Performance Evaluation of 1-Cyclohexylpiperidine as a Draw Solute for Forward Osmosis Water Separation and CO₂ Recovery

Abstract

Membrane-based technologies, such as forward osmosis (FO), offer the advantage of treating water through a spontaneous process that requires minimal energy input while achieving favorable water permeability and selectivity. However, the FO process still has some challenges that need to be solved or improved to become entirely feasible. The main impediment for this technology is the recovery of the draw solute used to generate the osmotic potential in the process. In this paper, we discuss the use of a switchable polarity solvent, 1-cyclohexylpiperidine (CHP), as a draw solute that responds to external stimuli. Specifically, the miscibility of CHP can be switched by the presence of carbon dioxide (CO 2 ) and is reversible by applying heat. Thus, in this study, the hydrophobic CHP is first converted to the hydrophilic ammonium salt (CHPH + ), and its capability as a draw solution (DS) is thoroughly evaluated against the typical osmotic agent, sodium chloride (NaCl). Our results show that the water permeability across the thin film composite membrane increases by 69% when CHPH + is used as the DS. Also, the water permeability when using different feed solutions: aqueous solutions of (a) urea and (b) NaCl were evaluated. In both cases, the CHPH + generates water fluxes in the range of 65 ± 4 LMH and 69 ± 2 LMH, respectively. We then separate the diluted DS by applying 75 °C to the solution to recover the pure CHP and water. The results of this work provide a proof-of-concept of a CHP wastewater and desalination method via an FO process.

Inhibition Strategies of Reverse Solute Flux in Osmotic Microbial Fuel Cells: Take Forward Osmosis as Reference

“…Although it can only obtain 0.347 LMH of water flux, it can be easily recovered at 45 °C and 2 bar . Switchable polarity solvents can respond to changes in CO 2 or temperature, so as to realize the mutual conversion of polarity and nonpolarity . This new type of draw solution makes the recycling process much simpler.…”

“…90 Switchable polarity solvents can respond to changes in CO 2 or temperature, so as to realize the mutual conversion of polarity and nonpolarity. 91 This new type of draw solution makes the recycling process much simpler. It can produce high osmotic pressures (325 atm), water fluxes up to 35 LMH, and a low RSF of less than 1.8% reverse diffusion.…”

Using Reverse Osmosis Membrane at High Temperature for Water Recovery and Regeneration from Thermo-Responsive Ionic Liquid-Based Draw Solution for Efficient Forward Osmosis

“…Several kinds of stimuli-responsive DSs have recently been proposed and developed. To separate water from stimuli-responsive DSs, heat [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ], magnetic force [ 37 ], pH [ 38 ], and CO 2 [ 39 , 40 , 41 ] can be used as external stimuli. Among these stimuli-responsive DSs, thermo-responsive DS is the most widely studied.…”