Sw. Peretti et al., Extraction of 4-nitrophenol from 1-octanol into aqueous solution in a hollow fiber liquid contactor, J MEMBR SCI, 195(2), 2002, pp. 193-202
p-Nitrophenol (PNP) was extracted from 1-octanol into an aqueous buffered s
olution using membrane-supported extraction in hollow fiber liquid contacto
rs (HFLCs) containing hydrophobic, microporous polypropylene fibers. PNP is
a weak acid and in aqueous solution may dissociate to form nitrophenolate
ion (PNP-). that has negligible solubility in 1-octanol. The ratio of the t
wo species in aqueous solution is governed by pH; therefore, the overall ma
ss transfer coefficient based on solvent phase concentrations was determine
d as a function of pH. The extraction of PNP is a four-step process. consis
ting of diffusion across the solvent boundary layer, diffusion through the
solvent-filled membrane, reaction (dissociation) at the solvent/aqueous int
erface, and diffusion across the aqueous boundary layer. The reaction step
is assumed much faster than the others; a model of the mass transfer capabi
lities of the system is presented based on this assumption. The overall mas
s transfer coefficients were determined experimentally by recirculating the
solvent phase through the shell space of a HFLC and the aqueous phase thro
ugh the fibers. The model closely predicts the experimentally measured tren
ds of the overall mass transfer coefficient. (C) 2002 Elsevier Science B.V.
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