JP2009220026A - Method for manufacturing environmental purification agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an environmental purification agent that can adsorb (absorb) cations and anions and remove them by ion-exchange, whose removal effect on various ions is high, and whose material costs and manufacturing costs can be more reduced considerably than those in a conventional method. <P>SOLUTION: Provided is the method for manufacturing an environmental purification agent preferable as a soil cleaning agent or a water-cleaning agent, wherein a mechanical distributed processing is performed on an artificial zeolite powder at a temperature of about 30 to 55°C (liquid temperature) for 20 to 60 minutes in an acid aqueous solution where pH is controlled within a scope of about 1.0 to 5.0, after the solution is solated (turned into slurry), the solution is subjected to still standing to obtain a product as a gel object (spongy solid matter: network structure object), and the gel object is usually used after it is crushed and classified. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a method for producing a novel environmental purification agent suitable for soil purification and water purification, which has a wide range of application and is capable of adsorbing or exchanging both cations and anions.

  Arsenic is an element that is abundant in the crust of volcanic areas, and is widely present in the environment.

  Naturally occurring arsenic pollution includes rock weathering and volcanic activity, and is often found in Hokkaido, Chugoku and Kyushu. In addition, human pollution includes emissions from mines, smelters, and plants that use arsenic, and in the past the use of pesticides containing arsenic.

  For this reason, arsenic contamination may be ongoing in many areas. In addition, there is concern about the risk of contamination from soil to groundwater. Therefore, it is highly necessary to treat arsenic that is very harmful to the human body, and the demand for an arsenic adsorbent is increasing.

  In addition, regarding soil contamination, water contamination, etc., it is extremely rare that the pollutant is alone.

  Usually, complex contamination is progressing, and there are more cases where the contaminant is a mixture of cations and anions.

  At present, there are adsorption removal methods by cation exchange of heavy metals (usually cations) with artificial zeolite, removal methods by adsorption of anions with activated alumina, chelate resin, cerium and the like.

  However, they can remove only anions and cations alone (cannot be removed at a time), and have many problems in terms of cost and efficiency.

  As an adsorbent or ion exchanger having both ion adsorption (sorption) ability, Patent Literature 1 describes a metal hydroxide / zeolite composite having a core-shell coating structure made of zeolite and a method for producing the same. (See paragraph 0001). However, the zeolite used in Patent Document 1 is a synthetic zeolite (regular particle structure: cubic system) (paragraphs 0022 to 0024), and the production conditions are alkali (for example, pH 10) suitable for the production of metal hydroxide. : Paragraph 0036), usually aging and reaction at high temperature for a long time (100 ° C. × 24 h: Paragraph 0032).

  On the other hand, the environmental purification agent based on the artificial zeolite of the present invention is a mechanical dispersion treatment (for example, 40 to 45 ° C.) of the artificial zeolite under an acidic aqueous solution having a pH of about 1.0 to 5.0, usually at a low temperature. X30 min) and then left for about 1 h.

  Therefore, it is presumed that the environmental purification agent based on the artificial zeolite in Patent Document 1 and the present invention has a different structure as well as the production method.

  In addition, patent documents 2-5 etc. can be mentioned as publicly known literature related to the purification of contaminated soil and contaminated water containing arsenic, both of which use Schwertmannite and are patentable in the present invention. It does not affect.

    Patent Document 2: A system for purifying contaminated water that effectively uses an adsorbent (adsorbent) for contaminants such as Schwbertmannite, which is a low crystalline iron compound.

    Patent Document 3: By adding an iron compound such as Schwertmannite to contaminated soil containing arsenic or heavy metal, arsenic or heavy metal in the contaminated soil is adsorbed on the iron compound, and the contaminated soil is passivated. How to purify.

    Patent Document 4: A culture solution of iron-oxidizing bacteria is added to contaminated soil containing arsenic or heavy metals to produce iron compounds such as schwertmannite, and arsenic or heavy metals in contaminated soils are sorbed to iron compounds A method of purifying contaminated soil by passivating.

Patent Document 5: Contaminated water in which a new compound obtained by stabilizing Schwertmannite is added to contaminated water or contaminated soil, and arsenic, phosphoric acid, selenium or chromium contained in the contaminated water or contaminated soil is adsorbed with the new compound Or the purification method of contaminated soil.
JP 2005-272170 A JP 2005-161231 A (summary etc.) JP 2003-112162 (Claims) JP 2003-112163 A (Claims) Japanese Patent No. 3828887 (Claim 5)

  The present invention can adsorb (sorb) or remove ions by anion as well as cations, and has a high removal effect on various ions. It is another object of the present invention to provide a method for producing an environmental purification agent that can be remarkably reduced, and to make it possible to implement soil purification and water quality purification at low cost using the environmental purification agent.

  In order to solve the above problems, the inventors of the present invention are able to easily produce an environmental purification agent in a short time if it is produced by the following method in the course of intensive development, and by adding to a small amount of soil, etc. Knowing that anions (especially arsenate anions, etc.) can be efficiently removed together with cations (lead, cadmium, etc.), which are the primary functions of artificial zeolite, we have come up with a method for producing an environmental purification agent having the following constitution. .

  About 30-55 ° C. (liquid temperature) × 20-60 min (preferably about 30 to 55 ° C. (liquid temperature)) in an acidic aqueous solution in which the artificial zeolite powder is maintained within the range of adjusted pH: about 1.0 to 5.0 (preferably less than 2.0). After passing through mechanical dispersion treatment under conditions of 40 to 50 ° C. (liquid temperature) × 25 to 50 min), it is allowed to stand to obtain a gel body (spongy solid).

  Outside the above range, it is difficult to obtain the sorption (adsorption) ability of anions such as arsenate anions, and the productivity is lowered.

  In other words, by adding artificial zeolite in an acidic aqueous solution and carrying out mechanical dispersion treatment, sol (slurry) accompanying the micronization (colloidization) of artificial zeolite proceeds and one of the surface charges of artificial zeolite is increased. The part is converted to plus as described below, and anion adsorption becomes possible.

Alumina (aluminum oxide), which is the main component of artificial zeolite, often exists as negative ions such as AlO ₃ ^{3− on the} surface. And, as in the present invention, artificial zeolite is negatively ionized on the surface of the artificial zeolite by mechanical dispersion (stirring) in an acidic aqueous solution having a pH which is larger than the isoelectric point (pH 9) of alumina and located on the acidic side. A part of AlO ₃ ³⁻ is converted to Al ³⁺ to enable anion adsorption, and at the same time, the ion adsorption capacity is also increased by surface amorphousization of the artificial zeolite. Further, when the pH is less than 2, silica (silicon dioxide) is also often present as negative ions such as SiO ₄ ^{4- on the} surface. For this reason, by maintaining and adjusting the pH of the acidic aqueous solution to be more acidic than the isoelectric point (pH 2) of silica, the surface charge of the artificial zeolite is more easily converted to a positive value and the surface of the artificial zeolite is easily amorphized. Further increase in anion adsorption capacity can be expected.

  The sol becomes a gel (spongy solid) when the mechanical dispersion treatment is stopped and the temperature is lowered.

  If the pH is too high, it is difficult to cause a part of the surface charge of the artificial zeolite to shift to the positive side and to become amorphous. If the pH is too low, the artificial zeolite may collapse or dissolve due to strong acid. When added to soil, there is a risk of acidifying the soil, and there is a risk of diminishing the effects of soil improvement, such as fields originally possessed by artificial zeolite.

  Even if the gel body (sponge-like solid) is dried as it is, it is spongy and can be used as it is after being put into a water purification tank or the like.

  However, usually, the spongy solid is dried and pulverized into a granular form and appropriately sieved to obtain an environmental purification agent.

  When it is in the form of powder, it is excellent in handleability (for storage, transportation, soil application, soil mixing, etc.) and can be suitably used as a soil purification agent, and can also be used as a filler for a water purification tank.

In each of the above structures, as the artificial zeolite, all or part of the alkali ions may be cation exchanged with iron ions (Fe ²⁺ and / or Fe ³⁺ ; the same shall apply hereinafter), or the fourth period transition metal ions It is desirable to use an acidic aqueous solution containing (in particular, iron ions). These configurations are not alternatives and may include both.

  In this configuration, the reason is unknown, but the gelation (sponge-like solids) after the artificial zeolite is solated in an acidic aqueous solution is promoted to improve productivity and arsenic adsorption capacity. Increase.

  It is presumed that most of transition metal ions including iron ions have catalytic action or complex forming ability.

  The environmental purification agent produced by the production method of each of the above constitutions can be used for purification of contaminated soil by adding and mixing it with the soil as appropriate slurry.

  The environmental purification agent obtained by each of the above methods is capable of adsorbing or exchanging both a cation group selected from the group of lead, cadmium and chromium, and an anion group of arsenic acid, selenic acid and fluorine.

  Artificial zeolite has an adsorption effect only on cations, and the types of adsorbate that can be applied are limited.

  In addition, when an anion is contained in the object to be contaminated, additional equipment, construction, and materials are required, and cost, site, time, and the like are separately required.

The environmental purification agent obtained by the acid treatment by the method of the present invention can exhibit an adsorption effect on both anions and anions, and can increase the number of adsorbable ions that can be applied. In addition to cations such as lead (Pb ²⁺ ) and cadmium (Cd ²⁺ ) that have adverse effects on the environment and the human body, anions such as arsenate (AsO ₄ ³⁻ ) and selenate (SeO ₄ ²⁻ ) One type can be handled, and environmental purification can be achieved without going through complicated processes.

  In other words, by performing dispersion treatment under specific conditions in an acidic aqueous solution in which powdered artificial zeolite is maintained at a specific adjusted pH, an anion adsorption site is independently generated in addition to the conventional cation adsorption site of artificial zeolite. It becomes possible to make it. Therefore, the artificial zeolite-based environmental purification agent prepared in this way can simultaneously adsorb the adsorbate even when multiple adsorbates (lead, cadmium, selenate, arsenate, etc.) exist. It will be shown.

  The reason is presumed that, as described above, by treating in an acidic aqueous solution, a part of the negative charge on the surface of the artificial zeolite is converted into a positive charge and at the same time becomes amorphous (amorphized).

  The present inventors have confirmed by X-ray diffraction measurement that the crystallinity of the surface portion of the artificial zeolite before and after the stirring treatment has changed.

  The environmental purification agent of the present invention is not only used for the purification of soil contamination but also for the purification of secondary contamination from contaminated soil (such as penetration into groundwater), and also for the purification of contaminated water. Applicable. Furthermore, it can be expected to be applied to the purification process of the atmosphere (particularly the site where harmful gases are generated).

  Hereinafter, desirable modes of the present invention will be described.

  In the present invention, the first characteristic requirement is to use artificial zeolite as a material (raw material) of the environmental purification agent.

In general, zeolite belongs to a crystalline aluminosilicate composed of silica and alumina, and the aluminosilicate is basically a three-dimensional skeleton in which tetrahedrons of SiO ₄ and AlO ₄ share cross-linking with oxygen atoms. It consists of a structure. Zeolites include natural, synthetic and artificial zeolites.

  Here, natural zeolite is inexpensive in price, but the quality varies depending on the production area, and generally cannot be used for the molding material of the present invention. Synthetic zeolite is stable in quality, but is expensive in price, and the resulting molding material is expensive, which is not preferable.

  Artificial zeolites include coal ash, paper sludge, aluminum dross residual ash, slag, pearlite, pearlite ore, casting waste sand, volcanic ash deposits such as volcanic ash and shirasu, and waste products such as RDF incinerated ash, or by-products of industrial products, etc. Is a metal salt of silicic acid / aluminic acid obtained by alkaline hydrothermal synthesis treatment, and has water absorption and cation exchange characteristics and is stable in quality.

  For this reason, in the present invention, artificial zeolite is adopted as the adsorbent material.

  Artificial zeolite is a mixture of fly ash and bottom ash coal ash (amorphous) and alkali metal hydroxide (for example, caustic soda) generated in coal-fired power plants, hydrothermally synthesized, and the surface of coal ash And an alkali metal type in which zeolite crystals are produced and a product obtained by exchanging part or all of the alkali metal ions with other ions.

  For example, a product marketed under the registered trade name of “Cyculus” (Registration 4846846) can be suitably used. Of these, those exchanged with iron group ions or alkaline earth metal ions can be preferably used. It is easy to obtain a material excellent in anion adsorption ability such as arsenic acid (oxo acid anion).

  For example, when an artificial zeolite in which all or part of alkali ions are cation-exchanged with iron ions is eluted with 5 times water, pH 6-9 is usually indicated.

  Here, the alkali metal is lithium, sodium, potassium, rubidium or the like shown in the periodic table group 1 (IA), preferably sodium or potassium. The alkaline earth metal is beryllium, magnesium, calcium, strontium or the like shown in the periodic table 2 (IIA) group, preferably magnesium or calcium. The iron group metal is represented by groups 8 to 10 (VIII) of Period 4 of the periodic table, and preferably iron (II, III).

  The particle size of the artificial zeolite is not particularly limited. It can be appropriately selected from a commercially available particle size range (0.01 to 500 μm). From the viewpoint of ease of dispersion treatment in an acidic aqueous solution and / or handling properties required for an environmental cleaner, those having a size of 1 to 100 μm are usually used.

  By adding artificial zeolite to an acidic aqueous solution and stirring it at a low temperature, part of the surface charge of the zeolite is converted to the positive side, and at the same time, part of the zeolite crystal is made amorphous, resulting in arsenic. An adsorption site of an oxo acid anion (anion) such as an acid is formed.

The artificial zeolite before the stirring treatment has a high specific surface area (for example, 30 to 100 m ² g ⁻¹ : BET method in the case of an average particle diameter of 10 to 50 μm). Even if it exists, many anion adsorption sites are formed.

  Here, as the acidic aqueous solution to be used, an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or the like can be usually used, but it may be appropriately prepared containing a water-soluble fourth-period transition metal salt.

  These acidic aqueous solutions often have an adjusted pH of less than 1.0 before the artificial zeolite is charged. Therefore, the pH is adjusted to about 1.0 to 5.0 (desirably less than 2.0) using a pH adjuster (for example, hydroxide or oxide of alkali metal or alkaline earth metal).

Here, the mechanical dispersion treatment (reaction) conditions are usually 30 to 55 ° C. × 20 to 60 min, preferably 40 to 50 ° C. × 25 to 50 min. The mechanical dispersion treatment may be performed by a container motion type such as a rotating drum or shaking, but is usually a container fixed type such as stirring (stirrer, propeller type) or screw kneading. The number of rotations when using a stirrer is usually appropriately selected within the range of 120 to 1300 min ⁻¹ .

Prior to the dispersion treatment, the artificial zeolite is usually charged into the acidic aqueous solution in small portions continuously or intermittently while stirring at a low speed (rotation speed: 400 to 600 min ⁻¹ ). This is to perform the distributed processing smoothly. Further, the heating to the temperature of the dispersion treatment is not performed rapidly but is gradually increased. For example, it is performed in the range of 3 to 10 ° C. min ⁻¹ . When the temperature is rapidly increased, temperature control becomes difficult and the charge of the fourth-period transition metal ions in the acidic aqueous solution may increase.

  And the artificial zeolite, which has been dispersed in an acidic aqueous solution at a slight temperature (30 to 55 ° C) and made into a sol, gelled and spongy when stirring (mechanical dispersion) was stopped and allowed to stand to return to room temperature. A solid product is formed. The production time varies depending on the pH of the acidic aqueous solution and / or the type of raw material artificial zeolite, and the ambient temperature, but is usually 0.5 to 2 hours.

  The spongy solid is taken out from the dispersion tank or held in the dispersion tank, and is allowed to stand and dry at room temperature to a slight temperature (50 ° C. or less), and then pulverized to obtain a powder having the required particle size (usually 0.1 to 1000 μm, preferably 1 to 100 μm).

  Here, the pulverizing means is not particularly limited, but usually a fine pulverizer is used. Examples of the fine pulverizer include a ball mill, a tube mill, a rod mill, a vibrating ball mill, a high swing ball mill, a ring roller mill, a ball roller mill, and an attrition mill. Then, it is appropriately adjusted to a predetermined particle size (for example, under 100 μm) with a vibrating sieve or the like.

  The particulate environmental purification agent thus produced is sprayed on the soil and driven in as appropriate, and further used as a slurry with water and sprayed on the soil.

  The amount of application at this time is 0.1 to 5 wt% although it depends on the degree of soil contamination. That is, 1 to 50 kg is added to 1 t of soil.

  Hereinafter, the present invention will be described in more detail based on examples.

<Preparation of environmental cleaner>
1) Preparation of powdered environmental cleaner:
Prepare 500 mL of acidic aqueous solution adjusted to pH about 1.5 with sulfuric acid base in 1 L beaker.

300 g of artificial zeolite (“Fe-type Cyculus” average particle size: 40 μm) is continuously added to the 1 L beaker in about 15 minutes while maintaining the liquid temperature at 20 ° C. and rotating the stirrer (rotation speed: 1000 min ⁻¹ ). (Input speed: about 20 g / min).

After completion of the artificial zeolite charging, the liquid temperature is raised to 45 ° C. in about 5 minutes while continuing to rotate the stirring device (heating rate 5 ° C. min ⁻¹ ). Furthermore, the rotation of the stirrer is continued for 30 min while maintaining the liquid temperature at 45 ° C. (rotation speed: about 1000 min ⁻¹ ).

  After stirring, the mixture was allowed to stand at room temperature (20-30 ° C.) for about 1 h. Then, a sponge (sponge) -like solid was produced. The total time so far is 1 hour 50 minutes.

  And after taking out this sponge-like solid substance from a 1L beaker, it dry-processes on conditions of 35 degreeC * 22h using a thermostat.

  The dried product was pulverized in a mortar, and the product with a size exceeding 100 μm was removed using a vibration sieve to prepare an experimental environmental cleaner.

<Confirmation of adsorption effect using simulated contaminated soil>
1) Preparation of simulated contaminated soil Dissolve a prescribed amount of disodium hydrogen arsenate heptahydrate (Na ₂ HAsO ₄ .7H ₂ O) in pure water to prepare an As (V) solution (arsenic acid solution). A mixture added to sand was used as a simulated contaminated soil.

2) Arsenic adsorption test 1 wt% of environmental cleanser was added to the simulated contaminated soil and mixed uniformly, and then left for 24 hours as an example sample, and no environmental cleanser added as a control sample. did.

  And about each sample, the arsenic elution density | concentration was measured by the following method as described in Ministry of the Environment notification 46th elution test.

“1) Preparation of sample solution Sample (unit g) and solvent (hydrochloric acid added to pure water so that the hydrogen ion concentration index is 5.8 to 6.3) (unit mL) Mix at a ratio and make the mixture 500 mL or more.

2) Elution The prepared sample solution is shaken at room temperature (generally 20 ° C) and normal pressure (generally 1 atm: 101.325 kPa) (previously shaken approximately 200 times per minute, and the shaking width is 4 cm or more and 5 cm or less. Infiltrate continuously for 6 hours.

3) Preparation of test solution After leaving the sample solution obtained in 2) above for about 10 to 30 minutes and then centrifuging at about 3000 rpm for 20 minutes, the supernatant is filtered through a membrane filter (filtered) with a pore size of 0.45 μm. The filtrate is filtered through a membrane), the amount required for quantification is accurately measured, and this is used as a test solution. "
3) Measurement results and discussion In the arsenic elution concentration, the control sample (without the addition of the environmental cleaner): 5.04 mg / L, whereas the example sample (with the environmental cleaner of the present invention added) was 0.00954 mg / L. It became. That is, it was confirmed that the addition of 1 wt% to the soil satisfied the arsenic environmental standard of the above Ministry of the Environment Notification No. 46: 0.01 mg / L.

Claims (8)

  The artificial zeolite powder is subjected to mechanical dispersion treatment in an acidic aqueous solution maintained within a range of adjusted pH: about 1.0 to 5.0 through a mechanical dispersion treatment under the condition of about 30 to 55 ° C. (liquid temperature) × 20 to 60 min. A method for producing an environmental purification agent, characterized by obtaining a gel body (spongy solid: network structure) by allowing to stand after formation of a slurry.   2. The method for producing an environmental purification agent according to claim 1, wherein the sponge-like solid is dried and pulverized into a powder form and appropriately sieved. 2. The production of an environmental purification agent according to claim 1, wherein the artificial zeolite is obtained by cation exchange of all or part of alkali ions with iron ions (Fe ²⁺ and / or Fe ³⁺ ). Method.   The method for producing an environmental purification agent according to claim 1, wherein the acidic aqueous solution contains a fourth-period transition metal ion. The method for producing an environmental purification agent according to claim 4, wherein the fourth period transition metal ion is an iron ion (Fe ²⁺ and / or Fe ³⁺ ).   2. The method for producing an environmental purification agent according to claim 1, wherein the pH of the acidic aqueous solution is less than 2.0, and the condition of the dispersion treatment is about 40 to 50 ° C. (liquid temperature) × 25 to 50 min. .   A method for purifying soil, wherein the polluted soil is purified by adding and mixing the particulate environmental cleaner obtained by the production method according to claim 2 as appropriate slurry into the soil. An environmental purification agent produced by the production method according to any one of claims 1 to 6, wherein the environmental purification agent is a cation group selected from the group consisting of lead, cadmium and chromium, arsenic acid or An environmental purification agent characterized by being capable of adsorbing or exchanging both anions of selenic acid and fluorine.