immobilized thereon (CMO/CNT) was found to have higher EE2 removal speed and removal rate than the carbon nanotubes (CNTs), and the mixture (CMO/CNT+HP) of CMO/CNT and hydrogen peroxide was found to have higher EE2 removal speed and removal rate than the CMO/CNT. In this instance, the initial concentration of the EE2 was 4 mg/L, the concentration of the CMO/CNT was 100 mg/L, the concentration of the hydrogen peroxide was 1,000 mg/L.

(33) On the other hand, FIG. 5 is a flowchart showing a method of preparing a water treatment agent according to one embodiment of the present disclosure. Hereinafter, the method of preparing a water treatment agent according to the present disclosure is described with reference to FIG. 5.

(34) First, potassium permanganate, distilled water, alcohol and a carbon nanotube support are mixed to prepare a mixed solution (S1).

(35) In this instance, a weight ratio of the potassium permanganate and the distilled water may be from 1:50 to 1:200, and if the numerical range is satisfied, a maximum amount of -manganese dioxide nanoparticles having an optimum size can be supported on carbon nanotubes. In relation to the weight ratio, if an amount of the distilled water exceeds the numerical range, an amount of potassium permanganate which forms -manganese dioxide nanoparticles is relatively low, reducing an amount of -manganese dioxide nanoparticles immobilized on carbon nanotubes, and as a consequence, reducing pollutant removal efficiency. On the contrary, if an amount of the distilled water is less than the numerical range, an amount of potassium permanganate which forms -manganese dioxide nanoparticles is relatively high, forming an excessive amount of -manganese dioxide nanoparticles. In this instance, an amount of -manganese dioxide nanoparticles immobilized on carbon nanotubes increases, but the formed -manganese dioxide nanoparticles aggregate together and act as a single particle larger than nanoparticles, reducing the pollutant removal efficiency.

(36) Also, a volume ratio of the distilled water and the alcohol may be from 1:20 to 1:150. If the volume ratio of the distilled water and the alcohol satisfies the numerical range, crystallinity is high, making it create sufficient temperature, pressure and oxidation conditions to form -manganese dioxide nanoparticles with high pollutant oxidation efficiency. However, in relation to the volume ratio, if an amount of the alcohol exceeds the numerical range, the pressure and temperature may rise too much, resulting in modification of thermal decomposition of the generated -manganese dioxide nanoparticles.

(37) Also, to increase an amount of immobilization and immobilization performance of the -manganese dioxide on the carbon nanotube support, the carbon nanotube support may be pre-treated using acids, alkalis, and salts.

(38) A method of pre-treating the carbon nanotube support is as follows.

(39) First, a carbon nanotube support to be pre-treated is impregnated with an aqueous solution such as hydrochloric acid (HCl), nitric acid (HNO.sub.3), sulfuric acid (H.sub.2SO.sub.4), sodium chloride (NaCl), sodium hydroxide (NaOH) for a predetermined period of time. Subsequently, the impregnated carbon nanotube support is separated from the aqueous solution by precipitation or filtration. Subsequently, the separated carbon nanotube support is dried, yielding a pre-treated carbon nanotube support.

(40) Subsequently, the mixed solution is heat-treated at 120200 C. for 1536 hours, to form a carbon nanotube support having -manganese dioxide nanoparticles of a particle size less than or equal to 1,000 nm immobilized thereon (S2).

(41) On the other hand, in addition to the carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon, a product after the step (S2) may include reaction by-products, and when they are removed and washing and drying is performed, only the carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon may be separated.

(42) Also, to improve the crystallinity of the carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon, after the step (S2), the method may further include heat-treating at 250 to 500 C. for 2 to 8 hours, followed by cooling. Thereby the quality and purity of the water treatment agent may be further improved.

(43) The carbon nanotube support having -manganese dioxide nanoparticles immobilized thereon as described above may be used in various fields including general water treatment, water recycling, and treatment of soils and groundwater, and related markets are wide.

(44) FIGS. 6 and 7 are outline diagrams respectively showing a water treatment apparatus including a reaction tank and an in-situ groundwater treatment apparatus including a permeable reactive barrier.

(45) Hereinafter, referring to FIGS. 6 and 7, for the water treatment apparatus 100 including the reaction tank 150 according to the present disclosure, the reaction tank 150 is filled with a water treatment agent 151 according to the present disclosure as described above. In this instance, according to necessity, the reaction tank 150 may be driven as fixed bed or fluidized bed. Also, according to necessity, the reaction tank 150 may be driven by up-flow or down-flow. Further, when needed, to improve the treatment efficiency, a chemical (an oxidant) may be further fed.

(46) Also, for the in-situ groundwater treatment apparatus 200 including the permeable reactive barrier 250 according to the present disclosure, the permeable reactive barrier 250 is filled with a water treatment agent 251 according to the present disclosure as described above. In this instance, according to necessity, to improve the treatment efficiency, a chemical (an oxidant) may be further fed.

(47) As described above, the water treatment agent according to the present disclosure may be applied to various water treatment including surface water and groundwater treatment and sewage recycling. In this instance, surface water and groundwater is used as a water source for a water purification process, and for water recycling, removal of toxic trace elements is required to produce safe recycled water.

(48) Particularly, recently, water resources of good quality are in shortage due to water resource pollution, climate change, and population growth and water demand exceeds water supply, so the world's population suffering water shortages is about 0.7 billion people in 2008 and will be about 3 billion people by 2025 (UN, 2007). Therefore, for the benefit of supply of water resources of good quality in sufficient amount, there is an urgent need for appropriate treatment technology of toxic trace elements in all water purification and sewage/wastewater treatment, and the water treatment agent according to the present disclosure may be a solution to the above problem.

(49) While the embodiments of the present disclosure disclosed hereinabove present merely particular examples to help the understanding, such embodiments are not intended to limit the scope of the present disclosure. It is obvious to those skilled in the art that in addition to the disclosed embodiments, modifications may be made based on the technical features of the present disclosure.