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Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures
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Journal of Industrial and Engineering Chemistry xxx (2019) xxx–xxx
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Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures Shivshankar Chaudharia , YongSung Kwona , MinYoung Shona,* , SeungEun Namb , YouIn Parkb a b
Department of Industrial Chemistry, Pukyong National University, San 100, Yongdang-Dong, Nam-Gu, Busan 608-739, South Korea Center for membranes, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon 305-600, South Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 13 June 2019 Received in revised form 29 July 2019 Accepted 1 September 2019 Available online xxx
Conventional distillation failed to separate a ternary azeotropic mixture of ECH, IPA and water (50/30/ 20 w/w, %) exist in the epoxy resin manufacturing process. Thus, we prepared a PVA-tetraethyl orthosilicate organic–inorganic hybrid membrane and modified the membrane by layer-by-layer deposition of a PVAm/silicotungstic acid polyelectrolyte for the pervaporation (PV) dehydration of ECH/ IPA/water mixtures. In PV experiments at 30 C, the flux decreased from 0.14 to 0.05 kg m2 h1 and separation factor increased from and 2099 to 13,320 with TEOS addition in the PVA membrane was observed. And for the layer by layer deposition on PVA-TEOS (4) membranes flux increased and separation factor decreased from 0.14 to 0.28 kg m2 h1 and 2099 to 416 with the number of layer of deposition were observed respectively. On varying the feed water content from 20 to 10 wt. %, the pervaporation flux at 30 C decreased from 0.22 to 0.0066 kg m2 h1 and the separation factor increased from 1061 to 9094 was observed. By applying the Arrhenius equation, permeation activation energies of ECH and IPA (97.42 and 111.96 kJ mol-1, respectively) are higher than that of water (40.88 kJ mol1) were reported for the layer by layer membrane. © 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Keywords: Pervaporation Surface modification Poly (vinyl alcohol) (PVA) (PVAm) Epichlorohydrin Poly (vinyl amine) Silicotungstic acid (STA)
Introduction Epichlorohydrin (ECH) is made up of organochlorine moieties and epoxide ring, is an extremely susceptible electrophilic compound primarily employed in the manufacturing of epoxy resins, plastics and glycerol [1,2]. The polymerization of ECH with phenol gives an epoxy resin product. The bisphenol-A (BPA) and isopropyl alcohol (IPA) is served as the solvent and excess of ECH is charge in the reaction batch to adjust the molecular weight of the finished epoxy resin yield. In the final stages of reaction; a chlorine-containing impurities and ECH/IPA/water mixture as byproducts are present along with the finished product epoxy resin. A vacuum distillation can be used to recover the ECH and IPA and again recycled in the form of raw materials. However, during the recycling; the impurity content concentrate gradually in the byproduct mixture. This is because, ECH and IPA exhibit an azeotropic mixture with water at ECH/IPA/water, 50:30:20 (wt. %)
* Corresponding author. E-mail address: [email protected] (M. Shon).
composition; in the recovery of IPA and ECH by vacuum distillation that restrict the recovery process to purify an IPA and ECH at desired purity level. In addition not only point of energy consumption and reuse of recycled materials concern, but ECH can also have serious environmental hazards if it released as waste in environment, because ECH is carcinogenic compound [3,4]. Adsorption method can be used to dehydrate the ECH/IPA/water, 50:30:20 (wt. %) azeotropic composition, however the adsorption of water from the mixture demands a high capacity adsorption bed depending on epoxy resin production process, 0.6 ton of ECH/IPA/ water mixture generated per 1 ton of epoxy resin production. Additionally, frequent regeneration of adsorption bed was required to remove the contaminants through series of different step, that may further increase the operation cost of epoxy resin production process [5]. On other hand, PV-distillation is a hybrid process consist of synergy between the feature of pervaporation (PV) and distillation process individually. PV can successfully remove the moisture from recovery mixture and by the distillation, recovery and purification of ECH and IPA can be increase energy efficiency and competitiveness of product. By this approach the costs associated with the
https://doi.org/10.1016/j.jiec.2019.09.007 1226-086X/© 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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epoxy resin manufacturing process can be easily reduced in the green way. However, to treat the highly reactive epichlorohydrincontaining feed mixture, the membrane material must have excellent chemical and mechanical stability and good thermal properties. Poly(vinyl alcohol) (PVA) has consistently been shown to be an excellent membrane material with good membrane forming properties and robustness and chemical stability in organic solvents [6–13]. In our last report we used a PVA/poly(vinyl amine) (PVAm) blended membrane for the dehydration of azeotropic ECH/IPA/water mixtures (50/30/20 (w/w, %)), and the
PVA membrane was found to have remarkable pervaporation stability along with good pervaporation performance [14]. However, by the survey of literature it has been observed that in the water based feed system, the pristine PVA membranes undergo high amount of swelling. Thus; the several methods such as crosslinking of PVA chain with chemical agent, blending with different polymers, polymer grafting, and thermal treatment have used to compensate the excessive PVA membrane swelling. Among these methods, inorganic–organic crosslinking of PVA with tetraethyl orthosilicate (TEOS) as an inorganic crosslinking agent has been shown to yield membranes with remarkable stability. The
Fig. 1. (a) The real photographs of PVAm/STA polyelectrolyte complex and PVA-TEOS (4) (15 L-L) membrane (b) Schematic diagram of membrane preparation process.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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main advantages of the PVA-TEOS crosslinking reaction is that it takes place at relatively mild temperatures, and covalent bonding between the silicon-based inorganic compound and the organic polymer is facile, producing a membrane material having excellent mechanical stability that can resist most organic solvents used in pervaporation [15]. However, the introduction of a hydrophobic inorganic compound (TEOS) to the PVA reduces the membrane hydrophilicity and, thus, reduces the permeation rate of the membrane. This phenomenon has been reported in the literature for PVA/TEOS hybrid membranes used for the pervaporation dehydration of isopropanol and acetic acid [16–18]. One promising method to ameliorate this difficulty is the functionalization of the PVA membrane surface. Recently, surface initiated polymerization for surface modification with fluorescent nanodiamonds has been investigated for cell imaging application [19]. Based on mussel inspired chemistry, polydopamine structure is emerge as promising surface functionalization material for all kind of surface regardless to their material chemistry [20–22]. Which was found a numerous application in various field such as drug delivery [23,24], water treatment [25,26], Bio imaging, [27,28], tissue engineering, cell adhesion [20], encapsulation and patterning [20,29] and the treatment of water including separation of organic pollutant, bacteria and heavy metal from water [30]. Cao et al. studied the coating of membrane surface through the polydopamine based mussel inspired chemistry and they found it was very efficient and membrane was easily cleaned for separation of water from the oil [31]. They have also reported that, it is an important method rely on the non-covalent self-assembly and covalent self-polymerization through which can form a strong covalent and non-covalent interaction with the all type of organic or inorganic substrates. However, although the above techniques showed very promising and convincing results in the field of surface coating for the verities of substrates, the thickness of film on surface is limited up to the 50 nm in single reaction and can occur only in the acidic condition in the presence of specific oxidants. Additionally, not only these modification methods exhibit in the complex experimental procedure but also the cost associated with material is an issue. For that reason, polyelectrolyte complex deposition in the form of nanoscale layer on the surface of the PVA membrane was conducted. Such layer deposition charge the film surface, giving it an immense hydrophilic character and, with result of that, a high affinity for water. Furthermore, when in contact with water; a moderate swelling of the membrane occurred due to the formation of compact electrostatic layer. According to the solution diffusion model, mass transport across the pervaporation membrane occurs
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via through solution sorption and the diffusion and desorption of permeants in the pervaporation process [32,33]. It is well known that sorption plays key role in determining the selectivity of the membranes toward a particular feed system [34]. Thus, surface functionalization by polyelectrolyte deposition on the PVA/TEOS hybrid membrane surface can significantly enhance the water sorption on the upstream side of the membrane. Polyelectrolyte complexes are produced by the electrostatic interaction of polyelectrolyte polycation and polyanions [35]. There are several different polyelectrolyte pairs, for example, chitosan/sodium hyaluronate, poly(allyl amine hydrochloride / poly(sodium 4-styrene sulfonate), sodium alginate/polyethyleneimine, chitosan/polystyrene sulfonic acid-co-maleic acid and sodium carboxymethyl cellulose/poly(diallydimethyl ammonium chloride), and these have been used for the fabrication of pervaporation dehydration membranes [36–39,40]. PVAm has a primary amine group in the polymer backbone and is positively charged in aqueous media [41,42]. Silicotungstic acid is a heteropoly acid is a kind of acid comprised of a distinct combination of oxygen and hydrogen with fixed metals [M] and non-metals [X]. Silicotungstic acid is based on Keggin units and has a polyanionic structure ([XM12O40]n) with a three-dimensional combination of hetero polyanions consist of four acidic hydrogen atoms [43]. In aqueous solution, the STA polyanion forms a stable polyelectrolyte complex with the PVAm. In this study, we prepared PVA/TEOS inorganic–organic hybrid membranes, as well as PVA/TEOS membrane modified bylayer-by-layer (L-L) coating with PVAm/STA by interfacial complexation, because the pervaporation properties of membranes are strongly influenced by this type of modification. The nanoscale layer of polyelectrolyte on the membrane surface can increase the hydrophilicity of the membrane surface, resulting in an increase in the transport properties of the membrane. Subsequently, the pervaporation dehydration of a ternary ECH/IPA/water mixture was carried out under diverse operating conditions. Experimental section Materials Tetraethyl orthosilicate was obtained from Sigma–Aldrich Co. (China). Silicotungstic acid hydrate [H4 (Si (W3O10)10)4] nH2O was reserved from Sigma–Aldrich (USA). Poly (vinyl alcohol) having a 98–99% degree of hydrolysis (molecular weight of 88,000–97,000) was procured from Alfa Aesar (USA). ECH, Isopropyl alcohol (99.5 wt. %) were purchased from Dae-Jung Chemicals & Metal
Fig. 2. (A) Schematic diagram of pervaporation apparatus: (a) water bath (b) feed tank (c) temperature indicator (d) circulation pump (e) membrane cell, (f) vacuum gauge (g), (h) cold trap + liquid nitrogen (i) vacuum pump, (B) Real photographs of pervaporation apparatus.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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Co., Korea. Readymade 10 wt. % solution of Poly (vinyl amine) was supplied by BASF Co. Indonesia having a brand name Lupamin-9095 (Mw 340000,). Desired feed solutions for pervaporation run were made by mixing predetermined quantities of ECH/IPA/Water (w/w, %) in the laboratory. The deionized water (Puris, Expe-RO EDI water system) was used for study. Preparation of PVA/TEOS membranes First, 4 g PVA powder was dissolved in 96 g of water in a beaker with continuous stirring using a magnetic stirrer at 80 C for 6 h. After complete dissolution, a clear solution was obtained by filtering the solution through 80-mesh molecular sieves. The solution was then left to cool to room temperature and to allow any bubbles to be lost. Subsequently, a catalytic quantity (1 g) of hydrochloric acid was added to the beaker, and the solution was stirred for 1 h. Then, 4, 6, or 8 g of TEOS was added, and the reaction mixture was stirred at room temperature for 24 h to allow the reaction of PVA with TEOS. The next day, the reaction mixture was filtered to remove the unreacted material, sonicated for 5 min, and, after 2 h, the mixture was cast using the amount of solution required to achieve the desired membrane thickness on a petri dish. The dish and solution were then dried in an oven (Memmert, UN55) at 25 C until the water was fully evaporated from the membrane. Thereafter, the membrane was placed in water to remove the unreacted TEOS and remaining catalyst. The obtained membranes are denoted PVA-TEOS (4), PVA-TEOS (6), and PVA-TEOS (8) depending on the amount of TEOS used. The addition of a larger amount of TEOS resulted in a brittle membrane, so the maximum amount of TEOS used was 8 g. For comparison a classical PVA–GA crosslinked membrane was also prepared using same PVA solution composition as previously described procedure [14]. Preparation of the L-L membrane The PVA-TEOS (4) membrane showed sufficient flexibility; thus, it was used to for layer-by-layer coating of PVAm and STA. Fig. 1a shows the PVAm and STA ex-situ polyelectrolyte complex that was prepared. Layer-by-layer deposition of PVAm and STA on the PVA-TEOS (4) membrane surface was achieved using the interfacial complexation method. Briefly, 0.01 M STA was prepared by dissolving 0.28 g of STA in 100 g of water. Similarly, a 0.5 wt. % PVAm solution was prepared by the dilution of a 10 wt. % PVAm solution with water. To deposit the PVAm layer on the PVA-TEOS (4) membrane, the 10 g solution of PVAm (0.5 wt.%) was poured onto the membrane and left for 5 min to allow the solution to be adsorbed on the membrane surface. Subsequently, the membrane surface was washed with deionized water (twice) and dried in an oven at 30 C. Then, the 0.01 M STA solution was poured onto the membrane, left for 5 min, and, then, washed with deionized (twice). The resultant membrane is denoted 1 L-L. Using the same method, different L-L membranes were prepared: 5 (L-L) and 10 (L-L). When more than 10 PVA-STA layers (beyond 10 L-L) were deposited on the membrane, cracking was observed, as shown in Fig. 1a. Thus, only the two L-L membranes were prepared. The average thickness of the membranes was determined using a digital thickness gauge (PosiTector 6000) and found to be 65–70 mm. The schematic diagram of membrane preparation process is as shown in Fig. 1b.
Fig. 3. FTIR spectra of the (a) pure STA, PVAm, PVAm-STA polyelectrolyte complex, (b) pristine PVA and PVA/TEOS (4) crosslinked membrane.
Characterization The pristine PVA and PVA-TEOS (4) films and PVAm and PVAm/STA polyelectrolyte complex were analyzed by attenuated total reflection (ATR)-FTIR spectroscopy (ATR mode FT-IR, Nicolet iS10, USA) between 400 and 4000 cm1. All spectra were recorded by accumulating 32 scans at 2 cm1 resolution frequency.
Fig. 4. TGA curves of pristine PVA and PVA-TEOS (4) membranes.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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Thermal degradation pattern and thermal stability of pristine PVA and PVA-TEOS membranes were studied by the thermogravimetric analysis (TGA) using the TA instrument (Perkin Elmer, USA, TGA 7). The membranes sample were subjected to heat from 25 to 600 C with the heating rate 10 C/min. The surface morphology of the PVA-TEOS (4) and 5 L-L PVA-TEOS (4) membranes were examined by FE-SEM (Vega II, Tescan, Czech Republic). The elemental composition of the PVA-TEOS (4) and 5 L-L PVA-TEOS (4) membranes were evaluated using EDS measurements. The platinum coating of all the specimens were done prior to analysis for adhering conductive film surface. The X-ray photo dispersive spectroscopy (XPS) analysis of the pristine PVA, PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes surfaces were performed by XPS instrument (Thermo VG Scientific (UK), Multilab 2000, Kratos- HP). A 250 W Al K/ monochromatic X- ray source was applied to provide a 500 mm X-ray spot on the membranes specimens. A 3 1010 mbar pressure was maintained in the analysis chamber. The 1.0 eV step and 160 eV pass energy were applied for survey scan of each specimens. Pervaporation apparatus and measurements The same pervaporation apparatus that was designed in our previous study used for PV experiments of ECH/IPA/water feed
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mixtures [44], the schematic diagram and real photograph of PV apparatus is as shown Fig. 2. Briefly, membrane cell containing the two compartment one connected to (upstream) feed side and other is joint with vacuum side (downstream). The membranes were placed in center of cell to divide the both compartment. At flow rate of 70 g min1 the feed mixture was continually pumped across the membrane surface. According to design of membrane cell the effective area of each tested membranes were 0.0019643 m2. The pressure on the permeate side was maintained (less than 10 mbar) by using vacuum pump (Edwards, RV8). To obtain the desired operating temperature for PV experiment, the feed solution tank with an outside water circulation jacket was maintained in different (30–50 C) temperature range. The cold liquefied nitrogen trap connected downstream side was used to collect the permeate solution and then weighed with electronic balance (Sartorius BA210S). Since permeate solution obtained from the PV test was very low for feed containing ECH/IPA/water (50/40/10, w/w, %) therefore, the experimental run time was prolonged up to the 20 h. Except that, PV run time for all other feed solutions was limited to 5 h. To ensure the accuracy of pervaporation results three successive measurements were performed and average value of the flux and separation factor with relative standard deviation less than 5 % were reported. The feed mixture solutions were used in an azeotropic composition of range of ECH, IPA, and water from
Fig. 5. Surface and cross-sectional FESEM and real images of all the membranes.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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Fig. 6. FE-SEM EDS spectra of PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes.
50:40:10 (wt. %) to 50:30:20 (wt. %). The permeate solutions were analyzed to determined exact composition of ECH, IPA and water using a gas chromatograph (DS Sci. DS7200) equipped with a Flame ionization detector (FID) detector. The Eqs. (1)–(3) were used to evaluate the membranes performance by calculating pervaporation flux, separation factor, flux of individual components for each membranes. M Flux ðJÞ ¼ A t
ð1Þ 2
1
Here, J is the permeation flux (kg m h ), M describe the mass of the permeated solution collected in the cold trap (kg) with respect to the effective area A (m2) over time t (h). In this study, the target component for removal is water (i.e., the dehydration of organics). Therefore, the separation factor (α) was calculated for water with respect to ECH and IPA in the ternary feed mixture system. Separation Factor ðaÞ ¼
PWater =PðIPAþECHÞ FWater =FðIPAþECHÞ
ð2Þ
Here, symbols Pwater, P(IPA+ECH), Fwater, and F(IPA+ECH) are defines the weight fractions of water and the ECH + IPA organic solution in feed solutions and permeate solution and, respectively. Flux of Individual component ðJiÞ ¼
Ji Pi 100
ð3Þ
Fig. 7. XPS spectra of PVA, PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes.
Here, Ji is the flux of component i (kg m2 h1), and Pi is the weight fraction of component i (ECH, IPA, or water) in the permeate solution (wt. %). Results and Discussion As described in the Experimental section, three PVA/TEOS membranes were prepared. These are labeled by the amount of TEOS (in grams) used in their preparation: PVA-TEOS (4), PVATEOS (6), and PVA-TEOS (8). The base membrane used for the layerby-layer modification was the PVA-TEOS (4) membrane. The modified membranes are labeled according to the number of added layers, for example, PVA-TEOS (4) (5 L-L), which was subjected to five layer-by-layer deposition cycles. Membrane characterization Fig. 3a shows the FTIR spectra of pure STA, PVAm, and the PVAm–STA polyelectrolyte complex. Bands between 700 and 1200 cm1 in the FTIR spectra of pure STA are characteristic of the Keggin structure [45], and these bands were also observed in the spectrum of the STA-PVAm polyelectrolyte complex. In the spectrum of PVAm, the broad band between 3100 and 3600 cm1 corresponds to the NH2 amine groups, and the strong bands at 1580 and 770 cm1 correspond to N-H bending and out-of-plane wagging vibrations of the amine groups, respectively. Additionally the band at 1650 cm1 can be attributed to the C¼O group, which might arise from remaining poly(vinyl formamide) (PVNF), which is used to prepare PVAm [41] The presence of bands corresponding to STA and PVAm and bands at 1510–1620 cm1, which are attributed to the NH3+ deformation [46], in the PVAm polyelectrolyte spectrum confirms the successful formation of the STA-PVAm complex by electrostatic interactions. PVA and TEOS crosslinking was also confirmed by FTIR analysis. As shown in the FTIR spectrum of the crosslinked membrane (PVATEOS (4) in Fig. 3b, there was an increase in the intensity of the band at 1000–1100 cm1, which corresponds to the Si O bonds in the PVA-TEOS (4) membrane. This confirms the presence of C O Si bonds formed by the condensation of the OH groups in PVA and ethoxide (OCH2 CH3) groups in TEOS. Additionally, the reduction in the intensity of the band around 3300 cm1, which corresponds to OH stretching, was also observed [17]. This reflects the consumption of hydroxyl groups in PVA. Therefore, the results of FTIR analysis indicated that the crosslinking of PVA and TEOS was successfully occurred. In order to evaluate the effects of TEOS on thermal stability of the PVA membranes was analyzed by TGA. The TGA curves for PVA and PVA-TEOS (4) membranes described in Fig. 4. From the results, it was clearly noticed that initial 5–10% of weight loss at
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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Fig. 8. Postulated reaction scheme for PVA-TEOS membrane surface with the PVAm and STA layer-layer deposition.
Fig. 9. Effect of TEOS content on the pervaporation flux and separation factor, at 30 C, Feed, ECH/IPA/water (50/30/20, w/w, %).
Fig. 10. Effect of layer by layer (PVAm/STA) on the flux and separation factor, at 30 C, Feed, ECH/IPA/water (50/30/20, w/w, %).
temperature range between 50 to 110 C was corresponding to the physically or bounded state water occurred for the PVA and PVATEOS (4) membranes. Despite of that the two different main non oxidative degradation step occurred for both of the membrane. For pristine PVA membrane, the first weigh loss of 70% at temperature 320 C due to PVA side chain elimination and second weight loss of 20% at 440 C was arises from the degradation from main chain was observed [47]. On other hand, the decomposition temperature of PVA-TEOS (4) membrane is shifted to the higher temperature (350 C) at the 1st stage compared to pristine PVA membrane indicating the higher thermal stability of PVA-TEOS (4) membrane in comparison to the pristine PVA membrane. The higher thermal stability of PVA-TEOS (4) membrane may resulted from the covalently bonded SiO in the PVA side chain. TGA study well support the explanation of crosslinking reaction of PVA-TEOS given in the FTIR studies. Fig. 5 shows the surface and cross-sectional field-emission scanning electron microscopy (FE-SEM) images of the unmodified (PVA-TEOS (0 L-L)) membrane and the membranes modified with PVAm/STA polyelectrolyte complex by layer-by-layer deposition (modified PVA-TEOS (4)). The surface images of all membranes show a smooth and continuous surface with no cracks or defects, even after the layer-by-layer deposition of the polyelectrolyte complex. From the cross-sectional images of the modified (5 (L-L) and 10 (L-L)) membranes, it was observed that the substrate (PVA-TEOS (4)) and the polyelectrolyte complex have a good compatibility and adhesion and, thus, form a uniform coating. This compatibility might originate from the hydrogen bonding of the hydroxyl and amine groups in the PVA and PVAm. The thicknesses of the polyelectrolyte complex layers on the membrane surfaces were approximately 200 and 400 nm for the 5 (L-L) and 10 (L-L) membranes, respectively. At higher magnification, FE-SEM energy dispersive spectroscopy (EDS) analysis was performed to determine the elemental composition after the layer-by-layer deposition on the membrane surface. Fig. 6 shows the FE-SEM EDS spectra of the 0 L-L and 5 L-L membranes. Signals corresponding to Si, W, and N were observed in the spectrum of the 5 L-L membrane, confirming the deposition of PVAm/STA on the PVA-TEOS (4) membrane surface. This is consistent with the FE-SEM images in Fig. 4. Additionally, the
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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Fig. 11. Effect of water content in the feed composition on flux and separation factor for membrane of PVA-TEOS (4) (5 L-L), at 30 C.
presence of a signal corresponding to Si in the 0 (L-L) membrane surfaces is indicative of bonding between TEOS and PVA, which is consistent with the FTIR analysis after the PVA-TEOS reaction. Fig. 7 depicts the survey of XPS spectra for pristine PVA, PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes. The pristine PVA membrane exhibited only two characteristics peaks at binding energy 285 eV and 532 eV those were assigned to C 1s (CH2) and O 1s (OH) for PVA polymer chain respectively [48]. On other hand, one additional peak at binding energy 103.8 eV which correspond to the Si 2P in the PVA-TEOS (4) membrane was observed with confirming the crosslinking reaction between the PVA and TEOS molecules. In XPS spectra of layer by layer PVAm and STA surface deposition on PVA-TEOS (4) membrane (PVA-TEOS (4) (5 L-L)), two additional peaks at binding energy 36 eV and 400.9 eV assigned to the hetero poly anion W 4f (W(VI) [49] and N 1s (NH3+) were observed [50]. Consequently, XPS analysis confirmed the successful deposition PVA-STA polyelectrolyte complexon the 0 L-L membrane surface and it is well agreed with results of SEM-EDS analysis. Based on the FTIR, FE-SEM, TGA, XPS and EDS measurements, a postulated reaction mechanism and membrane structure is shown in Fig. 8. Effect of TEOS content of pervaporation flux and separation factor
out using the prepared PVA-TEOS membranes. In addition, the pervaporation output was compared with that of a PVA– glutaraldehyde (PVA-GA) crosslinked membrane, which we have reported previously [14]. The results are shown in Fig. 9. All the PVA-TEOS membranes showed superior pervaporation performance compared to the PVA-GA membrane. As shown in Fig. 9, the flux value decreased from 0.14 to 0.05 kg m2 h1 and the separation factor increased from 2099 to 13,320 in the membrane with TEOS. An important factor that influences the pervaporation transport mechanism across the polymeric membranes is the sorption and diffusion of the components. Sorption depends on the specific interaction of the components with the membrane material [33] and, in pervaporation dehydration, the solubility of water in the membrane material depends on the hydrophilicity of the membrane. Interactions responsible for the association of water at the membrane surface are hydrogen bonding, polar interactions, and dispersion interactions [51]. Increasing the TEOS content reduces the hydrophilicity of the membrane by consuming the hydroxyl groups in the PVA. The hydrophobic character of the membrane is also increased by the formation of CO Si bonds at the surface of the PVA membrane. Therefore, the membrane flux decreased with increasing TEOS content. However, the addition of TEOS significantly decreases the mobility of the PVA chains and increases the density of the polymer, which are both preferable for selective water transport (lower size) because they restrict the permeation of larger molecules (ECH and IPA). Therefore, the separation factor was noticeably increased on the addition of TEOS. Overall, all the PVA-TEOS membranes showed superior pervaporation performance to the PVA-GA membrane, possibly because glutaraldehyde, which crosslinks the PVA chains [52], reduces the free volume of the polymer matrix by increasing the polymer compactness to a greater extent than TEOS. TEOS is a comparatively small molecule that reacts with hydroxyl groups in the same PVA chain in a pendant fashion [17], so PVA-TEOS could contain more transport pathways for the small water molecules than the PVA-GA membrane. Effect of layer-by-layer PVAm/STA treatment of the PVA-TEOS (4) membrane Fig. 10 shows the effects of layer-by-layer PVAm/STA treatment of the PVA-TEOS (4) membrane surface on the pervaporation flux and separation factor at 30 C for a ECH/
Pervaporation dehydration experiments with a feed mixture containing ECH/IPA/water (50/30/20, w/w, %) at 30 C were carried
Fig. 12. Effect of feed temperature on flux and separation factor for membrane of PVA-TEOS (4) (5 L-L), feed composition ECH/IPA/water (50/35/15, w/w, %).
Fig. 13. Variation of LnJwater, LnJIPA, LnJECH with temperature (K) using the PVA-TEOS (4) (5 L-L) membrane at ECH/IPA/water (55/35/15, w/w, %) feed composition.
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IPA/water (50/30/20, w/w, %) feed. The flux increased with increasing number of deposited surface layers: 0.14 to 0.28 kg m2 h1. However, the separation factor decreased from 2099 to 416. The increased flux after L-L deposition can be attributed to the formation of small hydrophilic meshes induced by the higher charge density of the polyelectrolyte layer, which favors the penetration of water [53]. However, because of the increase in hydrophilicity at the membrane surface, the swelling of the membrane surface also increased, thus promoting IPA/ECH absorption along with water absorption at the membrane surface. Consequently, the separation factor decreased. The (PVA-TEOS (4) (5 L-L) membrane exhibited the best performance of all surface-modified membranes; thus, it was used for further testing under a range of operating conditions. Effect of feed composition The effect of different feed compositions on the membrane (PVA-TEOS (4) (5 L-L)) performance were examined by reducing the water content in the ternary feed mixture. Fig. 11 shows the effect of water content in the feed on the flux and separation factor at 30 C. Fig. 11 shows that the pervaporation flux decreased as the water content decreased from 20 to 10 wt. %, from 0.22 to 0.0066 kg m2 h1 and the separation factor abruptly increased from 1061 to 9094. According to the solution diffusion model, a well-accepted mechanism for pervaporation transport through membranes [32,33], a higher content of the preferential component on the feed side results in a higher driving force, dissolution, and, consequently, diffusion of this component across the membrane. Therefore, increasing the water content in the feed, resulted in an increase in membrane surface wetting. As a result, the membrane became more swollen, resulting in easier transport of the permeants across the membrane. Hence, the flux increased and the separation factor decreased.
9
Effect of temperature The effect of operating temperature on the membrane was examined at 30 to 50 C with fixed ECH/IPA/water feed composition (55/35/15, (w/w, %)). The results are shown in Fig. 12. As the feed temperature increased from 30 to 50 C, the flux increased from 0.07 to 0.19 kg m2 h1, respectively, whereas the separation factor decreased from 7991 to 1729, respectively. The individual fluxes of water, IPA, and ECH were calculated by using Eq. (3). The Arrhenius equation can be used to express the temperaturedependent permeation flux, is as shown in Eq. (4) [10]. Flux (Ji) = Ap. eEp/RT 2
(4)
1
Here, Ji (kg m h ) is the flux of component i, either ECH, IPA, or water; T (K) is the absolute temperature; R (J mol1 K1) is the universal gas constant; and Ap (kg m2 h1) and Ep (kJ mol1), are the pre-exponential factor and the apparent activation energy for permeation, respectively. A plot of the natural logarithmic of the individual fluxes of ECH, IPA, and water over the studied temperature range is shown in Fig. 13. From the slope of the linear fitting regression line, the apparent activation energies (Ea) for the permeation of ECH, IPA, and water were calculated. The apparent activation energies for the permeation of ECH (97.42 kJ mol1) and IPA (111.96 kJ mol1) were calculated. Both of these values are higher than that of water (40.88 kJ mol1) was observed. The results reveal that the permeation of water was easier than those of ECH and IPA. Interestingly, although IPA is larger than ECH, the permeation Ea for IPA was marginally higher that of the ECH. This could be because, in pervaporation transportation through a hydrophilic membrane, the preferential component (water) interacts with the membrane via hydrogen bonding, dipole–dipole, and ion–dipole interactions [51], and ECH is more polar (dipole moment = 1.80 D) than isopropanol (dipole moment = 1.58 D). Thus, because of the dipole–dipole interactions of ECH molecules with the surface modified membrane, the ECH molecules might undergo
Fig. 14. Stability study of PVAm-STA complex.
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Fig. 15. Stability evaluation of PVA-TEOS (4) (5 L-L) membrane in terms of pervaporation test (Feed composition; ECH/IPA/water (50/30/20 w/w, %) at 30 C).
operation time, the water content in permeate dropped to 96.23%, then there was no major deviation (water content >96 wt. %) until 168 h was observed. This deviation can be attributed to conditioning and relaxation effects which are commonly observed in PVA based membranes [54,55]. The pervaporation data for the PVA-TEOS (4) (5 L-L) membrane indicated that, well stability of PVAm/ STA polyelectrolyte complex on the membrane surface with remarkable pervaporation performance over long operating periods was observed. FE-SEM analysis was performed to observe the state of the PVAm/STA polyelectrolyte layer on the PVA-TEO (4) membrane surface after long-term pervaporation tests, as shown in Fig. 16. As expected, the PVAm/STA layer was stable after contact with the ECH-containing feed mixture. Even after the long-term pervaporation experiments, the PVAm/STA polyelectrolyte remained on the surface of PVA-TEO (4) membrane, thus confirming the stability of polyelectrolyte layer at the membrane surface. Conclusion
Fig. 16. FE-SEM images of PVA-TEOS (4) (5 L-L) membrane cross-section after long term pervaporation test (Feed composition; ECH/IPA/water (50/30/20 w/w, %) at 30 C).
pervaporation transport through the membrane more easily than IPA [14]. Additionally, the higher content of ECH in the feed composition (50 wt. %) increases the driving force in the feed boundary layer for absorption on the feed side of the membrane [33]. Stability of PVAm/STA polyelectrolyte complex and stability of polyelectrolyte complex layer coated on the PVA-TEOS (4) membrane surface The PVAm/STA complex was crosslinked by ionic interactions; thus, we investigated the stability of the PVAm/STA complex in the ECH/IPA/water (50/30/20, w/w, %) feed. An ex situ prepared PVAm/ STA complex was dispersed in the feed solution and heated for 3 days at 60 C. Every 24 h, the solution was sonicated for 30 min. After immersion at 60 C for several days, no dissolution of the PVAm/STA polyelectrolyte complex was observed as shown in Fig. 14. Therefore, the PVAm/STA polyelectrolyte complex is stable in the ECH-containing feed solution was confirmed. Fig. 15 shows long term stability of surface-modified PVA-TEOS (4) (5 L-L) membrane. Fig. 15 reflect that, after pervaporation tests at 30 C using an ECH/IPA/water (50/30/20, w/w. %)) feed, with increasing operating time, the flux only increased marginally, thereafter remaining constant. On other hand, after 24 h of
Two different membranes were prepared: PVA/TEOS and a PVA/ TEOS membrane layer-by-layer modified with PVAm and STA. Membranes characterization was performed by using FTIR, FE-SEM, TGA, XPS and SEM-EDS measurements. Pervaporation tests were performed using membranes with different PVA/TEOS ratios (wt.%). For a feed containing ECH/IPA/water (50/30/20, w/w, %) at 30 C, the pervaporation flux decreased from 0.14 to 0.05 kg m2 h1 and the separation factor increased from 2099 to 13,320 with increasing TEOS content was obtained. Pervaporation tests were also performed using the PVA/TEOS (4) membrane surface modified with PVAm/STA polyelectrolyte complex. For a feed containing ECH/IPA/water (50/30/20, w/w, %) at 30 C, the pervaporation flux increased from 0.14 to 0.28 kg m2 h1 and the separation factor decreased from 2099 to 416 with increasing number of L-L layers was reported. The stability of the PVAm/STA polyelectrolyte complex was examined in a feed containing ECH/IPA/water (50/30/20, w/w, %) at 60 C. The PVAm/STA polyelectrolyte complex remained stable in the feed for 72 h. Additionally, the long-term stability of PVAm/STA polyelectrolyte complex layer on the PVA-TEO (4) membrane surface was confirmed by operating the long term pervaporation tests at 30 C using a ECH/IPA/ water (50/30/20, w/w, %) feed. The PVAm/STA polyelectrolyte layer was retained on the surface, even after 168 h. The effects of the feed composition and feed temperature on the pervaporation performance of the PVA/TEOS (4) 5 (L-L) membrane were determined. The flux increased and separation factor decreased with increasing water content in the feed (ECH/IPA/water) and increasing feed temperature (30–50 C) was obtained. Overall, the pervaporation output of the PVATEOS and layer by layer PVA-TEOS membranes reflected that both membranes have excellent ability in epichlorohydrin, isopropanol and water ternary mixture pervaporation dehydration. Acknowledgement This work was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry and Energy, Republic of Korea (No. 20172010106170). References [1] G. Jungang, J. Appl. Polym. Sci. 48 (1993) 237, doi:http://dx.doi.org/10.1002/ app.1993.070480208. [2] C. Chang, W. Lee, J. Appl. Polym. Sci. 116 (2010) 2065, doi:http://dx.doi.org/ 10.1002/app.31703. [3] B. Hirakawa, Epichlorohydrin, Encyclopedia Toxic, Third Edition), (2014), pp. 431, doi:http://dx.doi.org/10.1016/B978-0-12-386454-3.00019-1.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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S. Chaudhari et al. / Journal of Industrial and Engineering Chemistry xxx (2019) xxx–xxx [4] P. Wester, C. Heijden, A. Bisschop, G. Esch, Toxicology 36 (1985) 325, doi:http:// dx.doi.org/10.1016/0300-483X(85)90034-4. [5] W. Raza, J. Lee, N. Raza, Y. Luo, K. Kim, J. Yang, J. Ind. Eng. Chem. 71 (2019) 1, doi: http://dx.doi.org/10.1016/j.jiec.2018.11.024. [6] M. Amirilargani, B. Sadatnia, J. Membr. Sci. 469 (2014) 1, doi:http://dx.doi.org/ 10.1016/j.memsci.2014.06.034. [7] H. Zhang, Y. Wang, AICHE J. 62 (2016) 1728, doi:http://dx.doi.org/10.1002/ aic.15140. [8] A. Penkova, S. Acquah, M. Dmitrenko, M. Sokolova, M. Mikhailova, E. Polyakov, S. Ermakov, D. Markelov, D. Roizard, Mater. Des. 96 (2016) 416, doi:http://dx. doi.org/10.1016/j.matdes.2016.02.046. [9] L. Xia, C. Li, Y. Wang, J. Membr. Sci. 498 (2016) 263, doi:http://dx.doi.org/ 10.1016/j.memsci.2015.10.025. [10] L. Liu, S.E. Kentish, J. Membr. Sci. 553 (2018) 63, doi:http://dx.doi.org/10.1016/j. memsci.2018.02.021. [11] F. Kursun, N. Isiklan, J. Ind. Eng. Chem. 25 (2016) 91, doi:http://dx.doi.org/ 10.1016/j.jiec.2016.07.011. [12] M. Pedram, M. Omidkhah, A. Amooghin, J. Ind. Eng. Chem. 20 (2014) 74, doi: http://dx.doi.org/10.1016/j.jiec.2013.04.024. [13] A. Sajjan, B.K. Kumar, A.A. Kittur, M.Y. Kariduraganavar, J. Ind. Eng. Chem. 19 (2013) 427, doi:http://dx.doi.org/10.1016/j.jiec.2012.08.032. [14] S. Chaudhari, Y. Kwon, M. Shon, S. Nam, Y. Park, RSC Adv. 9 (2019) 5908, doi: http://dx.doi.org/10.1039/C8RA07136E. [15] Z. Xie, M. Hoang, D. Ng, C. Doherty, A. Hill, S. Gray, Sep. Purif. Technol. 127 (2014) 10, doi:http://dx.doi.org/10.1016/j.seppur.2014.02.025. [16] P. Das, S.K. Ray, S.B. Kuila, H.S. Samanta, N.R. Singha, Sep. Purif. Technol. 81 (2011) 159, doi:http://dx.doi.org/10.1016/j.seppur.2011.07.020. [17] M.Y. Kariduraganavar, S.S. Kulkarni, A.A. Kittur, J. Membr. Sci. 246 (2005) 83, doi:http://dx.doi.org/10.1016/j.memsci.2004.09.001. [18] L. Ye. Q. Lin, Q. Zhang, A. Zhu, G. Zhou, J. Appl. Polym. Sci. 105 (2007) 3640, doi: http://dx.doi.org/10.1002/app.26446. [19] J. Chen, M. Liu, Q. Huang, L. Huang, H. Huang, F. Deng, Y. Wen, J. Tian, X. Zhang, Y. Wei, Chem. Eng. J. 337 (2018) 82, doi:http://dx.doi.org/10.1016/j.cej.2017.12.085. [20] Y. Liu, K. Ai, L. Lu, Chem. Rev. 114 (2014) 5057, doi:http://dx.doi.org/10.1021/ cr400407a. [21] X. Zhang, Q. Huang, F. Deng, H. Huang, Q. Wan, M. Liu, Appl. Mater. Tod. 7 (2017) 222, doi:http://dx.doi.org/10.1016/j.apmt.2017.04.001. [22] G. Zeng, L. Huang, Q. Huang, M. Liu, D. Xu, H. Huang, Z. Yang, F. Deng, X. Zhang, Y. Wei, Surf. Sci. 459 (2018) 588, doi:http://dx.doi.org/10.1016/j.apsusc.2018.07.144. [23] L. Huang, M. Liu, H. Huang, Y. Wen, X. Zhang, Y. Wei, Biomacromolecules 19 (2018) 1858, doi:http://dx.doi.org/10.1021/acs.biomac.8b00437. [24] M. Liu, G. Zeng, K. Wang, Q. Wan, L. Tao, X. Zhang, Y. Wei, Nanoscale 8 (2016) 16819, doi:http://dx.doi.org/10.1039/C5NR09078D. [25] Q. Huang, M. Liu, L. Mao, D. Xu, G. Zeng, H. Huang, R. Jiang, F. Deng, X. Zhang, Y. Wei, J. Coll. Inter. Sci. 499 (2017) 170, doi:http://dx.doi.org/10.1016/j.jcis.2017.03.102. [26] X. Zhang, Q. Huang, M. Liu, J. Tian, G. Zeng, Z. Li, Q. Zhang, Q. Wan, F. Deng, Y. Wei, Appl. Surf. Sci. 343 (2015) 19, doi:http://dx.doi.org/10.1016/j.apsusc.2015.03.081. [27] M. Liu, J. Ji, X. Zhang, X. Zhang, B. Yang, F. Deng, Z. Li, K. Wang, Y. Yang, Y. Wei, J. Mater. Chem. B 3 (2015) 3476, doi:http://dx.doi.org/10.1039/C4TB02067G. [28] Y. Shi, R. Jiang, M. Liu, L. Fu, G. Zeng, Q. Wan, L. Mao, F. Deng, X. Zhang, Y. Wei, Mater. Sci. Eng. C 77 (2017) 972, doi:http://dx.doi.org/10.1016/j.msec.2017.04.033. [29] Y. Shi, M. Liu, F. Deng, G. Zeng, Q. Wan, X. Zhang, Y. Wei, J. Mater. Chem. B 5 (2017) 194, doi:http://dx.doi.org/10.1039/C6TB02249A.
11
[30] Q. Huang, M. Liu, J. Chen, Q. Wan, J. Tian, L. Huang, R. Jiang, X. Wen, X. Zhang, Y. Wei, Appl. Surf. Sci. 419 (2017) 35, doi:http://dx.doi.org/10.1016/j.apsusc.2017.05.006. [31] Y. Cao, X. Zhang, L. Tao, K. Li, Z. Xue, L. Feng, Y. Wei, Appl. Mater. Inter. 5 (2013) 4438, doi:http://dx.doi.org/10.1021/am4008598. [32] J.G. Wiljmans, R.W. Baker, J. Membr. Sci. 107 (1995) 1, doi:http://dx.doi.org/ 10.1016/0376-7388(95)00102-I. [33] P. Shao, R.Y.M. Huang, J. Membr. Sci. 287 (2007) 162, doi:http://dx.doi.org/ 10.1016/j.memsci.2006.10.043. [34] V. Freger, E. Korin, J. Wisniak, E. Korngold, J. Membr. Sci. 164 (2000) 251, doi: http://dx.doi.org/10.1016/S0376-7388(99)00198-2. [35] Q. Zhao, Q. An, Y. Ji, J. Qian, C. Gao, J. Membr. Sci. 379 (2011) 19, doi:http://dx. doi.org/10.1016/j.memsci.2011.06.016. [36] S. Kononova, E. Kruchnina, V. Petrova, Y. Bakilagina, V. Klechkovskaya, A. Orekhov, E. Vlasova, E. Popova, G. Gubunova, Y. Skorik, Carbohy. Polym. 209 (2019) 10, doi:http://dx.doi.org/10.1016/j.carbpol.2019.01.003. [37] J. Li, X. Si, X. Li, N. Wang, Q. An, S. Ji, Sep. Purif. Technol. 192 (2018) 205, doi: http://dx.doi.org/10.1016/j.seppur.2017.09.038. [38] M. Dmitrenko, A. Penkova, A. Kuzminova, M. Morshed, M. Larionov, H. Alem, A. Zolotarev, S. Ermakov, D. Roizard, Appl. Surf. Sci. 450 (2018) 527, doi:http://dx. doi.org/10.1016/j.apsusc.2018.04.169. [39] Z. Tong, X. Liu, B. Zhang, J. Membr. Sci. 575 (2019) 9, doi:http://dx.doi.org/ 10.1016/j.memsci.2019.01.001. [40] D. Achari, P. Rachipudi, S. Naik, R. Karuppannan, M.Y. Kariduraganavar, J. Ind. Eng. Chem. (2019), doi:http://dx.doi.org/10.1016/j.jiec.2019.05.031. [41] R. Pelton, Langmuir 30 (2014) 15373, doi:http://dx.doi.org/10.1021/la5017214. [42] S. Chaudhari, Y. Kwon, M. Moon, M. Shon, S. Nam, Y. Park, J. Appl. Polym. Sci. 134 (2017) 45572, doi:http://dx.doi.org/10.1002/app.45572. [43] Z. Cui, Xing Wei, C. Liu, J. Liao, H. Zhang, J. Power Sources 188 (2009) 24, doi: http://dx.doi.org/10.1016/j.jpowsour.2008.11.108. [44] S. Chaudhari, Y. Kwon, M. Moon, M. Shon, S. Nam, Y. Park, Vacuum 147 (2018) 115, doi:http://dx.doi.org/10.1016/j.vacuum.2017.10.024. [45] A.H. Jadhav, H. Kim, RSC Adv. 3 (2013) 5131, doi:http://dx.doi.org/10.1039/ C3RA22663H. [46] M. Llusar, G. Monros, Cecile Roux, J. Pozzo, C. Sanchez, J. Mater. Chem. 13 (2003) 2505, doi:http://dx.doi.org/10.1039/B304479N. [47] R. Bryaskova, N. Georgieva, T. Andreeva, R. Tzoneva, Surf. Coat. Technol. 235 (2013) 186, doi:http://dx.doi.org/10.1016/j.surfcoat.2013.07.032. [48] H. Pingan, J. Mengjun, Z. Yanyan, H. Ling, RSC Adv. 7 (2017) 2450, doi:http://dx. doi.org/10.1039/C6RA25579E. [49] V. Kumar, I. Pulidindi, A. Gendanken, Renewable Energy 78 (2015) 141, doi: http://dx.doi.org/10.1016/j.renene.2014.12.070. [50] A. Wach, M. Drozdek, B. Dudek, E. Szneler, P. Kustrowski, Catal. Commun. 64 (2015) 52, doi:http://dx.doi.org/10.1016/j.catcom.2015.02.002. [51] S. Semenova, H. Ohya, K. Soontarapa, Desalination 110 (1997) 251, doi:http:// dx.doi.org/10.1016/S0011-9164(97)00103-3. [52] C. Yeom, K. Lee, J. Membr. Sci. 109 (1996) 257, doi:http://dx.doi.org/10.1016/ 0376-7388(95)00196-4. [53] B. Tieke, F. Ackern, L. Krasemann, A. Toutianoush, Eur. Phys. J. 5 (2001) 29, doi: http://dx.doi.org/10.1007/s101890170084. [54] Z. Huang, Y. Shi, R. Wen, Y. Guo, J. Su, T. Matsurra, Sep. Purif. Technol. 51 (2) (2006) 126, doi:http://dx.doi.org/10.1016/j.seppur.2006.01.005. [55] E. Otsuka, A. Suzuki, Prog. Coll. Polym. Sci. 136 (2009) 121, doi:http://dx.doi. org/10.1007/978-3-642-00865-8_17.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
Journal of Industrial and Engineering Chemistry xxx (2019) xxx–xxx
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Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures Shivshankar Chaudharia , YongSung Kwona , MinYoung Shona,* , SeungEun Namb , YouIn Parkb a b
Department of Industrial Chemistry, Pukyong National University, San 100, Yongdang-Dong, Nam-Gu, Busan 608-739, South Korea Center for membranes, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon 305-600, South Korea
A R T I C L E I N F O
A B S T R A C T
Article history: Received 13 June 2019 Received in revised form 29 July 2019 Accepted 1 September 2019 Available online xxx
Conventional distillation failed to separate a ternary azeotropic mixture of ECH, IPA and water (50/30/ 20 w/w, %) exist in the epoxy resin manufacturing process. Thus, we prepared a PVA-tetraethyl orthosilicate organic–inorganic hybrid membrane and modified the membrane by layer-by-layer deposition of a PVAm/silicotungstic acid polyelectrolyte for the pervaporation (PV) dehydration of ECH/ IPA/water mixtures. In PV experiments at 30 C, the flux decreased from 0.14 to 0.05 kg m2 h1 and separation factor increased from and 2099 to 13,320 with TEOS addition in the PVA membrane was observed. And for the layer by layer deposition on PVA-TEOS (4) membranes flux increased and separation factor decreased from 0.14 to 0.28 kg m2 h1 and 2099 to 416 with the number of layer of deposition were observed respectively. On varying the feed water content from 20 to 10 wt. %, the pervaporation flux at 30 C decreased from 0.22 to 0.0066 kg m2 h1 and the separation factor increased from 1061 to 9094 was observed. By applying the Arrhenius equation, permeation activation energies of ECH and IPA (97.42 and 111.96 kJ mol-1, respectively) are higher than that of water (40.88 kJ mol1) were reported for the layer by layer membrane. © 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Keywords: Pervaporation Surface modification Poly (vinyl alcohol) (PVA) (PVAm) Epichlorohydrin Poly (vinyl amine) Silicotungstic acid (STA)
Introduction Epichlorohydrin (ECH) is made up of organochlorine moieties and epoxide ring, is an extremely susceptible electrophilic compound primarily employed in the manufacturing of epoxy resins, plastics and glycerol [1,2]. The polymerization of ECH with phenol gives an epoxy resin product. The bisphenol-A (BPA) and isopropyl alcohol (IPA) is served as the solvent and excess of ECH is charge in the reaction batch to adjust the molecular weight of the finished epoxy resin yield. In the final stages of reaction; a chlorine-containing impurities and ECH/IPA/water mixture as byproducts are present along with the finished product epoxy resin. A vacuum distillation can be used to recover the ECH and IPA and again recycled in the form of raw materials. However, during the recycling; the impurity content concentrate gradually in the byproduct mixture. This is because, ECH and IPA exhibit an azeotropic mixture with water at ECH/IPA/water, 50:30:20 (wt. %)
* Corresponding author. E-mail address: [email protected] (M. Shon).
composition; in the recovery of IPA and ECH by vacuum distillation that restrict the recovery process to purify an IPA and ECH at desired purity level. In addition not only point of energy consumption and reuse of recycled materials concern, but ECH can also have serious environmental hazards if it released as waste in environment, because ECH is carcinogenic compound [3,4]. Adsorption method can be used to dehydrate the ECH/IPA/water, 50:30:20 (wt. %) azeotropic composition, however the adsorption of water from the mixture demands a high capacity adsorption bed depending on epoxy resin production process, 0.6 ton of ECH/IPA/ water mixture generated per 1 ton of epoxy resin production. Additionally, frequent regeneration of adsorption bed was required to remove the contaminants through series of different step, that may further increase the operation cost of epoxy resin production process [5]. On other hand, PV-distillation is a hybrid process consist of synergy between the feature of pervaporation (PV) and distillation process individually. PV can successfully remove the moisture from recovery mixture and by the distillation, recovery and purification of ECH and IPA can be increase energy efficiency and competitiveness of product. By this approach the costs associated with the
https://doi.org/10.1016/j.jiec.2019.09.007 1226-086X/© 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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epoxy resin manufacturing process can be easily reduced in the green way. However, to treat the highly reactive epichlorohydrincontaining feed mixture, the membrane material must have excellent chemical and mechanical stability and good thermal properties. Poly(vinyl alcohol) (PVA) has consistently been shown to be an excellent membrane material with good membrane forming properties and robustness and chemical stability in organic solvents [6–13]. In our last report we used a PVA/poly(vinyl amine) (PVAm) blended membrane for the dehydration of azeotropic ECH/IPA/water mixtures (50/30/20 (w/w, %)), and the
PVA membrane was found to have remarkable pervaporation stability along with good pervaporation performance [14]. However, by the survey of literature it has been observed that in the water based feed system, the pristine PVA membranes undergo high amount of swelling. Thus; the several methods such as crosslinking of PVA chain with chemical agent, blending with different polymers, polymer grafting, and thermal treatment have used to compensate the excessive PVA membrane swelling. Among these methods, inorganic–organic crosslinking of PVA with tetraethyl orthosilicate (TEOS) as an inorganic crosslinking agent has been shown to yield membranes with remarkable stability. The
Fig. 1. (a) The real photographs of PVAm/STA polyelectrolyte complex and PVA-TEOS (4) (15 L-L) membrane (b) Schematic diagram of membrane preparation process.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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main advantages of the PVA-TEOS crosslinking reaction is that it takes place at relatively mild temperatures, and covalent bonding between the silicon-based inorganic compound and the organic polymer is facile, producing a membrane material having excellent mechanical stability that can resist most organic solvents used in pervaporation [15]. However, the introduction of a hydrophobic inorganic compound (TEOS) to the PVA reduces the membrane hydrophilicity and, thus, reduces the permeation rate of the membrane. This phenomenon has been reported in the literature for PVA/TEOS hybrid membranes used for the pervaporation dehydration of isopropanol and acetic acid [16–18]. One promising method to ameliorate this difficulty is the functionalization of the PVA membrane surface. Recently, surface initiated polymerization for surface modification with fluorescent nanodiamonds has been investigated for cell imaging application [19]. Based on mussel inspired chemistry, polydopamine structure is emerge as promising surface functionalization material for all kind of surface regardless to their material chemistry [20–22]. Which was found a numerous application in various field such as drug delivery [23,24], water treatment [25,26], Bio imaging, [27,28], tissue engineering, cell adhesion [20], encapsulation and patterning [20,29] and the treatment of water including separation of organic pollutant, bacteria and heavy metal from water [30]. Cao et al. studied the coating of membrane surface through the polydopamine based mussel inspired chemistry and they found it was very efficient and membrane was easily cleaned for separation of water from the oil [31]. They have also reported that, it is an important method rely on the non-covalent self-assembly and covalent self-polymerization through which can form a strong covalent and non-covalent interaction with the all type of organic or inorganic substrates. However, although the above techniques showed very promising and convincing results in the field of surface coating for the verities of substrates, the thickness of film on surface is limited up to the 50 nm in single reaction and can occur only in the acidic condition in the presence of specific oxidants. Additionally, not only these modification methods exhibit in the complex experimental procedure but also the cost associated with material is an issue. For that reason, polyelectrolyte complex deposition in the form of nanoscale layer on the surface of the PVA membrane was conducted. Such layer deposition charge the film surface, giving it an immense hydrophilic character and, with result of that, a high affinity for water. Furthermore, when in contact with water; a moderate swelling of the membrane occurred due to the formation of compact electrostatic layer. According to the solution diffusion model, mass transport across the pervaporation membrane occurs
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via through solution sorption and the diffusion and desorption of permeants in the pervaporation process [32,33]. It is well known that sorption plays key role in determining the selectivity of the membranes toward a particular feed system [34]. Thus, surface functionalization by polyelectrolyte deposition on the PVA/TEOS hybrid membrane surface can significantly enhance the water sorption on the upstream side of the membrane. Polyelectrolyte complexes are produced by the electrostatic interaction of polyelectrolyte polycation and polyanions [35]. There are several different polyelectrolyte pairs, for example, chitosan/sodium hyaluronate, poly(allyl amine hydrochloride / poly(sodium 4-styrene sulfonate), sodium alginate/polyethyleneimine, chitosan/polystyrene sulfonic acid-co-maleic acid and sodium carboxymethyl cellulose/poly(diallydimethyl ammonium chloride), and these have been used for the fabrication of pervaporation dehydration membranes [36–39,40]. PVAm has a primary amine group in the polymer backbone and is positively charged in aqueous media [41,42]. Silicotungstic acid is a heteropoly acid is a kind of acid comprised of a distinct combination of oxygen and hydrogen with fixed metals [M] and non-metals [X]. Silicotungstic acid is based on Keggin units and has a polyanionic structure ([XM12O40]n) with a three-dimensional combination of hetero polyanions consist of four acidic hydrogen atoms [43]. In aqueous solution, the STA polyanion forms a stable polyelectrolyte complex with the PVAm. In this study, we prepared PVA/TEOS inorganic–organic hybrid membranes, as well as PVA/TEOS membrane modified bylayer-by-layer (L-L) coating with PVAm/STA by interfacial complexation, because the pervaporation properties of membranes are strongly influenced by this type of modification. The nanoscale layer of polyelectrolyte on the membrane surface can increase the hydrophilicity of the membrane surface, resulting in an increase in the transport properties of the membrane. Subsequently, the pervaporation dehydration of a ternary ECH/IPA/water mixture was carried out under diverse operating conditions. Experimental section Materials Tetraethyl orthosilicate was obtained from Sigma–Aldrich Co. (China). Silicotungstic acid hydrate [H4 (Si (W3O10)10)4] nH2O was reserved from Sigma–Aldrich (USA). Poly (vinyl alcohol) having a 98–99% degree of hydrolysis (molecular weight of 88,000–97,000) was procured from Alfa Aesar (USA). ECH, Isopropyl alcohol (99.5 wt. %) were purchased from Dae-Jung Chemicals & Metal
Fig. 2. (A) Schematic diagram of pervaporation apparatus: (a) water bath (b) feed tank (c) temperature indicator (d) circulation pump (e) membrane cell, (f) vacuum gauge (g), (h) cold trap + liquid nitrogen (i) vacuum pump, (B) Real photographs of pervaporation apparatus.
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Co., Korea. Readymade 10 wt. % solution of Poly (vinyl amine) was supplied by BASF Co. Indonesia having a brand name Lupamin-9095 (Mw 340000,). Desired feed solutions for pervaporation run were made by mixing predetermined quantities of ECH/IPA/Water (w/w, %) in the laboratory. The deionized water (Puris, Expe-RO EDI water system) was used for study. Preparation of PVA/TEOS membranes First, 4 g PVA powder was dissolved in 96 g of water in a beaker with continuous stirring using a magnetic stirrer at 80 C for 6 h. After complete dissolution, a clear solution was obtained by filtering the solution through 80-mesh molecular sieves. The solution was then left to cool to room temperature and to allow any bubbles to be lost. Subsequently, a catalytic quantity (1 g) of hydrochloric acid was added to the beaker, and the solution was stirred for 1 h. Then, 4, 6, or 8 g of TEOS was added, and the reaction mixture was stirred at room temperature for 24 h to allow the reaction of PVA with TEOS. The next day, the reaction mixture was filtered to remove the unreacted material, sonicated for 5 min, and, after 2 h, the mixture was cast using the amount of solution required to achieve the desired membrane thickness on a petri dish. The dish and solution were then dried in an oven (Memmert, UN55) at 25 C until the water was fully evaporated from the membrane. Thereafter, the membrane was placed in water to remove the unreacted TEOS and remaining catalyst. The obtained membranes are denoted PVA-TEOS (4), PVA-TEOS (6), and PVA-TEOS (8) depending on the amount of TEOS used. The addition of a larger amount of TEOS resulted in a brittle membrane, so the maximum amount of TEOS used was 8 g. For comparison a classical PVA–GA crosslinked membrane was also prepared using same PVA solution composition as previously described procedure [14]. Preparation of the L-L membrane The PVA-TEOS (4) membrane showed sufficient flexibility; thus, it was used to for layer-by-layer coating of PVAm and STA. Fig. 1a shows the PVAm and STA ex-situ polyelectrolyte complex that was prepared. Layer-by-layer deposition of PVAm and STA on the PVA-TEOS (4) membrane surface was achieved using the interfacial complexation method. Briefly, 0.01 M STA was prepared by dissolving 0.28 g of STA in 100 g of water. Similarly, a 0.5 wt. % PVAm solution was prepared by the dilution of a 10 wt. % PVAm solution with water. To deposit the PVAm layer on the PVA-TEOS (4) membrane, the 10 g solution of PVAm (0.5 wt.%) was poured onto the membrane and left for 5 min to allow the solution to be adsorbed on the membrane surface. Subsequently, the membrane surface was washed with deionized water (twice) and dried in an oven at 30 C. Then, the 0.01 M STA solution was poured onto the membrane, left for 5 min, and, then, washed with deionized (twice). The resultant membrane is denoted 1 L-L. Using the same method, different L-L membranes were prepared: 5 (L-L) and 10 (L-L). When more than 10 PVA-STA layers (beyond 10 L-L) were deposited on the membrane, cracking was observed, as shown in Fig. 1a. Thus, only the two L-L membranes were prepared. The average thickness of the membranes was determined using a digital thickness gauge (PosiTector 6000) and found to be 65–70 mm. The schematic diagram of membrane preparation process is as shown in Fig. 1b.
Fig. 3. FTIR spectra of the (a) pure STA, PVAm, PVAm-STA polyelectrolyte complex, (b) pristine PVA and PVA/TEOS (4) crosslinked membrane.
Characterization The pristine PVA and PVA-TEOS (4) films and PVAm and PVAm/STA polyelectrolyte complex were analyzed by attenuated total reflection (ATR)-FTIR spectroscopy (ATR mode FT-IR, Nicolet iS10, USA) between 400 and 4000 cm1. All spectra were recorded by accumulating 32 scans at 2 cm1 resolution frequency.
Fig. 4. TGA curves of pristine PVA and PVA-TEOS (4) membranes.
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Thermal degradation pattern and thermal stability of pristine PVA and PVA-TEOS membranes were studied by the thermogravimetric analysis (TGA) using the TA instrument (Perkin Elmer, USA, TGA 7). The membranes sample were subjected to heat from 25 to 600 C with the heating rate 10 C/min. The surface morphology of the PVA-TEOS (4) and 5 L-L PVA-TEOS (4) membranes were examined by FE-SEM (Vega II, Tescan, Czech Republic). The elemental composition of the PVA-TEOS (4) and 5 L-L PVA-TEOS (4) membranes were evaluated using EDS measurements. The platinum coating of all the specimens were done prior to analysis for adhering conductive film surface. The X-ray photo dispersive spectroscopy (XPS) analysis of the pristine PVA, PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes surfaces were performed by XPS instrument (Thermo VG Scientific (UK), Multilab 2000, Kratos- HP). A 250 W Al K/ monochromatic X- ray source was applied to provide a 500 mm X-ray spot on the membranes specimens. A 3 1010 mbar pressure was maintained in the analysis chamber. The 1.0 eV step and 160 eV pass energy were applied for survey scan of each specimens. Pervaporation apparatus and measurements The same pervaporation apparatus that was designed in our previous study used for PV experiments of ECH/IPA/water feed
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mixtures [44], the schematic diagram and real photograph of PV apparatus is as shown Fig. 2. Briefly, membrane cell containing the two compartment one connected to (upstream) feed side and other is joint with vacuum side (downstream). The membranes were placed in center of cell to divide the both compartment. At flow rate of 70 g min1 the feed mixture was continually pumped across the membrane surface. According to design of membrane cell the effective area of each tested membranes were 0.0019643 m2. The pressure on the permeate side was maintained (less than 10 mbar) by using vacuum pump (Edwards, RV8). To obtain the desired operating temperature for PV experiment, the feed solution tank with an outside water circulation jacket was maintained in different (30–50 C) temperature range. The cold liquefied nitrogen trap connected downstream side was used to collect the permeate solution and then weighed with electronic balance (Sartorius BA210S). Since permeate solution obtained from the PV test was very low for feed containing ECH/IPA/water (50/40/10, w/w, %) therefore, the experimental run time was prolonged up to the 20 h. Except that, PV run time for all other feed solutions was limited to 5 h. To ensure the accuracy of pervaporation results three successive measurements were performed and average value of the flux and separation factor with relative standard deviation less than 5 % were reported. The feed mixture solutions were used in an azeotropic composition of range of ECH, IPA, and water from
Fig. 5. Surface and cross-sectional FESEM and real images of all the membranes.
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Fig. 6. FE-SEM EDS spectra of PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes.
50:40:10 (wt. %) to 50:30:20 (wt. %). The permeate solutions were analyzed to determined exact composition of ECH, IPA and water using a gas chromatograph (DS Sci. DS7200) equipped with a Flame ionization detector (FID) detector. The Eqs. (1)–(3) were used to evaluate the membranes performance by calculating pervaporation flux, separation factor, flux of individual components for each membranes. M Flux ðJÞ ¼ A t
ð1Þ 2
1
Here, J is the permeation flux (kg m h ), M describe the mass of the permeated solution collected in the cold trap (kg) with respect to the effective area A (m2) over time t (h). In this study, the target component for removal is water (i.e., the dehydration of organics). Therefore, the separation factor (α) was calculated for water with respect to ECH and IPA in the ternary feed mixture system. Separation Factor ðaÞ ¼
PWater =PðIPAþECHÞ FWater =FðIPAþECHÞ
ð2Þ
Here, symbols Pwater, P(IPA+ECH), Fwater, and F(IPA+ECH) are defines the weight fractions of water and the ECH + IPA organic solution in feed solutions and permeate solution and, respectively. Flux of Individual component ðJiÞ ¼
Ji Pi 100
ð3Þ
Fig. 7. XPS spectra of PVA, PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes.
Here, Ji is the flux of component i (kg m2 h1), and Pi is the weight fraction of component i (ECH, IPA, or water) in the permeate solution (wt. %). Results and Discussion As described in the Experimental section, three PVA/TEOS membranes were prepared. These are labeled by the amount of TEOS (in grams) used in their preparation: PVA-TEOS (4), PVATEOS (6), and PVA-TEOS (8). The base membrane used for the layerby-layer modification was the PVA-TEOS (4) membrane. The modified membranes are labeled according to the number of added layers, for example, PVA-TEOS (4) (5 L-L), which was subjected to five layer-by-layer deposition cycles. Membrane characterization Fig. 3a shows the FTIR spectra of pure STA, PVAm, and the PVAm–STA polyelectrolyte complex. Bands between 700 and 1200 cm1 in the FTIR spectra of pure STA are characteristic of the Keggin structure [45], and these bands were also observed in the spectrum of the STA-PVAm polyelectrolyte complex. In the spectrum of PVAm, the broad band between 3100 and 3600 cm1 corresponds to the NH2 amine groups, and the strong bands at 1580 and 770 cm1 correspond to N-H bending and out-of-plane wagging vibrations of the amine groups, respectively. Additionally the band at 1650 cm1 can be attributed to the C¼O group, which might arise from remaining poly(vinyl formamide) (PVNF), which is used to prepare PVAm [41] The presence of bands corresponding to STA and PVAm and bands at 1510–1620 cm1, which are attributed to the NH3+ deformation [46], in the PVAm polyelectrolyte spectrum confirms the successful formation of the STA-PVAm complex by electrostatic interactions. PVA and TEOS crosslinking was also confirmed by FTIR analysis. As shown in the FTIR spectrum of the crosslinked membrane (PVATEOS (4) in Fig. 3b, there was an increase in the intensity of the band at 1000–1100 cm1, which corresponds to the Si O bonds in the PVA-TEOS (4) membrane. This confirms the presence of C O Si bonds formed by the condensation of the OH groups in PVA and ethoxide (OCH2 CH3) groups in TEOS. Additionally, the reduction in the intensity of the band around 3300 cm1, which corresponds to OH stretching, was also observed [17]. This reflects the consumption of hydroxyl groups in PVA. Therefore, the results of FTIR analysis indicated that the crosslinking of PVA and TEOS was successfully occurred. In order to evaluate the effects of TEOS on thermal stability of the PVA membranes was analyzed by TGA. The TGA curves for PVA and PVA-TEOS (4) membranes described in Fig. 4. From the results, it was clearly noticed that initial 5–10% of weight loss at
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Fig. 8. Postulated reaction scheme for PVA-TEOS membrane surface with the PVAm and STA layer-layer deposition.
Fig. 9. Effect of TEOS content on the pervaporation flux and separation factor, at 30 C, Feed, ECH/IPA/water (50/30/20, w/w, %).
Fig. 10. Effect of layer by layer (PVAm/STA) on the flux and separation factor, at 30 C, Feed, ECH/IPA/water (50/30/20, w/w, %).
temperature range between 50 to 110 C was corresponding to the physically or bounded state water occurred for the PVA and PVATEOS (4) membranes. Despite of that the two different main non oxidative degradation step occurred for both of the membrane. For pristine PVA membrane, the first weigh loss of 70% at temperature 320 C due to PVA side chain elimination and second weight loss of 20% at 440 C was arises from the degradation from main chain was observed [47]. On other hand, the decomposition temperature of PVA-TEOS (4) membrane is shifted to the higher temperature (350 C) at the 1st stage compared to pristine PVA membrane indicating the higher thermal stability of PVA-TEOS (4) membrane in comparison to the pristine PVA membrane. The higher thermal stability of PVA-TEOS (4) membrane may resulted from the covalently bonded SiO in the PVA side chain. TGA study well support the explanation of crosslinking reaction of PVA-TEOS given in the FTIR studies. Fig. 5 shows the surface and cross-sectional field-emission scanning electron microscopy (FE-SEM) images of the unmodified (PVA-TEOS (0 L-L)) membrane and the membranes modified with PVAm/STA polyelectrolyte complex by layer-by-layer deposition (modified PVA-TEOS (4)). The surface images of all membranes show a smooth and continuous surface with no cracks or defects, even after the layer-by-layer deposition of the polyelectrolyte complex. From the cross-sectional images of the modified (5 (L-L) and 10 (L-L)) membranes, it was observed that the substrate (PVA-TEOS (4)) and the polyelectrolyte complex have a good compatibility and adhesion and, thus, form a uniform coating. This compatibility might originate from the hydrogen bonding of the hydroxyl and amine groups in the PVA and PVAm. The thicknesses of the polyelectrolyte complex layers on the membrane surfaces were approximately 200 and 400 nm for the 5 (L-L) and 10 (L-L) membranes, respectively. At higher magnification, FE-SEM energy dispersive spectroscopy (EDS) analysis was performed to determine the elemental composition after the layer-by-layer deposition on the membrane surface. Fig. 6 shows the FE-SEM EDS spectra of the 0 L-L and 5 L-L membranes. Signals corresponding to Si, W, and N were observed in the spectrum of the 5 L-L membrane, confirming the deposition of PVAm/STA on the PVA-TEOS (4) membrane surface. This is consistent with the FE-SEM images in Fig. 4. Additionally, the
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Fig. 11. Effect of water content in the feed composition on flux and separation factor for membrane of PVA-TEOS (4) (5 L-L), at 30 C.
presence of a signal corresponding to Si in the 0 (L-L) membrane surfaces is indicative of bonding between TEOS and PVA, which is consistent with the FTIR analysis after the PVA-TEOS reaction. Fig. 7 depicts the survey of XPS spectra for pristine PVA, PVA-TEOS (4) and PVA-TEOS (4) (5 L-L) membranes. The pristine PVA membrane exhibited only two characteristics peaks at binding energy 285 eV and 532 eV those were assigned to C 1s (CH2) and O 1s (OH) for PVA polymer chain respectively [48]. On other hand, one additional peak at binding energy 103.8 eV which correspond to the Si 2P in the PVA-TEOS (4) membrane was observed with confirming the crosslinking reaction between the PVA and TEOS molecules. In XPS spectra of layer by layer PVAm and STA surface deposition on PVA-TEOS (4) membrane (PVA-TEOS (4) (5 L-L)), two additional peaks at binding energy 36 eV and 400.9 eV assigned to the hetero poly anion W 4f (W(VI) [49] and N 1s (NH3+) were observed [50]. Consequently, XPS analysis confirmed the successful deposition PVA-STA polyelectrolyte complexon the 0 L-L membrane surface and it is well agreed with results of SEM-EDS analysis. Based on the FTIR, FE-SEM, TGA, XPS and EDS measurements, a postulated reaction mechanism and membrane structure is shown in Fig. 8. Effect of TEOS content of pervaporation flux and separation factor
out using the prepared PVA-TEOS membranes. In addition, the pervaporation output was compared with that of a PVA– glutaraldehyde (PVA-GA) crosslinked membrane, which we have reported previously [14]. The results are shown in Fig. 9. All the PVA-TEOS membranes showed superior pervaporation performance compared to the PVA-GA membrane. As shown in Fig. 9, the flux value decreased from 0.14 to 0.05 kg m2 h1 and the separation factor increased from 2099 to 13,320 in the membrane with TEOS. An important factor that influences the pervaporation transport mechanism across the polymeric membranes is the sorption and diffusion of the components. Sorption depends on the specific interaction of the components with the membrane material [33] and, in pervaporation dehydration, the solubility of water in the membrane material depends on the hydrophilicity of the membrane. Interactions responsible for the association of water at the membrane surface are hydrogen bonding, polar interactions, and dispersion interactions [51]. Increasing the TEOS content reduces the hydrophilicity of the membrane by consuming the hydroxyl groups in the PVA. The hydrophobic character of the membrane is also increased by the formation of CO Si bonds at the surface of the PVA membrane. Therefore, the membrane flux decreased with increasing TEOS content. However, the addition of TEOS significantly decreases the mobility of the PVA chains and increases the density of the polymer, which are both preferable for selective water transport (lower size) because they restrict the permeation of larger molecules (ECH and IPA). Therefore, the separation factor was noticeably increased on the addition of TEOS. Overall, all the PVA-TEOS membranes showed superior pervaporation performance to the PVA-GA membrane, possibly because glutaraldehyde, which crosslinks the PVA chains [52], reduces the free volume of the polymer matrix by increasing the polymer compactness to a greater extent than TEOS. TEOS is a comparatively small molecule that reacts with hydroxyl groups in the same PVA chain in a pendant fashion [17], so PVA-TEOS could contain more transport pathways for the small water molecules than the PVA-GA membrane. Effect of layer-by-layer PVAm/STA treatment of the PVA-TEOS (4) membrane Fig. 10 shows the effects of layer-by-layer PVAm/STA treatment of the PVA-TEOS (4) membrane surface on the pervaporation flux and separation factor at 30 C for a ECH/
Pervaporation dehydration experiments with a feed mixture containing ECH/IPA/water (50/30/20, w/w, %) at 30 C were carried
Fig. 12. Effect of feed temperature on flux and separation factor for membrane of PVA-TEOS (4) (5 L-L), feed composition ECH/IPA/water (50/35/15, w/w, %).
Fig. 13. Variation of LnJwater, LnJIPA, LnJECH with temperature (K) using the PVA-TEOS (4) (5 L-L) membrane at ECH/IPA/water (55/35/15, w/w, %) feed composition.
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IPA/water (50/30/20, w/w, %) feed. The flux increased with increasing number of deposited surface layers: 0.14 to 0.28 kg m2 h1. However, the separation factor decreased from 2099 to 416. The increased flux after L-L deposition can be attributed to the formation of small hydrophilic meshes induced by the higher charge density of the polyelectrolyte layer, which favors the penetration of water [53]. However, because of the increase in hydrophilicity at the membrane surface, the swelling of the membrane surface also increased, thus promoting IPA/ECH absorption along with water absorption at the membrane surface. Consequently, the separation factor decreased. The (PVA-TEOS (4) (5 L-L) membrane exhibited the best performance of all surface-modified membranes; thus, it was used for further testing under a range of operating conditions. Effect of feed composition The effect of different feed compositions on the membrane (PVA-TEOS (4) (5 L-L)) performance were examined by reducing the water content in the ternary feed mixture. Fig. 11 shows the effect of water content in the feed on the flux and separation factor at 30 C. Fig. 11 shows that the pervaporation flux decreased as the water content decreased from 20 to 10 wt. %, from 0.22 to 0.0066 kg m2 h1 and the separation factor abruptly increased from 1061 to 9094. According to the solution diffusion model, a well-accepted mechanism for pervaporation transport through membranes [32,33], a higher content of the preferential component on the feed side results in a higher driving force, dissolution, and, consequently, diffusion of this component across the membrane. Therefore, increasing the water content in the feed, resulted in an increase in membrane surface wetting. As a result, the membrane became more swollen, resulting in easier transport of the permeants across the membrane. Hence, the flux increased and the separation factor decreased.
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Effect of temperature The effect of operating temperature on the membrane was examined at 30 to 50 C with fixed ECH/IPA/water feed composition (55/35/15, (w/w, %)). The results are shown in Fig. 12. As the feed temperature increased from 30 to 50 C, the flux increased from 0.07 to 0.19 kg m2 h1, respectively, whereas the separation factor decreased from 7991 to 1729, respectively. The individual fluxes of water, IPA, and ECH were calculated by using Eq. (3). The Arrhenius equation can be used to express the temperaturedependent permeation flux, is as shown in Eq. (4) [10]. Flux (Ji) = Ap. eEp/RT 2
(4)
1
Here, Ji (kg m h ) is the flux of component i, either ECH, IPA, or water; T (K) is the absolute temperature; R (J mol1 K1) is the universal gas constant; and Ap (kg m2 h1) and Ep (kJ mol1), are the pre-exponential factor and the apparent activation energy for permeation, respectively. A plot of the natural logarithmic of the individual fluxes of ECH, IPA, and water over the studied temperature range is shown in Fig. 13. From the slope of the linear fitting regression line, the apparent activation energies (Ea) for the permeation of ECH, IPA, and water were calculated. The apparent activation energies for the permeation of ECH (97.42 kJ mol1) and IPA (111.96 kJ mol1) were calculated. Both of these values are higher than that of water (40.88 kJ mol1) was observed. The results reveal that the permeation of water was easier than those of ECH and IPA. Interestingly, although IPA is larger than ECH, the permeation Ea for IPA was marginally higher that of the ECH. This could be because, in pervaporation transportation through a hydrophilic membrane, the preferential component (water) interacts with the membrane via hydrogen bonding, dipole–dipole, and ion–dipole interactions [51], and ECH is more polar (dipole moment = 1.80 D) than isopropanol (dipole moment = 1.58 D). Thus, because of the dipole–dipole interactions of ECH molecules with the surface modified membrane, the ECH molecules might undergo
Fig. 14. Stability study of PVAm-STA complex.
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Fig. 15. Stability evaluation of PVA-TEOS (4) (5 L-L) membrane in terms of pervaporation test (Feed composition; ECH/IPA/water (50/30/20 w/w, %) at 30 C).
operation time, the water content in permeate dropped to 96.23%, then there was no major deviation (water content >96 wt. %) until 168 h was observed. This deviation can be attributed to conditioning and relaxation effects which are commonly observed in PVA based membranes [54,55]. The pervaporation data for the PVA-TEOS (4) (5 L-L) membrane indicated that, well stability of PVAm/ STA polyelectrolyte complex on the membrane surface with remarkable pervaporation performance over long operating periods was observed. FE-SEM analysis was performed to observe the state of the PVAm/STA polyelectrolyte layer on the PVA-TEO (4) membrane surface after long-term pervaporation tests, as shown in Fig. 16. As expected, the PVAm/STA layer was stable after contact with the ECH-containing feed mixture. Even after the long-term pervaporation experiments, the PVAm/STA polyelectrolyte remained on the surface of PVA-TEO (4) membrane, thus confirming the stability of polyelectrolyte layer at the membrane surface. Conclusion
Fig. 16. FE-SEM images of PVA-TEOS (4) (5 L-L) membrane cross-section after long term pervaporation test (Feed composition; ECH/IPA/water (50/30/20 w/w, %) at 30 C).
pervaporation transport through the membrane more easily than IPA [14]. Additionally, the higher content of ECH in the feed composition (50 wt. %) increases the driving force in the feed boundary layer for absorption on the feed side of the membrane [33]. Stability of PVAm/STA polyelectrolyte complex and stability of polyelectrolyte complex layer coated on the PVA-TEOS (4) membrane surface The PVAm/STA complex was crosslinked by ionic interactions; thus, we investigated the stability of the PVAm/STA complex in the ECH/IPA/water (50/30/20, w/w, %) feed. An ex situ prepared PVAm/ STA complex was dispersed in the feed solution and heated for 3 days at 60 C. Every 24 h, the solution was sonicated for 30 min. After immersion at 60 C for several days, no dissolution of the PVAm/STA polyelectrolyte complex was observed as shown in Fig. 14. Therefore, the PVAm/STA polyelectrolyte complex is stable in the ECH-containing feed solution was confirmed. Fig. 15 shows long term stability of surface-modified PVA-TEOS (4) (5 L-L) membrane. Fig. 15 reflect that, after pervaporation tests at 30 C using an ECH/IPA/water (50/30/20, w/w. %)) feed, with increasing operating time, the flux only increased marginally, thereafter remaining constant. On other hand, after 24 h of
Two different membranes were prepared: PVA/TEOS and a PVA/ TEOS membrane layer-by-layer modified with PVAm and STA. Membranes characterization was performed by using FTIR, FE-SEM, TGA, XPS and SEM-EDS measurements. Pervaporation tests were performed using membranes with different PVA/TEOS ratios (wt.%). For a feed containing ECH/IPA/water (50/30/20, w/w, %) at 30 C, the pervaporation flux decreased from 0.14 to 0.05 kg m2 h1 and the separation factor increased from 2099 to 13,320 with increasing TEOS content was obtained. Pervaporation tests were also performed using the PVA/TEOS (4) membrane surface modified with PVAm/STA polyelectrolyte complex. For a feed containing ECH/IPA/water (50/30/20, w/w, %) at 30 C, the pervaporation flux increased from 0.14 to 0.28 kg m2 h1 and the separation factor decreased from 2099 to 416 with increasing number of L-L layers was reported. The stability of the PVAm/STA polyelectrolyte complex was examined in a feed containing ECH/IPA/water (50/30/20, w/w, %) at 60 C. The PVAm/STA polyelectrolyte complex remained stable in the feed for 72 h. Additionally, the long-term stability of PVAm/STA polyelectrolyte complex layer on the PVA-TEO (4) membrane surface was confirmed by operating the long term pervaporation tests at 30 C using a ECH/IPA/ water (50/30/20, w/w, %) feed. The PVAm/STA polyelectrolyte layer was retained on the surface, even after 168 h. The effects of the feed composition and feed temperature on the pervaporation performance of the PVA/TEOS (4) 5 (L-L) membrane were determined. The flux increased and separation factor decreased with increasing water content in the feed (ECH/IPA/water) and increasing feed temperature (30–50 C) was obtained. Overall, the pervaporation output of the PVATEOS and layer by layer PVA-TEOS membranes reflected that both membranes have excellent ability in epichlorohydrin, isopropanol and water ternary mixture pervaporation dehydration. Acknowledgement This work was supported by the New & Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry and Energy, Republic of Korea (No. 20172010106170). References [1] G. Jungang, J. Appl. Polym. Sci. 48 (1993) 237, doi:http://dx.doi.org/10.1002/ app.1993.070480208. [2] C. Chang, W. Lee, J. Appl. Polym. Sci. 116 (2010) 2065, doi:http://dx.doi.org/ 10.1002/app.31703. [3] B. Hirakawa, Epichlorohydrin, Encyclopedia Toxic, Third Edition), (2014), pp. 431, doi:http://dx.doi.org/10.1016/B978-0-12-386454-3.00019-1.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007
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S. Chaudhari et al. / Journal of Industrial and Engineering Chemistry xxx (2019) xxx–xxx [4] P. Wester, C. Heijden, A. Bisschop, G. Esch, Toxicology 36 (1985) 325, doi:http:// dx.doi.org/10.1016/0300-483X(85)90034-4. [5] W. Raza, J. Lee, N. Raza, Y. Luo, K. Kim, J. Yang, J. Ind. Eng. Chem. 71 (2019) 1, doi: http://dx.doi.org/10.1016/j.jiec.2018.11.024. [6] M. Amirilargani, B. Sadatnia, J. Membr. Sci. 469 (2014) 1, doi:http://dx.doi.org/ 10.1016/j.memsci.2014.06.034. [7] H. Zhang, Y. Wang, AICHE J. 62 (2016) 1728, doi:http://dx.doi.org/10.1002/ aic.15140. [8] A. Penkova, S. Acquah, M. Dmitrenko, M. Sokolova, M. Mikhailova, E. Polyakov, S. Ermakov, D. Markelov, D. Roizard, Mater. Des. 96 (2016) 416, doi:http://dx. doi.org/10.1016/j.matdes.2016.02.046. [9] L. Xia, C. Li, Y. Wang, J. Membr. Sci. 498 (2016) 263, doi:http://dx.doi.org/ 10.1016/j.memsci.2015.10.025. [10] L. Liu, S.E. Kentish, J. Membr. Sci. 553 (2018) 63, doi:http://dx.doi.org/10.1016/j. memsci.2018.02.021. [11] F. Kursun, N. Isiklan, J. Ind. Eng. Chem. 25 (2016) 91, doi:http://dx.doi.org/ 10.1016/j.jiec.2016.07.011. [12] M. Pedram, M. Omidkhah, A. Amooghin, J. Ind. Eng. Chem. 20 (2014) 74, doi: http://dx.doi.org/10.1016/j.jiec.2013.04.024. [13] A. Sajjan, B.K. Kumar, A.A. Kittur, M.Y. Kariduraganavar, J. Ind. Eng. Chem. 19 (2013) 427, doi:http://dx.doi.org/10.1016/j.jiec.2012.08.032. [14] S. Chaudhari, Y. Kwon, M. Shon, S. Nam, Y. Park, RSC Adv. 9 (2019) 5908, doi: http://dx.doi.org/10.1039/C8RA07136E. [15] Z. Xie, M. Hoang, D. Ng, C. Doherty, A. Hill, S. Gray, Sep. Purif. Technol. 127 (2014) 10, doi:http://dx.doi.org/10.1016/j.seppur.2014.02.025. [16] P. Das, S.K. Ray, S.B. Kuila, H.S. Samanta, N.R. Singha, Sep. Purif. Technol. 81 (2011) 159, doi:http://dx.doi.org/10.1016/j.seppur.2011.07.020. [17] M.Y. Kariduraganavar, S.S. Kulkarni, A.A. Kittur, J. Membr. Sci. 246 (2005) 83, doi:http://dx.doi.org/10.1016/j.memsci.2004.09.001. [18] L. Ye. Q. Lin, Q. Zhang, A. Zhu, G. Zhou, J. Appl. Polym. Sci. 105 (2007) 3640, doi: http://dx.doi.org/10.1002/app.26446. [19] J. Chen, M. Liu, Q. Huang, L. Huang, H. Huang, F. Deng, Y. Wen, J. Tian, X. Zhang, Y. Wei, Chem. Eng. J. 337 (2018) 82, doi:http://dx.doi.org/10.1016/j.cej.2017.12.085. [20] Y. Liu, K. Ai, L. Lu, Chem. Rev. 114 (2014) 5057, doi:http://dx.doi.org/10.1021/ cr400407a. [21] X. Zhang, Q. Huang, F. Deng, H. Huang, Q. Wan, M. Liu, Appl. Mater. Tod. 7 (2017) 222, doi:http://dx.doi.org/10.1016/j.apmt.2017.04.001. [22] G. Zeng, L. Huang, Q. Huang, M. Liu, D. Xu, H. Huang, Z. Yang, F. Deng, X. Zhang, Y. Wei, Surf. Sci. 459 (2018) 588, doi:http://dx.doi.org/10.1016/j.apsusc.2018.07.144. [23] L. Huang, M. Liu, H. Huang, Y. Wen, X. Zhang, Y. Wei, Biomacromolecules 19 (2018) 1858, doi:http://dx.doi.org/10.1021/acs.biomac.8b00437. [24] M. Liu, G. Zeng, K. Wang, Q. Wan, L. Tao, X. Zhang, Y. Wei, Nanoscale 8 (2016) 16819, doi:http://dx.doi.org/10.1039/C5NR09078D. [25] Q. Huang, M. Liu, L. Mao, D. Xu, G. Zeng, H. Huang, R. Jiang, F. Deng, X. Zhang, Y. Wei, J. Coll. Inter. Sci. 499 (2017) 170, doi:http://dx.doi.org/10.1016/j.jcis.2017.03.102. [26] X. Zhang, Q. Huang, M. Liu, J. Tian, G. Zeng, Z. Li, Q. Zhang, Q. Wan, F. Deng, Y. Wei, Appl. Surf. Sci. 343 (2015) 19, doi:http://dx.doi.org/10.1016/j.apsusc.2015.03.081. [27] M. Liu, J. Ji, X. Zhang, X. Zhang, B. Yang, F. Deng, Z. Li, K. Wang, Y. Yang, Y. Wei, J. Mater. Chem. B 3 (2015) 3476, doi:http://dx.doi.org/10.1039/C4TB02067G. [28] Y. Shi, R. Jiang, M. Liu, L. Fu, G. Zeng, Q. Wan, L. Mao, F. Deng, X. Zhang, Y. Wei, Mater. Sci. Eng. C 77 (2017) 972, doi:http://dx.doi.org/10.1016/j.msec.2017.04.033. [29] Y. Shi, M. Liu, F. Deng, G. Zeng, Q. Wan, X. Zhang, Y. Wei, J. Mater. Chem. B 5 (2017) 194, doi:http://dx.doi.org/10.1039/C6TB02249A.
11
[30] Q. Huang, M. Liu, J. Chen, Q. Wan, J. Tian, L. Huang, R. Jiang, X. Wen, X. Zhang, Y. Wei, Appl. Surf. Sci. 419 (2017) 35, doi:http://dx.doi.org/10.1016/j.apsusc.2017.05.006. [31] Y. Cao, X. Zhang, L. Tao, K. Li, Z. Xue, L. Feng, Y. Wei, Appl. Mater. Inter. 5 (2013) 4438, doi:http://dx.doi.org/10.1021/am4008598. [32] J.G. Wiljmans, R.W. Baker, J. Membr. Sci. 107 (1995) 1, doi:http://dx.doi.org/ 10.1016/0376-7388(95)00102-I. [33] P. Shao, R.Y.M. Huang, J. Membr. Sci. 287 (2007) 162, doi:http://dx.doi.org/ 10.1016/j.memsci.2006.10.043. [34] V. Freger, E. Korin, J. Wisniak, E. Korngold, J. Membr. Sci. 164 (2000) 251, doi: http://dx.doi.org/10.1016/S0376-7388(99)00198-2. [35] Q. Zhao, Q. An, Y. Ji, J. Qian, C. Gao, J. Membr. Sci. 379 (2011) 19, doi:http://dx. doi.org/10.1016/j.memsci.2011.06.016. [36] S. Kononova, E. Kruchnina, V. Petrova, Y. Bakilagina, V. Klechkovskaya, A. Orekhov, E. Vlasova, E. Popova, G. Gubunova, Y. Skorik, Carbohy. Polym. 209 (2019) 10, doi:http://dx.doi.org/10.1016/j.carbpol.2019.01.003. [37] J. Li, X. Si, X. Li, N. Wang, Q. An, S. Ji, Sep. Purif. Technol. 192 (2018) 205, doi: http://dx.doi.org/10.1016/j.seppur.2017.09.038. [38] M. Dmitrenko, A. Penkova, A. Kuzminova, M. Morshed, M. Larionov, H. Alem, A. Zolotarev, S. Ermakov, D. Roizard, Appl. Surf. Sci. 450 (2018) 527, doi:http://dx. doi.org/10.1016/j.apsusc.2018.04.169. [39] Z. Tong, X. Liu, B. Zhang, J. Membr. Sci. 575 (2019) 9, doi:http://dx.doi.org/ 10.1016/j.memsci.2019.01.001. [40] D. Achari, P. Rachipudi, S. Naik, R. Karuppannan, M.Y. Kariduraganavar, J. Ind. Eng. Chem. (2019), doi:http://dx.doi.org/10.1016/j.jiec.2019.05.031. [41] R. Pelton, Langmuir 30 (2014) 15373, doi:http://dx.doi.org/10.1021/la5017214. [42] S. Chaudhari, Y. Kwon, M. Moon, M. Shon, S. Nam, Y. Park, J. Appl. Polym. Sci. 134 (2017) 45572, doi:http://dx.doi.org/10.1002/app.45572. [43] Z. Cui, Xing Wei, C. Liu, J. Liao, H. Zhang, J. Power Sources 188 (2009) 24, doi: http://dx.doi.org/10.1016/j.jpowsour.2008.11.108. [44] S. Chaudhari, Y. Kwon, M. Moon, M. Shon, S. Nam, Y. Park, Vacuum 147 (2018) 115, doi:http://dx.doi.org/10.1016/j.vacuum.2017.10.024. [45] A.H. Jadhav, H. Kim, RSC Adv. 3 (2013) 5131, doi:http://dx.doi.org/10.1039/ C3RA22663H. [46] M. Llusar, G. Monros, Cecile Roux, J. Pozzo, C. Sanchez, J. Mater. Chem. 13 (2003) 2505, doi:http://dx.doi.org/10.1039/B304479N. [47] R. Bryaskova, N. Georgieva, T. Andreeva, R. Tzoneva, Surf. Coat. Technol. 235 (2013) 186, doi:http://dx.doi.org/10.1016/j.surfcoat.2013.07.032. [48] H. Pingan, J. Mengjun, Z. Yanyan, H. Ling, RSC Adv. 7 (2017) 2450, doi:http://dx. doi.org/10.1039/C6RA25579E. [49] V. Kumar, I. Pulidindi, A. Gendanken, Renewable Energy 78 (2015) 141, doi: http://dx.doi.org/10.1016/j.renene.2014.12.070. [50] A. Wach, M. Drozdek, B. Dudek, E. Szneler, P. Kustrowski, Catal. Commun. 64 (2015) 52, doi:http://dx.doi.org/10.1016/j.catcom.2015.02.002. [51] S. Semenova, H. Ohya, K. Soontarapa, Desalination 110 (1997) 251, doi:http:// dx.doi.org/10.1016/S0011-9164(97)00103-3. [52] C. Yeom, K. Lee, J. Membr. Sci. 109 (1996) 257, doi:http://dx.doi.org/10.1016/ 0376-7388(95)00196-4. [53] B. Tieke, F. Ackern, L. Krasemann, A. Toutianoush, Eur. Phys. J. 5 (2001) 29, doi: http://dx.doi.org/10.1007/s101890170084. [54] Z. Huang, Y. Shi, R. Wen, Y. Guo, J. Su, T. Matsurra, Sep. Purif. Technol. 51 (2) (2006) 126, doi:http://dx.doi.org/10.1016/j.seppur.2006.01.005. [55] E. Otsuka, A. Suzuki, Prog. Coll. Polym. Sci. 136 (2009) 121, doi:http://dx.doi. org/10.1007/978-3-642-00865-8_17.
Please cite this article in press as: S. Chaudhari, et al., Surface-modified polyvinyl alcohol (PVA) membranes for pervaporation dehydration of epichlorohydrin (ECH), isopropanol (IPA), and water ternary feed mixtures, J. Ind. Eng. Chem. (2019), https://doi.org/10.1016/j.jiec.2019.09.007