Engineered barriers chemical mass transfer

A common procedure presently used is to specify a limiting maximum value of hydraulic conductivity for the engineered clay barrier for control of transport and transfer of contaminants to the substrate (Jessberger 1995 Yong 1996 Manassero et al. 1997) However, this approach does not necessarily pay attention to the specific role of chemical mass transfer and/or the natural attenuation phenomenon. Contaminant retardation occurs via control on the limiting hydraulic conductivity. If retention... 

The membrane in a contactor acts as a passive barrier and as a means of bringing two immiscible fluid phases (such as gas and hquid, or an aqueous hquid and an organic hquid, etc.) in contact with each other without dispersion. The phase interface is immobilized at the membrane pore surface, with the pore volume occupied by one of the two fluid phases that are in contact. Since it enables the phases to come in direct contact, the membrane contactor functions as a continuous-contact mass transfer device, such as a packed tower. However, there is no need to physically disperse one phase into the other, or to separate the phases after separation is completed. Several conventional chemical engineering separation processes that are based on mass exchange between phases (e.g., gas absorption, gas stripping, hquid-hquid extraction, etc.) can therefore be carried out in membrane contactors. 

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