Discontinuous Dissolution Mechanism of Olivine Deduced from a Topography Observation Method

Area of Science:

• Geochemistry
• Materials Science
• Environmental Science

Background:

• Olivine dissolution is vital for global element cycling and carbon capture technologies.
• Previous research primarily focused on dissolution rates via chemical effluent analysis.
• Understanding surface reactivity is key to elucidating olivine dissolution mechanisms.

Purpose of the Study:

• To investigate the dissolution mechanism of an olivine (010) plane under specific experimental conditions.
• To quantitatively analyze spatial and temporal changes in mineral surface topography during dissolution.
• To propose a new dissolution mechanism based on surface observations.

Main Methods:

• Utilized a flow-through reaction cell with acidic solutions.
• Employed vertical scanning interferometry and atomic force microscopy for direct surface topography measurements.
• Studied dissolution under surface-controlled and far-from-equilibrium conditions.

Main Results:

• Observed discontinuous dissolution over time across different surface sites, creating a heterogeneous dissolution rate map.
• Found varying dissolution rate distributions relative to etch pit centers and edges based on pit depth.
• Proposed a dissolution mechanism involving the competition between Gibbs free energy (ΔG) and critical etch pit opening energy (ΔGcrit).

Conclusions:

• Olivine dissolution is a complex, spatially and temporally heterogeneous process.
• The proposed mechanism highlights the role of step-wave dynamics, surface defects, and etch pit strain fields.
• Findings offer new perspectives for optimizing crystalline mineral applications and predicting material behavior in dissolution processes.