Performance evaluation of trimethylamine–carbon dioxide thermolytic draw solution for engineered osmosis

Abstract

We evaluated the performance of trimethylamine−carbon dioxide (TMA−CO 2 ) as a potential thermolytic draw solution for engineered osmosis. Water flux and reverse solute flux with TMA−CO 2 draw solution were measured in forward osmosis (FO) and pressure retarded osmosis (PRO) modes using thin-film composite (TFC) and cellulose triacetate (CTA) FO membranes.Water flux with the TMA−CO 2 draw solution was comparable to that obtained with the more common ammonia−carbon dioxide (NH 3 −CO 2 ) thermolytic draw solution at similar (1 M) concentration. Using a TFC-FO membrane, the water fluxes produced by 1 M TMA−CO 2 and NH 3 −CO 2 draw solutions with a DI water feed were, respectively, 33.4 and 35.6 L m -2 h -1 in PRO mode and 14.5 and 15.2 L m -2 h -1 in FO mode. Reverse draw permeation of TMA−CO 2 was relatively low compared to NH 3 −CO 2 , ranging from 0.1 to 0.2 mol m -2 h -1 in all experiments, due to the larger molecular size of TMA. Thermal separation and recovery efficiency for TMA−CO 2 was compared to NH 3 −CO 2 by modeling low-temperature vacuum distillation utilizing low-grade heat sources. We also discuss possible challenges in the use TMA−CO 2 , including potential adverse impact on human health and environments. Osmosis  − = D S J k J J B k J D S J A J FO w

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.…”

“…Recent research [17][18][19][20][60][61][62][63][64] has led to numerous ideas for draw solutes, including polyelectrolytes [18], hydrophilic magnetic nanoparticles [63], hydrogels [61,62], and switchable polarity solvents [19,65]. A major driver in these studies is finding a draw solute that can decrease the energy of draw solution regeneration.…”

“…Indeed, one of the main advantages of polymer and nanoparticlebased draw solutions is essentially eliminating reverse draw solute flux. However, with the recent commercialization of TFC-FO membranes, which have much higher RSFS than CTA membranes [10,60], reverse draw solute flux for small inorganic solutes has been greatly reduced. This trend will continue with the expected commercialization of more highly selective TFC-FO membranes, further decreasing the need for exploring large draw solutes, and further promoting the use of small, highly-mobile solutes.…”

Effective energy management by combining gas turbine cycles and forward osmosis desalination process

“…The water permeability is affected by the membrane property and the water viscosity [25]. However, the B value is dependent on the type of the draw solution [26]. Draw solutes with high mass transfer coefficient induces a higher solute permeability coefficient.…”

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

“…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.…”