(730f) Organic Solvent Nanofiltration through a Specific Carbonaceous Barrier Containing Interpenetrating Perfluoro-Segments

Our study focuses on development of a solid-foam composite membrane composed of a zeolite-carbonaceous amalgam framework for conducting nanofiltration (NF). NF offers promising prospects in recovering solvents from the effluents, which is of paramount importance to the pharma and petrochemical productions.

The zeolite-carbonaceous amalgam framework (ZCF) is fabricated via a pressure-driven amalgamation, in sub-micron scale, of a moderate-T_g polymer, zeolite-Y powder and a perfluoro compound. This is then followed by moderate pyrolysis of the precursor to convert the highly extruded polymer phase into a perfluoro-modified carbonaceous phase (with a very high C/H ratio). Consequently, the zeolite particles are intimately bonded by carbonaceous to constitute a dendritic network of ZCF, which surrounds abundant submicron-sized voids. The novel aspect of this membrane structure is related to its prevailed closed-cell matrix. Thus, each sub-micron closed cell behaves as a tiny NF step and hence benefits permeability at lower transmembrane pressures without compromising solute rejection. Organic solutions of dyes were used to examine the property and performance of the membrane. The membrane shows high rejection (>90%) to traces of dyes namely Methylene Blue and Brilliant Blue G, used as surrogate solutes, in IPA and Ethyl Acetate, respectively, with reasonable solvent permeation flux (average of 75L/hr m²bar) over a time period of 20 h. The separation mechanism can primarily be explained by a more favorable solvent-membrane interaction over solute-membrane interaction. This is attributed to the embedded perfluoro segments that constitute an interpenetrating network in the carbonaceous. Such perfluoro-network defers passage of the solvated dye molecules due to their incompatible polarities, whereas solvent molecules are able to penetrate meshes of the perfluoro-network. The carbonaceous confers permeation channels and serves as an immobilization medium for perfluoro-segments. Lastly, the zeolite grains in carbonaceous also tunnels the solvent molecules but excludes the dye. In a word, the innovative aspect of this NF process is the hydrophobic recognition inside the carbonaceous.