Solvent extraction with immobilized interfaces in a microporous hydrophobic membrane

A new technique for solvent extraction with immobilized interfaces in a hydrophobic microporous membrane is described. No dispersion or coalescence is necessary. Extraction of acetic acid from aqueous solutions of different concentrations into either methyl isobutyl ketone or xylene through a fiat thin Celgard® 2400 microporous polypropylene film has been studied in a flow-type test cell primarily at an aqueous phase pressure 40 psi (2.75 x 10⁵ Pa) greater than an essentially atmospheric organic phase pressure. Studies over a range of 20 to 60 psi (1.378 x 10⁵ to 4.134 x 10⁵ Pa) did not indicate any significant pressure effect for extraction with methyl isobutyl ketone. Extraction rates reported as an overall organic phase based mass transfer coefficient are influenced by the boundary layer resistances on the organic and aqueous sides. Boundary layer resistance free overall transfer coefficients have been used to obtain the intrinsic membrane transfer coefficient. A description of this intrinsic membrane transfer coefficient for acetic acid extraction using the notion of a simple unhindered diffusion of a solute through a solvent-filled tortuous porous medium of uniform pore size yields realistic estimates of the tortuosity factor of the membrane used. The potential of this new technique has been described and compared with conventional extraction techniques if hollow microporous hydrophobic fibers are utilized.