1. Diffusion of Water and Electrolytes in Mesoporous Silica with a Wide Range of Pore Sizes
- Author
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Fabián Vaca Chávez, Mariano M. Bruno, Rodolfo H. Acosta, M. Paula Longinotti, Diana C. Martínez Casillas, and Horacio R. Corti
- Subjects
Materials science ,Morphology (linguistics) ,Físico-Química, Ciencia de los Polímeros, Electroquímica ,Diffusion ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,01 natural sciences ,Tortuosity ,Ion ,Difusion ,Physical and Theoretical Chemistry ,Ciencias Químicas ,Silica ,Agua ,Microporous material ,Mesoporous silica ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Chemical engineering ,Litio ,0210 nano-technology ,Mesoporous material ,CIENCIAS NATURALES Y EXACTAS - Abstract
The diffusion of alkaline chlorides (LiCl, KCl, and CsCl) and water in mesoporous silica samples with pore sizes covering the range from micropores (2 nm) up to mesopores larger than 30 nm have been measured by resorting to a simple diffusional technique in the case of electrolytes and 1H NMR in the case of water. The morphology of the silica samples varies from a microporous structure, an interconnected network of pores, and typical mesoporous materials with ink-bottle pores, with increasing pore size. The release of electrolytes from the silica as a function of time exhibits two differentiated regimes, at short and long times, which correlates quite well with the size of the pores and that of necks of the pores, respectively. The diffusion of water inside the pores follows the same trend with pore size that the diffusion of electrolytes, indicating a coupling between the ions and water diffusional mobilities. The tortuosity effect on the diffusion of all studied electrolytes and water shows a monotonic slight increase with decreasing diameter for pores larger than 5 nm, while the tortuosity factor increases markedly for smaller pores. In microporous and mesoporous silica with pore sizes below 10 nm, the tortuosity factor of Li+ ion is much larger than those for K+ and Cs+ ions, since its diffusion is hindered by a stronger electrostatic interaction with the ionizable silanol groups on the pore wall; and also larger than that for water diffusion which it is retarded by a weaker hydrogen bond interaction with the silanol groups. The differences in tortuosity factors among alkaline chlorides and water become negligible for pore sizes larger than 10 nm. The spin-lattice relaxation time measurements of 1H-water and Li+ ions confirm this behavior. Fil: Martínez Casillas, Diana Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Longinotti, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Bruno, Mariano Martín. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Vaca Chávez Fornasero, Fabián. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina Fil: Acosta, Rodolfo Héctor. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina Fil: Corti, Horacio Roberto. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
- Published
- 2018