Polyamide membrane surface and bulk modification using humid environment as a new heat curing medium

Karimi, Hossein; Bajestani, Majid Bazrgar; Mousavi, Seyyed Abbas; Garakani, Rasoul Mokhtari

doi:10.1016/j.memsci.2016.09.042

Cited by 34 publications

(9 citation statements)

References 38 publications

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“…The characteristic peaks of PA top layer at 1550, 1610, and 1660 cm −1 are observed in the spectra of the TFC membranes, confirming that the PA layer has been well formed on top of the PSf layer . On the other hand, the peak at 1730 cm −1 in the spectra of membranes C2 and T2 which represents the hydrolysis of some of the TMC acyl chloride groups to carboxylic acid groups cannot be observed in the spectrum of membrane C1 . The crosslinking degree of PA layers can be estimated by comparing the absorption intensity ratio of the bands at 1666 cm −1 (amide I) and 1730 cm −1 (carboxylic CO) .…”

Section: Resultsmentioning

confidence: 84%

Optimization of water flux and salt rejection properties of polyamide thin film composite membranes

Azizi

Sharif

2019

J of Applied Polymer Sci

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Optimizing synthesis factors of polyamide top layers is an important requirement in the design of thin film composite (TFC) membranes. In this research, the top layer fabrication method (conventional, heat curing, and spin coating), type of acid acceptor (sodium carbonate, sodium hydroxide, and triethylamine), type of organic phase solvent (hexane, heptane, and mixed hexane/heptane), and concentration of surfactant sodium dodecyl sulfate (0, 0.5, and 1 wt %) are selected as the control parameters of this synthesis and optimized using the Taguchi approach. The analysis of variance shows that the layer fabrication method is the most influential parameter on water flux and salt (NaCl) rejection of TFCs. Furthermore, although the type of organic solvent has not a significant contribution to the water flux, it is another significant factor affecting the rejection. The optimized membrane is then used to construct structureproperty relationships and to understand the influence of each individual factor on the desalination performance. Accordingly, a TFC membrane with the top layer fabricated by the heat curing method, in the presence of Na 2 CO 3 as the acid acceptor, hexane as the organic phase solvent and 0.5 wt % of the surfactant is prepared that shows water permeance of 2.73 L m −2 h −1 bar −1 and NaCl rejection of 98.1%. centration demonstrated the importance of these parameters in the preparation process of TFCs. The same group recently studied the synergistic effects of different additives on desalination properties of PA-TFC membranes. 23 The additives, which Additional Supporting Information may be found in the online version of this article.

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Section: Resultsmentioning

confidence: 84%

Optimization of water flux and salt rejection properties of polyamide thin film composite membranes

Azizi

Sharif

2019

J of Applied Polymer Sci

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“…ATR‐FTIR spectra of these membranes, in the range of 1000–4000 cm −1 (Figure 4) and 1300–1700 cm −1 (Figure 4(b)), for the sake of clarification, show characteristic peaks at 1546, corresponding to NH (amide II), 1627, attributed to CO stretching (amide I) for NCHO and 3364 cm −1 , emanating from amine group (NH, NH 2 ) and carboxylic acid (COOH) which can be ascribed to the PA layers atop the PSf substrates 8,21,22 . Moreover, it can be inferred from the peaks appeared at 1742 cm −1 that some of the TMC acyl chlorides were hydrolyzed to carboxylic acid groups 23 . The hydrolysis could result in incomplete reactions between TMC and TETA monomers during IP and finally in a decrease in cross‐linking densities of the PA layers 7,10 …”

Section: Resultsmentioning

confidence: 99%

“…The degree of cross‐linking of the PA layers estimated from the ATR‐FTIR spectra. The estimated cross‐linking densities on the basis of ATR‐FTIR would be even more reliable than those usually derived from X‐ray photoelectron spectroscopy (XPS) analysis 13,23 . Table 4 lists the ratios of absorption intensities of the bands at 1627 cm −1 (amide I) and 1742 cm −1 (carboxylic CO) which are measures of the cross‐linking degree of the top layer 24 .…”

Section: Resultsmentioning

confidence: 99%

A systematic study on the effects of synthesis conditions of polyamide selective layer on the CO₂/N₂ separation of thin film composite polyamide membranes

Kamali

Gharibi

Sharif

2021

J of Applied Polymer Sci

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Different top layer fabrication methods (amine‐first, acid‐first, spin coating), organic phase solvents (hexane, heptane, mixed hexane/heptane), acid acceptors (triethylamine, sodium carbonate, sodium hydroxide), and surfactant sodium dodecyl sulfate concentrations (0, 0.05, and 0.1 wt%) were utilized to fabricate thin film composite polyamide membranes for CO2/N2 separation. The results, according to an L9 orthogonal array of Taguchi approach, showed that employing acid‐first method increases both CO2 permeance and CO2/N2 selectivity of the membranes at a feed gas pressure of 3 bars. On the other hand, sodium hydroxide, and triethylamine should be used, as acid acceptors, to maximize CO2 permeance and CO2/N2 selectivity, respectively. Moreover, the use of hexane solvent and 0 wt% surfactant led to maximum permeance, while, hexane solvent and 0.1 wt% surfactant were needed to reach the highest selectivity. The above level setting of synthesis parameters also resulted in the minimum sensitivity of the fabrication process to the noise factors effects. As shown by the analysis of variance, acid acceptor, and organic solvent types were the most influential parameters on CO2 permeance and CO2/N2 selectivity, respectively. The effects of fabrication method and surfactant concentration, as single factors, on permeation/selectivity responses were also investigated.

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“…The influence mechanism of the heat-curing method on the formation processes of interfacially polymerized PA active layer on electrospun nanofiber support was deducted based on the experimental results mentioned above. Figure 11 illustrated the speculative formation process of PA active layers via interfacial polymerization of MPD in DI water with TMC in hexane using different heat-curing methods (curing in the hot-air oven and on hot water bath), which referred to the discussion in the literature [ 44 ]. PAN nanofiber exhibited good hydrophilicity with swelling behavior, which could first absorb an aqueous solution into the bulk or voids of the nanofiber support.…”

Section: Resultsmentioning

confidence: 99%

“…Zhan et al Ghosh et al, and Han et al respectively investigated the effects of curing conditions (temperature, time) on the morphologies and performances of the as-prepared PA-TFC membranes in nanofiltration (oven-curing), reverse osmosis (oven-curing) and FO (specific hot-water-curing) [ 40 , 41 , 42 ]. In addition, several studies demonstrated that conducting different heat-curing methods would make a significant difference in surface morphologies, physicochemical properties and separation performances of reverse osmosis membranes [ 43 , 44 ]. However, as almost all related studies were based on the phase-inversion support, none are on the electrospun nanofiber support.…”

Section: Introductionmentioning

confidence: 99%

Alleviation of Reverse Salt Leakage across Nanofiber Supported Thin-Film Composite Forward Osmosis Membrane via Heat-Curing in Hot Water

Chen

et al. 2021

Membranes

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Electrospun nanofiber with interconnected porous structure has been studied as a promising support layer of polyamide (PA) thin-film composite (TFC) forward osmosis (FO) membrane. However, its rough surface with irregular pores is prone to the formation of a defective PA active layer after interfacial polymerization, which shows high reverse salt leakage in FO desalination. Heat-curing is beneficial for crosslinking and stabilization of the PA layer. In this work, a nanofiber-supported PA TFC membrane was conceived to be cured on a hot water surface with preserved phase interface for potential “defect repair”, which could be realized by supplementary interfacial polymerization of residual monomers during heat-curing. The resultant hot-water-curing FO membrane with a more uniform superhydrophilic and highly crosslinked PA layer exhibited much lower reverse salt flux (FO: 0.3 gMH, PRO: 0.8 gMH) than that of oven-curing FO membrane (FO: 2.3 gMH, PRO: 2.2 gMH) and achieved ∼4 times higher separation efficiency. It showed superior stability owing to mitigated reverse salt leakage and osmotic pressure loss, with its water flux decline lower than a quarter that of the oven-curing membrane. This study could provide new insight into the fine-tuning of nanofiber-supported TFC FO membrane for high-quality desalination via a proper selection of heat-curing methods.

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Polyamide membrane surface and bulk modification using humid environment as a new heat curing medium

Cited by 34 publications

References 38 publications

Optimization of water flux and salt rejection properties of polyamide thin film composite membranes

Optimization of water flux and salt rejection properties of polyamide thin film composite membranes

A systematic study on the effects of synthesis conditions of polyamide selective layer on the CO₂/N₂ separation of thin film composite polyamide membranes

Alleviation of Reverse Salt Leakage across Nanofiber Supported Thin-Film Composite Forward Osmosis Membrane via Heat-Curing in Hot Water

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Polyamide membrane surface and bulk modification using humid environment as a new heat curing medium

Cited by 34 publications

References 38 publications

Optimization of water flux and salt rejection properties of polyamide thin film composite membranes

Optimization of water flux and salt rejection properties of polyamide thin film composite membranes

A systematic study on the effects of synthesis conditions of polyamide selective layer on the CO2/N2 separation of thin film composite polyamide membranes

Alleviation of Reverse Salt Leakage across Nanofiber Supported Thin-Film Composite Forward Osmosis Membrane via Heat-Curing in Hot Water

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A systematic study on the effects of synthesis conditions of polyamide selective layer on the CO₂/N₂ separation of thin film composite polyamide membranes