Bentonite Mineralogy Part 1: Methods of Investigation - Posiva

31
Table 6-2. Instrumental detection limits of major elements. Limits are given only for the
elements that were determined using the respective method.
Element Detection limit (mg/k2)
XRF ICP/AES S/C-analyzer
Al 100
Ca 50 5
Fe 200
K 50 5- 10
Mg 200 1 - 5
Mn 40
Na 500 3
s 100 100
c 100 100
Table 6-3. Detection limits of minor elements, XRF
6.1 X-ray powder diffraction
6.1.1 Bulk samples
Detection
limit (m2/k2)
Elemets
60
p
30 As, Bi, Ce, Cr, Ga, La,
Pb, Sb, Se, Sn, Ti, V, Y
20 Ba, Cu, Ni, Zn
10 Mo, Nb, Rb, Sr, Th, U,
Zr
Bulk samples were mixed with acetone and ground using agate mortar and pestle. The
thick slurry was spread evenly on a glass slide and let to dry at ambient temperature.
Acetone was used to allow rapid drying and, consequently, diminish preferred
orientation of platy sheet silicate particles. Two or three mounts were prepared of each
sample because the diffractograms were used for semiquantitative evaluation of mineral
composition. Most of the samples are raw material and therefore heterogeneous. MX-80
is homogenized and Milos activated and Friedland ground to very fine-grained powder.
The XRD data was collected on a Philips X'Pert diffractometer equipped with a vertical
goniometer, a diffracted beam monochromator and a rotating sample holder at the
Research Laboratory of the Geological Survey of Finland. CuKa-radiation was used
and the applied voltage was 40 kV with a 55 mA current. The patterns were recorded
from 2 to 70°20. The counting time was 1 s per 0,02°20. The position of the smectite