Chemical Engineering Research & Design, Vol.73, No.7, 782-797, 1995
Self-Supported Porous Channel Filtration Modules - Preparation, Properties and Performance
The preparation, properties and performance of a novel membrane system are given. This membrane system is based on a highly porous (up to 97%) cross-linked polymeric foam which is produced through the polymerisation of a high internal phase emulsion. It is shown that a skin!core structure (asymmetric membrane) can be achieved in these polymeric foams through the epitaxial polymerisation at the interface with a suitable substrate. The porosity of the skin is controlled by the difference (Delta delta = delta(s) - delta(m)) between the solubility parameters of the substrate (delta(s)) and the monomer (delta(m)) which constitutes the continuous phase of the high internal phase emulsion. The porosity of the skin layer decreases with decreasing Delta delta. If Delta delta is positive and high, the surface porosity is identical to the bulk porosity. The thickness of the skin layer (0.1-1 mu m) is equal to the wall thickness of the porous polymer which can be controlled through the processing or phase volume of the emulsion. A number of self-supported porous channel (SPC) filtration modules have been prepared and used in the crossflow filtration of calcium carbonate (aragonite) and surfactant suspensions. SPC filtration modules are similar to hollow fibre membranes except that the capillaries in SPC modules are self supporting on a microscopic scale. Effects of membrane skin porosity and surface modification on the filtration characteristics of SPC modules are evaluated. The solute deposition mechanism during aragonite suspension filtration is deduced.