Development of novel seperation system for the removal of volatile organic compounds (VOCs) from contamaninated water using modified ceramic based membranes

Abstract

Originally we aimed to develop a novel separation system for the removal of volatile organic compounds (VOCs) from waste water using ceramic based membranes. We proposed the project with an expected total cost of RM276, 670. However, the total fund approved by MOSTI was only RM80, 000; the approved amount was not sufficient to complete the proposed project. With the limited fund, we had to make significant changes accordingly. So in this project, we investigates the potential of modified Polydimethylsiloxane (PDMS) / Polystyrene (PS) Interpenetrating Polymer Network (IPN) membrane supported on Teflon (Polytetraflouroethylene) ultrafiltration membrane for the separation of 10 wt. % ethanol in water by pervaporation application. These studies consist of two segments which are (i) development/ synthesis of the membranes and (ii) membranes characterization tests. The PDMS/PS IPN supported membranes were prepared by sequential IPN technique. Tetraethylorthosilicate and divinyl benzene (DVB) were used as the crosslinker for PDMS and PS monomer respectively, with dicumyl peroxide (DCP) as the initiator for PS network and dibutyltin dilaurate as the catalyst for PDMS network. DCP can also act as a crosslinker in the IPN system. The IPN supported membranes were prepared by the bulk copolymerization of styrene, DVB and DCP in the PDMS network; where fixed volume solution of PDMS/PS was poured onto Teflon support membrane on a stainless steel plate. The IPN supported membranes were tested for the separation performance on 10 wt.% ethanol in water and were characterized by evaluating their mechanical properties, swelling behavior, density and degree of crosslinking. Morphology of the supported membranes was studied using Scanning Electron Microscope (SEM) micrographs. The results indicated that separation performance, mechanical properties, density and the percentage of swelling of IPN membranes were influenced by degree of crosslink density. Throughout the separation experiment, it was found that the IPN membranes were ethanol selective. The maximum permeation rate and separation factor for the PDMS/PS IPN supported membranes with PS content of 50 wt.% and crosslinking agent dicumyl peroxide of 5 wt.% (from PS network) for the pervaporation of 10 wt.% ethanol in water were 428.25 g/m2.h and 2.54 respectively. The SEM micrograph verified that the IPN supported membranes were dense and free from visible pore of up to 5000 times magnification. Although the mechanical properties and degree of swelling for the PDMS/PS IPN supported membranes show great improvement compared to crosslinked PDMS membrane, the separation ability and flux of the membrane towards pervaporation application were not that high.