TY - JOUR
T1 - Molecular-sieving capabilities of mesoporous carbon membranes
AU - Hou, Chia Hung
AU - Wang, Xiqing
AU - Liang, Chengdu
AU - Yiacoumi, Sotira
AU - Tsouris, Costas
AU - Dai, Sheng
PY - 2008/7/24
Y1 - 2008/7/24
N2 - The size-sieving properties of a mesoporous carbon membrane were studied via molecular permeation and cyclic voltammetry experiments. Two phenomena, simple diffusion and electrochemically aided diffusion, were investigated. Molecular diffusion through the membrane was caused by a concentration gradient across the membrane and was facilitated by electrosorption of ions under an externally applied electric field. The diffusion of molecules transported through the membrane was characterized by the values of permeability and apparent diffusion coefficient in the membrane. Because larger molecules are more restricted in terms of penetrating the pores, the size-based selectivity of the mesoporous carbon membrane could be readily observed. For example, in the two-component permeation experiment, a high selectivity (α = 56.9) of anilinium over Rhodamine B was found. It is inferred that the diffusive transport of the larger Rhodamine B molecules with a more extensive retardation comes from the competitive mechanism between the two kinds of molecules in accessing the pore. A series of voltammetric experiments involving a mesoporous carbon membrane immersed in various electrolytes with ions of different sizes allowed the observation of ion-exclusion phenomena. It was found that the size effect is significant for electrochemically aided diffusion and electrosorption processes. The number of cations inside the pores of the membrane decreases with increasing cation size. This phenomenon is due to the size-exclusion effect, which could be demonstrated by the values of electrical double-layer capacitance for sodium, magnesium, and tetrahexylammonium cations, at potentials ranging from negative values to the point of zero charge, corresponding to 86.7, 73.1, and 50.0 F/g, respectively. The findings of this work manifest that the relationship between the pore size and the dimensions of the molecules determines the transport and sorption behavior of nanoporous carbon materials.
AB - The size-sieving properties of a mesoporous carbon membrane were studied via molecular permeation and cyclic voltammetry experiments. Two phenomena, simple diffusion and electrochemically aided diffusion, were investigated. Molecular diffusion through the membrane was caused by a concentration gradient across the membrane and was facilitated by electrosorption of ions under an externally applied electric field. The diffusion of molecules transported through the membrane was characterized by the values of permeability and apparent diffusion coefficient in the membrane. Because larger molecules are more restricted in terms of penetrating the pores, the size-based selectivity of the mesoporous carbon membrane could be readily observed. For example, in the two-component permeation experiment, a high selectivity (α = 56.9) of anilinium over Rhodamine B was found. It is inferred that the diffusive transport of the larger Rhodamine B molecules with a more extensive retardation comes from the competitive mechanism between the two kinds of molecules in accessing the pore. A series of voltammetric experiments involving a mesoporous carbon membrane immersed in various electrolytes with ions of different sizes allowed the observation of ion-exclusion phenomena. It was found that the size effect is significant for electrochemically aided diffusion and electrosorption processes. The number of cations inside the pores of the membrane decreases with increasing cation size. This phenomenon is due to the size-exclusion effect, which could be demonstrated by the values of electrical double-layer capacitance for sodium, magnesium, and tetrahexylammonium cations, at potentials ranging from negative values to the point of zero charge, corresponding to 86.7, 73.1, and 50.0 F/g, respectively. The findings of this work manifest that the relationship between the pore size and the dimensions of the molecules determines the transport and sorption behavior of nanoporous carbon materials.
UR - http://www.scopus.com/inward/record.url?scp=49149113441&partnerID=8YFLogxK
U2 - 10.1021/jp8006427
DO - 10.1021/jp8006427
M3 - Article
AN - SCOPUS:49149113441
SN - 1520-6106
VL - 112
SP - 8563
EP - 8570
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 29
ER -