JP2009254920A - Heavy metal treating agent and method of making heavy metal-contaminated matter harmless - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy metal treating agent containing a novel manganese compound oxide having excellent heavy metal treating characteristics as an active ingredient and a method of making harmless waste, waste water and/or soil containing various types of heavy metals by using the heavy metal treating agent. <P>SOLUTION: The heavy metal treating agent utilizes a complex oxide comprising Ca and/or Mg and Mn in a (Ca and/or Mg)/Mn ratio of 0.1-0.8. The complex oxide is preferably in a layer crystal form. Most preferably, Ca and/or Mg is eluted from the complex oxide and the (Ca and/or Mg)/Mn ratio is made 0.1-0.3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is contained in solid waste containing heavy metals, for example, incineration ash and fly ash discharged from garbage incineration plants, soil contaminated with heavy metals, sludge generated after wastewater treatment, wastewater discharged from factories, etc. Heavy metal treatment agent that can detoxify harmful heavy metals such as lead, cadmium, copper, zinc, nickel, thallium, etc. easily, efficiently, and detoxify heavy metal contaminants is there.

  Manganese oxides are known to adsorb heavy metals. For example, manganese dioxide is classified into α, β, γ, η, δ, and ε in terms of crystal structure, and a method of using them to adsorb various heavy metals contained in waste water and the like and make them harmless is known.

  For example, gamma (γ) -type manganese dioxide or powder containing gamma (γ) -type manganese dioxide as a main component is kneaded with an acidic solution containing other metal ions, granulated, and heated by beta ( A method using β) type manganese dioxide as a filter medium for purification is disclosed (see Patent Document 1).

  In addition, a method for removing heavy metal ions is disclosed in which manganese dioxide powder is added to sewage water containing heavy metals and the metal ions are precipitated and separated by stirring in a neutral region (see Patent Document 2).

Furthermore, activated manganese dioxide having an average particle size of 0.1 to 5 μm, which is mainly spherical and has a surface area with numerous protrusions and a specific surface area (BET value) of 50 m ² / g or more is excellent as an adsorbent. Is disclosed (see Patent Document 3).

  A heavy metal immobilizing agent containing α-manganese dioxide containing one or more cations selected from the group consisting of K, Na, H, Ca, Mg and Ba is disclosed (see Patent Document 4). .

  However, the manganese oxides used in these methods are insufficient in terms of performance as treatment agents applicable to water pollution prevention methods and waste cleaning methods, which have been tightened in recent years. Since it was necessary to use, it was not practical.

JP-A-61-120689 JP-A-62-53789 JP 06-92639 A Japanese Patent Application Laid-Open No. 08-267053 JP 2001-79515 A

  The present invention provides a heavy metal treating agent and a detoxifying treatment method that can treat heavy metals contained in incineration fly ash, waste water, etc. to environmental standards or less using a small amount of manganese oxide.

  As a result of intensive studies to solve the above problems, the present inventors have found that Ca and / or a composite oxide of Mg and Mn is very effective for detoxification in the treatment of heavy metal contaminants. Furthermore, it has been found that the processing performance of the composite oxide obtained by partially leaching Ca and / or Mg is further improved, and the present invention has been completed.

  Hereinafter, the present invention will be described in detail.

  The heavy metal treating agent of the present invention is a composite oxide of Ca and / or Mg and Mn in which 0.1 ≦ x ≦ 0.8 in the notation of Ax-Mn composite oxide (where A is Ca and / or Mg). Is included.

  The heavy metal treating agent of the present invention can particularly enhance the heavy metal treating ability by eluting and using a part of Ca and / or Mg. In that case, it is preferable that 0.1 ≦ x <0.3 in the notation of Ax—Mn composite oxide (where A is Ca and / or Mg).

  The composite oxide of the heavy metal treating agent of the present invention preferably has an amorphous layered structure or a layered crystal structure.

In the case of the heavy metal treating agent of the present invention, for example, in the case of A = Ca, x = 0.5, and the chemical formula CaMn ₂ O ₄ , the interplanar spacing is about 2.4 mm (the CaCO ₃ impurity peak at the interplanar spacing about 3.0 mm It has a crystallized layered crystal structure different from the conventionally known CaMn ₂ O ₄ (the standard material of ASTM card is 4.82, 2.69, 2.22 and 2.05 mm). High performance was obtained.

Similarly, when A = Mg and x = 0.5, the surface spacing is 9.3, 7.2, 4.7 and 3.5 mm, and the conventional MgMn ₂ O ₄ (ASTM card standard material surface The distances of 4.9, 3.1, 2.9, 2.8 and 2.5 cm) have a layered crystal structure with different crystallinity, and high performance was obtained.

In the case where A is Ca, when Ca is eluted, it becomes a layered type similar to δ-type manganese dioxide, and in the case of Mg, it becomes a layered type of birnessite (Na ₄ Mn ₁₄ O ₂₇ · 9H ₂ O).

  The Ax-Mn composite oxide used for the heavy metal treating agent of the present invention is obtained by mixing a water-soluble manganese compound and a compound containing Ca and / or Mg, and hydrolytically neutralizing with an aqueous alkali solution such as sodium hydroxide. It can be obtained by oxidizing with an oxidizing agent.

  The manganese compound to be used is not limited, and any compound can be applied as long as it is water-soluble, but it is preferable to use a sulfate from the viewpoint of economy and corrosion.

  As the compound containing Ca, sulfates, nitrates, hydrochlorides, carbonates and hydroxides can be used, but nitrates or hydroxides are preferable from the viewpoint of detoxification treatment performance, and hydroxides are particularly preferable from the viewpoint of economy. preferable.

  As the compound containing Mg, sulfates, nitrates, hydrochlorides, carbonates and hydroxides can be used, but nitrates and sulfates are preferred.

  As the alkaline aqueous solution used for hydrolysis neutralization, those exhibiting strong alkali are preferably used. For example, sodium hydroxide, potassium hydroxide, aqueous ammonia and the like can be used, and sodium hydroxide is particularly preferably used.

  The composition of Ca and / or Mg is preferably synthesized in the range of 0.1 mol to 0.8 mol with respect to Mn, and particularly preferably 0.3 mol to 0.8 mol. When some of them are used after elution, it is preferable to use them in a composition ratio of 0.1 mol to 0.3 mol after elution.

  When the composition ratio of Ca and / or Mg to Mn is less than 0.1 mol from the beginning, the detoxification performance of heavy metals decreases. In addition, when it exceeds 0.8, the processing performance tends to be lowered.

  Ca and / or Mg can be eluted with an oxidizing agent and an acid, but it is preferable to use an inexpensive acid.

  Although an organic acid and an inorganic acid can be applied as the acid, it is preferable to use common mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid, and sulfuric acid is particularly preferable. The acid concentration is not particularly limited.

  The Ax-Mn composite oxide of the present invention can treat heavy metals by adding to and mixing with pollutants containing various heavy metals such as incinerated ash or fly ash, soil, groundwater and wastewater. When adding, it is preferable to add water and knead.

  Heavy metals contained in various types of garbage are concentrated in the waste incineration ash and fly ash. This is particularly noticeable in fly ash and molten fly ash, and many of the molten fly ash contain heavy metals such as lead in a percent order, and thus a detoxification treatment is required. Fly ash and molten fly ash are classified into alkaline fly ash, neutral fly ash, alkaline molten fly ash, neutral molten fly ash, etc., depending on the structure and operation method of the incinerator, and the type of garbage to be incinerated. The types and contents of heavy metals contained are greatly different. The heavy metal treating agent of the present invention can be used for any type of fly ash.

  The heavy metal treating agent of the present invention is also effective for treating soil containing heavy metals, and can be rendered harmless by adding and kneading the heavy metal treating agent to soil containing heavy metals. Also in this case, it is preferable to add water and knead as necessary.

  Furthermore, the heavy metal treating agent of the present invention can be used for treating wastewater containing heavy metals. Detoxification can be achieved by adding a heavy metal treatment agent to wastewater containing heavy metals, or by mixing the heavy metal treatment agent into a column or the like and passing wastewater contaminated with heavy metals. .

  The amount of the heavy metal treating agent of the present invention varies depending on the heavy metal content in the pollutant and cannot be defined unconditionally. However, it is not suitable for solid-type treated products that are difficult to mix, such as incineration ash and fly ash. It is preferable to add 1 to 50 wt%, preferably 0.5 to 30 wt%. In particular, for water-based treated products (drainage, groundwater) that are easily dispersed uniformly, 0.01 to 20 wt%, preferably 0.05 to 10 wt% can be mixed and used.

  Moreover, you may add and use another adjuvant in the range which does not impair the effect of this invention.

  The heavy metals that can be treated with the heavy metal treating agent of the present invention are particularly capable of treating Pb, Cd, Zn, Cu, and Tl. Particularly, the performance to Pb and Cu is high, and high-level treatment is possible with a small amount of addition. It becomes possible.

  The heavy metal treatment agent of the present invention can be highly detoxified by adding a small amount to heavy metal contaminants, and the heavy metal element after treatment is completely fixed, so that extremely stable treatment without re-elution is possible. Become.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1
0.25 mol / L calcium hydroxide (Ca (OH) ₂ ) is dispersed in 0.5 mol / L manganese sulfate (MnSO ₄ .5H ₂ O), and 1.5 mol / L sodium hydroxide is dispersed in the slurry. Solution (NaOH) was added with stirring. Thereafter, the mixture was aged for 3 days while introducing 500 mL / min of air with an air pump. The resulting product was filtered, washed with water and dried.

  When the obtained product was dissolved and the composition analysis was conducted, the Ca / Mn molar ratio was 0.48. Moreover, the XRD measurement result of a product is shown in FIG.

Example 2
The procedure was the same as in Example 1 except that the concentration of Ca (OH) ₂ was 0.375 mol / L.

  When the composition of the obtained product was analyzed, the Ca / Mn molar ratio was 0.67, and the crystallinity was the same as in Example 1.

Example 3
A 2.6 mol / L sodium hydroxide solution (NaOH) was stirred in an aqueous solution in which 0.25 mol / L magnesium sulfate (MgSO ₄ ) was dissolved in 0.5 mol / L manganese sulfate (MnSO ₄ .5H ₂ O). While adding. Thereafter, the mixture was aged for 3 days while introducing 500 mL / min of air with an air pump. The resulting product was filtered, washed with water and dried.

  The obtained product was dissolved and subjected to composition analysis. As a result, the Mg / Mn molar ratio was 0.45. Moreover, the XRD measurement result of a product is shown in FIG.

Example 4
The procedure was the same except that the concentration of Ca (OH) _{2 in} Example 1 was 0.125 mol / L.

  When the composition analysis of the obtained product was performed, the Ca / Mn molar ratio was 0.23.

(Test 1)
Using the products obtained in Example 1, Example 2, Example 3, and Example 4, 500 mL of a solution having an initial Pb concentration of 10 ppm and a pH of 7 was treated for 30 minutes, and the residual Pb concentration in the solution was determined. It was measured.

  The results of Example 1, Example 2 and Example 4 are shown in FIG. 3, and the result of Example 3 is shown in FIG. In Examples 1 to 3, the water quality standard value of 0.01 mg / L was achieved by adding 50 to 80 mg of the treatment agent, but in Example 4, the performance was slightly reduced.

(Test 2)
Using the product obtained in Example 1, a solution having an initial concentration of 10 ppm of Pb, Cu, Cd, Zn and Tl was treated in the same manner as in Test 1.

  The results are shown in Table 1. The residual concentration of any heavy metal element could be reduced to 1/10 or less when 100 mg was added.

(Test 3)
The product of Example 1 was added to neutral fly ash having an elution concentration of Pb of 31 ppm and Cu of 2 ppm, and treated in accordance with the Environmental Agency Notification No. 13 test. The results are shown in Table 2. A treatment of 0.01 mg / L was achieved with 25% addition to fly ash.

Example 5
The product obtained in Example 1 was immersed in 1N sulfuric acid and nitric acid, and the product in Example 3 was immersed in 1N hydrochloric acid for 3 hours.

  When the composition analysis of each powder after acid treatment was performed and the Ca / Mn molar ratio was measured, the sulfuric acid treatment of Example 1 was 0.28 (0.48 → 0.28), and the nitric acid treatment was 0.12 ( 0.48 → 0.12), and the hydrochloric acid treatment of Example 3 was 0.15 (0.45 → 0.15). Moreover, the result of the XRD measurement after the sulfuric acid treatment of Example 1 is shown in FIG. 5, and the XRD measurement result after the hydrochloric acid treatment of Example 3 is shown in FIG. 6, and all showed a layered pattern.

Comparative Example 1
The product obtained in Example 1 was treated by immersion for 3 days using 2N sulfuric acid.
The Ca / Mn molar ratio after acid treatment was 0.06.

(Test 4)
Using the sulfuric acid-treated product of Example 5 and the treated product of Comparative Example 1, 500 mL of a solution having an initial Pb concentration of 10 ppm and pH 7 was treated for 30 minutes, and the residual Pb concentration in the solution was measured.

  The results are shown in FIG. In Example 5, high performance was exhibited with a small amount of addition, but in Comparative Example 1 having an x value of less than 0.1, the performance was low.

XRD measurement diagram of Ca-Mn composite oxide (Example 1) XRD measurement diagram of Mg-Mn composite oxide (Example 3) The graph which shows the processing capability of Pb using Ca-Mn complex oxide (Example 1, Example 2, Example 4) Graph showing the processing ability of Pb using Mg—Mn composite oxide (Example 3) XRD measurement diagram of Ca-Mn composite oxide eluted with Ca (Example 5) Example of XRD measurement of Mg-Mn composite oxide eluted with Mg (Example 5) The graph which shows the processing capability of Pb using the Ca-Mn complex oxide which eluted Ca (Example 5, Comparative example 1)

Claims (6)

A heavy metal treating agent comprising Ax-Mn composite oxide (where A is Ca and / or Mg, 0.1 ≦ x ≦ 0.8). A heavy metal treating agent comprising an Ax-Mn composite oxide (provided that 0.1 ≦ x <0.3) obtained by partially eluting the A component from the heavy metal treating agent according to claim 1. The heavy metal treating agent according to any one of claims 1 to 2, wherein the crystal structure is a layered crystal structure. 4. The heavy metal treating agent according to claim 3, wherein the layered crystal structure is a birnessite structure. The detoxification processing method which adds the heavy metal processing agent in any one of Claim 1 to Claim 4 to any one of the incineration ash or fly ash containing heavy metals, soil, groundwater, and wastewater. The detoxification method according to claim 5, wherein the heavy metal is one or more selected from the group consisting of Pb, Cd, Zn, Cu and Tl.

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