Influence of temperature and temperature difference in the performance of forward osmosis desalination process

Abstract

Forward osmosis (FO) is an emerging technology for low energy desalination. Amongst the many other factors, temperature of the draw solution (DS) and feed solution (FS) plays an important role in influencing the performance of the FO process. In this study, the influence of the temperature and the temperature difference on the performance of FO process has been studied in terms of water and solute fluxes. Temperature difference was maintained by elevating only one of the solutions (either DS or FS). The results indicate that, water flux on average increases by up to 1.2% for every degree rise in temperature from 25 degrees C to 35 degrees C while this rise is 2.3% from 25 degrees C to 45 degrees C. Providing a temperature difference by elevating only the DS also enhanced the water flux significantly, although it was lower than FO process operated at isothermal conditions. However, elevating only the temperature of FS did not significantly improve the water flux although it was higher than the FO process operated at 25 degrees C. This has significant implications in FO process because the total mass of the DS requiring heat energy is significantly less than the total FS used. The influences of temperature in the FO process such as through changes in the thermodynamic properties of the solutions and the various concentration polarisation effects are also explained in details. (c) 2012 Elsevier B.V. All rights reserved.