Innovation in Draw Solute for Practical Zero Salt Reverse in Forward Osmosis Desalination

Abstract

In forward osmosis (FO), reverse salt diffusion not only reduces water flux but also increases the requirement of draw solute replenishment. FO would be very desirable if there was no draw solute leakage and the recovery of draw solutes was easy. In this study, a novel draw solute, ethylenediaminetetraacetic acid (EDTA)-2Na coupled with Triton X-100 was explored with the aim of minimizing reverse salt diffusion. The results indicated that reverse salt diffusion achieved zero the first time when using 0.1 M EDTA-2Na coupled with 0.5 mM Triton X-100 as draw solution and DI water as feed solution. A water flux of 4.6 L/m 2 h was reached when 35 g/L NaCl of model seawater was used as the feed solution and 1 M EDTA-2Na coupled with 0.5 mM Triton X-100 was used as the draw solute. Moreover, a nanofiltration (NF) membrane was employed to recover the draw solute, achieving a high rejection of 95% due to the high charge and large size of the draw solute.

Innovative sponge-based moving bed–osmotic membrane bioreactor hybrid system using a new class of draw solution for municipal wastewater treatment

“…The contact angle of the FO membrane was measured by CAM 100 (KSV Instruments Inc., USA).The fouled membranes were observed and examined using SEM-EDS (JSM-5600, JEOL, Tokyo, Japan). and reduced the reverse salt diffusion of Mg 2+ and Cl − , as illustrated in Figure 3 (Nguyen et al 2015a, Nguyen et al 2015b. This phenomenon agrees with the observation by Kiso et al, that: firstly, the hydrophobic interactions between selected pharmaceuticals and CTA FO membranes were the dominant organic removal mechanism; and secondly, the hydrophobicity of the pharmaceuticals strongly influenced their rejection.…”

“…Schematic illustration of reduced back diffusion of anions and cations with presence of non-ionic surfactant Triton X-114 during FO(Nguyen et al 2015a, Nguyen et al 2015b). …”

Exploring high charge of phosphate as new draw solute in a forward osmosis–membrane distillation hybrid system for concentrating high-nutrient sludge

“…However, the reverse salt diffusion showed a slight increase from 0.95 to 1.12 g/ m 2 h in the FO mode and from 1.30 to 1.57 g/m 2 h in the PRO mode when the draw solute concentration increased from 0.2 to 0.4 M. This may be due to the combined influence of the increased viscosity and concentration polarization at high Na 3 PO 4 concentrations. This phenomenon was also recorded by Ge et al (2012b) and Nguyen et al (2015a) as the higher draw solution viscosity caused the lower exchange speed of draw solution on membrane sides leading to the higher concentration polarization degree, subsequently the declined water flux. The results showed that for the present study 0.2 M to be the preferred concentration of Na 3 PO 4 draw solution.…”

A new class of draw solutions for minimizing reverse salt flux to improve forward osmosis desalination

“…Furthermore, NP9, which has a higher CMC, exhibited more reverse transport than NP7, which has a lower CMC (Gadelha et al, 2014). The osmotic (Nguyen et al, 2015). pressure of the draw solution slightly increased and the viscosity increased rapidly with an increase in the NP9 concentration ( Fig.…”

“…Among the currently used draw solutions, ethylenediaminetetraacetic acid (EDTA-2Na) not only has a high water flux and low reverse salt diffusion but also can be recovered relatively easily by using a nanofiltration (NF-TS80) membrane, as demonstrated in our previous study (Hau et al, 2014;Nguyen et al, 2015). To increase efficiency with minimal salt leakage, nonylphenol ethoxylates (Tergitol NP7 and NP9) combined with EDTA-2Na are selected as the proposed draw solution.…”