A series of experiments on the facilitated transport of
CO2 through supported liquid membranes
containing monoethanolamine (MEA) and diethanolamine (DEA) was
performed. The feed gas
was a mixture of CO2 and CH4, and the
CO2 partial pressure
p
CO
2
,F was
in the range from 0.05
to 0.97 atm. Compared to the MEA membranes, the DEA membranes
showed a little higher
permeation rate of CO2 since the equilibrium constant of
the reaction between CO2 and MEA is
too large for CO2 to be released to the receiving phase
rapidly. When
p
CO
2
,F and
the MEA
concentration were 0.05 atm and 4 mol/dm3, respectively,
the separation factor α(CO2/CH4)
was
about 2000. It was found that if the membrane thickness multiplied
by the square root of the
tortuosity factor of the microporous support membrane is used as the
effective pore length, the
experimentally observed permeation rates of CO2 can be
satisfactorily simulated by the theory
of facilitated transport of CO2 through aqueous amine
membranes. A method for estimating
the solubilities of CO2 in the membrane solutions from the
permeation rates of CH4 was also
proposed. It was also found that permeation rates of
CO2 through aqueous DEA membranes
reported by Guha et al. were quantitatively explained by the proposed
theory.
Experiments on the extraction of ethyl and methyl esters of polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from various organic solvents into aqueous silver nitrate solutions were performed. The esters of PUF As with high degree of unsaturation such as DHA and EPA could be selectively extracted into aqueous solutions. On the basis of the slope analysis, the extracted complex of PUFA ester (PUFA-E) was deduced to be (PUFA-E-nAg)n+ where n is the number of the carbon-carbon double bonds in PUFA. The distribution ratio D increased drastically with a decrease in temperature and also by addition of water-soluble alcohols such as methanol, ethanol, and n-propanol to aqueous solutions. The value of D was found to be highly dependent on the organic solvent used as the diluent of PUFA-E, and the D value of EPA ethyl ester (EPA-Et) was correlated by the activity coefficient of EPA-Et in the organic phase estimated by the UNIFAC equation.
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