Simultaneous cooling and provision of make-up water by forward osmosis for post-combustion CO2 capture
This study evaluates the feasibility of forward osmosis (FO) for simultaneous post-combustion CO2 capture and make-up water provision using seawater and treated effluent as the feed. Three amine-based CO2 adsorbents (glycine, sodium glycinate, and monoethanolamine (MEA)) were used as draw solutes. A non-linear relationship between concentration of these adsorbents and conductivity (thus osmotic pressure) was observed. Glycine showed higher water flux and lower reverse salt flux and specific reverse salt flux than sodium glycinate and MEA in both membrane orientations, thus was selected for further investigations. A higher water flux but with the considerable flux decline were observed when active layer faced draw solution. In addition, temperature increase in draw solution could alter thermodynamic properties of glycine, resulting in an increase of reverse salt flux. Water flux increase was also observed due to diminishing concentrative internal concentration polarisation. Changes in water flux were insignificant when active layer faced feed solution even as temperature increased. Temperature increase was likely to aggravate the severity of dilutive internal concentration polarisation and offset the growth of osmotic pressure. Seawater could also be a potential source for simultaneous cooling and providing the make-up water, although the water flux was lower compared to treated effluent.