ABSTRACT OF THE DISSERTATION

Development of Ceramic-Supported Polymer Pervaporation Membranes

by Jeng-dung Jou

Department of Chemical Engineering

University of California, Los Angeles, 1998

Professor Yoram Cohen, Chair

A systematic approach was developed for the synthesis of a novel class of ceramic-supported polymer (CSP) pervaporation membranes. The approach is based on the surface modification of a ceramic support membrane by a graft-polymerization procedure.  The two step modification procedure consists of silylation of surface hydroxyls, which provides the anchoring sites for the grafted chains, followed by a free radical graft polymerization reaction. This procedure allows for the attachment of either hydrophilic or hydrophobic polymers. For pervaporation applications the polymer phase serves to allow permeation of the selected compound while preventing others from passing through the membrane. The polymer for a specific separation task is selected based on a thermodynamic approach which makes use of the Hansen solubility parameters. In this work two polymers, polyvinylpyrrolidone (PVP) andpolyvinylacetate (PVAc) were selected to demonstrate the graft polymerization approach and its applicability to the synthesis of CSP membranes. In order to control the degree of graft polymerization, a kinetic model was developed. The kinetic model allows for the choice of reaction conditions needed to achieve the desired uniformity and surface polymer concentration. The applicability of the CSP membrane for pervaporation was evaluated for the removal of volatile organics from water using a tubular PVAc-silica membrane. Removal of the selected organics from water was studied over a range of tube-side Reynolds number, transmembrane pressure drop and feed concentration. Data collected, to date, for the removal of trichloroethylene (TCE) from water demonstrated that the resistance of the PVAc-silica membrane to mass transfer is negligible with the mass transfer process controlled essential by  the boundary layer near the membrane surface. Also, membrane performance was independent of concentration over the range of concentrations studied (30 ppm-700 ppm). The overall permeate concentration was enriched by a factor 73-82 relative to the feed concentration, hence, enabling the recovery of a pure TCE phase.

Note: Current work is ongoing to develop the next generation of tubular CSP membranes which will possess a denser grafted polymer phase to decrease water flux and increase membrane performance.