Patent Application
20070253891
In describing the embodiments of the invention, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.
As used herein, the term “solution” shall mean a mixture formed by a process by which a solid, liquid, or gaseous substance is mixed with a liquid, whether that liquid is a droplet, aerosol, vapor, or mist. Also, as used herein, the term “moist environment” shall mean that the environment in which the reaction occurs contains moisture, ranging from a slightly humid environment to a fully wet environment, such as an aqueous solution. Also, as used herein, the term “precursor” shall be used to mean any solution and/or combination of solutions used to generate the halogen dioxide, chlorine dioxide. Also, as used herein, the term “disposable” shall be used to mean that the ion exchange media is used once and discarded.
For purposes of the present invention, counter ions can be an ion of any element. However, in the present invention it is preferable to choose from among strong counter ions. Examples of strong counter ions for the present invention include hydrogen, calcium, magnesium, manganese, iron, potassium and lithium for cations and hypochlorite, chlorite, chlorate, chloride, sulfate, phosphate, and nitrate for anions.
Ion exchange materials which may be used in the present invention, such as inorganic and organic resins, membranes, powders, gels, and solutions, are well known to those skilled in the art, and the type or types of ion exchange materials used is not intended to limit the invention. Examples of ion exchange materials which can be used in carrying out the present invention include, but are not limited to, weak acid cation resins and powders, strong acid cation resins and powders, weak base anion resins and powders, strong base anion resins and powders, sulfonated polystyrene solutions, zeolites, cation and anion selective membranes. Selection of a particular ion exchange material is considered within the skill of those knowledgeable in the field. Further, the choice of a particular configuration, whether in a singular, layered or mixed form, for the ion exchange materials and/or the combination of ion exchange materials and/or inert materials is considered within the skill of those knowledgeable in the field.
It is also within the skill of one knowledgeable in the art to add one or more additives to the ion exchange material. Such additives may include, but are not limited to, inert insoluble materials, such as the base material for ion exchange resin before it is converted into its cationic or anionic form, which may also be provided in a mixed or layered form within the ion exchange material. The additives can also be soluble materials which, when dissolved, may or may not contribute counter ions to the process.
By definition, catalysts work by changing the activation energy for a reaction, i.e. the minimum energy needed for the reaction to occur. This is accomplished by providing a new mechanism or reaction path through which the reaction can proceed. When the new reaction path has a lower activation energy, the reaction rate is increased, and the reaction is said to be catalyzed.
There are many catalysts that can be used within the scope of the present invention. These include, but are not limited to platinum, palladium, manganese dioxide, carbon, silver, and ion exchange material. Further, it is well known that depositing catalysts on various substrates, such as zeolites or porous non-ionic substrates, aids in the catalysis by increasing surface area. Such catalysts and catalyst substrates are commercially available, and it is within the scope of those skilled in the art to choose an appropriate catalytic material and/or substrate to catalyze the reaction of an inactive precursor to the active halogen oxide, chlorine dioxide.
In one preferred embodiment of the present invention, a cation exchange resin in the hydrogen form is layered with a mixture of: 1) an anion exchange resin in the chlorite form and 2) an insoluble catalyst, such that the singular cation resin forms the first layer, and the mixture of anion resin and insoluble catalyst forms the second layer. A solution containing sodium sulfate (Na2SO4) is then passed over the ion exchange resins such that the sodium ion of the sodium sulfate is exchanged with the hydrogen ion on the cation exchange resin, and the sulfate ion of the sodium sulfate is exchanged with the chlorite ion on the anion exchange resin, in the presence of an insoluble catalyst, to form the active halogen dioxide, chlorine dioxide, within the ion exchange resin bed. The equation describing this reaction follows:
5Na2SO4+10RH+10RClO2->catalyst ->
8ClO2+10RNa+5R2SO4->+4H2O+2HCl (5).
A further property of this embodiment is that any cationic contaminant, either from the precursor solution or formed as a byproduct of the reaction, is removed with the cation exchange resin, and in the same manner, any anionic contaminant, either from the precursor solution, or formed as a byproduct of the reaction, is removed with the anion exchange resin of the present invention.
In a further embodiment of the present invention, a cation exchange resin in the -hydrogen form is layered with anion exchange resin in the chlorite form. A NaCl solution containing sodium ion and chloride ion, where the chloride ion is acting as the soluble catalyst, is passed over the ion exchange resins such that the sodium ion from the NaCl solution is exchanged with the hydrogen ion on the cation exchange resin, and the soluble catalyst chloride ion from the NaCl solution, is exchanged with the chlorite ion on the anion exchange resin to form the active halogen dioxide, chlorine dioxide, within the ion exchange resin bed. The equation describing this reaction follows:
5NaCl+5RH+5RClO2->catalyst ->
4ClO2+5RNa+5RCl+2H2O+->->HCl (6).
In a still further embodiment, activated halogen dioxide, chlorine dioxide, is made by providing a cation exchange resin in the H+ form and also providing an anion exchange resin with a mixture of anions attached thereto. The mixture of anions attached to the anion exchange resin can be achieved, for example, by starting with an anion exchange resin already in the hydroxyl (OH−) form and dividing the resin into two parts. One part is treated to exchange the chlorite ion for some of the hydroxyl ion, and the second part is treated to exchange the hypochlorite ion for some of the hydroxyl ion. The hydroxyl ion part of the anion exchange resin is retained to help ensure stability of the chlorite and hypochlorite ions through its (OH−) effect on the pH of the resin. Other methods for achieving an anion exchange resin with mixed anions will be readily understood by those skilled in the art of ion exchange.
The chemistry of chlorination of chlorite to form chlorine dioxide follows:
2 HClO2+HOCl>2ClO2+HCl+H2O (7).
This chemistry is well known and used frequently to make chlorine dioxide. However, an additional reaction occurs when ion exchange resins are used, and it follows:
RH+ROH>H2O (8).
This “water reaction” does not interfere with the reaction to form the chlorine dioxide, and the water produced is not considered to be a contaminant in the reaction. It is merely a side reaction that takes place when H+ ion and OH− ion are exchanged off of the resin.
The cation and anion exchange resins can each be placed either in the same or different columns or tubes or other containers or platforms that can be operated singularly or connectively attached to each other by tubing that will allow a liquid solution to flow from one column or container to the next, and each column or container also having at least an inlet and outlet tubing.
The separate columns contemplated in the present invention would then be placed in sequence such that the cation exchange resin is contacted by the precursor solution first, followed by the solution contacting the anion exchange resin mixture or mixtures. For example, a known concentration of a solution containing Na2SO4 is fed into the inlet tube connected to the first resin column having the cation exchange resin. The Na2SO4 solution would flow through into the cation exchange resin where the Na+ ions would exchange with the H+ ions on the cation resin to form H2SO4, and the cation resin will exhaust to the Na+ form. Further, any cationic contaminant, either from the precursor solution or formed as a byproduct of the reaction, is removed with the cation exchange resin.
The decationized solution will pass into and contact the second column having the anion exchange resin mixture, where the SO4− ions from the original Na2SO4 solution will exchange with the OCl−, ClO2−, and OH− ions on the anion exchange resin, forming the active halogen dioxide, chlorine dioxide, within the ion exchange material. Further, any anionic contaminant, either from the precursor solution or formed as a byproduct of the reaction, is removed with the anion exchange resin.
Additionally, the anion exchange resin of the above example can also be mixed or layered with an insoluble catalyst in order to enhance the formation of chlorine dioxide. Furthermore, it is also contemplated that the precursor solution of the above example may also contain a soluble catalyst, such as chloride ion (Cl−).
In another preferred embodiment of the present invention, a cation exchange resin is placed in the hydrogen form. The stable halogen oxide, sodium hypochlorite, and the stable halogen dioxide, sodium chlorite, are passed over the cation exchange resin such that the sodium ion of both precursor solutions exchanges with the hydrogen ion on the resin and then reacts to form the active halogen dioxide, chlorine dioxide. This reaction is described by equation (7) shown previously.
One skilled in the art of ion exchange would understand that different types of resins could be substituted in the above examples. For example, the cation resin used in the above examples can also be substituted for a weak acid cation resin, and the anion resin can be substituted for a weak base anion resin. Also, higher or lower cross-linked resins may be used as the application requires.
The potential sources for the NaCl solution in the previous examples can be varied, and include, for example, making the solution as needed, or from a brine tank of a water softening system. Water softeners employing ion exchange columns contain resin beads. The resin beads have a surface that attracts sodium, calcium and magnesium ions. The resin beads preferably bind calcium and magnesium ions. The beads are initially in the sodium ion state and the sodium ions will exchange off the resin with calcium and magnesium ions, thus softening the water that flows through the ions exchange column. The column may be cleaned of calcium and magnesium ions and the beads resupplied with sodium ions, by exposing the beads to a very high concentration of sodium ions, thus causing the exchange of the sodium ions in the brine with the hardness ions on the cation resin of the softener. The conventional source of sodium ions in these water softener systems is common salt i.e. sodium chloride. A brine tank containing salt crystals or pellets is partially flooded with water. The water dissolves the salt pellets and becomes saturated with salt. The saturated brine solution is then periodically run through the ion exchange column to regenerate the resin beads.
In the present invention, the reject effluent stream from a reverse osmosis system can be used as the source of acceptable counter ions. This source of counter ions would be especially useful if the active chlorine dioxide solution were being used to disinfect the reverse osmosis membranes to prevent, reduce, or eliminate biofouling. Reverse osmosis units have been used for a number of decades to purify water for home, municipal and industrial uses. Examples of purification systems using reverse osmosis units to provide quantities of potable water suitable for home or other relatively limited uses are shown in the following patents of Donald T. Bray: U.S. Pat. Nos. 3,568,843; 3,794,172; 3,794,173 and 3,939,074. Such self-contained systems were generally designed to provide potable water on demand by being essentially permanently connected to a municipal water supply line pressure. They created a ready reservoir of purified or potable water which would be available to be dispensed to a user, either by gravity flow or by flow driven by the expansion of air compressed behind a bladder within a confined tank or the like.
The particular configuration of the reverse osmosis system used does not matter. Basically, all reverse osmosis systems operate in a manner such that the unpurified water feed is introduced into the system at a pressure greater than the osmotic pressure of the unpurified water involved. This causes the water to permeate through a semi-permeable membrane by reverse osmosis. The purified water is removed from the system via a purified product outlet. As the water permeates through semi-permeable membrane, substantially all of the dissolved salts in such water are prevented from passing through the membrane, in accordance with known reverse osmosis principles. Such salts are maintained on the upstream side of the membrane. There is constantly removed from the upstream side of the membrane a reject effluent of the unpurified water, such reject effluent having the dissolved salt concentration thereof increased by the salts which are prevented from passing through the membrane. Such reject effluent is normally discharged either down the drain, or back to the source.
In addition, the ions in tap water may be used as a source of counter ions for the present invention.
The ion exchange materials of the present invention may be recharged or regenerated in a variety of ways known in the art. Complete regeneration of the ion exchange resins described herein is not necessary for the invention to work. In fact, it may be desirable in certain circumstances to leave the resin in a partially regenerated form to increase the stability of the precursor ion on the resin.
As used herein, the term “partially regenerated” shall refer to an ion exchange material wherein some of the ion exchange sites are intentionally placed in more than one form by conventional regeneration methods. To accomplish a partial regeneration, the ion exchange material should first be completely regenerated or placed in a state such that virtually all of the ion exchange sites are in a single form. Then a solution containing less than a stoichiometric quantity of a second ion is passed over the ion exchange material such that the solution partially regenerates the ion exchange material. This procedure can be repeated such that the ion exchange material is in multiple forms.
For example, it is contemplated in accordance with the present invention that one would leave an anion resin partially in the hydroxyl form to ensure a high pH and further stabilize a reactant such as hypochlorite ion or chlorite ion. It is also important to note that the ion exchange materials need not be regenerated at all. If the application warrants, the ion exchange materials can be placed in a disposable container and disposed of when they have no more useful life for the application.
The activated halogen dioxide, chlorine dioxide of the present invention can be used for many purposes. In a preferred embodiment of the present invention, the activated chlorine dioxide would be used to disinfect small volume applications. Such applications include, but are not limited to, ice machines, residential water softeners, residential water wells, hard surfaces, medical devices, and residential reverse osmosis systems. Use in larger commercial applications is also contemplated for the present invention; however, the economic advantages of the process become limited for such applications as they increase in scale. However, in a case such as large volume reverse osmosis systems, the amount of chlorine dioxide needed to disinfect the reverse osmosis membranes is small in comparison to the amount of water produced by the reverse osmosis system as demonstrated by Adams. Therefore, there are larger volume applications for which this process is applicable.
Small volume applications, as described previously, are good applications for the use of disposable ion exchange media. Such media would be placed in a container and used only until the media had exhausted, and the quality of the halogen dioxide, chlorine dioxide being produced by the media was inadequate for the application. At that time, the ion exchange media would be discarded. In applications such as residential water softeners, the ion exchange media may be discarded once per month. In other applications, such as the disinfection of medical devices, the ion exchange media may only be used for a few minutes and then discarded. If the application warranted, the entire container containing the ion exchange media would be discarded. However, if it were not viable to discard the container, it could be emptied of the exhausted ion exchange media and then refilled with ion exchange media in the stable reactant form.
It can be seen by the examples of these embodiments that the active halogen dioxide, chlorine dioxide can be formed by numerous configurations of precursor solutions and ion exchange media. Once the present invention is understood, it is within the scope of one skilled in the art to choose which configuration best suits a particular application.
Containers in the form of plastic tubes used for carrying out the tests set forth in Examples 1-5 in the present application are shown in
A first 30 ml plastic test tube 100 as shown in
In example 1, the first ion exchange resin layer 133 was comprised of a commercially available strong cation exchange resin, Resintech CG-8 (ResinTech, Inc., West Berlin, N.J.), in the hydrogen form (H+). The second layer 134 was comprised of a strongly basic organic anion resin, ResinTech SBG1, in essentially complete chlorite form (ClO2−) and mixed with a suitable insoluble catalyst such as platinum on zeolite. Such suitable catalysts may or may not be deposited onto the surface of a suitable substrate, such as zeolites or Macrolite® Media (Kinetico Inc. Newbury, Ohio). Examples of suitable insoluble catalysts can be platinum on zeolite, on Macrolite® media, or on carbon. However, other suitable catalysts are known to those schooled in the art. A continuous stream of 1000 mg/l of Na2SO4 solution was passed upwardly through the test tube 132. The resultant concentration of ClO2 was 492 mg/l with a pH of 2.4.
Example 1 illustrates that ion exchange media can be effectively used to contribute reactants such that the activated halogen dioxide, chlorine dioxide, is formed from the exchange of the counter ions in the precursor solution. In this specific example, an insoluble catalyst is mixed with the ion exchange media so as to lower the activation energy of the formation of the active halogen dioxide, chlorine dioxide, and thus, increase the yield.
A first 30 ml plastic test tube 100 as shown in
Example 2 illustrates that ion exchange media can be effectively used to contribute reactants such that the activated halogen dioxide, chlorine dioxide, is formed from the exchange of the counter ions in the precursor solution. In this specific example, a soluble catalyst is used as counter ion in the precursor solution so as to lower the activation energy of the formation of the active halogen dioxide, chlorine dioxide, and thus, increase the yield.
A first 30 ml plastic test tube 100 as shown in
In Example 3, the first test tube 115 was filled with a commercially available strong cation exchange resin 112, Resintech CG-8, in the hydrogen form (H+). The second test tube 116 was filled with a strongly basic organic anion resin 113, Resintech SBG1, and was partially in the ClO2− form and partially in the OCl− form. The remaining anionic sites were in the hydroxyl (OH−) form to help ensure the stability of the chlorite and hypochlorite ions. A continuous stream of the Na2SO4 solution at a concentration of 1000 mg/l was passed upwardly through the first test tube 115 and into and through the second tube 116. A sample of solution was taken from the sample port 122 and had a pH of 1.7. The pH of the resultant solution from the outlet of the second tube taken at sample port 123 was 2.5, and the concentration of ClO2 was 802 mg/l.
Example 3 illustrates that ion exchange media can be effectively used to contribute more than one reactant from a mixture of ion exchange material such that the activated halogen dioxide, chlorine dioxide, is formed from the exchange of the counter ions in the precursor solution. Hence, many variations eof mixing, layering, or separating the ion exchange media in the stable reactant form can be used within the present invention.
A first 30 ml plastic test tube 100 as shown in
The first tube 115 was filled with a commercially available weak cation exchange resin 112, Resintech WACMP in the hydrogen form (H+). The second tube 116 was filled with a weakly basic organic anion resin 113, Resintech WBMP, which was partially in the ClO2− form and partially in the OCl− form. The remaining anionic sites were in the hydroxyl (OH−) form to help ensure stability of the chlorite and hypochlorite ions. A continuous stream of the Na2SO4 solution at a concentration of 1000 mg/l was passed upwardly through the first test tube 115 and into and through the second tube 116. The pH of the solution exiting the cation tube outlet was 3.7 as taken at sample port 122. The pH of the resultant solution was 4.1 as taken at sample port 123, and the concentration of ClO2 was 720 mg/l.
Example 4 demonstrates that various types of ion exchange media, such as weak acid cation and weak base anion, can be used in the context of the present invention, and the selection of such ion exchange media is within the skill of one knowledgeable in the art.
A first 30 ml plastic test tube 100 as shown in
In Example 5, the first test tube 152 was filled with a commercially available strong cation exchange resin 153 sold under the name Resintech CG-8 and is in the hydrogen form (H+). The second test tube 158 was filled with an immobile catalyst of platinum on zeolite 154. Also in this example, the concentration of sodium hypochlorite 149 was varied to determine the effect of the oxidizer in the reaction to form chlorine dioxide, but the inlet concentration of ClO2−139 was held constant at 902 mg/l. A continuous stream of the precursor solutions was passed upwardly through the first test tube 152 and into and through the second tube 158. Samples of solution were taken after both the first and the second tube's top outlet ends through sample ports 159 and 160 and analyzed for the activated halogen dioxide, chlorine dioxide. The results are shown in Table 1 below.
Example 5 demonstrates that two or more precursor solutions, themselves containing stable reactants, can be used in the context of the present invention. Thus, multiple precursor solutions can also be utilized. Also shown in this example is how controllable the chemistry is within the present invention. As the sodium hypochlorite feed solution rate was varied, the concentration of the resultant chlorine dioxide approached theoretical conversion as shown in equation 7. It is also well known that when using the chemistry described in equation 7 chlorate formation is expected as the ratio of hypochlorous to chlorite ion increases, because chlorine dioxide is destroyed by the hypochlorous acid via the following reaction:
HOCl+2ClO2+H2O>2HClO3−+HCl (9)
The formation of chlorate is further illustrated by the decrease in concentration of chlorine dioxide after the catalyst column when the stoichiometric percentage of OCl− exceeds 66%. As the activation energy of the reaction is lowered, chlorine dioxide is decomposed to chlorate by the catalyst by a similar mechanism as it does when exposed to UV light.
Having described the invention, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.
This application claims priority to Provisional U.S. Patent Application Ser. No. 60/795,598, filed Apr. 28, 2006, and incorporated by reference as if set forth herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60795598 | Apr 2006 | US |
