No abstract

Gas-liquid membrane contactors frequently suffer from wetting of the microporous membrane. Stabilization layers at the liquid side of the membrane potentially prevent this wetting. We applied such stabilized membranes to the separation of olefins and paraffins using AgNO 3 solutions as absorption liquid. The stabilization material requires permeation of olefins at minimum counter transport of water. Appropriate selection of the top layer material is crucial in this application. This report describes the selection of potential top layer materials. Dense films of the selected materials were prepared and used to determine ethylene and ethane permeabilities, to perform pervaporation experiments with water and a 3.5M solution of silver nitrate in water, and to determine the swelling behavior of the dense films in water and in a 3.5M silver nitrate solution. Based on the characterization experiments, ethylene propylenediene terpolymer is the most appropriate candidate with the highest potential for application in a gas-liquid membrane contactor for the separation of paraffins and olefins. It has a relatively high olefin permeability (46.4 Barrer) and a corresponding low water vapor permeability and low swelling tendency in a 3.5M silver nitrate solution (1490 Barrer and 0.14 wt %, respectively).

In this work, the development of a gel reservoir for a timolol (TM) transdermal iontophoretic delivery system is investigated. TM gel is prepared using hydroxypropyl cellulose (HPC) and the permeability of TM from the gel through an artificial membrane (Polyflux) and pig stratum corneum (SC) is studied. For a constant TM donor concentration, the TM transport across the Polyflux membrane alone decreases when the concentration of the gel increases due to increase of the gel viscosity. For constant gel concentration, however, the TM permeation across the membrane increases when the TM donor concentration increases. In addition, no effect of the electrical current (iontophoresis, current density 0.5 mA cm-2) on the TM permeation is found. For the combination of the Polyflux membrane with pig SC, the TM transport is much lower than for the membrane alone and the SC fully controls the TM delivery. In this case, the application of electrical current enhances the TM delivery 13-15 times in comparison to passive (no current) transport. According to our estimation, the daily TM dose (10-60 mg) can be delivered by an iontophoretic patch with Polyflux membrane area of 6-36 cm2 containing 20% (w/w) HPC gel and 15 mg cm-3 of TM.