In this paper, we examine the effect of magnetic iron oxide nanoparticles on gas−liquid mass transfer rates. Carbon dioxide and oxygen are the gases absorbed, into a variety of reactive and nonreactive liquids. Experiments have been carried out in a wetted wall column (where the hydrodynamics can be rigorously modeled) and in a capillary tube (with the liquid phase being quiescent). In the case of absorption with reaction, studies have been conducted in several absorption regimes, representing different levels of transport limitations. The experiments convincingly demonstrate that the liquid phase mass transfer coefficients are significantly enhanced in the presence of nanoparticles in the region of concentration gradients, the extent of enhancement depending on the volume fraction of solid particles in the fluid, and on the particle size scaled with respect to the depth of penetration of the diffusing solute. A modified Sherwood number has been identified, based on the traditional theories of interphase mass transfer, as the dominant parameter which determines the magnitude of the mass transfer intensification effect at a given particle holdup, and a correlation has been derived for the enhancement, which explains not only the data obtained in this work, but also data from the literature. The enhancement effect, having been observed in the presence and absence of reaction and flow, points to the fundamental molecular-level transport processes being influenced by the nanoparticles, but the exact mechanisms remain to be established.
BACKGROUND: In this paper a novel approach for increasing the mass transfer coefficient in gas/liquid mass transfer is reported and applied to the industrially important system of CO 2 absorption. The approach makes use of a ferrofluid additive to the liquid phase. To demonstrate this strategy, a wetted wall column has been built and experiments have been conducted on the CO 2 /methyl diethanolamine (MDEA) system. This reaction system allows the absorption to be carried out in the transition regime between slow and fast regimes, so that the mass transfer coefficient (k L ) and interfacial area (a i ) can be measured independently, in the presence and absence of ferrofluids. A surfactant-coated aqueous magnetic fluid was prepared and shown to be stable in MDEA solutions.
Pt nanoparticles of sub-3 nm diameter immobilized within a crosslinked polysiloxane network covalently attached to a silica support have been shown to be highly efficient recyclable leach-resistant catalysts for olefin...
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