Extraction of clay fraction'

1
Extraction of clay fraction.

• Objective Obtain lt2µm size fraction rich in clay
  minerals.

Basis Application of Stokes Law.
Restrictions Based on settling of 2µm spherical
quartz particle under specific laboratory
conditions.
DO NOT MODIFY!
2
Preliminary

• Determine whether sample will slake
  (disaggregate) in water.
• Gently crush by impact to produce 1-2 mm
  particles.
• Use pH control or selective dissolution (CBD,
  etc.) to remove cementing compounds.

3
Settling

• Add about 40 g of sample to 400 ml beaker.
• Fill to top mark with water or 0.01wt
  Na-phosphate solution.
• Let stand overnight.
• Stir vigorously.
• Allow to settle for 3 hrs and 30 min.

4
Problem

• Flocculation is evident by the formation of a
  particle-dense fluid layer after a short time.
• Alleviate by diluting clay concentration,
  adjusting pH to about 9.0, or washing to remove
  interstitial salts.

5
Extraction

• Remove material in top 5 cm of the suspension by
  slowly extracting with a syringe or siphon.
• Begin extraction at the top and follow declining
  liquid to avoid inclusion of coarser particles
  from below.

6
Concentration

• Repeat extraction 2-3X and combine.
• Pour into 50 ml tubes and weigh so that pairs are
  within 0.1 g of each other.
• Centrifuge in IEC HT at 60 setting for 15 min.
• Discard clear supernatant and scrape paste from
  tube.

7
Step-by-Step
1. Obtain a representative sample with 1-2 mm
particle size.
2. Add 40 g to a marked, 400 ml beaker.
3. Add distilled water and soak overnight. Rinse
to remove soluble salts.
4. Fill to upper mark and stir vigorously.
5. Allow to settle for 3 hrs. and 30 min. Check
for evidence of flocculation.
6. Siphon or use syringe to remove suspended
material between the 5 cm-apart marks.
7. Repeat steps 3-6 several times and combine
suspensions.
8. Centrifuge to concentrate clay-sized material.