Strategic Project - UI 619 - 2014

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Porosity in ion-exchanged and acid activated clays evaluated using n-nonane pre-adsorption

Publication . Ribeiro Carrott, M.M.L.; Cansado, I.P.P.; Carrott, P.J.M.; Russo, P.A.; Castilho, P.; Fernandes, C.; Catrinescu, C.; Breen, C.

The applicability of the n-nonane pre-adsorption method for characterising the porosity in clays is presented. Na-SD, a Naþ-exchanged purified bentonite, and materials obtained by Al3þ-exchange and acid treatments of Na-SD and SAz-1 were used. Nitrogen adsorption isotherms, at 196 C, were determined before and after n-nonane pre-adsorption on each of the samples. In all materials, n-nonane remained adsorbed in ultramicropores after outgassing at 25 C. Outgassing at higher temperatures (50, 75 and 200 C) removed nonane and ultramicropores became available for nitrogen adsorption. All treatments on Na-SD led to increase in micropore volume. Larger ultramicropore and supermicropore volumes were obtained for Na-SD acid activated with HCl at 95 C than for treatments at 25 C with HCl or following Al3þ-exchange (Al-SD), and increased with increasing acid concentration to 3 M. Activation with 4 M HCl led to the largest pore volume with contribution from mesopores. However, the specific external surface area was the same as that obtained for Na-SD, Al-SD and for most of the other acid activated samples. Treatments at 95 C with 1 M and 6 M HCl promoted increase in specific external surface area. The micropore volumes and specific external surface area for SAz-1 treated with 1 M HCl at 95 C were larger than those of Al-SAz-1, but lower than those obtained for corresponding materials derived from Na-SD. The n-nonane pre-adsorption method enabled micropore volumes and specific external surface areas to be obtained for all samples.

2016Journal article

Open access