Piperazine-Based Functional Materials as Draw Solutes for

Subscriber access provided by Washington University | Libraries

Article

Piperazine-Based Functional Materials as Draw Solutes for Desalination via Forward Osmosis Yanhuang Wu, Wen-Hua Zhang, and Qingchun Ge ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b02796 • Publication Date (Web): 14 Sep 2018 Downloaded from http://pubs.acs.org on September 14, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Piperazine-Based Functional Materials as Draw Solutes for Desalination via Forward Osmosis Yanhuang Wu†, Wenhua Zhang‡, Qingchun Ge*,† †College of Environment and Resources, Fuzhou University, No.2 Xueyuan Road, Fujian 350116, P. R. China ‡College of Chemistry, Chemical Engineering and Materials Science, Soochow University, No.199 Renai Road, Suzhou Industrial Park, Suzhou 215123, P. R. China Correspondence to: Q. C. Ge (E-mail: [email protected]), Tel: (86)591-22866219

ABSTRACT: The advancement of forward osmosis (FO) technology can be promoted greatly with appropriate draw solutes. In this study, a series of piperazine-based ionized functional materials (PIFMs) with three-dimensional configurations are designed for FO desalination. All PIFMs produce high FO water fluxes with negligible reverse solute diffusion, in which 1, 4piperazinediethanesulfonic acid disodium salt (P-2SO3-2Na) at 1.0 M generates a water flux up to 76.4 LMH against the feed of DI water. With saline water (0.1-3.5 wt% NaCl) as the feed, P2SO3-2Na produces water fluxes of 11.3-35.0 LMH, sufficient for handling large quantity of saline water. In FO seawater desalination P-2SO3-2Na produces a water flux 25-77% higher than recently proposed synthetic draw solutes. The characteristics of abundant ionic groups coupled

ACS Paragon Plus Environment

1

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 24

with a three-dimensional configuration account for the good FO performance of PIFMs draw solutes.

KEYWORDS: membrane separation, draw solute, piperazine-based functional material, water treatment, desalination, membrane distillation

■ INTRODUCTION Freshwater scarcity has caused worldwide concern. Clean water production via saline water desalination has proven to be effective in alleviating this problem.1-4 Reverse osmosis (RO) has currently become one of the most popular seawater desalination technologies.5,6 However, RO suffers the disadvantages of high pressure requirement, serious membrane fouling, and low water permeation rate.6 Unlike RO, forward osmosis (FO) requires much lower hydraulic pressure and has low fouling tendency with a comparatively high water recovery.7 With these strengths, FO has been applied to areas including seawater desalination,1,3 wastewater treatment,8,9 pharmaceutical enrichment10 and osmotic power generation.11 As a key element in FO, draw solute is crucial to FO applications. A wide range of materials have been used for draw solutes to date.12 Commercial substances,13 such as NaCl, MgCl2, NH4HCO3, have been served initially as draw solutes for FO processes. They create high water fluxes but with high salt flux simultaneously and are usually regenerated via high energy-consumed processes. To mitigate these problems, various synthetic materials, such as smart compounds,14,15 polyelectrolytes,16 hydroacid complexes,17 have been explored to be draw solutes in recent years. These compounds have much lower reverse solute fluxes in separation processes and can be recycled using relatively energy-effective approaches such as magnetic separation,14 and low-strength mechanical compression.12,15 However, most of them


2

Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


have low FO water recovery efficiency. Other synthetic draw solutes including magnetic nanoparticles,18 thermal hydrogels19 cannot even generate an efficient osmotic pressure for seawater desalination. Other problems, such as complicated synthesis routes, chemical instability and incompatibility with membrane are also present widely.20 Clearly, appropriate draw solutes are needed to promote FO desalination. Ideal draw solutes should ionize easily to create a high osmotic pressure and have pH-neutral property with a reasonable molecular size.12 Such characteristics ensure the compounds to form a neutral solution which is compatible with membranes, whilst producing a sufficient osmotic pressure for water transport with minimal reverse solute diffusion in FO. Guided by these strategies, we designed and synthesized sodium salts of piperazine-based ionic functional materials (PIFMs) which had a three-dimensional configuration centered on a six-membered piperazine ring and carried a large number of carboxylic or sulfonic groups. The chemistry and structural characteristics determined that the PIFMs dissociated fully in water which benefits the generation of a high osmotic pressure and the FO process as well owing to its osmotically driven principle. Meanwhile, a minimal reverse solute diffusion was achieved when the PIFMs used as FO draw solutes in view of their three-dimensional configurations. These advantages demonstrate the suitability of PIFMs as draw solutes and good performance in FO desalination. The PIFMs were recovered from their diluted solutions via membrane distillation (MD) processes (Figure 1). Crucially, PIFMs draw solutes produced high FO water fluxes with negligible reverse solute diffusion concurrently and were completely recyclable via the MD process with reproducible results when reused in FO, validating their suitability and potentials as FO draw solutes.


3


Page 4 of 24

Figure 1. Draw solutes made from PIFMs to treat saline water through FO processes and recovered by in-line MD processes. ■ MATERIALS AND METHODS Starting materials. Piperazine (99%), 1-(2-Hydroxyethyl) piperazine (99%), sodium iodoacetate

(ICH2COONa)

(ClCH2CH2SO3Na)

(99%),

(99%), and

sodium sodium

2-chloroethane

sulfonatemonohydrate

2-hydroxy-3-chloropropanesulfonate

(ClCH2CH(OH)CH2SO3Na) (99.5%) were supplied by Aladdin Industrial Corporation. Sodium hydroxide (99%) and sodium chloride (99%) were purchased from Tianjin Fuchen chemical reagents company. Ethanol (99%) was provided by Sinopharm Chemical Reagent Co., Ltd. All the chemicals were used as received. Deionized (DI) water with a resistivity of 18.25 MΩ·cm was produced by an ultrapurewater system (Millipore, United States). Synthesis of the PIFMs. 1, 4-Piperazinediethanesulfonic acid disodium salt (P-2SO3-2Na): Piperazine (2.15 g, 25 mmol) was dissolved in 20 mL DI water. ClCH2CH2SO3Na (9.23 g, 50


4

Page 5 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


mmol) and NaOH (1.60 g, 50 mmol) were then added successively. The resultant solution was continuously stirred overnight at 40 °C. A crystal clear solution was formed. Products were obtained by precipitation from cold ethanol and purified from H2O/EtOH. White powders were collected after drying (yield > 99 %). 1H NMR (300 MHz, D2O, 25 °C, δ): 2.60 (t, 8H, NCH2CH2N), 2.83 (t, 4H, NCH2), 3.13 (t, 4H, CH2S). 1, 4-Piperazinediethanecarboxylic acid disodium salt (P-2CO2-2Na) and piperazine-N, N'-bis (2-hydroxypropanesulphonic acid) disodium salt (P-2SO3-2OH-2Na) were synthesized similarly except that ICH2COONa and ClCH2CH(OH)CH2SO3Na replaced ClCH2CH2SO3Na, respectively, as the starting materials. Sodium 2-[4-(2-hydroxyethyl) piperazin-1-yl] ethanesulfonate (P-SO3OH-Na) was also prepared similar to P-2SO3-2Na except that 1-(2-hydroxyethyl) piperazine replaced piperazine as the starting material. P-2SO3-2OH-2Na: 1H NMR (300 MHz, D2O, 25 °C, δ): 2.71 (t, 8H, NCH2CH2N), 2.63 (d, 4H, NCH2), 3.5 (m, 2H, CH2CHCH2), 3.58 (d, 2H, CHOH), 3.69 (d, 4H, CH2S); P-SO3-OH-Na: 1H NMR (300 MHz, D2O, 25 °C, δ): δ 2.35 (t, 8H, NCH2CH2N), 2.92 (t, 2H, NCH2CH2S), 3.51 (t, 2H, NCH2CH2S), 2.53 (t, 2H, NCH2CH2OH), 3.45 (t, 2H, NCH2CH2OH), 3.65 (s, 1H, NCH2CH2OH). Characterizations of the PIFMs. The X-ray single crystal of P-2SO3-2Na and P-2CO2-2Na were grown by slow evaporation of H2O from their respective aqueous solutions. The X-ray diffraction measurements were performed via a Bruker SMART CCD diffractometer with MoKa radiation (l = 0.71073 A˚). The programs of SMART21 and SHELXTL22 were deployed to collect crystal data and structure information, respectively. Nuclear magnetic resonance (NMR) spectrometry was deployed to determine the chemical structure of PIFMs. Purified samples were dissolved in D2O prior to measurements and the analysis was performed Bruker ACF300 300


5


Page 6 of 24

MHz FT NMR spectrometers. The functional groups of PIFMs were evaluated by NicoLET iS10 Fourier transforminfrared spectroscopy (FTIR) with the range of 4000 to 400 cm-1. Physicochemical properties of the PIFMs. Relative viscosities (ηr) of draw solution at a range of concentrations against that of DI water were calculated by equation (1)23:

ηr =

η tρ = η 0 t0 ρ 0

(1)

where t and t0 (s) are the flowing times of draw solution and DI water, respectively, tested by a SYP1003-Ⅲ pertroleum products kinematic viscometer at 25 °C; ρ and ρ0 (g/mL) are the respective densities measured by a density meter (DMA35, Anton Paar). The size distribution of the PIFMs in their aqueous solutions was measured with a dynamic light scattering Nano-particle Size Analyzer (DLS, Brookhaven Instruments, NanoBrook Omni). The testing duration was 5 min and the reported results were the average obtained by 6 parallel measurements. The electrical conductivity and osmotic pressure of PIFMs solutions were determined respectively with a conductivity meter (DDSJ-308F) and a portable osmometer (Gonotec 3000, Germany). FO performance of the PIFMs. FO experiments were performed on a self-developed FO set-up (Suzhou Faith & Hope Membrane Technology Co. Ltd.). Home-made thin-film composite (TFC) membranes coated on polyethersulfone (PES) support layer of either flat sheet (TFC-PES(FS)) or hollow fiber (TFC-PES(HF)) were used in FO experiments.24 Solutions flowed co-currently in flat sheet permeation cell or hollow fiber module at 0.014 L·min-1 and room temperature. A digital balance (BSA224S, Sartorius) was used to record the weight change of the draw solution. PIFMs solutions served as draw solutions and DI water or saline water (0.1-3.5 wt% NaCl) acted as feed solutions. Experimental operations were conducted with FO mode (a


6

Page 7 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


feed solution facing the membrane dense layer) or pressure retarded osmosis (PRO) mode (a feed solution facing the membrane porous layer). The permeation flux, Jw, (L·m-2·hr-1, denoted as LMH) was determined using equation (2).

Jw =

∆V Am∆t

(2)

where ∆V (L) is the volume of permeate water collected over a time interval of ∆t (h), Am is the membrane area (m2). The salt flux, Js (g·m-2·hr-1, denoted as gMH) was calculated by equation (3).

Js =

(CtVt ) − (C0V0 ) Am∆t

(3)

where Ct (g·L−1) and Vt (L) are the salt concentration and volume, respectively, of the feed solution at time interval of ∆t, while C0 (g·L−1) and V0 (L) are the respective initial salt concentration and volume of the feed solution, respectively. Regeneration of the PIFMs. An membrane distillation (MD) process using self-made polyvinylidene fluoride (PVDF) composite hollow fiber membranes25 was applied to regenerate the PIFMs from their diluted solutions after FO. The diluted PIFMs solutions at 55 ± 0.5 ºC flowed on the shell side of an MD module at 450 mL/min, while DI water at 20 ± 0.5 ºC cocurrently flowed on the lumen side at 220 mL/min. The water flux and permeate were calculated using equation (2) and equation (3), respectively. ■ RESULTS AND DISCUSSION Synthesis and characterization of the PIFMs. Both the synthesis reaction and properties of materials are the priorities in exploring novel draw solutes. Having abundant ionic groups and a reasonable large molecular structure are preferred for an FO draw solute that can benefit FO with


7


Page 8 of 24

high water permeation and low reverse solute diffusion.12 Based on these considerations, we synthesized a series of PIFMs carrying carboxylate or sulfonate and hydroxyl groups from a facile one-pot reaction between piperazine or substituted piperazine and halogen sulfonate or halogen carboxylate (Scheme 1). Quantitative yields (> 95%) were achieved for all compounds. With variation in the type or/and number of functional groups, the as-synthesized PIFMs exhibited different physicochemical properties and hence different FO performance. Compared to those recently proposed synthetic draw solutes which were obtained via multiple reactions, such as magnetic nanoparticles,12 dendrimers,26 and stimuli–responsive aerogel,15 the synthesis of PIFMs here is more efficient with a simple one-step nucleophilic substitution reaction under mild conditions. Meanwhile, the presence of carboxylate or sulfonate and hydroxyl groups makes the PIFMs easy to ionize and hence promotes FO performance which will be discussed in the subsequent sections.

Scheme 1. The design strategy and synthesis of the PIFMs.


8

Page 9 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The identities of P-2CO2-2Na and P-2SO3-2Na were verified through the single crystal X-ray chromatography (Figure 2, Table S1) and are consistent with the structures proposed in Scheme 1.

Figure 2. Single crystal X-ray diffraction of (a) P-2CO2-2Na, and (b) P-2SO3-2Na. The functional groups in the PIFMs were examined by FTIR measurements (Figure S1). Absorptions at 3300 ∼ 3500 cm−1 correspond to the -OH group27 from either the PIFMs or the crystal water molecules. The absorption at ∼ 1163cm−1 observed in P-2SO3-2Na, P-2SO3-2OH2Na and P-SO3-OH-Na originates from the stretching vibration of S=O.28 The signals at 1648 ∼ 1690 cm−1 and 1252 ∼ 1265 cm−1 in P-2CO2-2Na correlates to the stretching vibrations of C=O and C–O groups,29 respectively. All these results verify the successful syntheses of the PIFMs. Important properties that govern FO applications of draw solutes include relative viscosity and osmotic pressure. These properties were evaluated at a range of concentrations from 0.1 to 1.0 M for all PIFMs except P-2CO2-2Na which was studied with the highest concentration of 0.75 M due to solubility limitation. The PIFMs follow a decreased order in which P-2SO3-2OH-2Na > P2SO3-2Na > P-2CO2-2Na > P-SO3-OH-Na in their relative viscosities (Figure 3a), agreement with the sequence of their molecular weights. Viscosities of the PIFMs are higher than those of NaCl but lower than those of other reported draw solutes (Figure 3b).24,26,30


9


Page 10 of 24

Figure 3. (a) The relative viscosities of the PIFMs and NaCl. (b) A relative viscosity comparison between P-2SO3-2Na and other reported draw solutes. (c) The osmotic pressures of the PIFMs and NaCl. (d) An osmotic pressure comparison between P-2SO3-2Na and other reported draw solutes. (Noted: in (b) and (d) NaCl: 1.0 M; P-2SO3-2Na: 1.0 M; NMe4-Cr-OA24: [N(CH3)4]3[Cr(C2O4)3, 1.0 M; PAMAM-COONa26: poly(amidoamine) terminated with sodium carboxylate, 33.3 wt%; Na10-phytate30: decasodium phytate, 1.25 M) An increased osmotic pressure was achieved when elevating the solute concentration but in a non-linear relationship especially at higher concentrations for all compounds (Figure 3c). The PIFMs can release multiple ionic particles in water which enables P-2SO3-2Na to generate an osmotic pressure much higher than that of NaCl at the same concentration (Figure 3c), consistent with the Van’t Hoff Law.31,32 The ionization degree of the compounds decreases due


10

Page 11 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


to more ion pairs formed with solute concentration increase. The PIFMs show a downtrend in which P-2SO3-2Na ≈ P-2SO3-2OH-2Na > P-2CO2-2Na > P-SO3-OH-Na in their osmotic pressures. This is linked to the ionization ability of these compounds and in accordance with the order of their conductivity. The osmotic pressure generated by P-2SO3-2Na at 1.0 M is higher than those of reported draw solutes (Figure 3d).24,26,30 Substances generating a high osmotic pressure are preferred to be draw solutes for FO since a high driving force could be achieved. The FO performance of the PIFMs. The FO performance of PIFMs draw solutes was measured systematically. As a widely used draw solute, NaCl was also examined in FO experiments for reference. Parameters including draw solution concentration and membrane type have a remarkable impact on FO performance and were studied through screening tests. Figure 4 and Figure 5 present the FO performance as a function of the solute concentration via either TFC-PES(FS) (Figure 4) or TFC-PES(HF) membranes (Figure 5).


11


Page 12 of 24

Figure 4. Water fluxes ((a) PRO mode, (b) FO mode) and reverse solute flux ((c) PRO mode, (d) FO mode) of PIFMs and NaCl through the TFC-PES(HF) membranes. DI water as the feed.

Figure 5. (a) The FO performance of PIFMs and NaCl through the TFC-PES(HF) membrane: water flux (left), reverse flux (right); (b) An FO performance comparison of P-2SO3-2Na with other draw solutes: water flux (left), reverse flux (right). DI water as the feed, PRO mode. (Noted: in (b) cationic starch16: 30 wt%; Gluconate34: 2.0 M; PSS35: poly(sodium 4styrenesulfonate), 0.24 g/mL; PAMAM-COONa (1.5G)36: poly(amidoamine) terminated with sodium carboxylate, 33.3 wt %; NaCl: 1.0M; P-2SO3-2Na: 1.0 M) A continuous increase in water flux was observed when elevating the PIFMs concentration regardless of membrane and membrane orientation. A smaller increment in water flux was achieved at a higher concentration which is ascribed to the severer membrane fouling and


12

Page 13 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


concentration polarization at a higher solute concentration. The water fluxes under the PRO mode are larger those under the FO mode as a result of the adverse influence of ICP in the latter which is ubiquitously present in FO when an asymmetric membrane applied.33 Water permeating from the feed side dilutes the draw solution within the thick porous supporting layer that causes a noticeable decline in driving force, leading to a reduced water flux. The water flux of the TFCPES(HF) membrane is 2 times higher than that of the TFC-PES(FS) membrane with negligible reverse solute diffusion. The marked increase in water flux from the flat sheet to hollow fiber membranes is ascribed to the difference in membrane properties in which the hollow fiber membrane is more beneficial to FO processes (Figure S2 & Table S2). Regardless of the membrane, the water fluxes produced by the PIFMs follow the sequence where P-2SO3-2Na > P2SO3-2OH-2Na > P-2CO2-2Na > P-SO3-OH-Na (Figures 4a & 4b, Figure 5a). The screening tests indicate that the FO performance of PIFMs is optimized with the TFCPES(HF) membrane. A much better FO performance was achieved for P-2SO3-2Na as compared to NaCl and other reported draw solutes including cationic starch,16 gluconate,34 poly(sodium 4styrenesulfonate) (PSS),35 poly(amidoamine) terminated with sodium carboxylate (PAMAMCOONa)26 (Figure 5b). The specific salt flux (Js/Jw) which indicates the solute loss in treating per volume of feed water is lower than 0.003 g/L for P-2SO3-2Na, indicating a negligible solute loss in recovering one liter of feed solution. The impressive performance is primarily linked to the distinctive characteristics of the P-2SO3-2Na in its structure, chemical composition and properties. Structurally, P-2SO3-2Na is composed of a three-dimensional configuration centered on a six-membered piperazine ring. Such a spatial configuration conduces to low reverse solute diffusion in FO. In property, P-2SO3-2Na is easy to dissociate into ionic species which favors to not only produce a high osmotic pressure31,32 but also increase the mutual repulsion among the


13


Page 14 of 24

charged sulfonate groups and the negative TFC-PES membrane.36 Therefore P-2SO3-2Na draw solute not only provides high water recovery efficiency when used in FO, but also is able to lower the draw solute replenishment cost. P-2SO3-2Na as an FO draw solute for desalination. In view of the best performance, P2SO3-2Na was applied for FO desalination via the TFC-PES(HF) membrane. Water flux drops constantly when increasing the feed concentration gradually. Saline water replacing DI water elevates the feed osmotic pressure, leading to a decline in the osmotic pressure differential across the membrane and hence a reduced water flux. Nevertheless, efficient water recovery with water fluxes of 11.3-35.5 LMH was still achieved via the P-2SO3-2Na (1.0 M) facilitated FO desalination with the saline concentration increasing from 0.1 wt% to 3.5 wt% NaCl, sufficient to handle large quantity of saline water. Compared to other draw solutes, such as smart draw agents of PSSS-PNIPAM,37 Na-CQDs38 and CA-MNP,39 polyelectrolytes of sodium ligin sulfonate,40 PAA-Na41 and PAMAM-COONa,26 complex of EDTA-ZnNa2,42 and ionic liquids,43,44 P-2SO3-2Na produced a water flux 25-77% higher than the above materials with a negligible solute loss in FO seawater desalination (Figure 6), manifesting the advantages of the P-2SO3-2Na as a new class of draw solute. The good desalination performance in terms of high water recovery efficiency without solute loss ensures the great potential of P-2SO3-2Na as an FO draw solute when used in other applications, such as protein enrichment which has stringent requirements on the reverse diffusion of draw solutes.


14

Page 15 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. A comparison of water recovery rate of 1.0 M P-2SO3-2Na with those synthetic draw solutes in seawater desalination via FO. Conditions: 3.5 wt% NaCl as the feed, PRO mode. Noted: 1.0 M EDTA-ZnNa2: Zinc disodium EDTA (HTI-TFC membrane),42 60 wt% Sodium lignin sulfonate (CTA membrane),40 0.72 g/mL PAA-Na: polyacrylic acid sodium salts (CA membrane),41 33.3 wt% PAMAM-COONa: poly(amidoamine) terminated with sodium carboxylate groups (HTI-TFC membrane),26 33.3 wt% PSSS-PNIPAM: poly(sodiumstyrene-4sulfonate-co-n-isopropylacrylamide) (HTI-TFC membrane),37 0.4 g/mL Na-CQDs: Na+functionalized carbon quantum dots (HTI-TFC membrane),38 0.6 g/mL CA-MNP: magnetic nanoparticles with citric acid (self-made TFC-PES membrane),39 80 wt% P4444TMBS: Tetrabutylphosphonium mesitylenesulfonate (self-made TFC-PES membrane),43 5.0 M 2methylimidazole-based compounds (CTA membrane).44 Regeneration of the PIFMs. To maximize the advantages of FO for desalination, draw solutes must be regenerated. MD is effective in recovering synthetic draw solutes including


15


Page 16 of 24

complexes,24 sodium phytate,30 and thermal draw agents37 from their diluted solutions. The PIFMs were also recovered via MD processes after FO. The MD performance (water flux and solute rejection) was affected insignificantly compared to that of FO when varying the feed concentration and experimental time (Figure 7a & Figure 7b). Unlike FO, MD is a thermaldriven process. Therefore factors including feed concentration and operation time influence slightly its performance. Increasing the feed concentration from 0.1 to 1.0 M, only a small decline in water flux was observed (Figure 7a). This may be attributed to a decrease in the molecular motion of water in the feed solution, leading to a reduced vapor pressure difference and hence a declined water flux. P-2SO3-2Na draw solute was rejected 100% regardless of the experimental conditions and not detected in the MD permeate side, indicating a complete recovery of the draw solute. Reproducible results were achieved when the recovered P-2SO32Na was reused to the FO process (Figure 7c).


16

Page 17 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 7. Effects of (a) P-2SO3-2Na concentration (Operation time: 30 min) and (b) experimental time on the MD performance (P-2SO3-2Na with initial concentration of 1.0 M as the feed). Operation process: MD process with P-2SO3-2Na solution at 55°C on the feed side, DI water at 20°C on the permeate side. (c) FO water fluxes produced by the recycled P-2SO3-2Na draw solute (1.0 M). Conditions: DI water as the feed, TFC-PES(HF) membranes under the PRO mode. ■ CONCLUSIONS Using a facile one-pot substitution reaction under mild conditions, we have successfully synthesized a series of novel PIFMs. All PIFMs demonstrate their suitability as draw solutes in which P-2SO3-2Na produces a water flux of 76.4 LMH at 1.0 M with negligible reverse solute diffusion. The FO performance of PIFMs draw solutes can be further promoted when using a more ideal FO membrane. P-2SO3-2Na generates a water recovery rate 25-77% higher than other draw solutes in FO seawater desalination. The encouraging results make P-2SO3-2Na a promising draw solute for FO and suitable for other FO water treatment. ■ AUTHOR INFORMATION Corresponding Author E-mail: [email protected]; Tel: (86)591-22866219 ■ ACKNOWLEDGMENT The authors thank the National Natural Science Foundation of China (Grant No.: 21677035), the Natural Science Foundation of Fujian Province (Grant No.: 2016J01056) and Fuzhou University (Grant No.: XRC-1259) for financial support. Special thanks are also given to Ms. Qiaozhen Chen for her valuable help.


17


Page 18 of 24

■ ASSOCIATED CONTENT Supporting Information Available Crystal data; FTIR spectra; SEM images; membrane parameters. ■ REFERENCES (1) Elimelech, M.; Phillip, W. A. The future of seawater desalination: energy, technology, and the environment. Science 2011, 333, 712 ‒ 717. (2) Liang, B.; Li, Q.; Cao, B.; Li, P. Water permeance, permeability and desalination properties of the sulfonic acid functionalized composite pervaporation membranes. Desalination 2018, 433, 132 ‒ 140. (3) Shannon, M. A.; Bohn, P. W.; Elimelech, M.; Georgiadis, J. G. B.; Mariñas, J.; Mayes, A. M. Science and technology for water purification in the coming decades. Nature 2008, 452, 301 ‒ 310. (4) Xu, Y.; You, F.; Sun, H.; Shao, L. Realizing mussel-inspired polydopamine selective layer with strong solvent resistance in nanofiltration towards sustainable reclamation. ACS Sustain. Chem. Eng. 2017, 5, 5520 ‒ 5528. (5) Lee, K. P.; Arnot, T. C.; Mattia, D. A review of reverse osmosis membrane materials for desalination ‒ Development to date and future potential. J. Membr. Sci. 2011, 370, 1 ‒ 22. (6) Greenlee, L. F.; Lawler, D. F.; Freeman, B. D.; Marrot, B.; Moulin, P. Reverse osmosis desalination: water sources, technology, and today's challenges. Water Res. 2009, 43 (9), 2317 ‒ 2348. (7) Zhao, S.; Zou, L.; Tang, C. Y.; Mulcahy, D. Recent developments in forward osmosis: opportunities and challenges. J. Membr. Sci. 2012, 396, 1 ‒ 21.


18

Page 19 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(8) Cui, Y.; Liu, X.; Chung, T. Removal of organic micro-pollutants (phenol, aniline and nitrobenzene) via forward osmosis (FO) process: evaluation of FO as an alternative method to reverse osmosis (RO). Water Res. 2016, 91, 104 ‒ 114. (9) Cui, Y.; Ge, Q.; Liu, X.; Chung, T. Novel forward osmosis process to effectively remove heavy metal ions. J. Membr. Sci. 2014, 467, 188 ‒ 194. (10) Huang, M.; Chen, Y.; Huang, C.; Sun, P.; Crittenden, J. Rejection and adsorption of trace pharmaceuticals by coating a forward osmosis membrane with TiO2. Chem. Eng. J. 2015, 279, 904–911. (11) Kim, Y. C.; Elimelech, M. Potential of osmotic power generation by pressure retarded osmosis using seawater as feed solution: analysis and experiments. J. Membr. Sci. 2013, 429, 330–337. (12) Johnson, D. J.; Suwaileh, W. A.; Mohammed, A.W. Osmotic's potential: an overview of draw solutes for forward osmosis. Desalination 2018, 434, 100 ‒ 120. (13) Achilli, A.; Cath, T. Y.; Childress, A. E. Selection of inorganic-based draw solutions for forward osmosis applications. J. Membr. Sci. 2010, 364, 233 ‒ 241. (14) Zhao, Q.; Chen, N.; Zhao, D.; Lu, X. Thermoresponsive magnetic nanoparticles for seawater desalination. ACS Appl. Mater. Interfaces 2013, 5 (21), 11453 ‒ 11461. (15) Yu, M.; Zhang, H.; Yang, F. Hydrophilic and compressible aerogel: a novel draw agent in forward osmosis. ACS Appl. Mater. Interfaces 2017, 9 (39), 33948 ‒ 33955. (16) Laohaprapanon, S.; Fu, Y.; Hu, C.; You, S.; Tsai, H.; Hung, W.; Lee, K.; Lai, J. Evaluation of a natural polymer-based cationic polyelectrolyte as a draw solute in forward osmosis. Desalination 2017, 421, 72 ‒ 78.


19


Page 20 of 24

(17) Ge, Q.; Amy, G. L.; Chung, T. S. Forward osmosis for oily wastewater reclamation: multi-charged oxalic acid complexes as draw solutes. Water Res. 2017, 122, 580 ‒ 590. (18) Na, Y.; Yang, S.; Lee, S. Evaluation of citrate-coated magnetic nanoparticles as draw solute for forward osmosis. Desalination 2014, 347, 34 – 42. (19) Zhang, H.; Li, J.; Cui, H.; Li, H.; Yang, F. Forward osmosis using electric-responsive polymer hydrogels as draw agents: Influence of freezing–thawing cycles, voltage, feed solutions on process performance. Chem. Eng. J. 2015, 259, 814 ‒ 819. (20) Stone, M. L.; Wilson, A. D.; Harrup, M. K.; Stewart, F. F. An initial study of hexavalent phosphazene salts as draw solutes in forward osmosis. Desalination 2013, 312, 130 ‒ 136. (21) SMART & SAINT Software Reference Manuals, Version 4.0, Siemens Energy & Automation, Inc., Analytical Instrumentation, Madison, WI, 1996. (22) SHELXTL Reference Manual, Version 5.03, Siemens Energy & Automation, Inc., Analytical Instrumentation, Madison, WI, 1996. (23) McNaught, A. D.; Wilkinson, A. Compendium of chemical terminology (the ‘gold book’), 2nd ed.; Blackwell Scientific Publications: Oxford, U.K., 1997. (24) Chen, Q.; Xu, W.; Ge, Q. Novel multicharge hydroacid complexes that effectively remove heavy metal ions from water in forward osmosis processes. Environ. Sci. Technol. 2018, 52 (7), 4464 ‒ 4471. (25) Wang, P.; Teoh, M. M.; Chung, T. S. Morphological architecture of dual-layer hollow fiber for membrane distillation with higher desalination performance. Water Res. 2011, 45, 5489 ‒ 5500.


20

Page 21 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(26) Zhao, D.; Chen, S.; Wang, P.; Zhao, Q.; Lu, X. A dendrimer-based forward osmosis draw solute for seawater desalination. Ind. Eng. Chem. Res. 2014, 53 (42), 16170 ‒ 16175. (27) Sun, S.; Chan, S.; Xing, W.; Wang, Y.; Chung, T. Facile synthesis of dual-layer organic solvent nanofiltration (OSN) hollow fiber membranes. Acs. Sustain. Chem. Eng. 2015, 3, 3019 ‒ 3023. (28) Taha, M.; E Silva, F. A.; Quental, M. V.; Ventura, S. P. M.; Freire, M. G.; Coutinho, J. A. P. Good's buffers as a basis for developing self-buffering and biocompatible ionic liquids for biological research. Green Chem. 2014, 16 (6), 3149 ‒ 3159. (29) Yu, M.; Zhang, H.; Yang, F. A study of a ferric-lactate complex as draw solute in forward osmosis. Chem. Eng. J. 2017, 314, 132 ‒ 138. (30) Ge, Q.; Lau, C. H.; Liu, M. A novel multi-charged draw solute that removes organic arsenicals from water in a hybrid membrane process. Environ. Sci. Technol. 2018, 52 (6), 3812 ‒ 3819. (31) Wilson, A. D.; Frederick, F. S. Deriving osmotic pressures of draw solutes used in osmotically driven membrane processes. J. Membr. Sci. 2013, 431, 205 ‒ 211. (32) Lewis, G. N. The osmotic pressure of concentrated solutions, and the laws of the perfect solution. J. Am. Chem. Soc. 1908, 30 (5), 668 ‒ 683. (33) Gray, G. T.; McCutcheon, J. R.; Elimelech, M. Internal concentration polarization in forward osmosis: role of membrane orientation. Desalination 2006, 197, 1 ‒ 8. (34) Long, Q.; Qi, G.; Wang, Y. Evaluation of renewable gluconate salts as draw solutes in forward osmosis process. ACS Sustain. Chem. Eng. 2016, 4 (1), 85 ‒ 93.


21


Page 22 of 24

(35) Tian, E.; Hu, C.; Qin, Y.; Ren, Y.; Wang, X.; Wang, X.; Xiao, P.; Yang, X. A study of poly (sodium 4-styrenesulfonate) as draw solute in forward osmosis. Desalination 2015, 360, 130 ‒ 137. (36) Xu, W.; Chen, Q.; Ge, Q. Recent advances in forward osmosis (FO) membrane: chemical modifications on membranes for FO processes. Desalination 2017, 419, 101 ‒ 116. (37) Zhao, D.; Wang, P.; Zhao, Q.; Chen, N.; Lu, X. Thermoresponsive copolymer-based draw solution for seawater desalination in a combined process of forward osmosis and membrane distillation. Desalination 2014, 348, 26 ‒ 32. (38) Guo, C. X.; Zhao, D.; Zhao, Q.; Wang, P.; Lu, X. Na+-functionalized carbon quantum dots: a new draw solute in forward osmosis for seawater desalination. Chem. Commun. 2014, 50 (55), 7318 ‒ 7321. (39) Ge, Q.; Yang, L.; Cai, J.; Xu, W.; Chen, Q.; Liu, M. Hydroacid magnetic nanoparticles in forward osmosis for seawater desalination and efficient regeneration via integrated magnetic and membrane separations. J. Membr. Sci. 2016, 520, 550 ‒ 559. (40) Duan, J.; Litwiller, E.; Choi, S.; Pinnau, I. Evaluation of sodium lignin sulfonate as draw solute in forward osmosis for desert restoration. J. Membr. Sci. 2014, 453, 463 ‒ 470. (41) Ge, Q.; Su, J.; Amy, G. L.; Chung, T. S. Exploration of polyelectrolytes as draw solutes in forward osmosis processes. Water Res. 2012, 46 (4), 1318 ‒ 1326. (42) Zhao, Y.; Ren, Y.; Wang, X.; Xiao, P.; Tian, E.; Wang, X.; Li, J. An initial study of EDTA complex based draw solutes in forward osmosis process. Desalination 2016, 378, 28 ‒ 36.


22

Page 23 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(43) Cai, Y.; Shen, W.; Wei, J.; Chong, T. H.; Wang, R.; Krantz, W. B.; Fane, A. G.; Hu, X. Energy-efficient desalination by forward osmosis using responsive ionic liquid draw solutes. Environ. Sci.: Water Res. Technol. 2015, 1 (3), 341 ‒ 347. (44) Yen, S. K.; Mehnas Haja N., F.; Su, M.; Wang, K. Y.; Chung, T. Study of draw solutes using 2-methylimidazole-based compounds in forward osmosis. J. Membr. Sci. 2010, 364, 242 ‒ 252.


23


Page 24 of 24

For Table of Contents Use Only

■ TOC Art

Piperazine-based draw solutes are used for FO desalination and regenerated via MD. The recycled draw solutes are subsequently reused to FO.


24

Piperazine-Based Functional Materials as Draw Solutes for

Recommend Documents