(587a) Multistage Countercurrent Liquid-Liquid Extraction Enabled By Membrane-Based Separations

AIChE
2015: Separation Divisions

Sessions:
Developments in Extractive Separations

Title: Multistage Countercurrent
Liquid-Liquid Extraction Enabled by Membrane-Based Separations

Author: Nopphon
Weeranoppanant, Andrea Adamo, Galym Saparbaiuly, and Klavs F Jensen

Liquid-liquid extraction is often
the most common workup strategy in the pharmaceutical production due to its
high selectivity and large capacity at relatively small energy consumption. In
many cases, multiple stages of extraction are required to achieve a high degree
of separation. Industrially, mixer-settlers, centrifugal extractors, spray and
tray columns are widely used. However, they have the disadvantages of
excessively large footprint, limited flow capacity, and difficult scale-up
procedures. Their moving parts and/or gravity-driven operation complicate, and in
some cases preclude, their use on a laboratory scale. In this work, we
construct a multistage countercurrent liquid-liquid extraction at the ml/min
scale. The membrane-based separators are used to separate the two phases at
each extraction stage, depending on their wettability nature and pressure
differential across the membrane. By virtue of an integrated pressure control
element that ensures successful separation and decouples the operation from
downstream pressure, the setup is greatly simplified. The use of multichannel
peristaltic pump as a means of interstage pumping significantly reduces the
number of pumps required. We demonstrate two classical examples of solvent
recovery: (1) extraction of acetone from an aqueous solution using toluene, (2)
extraction of acetic acid from an aqueous solution with ethyl acetate, representing
systems with relatively high and low interfacial tensions, respectively. Increasing
number of stages is shown to significantly increase the degree of recovery. The
extraction of the aqueous acetone solution with mass fraction of 0.50 using
toluene, with a solvent-to-feed ratio of 1:2 yields 49.6%, 73.4%, 81.1%, and
94.9% recovery for 1, 3, 5, and 7 stages, respectively, and these are found to
be in a close agreement with the simulation assuming 100% extraction
efficiency.  Similarly, the extraction of the aqueous acetic acid solution with
mass fraction of 0.05 with a solvent-to-feed ratio of 4:1 yields 64.6%, 77.9%,
93.3%, and 99.6% recovery for 1, 3, 5, and 7 stages, respectively. Scale-up
strategies, yielding high extraction efficiency at short residence time, are also
presented.