QUALITY CONTROL IN PLANT
Samples are collected on a daily basis, for each
lot and run for a granular particle size and
moisture. The CEC is typically run on a monthly
basis from a composite sample for the month.
CATION EXCHANGE CAPACITY
There are many methods that have been
used to determine the CEC in natural zeolites.
Some tests are more popular than others, but
there is no universally accepted method such as
an ASTM methods.
Quoting Pete Bunger “The BRZ natural
zeolite cation exchange (CEC) as measured by
typical test methods is much lower than the
actual CEC. The higher potassium in BRZ causes
the CEC to be lower than zeolites with lower
potassium. Accurately determining the CEC is
difficult primarily due to clinoptilolite having
a greater selectivity for the potassium ion than
ammonium ion. The attached research publication
discusses the differences in both selectivity
and kenetics. The widely used CEC methods have
an ammonium acetate solution soak step for
typically 30 to 60 minutes. The CEC results from
our soaking various zeolites for extended times
shows that even after 192 hours (8 days) of
soaking the CEC is continuing to increase, and
the 30 to 60 minute soak time is too short for
an accurate determination of CEC. For a lab test
method, a soak time of several days is
impractical. Further complications involve the
diffusion rate and partitioning. Nearly all of
these complicating factors can be mitigated by
changing from a timed soak to a column
extraction. I suggest a 2.5 cm diameter column
with a 15 cm bed depth and a 1 N (5.2%) ammonium
chloride solution flow rate of 50 ml per hour.
Due to the slightly basic properties of natural
zeolites, the more acidic ammonium chloride is
recommended over ammonium acetate.”
The fast methods, “soak tests”, are good
for field quality control, but they do not
reflect the accurate CEC. However, they also
show comparative results from different
clinoptilolite properties. Accordingly, Pete
Bunger provides the following soak tests: Here
are the single soak results (Idaho USA is BRZ).
For more information the reader is
APPARATUS AND REAGENTS
Ring stands to hold burets and separatory
Burets of approximately 2.5 cm diameter.
Separatory funnels with PTFE plug stop
cock, a capacity of 500 mls minimum.
500 ml beakers.
Drying oven with internal fan and
COLUMN METHOD OF DETERMINING CEC
Determine the percentage of moisture in
the zeolite by drying 100 grams in a drying oven
for 2 hours at 105 degrees centigrade.
Prepare a 1 N (5.2%) ammonium chloride
solution using distilled water in quantities of
at least 500 ml.
Swirl 100 grams of 14 x 40 sample with
500 ml of water. Pour off the cloudy water.
Repeat two more times.
Place a bed depth of 15 cm of the sample
in the buret partially filled with water.
Fill the separatory funnel with a minimum
of 500 mls of ammonium chloride solution (10
hors worth) so that it feeds into the top of the
buret on the ring stand.
Adjust the flow from the separatory
funnel to 50 mls/hour.
Adjust the discharge from the buret so
that the bed stays immersed and the buret
discharges 50 mls/hour.
After 192 continuous hours of running,
allow the ammonium chloride solution to run out.
Wash and refill the separatory filter
with distilled water. Allow a 5000 ml wash of
the bed in the column at a rate that is a fast
Discharge the zeolite and allow it to air
dry (increased temperature will volatize the
nitrogen as ammonia).
The samples are submitted to Huffman
Laboratory of 4630 Indiana Street, Golden CO,
80403 (phone 303-278-4455) for the total
nitrogen exchanged. The procedure is described
by Ed Huffman: “Nitrogen is determined on a
Therm Flash EA 1112 analyzer. The technique is
based on the classical Dumas method with thermal
conductivity detection (TCD). The method is
described in ASTM D5373 (coal) and ASTN D529
(petroleum products). Weighed samples are
combusted in oxygen at 950 degrees C. The
combustion products (including N2 and NOx) are
swept with helium carrier gas through combustion
catalysts, scrubbers and through a tube filled
with reduced copper. The copper removes excess
oxygen and reduces the NOx to N2. The N2 is then
separated from other gas on the chromatography
column and measured with the TCD. We use
relatively large samples so the precision should
be better than
+/- 0.1% absolute.”
Calculate the CEC as follows:
CEC (meqs/100gms) = Nitrogen exchanged as %
Divide the CEC by the percentage dry weight
determined in Step 1. For instance, if the
moisture was 12%, the dry weight should be .88.
With a CEC of 160.00, the CEC would be 181.82.
Representative product samples are collected on
a daily basis of all BRZ™. A composite sample is
prepared for each month and loaded with nitrogen
BRZ™ FAST PROCEDURE FOR CEC DETERMINATION, 27
Weigh 100 grams of BRZ™. Dry sample in drying
oven for exactly 2 hours at 100 degrees
Place in a 400 ml. deep beaker
Just cover the BRZ™ with an ammonium nitrate
solution. Prepare the ammonium nitrate solution
by dissolving 20 grams of ammonium nitrate in 15
mls. of boiling distilled water (this solution
is known as “AN 20” in the agricultural world).
Soak the BRZ™ for 24 hours stirring the beaker
at least 2 to 3 times.
Pour off the ammonium nitrate solution, and let
it “drip dry” from the beaker placed on its
Fill the beaker three times as full as the
beaker will hold with distilled water and each
time stir it with a glass rod, let it soak for
one hour, and pour it off.
Dry the BRZ™ in a drying oven at 100 degrees C
for one hour.
Pulverize the sample.
Send sample to Huffman Laboratories, Inc., 4630
Indiana St., Golden, CO 80403-1849
(303-278-4555). Huffman will
report the total nitrogen exchanged.
CATION EXCHANGE CAPACITY (CEC):
CEC (meqs/100gms) = Nitrogen exchanged as %
The accepted test for CEC involves 5 immersions
of the sample in AN-20. Each immersion involves
1 day. Empirically one immersion corresponds to
80% of the actual CEC. Five immersions have
been avoided due to the time requirement.
Drying the sample is very critical. The
clinoptilolite contain free water and water of
hydration. At 100 degrees centigrade different
moisture contents are a function of time.
Further, samples must be packaged immediately
after removing an aliquot, because the
clinoptilolite is a very effective desiccant.
The samples are submitted to Huffman Laboratory
of 4630 Indiana St., Golden CO., 80403 (phone
303-278-4455) for the total nitrogen exchanged.
The procedure is described by Ed Hufffman Jr. as
“Nitrogen is determined on a Thermo Flash EA
1112 analyzer. The technique is based on the
classical Dumas method with thermal conductivity
detection (TCD). The method is described in ASTM
D5373 (coal) and ASTM D529 (petroleum products).
Weighed samples are combusted in oxygen at 950
degrees C. The combustion products (including N2
and NOx) are swept with a helium carrier gas
through combustion catalysts, scrubbers and
through a tube filled with reduced copper. The
copper removes excess oxygen and reduces NOx to
N2. The N2 is then separated from other gas on a
chromatography column and measured with the TCD.
use relatively large samples so the precision
should be better than +- 0.1% absolute.”
composite sample is collected and the free
moisture is determined in a drying oven set at
100-105 degrees C for two hours using an initial
sample weight of 100 grams.
Weights are determined by calibrated scales for
packaged product or by certified truck scales.
HEAVY METALS AND MINERALOGIC COMPOSITION
Quoting the late George Desborough:
“This work was done using the modem U. S.
Geological Survey (USGS in Denver, CO) XRD
equipment using the computerized JADE mineral
identification programs to assist in
identification of minerals. … More than 20 XRD
samples (including composite samples from 3-15
foot thick zones at what is now the main mining
pit of BRZ™) were studied. Quartz was never
detected. Clinoptilolite was the only zeolite
found. Opaline silica commonly referred to as
“opal C-T” was the major diluent. Bulk chemical
compositions were determined using XRF at USGS
to determine concentrations of Na, Ca, K, Al,
Si, Fe, Ti, P, etc. Energy dispersive analysis
was used to quantitatively determine trace
elements such as As, Se, Rb, Pb, Sr, etc.”