Chemical weathering mechanism of Albite-rich rocks in Grottoes under an acidic environment: An atomistic view from ReaxFF simulation

Abstract

This current ReaxFF simulation provides atomic-level monitoring of the reaction details as well as dynamics of Albite under acidic solution over a nanosecond time scale. 30% H-O bond dissociation in 10% H2SO4 solution and ∼ 0.9% Si-O/Al-O bonds breakage in Albite during 20 ps was evaluated according to the time evolution of number of H-O bonds, Si-O and Al-O bonds at a higher temperature of 323 K. The breakage of Si-O/Al-O bonds within the tetrahedron configuration makes Na atoms be less restricted within the network and generates open channel for Na migration, resulting in further diffusion to the Albite-water interface and complete release into the aqueous medium. A consecutive dissociation of H2SO4 can further accelerate the formation of SO42- products as the H dissociate from H2SO4 molecules. The migrated Na cations tend to combine with SO42- and form Na-SO4 ions pair, leading to a complicated zigzag motion in 3D space and a migration trend towards the aqueous medium along Z-axis direction and a sharp peak at 2.3 Å in Na-O pair RDF.