Optimisation of organofunction PDMS membranes for the pervaporative recovery of phenolic compounds from aqueous streams

Abstract

Experimental studies for optimising organofunctionalised PDMS membranes for the pervaporative recovery of phenolic compounds from water are presented. Four functional groups i.e. acetate, ethylether, dimethylamino and pyridyl were loaded into pure PDMS membranes with the functional loading ranging from 10 to 25%. Composite membranes were fabricated and tested in short term trials with 5% (w/w) phenol/water and 2% (w/w) p-cresol/water binary systems. The influences of the pH and temperature of the feed solution were also examined. It was found that significant performance enhancements were achieved for functionalised PDMS membranes, especially those loaded with either the dimethylamino or the ethylether group. The optimal loading level for the dimethylamino group is about 20%. For this membrane, increasing the pH of the feed solution within the range 5–8.5 would double the selectivity for p-cresol/water separation. For the phenol/water separation the effect is more modest. The results also showed that an increasing feed temperature from 50 to 90°C resulted in an increase of 300% in flux, but had a negligible effect on selectivity.