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Understanding the chemistry of cation leaching in illite/water interfacial system using reactive molecular dynamics simulations and hydrothermal experiments

Summary

This page tracks the Elsevier page-proof PDF at pdf_path; for figures, pagination, and the same science with the version-of-record file, see [[2020muraleedharan-acta-materia-understanding-chemistry]]. Prose is grounded in the Acta Materialia abstract and the short extract in normalized/extracts/2020muraleedharan-venue-paper_p1-2.txt.

Leaching—release of cations from minerals to fluids—matters for energy, hydrometallurgy, agriculture, and clay geochemistry, yet molecular pathways remain debated. The work combines large-scale ReaxFF MD with hydrothermal experiments on illite in water to dissect K⁺, Al, and Si release. Simulations show K⁺ exits earlier and at higher concentration than network Al/Si. Trajectory analysis describes protons from water attacking non-bridging oxygens in Al–O–Si linkages, forming [Al–O–Si]–H-like transition states that evolve toward silanol formation upon Al–O bond cleavage; protonation also weakens interlayer K–O bonds, driving K⁺ toward the surface where KOH forms and diffuses outward via proton exchange. Continued protonation yields Al(OH)₃ and Si(OH)₄-like species that release into solution. The authors compare MD-derived surface kinetics to bulk leaching curves, finding orders-of-magnitude gaps without additional transport modeling, and relate structural distortion to >20% cumulative cation loss thresholds.

Methods

1 — MD application (atomistic dynamics). Protocol numbers follow [[2020muraleedharan-acta-materia-understanding-chemistry]] and the Acta Materialia text: ReaxFF reactive MD of illite with an aqueous interlayer/interface (slab + water). Integration uses 0.25 fs timesteps and a velocity-Verlet integrator; the dynamics use NVT control with a Berendsen thermostat (0.1 ps damping) as in the published protocol. The models are three-dimensional supercells with periodic boundary conditions along in-plane directions for the clay slab + water stack (standard slab-style setup; any open-boundary details are in the VOR paper). N/A — explicit atom counts, production lengths in ns, and the MD program name are not taken from the short proof extract here; confirm in the VOR PDF or the sibling page. N/A — barostat / external pressure for the MD stages as summarized (constant-volume NVT style control). Electric field: N/A — not used. Shear / shock: N/A — not used. Replica or enhanced sampling: N/A — not reported. Experiments (hydrothermal leaching). Complementary batch hydrothermal experiments track K⁺, Al, and Si release in solution versus time for comparison to modeled surface reactivity, as described in the article. Static QM / DFT: N/A — not a DFT-benchmarking study. Force-field training: N/A — application of an existing ReaxFF parameterization, not a new fit in this paper. Provenance of this file: this slug tracks the Elsevier page-proof PDF at pdf_path for manifest alignment; for pagination, figures, and final tables, use [[2020muraleedharan-acta-materia-understanding-chemistry]].

Findings

K⁺ leaches faster than Al/Si network dissolution in the neutral-water scenarios highlighted. The multi-step protonation narrative links interlayer K mobility to surface KOH ejection, while Al/Si release follows hydroxide cluster formation. Surface MD rates do not collapse onto bulk kinetics without transport or scaling arguments. Structural distortion diagnostics connect extensive cation loss to measurable illite deformation in the model. Comparisons: the authors state MD-derived surface reactivity does not match bulk leaching kinetics without a transport or multi-scale model (orders of magnitude gap; see abstract and Discussion on the VOR). Limitations (as written): proof PDF; prefer [[2020muraleedharan-acta-materia-understanding-chemistry]] for VOR locators. Open direction: the abstract frames a need to reconcile surface reaction kinetics with reservoir-scale leaching.

Limitations

Proof PDF may lack final pagination; clay-edge chemistry complexity exceeds any single slab model; ReaxFF geochemistry parameters carry uncertainty. See [[2020muraleedharan-acta-materia-understanding-chemistry]] for the authoritative article page.

Relevance to group

van Duin (corresponding) with University of Wyoming experimental partners on clay–water reactive MD; this slug preserves hash-level provenance for the Elsevier proof PDF while the scientific narrative lives on the VOR companion page.

Reader notes (navigation)

Citations and evidence anchors

  • DOI 10.1016/j.actamat.2019.12.059 — proof path papers/Muraleedharan_ActaMater_2020_Cation_Leaching_proof.pdf; extract normalized/extracts/2020muraleedharan-venue-paper_p1-2.txt.