Innovative polymer-complex draw solution for copper(II) removal using forward osmosis

Abstract

In forward osmosis (FO) process, reverse solute flux (RSF) is considered as a major disadvantage that limits the potential of FO. In this study, an innovative approach to reduce RSF was developed by introducing complexing agent into draw solution (DS) containing magnesium chloride (MgCl2). A water-soluble complexing agent namely poly(sodium 4-styrenesulfonate) (PSS) was chosen for this study and its affinity towards complexation with MgCl2 was investigated in terms of its loadings (0.1-5.0 w/w%) and pH condition (3.0, 5.0, 7.0 and 9.0). It was found out that the addition of PSS was able to reduce the effect of RSF due to its complexation with MgCl2 which enhanced the molecular weight and inhibited the movement of MgCl2 across thin film composite (TFC) membrane. Under pH studies, it is demonstrated that the optimum DS condition for complexation affinity was at none-adjusted pH. Compared to RSF value without the PSS addition, reduced RSF value (0.3 g/m2.h) was achieved at 1.0 w/w% PSS. When copper(II) sulphate was used as feed solution, the rejection was maintained at an average value of 95%. Based on these findings, this study promotes the feasibility of polymer-complex DS to be used in FO process for heavy metals removal.