Ultrathin Polyamide Membrane with Decreased Porosity Designed for

Subscriber access provided by Kaohsiung Medical University

Applications of Polymer, Composite, and Coating Materials

Ultrathin Polyamide Membrane with Decreased Porosity Designed for Outstanding Water Softening Performance and Superior Antifouling Properties Bingbing Yuan, Chi Jiang, Pengfei Li, Honghong Sun, Peng Li, Tao Yuan, Haixiang Sun, and Qingshan Jason Niu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b15883 • Publication Date (Web): 12 Nov 2018 Downloaded from http://pubs.acs.org on November 18, 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 34 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 Applied Materials & Interfaces

Ultrathin Polyamide Membrane with Decreased Porosity Designed for Outstanding Water Softening Performance and Superior Antifouling Properties Bingbing Yuana, Chi Jianga , Pengfei Lia, Honghong Suna, Peng Lia, Tao Yuana, Haixiang Suna, Q. Jason Niua* a

State Key Laboratory of Heavy Oil Processing, China University of Petroleum (East

China), Qingdao 266555, PR China *Corresponding authors. Tel.: +86 532 86981850 E-mail address: [email protected]

KEYWORDS:

nanofiltration membrane, cyclobutane tetracarboxylic acid chloride

(BTC), decreased porosity, water softening, antifouling 1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

ABSTRACT Poly(piperazine-amide)-based nanofiltration membranes exhibit a smooth surface and superior antifouling properties, but often have lower Ca2+ and Mg2+ rejection due to their larger inner micropore, and thus cannot be extensively used in water softening applications. To decrease the pore size of poly(piperazine-amide) membranes, we designed and synthesized a novel monomer, 1,2,3,4-cyclobutane tetracarboxylic acid chloride (BTC), which possesses a smaller molecular conformation than trimesoyl chloride (TMC). The thickness of the prepared BTC-piperazine (PIP) polyamide nanofilm via interfacial polymerization is as thin as 15 nm, significantly lower than the 50 nm thickness of the TMC-PIP nanofilm. The surface characterization reveals that the BTC-PIP polyamide membrane exhibits an enhanced hydrophilicity, a smooth surface and a decreased surface negative charge. The desalination performance (both rejection and water flux) of these membranes in terms of Ca2+ and Mg2+ exceeds that of the current commercial NF90 and NF270 membranes. In addition, the BTC-PIP polyamide membrane also exhibits superior antifouling properties compared to the TMC-based polyamide membrane. More importantly, molecular simulations show that the BTC-PIP membrane has a lower pore distribution than the TMC-PIP membrane, which demonstrates an enhanced steric hindrance effect, as confirmed by desalination performance. Our results demonstrate that in the household and industrial water softening market, BTC-PIP membranes with decreased porosity, enhanced hydrophilicity and smooth surface, are preferred alternatives to the conventional TMC-based polyamide membrane.

1. INTRODUCTION Interfacial polymerization (IP) technology has been extensively employed to fabricate reverse osmosis and nanofiltration membranes for large-scale and low-cost water treatment applications since 1963.1,2 This is a reaction-diffusion process far from thermodynamic equilibrium.3 The polymerization of two reactive multifunctional monomers occurs at the interface boundary of two immiscible phases of a 2


Page 2 of 34

Page 3 of 34 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


heterogeneous liquid system.4,5 The TMC-PIP polyamide membrane often indicates a smooth surface due to the difference in the diffusion-reaction rate of PIP and m-phenylenediamine (MPD). The antifouling property is thus superior.6,7 However, the average pore size of the TMC-PIP nanofilm always ranges from 1 nm to 2 nm due to the distorted conformation of PIP molecule. The rejection for Ca2+ and Mg2+ is lower, such as DOW NF 270.8−10 On the other hand, due to the planar conformation of MPD molecule, the TMC-MPD nanofilm more commonly forms a polyamide membrane with a pore diameter less than 0.2 nm during interfacial reaction, exhibiting a high rejection for Ca2+ and Mg2+. Unfortunately, the surface of TMC-MPD membrane is rougher and thus has poor antifouling properties, such as DOW NF 90.11,12 Hence, in the industrial applications such as water softening process, both desalination efficiency and membrane lifespan would be improved if the prepared poly(piperazine-amide) membrane exhibits excellent Ca2+ and Mg2+ rejection rates, a smooth membrane surface, and an excellent antifouling performance. In a typical poly(piperazine-amide) membrane fabrication process, PIP are dissolved in water while TMC are dissolved in an organic solvent. The interfacial reaction is initiated when the aqueous solution is contacted with the organic solution. Because the solubility of PIP in organic solvents is higher than the solubility of TMC in water, the interfacial reaction occurs predominantly on the organic side of the interface, in which the PIP monomer diffuses from water to the organic phase. The diffusion of the PIP monomer is inhibited with the formation of the dense polyamide nanofilm, and finally, a cross-linked PIP polyamide membrane forms on the ultrafiltration support. During this process, in order to increase the desalination performance of polyamide membrane such as rejection and water flux, many researchers have successfully reduced the thickness of the prepared active layer or altered the surface morphology of the membrane by advanced technology and processes. Constructing an interlayer and introducing macromolecule additives are the main

two

approaches,

polydopamine/ZIF-8,14

including

nanofiber,15

carbon

polyvinyl

alcohol

nanotube/polydopamine,13 (PVA),7,12,16

polyvinyl

pyrrolidone (PVP),17 and polyester,18etc. However, due to the fixed chemical structure 3



of the TMC-PIP polyamide membrane, despite a smooth membrane surface, its pore size did not change significantly, and thus, the rejection for Ca2+ and Mg2+ was basically unchanged. On the other hand, other researchers19,20 have also prepared new types of acid chloride monomers, such as

2,2′,4,4′,6,6′-biphenyl hexaacyl chloride

(BHAC), and 3,3',5,5'-biphenyl tetraacyl chloride (mm-BTEC), to replace TMC and react with PIP to prepare the polyamide membrane. Since the pore diameter of these membranes was not significantly lower than that of the TMC-PIP membrane, the prepared polyamide membrane exhibited no significant increase in the rejection rate of Ca2+ and Mg2+. Currently, there are no published studies on the successful fabrication of the poly(piperazine-amide) membrane with a lower pore diameter than that of the current commercially available TMC-PIP membrane. In this work, we have proposed a novel acid chloride monomer, cyclobutane tetrachloride (BTC), which exhibits a smaller molecular conformation than the TMC molecule. Compared with the TMC monomer, the BTC molecules located on the interface can be reacted with more PIP molecules diffused from the aqueous phase side, and subsequently reacted to form a denser polyamide nanofilm. Furthermore, since the formed BTC-PIP nanofilm is denser, the inhibition of diffusion-reaction of PIP molecule is earlier than that of TMC-PIP nanofilm during interfacial polymerization. The formation of dense BTC-PIP nanofilm is thus faster than that of the TMC-PIP nanofilm. The thickness of BTC-PIP polyamide membrane is as thin as 15 nm compared to the 50 nm thickness of the TMC-PIP membrane using the same interfacial reaction time. Surface characterization demonstrated that the BTC-PIP membrane exhibited enhanced hydrophilicity and smooth nanofilm surface, but a reduced surface negative charge. Desalination experiments revealed that the BTC polyamide membrane showed an above 99% rejection rate for CaCl2, MgCl2 and MgSO4, and a water flux of more than 82.9 kg m−2 h−1, which are higher than those of the TMC polyamide membranes such as NF 90 (fabricated by TMC-MPD) and NF 270 (fabricated by TMC-PIP). The BTC-PIP membrane also maintained superior antifouling properties compared to the TMC-MPD polyamide membrane that has comparably excellent Ca2+ and Mg2+ rejection such as NF 90. More importantly, as 4


Page 4 of 34

Page 5 of 34 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


confirmed by molecular simulations, due to the smaller molecular conformation for BTC than for TMC, the BTC-PIP nanofilm exhibits a decreased pore size compared to the TMC-PIP nanofilm. This result is consistent with the outstanding Ca2+ and Mg2+ rejection rate. With the advantage of simple magnification of interfacial polymerization, the BTC-PIP polyamide membrane with a reduced porosity has substantial industrial potential to replace the traditional TMC-MPD polyamide membrane used for water softening.

2. EXPERIMENTAL SECTION 2.1. Materials and Methods 1,2,3,4-cyclobutane tetracarboxylic acid anhydride (≥98%) and diethylenediamine (commonly called piperazine, PIP) were purchased from Tokyo Chemical Industry (TCI). Phosphorus pentachloride (PCl5), sodium chloride (NaCl), magnesium chloride hexahydrate (MgCl2 6H2O), magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), calcium chloride (CaCl2), cyclohexane, hexane, bovine serum albumin (BSA) (Sinopharm Chemical Reagent Co., Ltd.). Deionized (DI) water (0.5−1.5 μs/cm) was prepared in a two-stage reverse osmosis purification system. Polyether sulfone (PES) ultrafiltration membranes used were obtained from Vontron Co., Ltd. Coverslips with a thickness of 0.13−0.17 mm were purchased from Sail Brano Corps and used as a support for scanning electron microscopy (SEM).

2.2. Preparation and Isolation of 1,2,3,4-Cyclobutane Tetracarboxylic Acid Chloride (BTC) A mixture of 1,2,3,4-cyclobutane tetracarboxylic acid anhydride (18.62 g, 0.095 mol) and phosphorus pentachloride (45.38 g, 0.218 mol) was heated under stirring. Using the by-product phosphorus oxychloride was as a solvent in this synthesis. The reaction mixture, after being refluxed for 48 hours, was filtered, first at atmospheric pressure to remove the phosphorus oxychloride and finally at 0.2 mm Hg. The prepared acid chloride was added into the warm carbon tetrachloride, precipitated 5



Page 6 of 34

with hexane, yielding a white crystal powder (43.6%, 12.67 g).

2.3. Fabrication of Poly(piperazine-amide) Membranes Poly(piperazine-amide) membranes were prepared by depositing polyamide selective layers on PES ultrafiltration membranes via the interfacial polymerization (IP) process.21 The ultrafiltration membrane was immersed into the PIP aqueous solution for 2 min, and subsequently the surface excess amine solution was removed by air knife. Then, the acid chloride solution contacted and reacted with amine for a certain reaction time. Then, the hexane or cyclohexane was used to wash the fresh nanofilm. Finally, the membrane prepared was dried at 60°C for 2 min, stored in DI water until use. Optimizing the IP time and monomer concentration was conducted according to desalination performance. Specifically, the poly(piperazine-amide) membranes were fabricated under the following two specific conditions: 1) PIP (1.5 wt%, 2 min)-TMC (0.15 wt%, 30 s) and 2) PIP (1.6 wt%, 2 min)-BTC (0.18 wt%, 30 s).

2.4. Characterizations Nuclear magnetic resonance spectroscopy (BRUKER, Germany) was performed to verify the purity of the prepared 1,2,3,4-cyclobutane tetracarboxylic acid chloride (BTC).

The

chemical

poly(piperazine-amide)

composition

membranes

and

were

structure

of

characterized

by

the

fabricated

attenuated

total

reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), respectively, which were conducted on the surface of the polyamide membrane. The surface potential values of the polyamide membrane were determined with an Anton Paar SurPass solid surface analyzer. Surface zeta potential was measured at a background aqueous solution of KCl (10 mM) containing mobility-monitoring particles at pH values from 3−10. The water contact angle (WCA) of the membrane surface was measured at room temperature (25 °C) using a Drop Shape Analyzer-DSA30 (KRÜSS, Germany) equipped with video capture in sessile drop mode. A scanning probe microscope (SPM-9700, SHIMADZU, and 6


Page 7 of 34 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


Japan) was used to measure the surface morphology and the roughness of the polyamide membranes. To measure the thickness of the TMC-PIP nanofilm, the nonwoven fabric was peeled off with the assistance of adhesive tape. Then, the polyamide layer was soaked in N,N-Dimethylformamide (DMF) until the membrane became fully transparent, and washed with methanol. Afterwards, the alone TMC-PIP layer was deposited on the coverslips using floating method, and then was fractured in liquid nitrogen for the SEM observation. For the BTC-PIP membrane, the polyamide layer with the PES support was directly fractured in liquid nitrogen for the SEM observation. To measure the thickness of nanofilm vs time, the fabricated polyamide nanofilms with different interfacial polymerization time were measured using the spectroscopic ellipsometry (HORIBA UVISELTM).

2.5. Performance Tests of Polyamide Nanofiltration Membranes Desalination performance of the prepared polyamide membrane was determined with different salt or mixed ion solutions in a cross-flow system with an effective test area (A) of 19.25 cm2. The concentration of the single salt, such as MgCl2, CaCl2, MgSO4, Na2SO4, and NaCl, in the feed solution was 2 g L−1 (2000 ppm). For the mixed ion experiments, the feed solution was composed of 8.325 g L−1 CaCl2, 2.500 g L−1 MgSO4, and 2.543 g L−1 NaCl, including 3000 ppm Ca2+, 500 ppm Mg2+, 1000 ppm Na+, 7000 ppm Cl−1 and 2000 ppm SO42−. The desalination performance tests were conducted at an osmotic pressure of 1 MPa and a temperature of 25 °C. The performance data were determined after the water flux and the conductivity reached a steady state. The water flux (kg m−2 h−1) was calculated from the weight of the permeate (M) for a specified time, as given by the following equation: Water Flux (kg m−2 h−1) = 𝑀 𝐴𝑡.

(1)

The salt/ion rejection was determined from the conductivity of the feed solution (Cf) and the permeate (Cp). Hence, the salt/ion rejection can be calculated from the following equation: Rejection (%) = (1 ― 𝐶𝑝 𝐶𝑓) × 100%.

(2) 7



Page 8 of 34

Here, Cp and Cf can also be the specific amount of anions or cations in the permeate and feedstocks during the mixed ion solution test, which are analyzed by ion chromatography (Metrohm 883 Basic IC Plus).

2.6. Antifouling Testing The same cross-flow system described above was employed to evaluate the antifouling property. Before the fouling test, the membranes were equilibrated with pure water for 4 h. To reach the target water flux (88 kg m−2 h−1), the BTC-PIP membrane was operated at approximately 9.5−10 bar (138−145 psi), while the TMC-PIP membrane was operated in the range of 15−17 bar (218−247 psi), and the commercial TMC-MPD membrane (NF90) was operated in the range of 10−10.1 bar (145−160 psi). After a 4 h equilibration, a 0.5 g L−1 BSA solution was added into the feed solution tank to achieve an initial fouling. The fouling stage was continued for 27~30 h, during which the flux was recorded at fixed intervals.

3. RESULTS AND DISCUSSION 3.1. Synthesis of BTC and Fabrication of BTC and TMC Membranes O

O

O O

O

O

+

O

Cl

Cl P Cl

Cl

48h

Cl

160 oC

Cl O

Cl

Cl

O Cl

Cl

+

Cl

P

O Cl

O

1,2,3,4-cyclobutane tetracarboxylic acid chloride

1,2,3,4-cyclobutane tetracarboxylic acid anhydride

Figure 1. Synthesis of 1,2,3,4-cyclobutane tetracarboxyl chloride (BTC).

8


Page 9 of 34 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 2. Interfacial reactions of BTC and TMC with PIP to form the BTC-PIP (a) and TMC-PIP (b) polyamide membrane, respectively. The synthesis step of the BTC is shown in Figure. 1. PCl5 used reacts with anhydride to form the acid chloride. NMR characterized the purity of the prepared BTC (Figure S1). Figure 2 presents the fabrication process and chemical networked structure of the BTC-PIP and TMC-PIP polyamide membranes via IP. BTC molecule with smaller conformation can react with more PIP molecules at interface boundary to form a 9



denser BTC-PIP polyamide nanofilm during interfacial polymerization compared with that of TMC molecule. The content of amide bond per unit in BTC-PIP polyamide is thus higher than that of TMC-PIP polyamide. Moreover, we reasonably estimate the average pore size of the BTC-PIP polyamide is also lower than that of TMC-PIP polyamide.

3.2. Thickness and Chemical Structure of the BTC and TMC Membranes

Figure 3. (a b) Cross-sectional SEM images of the BTC-PIP nanofilm supported on the PES porous ultrafiltration support. (c) Cross-sectional SEM image of the TMC-PIP nanofilm supported on the PES porous ultrafiltration support. (d) Cross-sectional SEM image of the TMC-PIP nanofilm supported on the coverslip substrate.

10


Page 10 of 34

Page 11 of 34

BTC-PIP TMC-PIP

45 40

Thickness (nm)

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


35 30 25 20 15

2

4

6

8

10

12

Time (s)

Figure 4. The thickness of BTC-PIP and TMC-PIP nanofilms varies with the interfacial polymerization time.

3.2.1. Thickness of the BTC and TMC Membrane. SEM images depicting the thickness of the selective layer of the BTC-PIP and TMC-PIP membranes are shown in Figure 3. In Figure 3(a) and 3(b), there is an obvious boundary between the BTC-PIP nanofilm and the PES support. After the amplified image, we measured that the thickness of the BTC-PIP polyamide nanofilm is as thin as 15 nm. However, the boundary of PES substrate and TMC-PIP nanofilm is unidentifiable. Thus, for an intuitive and clear observation, as shown in Figure 3(d), we elaborately transferred the TMC-PIP nanofilm onto the coverslips and obtained a selective layer with a thickness of 50 nm. We investigated the correlation of nanofilm growth and interfacial reaction time. For controlling the interfacial polymerization finely, we used the spinning coating method to form the nanofilm. The interfacial polymerization time was shortened to 2s, 4s, 6s, 8s, 10s and 12s. Spectroscopic ellipsometry was employed to measure the thickness of the formed nanofilm. Figure 4 demonstrates that the thickness growth of the BTC-PIP polyamide layer essentially stops with time scales of the order of seconds, while that of the TMC-PIP nanofilm still proceeds. That is, the termination time of interfacial reaction for BTC-PIP nanofilm is earlier than that of 11



the TMC-PIP nanofilm. The thickness of the BTC-PIP nanofilm is thus lower than that of TMC-PIP nanofilm. Based on the diffusion-limited theory, the self-limited formation of the BTC-PIP nanofilm completes when the mass transfer resistance of the polyamide layer becomes great enough to decrease PIP diffuse into the organic phase. This reveals that the BTC-PIP nanofilm is denser than that of TMC-PIP nanofilm, as depicted in Figure 2. Hence, the formation of dense BTC-PIP nanofilm is faster than that of the TMC-PIP nanofilm.

100

Transmittance (a.u.)

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 12 of 34

80

-NH-

-NH-

-

-C=O -OH

-C=O

-Ph -OH

60

40

PES TMC-PIP BTC-PIP

3600

3300

3000

1500

Wavenumber (cm-1)

1200

Figure 5. ATR-FTIR spectra of the PES ultrafiltration membrane and TMC-PIP and BTC-PIP membranes.

3.2.2. Chemical Structure of the BTC and TMC Membrane. The chemical composition and structure of the prepared BTC-PIP and TMC-PIP membranes were studied by ATR-FTIR and XPS. The spectra are the coupling results formed by the selective layer and the PES ultrafiltration membrane, since the detected depth of ATR-FTIR is more than 150 nm in the whole wavenumber region. As shown in Figure 5, the prominent peaks at 1657 cm−1 and 1622 cm−1 are attributed to the –C=O stretching vibration of the amide.22,23 The –OH absorbance peaks of the carboxylic acid groups (resulting from the hydrolysis of unreacted acyl chloride groups) for the BTC-PIP and TMC-PIP membranes are located at 1439 cm−1 and 1443 cm−1, 12


Page 13 of 34 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


respectively. The unreacted amine groups of the BTC-PIP and TMC-PIP membranes appear at 3430 cm−1, which confirms that the nanofilm consists of a network cross-linked part and a linear-cross-linked part.6 The –CH bending vibration peak of the benzene ring of the TMC-PIP nanofilms is located at 1028 cm−1, but the BTC-PIP membrane has no absorption band in this area. Table 1. XPS results of the TMC and BTC membranes. C, O, N element composition, and the calculated O/N were determined from the XPS spectra. -COOH and −N-C=O percentage calculated from O1s spectra.

BTC-PIP TMC-PIP

C (%)

O (%)

N (%)

67.8 70.8

17.4 17.0

14.8 12.3

-N-C=O (%) 68.03 59.65

-COOH (%) 31.97 40.35

O/N 1.18 1.38

To further investigate the specific element composition and content of the BTC-PIP and TMC-PIP nanofilms, we conducted the XPS characterization for a more detailed analysis. The C1s, O1s, and N1s peaks of the XPS spectra (see Supplementary Figure S6) are summarized in Table 1. The deconvolution of the C1s and O1s spectra (See Supplementary Table S1) reveals the percentage of functional groups such as amide and carboxyl groups, and the O/N ratio calculated from the relative values of N and O measured from XPS (Table 1). The carboxyl content and O/N ratio of BTC-PIP nanofilm is slightly lower than that of TMC-PIP nanofilm. The percentage of carboxyl groups and the O/N ratio often represent the extent of chemical cross-linking. Hence, we reasonably conclude that the BTC-PIP nanofilm shows a higher extent of chemical cross-linking than the TMC-PIP nanofilm, which demonstrates a denser polyamide structure (depicted in Figure 2). Undoubtedly, the denser polyamide structure is beneficial to the rejection of Ca2+ and Mg2+.

3.3. Desalination Performance of the BTC and TMC Membranes Table 2 The single salt rejection and the water flux of the TMC-PIP, commercial TMC-MPD (C-TMC-MPD, NF 90) and BTC-PIP membranes fabricated by the IP process. The single salt concentration was 2000 ppm, and the test was performed with a cross-flow operation at 25 °C and 1 MPa. 13



Salt

TMC-PIP

Page 14 of 34

C-TMC-MPD

BTC-PIP

Rejection

Water flux

Rejection

Water flux

Rejection

Water flux

/%

/kg m−2 h−1

/%

/kg m−2 h−1

/%

/kg m−2 h−1

CaCl2

81.80±0.5

60.0±0.1

97.93±0.4

75.82±2.01

99.1±0.11

84.6±0.91

MgCl2

94.30±0.5

58.0±1.0

97.35±0.5

72.4±2.4

99.1±0.31

82.9±0.82

MgSO4 98.30±0.2

56.0±2.3

99.1±0.6

79.78±2.8

99.4±0.04

88.3±0.24

Na2SO4 98.82±0.1

53.7±1.2

99.2±0.34

78.35±2.2

99.1±0.13

86.8±0.61

63.1±0.4

97.47±0.3

63.1±0.4

83.3±0.54

96.7±0.30

NaCl

46.52±1.7

The desalination performances of the TMC-PIP, C-TMC-MPD, and BTC-PIP membranes are shown in Table 2. The salt rejection for the TMC-PIP membrane shows a typical nanofiltration performance, i.e., decreases in the order as Na2SO4 > MgSO4 > MgCl2 > CaCl2 > NaCl. The C-TMC-MPD and BTC-PIP membranes exhibit better salt rejection and higher flux than the TMC-PIP membrane. Specifically, the rejection of divalent salt (CaCl2, MgCl2, MgSO4 and Na2SO4) for the BTC-PIP membrane is more than 99%, while the rejection of CaCl2 and MgCl2 for the TMC-PIP membrane is 81.80% and 94.30%, respectively, which is lower than that of the BTC-PIP membrane. This result demonstrates that the BTC-PIP membrane exhibits an outstanding removal performance of Ca2+ and Mg2+. In addition, NaCl rejection of the TMC-PIP membrane is always lower due to the smaller hydrated radius of monovalent ions (Table S2)

24,25.

However, thanks to the denser polyamide

structure, the NaCl rejection (83.3%) for the BTC-PIP membrane is also higher than that of the TMC-PIP membrane (46.52%) but is still lower than that of C-TMC-MPD( 97.47%). On the other hand, the water flux of the BTC-PIP membrane with a thickness of 15 nm is in the range of 84.6 to 96.7 kg m−2 h−1, which is 1.41−1.62 times higher than that of the TMC-PIP membrane. The desalination experiments demonstrate that compared to the TMC membrane, the BTC-PIP membrane exhibits outstanding rejection for divalent salts (Ca2+ and Mg2+) and a significant increase in the water flux, and thus can replace the C-TMC-MPD membrane and be used in the water softening application. 14


Page 15 of 34 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


Table 3 Comparison of the water softening performance of the TMC-PIP, commercial TMC-MPD (C-TMC-MPD, NF 90) and BTC-PIP membranes. The composition of the feed solution was 3000 ppm Ca2+, 500 ppm Mg2+, 1000 ppm Na+, 7000 ppm Cl−1 and 2000 ppm SO42−, and the test was performed with a cross-flow operation at 25 °C and 1 MPa. TMC-PIP

C-TMC-MPD

BTC-PIP

Rejection

Water flux

Rejection

Water flux

Rejection

Water flux

/%

/kg m−2 h−1

/%

/kg m−2 h−1

/%

/kg m−2 h−1

Na+

4.2±2.1

83.3±1.4

17.7±1.8

Ca2+

90.4±1.6

98.4±0.7

99.3±0.3

Mg2+

98.9±0.7

Cl−1

62.2±2.4

95.6±1.2

81.2±1.9

SO42−

99.9±0

99.0±0.1

98.9±0.6

42.0±3.2

98.6±0.4

42.9±2.7

99.1±0.2

53.6±2.6

A comparison for the desalination performance of the C-TMC-MPD membrane, as well as the TMC-PIP and BTC-PIP membranes is provided in Table 3. The C-TMC-MPD membrane used in this experiment is NF 90, which is known for its outstanding desalination performance.26−28 To completely evaluate the water softening performance of the TMC and BTC membranes, a feed solution containing 13500 ppm ions was used in this experiment, which contained 3000 ppm Ca2+ and 500 ppm Mg2+. For the three kinds of polyamide membranes with different chemical structures, we observe that the BTC-PIP and TMC-MPD membranes, present excellent Ca2+ and Mg2+ retention and a higher permeation flux than the TMC-PIP membrane. Specifically, the rejection of Ca2+ for the BTC-PIP and TMC-MPD membranes is as high as 99.31% and 98.35%, respectively, while the Ca2+ rejection of the TMC-PIP membrane decreases to 90.35%. The rejection of monovalent ion such as Cl−1 and Na+ for the BTC-PIP membrane is lower than that of the C-TMC-MPD membrane, and further improvement is needed in the future. The comparison suggests that the performance of the BTC-PIP membrane is significantly superior to that of the TMC-PIP membranes. It is worth noting that the ultrathin selective layer is often correlated with the increase in permeation flux. The permeation flux of the BTC 15



membrane is thus as high as 53.6 kg m−2 h−1 MPa−1, whereas the permeation fluxes of the TMC-PIP and TMC-MPD membranes are slightly lower, with a water flux of 42 and 42.9 kg m−2 h−1 MPa−1, respectively. These results indicate that the rejection rate of Ca2+ and Mg2+ for the BTC-PIP membrane is equal or even superior to that of the commercial TMC-MPD membrane, and the permeation flux is enhanced. Furthermore, combined the denser polyamide structure and decreased carboxyl content, we estimate that the influence of steric hindrance and electrostatic repulsion effect on the rejection of Ca2+ and Mg2+ for the BTC-PIP membrane is higher than that of the TMC-PIP membrane, which consequently leads to an outstanding water softening performance.

BTC-PIP

100

Upper bound

NF90 90

Rejection (%)

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 16 of 34

80

70 Ca

2+

Mg

2+

Ca

60

50

literature

2+

literature

Mg

0

BTC-PIP

2+

Ca

2+

Mg

2+

NF 90

Ca

2+

Mg

2+

NF 270

40

80

-2

120

-1

160

Water Flux (kg m MPa )

Figure 6. The rejection of Ca2+ (CaCl2) and Mg2+ (MgCl2 or MgSO4) versus the water flux for the BTC-PIP membrane. Typical desalination data of the interfacial polymerization membranes, a commercial TMC-PIP membrane (NF 270), a commercial TMC-MPD membrane (NF 90), mixed matrix membranes and polyelectrolyte membranes are included. Based on the reported literature value, the upper-bound line is manually added to show a trade-off between the water flux and the rejection of Ca2+ and Mg2+. The performance in terms of permeation flux and salt rejection of the BTC-PIP 16


Page 17 of 34 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


membrane is compared with the performance of the state-of-the-art NF membranes reported in the literature (Table S4) 29−52 and commercial NF membranes (NF 90 and NF 270) (Figure 6). The comparison suggests that the performance of the BTC-PIP membrane is superior to the nanofiltration membranes recently developed by others, including the polyamide membranes prepared by different monomers, 2D or 3D nanomaterial-mixed

polyamide

membranes,

polyelectrolyte

membranes,

and

commercial NF membranes. The BTC-PIP membrane shows a significantly outstanding performance with a rejection of more than 99% for Ca2+ and Mg2+ compared to most other nanofiltration membranes, while simultaneously maintains a high permeation flux. It confirms that the BTC monomer with a smaller molecular conformation is better than the TMC on the construction of poly(piperazine-amide) membranes for water softening.

3.4. Effects of Surface charge, Hydrophilicity and Surface Roughness of the BTC and TMC Membranes on the Antifouling Performance In the water softening application, membrane fouling by effluent organic matters (EfOMs) is a major hindrance to the effective application of the nanofiltration (NF) technology. Fouling decreases the permeation flux, deteriorates the permeation quality, and shortens the membrane lifespan. Noteworthy is that membrane fouling will take place only on the membrane surface. The antifouling property of the BTC and TMC membranes are greatly affected by the membrane surface properties. However, the current TMC-MPD membrane used in water softening often exhibits a rough surface and moderate hydrophilicity. Hence, before conducting the fouling experiments, we characterized the membrane zeta potential, hydrophilicity, and surface roughness to understand better the difference in fouling behavior between the BTC and TMC membranes.

17



BTC-PIP C-TMC-MPD TMC-PIP

20 IEP 4.13

Zeta potential  (mv)

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 18 of 34

IEP 4.75

0 IEP 3.31 -20

33.23 mv 35.27 mv

-40 37.92 mv

2

4

6

pH

8

10

Figure 7. Streaming zeta potential of the commercial TMC-MPD (C-TMC-MPD), and polyamide membranes prepared by BTC-PIP and TMC-PIP.

3.4.1. Surface Charge. Figure 7 shows the streaming zeta potentials of the C-TMC-MPD, BTC-PIP and TMC-PIP membranes as a function of pH. For the C-TMC-MPD membrane, the isoelectric point (IEP) is located at pH 3.31, while it shifts to pH 4.13 for the TMC-PIP membrane and pH 4.75 for the BTC-PIP membrane. Combined with the streaming zeta potential values measured from pH 3 to 6, we observe that the BTC-PIP membrane shows a decreased streaming negative potential compared with the TMC-PIP and C-TMC-MPD membranes. This result is consistent with the XPS characterization. The surface zeta potential often correlates with the foulant-membrane interaction, and affects the deposition of foulant on the surface. For the negatively charged foulant in the feed solution at pH=7, such as BSA with isoelectric point 4.8, highly negatively charged surface can bring about the strong electrostatic repulsion between foulant and membrane and effectively reduce the membrane fouling.43 However, for some macromolecules with carboxyl such as some polysaccharides, these foulants can form the solid-like gel layer via metal– ligand complex interaction and rapidly deposit on the membrane surface with the assistance of calcium bridging in the presence of Ca2+, consequently, the membrane 18


Page 19 of 34

fouling is increased.11 The decreased surface negative surface charge (lacking carboxylic groups) is beneficial to suppress the formation of calcium bridging between foulants and membrane surface. In this work, we used BSA as model foulant, and the negatively charged surface is thus more beneficial to enhance the antifouling properties of the membrane. Hence, we mainly investigate the influence of the zeta potential value at pH=7 of the membrane surface on the antifouling properties.

80

Water contact angle()

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


60

40

20

0

BTC-PIP

TMC-PIP

TMC-MPD

Figure 8. Water contact angle of the BTC-PIP, TMC-PIP and commercial TMC-MPD (C-TMC-MPD) membranes.

3.4.2. Hydrophilicity. The surface hydrophilicity of the polyamide membranes is evaluated by measuring the water contact angle (WCA) (Figure 8). For the BTC-PIP membrane, the WCA is only 32.13°, which is significantly lower than the values of 61.86° for TMC-PIP and 66.4° for TMC-MPD. The water contact angles on the surfaces of the TMC-PIP and C-TMC-MPD membranes are almost identical and comparable to the values reported in the literature.53 The hydrophilicity is often correlated with the value of the dipole moment of polar groups or molecules and the hydration numbers. The dipole moment value and hydration numbers for amide is larger than that of carbonyl and hydroxyl (Table S6).54 Hence, as hydrophilic groups, the amide is considerably more hydrophilic than carboxyl. XPS characterization 19



reveals that the amide content of the BTC-PIP nanofilm is 68.03%, while that of TMC-PIP nanofilm is 59.65% (calculated from the core-level O1s XPS spectra, Table S1, Supporting Information). The BTC-PIP membrane thus exhibits an increased hydrophilicity. The more hydrophilic membrane surfaces tend to show better antifouling properties.

20


Page 20 of 34

Page 21 of 34 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 9. (a b) AFM images of the BTC-PIP surface morphology on the PES porous support, height 2D (a) and height 3D (b) images. (c d) AFM images of the TMC-PIP nanofilm supported on the PES porous substrate, height 2D (c) and height 3D (d) images. (e f) AFM images of the commercial TMC-MPD (C-TMC-MPD) membrane, height 2D (e) and height 3D (f) images.

3.4.3. Roughness. The surface morphology and roughness of the BTC-PIP, TMC-PIP and C-TMC-MPD membranes was shown in Figure 9. The roughness of the BTC-PIP and TMC-PIP membranes is 5.39 nm and 5.32 nm, respectively, indicating a smooth surface. In contrast, the C-TMC-MPD membrane exhibits the 21



special ridge-and-valley morphology, with a roughness of 29.48 nm. The BTC-PIP membrane is smoother than the TMC-MPD membrane. It is well known that a larger value of surface roughness is often correlated with the poor antifouling properties.55 Based on the zeta potential, WCA and surface roughness characterizations, we conclude that the BTC membrane exhibited a comparable surface negative charge at pH=7, enhanced hydrophilicity and a smooth surface, indicating better fouling resistance against BSA deposition compared with the TMC membranes during the fouling experiment.

BTC-PIP TMC-MPD TMC-PIP

90

Water Flux (kg m-2 h-1 )

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 22 of 34

80

70

60

50 0

5

10

15

20

25

30

Operational time (h)

Figure 10. Fouling studies of the BTC-PIP, TMC-PIP and commercial TMC-MPD (C-TMC-MPD) membranes. The water flux was recorded before and after the addition of BSA foulants (0.5 g L−1). The initial flux values were 87.6 kg m−2 h−1, 88.4 kg m−2 h−1 and 88.63 kg m−2 h−1 for the BTC-PIP, TMC-PIP and C-TMC-MPD membranes, respectively. Each fouling run was carried out for 27 h.

3.4.4. Antifouling Performance. The desalination experiment demonstrated that the BTC-PIP membrane maintains outstanding water softening performances such as a more than 99% rejection rate for Ca2+ and Mg2+ and an increased water flux. The surface characterization also highlighted the superiority of the BTC-PIP membrane in creating a more hydrophilic and thinner skin layer with a much smoother surface compared with the TMC membranes. Hence, we estimate that these advantages of the 22


Page 23 of 34 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


BTC-PIP membrane would greatly influence the antifouling property. To confirm this aspect, the pure water fluxes of the BTC-PIP, TMC-PIP and C-TMC-MPD membranes are monitored as a function of time during the filtration with a feed solution containing 0.5 g L−1 BSA. The pure water flux for all membranes decreases rapidly with the introduction of the BSA feed solution and reaches a plateau within one hour. However, the BTC-PIP membrane presents a lower ultimate flux decline (≈14%) than the TMC-PIP (≈29.9%) and TMC-MPD (≈37.5%) membranes, demonstrating its superior antifouling properties. The highly negative surface charge is a desirable membrane property to reduce the fouling, especially for the BSA that is negatively charged in the feed solution at pH = 7.56,57 The adsorption of negatively charged BSA onto a negatively charged surface is suppressed by electrostatic repulsion. The order of the surface negative zeta potential at pH 7 for the BTC and TMC membranes was TMC-PIP (−33.223 mv)>BTC-PIP (−35.27 mv)>C-TMC-MPD (−37.92 mv).

This result indicates that the C-TMC-MPD membrane imposes more

considerable electrostatic repulsion in terms of the suppression deposition of BSA than the BTC-PIP and TMC-PIP membranes. However, due to the rough surface and the lower hydrophilicity of the C-TMC-MPD membrane, BSA is more likely to adhere to the membrane surface, resulting in a significant decrease in water flux. On the other hand, despite a smooth surface, the antifouling property of the TMC-PIP membrane is lower than that of the BTC-PIP membrane due to the lower hydrophilicity. Hence, we conclude that, the enhanced fouling resistence to the BSA for the BTC-PIP membrane is mainly attributed to the smooth surface and signficant hydrophilicity, which is beneficial to reduce the adhesive forces between BSA and the membrane surface.58,59 In addition, based on the enhanced water flux and the excellent rejection for Ca2+ and Mg2+, we reasonably estimate that the lifespan and desalination efficiency of current membrane would be improved if the BTC-PIP membrane were applied in water softening.

3.5. Molecular Simulation 23



TMC-PIP BTC-PIP 0.02

Probability

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 24 of 34

Decreased cavity size

0.01 Larger and ridge-shaped cavity size

0.00

1.5

2.0

2.5

3.0

3.5

Cavity radius (Å)

4.0

4.5

Figure 11. Simulated cavity size distributions in the BTC-PIP and TMC-PIP polymers. The desalination experiment demonstrates that the BTC-PIP membrane exhibits an excellent water softening performance compared with the TMC-PIP membrane. To investigate the interconnected cavity size of the BTC-PIP and TMC-PIP nanofilms, we performed molecular simulations proposed by Bhattacharya and Gubbins.60−62 For example, the cavity sizes were estimated by probing the local free space using a particle with a specified radius size, and the initial probe size was set at 1.6 Å in this work. From Figure 11, we noted that the value of the probability of cavity size for the BTC-PIP polymer is substantially decreased when the cavity radius is changed in the range of 1.5 Å to 4.5 Å. However, the TMC-PIP polymer presents a slowly reduced probability of cavity size and exhibits an increased probability between 3.2 Å and 3.6 Å, demonstrating an increased void size in this interval. It is worth noting that the pore sizes ranging from 1.5 Å to 4 Å are much smaller than the hydrated radious of Ca2+ and Mg2+ studied in this work (see Supplementary Table S2), so in principle, Ca2+ and Mg2+ should not be able to pass them because of the steric hindrance. On the other hand, according to the water softening experiments, basically no Ca2+ and Mg2+ passages are observed for the BTC-PIP membrane, suggesting that the pore 24


Page 25 of 34 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


probability beyond 4.2 Å for the BTC-PIP networks does not exist, as rationalized by the molecular simulations (Figure 11). Hence, the simulation and experimental results confirm that the BTC-PIP membrane provides a relatively decreased pore size compared with the TMC-PIP nanofilm, thus imposing an enhanced steric hindrance effect on the divalent cations such as Ca2+ and Mg2+.

4. CONCLUSIONS In summary, by using the novel 1,2,3,4-cyclobutane tetracarboxylic acid chloride (BTC) monomer to replace the commonly commercial TMC molecule for interfacial polymerization, we have prepared a defect-free and higher cross-linked polyamide membrane with a thickness of 15 nm. This resulted BTC-PIP membrane has an excellent water softening performance compared with the TMC-PIP membrane due to its smaller molecular conformation. In particular, the prepared BTC-PIP membranes have an excellent water flux and rejection rate than the classic TMC membranes such as NF 90 and NF 270. Furthermore, as confirmed by molecular simulations, the outstanding rejection for Ca2+ and Mg2+ is mainly attributed to the significantly decreased interconnected void size of the polyamide structure at the molecular level. More importantly, due to its smooth surface and substantially increased hydrophilicity, the BTC-PIP membrane exhibits superior antifouling properties than the TMC membranes during the fouling experiments. The novel acid chloride can be synthesized by the facile acyl chloride reaction and by making the scaling-up of the interfacial polymerization process feasible, the BTC-PIP membrane with a decreased porosity would be conveniently industrialized in real applications. This work might inspire the design of the monomer molecules with different conformations to form the polyamide membrane that has great potential for applications in molecular or ion separations,

including

the

salt/dye

separation,

water

multivalent/monovalent salt separation and organic solvent nanofiltration.

ASSOCIATED CONTENT Supporting Information 25


purification,


Detailed methods, H1 and C13 NMR of BTC molecule, SEM images of BTC-PIP and TMC-PIP nanofilms, roughness and morphology of the PES substrates used, element and composition of BTC-PIP and TMC-PIP nanofilms, hydrated radius of the ions used, composition of the commercial nanofiltration membranes, cation and anion performance of the BTC-PIP and commercial NF membrane made by TMC-MPD varied with the operational pressure, comparison of desalination performance of various composite nanofiltration membranes, and molecular simulation process.

Conflict of Interest The authors declare no conflict of interest.

ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support from the Fundamental Research Funds for the Central Universities (No. 15CX02015A, 16CX05009A, 18CX05006A), the National Natural Science Foundation of China (grant no. 21502227), the Province Key Research and Development Program of Shandong (No. 2016GSF115032), Postdoctoral application Program of Qingdao (No. T1604013), the State Key Laboratory of Separation Membranes and Membrane Processes (Tianjin Polytechnic University, NO. M1-201601), State Key Laboratory of Heavy Oil Processing (SLKZZ-2017009), Qingdao Science and Technology Plan Project (176319gxx) and Shandong Province Major Science and Technology Innovation Project (2018CXGC1002).

REFERENCES 1.

Cadotte, J. E.; King, R. S.; Majerle, R. J.; Petersen, R. J. Interfacial Synthesis in

the Preparation of Reverse Osmosis Membranes. J. Macromol. Sci. Chem. 1981, 15 (5), 727−755. 2.

Petersen, R. J. Composite Reverse Osmosis and Nanofiltration Membranes. J.

Membr. Sci. 1993, 83(1), 81−150. 26


Page 26 of 34

Page 27 of 34 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


3.

Morgan, P. W. Condensation Polymers: By Interfacial and Solution Methods. J.

Polym. Sci., Polym. Phys. Ed. 1965, 82(3), 259−276. 4.

Beaman, R. G.; Morgan, P. W.; Koller, C. R.; Wittbecker, E. L.; Magat, E. E.

Interfacial polycondensation. III. Polyamides. J. Polym. Sci., Polym. Phys. Ed. 1959, 40 (137), 329−336. 5.

Morgan, P. W.; Kwolek, S. L. Interfacial Polycondensation. II. Fundamentals of

Polymer Formation at Liquid Interfaces. J. Polym. Sci., Pol. Chem. 1996, 34(4), 531−559. 6.

Karan, S.; Jiang, Z.; Livingston, A. G. Sub-10 nm Polyamide Nanofilms with

Ultrafast Solvent Transport for Molecular Separation. Science 2015, 348(6241), 1347−1351. 7.

Tan, Z.; Chen, S.; Peng, X.; Zhang, L.; Gao, C. Polyamide Membranes with

Nanoscale Turing Structures for Water Purification. Science 2018, 360(6388), 518−521. 8.

Jimenez-Solomon, M. F.; Song, Q.; Jelfs, K. E.; Munoz-Ibanez, M.; Livingston,

A.

G.

Polymer

Nanofilms

with

Enhanced

Microporosity

by

Interfacial

Polymerization. Nat. Mater. 2016, 15(7), 760−767. 9.

Paul, M.; Jons, S. D. Chemistry and Fabrication of Polymeric Nanofiltration

Membranes: A review. Polymer 2016, 103, 417−456. 10. Ahmad, A. L.; Ooi, B. S.; Mohammad, A. W.; Choudhury, J. P. Composite Nanofiltration Polyamide Membrane: A Study on the Diamine Ratio and Its Performance Evaluation. Ind. Eng. Chem. Res. 2004, 43(25), 8074−8082. 11. Tang, C. Y.; Chong, T. H.; Fane, A. G. Colloidal Interactions and Fouling of NF and RO Membranes: A review. Adv. Colloid. Interfac. 2011, 164(1), 126−143. 12. Tang, C. Y.; Kwon, Y.-N.; Leckie, J. O. Effect of Membrane Chemistry and Coating Layer on Physiochemical Properties of Thin Film Composite Polyamide RO and NF Membranes. Desalination 2009, 242(1), 149−167. 13. Zhu, Y.; Xie, W.; Gao, S.; Zhang, F.; Zhang, W.; Liu, Z.; Jin, J. Single-Walled Carbon Nanotube Film Supported Nanofiltration Membrane with a Nearly 10 nm Thick Polyamide Selective Layer for High-Flux and High-Rejection Desalination. 27



Page 28 of 34

Small 2016, 12, 5034–5041. 14. Wang, Z.; Wang, Z.; Lin, S.; Jin, H.; Gao, S.; Zhu, Y.; Jin, J. Nanoparticle-templated Nanofiltration Membranes for Ultrahigh Performance Desalination. Nat. Commun. 2018, 9(1), 2004–2013. 15. Rajesh, S.; Zhao, Y.; Fong, H.; Menkhaus, T. J. Nanofiber Multilayer Membranes with Tailored Nanochannels Prepared by Molecular Layer-by-Layer Assembly for High Throughput Separation. J. Mater. Chem. A 2017, 5(9), 4616−4628. 16. Saidani, H.; Ben Amar, N.; Palmeri, J.; Deratani, A. Interplay between the Transport of Solutes Across Nanofiltration Membranes and the Thermal Properties of the Thin Active Layer. Langmuir 2010, 26(4), 2574−83. 17. Hara, S.; Hayashi, Y.; Kawaguchi, T.; Sasaki, N.; Taketani, Y.; Minematsu, H. US4619767 Semipermeable Composite Membrane. 1982, Nitto Electric Industrial Co., Ltd., Japan. 18. Kong, X.; Qiu, Z.-L.; Lin, C.-E.; Song, Y.-Z.; Zhu, B.-K.; Zhu, L.-P.; Wei, X.-Z. High Permselectivity Hyperbranched Polyester/polyamide Ultrathin Films with Nanoscale Heterogeneity. J. Mater. Chem. A 2017, 5(17), 7876−7884. 19. Wang, T., Yang, Y., Zheng, J., Zhang, Q., Zhang, S. A Novel Highly Permeable Positively

Charged

Nanofiltration

Membrane

Based

on

a

Nanoporous

Hyper-crosslinked Polyamide Barrier Layer. J. Membr. Sci. 2013, 448, 180−189. 20. Li,

L.;

Zhang,

Poly(piperazineamide)

S.;

Zhang,

Composite

X.

Preparation

Nanofiltration

and

Characterization

Membrane

by

of

Interfacial

Polymerization of 3,3′,5,5′-Biphenyl Tetraacyl Chloride and Piperazine. J. Membr. Sci. 2009, 335(1−2), 133−139. 21. Xie, W.; Geise, G. M.; Freeman, B. D.; Lee, H.-S.; Byun, G.; McGrath, J. E. Polyamide Interfacial Composite Membranes Prepared from m-Phenylene Diamine, Trimesoyl Chloride and a New Disulfonated Diamine. J. Membr. Sci. 2012, 403−404, 152−161. 22. Zhang, J.; Hai, Y.; Zuo, Y.; Jiang, Q.; Shi, C.; Li, W. Novel Diamine-modified Composite Nanofiltration Membranes with Chlorine Resistance Using Monomers of 1,2,4,5-Benzene Tetracarbonyl Chloride and m-Phenylenediamine. J. Mater. Chem. A 28


Page 29 of 34 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


2015, 3(16), 8816−8824. 23. Lai, G. S.; Lau, W. J.; Gray, S. R.; Matsuura, T.; Gohari, R. J.; Subramanian, M. N.; Lai, S. O.; Ong, C. S.; Ismail, A. F.; Emazadah, D.; Ghanbari, M. A Practical Approach to Synthesize Polyamide Thin Film Nanocomposite (TFN) Membranes with Improved Separation Properties for Water/Wastewater Treatment. J. Mater. Chem. A 2016, 4(11), 4134−4144. 24. Samson, E.; Marchand, J.; Snyder, K. A. Calculation of Ionic Diffusion Coefficients on the Basis of Migration Test Results. Mater. Struct. 2003, 36(3), 156−165. 25. Jr, E. R. N. Phenomenological Theory of Ion Solvation. Effective Radii of Hydrated Ions. Biochimica. Et. Biophysica. Acta. 1959, 63(9), 566–567. 26. Shardul S. Wadekar, R. D. V. Influence of Active Layer on Separation Potentials of Nanofiltration Membranes for Inorganic Ions. Environ. Sci. Technol. 2017, 51, 5658−5665. 27. Verbeke, R.; Gómez, V.; Vankelecom, I. F. J. Chlorine-resistance of Reverse Osmosis (RO) Polyamide Membranes. Prog. Polym. Sci. 2017, 72, 1–15. 28. Shardul S. Wadekar, T. H., Omkar R. Lokare, Devesh Mittal, Radisav D. Vidic. Laboratory and Pilot-Scale Nanofiltration Treatment of Abandoned Mine Drainage for the Recovery of Products Suitable for Industrial Reuse. Ind. Eng. Chem. Res. 2017, 56, 7355−7364. 29. Zhao, F.-Y.; An, Q.-F.; Ji, Y.-L.; Gao, C.-J. A Novel Type of Polyelectrolyte Complex/MWCNT Hybrid Nanofiltration Membranes for Water Softening. J. Membr. Sci. 2015, 492, 412−421. 30. Fang, W.; Shi, L.; Wang, R. Mixed Polyamide-based Composite Nanofiltration Hollow Fiber Membranes with Improved Low-pressure Water Softening Capability. J. Membr. Sci. 2014, 468, 52−61. 31. Qian, H.; Li, S.; Zheng, J.; Zhang, S. Ultrathin Films of Organic Networks as Nanofiltration Membranes via Solution-based Molecular Layer Deposition. Langmuir 2012, 28(51), 17803−17810. 32. Liu, C.; Shi, L.; Wang, R. Crosslinked Layer-by-Layer Polyelectrolyte 29



Page 30 of 34

Nanofiltration Hollow Fiber Membrane for Low-pressure Water Softening with the Presence of SO42− in Feed Water. J. Membr. Sci. 2015, 486, 169−176. 33. Wang, H.; Zhang, Q.; Zhang, S. Positively Charged Nanofiltration Membrane Formed by Interfacial Polymerization of 3,3,5,5-Biphenyl Tetraacyl Chloride and Piperazine on a Poly(acrylonitrile) (PAN) Support. J. Membr. Sci. 2011, 378, 243– 249. 34. Zhao, F. Y.; Ji, Y. L.; Weng, X. D.; Mi, Y. F.; Ye, C. C.; An, Q. F.; Gao, C. J. High-Flux Positively Charged Nanocomposite Nanofiltration Membranes Filled with Poly(dopamine) Modified Multiwall Carbon Nanotubes. ACS. Appl. Mater. Inter. 2016, 8(10), 6693–6700. 35. Feng, C.; Xu, J.; Li, M.; Tang, Y.; Gao, C. Studies on a Novel Nanofiltration Membrane Prepared by Cross-linking of Polyethyleneimine on Polyacrylonitrile Substrate. J. Membr. Sci. 2014, 451, 103−110. 36. Chen, Y.; Liu, F.; Wang, Y.; Lin, H.; Han, L. A Tight Nanofiltration Membrane with Multi-charged Nanofilms for High Rejection to Concentrated Salts. J. Membr. Sci. 2017, 537, 407−415. 37. Lee, K. P.; Bargeman, G.; de Rooij, R.; Kemperman, A. J. B.; Benes, N. E. Interfacial Polymerization of Cyanuric Chloride and Monomeric Amines: pH Resistant Thin Film Composite Polyamine Nanofiltration Membranes. J. Membr. Sci. 2017, 523, 487−496. 38. Kong, X.; Zhou, M.-Y.; Lin, C.-E.; Wang, J.; Zhao, B.; Wei, X.-Z.; Zhu, B.-K. Polyamide/PVC Based Composite Hollow Fiber Nanofiltration Membranes: Effect of Substrate on Properties and Performance. J. Membr. Sci. 2016, 505, 231−240. 39. Li, X.; Cao, Y.; Yu, H.; Kang, G.; Jie, X.; Liu, Z.; Yuan, Q. A novel composite nanofiltration

membrane

prepared

with

PHGH

and

TMC

by

interfacial

polymerization. J. Membr. Sci. 2014, 466, 82−91. 40. Wu, C.; Liu, S.; Wang, Z.; Zhang, J.; Wang, X.; Lu, X.; Jia, Y.; Hung, W.-S.; Lee, K.-R. Nanofiltration Membranes with Dually Charged Composite Layer Exhibiting Super-high Multivalent-salt Rejection. J. Membr. Sci. 2016, 517, 64−72. 41. Cheng, X. Q.; Shao, L.; Lau, C. H. High Flux Polyethylene Glycol Based 30


Page 31 of 34 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


Nanofiltration Membranes for Water Environmental Remediation. J. Membr. Sci. 2015, 476, 95−104. 42. Hu, J.; Lv, Z.; Xu, Y.; Zhang, X.; Wang, L. Fabrication of a High-flux Sulfonated Polyamide Nanofiltration Membrane: Experimental and Dissipative Particle Dynamics Studies. J. Membr. Sci. 2016, 505, 119−129. 43. Ishigami, T.; Amano, Kuniaki.; Fujii, A.; Ohmukai, Y.; Kamio, E.; Maruyama, T.; Matsuyama, H. Fouling Reduction of Reverse Osmosis Membrane by Surface Modification via Layer-by-Layer Assembly. Sep. Purif. Technol. 2012, 99, 1−7. 44. Wang, T.; Yang, Y.; Zheng, J.; Zhang, Q.; Zhang, S. A Novel Highly Permeable Positively

Charged

Nanofiltration

Membrane

Based

on

a

Nanoporous

Hyper-crosslinked Polyamide Barrier Layer. J. Membr. Sci. 2013, 448, 180−189. 45. Homayoonfal, M.; Akbari, A.; Mehrnia, M. R. Preparation of Polysulfone Nanofiltration Membranes by UV-assisted Grafting Polymerization for Water Softening. Desalination 2010, 263(1), 217−225. 46. Hu, D.; Xu, Z.-L.; Wei, Y.-M.; Liu, Y.-F. Poly(styrene sulfonic acid) Sodium Modified Nanofiltration Membranes with Improved Permeability for the Softening of Highly Concentrated Seawater. Desalination 2014, 336, 179−186. 47. Zhang, H.-Z.; Xu, Z.-L.; Ding, H.; Tang, Y.-J. Positively Charged Capillary Nanofiltration Membrane with High Rejection for Mg2+ and Ca2+ and Good Separation for Mg2+ and Li+. Desalination 2017, 420, 158−166. 48. Wei, X.; Wang, S.; Shi, Y.; Xiang, H.; Chen, J.; Zhu, B. Characterization of a Positively Charged Composite Nanofiltration Hollow Fiber Membrane Prepared by a Simplified Process. Desalination 2014, 350, 44−52. 49. Guo, H.; Chen, M.; Liu, Q.; Wang, Z.; Cui, S.; Zhang, G. LbL Assembly of Sulfonated

Cyclohexanone–formaldehyde

Condensation

Polymer

and

Poly(ethyleneimine) towards Rejection of Both Cationic Ions and Dyes. Desalination 2015, 365, 108−116. 50. Li, X.; Zhao, C.; Yang, M.; Yang, B.; Hou, D.; Wang, T. Reduced Graphene oxide-NH2 Modified Low Pressure Nanofiltration Composite Hollow Fiber 31



Page 32 of 34

Membranes with Improved Water Flux and Antifouling Capabilities. Appl. Surf. Sci. 2017, 419, 418−428. 51. Gherasim, C. V.; Luelf, T.; Roth, H.; Wessling, M. Dual-Charged Hollow Fiber Membranes for Low-Pressure Nanofiltration Based on Polyelectrolyte Complexes: One-Step Fabrication with Tailored Functionalities. ACS. Appl. Mater. Inter. 2016, 8(29), 19145−19157. 52. de Grooth, J.; Reurink, D. M.; Ploegmakers, J.; de Vos, W. M.; Nijmeijer, K. Charged Micropollutant Removal With Hollow Fiber Nanofiltration Membranes Based On Polycation/Polyzwitterion/Polyanion Multilayers. ACS. Appl. Mater. Inter. 2014, 6(19), 17009−17017. 53. Saha, N. K.; Joshi, S. V. Performance Evaluation of Thin Film Composite Polyamide Nanofiltration Membrane with Variation in Monomer Type. J. Membr. Sci. 2009, 342(1), 60−69. 54. Sagawa, N.; Shikata, T. Are All Polar Molecules Hydrophilic? Hydration Numbers

of

Nitro

Compounds

and

Nitriles

in

Aqueous

Solution.

Phys.Chem.Chem.Phys. 2014, 16, 13262−13270. 55. Vrijenhoek, E. M.; Hong, S.; Elimelech, M. Influence of Membrane Surface Properties on Initial Rate of Colloidal Fouling of Reverse Osmosis and Nanofiltration Membranes. J. Membr. Sci. 2001, 188(1), 115−128. 56. Thomas. F. S.; R. Scott. S.; Gusses. A. M. Nanofiltration Foulants from a Treated Surface Water. Environ. Sci. Technol. 1998, 32(22), 3612−3617. 57. Mulyati, S.; Takagi, R.; Fujii, A.; Ohmukai, Y.; Matsuyama, H. Simultaneous Improvement of the Monovalent Anion Selectivity and Antifouling Properties of an Anion Exchange Membrane in An Electrodialysis Process, Using Polyelectrolyte Multilayer Deposition. J. Membr. Sci. 2013, 431, 113−120. 58. Mo, Y.; Tiraferri, A.; Yip, N. Y.; Adout, A.; Huang, X.; Elimelech, M. Improved Antifouling Properties of Polyamide Nanofiltration Membranes by Reducing the Density of Surface Carboxyl Groups. Environ. Sci. Technol. 2012, 46(24), 13253−13261. 59. Childress, A. E.; Elimelech, M. Relating Nanofiltration Membrane Performance 32


Page 33 of 34 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 Membrane Charge (Electrokinetic) Characteristics. Environ. Sci. Technol. 2000, 34 (17), 3710−3716. 60. Bhattacharya, S.; Gubbins, K. E. Fast Method for Computing Pore Size Distributions of Model Materials. Langmuir 2006, 22(18), 7726−7731. 61. Ding, M.; Szymczyk, A.; Goujon, F.; Soldera, A.; Ghoufi, A. Structure and Dynamics of Water Confined in a Polyamide Reverse-osmosis Membrane: A Molecular-simulation Study. J. Membr. Sci. 2014, 458(458), 236−244. 62. Jiang, C.; Hou, Y.; Wang, N.; Li, L.; Lin, L.; Niu, Q. J. Propylene/Propane Separation by Porous Graphene Membrane: Molecular Dynamic Simulation and First-principle Calculation. J. Taiwan. Inst. Chem. E. 2017, 78, 477–484.

33



Graphic Abstract

34


Page 34 of 34

Ultrathin Polyamide Membrane with Decreased Porosity Designed for

Recommend Documents