U.S. patent application number 11/467649 was filed with the patent office on 2008-02-28 for media for the removal of heavy metals and volatile byproducts from drinking water.
This patent application is currently assigned to BASF CATALYSTS LLC. Invention is credited to Colin Beswick, Thomas Shaniuk.
Application Number | 20080047902 11/467649 |
Document ID | / |
Family ID | 39112373 |
Filed Date | 2008-02-28 |
United States Patent
Application |
20080047902 |
Kind Code |
A1 |
Beswick; Colin ; et
al. |
February 28, 2008 |
MEDIA FOR THE REMOVAL OF HEAVY METALS AND VOLATILE BYPRODUCTS FROM
DRINKING WATER
Abstract
Water purification media contain an activated carbon having at
least one of specific a particle size, surface area, and porosity;
and a microcrystalline and/or amorphous titanosilicate at least
partially coating the activated carbon. Methods of making the media
of microcrystalline and/or amorphous titanosilicate coated
activated carbon involve contacting activated carbon with
titanosilicate precursors. Methods of purifying water involve
contacting water containing both heavy metals and volatile
byproducts with the media.
Inventors: |
Beswick; Colin; (Middlesex,
NJ) ; Shaniuk; Thomas; (Strongsville, OH) |
Correspondence
Address: |
AMIN, TUROCY & CALVIN, LLP
1900 EAST 9TH STREET, NATIONAL CITY CENTER, 24TH FLOOR,
CLEVELAND
OH
44114
US
|
Assignee: |
BASF CATALYSTS LLC
Iselin
NJ
|
Family ID: |
39112373 |
Appl. No.: |
11/467649 |
Filed: |
August 28, 2006 |
Current U.S.
Class: |
210/688 ;
210/681; 210/683; 210/694 |
Current CPC
Class: |
C02F 2101/20 20130101;
C02F 1/281 20130101; C02F 1/288 20130101; C02F 2303/26 20130101;
C02F 1/283 20130101; C02F 2101/322 20130101 |
Class at
Publication: |
210/688 ;
210/694; 210/681; 210/683 |
International
Class: |
C02F 1/28 20060101
C02F001/28 |
Claims
1. A water purification composition comprising: an activated carbon
having at least one of a particle size distribution from about 50
.mu.m to about 500 .mu.m, a surface area of about 300 m.sup.2/g or
more and about 1,600 m.sup.2/g or less, and a porosity of at least
about 0.25 cc/g in pores having a diameter of at least about 10
.ANG. and at most about 500 .ANG.; and a microcrystalline and/or
amorphous titanosilicate at least partially coating the activated
carbon.
2. The water purification composition of claim 1, wherein the
activated carbon has at least two of a particle size distribution
from about 60 .mu.m to about 300 .mu.m, a surface area of about 500
m.sup.2/g or more and about 1,400 m.sup.2/g or less, and a porosity
of at least about 0.4 cc/g in pores having a diameter of at least
about 10 .ANG. and at most about 500 .ANG..
3. The water purification composition of claim 1 comprising from
about 0.1% to about 15% by weight of microcrystalline and/or
amorphous titanosilicate coated on the activated carbon.
4. The water purification composition of claim 1, wherein the
activated carbon has less than 50% microporosity and from 50% to
about 100% mesoporosity and/or macroporosity.
5. The water purification composition of claim 1, with the proviso
that the water purification composition does not comprise more than
about 5% by weight of crystalline titanosilicate.
6. The water purification composition of claim 1, further
comprising at least one of ferric hydroxide, alumina, magnesia,
bauxite, and zeolites.
7. The water purification composition of claim 1 comprising from
about 0.01 g/in.sup.3 to about 1 g/in.sup.3 of microcrystalline
and/or amorphous titanosilicate on the activated carbon.
8. The water purification composition of claim 1 consisting
essentially of the activated carbon and the microcrystalline and/or
amorphous titanosilicate at least partially coating the activated
carbon.
9. An end of tap filter comprising the water purification
composition of claim 1.
10. A fixed-bed column comprising the water purification
composition of claim 1.
11. A method of making a water purification composition comprising:
contacting activated carbon, a titanium compound, a silicon
compound, and optionally a hydroxide compound to form a mixture,
the activated carbon having at least one of a particle size
distribution from about 50 .mu.m to about 500 .mu.m, a surface area
of about 300 m.sup.2/g or more and about 1,600 m.sup.2/g or less,
and a porosity of at least about 0.25 cc/g in pores having a
diameter of at least about 10 .ANG. and at most about 500 .ANG.;
and drying the mixture to provide a microcrystalline and/or
amorphous titanosilicate coated activated carbon capable of
purifying water.
12. The method of claim 11, wherein the activated carbon, the
titanium compound, and the silicon compound are contacted under a
pH from about 6 to about 12.
13. The method of claim 11, wherein the mixture is dried at a
temperature from about 30.degree. C. to about 150.degree. C. for a
time from about 1 minute to about 50 hours.
14. The method of claim 11, wherein at least one of the activated
carbon, the titanium compound, and the silicon compound are in
water when contacted.
15. A method of purifying water comprising: contacting water
comprising a first amount of a heavy metal and a first amount of a
volatile byproduct with a composition comprising an activated
carbon having at least one of a particle size distribution from
about 50 .mu.m to about 500 .mu.m, a surface area of about 300
m.sup.2/g or more and about 1,600 m.sup.2/g or less, and a porosity
of at least about 0.25 cc/g in pores having a diameter of at least
about 10 .ANG. and at most about 500 .ANG.; and a microcrystalline
and/or amorphous titanosilicate at least partially coating the
activated carbon; and recovering water comprising a second amount
of the heavy metal and a second amount of the volatile byproduct,
wherein the second amount of the heavy metal is less than the first
amount of the heavy metal and the second amount of the volatile
byproduct is less than the first amount of the volatile
byproduct.
16. The method of claim 15, wherein the water recovered has a lead
content of about 15 ppb or less and a total trihalomethane content
of about 100 ppb or less.
17. The method of claim 15, wherein the composition is in granule
form, the average granule size by weight is from about 60 .mu.m to
about 300 .mu.m.
18. The method of claim 15, wherein the heavy metal comprises at
least one selected from the group consisting of lead, cadmium,
zinc, copper, chromium, arsenic, cobalt, and mercury; and the
volatile byproduct comprises at least one selected from the group
consisting of trihalomethane, bromate, chlorite, haloacetic acids,
chloramines, benzene, halobenzenes, acrylamide,
carbontetrachloride, bromodichloromethane, chlorodibromomethane,
dichloroethylene, dichloromethane, halopropanes, dioxin,
alkylbenzenes, PCBs, toluene, xylenes, vinyl chloride, and
styrene.
19. The method of claim 15, wherein the composition is comprised in
an end of tap filter.
20. The method of claim 19, wherein the composition removes at
least about 75% of the heavy metal and at least about 75% of the
volatile byproduct in 800 gallons of water passed therethrough.
Description
TECHNICAL FIELD
[0001] The invention generally relates to media that can remove
heavy metals and volatile byproducts from aqueous systems, as well
as methods of making and using the media including methods of
purifying drinking water.
BACKGROUND
[0002] Even low levels of heavy metals (for example arsenic, lead,
cadmium, mercury, etc.) in drinking water are considered
detrimental to a person's health, and in the case of infants, are
believed to impede intellectual development. For example, in babies
and children, exposure to lead in drinking water above the action
level can result in delays in physical and mental development,
along with slight deficits in attention span and learning
abilities. In adults, lead exposure via drinking water can cause
increases in blood pressure, as well as the development of kidney
problems.
[0003] Recognizing these hazards, the Environmental Protection
Agency (EPA) has established limits on the presence of heavy metals
in drinking water. For example, no more than 15 parts per billion
(15 ppb) of lead may be present in public water systems. In
addition, industrial water streams must contain less than 0.5 ppm
of heavy metals before the water can be discharged.
[0004] In addition to reducing the heavy metals to acceptable EPA
levels, it is desirable to improve the taste, odor and smell of
drinking water by removing chlorine, ionic metals, organic
molecules and colloidal particles. Ion exchangers, both organic and
inorganic, including crystalline molecular sieve zeolites, are
known to remove certain metals from aqueous systems such as
drinking water. Activated carbon is also used in water purification
or remediation processes. Activated carbon improves taste, odor and
smell by adsorbing ionic metals, organic molecules and colloidal
particles and also removes chlorine.
[0005] In addition to esthetic effects, elevated levels of certain
contaminants, for example halogenated organic compounds, are known
to be able to detrimentally impact health in ways such as
increasing the risk of certain cancers.
[0006] The purification of drinking water is often accomplished at
its point of use, such as under-the-counter, on-the-counter, whole
house systems, end-of-tap, or free standing gravity flow carafe
type devices. For industrial/commercial applications, packed bed
systems are typically used.
[0007] There is an ongoing effort to develop improved products
which meet or exceed EPA and other regulatory body requirements for
heavy metals and halogentated byproducts removal as well as
improved taste, color and odor, and have flow rates which are
commercially acceptable. In circumstances where the filter size is
limited and/or high flow rates are required, there is particular
need for effective drinking water purification techniques.
SUMMARY
[0008] The following presents a simplified summary of the invention
in order to provide a basic understanding of some aspects of the
invention. This summary is not an extensive overview of the
invention. It is intended to neither identify key or critical
elements of the invention nor delineate the scope of the invention.
Rather, the sole purpose of this summary is to present some
concepts of the invention in a simplified form as a prelude to the
more detailed description that is presented hereinafter.
[0009] The subject invention provides a media that can
advantageously remove both heavy metals and volatile byproducts
from water. The media can be employed effectively in end of tap
applications and granular bed applications, where high water flow
rates are encountered, coupled with limited filter size
restraints.
[0010] One aspect of the invention relates to water purification
media or compositions containing an activated carbon having at
least one of a specific particle size, surface area, and porosity
with a microcrystalline and/or amorphous titanosilicate at least
partially coating the activated carbon.
[0011] Another aspect of the invention relates to methods of making
a water purification composition by contacting activated carbon, a
titanium compound, a silicon compound, and optionally a hydroxide
compound to form a mixture, typically an aqueous mixture, and
drying the mixture to provide a microcrystalline and/or amorphous
titanosilicate coated activated carbon capable of purifying
water.
[0012] Yet another aspect of the invention relates to methods of
purifying water or removing heavy metals and volatile byproducts
from water involving contacting water comprising a first amount of
a heavy metal and a first amount of a volatile byproduct with the
water purification media and recovering water comprising a second
amount of the heavy metal and a second amount of the volatile
byproduct, wherein the second amount of the heavy metal is less
than the first amount of the heavy metal and the second amount of
the volatile byproduct is less than the first amount of the
volatile byproduct.
[0013] To the accomplishment of the foregoing and related ends, the
invention comprises the features hereinafter fully described and
particularly pointed out in the claims. The following description
sets forth in detail certain illustrative aspects and
implementations of the invention. These are indicative, however, of
but a few of the various ways in which the principles of the
invention may be employed. Other objects, advantages and novel
features of the invention will become apparent from the following
detailed description of the invention.
DETAILED DESCRIPTION
[0014] The media is suitable for use in the removal of both heavy
metals and volatile byproducts from aqueous systems that contain at
least one heavy metal and at least one volatile byproduct. The
media is particularly effective at removing lead and volatile
chlorination byproducts from drinking water.
[0015] For purposes of this invention, the term heavy metals
includes heavy metal ions (for example Pb (II), Pb (IV), Hg (II),
Cr (III), Co (II), Co (III), Cd (II), Ag (I) As (III), As (V), and
the like), heavy metals, and compounds containing at least one
heavy metal atom (for example, sodium arsenate). Examples of heavy
metals include one or more of lead, cadmium, zinc, copper,
chromium, cobalt, arsenic, and mercury. For purposes of this
invention, the term volatile byproducts include carbon containing
compounds and particularly halocarbons. Examples of volatile
byproducts include volatile chlorination byproducts such as
trihalomethanes (for example; chloroform, bromoform,
bromodichloromethane, and chlorodibromomethane), bromate, chlorite,
haloacetic acids, chloramines, and the like and volatile organic
byproducts such as benzene, halobenzenes, acrylamide,
carbontetrachloride, bromodichloromethane, chlorodibromomethane,
dichloroethylene, dichloromethane, halopropanes, dioxin,
alkylbenzenes, PCBs, toluene, xylenes, vinyl chloride, styrene, and
the like.
[0016] The aqueous systems to which the methods are typically
applied are industrial, municipal, remote, or residential water
streams. For example, the media can be employed in the treatment of
drinking water, in an industrial, municipal, residential, or remote
(portable) context to decrease the amount of heavy metals and
volatile byproducts in the water. In residential water streams, the
media can be particularly useful in end of tap (EOT) or inline
applications where limited filter or cartridge size and high flow
rates may otherwise raise concerns.
[0017] The media contains activated carbon having a specific
particle size, pore structure, and/or surface area, which
contribute to its ability to remove unwanted heavy metals and
volatile byproducts from aqueous systems. The activated carbon may
also have levels of microporosity, mesoporosity, and/or
macroporosity, which further contribute to its ability to remove
unwanted heavy metals and volatile byproducts from aqueous systems.
The activated carbon has titanosilicate precursors secured on its
surface.
[0018] The media is formed in a manner that maximizes the ability
to remove unwanted heavy metals and volatile byproducts from
aqueous systems. The media has a high capacity for both heavy
metals and volatile byproducts compared to conventional water
purification materials, which often can remove either heavy metals
or volatile byproducts, but not both effectively.
[0019] The media is made by combining activated carbon with
titanosilicate precursors in a suitable manner to secure the
titanosilicate precursors on the surface of the activated carbon.
While not wishing to be bound by any theory, it is believed that
the titanosilicate precursors form a microcrystalline and/or
amorphous titanosilicate on the surface of the activated carbon, as
opposed to a purely crystalline form of titanosilicate. The
activated carbon having specific particle size, pore structure,
and/or surface area with a microcrystalline and/or amorphous
titanosilicate on its surface is effective in removing both heavy
metals and volatile byproducts from aqueous streams. It has been
determined that certain activated carbon can remove volatile
chlorination byproducts from water and that crystalline
titanosilicate can remove lead from water. It has also been found
in some cases that the traditional combination of crystalline
and/or amorphous titanosilicate on activated carbon is not
effective in removing both heavy metals and volatile byproducts
from aqueous streams to levels below regulatory limits in cases
where filter or cartridge size is limited and flow rates are
relatively high.
[0020] In one embodiment, thus, the media of microcrystalline
and/or amorphous titanosilicate on the surface of the activated
carbon does not comprise more than about 5% by weight of
crystalline titanosilicate. In another embodiment, the media of
microcrystalline and/or amorphous titanosilicate on the surface of
the activated carbon does not comprise more than about 2% by weight
crystalline titanosilicate. In yet another embodiment, the media of
microcrystalline and/or amorphous titanosilicate on the surface of
the activated carbon does not comprise any detectable crystalline
titanosilicate.
[0021] The activated carbon has at least one of a specific particle
size, pore structure, and surface area. In another embodiment, the
activated carbon has at least two of a specific particle size, pore
structure, and surface area. In yet another embodiment, the
activated carbon has at least three of a specific particle size,
pore structure, and surface area.
[0022] The activated carbon may have a particle size distribution
which contributes to the ability of the media to remove both heavy
metals and volatile byproducts from aqueous systems. In one
embodiment, the activated carbon has a particle size range
distributed mostly (more than 50% by weight) from about 50 to about
500 .mu.m. In another embodiment, the activated carbon has a
particle size range distributed mostly from about 60 to about 300
.mu.m. In yet another embodiment, the activated carbon has a
particle size range distributed mostly from about 70 to about 250
.mu.m. In the case where the activated carbon is in the form of
fibers and not particles, the particle size range distributions
listed above refer to average cross-sectional diameter of the
carbon fibers.
[0023] The activated carbon may have a surface area which
contributes to the ability of the media to remove both heavy metals
and volatile byproducts from aqueous systems. In one embodiment,
the surface area of the activated carbon is about 300 m.sup.2/g or
more and about 1,600 m.sup.2/g or less. In another embodiment, the
surface area of the activated carbon is about 500 m.sup.2/g or more
and about 1,400 m.sup.2/g or less. In yet another embodiment, the
surface area of the activated carbon is about 700 m.sup.2/g or more
and about 1,200 m.sup.2/g or less.
[0024] The activated carbon may have a unique distribution of pore
sizes that contributes to the ability of the media to remove both
heavy metals and volatile byproducts from aqueous systems. In one
embodiment, the activated carbon has a porosity of at least about
0.25 cc/g in pores diameter of at least about 10 and at most about
500 .ANG. (Hg intrusion porosimetry, such as using a Micromeritics
model AutoPore-II 9220 porosimeter in accordance with the analysis
method outlined in one or more of U.S. Pat. Nos. 5,186,746;
5,316,576; and 5,591,256). In another embodiment, the activated
carbon has a porosity of at least about 0.4 cc/g in pores diameter
of at least about 10 and at most about 500 .ANG.. In yet another
embodiment, the activated carbon has a porosity of at least about
0.4 cc/g in pores diameter of at least about 10 and at most about
500 .ANG..
[0025] The activated carbon may have levels of microporosity,
mesoporosity, and/or macroporosity which contribute to the ability
of the media to remove both heavy metals and volatile byproducts
from aqueous systems. In particular, the activated carbon has a
relatively high percentage (a major amount) of its pores as
mesoporous and relatively low percentages (minor amounts) of its
pores as microporous.
[0026] Microporosity refers to pores having a size (average
cross-section) of less than 2 nm, mesoporosity refers to pores
having a size from 2 nm to 50 nm, while macroporosity refers to
pores having a size greater than 50 nm. A major amount refers to
50% or more while a minor amount refers to less than 50%.
[0027] In one embodiment, the levels of porosity in the activated
carbon are less than 50% microporosity, from 50% to about 100%
mesoporosity and/or macroporosity. In another embodiment, the
levels of porosity in the activated carbon are less than about 40%
microporosity, from about 60% to about 99% mesoporosity and/or
macroporosity. In yet another embodiment, the levels of porosity in
the activated carbon are less than about 35% microporosity, from
about 65% to about 95% mesoporosity and/or macroporosity. The
relatively high levels of mesoporosity and/or macroporosity improve
the adsorptive characteristics of the media.
[0028] In one embodiment, in the mesoporosity and/or macroporosity
fraction, the levels of porosity are from about 0% to about 100%
mesoporosity and from about 0% to about 100% macroporosity. In
another embodiment, in the mesoporosity and/or macroporosity
fraction, the level of mesoporosity is greater than the level of
macroporosity. In yet another embodiment, in the mesoporosity
and/or macroporosity fraction, the levels of porosity are from
about 60% to about 99% mesoporosity and from about 1% to about 40%
macroporosity.
[0029] The activated carbon may be chemically activated or
non-chemically activated. Chemical activating agents include one or
more of alkali metal hydroxides, alkali metal carbonates, alkali
metal sulfide, alkali metal sulfates, alkaline earth metal
carbonates, alkaline earth metal chlorides, alkaline earth metal
sulfates, alkaline earth metal phosphates, phosphoric acid,
polyphosphoric acid, pyrophosphoric acid, zinc, chloride, sulfuric
acid, and the like. Chemical activation is conducted by contacting
one or more carbonaceous materials with one or more chemical
activating agents, mixing, optionally heating, optionally
washing/rinsing, and optionally drying the chemically activated
material. Non-chemical activation is conducted by heating.
[0030] The titanosilicate precursors include a titanium compound
and a silicon compound. A hydroxide compound may be combined with
either the titanium compound and/or the silicon compound to
facilitate application to the activated carbon. The titanium
compound and/or silicon compound form a microcrystalline and/or an
amorphous titanosilicate on the surface of the activated
carbon.
[0031] The titanium compound has the ability to react with the
silicon compound under suitable conditions to form a
microcrystalline and/or amorphous titanosilicate on the surface of
the activated carbon. The titanium compound may or may not be water
soluble. General examples of the titanium compound include
titanates such as metal titanates, organic titanates, and
halotitanates; titanium oxides such as titanium dioxide; and the
like. Specific examples of the titanium compound include sodium
titanate, calcium titanate, potassium titanate, magnesium titanate,
dichloro-oxy-titanate, difluoro-oxy-titanate, dibromo-oxy-titanate,
titanium ethoxide, titanium butoxide, titanium propoxide, titanium
isopropoxide, titanium ethylhexoxide, and the like.
[0032] The silicon compound has the ability to react with the
titanium compound under suitable conditions to form a
microcrystalline and/or amorphous titanosilicate on the surface of
the activated carbon. The silicon compound may or may not be water
soluble. General examples of the silicon compound include metal
silicates and organic silicates. Specific examples of the silicon
compound include sodium silicate, potassium silicate, calcium
silicate, magnesium silicate, phosphosilicate,
tetraethylorthosilicate, and the like.
[0033] General examples of hydroxide compounds include ammonium
hydroxides, alkali metal hydroxides, and alkaline earth metal
hydroxides. Specific examples of hydroxide compounds include
ammonia hydroxide, alkyl ammonium hydroxide, tetra-alkylammonium
hydroxides, sodium hydroxide, potassium hydroxide, calcium
hydroxide, magnesium hydroxide, mixtures of two or more thereof,
and the like. In embodiments where a hydroxide compound is
employed, it is typically combined with one or both of the titanium
compound and the silicon compound in an aqueous solution before
contact with the activated carbon.
[0034] The activated carbon and the titanosilicate precursors may
be in aqueous solutions when combined. Alternatively, one of the
activated carbon and one or more the titanosilicate precursors may
be in an aqueous solution and the other(s) in dry form when
combined.
[0035] In embodiments where aqueous solutions of the one or more
the titanosilicate precursors are combined, the concentrations of
the titanium compound and the silicon compound are sufficient to
facilitate formation of a microcrystalline and/or amorphous
titanosilicate on the surface of the activated carbon. In one
embodiment, one or more aqueous solutions contain from about 1% to
about 50% by weight of at least one titanium compound and from
about 0% to about 50% by weight, and more typically from about 1%
to about 50% by weight of at least one silicon compound and
optionally from about 1% to about 50% by weight of at least one
hydroxide compound. In another embodiment, one or more aqueous
solutions contain from about 5% to about 40% by weight of at least
one titanium compound and from about 5% to about 40% by weight of
at least one silicon compound and optionally from about 5% to about
30% by weight of at least one hydroxide compound. In yet another
embodiment, one or more aqueous solutions contain from about 10% to
about 35% by weight of at least one titanium compound and from
about 10% to about 35% by weight of at least one silicon compound
and optionally from about 10% to about 25% by weight of at least
one hydroxide compound.
[0036] In some instances, the microcrystalline and/or amorphous
titanosilicate formed on the surface of the activated carbon is
made with at least one titanium compound and at least one hydroxide
compound, but not a silicon compound. As used herein, the term
titanosilicate is intended to cover this possibility.
[0037] Once combined, the combination solution containing the
activated carbon, titanium compound, silicon compound, and
optionally the hydroxide compound is mixed to facilitate formation
of a microcrystalline and/or amorphous titanosilicate on the
surface of the activated carbon. In order to facilitate formation
of the microcrystalline and/or amorphous titanosilicate on the
surface of the activated carbon, the pH is maintained in the
neutral to moderately basic range. In one embodiment, the
combination solution is maintained at a pH from about 6 to about 12
to facilitate formation of the microcrystalline and/or amorphous
titanosilicate on the surface of the activated carbon. In another
embodiment, the combination solution is maintained at a pH from
about 7 to about 10.
[0038] In one embodiment, the amount of water employed is an amount
up to the point of incipient wetness. Reference is made to the
method described in U.S. Pat. No. 4,134,860, which is hereby
incorporated by reference. The point of incipient wetness is the
point at which the amount of liquid such as water added is the
lowest concentration at which the dry or powdered mixture is
sufficiently dry so as to absorb essentially all of the liquid. In
this way, soluble titanosilicate precursors in water can be added
into the activated carbon.
[0039] After the microcrystalline and/or amorphous titanosilicate
coating is formed on the surface of the activated carbon, the
combination solution or slurry is filtered and washed in any
suitable manner to recover the media. For example, the
microcrystalline and/or amorphous titanosilicate coated activated
carbon slurry may be filtered in a filter press, centrifuge, drum
filter, or any other filtration process. The recovered media may be
optionally washed with water to remove any undesirable residual
compounds or salts (such as NaCl, KCl, NH.sub.4Cl, and the
like).
[0040] The media is then dried. The media can be allowed to dry
without introducing heat. Alternately, the media can be milled
and/or screened in a wet state or dry state to produce a smaller
size material or obtain a subset particle size distribution.
[0041] Drying may involve at least one of heating, storing under
vacuum, spray drying, spin flash drying, and dessication. Heating
involves exposing the media to elevated temperatures for a suitable
period of time to induce the release of water. In one embodiment,
the media is exposed to temperatures from about 30.degree. C. to
about 150.degree. C. for a time from about 1 minute to about 50
hours. In another embodiment, the media is exposed to temperatures
from about 50.degree. C. to about 100.degree. C. for a time from
about 10 minutes to about 20 hours. In yet another embodiment, the
media is exposed to temperatures from about 70.degree. C. to about
90.degree. C. for a time from about 1 hour to about 15 hours.
Advantageously, heating does not significantly decrease the removal
capacity of the media.
[0042] The media can consist essentially of the titanosilicate
coated activated carbon. However, the media containing the
titanosilicate coated activated carbon may optionally further
contain other adsorptive material, such as one or more of untreated
activated carbon, activated carbon treated or coated in some other
process, ionic resin, granular titanosilicate, ferric hydroxide,
alumina, magnesia, bauxite, zeolites, and the like. In one
embodiment, the media contains from about 1% to 100% by weight of
the titanosilicate coated activated carbon and from 0% to about 95%
of at least one of additional untreated activated carbon, activated
carbon treated or coated in some other process, ionic resin,
granular titanosilicate, ferric hydroxide, alumina, magnesia,
bauxite, and zeolites. In another embodiment, the media contains
from about 25% to about 95% by weight of the titanosilicate coated
activated carbon and from about 5% to about 75% of at least one of
untreated activated carbon, activated carbon treated or coated in
some other process, ionic resin, granular titanosilicate, ferric
hydroxide, alumina, magnesia, bauxite, and zeolites.
[0043] The media contains a sufficient amount of microcrystalline
and/or amorphous titanosilicate coated on the activated carbon to
facilitate removal of both heavy metals and volatile byproducts
from aqueous systems. In this connection, the microcrystalline
and/or amorphous titanosilicate at least partially coats the
activated carbon, although it may completely coat the activated
carbon. In one embodiment, the media contains from about 0.01
g/in.sup.3 to about 1 g/in.sup.3 of microcrystalline and/or
amorphous titanosilicate on the activated carbon. In another
embodiment, the media contains from about 0.025 g/in.sup.3 to about
0.5 g/in.sup.3 of microcrystalline and/or amorphous titanosilicate
on the activated carbon. In yet another embodiment, the media
contains from about 0.05 g/in.sup.3 to about 0.25 g/in.sup.3 of
microcrystalline and/or amorphous titanosilicate on the activated
carbon.
[0044] In one embodiment, the media contains from about 0.1% to
about 15% by weight of microcrystalline and/or amorphous
titanosilicate and from about 85% to about 99.9% by weight
activated carbon. In another embodiment, the media contains from
about 1% to about 10% by weight of microcrystalline and/or
amorphous titanosilicate and from about 90% to about 99% by weight
activated carbon. In yet another embodiment, the media contains
from about 4% to about 8% by weight of microcrystalline and/or
amorphous titanosilicate and from about 92% to about 98% by weight
activated carbon.
[0045] The media when in granule form contains titanosilicate
coated activated carbon having a certain particle size that
contributes to its ability to remove unwanted heavy metals and
volatile byproducts from aqueous systems. In one embodiment, when
the media is employed in granule form, the average particle size
distribution is from about 50 .mu.m to about 500 .mu.m. In another
embodiment, when the media is employed in granule form, the average
particle size by weight is from about 60 .mu.m to about 300 .mu.m.
In yet another embodiment, when the media is employed in granule
form, the average particle size by weight is from about 70 .mu.m to
about 250 .mu.m.
[0046] When in granule form, the media contains low levels of
fines. Fines are particles smaller than about the lower size limit
in the embodiment particle size distribution. The low level of
fines contributes to low pressure drop characteristics of the media
when used in applications such as in a filter for EOT filtration.
In one embodiment, when the media is employed in granule form, the
media contains less than about 5% by weight fines. In another
embodiment, when the media is employed in granule form, the media
contains less than about 2% by weight fines. In yet another
embodiment, when the media is employed in granule form, the media
contains less than about 1% by weight fines.
[0047] The heavy metal and volatile byproduct removal media may be
packed into a fixed-bed adsorbent column or container. An aqueous
stream containing heavy metals and volatile byproducts is charged
or pumped into/through the media in either up-flow or down-flow
fashion. Purified water with significantly reduced levels of heavy
metals and volatile byproducts flows out of the media. The media
provides for a high level of heavy metal and volatile byproduct
removal capacity along with easier and smoother operation of EOT
applications and/or water treatment systems.
[0048] The media may be formed into a multi-component block
cartridge filter or formed into a singular-active component block
cartridge filter. The media can also be used as is in water
treatment or clarification systems and in pre-coat
filter/adsorption systems.
[0049] In some instances, heavy metal and volatile byproduct
removal from aqueous streams can be complicated by the presence of
other contaminants such as competing ions and compounds. Such
entities include alkaline earth metal ions, often present as
calcium or magnesium sulfates, phosphates and silicates, and halide
ions such as chlorides or fluorides. The presence of these
competing ions in aqueous systems can vary greatly. In one
embodiment, an aqueous system that is contacted with the media
contains from about 10 ppm to about 1,000 ppm of competing ions and
compounds. In another embodiment, an aqueous system that is
contacted with the media contains from about 25 ppm to about 800
ppm of competing ions and compounds. In yet another embodiment, an
aqueous system that is contacted with the media contains from about
50 ppm to about 300 ppm of competing ions and compounds. In yet
another embodiment, an aqueous system that is contacted with the
media contains from about 75 ppm to about 200 ppm of competing ions
and compounds.
[0050] The presence of these competing ions and compounds can
particularly make heavy metal removal and VOC removal from aqueous
systems much more difficult. This is because the competing ions and
compounds present compete for available adsorption sites on the
media and consequently lower the heavy metal or VOC removal
efficiency of the media. In drinking water treatment, common
competing cations are calcium, magnesium, iron from rusty pipes,
and copper from plumbing, the most common competing anions are
sulfate, phosphate, chloride, carbonate, and fluoride ions, the
most common competing compounds are dissolved organic content and
silica.
[0051] In one embodiment, a EOT filter loaded with the media
removes at least about 75% of the heavy metals and at least about
75% of the volatile byproducts in 800 gallons of an aqueous system
passed therethrough. In another embodiment, a EOT filter loaded
with the media removes at least about 90% of the heavy metals and
at least about 90% of the volatile byproducts in 800 gallons of an
aqueous system passed therethrough.
[0052] In order to meet the EPA standards (United States
Environmental Protection Agency), lead concentrations in the
effluent or drinking water should be less than 15 ppb and arsenic
concentrations in the effluent or drinking water should be less
than 10 ppb. As may be seen from the data set forth, the media
described herein has the capability of reducing lead and/or arsenic
concentrations in aqueous systems well below the EPA levels, while
maintaining commercially attractive adsorption capacities and
performance.
[0053] In one embodiment, aqueous systems passed through the media
have at least two of a lead content of about 15 ppb or less, an
arsenic content of about 10 ppb or less, and a trihalomethane
content of about 100 ppb or less for about 800 gallons or more at a
pH of 8.5 in accordance with the NSF International Standard 53. In
another embodiment, aqueous systems passed through the media have
at least one of a lead content of about 10 ppb or less and a
trihalomethane content of about 70 ppb or less for about 800
gallons or more at a pH of 8.5 in accordance with the NSF
International Standard 53. In yet another embodiment, aqueous
systems passed through the media have at least one of a lead
content of about 5 ppb or less and a trihalomethane content of
about 60 ppb or less for about 800 gallons or more at a pH of 8.5
in accordance with the NSF International Standard 53.
[0054] The media can be packed into a filter or container such as
an inline filter, a EOT filter, or a fixed-bed column. The heavy
metal and volatile byproduct containing aqueous stream moves
through or passes through the media. Treated water with
significantly reduced levels of heavy metals and volatile
byproducts flows out of the column or container. For example
arsenic and/or lead concentrations in the effluent are typically
less than about 15 ppb (micrograms/liter), and often the effluent
concentrations can be less than about 2 ppb of each heavy metal.
The capacity of the media is higher with higher levels of heavy
metal permitted in the effluent stream. In residential or remote
applications, the media can be used as an EOT filter or a
free-flowing granular media, filled into a cartridge with holes on
the top to permit entry of the contaminant solution, which is
allowed to trickle via gravity flow through the bed of the
composite material and then exit through holes on the bottom of the
cartridge, possibly into a reservoir to hold the treated water.
[0055] The following examples illustrate the subject invention.
Unless otherwise indicated in the following examples and elsewhere
in the specification and claims, all parts and percentages are by
weight, all temperatures are in degrees Centigrade, and pressure is
at or near atmospheric pressure.
EXAMPLE 1
[0056] An aqueous solution of sodium silicate solution
(N-Brand.RTM., 8.93% Na.sub.2O, 29.2% SiO.sub.2) (36 g), 50% sodium
hydroxide solution (44 g), and deionized (DI) water (20 g) was
added dropwise to activated carbon (250 g). When the addition was
completed, an aqueous solution of titanium oxychloride solution
(21.9% TiO.sub.2, 34.8% Cl) (44.9 g) and DI water (20 g) was added
dropwise the same activated carbon. The resultant material was then
washed approximately 15 times by decantation with DI water and then
dried at 105.degree. C. overnight.
[0057] A sample (63.7 g) of the dried material was loaded into an
End of Tap filter. The filter was fixed to an apparatus and exposed
to an aqueous influent stream containing chloroform (45 .mu.g/L),
bromodichloromethane (30 .mu.g/L), chlorodibromomethane (20
.mu.g/L), and bromoform (5 .mu.g/L). After passing approximately
800 gallons of the charge at a flow rate of approximately 0.5 GPM
(gallons per minute) the Total THM (Total TriHaloMethane)
concentration was still reduced below (60 .mu.g/L).
[0058] Another sample (64.1 g) of the dried material was loaded
into an End of Tap filter. The filter was fixed to an apparatus and
exposed to an aqueous influent stream containing lead nitrate (lead
concentration=150 .mu.g/L), and additional dissolved compounds.
After passing approximately 800 gallons at a flow rate of
approximately 0.5 GMP the lead concentration of the effluent was
still below the detection limit (<2 .mu.g/L).
[0059] With respect to any figure or numerical range for a given
characteristic, a figure or a parameter from one range may be
combined with another figure or a parameter from a different range
for the same characteristic to generate a numerical range.
[0060] While the invention has been explained in relation to
certain embodiments, it is to be understood that various
modifications thereof will become apparent to those skilled in the
art upon reading the specification. Therefore, it is to be
understood that the invention disclosed herein is intended to cover
such modifications as fall within the scope of the appended
claims.
* * * * *