Dr. Callegari, Gerardo

 Rutgers University, Estados Unidos.

Powder wettability characterization with advancing and receding liquid front in a closed column

Wettability characterization of porous materials has been done in the past by measuring the height of a non-interacting (non-reacting) liquid front in equilibrium after the liquid bath was placed in contact with the material and it rise by capillarity through the pores of the media. Powders with particle sizes in the range of few tens of microns cannot be characterized in this way in an open column as the height of the column needs to be in the range of meters. In those cases, a dynamic (Washburn column) technique is used in which the only fitting parameter is related to two coupled properties: capillary pressure (PC) and permeability (K), and a second measurement is required. One approach is to measure saturated permeability (K) in a separate test, and to assume K in W-model is the same. A second method relies on the spontaneous imbibition of two liquids one of them with assumed zero contact angle with the porous media and assume that the permeability in both cases is the same, the ratio of W fitting constant gives the contact angle of the second material, assuming the permeability is the same in both cases. Here, we propose to use a closed column to characterize PC and K independently. One obvious advantage of the technique is that static PC can be measured even for a material with small pores.  A second advantage unique to this system is to allow exploration of both drainage and imbibition situations to extract effective advancing and receding contact angles. Finally, and more importantly, we show that results contradict the basic assumptions made in the traditional approaches as the permeability measured, doesn’t always equate to the saturated permeability sometimes leading to different unsaturated permeability when two different liquids are used. This means that the aforementioned techniques may misleadingly characterize wettability of the porous material.