Polyelectrolyte-promoted forward osmosis process for dye wastewater treatment – Exploring the feasibility of using polyacrylamide as draw solute

• Polyacrylamide (PAM, MW ∼ 3,000,000) was explored as draw solute in the FO process.
• The diluted PAM solution can be used directly to polymer flooding.
• PAM had superiority in steadier water flux and less salt leakage.
• A high temperature was preferable when using PAM as draw solute.
• The application of PAM in FO to treat dye wastewater was proven to be feasible.

In this study, polyacrylamide (PAM, MW ∼ 3,000,000) was applied as draw solute in forward osmosis (FO) process. The influence of temperature, concentration and membrane orientation on FO performance was investigated. The PAM solution was diluted during the FO process, which could maintain the relatively high viscosity and be used directly to polymer flooding in many oilfields to increase oil production. When comparing the FO performance between KCl and PAM via the same membranes, the water flux of PAM (the time of achieving a balance was less than 2 h) was more stable than that of KCl (a sustained downward trend all though the 5 h). The loss of PAM in recovering each liter of water from FS (<0.009 g) was much smaller than that of KCl which was more than 0.2 g. The stable water flux with almost a complete salt rejection in the FO process revealed the superiority of PAM to conventional ionic salts. Furthermore, the application of PAM in FO to treat the Reactive Brilliant Red K-2BP (RBR) dye solution was investigated and proven to be feasible, where the membrane fouling caused by RBR dye solution was slight and the dye rejection was high (almost 1). The overall performance demonstrated that PAM is a promising draw solute.