posted on 2023-08-04, 18:34authored byChen Song, Gregory C. Rutledge
The removal of emulsified oils from water has always
been a challenge
due to the kinetic stability resulting from the small droplet size
and the presence of stabilizing agents. Membrane technology can treat
such mixtures, but fouling of the membrane leads to dramatic reductions
in the process capacity. Liquid-infused membranes (LIMs) can potentially
resolve the issue of fouling. However, their low permeate flux compared
with conventional hydrophilic membranes remains a limitation. To gain
insight into the mechanism of transport, we use 3D images acquired
by confocal laser scanning microscopy (CLSM) to reconstruct the sequence
of events occurring during startup and operation of the LIM for removal
of dispersed oil from oil-in-water emulsions. We find evidence for
coalescence of oil droplets on the surface of and formation of oil
channels within the LIM. Using image analysis, we find that the rate
at which oil channels are formed within the membrane and the number
of channels ultimately govern the permeate flux of oil through the
LIMs. Oil concentration in the feed affects the rate of coalescence
of oil on the surface of the LIM, which, in turn, affects the channel
formation dynamics. The channel formation dynamics also depend on
the viscosity of the infused liquid and the operating pressure. A
higher affinity to the pore wall for infused liquid than permeating
liquid is essential to antifouling behavior. Overall, this work offers
insight into the selective permeation of a dispersed liquid phase
through a LIM.