Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature

Abstract Storing CO2 in underground saline aquifers is an important way to reduce CO2 emission in atmosphere, where gas/fluid diffusion in clay plays a key role in CO2 leakage and migration. Various diffusivities, self-diffusivity, Maxwell–Stefan (M–S) diffusivity and Fick diffusivity, in clay inter...

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Autores principales:	Haixiang Hu, Yanfei Xing, Xiaochun Li
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2017
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/bdb58118df234b5cb6fe685cb939d1b1
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spelling	oai:doaj.org-article:bdb58118df234b5cb6fe685cb939d1b12021-12-02T16:06:44ZSelf-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature10.1038/s41598-017-05758-32045-2322https://doaj.org/article/bdb58118df234b5cb6fe685cb939d1b12017-07-01T00:00:00Zhttps://doi.org/10.1038/s41598-017-05758-3https://doaj.org/toc/2045-2322Abstract Storing CO2 in underground saline aquifers is an important way to reduce CO2 emission in atmosphere, where gas/fluid diffusion in clay plays a key role in CO2 leakage and migration. Various diffusivities, self-diffusivity, Maxwell–Stefan (M–S) diffusivity and Fick diffusivity, in clay interlayer are investigated by molecular dynamics (MD). Self-diffusivity varies with CO2 concentration, and reaches the maximum value at 2 molecules/unit-cell. High fluid concentration leads to clay swelling, thereby increasing self-diffusivity. However, the fractional free volume of clay explains the trend of CO2 self-diffusivity, which does not decrease with CO2 concentration monotonously but reaches the maximum when CO2 concentration reaches 2. Displacement distribution of CO2 molecules is analysed to explore the microscopic diffusion mechanism, which is characterised by logarithmic normal distribution. The mean value of such distribution further explains the self-diffusivity dependence on CO2 concentration. M–S and Fick diffusivities of CO2 are calculated by MD for the first time, both of which increase with increasing CO2 and H2O concentration and temperature. Based on self-diffusivity and M–S diffusivity, a quantity representing the coupling strength between CO2 molecules is presented; it increases firstly with CO2 concentration but begins to decrease when CO2 concentration is beyond 2.Haixiang HuYanfei XingXiaochun LiNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 7, Iss 1, Pp 1-10 (2017)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Haixiang Hu Yanfei Xing Xiaochun Li Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature
description	Abstract Storing CO2 in underground saline aquifers is an important way to reduce CO2 emission in atmosphere, where gas/fluid diffusion in clay plays a key role in CO2 leakage and migration. Various diffusivities, self-diffusivity, Maxwell–Stefan (M–S) diffusivity and Fick diffusivity, in clay interlayer are investigated by molecular dynamics (MD). Self-diffusivity varies with CO2 concentration, and reaches the maximum value at 2 molecules/unit-cell. High fluid concentration leads to clay swelling, thereby increasing self-diffusivity. However, the fractional free volume of clay explains the trend of CO2 self-diffusivity, which does not decrease with CO2 concentration monotonously but reaches the maximum when CO2 concentration reaches 2. Displacement distribution of CO2 molecules is analysed to explore the microscopic diffusion mechanism, which is characterised by logarithmic normal distribution. The mean value of such distribution further explains the self-diffusivity dependence on CO2 concentration. M–S and Fick diffusivities of CO2 are calculated by MD for the first time, both of which increase with increasing CO2 and H2O concentration and temperature. Based on self-diffusivity and M–S diffusivity, a quantity representing the coupling strength between CO2 molecules is presented; it increases firstly with CO2 concentration but begins to decrease when CO2 concentration is beyond 2.
format	article
author	Haixiang Hu Yanfei Xing Xiaochun Li
author_facet	Haixiang Hu Yanfei Xing Xiaochun Li
author_sort	Haixiang Hu
title	Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature
title_short	Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature
title_full	Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature
title_fullStr	Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature
title_full_unstemmed	Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature
title_sort	self-diffusivity, m–s and fick diffusivity of co2 in na-clay: the influences of concentration and temperature
publisher	Nature Portfolio
publishDate	2017
url	https://doaj.org/article/bdb58118df234b5cb6fe685cb939d1b1
work_keys_str_mv	AT haixianghu selfdiffusivitymsandfickdiffusivityofco2innaclaytheinfluencesofconcentrationandtemperature AT yanfeixing selfdiffusivitymsandfickdiffusivityofco2innaclaytheinfluencesofconcentrationandtemperature AT xiaochunli selfdiffusivitymsandfickdiffusivityofco2innaclaytheinfluencesofconcentrationandtemperature
_version_	1718384867053404160

Self-diffusivity, M–S and Fick diffusivity of CO2 in Na-clay: The influences of concentration and temperature

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