Hydrotalcite like substance, process for producing the same and method of immobilizing hazardous substance

• US 9,216,310 B2
• Filed: 10/11/2013
• Issued: 12/22/2015
• Est. Priority Date: 03/16/2004
• Status: Active Grant

• Current Assignee: JDC Corporation
• Original Assignee: JDC Corporation, Waseda University (Waseda University Educational Association)
• Inventors: Yamazaki, Atsushi, Takahashi, Mai
• Primary Examiner(s): Zimmer, Anthony J
• Application Number:
  US14/052,400
• Publication Number:
  US 20140039236A1
• Time in Patent Office: 802 Days
• Field of Search: 423/600, 423/593.1, 423/594.16, 252/184
• US Class Current: 1/1
• CPC Class Codes: A62D 3/33 by chemical fixing the harmful substance, e.g. by chelation or complexation
• CPC Class Codes: A62D 3/36 Detoxification by using acid or alkaline reagents
• CPC Class Codes: B01J 20/041 Oxides or hydroxides
• CPC Class Codes: B01J 20/08 comprising aluminium oxide or hydroxide; comprising bauxite
• CPC Class Codes: B01J 20/12 Naturally occurring clays or bleaching earth
• CPC Class Codes: B01J 20/165 Natural alumino-silicates, e.g. zeolites
• CPC Class Codes: B01J 20/18 Synthetic zeolitic molecular sieves
• CPC Class Codes: B01J 2220/42 Materials comprising a mixture of inorganic materials materials coated or impregnated on a carrier B01J20/32
• CPC Class Codes: B01J 41/10 Inorganic material
• CPC Class Codes: B09B 3/25 using mineral binders or matrix
• CPC Class Codes: B09C 1/08 chemically
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01F 7/785 Hydrotalcite
• CPC Class Codes: C01P 2002/22 layered hydroxide-type, e.g. of the hydrotalcite-type
• CPC Class Codes: C01P 2002/60 Compounds characterised by their crystallite size
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/78 by stacking-plane distances or stacking sequences
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer

Abstract

A hydrotalcite-like substance capable of ion exchange with target anions, being of small crystal size that exhibits large basal spacing and excels at anion exchange performance; a process for producing the same; and a method of immobilizing hazardous substances. The hydrotalcite-like substance is produced by mixing an acidic solution containing aluminum and magnesium ions with an alkaline solution containing an alkali to synthesize a hydrotalcite-like substance, followed by, without ageing, water removal or neutralization. The molar ratio of aluminum ions and magnesium ions is preferably in the range of 1:5 to 1:2. Hazardous substances can be immobilized by pulverizing the hydrotalcite-like substance after synthesis and adding the powder to a subject, or adding a hydrotalcite-like substance in slurry form to a subject, or carrying out addition so as to cause the synthesis directly at the position of the subject. Furthermore, anion adsorption can be performed by a filter containing the hydrotalcite-like substance.

Claims

1. A process for immobilizing a hazardous substance, which comprises the step of adding a hydrotalcite-like substance to an object to be immobilized in a manner that the synthesis of the hydrotalcite-like substance occurs directly on the object to be immobilized through the mixing of an acidic solution containing aluminum ions and magnesium ions with an alkaline solution containing alkali, and then subjecting the hydrotalcite-like substance to water removal process or neutralization process;

wherein the hydrotalcite-like substance is represented by a general chemical formula;

Mg²⁺_1-xAl³⁺_X(OH)₂(Aⁿ⁻

)_x/n·

mH₂O, said Aⁿ⁻

being anion with charge −

n, and

wherein zeolite and/or bentonite are/is used together with said hydrotalcite-like substance.

2. The process for immobilizing a hazardous substance, according to claim 1, wherein said acidic solution is added to the object to be immobilized after adding alkali to the object.

3. The process for immobilizing a hazardous substance according to claim 1, wherein a molar ratio of said aluminum ions to said magnesium ions is in a range of from 1:

5 to 1;

2.

4. The process for immobilizing a hazardous substance according to claim 1, wherein said acidic solution contains aluminum compound and/or magnesium compound that are/is not dissolved therein.

5. The process for immobilizing a hazardous substance according to claim 1, wherein at least one selected from a group consisting of alumina, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminum nitrate, bauxite, residue left after producing alumina from bauxite and aluminum sludge is used as an aluminum source of said aluminum ions.

6. The process for immobilizing a hazardous substance according to claim 1, wherein at least one selected from a group consisting of brucite, magnesium chloride, magnesium hydroxide, magnesite and calcined magnesite is used as a magnesium source of said magnesium ions.

7. The process for immobilizing a hazardous substance according to claim 1, wherein at least one selected from a group consisting of sodium hydroxide, calcium hydroxide, lime and solidification material for cement is used as said alkali.

8. The process for immobilizing a hazardous substance according to claim 1, wherein neither said acidic solution nor said alkaline solution contains carbonate ions.

9. The process for immobilizing a hazardous substance according to claim 1, wherein the object to be immobilized is a contaminated soil polluted with a hazardous substance, wastes containing contaminated water or a hazardous substance, or a leachate thereof, and said hydrotalcite-like substance is added to the contaminated soil or wastes together with zeolite and/or bentonite.

10. The process for immobilizing a hazardous substance according to claim 1, wherein said contaminated soil is covered with a filter layer of zeolite and/or bentonite, and another filter layer of said hydrotalcite-like substance.

11. A process for immobilizing a hazardous substance according to claim 1, comprising the step of adding to said object to be immobilized an acidic solution containing aluminum ions and magnesium ions, while mixing with alkali.