Desalination by ammonia–carbon dioxide forward osmosis: Influence of draw and feed solution concentrations on process performance

Forward (direct) osmosis (FO) using semi-permeable polymeric membranes may be a viable alternative to reverse osmosis as a lower cost and more environmentally friendly desalination technology. The driving force in the described FO process is provided by a draw solution comprising highly soluble gases—ammonia and carbon dioxide. Using a commercially available FO membrane, experiments conducted in a crossflow, flatsheet membrane filtration cell yielded water fluxes ranging from 1 to 10 m/s (2.1 to 21.2 gal ft−2 d−1 or 3.6 to 36.0 l m−2 h−1) for a wide range of draw and feed solution concentrations. It was found, however, that the experimental water fluxes were far lower than those anticipated based on a t a t s ©