Liquid purification or separation – Processes – Ion exchange or selective sorption
Reexamination Certificate
2001-08-10
2003-07-29
Cintins, Ivars (Department: 1724)
Liquid purification or separation
Processes
Ion exchange or selective sorption
C210S679000, C210S688000
Reexamination Certificate
active
06599427
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
As the quality of municipally supplied water has declined the consumer has maintained a desire for “good tasting” water. The public has also become aware of the negative health effects associated with chlorination, used to disinfect tap water. Consumers seeking an alternative to tap water for better quality and taste have driven commercial “Bottled Water” sales to more than three billion dollars a year. A variety of filtration products have been introduced to compete with Bottled Water in providing these benefits, plus convenience and economy. The most popular of the filtration products has been the variety known as pour through carafes, or pitchers. While popular, the products presently marketed possess several drawbacks, that have kept the filters (treatment elements are all covered by the descriptor “filter(s)”) from achieving greater favor. Major inadequacies have included the time element required to operate a pour through carafe. These devices must be cycled through filling a water chamber, generally comprising about half the volume of the overall container, and waiting until the water has trickled through the filtering element into a second, lower compartment occupying the second half of the container. The time required for filtration is typically 15-30 minutes for two to three liters of water. In addition, as only one-half of the container volume is usable, the containers are typically larger than fit conveniently within the refrigerator. Further, the quantity of treated water available is frequently less than needed, yet the time required to replenish (filter) the water is too long for the filter to be of practical value (i.e. fill a coffee pot etc.) if water had previously been withdrawn and not immediately refilled.
The drawbacks of filtration pitchers and carafes have been overcome by the invention herein disclosed, without diminishing the performance or economy. In addition, greater utility and convenience is achieved by the subject invention.
The product and technology disclosed comprises or consists of a novel new media and a water treatment product specifically designed to utilize and take advantages of the characteristics inherent with the media further described in this disclosure. The product described achieves high levels of water treatment efficiently, fills rapidly, and permits the total volume of the container to be filled and utilized. Clean, fresh tasting water may be delivered within sixty seconds of filling. Typically within five minutes after filling, water is delivered with =90% of lead, chlorine, and certain other contaminants removed. This is accomplished with the development of a new treatment concept combining static treatment with a water feed reservoir. To operate at optimum efficiency it is desirable to use a configuration design that basically controls the length of time the water is in contact with the treatment media. While there are several ways to accomplish this the configurations disclosed use a water in-feed orifice, or tube, which under the available head pressure allows the amount of water entering the treatment unit, or filter, to equal the void volume contained therein. By directing the in-feed water to the point furthest from the out feed, or pouring port, maximum treatment is achieved within the residence time limit designed into the product.
To achieve static treatment, activated carbon, as well as other media, are affixed to randomly oriented fibers, or other highly porous and compressible substrates. Examples of static treatment media are disclosed in my prior European Patent Application Publication number 0 402 661, the disclosure of which is incorporated herein by this reference. In accordance with the invention, the resulting matrix is compressed to form a treatment zone whereby the contaminant molecules contained within the treatment zone are within 1.5 millimeters, or less of a carbon, or other media element. Such a configuration provides for the movement of contaminant molecules to an active site on the media within a practical amount of time, without requiring convective flow. Diffusivities of common water contaminants are on the order of 5×10
−6
cm
2
/s, allowing treatment of the water within a time span of seconds to minutes, even without water flowing through the filter. Diffusion and equilibrium within a body of fluid are well known phenomena, which form the basics of the mechanism by which static treatment functions. Static treatment requires the body of water being filtered to be placed within the treatment media and left in contact for a specific period of time. The time element for contact is generally from 30 seconds to 10 minutes depending upon the contamination and removal percentage required. As an indicator of the validity of the concept, one may model the diffusion of a well-mixed solution poured into a static treatment device as a plane source of contaminant between two planes of adsorbent. If the diffusivity is assumed to remain constant, the amount of contaminant which has traveled the distance to the adsorbent planes can be readily calculated. While an actual estimation of the degree of removal with time depends on the concentration profiles employed, these calculations illustrate the general nature of solute migration within the low-density medium.
The equation for diffusion in one dimension when the diffusivity (D) is constant is written
∂
C
∂
t
=
D
∂
2
C
∂
x
2
Differentiation of this diffusion equation results in a solution for the concentration profile
C
=
A
t
2
exp
(
-
x
2
/
4
Dt
)
where A is an arbitrary constant. This solution is symmetrical with respect to x=0 and approaches zero as x approaches positive or negative infinity for time>0. For a reference cylinder of infinite length and unit cross sectional area, the total amount of substance diffusing (M) is given by
M
∫
-
∞
∞
C
ⅆ
x
If we rewrite the equation for the concentration distribution given above so that
x
2
/4
Dt=&xgr;
2
, dx=
2(
Dt
)
0.5
d&xgr;
we see that the amount of substance diffusing remains constant and equal to the amount originally deposited on the plane at t=0 and x=0.
M
=
2
AD
0.5
∫
-
∞
∞
exp
(
-
ξ
2
)
ⅆ
ξ
=
2
A
(
π
D
)
0.5
Substituting for A in the equation for the concentration distribution yields
C
=
M
2
(
π
Dt
)
0.5
exp
(
-
x
2
/
4
Dt
)
or alternatively
C
M
=
1
2
(
π
Dt
)
0.5
exp
(
-
x
2
/
4
Dt
)
The following table describes the relationship between the percentage of starting material which has diffused to the adsorptive sites (C/M), the distance between adjacent adsorptive particles (assuming the plane of initial contamination was equidistant between them), and the time required for this diffusion to take place.
Distance between particles
Time Required
Percentage Diffused
(Cm)
(seconds)
0.90
0.05
8.0
0.10
40.4
0.20
223.4
0.30
664.3
0.75
0.05
7.6
0.10
37.8
0.20
202.4
0.30
578.4
0.50
0.05
6.8
0.10
33.1
0.20
168.5
0.30
455.5
Generally speaking, with static treatment, no water flow takes place during the treatment process. In contrast dynamic filtration, which is used in all current consumer products, has the water flowing through the filtration media. This provides a shortened time in contact unless the water is trickled through slowly, thus requiring an inordinate period of time to deliver water in a non-pressurized system, or an impracticably large filter.
The rate of contaminant removal in porous materials is controlled by two principle mechanisms: mass transfer resistances and the kinetics of adsorption/desorption. In filtration using activated carbon (and most other adsorbents), the kinetics of adsorption/desorption are very rapid compared to the rate of mass
Larsen Gerald
Mierau Brad
Nohren John E.
Cintins Ivars
Innova Pure Water Inc.
Nixon & Vanderhye P.C.
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