I want to measure the portion of adsorbed water in a mudrock. There are some references where the adsorbed water is measured in clays, but not in shales or mudrock.
So I asked myself if thermal analysis is a suitable method. If yes, is it better to use differential thermal analysis or thermogravimetry?
Sehr geehrter Herr Günther,
Dr. Towe has clearly mentioned the boundary at 110°C where per definition the water absorbed to the rock sample, whatever type it may be, is drawn. The other type of reaction to show a decomposition of the rock involving dehydration, decarbonization etc. is placed under the header LOI (= loss on ignition).
Thermoanalytical methods like diffential thermal analysis (DTA) or thermogravimetry (TG) reflect intracrystalline changes, involving among others the release of (OH)-, (CO3)--... which are typical of the minerals under study. See e.g. the classical book " Differential Thermal Analysis Application and Results in Mineralogy" published by Smykatz-Kloss, W. (1974)
You can use your own or "personal TG" by measurig the water released at various levels on temperature increase below 110°C.
Viel Glück !
Harald G. Dill
Dear Christian,
TGA or DTA will give you an idea about the amount of water in a shale/mudrock at the state you analyze it. That state could be 'equilibrated to lab humidity' or preconditioned at a specific, desired humidity above a certain saturated salt solution.
Generally you'd want to know more than just that, and the better thing to do then is to measure water sorption isotherms. Those give you the amount of water adsorbed in your mudrock at a specific temperature as function of relative humidity. A set of isotherms at different T give you an idea of the temperature dependancy.
We measure such isotherms by dynamic vapour sorption (DVS). The other commonly used method is manometric/volumetric, similar to gas physisorption analysis. The advantage of those methods is that you get full isotherms with
I agree with other responders that TGA/DTA can give you some insights about the water content of rocks. Ideally, the TGA/DTA setup should be hooked up to something else like mass spectrometry so you can determine what gases are being given off as a function of temperature. This would allow you to infer what consistuents might be evolving to the products detected by mass spectrometry.
My experiences suggests that water exists in mudrocks in a number of forms (besides as hydroxides, aka structural water) and also applying a 110C cutoff may not capture all the complexity of water content in mudrocks. Also one should be aware that other fluids/gases exist in mudrocks; these can include hydrocarbons, especially if dealing with organic-rich mudrocks. Some are even miscible in water and therefore may affect the temperature of boiling.
- Badges
- Science topic
- Similar topics
- Linguistics
- Composition Studies
- Publications