Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
2000-04-14
2002-07-09
Griffin, Steven P. (Department: 1754)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C422S028000, C422S037000
Reexamination Certificate
active
06417423
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is broadly concerned with compositions and methods for sorbing and/or destroying dangerous substances such as chemical and biological warfare agents. The methods of the invention are carried out by simply contacting the target substance with particulate metal oxide compositions. These compositions can be unmodified, or alternately, the particulate metal oxides can be coated with a second metal oxide, have reactive atoms or mixtures of reactive atoms stabilized on their surfaces, or have species adsorbed on their surfaces. In another embodiment, the particulate metal oxides (unmodified or modified) can be pressed to form pellets which possess the same destructive abilities as the metal oxides in powder form. Methods in accordance with the invention require the use of minimal liquids, thus resulting in very little effluent. Furthermore, the particulate metal oxide compositions utilized in the methods of the invention are not harmful to equipment or to humans and can easily be used directly at the site of contamination.
2. Description of the Prior Art
The threat of biological and chemical warfare has grown considerably in recent times. Numerous countries are capable of developing deadly biological and chemical weapons. Some potent biological agents include the following: bacteria such as
Bacillus anthracis
(anthrax) and
Yersinia pestis
(plague); viruses such as variola virus (small pox) and flaviviruses (hemorrhagic fevers); and toxins such as botulinum toxins and saxitoxin. Some potent chemical agents include: blister or vesicant agents such as mustard agents; nerve agents such as methylphosphonothiolate (VX); lung damaging or choking agents such as phosgene (CG); cyanogen agents such as hydrogen cyanide; incapacitants such as 3-quinuclidinyl benzilate; riot control agents such as CS (malonitrile); smokes such as zinc chloride smokes; and some herbicides such as 2,4-D (2,4-dichlorophenoxy acetic acid).
All of the above agents, as well as numerous other biological and chemical agents, pose a significant risk to private citizens as well as to military personnel. For example, vesicant agents bum and blister the skin or any other part of the body they contact, including eyes, mucus membranes, lungs, and skin. Nerve agents are particularly toxic and are generally colorless, odorless, and readily absorbable through the lungs, eyes, skin, and intestinal track. Even a brief exposure can be fatal and death can occur in as quickly as 1 to 10 minutes. Biological agents such as anthrax are easily disseminated as aerosols and thus have the ability to inflict a large number of casualties over a wide area with minimal logistical requirements. Many biological agents are highly stable and thus can persist for long periods of time in soil or food.
There are currently two general types of decontamination methods for biological agents: chemical disinfection and physical decontamination. Chemical disinfectants, such as hypochlorite solutions, are useful but are corrosive to most metals and fabrics, as well as to human skin. Physical decontamination, on the other hand, usually involves dry heat up to 160° C. for 2 hours, or steam or super-heated steam for about 20 minutes. Sometimes UV light can be used effectively, but it is difficult to develop and standardize for practical use.
These methods have many drawbacks. The use of chemical disinfectants can be harmful to personnel and equipment due to the corrosiveness and toxicity of the disinfectants. Furthermore, chemical disinfectants result in large quantities of effluent which must be disposed of in an environmentally sound manner. Physical decontamination methods are lacking because they require large expenditures of energy. Both chemical and physical methods are difficult to use directly at the contaminated site due to bulky equipment and/or large quantities of liquids which must be transported to the site. Finally, while a particular decontamination or disinfection method may be suitable for biological decontamination, it is generally not effective against chemical agents. There is a need for decontamination compounds which are effective against a wide variety of both chemical and biological agents, have low energy requirements, are easily transportable, do not harm skin or equipment, and employ small amounts of liquids with minimal or no effluent.
SUMMARY OF THE INVENTION
The present invention overcomes these problems and provides compositions and methods for sorbing (e.g., adsorption and chemisorption) and destroying biological and chemical agents. To this end, the invention contemplates the use of finely divided nanoscale metal oxide adsorbents. These adsorbents can be used in an unmodified form or can be pelletized, coated with a second metal oxide, or have reactive atoms stabilized on their surfaces. These decontamination reactions can be carried out over a wide range of temperatures and can be conducted at the contaminated site. Furthermore, these adsorbents are not harmful to equipment or to humans.
In more detail, the nanoscale adsorbents used in the methods of the invention are formed from metal oxides selected from the group consisting of MgO, CaO, TiO
2
, ZrO
2
, FeO, V
2
O
3
, V
2
O
5
, Mn
2
O
3
, Fe
2
O
3
, NiO, CuO, Al
2
O
3
, ZnO, and mixtures thereof. While conventionally prepared powders can be used in the methods of the invention, the preferred powders are prepared by aerogel techniques from Utamapanya et al.,
Chem. Mater.,
3:175-181 (1991), incorporated by reference herein. The adsorbents should have an average crystallite size of up to about 20 nm, preferably from about 3-8 nm, and more preferably 4 nm, and exhibit a Brunauer-Emmett-Teller (BET) multi-point surface area of at least about 15 m
2
/g, preferably at least about 200 m
2
/g, and more preferably about 400 m
2
/g. In terms of pore radius, the preferred adsorbents should have an average pore radius of at least about 45 Å, more preferably from about 50-100 Å, and most preferably from about 60-75 Å.
These nanoscale adsorbents can be used alone and in their powder form, or they can be modified. For example, the finely divided particles of the metal oxides can have at least a portion of their surfaces coated with a quantity of a second metal oxide different than the first metal oxide and selected from oxides of metals selected from the group consisting of Ti, V, Fe, Cu, Ni, Co, Mn, Zn and mixtures thereof In preferred forms, the coated metal oxide particles comprise a first metal oxide selected from the group consisting of MgO and CaO, whereas the second metal oxide is preferably Fe
2
O
3
. For most efficient uses, the particles of the first metal oxide should have the average crystallite sizes and multi-point surface areas set forth above. As is conventional in the art, the term “particles” is used herein interchangeably with the term “crystallite.” The second metal oxide should be in the form of an extremely thin layer or coating applied onto the surface of the first metal oxide, thus giving an average overall size for the composite of up to about 21 nm, more preferably from about 5-11 nm, and most preferably about 5 nm. Generally, the first metal oxide should be present in substantial excess relative to the second metal oxide. Thus, the first metal oxide comprises from about 90-99% by weight of the total composite material, and more preferably from about 95-99% by weight. Correspondingly, the second metal oxide should comprise from 1-10% by weight of the total composite, and more preferably from about 1-5% by weight. At least 75% of the surface area of the first metal oxide particles should be covered with the second oxide, and more preferably from about 90-100% of this surface area should be covered.
The coated metal oxide particles or crystallites of this embodiment are preferably fabricated by first forming the very finely divided first particulate material using known aerogel techniques. Thereafter, the second material is applied onto the surface of the first metal o
Klabunde John S.
Klabunde Kenneth J.
Koper Olga
Griffin Steven P.
Hovey & Williams, LLP
Nanoscale Materials, Inc.
Vanoy Timothy C.
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