U.S. patent application number 10/675812 was filed with the patent office on 2004-03-25 for filterable composite adsorbents.
Invention is credited to Palm, Scott K., Roulston, John S., Shiuh, Jerome C., Smith, Timothy R..
Application Number | 20040055957 10/675812 |
Document ID | / |
Family ID | 31996380 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055957 |
Kind Code |
A1 |
Palm, Scott K. ; et
al. |
March 25, 2004 |
Filterable composite adsorbents
Abstract
This invention relates to filterable composite adsorbents
comprising one or more adsorbent components and one or more
filtration components, and methods for preparing and using same.
More particularly, this invention pertains to filterable composite
adsorbents and filterable composite adsorbent products which are
suitable for use in filtration applications, and which comprise one
or more microparticulate or colloidal adsorbent components selected
from the group consisting of silica gel, fumed silica, neutral
clay, alkaline clay, zeolite, solid catalyst, alumina, adsorbent
polymer, alkaline earth silicate hydrate, and combinations thereof,
which bear the property of adsorption, which are intimately bound
to one or more functional filtration components selected from the
group consisting of biogenic silica (e.g., diatomite, rice hull
ash, sponge spicules), natural glass (e.g., expanded perlite,
pumice, expanded pumice, pumicite, expanded obsidian, expanded
volcanic ash), buoyant glass, buoyant polymer, cellulose, and
combinations thereof, which bear a distinguishing porous and
intricate structure and buoyancy suitable for filtration.
Inventors: |
Palm, Scott K.; (Santa
Maria, CA) ; Smith, Timothy R.; (Lompoc, CA) ;
Shiuh, Jerome C.; (Lompoc, CA) ; Roulston, John
S.; (Lompoc, CA) |
Correspondence
Address: |
MORRISON & FOERSTER LLP
755 PAGE MILL RD
PALO ALTO
CA
94304-1018
US
|
Family ID: |
31996380 |
Appl. No.: |
10/675812 |
Filed: |
September 29, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10675812 |
Sep 29, 2003 |
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09145796 |
Sep 2, 1998 |
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09145796 |
Sep 2, 1998 |
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09001965 |
Dec 31, 1997 |
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09001965 |
Dec 31, 1997 |
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08781325 |
Jan 10, 1997 |
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Current U.S.
Class: |
210/660 |
Current CPC
Class: |
B01J 20/10 20130101;
F23J 2219/60 20130101; B01J 20/28033 20130101; B01J 20/2803
20130101; B01J 20/106 20130101; B01J 20/28014 20130101; F23J
2217/105 20130101; B01D 39/06 20130101; B01J 20/28042 20130101 |
Class at
Publication: |
210/660 |
International
Class: |
C02F 001/28 |
Claims
1. A composite comprising: one or more first components selected
from the group consisting of silica gel, fumed silica, neutral
clay, alkaline clay, zeolite, solid catalyst, alumina, adsorbent
polymer, and alkaline earth silicate hydrate; intimately bound to
one or more second components selected from the group consisting of
biogenic silica, natural glass, buoyant glass, buoyant polymer, and
cellulose.
2. The filterable composite adsorbent according to claim 1, wherein
said functional filtration component is a natural glass.
3. The filterable composite adsorbent according to claim 1, wherein
said functional filtration component is biogenic silica.
4. A filterable composite adsorbent comprising: one or more
adsorbent components selected from the group consisting of silica
gel, fumed silica, neutral clay, alkaline clay, zeolite, solid
catalyst, alumina, adsorbent polymer, and alkaline earth silicate
hydrate; intimately bound to one or more functional filtration
components selected from the group consisting of diatomite, rice
hull ash, sponge spicules, expanded perlite, pumice, expanded
pumice, pumicite, expanded obsidian, expanded volcanic ash, natural
glass, buoyant glass, buoyant polymer, and cellulose.
5. The filterable composite adsorbent according to claim 4, wherein
said adsorbent component is selected from the group consisting of
silica gel and fumed silica.
6. The filterable composite adsorbent according to claim 4, wherein
said adsorbent component is selected from the group consisting of
neutral clays and alkaline clays.
7. The filterable composite adsorbent according to claim 4, wherein
said adsorbent component is selected from the group consisting of
zeolite, alumina, and alkaline earth silicate hydrate.
8. The filterable composite adsorbent according to claim 4, wherein
said functional filtration component is diatomite.
9. The filterable composite adsorbent according to claim 4, wherein
said functional filtration component is rice hull ash.
10. The filterable composite adsorbent according to claim 4,
wherein said functional filtration component is sponge
spicules.
11. The filterable composite adsorbent according to claim 4,
wherein said functional filtration component is a selected from the
group consisting of expanded perlite, pumice, expanded pumice,
pumicite, expanded obsidian, and expanded volcanic ash.
12. The filterable composite adsorbent according to claim 4,
wherein said functional filtration component is expanded
perlite.
13. A filterable composite adsorbent comprising silica gel
intimately bound to biogenic silica.
14. A filterable composite adsorbent comprising silica gel
intimately bound to a natural glass.
15. A filterable composite adsorbent comprising silica gel
intimately bound to a material selected from the group consisting
of expanded perlite, pumice, expanded pumice, pumicite, expanded
obsidian, and expanded volcanic ash.
16. A filterable composite adsorbent comprising silica gel
intimately bound to expanded perlite.
17. A filterable composite adsorbent comprising fumed silica
intimately bound to biogenic silica.
18. A filterable composite adsorbent comprising fumed silica
intimately bound to a natural glass.
19. A filterable composite adsorbent comprising fumed silica
intimately bound to a material selected from the group consisting
of expanded perlite, pumice, expanded pumice, pumicite, expanded
obsidian, and expanded volcanic ash.
20. A filterable composite adsorbent comprising fumed silica
intimately bound to expanded perlite.
21. A filterable composite adsorbent comprising neutral clay or
alkaline clay intimately bound to biogenic silica.
22. A filterable composite adsorbent comprising neutral clay or
alkaline clay intimately bound to a natural glass.
23. A filterable composite adsorbent comprising neutral clay or
alkaline clay intimately bound to a material selected from the
group consisting of expanded perlite, pumice, expanded pumice,
pumicite, expanded obsidian, and expanded volcanic ash.
24. A filterable composite adsorbent comprising neutral clay or
alkaline clay intimately bound to expanded perlite.
25. A filterable composite adsorbent comprising zeolite intimately
bound to biogenic silica.
26. A filterable composite adsorbent comprising zeolite intimately
bound to a natural glass.
27. A filterable composite adsorbent comprising zeolite intimately
bound to a material selected from the group consisting of expanded
perlite, pumice, expanded pumice, pumicite, expanded obsidian, and
expanded volcanic ash.
28. A filterable composite adsorbent comprising zeolite intimately
bound to expanded perlite.
29. A filterable composite adsorbent comprising alumina intimately
bound to biogenic silica.
30. A filterable composite adsorbent comprising alumina intimately
bound to a natural glass.
31. A filterable composite adsorbent comprising alumina intimately
bound to a material selected from the group consisting of expanded
perlite, pumice, expanded pumice, pumicite, expanded obsidian, and
expanded volcanic ash.
32. A filterable composite adsorbent comprising alumina intimately
bound to expanded perlite.
33. A filterable composite adsorbent comprising adsorbent polymer
intimately bound to biogenic silica.
34. A filterable composite adsorbent comprising adsorbent polymer
intimately bound to a natural glass.
35. A filterable composite adsorbent comprising adsorbent polymer
intimately bound to a material selected from the group consisting
of expanded perlite, pumice, expanded pumice, pumicite, expanded
obsidian, and expanded volcanic ash.
36. A filterable composite adsorbent comprising adsorbent polymer
intimately bound to expanded perlite.
37. A filterable composite adsorbent comprising alkaline earth
silicate hydrate intimately bound to biogenic silica.
38. A filterable composite adsorbent comprising alkaline earth
silicate hydrate intimately bound to a natural glass.
39. A filterable composite adsorbent comprising alkaline earth
silicate hydrate intimately bound to a material selected from the
group consisting of expanded perlite, pumice, expanded pumice,
pumicite, expanded obsidian, and expanded volcanic ash.
40. A filterable composite adsorbent comprising alkaline earth
silicate hydrate intimately bound to expanded perlite.
41. The composite according to claim 1, wherein the permeability of
said composite is greater than the permeability of a simple mixture
of said one or more first components and said one or more second
components, wherein the proportions of said one or more first
components and said one or more second components in said simple
mixture are identical to those used in the preparation of said
composite.
42. The composite according to claim 1, wherein the permeability of
said composite is at least 5% greater than the permeability of a
simple mixture of said one or more first components and said one or
more second components, wherein the proportions of said one or more
first components and said one or more second components in said
simple mixture are identical to those used in the preparation of
said composite.
43. The composite according to claim 1, wherein the median particle
diameter of said composite is greater than the median particle
diameter of a simple mixture of said one or more first components
and said one or more second components, wherein the proportions of
said one or more first components and said one or more second
components in said simple mixture are identical to those used in
the preparation of said composite.
44. The composite according to claim 1, wherein the median particle
diameter of said composite is at least 5% greater than the median
particle diameter of a simple mixture of said one or more first
components and said one or more second components, wherein the
proportions of said one or more first components and said one or
more second components in said simple mixture are identical to
those used in the preparation of said composite.
45. The composite according to claim 1, wherein each of said one or
more second components has a permeability of 0.001 to 1000 Da.
46. The composite according to claim 1, wherein said composite is
prepared using a stationary bed furnace or a rotary kiln
furnace.
47. The composite according to claim 1, wherein said composite is
in the form of a powder, a sheet, a pad, or a cartridge.
48. The composite according to claim 1, wherein said composite is
thermally sintered and/or chemically bonded in the form of a rigid
shape.
49. The composite according to claim 1, wherein said composite is
in the form of a monolithic support, an aggregate support, a
monolithic substrate, or an aggregate substrate.
50. A method of adsorption and filtration comprising the step of
(i) suspending a filterable composite adsorbent according to claim
4 in a fluid containing suspended particulates or constituents to
be adsorbed, followed by the step of (ii) separating said
filterable composite adsorbent from said fluid.
51. A method of adsorption and filtration comprising the step of
(i) suspending a filterable composite adsorbent according to claim
4 in a fluid containing suspended particulates or constituents to
be adsorbed, followed by the step of (ii) passing said fluid with
suspended filterable composite adsorbent through a filterable
composite adsorbent according to claim 4 supported on a septum.
52. A method of adsorption and filtration comprising the step of
passing a fluid containing suspended particles or constituents to
be adsorbed through a filterable composite adsorbent according to
claim 4 which is supported on a septum.
53. A method of adsorption and filtration comprising the step of
passing a fluid containing suspended particles or constituents to
be adsorbed through a filterable composite adsorbent according to
claim 4 which is in the form of a rigid shape.
54. A method of adsorption and filtration according to claim 50,
wherein said fluid is a liquid, a molten solid, or a gas.
55. A method of adsorption and filtration according to claim 51,
wherein said fluid is a liquid, a molten solid, or a gas.
56. A method of adsorption and filtration according to claim 52,
wherein said fluid is a liquid, a molten solid, or a gas.
57. A method of adsorption and filtration according to claim 53,
wherein said fluid is a liquid, a molten solid, or a gas.
58. A method for the preparation of a filterable composite
adsorbent according to claim 4, said method comprising the steps of
(i) blending one or more adsorbent components with one or more
functional filtration components, and (ii) applying microwave
radiation applied to the blend, thereby forming said filterable
composite adsorbent.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. Ser. No.
09/001,965 filed Dec. 31, 1997, which is a continuation-in-part of
U.S. Ser. No. 08/781,325 filed Jan. 10, 1997. The prior
applications are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] This invention relates to composites comprising one or more
adsorbent components and one or more filtration components, and
methods for preparing and using same. More particularly, this
invention pertains to filterable composite adsorbents and
filterable composite adsorbent products which are suitable for use
in filtration applications, and which comprise one or more
microparticulate or colloidal adsorbent components selected from
the group consisting of silica gel, fumed silica, neutral clay,
alkaline clay, zeolite, solid catalyst, alumina, adsorbent polymer,
alkaline earth silicate hydrate, and combinations thereof, which
bear the property of adsorption, which are intimately bound to one
or more functional filtration components selected from the group
consisting of biogenic silica (e.g., diatomite, rice hull ash,
sponge spicules), natural glass (e.g., expanded perlite, pumice,
expanded pumice, pumicite, expanded obsidian, expanded volcanic
ash), buoyant glass, buoyant polymer, cellulose, and combinations
thereof, which bear a distinguishing porous and intricate structure
and buoyancy suitable for filtration.
DESCRIPTION OF THE RELATED ART
[0003] Throughout this application, various publications, patents,
and published patent applications are referred to by an identifying
citation; full citations for these documents may be found at the
end of the specification immediately preceding the claims. The
disclosures of the publications, patents, and published patent
specifications referenced in this application are hereby
incorporated by reference into the present disclosure to more fully
describe the state of the art to which this invention pertains.
[0004] Adsorption is the term commonly used to describe the
tendency of molecules from an ambient fluid phase to adhere to the
surface of a solid, and has been recently reviewed in detail
(Ruthven, 1991). Adsorption is a fundamental property of matter,
having its origin in the attractive forces between molecules. The
solid's force field creates a region of low potential energy near
the solid's surface such that the molecular density close to the
solid's surface is generally greater than in the bulk fluid. This
results in the phenomenon of adsorption, in which the solid surface
adsorbs various constituents from a multiconstituent fluid, to a
degree which varies according to the solid surface's affinity for a
particular constituent.
[0005] To achieve a significant adsorptive capacity, and thus to be
highly practical for commercial use, an adsorbent preferably has a
high specific area, which implies a highly porous structure with
very small micropores. A method that is often preferred for
determining specific area is performed by specialized instruments
which use a BET (Brunauer et al., 1938) modification of Langmuir
adsorption (Langmuir, 1916a, 1916b, 1918) of nitrogen, krypton, or
other suitable gas at the surface of a sample of the solid under
highly controlled conditions. Pore size and distribution are often
determined by mercury intrusion porosimetry instruments operated
under highly controlled conditions, which are capable of providing
detailed information about pore sizes from about 6 nanometers to
about 300 micrometers in diameter. Generally speaking, specific
surface areas of practical adsorbents range from about 300 to 1200
m.sup.2/g, with macropores greater than about 0.050 .mu.m (i.e., 50
nanometers) in diameter contributing little to adsorptive
behavior.
[0006] The specific adsorptive properties of a practical adsorbent
depend on its pore size and pore size distribution as well as on
the nature of the solid surface. For example, a crystalline zeolite
has a comparatively narrow pore size distribution and a polar
surface; an amorphous silica gel has a comparatively broad pore
size distribution and a polar surface; and a carbon molecular sieve
is comparatively narrow in pore size distribution with a nonpolar
surface. These principal characteristics for many adsorbents have
been successfully engineered to permit the selective adsorption of
components from fluids.
[0007] One common method of using an adsorbent is to simply place
it in contact with a fluid containing one or more constituents that
need to be adsorbed from it, either to purify the fluid by
selectively removing the constituents, or to isolate the
constituents so as to purify them from the fluid in which they are
contained. Usually, the adsorbent containing the adsorbed
constituents is then separated from the fluid, typically by
filtration.
[0008] One typical method for separating adsorbents from fluids is
through the use of filtration, in which the fluid can be in either
a liquid or gaseous state. In the field of filtration, many methods
of particle separation from fluids employ, for example, expanded
perlite or natural glasses, or diatomite products, as porous
filtration media. Although not usually as effective for the
selective adsorption as commercial adsorbents, these products do
have intricate and porous structures of greater size that are
uniquely suited to the effective physical entrapment of particles,
for example in filtration processes. These intricate and porous
structures create networks of void spaces that result in buoyant
filtration media particles that have apparent densities similar to
those of the fluids in which they are suspended. It is common
practice to employ porous filtration media when improving the
clarity of fluids that contain suspended particles or particulate
matter such as adsorbents, or have turbidity.
[0009] Since the requirement for high specific surface area is
inextricably coupled with extremely fine pore size in order to
create an effective, practical adsorbent, many adsorbents are not
readily separated (e.g., filtered) from the fluids in which they
have been suspended, because the individual particles of adsorbents
cannot be made larger than the colloidal or fine microparticulate
size range in their pure form and still retain both buoyancy and
the desired adsorbent properties. The efficiency of many adsorbents
in fluid system applications would be improved if the adsorbents
were made more permeable or if more buoyant adsorbents were
possible.
[0010] The filtration of microparticulate or colloidal adsorbents
is usually difficult, since the adsorbent particles are not readily
and/or effectively filterable. For example, merely blending
microparticulate or colloidal adsorbents into porous filtration
media products reduces the efficiency and permeability of the
porous filtration media, as the adsorbents are typically of such a
size as to behave as particles that detrimentally occupy the
valuable void spaces that result from the intricate structure of
the porous filtration media. Often, blended mixtures do not have
the flow rate of the more permeable filterable composite adsorbent
products of the present invention.
[0011] References which pertain to the filtration problems
associated with adsorbents and methods of overcoming these problems
in conjunction with the use of filter aids include Guiambo et al.
(1991), Patel et al. (1992), Kucera et al. (1987), Machel et al.
(1973), Schuler et al. (1990), and Fukua (1988).
[0012] McCollum (1961) describes a method of introducing an acidic
montmorillonite clay as a mixture into a perlite ore prior to
subjecting the mixture to a conventional perlite expansion process.
This method appears to be highly limited with regard to the
quantity of acidic montmorillonite clay that can be effectively
bound to the perlite after expansion, as perlite particles greatly
increase in volume, up to twenty times, during expansion. In fact,
it appears that McCollum achieved at most about 15% attached acidic
montmorillonite clay. McCollum did not teach that more buoyant
glasses, such as expanded perlite, can be used as starting
materials, or that materials other than acidic montmorillonite clay
could be used as an adsorbent component. McCollum also did not
teach that material other than perlite or its derivatives could be
used as a functional filtration component. While McCollum does not
disclose any means to discriminate whether the acidic clay has
actually been intimately bound to the functional filtration
component or it is has formed merely a mixture with it, the methods
described in the examples of the present invention, which provide
for more intimate contact, are far more efficient for achieving
intimate binding of adsorbents to functional filtration components,
as demonstrated in the examples.
[0013] The filterable composite adsorbents of the present
invention, inter alia, overcome the filtration difficulties
encountered with microparticulate or colloidal adsorbents.
[0014] In the filterable composite adsorbents of the present
invention, one or more microparticulate or colloidal adsorbent
components is intimately bound to one or more functional filtration
components. The filterable composite adsorbents of the present
invention retain both the adsorptive properties of the adsorbent
component and the intricate and porous structure of the functional
filtration component, thus greatly enhancing the utility of the
filterable composite adsorbents in practical applications. The
filterable composite adsorbents of the present invention offer a
spectrum of permeabilities comparable to the range offered by their
functional filtration components.
SUMMARY OF THE INVENTION
[0015] One aspect of the present invention pertains to a novel
composite comprising one or more first components selected from the
group consisting of silica gel, fumed silica, neutral clays,
alkaline clays, zeolite, solid catalyst, alumina, adsorbent
polymer, alkaline earth silicate hydrate, and combinations thereof,
intimately bound to one or more functional second components
selected from the group consisting of biogenic silica (e.g.,
diatomite, rice hull ash, sponge spicules), natural glass (e.g.,
expanded perlite, pumice, expanded pumice, pumicite, expanded
obsidian, expanded volcanic ash), buoyant glass, buoyant polymer,
cellulose, and combinations thereof.
[0016] In one embodiment, the first component(s) is an adsorbent
component and imparts absorbent properties to the composite,
whereas the second component(s) is a functional filtration
component, and confers filtration ability to the composite.
[0017] In one embodiment, the adsorbent (first) component is
selected from the group consisting of silica gel and fumed silica.
In one embodiment, the adsorbent component is selected from the
group consisting of neutral clays and alkaline clays. In one
embodiment, the adsorbent component is selected from the group
consisting of zeolite, alumina, and alkaline earth silicate
hydrate. In one embodiment, the adsorbent component is adsorbent
polymer.
[0018] In one embodiment, the functional filtration (second)
component is biogenic silica. In one embodiment, the functional
filtration component is diatomite. In one embodiment, the
functional filtration component is rice hull ash. In one
embodiment, the functional filtration component is sponge spicules.
In one embodiment, the functional filtration component is a natural
glass. In one embodiment, the functional filtration component is
selected from the group consisting of expanded perlite, pumice,
expanded pumice, pumicite, expanded obsidian, and expanded volcanic
ash. In one embodiment, functional filtration component is expanded
perlite.
[0019] In one embodiment, the adsorbent component is silica gel,
and the function filtration component is biogenic silica. In one
embodiment, the adsorbent component is silica gel, and the
functional filtration component is a natural glass. In one
embodiment, the adsorbent component is silica gel, and the
functional filtration component is selected from the group
consisting of expanded perlite, pumice, expanded pumice, pumicite,
expanded obsidian, and expanded volcanic ash. In one embodiment,
the adsorbent component is silica gel, and the functional
filtration component is expanded perlite.
[0020] In one embodiment, the adsorbent component is fumed silica,
and the functional filtration component is biogenic silica. In one
embodiment, the adsorbent component is fumed silica, and the
functional filtration component is a natural glass. In one
embodiment, the adsorbent component is fumed silica, and the
functional filtration component is selected from the group
consisting of expanded perlite, pumice, expanded pumice, pumicite,
expanded obsidian, and expanded volcanic ash. In one embodiment,
the adsorbent component is fumed silica, and the functional
filtration component is expanded perlite.
[0021] In one embodiment, the adsorbent component is a neutral clay
or alkaline clay, and the functional filtration component is
biogenic silica. In one embodiment, the adsorbent component is a
neutral clay or alkaline clay, and the functional filtration
component is a natural glass. In one embodiment, the adsorbent
component is a neutral clay or alkaline clay, and the functional
filtration component is selected from the group consisting of
expanded perlite, pumice, expanded pumice, pumicite, expanded
obsidian, and expanded volcanic ash. In one embodiment, the
adsorbent component is a neutral clay or alkaline clay, and the
functional filtration component is expanded perlite.
[0022] In one embodiment, the adsorbent component is a zeolite, and
the functional filtration component is biogenic silica. In one
embodiment, the adsorbent component is a zeolite, and the
functional filtration component is a natural glass. In one
embodiment, the adsorbent component is a zeolite, and the
functional filtration component is selected from the group
consisting of expanded perlite, pumice, expanded pumice, pumicite,
expanded obsidian, and expanded volcanic ash. In one embodiment,
the adsorbent component is a zeolite, and the functional filtration
component is expanded perlite.
[0023] In one embodiment, the adsorbent component is alumina, and
the functional filtration component is biogenic silica. In one
embodiment, the adsorbent component is alumina, and the functional
filtration component is a natural glass. In one embodiment, the
adsorbent component is alumina, and the functional filtration
component is selected from the group consisting of expanded
perlite, pumice, expanded pumice, pumicite, expanded obsidian, and
expanded volcanic ash. In one embodiment, the adsorbent component
is alumina, and the functional filtration component is expanded
perlite.
[0024] In one embodiment, the adsorbent component is an adsorbent
polymer, and the functional filtration component is biogenic
silica. In one embodiment, the adsorbent component is an adsorbent
polymer, and the functional filtration component is a natural
glass. In one embodiment, the adsorbent component is an adsorbent
polymer, and the functional filtration component is selected from
the group consisting of expanded perlite, pumice, expanded pumice,
pumicite, expanded obsidian, and expanded volcanic ash. In one
embodiment, the adsorbent component is an adsorbent polymer, and
the functional filtration component is expanded perlite.
[0025] In one embodiment, the adsorbent component is an alkaline
earth silicate hydrate, and the functional filtration component is
biogenic silica. In one embodiment, the adsorbent component is an
alkaline earth silicate hydrate, and the functional filtration
component is a natural glass. In one embodiment, the adsorbent
component is an alkaline earth silicate hydrate, and the functional
filtration component is selected from the group consisting of
expanded perlite, pumice, expanded pumice, pumicite, expanded
obsidian, and expanded volcanic ash. In one embodiment, the
adsorbent component is an alkaline earth silicate hydrate, and the
functional filtration component is expanded perlite.
[0026] In one embodiment, the permeability of the filterable
composite adsorbent is greater than the permeability of a simple
mixture of the adsorbent component(s) and the functional filtration
component(s) (more preferably greater by 5% or more), wherein the
proportions of said adsorbent component(s) and said functional
filtration component(s) in said simple mixture are identical to
those used in the preparation of said filterable composite
adsorbent.
[0027] In one embodiment, the median particle diameter of the
filterable composite adsorbent is greater than the median particle
diameter of a simple mixture of the adsorbent component(s) and the
functional filtration component(s) (more preferably greater by 2%
or more), wherein the proportions of said adsorbent component(s)
and said functional filtration component(s) in said simple mixture
are identical to those used in the preparation of said filterable
composite adsorbent.
[0028] In one embodiment, the adsorbent component is selected from
the group consisting of silica gel; fumed silica; neutral clay;
alkaline clay; zeolite; solid catalyst; alumina, such as activated
alumina; adsorbent polymer, for example, expanded
polystyrene-divinylbenzene copolymer; and alkaline earth silicate
hydrate, such as calcium silicate hydrate and magnesium silicate
hydrate.
[0029] In another embodiment, the functional filtration component
is selected from the group consisting of biogenic silica, for
example diatomite; natural glass (such as expanded perlite, pumice,
expanded pumice, pumicite, expanded obsidian, and expanded volcanic
ash); buoyant glass (such as sand); synthetic glass (such as fiber
glass, controlled pore glass, foamed glass); buoyant polymer, for
example, a fibrous polymer (such as fibrous nylon, fibrous
polyester) or a powdered polymer (such as polyvinylchloride-acrylic
copolymer powder); and cellulose.
[0030] In another embodiment, the filterable composite adsorbent
has a permeability of about 0.001 to about 1000 darcy. In another
preferred embodiment, the filterable composite adsorbent has a
permeability of about 0.01 to about 30 Da.
[0031] In one embodiment, the filterable composite adsorbent is
prepared using a stationary bed furnace (e.g., muffle furnace, tray
furnace, travelling grate furnace) or a rotary kiln.
[0032] Another aspect of the present invention pertains to
compositions comprising a filterable composite adsorbent, as
described above. In one embodiment, the composition is in the form
of a powder. In another embodiment, the composition is in the form
of a sheet, pad, or cartridge. In another embodiment, the
composition is thermally sintered and/or chemically bonded in the
form of a rigid shape (e.g., disk, cylinder, plate, polyhedron). In
another embodiment, the composition is in the form of a monolithic
support or an aggregate support. In another embodiment, the
composition is in the form of a monolithic substrate or an
aggregate substrate.
[0033] Yet another aspect of the present invention pertains to
methods of adsorption and filtration which employ a filterable
composite adsorbent, as described above. In one embodiment, the
method of adsorption and filtration comprises the step of (i)
suspending a filterable composite adsorbent, as described above, in
a fluid containing suspended particulates or constituents to be
adsorbed, followed by the step of (ii) separating the filterable
composite adsorbent from the fluid.
[0034] In another embodiment, the method of adsorption and
filtration comprises the step of (i) suspending a filterable
composite adsorbent, as described above, in a fluid containing
suspended particulates or constituents to be adsorbed, followed by
the step of (ii) passing said fluid with suspended filterable
composite adsorbent through a filterable composite adsorbent, as
described above, supported on a septum.
[0035] In another embodiment, the method of adsorption and
filtration comprises the step of passing a fluid containing
suspended particles or constituents to be adsorbed through a
filterable composite adsorbent, as described above, supported on a
septum.
[0036] In another embodiment, the method of adsorption and
filtration comprises the step of passing a fluid containing
suspended particles or constituents to be adsorbed through a
filterable composite adsorbent, in the form of a rigid shape, as
described above.
[0037] In a embodiment, the fluid is a liquid (e.g., beer). In
another embodiment, the fluid is a molten solid (e.g., oils high in
saturated fats). In another embodiment, the fluid is a gas (e.g,
air).
[0038] Other methods of adsorption and filtration which employ a
filterable composite adsorbent include combinations of the above
methods.
[0039] Still another aspect of the present invention pertains to
methods for the preparation of filterable composite adsorbents
which employ microwave radiation. In one embodiment, one or more
adsorbent components are blended with one or more functional
filtration components, and microwave radiation applied to the
blend, thereby forming the filterable composite adsorbent.
[0040] As will become apparent, preferred features and
characteristics of one aspect of the invention are applicable to
any other aspect of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] A. Filterable Composite Adsorbents of the Present
Invention
[0042] The filterable composite adsorbents of the present invention
are suitable for use in filtration applications, and comprise one
or more adsorbent components which are intimately bound to one or
more functional filtration components. By the phrase "intimately
bound" is it meant that the components are intimately and directly
bound to each other without a binder material (although a fluxing
chemical may be used, see below).
[0043] The filterable composite adsorbents of the present invention
retain both the adsorptive properties of the adsorbent component
and the intricate and porous structure of a functional filtration
component, thus greatly enhancing the utility of the filterable
composite adsorbents in practical applications. The filterable
composite adsorbents of the present invention offer a spectrum of
permeabilities comparable to the range offered by their functional
filtration components.
[0044] Many methods for the separation of particles from fluids
employ porous filtration media, the intricate and porous structures
of which are particularly effective for the physical entrapment of
particles in filtration processes; hence, they are useful as
functional filtration components in the current invention. High
specific surface area and extremely small pore size are
characteristic features of adsorbents (e.g., silica gel, fumed
silica, etc.) which make them useful as adsorbent components in the
present invention.
[0045] In the filterable component adsorbents of the present
invention, adsorbent components are intimately bound to functional
filtration components, preferably by thermal sintering and/or
chemical bonding, and are not merely mixed or blended together.
Unlike the filterable composite adsorbents of the present
invention, such simple mixtures tend to segregate upon suspension
(e.g., in fluids) or conveyance or transport. The term "simple
mixture" is used herein in the conventional sense to mean
mechanical mixtures or blends (e.g., which have not been subjected
to thermal sintering and/or chemical bonding).
[0046] The filterable composite adsorbent of the present invention
may conveniently be considered to be an agglomerate of one or more
adsorbent components and one or more functional filtration
components. The term "agglomeration" is used herein in the
conventional sense to refer to any method or effect in which
particles are assembled into a coherent mass. One example of an
agglomeration method is thermal sintering, wherein particles are
caused to become a coherent mass (i.e., are intimately bound), and
therefore an "agglomerate," by heating without melting. Note that,
in thermal sintering, agglomeration does not proceed to the point
of forming a homogeneous medium (e.g., a ceramic). Thus, in the
filterable composite adsorbents of the present invention, adsorbent
component(s) and functional filtration component(s) and are
agglomerated and intimately bound, but retain those physical and
chemical properties of these components which are deemed to be
desirable in the resulting product, and therefore enhance the
overall properties of the resulting product.
[0047] 1. Adsorbent Components
[0048] Adsorbent components suitable for use in preparation of the
filterable composite adsorbents of the present invention are
microparticulate or colloidal adsorbent components which are
characterized by the property of having adsorbency. Preferred
adsorbent components have a specific surface area of about 300 to
about 1200 m.sup.2/g, having a high proportion of pores with a size
of less than about 50 nm.
[0049] The term "colloidal" is used herein to refer to adsorbent
particles having a particle size of less than about 1 .mu.m (and
typically greater than about 0.5 nm). The term "microparticulate"
is used herein to refer to adsorbent particles having an particle
size of about 1 .mu.m to about 500 .mu.m, but more commonly about 1
.mu.m to about 30 .mu.m.
[0050] In a preferred embodiment, the adsorbent component is
selected from the group consisting of silica gel; fumed silica;
neutral clay; alkaline clay; zeolite; solid catalyst; alumina, such
as activated alumina; adsorbent polymer, for example, expanded
polystyrene-divinylbenzene copolymer; and alkaline earth silicate
hydrate, such as calcium silicate hydrate and magnesium silicate
hydrate.
[0051] 2. Functional Filtration Components
[0052] Functional filtration components suitable for use in
preparation of the filterable composite adsorbents of the present
invention are characterized by a distinguishing porous and
intricate structure and buoyancy suitable for filtration. These
materials usually possess relatively large pore sizes especially
suitable for particle entrapment, thereby permitting mechanical
filtration and/or clarification by means of removal of
microparticulate or colloidal particulates.
[0053] In a preferred embodiment, the functional filtration
component is selected from the group consisting of biogenic silica
(for example, diatomite, rice hull ash, sponge spicules); buoyant
glass, for example natural glass (such as expanded perlite, pumice,
expanded pumice, pumicite, expanded obsidian, expanded volcanic
ash, other natural glasses, sand), synthetic glass (such as fiber
glass, controlled pore glass, foamed glass); buoyant polymer, for
example, a fibrous polymer (such as fibrous nylon, fibrous
polyester) or a powdered polymer (such as polyvinylchloride-acrylic
copolymer powder); and cellulose.
[0054] The term "biogenic silica" is used herein in the
conventional sense and refers to silica produced or brought about
by living organisms. A common example of biogenic silica is
diatomite, obtained from diatomaceous earth (also known as
kieselguhr), which is a sediment enriched in biogenic silica in the
form of the siliceous frustules (i.e., shells or skeletons) of
diatoms. Diatoms are a diverse array of microscopic, single-celled
golden brown algae of the class Bacillariophyceae, which possess an
ornate siliceous skeleton (i.e., fustule) of varied and intricate
structure consisting of two valves which, in the living diatom, fit
together much like a pill box. The morphology of the fustules
varies widely among species and serves as the basis for taxonomic
classification; over at least 2,000 distinct species are known. The
surface of each valve is punctuated by a series of openings that
comprise the complex fine structure of the fustule and impart a
design that is distinctive to individual species. The size of
typical frustules ranges from 0.75 to 1,000 .mu.m, although the
majority are in the range of 10 to 150 .mu.m. These frustules are
sufficiently durable to retain much of their porous and intricate
structure virtually intact through long periods of geologic time
when preserved in conditions that maintain chemical equilibrium.
Other sources of biogenic silica are known, as many plants,
animals, and microorganisms provide concentrated sources of silica
with unique characteristics. For example, rice hulls contain
sufficient silica that they are commercially ashed for their
siliceous residue, a product known familiarly as "rice hull ash."
Certain sponges are also concentrated sources of silica, the
remnants usually occurring in geologic deposits as acicular
spicules.
[0055] The term "natural glass" is used herein in the conventional
sense and refers to natural glasses, commonly referred to as
volcanic glasses, which are formed by the rapid cooling of
siliceous magma or lava. Several types of natural glasses are
known, including, for example, perlite, pumice, pumicite, obsidian,
and pitchstone. Prior to processing, perlite is generally gray to
green in color with abundant spherical cracks which cause it to
break into small pearl-like masses. Pumice is a very lightweight
glassy vesicular rock. Obsidian is generally dark in color with a
vitreous luster and a characteristic conchoidal fracture.
Pitchstone has a waxy resinous luster and is frequently brown,
green, or gray. Volcanic glasses such as perlite and pumice occur
in massive deposits and find wide commercial use. Volcanic ash,
often referred to as tuff when in consolidated form, consists of
small particles or fragments which are often in glassy form; as
used herein, the term natural glass encompasses volcanic ash.
[0056] Most natural glasses are chemically equivalent to rhyolite.
Natural glasses which are chemically equivalent to trachyte,
dacite, andesite, latite, and basalt are known but are less common.
The term obsidian is generally applied to massive natural glasses
that are rich in silica. Obsidian glasses may be classified into
subcategories according to their silica content, with rhyolitic
obsidians (containing typically about 73% SiO.sub.2 by weight) as
the most common (Berry, 1983).
[0057] Perlite is a hydrated natural glass containing typically
about 72-75% SiO.sub.2, 12-14% Al.sub.2O.sub.3, 0.5-2%
Fe.sub.2O.sub.3, 3-5% Na.sub.2O, 4-5% K.sub.2O, 0.4-1.5% CaO (by
weight), and small concentrations of other metallic elements.
Perlite is distinguished from other natural glasses by a higher
content (2-5% by weight) of chemically bonded water, the presence
of a vitreous, pearly luster, and characteristic concentric or
arcuate onion skin-like (i.e., perlitic) fractures.
[0058] Perlite products are often prepared by milling and thermal
expansion, and possess unique physical properties such as high
porosity, low bulk density, and chemical inertness. Expanded
perlite has been used in filtration applications since about the
late 1940's (Breese and Barker, 1994). Conventional processing of
perlite consists of comminution (crushing and grinding), air size
classification, thermal expansion, and air size classification of
the expanded material to meet the specifications of the finished
product. For example, perlite ore is crushed, ground, and
classified to a predetermined particle size range (e.g., passing 30
mesh), then classified material is heated in air at a temperature
of 870-1100.degree. C. in an expansion furnace, where the
simultaneous softening of the glass and vaporization of contained
water leads to rapid expansion of glass particles to form a frothy
glass material with a bulk volume up to 20 times greater than that
of the unexpanded ore. Often, the expanded perlite is then air
classified and optionally milled to meet the size specification of
a desired product. The presence of chemically bonded water in other
natural glasses (for example, pumice, obsidian, and volcanic ash)
often permits "thermal expansion" in a manner analogous to that
commonly used for perlite. The resulting products are commonly
referred to as expanded natural glasses (i.e., expanded pumice,
expanded obsidian, and expanded volcanic ash, respectively).
[0059] Pumice is a natural glass characterized by a mesoporous
structure (e.g., having pores or vesicles with a size up to about 1
mm). The highly porous nature of pumice gives it a very low
apparent density, in many cases allowing it to float on the surface
of water. Most commercial pumice contains from about 60 to about
70% SiO.sub.2 by weight. Pumice is typically processed by milling
and classification (as described above for perlite), and products
are primarily used as lightweight aggregates and also as abrasives,
absorbents, and fillers. Unexpanded pumice and thermally expanded
pumice (prepared in a manner analogous to that used for perlite)
may also be used as filter aids in some cases (Geitgey, 1979), as
can volcanic ash.
[0060] 3. Examples of Filterable Composite Adsorbents
[0061] The appropriate selection of adsorbent components and
functional filtration components of a filterable composite
adsorbents is determined by the specific application intended. For
example, in a filtration process that demands exceptional clarity
but tolerates slower flow rate, a filterable composite adsorbent
product of low permeability is preferred, whereas in a filtration
process that demands high flow rate but does not require
exceptional clarity, a filterable composite adsorbent product of
high permeability is preferred. Similar reasoning applies to the
choice of adsorbent components, and to the composite adsorbent
products when used in conjunction with other materials, or when
preparing mixtures containing the products.
[0062] Silica gel adsorbents are commonly used in the chillproofing
of beer. Beer contains certain high molecular weight proteins
(e.g., anthocyanodins) that precipitate when finished beer is
chilled, creating a haze in beer that is deemed undesirable by
brewers. By adding a silica gel adsorbent to the beer before
filtration, a large concentration of these proteins are adsorbed by
the silica gel, but the silica gel-protein complexes must be
thoroughly removed during a subsequent filtration, usually by means
of a porous filtration media. The porous filtration media is also
used to remove yeast and other turbid particulate matter from the
brewing process. Removing the silica gel-protein complexes from the
beer significantly adds to the filtration burden such that the
efficiency of the porous filtration media is reduced.
[0063] In one embodiment of the present invention, a silica gel
adsorbent of a variety useful in chillproofing of beer, is
thermally sintered to expanded perlite, a natural glass that is
commonly used as a porous filtration media. The resulting
filterable composite adsorbent has both the properties of the
chillproofing obtained from the silica gel adsorbent, as well as
the filtration properties of the expanded perlite porous filtration
media. The filterable composite adsorbent is capably of performing
both the functions of protein adsorption to reduce chill haze, as
well as filtration of the other undesirable constituents of the
beer. To maximize the adsorption of proteins contributing to chill
haze, a preferred mode of using this particular filterable
composite adsorbent is through body feeding in addition to
precoating.
[0064] Bleaching clay (i.e., a neutral or alkaline form of clay) is
commonly used to remove color bodies from edible oils, which
commonly contain undesirable chlorophylls when the oils are pressed
from botanical sources. However, bleaching clay is a very fine
powder, and must be separated from the oil after adsorption has
taken place; this separation is a slow and tedious process.
[0065] In another embodiment of the present invention, an activated
bleaching clay, of a variety useful in decolorizing edible
vegetable oils, is thermally sintered to expanded perlite, a
natural glass product that is commonly used as a porous filtration
media. The resulting filterable composite adsorbent has both the
bleaching properties of the activated clay adsorbent, as well as
the filtration properties of the expanded perlite porous filtration
media. The ease of adsorbent use and the utility and effectiveness
of filtration are both greatly improved. Again, the preferred mode
of using this particular filterable composite adsorbent is through
body feeding in addition to precoating.
[0066] B. Methods for Characterizing the Filterable Composite
Adsorbents of the Present Invention
[0067] The filterable composite adsorbents of the present invention
possess unique properties, as they are comprised of both an
adsorbent component as well as a functional filtration component.
These filterable composite adsorbents retain both the adsorbent
properties of the adsorbent component and the intricate and porous
structure that is characteristic of the functional filtration
component as evidenced by the media having suitable permeability in
ranges useful to filtration.
[0068] Important properties of the filterable composite adsorbents
of the present invention, and suitable methods for their
determination, are described in detail below.
[0069] 1. Permeability
[0070] The filterable composite adsorbents of the present invention
may be processed to provide a range of filtration rates, which are
closely related to their permeability, P. Permeability is often
reported in units of darcies, commonly abbreviated "Da"; 1 darcy
corresponds to the permeability through a filter medium 1 cm thick
which allows 1 cm.sup.2 of fluid with a viscosity of 1 centipoise
to pass through an area of 1 cm.sup.2 in 1 sec under a pressure
differential of 1 atm (i.e., 101325 kPa). Permeability is readily
determined (European Brewery Convention 1987) using a specially
constructed device designed to form a filter cake on a septum from
a suspension of functional filtration media in water, and then
measuring the time required for a specified volume of water to flow
through a measured thickness of filter cake of known
cross-sectional area. The principles have been previously derived
for porous media from Darcy's law (Bear, 1988), and so an array of
alternative devices and methods are in existence that correlate
well with permeability. Most functional filtration media suitable
for microfiltration, such as diatomite and perlite products that
are commercially available span a wide range of permeability, from
about 0.001 Da (more typically 0.05 Da) to over 30 Da, while those
suitable for coarse filtration, such as sand, have much greater
permeabilities of approximately 1000 Da or more.
[0071] The filterable composite adsorbents of the present invention
offer a spectrum of permeabilities comparable to the range offered
by their functional filtration components.
[0072] Evidence of the intimate binding of the adsorbent
component(s) and the functional filtration component(s), and thus
the formation of the filterable composite adsorbent may generally
be provided by observing a larger permeability for the filterable
composite adsorbent (e.g., after thermal sintering and/or chemical
bonding, and unmilled, i.e., without further attrition or
classification) than for the simple mixture of its components
(i.e., prior to thermal sintering and/or chemical bonding).
[0073] For example, if a simple mixture of an adsorbent component
and a functional filtration component (having permeabilities of
0.71 Da and 9.30 Da, respectively) has a permeability, P(a+b), of
2.96 Da, and the filterable composite adsorbent prepared from this
simple mixture has a permeability, P(c), of 7.43 Da, then the
increase in permeability is evidence of agglomeration. Preferably,
P(c) is greater than P(a+b) by 5% or more, more preferably 10% or
more, yet more preferably 20% or more.
[0074] The selection of filtration permeability for a specific
filtration process depends on the flow rate and degree of fluid
clarification required for the particular application. In many
cases, the flow of fluid through a functional filtration component
is closely related to the nature of the functional filtration
component's porosity. Within a given family of functional
filtration components of the same kind, those of low permeability
have smaller pores capable of providing greater clarity because
smaller particles can be retained during the filtration process,
whereas those of high permeability have larger pores capable of
providing greater fluid flow, but usually at the expense of the
ability to remove particles as small as those removed by their low
permeability counterparts.
[0075] 2. Particle Size
[0076] An important characteristic of the filterable composite
adsorbent of the present invention relates to agglomeration of the
component particles, preferably through thermal sintering and/or
chemical bonding. One method for quantifying the degree of
agglomeration involves determining the difference in particle size
distribution between the components (i.e., before agglomeration)
and the resulting filterable composite adsorbent.
[0077] The preferred method for determining particle size
distribution employs laser diffraction.
[0078] The preferred instrument for determining the particle size
distribution of the advanced composite filtration media, or its
components, is a Leeds & Northrup Microtrac Model X-100. The
instrument is fully automated, and the results are obtained using a
volume distribution formatted in geometric progression of 100
channels, running for 30 seconds with the filter on. The
distribution is characterized using an algorithm to interpret data
from the diffraction pattern which assumes the particles have
spherical shape characterized by a diameter, D. A median particle
diameter is identified by the instrument as D.sub.50, that is, 50%
of the total particle volume is accounted for by particles having a
diameter equal to or less than this value.
[0079] Evidence of agglomeration and thus the formation of the
filterable composite adsorbent (i.e., wherein the adsorbent
component and the functional filtration component are intimately
bound) may be provided by calculating the weighted average of the
median particle diameter of the simple mixture of the adsorbent
component and the functional filtration component (i.e., prior to
thermal sintering and/or chemical bonding) and the median particle
diameter of the filterable composite adsorbent prepared using that
mixture (e.g., after thermal sintering and/or chemical bonding, and
unmilled, i.e., without further attrition or classification).
[0080] For example, agglomeration has occurred when the weighted
average, D.sub.50(a+b), of the median particle diameter of the
adsorbent component, D.sub.50(a), and the median particle diameter
of the functional filtration component, D.sub.50(b), is less than
the median particle diameter of the filterable composite adsorbent,
D.sub.50(c). For example, if D.sub.50(a) is equal to 24.61 .mu.m
and comprises 67% by weight of the advanced composite filtration
media, and if D.sub.50(b) is equal to 2.29 .mu.m and comprises 33%
by weight of the advanced composite filtration media, then, 1 D 50
( a + b ) = [ ( 0.667 .times. 24.61 ) + ( 0.333 .times. 2.29 ) ] =
17.17 m
[0081] If the actual measured median particle diameter of the
filterable composite adsorbent, D.sub.50(c), is equal to 26.47
.mu.m, then agglomeration has occurred, since D.sub.50(a+b) is less
than D.sub.50(c). Preferably, D.sub.50(c) is greater than
D.sub.50(a+b) by 1% or more, more preferably 2% or more, more
preferably 5% or more, still more preferably 10% or more, yet more
preferably 20% or more.
[0082] The application of the particle size method is most
appropriate when particles of the adsorbent component, the
functional filtration component, and the filterable composite
adsorbent all have approximately equal densities and approximate
the spherical shape of particles assumed by the algorithm. In cases
where the adsorbent component is fibrous in nature, the more
general permeability method is preferred.
[0083] C. Methods for Preparing the Filterable Composite Adsorbent
of the Present Invention
[0084] The filterable composite adsorbents of the present invention
comprise one or more microparticulate or colloidal adsorbent
components which are intimately bound to one or more functional
filtration components. One convenient method of preparing
filterable composite adsorbents of the present invention is by
blending an adsorbent component with a functional filtration
component, followed by treatment of the blend so that the adsorbent
component(s) are intimately bound to the functional filtration
component(s). An example of a suitable treatment which may be used
is chemical bonding, and may include the practice of thermal
sintering.
[0085] In one preferred method, filterable composite adsorbents of
the present invention are prepared by blending an adsorbent
component with a functional filtration component, followed by the
application of heat to cause thermal sintering (i.e., chemical
bonding) to occur. Another convenient method of preparing
filterable composite adsorbents of the present invention is by
blending an adsorbent component with a functional filtration
component, followed by the application of heat and/or radiation,
and optionally in the presence of a fluxing chemical (e.g., soda
ash), to cause the formation of strong chemical bonds between the
adsorbent component and the functional filtration component.
[0086] The adsorbent component and the functional filtration
component may be mixed in any proportion, and the proportions
employed are determined by the selected adsorbent component and
functional filtration component and by the filterable composite
adsorbent sought. For example, at the adsorbent component-poor end
of the spectrum, the adsorbent component may typically comprise as
little as 0.1 to 5% by weight (i.e., of the simple mixture
comprising the adsorbent component and the functional filtration
component, prior to treatment), whereas, at the adsorbent
component-rich end of the spectrum, the functional filtration
component may typically comprise as much as 70 to 99% by weight
(i.e., of the simple mixture comprising the adsorbent component and
the functional filtration component, prior to treatment).
[0087] Blending of the adsorbent component with a functional
filtration component, prior to treatment (e.g., thermal sintering
and/or chemical bonding), may be readily accomplished using, for
example, a mechanical mixer, for a suitable length of time to allow
the components to become thoroughly mixed. More intimate blends may
be obtained when the components are introduced in a fluidized form,
for example, as a liquid slurry.
[0088] For thermal sintering, heat may be applied using, for
example, a conventional oven, microwave oven, infrared oven, muffle
furnace, kiln, or a thermal reactor, in ambient atmospheres such
as, for example, air, or artificial atmospheres such as, for
example, nitrogen (i.e., N.sub.2) or oxygen (i.e., O.sub.2) at
temperatures typically ranging from 100 to 2500.degree. F. (i.e.,
40 to 1400.degree. C.) and at pressures ranging from 0.1 to 50 atm
(i.e., 1 to 5000 kPa). Heat treatment parameters, such as
temperature and duration, are determined by the selected adsorbent
component and functional filtration component and by the filterable
composite adsorbent sought. For example, durations may range from
about 1 ms (e.g., in fluidized bed reactors) to about 10 hours
(e.g., in conventional furnaces).
[0089] Specific properties of filterable composite adsorbents can
be further modified by further physical or chemical reaction of the
media after the initial filterable composite adsorbent has been
made, especially to enhance one or more particular properties (for
example, solubility or surface characteristics), or to yield a new
product with a specialized use. Examples of such further
modifications include, for example, hydration, acid washing,
surface treatment, and/or organic derivatization.
[0090] 1. Hydration
[0091] Another class of filterable composite adsorbent products may
be prepared from the filterable composite adsorbents described
above by washing, rinsing, immersing, or otherwise contacting with
water (i.e., H.sub.2O), followed by drying to achieve a suitable
degree of hydration (e.g., 0.1 to 60% water by weight). For
example, it may be desirable to hydrate a sintered silica gel
filterable composite adsorbent to yield a filterable composite
adsorbent product with enhanced adsorptive properties.
[0092] 2. Acid Washing
[0093] Another class of filterable composite adsorbent products may
be prepared from the filterable composite adsorbents described
above by washing with an acidic substance, followed by rinsing with
deionized water to remove deionized water to remove residual acid,
and subsequent drying. Acid washing of filterable composite
adsorbent products may be beneficial in reducing the concentration
of soluble contaminants, e.g., iron or aluminum, or in activating
the adsorbent. Suitable acids include mineral acids, for example,
sulfuric acid (i.e., H.sub.2SO.sub.4), hydrochloric acid (i.e.,
HCl), phosphoric acid (ie., H.sub.3PO.sub.4), or nitric acid (i.e.,
HNO.sub.3), as well as organic acids, for example, citric acid
(i.e., C.sub.6H.sub.8O.sub.7) or acetic acid (i.e.,
CH.sub.3COOH).
[0094] 3. Surface Treatment
[0095] Another class of filterable composite adsorbent products may
be prepared by treatment of the filterable composite adsorbents
described above, for example, by silanization, thereby modifying
the product's surface such that it is rendered either more
hydrophobic or more hydrophilic. Silanization is of particular
utility if either the adsorbent components or functional filtration
components are siliceous, or are polymeric in nature.
[0096] For example, the filterable composite adsorbent may be
placed in a plastic vessel, and a small quantity of
dimethyldichlorosilane (i.e., SiCl.sub.2(CH.sub.3).sub.2) or
hexamethyldisilazane (i.e.,
(CH.sub.3).sub.3Si--NH--Si(CH.sub.3).sub.3) is added to the vessel.
Reaction is allowed to take place at the surface in the vapor phase
over a 24 hour period, resulting in more hydrophobic products. Such
products have particular utility in applications involving
hydrocarbons and oils.
[0097] Similarly, the filterable composite adsorbent can be
reacted, for example, by suspending it in a solution containing 10%
(w/v) aminopropyltriethoxysilane (i.e., C.sub.9H.sub.23NO.sub.3Si)
in water, refluxing at 700.degree. C. for 3 hours, filtering the
mixture, and drying the remaining solids to obtain more hydrophilic
products. Such products have particular utility in applications
involving aqueous systems, and permit further derivatization of the
product, having converted terminal hydroxyl (i.e., --OH) functional
groups of the advanced composite filtration media product surface
to aminopropyl groups (i.e., --(CH.sub.2).sub.3NH.sub.2).
[0098] 4. Organic Derivatization
[0099] Hydrophilic modified filterable composite adsorbent products
can be further reacted to bind organic compounds, for example, a
protein. The filterable composite adsorbent may thereby serve as a
support for the immobilization of organic compounds. So modified,
the product has utility in applications such as biochemical
purification. A number of other reactions pertaining to
derivatization of siliceous and polymeric products have been
previously described (Hermanson, 1992). However, derivatization of
the filterable composite adsorbents of the present invention yields
modified filterable composite adsorbent products (which are within
the scope of the present invention) with substantially superior
efficacy as a result of the intimate binding of one or more
adsorbent components with one or more functional filtration
components.
[0100] D. Methods of Using the Filterable Composite Adsorbent of
the Present Invention
[0101] The filterable composite adsorbents of the present invention
are useful in many of the same applications as currently available
adsorbents, but offer the added properties of functional filtration
media, such as, for example, increased permeability, low
centrifuged wet density, uniquely shaped particles (e.g., fibers)
as well as improved efficiency and/or economy, which are
particularly valuable characteristics for adsorbent
applications.
[0102] The filterable composite adsorbent of the present invention,
and their further modifications, may be used in filtration
applications in a manner analogous to that of porous filtration
media. Filterable composite adsorbents may be applied to a septum
to improve clarity and increase flow rate in filtration processes
in a step sometimes referred to as "precoating," or added directly
to a fluid as it is being filtered to reduce the loading of
undesirable particulate at the septum while maintaining a designed
liquid flow rate, in a step often referred to as "body feeding."
Depending on the particular separation involved, filterable
composite adsorbents may be used in precoating, body feeding, or
both. The working principles involved with porous media filtration
have been developed over many years, and have recently been
reviewed in detail from both practical perspectives (Cain, 1984;
Kiefer, 1991) as well as from their underlying theoretical
principles (Bear, 1988; Nordn, 1994).
[0103] The filterable composite adsorbents of the present invention
can be shaped, molded, extruded, or sintered into permeable sheets,
plates, disks, polyhedrons, or other formed shapes that have
adsorbent properties. Fluids can then be passed through these
modifications of the filterable composite adsorbents to achieve
both filtration and adsorption.
[0104] The filterable composite adsorbents of the present invention
may be used in conjunction with other media (e.g., different porous
filtration media products) to form a filter aid composition for use
in filtration applications and/or to further modify or optimize a
filtration process. For example, mixtures of the filterable
composite adsorbent with, for example, diatomite, expanded perlite,
pumicite, natural glass, cellulose, activated charcoal, clay, or
other materials, are useful filter aid compositions. Sometimes,
these blends are more elaborate, and enable the blend to be formed
into sheets, pads, cartridges, or monolithic or aggregate media
capable of being used as supports or substrates.
[0105] The appropriate selection of which composition or
modification of a filterable composite adsorbents is preferred is
determined by the specific application. For example, in a
filtration process that demands exceptional clarity but tolerates
slower flow rate, a filterable composite adsorbent product of low
permeability is preferred, whereas in a filtration process that
demands high flow rate but does not require exceptional clarity, a
filterable composite adsorbent product of high permeability is
preferred. Similar reasoning applies to the choice of adsorbent
components, and to the composite adsorbent products when used in
conjunction with other materials, or when preparing mixtures
containing the products. The quantity of product which is used is
similarly determined by the specific process to which it is
applied.
[0106] The silanized hydrophobic or hydrophilic filterable
composite adsorbent products are desirable when these properties
further improve the filtration performance, owing to their greater
compatibility with other materials or ingredients in a specific
application.
[0107] The composite products of the present invention can also be
useful in applications other than filtration, since adsorbents or
filtration media can be useful in applications that do not
necessarily depend explicitly on either conventional adsorption or
filtration. For example, substances such as silica gel, fumed
silica, neutral clay, alkaline clay, zeolites, catalysts, polymers,
and alkaline earth silicate hydrates can be used as fillers, and
biogenic silica, natural glass, expanded perlite, pumice, expanded
pumice, pumicite, expanded obsidian, expanded volcanic ash, buoyant
glass, buoyant polymer, and cellulose can also be used as fillers.
Thus, the filterable composite adsorbent products of the present
invention may be useful as composite products used in numerous
filler applications. For example, they may be used to alter the
appearance or properties of paints, enamels, lacquers, and related
coatings and finishes. The products may also be useful in paper
formulations and paper processing applications, to provide
antiblock or reinforcing properties to polymers, as abrasives,
buffing, or polishing compounds, or other filler applications. In
particular, the use of composites of the present invention offer
increased flexibility for the use of these materials in filler
applications. The composites of the present invention are also
useful in the processing and preparation of a variety of catalysts,
as chromatographic supports, and as other support media. In such
other applications, the filterable composite adsorbent may be
blended with other ingredients to make monolithic or aggregate
media useful as supports (e.g., for microbe immobilization),
substrates (e.g., for enzyme immobilization), or in the preparation
of catalysts.
[0108] Many other modifications and variations of the invention as
hereinbefore set forth can be made without departing from the
spirit and scope thereof and therefore only such limitations should
be imposed as are indicated by the appended claims.
E. EXAMPLES
[0109] Several filterable composite adsorbents of the present
invention, and methods for preparing them, are described in the
following examples, which are offered by way of illustration and
not by way of limitation.
Example 1
[0110] Silica Gel/Expanded Perlite Filterable Composite
Adsorbent
[0111] A mixture containing 60.6% (w/w) expanded perlite as a
functional filtration component (Harborlite.RTM. 2000S, Harborlite
Corporation, Lompoc, Calif.), 36.4% (w/w) silica gel as an
adsorbent component (Britesorb.RTM. 100, PQ Corporation, Valley
Forge, Pa., first dried at 110.degree. C. for 2 hours, with the
microparticulates then dispersed with gentle grinding), and 3%
(w/w) milled soda ash (Na.sub.2CO.sub.3) as a chemical sintering
aid, were placed in a sealed plastic bag and shaken for
approximately 5 minutes to thoroughly blend the ingredients. The
mixture was then placed in a muffle furnace at 800.degree. C. in
air for 20 minutes, then the furnace door was opened and the
material raked to disperse the particles for even sintering, and
allowed to continue to heat in the muffle furnace at 800.degree. C.
in air for an additional 20 minutes.
[0112] The product was then removed and allowed to cool to room
temperature. Upon cooling, the material was brushed through a 30
mesh (ie., with nominal openings of 600 .mu.m) screen to disperse
the particles, thus resulting in the filterable composite adsorbent
product.
[0113] Permeabilities of the expanded perlite and silica gel were
determined to be 9.30 and 0.71 Da, respectively, and a simple
mixture of the two (i.e., without intimate binding) was determined
to have a permeability of 2.96. The filterable composite adsorbent,
however, had a permeability of 7.43, substantially greater than
that of the simple mixture, and thereby greatly increasing the
filterability and utility of the silica gel adsorbent.
[0114] In addition to studying the improved filterability,
verification of adsorbent activity of this example of the present
invention was performed using a saturated ammonium sulfate
precipitation limit test, as described below.
[0115] One particularly useful method of determining the
effectiveness of chillproofing adsorbents for beer is to titrate
beer with a solution of saturated ammonium sulfate (i.e.,
(NH.sub.4).sub.2SO.sub.4), thereby precipitating proteins of high
molecular weight involved in haze formation, and measuring the
turbidity produced.
[0116] In practice, a solution of saturated ammonium sulfate is
prepared by dissolving 100 g of ammonium sulfate in about 100 mL of
deionized water in a flask at room temperature, shaking it well,
and allowing the solution to stand for 16 hours. The saturated
solution will normally have undissolved ammonium sulfate crystals
at the bottom of the flask after standing, and the working
saturated solution is decanted from the top. A 2.5 g sample of the
material to be tested is placed in a 250 mL Erlenmeyer flask, 100
mL of decarbonated beer added, and the mixture shaken on a platform
shaker for 30 minutes. The mixture is then filtered by vacuum
through Whatman No. 5 filter paper on a Buchner funnel, and a 50 mL
aliquot is transferred into a wide-mouth titration flask. The
turbidity is first measured prior to titration using a turbidimeter
(Hach Model 2100 AN). From a 50 mL Class A buret, saturated
ammonium sulfate solution is added to the flask in 1.00 mL
increments, the solution swirled to mix well before each
measurement, and the turbidity measured. After each measurement,
the solution is poured back into the titration flask, and another
1.00 mL increment is added. The point in the titration in which
turbidity becomes substantially pronounced represents the endpoint.
At least five additional endpoints should be measured in order to
increase the accuracy of determining the endpoint.
[0117] For convenience, the results can be expressed in units of
SASPL ("saturated ammonium sulfate precipitation limit"), which are
equal to the milliliters of saturated ammonium sulfate solution
required to reach the endpoint. For an untreated beer having a
known SASPL, the greater the SASPL is after treatment with an
adsorbent, the more effective the adsorbent is.
[0118] For this example of the present invention, untreated beer
was determined to have 6 SASPL units, and treatment with expanded
perlite alone increased the SASPL only to 6.5 units, while
treatment with silica gel alone increased the SASPL to 12.5 units.
Treatment of the beer with the filterable composite adsorbent of
this example increased the SASPL to 9.5 units. The combining of
these features of chillproofing ability with substantially greater
permeability, as shown above, shows that the filterable composite
adsorbent clearly offers greater utility and economy to this
application.
Example 2
[0119] Clay/Expanded Perlite Filterable Composite Adsorbent
[0120] A 10 g sample of activated clay was selected as the
adsorbent component (Filtrol.RTM. 105, Engelhard Corporation,
Jackson, Miss.), was dispersed in sufficient deionized water to
result in a 5% (w/v) slurry, and mixed for 1.5 hours using magnetic
stirring to aid in dispersal of the clay microparticles. To the
slurry were added 10 g of expanded perlite as the functional
filtration component (Harborlite.RTM. 635, Harborlite Corporation,
Lompoc, Calif.), 0.5 g of pulverized soda ash (Na.sub.2CO.sub.3) as
a chemical sintering aid, and the mixture was further stirred for
15 minutes. The contents were then placed in a conventional
microwave oven and dried at high power, which took approximately 20
minutes. The resulting cake was brushed through a mesh screen
(i.e., with nominal openings of 600 .mu.m) to disperse the
particles of the filterable composite adsorbent.
[0121] Permeabilities of the expanded perlite and activated clay
were determined to be 1.36 Da and 0.01 Da, respectively, and a
simple mixture (ie., without intimate binding) was determined to
have a permeability of 0.25 Da. The filterable composite adsorbent,
however, had a permeability of 0.37 Da, greater than that of the
simple mixture, and thereby increasing the filterability and
utility of the activated clay adsorbent.
Example 3
[0122] Calcium Silicate Hydrate/Buoyant Polymer Filterable
Composite Adsorbent
[0123] A 20 g sample of calcium silicate hydrate product
(Micro-Cel.RTM. E, Celite Corporation, Lompoc, Calif.) was selected
as an adsorbent component, and spread thinly over a flat plastic
surface. Using a 140 mesh (ie., with nominal openings of 106 .mu.m)
screen, 10 g of polyvinylchloride-acrylic copolymer (Geon.RTM.
Resin 138, Geon, Avon Lake, Ohio) were brushed lightly over the
surface of the calcium silicate hydrate layer. The resulting
mixture was collected and further mixed in a sealed plastic bag by
shaking for 5 minutes, and the mixture was then heated in an oven
at 120.degree. C. in air for 1 hour. The resulting material was
removed from the oven, cooled, and screened through a 30 mesh
(i.e., with nominal openings of 600 .mu.m) screen to disperse the
particles, thus resulting in the filterable composite
adsorbent.
[0124] In this example, the functional filtration component was
formed concurrently with the filterable composite adsorbent
product. The median particle diameter of the calcium silicate
hydrate adsorbent component and copolymeric functional filtration
component were 24.61 .mu.m and 2.29 .mu.m, respectively, and
weighted median particle diameter of a simple mixture, representing
the proportions described, calculates to 17.17 .mu.m. The
filterable composite adsorbent product, however, had a median
particle diameter of 26.47, thereby increasing the filterability
and utility of the calcium silicate hydrate adsorbent.
Example 4
[0125] Silica Gel/Biogenic Silica Filterable Composite
Adsorbent
[0126] A mixture containing 48.5% (w/w) diatomite (Celite.TM. 500,
Celite Corporation, Lompoc, Calif.) as a functional filtration
component, 48.5% (w/w) silica gel as an adsorbent component
(Sil-Proof BG-6, Millenium Corporation, Baltimore, Md.) and 2.9%
(w/w) milled soda ash (Na.sub.2CO.sub.3) as a chemical sintering
aid, were placed in a plastic container and shaken for 30 minutes
using a paint mixer (Red Devil Model No. 5410-0H) to thoroughly
blend the ingredients. The mixture was then heated using a rotary
tube furnace (Model No. HOU-3D 18-RT-28, Harper Electric Furnace
Corporation, Lancaster, N.Y.) set at an inclination angle of
4.degree., 882.degree. C. and a rotation speed of 3.5 revolutions
per minute. Upon exiting the rotary tube furnace, the material was
allowed to cool to room temperature and then dispersed by passage
through a 30 mesh (i.e., nominal openings of 60 .mu.m screen) in
order to obtain the filterable composite adsorbent material.
[0127] Permeabilities of the diatomite and silica gel were
determined to be 0.048 and 0.011 Da respectively, and a simple
mixture of the two (i.e., without intimate binding) was determined
to have a permeability of 0.064 Da. The filterable composite
adsorbent, however, has a permeability of 0.349 Da, substantially
greater than that of the simple mixture, and thereby greatly
increasing the filterability and utility of the silica gel
adsorbent.
[0128] In addition to studying the improved filterability,
verification of adsorbent activity of this example of the present
invention was performed using a saturated ammonium sulfate
precipitation test, as described below.
[0129] One useful method of determining the effectiveness of
chillproofing adsorbents for beer is to add a solution of saturated
ammonium sulfate (i.e., (NH.sub.4).sub.2SO.sub.4), thereby
precipitating involved in haze formation, and measuring the
turbidity produced.
[0130] In practice, a solution of saturated ammonium sulfate is
prepared by dissolving 100 g of ammonium sulfate in about 100 mL of
deionized water in a flask at room temperature, shaking it well,
and allowing the solution to stand for 16 hours. The saturated
solution will normally have undissolved ammonium sulfate crystals
at the bottom of the flask after standing, and the working
saturated solution is decanted from the top. A 0.1 g sample of the
material to be tested is placed in a 250 ml Erlenmeyer flask, 200
mL of decarbonated beer added, and the mixture shaken on a platform
shaker for 30 minutes. The mixture is then filtered by vacuum
through Whatman No. 5 filter paper on a Buchner funnel, and a 50 mL
aliquot is transferred into a 125 mL Erlenmeyer flask. The
turbidity is first measured prior to addition of saturated ammonium
solution using a turbidimeter (Hach model 2100 AN). From a 50 mL
graduated cylinder, 30 mL of saturated ammonium sulfate solution is
added to the flask, the mixture is swirled in order to mix well,
and the mixture is then allowed to stand for 10 minutes. After 10
minutes, the turbidity of the mixture is measured. For an untreated
beer having a known turbidity after saturated ammonium sulfate
solution, the lower the turbidity is after treatment with an
adsorbent, the more effective the adsorbent is.
[0131] For this example of the present invention, untreated beer
(original, degassed turbidity 86.0 NTU) was determined to have a
turbidity of 474 NTU after saturated ammonium sulfate solution
addition, while treatment with silica gel alone resulted in a beer
with a turbidity of 203 NTU. Treatment of the beer with the
filterable composite adsorbent of this example resulted in a
turbidity of 299 NTU. The combining of these features of
chillproofing ability with substantially greater permeability, as
shown above, shows that the filterable composite adsorbent clearly
offers greater utility and economy to this application.
Example 5
[0132] Fumed Silica/Biogenic Silica Filterable Composite
Adsorbent
[0133] A portion of fumed silica, as an adsorbent component, a
portion of biogenic silica as a functional filtration component,
and optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 6
[0134] Fumed Silica/Expanded Perlite Filterable Composite
Adsorbent
[0135] A portion of fumed silica, as an adsorbent component, a
portion of expanded perlite as a functional filtration component,
and optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 7
[0136] Neutral Clay or Alkaline Clay/Biogenic Silica Filterable
Composite Adsorbent
[0137] A portion of neutral clay or alkaline clay, as an adsorbent
component, a portion of biogenic silica as a functional filtration
component, and optionally a portion of a chemical sintering aid,
are mixed and thoroughly blended. The mixture is then heated and
thermally sintered. The resulting agglomerate product is then
cooled, and optionally screened according to particle size, to
yield the desired filterable composite adsorbent.
Example 8
[0138] Neutral Clay or Alkaline Clay/Expanded Perlite Filterable
Composite Adsorbent
[0139] A portion of neutral clay or alkaline clay, as an adsorbent
component, a portion of expanded perlite as a functional filtration
component, and optionally a portion of a chemical sintering aid,
are mixed and thoroughly blended. The mixture is then heated and
thermally sintered. The resulting agglomerate product is then
cooled, and optionally screened according to particle size, to
yield the desired filterable composite adsorbent.
Example 9
[0140] Zeolite/Biogenic Silica Filterable Composite Adsorbent
[0141] A portion of zeolite, as an adsorbent component, a portion
of biogenic silica as a functional filtration component, and
optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 10
[0142] Zeolite/Expanded Perlite Filterable Composite Adsorbent
[0143] A portion of zeolite, as an adsorbent component, a portion
of expanded perlite as a functional filtration component, and
optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 11
[0144] Alumina/Biogenic Silica Filterable Composite Adsorbent
[0145] A portion of alumina, as an adsorbent component, a portion
of biogenic silica as a functional filtration component, and
optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 12
[0146] Alumina/Expanded Perlite Filterable Composite Adsorbent
[0147] A portion of alumina, as an adsorbent component, a portion
of expanded perlite as a functional filtration component, and
optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 13
[0148] Adsorbent Polymer/Biogenic Silica Filterable Composite
Adsorbent
[0149] A portion of adsorbent polymer, as an adsorbent component, a
portion of biogenic silica as a functional filtration component,
and optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 14
[0150] Adsorbent Polymer/Expanded Perlite Filterable Composite
Adsorbent
[0151] A portion of adsorbent polymer, as an adsorbent component, a
portion of expanded perlite as a functional filtration component,
and optionally a portion of a chemical sintering aid, are mixed and
thoroughly blended. The mixture is then heated and thermally
sintered. The resulting agglomerate product is then cooled, and
optionally screened according to particle size, to yield the
desired filterable composite adsorbent.
Example 15
[0152] Alkaline Earth Silicate Hydrate/Biogenic Silica Filterable
Composite Adsorbent
[0153] A portion of alkaline earth silicate hydrate, as an
adsorbent component, a portion of biogenic silica as a functional
filtration component, and optionally a portion of a chemical
sintering aid, are mixed and thoroughly blended. The mixture is
then heated and thermally sintered. The resulting agglomerate
product is then cooled, and optionally screened according to
particle size, to yield the desired filterable composite
adsorbent.
Example 16
[0154] Alkaline Earth Silicate Hydrate/Expanded Perlite Filterable
Composite Adsorbent
[0155] A portion of alkaline earth silicate hydrate, as an
adsorbent component, a portion of expanded perlite as a functional
filtration component, and optionally a portion of a chemical
sintering aid, are mixed and thoroughly blended. The mixture is
then heated and thermally sintered. The resulting agglomerate
product is then cooled, and optionally screened according to
particle size, to yield the desired filterable composite
adsorbent.
[0156] F. References
[0157] The disclosures of the publications, patents, and published
patent specifications referenced below are hereby incorporated by
reference into the present disclosure to more fully describe the
state of the art to which this invention pertains.
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* * * * *