The following article may answer your request:

Schawe, J.E., Vermeulen, P.A. and van Drongelen, M., 2015. A new crystallization process in polypropylene highly filled with calcium carbonate. Colloid and polymer science, 293(6), pp.1607-1614.

I. In oxidizing (open) atmosphere (dry air), we can chiefly consider the following iron addition effects: (i) Fe can be expected to first oxidate to Fe3O4 (i.e. FeO·Fe2O3); (ii) Fe3O4 can then oxidate to Fe2O3: 2Fe3O4 + ½O2 ⇌ 3Fe2O3 (exothermic); (iii) Fe2O3 can be expected to react with CaO at interfaces to generate lime ferrite(s) (xCaO·yFe2O3; x ⋀ y ∊ {1, 2}); (iv) lime ferrites favour sintering (≥ ~1250 ºC), with possible pelletizing effect.

II. About humidity effect in (open) oxidizing atmosphere (air): (i) most unbound water should be early released upon mild heating; (ii) equilibrium CaO + H2O ⇌ Ca(OH)2 (exothermic hydration) may play a significant role; (iii) dehydration of Ca(OH)2 at higher temperature tends to increase porosity and specific surface area; (iv) ferric iron may possibly first occur as limonite-type oxide-hydroxide(s) (FeO(OH)·nH2O); which can then (partially) dehydrate to goethite-type oxyhydroxide (FeO(OH)) at higher temperature (v).

Sumit

If TGA analysis of carbonate minerals is carried out, changes in TGA curves will occur depending on purity of mineral and the heating rate from room temperature to say 1000C, and if metallic iron powder is added, then, there will be a reaction between the associated water molecules in calcite and the evolving CO2 gas with increase in temperature. Curve profile depends upon the reaction phase occurring with temperature. Try to look at following papers - Carl W Beck - Am. Mineral 35, page 508 , (1950) and also J of Thermal Analysis and Calorimetric - 95, 3, 998 (2009). Also search on Google. Hope this helps.

Dr. K

Hello everyone,

Thank you very much for the replies!

Dr Azeez Barzinjy, the paper you suggested looks interesting. However, what I see from literature is that some of these additives in carbonate decomposition act as inert materials, while others effect the resulting TGA and DSC curves. Two examples of interest were those on Na2CO3 decomposition [1] and of other carbonates [2]. That is why I was looking if someone had especially performed an experiment with metallic iron. And if the metallic iron would act as an inert additive or as a reactive additive. :)

Carlos Araújo Queiroz , I am really sorry that I missed to mention that the experiments are to be performed in inert N2 environment. However, this looks interesting. Thank you very much. :)

Navin Kothari , thank you very much for your answer. We are looking to perform a comparative analysis on samples with pure CaCO3 without moisture and at the same conditions (including the rate of heating, sample mass, rate of N2 purging etc). The only variable we are looking at, is the effect of additives. Thank you very much for the interesting reference. I will go through it too. :)

[1] Siriwardane, Ranjani V., et al. "Effect of additives on decomposition of sodium carbonate: Precombustion CO2 capture sorbent regeneration." Energy & Fuels 25.3 (2011): 1284-1293.

[2] Kemp, S., D. Wagner and I. Mounteney (2010). "Low level detection and quantification of carbonate species using thermogravimetric and differential thermal analysis."

Sumit

Are you looking carbon capture using CaCO3 with added metallic powders. As you are going to use metallic powders, then, use the powder with finer partcles ( nanopowders) as they have a larger surface area in relation to weight and also larger absorping capacity.

Prof Dr. K