Effect of the size of aggregates on pore characteristics of minerals measured by mercury intrusion and water-vapor desorption techniques
Jozefaciuk, Grzegorz (Institute of Agrophysics of the Polish Academy of Sciences)

Fecha:	2009
Resumen:	The size, shape, and continuity of pores in mineral solids greatly influence the behavior of percolating liquids and solids in porous media, which has significant practical environmental implications. In order to expand understanding of these properties in soil minerals, the present study was undertaken to analyze the pore characteristics of bentonite, illite, and kaolinite in the forms of powder and aggregates of different dimensions, combining water-vapor desorption and mercury-intrusion techniques. Different granulometric fractions of milled quartz glass were also studied. With increasing aggregate size of the minerals, larger pore volumes (up to 25%), smaller surface areas (down to 15%), larger average radii (up to 15%), and smaller fractal dimensions (down to 6%) were measured using water-vapor adsorptiondesorption data. The differences were smallest for bentonite, possibly due to the smallest particle size of this mineral and/or to its very large water-vapor adsorption capacity. The degree of water-vapor adsorption on quartz was too small to rely on the data obtained. The pore volumes and average radii, measured by mercury-intrusion porosimetry, were up to few times larger for the mineral powders than for their aggregate counterparts. Similar values were noted for aggregates >1 mm in diameter, for which the input of interaggregate spaces into total porosity of the sample bed was negligible. Two pathways of mercury intrusion were detected in porosimetric curves: filling of interaggregate spaces, and penetration into aggregates. Similar penetration thresholds into aggregates of different sizes were calculated. With increasing size of quartz grains, the pore volume of the quartz bed decreased whereas the average pore radius increased. Mercury intrusion detected pore-fractal behavior of bentonite and kaolinite, but for aggregated minerals the calculated values of fractal dimensions were >3, values which increased with increasing aggregate size. Very similar pore parameters were measured for aggregates prepared from a natural deposit of kaolinite and for artificially prepared aggregates from powder of the same mineral, indicating that artificial aggregation can simulate natural processes. Both water desorption and mercury intrusion detected fractal behavior in the limited range of pores. A test to find fractal build up of the aggregates in extended scales based on a dependence of surface area of unit volume of aggregate bed on aggregate size showed no fractal-aggregate build-up.
Derechos:	Tots els drets reservats.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Aggregate ; Adsorption Isotherms ; Mercury Intrusion ; Mineral ; Porosity
Publicado en:	Clays and Clay Minerals, Vol. 57, Núm. 5 (2009) , p. 586-601, ISSN 1552-8367

DOI: 10.1346/CCMN.2009.0570507

16 p, 1.2 MB  Acceso restringido a la UAB

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