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- Add 25 mL of 1% Borax solution to the clay plug
- Dismembrate the sample (machine is auto set on time), to remove the >2 µm clay fraction
- Centrifuge for 4 mins at 750 rpm, decant the supernatant liquid into a separate centrifuge tube (you should end up with a ~full centrifuge tube of suspended clay)
- Repeat steps 1–3 on the remaining >2 µm fraction
- Centrifuge the <2 µm fraction for 15 mins at 1500 rpm to remove the Borax solution
- Decant and add 25 mL of nanopure water
- Centrifuge for 60 mins at 3000 rpm, the liquid is decanted before loading onto a zero background silica disk.
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Figure 14. A. Dessicator and oven for glycolation. B. Dried sample preparation after dessication.
Additional Clay Treatments before Scanning
Treating with Ethylene Glycol
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- Take the <2 µm clay fraction, this should be rinsed and free of any treatments.
- In centrifuge tube, add ~20 mL of 1N HCl.
- Vortex the sample to completely dislodge all material before pouring sample into a 100 mL beaker, add stir bar once sample is in place.
- Set hotplate to 300°C (boiling point of HCl is ~101ºC, but in order to maintain a continuous boil the hotplate needs to be much hotter)
- Set the stir RPM below 100, this is only to keep the material suspended within the HCl
- Start time once the samples have come to a complete boil, leave for 2 hours — add more HCl as necessary (DO NOT let the sample go dry and burn)
- Once the sample has boiled for 2 hours, turn off the hot plate and allow sample to return to room temperature before pouring beaker contents back into a clean centrifuge tube. Rinse beaker with DI water to collect all material
- Centrifuge down for 15 mins at 1500 rpm, decant acid and rinse with 25 mL nanopure (DI) water. Repeat the washing cycle 3 times.
- After samples has been washed 3 times and is free of HCl, centrifuge for 60 mins at 3000 rpm
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References
Jackson, M.L., 1956. Soil Chemical- Analysis Advanced Course by Hsueh-Wen Yeh, Hawaii Institute of Geophysics, 1980.
Moore, D.M., and Reynolds, R.C., Jr., 1989. X-ray Diffraction and the Identification and Analysis of Clay Minerals: New York (Oxford University Press).
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