Microporous zirconium silicate and its method of production
The present invention relates to novel microporous zirconium silicate compositions having a desired particle size distribution and methods of making those compositions. These compositions have an ideal particle size distribution for use ex vivo, for example in a dialysis exchange cartridge, yet retain many of the desirable properties of prior improved absorbers including high cation exchange capacity. Further, the new zirconium silicate molecular sieve absorbers can be manufactured using a technique that achieves the desired particle size distribution while eliminating the screening step that was previously necessary.
1. A method for making a cation exchange composition comprising a zirconium silicate, the method comprising:
providing a reaction mixture comprising a reactive source of silica and a reactive source of zirconium in a reactor;
agitating the reaction mixture in a 200 liter reactor with an agitator in the presence of four vertically placed baffle-like structures on the inner reactor sidewall with an agitation speed within a range of 80 rpm to 350 rpm, at a basic pH, and at a temperature of 100° C. to 250° C. for a duration of 1 day to 30 days; and
obtaining the cation exchange composition from the reactor
wherein the zirconium silicate is of formula (I):
A p M x Zr 1-x Si n Ge y O m (I)
where
A is a potassium ion, sodium ion, rubidium ion, cesium ion, calcium ion, magnesium ion, hydronium ion or mixtures thereof,
M is at least one framework metal, wherein the framework metal is hafnium (4+), tin (4+), niobium (5+), titanium (4+), cerium (4+), germanium (4+), praseodymium (4+), terbium (4+) or mixtures thereof,
“p” has a value from about 1 to about 20,
“x” has a value from 0 to less than 1,
“n” has a value from about 1 to about 12,
“y” has a value from 0 to about 12,
“m” has a value from about 3 to about 36 and 1≤n+y≤12,
wherein the composition exhibits a volume weighted mean particle size between 5 and 20 microns wherein less than 10% of the particles have a size below 5 microns.
2. The method of claim 1 , further comprising contacting the zirconium silicate with a dilute solution of strong acid and/or water.
3. The method of claim 1 , further comprising blending different lots of the cation exchange composition to produce a desired particle size distribution.
4. The method of claim 1 , wherein the agitation speed is within the range of 120 and 170 rpm.
5. The method of claim 4 , wherein the agitation speed is approximately 150 rpm.
6. The method of claim 1 , wherein the agitation speed is within the range of 190 and 320 rpm.
7. The method of claim 6 , wherein the agitation speed is approximately 307 rpm.
8. The method of claim 1 , wherein the reactive source of silica is sodium silicate.
9. The method of claim 1 , wherein the reactive source of zirconium is zirconium acetate.
10. The method of 1 , wherein the zirconium silicate is a ZS-9.
11. The method of 1 , wherein A is a hydronium ion.
12. The method of claim 1 , wherein x is 0, n is 3, and m is 9.
13. The method of claim 1 , wherein the zirconium silicate has a X-ray diffraction pattern generated using a copper K-alpha radiation source of:
d(Å)
5.9-6.7
5.3-6.1
2.7-3.5
2.0-2.8
1.6-2.4.