Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Free carbon containing
Reexamination Certificate
1998-11-03
2001-07-31
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Free carbon containing
C502S350000, C502S439000, C423S578200, C423S608000
Reexamination Certificate
active
06268307
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to ion exchange compositions; and more particularly to a titania bound ion exchange composition comprising a crystalline sodium titanate and a hydrolyzable titanium compound.
2. Description of the Art
Ever since nuclear weapons were first produced at the end of World War II, large amounts of nuclear waste have been generated and stored at various facilities. The nuclear waste, which consists largely of the byproducts of uranium and plutonium production and purification, was disposed of in ways which were deemed suitable at the time, but which in retrospect are now inadequate. Much of the nuclear waste is now stored in tanks as a highly alkaline mixture of salts and liquids which, if not recovered and properly remediated, will potentially create severe environmental problems.
Most of the stored aqueous nuclear waste is alkaline (pH 14), and contains high concentrations of sodium nitrate. The tanks contain various complexing agents, fission products, transuranic elements and other materials. Much of the stored nuclear waste is in the form of sludge created when alkali was added to the waste to prevent tank corrosion. Some of the radioactive material has been incorporated into salt cakes which is the evaporative product of the alkaline aqueous material. It is desired to remove the radioactive elements from the waste in order to allow for subsequent safe disposal of the non-radioactive materials. The removal of two of the metallic radionuclides, cesium and strontium, is particularly important because their half-lives are long enough to represent a hazard for an extended period of time.
Sodium nonatitanate is known as a strontium ion exchanger. J. Lehto; J. Radioanal. Nucl. Chem. Letters, 118: 1-13 (1987) describes the ion exchange behavior of Na
4
Ti
9
O
20
.xH
2
O toward strontium. The sodium titanate was prepared hydrothermally at 300° C. followed by boiling with NaOH.
Other references that disclose the preparation and use of sodium titanates as strontium ion exchangers include R. G. Dosch, “Final Report on the Application of Titanates, Niobates, and Tantalates to Neutralized Defense Waste Contamination Materials Properties, Physical Forms and Regeneration Techniques; National Technical Information Service” (1981); R. M. Merrill;
Journal of Radioanalytical Chemistry
; 43: 93-100 (1978); J. Lehto et al.;
J. Chem. Soc. Dalton Trans
., 101-103 (1989); and S. P. Mishra et al.:
J. Radioanalytical and Nuclear Chemistry, Articles
; 162:2, 299-305 (1992).
Various types of sodium titanates are described in the prior art as well as various uses for sodium titanates as an ion exchanger for ions besides strontium. M. Watanabe;
Journal of Solid State Chemistry
, 36: 91-96 (1981) describes the preparation of sodium titanate compounds from hydrothermal reactions involving TiO
2
with NaOH. The titanates described were TiO
2
, Na
2
OnTi
2
Na
x
TiO
2
. J. Akimoto et al., Journal of Solid State Chemistry, 90: 147-154 (1991) describes the synthesis of monosodium titanates NaTi
8
O
13
, which are distinct from the sodium nonatitanates disclosed here. H. Leinonen et al.,
Reactive Polymers
, 23: 221-228 (1994) describes the use of sodium titanates as ion exchangers for nickel and zinc.
Lehto et al.;
Radiochem. Radioanal. Letters
, 50:6, 375-384 (1982) describes the effects of gamma radiation on sodium titanate and other solid ion exchangers. The study concluded that gamma radiation had very little impact on the strontium ion exchange capacity of sodium titanate.
PCT Application WO 94/19277 discloses silico-titanates and methods for making and using them. The silico-titanates disclosed are useful for removing cesium from radioactive wastes. U.S. Pat. No. 4,156,646 discloses removal of plutonium and americium from aqueous alkaline waste solutions using sodium titanate ion exchangers. The sodium titanate used is a monosodium titanate. U.S. Pat, No. 5,352,644 describes a titania bound zeolite made by combining the zeolite, a low acidity titania binder material, and an aqueous slurry of titanium oxide hydrate.
SUMMARY OF THE INVENTION
An object of this invention is a novel titania bound ion exchange composition that has good physical strength.
Another object of this invention is a titania bound ion crystalline sodium titanate ion exchange composition wherein the ion exchange capacity of the titania bound crystalline sodium titanate is not degraded by the binder.
Yet another object of this invention is a titania bound ion exchange composition that is resistant to highly alkaline solutions.
Still another object of this invention is a titania bound ion exchange composition that is resistant to radioactive solutions.
Still another object of this invention is a titania bound crystalline sodium titanate ion exchange composition in which the binder enhances the ion exchange properties of the bound crystalline sodium titanate.
In one embodiment, this invention is an ion exchange composition of matter comprising crystalline sodium titanate and a hydrolyzable titanium compound.
In another embodiment, this invention is a titania bound ion exchange composition of matter comprising from about 40 to about 95 weight percent crystalline sodium titanate and from about 5 to about 60 weight percent titania binder having a strontium K
d
of at least 20,000.
In yet another embodiment, this invention is a method of manufacturing an titania bound ion exchange composition of matter. The method comprises admixing a hydrolyzed titanium compound having the formula Ti XX
I
X
II
X
III
wherein X is any constituent, and X
I,
X
II,
and X
III
are each chosen from the group consisting of Cl, Br, I, or OR where R is any acyl or alkyl group containing between 1 and 9 carbons and wherein R may make one or two points of contact with Ti via the oxygen with a crystalline sodium titanate and with methanol to give a wet titania bound ion exchange composition. The wet titania bound ion exchange composition is dried to give a dried titania bound ion exchange composition. The dried titania bound ion exchange composition is then compacted to a piece density of from 1.5 to 2.5 g/ml to give a compacted titania bound ion exchange composition. Finally, the compacted titania bound ion exchange composition is calcined at a temperature of from about 200° C. to about 500° C. for a period of time ranging from about 30 minutes to about 5 hours or more to give a calcined titania bound ion exchange composition.
In still another embodiment, this invention is a method of manufacturing a sodium titanate bound crystalline sodium titanate composition of matter comprising preparing a wet ion exchange composition by admixing crystalline sodium titanate having the formula Na
3.4-4.4
Ti
8.4-9.2
O
18.5-20.6
with titanium isopropoxide and methanol to give a wet titania bound ion exchange composition. The wet titania bound ion exchange composition is dried in air to give a dried titania bound ion exchange composition. The dried titania bound ion exchange composition is ground to give a powdered titania bound ion exchange composition and the powdered titania bound ion exchange composition is compacted to give a compacted titania bound ion exchange composition having a piece density of from 1.8 to 2.2 g/ml. Finally, the compacted titania bound ion exchange composition is calcined at a temperature of from about 200° C. To about 500° C. for a period of time ranging from about 30 minutes to about 5 hours or more.
In yet another embodiment, this invention is an titania bound ion exchange composition of matter comprising from about 40 to about 95 weight percent crystalline sodium titanate and from about 5 to about 60 weight percent titania binder and preferably a titania bound ion exchange composition wherein the crystalline sodium titanate has the formula Na
4
Ti
9
O
20
.
REFERENCES:
patent: 4156646 (1979-05-01), Schulz
patent: 5177045 (1993-01-01), Anthony et al.
patent: 5352644 (1994-10-01), Timken
patent: 5885925 (1999-03-01), DeFilippi et al.
patent: WO 94/19277 (1994-09-01), None
J
Anderson David Joseph
DeFilippi Irene C. G.
Gaita Romulus
Sedath Robert Henry
Seminara Gary Joseph
Allied-Signal Inc.
Griffin Steven P.
Ildebrando Christina
Szuch Colleen D.
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