Pb2+ uptake by magnesite: The competition between thermodynamic driving force and reaction kinetics

Di Lorenzo, Fulvio; Arnold, Tobias; Churakov, Sergey V. (2021). Pb2+ uptake by magnesite: The competition between thermodynamic driving force and reaction kinetics. Minerals, 11(4), pp. 1-18. MDPI 10.3390/min11040415

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The thermodynamic properties of carbonate minerals suggest a possibility for the use of the abundant materials (e.g., magnesite) for removing harmful divalent heavy metals (e.g., Pb2+). Despite the favourable thermodynamic condition for such transformation, batch experiments performed in this work indicate that the kinetic of the magnesite dissolution at room temperature is very slow. Another set of co‐precipitation experiments from homogenous solution in the Mg‐PbII‐ CO2‐H2O system reveal that the solids formed can be grouped into two categories depending on the Pb/Mg ratio. The atomic ratio Pb/Mg is about 1 and 10 in the Mg‐rich and Pb‐rich phases, respectively. Both phases show a significant enrichment in Pb if compared with the initial stoichiometry of the aqueous solutions (Pb/Mg initial = 1∙10−2–1∙10−4). Finally, the growth of {10.4} magnesite surfaces in the absence and in the presence of Pb2+ was studied by in situ atomic force microscopy (AFM) measurements. In the presence of the foreign ion, a ten‐fold increase in the spreading rate of the obtuse steps was observed. Further, the effect of solution ageing was also tested. We observed the nucleation of a secondary phase that quickly grows on the {10.4} surfaces of magnesite. The preferential incorporation of Pb2+ into the solid phase observed during precipitation and the catalytic effect of Pb2+ on magnesite growth are promising results for the development of environmental remediation processes. These processes, different from the transformation of magnesite into cerussite, are not limited by the slow dissolution rate of magnesite. Precipitation and growth require an external carbon source, thus they could be combined with carbon sequestration techniques.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geological Sciences

UniBE Contributor:

Di Lorenzo, Fulvio; Arnold, Tobias and Churakov, Sergey

Subjects:

500 Science > 550 Earth sciences & geology

ISSN:

2075-163X

Publisher:

MDPI

Funders:

[4] Swiss National Science Foundation

Projects:

Projects 164017 not found.

Language:

English

Submitter:

Fulvio Di Lorenzo

Date Deposited:

11 Apr 2022 14:56

Last Modified:

11 Apr 2022 14:56

Publisher DOI:

10.3390/min11040415

BORIS DOI:

10.48350/168610

URI:

https://boris.unibe.ch/id/eprint/168610

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