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 polymeris ation of a high internal phase emulsion. It is shown that a skin!core structure (asymmetric membrane) can be achieved in these polymeric foa ms through the epitaxial polymerisation at the interface with a suitab le 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 constitu tes the continuous phase of the high internal phase emulsion. The poro sity 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 t o the wall thickness of the porous polymer which can be controlled thr ough the processing or phase volume of the emulsion. A number of self- supported porous channel (SPC) filtration modules have been prepared a nd used in the crossflow filtration of calcium carbonate (aragonite) a nd surfactant suspensions. SPC filtration modules are similar to hollo w fibre membranes except that the capillaries in SPC modules are self supporting on a microscopic scale. Effects of membrane skin porosity a nd surface modification on the filtration characteristics of SPC modul es are evaluated. The solute deposition mechanism during aragonite sus pension filtration is deduced.