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Connecting molecular simulations and laboratory experiments for the study of time-resolved cation-exchange process in the interlayer of swelling clay minerals
https://orcid.org/0000-0002-9008-7984
https://orcid.org/0000-0003-0920-8169
Abstract In the context of element migration in clay-rich media, self-diffusion coefficients of interlayer cations in swelling clay minerals obtained from molecular simulations are rarely used by macroscopic models predicting cation-exchange processes. Based on experiments and simulations, this study aims at (i) making a connection between molecular and sample scale processes to predict the dynamics of cation-exchange reactions between the interlayer space of millimetre disks of vermiculite and aqueous reservoirs, and (ii) assessing the role played by both self-diffusion and selectivity coefficients on this process. Time-resolved cation exchange experiments were performed using Ca-saturated vermiculite disks immersed in aqueous reservoirs with different NaCl or SrCl2 salinities. The results were reproduced via a finite-volume model constrained by (i) cation self-diffusion coefficients calculated by molecular dynamics simulations and (ii) interlayer selectivity coefficients drawn from “batch” cation-exchange isotherms. Results showed that considering the averaged values for both the cation-exchange selectivity coefficients and self-diffusion coefficients of the slowest interlayer cation led to good agreement between the experiments and simulations, validating the modelling strategy for the connection between the molecular and laboratory time scales. A sensitivity test regarding the influence of the two input parameters on the overall results was then performed. This study underlined a constrained upscaling strategy to better assess the role played by different intrinsic parameters of the clay/water systems (molecular self-diffusion coefficients in the interlayer space vs. selectivity coefficient) on the diffusion of cations during cation-exchange reaction in clay-rich media.
Graphical abstract Display Omitted
Highlights Dynamics of cation exchange in interlayer of swelling clay minerals. Variation of self-diffusion coefficients of cation with its occupancy in interlayer. Finite-volume model constrained by self-diffusion and selectivity coefficients. Upscaling approach predicting the macroscopic dynamics of the cation-exchange.
Connecting molecular simulations and laboratory experiments for the study of time-resolved cation-exchange process in the interlayer of swelling clay minerals
https://orcid.org/0000-0002-9008-7984
https://orcid.org/0000-0003-0920-8169
Abstract In the context of element migration in clay-rich media, self-diffusion coefficients of interlayer cations in swelling clay minerals obtained from molecular simulations are rarely used by macroscopic models predicting cation-exchange processes. Based on experiments and simulations, this study aims at (i) making a connection between molecular and sample scale processes to predict the dynamics of cation-exchange reactions between the interlayer space of millimetre disks of vermiculite and aqueous reservoirs, and (ii) assessing the role played by both self-diffusion and selectivity coefficients on this process. Time-resolved cation exchange experiments were performed using Ca-saturated vermiculite disks immersed in aqueous reservoirs with different NaCl or SrCl2 salinities. The results were reproduced via a finite-volume model constrained by (i) cation self-diffusion coefficients calculated by molecular dynamics simulations and (ii) interlayer selectivity coefficients drawn from “batch” cation-exchange isotherms. Results showed that considering the averaged values for both the cation-exchange selectivity coefficients and self-diffusion coefficients of the slowest interlayer cation led to good agreement between the experiments and simulations, validating the modelling strategy for the connection between the molecular and laboratory time scales. A sensitivity test regarding the influence of the two input parameters on the overall results was then performed. This study underlined a constrained upscaling strategy to better assess the role played by different intrinsic parameters of the clay/water systems (molecular self-diffusion coefficients in the interlayer space vs. selectivity coefficient) on the diffusion of cations during cation-exchange reaction in clay-rich media.
Graphical abstract Display Omitted
Highlights Dynamics of cation exchange in interlayer of swelling clay minerals. Variation of self-diffusion coefficients of cation with its occupancy in interlayer. Finite-volume model constrained by self-diffusion and selectivity coefficients. Upscaling approach predicting the macroscopic dynamics of the cation-exchange.
Connecting molecular simulations and laboratory experiments for the study of time-resolved cation-exchange process in the interlayer of swelling clay minerals
https://orcid.org/0000-0002-9008-7984
https://orcid.org/0000-0003-0920-8169
Abstract In the context of element migration in clay-rich media, self-diffusion coefficients of interlayer cations in swelling clay minerals obtained from molecular simulations are rarely used by macroscopic models predicting cation-exchange processes. Based on experiments and simulations, this study aims at (i) making a connection between molecular and sample scale processes to predict the dynamics of cation-exchange reactions between the interlayer space of millimetre disks of vermiculite and aqueous reservoirs, and (ii) assessing the role played by both self-diffusion and selectivity coefficients on this process. Time-resolved cation exchange experiments were performed using Ca-saturated vermiculite disks immersed in aqueous reservoirs with different NaCl or SrCl2 salinities. The results were reproduced via a finite-volume model constrained by (i) cation self-diffusion coefficients calculated by molecular dynamics simulations and (ii) interlayer selectivity coefficients drawn from “batch” cation-exchange isotherms. Results showed that considering the averaged values for both the cation-exchange selectivity coefficients and self-diffusion coefficients of the slowest interlayer cation led to good agreement between the experiments and simulations, validating the modelling strategy for the connection between the molecular and laboratory time scales. A sensitivity test regarding the influence of the two input parameters on the overall results was then performed. This study underlined a constrained upscaling strategy to better assess the role played by different intrinsic parameters of the clay/water systems (molecular self-diffusion coefficients in the interlayer space vs. selectivity coefficient) on the diffusion of cations during cation-exchange reaction in clay-rich media.
Graphical abstract Display Omitted
Highlights Dynamics of cation exchange in interlayer of swelling clay minerals. Variation of self-diffusion coefficients of cation with its occupancy in interlayer. Finite-volume model constrained by self-diffusion and selectivity coefficients. Upscaling approach predicting the macroscopic dynamics of the cation-exchange.
Connecting molecular simulations and laboratory experiments for the study of time-resolved cation-exchange process in the interlayer of swelling clay minerals
Tertre, Emmanuel (author) / Dazas, Baptiste (author) / Asaad, Ali (author) / Ferrage, Eric (author) / Grégoire, Brian (author) / Hubert, Fabien (author) / Delville, Alfred (author) / Delay, Frédérick (author)
Applied Clay Science ; 200
2020-10-28
Article (Journal)
Electronic Resource
English
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