Complete parametric investigation of a forward osmosis process using sodium chloride draw solution

Abstract

The design and operation of FO systems require accurate prediction of performance according to the operating parameters. Performance parameters such as water flux, reverse solute flux (RSF), specific reverse solute flux (SRSF), recovery and rejection are influenced by operating parameters including temperature, concentration difference (CD), and flow rates of feed solution (FS) and draw solution (DS). Whereas previous studies analysed the effect of only one or two operating parameters on one or two output parameters, this study provides a complete investigation into the effects of all operating parameters on all output parameters important for performance. A bench-scale FO setup using an advanced FO membrane and NaCl draw solution has been studied and compared to a predictive model, giving agreement within 10 %. Water flux and RSF increased with temperature, CD and flow rate. SRSF decreased with temperature, increased with CD, and increased as flow rates of FS and DS increased. Increasing temperature or CD increased the recovery; whereas increasing the flow rate of FS or DS reduced the recovery. Rejection dropped at higher CD and flow rates. Hence, it is recommended to operate at lower CD and flow rates to achieve higher recovery and rejection.