Application of an innovative draw solute in forward osmosis (FO) processes

Abstract

More attention is being paid to forward osmosis (FO) as a breakthrough technology to tackle environmental pollution due to advantages such as high contaminant removal and low energy consumption. Nevertheless, FO applications remain limited by the lack of ideal draw solutes that simultaneously achieve high permeate flux and low salt leakage flux. Therefore, this paper aims to increase water flux while maintaining low reverse salt diffusion by using a low concentration of a highly charged organic EDTA compound coupled with inorganic NaCl salt as a novel draw solute. Results of the FO performance revealed that a draw solute of 0.3 M EDTA-2Na mixed with 0.6 M NaCl yielded a higher water flux (Jw=8.82 l/m2 h) when compared to 0.9 M NaCl only (Jw=7.61 l/m2 h). Moreover, the FOmembrane distillation system produced good quality drinking water with a total dissolved solid (TDS) of <5 mg/l from the permeate stream originating from influent brackish water with a TDS of 6000 mg/l. The analysis results from scanning electron microscopy and energy dispersive X-ray spectroscopy (SEMEDX) images observed a cake layer of NaCl on the FO membrane surface.

Keywords

• brackish water
• distillation
• forward osmosis
• membrane draw solute
• reverse salt flux