Abstract
Several forward osmosis (FO) experiments were carried out using different concentrations of sodium chloride (NaCl) aqueous solutions as draw solution (DS) and freshwater as feed solution. The experiments were carried out at different temperatures using a symmetric cellulosic membrane. The study investigates the relationship between water flux and DS solute flux (the reverse solute diffusion) across the membrane. The solute flux is one of the important factors that determine the practicality of FO processes. The results show that both water flux and solute flux increase as the solute concentration difference across the membrane increases, as well as with the temperature increase. It is found that water flux is proportional to solute flux, and a similar trend was also found between water permeability and solute permeability. Proportionality factors (k(J)) and (k(E)) are suggested to represent the flux and the permeability proportionalities, respectively. The k(J) was calculated experimentally and found to be almost constant and approaching the saturation concentration of the solute, NaCl in this case.