Switchable polarity solvents as draw solutes for forward osmosis

Recent advancements in forward osmosis desalination: A review

“…However, argument holds that the regeneration step using UF is still energetically demanding, which suggests that the use of polyelectrolytes would not be any different from using inorganic salts with an RO recovery step [2]. Very recently, discovery of the use of switchable polarity solutes and trimethylamine (TMA)-carbon dioxide revealed that solutions with very high osmotic strengths that are high enough to draw water from feeds as saline as seawater and brine can be obtained [103]. The miscibility of this type of draw solutes can be manipulated via the addition or removal of carbon dioxide from the solution, thereby making recovery a potentially simple step through the addition or removal of CO 2 [103].…”

“…Very recently, discovery of the use of switchable polarity solutes and trimethylamine (TMA)-carbon dioxide revealed that solutions with very high osmotic strengths that are high enough to draw water from feeds as saline as seawater and brine can be obtained [103]. The miscibility of this type of draw solutes can be manipulated via the addition or removal of carbon dioxide from the solution, thereby making recovery a potentially simple step through the addition or removal of CO 2 [103]. However, the economic and energetic opportunity of this system still needs to be assessed to determine its feasibility for FO desalination [2].…”

Forward osmosis: Where are we now?

“…In addition, draw solutes should be able to generate high osmotic pressures and be completely regenerated using simple, efficient techniques. Due to these numerous and sometimes conflicting requirements and the large number of potential solutes that could be used, draw solutes with strikingly different properties have been tested for FO [17][18][19][20][60][61][62][63][64]. It is clear that a focused and updated discussion of desired draw solute properties is needed.…”

“…The introduction of the ammoniacarbon dioxide FO process in 2005 as a potential desalination process that utilizes low-grade thermal energy [3] has stimulated academic and industrial interest in FO, which resulted in a dramatic increase in the number of research articles and patents in subsequent years [2,4]. These studies on FO involved membrane development [5][6][7][8], mass transfer analysis [4,9], membrane characterization [10,11], fouling phenomena [12][13][14][15][16], and introduction and characterization of new draw solutions [17][18][19][20]. Concurrently, conceptual and bench-scale studies on various potential applications of FO have been published, including the use of FO coupled with a draw solution separation/regeneration stage [21,22], FO in osmotic dilution processes [23,24], and various hybrid systems incorporating FO [25][26][27][28].…”

A Thermodynamical Approach for Evaluating Energy Consumption of the Forward Osmosis Process Using Various Draw Solutes

“…After FO, the ammonium salts in the diluted draw solution can be thermo-decomposed into NH 3 and CO 2 gases at elevated temperature, and then the concentrated ammonium salt solution is regenerated from the mixture of NH 3 and CO 2 gases. Switchable polarity solvent (SPS), which is capable of changing its solubility in water by the addition and removal of CO 2 , was proposed as a new FO draw solute [14][15][16]. By heating up the SPS solution, CO 2 is driven off and the hydrophobic form of SPS is separated from the diluted draw solution.…”