Hi All I am drying marine sediment which is composed of a lot of fine grains. I have washed the sample and both placed in an oven and air dried. However, both times I develop a clay crust on top of the sediment (looks like mudcracks). How can I get rid of this curst, as I need to do run some analyses, but require "flowing sand"?
Hi Uzair,
I have had a similar problem in the past. If you are able to analyse 'wet' samples, mixing with Sodium hexametaphosphate (calgon) can help with this. You will usually have to work the crust with something like a spatula or spoon (do this gently to ensure there is minimal damage to the grain). I have done this for grain-size analysis in the past (LPSA), but it won't be suitable if you need dry samples.
If samples must be dry, you can bag the samples and work them by hand in the bag. I'm not aware of any drying technique that avoids this. If you only need sand-sized grains, you could sieve the samples to remove the clay fraction ahead of drying.
Hi Christopher D. Stringer
Thank you for the reply. The analysis that I am performing is a magnetic separation to determine weight % of magnetic to non-magnetic in the sample. Would the Calgon still work for that?
The sieving won't work, as I would like the whole sample, and if there are magnetic minerals in the clay crust, I'd lose them.
Uzair Adam
Magnetic separation isn't a technique I have used to any great degree before but I don't believe it should affect magnetic separation. I would consult with your colleagues working on this project to ensure it won't cause an issue.
I have done a quick google and I have seen a few papers have used Calgon as a pre-treatment when using magnetic separation (e.g. Article Effect of carboxymethyl starch on fine-grained hematite reco...
), but this is not an in-depth search on my part!
Hi Christopher D. Stringer
Thank you very much. My colleagues had suggested the oven drying. However, I will do some more research on the use of Calgon.
Wash it on sieve 0.075mm then collect the washed out and dry it to hydrometer test, and retain grains to sieving. I think it is better to find the particle size distribution.
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