Cadmium capture through coupled dissolution-precipitation reactions

Maude Julia^a,*, Christine V. Putnis^a,b

^a Institute für Mineralogie, Universität Münster, Münster, Germany

^b School of Molecular and Life Sciences, Curtin University, Perth, Australia

^*corresponding author: mjulia@uni-muenster.de

Mineral replacement through coupled dissolution-precipitations has been widely studied in the last years both in natural and laboratory systems. This mechanism is of interest to understand the natural alteration of some rocks, such as weathering and serpentinization of olivines or albitization of feldspars, but can also be tuned in the laboratory with the aim of designing new materials with functional uses or for sequestration of elements of choice¹. Capture of toxic elements through coupled dissolution-precipitation has been studied using various element-mineral systems. We have focused on the capture of cadmium (Cd) from solution through two distinct reactions: 1) dissolution of CaCO₃ in Cd solution and precipitation of (Ca,Cd)CO₃ and 2) precipitation of Cd-containing hydroxylapatite (HAP) from the dissolution of CaCO₃ in NH₄H₂PO₄ – Cd solutions. The first study showed that when exposing CaCO₃ to a Cd solution, coupled dissolution-precipitation takes place initially at the mineral surface. The new phase precipitating is a (Ca,Cd)CO₃ solid solution and the extent of the reaction is greatly impacted by the type of CaCO₃ used: calcite single crystals were armoured by the new solid solution growing epitaxially on their surface while Carrara marble (polycrystalline calcite) and aragonite were partially replaced by the new phase². In the second study it was observed that the replacement of CaCO₃ by HAP in phosphate solution, which had been previously studied³, could sequester small amounts of Cd. However the uptake of Cd in the replaced phase and the reaction rate were greatly limited, possibly by the interactions resulting from the formation of Cd complexes adsorbed at the mineral surface⁴. Both these Cd sequestration mechanisms will be discussed and their efficiency towards environmental remediation will be assessed using both nanoscale observations by in-situ atomic force microscopy and microscale hydrothermal experiments.

References:

(1)           Bañuelos, J. L.; Borguet, E.; Brown, G. E.; Cygan, R. T.; DeYoreo, J. J.; Dove, P. M.; Gaigeot, M.-P.; Geiger, F. M.; Gibbs, J. M.; Grassian, V. H.; Ilgen, A. G.; Jun, Y.-S.; Kabengi, N.; Katz, L.; Kubicki, J. D.; Lützenkirchen, J.; Putnis, C. V.; Remsing, R. C.; Rosso, K. M.; Rother, G.; Sulpizi, M.; Villalobos, M.; Zhang, H. Oxide– and Silicate–Water Interfaces and Their Roles in Technology and the Environment. Chem. Rev. 2023, 123 (10), 6413–6544. https://doi.org/10.1021/acs.chemrev.2c00130.

(2)           Julia, M.; Putnis, C. V.; King, H. E.; Renard, F. Coupled Dissolution-Precipitation and Growth Processes on Calcite, Aragonite, and Carrara Marble Exposed to Cadmium-Rich Aqueous Solutions. Chemical Geology 2023, 621, 121364. https://doi.org/10.1016/j.chemgeo.2023.121364.

(3)           Pedrosa, E. T.; Putnis, C. V.; Putnis, A. The Pseudomorphic Replacement of Marble by Apatite: The Role of Fluid Composition. Chemical Geology 2016, 425, 1–11. https://doi.org/10.1016/j.chemgeo.2016.01.022.

(4)           Stumm, W. Reactivity at the Mineral-Water Interface: Dissolution and Inhibition. Colloids and Surfaces A: Physicochemical and Engineering Aspects 1997, 120 (1–3), 143–166. https://doi.org/10.1016/S0927-7757(96)03866-6.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 956127