Presentation on theme: "Extraction of “clay fraction”."— Presentation transcript:
1 Extraction of “clay fraction”. Objective: Obtain <2µm size fraction rich in clay minerals.Basis: Application of Stoke’s Law.Restrictions: Based on settling of 2µm spherical quartz particle under specific laboratory conditions.DO NOT MODIFY!
2 PreliminaryDetermine 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 ProblemFlocculation 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 ExtractionRemove 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-Step1. 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.