Siriluk Chiarakorn, Nurak Grisdanurak, and Miller, R.C.

pp. 37 - 44

Abstract

RH-MCM-41 particles were synthesized using sodium silicate prepared from rice husk as a silica
source and hexadecyltrimethylammonium bromide (CTAB) as a surfactant. The molar compositions were
1.0SiO₂: 1.1NaOH: 0.13CTAB: 0.12H₂O. This material was used for adsorption isotherm studies of carbon
tetrachloride (CT) at 25 ^oC using a magnetically coupled microbalance, and compared with adsorption
isotherms using nitrogen at 77 K. The CT isotherms were classified as reversible Type V isotherms, and the
nitrogen adsorption isotherm was Type IVc. Capillary condensation was found in a very narrow pressure
range, indicating the presence of nearly uniform pores in the RH-MCM-41 particles, which agrees very well
with TEM results. The surface area estimated by using the BET method was (800 ± 8) m²g^-1. Pore size distributions (PSD) of nitrogen and CT adsorption isotherms for a series of MCM-41 were calculated by using
method recommended by Naono and Hakuman (1997). The pore size distributions from the nitrogen isotherm using the BJH and Naono methods showed quite narrow pore diameter distributions, centered
around 27 and 29 Å, respectively. Similarly, the peak pore diameters calculated from CT isotherms using
the BJH and Naono methods were 24 and 28 Å. It was found that the PSDs analyzed by the BJH method
were underestimated compared to that from Naono method.