Adsorbent for metal ions and method of making and using

A method comprises the step of spray-drying a solution or slurry comprising (alkali metal or ammonium) (metal) hexacyanoferrate particles in a liquid, to provide monodisperse, substantially spherical particles in a yield of at least 70 percent of theoretical yield and having a particle size in the range of 1 to 500 micrometers, said particles being active towards Cs ions. The particles, which can be of a single salt or a combination of salts, can be used free flowing, in columns or beds, or entrapped in a nonwoven, fibrous web or matrix or a cast porous membrane, to selectively remove Cs ions from aqueous solutions.

FIELD OF THE INVENTION 
The present invention pertains to substantially spherical, monodisperse 
sorptive particles and a method therefor, and a method of using the 
particles in loose form, in a column, or enmeshed in a web or membrane for 
extraction of cesium ions from solution. The method and particles are 
useful in the remediation of nuclear wastes. 
BACKGROUND OF THE INVENTION 
Potassium cobalt hexacyanoferrate is known in the art as an effective 
adsorbent for cesium ions and has found important use in removing 
radioactive cesium ions from nuclear wastes via an ion exchange process. 
The method has been described, for example, in U.S. Pat. No. 3,296,123; in 
"A Review of Information on Ferrocyanate Solids for Removal of Cesium from 
Solutions," P. A. Haas, Sep. Sci. Technol. 28 (17-18), 2479-2508 (1993); 
and in "Evaluation of Selected Ion Exchangers for the Removal of Cesium 
and Strontium from MVST W-25 Supemate," J. L. Collins, et al., 
ORNL/TM-12938, April 1995. 
Potassium cobalt hexacyanoferrate, hereinafter referred to as "KCOHEX," has 
typically been prepared by a method in granular form as described in U.S. 
Pat. No. 3,296,123, wherein an aqueous acidic solution of potassium 
ferrocyanide is slowly mixed with an aqueous solution of cobalt nitrate, 
as shown in Formula I. 
EQU potassium ferrocyanide+cobalt nitrate.fwdarw.KCOHEX+potassium nitrate 
Water is removed by centrifugation, the wet cake is washed with water, then 
dried in an oven to form a dried solid mass. The solid mass is ground and 
sized, and particles of from about 150 micrometers to about 450 
micrometers are packed into columns for subsequent exposure to radioactive 
wastes containing, in particular, Cesium-137. 
The method of preparing particulate KCOHEX and other hexacyanoferrates 
suffers from two significant drawbacks. First, grinding the dried solids 
must be done carefully so as to minimize formation of unusable fines. 
Second, since a wide range of particle sizes results from grinding, the 
particulate must be sized through sieves. These operations are 
time-consuming and inevitably cause loss of product. 
As described in the references noted above, sized KCOHEX is then loaded 
into columns in order to remove cesium from radioactive waste solutions. 
Spray-drying of solid materials is a method known in the art for 
preparation of useful solids. See, for example, Kirk-Othmer Encyclopedia 
of Chemical Technology, 4th Ed., John Wiley & Sons, New York, 1993; Vol. 
8, p. 475-519, particularly pp. 505-508; and C. Strumillo and T. Kudra, 
"Drying: Principles, Applications and Design," Gordon and Breach, New 
York, 1986, pp. 352-359. However, in all of the reports of preparation and 
use of KCOHEX, a spray drying process has not been described. 
SUMMARY OF THE INVENTION 
Briefly, the present invention provides a method comprising the step of: 
spray-drying a solution or slurry comprising (alkali metal or ammonium) 
(metal) hexacyanoferrate particles, wherein metal is selected from 
Periodic Table (CAS version) Groups VIII, IB, and IIB to provide 
monodisperse, sorbent particles in a yield of at least 70 percent of 
theoretical yield and having an average particle size in the range of 1 to 
500 micrometers, said sorbents being active towards Cs ions. Preferably, 
the hexacyanoferrate particles are substantially spherical in shape and 
less than 20 percent by weight of particles have a size 5 micrometers or 
smaller. Combinations of hexacyanoferrates can be especially useful to 
remove Cs ions from aqueous solutions. 
The sorbents preferably are selected from the group consisting of 
(potassium or ammonium) (metal) hexacyanoferrates wherein the metal 
preferably is selected from Fe, Ru, Os, Rh, Ir, Co, Ni, Pd, Pt, Cu, Ag, 
Au, Zn, Cd, and Hg. More preferably, the sorbents are selected from the 
group consisting of potassium cobalt hexacyanoferrate (KCOHEX), potassium 
zinc hexacyanoferrate (KZNHEX), potassium iron hexacyanoferrate, potassium 
copper hexacyanoferrate, potassium nickel hexacyanoferrate, potassium 
cadmium hexacyanoferrate, and ammonium iron hexacyanoferrate. The liquid 
in the solution or slurry can be aqueous or organic liquid. 
In a further aspect, there are disclosed substantially spherical sorbent 
particles having a particle size in the range of 1 to 500 micrometers, the 
particles being sorptive towards Cs ions in solution. Preferably, the 
spherical particles can be potassium cobalt hexacyanoferrate, potassium 
zinc hexacyanoferrate, potassium iron hexacyanoferrate, potassium copper 
hexacyanoferrate, potassium nickel hexacyanoferrate, potassium cadmium 
hexacyanoferrate, and ammonium iron hexacyanoferrate. The particles can be 
used in columns or beds to selectively remove Cs ions which can be 
radioactive from aqueous solutions. 
In yet another aspect, the loose spray-dried sorbents which preferably are 
potassium cobalt hexacyanoferrate, potassium zinc hexacyanoferrate, 
potassium nickel hexacyanoferrate, potassium copper hexacyanoferrate, 
potassium iron hexacyanoferrate, potassium cadmium hexacyanoferrate, or 
ammonium iron hexacyanoferrate particles can be introduced into a Cs ion 
containing solution, equilibrated with the solution, and then separated 
from the sorbed and/or exchanged metal ions. 
In a still further aspect, the spherical sorptive particles that have been 
spray-dried can be enmeshed in nonwoven, fibrous webs, matrices, or 
membranes. The webs, matrices, or membranes, which preferably are porous, 
can be used in solid phase extraction (SPE) procedures to selectively 
remove Cs ions from aqueous solutions. 
In yet another aspect, the invention provides an SPE device, such as a 
cartridge which in preferred embodiments can be pleated or spirally wound, 
comprising a fibrous non-woven SPE web comprising spherical, monodisperse 
particles which, in preferred embodiments, can be any of potassium cobalt 
hexacyanoferrate, potassium zinc hexacyanoferrate, potassium iron 
hexacyanoferrate, potassium copper hexacyanoferrate, potassium nickel 
hexacyanoferrate, potassium cadmium hexacyanoferrate, and ammonium iron 
hexacyanoferrate or potassium nickel hexacyanoferrate particulate and 
aramid fibers enclosed in a cartridge device. Preferably, the web is 
porous. 
In yet another embodiment, the invention provides a method of removing the 
specified metal ions from an aqueous solution comprising passing the 
aqueous solution by or through a fibrous non-woven SPE web or matrix or 
membrane comprising the above-described spherical, monodisperse particles 
which can be any of the sorptive particles made by the method of this 
invention, the particles preferably being any of hexacyanoferrates 
disclosed herein. Preferably, the web is porous. 
In another embodiment, the invention provides a method of removing the 
specified metal ion from an aqueous solution comprising passing the 
aqueous solution through an SPE column comprising spherical, monodisperse 
sorptive particles made by the method of this invention, the particles 
preferably being any of hexacyanoferrate particulates disclosed herein. 
In yet another aspect, the method further comprises the step of heating 
spherical metal or ammonium hexacyanoferrate particles, after drying, at a 
temperature of at least 115.degree. C., preferably 115 to 130.degree. C. 
for up to 12 hours. In the case of KCOHEX, the particles can be heated 
until their color changes from green to purplish-black. 
In this application, 
"size" means the diameter of a spherical particle or the largest dimension 
of an irregularly shaped particle; 
"monodisperse" means a monomodal particle size distribution (i.e., 
particles of uniform size in a dispersed phase) having an average size 
range of 1 up to about 60 micrometers, preferably about 5 to about 30 
micrometers, as illustrated by FIG. 1; 
"drain time" means the time required to dewater a slurry of particles and 
fibers when making a sheet; and 
"substantially spherical" means particles that are spherical, ovoid (having 
an elliptical cross-section), raspberry-like, or toroidal, and are free of 
sharp comers; 
"particles" and "particulate" are used interchangeably; 
"web", "matrix", and "membrane" are used interchangeably and each term 
includes the others; 
"sorptive" or "sorb" means by one or both of absorption and adsorption; and 
"heavy metal" refers to metals having a molecular weight of at least 50; 
and 
The overall process yield in making particles of the invention using a 
spray-dryer with a diameter of at least 1 meter is at least 70 percent, 
preferably 80-90 percent, or more compared to a yield of about 60 percent 
or less when using prior art ground and sieved particles. Preferably, the 
resulting particles are free of submicron size particles, with not more 
than 20 percent of particles being &lt;5 .mu.m in size. The spray-drying 
process substantially eliminates product particles having submicron sizes. 
Additionally, free-flowing spherical particles will pack with point contact 
in columns, resulting in less channeling and a lower pressure drop during 
extraction compared with, for example, irregularly shaped prior art 
particles having the same average size. Irregularly shaped prior art 
particles, particularly those less than 5 micrometers in size can pack 
tightly and lead to a high pressure drop in extraction applications. When 
irregularly shaped prior art particles are greater than 50 micrometers in 
size, channeling can result as liquids pass through, resulting in poor 
separations. 
Further, the advantages of the particles of the invention include reduced 
drain time by a factor of at least about 1.5 times or more compared to 
non-spherical, irregularly shaped, prior art particles typically obtained 
from a grinding process, when incorporated in a sheet article. 
Further, sheet articles can be made using particles of this invention, 
whereas in many cases sheet articles cannot be made from prior art ground 
and sieved particles because of excessive drain time or inability to 
control the sheet forming process. The sheet articles formed from 
spray-dried particles often have lower flow resistance than sheet articles 
made from ground and screened particles and are therefor more efficient in 
use.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
In preferred embodiments, sorptive particles useful in the present 
invention include substantially spherical sorptive particles of 
hexacyanoferrates, preferably any of potassium cobalt hexacyanoferrate 
(KCOHEX), potassium zinc hexacyanoferrate (KZNHEX), potassium nickel 
hexacyanoferrate (KNIHEX) potassium iron hexacyanoferrate (KFEHEX), 
potassium copper hexacyanoferrate (KCUHEX), potassium cadmium 
hexacyanoferrate (KCDHEX), and ammonium iron hexacyanoferrate, (NH.sub.4 
FEHEX). These particles are useful to sorb cesium (Cs), which may be in 
its radioactive forms. 
It is desirable to have low solubility because it is preferred the 
adsorbent does not dissolve in use. 
It is now recognized that spherical (potassium or ammonium) (metal) 
hexacyanoferrate particles can be prepared by mixing at 0.degree. to 
5.degree. C. an aqueous solution of potassium ferrocyanide (available from 
Aldrich Chemical Co., and many other suppliers) with an aqueous solution 
of metal nitrate, buffered to a pH of 5-6 using acetic acid as the 
buffering agent. The immediately formed precipitate of (potassium or 
ammonium) (metal) hexacyanoferrate is collected and thoroughly washed with 
water. When cobalt nitrate solution or zinc nitrate solution are used, for 
example, the resulting slurry will contain potassium cobalt 
hexacyanoferrate (KCOHEX) or potassium zinc hexacyanoferrate (KZNHEX) 
respectively. 
The wet precipitate of (alkali metal or ammonium) (metal) hexacyanoferrates 
which comprises particles of irregular shapes can be slurried with liquid, 
preferably water, and then spray-dried preferably using a spinning disk 
atomizer and collecting the resulting substantially spherical KCOHEX or 
other metal hexacyanoferrate particles having an average size in the range 
of about 1 to 60 micrometers, preferably 5 to 30 micrometers, most 
preferably 5 to 15 micrometers, with a most preferred average size of 
about 9 to 12 micrometers. In the case of KCOHEX, preferably, the 
spherical particles are then heated until the color changes from green to 
purplish black but the particle size remains substantially unchanged. It 
is desirable to avoid drying the hexacyanoferrate particles prior to the 
spray-drying procedure. 
In some applications it may be desirable to limit the size of the metal or 
ammonium/metal particles in the slurry that is to be spray-dried. For 
example, particles that are to be incorporated into nonwoven fibrous webs, 
matrices, or membranes desirably are spray-dried from slurries wherein the 
particles are at most 20 micrometers, preferably at most 10 micrometers, 
and most preferably at most 1 micrometer in average size, to provide the 
monodisperse, substantially spherical sorbent particles described above. 
It is preferred that the particles in the slurry not be dried prior to 
subjecting to the spray drying technique. 
Spray-drying of the slurry can be accomplished using well-known techniques 
which include the steps of: 
1) atomization, using a spinning disk, of the material introduced into the 
dryer; 
2) removing of moisture, as, for example, by contact of the material with 
hot gas; and 
3) separation of dry product from the exhaust drying agent. 
The slurry preferably has a solids content in the range of 3 to 15 percent 
by weight, more preferably 5 to 10 percent by weight, and most preferably 
5 to 7.5 percent by weight, to ensure smooth operation of the apparatus. 
After spray-drying, the particles are free-flowing with most preferred 
average diameters in the range of 9-12 micrometers. When KCOHEX is used, 
particles are dark green in color. The cyanoferrates preferably are heated 
at about 115.degree. C. for about 12 hours after drying to achieve maximum 
absorption capacity for cesium or other metal ions. 
The particle can be evaluated for its ion exchange capacity (see Brown, G. 
N., Carson, K. J., DesChane, J. R., Elovich, R. J., and P. K. Berry. 
September 1996. Chemical and Radiation Stability of a Proprietary Cesium 
Ion Exchange Material Manufactured from WWL Membrane and Superlig .TM.644. 
PNNL-11328, Pacific Northwest National Laboratory, Richland, Wash.) by 
testing for the batch distribution coefficient or K.sub.d which is 
described as follows: 
The batch distribution coefficient, K.sub.d is an equilibrium measure of 
the overall ability of the solid phase ion exchange material to remove an 
ion from solution under the particular experimental conditions that exist 
during the contact. The batch K.sub.d is an indicator of the selectivity, 
capacity, and affinity of an ion for the ion exchange material in the 
presence of a complex matrix of competing ions. In most batch K.sub.d 
tests, a known quantity of ion exchange material is placed in contact with 
a known volume of solution containing the particular ions of interest. The 
material is allowed to contact the solution for a sufficient time to 
achieve equilibrium at a constant temperature, after which the solid ion 
exchange material and liquid supernate are separated and analyzed. In this 
application, the batch K.sub.d s were determined by contacting 0.01 g of 
the particle with 20 mL of PWTP (Process Waste Treatment Plant simulant 
solution) (see formulation below). 
______________________________________ 
PWTP Waste Simulant Composition 
Species Molarity (M) 
______________________________________ 
CaCO.sub.3 9.14 E.sup.-4 
Ca(NO.sub.3).sub.2 --4H.sub.2 O 
4.27 E.sup.-5 
CaCl.sub.2 1.60 E.sup.-5 
MgSO.sub.4 2.1 E.sup.-4 
MgCl.sub.2.6H.sub.2 O 1.18 E.sup.-4 
Ferri-Floc 0.04 ml/L 
NaF 4.21 E.sup.-5 
Na.sub.3 PO.sub.4.12H.sub.2 O 
2.2 E.sup.-5 
Na.sub.2 SiO.sub.3.9H.sub.2 O 
1.1 E.sup.-4 
NaHCO.sub.3 1.29 E.sup.-3 
K.sub.2 CO.sub.3 1.28 E.sup.-5 
CsNO.sub.3 3.4 E.sup.-4 
______________________________________ 
Ferri-Floc.TM. (Tennessee Chemical Co., Atlanta, Ga.) is a solution 
containing 10,000 ppm Iron and 25,800 ppm SO.sub.4. 
The equation for determining the K.sub.d can be simplified by determining 
the concentration of the analyte before and after contact and calculating 
the quantity of analyte on the ion exchanger by difference. 
##EQU1## 
Where: C.sub.I is the initial amount or activity of the ion of interest in 
the feed solution prior to contact, 
C.sub.f is the amount or activity after contact, 
V is the solution volume, 
M is the exchanger mass, 
F is the mass of dry ion exchanger divided by the mass of wet ion exchanger 
(F-factor). 
K.sub.d (normal units are mL/g) represents the theoretical volume of 
solution (mL) that can be processed per mass of exchanger (dry weight 
basis) under equilibrium conditions. Lambda, the theoretical number of bed 
volumes of solution that can be processed per volume of exchanger, is 
obtained by multiplying K.sub.d by the exchanger bed density, P.sub.b (g 
of resin per mL of resin) as shown below: 
EQU .lambda.=K.sub.d *P.sub.b 
The lambda value provides a method for comparing the ion exchange 
performance of a wide variety of materials on a volume basis (e.g., in an 
ion exchange column). 
More preferably, the experimental equipment that was required to complete 
the batch K.sub.d determinations included an analytical balance, a 
constant temperature water bath, an oven for F-factor determinations, a 
variable speed shaker table, 20-mL scintillation vials, 0.45 .mu.m syringe 
filters, the appropriate ion exchanger, and simulant solutions. The 
particles were all dried thoroughly prior to testing. Approximately 0.01 g 
of each material was contacted with 20 mL of the PWTP solution. The sample 
bottles were placed into a 25.degree. C. constant temperature bath and 
shaken lightly for 20 hours. The samples were then filtered with a 0.45 
micrometer syringe filter to separate the resin material from the solution 
and the resulting liquid was analyzed for cesium by ICP-MS(Inductively 
coupled plasma-mass spectrometry) for Cs. 
The particles of the invention can be enmeshed in various fibrous, nonwoven 
webs or matrices which preferably are porous. Types of webs or matrices 
include fibrillated polytetrafluoroethylene (PTFE), microfibrous webs, 
macrofibrous webs, and polymer pulps. 
1. Fibrillated PTFE 
The PTFE composite sheet material of the invention is prepared by blending 
the particulate or combination of particulates employed with a PTFE 
emulsion until a uniform dispersion is obtained and adding a volume of 
process lubricant up to approximately one half the volume of the blended 
particulate. Blending takes place along with sufficient process lubricant 
to exceed sorptive capacity of the particles in order to generate the 
desired porosity level of the resultant article. Preferred process 
lubricant amounts are in the range of 3 to 200 percent by weight in excess 
of that required to saturate the particulate, as is disclosed in U.S. Pat. 
No. 5,071,610, which is incorporated herein by reference. The aqueous PTFE 
dispersion is then blended with the particulate mixture to form a mass 
having a putty-like or dough-like consistency. The sorptive capacity of 
the solids of the mixture is noted to have been exceeded when small 
amounts of water can no longer be incorporated into the mass without 
separation. This condition should be maintained throughout the entire 
mixing operation. The putty-like mass is then subjected to intensive 
mixing at a temperature and for a time sufficient to cause initial 
fibrillation of the PTFE particles. Preferably, the temperature of 
intensive mixing is up to 90.degree. C., more preferably it is in the 
range of 0.degree. to 90.degree. C., most preferably 20.degree. to 
60.degree. C. Minimizing the mixing at the specified temperature is 
essential in obtaining extraction media and chromatographic transport 
properties. 
Mixing times will typically vary from 0.2 to 2 minutes to obtain the 
necessary initial fibrillation of the PTFE particles. Initial mixing 
causes partial disoriented fibrillation of a substantial portion of the 
PTFE particles. 
Initial fibrillation generally will be noted to be at an optimum within 60 
seconds after the point when all components have been fully incorporated 
into a putty-like (dough-like) consistency. Mixing beyond this point will 
produce a composite sheet of inferior extraction medium and 
chromatographic properties. 
Devices employed for obtaining the necessary intensive mixing are 
commercially available intensive mixing devices which are sometimes 
referred to as internal mixers, kneading mixers, double-blade batch mixers 
as well as intensive mixers and twin screw compounding mixers. The most 
popular mixer of this type is the sigma-blade or sigma-arm mixer. Some 
commercially available mixers of this type are those sold under the common 
designations Banbury mixer, Mogul mixer, C. W. Brabender Prep mixer and C. 
W. Brabender sigma blade mixer. Other suitable intensive mixing devices 
may also be used. 
The soft putty-like mass is then transferred to a calendering device where 
the mass is calendered between gaps in calendering rolls preferably 
maintained at a temperature up to 125.degree. C., preferably in the range 
of 0.degree. to about 100.degree. C., more preferably in the range of 
20.degree. C. to 60.degree. C., to cause additional fibrillation of the 
PTFE particles of the mass, and consolidation while maintaining the water 
level of the mass at least at a level of near the sorptive capacity of the 
solids, until sufficient fibrillation occurs to produce the desired 
extraction medium. Preferably the calendering rolls are made of a rigid 
material such as steel. A useful calendering device has a pair of 
rotatable opposed calendering rolls each of which may be heated and one of 
which may be adjusted toward the other to reduce the gap or nip between 
the two. Typically, the gap is adjusted to a setting of 10 millimeters for 
the initial pass of the mass and, as calendering operations progress, the 
gap is reduced until adequate consolidation occurs. At the end of the 
initial calendering operation, the resultant sheet is folded and then 
rotated 90.degree. to obtain biaxial fibrillation of the PTFE particles. 
Smaller rotational angles (e.g., 20.degree. to less than 90.degree.) may 
be preferred in some extraction and chromatographic applications to reduce 
calender biasing, i.e., unidirectional fibrillation and orientation. 
Excessive calendering (generally more than two times) reduces the porosity 
which in turn reduces the solvent wicking in thin layer chromatography 
(TLC) and the flow-through rate in the filtration mode. 
During calendering, the lubricant level of the mass is maintained at least 
at a level of exceeding the absorptive capacity of the solids by at least 
3 percent by weight, until sufficient fibrillation occurs and to produce 
porosity or void volume of at least 30 percent and preferably 40 to 70 
percent of total volume. The preferred amount of lubricant is determined 
by measuring the pore size of the article using a Coulter Porometer as 
described in the Examples below. Increased lubricant results in increased 
pore size and increased total pore volume as is disclosed in U.S. Pat. No. 
5,071,610. 
The calendered sheet is then dried under conditions which promote rapid 
drying yet will not cause damage to the composite sheet or any constituent 
therein. Preferably drying is carried out at a temperature below 
200.degree. C. The preferred means of drying is by use of a forced air 
oven. The preferred drying temperature range is from 20.degree. C. to 
about 70.degree. C. The most convenient drying method involves suspending 
the composite sheet at room temperature for at least 24 hours. The time 
for drying may vary depending upon the particular composition, some 
particulate materials having a tendency to retain water more than others. 
The resultant composite sheet preferably has a tensile strength when 
measured by a suitable tensile testing device such as an Instron (Canton, 
Mass.) tensile testing device of at least 0.5 MPa. The resulting composite 
sheet has uniform porosity and a void volume of at least 30 percent of 
total volume. 
The PTFE aqueous dispersion employed in producing the PTFE composite sheet 
of the invention is a milky-white aqueous suspension of minute PTFE 
particles. Typically, the PTFE aqueous dispersion will contain about 30 
percent to about 70 percent by weight solids, the major portion of such 
solids being PTFE particles having a particle size in the range of about 
0.05 to about 0.5 micrometers. The commercially available PTFE aqueous 
dispersion may contain other ingredients, for example, surfactant 
materials and stabilizers which promote continued suspension of the PTFE 
particles. 
Such PTFE aqueous dispersions are presently commercially available from 
Dupont de Nemours Chemical Corp., for example, under the trade names 
Teflon.TM. 30, Teflon.TM. 30B or Teflon.TM. 42. Teflon.TM. 30 and 
Teflon.TM. 30B contain about 59 percent to about 61 percent solids by 
weight which are for the most part 0.05 to 0.5 micrometer PTFE particles 
and from about 5.5 percent to about 6.5 percent by weight (based on weight 
of PTFE resin) of non-ionic wetting agent, typically octylphenol 
polyoxyethylene or nonylphenol polyoxyethylene. Teflon.TM. 42 contains 
about 32 to 35 percent by weight solids and no wetting agent but has a 
surface layer of organic solvent to prevent evaporation. A preferred 
source of PTFE is FLUON.TM., available from ICI Americas, Inc. Wilmington, 
Del. It is generally desirable to remove, by organic solvent extraction, 
any residual surfactant or wetting agent after formation of the article. 
In other embodiments of the present invention, the fibrous membrane (web) 
can comprise non-woven, macro- or microfibers preferably selected from the 
group of fibers consisting of polyamide, polyolefin, polyester, 
polyurethane, glass fiber, polyvinylhalide, or a combination thereof. The 
fibers preferably are polymeric. (If a combination of polymers is used, a 
bicomponent fiber may be obtained.) If polyvinylhalide is used, it 
preferably comprises fluorine of at most 75 percent (by weight) and more 
preferably of at most 65 percent (by weight). Addition of a surfactant to 
such webs may be desirable to increase the wettability of the component 
fibers. 
2. Macrofibers 
The web can comprise thermoplastic, melt-extruded, large-diameter fibers 
which have been mechanically-calendered, air-laid, or spunbonded. These 
fibers have average diameters in the general range of 50 .mu.m to 1,000 
.mu.m. 
Such non-woven webs with large-diameter fibers can be prepared by a 
spunbond process which is well known in the art. (See, e.g., U.S. Pat. 
Nos. 3,338,992, 3,509,009, and 3,528,129, the fiber preparation processes 
of which are incorporated herein by reference.) As described in these 
references, a post-fiber spinning web-consolidation step (i.e., 
calendering) is required to produce a self-supporting web. Spunbonded webs 
are commercially available from, for example, AMOCO, Inc. (Naperville, 
Ill.). 
Non-woven webs made from large-diameter staple fibers can also be formed on 
carding or air-laid machines (such as a Rando-Webber.TM. Model 12BS made 
by Curlator Corp., East Rochester, N.Y.), as is well known in the art. 
See, e.g., U.S. Pat. Nos. 4,437,271, 4,893,439, 5,030,496, and 5,082,720, 
the processes of which are incorporated herein by reference. 
A binder is normally used to produce self-supporting webs prepared by the 
air-laying and carding processes and is optional where the spunbond 
process is used. Such binders can take the form of resin systems which are 
applied after web formation or of binder fibers which are incorporated 
into the web during the air laying process. 
Examples of common binder fibers include adhesive-only type fibers such as 
Kodel.TM. 43UD (Eastman Chemical Products, Kingsport, Tenn.) and 
bicomponent fibers, which are available in either side-by-side form (e.g., 
Chisso ES Fibers, Chisso Corp., Osaka, Japan) or sheath-core form (e.g., 
Melty.TM. Fiber Type 4080, Unitika Ltd., Osaka, Japan). Application of 
heat and/or radiation to the web "cures" either type of binder system and 
consolidates the web. 
Generally speaking, non-woven webs comprising macrofibers have relatively 
large voids. Therefore, such webs have low capture efficiency of 
small-diameter particulate (reactive supports) which is introduced into 
the web. Nevertheless, particulate can be incorporated into the non-woven 
webs by at least four means. First, where relatively large particulate is 
to be used, it can be added directly to the web, which is then calendered 
to actually enmesh the particulate in the web (much like the PTFE webs 
described previously). Second, particulate can be incorporated into the 
primary binder system (discussed above) which is applied to the non-woven 
web. Curing of this binder adhesively attaches the particulate to the web. 
Third, a secondary binder system can be introduced into the web. Once the 
particulate is added to the web, the secondary binder is cured 
(independent of the primary system) to adhesively incorporate the 
particulate into the web. Fourth, where a binder fiber has been introduced 
into the web during the air laying or carding process, such a fiber can be 
heated above its softening temperature. This adhesively captures 
particulate which is introduced into the web. Of these methods involving 
non-PTFE macrofibers, those using a binder system are generally the most 
effective in capturing particulate. Adhesive levels which will promote 
point contact adhesion are preferred. 
Once the particulate (reactive supports) has been added, the loaded webs 
are typically further consolidated by, for example, a calendering process. 
This further enmeshes the particulate within the web structure. 
Webs comprising larger diameter fibers (i.e., fibers which average 
diameters between 50 .mu.m and 1,000 .mu.m) have relatively high flow 
rates because they have a relatively large mean void size. 
3. Microfibers 
When the fibrous web comprises non-woven microfibers, those microfibers 
provide thermoplastic, melt-blown polymeric materials having active 
particulate dispersed therein. Preferred polymeric materials include such 
polyolefins as polypropylene and polyethylene, preferably further 
comprising a surfactant, as described in, for example, U.S. Pat. No. 
4,933,229, the process of which is incorporated herein by reference. 
Alternatively, surfactant can be applied to a blown microfibrous (BMF) web 
subsequent to web formation. Polyamide can also be used. Particulate can 
be incorporated into BMF webs as described in U.S. Pat. No. 3,971,373, the 
process of which is incorporated herein by reference. 
Microfibrous webs of the present invention have average fiber diameters up 
to 50 .mu.m, preferably from 2 .mu.m to 25 .mu.m, and most preferably from 
3 .mu.m to 10 .mu.m. Because the void sizes in such webs range from 0.1 
.mu.m to 10 .mu.m, preferably from 0.5 .mu.m to 5 .mu.m, flow through 
these webs is not as great as is flow through the macrofibrous webs 
described above. 
4. Cast Porous Membranes 
Solution-cast porous membranes can be provided by methods known in the art. 
Such polymeric porous membranes can be, for example, polyolefin including 
polypropylene, polyamide, polyester, polyvinyl chloride, and polyvinyl 
acetate fibers. 
5. Fibrous Pulps 
The present invention also provides a solid phase extraction sheet 
comprising a porous fibrous pulp, preferably a polymeric pulp, comprising 
a plurality of fibers that mechanically entrap active particles, and 
preferably a polymeric hydrocarbon binder, the weight ratio of particles 
to binder being at least 13:1 and the ratio of average uncalendered sheet 
thickness to effective average particle diameter being at least 125:1. 
Generally, the fibers that make up the porous polymeric pulp of the SPE 
sheet of the present invention can be any pulpable fiber (i.e., any fiber 
that can be made into a porous pulp). Preferred fibers are those that are 
stable to radiation and/or to a variety of pHs, especially very high pHs 
(e.g., pH=14) and very low pHs (e.g., pH=1). Examples include polyamide 
fibers and those polyolefin fibers that can be formed into a pulp 
including, but not limited to, polyethylene and polypropylene. 
Particularly preferred fibers are aromatic polyamide fibers and aramid 
fibers because of their stability to both radiation and highly caustic 
fluids. Examples of useful aromatic polyamide fibers are those fibers of 
the nylon family. Polyacrylic nitrile, cellulose, and glass can also be 
used. Combinations of pulps can be used. 
Examples of useful aramid fibers are those fibers sold under the trade name 
Kevlar.TM. (DuPont, Wilmington, Del.). Kevlar.TM. fiber pulps are 
commercially available in three grades based on the length of the fibers 
that make up the pulp. Regardless of the type of fiber(s) chosen to make 
up the pulp, the relative amount of fiber in the resulting SPE sheet (when 
dried) ranges from about 12.5 percent to about 30 percent (by weight), 
preferably from about 15 percent to 25 percent (by weight). 
Useful binders in the SPE sheet of the present invention are those 
materials that are stable over a range of pHs (especially high pHs) and 
that exhibit little or no interaction (i.e., chemical reaction) with 
either the fibers of the pulp or the particles entrapped therein. 
Polymeric hydrocarbon materials, originally in the form of latexes, have 
been found to be especially useful. Common examples of useful binders 
include, but are not limited to, natural rubbers, neoprene, 
styrene-butadiene copolymer, acrylate resins, and polyvinyl acetate. 
Preferred binders include neoprene and styrene-butadiene copolymers. 
Regardless of the type of binder used, the relative amount of binder in 
the resulting SPE sheet (when dried) is about 3 percent to about 7 
percent, preferably about 5 percent. The preferred amount has been found 
to provide sheets with nearly the same physical integrity as sheets that 
include about 7 percent binder while allowing for as great a particle 
loading as possible. It may be desirable to add a surfactant to the 
fibrous pulp, preferably in small amounts up to about 0.25 weight percent 
of the composite. 
Because the capacity and efficiency of the SPE sheet depends on the amount 
of particles included therein, high particle loading is desirable. The 
relative amount of particles in a given SPE sheet of the present invention 
is preferably at least about 65 percent (by weight), more preferably at 
least about 70 percent (by weight), and most preferably at least about 75 
percent (by weight). Additionally, the weight percentage of particles in 
the resulting SPE sheet is at least 13 times greater than the weight 
percentage of binder, preferably at least 14 times greater than the weight 
percentage of binder, more preferably at least 15 times greater than the 
weight percentage of binder. 
Regardless of the type or amount of the particles used in the SPE sheet of 
the present invention, they are mechanically entrapped or entangled in the 
fibers of the porous pulp. In other words, the particles are not 
covalently bonded to the fibers. 
Objects and advantages of this invention are further illustrated by the 
following examples. The particular materials and amounts thereof, as well 
as other conditions and details, recited in these examples should not be 
used to unduly limit this invention. 
EXAMPLES 
Example 1 
Potassium cobalt hexacyanoferrate (KCOHEX) was prepared by slowly adding an 
aqueous solution of 1 part 0.3 M potassium ferrocyanide in an acetic acid 
buffer (approximately 1.8.times.10.sup.-3 M in acetic acid) cooled to 
between 0.degree. C. and 4.degree. C. at pH of between 5 and 6 to an 
aqueous solution of 2.4 parts 0.5 M cobalt nitrate (present in excess) 
cooled to between 0.degree. C. and 4.degree. C. with constant stirring. 
Precipitate was separated from the reaction mixture using a centrifuge 
(Bird Centrifuge Model IIP200, Bird Machine Co., South Walpole, Mass.) by 
separating the initial precipitate, then repeatedly slurrying the 
precipitate in water and re-centrifuging, for a total of four washings. 
Excess cobalt nitrate is pink in color, so the desired solid material was 
centrifuged until the supernatant liquid was no longer pink. 
The clean precipitate was again slurried in water at a concentration of 7.5 
percent by weight, then spray-dried using a Bowen Model BE-1174 spray 
dryer (Niro Atomizer, Inc., Columbia, Md.), as follows: 
Inlet air temperature: 210.degree. C. 
Atomizing pressure: 276 Kpa (40 psig) 
Slurry feed rate: 1.25 gal/hr (4.73 L/hr) 
Outlet temperature: 95.degree. C. 
Cyclone differential pressure: 4.5 in H.sub.2 O (11.43.times.10.sup.-3 
kg/cm.sup.2). 
Recovered dried potassium cobalt hexacyanoferrate represented 92 percent 
yield, and was observed under an Olympus BH2 microscope (Olympus America, 
Inc., Melville, N.Y.) to be spherical in shape. Measurement of the 
particles using a Horiba Model LA-900 Particle Size Analyzer (Horiba 
Instruments, Inc., Irvine, Calif.), showed an average particle size of 
approximately 11 micrometers and a particle size distribution of from 
about 7 micrometers to about 60 micrometers. 
The spray-dried material was dark green in color. The spherical particles 
were heated in an air-vented oven at approximately 100.degree. C. until 
they changed to a purplish-black color. Recovery from heating was 
essentially quantitative, and no loss of size or shape was noted as a 
result of the heating procedure. 
Example 2 (Comparative) 
Potassium cobalt hexacyanoferrate was prepared as described in Example 1, 
except that the solid precipitate obtained from the final centrifuge wash 
was spread out in a thin layer about 2.5 cm thick on a drying tray and 
heated in air at 110.degree. C.-115.degree. C. until the solid had dried 
and its color had changed from green to purplish-black. The dried solid 
was subjected to cryogenic hammer-milling by means of a Model D Comminutor 
(Fitzpatrick Co., Elmhurst, Ill.) using a 325-mesh screen (0.044 mm sieve 
opening) and the resulting powder was sized in a hydrocyclone (Richard 
Mozley Ltd., Comwall, UK). Particles in the range of from about 1 to about 
50 micrometers in their largest dimension were retained, with an average 
particle size of approximately 10-15 micrometers. Yield of sized particles 
was approximately 60 percent. As expected from a milling process, 
particles were typically irregular in shape (significant deviation from 
spherical) and a broad particle size distribution was obtained. The yield 
was significantly less in the particle size range desired. 
Example 3 
Potassium zinc hexacyanoferrate (KZNHEX) was prepared by slowly adding an 
aqueous solution of 1 part 0.5 M potassium ferrocyanide (0.28 moles) (pH 
was adjusted to pH 5.0-5.1 using concentrated acetic acid) cooled to 
between 0.degree. C. and 4.degree. C. at to an aqueous solution of 2.0 
parts 0.3 M zinc nitrate (0.34 moles) cooled to between 0.degree. C. and 
4.degree. C. with constant stirring. Precipitate was separated from the 
reaction mixture using a centrifuge (Centrifuge Model 460G, International 
Equipment Company, Boston, Mass.) by separating the initial precipitate, 
then repeatedly slurrying the precipitate in water and re-centrifuging, 
for a total of four washings. 
The clean precipitate was again slurried in water at a concentration of 7.5 
percent by weight, then spray-dried using a Niro Atomizer, Model 68 Order 
# 093-1413-00, Serial #2402 spray dryer (Niro Atomizer, Inc., Columbia, 
Md.), as follows: 
Inlet air temperature: 190.degree. C. 
Spinning Disc RPM's: 400 KPa (58 psig) 
Slurry feed rate: 2.4 L/hr 
Outlet temperature: 85.degree. C. 
Cyclone magnahelic pressure: 0.47 in H.sub.2 O (1.19.times.10.sup.-3 
kg/cm.sup.2). 
Recovered dried potassium zinc hexacyanoferrate was observed under an SEM 
(Cambridge model S240, LEO Electromicroscopy, Inc., Thornwood, N.Y.) to be 
spherical in shape. Measurement of the particles using a Horiba Model 
LA-900 Particle Size Analyzer (Horiba Instruments, Inc., Irvine, Calif.), 
showed an average particle size (average diameter) of approximately 11.8 
micrometers with about 20 weight percent less than 5 .mu.m in size. 
The raspberry-shaped particles were heated in an air-vented oven at 
approximately 115.degree. C. for 18 hours. Recovery from heating was 
essentially quantitative, and no loss of size or shape was noted as a 
result of the heating procedure. 
Example 4 (Comparative) 
Potassium zinc hexacyanoferrate was prepared as described in Example 3, 
except that the solid precipitate obtained from the final centrifuge wash 
was spread out in a thin layer about 2.5 cm thick on a drying tray and 
heated in air at 115.degree. C. for 18 hours until the solid had dried. 
The dried solid was broken up from its clumps using a mortar and pestle. 
The average particle size of the material was 0.636 micrometers so no 
further grinding was done. The particles were observed under an SEM 
(Cambridge Model S240), and were observed to be typically irregular in 
shape (significant deviation from spherical). All particles were less than 
1 .mu.m in size. 
Example 5 
Potassium nickel hexacyanoferrate (KNIHEX) was prepared by slowly adding an 
aqueous solution of 1 part 0.3 M potassium ferrocyanide (0.86 moles) (pH 
was adjusted to pH 5.0-5.1 using concentrated acetic acid) cooled to 
between 0.degree. C. and 4.degree. C. at to an aqueous solution of 1.44 
parts 0.3 M nickel nitrate (1.23 moles) cooled to between 0.degree. C. and 
4.degree. C. with constant stirring. Precipitate was separated from the 
reaction mixture using a centrifuge (Centrifuge Model 460G, International 
Equipment Company, Boston, Mass.) by separating the initial precipitate, 
then repeatedly slurrying the precipitate in water and re-centrifuging, 
for a total of four washings. 
The clean precipitate was again slurried in water at a concentration of 7.5 
percent by weight, then spray-dried using a Niro Atomizer Model 68, order 
#093-1413-00, Serial #2402 spray dryer (Niro Atomizer, Inc., Columbia, 
Md.), as follows: 
Inlet air temperature: 192.degree. C. 
Spinning Disc RPM's: 400 KPa (58 psig) 
Slurry feed rate: 2.4 L/hr 
Outlet temperature: 79.3.degree. C. 
Cyclone magnahelic pressure: 0.47 in H.sub.2 O (1.19.times.10.sup.-3 
kg/cm.sup.2). 
Recovered dried potassium nickel hexacyanoferrate was observed under an SEM 
(Cambridge model S240) to be spherical in shape. Measurement of the 
particles using a Horiba Model LA-900 Particle Size Analyzer (Horiba 
Instruments, Inc., Irvine, Calif.), showed an average particle size of 
approximately 9.5 micrometers with about 10 weight percent of the particle 
less than 5 micrometers. 
The spherical particles were heated in an air-vented oven at approximately 
115.degree. C. for 18 hours. Recovery from heating was essentially 
quantitative, and no loss of size or shape was noted as a result of the 
heating procedure. 
FIG. 1 shows that the particle size distribution of the KNIHEX particles 
was monodisperse. 
Example 6 (Comparative) 
Potassium nickel hexacyanoferrate was prepared as described in Example 5, 
except that the solid precipitate obtained from the final centrifuge wash 
was spread out in a thin layer about 2.5 cm thick on a drying tray and 
heated in air at 115.degree. C. for 18 hours until the solid had dried. 
The dried solid was broken up from its clumps using a mortar and pestle. 
The material was then ground with a ball mill using Zirconia media for 90 
minutes. The average particle size was 16.77 micrometers with about 30% of 
the material less than 5 micrometers in size. The particles were observed 
under an SEM (Cambridge Model S240) and found to be typically irregular in 
shape (significant deviation from spherical). 
FIG. 2 shows the particle size distribution of the ground KNIHEX particles 
was large compared to that of Example 5 (FIG. 1) where the particle size 
distribution was narrow. 
Example 7 
Ammonium ferric hexacyanoferrate (NH.sub.4 Fe.sup.III Fe.sup.II (CN).sub.6 
! was prepared by slowly adding an aqueous solution of 1 part 0.3 M 
ammonium ferrocyanide (0.86 moles) (pH was adjusted to pH 5.0-5.1 using 
concentrated acetic acid) cooled to between 0.degree. C. and 4.degree. C. 
at to an aqueous solution of 1 parts 0.5 M ferric nitrate (0.86 moles) 
cooled to between 0.degree. C. and 4.degree. C. with constant stirring. 
Precipitate was separated from the reaction mixture using a centrifuge 
(Centrifuge Model 460G, International Equipment Company, Boston, Mass.) by 
separating the initial precipitate, then repeatedly slurrying the 
precipitate in water and re-centrifuging, for a total of four washings. 
The clean precipitate was again slurried in water at a concentration of 7.5 
percent by weight, then spray-dried using a Niro Atomizer, Serial #2402 
spray dryer (Niro Atomizer, Inc., Columbia, Md.), as follows: 
Inlet air temperature: 1 90.degree. C. 
Spinning Disc RPM's: 400 KPa (58 psig) 
Slurry feed rate: 2.4 L/hr 
Outlet temperature: 67.6.degree. C. 
Cyclone magnahelic pressure: 0.47 in H.sub.2 O (1.19.times.10.sup.-3 
kg/cm.sup.2). 
Recovered dried ammonium ferric hexacyanoferrate was observed under an SEM 
(Cambridge model S240) to be spherical in shape. Measurement of the 
particles using a Horiba Model LA-900 Particle Size Analyzer (Horiba 
Instruments, Inc., Irvine, Calif.), showed an average particle size of 
approximately 16.11 micrometers with less than about 10 weight percent of 
the particles less than 5 micrometers. 
The spherical particles were heated in an air-vented oven at approximately 
115.degree. C. for 18 hours. Recovery from heating was essentially 
quantitative, and no loss of size or shape was noted as a result of the 
heating procedure. 
Example 8 (Comparative) 
Ammonium ferric hexacyanoferrate was prepared as described in Example 7, 
except that the solid precipitate obtained from the final centrifuge wash 
was spread out in a thin layer about 2.5 cm thick on a drying tray and 
heated in air at 115.degree. C. for 18 hours until the solid had dried. 
The dried solid was broken up from its clumps using a mortar and pestle. 
The material was then ground with a ball mill using Zirconia media for 40 
minutes. The average particle size was 5.00 micrometers with about 98% of 
the material less than 5 micrometers in size. The particles were typically 
irregular in shape (significant deviation from spherical). 
Example 9 
Potassium nickel hexacyanoferrate (KNIHEX) was prepared by slowly adding an 
aqueous solution of 1 part 0.3 M potassium ferrocyanide (0.29 moles) (pH 
was adjusted to 5.0-5.1 using concentrated acetic acid) cooled to between 
0.degree. C. and 4.degree. C. at to an aqueous solution of 1.44 parts 0.3 
M nickel nitrate (0.42 moles) cooled to between 0.degree. C. and 4.degree. 
C. with constant stirring. Precipitate was separated from the reaction 
mixture using a centrifuge (Centrifuge Model 460G, International Equipment 
Company, Boston, Mass.) by separating the initial precipitate, then 
repeatedly slurrying the precipitate in water and re-centrifuging, for a 
total of four washings. 
The clean precipitate was again slurried in water at a concentration of 7.5 
percent by weight, then spray-dried using a Niro Atomizer, Serial #2402 
spray dryer (Niro Atomizer, Inc., Columbia, Md.), as follows: 
Inlet air temperature: 192.degree. C. 
Spinning Disc RPM's: 400 KPa (58 psig) 
Slurry feed rate: 2.4 L/hr 
Outlet temperature: 79.3.degree. C. 
Cyclone magnahelic pressure: 0.47 in H.sub.2 O (1.19.times.10.sup.-3 
kg/cm.sup.2). 
Recovered dried potassium nickel hexacyanoferrate was observed under an SEM 
(Cambridge model S240) to be spherical in shape. Measurement of the 
particles using a Horiba Model LA-900 Particle Size Analyzer (Horiba 
Instruments, Inc., Irvine, Calif.), showed an average particle size of 
approximately 12 micrometers with less than about 10% of the particle less 
than 5 micrometers. 
The spherical particles were heated in an air-vented oven at approximately 
115.degree. C. for 18 hours. The yield was 78% by weight of the reacted 
prepared material. No change in size or shape was noted as a result of the 
heating procedure. 
Example 10 (Comparative) 
Potassium nickel hexacyanoferrate was prepared as described in Example 9, 
except that the solid precipitate obtained from the final centrifuge wash 
was spread out in a thin layer about 2.5 cm thick on a drying tray and 
heated in air at 115.degree. C. for 18 hours until the solid had dried. 
The dried solid was broken up from its clumps using a mortar and pestle. 
The material was then ground in a freezer mill (SPEX model 6700 SPEX 
Industries, Inc., Edison, N.J.) for 6 minutes. The material was sieved 
with a 200 mesh screen (74 .mu.m) to remove large particles and then 
hydrocycloned to remove fines below 5 .mu.m. The average particle size 
after hydrocycloning was 21 micrometers with about 27 weight percent of 
the material less than 5 micrometers in size. The particles were typically 
irregular in shape (significant deviation from spherical). The total yield 
after grinding, sieving and hydrocycloning was 3.7%. 
Example 11 
Ammonium ferric hexacyanoferrate was prepared by slowly adding an aqueous 
solution of 1 part 0.3 M ammonium ferrocyanide (0.35 moles) (pH was 
adjusted to pH 5.0-5.1 using concentrated acetic acid) cooled to between 
0.degree. C. and 4.degree. C. at to an aqueous solution of 2 parts 0.5 M 
ferric nitrate (0.50 moles) cooled to between 0.degree. C. and 4.degree. 
C. with constant stirring. Precipitate was separated from the reaction 
mixture using a centrifuge (Centrifuge Model 460G, International Equipment 
Company, Boston, Mass.) by separating the initial precipitate, then 
repeatedly slurrying the precipitate in water and re-centrifuging, for a 
total of four washings. 
The clean precipitate was again slurried in water at a concentration of 7.5 
percent by weight, then spray-dried using a Niro Atomizer, Serial #2402 
spray dryer (Niro Atomizer, Inc., Columbia, Md.), as follows: 
Inlet air temperature: 192.degree. C. 
Spinning Disc RPM's: 400 KPa (58 psig) 
Slurry feed rate: 2.4 L/hr 
Outlet temperature: 79.3.degree. C. 
Cyclone magnahelic pressure: 0.47 in H.sub.2 O (1.19.times.10.sup.-3 
kg/cm.sup.2). 
Recovered dried ammonium ferric hexacyanoferrate represented 75 percent 
yield, and was observed under an SEM (Cambridge model S240) to be 
spherical in shape. Measurement of the particles using a Horiba Model 
LA-900 Particle Size Analyzer (Horiba Instruments, Inc., Irvine, Calif.), 
showed an average particle size of approximately 14.0 micrometers with 
less than about 10% of the particle less than 5 micrometers. 
The spherical particles were heated in an air-vented oven at approximately 
115.degree. C. for 18 hours. No change of size or shape was noted as a 
result of the heating procedure. 
Example 12 (Comparative) 
Ammonium ferric hexacyanoferrate was prepared as described in Example 11, 
except that the solid precipitate obtained from the final centrifuge wash 
was spread out in a thin layer about 2.5 cm thick on a drying tray and 
heated in air at 115.degree. C. for 18 hours until the solid had dried. 
The dried solid was broken up from its clumps using a mortar and pestle. 
The average particle size was 1.15 .mu.m micrometers with 98.5% of the 
material less than 5 micrometers. The particles were typically irregular 
in shape (significant deviation from spherical) and were too small to 
process further. 98.5% of the material was less than 5 .mu.m in size. The 
yield was 1.5%. 
Example 13 
A particle-filled porous web was prepared from the spherical potassium 
cobalt hexacyanoferrate particles of Example 1. An agitated slurry of 20 g 
Kevlar.TM. 1F306 dry aramid fiber pulp (DuPont, Wilmington, Del.) in 2000 
g water was blended in a 4 L Waring.TM. blender at a low speed for 30 
seconds, then mixed with 0.25 g Tamol 850.TM. dispersant (Rohm & Haas Co., 
Philadelphia, Pa.), followed by 8.75 g (3.5 g dry weight) Goodrite.TM. 
1800.times.73 styrene-butadiene latex binder aqueous slurry (B. F. 
Goodrich Co., Brecksville, Ohio). Blending was continued for 30 seconds at 
a low speed. To this mixture was added 53.6 g potassium cobalt 
hexacyanoferrate, followed by 20 g powdered alum (aluminum sulfate), and 
stirring was continued for an additional minute. The mixture was poured 
into a Williams sheet mold (Williams Apparatus Co., Watertown, N.Y.) 
equipped with a 930.3 cm.sup.2 porous screen having pores of approximately 
0.14 mm (100 mesh) at the bottom to allow water to drain. The resulting 
wet sheet was pressed in a pneumatic press (Mead Fluid Dynamics, Chicago, 
Ill.) at approximately 620 KPa for approximately five minutes to remove 
additional water. Drain time was 25 seconds, and no loss of KCOHEX could 
be observed in the drain water. Finally, the porous web was dried in an 
oven at 250.degree. F. (121.degree. C.) for 120 minutes. 
Example 14 (Comparative) 
Example 13 was repeated using ground and sized particulate as obtained in 
Example 2 in place of spray-dried particles. Drain time was 60 seconds. 
This showed that prior art particles loaded in a web, required more than 2 
times the drain time compared to spray-dried particles of the invention 
loaded in the web. 
Example 15 
A 90 mm diameter disk having a thickness of 3.2 mm was die cut from the 
particle-filled porous web of Example 13. The disk was placed in a 
stainless steel disk holder (Cole Parmer Instrument Co. Niles, Ill.) 
fitted with inlet and outlet pipes, so that the effective disk diameter 
was 80 mm. The disk was washed with water, then an aqueous solution 
containing 12 mg/L cesium ion was pumped first through two canister-style 
prefilters in series (Filtrete.TM. Cartridges, Memtec America Corp., 
Timonium, Md.) then through the disk at a flow rate of 105 mL/min., which 
corresponds to 6.49 bed volumes/min., wherein bed volume means the volume 
of the disk. Cesium removal, reported as C/C.sub.o, where C represents the 
cesium concentration in the effluent and C.sub.o represents initial cesium 
concentration, as a function of bed volumes is shown in Table 1. The 
pressure drop across the membrane was found to be constant at 55 KPa 
throughout the evaluation. 
TABLE 1 
______________________________________ 
Bed Volumes 
C/C.sub.o 
______________________________________ 
0 0 
389 0 
778 0 
1167 0.019 
1557 0.167 
1946 0.358 
2335 0.60 
2724 0.717 
3113 0.792 
3506 0.833 
4186 0.917 
______________________________________ 
The data of Table 1 show that spherical KCOHEX particles in a porous web 
are very effective in removing cesium ions from aqueous solution. 
Example 16 
A particle-filled porous web was prepared from the spherical potassium zinc 
hexacyanoferrate particles of Example 3. Into a 4 L Waring.TM. blender was 
added 2000 g water with 0.25 g Tamol 850.TM. dispersant (Rohm & Haas Co., 
Philadelphia, Pa.) and then 9.6 g Kevlar.TM. 1F306 dry aramid fiber pulp 
(DuPont, Wilmington, Del.) was added and blended at low speed for 30 
seconds. To this slurry was then added 36 g of the particle from Example 3 
with blending on low speed, followed by 6.15 g (2.4 g dry weight) 
Goodrite.TM. 100.times.73 styrene-butadiene latex binder aqueous slurry 
(B. F. Goodrich Co., Brecksville, Ohio). Blending was continued for 30 
seconds at a low speed. To this mixture was added 20 g of a 25% solution 
of Alum (aluminum sulfate in water), and stirring was continued for an 
additional minute. After which 1 gram of a 1% solution of Nalco 7530 
(Nalco Chemical Company, Chicago, Ill.) was added and the solution mixed 3 
seconds on low. The mixture was poured into a Williams sheet mold 
(Williams Apparatus Co., Watertown, N.Y.) equipped with a 413 cm porous 
screen having a pore size of 80 mesh (approximately 177 .mu.m) at the 
bottom to allow water to drain, drain time was 120 seconds. The resulting 
wet sheet was pressed in a pneumatic press (Mead Fluid Dynamics, Chicago, 
Ill.) at approximately 551 KPa for approximately five minutes to remove 
additional water. Finally, the porous web was dried on a handsheet dryer 
for 120 minutes at 150.degree. C. 
Example 17 
Example 16 was repeated using ground and sized particulate as obtained in 
Example 4 in place of spray-dried particles. Drain time was 240 seconds. 
This showed that prior art particles loaded in a web required 2 times the 
drain time compared to spray-dried particles of the invention loaded in a 
web. 
Example 18 
A particle-filled porous web was prepared from the spherical potassium 
nickel hexacyanoferrate particles of Example 5. Into a 4 L Waring.TM. 
blender was added 2000 g water with 0.25 g Tamol 850.TM. dispersant (Rohm 
& Haas Co., Philadelphia, Pa.) and then 14.35 g Kevlar.TM. 1F306 (12 g, 
83.5% solids) aramid fiber pulp (DuPont, Wilmington, Del.) was added and 
blended at low speed for 30 seconds. To this slurry was then added 45 g of 
the particle from Example 5 with blending on low speed, followed by 7.69 g 
(3.0 g dry weight) Goodrite.TM. 1800.times.73 styrene-butadiene latex 
binder aqueous slurry (B. F. Goodrich Co., Brecksville, Ohio). Blending 
was continued for 30 seconds at a low speed. To this mixture was added 20 
g of a 25% solution of Alum (aluminum sulfate in water), and stirring was 
continued for an additional minute. After which 1 gram of a 1% solution of 
Nalco 7530 (Nalco Chemical Company, Chicago, Ill.) was added and the 
solution mixed 3 seconds on low. The mixture was poured into a Williams 
sheet mold (Williams Apparatus Co., Watertown, N.Y.) equipped with a 413 
cm.sup.2 porous screen having a pore size of 80 mesh (approximately 177 
.mu.m) at the bottom to allow water to drain, drain time was 30 seconds. 
The resulting wet sheet was pressed in a pneumatic press (Mead Fluid 
Dynamics, Chicago, Ill.) at approximately 551 KPa for approximately five 
minutes to remove additional water. Finally, the porous web was dried on a 
handsheet dryer for 120 minutes at 150.degree. C. 
Example 19 
Example 18 was repeated using ground particles obtained in Example 6 in 
place of spray-dried particles. Drain time was 45 seconds. This showed 
that prior art particles loaded in a web required more than 1.5 times the 
drain time compared to spray-dried particles of the invention loaded in a 
web. 
Example 20 
A particle-filled porous web was prepared from the spherical ammonium 
ferric hexacyanoferrate particles of Example 7. Into a 4 L Waring.TM. 
blender was added 2000 g water with 0.25 g Tamol 850.TM. dispersant (Rohm 
& Haas Co., Philadelphia, Pa.) and then 12.9 g Kevlar.TM. 1F306 (10.8 g, 
83.5% solids) aramid fiber pulp (DuPont, Wilmington, Del.) was added and 
blended at low speed for 30 seconds. To this slurry was then added 40.5 g 
of the particle from Example 7 with blending on low speed, followed by 6.9 
g (2.7 g dry weight) Goodrite.TM. 1800.times.73 styrene-butadiene latex 
binder aqueous slurry (B. F. Goodrich Co., Brecksville, Ohio). Blending 
was continued for 30 seconds at a low speed. To this mixture was added 20 
g of a 25% solution of Alum (aluminum sulfate in water), and stirring was 
continued for an additional minute. After which 1 gram of a 1% solution of 
Nalco 7530 (Nalco Chemical Company, Chicago, Ill.) was added and the 
solution mixed 3 seconds on low. The mixture was poured into a Williams 
sheet mold (Williams Apparatus Co., Watertown, N.Y.) equipped with a 413 
cm.sup.2 porous screen having a pore size of 80 mesh (approximately 177 
.mu.m) at the bottom to allow water to drain, drain time was 15 seconds. 
The resulting wet sheet was pressed in a pneumatic press (Mead Fluid 
Dynamics, Chicago, Ill.) at approximately 551 KPa for approximately five 
minutes to remove additional water. Finally, the porous web was dried on a 
handsheet dryer for 120 minutes at 150.degree. C. 
Example 21 
Example 20 was repeated using ground and sized particulate as obtained in 
Example 8 in place of spray-dried particles. Drain time was 120 seconds. 
This showed that prior art particles loaded in a web required 8 times the 
drain time compared to spray-dried particles of the invention loaded in a 
web. 
Example 22 
A 25 mm diameter disk having a thickness of 1.98 mm was die cut from the 
particle-filled porous web of Example 20, spray dried NH.sub.4 Fe.sup.III 
Fe.sup.II (CN).sub.6). The disk weight was 0.69 g with 72.7% particle, 
weight of particle in membrane at 22 mm (flow area) was 0.39 g. The disk 
was placed in a stainless steel disk holder (Cole Parmer Instrument Co., 
Niles, Ill.) fitted with inlet and outlet pipes, so that the effective 
disk diameter was 22 mm. The disk was washed with water, then an aqueous 
solution containing 50 mg/L cesium ion was pumped through the disk at a 
flow rate of 5 mL/min., which corresponds to 6.6 bed volumes/min., wherein 
bed volume means the volume of the disk. Cesium removal, reported as 
C/C.sub.o, where C represents the cesium concentration in the effluent and 
C.sub.o represents initial cesium concentration, as a function of bed 
volumes is shown in Table 2. 
TABLE 2 
______________________________________ 
Bed Volumes C/C.sub.o 
.DELTA.P (Kpa) 
______________________________________ 
0 0 21 
32 0.016 21 
66 0.188 21 
99 0.447 21 
132 0.498 21 
232 0.597 21 
298 0.662 21 
365 0.731 21 
464 0.707 21 
597 0.738 21 
730 0.826 21 
1129 0.866 27 
______________________________________ 
The data of Table 2 show that spherical NH.sub.4 FEHEX particles in a 
porous web are effective in removing cesium ions from aqueous solution. 
The back pressure build up was constant (i.e. about 21 KPa) during about 
3/4 of the run, and increased slightly to about 27 KPa at the end of the 
run. 
Example 23 (Comparative) 
A 25 mm diameter disk having a thickness of 2.16 mm was die cut from the 
particle-filled porous web of Example 21, ground NH.sub.4 Fe.sup.III 
(Fe.sup.II (CN).sub.6). The disk weight was 0.76 g and contained 72% by 
weight particle, therefore at 22 mm (flow area) the particle weight was 
0.34 g. The disk was placed in a stainless steel disk holder (Cole Parmer 
Instrument Co., Niles, Ill.) fitted with inlet and outlet pipes, so that 
the effective disk diameter was 22 mm. The disk was washed with water, 
then an aqueous solution containing 50 mg/L cesium ion was pumped through 
the disk at a flow rate of mL/min., which corresponds to bed volumes/min., 
wherein bed volume means the volume of the disk. Cesium removal, reported 
as C/C.sub.o, where C represents the cesium concentration in the effluent 
and C.sub.o represents initial cesium concentration, as a function of bed 
volumes is shown in Table 3. The pressure drop across the membrane 
increased to 151 KPa during the evaluation. 
TABLE 3 
______________________________________ 
Bed Volumes C/C.sub.o 
.DELTA.P (KPa) 
______________________________________ 
47 0.34 41 
94 0.54 41 
141 0.50 48 
188 0.45 55 
235 0.43 55 
376 0.37 66 
471 0.34 69 
565 0.37 76 
753 0.40 90 
942 0.45 97 
1130 0.52 110 
______________________________________ 
The data of Table 3 show that irregular NH.sub.4 FEHEX particles in a 
porous web are effective in removing cesium ions from aqueous solution. 
The back pressure build up during the evaluation was 151 KPa which was 
more than five times greater than back-pressure for the spray-dried 
material in Example 22. 
Example 24 
Comparative capacity data derived from K.sub.d determination is presented 
in Table 4 below, both for spray-dried and ground material. 
TABLE 4 
______________________________________ 
Example Processing Capacity (g Cs/g 
Particle Number Method particle) 
______________________________________ 
K.sub.2 ZnFe(CN).sub.6 * 
4 Raw product 
0.1125 
K.sub.2 ZnFe(CN).sub.6 
3 Spray dried 
0.115 
KNiFe(CN).sub.6 * 
6 Ground 0.0997 
KNiFe(CN).sub.6 
5 Spray dried 
0.1093 
______________________________________ 
*comparative 
The data of Table 4 show that the capacities for spray-dried materials of 
the invention were improved compared to a raw product of ground particles. 
Example 25 Mixed Metal Hexacyanoferrate adsorbents 
Table 5, below, gives compositions and capacities for cesium for a number 
of adsorbents with a composition of: potassium metal hexacyanoferrate 
where metal may be cobalt, copper, nickel, zinc or mixtures of those 
metals. 
TABLE 5 
______________________________________ 
Metal/metal 
Capacity 
Particle ratio mMol/gram 
______________________________________ 
KCOCUHEX Co/Cu = 1 0.84 
KCOCUHEX Co/Cu = 1/3 
0.84 
KCOCUHEX Co/Cu-3 0.79 
KCONIHEX Co/Ni = 1 0.81 
KCOHIHEX Co/Ni = 1/3 
0.78 
KCOHEX KCOHEX 0.85 
KCOZNHEX Co/Zn = 1 0.79 
KCOZNHEX Co/Zn = 1/3 
0.81 
KCOZNHEX Co/Zn = 3 0.83 
KCOZNHEX Cu/Zn = 1 0.79 
KZNHEX KZNHEX 0.85 
KCUHEX KCUHEX 0.76 
KCOCUHEX Co/Cu = 1/2 
0.77 
KCOCUHEX Co/Cu = 2 0.81 
KCOZNHEX Co/Zn = 1/2 
0.41 
______________________________________ 
All of these adsorbents were prepared essentially following the procedure 
given in Example 1 using appropriate starting materials. In all cases an 
excess of metal (as compared with potassium) existed and amounts of the 
solutions of each metal were adjusted to yield the ratios shown in the 
second column. 
All of these compositions had good or high capacity for cesium and all had 
reasonably low solubility. 
Various modifications and alterations that do not depart from the scope and 
intent of this invention will become apparent to those skilled in the art. 
This invention is not to be unduly limited to the illustrative embodiments 
set forth herein.