JP2019136703A - Manufacturing method of adsorbent containing fine hydrotalcite - Google Patents

Abstract

To provide a manufacturing method of an adsorbent containing fine hydrotalcite excellent in adsorption performance, and the adsorbent obtained by the manufacturing method, and an adsorbent which can be suitably used for environmental cleanup of harmful elements such as fluorine, boron, selenium or the like which is hard to be treated by prior art, further treatments such as water treatment, contaminated soil, burned ash, waste or the like, is economic and high in performance.SOLUTION: An adsorbent containing fine hydrotalcite and having excellent adsorption performance by using magnesium oxide and aluminum chloride as raw materials, adding water adjusted to have sum of mass of water and mass of crystalline water in the raw materials of 1 or less when sum of mass of a solid component excluding the crystalline water in the raw materials and mixing, then curing them. A granular adsorbent having magnetism is obtained by mixing an iron powder and a magnetic iron ore powder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an adsorbent containing fine hydrotalcite for adsorbing and removing anionic harmful substances such as arsenic, selenium, fluorine, boron, hexavalent chromium, cyan and phosphoric acid, and halogen substances such as chlorine and bromine. It relates to the manufacturing method.

  In Japan, the Soil Contamination Countermeasures Law has been in force since 2003, and since then, soil contamination surveys have been conducted on a scale exceeding 10,000 cases per year. In most cases, soil contamination detected from the survey has been implemented by excavation and removal measures in order to remove the contamination in a short period of time. According to the statistics, more than 90% of the contaminated soil is taken out of the site by excavation and removal measures, and about half of it is processed at the cement factory. While the preponderance of countermeasures for excavation and removal of contaminated soil continues, the Soil Contamination Countermeasures Law was revised in 2010 to incorporate a policy for suppressing excavation and removal countermeasures from the viewpoint of environmental risk reduction and economic rationality.

  With this revision of the law, there is an increasing need for in-situ treatment of contaminated soil. Recently, large-scale soil excavation work, such as large-scale railway construction and the construction of expressway networks in the Tokyo metropolitan area following the Olympic Games, has been carried out. . Among toxic substances contained in contaminated soil and groundwater, it is difficult to efficiently treat fluorine, boron, selenium, etc. that exist as anions in the environment. There is a demand for the development of adsorbent products that have high adsorption performance for these harmful substances and are excellent in economic efficiency.

  In the Asian region, since the 1980s, economic expansion has occurred due to an increase in industrial production. Until now, sufficient measures have not been taken to control the release of harmful substances, and soil and groundwater contamination has become serious. . For example, in countries such as China, there are many cases where the content of harmful substances causes a high concentration of soil contamination of several grams per kg of soil. Under these circumstances, there is a need for an adsorbent capable of efficiently treating high concentrations of harmful substances in the Asian region.

  Next, in Japan's Water Pollution Control Law, uniform drainage standards for boron and its compounds of 10 mg / L or less and fluorine and its compounds of 8 mg / L or less were set in 2001 as drainage standards for boron and fluorine. However, since economical water treatment methods for boron and fluorine have not yet been established, provisional drainage standards are set for industries with technical problems in actual operations, and regulations are relaxed. It was. After that, some revisions have been made, but some industries have been operating according to the provisional drainage standards to date.

  As described above, it is of great social significance to establish a technique for efficiently treating harmful elements of anions such as boron and fluorine. In Asia, such as China and Thailand, wastewater regulations are gradually being strengthened, and as in Japan, demand for water treatment technologies for harmful elements of anions such as boron and fluorine is increasing. It is.

Hydrotalcite is known to be a layered anion exchanger represented by the structural formula Mg ²⁺ _1-x Al ³⁺ _X (OH) ₂ (A ⁿ⁻ ) _{X / n} · zH ₂ O. Therefore, research using it as an adsorbent has been conducted. However, since hydrotalcite is expensive to manufacture and the treatment performance does not match the cost, it has not been generally used as a soil treatment agent or a water treatment agent.

Under such circumstances, in recent years, various research and development have been conducted to improve the adsorption performance of hydrotalcite. Patent Documents 1 to 3 can be cited as prior art relating to a nano-sized hydrotalcite adsorbent having high adsorption performance and a method for producing the same. Patent Document 1 is characterized in that it is synthesized by mixing an acidic solution containing aluminum ions and magnesium ions and an alkaline solution, and removing or neutralizing moisture without aging, and the crystallite size is 20 nm or less. The hydrotalcite-like substance is shown. Patent Document 2 describes a crystalline layered double hydroxide powder containing no carbonic acid and having a crystallite size of 20 nm or less, and under conditions where carbonic acid is not contained, a divalent metal cation and a trivalent metal cation are used. It is shown that it is produced by a process in which an acidic solution containing a metal cation and an alkaline solution containing an alkali are mixed at once to form a precipitate, which is immediately dried into powder. Patent Document 3 discloses a layered double hydroxide characterized by having a high ion exchange capacity, being hardly contaminated with carbon dioxide, maintaining an anion adsorption capacity over a long period of time, and being excellent in stability. It is shown that there is an acidic solution and an alkali metal element (A ⁺ ) in which a divalent metal cation (M ²⁺ ) and a trivalent metal cation (M ³⁺ ) and an n-valent anion are present. It is shown that the alkaline aqueous solution can be obtained by a production method in which the molar ratio of A ⁺ / M ²⁺ is adjusted to a range of 2.5 to 3.0 so that the reaction system always has a pH of 8 or less and mixed at a time. ing.

  These prior art hydrotalcites are composed of nano-sized crystallites and have a large surface area and are therefore characterized by excellent adsorption performance. However, in these production methods, in order to obtain nano-sized crystallites, facilities such as freeze-drying and freeze-vacuum drying are required in which an acidic solution and an alkaline solution are mixed at once and the hydrotalcite precipitate is immediately dried. Therefore, the manufacturing cost becomes expensive. Further, in these production methods, a sodium salt corresponding to several times the mass of hydrotalcite is simultaneously generated at the time of hydrotalcite synthesis, and the production cost becomes expensive due to this separation / removal, drying, and waste liquid treatment. Furthermore, there existed a problem that the adsorption | suction performance of the synthesized hydrotalcite fell with residual sodium salt.

  Patent Document 4 describes a method for producing an adsorbent using magnesium oxide and a soluble aluminum salt as raw materials. Further, an adsorbent obtained by repeatedly reacting magnesium oxide and an aluminum salt in an aqueous solution for a long time and having magnesium oxide particles coated with hydrosite is shown. In the production method of Patent Document 4, since the adsorbent is produced by stirring for a long time in an aqueous solution for the purpose of improving the yield of the adsorbent, the hydrotalcite crystallites synthesized become large and fine. An adsorbent containing hydrotalcite cannot be obtained. Furthermore, in this production method, there is a problem that requires large energy, such as solid-liquid separation, drying, and water treatment, in the step of synthesizing the adsorbent.

  Patent Document 5 discloses a method for producing fine hydrotalcite particles, in which a mixed aqueous solution of magnesium salt and aluminum salt, an alkaline substance and an interlayer anion are reacted in a thin film microreactor having a reaction field clearance of 1 to 30 μm. It is shown.

  Thus, various techniques have been improved so far, and methods for producing hydrotalcite having fine crystallites have been studied. However, in these technologies, since a raw material containing a large amount of chloride and nitric acid is dissolved in an aqueous solution and synthesized, a sodium salt several times the mass of hydrotalcite is generated at the same time. There is a problem that a large amount of energy is required for waste liquid treatment, drying, etc., and the production becomes extremely difficult.

  As a method for separating and removing the sodium salt which is a by-product generated during the synthesis of hydrotalcite, first, dehydration by a filter press can be considered. However, dehydration with a filter press usually leaves about 40 to 50% of the sodium salt and is difficult to remove sufficiently.

  As a method for reliably removing the sodium salt, there is a method of repeating washing several times with 3 to 5 times the mass of hydrotalcite water. According to this method, it is possible to surely remove the sodium salt, but for example, it takes several days to one week to produce several tons of dried hydrotalcite.

  As described above, in the prior art, it is difficult to efficiently produce hydrotalcite by steps such as solid-liquid separation, drying, removal of by-products, and waste liquid treatment. It takes a long time to manufacture. Further, there is a problem that the adsorption performance is lowered due to the blockage of the hydrotalcite pores and the competition of the remaining chloride ions and nitrate ions due to the remaining sodium salt produced during the production. The deterioration in performance due to residual ions is particularly affected in the treatment of harmful substances such as selenium and boron having low adsorption selectivity.

International Publication WO2005 / 087664 Pamphlet JP 2005-306667 A JP 2006-334456 A JP 2012-106227 A International Publication WO2013 / 147285 Pamphlet

  The problem to be solved by the present invention is to provide a method for producing an adsorbent containing hydrotalcite which is excellent in anion-type harmful element adsorption performance. It is another object of the present invention to provide an adsorbent that is economical and has high performance that can be suitably used for environmental purification of harmful elements such as fluorine, boron, and selenium that are difficult to treat with conventional techniques.

  When the present inventor uses magnesium oxide and aluminum chloride as raw materials and the sum of the masses of solids excluding crystallization water in the raw materials is 1, the sum of the mass of water and the mass of crystallization water in the raw materials is 1. After adding and mixing the water adjusted so that it might become the following, it discovered that the adsorbent which has the outstanding adsorption | suction performance containing a fine hydrotalcite could be obtained by performing curing, and came up with this invention.

  The method for producing an adsorbent containing fine hydrotalcite of the present invention uses magnesium oxide and aluminum chloride as raw materials, and the mass of water when the sum of the masses of solids excluding crystal water in the raw material is 1. And a mixing step of adding water adjusted so that the sum of the masses of crystal water in the raw material is 1 or less and mixing to obtain a mixture, and curing to obtain an adsorbent by curing the mixture obtained in this mixing step A process is provided.

  In the mixing step, the molar ratio of magnesium and aluminum in the raw material is in the range of 3: 1 to 13: 1.

  In the mixing step, at least one of slaked lime, clinoptilolite, mordenite, A-type zeolite, X-type zeolite, iron powder, and magnetite powder is further mixed.

  The adsorbent obtained after the curing step is washed with water, dried and pulverized.

  The adsorbent containing fine hydrotalcite and magnesium oxide of the present invention is produced by the method for producing an adsorbent containing fine hydrotalcite of the present invention.

  According to the present invention, an adsorbent containing fine hydrotalcite having excellent adsorption performance can be efficiently produced. The adsorbent of the present invention is suitable as an adsorbent for the treatment of waste liquid, drainage, ground water, purified water, contaminated soil, incinerated ash, waste, etc., and an additive for plastics for removing halogen substances. Can be used.

It is an X-ray diffraction pattern of the adsorption agent containing the fine hydrotalcite of one Example of this invention.

The general formula of hydrotalcite is represented by Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ (A ⁿ⁻ ) _{X / n} · zH ₂ O. Here, A ⁿ⁻ _{X / n} represents an interlayer anion. Under hydrotalcite synthesis conditions, the molar ratio of magnesium to aluminum is generally in the range of 2: 1 to 5: 1. By adopting this composition condition, a high yield can be obtained. . Hydrotalcite is a hydroxide, and when a mixed salt aqueous solution of magnesium ions and aluminum ions is mixed with an alkaline solution, it is immediately formed as a precipitate. As a method for producing hydrotalcite, a method of neutralizing and synthesizing an aqueous solution in which magnesium ions and aluminum ions are dissolved is usually employed by utilizing this property.

  Hereinafter, the adsorption | suction containing the fine hydrotalcite of this invention and its manufacturing method are demonstrated in detail.

  The method for producing an adsorbent containing fine hydrotalcite of the present invention uses magnesium oxide and aluminum chloride as raw materials, and the mass of water when the sum of the masses of solids excluding crystal water in the raw material is 1. And a mixing step of adding water adjusted so that the sum of the masses of crystal water in the raw material is 1 or less and mixing to obtain a mixture, and curing to obtain an adsorbent by curing the mixture obtained in this mixing step A process is provided. Hereinafter, in this specification, the ratio of the sum of the mass of solids excluding crystallization water in the raw material and the sum of the mass of water and the sum of the mass of crystallization water in the raw material is expressed as a solid-liquid ratio (mass ratio). ). Accordingly, when aluminum chloride hexahydrate containing crystallization water is used as aluminum chloride, the amount of water to be added is adjusted in consideration of the mass of crystallization water contained in aluminum chloride hexahydrate. .

  Moreover, in this invention, Preferably, in the said mixing process, it adjusts so that the molar ratio of magnesium and aluminum in a raw material may become the range of 3: 1-13: 1. The obtained adsorbent has a composite composition containing fine hydrotalcite and magnesium oxide, but contains fine hydrotalcite with an average crystallite size of 10 nm or less and has a large surface area. Has excellent adsorption performance of substances.

  In the method for producing an adsorbent containing fine hydrotalcite according to the present invention, the amount of water to be mixed is set to a solid-liquid ratio (mass ratio) of 1: 1 or less. This condition is different from a general hydrotalcite synthesis method in which an aqueous solution in which magnesium and aluminum are dissolved is used. Due to such characteristics, in the production of the adsorbent of the present invention, the mixture after curing becomes powdery, which is greatly different from the conventional method of synthesizing hydrosites in the liquid phase. By adopting this new production method, in the present invention, an adsorbent with excellent performance is produced economically by a simple method using a mixing device such as a known powder mixer, a mixing granulation device or the like. be able to.

  In the production of the adsorbent containing fine hydrotalcite of the present invention, magnesium oxide and aluminum chloride are used as raw materials, and adjustment is made so that the molar ratio of magnesium to aluminum is in the range of 3: 1 to 13: 1. Preferably it is done. The molar ratio of magnesium to aluminum is more preferably 3: 1 to 9: 1. This composition condition is a composition with more magnesium components than general hydrotalcite synthesis conditions. This is for the purpose of adjusting the pH to the range of neutral to weak alkali and suppressing the amount of chloride ions remaining in the adsorbent without using caustic soda that requires handling.

  In the method for producing the adsorbent of the present invention, magnesium oxide is used. The magnesium oxide used here is preferably light-burned magnesia obtained by baking magnesium carbonate at 700 to 900 ° C. In addition, it is preferable to use a product having a particle size of 200 to 325 mesh or finer than magnesium oxide.

  As aluminum chloride used in the method for producing an adsorbent of the present invention, aluminum chloride hexahydrate is preferably used. It is also possible to use powdered polyaluminum chloride as a raw material for the adsorbent of the present invention. Since polyaluminum chloride is inexpensive, the adsorbent of the present invention can be produced more economically by using it as a raw material. However, since polyaluminum chloride contains a sulfate group in order to stabilize the basicity, the use of this tends to lower the performance of the adsorbent.

  It is also possible to replace a part of magnesium oxide with magnesium chloride hexahydrate or the like. However, if this is used as a raw material, the amount of residual chloride is increased and the performance of the adsorbent is lowered, which is not preferable. It is possible to add sodium hydroxide and slaked lime as raw materials to the production method of the present invention. However, when the pH increases, aluminum changes to aluminate and becomes unsuitable for the synthesis of hydrotalcite. It is necessary to adjust to the extent.

  In the method for producing an adsorbent containing fine hydrotalcite according to the present invention, as described above, heat is generated due to the generation of hydrotalcite by mixing magnesium oxide, aluminum chloride hexahydrate and water whose composition is adjusted, The temperature of the mixed composition rises to about 90 ° C., and fine hydrotalcite is synthesized. This production method is characterized in that the adsorbent solidifies because the hydrotalcite aggregates and is heated. In the production of the adsorbent of the present invention, a known mixing device such as a powder processing mixer, a mixing granulation device or the like can be used, but if these devices are equipped with a cooling facility such as water cooling, the device Advantages such as controlling the temperature of the product and enabling continuous production are born.

  In the curing in the method for producing an adsorbent of the present invention, since heat is generated during production, it is not necessary to heat the mixture. Since the heat generated by the synthesis reaction usually lasts for about 20 to 30 hours, the mixture is taken out from the mixing apparatus and cured while keeping the mixture sealed and wet. Here, the curing time is suitably several hours to 72 hours, and if the curing time is short, a sufficient amount of hydrotalcite is not synthesized, which is not preferable. Moreover, after taking out a mixture from a mixing apparatus, after discharging | emitting water vapor | steam for 1 hour-several hours, you may seal a mixture and perform curing for several hours-72 hours. Further, in the production of the adsorbent of the present invention, the mixture can be sealed and heated for several hours to 72 hours under a temperature condition of 200 ° C. or lower.

  As will be described later, the adsorbent produced by the production method of the present invention is mainly composed of hydrotalcite and unreacted magnesium oxide, and also has a composite composition consisting of aluminum hydroxide and magnesium chloride. However, since it contains fine hydrotalcite having an average crystallite size of 10 nm or less, it has excellent adsorption performance for anionic harmful substances.

  In the production of the adsorbent of the present invention, water having a solid-liquid ratio (mass ratio) of 1: 1 or less is added to the raw material, and the mixture is mixed under the condition that the solid content is higher than that of the conventional production method. An adsorbent containing is synthesized. The amount of water used is preferably such that the solid-liquid ratio (mass ratio) is in the range of 1: 0.2 to 1: 0.8. More preferably, it is in the range of 1: 0.4 to 1: 0.7. Even more preferably, it is in the range of 1: 0.5 to 1: 0.6. If the amount of water is too small, it becomes difficult to uniformly disperse water in the mixture, and if the amount of water is too large, it becomes a slurry and the whole is solidified after curing, making handling difficult. Here, the solid-liquid ratio (mass ratio) is obtained by dividing the total mass of magnesium oxide and aluminum chloride excluding crystal water by the total mass of the crystal water and water to be added. The added water is consumed for the synthesis of hydrotalcite, and part of it is vaporized as water vapor due to the heat generated by the chemical reaction. If an appropriate amount of water is added according to the raw material composition, a powder having a dry surface can be obtained after curing, and it can be used as an adsorbent without drying. The adsorbent of the present invention has the property of solidifying due to aggregation of hydrotalcite and heat generation during synthesis. The solidified composition can be used after being pulverized using a known pulverizer or pulverizer. When a large amount of moisture is added during production, the mixture may be largely consolidated and moisture may remain on the surface. Even in such a case, if it is dried and pulverized, it can be used as an adsorbent. In the method for producing an adsorbent of the present invention, a granular adsorbent can be suitably produced by using a granulator such as a mixing granulator.

  Next, in the adsorbent manufacturing method of the present invention, various additives can be homogeneously mixed in the adsorbent in the mixing step. If a porous material such as pearlite, zeolite, pumice, or foamed glass pulverized product is mixed as an additive, the porosity of the produced adsorbent can be improved. Further, if a natural zeolite such as clinoptilolite or mordenite, or a synthetic zeolite such as A-type zeolite or X-type zeolite is added, cation adsorption performance can be added. If slaked lime is added, the pH of the adsorbent can be adjusted to the alkali side.

  Furthermore, if magnetic powder, such as iron powder and magnetite (magnetite), is mixed, magnetism can be imparted to the adsorbent and magnetic selection can be performed. Thereby, it becomes possible to adsorb, concentrate and separate and remove harmful substances from contaminated soil, drainage, and the like. The mixing ratio of the iron powder and the magnetite powder is preferably 10 to 80% by mass, more preferably 20 to 60% by mass, based on the total mass of the powder raw material including crystal water. If the mixing amount of iron powder and magnetite powder is small, magnetic separation becomes difficult, and if the mixing amount of iron powder and magnetite powder is too large, the adsorption performance of anionic toxic substances will be reduced.

  Fine iron powder is difficult to handle because it reacts exothermically with oxygen in the air. The safety at the time of manufacture can be improved by using it mixed with magnetite.

  In addition, when adding additives such as slaked lime, clinoptilolite, mordenite, A-type zeolite, X-type zeolite, iron powder, magnetite powder, etc., the amount of water added in the mixing process is adjusted according to these addition amounts do not have to. That is, in the mixing step, an amount of water calculated by paying attention only to the masses of magnesium oxide and aluminum chloride may be added according to the definition of the solid-liquid ratio described above.

  As described above, the adsorbent containing the fine hydrotalcite of the present invention can be synthesized by a simple process of adding a small amount of water to the raw material powder, mixing and curing, and the conventional magnesium. Compared with the method for producing hydrotalcite synthesized in an aqueous solution in which aluminum is dissolved, it can be produced with extremely low energy. Further, according to the production method of the present invention, it is basically unnecessary to perform separation / removal treatment and waste liquid treatment of the sodium salt generated during the synthesis, so that the adsorbent can be produced efficiently.

  Furthermore, in order to improve the adsorption performance of the adsorbent containing fine hydrotalcite of the present invention, the adsorbent obtained by the above production method is washed with water to remove residual chloride ions, and then dried. You may grind | pulverize. For example, in the treatment of selenic acid or boron having low adsorption selectivity, a method of removing and modifying chloride ions that are inhibitors by such a method is effective. The adsorbent produced according to the present invention has an advantage that solid-liquid separation and dehydration after washing are easy because hydrotalcite aggregates and solidifies through a chemical reaction accompanied by heat generation. In addition, the adsorbent containing fine hydrotalcite of the present invention has a feature that a granular composite adsorbent mixed with iron powder, zeolite or the like can be produced by utilizing the property of solidifying during production.

  Since the adsorbent containing fine hydrotalcite of the present invention contains hydrotalcite having an average crystallite size of 10 nm or less and has excellent adsorption performance, arsenic, selenium, fluorine, boron, hexavalent chromium, It can be used to remove various anionic substances such as cyan, phosphoric acid and silicic acid. Fields of application include water treatment of waste liquid, drainage, ground water, purified water, treatment for elution of contaminated soil, incinerated ash, waste, and the like. Further, the adsorbent of the present invention processed into a granular form can be suitably used as a water treatment agent used in a column treatment method.

  The particle size of the adsorbent of the present invention can be adjusted to a size of 0.1 to several mm and filled into a cloth mat or bag. Thus, by processing into a product combined with a cloth, the flow velocity of the water flow passing through the adsorbent can be controlled, and the adsorbent can be prevented from running away with running water. Such a product can be used as an adsorbent for treating contaminated soil and an adsorbent for purifying groundwater.

  Furthermore, the adsorbent containing fine hydrotalcite of the present invention has excellent adsorption performance and is used as an additive for plastics for removing halogen substances such as chlorine and bromine generated from the resin by heating and deterioration. It is also possible.

  An adsorbent containing the fine hydrotalcite of the present invention was produced by the following method.

  (1) A total of 700 g of powder raw materials of magnesium oxide and aluminum chloride hexahydrate was put into a desktop Hobart mixer and mixed for 3 minutes, and then a predetermined amount of ion-exchanged water was added and mixed for 4 minutes. Here, the raw materials were blended and adjusted so that the molar ratio of magnesium to aluminum was Mg / Al = 8.6, and ion-exchanged water was added under the condition of a solid-liquid ratio of 1.0: 0.64.

  (2) The temperature after mixing was measured and found to be 68 ° C. After being left for 1 hour, the mixture in the mixer was transferred to a resin container, and the top was covered and sealed.

  (3) The mixture was allowed to stand for 24 hours as described above for curing. The temperature of the mixture after curing was room temperature 20 ° C.

  (4) 100 g of the mixture was weighed and pulverized in a mortar so that the particle size was 1 mm or less.

  Here, in the above trial manufacture, magnesium oxide (produced in China, purity 90%, particle size -325 mesh), aluminum chloride hexahydrate (manufactured by Nippon Light Metal Co., Ltd., purity 97% or more) is used as magnesium and aluminum raw materials. did.

  Using RINT ULTIMA3 manufactured by Rigaku Co., Ltd., the prototype adsorbent was analyzed by X-ray diffraction. This X-ray diffraction diagram is shown in FIG.

  FIG. 1 shows that the adsorbent of the present invention has a composition containing hydrotalcite and magnesium oxide as main components and a slight amount of aluminum hydroxide and magnesium chloride. As shown in FIG. 1, the synthesized hydrotalcite has a broad peak shape, and the crystallite size was determined by the Scherrer method. The crystallite size was 20 nm or less, and the average crystallite size was 8 .6 nm. As described above, it was confirmed that an adsorbent composition containing fine hydrotalcite was synthesized by the production method of the present invention.

  In the same procedure as in Example 1, the adsorbent containing fine hydrotalcite of the present invention was prepared under the conditions of magnesium / aluminum molar ratio Mg / Al = 5.7 and solid / liquid ratio 1.0: 0.55. Prototype. Formation of hydrotalcite having the same crystallite size as in Example 1 was confirmed by X-ray diffraction of the prototype adsorbent.

  When 100 g of the adsorbent prepared in Example 2 was put into a beaker, 300 g of purified water was added and stirred with a jar tester for 10 minutes, and filtered and dehydrated with an aspirator, the dehydrating property was good. The adsorbent after dehydration was dried at 120 ° C. with an electric furnace, and lightly pulverized with a mortar to a particle size of 1 mm or less.

  An adsorbent containing the fine hydrotalcite of the present invention was produced in the same procedure as in Example 1 using magnesium oxide and powdered polyaluminum chloride as raw materials.

  (1) A total of 500 g of powder raw materials of magnesium oxide and powdered polyaluminum chloride were put into a desktop Hobart mixer and mixed for 3 minutes, and then a predetermined amount of ion-exchanged water was added and mixed for 4 minutes. Here, the raw materials were blended and adjusted so that the molar ratio of magnesium and aluminum was Mg / Al = 3.8, and ion-exchanged water was added under the condition of a solid-liquid ratio of 1.0: 0.40.

  (2) The mixture was allowed to stand for 24 hours as described above and cured.

  (3) 10 g of the mixture was weighed and pulverized in a mortar so that the particle size was 1 mm or less.

Here, in the above trial production, magnesium oxide as a raw material of magnesium and magnesium (produced in China, purity 90%, particle size -325 mesh), powdered polyaluminum chloride (manufactured by Daimei Chemical Co., Ltd., Al ₂ O ₃ 30%) It was used.

Comparative Example 1

  In Comparative Example 1, a trial production was performed with a composition capable of obtaining high-purity hydrotalcite by a conventional synthesis method. According to the following procedure, hydrotalcite was synthesized in an aqueous solution having a solid-liquid ratio of 1: 5 and a molar ratio of magnesium and aluminum of Mg / Al = 2.0. After the hydrotalcite was dried, it was washed repeatedly with purified water to remove sodium salts.

  (1) Magnesium chloride hexahydrate and aluminum chloride hexahydrate were added to purified water to prepare 120 g of an acidic aqueous solution containing magnesium concentration = 0.88 mol / L and aluminum concentration = 0.43 mol / L.

  (2) While strongly stirring the above acidic liquid with a jar tester, 20.5 g of 48% sodium hydroxide solution was added by titration to adjust to pH = 8.1, followed by stirring for 1 hour.

  (3) All of the mixed slurry was placed in an electric furnace and boiled and dried at 130 ° C.

  (4) After adding purified water 4 times the weight of the dry powder and stirring for 1 hour, it was allowed to stand for 1 hour.

  (5) The coagulated and separated supernatant was removed using a tube pump.

  (6) The above operations (4) to (5) were further repeated twice.

  (7) The slurry from which the supernatant was removed was boiled and dried at 120 ° C. in an electric furnace.

  (8) The dried powder was pulverized in a mortar to obtain a particle size of 1 mm or less.

  Here, magnesium chloride hexahydrate (reagent manufactured by Nacalai Tesque, Inc., purity 97%) and aluminum chloride hexahydrate (produced by Nippon Light Metal Co., Ltd., purity 97% or more) were used. A 48% sodium hydroxide solution was prepared by diluting a sodium hydroxide reagent (Nacalai Tesque, Inc., purity 97%).

Comparative Example 2

  In Comparative Example 2, hydrotalcite was synthesized in an aqueous solution in which aluminum was dissolved using magnesium oxide and aluminum chloride hexahydrate by a conventional synthesis method. In this comparative example, the molar ratio of magnesium and aluminum was set to the same Mg / Al = 8.6 as in Example 1, and the solid-liquid ratio = 1: 10.

  (1) Aluminum chloride hexahydrate was added to 241 g of purified water to adjust the aluminum concentration to 0.23 mol / L, and it was completely dissolved by stirring with a jar tester.

  (2) Magnesium oxide was added to the aqueous solution under the above molar ratio Mg / Al = 8.6, and the mixture was stirred with a jar tester for 4 hours to synthesize hydrotalcite.

  (3) All the mixed liquid was dehydrated with an aspirator. The synthesized hydrotalcite-containing mixture was poor in dehydration and took 1 hour.

  (4) It dried at 120 degreeC with the electric furnace, and it grind | pulverized with the mortar so that the particle size was 1 mm or less.

  Here, magnesium oxide and aluminum chloride hexahydrate use magnesium oxide (made in China, purity 90%, particle size -325 mesh), aluminum chloride hexahydrate (manufactured by Nippon Light Metal Co., Ltd., purity 97% or more). did.

  When the synthesized hydrotalcite was analyzed by X-ray diffraction, formation of hydrotalcite, magnesium oxide and the like was confirmed. From the peak shape of hydrotalcite, the average crystallite was larger than 20 nm.

  Using the adsorbents produced in Example 1 and Comparative Example 1 by the following procedure, adsorption tests for arsenic acid and selenic acid were performed.

  (1) Using an arsenic acid solution reagent, a test solution targeting an As (V) concentration of 1 mg / L was prepared.

  (2) Using a sodium selenate reagent, a test solution having a Se (VI) concentration of 1 mg / L was prepared.

  (3) 250 ml of two kinds of test solutions are dispensed into resin bottles, and the adsorbent of Example 1 is added thereto under the condition of a solid-liquid ratio (mass ratio) of 1: 1000 and shaken for 24 hours ( Horizontal shaking) Adsorption test was conducted.

  (4) The supernatant was filtered from each resin bottle with a 0.45 μm syringe filter, and the concentration was measured using ICP-MS.

  (5) A similar adsorption test was performed using the hydrotalcite of Comparative Example 1.

  Here, an arsenic acid solution reagent (manufactured by Kanto Chemical Co., Ltd., purity 60%) and a sodium selenate reagent (manufactured by Nacalai Tesque Co., Ltd., purity 98%) were used.

  Table 1 shows the results of adsorption tests using two adsorbents. The adsorbent containing the fine hydrotalcite of the present invention resulted in excellent adsorption performance of arsenic and selenium, like the high purity hydrotalcite synthesized by the prior art. In the adsorption test of Se (VI), which has a low adsorption selectivity and is difficult to process, the performance of the adsorbent of the present invention exceeded.

  Using the adsorbents produced in Example 1 and Comparative Example 1, the fluorine water treatment test was performed according to the following procedure.

  (1) A test solution having a fluorine concentration of 20 mg / L was prepared using a sodium fluoride reagent.

  (2) 200 g of the test solution was dispensed into a beaker, 0.5 mass% of two kinds of adsorbents were added, and the mixture was stirred with a jar tester for 1 hour.

  (3) After standing for 15 minutes, the supernatant was filtered through a 0.45 μm syringe filter to collect a test solution.

  (4) The fluorine concentration was measured using a spectrophotometer.

  Here, in this example, a sodium fluoride reagent (manufactured by Nacalai Tesque, Inc., purity 98%) was used.

  The results of the water treatment test are shown in Table 2. In both adsorbents, the fluorine concentration after treatment was less than the wastewater standard value. Further, the adsorbent of the present invention was slightly superior in water treatment effect.

  The hexavalent chromium adsorption test was performed using the adsorbents produced in Examples 2 to 4 and Comparative Example 2 in the following procedure.

  (1) A test solution having a chromium concentration of 100 mg / L was prepared using a sodium dichromate reagent.

  (2) 200 g of the test solution was dispensed into a resin bottle, 1% by mass of various adsorbents were added, and a shaking adsorption test was performed for 24 hours.

  (3) After standing for 20 minutes, the supernatant was filtered through a 0.45 μm syringe filter, and a test solution was collected.

  (4) The concentration of chromium was measured using ICP-AES.

  Here, in this example, a sodium dichromate reagent (manufactured by Nacalai Tesque, Inc., purity 97%) was used.

  The adsorption test results are shown in Table 3. In Example 3, it became a result below the drainage standard value. The adsorbents of Examples 2 and 3 that were prototyped by the production method of the present invention were able to adsorb hexavalent chromium from the adsorbent containing hydrotalcite of Comparative Example 2 synthesized in an aqueous solution using the same raw materials. The result was excellent. In Example 3, the adsorbent prototyped in Example 2 was washed with water and dried, but the adsorption performance was improved by removing chloride ions contained in the adsorbent by this treatment. I understand. Further, Example 4 using powdered polyaluminum chloride as a raw material also has an adsorption performance exceeding that of Comparative Example 2.

  Using the adsorbents made as prototypes in Example 2, Example 3, and Comparative Example 2, a boron adsorption treatment test was performed by the following procedure.

  (1) A test solution having a boron concentration of 50 mg / L was prepared using a boric acid reagent. Sodium hydroxide was added thereto, and the pH was adjusted to 11.5.

  (2) 200 g of the test solution was taken into a resin bottle, 1% by mass of various adsorbents were added, and a 24-hour shaking adsorption test was performed.

  (3) After standing for 20 minutes, the supernatant was filtered through a 0.45 μm syringe filter, and the boron concentration was measured using ICP-AES.

  Here, in this example, a boric acid reagent (manufactured by Nacalai Tesque, Inc., purity 99.5%) was used.

  The adsorption test results are shown in Table 4. The adsorbents of Examples 2 and 3 prototyped according to the present invention have better boron adsorption performance than the hydrotalcite of Comparative Example 2 synthesized in an aqueous solution using the same raw materials. The processing result was below the reference value. In Example 3, the adsorbent produced in Example 2 was washed with water and dried, and it was confirmed that the adsorption performance was improved by removing chloride ions by this treatment.

  By the following method, an adsorbent containing the fine hydrotalcite of the present invention mixed with iron powder was prototyped.

  (1) A total of 630 g of powder raw materials of magnesium oxide and aluminum chloride hexahydrate and 70 g of iron powder were put into a desktop Hobart mixer and mixed for 3 minutes, and then a predetermined amount of ion-exchanged water was added and mixed for 4 minutes. Here, the raw materials were blended and adjusted so that the molar ratio of magnesium and aluminum was Mg / Al = 8.6, and ion-exchanged water was added under the condition of a solid-liquid ratio of 1.0: 0.46.

  (2) The temperature after mixing was measured and found to be 83 ° C. The mixture in the mixer was transferred to a resin container and sealed.

  (3) The resin container was placed in an incubator and heated at a temperature of 80 ° C. for 24 hours.

  (4) 100 g of the mixture was weighed and pulverized in a mortar so that the particle size was 0.5 mm or less, and a granular adsorbent containing iron powder was obtained.

  Here, in the trial production, the same raw materials as in Example 1 were used as the magnesium oxide and aluminum chloride raw materials. Moreover, the reduced iron powder E200 (average particle diameter of 45 micrometers) by DOWA IP Creation Co., Ltd. was used as iron powder.

  An adsorbent containing the fine hydrotalcite of the present invention mixed with magnetite powder was prototyped by the following method.

  (1) A total of 490 g of powder raw materials of magnesium oxide and aluminum chloride hexahydrate and 210 g of magnetite powder were put in a desktop Hobart mixer and mixed for 3 minutes, and then a predetermined amount of ion-exchanged water was added and mixed for 4 minutes. Here, the raw materials were blended and adjusted so that the molar ratio of magnesium and aluminum was Mg / Al = 8.6, and ion-exchanged water was added under the condition of a solid-liquid ratio of 1.0: 0.46.

  (2) The temperature after mixing was measured and found to be 83 ° C. The mixture in the mixer was transferred to a resin container and sealed, followed by curing at room temperature.

  (3) 100 g of the mixture was weighed and pulverized in a mortar so that the particle size was 0.5 mm or less, and a granular adsorbent containing magnetite was obtained.

  Here, in the trial production, the same raw materials as in Example 1 were used as the magnesium oxide and aluminum chloride raw materials. Moreover, the ferrite powder (average particle diameter of 12 micrometers) by DOWA F-Tech Co., Ltd. was used as magnetite powder.

  A fluorine water treatment test was performed using the adsorbents produced in Examples 9 and 10 in the following procedure.

  (1) A test solution having a fluorine concentration of 5 mg / L was prepared using a sodium fluoride reagent.

  (2) Aliquot 200 g of test solution into a 500 mL capacity plastic bottle, add 1.0% by mass of two kinds of adsorbents, respectively, and shake for 1 hour on a shaker at 200 rpm. It was.

  (3) After standing for 15 minutes, the supernatant was filtered through a 0.45 μm syringe filter to collect a test solution.

  (4) The fluorine concentration was measured using a spectrophotometer.

  Here, in this example, the same sodium fluoride reagent as in Example 6 was used.

  The adsorption test results are shown in Table 5. It was confirmed that the adsorbent obtained by mixing the iron powders and magnetite powders of Examples 9 and 10 manufactured according to the present invention has high fluorine adsorption performance.

  According to the following procedure, the recovery rate by magnetic separation of the adsorbents manufactured in Examples 9 and 10 was evaluated.

  (1) Dispense 200 g of ion-exchanged water into a 500 mL capacity plastic bottle, add 5.0% by mass of two kinds of adsorbents, and shake with a shaker at 200 rpm for 1 hour. It was.

  (2) The test solution after shaking was transferred to a stainless steel vat, and the upper surface of the test solution was scanned three times with a bar magnet having a surface magnetic force of 0.4 T to collect magnetic deposits.

  (3) The mass of the recovered magnetic deposit was measured after drying, and the recovery rate was determined from the difference in the added mass in (1).

  The results are shown in Table 6. It was confirmed that Examples 9 and 10 prototyped according to the present invention had a high magnetic separation recovery rate, and had both the performance as an adsorbent and good characteristics as a magnetic material. Moreover, it was found that these prototype adsorbents had sufficient strength characteristics without separation of the adsorbent components from the iron powder and magnetite powder.

Claims (5)

When using magnesium oxide and aluminum chloride as raw materials and the sum of the mass of solids excluding crystallization water in the raw material is 1, the sum of the mass of water and the mass of crystallization water in the raw material is 1 or less. Adsorption including fine hydrotalcite characterized by comprising a mixing step of adding and mixing adjusted water to obtain a mixture, and a curing step of curing the mixture obtained in this mixing step to obtain an adsorbent Manufacturing method. The method for producing an adsorbent containing fine hydrotalcite according to claim 1, wherein in the mixing step, the molar ratio of magnesium and aluminum in the raw material is in the range of 3: 1 to 13: 1. The said mixing process WHEREIN: At least 1 sort (s) of slaked lime, clinoptilolite, mordenite, A-type zeolite, X-type zeolite, iron powder, magnetite powder is further mixed. A method for producing an adsorbent containing fine hydrotalcite. The method for producing an adsorbent containing fine hydrotalcite according to any one of claims 1 to 3, wherein the adsorbent obtained after the curing step is washed with water, dried and pulverized. The adsorbent characterized by including the fine hydrotalcite and magnesium oxide manufactured by the manufacturing method of the adsorbent containing the fine hydrotalcite in any one of Claims 1-4.

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