ABSTRACT
Thermo-responsive ionic compounds were synthesized to examine if they have a powerful ability to draw solutes for forward osmosis (FO). The investigated compounds were tetrabutylammonium benzenesulfonate, tetrabutylphosphonium benzenesulfonate, tetrabutylammonium 2-naphthalenesulfonate, and tetrabutylphosphonium 2-naphthalenesulfonate (abbreviated as [N4444][BS], [P4444][BS], [N4444][NS], and [P4444][NS]). The lower critical solution temperature (LCST) characteristics of the materials that formed the monocyclic aromatic compound [BS] were not confirmed; however, the LCSTs of others that formed the bicyclic aromatic compound [NS] were confirmed to be approximately 37 °C ([N4444][NS]) and 19 °C ([P4444][NS]) at 20 wt% in aqueous solutions; this is valued in reducing the energy required for recovery of the draw solute. In addition, it suggests that ammonium-based ionic compounds have a higher recovery temperature than phosphonium-based ionic compounds. When an active layer was oriented to a draw solution (AL-DS mode) and using 20 wt% aqueous [N4444][NS] draw solution at room temperature, water and reverse solute fluxes were about 3.07 LMH and 0.58 gMH, respectively. Thus, this is the first study to investigate structural transformations of the anion and central atom of the cation and to examine prospective draw solutes of the FO system in this series.
ABSTRACT
A series of thermo-responsive tetrabutylphosphonium 1-alkanesulfonates (abbreviated as [P4444][C n S], n = 6, 8, 10, and 12), where n is the number of carbon atoms in the alkyl group on the 1-alkanesulfonate anion, were prepared by an ion-exchange reaction to investigate their potential ability toward the application of draw solutes in forward osmosis (FO). We systematically studied the recovery properties and FO performance of [P4444][C n S]. This series exhibited lower critical solution temperature (LCST) characteristics, which offer a clear advantage of being energy-efficient for recovering draw solutes; however, [P4444][C6S] was only observed at 20 wt %. The LCSTs of the 20 wt % [P4444][C6S], [P4444][C8S], [P4444][C10S], and [P4444][C12S] draw solutions were approximately 83, 54, 49, and 56 °C, respectively. Moreover, when the orientation of the active layer was heading toward the draw solution (AL-DS mode), the water and reverse solute flux of [P4444][C10S] were about 1.58 LMH and 0.81 gMH, respectively, at 20 wt % aqueous solutions. When the membrane was used in the active layer facing the feed solution (AL-FS) system, the water and reverse solute flux of [P4444][C10S] were approximately 0.71 LMH and 0.38 gMH, respectively, at 20 wt % aqueous solutions. Thus, this study is the first to examine the structural transformations of the bulkier alkyl group on the sulfonate anion moiety and its feasibility as the new draw solute for the FO system.
ABSTRACT
A series of phosphonium-based ionic liquids (ILs) based on benzenesulfonate derivatives (tetrabutylphosphonium benzenesulfonate ([TBP][BS]), tetrabutylphosphonium 4-methylbenzenesulfonate ([TBP][MBS]), tetrabutylphosphonium 2,4-dimethylbenzenesulfonate ([TBP][DMBS]), and tetrabutylphosphonium 2,4,6-trimethylbenzenesulfonate ([TBP][TMBS])) were synthesized via anion exchange with tetrabutylphosphonium bromide ([TBP][Br]). Then, we characterized the ILs and investigated their suitability as draw solutes for forward osmosis (FO), focusing on their thermoresponsive properties, conductivities, and osmotic pressures. We found that aqueous [TBP][BS] was not thermoresponsive, but 20 wt% aqueous [TBP][MBS], [TBP][DMBS], and [TBP][TMBS] had lower critical solution temperatures (LCSTs) of approximately 41, 25, and 21 °C, respectively, enabling their easy recovery using waste heat. Based on these findings, 20 wt% aqueous [TBP][DMBS] was tested for its FO performance, and the water and reverse solute fluxes were found to be approximately 9.29 LMH and 1.37 gMH, respectively, in the active layer facing the draw solution (AL-DS) mode and 4.64 LMH and 0.37 gMH, respectively, in the active layer facing the feed solution (AL-FS) mode. Thus, these tetrabutylphosphonium benzenesulfonate-based LCST-type ILs are suitable for drawing solutes for FO process.
ABSTRACT
BACKGROUND: There is currently no observational instrument for assessing pain in aged patients who are unable to provide self-report in long-term care hospitals in Korea. AIMS: The goal of this research was to culturally adapt and test the validity, reliability, and feasibility of the Korean version of the Pain Assessment in Advanced Dementia Scale. DESIGN: This was a methodologic study aiming to translate the Pain Assessment in Advanced Dementia Scale. PARTICIPANTS/SUBJECTS: The inpatients in a 270-bed LTC hospital in D metropolitan city were assessed pain levels. METHODS: The Pain Assessment in Advanced Dementia (PAINAD) Scale was used as an observation scale to assess 192 long-term care hospital patients, with observation durations of 1 and 5 minutes. RESULTS: The interrater reliability (1 minute) for the scale showed substantial kappa agreement of .62, and scores for the 1- and 5-minute observations showed almost perfect agreement of .95. The criterion validity of the scale (1 minute) was high relative to the Face-Legs-Activity-Cry-Consolability (FLACC) Scale, and low compared with the numeric rating scale (NRS). Discriminant validity was established between patients with and without pain. The feasibility of the Pain Assessment in Advanced Dementia Scale-Korean Version (PAINAD-K) (1 minute) indicated low sensitivity of 41.3% and high specificity of 92.6%. CONCLUSIONS: Therefore, the PAINAD-K is a valid and reliable tool to determine the absence of pain in non-verbal aged patients.
