U.S. patent application number 13/559760 was filed with the patent office on 2012-11-22 for composite filter aids having novel pore size characteristics.
This patent application is currently assigned to World Minerals, Inc.. Invention is credited to Jarrod R. Hart, Jie Lu.
Application Number | 20120292250 13/559760 |
Document ID | / |
Family ID | 45594527 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120292250 |
Kind Code |
A1 |
Lu; Jie ; et al. |
November 22, 2012 |
COMPOSITE FILTER AIDS HAVING NOVEL PORE SIZE CHARACTERISTICS
Abstract
Filter-aid materials are disclosed herein, as well as processes,
systems, and methods using such filter-aid materials for filtering
and removing particles and/or constituents from a fluid. Further
disclosed herein are filter-aid materials and processes, systems,
and methods using such filter-aid materials for filtering and
removing particles and/or constituents from a fluid, wherein the
filter-aid material comprises at least one composite filter-aid
having novel pore size distribution and comprising at least one
adsorbent component formed in-situ on at least one filtration
component.
Inventors: |
Lu; Jie; (Lompoc, CA)
; Hart; Jarrod R.; (Los Olivos, CA) |
Assignee: |
World Minerals, Inc.
|
Family ID: |
45594527 |
Appl. No.: |
13/559760 |
Filed: |
July 27, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12883529 |
Sep 16, 2010 |
8242050 |
|
|
13559760 |
|
|
|
|
61374832 |
Aug 18, 2010 |
|
|
|
Current U.S.
Class: |
210/502.1 |
Current CPC
Class: |
B01J 20/28054 20130101;
C12H 1/0408 20130101; B01J 20/12 20130101; B01D 39/06 20130101;
B01J 20/3234 20130101; B01J 20/10 20130101; B01D 2239/1216
20130101; B01J 20/14 20130101; B01J 20/28085 20130101; B01J 20/16
20130101; B01J 20/3204 20130101; B01J 20/28011 20130101; B01J
20/28042 20130101; B01J 20/041 20130101; B01J 20/28004 20130101;
B01J 20/103 20130101; B01D 2239/1208 20130101; B01J 20/28057
20130101 |
Class at
Publication: |
210/502.1 |
International
Class: |
B01J 20/14 20060101
B01J020/14; B01D 39/06 20060101 B01D039/06 |
Claims
1-39. (canceled)
40. A composite filter aid comprising: at least one filtration
component comprising at least one of diatomite and perlite; and at
least one adsorption component comprising precipitated silica, said
composite filter aid having a permeability ranging from 50
millidarcys to 5000 millidarcys, a BET surface area of greater than
about 10 m.sup.2/g, and a Total Pore Area ranging from about 10
m.sup.2/g to about 100 m.sup.2/g.
41. The composite filter aid of claim 40, wherein the composite
filter aid has an Average Pore Diameter 4 V/A ranging from about
0.1 micron to about 0.5 micron.
42. The composite filter aid of claim 40, wherein the composite
filter aid has a permeability ranging from about 150 millidarcys to
about 400 millidarcys.
43. The composite filter aid of claim 40, wherein the composite
filter aid has a Total Pore Area ranging from about 20 m.sup.2/g to
about 80 m.sup.2/g.
44. The composite filter aid of claim 40, wherein the composite
filter aid has a median pore diameter by area ranging from 1 nm to
50 nm.
45. The composite filter aid of claim 40, wherein the composite
filter aid has a median pore diameter by volume ranging from 1
micron to 10 microns.
46. The composite filter aid of claim 40, wherein the composite
filter aid has a BET surface area ranging from about 30 m.sup.2/g
to about 200 m.sup.2/g.
47. The composite filter aid of claim 40, wherein the composite
filter aid has a median particle size ranging from about 5 microns
to about 40 microns.
48. The composite filter aid of claim 40, wherein the composite
filter aid has a porosity ranging from about 70% to about 95%.
49. The composite filter aid of claim 40, wherein the at least one
adsorbent component comprises from about 5% to about 40% by weight
of the composite filter aid.
50. A composite filter aid comprising: at least one filtration
component and at least one adsorption component, wherein the
composite filter aid has an Average Pore Diameter 4 V/A ranging
from about 0.1 micron to about 0.5 micron and a Total Pore Area
ranging from about 10 m.sup.2/g to about 100 m.sup.2/g.
51. The composite filter aid of claim 50, wherein the composite
filter aid has an Average Pore Diameter 4 V/A ranging from about
0.1 micron to about 0.3 micron.
52. The composite filter aid of claim 50, wherein the composite
filter aid has a Total Pore Area ranging from about 20 m.sup.2/g to
about 80 m.sup.2/g.
53. The composite filter aid of claim 50, wherein the composite
filter aid has a Total Pore Area ranging from about 30 m.sup.2/g to
about 50 m.sup.2/g.
54. The composite filter aid of claim 50, wherein the composite
filter aid has a BET surface area ranging from about 30 m.sup.2/g
to about 200 m.sup.2/g.
55. The composite filter aid of claim 50, wherein the composite
filter aid has a median particle size ranging from about 5 microns
to about 40 microns.
56. The composite filter aid of claim 50, wherein the composite
filter aid has a permeability ranging from about 50 millidarcys to
about 1000 millidarcys.
57. The composite filter aid of claim 50, wherein the composite
filter aid has a porosity ranging from about 70% to about 95%.
58. The composite filter aid of claim 50, wherein the at least one
adsorbent component comprises from about 5% to about 40% by weight
of the composite filter aid.
59. A composite filter aid comprising: at least one filtration
component comprising at least one of diatomite and perlite; and at
least one adsorption component comprising precipitated silica, said
composite filter aid having a permeability ranging from 50
millidarcys to 5000 millidarcys, a BET surface area ranging from
0.5 m.sup.2/g to 500 m.sup.2/g, and a median pore diameter by area
ranging from 1 nm to 50 nm.
Description
RELATED APPLICATIONS
[0001] This application hereby claims the rights and benefits of
priority to U.S. Provisional Application No. 61/374,832, filed Aug.
18, 2010, the subject matter of which is incorporated by reference
herein in its entirety.
FIELD OF DISCLOSURE
[0002] Disclosed herein are composite filter-aid materials having
novel pore size characteristics, and processes, systems, and
methods using such composite filter-aid materials for filtering and
removing particles and/or constituents from a fluid. In one
embodiment, the composite filter-aid material comprises at least
one adsorbent component and at least one filtration component. In
another embodiment, the composite filter-aid material provides
surfaces with adsorbent capabilities.
BACKGROUND
[0003] In many filtration applications, a filtration device is
comprised of both a filter element, such as a septum, and a
filter-aid material. The filter element may be of any form such
that it may support a filter-aid material, for example, a
cylindrical tube or wafer-like structure covered with a plastic or
metal fabric of sufficiently fine weave. The filter element may be
a porous structure with a filter element void to allow material of
a certain size to pass through the filtration device. The
filter-aid material may comprise one or more filtration components,
which, for example, may be inorganic powders or organic fibrous
materials. Such a filter-aid material may be used in combination
with a filter element to enhance filtration performance. Often,
filtration components for use in a filter-aid material are
comprised of materials such as diatomite, perlite, and cellulose.
As an example illustrative of the field of filtration, the
filter-aid material may initially be applied to the septum in a
process known as "pre-coating." Pre-coating generally involves
mixing a slurry of water and filter-aid material and introducing
the slurry into a stream flowing through the septum. During this
process, a thin layer, such as about 1.5 mm to about 3.0 mm, of
filter-aid material may be eventually be deposited upon the septum,
thus forming the filtration device.
[0004] During the filtration of a fluid, various insoluble
particles in the fluid are trapped by the filter-aid material. The
combined layers of filter-aid material and particles and/or
constituents to be removed accumulate on the surface of the septum.
Those combined layers are known as "filter cake." As more and more
particles and/or constituents are deposited on the filter cake, the
filter cake may become saturated with debris to the point where
fluid is no longer able to pass through the septum. To combat that
problem, a process known as "body feeding" is often used. Body
feeding is the process of introducing additional filter-aid
material into the fluid to be filtered before the fluid reaches the
filter cake. The filter-aid material will follow the path of the
unfiltered fluid and will eventually reach the filter cake. Upon
reaching the filter cake, the added filter-aid material will bind
to the cake much the same way the filter-aid material bound to the
septum during the pre-coating process. That additional layer of
filter-aid material causes the filter cake to swell and thicken and
increases the capacity of the cake to entrap additional debris. The
filter aid typically has an open porous structure which maintains
an open structure in the filter cake, thus ensuring continued
permeability of the filter cake.
[0005] As mentioned above, in the field of fluid filtration many
methods of particle separation employ, for example, materials
chosen from diatomite, expanded perlite, natural glasses, and
cellulose materials as porous filtration components. Those
materials have intricate and porous structures that may be
particularly suited to the effective physical entrapment of
particles in filtration processes. Those intricate and porous
structures create networks of void spaces that may 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 components when
improving the clarity of fluids. The porous filtration component is
often used to remove undesired particles or constituents such as
particulate matter from a fluid. However, while well suited for the
task of removing particulate matter by physical entrapment, those
porous filtration components may not be as well suited for the task
of removing particulate matter from a fluid by the process of
adsorption and are thus often times used in combination with an
adsorbent component.
[0006] Diatomite, perlite, rice-hull ash, and cellulose are some
examples of filtration component materials that may be used for
particle separation. Diatomite, also known as diatomaceous earth,
is a sediment enriched in biogenic silica in the form of the
siliceous frustules of diatoms, a diverse array of microscopic,
single-cell algae. Those frustules are sufficiently durable to
retain much of their microscopic structure through long periods of
geological time and through thermal processing. Diatomite products
have an inherently intricate and porous structure composed
primarily of silica. Perlite is a naturally occurring volcanic
glass that may thermally expand upon processing. The structure of
perlite may not be as intricate as diatomite and, consequently,
perlite may be better suited for separating coarse
micro-particulates from liquids having high solids loading.
Finally, cellulose filtration component materials are generally
produced by sulfite or sulfate processing of hardwoods and/or
softwoods. Like perlite, cellulose filtration component materials
may possess a less intricate structure than diatomite filtration
component materials.
[0007] As used herein, "turbidity" is the cloudiness or haziness of
a fluid, where the haze may be caused by individual particles that
are suspended in the fluid. Materials that may cause a fluid to be
turbid include, for example, clay, silt, organic matter, inorganic
matter, and microscopic organisms. Turbidity may be measured by
using an instrument known as a nephelometric turbidimeter that
emits a beam of light through a column of the fluid being tested. A
detector positioned on the same side of the fluid column measures
the amount of light reflected by the fluid. A fluid that contains a
relatively large number of suspended particles will reflect a
greater amount of light than a fluid containing fewer particles.
Turbidity measured in this fashion may be quantified in
Nephelometric Turbidity Units ("NTU"). Turbidity may also be
measured via gravimetric methods.
[0008] A trade-off typically exists in filter-aid technology
between the permeability of the porous media used as a filtration
component and its turbidity removal capabilities. Filtration
components are produced in grades over a wide range of permeability
ratings. As the permeability of the filtration component decreases,
the ability of the filter-aid material to remove small particles
may increase, but often at the expense of a slower flow rate
through the filter-aid material. Conversely, as the filtration
component permeability increases, the ability of the filter-aid
material to filter particles may decrease and, consequently, the
fluid flow through the filter-aid material increases. The extent to
which this takes place will depend upon the type and particle size
distribution of the suspended particles being removed from the
fluid.
[0009] As used herein, "wet density" is an indicator of a
material's porosity. For example, wet density reflects the void
volume available to entrap particulate matter in a filtration
process and, consequently, wet density may be used to determine
filtration efficiency. Percent porosity may be expressed by the
following formula:
Porosity=100*[1-(wet density/true density)].
[0010] Thus, filtration components with lower wet densities may
result in products with greater porosity, and thus perhaps greater
filtration efficiency, provided that the true density stays
relatively constant. Typical wet densities for common filtration
components may range from at least about 12 lb/ft.sup.3 to about 30
lb/ft.sup.3 or greater.
[0011] As used herein, "adsorption" is the tendency of molecules
from an ambient fluid phase to adhere to the surface of a solid.
This is not to be confused with the term "absorption," which
results when molecules from an ambient fluid diffuse into a solid,
as opposed to adhering to the surface of the solid.
[0012] To achieve a desired adsorptive capacity, and thus to be
practical for commercial use, an adsorbent component may have a
relatively large surface area, which may imply a fine porous
structure. In certain embodiments, porous adsorbent components, in
their un-reacted powder form, can have surface areas ranging up to
several hundred m.sup.2/g.
[0013] One technique for calculating specific surface area of
physical adsorption molecules is with the Brunauer, Emmett, and
Teller ("BET") theory. The application of BET theory to a
particular adsorbent component yields a measure of the materials
specific surface area, known as "BET surface area." Generally
speaking, BET surface areas of practical adsorbent components in
their un-reacted powder form may range from about 50 to about 1200
m.sup.2/g. As used herein, "surface area" refers to BET surface
area.
[0014] Filtration components with different BET surface areas
and/or different total pore areas may result in different
adsorption capacity and filtration rate. Typically, a filter aid
with a lower BET and/or lower total pore area tends to have a lower
adsorption capacity and a faster filtration rate. Calcined
diatomaceous earth filter aids and expanded and milled perlite
filter aids are generally used as filter aids with minimal
adsorption function, because of the low surface area, typically
<10 m.sup.2/g. Adsorbent components, such as silica gels, are
generally high in BET surface areas or total pore areas, but their
filtration rates are generally slow, due to a much finer particle
size distribution and/or the lack of the porosity of a filter aids.
The fine particles can block the pores in filtration, and the high
surface area may create more drag on the flow, thus causing the
filtration rate drop significantly.
[0015] One technique for describing pores size distributions uses
mercury intrusion under applied isostatic pressure. In this method
an evacuated powder is surrounded by liquid mercury in a closed
vessel and the pressure is gradually increased. At low pressures,
the mercury will not intrude into the powder sample due to the high
surface tension of liquid mercury. As the pressure is increased,
the mercury is forced into the sample, but will first intrude into
the largest spaces, where the curvature of the mercury surface will
be the lowest. As pressure is further increased, the mercury is
forced to intrude into tighter spaces. Eventually all the voids
will be filled with mercury. The plot of total void volume vs.
pressure can thus be developed. The method can thus provide not
only total pore volume but also distinguish a distribution of pore
sizes. Note that Mercury Intrusion Porosimetry cannot distinguish
between intra- and inter-particle voidage and thus some knowledge
of particle size and shape may be needed for plot interpretation.
Furthermore, some pore shapes (such as large pores with small
access ports, the so-called inkwell pore) can fill at misleadingly
high pressures, so in effect the method is providing an estimation
of the true pore size distribution and not a direct measurement.
Once a distribution of pores has been estimated, it is possible to
calculate an estimation of surface area based on the pore sizes,
assuming a pore shape (a spherical shape is commonly assumed).
Median pore size estimates can also be calculated based on volume
or area. Median pore size (volume) is the pore size at 50.sup.th
percentile at the cumulative volume graph, while median pore size
(area) is the 50.sup.th percentile at the cumulative area graph.
The average pore size (diameter) is 4 times the ratio of total pore
volume to total pore area (4 V/A).
[0016] One method of using an adsorbent component is to place the
adsorbent component in contact with a fluid containing particles
and/or constituents to be adsorbed, either to purify the fluid by
removing the particles and/or constituents, or to isolate the
particles and/or constituents so as to purify them. In certain
embodiments, the adsorbent component containing the adsorbed
particles or constituents is then separated from the fluid, for
example by a conventional filtration process.
[0017] An illustrative example of an adsorption practice may be
seen in the process of beer "chill-proofing." It is currently known
that, unless specially treated, chilled beer may undergo a chemical
reaction that results in the production of insoluble particles. In
that chemical reaction, hydrogen bonds may form between haze-active
proteins and/or polyphenols in a chilled condition. The reacted
proteins and/or polyphenols may then grow to large particles, which
cause the beer to become turbid, a condition also known as
"chill-haze." Chill-haze may be undesirable to both consumers and
brewers. Turbidity may be most pronounced when the beer has been
chilled below room temperature. In certain instances, such as when
the particles are proteins, as the temperature increases, the
hydrogen bonds that hold the proteins together may be broken.
[0018] Chill-proofing may comprise a process that employs at least
one adsorption component and/or at least one filtration component
to remove particles creating chill-haze in the beer. One form of
chill-proofing involves, in one step, adding solid adsorbent
components, such as silica gel, to the beer prior to packaging. The
particles and/or constituents bind to the added adsorbent
components, and then, in a second step, the adsorbent components
are subsequently filtered from the beer, which is then packaged for
storage, sale, and/or consumption.
[0019] Filtration processes that implement both an adsorption step
and a filtration step may be less efficient because of the
difficulties of filtering the adsorbent components. For example,
the adsorbent components may occupy void spaces of the porous
filter-aid material. That occupancy may reduce the permeability of
the filter-aid material, leading to an overall lower filtration
flow rate, or may require the addition or more filter-aid material
at additional cost, and may also result in the faster consumption
of available volume in the filter housing.
[0020] There have been previous attempts to improve upon the
traditional process of chill-proofing. Earlier attempts involved
creating a simple mixture of an adsorbent component and a
filtration component to combine the filtration and adsorption steps
into one, thus eliminating the need to filter the adsorbent
components. The term "simple mixture" is used herein to describe a
composition comprising at least one adsorbent component and at
least one filtration component where the two components are not
chemically bonded, thermally sintered, or precipitated together.
Simple mixtures may be somewhat ineffective as the components may
be subject to separation due to physical distress often experienced
in packaging and shipping. Furthermore, the particle shape
characteristics of the adsorbent component may mean that these
particles do not aid filtration in the way the filtration component
particles do by ensuring the continued permeability of a filter
cake. Thus the particles of the adsorbing component would take up
valuable void space in the filter cake, thus reducing permeability
or requiring more of the filtration component to maintain
permeability.
SUMMARY
[0021] In one aspect, a composite filter aid may include at least
one filtration component and at least one adsorption component,
wherein the composite filter aid has an Average Pore Diameter (4
V/A) ranging from about 0.1 microns to about 0.5 microns and a
permeability ranging from about 50 to about 1000 millidarcies.
[0022] In another aspect, a composite filter aid include at least
one filtration component and at least one adsorption component,
wherein the composite filter aid has an Average Pore Diameter (4
V/A) ranging from about 0.1 microns to about 0.5 microns and a
Total Pore Area ranging from about 10 to about 100 m.sup.2/g.
[0023] In yet another aspect, a composite filter aid may include at
least one filtration component and at least one adsorption
component, wherein the composite filter aid has a pore diameter
ratio of at least about 200. For example, the composite filter aid
can have a pore size ratio of at least about 400 or at least about
500. In another aspect, the composite filter aid can have a pore
size ratio ranging from about 200 to about 2000 or from about 200
to about 1000.
[0024] In yet another aspect, the composite filter aid material
further has an Average Pore Diameter (4 V/A) ranging from about 0.1
microns to about 0.3 microns.
[0025] In yet another aspect, the composite filter aid material
further has a Total Pore Area ranging from about 20 to about 80
m.sup.2/g, such as from about 25 to about 65 m.sup.2/g, about 30 to
about 50 m.sup.2/g, or about 30 to about 40 m.sup.2/g.
[0026] In another aspect the composite filter aid material further
has a BET surface area ranging from about 30 to about 200
m.sup.2/g, such as from about 50 to about 110 m.sup.2/g.
[0027] In yet another aspect, the composite filter aid material has
a median particle size ranging from about 5 microns to about 40
microns.
[0028] In another aspect, the composite filter aid material has a
permeability ranging from about 50 millidarcies to about 5000
millidarcies, such as from about 50 millidarcies to about 1000
millidarcies, from about 100 millidarcies to about 500
millidarcies, or from about 125 millidarcies to about 400
millidarcies.
[0029] In yet another aspect, the composite filter aid material has
a median pore diameter (volume) ranging from about 1 micron to
about 10 microns, such as from about 3 microns to about 6
microns.
[0030] In another aspect, the composite filter aid material has a
median pore diameter (area) ranging from about 1 nm to about 50 nm,
such as from about 1 nm to about 10 nm.
[0031] In another aspect, the composite filter aid material has a
porosity ranging from about 70% to about 95%, such as, for example,
ranging from about 70% to about 80%.
[0032] In another aspect, the composite filter aid material can
include a diatomite. In some aspects the diatomite can include a
natural diatomite. In other aspects, the diatomite can include a
calcined diatomite, a flux-calcined diatomite, or a flash-calcined
diatomite. In other aspects, the composite filter aid material can
include perlite. In yet other aspects, the composite filter aid
material can include a precipitated silica.
[0033] In yet another aspect, the at least one adsorbent component
comprises from about 5% to about 40% by weight of the composite
filter-aid, such as from about 10% to about 30% by weight of the
composite filter-aid.
[0034] In another aspect, the composite filter-aid can be used for
the chill-proofing of beer.
[0035] In another aspect, the composite filter aid can be used for
the removal or adsorption of soluble metals from a liquid.
[0036] In yet another aspect, the composite filter aid includes at
least one filtration component and at least one adsorption
component, and has a permeability ranging from about 50
millidarcies to about 1000 millidarcies, a BET surface area ranging
from about 30 to about 200 m.sup.2/g, and a ratio of median pore
diameter (volume) to median pore diameter (area) of at least about
200.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] The accompanying drawings, which are incorporated in and
constitute a part of this description, illustrate several exemplary
embodiments and together with the description, serve to explain the
principles of the embodiments. In the drawings,
[0038] FIG. 1 shows the pore size distribution of the exemplary
composite filter-aid contrasted with a typical diatomite filter
aid.
[0039] FIG. 2 shows chill haze data for beer contacted with blends
of a diatomite filter aid and the diatomite-based composite
filter-aid.
DETAILED DESCRIPTION OF THE DISCLOSURE
A. Exemplary Composite Filter Aid
[0040] The present invention may provide a composite filter aid
having novel pore size characteristics. As used herein, the term
"composite filter aid" simply means a material comprising at least
one filter aid component and at least one adsorbent component that
is tightly bonded thereto. The composite filter aid can have
properties significantly different from either constituent
filtration or adsorbent component alone.
[0041] The composite filter-aid materials disclosed herein may
comprise at least one adsorbent component and at least one
filtration component, each having pores through which a fluid can
pass. In certain embodiments, a composite filter aid that has an
advantageous combination of pore size characteristics that can be
expressed as a "pore size ratio."
[0042] Porosity characteristics may be measured by any appropriate
measurement technique known to the skilled artisan or hereafter
discovered. Examples of porosity measurements may include, but are
not limited to, measurements of pore volume, average pore diameter,
median pore diameter, and total pore area. In some embodiments,
pore volume is measured with an AutoPore IV 9500 series mercury
porosimeter from Micromeritics Instrument Corporation (Norcross,
Ga., USA), which can measure pore diameters ranging from 0.006 to
600 .mu.m, using a contact angle set at about 130 degrees and a
pressure ranging from about 0 psi to about 33000 psi.
[0043] As defined herein, the term "pore size ratio" simply refers
to the ratio of pore size diameter (Volume) to pore size diameter
(Area) as measured using a Micromeritics AutoPore IV Porosimeter.
Median pore diameter (Volume; V50) is the median pore diameter
calculated at the 50% of the total intrusion volume; median pore
diameter (Area; A50) is the median pore diameter calculated at the
50% of the total pore area, as reported by the Micromeritics
AutoPore IV Porosimeter.
[0044] "BET surface area," as used herein, refers to the technique
for calculating specific surface area of physical absorption
molecules according to Brunauer, Emmett, and Teller ("BET") theory.
BET surface area may be measured by any appropriate measurement
technique known to the skilled artisan or hereafter discovered. In
some embodiments, BET surface area is measured with a Gemini III
2375 Surface Area Analyzer, using nitrogen as the sorbent gas, from
Micromeritics Instrument Corporation (Norcross, Ga., USA).
[0045] In certain embodiments, the pore size ratio of the composite
filter aid can have a value of greater than 200, such as, for
example, greater than 250, greater than 300, greater than 350,
greater than 400, greater than 450, greater than 500, greater than
550, greater than 600, greater than 650, or even greater than 700.
In other embodiments, the pore size ratio of the composite filter
aid ranges from about 200 to about 2000, such as, for example, from
about 200 to about 1000, or from about 200 to about 800. In yet
other embodiments, the pore size ratio of the composite filter aid
ranges from about 200 to about 1000, such as, for example, from
about 300 to about 1000, from about 400 to about 1000, from about
500 to about 1000, from about 600 to 1000, or from about 700 to
1000.
[0046] While not wishing to be bound by theory, it is hypothesized
that filter aids having a higher pore size ratio will exhibit
improved properties in some applications. For example, the high
median pore diameter (volume) of the composite filter aid material
appears to correlate to that of the filtration component and may
help to increase particulate holding capacity and higher
permeability. On the other hand, the median pore diameter (area) of
the composite filter aid material appears to correlate to that of
the adsorbent component and the adsorptive properties thereof,
which may provide for the beneficial removal the proteins that can
cause chill haze. Accordingly, composite filter aids according to
at least some embodiments have a pore size ratio engineered to
provide an advantageous combination of pore size characteristics of
both the filtration and adsorbent components when used in beverage
filtration applications.
[0047] In certain embodiments, the composite filter aid material
has a Median Pore Diameter (Volume) of greater than about 3.5
microns, such as greater than about 4 microns. In other
embodiments, the composite filter aid material has a Median Pore
Diameter (Volume) ranging from about 1 micron to about 10 microns,
such as from about 3 microns to about 6 microns, from about 4
microns to about 6 microns, or from about 4 microns to about 5
microns.
[0048] In certain embodiments, the composite filter aid material
can have a median pore diameter (Area) of less than about 100 nm,
such as, for example, less than about 50 nm or less than about 10
nm. In other embodiments, the composite filter aid material can
have a median pore diameter (Area) ranging from about 1 nm to about
50 nm, such as, for example, from about 1 nm to about 10 nm or from
about 5 nm to about 10 nm.
[0049] In yet other embodiments, the composite filter aid material
can have a Total Pore Area ranging from about 10 to about 100
m.sup.2/g, such as, for example, about 20 to about 80 m.sup.2/g,
from about 25 to about 65 m.sup.2/g, from about 30 to about 50
m.sup.2/g, or from about 30 to about 40 m.sup.2/g.
[0050] In some embodiments, the composite filter-aid material
comprises at least one adsorbent component that has been
precipitated in-situ on the surface of the at least one filtration
component. A filter element may be used to support the composite
filter-aid material. In some embodiments, the filter element
contains filter element voids through which fluid may flow. The
filter-aid materials comprising at least one composite filter-aid
may retain both the adsorptive properties of the at least one
adsorbent component and the porous structure of the at least one
filtration component, thus enhancing the utility of the filter-aid
materials comprising at least one composite filter-aid.
[0051] In some embodiments, the at least one adsorbent component is
precipitated in-situ onto the surface of the at least one
filtration component. As a result, while simple mixtures may
segregate upon suspension (e.g., in fluid, conveyance, or
transport), the filter-aid material comprising at least one
composite filter-aid may retain both its component adsorptive and
filtration properties. The in-situ precipitation of the at least
one adsorbent component on the at least one filtration component
may also have superior absorptive and filtration properties than a
thermally sintered or chemically bonded composite, because the
in-situ precipitation process may produce a filter-aid material
comprising at least one composite filter-aid, wherein the adsorbent
components are distributed evenly on the filtration component and,
consequently, exhibits a larger surface area for adsorption. The
larger surface area may allow the filter-aid material comprising at
least one composite filter-aid to adsorb a greater number of
particles and/or constituents which, in turn, may result in a lower
turbidity level for the filtered fluid.
[0052] In certain embodiments, the BET surface area of the at least
one filtration component is greater than about 2 m.sup.2/g. In some
embodiments, the BET surface area of the at least one filtration
component ranges from about 2 m.sup.2/g to about 10 m.sup.2/g.
[0053] In other embodiments, the BET surface area of the at least
one adsorbent component is greater than about 2 m.sup.2/g. In
another embodiment, the BET surface area of the at least one
adsorbent component is greater than about 10 m.sup.2/g. In yet
other embodiments, the BET surface area of the at least one
adsorbent component is greater than about 25 m.sup.2/g. In still
further embodiments, the BET surface area is greater than about 50
m.sup.2/g. In still other embodiments, the BET surface area of the
at least one adsorbent component is greater than about 85
m.sup.2/g. In still further embodiments, the BET surface area of
the at least one adsorbent component is greater than about 125
m.sup.2/g. In other embodiments, the BET surface area of the at
least one adsorbent component is greater than about 250 m.sup.2/g.
In further embodiments, the BET surface area of the at least one
adsorbent component ranges from about 30 m.sup.2/g to about 200
m.sup.2/g. In yet other embodiments, the BET surface area of the at
least one adsorbent component ranges from about 50 m.sup.2/g to
about 100 m.sup.2/g.
[0054] In some embodiments, the BET surface area of the composite
filter aid material is greater than about 10 m.sup.2/g, greater
than about 25 m.sup.2/g, or greater than about 50 m.sup.2/g. In a
further embodiment, the BET surface area of the composite filter
aid material ranges from about 30 to about 200 m.sup.2/g, such as,
for example, from about 50 to about 110 m.sup.2/g or from about 50
to about 75 m.sup.2/g.
[0055] The large BET surface area of the at least one adsorbent
component may allow the filter-aid materials comprising at least
one composite filter-aid to reduce the number of particles and/or
constituents that contribute to turbidity of the fluid. The
filter-aid materials comprising at least one composite filter-aid
may entrap particles and/or constituents from the unfiltered fluid,
resulting in the filtered fluid having fewer particles and/or
constituents. Further, the turbidity of a fluid filtered through
the filter-aid materials comprising at least one composite
filter-aid disclosed herein may be less than the turbidity of a
fluid filtered through a simple mixture of at least one adsorbent
component and at least one filtration component, where the
proportion of adsorbent component to filtration component in the
simple mixture is similar to, or even greater than, the proportion
of adsorbent component to filtration component of the filter-aid
materials comprising at least one composite filter-aid disclosed
herein. Further, the turbidity of a fluid filtered through the
filter-aid materials comprising at least one composite filter-aid
disclosed herein may be less than the turbidity of a fluid filtered
through a thermally-sintered or chemically-bonded composite of an
adsorbent component and a filtration component, where the
proportion of adsorbent component to filtration component in the
thermally-sintered or chemically-bonded composite is similar to, or
even greater than, the proportion of adsorbent component to
filtration component of the filter-aid materials comprising at
least one composite filter-aid disclosed herein.
[0056] The filter-aid materials comprising at least one composite
filter-aid disclosed herein may be processed to provide a wide
range of flow rates, which are directly related to permeability.
Permeability may be reported in units of darcies or millidarcies
("md"). One 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 second
under a pressure differential of 1 atm (i.e., 101.325 kPa).
Permeability may be determined using a device designed to form a
filter cake on a septum from a suspension of filter-aid material 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. Many filtration media suitable for
micro filtration, such as diatomite and perlite products, are
commercially available and span a wide range of permeability,
ranging from about 0.001 darcy to over 30 darcies, such as from
about 0.05 darcies to over 10 darcies. Filter-aid material for
coarse filtration, such as sand, may have greater permeabilities,
such as at least about 1000 darcies.
[0057] The selection of filtration permeability for a specific
filtration process depends in part on the flow rate and degree of
fluid clarification required for the particular application. In
many cases, the flow of fluid through a filter-aid material may be
closely related to the nature of the filtration component's
porosity. Within a given family of filtration components, those of
low permeability may have smaller pores capable of providing
greater clarity because smaller particles can be retained during
the filtration process, whereas those of high permeability may 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.
[0058] The adsorbent component may be selected from any suitable
adsorbent known to the skilled artisan or hereafter discovered. In
certain embodiments, the adsorbent may be a form of silica. In some
embodiments, the at least one adsorbent component may be chosen
from the various polymorphs of silica. Silica gels, for example,
are a form of silicon dioxide (SiO.sub.2), which may occur in
nature as sand. In general, however, sand is typically crystalline
and non-porous while silica gels are non-crystalline and may be
porous. In some embodiments, the at least one adsorbent component
may be a precipitated silica. In some embodiments, the at least one
adsorbent component may be a colloidal silica. In some embodiments,
the at least one adsorbent component may be a fumed silica. In some
embodiments, the at least one adsorbent component may be a silica
fume. In some embodiments, the at least one adsorbent component is
chosen from silicates. Non-limiting examples of suitable silicates
include aluminosilicate, calcium silicate, and magnesium silicate.
In still other embodiments, the at least one adsorbent component is
chosen from an alumina. In some embodiments, the alumina adsorbent
component is an aluminosilicate. In some embodiments, the alumina
adsorbent component is a porous alumina.
[0059] Filtration components suitable for use in preparation of the
filter-aid materials comprising at least one filterable composite
adsorbent disclosed herein may possess a variety of pore sizes. In
one embodiment, the filtration component pore size is a relatively
large pore size, for example, a mean pore diameter of about 1 to
about 10 microns, such as, for example, from about 2 to about 10
microns, such that it is particularly well-suited for particle
entrapment, thereby permitting mechanical filtration and/or
clarification by means of removal of particles and/or constituents.
In other embodiments, the filtration component pore size is a
relatively small pore size, for example, a mean pore diameter of
about 2 microns.
[0060] Filtration components suitable for use in the preparation of
the filterable composite adsorbent disclosed herein may possess a
variety of surface areas. In some embodiments, the filtration
component may have a relatively large surface area. In some
embodiments, the filtration component may have a relatively small
surface area.
[0061] Without wishing to be bound by theory, it is believed that a
filtration component with a large surface area may allow for a
reduction in the thickness of an adsorbent component coating which
may be formed thereon, for example, a precipitated silica.
[0062] The reduced thickness of the adsorbent coating is believed
to provide for more sites for adsorption of the particles and/or
constituents to be removed. In some embodiments, the surface area
of the filtration component is at least about 1 m.sup.2/g. In some
embodiments, the surface area is at least about 3 m.sup.2/g. In
some embodiments, the surface area is at least about 15 m.sup.2/g.
In some embodiments, the surface area is at least about 30
m.sup.2/g. In some embodiments, the surface area is at least about
50 m.sup.2/g. In some embodiments, the surface area ranges from
about 1 m.sup.2/g to about 100 m.sup.2/g. In some embodiments, the
surface area is less than about 500 m.sup.2/g.
[0063] In additional aspects, the filter-aid materials comprising
at least one composite filter-aid disclosed herein also may exhibit
various wet densities. For example, the filter-aid material
comprising at least one composite filter-aid may have a wet density
ranging from about 10 to about 25 lb/ft.sup.3. As wet density
reflects the void volume of the adsorbent component to entertain
matter in the filtration process, a lower wet density may indicate
that the adsorbent component has a high void volume and thus can
adsorb more particles and/or constituents in the fluid.
[0064] In some embodiments, the at least one filtration component
and/or the at least one additional filtration component includes
diatomite (a biogenic silica). In some embodiments, the at least
one filtration component includes perlite (a natural glass). In
some embodiments, the filtration components are chosen from
biogenic silica, including but not limited to diatomite, rice hull
ash, and sponge spicules. In some embodiments, the filtration
components are chosen from buoyant glasses. One example of buoyant
glasses are natural glasses, including but not limited to pumice,
expanded pumice, pumicite, expanded obsidian, expanded volcanic
ash, and sand. In some embodiments, the filtration components are
chosen from synthetic glasses. Examples of synthetic glasses
include but are not limited to fiber glass, controlled pore glass,
and foamed glass. In some embodiments, the filtration components
are chosen from buoyant polymers. Buoyant polymers include but are
not limited to fibrous polymers (such as fibrous nylon and fibrous
polyester) and powdered polymers (such as polyvinylchloride-acrylic
copolymer powder). In some embodiments, the filtration components
are chosen from cellulose. The at least one filtration component
and the at least one additional filtration component (if used) may
be the same or different. In some embodiments, the filtration
components are the same. In some embodiments, the filtration
components are different.
[0065] The term "biogenic silica" as used herein refers to silica
produced or brought about by living organisms. One 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 algae of the class Bacillariophyceae,
which possess an ornate siliceous skeleton (i.e., frustule) of
varied and intricate structure comprising two valves which, in the
living diatom, fit together much like a pill box. The morphology of
the frustules may vary widely among species and serves as the basis
for taxonomic classification; 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 frustule
and impart a design that is distinctive to individual species. The
size of typical frustules may range from about 0.75 .mu.m to about
1,000 .mu.m. In one embodiment, the size ranges from about 10 .mu.m
to about 150 .mu.m. Those 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.
[0066] The term "natural glass" as used herein refers to natural
glasses, commonly referred to as volcanic glasses, that 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
may be gray to green in color with abundant spherical cracks that
cause it to break into small pearl-like masses. Pumice is a
lightweight glassy vesicular rock. Obsidian may be dark in color
with a vitreous luster and a characteristic conchoidal fracture.
Pitchstone has a waxy resinous luster and may be 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, comprises small particles or
fragments that may be in glassy form. As used herein, the term
natural glass encompasses volcanic ash.
[0067] Natural glasses may be chemically equivalent to rhyolite.
Natural glasses that are chemically equivalent to trachyte, dacite,
andesite, latite, and basalt are known but may be less common. The
term obsidian is generally applied to large numbers of 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) being the most common.
[0068] Perlite is a hydrated natural glass that may contain, for
example, about 72 to about 75% SiO.sub.2, about 12 to about 14%
Al.sub.2O.sub.3, about 0.5 to about 2% Fe.sub.2O.sub.3, about 3 to
about 5% Na.sub.2O, about 4 to about 5% K.sub.2O, about 0.4 to
about 1.5% CaO (by weight), and small amounts of other metallic
elements. Perlite may be distinguished from other natural glasses
by a higher content (such as about 2 to about 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.
[0069] Perlite products may be prepared by milling and thermal
expansion, and may possess unique physical properties such as high
porosity, low bulk density, and chemical inertness.
[0070] 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 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 may be processed by milling and
classification, and products may be used as lightweight aggregates
and also as abrasives, adsorbents, and fillers. Unexpanded pumice
and thermally-expanded pumice may also be used as filtration
components in some cases as can volcanic ash.
[0071] The appropriate selection of the at least one adsorbent
component and the at least one filtration component of the
filter-aid materials comprising at least one composite filter-aid,
as well as any at least one additional filtration component,
disclosed herein may be determined by the specific application
intended. For example, in a filtration process that demands high
clarity but tolerates slower flow rate, a filter-aid material
comprising at least one composite filter-aid of low permeability
may be used, whereas in a filtration process that demands high flow
rate but does not require high clarity, a filter-aid materials
comprising at least one composite filter-aid of high permeability
may be used. Similar reasoning applies to the choice of the at
least one adsorbent component, and to the at least one composite
filter-aid when used in conjunction with other materials, or when
preparing mixtures containing the products.
[0072] In some embodiments, silica may be precipitated in-situ onto
diatomite, a biogenic silica. The resulting composite has both of
the adsorption capabilities, for example, beer chill-proofing
capability, obtained from the precipitated silica adsorbent, as
well as the filtration properties of the diatomite filtration
component. In some embodiments, the resulting precipitated
silica/diatomite composite filter-aid may further be mixed with an
at least one additional filtration component. In some embodiments,
the at least one additional filtration component may also comprise
diatomite. In some embodiments, the at least one additional
filtration component may comprise a filtration component that is
different than diatomite.
B. Exemplary Methods for Preparing Exemplary Composite
Filter-Aids
[0073] Sodium silicate is used herein to refer to any one of
several compounds comprising sodium oxide (Na.sub.2O) and silica
(SiO.sub.2). Such combinations may include, for example, sodium
ortho silicate (Na.sub.4SiO.sub.4), sodium meta silicate
(Na.sub.2SiO.sub.3), and sodium disilicate
(Na.sub.2Si.sub.2O.sub.5). In some embodiments, the sodium silicate
is a diatomite-based sodium silicate. In some embodiments, sodium
silicate is substituted in whole or in part for at least one
ammonium silicate and/or at least one alkali metal silicate, such
as lithium, sodium, potassium, rubidium, and cesium silicates.
Sodium silicate with a SiO.sub.2/Na.sub.2O ratio of .about.3.2:1
and a concentration of 20% may be purchased, for example, from
World Minerals Inc. Sodium silicate with a SiO.sub.2/Na.sub.2O
ratio of .about.3:1 and a concentration of 34.6% may be purchased,
for example, from PQ Corp.
[0074] A filtration component, chosen from among any suitable
filtration component previously known or hereinafter discovered,
can be mixed with water to form a free-flowing suspension. In some
embodiments, the filtration component can be the
commercially-available filtration component Celite Standard Super
Cel.RTM., manufactured by World Minerals, Inc. In some embodiments,
the filtration component can be a commercially-available filtration
component selected from the group including Celite 3Z.RTM., Celite
577.RTM., Celite 289.RTM., Celite 512.RTM., Celite Filter-Cel.RTM.,
and Celite Hyflo Super-Cel.RTM., all manufactured by World
Minerals, Inc.
[0075] Sodium silicate solution is then added to the filtration
component suspension, raising the pH. The mass ratio of sodium
silicate to the filtration component may be, for example, about
1:3, but any ratio is possible.
[0076] An acid, or a salt thereof, may then be added to the slurry
in an amount sufficient to increase the acidity (i.e., reduce the
pH) of the slurry to a pH range suitable for the precipitation of
silica gel. Any suitable acid may be selected, such selection being
within the know-how of one skilled in the art. In some embodiments,
the acid may be sulfuric acid. In other embodiments, the acid may
be phosphoric acid. In still other embodiments, the acid may by
hydrochloric acid. In yet other embodiments, the acid may be nitric
acid. In still other embodiments, the acid may be acetic acid.
[0077] As the pH lowers, the slurry is stirred periodically until
gelling occurs. This may take about 25 to about 60 minutes
depending upon the acidity of the solution and the sodium silicate
concentration in the slurry. The slurry is then filtered. Water may
be added to the suspension to aid filtration. The resulting cake
may be washed with water. Then the cake is dried until the excess
fluid in the cake has evaporated. For example, the cake may be
dried at a temperature ranging from about 110.degree. C. to about
200.degree. C.
[0078] The amount of the sodium silicate added may be chosen to
control the pore size distribution in the composite filter-aid
and/or final filter-aid material. While increasing the percentage
of silica gel generally acts to increase the filter-aid material's
ability to act as an adsorbent, it generally acts to decrease its
ability to act as a filter material. Conversely, decreasing the
percentage of silica gel generally acts to decrease the filter-aid
material's ability to act as an adsorbent while increasing its
ability to act as a filter material.
[0079] Accordingly, the amount of the adsorbent component in the
composite filter-aid may comprise from between greater than about 0
to about 100% by weight of the total composite filter-aid. In some
embodiments, the adsorbent component may comprise greater than
about 5% by weight of the total composite filter-aid. In other
embodiments, the adsorbent component may comprise greater than
about 15% by weight of the total composite filter-aid. In other
embodiments, the adsorbent component may comprise greater than
about 25% by weight of the total composite filter-aid. In other
embodiments, the adsorbent component may comprise less than about
40% by weight of the total composite filter-aid. In other
embodiments, the adsorbent component may comprise less than about
50% by weight of the total composite filter-aid. In other
embodiments, the adsorbent component may comprise from about 5% and
about 40% by weight of the total composite filter-aid. In other
embodiments, the adsorbent component may comprise from about 15%
and 25% by weight of the total composite filter-aid.
[0080] The amount of the filtration component in the composite
filter-aid may comprise from between greater than about 0 to about
100% by weight of the total composite filter-aid. In some
embodiments, the filtration component may comprise greater than
about 25% by weight of the total composite filter-aid. In other
embodiments, the filtration component may comprise greater than
about 50% by weight of the total composite filter-aid. In other
embodiments, the filtration component may comprise greater than
about 70% by weight of the total composite filter-aid. In other
embodiments, the filtration component may comprise less than about
80% by weight of the total composite filter-aid. In other
embodiments, the filtration component may comprise less than about
90% by weight of the total composite filter-aid. In other
embodiments, the filtration component may comprise from about 60%
to about 95% by weight of the total composite filter-aid. In other
embodiments, the filtration component may comprise from about 75%
to about 85% by weight of the total composite filter-aid.
[0081] In some embodiments, the adsorbent component may comprise
from about 5% to about 40% by weight of the total composite
filter-aid and the filtration component may comprise from about 60%
to about 95% by weight of the total composite filter-aid. In other
embodiments, the adsorbent component may comprise from about 15% to
about 25% by weight of the total composite filter-aid and the
filtration component may comprise from about 75% to about 85% by
weight of the total composite filter-aid. In further embodiments,
the composite filter-aid comprises a greater amount by weight of
the adsorbent component than the filtration component.
[0082] After formation of the filterable composite adsorbent, the
filterable composite adsorbent may then be mixed with at least one
additional filtration component. The at least one additional
filtration component may be chosen from any suitable filtration
component previously known or hereinafter discovered and may be
either the same or different from the at least one filtration
component in the filterable composite adsorbent. In some
embodiments, the additional filtration component is the
commercially-available filtration component Celite Standard
Super-Cel.RTM., manufactured by World Minerals, Inc. In other
embodiments, the additional filtration component is the
commercially-available filtration component Celite 3Z.RTM.,
manufactured by World Minerals Inc. In other embodiments, the
additional filtration component is the commercially-available
filtration component Celite Hyflo Super-Cel.RTM., manufactured by
World Minerals, Inc. In further embodiments, the additional
filtration component is the commercially-available filtration
component Celite 512.RTM., manufactured by World Minerals, Inc. In
further embodiments, the filtration component is the
commercially-available filtration component Celite 512Z.RTM.,
manufactured by World Minerals, Inc. In yet other embodiments, the
additional filtration component is the commercially-available
filtration component Celite 289.RTM., manufactured by World
Minerals, Inc. In yet a further embodiment, the additional
filtration component is the commercially-available filtration
component Filter-Cel.RTM., manufactured by World Minerals, Inc.
[0083] In embodiments in which the filter-aid material comprising
at least one composite filter-aid further comprises at least one
additional filtration component, the additional filtration
component may comprise from greater than about 0% to about 100% of
the total weight of the filter-aid material. In some embodiments,
the additional filtration component may comprise greater than about
5% by weight of the total filter-aid material. In other
embodiments, the additional filtration component may comprise
greater than about 30% by weight of the total filter-aid material.
In further embodiments, the additional filtration component may
comprise greater than about 50% by weight of the total filter-aid
material. In yet other embodiments, the additional filtration
component may comprise greater than about 65% by weight of the
total filter- aid material. In yet further embodiments, the
additional filtration component may comprise greater than about 80%
by weight of the total filter-aid material.
[0084] In embodiments in which the filter-aid material comprising
at least one composite filter-aid further comprises at least one
additional filtration component, the composite filter-aid may
comprise from greater than about 0% to about 100% of the total
weight of the filter-aid material. In some embodiments, the
composite filter-aid may comprise greater than about 5% by weight
of the total filter-aid material. In other embodiments, the
composite filter-aid may comprise greater than about 30% by weight
of the total filter-aid material. In further embodiments, the
composite filter-aid may comprise greater than about 50% by weight
of the total filter-aid material. In yet other embodiments, the
composite filter-aid may comprise greater than about 65% by weight
of the total filter-aid material. In yet further embodiments, the
composite filter-aid may comprise greater than about 80% by weight
of the total filter-aid material.
[0085] In some embodiments, the at least one additional filtration
component may comprise from about 60% to about 70% by weight of the
total filter-aid material, and the filterable composite adsorbent
may comprise from about 30% to about 40% by weight of the total
filter-aid material. Specific properties of filter-aid materials
comprising at least one filterable composite adsorbent can be
modified by further physical or chemical reaction of the material
after the initial filter-aid material comprising at least one
filterable composite adsorbent has been made, for example, to
enhance at least one property (for example, solubility and/or
surface characteristics) and/or to yield a new product with a
specialized use. Examples of such further modifications include,
for example, hydration, acid washing, surface treatment, and
organic derivatization, as disclosed, for example, in U.S. Pat. No.
6,712,974 to Palm et al.
C. Exemplary Methods of Using Exemplary Composite Filter-Aids
[0086] Filter-aid materials comprising at least one composite
filter-aid described herein may be used in many of the same
applications as currently available adsorbents, but may offer added
properties, such as, for example, increased permeability, low
centrifuged wet density, and uniquely shaped particles (e.g.,
fibers), as well as improved efficiency, and/or economy.
[0087] Filter-aid materials comprising at least one composite
filter-aid and their optional further modifications, may be used in
filtration applications in a manner analogous to that of porous
filtration media. Filter-aid materials comprising at least one
composite filter-aid may be applied to a septum to improve clarity
and increase flow rate in filtration processes or added directly to
the fluid. Depending on the particular separation involved,
filter-aid materials comprising at least one composite filter-aid
may be used in pre-coating, body feeding, or both.
[0088] In some embodiments, the method of adsorption and filtration
comprises (i) providing a filter-aid material comprising at least
one composite filter-aid, (ii) pre-coating a filter element with
the composite filter-aid, and (iii) suspending the filter-aid
material comprising at least one composite filter-aid in a fluid
containing particles and/or constituents to be removed from the
fluid, wherein the composite filter-aid may be supported on a
filter element.
[0089] In other embodiments, the method of adsorption and
filtration comprises (i) providing a composite filter-aid, (ii)
further mixing the composite filter-aid with an at least second
filtration component to form a filler-aid material (iii)
pre-coating a filter element with the filler-aid material, and (iv)
suspending the filter-aid material in a fluid containing particles
and/or constituents to be removed from the fluid, wherein the
filter-aid material may be supported on a filter element.
[0090] To increase or maximize the adsorption of particles and/or
constituents, such as, for example, proteins, contributing to chill
haze, some embodiments disclosed herein comprise a combination of
pre-coating and body feeding.
[0091] In other embodiments, the method of adsorption and
filtration comprises the step of passing a fluid containing
undesired particles or constituents to be adsorbed through a
filter-aid material comprising at least one composite filter-aid,
in the form of a rigid shape supported on a septum.
[0092] Filter-aid materials comprising at least one composite
filter-aid can be shaped, molded, extruded, sintered, or otherwise
formed into permeable sheets, plates, disks, polyhedrons, or other
formed shapes that have adsorbent properties. Fluids can then be
passed through the filter-aid material comprising at least one
composite filter-aid to achieve both filtration and adsorption.
[0093] The filter-aid material comprising at least one composite
filter-aid disclosed herein may be used in conjunction with other
media (e.g., different porous filtration component materials) to
form a filter-aid material for use in filtration applications
and/or to further modify a filtration process. For example,
mixtures of the composite filter-aid with, for example, diatomite,
expanded perlite, pumicite, natural glass, cellulose, activated
charcoal, clay, or other materials, may be useful additional
filtration components. 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.
[0094] The filter-aid materials comprising at least one composite
filter-aid disclosed herein 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.
[0095] Many other modifications and variations of the embodiments
of the invention as hereinbefore set forth can be made without
departing from the spirit and scope thereof. Other than in the
examples, or where otherwise indicated, all numbers expressing
quantities of ingredients, reaction conditions, and so forth used
in the specification and claims are understood as being modified in
all instances by the term "about." Accordingly, unless indicated to
the contrary, the numerical parameters set forth in the following
specification and attached claims are approximations that may vary
depending upon the desired properties sought to be obtained herein.
At the very least, and not as an attempt to limit the application
of the doctrine of equivalents to the scope of the claims, each
numerical parameter should be construed in light of the number of
significant digits and ordinary rounding approaches.
[0096] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope are approximations, the numerical
values set forth in the specific examples are reported as precisely
as possible. Any numerical value, however, inherently contain
certain errors necessarily resulting from the standard deviation
found in their respective testing measurements.
[0097] The headers used in this specification are presented for the
convenience of the reader and not intended to be limiting of the
inventions described herein. By way of non-limiting illustration,
concrete examples of certain embodiments of the present disclosure
are given below.
EXAMPLES
[0098] Filter-aid materials comprising at least one composite
filter-aid as disclosed herein, as well as 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
[0099] A composite filter-aid was made using a Celite.RTM. 3Z,
sodium silicate and sulphuric acid. 80 g of Celite.RTM. 3Z was
added to 800 g of water. Next, 70 g of sodium silicate solution at
38% concentration was added to the mixture with constant stirring.
Sulpuric acid (98%) is then added to adjust the pH to 8.5. When the
pH reached approximately 8.5, a gelling reaction occurred, and the
mixture thickened. With continued acid addition and stirring for 30
minutes, the slurry thinned out and the pH reached 8.0. The
suspension was then filtered using a Buchner funnel. The filter
cake was then reslurried with approximately 1 L of water and
filtered again, then slurried again, and filtered again, in order
to remove reaction byproducts (e.g., salts). Finally, the cake was
then dried by heating it at 110.degree. C. for three hours.
[0100] Table 1 provides porosimetry information for composite
filter-aid manufactured by the exemplary process described above.
Controls include three diatomite-based filter aids, Celite C3Z,
Celite SSC (both available from World Minerals, Inc.), Celatom FP3
(available from Eagle Picher Corp.), and three silica gel products,
including Lucilite.RTM. L10, Lucilite.RTM. XLC (both available from
INEOS Silicas Ltd.), and Britesorb.RTM. D300 (available from PQ
Corporation).
[0101] Table 1 below shows porosimetry and BET surface area for
five different batches of diatomite-based composite filter-aid,
compared with silica gels and regular calcined diatomite filter
aids. As shown in Table 1, the exemplary composite filter aid
material in samples A-E displays an Average Pore Diameter (4 V/A),
Total Pore Area, and BET Surface Area in ranges between those of
the precipitated silica or diatomite based controls. In contrast,
the Median Pore Size (Volume) of the exemplary composite filter aid
material in samples A-E appears to correlate more to that of the
diatomite control samples, while the Median Pore Size (Area) of the
composite filter aid material in samples A-E appears to correlate
more to that of the precipitated silica control samples.
[0102] One possible explanation for the difference between the two
median pore diameter estimation methods is that the composite
filter-aid may have a multimodal pore size distribution. When a
volume mean pore diameter is estimated, the composite exhibits
pores in the usual size range for diatomite-based filter aids.
However, when an area mean diameter is calculated, the result is
much lower than is found for a regular diatomite filter aid, and is
even lower than is typical for a precipitated silica. The ratio of
these diameters may been seen an indication of a presence of a
large number of very fine pores in addition to the large volume of
larger pores which is unique to this novel composite
filter-aid.
[0103] FIG. 1 shows the pore size distribution of the exemplary
composite filter-aid contrasted with a typical diatomite filter
aid. Fine pores (below 10 nm in size) are clearly evident in the
composite filter-aid, as measured using Mercury Intrusion
Porosimetry.
TABLE-US-00001 TABLE 1 Sample Sample Sample Sample Sample Lucilite
Lucilite Brite-sorb Celite Celite Celatom A B C D E L10 XLC D300 3Z
SSC FP-3 24.mu. 27.mu. 22.mu. 24.mu. 24.mu. Total Intrusion Volume
2.89 2.45 2.68 2.68 2.99 3.01 1.90 1.96 1.79 2.02 2.05 (mL/g) Total
Pore Area 322 193.4 278 3.79 5.85 5.20 35.7 32.8 32.0 61.2 52.0
(m.sup.2/g) Median Pore Diameter 1.25 3.05 1.83 4.83 3.37 4.54 4.95
5.13 4.46 4.44 4.62 (Volume) (.mu.m) Median Pore Diameter 0.0081
0.0095 0.0078 1.53 1.14 1.04 0.0070 0.0070 0.0068 0.0070 0.0067
(Area) (.mu.m) Average Pore Diameter 0.0360 0.0507 0.0385 2.82 2.05
2.32 0.2128 0.2397 0.2237 0.1322 0.1572 (4 V/A) (.mu.m) Bulk
Density at 0.28 0.2818 0.2838 0.2701 0.2985 0.2847 0.2905 0.3838
0.3824 0.4158 0.3807 0.3752 psia (g/mL) Apparent (skeletal) 1.53
0.93 0.97 1.49 1.93 2.30 1.42 1.54 1.63 1.65 1.61 Density (g/mL)
Porosity (%) 81.6 69.6 72.3 79.9 85.2 87.4 73.0 75.1 74.4 76.9 76.7
BET surface area 292 556 314 3.40 4.11 3.04 65 71 66 57 62
(m.sup.2/g) Pore size ratio = 155 322 235 3.15 2.94 4.36 707 733
656 635 689
Example 2
[0104] Quantities more useful for trials at breweries were prepared
as follows: 12,500 gallons of clean water were placed in a
closed-topped agitated vessel. 10,500 lbs of Celite Super-Cel.RTM.
were added to produce a well mixed slurry. 795 gallons of sodium
silicate (at 38% purity) were then added. Approximately 83 gallons
of 94% pure sulfuric acid was added to adjust the pH to 8.0. The
slurry was then filtered three times to remove reaction
byproducts.
[0105] To show the efficacy of the diatomite-based composite
filter-aid produced in this example, it is necessary to contact the
material with beer, then heat-age and chill the beer to force any
remaining haze precursors to precipitate. 300 ml of unfiltered
lager was contacted with 1.8 g of regular diatomite-based filter
aid for 10 minutes and was then filtered through a Buchner to
remove all suspended solids including the filter aid. This
experiment was repeated progressively replacing the regular
diatomite-based filter aid (Celite 3Z.RTM.) with the
diatomite-based composite filter-aid produced above. The beer
sample produced in each case was bottled, left at 40.degree. C. for
5 days, then refrigerated at 0.degree. C. for 24 hours before the
turbidity was measured using a nephelometric turbidimeter (model
2100N produced by Hach Company of Colorado). Table 2 below shows
chill haze data for beer contacted with blends of a diatomite
filter aid (Celite 3Z.RTM.) and the diatomite-based composite
filter-aid. The turbidity can be seen to decrease with increasing
dose of the diatomite-based composite filter-aid, with little
benefit beyond doses of around 3 g/L. FIG. 2 shows chill haze data
for beer contacted with blends of a diatomite filter aid (Celite
3Z.RTM.) and the diatomite-based composite filter-aid.
TABLE-US-00002 TABLE 2 Forced Aging Composite Diatomite Turbidity
at Dose Dose 0.degree. C. g/L g/L EBC 0 6 5.62 1.5 4.5 1.25 3 3
0.78 4.5 1.5 0.75 6 0 0.80
* * * * *