Towards temperature driven forward osmosis desalination using Semi-IPN hydrogels as reversible draw agents

Recent advancements in forward osmosis desalination: A review

“…It was also found that higher temperature would not only allow greater initial fluxes and more water passage but would also induce more hostile effects on the scaling of FO membrane. For -temperature-driven FO desalination as reported by [7], thermally responsive semi interpenetrating (semi-IPN) hydrogels have been employed as draw agents whereby cyclic heating and cooling ensured quasi-continuous desalination within a moderate change in temperature. Moreover, concentration of draw solution is crucial for maintaining the desired water flux across the membrane.…”

“…Hydrogels have the ability to absorb water across FO membrane as a result of their swelling pressure. Their insoluble cross-linked network enables dewatering under the influence of stimuli (thermal or mechanical) [7,8]. However, several drawbacks of hydrogels, such as energy-intensive dewatering process, low water flux and minimal recovery hinder their practicability as draw agents [9].…”

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

“…The terminology "smart" has been frequently linked to stimuli-responsiveness like temperature or magnetic-field responsive materials. Polymer hydrogels have been recently demonstrated as thermo-sensitive agents that can be recycled by changing the temperature of the draw solution above the critical point of the polymer [20,[30][31][32]. However, the osmotic pressure of these materials was not high enough to drive a cost effective FO process.…”

“…Several polymers feature high hydrophillicity and hence higher osmotic pressure. Among them PSA (or PAA-Na) has been reported as an efficient osmotic draw agent, with high osmotic pressure but low regeneration capability [30,32,33]. To leverage from the high osmotic pressure property of PSA and improve its regeneration in FO desalination, our approach was to prepare PSA-coated MNPs (PSA-MNP), where PSA acted as the high hydrophilic polymer contributing to SMDA's high osmotic pressure for FO process and the magnetic iron oxide core being responsible for easy regeneration of the SMDA.…”

Water desalination by forward (direct) osmosis phenomenon: A comprehensive review

“…However, low water flux and water recovery was reported. Similarly, Cai et al [222] used thermo-sensitive semi-IPN hydrogel draw agents that absorbed water from brackish water. The swelled hydrogels draw agents were then heated to release the product water.…”