Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2001-06-25
2004-08-31
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S692000, C210S292000, C210S908000
Reexamination Certificate
active
06783686
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention, in general, relates to removing MTBE from water or from an organic solvent and, more particularly, to a method for removing a portion of the MTBE from the water or from the organic solvent by exposure thereof to a molecularly imprinted polymer.
MTBE (Methyl tertiary-butyl ether) is a chemical compound blended into gasoline supplies with the intent of increasing the octane and reducing air emissions. It is a volatile, flammable, colorless liquid at room temperature, and it has an odor that resembles that of turpentine.
It mixes with gasoline and it is soluble in water. The production of MTBE and its domestic use decreases the need for foreign oil.
Health complaints related to MTBE were first reported in Fairbanks, Ak. in November, 1992. Since then health concerns related to the presence of MTBE in the environment has led to its use being either reduced or banned in certain areas. The cost of remediating the environmental effects of MTBE are estimated in the billions of dollars.
In Santa Monica, Calif. the city shut down several drinking water wells with MTBE concentrations of 600 ppb (parts per billion). The EPA limit is 16 ppb.
MTBE contamination of aquifers is due primarily to leaking underground storage tanks. The gasoline and MTBE eventually find their way into the aquifers. Clearly, a method of removing at least some of the MTBE from water prior to its consumption is desirable.
The petroleum producers are also seeking technologies that will prevent gasoline spills or leaking underground storage tanks from spreading MTBE into ground waters.
MTBE is difficult to remove from water or from other types of organic solvents. Water remediation processes take many forms but one typical procedure requires holding tanks, pumps, and adsorption materials. Generally, tons of absorbent are used at any one site.
Examples of such adsorbents include GAC (granulated activated charcoal) and a similar product known as “organoclay”. The primary producers of GAC are Calgon Carbon Corporation in Pittsburgh, Pa. and Norit NV in the Netherlands. Calgon Carbon Corporation estimates that United States customers recently purchased about 20,000 tons of a GAC annually that is specifically designed to adsorb small molecules, such as MTBE. This adsorbent product sells for about $3500.00 per ton presently.
Furthermore, these prior adsorbent technologies require that millions of tons of wood be burnt to produce the necessary charcoal, which by itself incurs a substantial negative environmental effect (i.e., consumption of resources, additional green-house gas emissions).
Furthermore, these prior products are, for the most part, non-recyclable.
In addition, these prior products are non-specific in the components that they adsorb. This, at best decreases their efficacy, and at worst has them removing components that are not intended to be removed from the water.
Obviously, the need for clean water is crucial. All of the community water systems (approx. 54,000) in the United States are protected by Federal, State, and Local regulations. These regulations specify the maximum contamination levels (MCL) for hazardous substances. They also provide the requirement and enforcement procedures for ground water remediation and mechanisms for limiting the concentration of substances entering water systems (i.e., aquifers).
The deleterious effects MTBE are only partially understood at present but they are substantial and clearly, a need to remove MTBE from water or from an organic solvent is desirable.
2. Description of Prior Art
Water remediation processes are, in general, known and they take many forms, one typical procedure requiring the use of holding tanks, pumps, and adsorption materials (i.e., GAC) to which the water is exposed.
While the structural arrangements of the above described methods, at first appearance, may have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior methods.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method for removing an MTBE molecule from water by exposing the water to a molecularly imprinted polymer having an imprint on a surface thereof that corresponds to at least a portion of the shape of an MTBE molecule.
It is also an important object of the invention to provide a method for removing MTBE from water using molecularly imprinted polymers that is economical to use.
Still another object of the invention is to provide a method for removing MTBE from water using molecularly imprinted polymers that is highly selective in removing the MTBE molecule while leaving unaffected other molecules.
Still yet another object of the invention is to provide a method for removing MTBE from water using molecularly imprinted polymers that does not expose the water to substantial amounts of organic solvents or other undesirable or toxic chemicals.
Yet another important object of the invention is to provide a method for removing MTBE from water using molecularly imprinted polymers that is safe to use.
Still yet another further important object of the invention is to provide a method for removing MTBE from water using molecularly imprinted polymers that is effective for commercial water remediation use.
Still one further object of the invention is to provide a reusable method for removing MTBE from water using molecularly imprinted polymers.
Briefly, a process in accordance with the principles of the present invention includes the formation of molecularly imprinted polymers (MIPS) that contain an imprint of the MTBE molecule. The formation of the MTBE imprinted molecular polymers are formed by exposing a polymer, in liquid form, to a concentration of MTBE molecules, and then hardening the polymer by heating or irradiating it. The polymer is then ground to form beads which have a plurality of exposed binding sites for MTBE. The beads are then washed using a preferred solution or solvent to remove the MTBE molecules from the surface of the beads to provide cavities which function as exposed binding sites that correspond to a molecular imprint (i.e., the shape) of at least a portion of the MTBE molecule. A solution (i.e., water) that is contaminated with MTBE is exposed to the washed beads. The MTBE molecules find receptor sites to which they then adhere. The aqueous solution is allowed to mix with the beads resulting in a purified water solution. Adherence of the MTBE molecule to each of the binding sites occurs through a variety of well-known methods, such as electrostatic bonding, hydrogen bonding, and other forms of non-covalent bonding as well as other bonding approaches including sacrificial spacer, covalent bonding, and copper binding site approaches. The use of other known and emergent approaches to forming the molecularly imprinted polymers to increase efficacy in solution are also anticipated.
REFERENCES:
patent: 5641539 (1997-06-01), Afeyan et al.
patent: 5814514 (1998-09-01), Steffan et al.
patent: 2003/0153001 (2003-08-01), Soane et al.
patent: 2003/0200796 (2003-10-01), Pawliszyn
Leone Anna Madeleine
Rinne, Jr. Risto Aadolf
Barry Chester T.
Rinne, Jr. Risto A.
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