A Dendrimer-Based Forward Osmosis Draw Solute for Seawater Desalination

Abstract

A dendrimer-based forward osmosis (FO) draw solute, poly­(amidoamine) terminated with sodium carboxylate groups (PAMAM-COONa), was investigated for seawater desalination. Compared with existing FO draw solutes, PAMAM-COONa offers unique advantages: (1) Its aqueous solution can generate high osmotic pressure because of the large number of −COONa groups. (2) The low viscosity of PAMAM-COONa solution can reduce internal concentration polarization (ICP), which adversely affects FO water flux. (3) PAMAM-COONa has a relatively large molecular size, favoring reduced reverse solute flux. In our FO tests using 2.5-generation (2.5G) PAMAM-COONa draw solution (33.3 wt %) and seawater (Singapore coast) feed solution, a relatively high water flux of 9 L m–2 h–1 was achieved with commercial HTI FO membrane. In addition, a considerably reduced reverse solute flux of PAMAM-COONa compared to that of NaCl was attained. After FO testing, the diluted PAMAM-COONa solution was reconcentrated to its original osmotic pressure with membrane distillation to produce desalinated water and to regenerate the draw solution. In addition to seawater desalination, the dendrimer-based FO draw solute may find applications in wastewater treatment and protein enrichment.

Magnetic nanoparticles boosting the osmotic efficiency of a polymeric FO draw agent: Effect of polymer conformation

“…On the other hand, a higher M w i.e., a longer polymeric chain -which is not fully ionisable -would provide a higher number of hydrophilic groups that can ionize by improving the osmotic pressure. Previously dendrimers [35] with multiple hydrophilic end groups have been reported to overcome this problem. Zhao and coworkers [35] had observed a decrease in water flux with increase in the dendrimer generation i.e., with increase in number of hydrophilic end groups as well as increase in M w .…”

Exploration of polyepoxysuccinic acid as a novel draw solution in the forward osmosis process

“…9 The outstanding advantages of FO include high water ux, low energy requirement, high salt rejection and low membrane fouling. 10,11 Currently, FO is widely applied in brackish water/ seawater desalination, [12][13][14] sludge dewatering, [15][16][17] and pharmaceutical factory. 18 However, its development is still hampered by two key factors, which are an ideal FO membrane and efficient draw solution.…”

Sodium Tetraethylenepentamine Heptaacetate as Novel Draw Solute for Forward Osmosis—Synthesis, Application and Recovery

“…A relative high initial flux of 9.7 LMH is observed, suggesting that STPH is a good candidate for seawater desalination by a FO process. This FO performance with the STPH draw solution was also benchmarked against most other reported draw solutes under comparable conditions, including dendrimers [18], hydroacid complexes [16,28], polyelectrolytes [29,30], responsive ionic liquid [31], and thermoresponsive copolymers [32,33]. Table 1 shows that the STPH draw solution exhibits superior FO performance to most of the other reported organic draw solutes.…”

“…In recent years, various novel draw solutes with enhanced properties have been reported based on different design strategies, including magnetic nanoparticles with enhanced surface hydrophilicity or expanded molecular size [11][12][13], and organic compounds with improved volatility [14,15] or physicochemical properties [16], etc. Previous works have reported polyacrylic acid salts (PAA-Na) with various molecular weights ranging from 1200 Da to 5000 Da [17], and Polyamidoamine with terminal carboxyl groups (PAMAM-COONa) [18] as novel draw solutes with good FO performance. Recently, we also demonstrated a novel ethylenediamine tetrapropionic sodium salts (EDTP) with multiple carboxyl groups [19].…”