Jordanian phillipsite tuff has a higher selectivity for ammonium
ion than sodium ions. The selectivity is at least
as high as for clinoptilolite. The exchange isotherms
show that effective removal of sodium ions can be easily
accomplished at the relatively low temperature of 18 7C.
However, the selectivity coefficient decreases. The release
of NH4 c from the saturated phillipsite tuff occurs over a
long period of time (630 days). These properties are favorable
for the processing and technical application of
Jordanian phillipsite tuff in the preparation of ammonium-
based slow-release fertilizer. This method offers an
alternative to the use of the highly soluble NH4 c -fertilizers
and may avoid environmental problems of surface-water
and groundwater contamination associated with their extensive
use in agriculture.