Draw Solution In Forward Osmosis Process Research Articles

Application of MnFe2O4 magnetic silica-covered ethylenediaminetetraacetic acid-functionalized nanomaterials to the draw solution in forward osmosis

Forward osmosis (FO) is an emerging and promising water treatment technology. However, selection of an optimal draw solution (DS) is essential for efficient FO process operations. In this study, the potential of ethylenediaminetetraacetic acid (EDTA) functionalized SiO2-covered magnetic nanoparticles (MNPs) as DS in FO process were investigated. The MNPs were synthesized and characterized for their morphology, size distribution, magnetic behavior, and dispersibility. Investigations were carried out to determine the effects of DS concentration and MNPs type, utilizing bare, SiO2 covered, and EDTA coated MNPs at concentrations of 20, 40, and 60 g/L. Furthermore, water flux generation capability and rejection efficiency of octanoic acid (OC) was evaluated with EDTA-MNPs as DS in FO mode (active layer facing feed solution) and PRO mode (active layer facing draw solution). Our results showed that a maximum water flux of 9.59 ± 2 LMH in FO mode, and 11.104 ± 2 LMH in PRO mode was achieved using 60 g/L of EDTA-MNPs. Additionally, we investigated the reusability of the EDTA-coated MNPs and found that their recovery was higher than (>90%) with no aggregation. The stability of EDTA-MNPs was due to strong covalent linkages between their four carboxylate groups and the hydrophilic SiO2 surface layer, which resulted in steric hindrance and prevented their aggregation. Finally, we assessed the rejection efficiency of OC at different pH values and found that it was low (30–39%) at pH values below pKa and high (90–97%) at pH values above pKa. Owing to internal concentration polarization, the rejection of OC in FO mode was (10–20%) higher than in PRO mode. The findings demonstrate EDTA-coated MNPs have significant potentials as an effective DS in FO process .

TETRABUTYLPHOSPHONIUM TRIFLUOROACETATE ([P4444]CF3COO) THERMORESPONSIVE IONIC LIQUID AS A DRAW SOLUTION FOR FORWARD OSMOSIS PROCESS

Forward osmosis (FO) is recognized as a potential membrane technology that utilizes low energy for water desalination. It is driven by natural osmotic pressure difference between draw solution and feed solution across semipermeable membrane. Pure water will permeated from the salinity feed water to the draw solution side. In order to produce pure water, it is necessary to find the best draw solute that exhibits high draw ability and can separate the permeated water efficiently from the draw solution. In the current study, lower critical solution temperature (LCST) thermos-responsive ionic liquid (IL) of tetrabutylphosphonium trifluoroacetate ([P4444]CF3COO) was synthesized as the draw solution for FO process. [P4444]CF3COO) is dissolved in water below it critical temperature of 29°C and becoming two layer above this critical temperature. [P4444]CF3COO IL showed high water flux of 0.44 ± 0.007 LMH compared to the water flux of 0.32 ± 0.049 LMH for the sodium chloride (NaCl) draw solution at the same draw solution concentration. Applying thermo-responsive IL as draw solute in FO process has the potential to treat high salinity of feed stream with eases water recovery and draw solute regeneration.