Add sodium chloride to the solution. If you increase the ionic activity of the solution by introducing salts, solids will flocculate and settle. You can pour off the water and ions, and then analyze your particulates.

Refer to M.L. Jackson, "Soil Chemical Analysis". It has more details than you'll probably care to read about suspension settlling.

Best Regards,

Neil Tabor
Huffington Department of Earth Sciences
Southern Methodist University
Dallas, Texas 75275-0395

(214) 768-4175

Office Hours for Fall 2018:
Room 306 Heroy Building
Tuesday: Noon - 1PM
Friday: 1PM - 2:15 PM

From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Steve Nelson <[log in to unmask]>
Sent: Thursday, September 27, 2018 2:33:29 PM
To: [log in to unmask]
Subject: [ISOGEOCHEM] off topic but ?relevant? question for smart folks
I’m interested in separating and collecting suspended stream sediments for SEM and XRD analysis.  There’s lots published on measuring concentrations (i.e., mg/L), but little on sediment recovery for futher analysis.

I’ve attempted recovery from 0.45 micron filters (cellulose nitrate) by placing the membranes in an ultrasonic bath.  I can recover enough sediment to ID the minerals by XRD, but the filters clog quite readily and the ultrasonic bath always produces a significant amorphous cellulose background as the membrane breaks apart.

Settling times for the clays will be enormous, but I will have access in the field to a nearby lab with standard centrifuges.

However, has anyone tried using one of the centrifuges used for separating soilds from oil?  They are set up to allow continuous flow of oil (water in my case) and rather than using bottles or tubes the sediment is deposited on the inside of a “bowl”.   While spinning, the sediment doesn’t have far to “fall.”

Any thoughts or other suggestions (offline) would be greatly appreciated.

Steve Nelson
Professor of Geochemistry
Dept. Geological Sciences
S-389 ESC
Brigham Young University
Provo, UT  84602
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