Alumina reticulate

Fig. 10.5 Removal rate of toluene in synthetic air (12 cm/s face velocity) against humidity. Alumina reticulate wash coated with P-25 photon (250-350 nm) power 33 mW/cm at the photocatalyst surface (Reprinted with the permission from Ref. [44]. Copyright 1995 Amcaiean...

For wall-coated open tubular (WCOT) columns, the stationary phase covers the inside surface of the column. The film thickness of the stationary phase can vary from 0.05 to 5 pm. It can be simply deposited on the surface, can originate from the reticulation of a polymer on the silica surface or can be bound to the silica through covalent bonds. The surface of the silica is treated before the stationary phase is deposited to avoid problems of wetability, desorption and stability over time. This treatment can involve attack by HC1 at 350 °C or the deposition of a fine coat of alumina particles. Afterward, the stationary phase is either deposited or prepared in situ by polymerisation at the inner surface of the column. Covalent bonding via Si-O—Si-C allows organic compounds to be bound to the silica surface. In the latter case, the columns are particularly stable and can be rinsed periodically allowing them to recover their initial performance. The efficiency of these columns can reach 150000 theoretical plates. 

Hale and Bohn [252] measured the scattered radiation from a finite sample of reticulated alumina from an incident laser beam at 488 nm. They then matched Monte Carlo predictions of the scattered radiation calculated from various values of extinction coefficient and scattering albedo and chose the values that best matched the experimental data for reticulated alumina samples of 10, 20, 30, and 65 ppi. A scattering albedo of 0.999 and an assumed isotropic scattering phase function reproduced the measured data for all pore sizes. The large reported albedo value indicates that alumina is very highly scattering and that radiative absorption is extremely small for this material. 

M. J. Hale and M. S. Bohn, Measurement of the Radiative Transport Properties of Reticulated Alumina Foams, ASME Paper 92-V-842, August, 1992. 

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