Electrolysis-assisted recovery of reverse-fluxed solutes in forward osmosis

Reverse solute flux (RSF) is a key issue for operating forward osmosis (FO) systems and can cause the loss of draw solute (DS) and salt accumulation in the feed. Herein, an electrolysis-assisted FO (e-FO) system was developed for simultaneous RSF reduction and recovery of the reverse-fluxed DS. Applying a voltage of 1.5 V led to RSF of 3.34 ± 0.01 mmol m⁻² h⁻¹ (0.47 g m⁻² h⁻¹) in the e-FO system, 67.5 ± 0.5% lower than that of the control system; in addition, the e-FO system recovered ~0.32 g L⁻¹ of the reverse-fluxed DS and this could not be realized in the control. When the e-FO system was examined with three types of the mimicked fertilizer, RSF reduction and DS recovery were largely affected by the individual components of a fertilizer DS. The energy consumption of the e-FO system was reduced by ~90%, from 0.38 ± 0.01 to 0.04 ± 0.01 kWh m⁻³ when the recirculation rate decreased from 60 to 15 mL min⁻¹. Those results have demonstrated the technical feasibility of an e-FO system that is capable of reducing RSF and recovering the lost DS and will encourage further investigation by addressing several identified challenges.