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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to devices, materials and processes for the
purification of water, and more particularly to a material and process for
making the material and to a device for removing heavy metals from water
utilizing chelating agents bound to filter bed materials.
2. Description of the Prior Art
Increased attention is being paid to the quality of our drinking water.
Studies continue to reveal frightening facts about the decline of water
quality, the increase of water-borne diseases, the exponential increase in
the amount of toxic chemicals in our water tables and an ever-growing
awareness that the chemicals employed in water treatment such as Chlorine
and Alum under certain conditions can do more harm than good.
Communities are, at last, addressing the task of keeping our common water
supply safe through the construction of sewage treatment facilities, water
purification plants, the levying of heavier fines against toxic waste
dumpers, etc., but these require years of legislative action and major
engineering construction programs. However, of the three types of
contaminants--bacterial and viral, toxic chemical, and heavy toxic
metals--only the first two are addressed in present home purification
methods employing filtration.
There is a need to remove toxic heavy metals from our drinking water
because of the severe nature of the health hazards. Of particular concern
is lead salts, which can leach from the pipes and solder joints of our
home plumbing. Therefore, even though the municipal water supply may be
free of these toxic materials, we may still be at risk in our homes.
Generally, three approaches can be taken by people at home. They can trust
their water supply, purchase water from outside vendors, and purify their
tap water at home. More and more people are leaving the first option and
choosing one of the others.
With regard to home water purification, there are three systems currently
available:
(1) Carbon Filters; these are designed to remove organics like chlorinated
hydrocarbons, pesticides, etc., and sediment if they contain cellulosic or
paper prefilters. They make water look, smell and taste better, but do not
remove significant amounts of bacteria or hazardous toxic metals. U.S.
Pat. Nos. 4,107,047, Turetsky, Aug. 15, 1978; 4,107,046, Corder, Aug. 15,
1978; and 3,561,602, Moltor, Feb. 9, 1971, are illustrative of the use of
carbon filters and impregnated carbon filters of the prior art.
(2) Reverse Osmosis Filtration; this process removes most larger molecules
and takes care of from less than 50% to more than 99% of contaminants,
depending upon the particular system. However, R.O. Filters are generally
expensive and can break down when saturated with pollutants.
(3) Distillers; steam distillation is a very effective method for reducing
nearly all contamination but it is an expensive unit, requires
considerable power with resulting operational costs involved, and can
produce limited amounts of water per day.
Two further methods exist for purifying water that have not become
generally available for drinking water purification. These methods are the
use of ion exchange resins (also known as water softeners) and the use of
chelating agents. The use of ion exchange resins in water purification has
been described in such U.S. Pat. Nos. as 4,182,676, Casolo, Jan. 8, 1980,
and 4,100,065, Etzel, July 11, 1978. In utilizing ion exchange resins,
heavy metal ions are removed from the water by replacing such ions with
lighter-weight ions such as sodium or potassium.
The use of chelating agents for removal of heavy metal ions from water is
described in U.S. Pat. No. 4,500,494, Sher, Feb. 19, 1985 in which
chelating agents are encapsulated in microcapsules to remove heavy metal
ions. U.S. Pat. No. 4,080,171, Sano, Mar. 21, 1978 describes a method for
the analysis of heavy metal ions in water utilizing chelating compounds on
filter paper to trap the heavy metal ions together with an analysis of the
filter paper to identify the heavy metal ions. U.S. Pat. No. 4,238,328,
Bowes, Dec. 9, 1980 describes the use of some types of chelating materials
in water purification. U.S. Pat. No. 4,220,726, Warshawsky, Sept. 2, 1980
utilizes some types of metal extraction chemicals in association with
certain resins for the recovery of heavy metal ions from liquid. None of
these prior art patents, however, appear to teach the application of
chelating agents to the purification of drinking water in the materials,
process and device described in the instant application.
Chelating agents have been found useful in a number of other applications
where metal ions must be extracted, deactivated or removed from fluids,
i.e., the use in blood banking to remove calcium from the plasma to
convert it to serum, or as a means of wiping up spills of radioactive
metallic ions in laboratories. Chelates have also been employed in
medicine, in Vivo, to remove toxic metals from over-exposed individuals as
in lead or mercury poisoning. Chelates enhance excretion of the metal from
the body by reducing the body burden of the tissues and passing the
chelate/metal complex harmlessly through the kidney and bladder, or they
decrease gastrointestinal absorption by the body by forming
non-absorbable, insoluble chelates.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a device, material and
process for the removal of heavy metal ions from water.
It is another object of the present invention to provide a device,
material, and process for the removal of heavy metal ions from drinking
water for industrial or municipal water supplies or at the point of use
within the home.
It is a further object of the present invention to provide materials which
include chelating agents for the purification of drinking water.
It is yet another object of the present invention to provide a process for
treating filter bed material with chelating agents such that the treated
bed material will remove a broad range of toxic chemicals from drinking
water.
It is yet a further object of the present invention to provide a device
which utilizes a bed material that is treated with chelating agents to
remove a broad range of toxic impurities from drinking water.
The present invention involves a material which utilizes chelating agents
to enhance the ability of a bed material treated therewith to remove heavy
metal ions from water. The bed material is preferably granulated activated
charcoal, such as is currently used in charcoal filters that are attached
proximate the point of use in the home. The chelating agent, which may
include a combination of several individual chelating compounds, is
formulated in a solution that is used to treat the bed materials. The
treated bed materials are utilized in a filtration device, whereby the
enhanced purification properties of the treated bed material results in a
more thoroughly purified drinking water.
It is an advantage of the present invention that it provides a device,
material and process for the removal of heavy metal ions from water.
It is another advantage of the present invention that it provides a device,
material and process for the removal of heavy metal ions from drinking
water for industrial or municipal water supplies or at the point of use
within the home.
It is a further advantage of the present invention that it provides
materials which include chelating agents for the purification of drinking
water.
It is yet another advantage of the present invention to provide a process
for treating charcoal with chelating agents such that the treated charcoal
will remove a broad range of toxic chemicals from drinking water.
It is yet a further advantage of the present invention that it provides a
device which utilizes a bed material that is treated with chelating agents
to remove a broad range of toxic impurities from drinking water.
The foregoing and other objects, features, and advantages of the present
invention will be apparent from the following detailed description of the
preferred embodiments which make reference to the several figures of the
drawing.
IN THE DRAWING
FIG. 1 is a side elevational view which represents a filter cartridge of
the present invention within a water tap filter container;
FIG. 2 is a side elevational view which represents an embodiment of a
filter cartridge of the present invention; and
FIG. 3 is a side elevational view of another embodiment of a filter
cartridge of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention includes a device, material and method of
manufacturing said material for removing toxic agents from water by
filtration. The invention incorporates chelating agents within filtering
bed material, whereby the chelating agents efficiently complex with toxic
metals and bind them to the bed. In the preferred embodiment, the bed
material consists of granulated charcoal, which is a well-known material
that is utilized in municipal filtration as well as filtration cartridges
proximate the outlet tap for home filtration of drinking water.
As indicated hereinabove, a material of the preferred embodiment is a
filter bed material into which a chelating chemical has been adsorbed.
Chelating chemicals like EDTA (ethylene diamine tetra acetic acid),
penicillamine (1 1 Dimethylcystine), BAL (2,3,3, dimercaptopropanol) and
DMS (dimercaptosuccinic acid) each have characteristic binding capacities
for specific metals. BAL, for example, is particularly effective for
binding mercury, arsenic, bismuth and antimony. DMS is particularly good
at binding lead and mercury. They also have different degrees of toxicity.
Thus, a blend of the appropriate chelates that are sufficiently bound to
the bed material will remove the heavy metals of concern in drinking
water, yet be non-toxic to the drinker.
______________________________________
Heavy Metal
EDTA PENICILLAMINE DMS BAL
______________________________________
Lead X X X
Mercury X X X
Arsenic X
Zinc X
Copper X
Chromium X
Antimony X
Bismuth X
______________________________________
From the above table, it is seen that various combinations of EDTA,
Penicillamine, DMS and BAL will sequester most of the toxic metals of
interest.
The chelates can be adsorbed directly onto and into the bed material or
combined with a polymer which binds onto the bed material.
In the preferred embodiment a polymer is used with chelates in a solution
which binds to the bed material. The preferred polymer is a polymer mix of
copolymers of acrylics, such as:
3 parts of methyl methacrylate
3 parts of butyl methacrylate
1 part styrene
The above copolymer mix is formulated in a stock which is 50% polymer resin
in 50% water. The preferred formulation for the chelating polymer which is
used to treat the bed material is a solution of 0.1% polymer stock (1 ml
stock per liter of distilled water) plus 0.05% calcium disodium EDTA (0.5
gms per liter) plus 0.05% DMS (0.5 gms per liter) plus 0.05% BAL (0.5 gms
per liter). However, the formulation material of the present invention may
contain one, two, three, or all four of the EDTA, Penicillamine, BAL,
and/or DMS chelates identified hereinabove. Alternatively, chelates can be
added to the bed material subsequent to the adsorption of non-chelated
polymer.
While the above formulation describes the preferred concentration of
chelating compounds, the Applicant's invention is not to be limited
thereto. Chelate concentrations in the ranges of 0.01% to 0.75% EDTA,
0.01% to 0.75% DMS, 0.01% to 0.75% Penacillamine and 0.01% to 0.75% BAL
are suitable ranges within which the instant invention produces acceptable
heavy metal ion removal.
The preferred process for treating a bed material such as granulated
activated charcoal with chelating agents utilizes a polymer stock to which
the chelating agents have been added prior to adsorption on the bed
material. The formulation described above is utilized in the treatment
process of the preferred embodiment. This treatment process is as follows:
Using activated charcoal granules of 15-40 mesh obtained from an industry
source, such as Supreme Supply Company of Inglewood, CA.
Soak the bed material in the polymer plus chelate formulation solution for
60 minutes with agitation.
Remove the bed material and dry thoroughly.
Soak the dried bed material with 0.1% glatial acetic acid (1.0 ml per liter
of distilled water) for 60 minutes with agitation.
Drain the bed material and dry well before use in a cartridge, column or
bed.
Upon first use, the bed material should be washed with several flushes of
deionized distilled water.
The dry filtration bed material of the present invention is thus a bed
material containing the chelating chemicals EDTA, Penicillamine, BAL or
DMS or a combination thereof. However, it is to be noted that the
chelating chemicals may be adsorbed directly onto the bed material in the
concentrations described above without the use of the polymer. Of the two
treated bed materials, the material which contains the polymer binding
agent is preferred.
The quantity of chelting agent that is bound to the dried filter bed
material will vary depending upon such factors as the amount and type of
chelating chemical(s) used in the formulation for treating the bed
material, the amount and type of polymer used (if any) in the formulation
for treating the bed material and the particular bed material that is
used. By way of example, when the preferred formulation of polymer plus
chelates described hereinabove is utilized to treat granulated activated
charcoal, it was found that 1 gram of treated dry granulated activated
charcoal would contain approximately 10 to 30 mg of chelating chemicals.
FIG. 1 depicts a side elevational view which represents a cross-sectional
view of a water filtration cartridge 10 within a container 12 adapted for
attachment to a water faucet 22. The cartridge 10 is held within a
thin-walled, substantially cylindrical jacket 12 which has an upper
portion 14 and a lower portion 16 that are demountably engaged, such as by
utilizing a threaded engagement 18.
The upper portion 14 is threadably engaged 20 to the faucet 22 to form an
inlet port 24. It is therefore to be appreciated that water will flow in
the direction of the arrows, through the faucet 22, into inlet port 24,
through the filtration cartridge 10, and out the outlet port 26 of the
filtration device 12. Such filtration devices, as generally described
hereinabove, typically utilize granulated charcoal in a replaceable
filtration cartridge 10, and are well-known in the prior art. The
foregoing generalized description of a filtration cartridge system is
provided for background explanatory purposes only, and the present
invention is not to be limited to this type of device. The material of the
instant invention is generally suitable to remove heavy metals wherever
filtration bed materials are utilized.
FIG. 2 depicts a side elevational view of a generalized cartridge 100 of
the present invention. The cartridge 100 consists of an upper section 102
and a lower section 104. Upper section 102 includes a filter bed material
that has been treated with chelating agents according to the process of
the present invention described hereinabove. The lower portion 104 of the
filter cartridge 100 contains untreated filter bed material. While the
preferred embodiment of FIG. 2 is depicted with the treated bed material
102 in the upper portion of the cartridge 100, it is to be understood that
the instant invention also comprises the reversed placement of the treated
and untreated bed material, such that the treated bed material portion 102
is the lower portion of the cartridge 100 and the untreated bed material
104 comprises the upper portion of the cartridge 100. The relative
proportions of treated and untreated bed material will vary according to
the toxicity of the water to be purified as well as the concentrations of
chelating agents utilized in the process to manufacture the bed material,
as described hereinabove.
FIG. 3 depicts a side elevational view of another preferred embodiment of a
filter cartridge 200 of the present invention. The cartridge 200 contains
a uniform filtration bed material that has been treated with a chelating
agent according to the process of the present invention. The bed material
in the cartridge 200 may consist of entirely treated bed material or a
uniform mixture of treated and untreated bed material.
In the preferred embodiments of the present invention, as have been
described with reference to FIGS. 2 and 3 hereinabove, the preferred bed
material may be any solid particulate material, porous or nonporous, to
which chelates, or polymers which can bind chelates, can be adsorbed to.
Porous materials like activated charcoal present much more surface area
and are a preferred filter bed material. Thus, in the preferred
embodiments the cartridges of FIGS. 2 and 3 contain treated activated
charcoal and untreated activated charcoal, it also being understood that
the filtration cartridge 200 may consist of entirely treated activated
charcoal.
The following examples indicate the efficacy of the various embodiments
described hereinabove.
EXAMPLE I
A prior art cartridge type activated carbon filter, designed for use on
kitchen faucets, was disassembled. It contained 59 grams of carbon
granules. Two 15 gram portions of the granulated carbon were used for this
set of tests. One portion was packed into a 1/2 inch diameter by 2 foot
long tube. This was referred to as filter #1. The other portion was
treated with a sodium salt of EDTA, dried, acidified with a minimal amount
of hydrochloric acid, rinsed and dried again. This material, when packed
as before, was referred to as filter #2. This filter material did not use
a polymer for chelate binding.
Three test solutions were filtered through each filter and the filtrates
collected for lead concentration measurements by atomic absorption (AA).
The first 20 ml of each filtrate was discarded so as to reduce the
possibility of cross sample contamination. The results have been presented
below.
______________________________________
Concentration (ppb)
Test Sample Type Filter #1
Filter #2
______________________________________
0.2 ppm Lead (200 ppb)
10. ND*
2.0 ppm Lead (2000 ppb)
30. ND
20.0 ppm Lead (20,000 ppb)
160. 20.
______________________________________
*ND means Not Detectable (less than 10. ppb).
The results indicate that the EDTA filter, filter #2, reduced the
concentration of lead by a factor of approximately 1000. to 1.
EXAMPLE II
Three filtration columns were prepared for lead removal from water, using
the packing materials as follows.
A. 7.0 grams of untreated activated charcoal.
B. 7.0 grams of activated charcoal treated with 0.1% of calcium disodium
EDTA solution, dried and then washed with dilute acetic acid (0.01%), then
evaporated to dryness.
C. 3.5 grams of untreated activated charcoal plus 3.5 grams of activated
charcoal treated with 10 ml. of 0.01% polymer dispersion with 0.1% calcium
disodium EDTA in water sample, and then evaporated to dryness and washed
with acetic acid solution as in B above and dried.
Each of the three columns were packed in a 30 cm. tube with a diameter of
approximately 1.2 cm. A standard 20 ppm lead solution was passed through
each column and the output from each column was analyzed for Na, Ca and Pb
using an atomic absorption spectrophotometer.
The proper operational conditions were established for each element and the
spectrophotometer was standardized with proven standards. The analytical
results were as follows.
______________________________________
Sample
Lead (ppb) Sodium (ppm)
Calcium (ppm)
______________________________________
A 50. 3.6 10.5
B 10. 16.0 58.
C ND* 5.8 18.3
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*ND means not detectable
After treating the column packings with dilute acetic acid several times (4
to 5 times of the original volume), the amount of both sodium and calcium
were reduced to below 1.0 ppm level.
EXAMPLE III
To determine potential toxicity of the EDTA, by leaching of the EDTA from
the treated charcoal, the water that was passed through columns B and C in
Example II was tested for EDTA.
Those results were as follows:
The EDTA output was measured titrimetrically with a standard magnesium
chloride sample using an eriochrome black T indicator.
These results are as follows:
______________________________________
Column Type
First 20 ml. Effluent
Last 20 ml. Effluent
______________________________________
Column B 11.84 ppm EDTA 1.50 ppm EDTA
Column C 7.40 0.70
______________________________________
Since the LD/50 for calcium disodium EDTA (the chelate employed) is 10
millimoles per kg, this is 2.9 gm/kg. A 30 kg child (66 pounds) would need
to consume and retain 90 gm of EDTA to be poisoned. This would be the
equivalent of drinking 30,000 gallons of water at one sitting with 0.7 ppm
EDTA present in the water.
EXAMPLE IV
To determine whether the adsorption of EDTA onto the charcoal had any
effect upon the ability of the charcoal to filter organic molecules from
the water, the filter columns A and B in Example II were tested for
chloroform removal from water as follows:
A 20. ppm chloroform solution in DI water was passed through columns A and
B, and was tested for its residual concentration by Gas Chromatography
(GC), using an electron capture detector (ECD). A GC packed column of 1%
SP-1000 on Supelcoport was used as in EPA method 601. Results are as
follows.
______________________________________
Input solution 20.0 ppm Chloroform
Column A output
2.0 ppm Chloroform
Column B output
1.8 ppm Chloroform
______________________________________
It has therefore been determined that the adsorption of EDTA onto the
charcoal had no deleterious effect upon the ability of the charcoal to
filter organic molecules from the water.
While the invention has been particularly shown and described with
reference to certain preferred embodiments, it will be understood by those
skilled in the art that various alterations and modifications in form and
detail may be made therein. Accordingly, it is intended that the following
claims cover all such alterations and modifications as may fall within the
true spirit and scope of the invention.
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