Exploitable results
The aim of the Network was to study and develop novel and advanced membranes for the separation of gas and liquid streams containing hazardous components. The research work was divided in: synthesis and characterization of polymers for membrane preparation; preparation of microfiltration and ultrafiltration supports; modification of the supports for Ultrafiltration (UF), Nanofiltration (NF), Gas separation (GS) and pervaporation (PV) membranes; testing of such membranes in permeation and separation experiments; implementation in industrial processes. The good results obtained stem from an integrated cooperation among the Participating laboratories.
Thermally gated membranes were prepared by post-grafting polymerization of diethylacrylamide on IJF supports. The interracial polycondensation of ME supports yielded low fouling UF membranes. New membrane modules were produced. High rejections and fluxes NF membranes were prepared by interracial polycondensation of a polyamine and a polyfimctional acid halide on the surface of a porous polymer matrix. As a result, a NF process for the concentrating of protein hydrolyzate from leather waste waters has been devised (reduction of pollution and production of food integrator for cattle) and implemented.
The separation of gases and vapors in harsh environments (high temperature, presence of aggressive compounds, etc.) demands the use of high performance materials. The intrinsic gas transport properties and the membrane formation of glassy polymers (poly(phenylene oxide)s, (PPO), polyetherketones, polyimides) was studied.
The free volume structure of PPOs was revealed to correspond to a three-dimensional network of -throats and cavities". Effective diameters of the throats are in the range of cat 0.4 (77 K) - 0.5 nm (room temperature). The mechanism of separation of gaseous mixtures by PPOs membranes is similar to molecular-sieving. Analysis of X-ray diffraction, permeability, sorption, diffusion of permanent gases and Positron Annihilation Lifetimes (PAL) data divides evidences that the crystalline fraction of poly(phenylene oxide) homopolymers is dearly as permeable as the amorphous one. Plasticization of all PPOs considered was observed at CC partial pressures beyond 1.0 MPa.
PEEKWC, a soluble polyetheretherketone, was formed in integrally skinned asymmetric membranes, coated with a silicone rubber layer, to be used in gas separation. High flux composite and asymmetric, integrally skinned PPO membranes were prepared on the laboratory scale which demonstrate the feasibility of industrial membranes based on these materials. The good selectivity of PEEKWC and PPOs, the high fluxes obtained and the high thermal resistance indicate the possibility to use them with good results even beyond 100°C.
Homogeneous PEEKWC and PEEKWC / ß-cyclodextrine (ß-CD) composite membranes were tested for the pervaporation of water/organic and organic/organic mixtures. The gas permeability of PDLC composite membranes was not influenced significantly by the alignment of the liquid crystal droplets in electromagnetic fields.
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