Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2001-06-27
2003-07-29
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C588S252000, C588S256000, C588S257000
Reexamination Certificate
active
06599357
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a detoxifying agent that is used when noxious wastes are treated with cement to solidify them. More particularly, the present invention relates to a detoxifying agent for use in disposal of noxious wastes, capable of providing cement-solidified materials having high strength, substantially free from exudation of toxic substances such as heavy metals, PCBs and dioxins.
2. Background Art
How to finally dispose of noxious wastes such as residues from the incineration of refuse, component (especially, molten slag and heavy metals) from the incineration of hazardous industrial wastes, polluted soil, river sludge, sewage sludge, waste glass and waste tires is now a serious social problem. These noxious wastes can discharge a variety of toxic substances, and, of these toxic substances, heavy metals, PCBs, dioxins, etc., in particular, are known to exert serious effects on ecosystem. For this reason, there has been strongly demanded a technique of finally disposing of noxious wastes without discharging the above toxic substances.
To meet the above demand, there have been proposed various methods for making noxious wastes innoxious, and subjecting them to recycling. One of these methods proposed is as follows: noxious waste containing the above-described toxic substances is mixed with cement, and the mixture is solidified to enclose the toxic substances in the cement; the cement-solidified material thus obtained is then subjected to recycling. However, the toxic substances tend to inhibit the agglomeration of cements, so that they retard the hardening of cement, and impart decreased strength to the cement-solidified material. Another problem is that the toxic substances enclosed in cement can ooze out of the cement-solidified material.
To solve these problems, the following method has been proposed as disclosed in Japanese Patent Laid-Open Publication No. 24276/1998: a solution containing, as main components, tannin and wood vinegar is diluted with water, and this aqueous solution is added as a detoxifying agent to noxious waste containing such toxic substances as heavy metals and PCBs to detoxify them. It is considered that, since tannin and wood vinegar exert a powerful chelating action on elemental compounds such as heavy metals, the detoxification of heavy metals and the like can successfully be attained by this method. However, although cement-solidified materials obtained by this method show strength to some degree, a further improvement in the strength has been expected.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a detoxifying agent that is used when noxious wastes are treated with cement to solidify them, and that can provide cement-solidified materials having high strength, substantially free from exudation of toxic substances such as heavy metals, PCBS and dioxins.
The present invention provides a detoxifying agent for use in disposal of noxious wastes that is conducted by solidifying them with cement, consisting essentially of an aqueous solution which comprises as main components (a) small-sized metal cations whose 6-coordination ion radii are less than 100 pm, (b) medium-sized metal cations whose 6-coordination ionic radii are between 100 pm and 140 pm, and (c) large-sized metal cations whose 6-coordination ionic radii are in excess of 140 pm. The present invention also provides cement-solidified materials that can be obtained through the use of the above-described detoxifying agent.
DETAILED DESCRIPTION OF THE INVENTION
The detoxifying agent according to the present invention, for use in disposal of noxious wastes that is conducted by solidifying them with cement will be described hereinafter.
Detoxifying Agent
In the present invention, the “detoxifying agent” is an additive that is used when noxious wastes are treated with cement to solidify them. The purposes of this agent are to detoxify toxic substances contained in noxious wastes, thereby enclosing the detoxified substances in cement without discharging them, and to prevent toxic substances from exerting their effect of inhibiting the setting of cement, thereby obtaining cement-solidified materials having increased strength.
In the present invention, the “treatment with cement for solidification” is conducted for the purpose of disposing of noxious wastes. This treatment is useful in enclosing, in cement, such toxic substances as heavy metals, PCBs and dioxins contained in noxious wastes, thereby obtaining recyclable cement-solidified materials.
The “noxious wastes” that can be disposed of by the present invention include a variety of wastes that can discharge toxic substances such as heavy metals, dioxins and PCBs, and there is no particular limitation on them. Examples of such noxious wastes include residues from the incineration of refuse, component (especially, molten slag and heavy metals) from the incineration of hazardous industrial wastes, polluted soil, river sludge, and sewage sludge. In addition, waste glass, tires, plastics and CD, and the like are also included in the noxious wastes.
As mentioned previously, even if the above-described noxious wastes are treated with cement and solidified, toxic substances enclosed in the cement can ooze out of the cement-solidified materials. Moreover, since the toxic substances have the effect of inhibiting the setting of cement, the hardening of cement is retarded, and the resulting cement-solidified materials are to have decreased strength.
We found that it is possible to make the degree of exudation of toxic substances extremely low, and, at the same time, to obtain cement-solidified materials having increased strength if a detoxifying agent having a specific composition is used when noxious wastes are treated with cement to solidify them.
A detoxifying agent according to the present invention consists essentially of an aqueous solution comprising as main components (a) small-sized metal cations whose 6-coordination ionic radii are less than 100 pm, (b) medium-sized metal cations whose 6-coordination ionic radii are from 100 to 140 pm, and (c) large-sized metal cations whose 6-coordination ionic radii are more than 140 pm.
The “6-coordination ionic radii” herein mean ionic radii where the coordination number is 6, and refer to the generally known values that were determined by Shannon and Prewitt on the basis of observed values, and improved by Shannon. These ion radii (CR: crystal ionic radii) are enumerated on pages 725-726 of “
Kaitei Yon
-
han, Kagaku Binran, Kiso
-
hen II
(Handbook of Chemistry, Basic Section II, Fourth Revised Edition)”, edited by The Chemical Society of Japan, published by Maruzen Co., Ltd., Japan.
The 6-coordination ionic radii of major ions useful for the present invention are as follows:
(a) as small-sized metal cations: Li
+
: 90 pm, Mg
2+
: 86 pm, Mn
2+
: 81 pm, 97 pm, Fe
3+
: 69 pm, 79 pm, Ni
2+
: 83 pm;
(b) as medium-sized metal cations: Na
+
: 116 pm, Ca
2+
: 114 pm, Sr
2+
: 132 pm; and
(c) as large-sized metal cations: Ba
2+
: 149 pm, K
+
: 152 pm, Rb
+
: 166 pm.
In addition, examples of halide anions include Cl
−
and Br
−
, and their ionic radii are 167 pm and 182 pm, respectively. Regarding the above-described ionic radii of Mn
2+
and Fe
3+
, the former value shows the radius of the ion that is in the low spin state, and the latter one shows the radius of the ion that is in the high spin state.
It is considered that, since metal cations selected from each of the three groups of ions that are different in the range of ionic radii are incorporated into the detoxifying agent of the present invention, the detoxifying agent can exert various detoxifying actions, such as a coagulating effect, on a wide variety of toxic substances. In the solidification of noxious wastes with cement, various toxic substances are considered to exist, and even if only a few of these toxic substances have the effect of inhibiting the setting of cement, it is unav
Isobe Toshiyuki
Sasada Kunio
Sugihara Shuichi
Ladas & Parry
Marcantoni Paul
With Gala Co., Ltd.
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