JP5950326B2 - Mesoporous alumina carrying arsenic ion-adsorbing compound, arsenic ion recovery method using the same, and arsenic-free aqueous solution production method - Google Patents

Description

The present invention relates to a mesoporous alumina having a regular arrangement supporting an arsenic ion-adsorbing compound capable of selectively adsorbing arsenic ions as a target metal, and is supported on mesoporous alumina. The present invention relates to a method and system for efficiently and selectively recovering arsenic ions contained in an arsenic ion dissolving solution (or arsenic ion aqueous solution) containing arsenic ions using an arsenic ion-adsorbing compound.

Arsenic (element symbol As) is one of the Group 15 elements and is widely distributed in the earth's crust. It is released naturally into the environment by volcanic activities, or by the mining of ores and fossil fuels and industrial activities. I'm leaning. Seawater also contains about 2 ppb of arsenic, and plankton and seaweed take in and accumulate arsenic from seawater. Since these foods are also stored in the seafood, we take arsenic into our human bodies. On the other hand, as represented by the arsenic milk incident, arsenic is toxic, and the lethal dose of inorganic arsenic is about 2 mg (2 ppm) per kg of body weight. In addition, ingestion of trace amounts of arsenic less than this concentration causes vomiting, abdominal pain, diarrhea and other symptoms, liver dysfunction, and more than sensation, and chronic arsenic intake is said to cause neuropathy and carcinogenicity. Yes. Therefore, since the mixing of arsenic ions into water for use is life-threatening, it is required to eliminate arsenic as much as possible from the food and drinking water we consume. (Non-Patent Documents 1 and 2)

Even if water is treated at a water purification plant to remove arsenic, arsenic is detected at a dangerous level in public drinking water supplies in many communities. For example, high arsenic concentrations in drinking water have recently been reported from USA, China, Bangladesh, Taiwan, Mexico, Argentina, Poland, Canada, Hungary, India, etc., and there are reports from Japan. In water, the most common valence state of arsenic exists in the form of pentavalent arsenic As (V), or arsenates, which are widely present in aerobic surface water. Trivalent arsenic As (III) exists in the form of arsenite, which is likely to be generated in groundwater with little oxygen. In the environmental level of pH 4 to 10, the dominant trivalent arsenic As (III) compound is neutral in terms of charge, while the pentavalent arsenic As (V) compound is negatively charged. doing.

Various methods have been developed to detect As as described below. Advanced analysis (Non-patent documents 3 and 4), Raman / infrared spectroscopy (Non-patent documents 5 and 6), ICP mass spectrometry (Non-patent document 7), electrochemical analysis (Non-patent document 8), chemiluminescence analysis ( Non-patent document 9), atomic absorption analysis (non-patent documents 10 and 11), atomic fluorescence spectroscopy (non-patent document 12), and chromatography (non-patent documents 13 and 14). While these methods are certainly valuable and each method has its own advantages, it cannot be denied that there are drawbacks. For example, Zhu et al. (Non-Patent Document 15) has announced that the detection limit of As ³⁺ in hydride generation atomic fluorescence spectrometry is 0.04 ngl-1 in As detection using a dielectric barrier discharge sprayer. Then, there is a concern about the great influence of temperature. Also, Vincent et al. (Non-Patent Document 16) announced the detection of As by the collision cell technology ICP-MS system, but despite the high sensitivity, polyatomic interference formation was seen in the collision cell. Heitland et al. (Non-Patent Document 17) published high-speed determination of urinary As by high performance liquid chromatography (HPLC) -ICP / MS, but is expensive and the large amount of organic solvent used is toxic. Matsunaga et al. (Non-Patent Document 4) newly developed a naked-eye detection method for a small amount of As in a water-soluble sample, but appropriately controlled advanced conditions are required. Furthermore, the detection limit in this method is 1 × 10 ⁻⁶ mol dm ⁻³ and the reaction is very slow.

For removing As ions present in water, an agglomeration method, a catalyst method and an adsorption method are known.
As an aggregating method, as shown in Patent Document 1, an iron salt or polyaluminum chloride (PAC) (general formula [Al ₂ (OH) _n Cl _6-n ] _m (where 1 <n <5, m <10 )) Is known to be removed by oxidative agglomeration, and its publication discloses that the As concentration is reduced to 0.001 ppm which satisfies the effluent standard of less than 0.001 ppm adopted in 1993. It is shown.
As a catalyst method, as shown in Patent Document 2, a catalyst in which rhodium is supported on alumina (rhodium content 5% by weight, manufactured by Aldrich) is used as a catalyst, and ions are reduced and removed by hydrogen aeration. It has been shown that the As ion concentration can be 10 ppb.
As for the adsorption method, those shown in Patent Documents 3 to 7 below are known. Patent Document 3 discloses an adsorbent containing a zirconium-based mesostructure containing a sulfate ion (pore diameter D20 to 50 nm, hexadecyltrimethylammonium bromide (HTAB) content 39% by weight, HTAB cross section diameter 30 to 40 nm). As, it is shown that the As concentration can be 4000 μmol / L or less. Patent Document 4 discloses that the As concentration of water permeated through a filter made of a chelate fiber (Kyrest Co., Ltd., Kyrest Fiber GRY) in which N-methyl-D-glucamine is immobilized on fibrous cellulose powder is 0.1 ppm or less. It is shown that.
In Patent Document 5, a γ-alumina support carrying a rare earth metal oxide or hydroxide in an amount of 5 to 60% by mass (average pore diameter 119 nm, pore volume 0.713 cm ³ / g, surface area 240 m ² / g). In an example in which the ratio of 90 to 200 nm pores in the total pore volume (88%) was used as the adsorbent, the As concentration was 0.8 ppm.
Patent Document 6 shows that when the aminopropyl group-modified magnetic fine particles were used as the adsorbent, the As concentration could be 0.1 ppm.
In Patent Document 7, 8 g of bis (2-ethylhexyl) ammonium bis (2-ethylhexyl) dithiocarbamate is supported on 20 g of a porous polyacrylate resin and an impregnating resin in a granular form is used. It has been shown to reduce to ^{x10 -7} mol / liter.

JP 07-088482 A JP-A-9-327694 JP 2000-176441 A JP 2005-000747 A JP 2000-024647 A JP 2005-046728 A JP-A-10-137504 Japanese Patent Laid-Open No. 08-267053

P. B. Tchounwou, J.M. A. Centeno, A.M. K. Patrolla, Mol. Cell. Biochem. 255 (2004) 47. M.M. F. Hughes, Toxicol. Lett. 133 (2002) X. Peng, G.M. S. Chen, Chin. J. et al. Anal. Chem. 31 (2003) 38. H. Matsunaga, C.I. Kanno, T .; M.M. Suzuki, Talanta 66 (2005) 1287. C. Ludwig, H.M. J. et al. Gotze, M.M. Dolny, Spectrochim. Acta Part A 56 (2000) 547. C. Ludwig, M.M. Dolny, H.M. J. et al. Gotze, Spectrochim. Acta Part A 53 (1997) 2363. V. Dufailly, L.M. Noel, T.W. Guerin, Anal. Chim. Acta 611 (2008) 134. R. Piech, W.M. W. Kubiak, J. et al. Electroanal. Chem. 599 (2007) 59. C. Lomonte, M.M. Currell, M.M. J. et al. S. Richard, Anal. Chim. Acta 583 (2007) 72. J. et al. Michelon, V.M. Deluchat, R.A. A. Shukry, C.I. Dagot, J.M. C. Bollinger, Talenta 71 (2007) 479. C. G. Bruhn, C.I. J. et al. Bustos, K.M. L. Saez, J .; Y. Neira, S.M. E. Alvarez, Talenta 71 (2007) 81. X. Li, Y. Su, K.K. Xu, Talenta 72 (2007 1728). A. L. Lindberg, W.M. Goessler, M.C. Grander, B.M. Nermell, M.M. Vahter, Toxicol. Lett. 168 (2007) 310. Y. C. Yip, H.M. S. Chu, C.I. F. Yuen, W .; C. Sham, J .; AOAC Int. 90 (2007) 284. Z. L. Zhu, J. et al. Liu, S .; H. Zhang, Anal. Chim. Acta 607 (2008) 136. D. Vincent, N.M. Laurent, G .; Thierry, Anal. Chim. Acta 611 (2008) 134. P. Heitland, H.M. D. Koster, J.A. Anal. Toxicol. 32 (2008) 308.

As described above, removing toxic arsenic ions from living water such as drinking water in the environment to reduce the arsenic ion concentration as much as possible should be realized in order to protect human life. There are few techniques and methods for reducing the concentration in an aqueous solution to an ultra trace level of the ppt to ppb level. Further, in the conventional technique, it takes a long time to lower the arsenic ion concentration in the drinking water, and the productivity is poor and the cost cannot be reduced. In addition, special equipment and devices are required, which increases costs. Adding acid or alkali to the solution to reduce the arsenic ion concentration means that even if the arsenic ion concentration decreases, the additive must be post-treated (removed or detoxified) at the next stage. There's a problem. In addition, the method of heating and promoting the reaction requires a large heating means even if the arsenic ion concentration decreases, and also requires a cooling system, increasing energy consumption and increasing the overall cost of arsenic recovery. Let

The present invention is a mesoporous-alumina supporting an arsenic ion-adsorbing compound that preferentially selectively adsorbs (extracts or binds) arsenic {As (V)} ions, The present invention provides a system and method for extracting arsenic ions from an arsenic ion solution in which arsenic ions are dissolved in an aqueous solution. The outline of the present invention is as follows.
(1) The present invention is an arsenic ion adsorptivity capable of adsorbing arsenic ions and releasing adsorbed arsenic ions from a solution (arsenic ion-dissolved solution) in which arsenic (As) ions as target elements are dissolved Compound-supported mesoporous alumina, which is made using aluminum nitrate and a surfactant, which is camphor sulfanic acid (CSA) or cetyltrimethylammonium bromide (CTAB) It is characterized by that. Alternatively, mesoporous alumina is produced by hydrolysis of aluminum isopropoxide (C ₉ H ₂₁ AlO ₃ ).

(2) In the present invention, the arsenic ion adsorbing compound is a compound capable of selectively adsorbing the target element, arsenic ions, the arsenic ion adsorbing compound is a heteropolyacid, and the heteropolyacid is ammonium molybdate. In addition, solid state alumina obtained after acting a surfactant on mesoporous alumina was mixed in an aqueous solution containing ammonium molybdate to support ammonium molybdate on mesoporous alumina, and ammonium molybdate. The temperature for adsorbing arsenic ions by contacting mesoporous alumina supporting arsenic ions with the arsenic ion dissolving solution is normal temperature, and the pH when adsorbing arsenic ions by contacting mesoporous alumina supporting ammonium molybdate with the arsenic ion dissolving solution is pH Pre-processing such as adjustment and / or Post-treatment is characterized by not performed.

(3) The present invention uses ascorbic acid to determine the concentration of adsorbed arsenic ions by color tone when adsorbing arsenic ions by contacting mesoporous alumina carrying an arsenic ion adsorbing compound with an arsenic ion solution. It is characterized by doing. Furthermore, when adsorbing arsenic ions by bringing mesoporous alumina into contact with the arsenic ion solution, the concentration of the adsorbed arsenic ions is determined by color tone using ascorbic acid. This is a method for detecting the arsenic ion concentration.

(4) The present invention is an arsenic collector characterized by collecting arsenic (As) from an arsenic ion-dissolved solution using mesoporous alumina, and is an arsenic removal filter using mesoporous alumina, which uses mesoporous alumina. Arsenic adsorbent.

(4) The present invention removes arsenic ions from arsenic ion-dissolved solution containing natural water, pre-purification water, industrial wastewater and domestic wastewater, and other aqueous solutions using soporous alumina, and the solution after removing arsenic ions An arsenic ion removal system characterized by being used as drinking water, domestic water, agricultural water, or industrial water.

(5) An arsenic ion-dissolving solution containing arsenic ions is introduced into a container containing mesoporous alumina carrying an arsenic ion-adsorbing compound, or arsenic ions are contained in a container containing arsenic ion-dissolving solution containing arsenic ions. Mesoporous alumina loaded with an adsorbing compound is added to remove arsenic ions, and a plurality of the above-mentioned melters are connected in series to add mesoporous alumina and arsenic ions loaded with an arsenic ion adsorbing compound. The arsenic concentration in the arsenic ion dissolving solution is reduced to a certain concentration or lower (for example, an allowable concentration of As or lower or an adsorption limit concentration or lower) by contacting with the arsenic ion dissolving solution containing a plurality of times. Arsenic ion removal device.

(6) The present invention includes a step of supporting an arsenic ion-adsorbing compound on mesoporous alumina, contacting an arsenic ion-dissolving solution containing arsenic ions with mesoporous alumina supporting the arsenic ion-adsorbing compound, and An arsenic recovery method using mesoporous alumina, comprising a step of selectively adsorbing arsenic ions and a step of liberating arsenic ions from the arsenic ion-adsorbing compound adsorbing arsenic ions.

(7) In addition to (6), the present invention can reuse mesoporous alumina carrying an arsenic ion adsorbing compound, and the arsenic ion adsorbing compound is a compound capable of selectively adsorbing arsenic ions, The arsenic recovery method is characterized in that the adsorptive compound is a heteropolyacid, and the heteropolyacid is ammonium molybdate.

(8) In addition to (7), the present invention mixes solid-state alumina obtained after acting a surfactant on mesoporous alumina in an aqueous solution containing ammonium molybdate, thereby adding ammonium molybdate. Mesoporous alumina is supported on mesoporous alumina, and the temperature of adsorbing arsenic ions by contacting mesoporous alumina supporting ammonium molybdate with arsenic ion dissolving solution is room temperature, and mesoporous alumina supporting ammonium molybdate is dissolved in arsenic ions. When adsorbing arsenic ions in contact with the solution, pre-treatment and / or post-treatment such as pH adjustment is not performed, and mesoporous alumina carrying an arsenic ion-adsorbing compound is contacted with the arsenic ion-dissolved solution When adsorbing arsenic ions, With bottles acid, arsenic recovery method, characterized by determining the color density of the adsorbed arsenic ions.

The mesoporous alumina of the present invention has a strong nanostructure skeleton, and its outer surface and inner surface have a porous structure with a large surface area. A large number of arsenic ion-adsorbing compounds are supported on the porous surface having a large surface area. Therefore, since the adsorption efficiency of arsenic ions in this arsenic ion adsorbing compound is very high, the arsenic ion removal efficiency from the arsenic ion solution is high, and arsenic ions can be adsorbed and removed quickly from the arsenic ion solution. . Moreover, since there are many adsorption sites and each nano-sized adsorption site acts on arsenic ion adsorption, not only ppm level arsenic ions can be removed, but also ppb to ppt level arsenic ions are removed. it can. In particular, when the arsenic ion-adsorbing compound is a heteropolyacid such as ammonium molybdate, it can selectively and preferentially adsorb arsenic ions compared to other cations and anions. In addition, when ammonium molybdate is allowed to act after treating mesoporous alumina with a surfactant, ammonium molybdate is efficiently supported on a porous surface having a large surface area, so that the adsorption sites of arsenic ions increase and arsenic ions are absorbed. It can adsorb efficiently from ultra-trace level to high concentration level. Furthermore, such mesoporous alumina supporting ammonium molybdate can rapidly and rapidly produce large amounts of arsenic ions even at room temperature without heating, without pretreatment and / or posttreatment such as pH adjustment of the arsenic ion solution. Therefore, it is economical without the need for post-treatment of the pH adjuster, the need for special heating means, and an increase in energy consumption. For example, in a system for purifying water before purification, only mesoporous alumina carrying ammonium molybdate is introduced, and mesoporous alumina carrying ammonium molybdate adsorbing arsenic ions with a filter or the like after adsorbing arsenic ions is used. Remove it. Furthermore, the multi-stage arsenic ion removal system using a plurality of arsenic ion removal apparatuses of the present invention can remove arsenic ions from water before purification at a low cost and in a large amount without any arsenic ions (arsenic-free). ) It is possible to provide an aqueous solution (drinking water).

FIG. 1 is a diagram showing an arsenic recovery system of the present invention. FIG. 2 is a diagram showing an embodiment of a method for producing alumina (Al ₂ O ₃ ) used in the present invention. FIG. 3 is a diagram showing a synthesis method for producing Al ₂ O ₃ -II and Al ₂ O ₃ -III using a surfactant. FIG. 4 is a diagram showing a wide-angle X-ray diffraction pattern of mesoporous alumina. FIG. 5 is a diagram showing a small angle X-ray scattering pattern of mesoporous alumina. FIG. 6 is a graph showing a nitrogen (N ₂ ) adsorption / desorption isotherm of Al ₂ O _{3 at} a temperature of 77K. FIG. 7 is a diagram showing the pore distribution of Al ₂ O ₃ . FIG. 8 is a diagram showing a TEM image of a mesoporous alumina structure. FIG. 9 is a schematic diagram showing a flow from the preparation of an alumina-capter to the adsorption of arsenic ions of the alumina-captor in the present invention. FIG. 10 is a diagram showing a method in which arsenic ions are recovered from a dissolved solution using an alumina-captor. FIG. 11 is a table showing the arsenic ion concentration in the aqueous solution. FIG. 12 is a diagram showing the color tone of the alumina capter after filtration from solutions containing various arsenic ion concentrations. FIG. 13 is a diagram schematically showing how arsenic ions are adsorbed from a solution containing various metal ions using the alumina-captor of the present invention. FIG. 14 is a diagram showing the effect of heating and contact time on the arsenic ion removal efficiency using an alumina capter. FIG. 15 is a diagram showing the difference in arsenic ion extraction efficiency depending on the presence or absence of ascorbic acid. FIG. 16 is a schematic diagram for explaining the role of ascorbic acid as a labeling agent having the effect of discoloration by adsorption of arsenic ions of the heteropolyacid of the present invention. FIG. 17 is a table showing data measured by ICP-OES at the arsenic ion concentration in the solution. FIG. 18 is a table showing arsenic ion concentration and removal efficiency before and after the treatment of alumina-captor in natural water. FIG. 19 is a diagram showing the removal efficiency of alumina-captor in natural water. FIG. 20 is a diagram showing a continuous arsenic recovery system that realizes arsenic ion-free using the alumina-captor of the present invention. It is a figure which shows the system which adsorb | sucks an arsenic ion from domestic drinking water using the alumina capter of this invention, and supplies arsenic-free drinking water.

The present invention provides an arsenic ion detection technique and an arsenic recovery technique using an arsenic ion-adsorbing compound having high selectivity and an optical detection function. Furthermore, the present invention provides a purification system that removes arsenic ions from domestic water such as drinking water, natural water, and agricultural water using this arsenic recovery technology. A feature of this technology is that it utilizes a nano-sized surface state arranged at the atomic level of a mesoporous material that is a nanostructure composed of different atoms. The present invention can recover an extremely small amount of arsenic ions at the ppt level, and further, from a waste (waste water) containing various cations and anionic ions in that it is quick and low-cost without giving an environmental burden. It is an excellent method for extracting arsenic.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a diagram showing an arsenic recovery system of the present invention. First, in the first stage, mesoporous alumina (abbreviated as MPA) is synthesized. Here, mesoporous alumina is a kind of porous alumina, which is called a mesopore region and has pores (mesopores) having a substantially uniform and regular diameter in the range of 2 to 50 nm. It is a group of porous materials that are known to have various properties depending on the type of network (spatial symmetry) created by the pores, the manufacturing method, and the like. However, in this patent application, porous alumina having micropores (pores of 2 nm or less) smaller than mesopores or macropores (pores of 50 nm or more) larger than mesopores is also referred to as mesoporous alumina.

Mesoporous alumina can be synthesized by various methods. For example, an acid aluminum salt (for example, aluminum nitrate {Al (NO ₃ ) ₃ }, aluminum sulfate {Al ₂ (SO ₄ ) ₃ }, aluminum acetate {Al (CH ₃ COO) ₃ }) and a surfactant {for example, Mesoporous alumina can be formed using cetyltrimethylammonium bromide (CTAB) or camphor-10-sulfanic acid (CSA)}. Alternatively, aluminum alkoxide {for example, aluminum isopropoxide} can be hydrolyzed and fired. The mesoporous alumina is a porous nanotube structure having an elongated cylindrical shape with a diameter of 2 to 50 nm. However, the structure of the mesoporous alumina may be a nanostructure having another shape such as a rod shape, a cone shape, or a spherical shape. Since the mesoporous alumina thus formed has a strong outer shell and a uniform shape, it can support the following arsenic adsorptive compounds and maintain stable quality even when used repeatedly for arsenic adsorption: Is possible.

Next, in the second stage, the arsenic ion adsorbing compound is supported on mesoporous alumina (MPA). At this stage, arsenic ions (and other cations and anions) are not adsorbed on the arsenic ion adsorbing compound. (The term "arsenic ion adsorbing compound" is used as a term indicating that arsenic ions are not adsorbed.) Arsenic ion adsorbing compounds used in the present invention include metal complexes, inorganic metal compounds, and organometallic compounds. Arsenic ion-adsorbing compounds such as cellulose and protein are also included. Examples of the metal complex include inorganic and organic metal complexes, metal carbonyl compounds, metal clusters, and organometallic compounds. Chelate compounds are also included. Basically, it is a compound that can adsorb arsenic (ion) among elements, can be supported on MPA, can release cations and anions other than arsenic, which is the target element, by chemical treatment, and then other chemical treatments It is a compound that can liberate arsenic as a target element.

The arsenic ion adsorbing compound is desirably a compound that selectively adsorbs a large amount of arsenic ions, which are target elements to be recovered. For example, a chelate compound that selectively binds to arsenic ions can be used. Arsenic ions, which are target elements, can be selectively adsorbed to the arsenic ion-adsorbing compound by adjusting the pH value, temperature, concentration, etc. of (various) ion-dissolved solutions in which various cations and anions containing arsenic are dissolved. Further, since the chelate compound can selectively adsorb a very small amount of arsenic (for example, ppb order to ppm order), it is efficient even if the amount of arsenic ions contained in the ion solution is small. Selectively adsorb arsenic ions.

Or a heteropoly acid is mentioned as an arsenic ion adsorption compound, for example. Examples of the heteropolyacid include ammonium molybdate ((NH ₄ ) ₆ Mo ₇ O ₂₄ ) such as ammonium molybdate tetrahydrate. The heteropolyacid is supported on the surface of the MPA porous and wide surface area, and uses molybdenum as a poly element and adsorbs arsenic ions {As (V)} as a hetero element. Therefore, since the priority and selectivity with respect to the arsenic ion {As (V)} are high, the arsenic ion {As (V)} is extracted (recovered) from the solution.

The present invention relates to mesoporous alumina (also referred to as an As adsorption element) carrying an arsenic ion adsorbing compound useful for the removal and detection of As ions, particularly As (V) {As ⁵⁺ } ions. . The existence of As (III) {As ³⁺ } ions is known, and a method for converting it to As ⁵⁺ is also known by Patent Document 8 and the like, and the present invention is known in the art. It also includes using the means to make detected water or purified water obtained by converting As ³⁺ ions into As ⁵⁺ ions.

Various methods can be mentioned as a method (also referred to as a composite method) for supporting (modifying) such an arsenic ion-adsorbing compound on MPA. For example, when the arsenic ion adsorbing compound to be held in MPA is neutral, a reagent impregnation method is used, and when it is anionic, a cation exchange method is used. In some cases an anion exchange method is used. These compounding methods belong to known general technical fields, not special conditions and operations. Therefore, for the details of these general technical fields, it is possible to refer to reviews, literatures and the like regarding the solid adsorption field.

As a method of supporting ammonium molybdate as a heteropoly acid on an MPA nanotube, which is a porous nanostructure, the surface of a mesoporous alumina nanotube is DDAB {dilauryl dimethyl ammonium bromide}. Alumina molybdate-supported alumina- (arsenic) captor (captures arsenic ions) after contact with an ammonium molybdate solution and functionalized with a surfactant. There is a method of making a “captor”).

Of course, the arsenic ion-adsorbing compound alone may selectively adsorb the target element, arsenic ions, but the arsenic ion-adsorbing compound aggregates, etc., so the functional group capable of adsorbing arsenic ions should be used effectively. I can't. That is, even if the target element arsenic ions are adsorbed to the functional group present on the surface of the aggregated (for example, particulate) arsenic ion adsorbing compound substance, the arsenic inside the arsenic ion adsorbing compound is diffused or penetrated Since the ion concentration decreases exponentially with respect to the distance (square), it is difficult for arsenic ions to be adsorbed to all functional groups of the arsenic ion-adsorbing compound inside the particulate matter. In addition, even if arsenic ions are adsorbed to the functional group of the arsenic ion adsorbing compound inside the particulate matter, it is difficult to take out (free or back extract) the adsorbed arsenic ions. . It is possible to diffuse arsenic ions inside the particulate matter and take it out for a long time, but moving arsenic ions inside the particulate matter over a long period of time results in poor productivity and Cannot be used.

In contrast, mesoporous alumina (MPA) has a very large pore surface area and a highly ordered orientation structure, so that an arsenic ion-adsorbing compound is supported on the surface of mesoporous alumina (MPA) and the inner wall of the pore. Since the arsenic ion adsorbing compounds are arranged in order and bonded, the arsenic ion adsorbing rate of the arsenic ion adsorbing compounds becomes very high. That is, it can be considered that each molecule of the arsenic ion adsorbing compound can be used for arsenic ion adsorption. Arsenic ion-dissolved solutions and free (back-extracted) solutions can easily and quickly penetrate the surface and pores of MPA, making it easy to use the arsenic ion-adsorbing compound (reactive group) supported on MPA. Contact immediately. This is quickly adsorbed when the arsenic ion-adsorbing compound supported on MPA comes into contact with the arsenic ion-dissolved solution. Further, when the adsorbed arsenic ions are liberated, it means that the adsorbed arsenic ions are rapidly liberated if they come into contact with the liberated solution, so that productivity is dramatically improved.

Next, in the third stage, contact is made with a mesoporous alumina (hereinafter abbreviated as MPA-AC) carrying an arsenic ion-dissolving solution containing arsenic ions and an arsenic ion-adsorbing compound (also referred to as AC) at high density ( Including immersion). The arsenic ion dissolution solution is an aqueous solution containing arsenic ions, but may contain other cations and anions. In the system of the present invention, in order to extract arsenic from rocks, a solution in which arsenic in rocks is forcibly dissolved with acid or alkali, natural water in which arsenic existing in nature, etc. is dissolved, arsenic ions The factory waste liquid containing arsenic becomes an arsenic ion solution. In particular, when used as agricultural water, drinking water or domestic water, the arsenic ion concentration needs to be reduced below an allowable limit, so that the present invention is capable of adsorbing a wide range of As ions in the ppt to ppb to ppm level from a very small amount to a very small amount. A system using the MPA-AC can be suitably applied.

The arsenic ion solution contains various cations and anions in addition to the target element, arsenic ions. The MPA-AC of the present invention is a target element under certain conditions (pH value, temperature, concentration, etc.). Since arsenic is selectively and preferentially adsorbed, if MPA-AC is immersed in an arsenic ion dissolving solution under the conditions, MPA-AC that adsorbs only the target element arsenic ions (ie, MPA- AC-As) can be obtained. However, since there is a possibility that a slight amount of various other ions (which may be described as M) may be adsorbed due to slight fluctuations in conditions and the like, ions other than arsenic that is the target element in the arsenic ion solution are preliminarily added. By reducing the amount, MPA-AC-As with a very small amount of adsorption of ions M other than arsenic can be obtained. For example, there is a method in which ions other than arsenic ions are deposited and removed by adjusting pH, chemical treatment, etc. in an arsenic ion solution.

The above-mentioned alumina (arsenic) captor with ammonium molybdate supported on the mesoporous alumina nanotube surface is immersed in an arsenic ion-dissolved solution at room temperature (0 ° C. to 40 ° C.) for a certain time (for example, 5 hours to 10 hours) and stirred. By doing so, a considerable amount of arsenic ions can be adsorbed. This alumina-captor (MPA-AC) does not require any special pretreatment (such as pH value adjustment treatment, treatment for removing other ions, treatment for adding a special agent, etc.). And / or without heating or applying pressure, arsenic ions can be adsorbed only by immersing and stirring in an arsenic ion-dissolving solution containing arsenic ions (including tap water and natural water). Therefore, since arsenic ions can be removed from the arsenic ion solution with very simple equipment, productivity can be improved and costs can be reduced, and energy consumption is not increased, which is friendly to the environment. Since the filtered filtrate has removed harmful arsenic, it can be used as drinking water or can be returned to the environment (nature).

If the initial arsenic ion concentration of the arsenic ion dissolution solution is Y and X% arsenic can be removed by one MPA-AC contact treatment (removal efficiency X%), the arsenic ion dissolution is repeated twice. The arsenic ion concentration in the solution is Y (1-X / 100) ² . For example, if X = 90, an arsenic ion concentration of 0.01Y is obtained by two contact treatments. Four contact treatments result in an arsenic ion concentration of 0.0001Y. Thus, it becomes possible to make the arsenic ion concentration below the allowable limit by performing the multi-step contact treatment. Since it can be easily realized without special equipment or equipment, the cost can be reduced. In addition, since no special chemicals are used, it is not necessary to provide a means for removing or detoxifying the special chemicals after the treatment (arsenic ion level is below the allowable limit). For example, it can be used for drinking water as it is. This indicates that the cost can be reduced as compared with the conventional method.

Next, in the fourth stage, MPA-AC-As that has adsorbed almost only arsenic, which is the target element, is contacted (immersed) with a solution (eluent) in which arsenic, which is the target element, can be dissolved. Is dissolved (eluted). In some cases, only the arsenic ions, which are target elements, can be liberated by adjusting conditions such as pH value, temperature, and solution concentration. Alternatively, the target element arsenic ions can be dissolved by immersing them in a solution that can release only the target element arsenic ions. In such a case, it is not always necessary to use MPA-AC-As that adsorbs only the arsenic ion that is the target element. In addition, when ions other than arsenic ions are adsorbed (described as MP-AC-As-M), a process of removing ionic species M is performed before or after removing arsenic ions from MPA-AC. Thereafter, MPA-AC from which arsenic ions as target elements are liberated is a solid, and is removed by filtration from the eluent. The MPA-AC removed as a solid can be used again. Since only arsenic ions are dissolved in the filtrate, arsenic, which is the target element, can be recovered by separating the target element by various methods (for example, electroplating). In addition, this process liberates As from MP-AC-As when it considers that arsenic which is a target element is made to adsorb | suck to MPA-AC and make arsenic which is a target element into MP-AC-As. Therefore, it can be called a back extraction step. For example, in order to release (elution) As ions from As ions (MPA-AC-As) adsorbed on MPA carrying ammonium molybdate as described above, MPA-AC-As is treated with alkaline water (for example, NaOH aqueous solution). It is sufficient to immerse in and stir. Thereafter, filtration, washing and drying can yield regenerated MPA-AC, and MPA-AC can be repeatedly used for As ion adsorption.

<Formation of Al ₂ O ₃ -I>
FIG. 2 is a diagram showing an embodiment of a method for producing alumina (Al ₂ O ₃ ) used in the present invention. As shown in FIG. 2, 20 g of aluminum isopropoxide (C ₉ H ₂₁ AlO ₃ ) was added to 100 ml of distilled water in a round bottom flask and stirred with a magnet at 80 ° C. for 1 hour. Thereafter, the pH of the aqueous solution was adjusted to 4 using nitric acid. The mixture was then stirred again at 80 ° C. for 8 hours in a round bottom flask. The solution was then filtered and a white solid was collected, dried at 60 ° C. overnight, and calcined at 550 ° C. for 6 hours in air. The organic components contained were removed by evaporation. This white powder obtained by calcination is alumina (Al ₂ O ₃ ). In the present application this alumina is referred to as _Al 2 _O 3 -I. Since the above values are examples, they may be varied somewhat. (The same applies to the following embodiments.)

<Formation of Al ₂ O ₃ -II>
25 g of aluminum nitrate {Al (NO ₃ ) ₃ 9H ₂ O} and 2.5 g of a surfactant, camphor sulfanic acid (CSA), were placed in 75 ml of distilled water, and the mixture was dissolved while stirring the magnet. Thereafter, the pH value of the solution was adjusted to 5.5 using an aqueous ammonia solution. The mixture became viscous after 10 minutes of stirring, and then transferred to an autoclave coated with polytetrafluoroethylene and subjected to hot water treatment at 160 ° C. to 180 ° C. for 24 hours. Then it was cooled to room temperature and the solid material was collected using a centrifuge and further washed several times with ethanol. The resulting white powdery product was dried at 60 ° C. overnight and further calcined at 550 ° C. for 6 hours in air, and the organic components contained were evaporated off. This white powder is alumina (Al ₂ O ₃ ). The alumina referred to as _Al 2 _O 3 -II in this application. FIG. 3 is a view showing an embodiment showing a synthesis method for producing Al ₂ O ₃ -II at pH 5.5 using the above-described surfactant. Incidentally, the _Al 2 _O 3 -II is mesoporous _Al 2 _{O 3} prepared using a surfactant.

<Formation of Al ₂ O ₃ -III>
Alumina was prepared using the surfactant cetyltrimethylammonium bromide (CTAB) instead of the surfactant CSA used in Example 2. That is, as shown in FIG. 3, 25 g of aluminum nitrate {Al (NO ₃ ) ₃ 9H ₂ O} and _2.5 g of surfactant CTAB are placed in 75 ml of distilled water, and the mixture is dissolved while stirring the magnet. did. Thereafter, the pH value of the solution was adjusted to 5.5 using an aqueous ammonia solution. The mixture became viscous after 10 minutes of stirring, and then transferred to an autoclave coated with polytetrafluoroethylene and subjected to hot water treatment at 160 ° C. to 180 ° C. for 24 hours. Then it was cooled to room temperature and the solid material was collected using a centrifuge and further washed several times with ethanol. The resulting white powdery product was dried at 60 ° C. overnight and further calcined at 550 ° C. for 6 hours in air, and the organic components contained were evaporated off. This white powder is alumina (Al ₂ O ₃ ). This alumina is referred to as Al ₂ O ₃ -III in the present application. Incidentally, the _Al 2 _O 3 -III is mesoporous _Al 2 _{O 3} prepared using a surfactant.

<Characteristics of mesoporous alumina (X-ray diffraction)>
FIG. 4 is a diagram showing a wide-angle X-ray diffraction {XRD (X-Ray Deffraction)} pattern of mesoporous alumina. FIG. 5 is a diagram showing a small angle X-ray scattering (SAXS) pattern of mesoporous alumina. The crystal structure of the calcined alumina powder produced in Examples 1-3 is characterized using XRD and SAXS. FIG. 5 shows the measurement results of small-angle X-ray scattering of three types of alumina (Al ₂ O ₃ -I, Al ₂ O ₃ -II, and Al ₂ O ₃ -III). The small-angle X-ray profile of mesoporous alumina nanotubes shows a broad decomposition diffraction peak in the region 0.45 ≦ 2θ ≦ 1.45 °, with no surfactant (Al ₂ O ₃ -I), surfactant CSA. If _{(Al 2 O} 3 -II), and if the surfactant CTAB relates _Al 2 _{O 3} of _{(Al 2 O 3 -III),} d ( the interparticle distance), respectively 13.768nm, 11.593nm and 14 .373 nm. Because disordered mesostructure enough strength is less broad alumina indicates that by increasing, mesoporous degree _Al 2 _O 3 -I is the _lowest, Al _{2 O} 3 -II and _Al 2 _{O 3} - It can be seen that III has a large mesoporous degree. This is the effect of using a surfactant during alumina formation.

FIG. 4 shows an X-ray wide angle diffraction pattern of alumina (Al ₂ O ₃ -III) prepared using the surfactant CTAB. All diffraction peaks could be assigned all the X-ray diffraction (hkl) of alumina using the interstitial distance fitting method. That is, these peak positions are strictly determined by using a single crystal diffractometer output conversion software {DIFRAC plus Evaluation Package (EVA) software} having a PDF-2 powder X-ray diffraction database (PDF-2 Release 2009 database). It was done. As can be seen from FIG. 4, a fully resolved representative diffraction peak of Al ₂ O ₃ -III is shown. Al ₂ O ₃ -III shows the crystal structure of single phase γ-Al ₂ O ₃ , which coincides with the peak position of Al ₂ O ₃ (JCPDS No. 029-0063) shown in the JCPDS card chart, and the lattice constant a = 7.924cm was shown. In conclusion, the broad low-resolution, low-intensity peak indicates a short-range ordered γ-Al ₂ O ₃ mesostructure.

<Characteristics of mesoporous alumina (hot spring such as nitrogen adsorption)>
We have been able to control the shape and size of the alumina material by the methods shown in Examples 1-3, but that evidence can also be obtained from the N ₂ adsorption isotherm. FIG. 6 is a nitrogen (N ₂ ) adsorption / desorption isotherm at a temperature of 77 K, the horizontal axis represents the relative pressure, and the vertical axis represents the adsorption amount. This nitrogen (N ₂ ) adsorption / desorption isotherm is a typical type IV (IUPAC classification) adsorption behavior, with a well-known sharp bend in the adsorption / desorption branch and showing a pronounced hysteresis loop. ₂ represents the characteristics of the N ₂ adsorption isotherm of the alumina sample. That is, the alumina material (Al ₂ O ₃ -I) shown in FIG. 6 is homogeneous and has high regularity. The hysteresis loop of this alumina material (Al ₂ O ₃ -I) is of the H2 type (classified by IUPAC), which is typical for a homogeneous mesoporous cubic structure produced with and without a surfactant. It is. This well characterized sharp bend line appears at 0.5 ≦ P / P0 ≦ 0.85.

FIG. 7 is a diagram showing the pore distribution at a temperature of 77 K, and is a diagram showing the pore distribution obtained based on the nitrogen (N ₂ ) adsorption / desorption isotherm in FIG. The horizontal axis represents the pore diameter, and the vertical axis represents the dVp differential value. The sharp bend line shown in the nitrogen (N ₂ ) adsorption / desorption isotherm in FIG. 6 indicates a sharp increase in the adsorption amount, and the pore peak is about 5.43 nm (in the case of Al ₂ O ₃ -I alone). Shows capillary condensation within a uniform mesoporous structure. Furthermore, in the case of alumina material modified (supported) with molybdenum ions {Mo ⁺⁶ }, as shown in the N ₂ adsorption isotherm data, the decrease in the width of the hysteresis loop is similar to that of the fabricated nanoprobe. All show a decrease in nanoscale pore size. In our series of alumina synthesis, Mo ⁺⁶ loading and arsenic adsorption / elution processes, the alumina mesoporous structure determined significant texture parameters: specific surface area and pore volume. Pore _{volume, Al 2 O 3 -I, Al} 2 O 3 -I modified with ^{Mo +6,} with respect to _Al 2 _O 3 -I modified with ^{Mo +6} after elution of As, respectively 0.405 cm ³ g ^-1, 0.261 cm ³ g ⁻¹ and 0.357 cm ³ g ⁻¹ . Further, BET specific surface _{area, Al 2 O 3 -I, Al} 2 O 3 -I modified with ^{Mo +6,} with respect to _Al 2 _O 3 -I modified with ^{Mo +6} after As elution, respectively 234.54 m ² g ^-1 156.78 m ² g ⁻¹ and 185.25 m ² g ⁻¹ . The BET specific surface area S before being supported by ammonium molybdate, which is an arsenic-adsorbing compound, is also 234.54 m ² / g, which is large. It can also be seen that even when ammonium molybdate is supported on Al ₂ O ₃ -I, the flexibility does not change and the mesostructure of alumina does not change. Furthermore, it can be seen that after the arsenic ions are adsorbed on the ammonium molybdate supported on Al ₂ O ₃ -I and the adsorbed arsenic ions are eluted, the flexibility does not change and the mesostructure of alumina does not change. . Thus, the mesostructure of alumina has been shown to be stable before and after the process.

<Characteristics of mesoporous alumina {Transmission electron microscope analysis (TEM)}>
FIG. 8 is a diagram showing a representative TEM image of a mesoporous alumina structure having a uniform shape. A high-resolution transmission electron microscope (HRTEM) of mesoporous alumina was performed to investigate the controlled morphology, mesoporous degree and crystal structure of alumina. Above figure _Al 2 _O 3 -I, middle diagram _Al 2 _O 3 -II, below is _Al 2 _O 3 -III. As can be seen from these HRTEM micrographs in FIG. 8, the mesoporous aluminas of the present invention produced by the methods according to Examples 1 to 3 are all elongated porous alumina nanotubes having a diameter range of 5 to 8 nm. . The typical preferred orientation of the crystal structure is [222], indicating that a broad nanocrystal domain with cubic Fd3m symmetry (symmetry) is formed. The most prominent feature of these TEM photographs is that the mesostructure of alumina has no distortion and has a continuous order of lattice stripes over a wide area, and has a more uniform arrangement. Wide nanocrystal domains along the preferred orientation are characteristic of alumina cubic lattice nanotubes. This TEM photograph, or HR-TEM image, clearly shows the large domain size of an ordered face-centered cubic mesoporous network.

<Alumina (Al ₂ O ₃ ) -Captor Simple Method>
The present invention relates to an arsenic {As (V)} adsorbing compound (arsenic captor or simply called a captor, where a captor means something to be captured) an aluminum metal oxide (alumina). ) Based on the unique properties of aluminum metal oxides that can be used as carriers for so-called arsenic captors. A method for producing alumina on a large scale on a large scale has been investigated. As shown in FIG. 9, it can be seen that production is simple because there is no complicated production facility. (FIG. 9 is a diagram schematically showing a series of flows in which arsenic ions are adsorbed using an Al ₂ O ₃ -captor supported on a highly functionalized mesoporous Al ₂ O ₃ with an arsenic ion adsorbing compound, That is, it is a schematic diagram showing a flow from alumina-captor production to arsenic ion adsorption to alumina-captor.) For example, the polarity of the surface matrix of mesoporous alumina (Al ₂ O ₃ ) produced in Examples 1 to 3 As shown in FIG. 9, fine adjustment is made by high-density dispersion of a cationic surfactant such as dilauryl dimethyl ammonium bromide (DDAB). By this treatment, the periphery of the mesoporous alumina nanotube is functionalized. This state is the alumina-carrier (Al ₂ O ₃ -Carrier) shown in FIG. 9 (here, a carrier is used in the sense of a captor).

Next, the alumina is treated appropriately with a heteropoly acid such as ammonium molybdate (Ammonium molybdate: (NH ₄ ) ₆ Mo ₇ O ₂₄ ), such as ammonium molybdate tetrahydrate, and functionalized. At the same time that the heteropolyacid is supported on the pore surface of the mesoporous alumina, the pore surface of the mesoporous alumina is also functionalized. The solvent and other reagents are then removed by a simple evacuation method using a rotary evaporator, and after 10-20 minutes, all processes are complete and carry the above heteropolyacid (or modified with a heteropolyacid). A) Powdered alumina was produced. The powdery alumina carrying the heteropolyacid is an arsenic captor and can adsorb arsenic {As (V)} by contacting with a solution containing arsenic {As (V)}. Mesoporous alumina adsorbed with arsenic {As (V)} {Al ₂ O ₃ -As (V) -Captured} in FIG. 9 is discolored and it can be observed with the naked eye that arsenic {As (V)} has been adsorbed. .

The procedure for supporting the ammonium molybdate on alumina (Al ₂ O ₃ -I, Al ₂ O ₃ -II, Al ₂ O ₃ -III) will be described in detail. 40 ml of ethanol was mixed and stirred with 1 mg of alumina and 0.3 mg of a surfactant DDAB, suctioned and exhausted with a rotary evaporator at 35 ° C. for 30 minutes, and then a vacuum pump attached to this evaporator was operated, Vacuum-dried at ° C. The solid thus obtained is washed with water and dried at 45 ° C. under normal pressure. Next, the solid thus obtained was added to 0.3 ml of ammonium molybdate {(NH ₄ ) ₆ Mo ₇ O ₂₄ . 24H ₂ O} is mixed with the mixed solution and stirred for 12 hours. The mixed water is filtered, and the resulting solid is washed with water and dried at 55 ° C. under atmospheric pressure. In this way, an alumina (arsenic) captor having ammonium molybdate supported on the surface of a mesoporous alumina nanotube can be obtained.

<Application of alumina (Al ₂ O ₃ ) -captor to an aqueous solution in which arsenic ions are dissolved>
The present invention is based on the idea that a molybdenum compound is supported on mesoporous alumina nanotubes, and this supported molybdenum compound utilizes the unique property that it can form a stable complex with As (V) ions. Further, by adding a dilute solution containing a small amount of ascorbic acid (for example, 0.1 mol (M)) to the complex forming solution, alumina (Al ₂ O ₃ ) supporting this complex containing As (V) is added. ) Will appear indigo. The darkness of the indigo color increases with the amount of adsorbed arsenic and can be identified with the naked eye. This complex can be formed only under conditions where the aqueous solution is acidic, and the arsenate-molybdate-complex can be formed in the aqueous solution while being supported on alumina (Al ₂ O ₃ ).

FIG. 10 is a diagram showing a method for recovering arsenic from an aqueous solution using an alumina-captor from an aqueous solution in which arsenic {As (V)} is dissolved. The procedure is as follows.
(1) To a flat bottom bottle with a cap equipped with a 50 ml magnet, 17.6 ml of an aqueous solution, 0.4 ml of a solution containing 100 ppm of arsenic {As (V)} ions, and 20 mg of an alumina captor were added. The alumina captor, alumina carrying ammonium molybdate tetrahydrate above _{(Al 2 O 3 -I, Al} 2 O 3 -II, Al 2 O 3 -III) is.
(2) The mixed solution containing the alumina capter was sufficiently stirred using a magnetic stirrer at 45 ° C. for 30 minutes.
(3) After standing at constant temperature (30 minutes), 2 ml of 0.1 M ascorbic acid is added to the aqueous solution.
(4) Stirring is continued for an additional 30-40 minutes, and the alumina collector (alumina capter) adsorbs arsenic (forms arsenate-molybdate complex) to exhibit an indigo color. Therefore, this indigo color indicates the detection of As (V).
(5) The solid material was filtered (eg, using a Whatman paper filter) and washed with deionized water.
(6) The resulting solid material is a transparent indigo alumina collector that adsorbs As (V), which indicates that As (V) can be successfully collected from the solution.
(7) The arsenic ion concentration in the solution was measured using ICP (Inductively Coupled Plasma) emission spectroscopy (ICP-OES) at each stage. FIG. 11 is a table showing the arsenic ion concentration in the aqueous solution at each stage. Although the arsenic ion concentration in the first aqueous solution was 2.035 ppm, the arsenic ion concentration in the aqueous solution after dipping the alumina captor was 0.636 ppm, and 1.363 ppm of arsenic ions in the aqueous solution was removed. Therefore, the arsenic ion removal efficiency by the alumina-captor is 67%.

<Ultra high sensitivity capture up to ppt level concentration>
The detection limit of the conventional arsenic concentration detection method and arsenic removal method is 10 ⁻⁶ M (mole), that is, the ppm level, but the alumina capter of the present invention has not only a simple manufacturing method but also ppb to ppt. A level of arsenic concentration can be detected or removed. FIG. 12 is a diagram showing the color developability (color tone) of the alumina capter after filtration from solutions containing various arsenic concentrations. In accordance with the method shown in Example 8, alumina captors were added to aqueous solutions containing various arsenic concentrations to obtain alumina captors that adsorbed arsenic. When arsenic is not included, the color is white. When arsenic is included, the color is changed to indigo (or blue). Moreover, as the arsenic (ion) concentration increases, the indigo color tone becomes deeper. That is, even at a very low arsenic concentration of 0.5 ppb (10 ⁻¹⁰ M level), it shows a light indigo color, and it can be seen that arsenic was adsorbed to the alumina captor even with the naked eye. At an arsenic (ion) concentration of 100 ppb, the color becomes bright indigo, and when it reaches 2000 ppb, it becomes a deep indigo color. As shown in FIG. 109, the indigo color continuously increases as the arsenic (ion) concentration increases. In other words, the arsenic (ion) concentration can be understood by looking at the color tone of the alumina-captor that has adsorbed arsenic (ions).

From this, the alumina capter of the present invention can not only remove arsenic ions in an aqueous solution, but can also be used as an arsenic concentration detection sensor. Moreover, since this arsenic concentration detection sensor can also detect an arsenic concentration at the ppt (ppb or lower) level, it can detect a trace amount of arsenic in the environment and determine whether there is a problem. In addition, since the alumina capter of the present invention can adsorb a small amount of arsenic ions at the ppt level, it becomes possible to remove arsenic ions at an extremely minute concentration ( ^{−10 −10} M) in the environment, thereby realizing an arsenic-free environment. it can. The present invention makes mesoporous alumina, adsorbs an arsenic adsorbing compound (for example, heteropolyacid), and adsorbs arsenic ions thereto. That is, it can be said to be one building block technology. The significant advantage of the high sensitivity of arsenic ion detection or arsenic ion adsorption in mesoporous alumina loaded with the arsenic adsorptive compounds of the present invention is that the electron acceptor / donor of the immobilized receptor fully controlled by this building block technology This contributes to high adaptability and high mobility.

<High sensitivity by collecting arsenic {As (V)} from an aqueous solution containing many cations>
The selectivity for the arsenic ion adsorptivity of the alumina-captor of the present invention, that is, the influence on the arsenic ion adsorptivity when a large number of competing metal ions are present was investigated.
The procedure is shown below.
(1) 16 ml of aqueous solution, 0.2 ppm of 100 ppm As (V) solution, various cations {Na ⁺ , Ca ⁺² , Mg ⁺² , Li ⁺ , Ho ⁺³ into a capped flat bottom bottle equipped with a 50 ml magnet , Co ⁺² , Zn ⁺² , Ni ⁺² , Cd ⁺² , La ⁺² , Mn ⁺² , Hg ⁺² , Ba ⁺² , Cu ⁺² , Al ⁺³ , Cr ⁺⁶ , Fe ⁺² , and Bi ⁺³ } was added at a concentration of 200 ppm from the stock solution to each 100 μml, a total of 1.8 ml, and alumina-captor 20 mg. Each concentration of each metal cation was kept at 1 ppm. Here, the alumina-capter is alumina (Al ₂ O ₃ -I, Al ₂ O ₃ -II, Al ₂ O ₃ -III) supporting the above-described ammonium molybdate tetrahydrate.
(2) This mixed solution was sufficiently stirred at 45 ° C. for 30 minutes using a magnetic stirrer.
(3) After standing at constant temperature (30 minutes), 2 ml of 0.1 M ascorbic acid was added to the solution.
(4) Stirring was continued for an additional 30-40 minutes, and the alumina-capter turned indigo. This indicates that the alumina captor detected and adsorbed As (V).
(5) The solid material was filtered using a paper filter and further washed with deionized water.
(6) The resulting solid material was a clear indigo alumina collector, indicating that As (V) could be successfully collected from the As (V) -containing solution.

FIG. 13 is a diagram schematically showing a state in which only arsenic ions are adsorbed by an alumina-captor from a solution containing various metal ions using the alumina-captor of the present invention. Here, HOM means “High Ordered Mesoporous” and means the mesoporous alumina of the present invention. When the HOM-capter (alumina-captor) of the present invention is added to a solution containing a large number of metal ions including arsenic ions, only the arsenic ions are preferentially adsorbed to obtain a HOM-capter whose color is changed to indigo. be able to. This indigo colored HOM-captor (solid) adsorbs arsenic but hardly adsorbs other metals. In addition, the arsenic ions are almost lost in the filtrate from which the HOM-capter (solid) changed to indigo color is removed, and the concentrations of other metal ions are hardly changed. As described above, the alumina-captor of the present invention hardly adsorbs metal ions other than arsenic ions in a solution containing a large number of competing metal ions, and has a very high preferential and selective adsorptivity for arsenic ions. I understood that.

<Effect without heating in As (V) ion adsorption>
Optimal conditions for recovering As (V) require heating to 45 ° C., which facilitates extraction of As (V) and shortens extraction time. However, heating requires equipment and energy, which leads to an increase in As (V) recovery costs. Then, it experimented about the method of increasing the collection amount of As (V) at normal temperature (no heating). As a result, it was found that the extraction of As (V) can be realized by increasing the contact time of As (V) ions and alumina-captor in order to achieve the same recovery amount. First, with and without heating (45 ° C.), in the case of the same fixed time (60 to 75 minutes), the recovery efficiency decreases by 20% without heating.

FIG. 14 is a diagram showing the effect of heating and contact time on the arsenic ion removal efficiency using an alumina capter. In the same manner as in Example 8, 20 mg of an alumina capter was added to a solution containing arsenic ions, and arsenic {As (V)} ions were adsorbed to the alumina capter without heating, and arsenic ions were removed from the solution. The arsenic ion concentration was measured by ICP-OES, and compared with before and after adsorption on an alumina captor to determine the removal efficiency. The vertical axis in FIG. 14 is the removal efficiency. When the alumina capter was brought into contact with the solution for about 3 hours while being heated at 45 ° C., the efficiency was 90%. However, when heating was not performed {that is, normal temperature (0 ° C. to 40 ° C.)}, the alumina was about 10 hours or longer. An efficiency of 89% was obtained with the contact of the captor. That is, it was confirmed that in the case of no heating, the alumina capter may be brought into contact with the arsenic ions in the solution for a long time. Without heating, there is no need for a heating device or equipment, and the time is the same as for heating if it is immersed in the solution overnight (that is, it only needs to be immersed and stirred when the equipment is resting). About arsenic {As (V)} ions can be recovered.

<Effect of addition of ascorbic acid>
As described above, ascorbic acid is added as an important factor for recovering arsenic {As (V)}. However, excessive treatment is required to dispose of ascorbic acid as a waste product. That is, since the consumption of chlorine used for the purification of drinking water is increased, the removal efficiency was investigated with respect to the effect of no ascorbic acid. As a result, ascorbic acid has no effect on the removal efficiency of As (V), and its role is to label the arsenate-molybdate complex and make its formation visible to the naked eye. It was clearly found that.

FIG. 15 is a diagram showing the difference in arsenic ion extraction efficiency depending on the presence or absence of ascorbic acid, that is, the effect of ascorbic acid on the efficiency of As (V) removal from an aqueous solution. In Example 8, even when no ascorbic acid was added, the removal effect of arsenic ions of the alumina-captor was examined. The solution containing arsenic ions was brought into contact with a 20 mg alumina-captor for 60-75 minutes. When ascorbic acid was added, the arsenic ion removal efficiency of the alumina-captor was 67%. In contrast, the removal efficiency of the arsenic ions of the alumina-captor when no ascorbic acid was added was 65%. This result clearly shows that ascorbic acid has little effect on As (V) removal efficiency.

FIG. 16 shows a discoloration (blue) discoloration to the extent that it is recognized by the naked eye by arsenic ion adsorption (complexation) of the heteropolyacid in the system for adsorbing arsenic ions using the alumina capter carrying the heteropolyacid of the present invention. It is a schematic diagram explaining the role as a labeling agent of ascorbic acid to do. In other words, FIG. 16 illustrates the proposed mechanism for capturing arsenic {As (V)} ions and the role of ascorbic acid in labeling only the complexes formed. An alumina-capter supported (modified) by ammonium molybdate {(NH ₄ ) ₆ MoO ₂₄ }, which is one of heteropoly acids, is brought into contact with a solution in which arsenic ions as target elements are dissolved. Arsenic {As (V)} ions are taken up (adsorbed) into the heteropolyacid to form a complex. This complexing is carried out in a state where it is supported on the surface of alumina, and the Captor on which As is adsorbed is ((NH ₄ ) ₃ [As (Mo ₃ O ₁₀ ) ₄ ] complex), and the valence valence of molybdenum is hexavalent. {Mo (VI)}. The (intermediate) complex in this state is colorless. Next, contact with ascorbic acid changes the complex supported on the surface of the alumina to an (NH ₄ ) ₇ [As (Mo ₃ O ₁₀ ) ₄ ] complex, and the molybdenum in the molybdate is reduced to form pentavalent molybdenum. It changes to {Mo (V)}, and as a result, the heteropolyacid changes to indigo (blue).

<Application of alumina-captor to tap water>
A major advantage of the alumina-captor of the present invention is that almost no complex conditions are required regardless of the water source, pH conditions, water-containing materials, and the like. The applicability when the alumina-captor of the present invention was applied to tap water was investigated. The deionized water (DW) used in the above examples was replaced with ordinary tap water, and further additives were added to investigate the effects of additives and other ions that may be present in the tap water. . The optimum conditions for removing arsenic {As (V)} from tap water are as follows.

(1) To a flat bottom bottle with a cap equipped with a 50 ml magnet, 17.6 ml of tap water, 0.4 ml of a 100 ppm As (V) solution, and 20 mg of an alumina captor were added.
(2) This mixed solution was sufficiently stirred using a magnetic stirrer for 70 minutes.
(3) After standing at a constant temperature (30 minutes), 0.1 M ascorbic acid was added to a 2 ml solution.
(4) Stirring was continued for another 30-40 minutes, the solid changed to indigo, indicating that As (V) was adsorbed by the alumina-captor.
(5) The solid material was filtered using a paper filter and washed with deionized water.
(6) The obtained solid material is an alumina capter that adsorbs transparent indigo blue arsenic {As (V)} ions. This indicates that As (V) can be successfully collected from the solution.
(7) The arsenic {As (V)} ion concentration in the solution at each stage was measured by ICP-OES. The data is shown in FIG.

As shown in FIG. 17, the arsenic ion concentration in tap water was very low, 0.0005 ppm, and the arsenic ion concentration after adding arsenic ion-containing water to this solution was 2.013 ppm. Filtration after removing the alumina-capter adsorbing arsenic ions after immersing and contacting the alumina (alumina capter) supporting the sodium polymolybdate of the heteropolyacid which is the arsenic ion adsorbing compound of the present invention The arsenic ion concentration in the liquid was 0.685 ppm. Therefore, the arsenic in the solution removed by the alumina captor of the present invention is 1.328 ppm and the arsenic removal rate is about 66%.

<Application of alumina-captor to natural wastewater>
The efficiency of alumina-captor as a high selective remover for As (V) was also investigated with natural water. Three different samples were brought from different locations in the lakes of Tsukuba City, Ibaraki Prefecture. These three samples were investigated without heating and without ascorbic acid, with the goal of performing at a low cost without using complex equipment or equipment on a 20 mg alumina-captor. Since it was not heated, the alumina capter was immersed and stirred in the sample solution overnight. A new innovative system, the alumina captor of the present invention, was confirmed to be applicable with natural outdoor water sources. The test procedure was the same as in Example 13, tap water was changed to the sample solution, and heating and ascorbic acid were not used. The arsenic {As (V)} ion concentration in each sample solution at each stage was measured by ICP-OES. The data is shown in FIG. That is, FIG. 18 is a table showing the arsenic {As (V)} ion concentration and removal efficiency before and after the treatment of the alumina-captor in natural water. FIG. 19 is a graph showing this. That is, FIG. 19 is a diagram showing the removal efficiency of alumina-captor in natural water. In FIG. 19, the removal efficiency is plotted on the vertical axis.

The As (V) ion concentration before treatment of each sample including tap water was 0.0007 ppm or less. After adding a solution containing arsenic ions to this sample, the concentration of As (V) ions was 2.011 ppm to 2.014 ppm. As a result, the alumina-captor of the present invention was added to this solution and As (V) ions were added. After adsorption, the As (V) ion concentration of the filtrate after filtration was 0.2147 to 0.2350 ppm. As a result, the removal efficiency is 88.3% to 89.6% for all samples. This removal efficiency is about 22% higher than that of Example 13 or the like. This effect is mainly an effect without heating, that is, an effect of being immersed and stirred overnight at room temperature. This result suggests that the heat treatment conditions can be further improved by further optimization. In addition, since ascorbic acid is not used, the alumina capter adsorbing the arsenic recovered in Example 14 is not indigo colored. This has shown that it can apply directly to drinking water etc. (agricultural water, domestic water etc.) after this, without processing ascorbic acid from a filtrate.

FIG. 20 is a diagram showing a continuous arsenic recovery system that realizes arsenic {As (V)} ion-free using the alumina-captor of the present invention. The container containing the alumina-captor of the present invention is constructed in two upper and lower stages. First, an ion-dissolved solution in which cations and anions such as various metal ions are dissolved is placed in the upper container and held for a certain time. The solution contained in the container can be stirred, and the alumina-captor in the container can sufficiently come into contact with the solution. After a certain period of time, the ion solution in the upper stage is transferred to the lower container. In this transfer, if the container is arranged up and down, energy is not required because it falls to the lower container by gravity simply by opening the opening / closing valve provided at the outlet under the upper container.

The alumina-capter of the present invention contained in the upper vessel adsorbs arsenic in an ion solution (a solution containing a cation or anion containing arsenic ions), so the arsenic concentration in the ion solution discharged from the upper vessel Has decreased considerably. If the arsenic concentration of the first ion solution to be injected was 2.029 ppm, the value obtained in Example 14 (about 89% removal efficiency) was used, for example, after being discharged from the upper vessel after contact overnight. The arsenic concentration of the ion solution is about 0.223 ppm. The lower container also contains the alumina capter of the present invention and is sufficiently brought into contact with the ion solution from the upper container injected into the lower container. For example, the ion solution in the lower container can be stirred. In the lower container, after the alumina capter and the ion solution are brought into contact with each other for a certain time, the ion solution is discharged from the lower container. Since the alumina-captor of the present invention contained in the lower vessel adsorbs arsenic in the ion solution, the arsenic concentration in the ion solution discharged from the lower vessel is considerably reduced. If the arsenic concentration of the ion solution transferred from the upper vessel is about 0.223 ppm, the arsenic concentration of the ion solution discharged from the lower vessel is about 0.025 ppm after overnight contact. Therefore, even if the arsenic concentration in the first solution is as high as 2 ppm, the value of the level of 0.1 ppm or less which is not problematic for the human body is obtained by using the two-stage arsenic recovery system of the present invention shown in FIG. Furthermore, if the contact time and temperature are optimized, the arsenic ion concentration can be reduced to about 0.0005 ppm as shown in FIG. 117, and the arsenic removal efficiency at that time is 99.97%, which is a very low level. Can be realized.

Furthermore, a solution having a lower arsenic ion concentration can be obtained by connecting the containers containing the alumina-captor of the present invention as shown in FIG. 20 in multiple stages. In particular, as shown in FIG. 109 (FIG. 7), the alumina-captor of the present invention can adsorb an extremely small amount of arsenic ions of 1 ppb or less, so if a multistage continuous arsenic recovery system is used, a solution with a considerably high concentration of arsenic ions is used. Even so, an arsenic-free solution of 1 ppb or less can be prepared with simple equipment and without taking time. Since the alumina-captor that has adsorbed arsenic ions does not adsorb arsenic ions at a certain concentration or more, when it approaches that level, it may be replaced with an alumina-captor that does not adsorb new arsenic. If ascorbic acid is contained in the solution, the arsenic ion concentration is known and easily exchanged by the deep blue color. However, if ascorbic acid is included, removal of ascorbic acid must also be considered when using a solution. The frequency of alumina-captor replacement can be determined in advance. Alternatively, if the function of measuring the arsenic concentration of the treatment liquid is measured by ICP-OES or the like, the replacement time of the alumina-captor can be known without using ascorbic acid. Alternatively, ascorbic acid can be added by taking a treatment solution as appropriate and the arsenic ion concentration in the solution can be measured. Thus, even if it uses normal temperature without heating (0-40 degreeC, preferably 20-40 degreeC) and ascorbic acid, if a multistage removal system like FIG. 20 is comprised, arsenic ion concentration Can be obtained an arsenic-free aqueous solution below the target limit.

A further advantage of the multi-stage continuous arsenic recovery system shown in FIG. 20 is that the time for keeping the ion solution in one container can be shortened by connecting a large number of connections. Therefore, a large amount of solution treatment can be performed, and the equipment is also inexpensive, so that arsenic ions can be removed from the solution considerably cheaply. By further developing this and making the alumina-captor of the present invention a continuous fluidized bed system, it becomes possible to carry out mass solution processing at a lower cost. Thus, using the mesoporous alumina carrying the arsenic ion adsorbing compound of the present invention as an arsenic ion adsorbent in the environment, an arsenic ion removing system and an arsenic removing apparatus as shown in FIG. Remove arsenic ions from arsenic ion-dissolved solutions that are expected to contain arsenic ions such as natural water such as water and lakes, pre-purification water, factory wastewater, and domestic wastewater. However, it is necessary to remove other ions, etc.), it can be used as drinking water, domestic water, agricultural water, or factory water. When removing iron ions (Fe ⁺² ), chlorine ions (Cl ⁻¹ ), manganese ions (Mn ⁺⁶ ) and the like shown in FIG. 20, the substance for removing these ions is used as the arsenic ion adsorbing substance of the present invention. It may be added together with mesoporous alumina supporting.

FIG. 21 shows the supply of arsenic-free drinking water by placing the alumina-captor of the present invention in a bag for a tea bag that is routinely used at home and adsorbing arsenic ions from domestic drinking water. It is a figure which shows the system to do. Arsenic ions can be carcinogenic if they are ingested for a long time, so it is desirable to remove even trace amounts of arsenic. However, although arsenic removal agents so far have been difficult to remove ppb-order arsenic, the alumina-captor of the present invention can adsorb an extremely small amount of arsenic ions at the ppt to ppb level, so arsenic-free drinking water Can be supplied. For example, as shown in FIG. 21, if arsenic capters are packed instead of black tea in a tea bag bag or the like and placed in a drinking water pot as an arsenic adsorption bag, the arsenic-free material is always free. You can drink water. That is, this arsenic adsorption bag can be used as an arsenic adsorbent. Since the arsenic ion-adsorbing compound supported on alumina has a strong binding force with alumina, it does not leave during use and can be safely used without being eluted into drinking water. If arsenic ions are in the order of ppm in drinking water, it is immediately related, but thanks to the arsenic adsorption bag placed in the drinking water pot as shown in FIG. The arsenic concentration is not at a level that would cause immediate problems. As described above, the used arsenic adsorption bag can be used again because it can be separated from the arsenic adsorbed on the alumina capter by treating with an alkaline water. As described above, arsenic-free drinking water can be easily provided at home using the small bag (arsenic adsorption bag) containing the mesoporous alumina carrying arsenic adsorption ions of the present invention. Moreover, since it can be used repeatedly, it is an arsenic-free drinking water supply system using an economical and low-cost small bag (arsenic adsorption bag).

In the present invention, an arsenic ion-adsorbing compound is supported on mesoporous alumina. For example, ammonium molybdate is supported on mesoporous alumina by mixing alumina obtained after acting a surfactant on mesoporous alumina in an aqueous solution containing ammonium molybdate. This mesoporous alumina carrying an arsenic ion adsorbing compound such as ammonium molybdate selectively adsorbs a small amount of arsenic ions in water during normal temperature treatment without adjusting the water quality such as pre-treatment and post-treatment such as pH adjustment. Can be removed. Therefore, since no special pretreatment (for example, acid or alkali treatment) is performed, no extra posttreatment is required, and no heating device or the like is used, so that a low-cost arsenic removal system can be constructed. Furthermore, by configuring the arsenic removal system and the arsenic removal treatment apparatus in multiple stages, an arsenic ion-free aqueous solution can be obtained quickly and in large quantities. It is possible to provide a system that can provide an arsenic ion-free (very small amount of arsenic ions) aqueous solution used for drinking water, domestic water, etc. at a low cost and in a large amount quickly. The mesoporous alumina carrying the arsenic ion adsorbing compound of the present invention can be used as an arsenic collector (alumina collector) because it can extract and collect arsenic ions in an aqueous solution. Furthermore, by using together with ascorbic acid, it can be used as an arsenic ion sensor using a color tone that changes at a ppm to ppb to ppt level. The mesoporous alumina carrying the arsenic ion adsorbing compound of the present invention can also be used as a filter capable of removing arsenic ions at ppm to ppb to ppt levels, and is installed in a supply part for domestic drinking water or industrial water. If you do, you can always supply arsenic-free water.

In addition, it cannot be overemphasized that the said content can be applied to the said other part regarding that it can apply without contradiction also to the other part which did not describe the content described and demonstrated in a certain part of the specification. Moreover, the said embodiment and an Example are examples, and it can be carried out by changing variously within the range which does not deviate from a summary, and it cannot be overemphasized that the right range of this invention is not limited to the said embodiment.

The present invention relates to an industrial field related to a strontium collector and a sensor, an industrial field that removes arsenic ions from substances and materials containing various cations, anions, surfactants, and the like, particularly an industrial field that purifies drinking water, and an industry that collects arsenic Can be used in the field.

Claims (24)

A mesoporous alumina carrying an arsenic ion-adsorbing compound capable of adsorbing arsenic ions and releasing adsorbed arsenic ions from a solution (arsenic ion-dissolved solution) in which arsenic (As) ions as target elements are dissolved. The mesoporous alumina according to claim 1 , wherein the arsenic ion adsorbing compound is a heteropolyacid. The mesoporous alumina according to claim 2 , wherein the heteropolyacid is ammonium molybdate. The mesoporous alumina according to claim 3 , wherein the mesoporous alumina supporting ammonium molybdate is brought into contact with an arsenic ion solution to adsorb arsenic ions at room temperature. Characterized in that it does not take place in the pretreatment and / or aftertreatment of the pH adjustment in the mesoporous alumina carrying ammonium molybdate by contacting the arsenic ions dissolved solution adsorbs arsenic ions, any of claim 3 or 4 The mesoporous alumina according to any of the above items. When adsorbing arsenic ions by bringing mesoporous alumina supporting ammonium molybdate, which is an arsenic ion-adsorbing compound, into contact with an arsenic ion solution, the concentration of the adsorbed arsenic ions is judged by color tone using ascorbic acid. The mesoporous alumina according to any one of claims 3 to 5 , wherein An arsenic collector that collects arsenic (As) from an arsenic ion-dissolved solution using the mesoporous alumina according to any one of claims 1 to 6 . An arsenic removal filter using the mesoporous alumina according to any one of claims 1 to 6 . An arsenic adsorbent using the mesoporous alumina according to any one of claims 1 to 6 . The arsenic adsorbent according to claim 9 , wherein the arsenic adsorbent is a small bag containing mesoporous alumina carrying an arsenic ion adsorbing compound. A solution after removing arsenic ions from an arsenic ion-dissolved solution containing natural water, pre-purification water, industrial waste water, and domestic wastewater, using the mesoporous alumina according to any one of claims 1 to 6. A system for removing arsenic ions, characterized in that water is used as drinking water, domestic water, agricultural water, or industrial water. An arsenic ion-dissolved solution containing arsenic ions is introduced into a container containing the mesoporous alumina supporting the arsenic ion-adsorbing compound according to any one of claims 1 to 6 , or arsenic ions containing arsenic ions Arsenic ion removal, characterized in that the mesoporous alumina carrying the arsenic ion-adsorbing compound according to any one of claims 1 to 6 is added to a container containing a dissolved solution to remove arsenic ions. apparatus. The arsenic concentration in the arsenic ion-dissolved solution is adjusted by connecting a plurality of the above-mentioned fusers in series and contacting the mesoporous alumina supporting the arsenic ion-adsorbing compound and the arsenic ion-dissolving solution containing arsenic ions multiple times The arsenic ion removing apparatus according to claim 12 , wherein the arsenic ion removing apparatus is reduced to a certain concentration or less. A step of supporting an arsenic ion-adsorbing compound on mesoporous alumina, and a mesoporous alumina supporting an arsenic ion-adsorbing compound in contact with an arsenic ion-dissolved solution containing arsenic ions to selectively select arsenic ions on the arsenic ion-adsorbing compound An arsenic recovery method using mesoporous alumina, characterized by comprising an adsorbing step,
The method for recovering arsenic using mesoporous alumina, wherein the arsenic ion adsorbing compound is a heteropolyacid. The method for recovering arsenic using mesoporous alumina according to claim 14 , further comprising the step of liberating arsenic ions from the heteropolyacid adsorbed with arsenic ions.

The arsenic recovery method according to claim 14 or 15 , wherein the mesoporous alumina supporting the heteropolyacid is reused. The arsenic recovery method according to any one of claims 14 to 16, wherein the mesoporous alumina is produced using aluminum nitrate and a surfactant. 18. The arsenic recovery method according to claim 17, wherein the surfactant 1 is camphor sulfanic acid (CSA) or cetyltrimethylammonium bromide (CTAB). Mesoporous alumina is made of aluminum isopropoxide (C ₉ H ₂₁ AlO ₃ The method for recovering arsenic according to any one of claims 14 to 16, wherein the arsenic recovery method is prepared by hydrolysis. The arsenic recovery method according to any one of claims 14 to 19 , wherein the heteropolyacid is ammonium molybdate. The alumina of the obtained solid state after acting a surfactant mesoporous alumina, by mixing in an aqueous solution containing ammonium molybdate, characterized by carrying ammonium molybdate mesoporous alumina, claim 20 A method for recovering arsenic according to 1. The method for recovering arsenic according to claim 20 or 21, wherein the mesoporous alumina carrying ammonium molybdate is brought into contact with an arsenic ion solution to adsorb arsenic ions at room temperature . Characterized in that it does not take place in the pretreatment and / or aftertreatment of the pH adjustment in the mesoporous alumina carrying ammonium molybdate by contacting the arsenic ions dissolved solution adsorbs arsenic ions, any claim 20 to 22 The arsenic recovery method according to any of the above items. When adsorbing arsenic ions by bringing mesoporous alumina supporting ammonium molybdate, which is an arsenic ion-adsorbing compound, into contact with an arsenic ion solution, the concentration of the adsorbed arsenic ions is judged by color tone using ascorbic acid. The arsenic recovery method according to any one of claims 14 to 23, wherein: