Experiments and modelling to understand FeCO<sub>3</sub> cement formation mechanism : time-evolution of CO<sub>2</sub>-species, dissolved-Fe, and pH during CO<sub>2</sub>-induced dissolution of Fe(0)
Srivastava, Sumit; Jacklin, Rob; Snellings, Ruben; Barker, Richard; Spooren, Jeroen; Cool, Pegie (2022-07-03)
Srivastava, S., Jacklin, R., Snellings, R., Barker, R., Spooren, J., & Cool, P. (2022). Experiments and modelling to understand FeCO3 cement formation mechanism: Time-evolution of CO2-species, dissolved-Fe, and pH during CO2-induced dissolution of Fe(0). Construction and Building Materials, 345, 128281. https://doi.org/10.1016/j.conbuildmat.2022.128281
© 2022 The Author(s). This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe2022113068227
Tiivistelmä
Abstract
FeCO3 cement can be produced by reacting CO2(aq) and particulate-Fe(0). Process conditions and solution compositions influence cement properties through kinetics of Fe-dissolution and FeCO3-precipitation. This study investigates Fe-dissolution in dilute systems (water(wt.)/Fe(wt.) = 1000) at 30/60 °C, and 1/10 barg CO2-pressures. Experimentally, time-evolution of solution composition shows increased [Fe] and solution-pH. As a proxy for high-pressure in-situ experiments, a modeling approach is developed to quantify with [Fe]-increase, the: decreased [H+], increased \([\mathit{HCO}_3^–]/[\mathrm{OH^–}]/[\mathit{CO}_3^{2–}],\), and undisturbed [CO2(aq)]/[H2CO3]. Fe-dissolution rates increase with: (a) pH-decrease with increased CO2-pressure, and (b) faster kinetics at higher temperatures, even with higher pH. Experimental and modeled pH are comparable at 1 bar, two causes are discussed for it being ∼ 1.2 times at 10 barg: CO2-depressurization, and Fe-precipitation. Lower CO2-mediated dissolution activation energies of ∼ 30 (1 barg) and ∼ 20 kJ/mol (10 barg) compared to strong acids (∼60 kJ/mol) are attributed to buffering action of CO2(aq).
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