Layer-by-layer assembled membranes from graphene oxide and polyethyleneimine for ethanol and isopropanol dehydration
Graphical abstract
Introduction
Pervaporation, a promising membrane-based technology, is applied in three main areas: 1) dehydration of organic solvents, 2) recovery of organic compounds from water, and 3) separation of organic-organic liquids (Shao and Huang, 2007, Ong et al., 2016, Feng and Huang, 1997). Among these, the dehydration of alcohols is the most-developed, especially when the feed has a low quantity of water or at an azeotropic point (<20 wt%) (Zhao et al., 2011, Nunes and Peinemann, 2001). Ethanol (EtOH) is the most common renewable biofuel resource (Vorayos et al., 2006), and isopropanol (IPA) is widely used in electronic and pharmaceutical industries where high purity IPA is needed (Qiao et al., 2005). Both EtOH and IPA form azeotropes with water at an alcohol concentration of around 96 and 88 wt%, respectively (Qiao et al., 2005, Chapman et al., 2008). Compared with such traditional separation processes as adsorption and distillation, pervaporation is generally a cost- and energy-effective approach to breaking azeotropes and removing a small amount of water (Zhao et al., 2011, Qiao et al., 2005). Moreover, pervaporation separation is based on the solution-diffusion mechanism and only the latent heat of evaporation of the permeate is needed for the separation. Therefore, pervaporation is not limited by thermodynamics of vapor-liquid equilibrium (VLE) and can be used to separate azeotropic or close-boiling mixtures (Ong et al., 2016). Integrating pervaporation with other conventional separation processes is shown to be effective to further improve the separation efficiency (Chapman et al., 2008).
Hydrophilic membranes permselective to water are the key component for dehydration of organic solvents (Semenova et al., 1997), and the layer-by-layer (LbL) assembly is one of the well-known methods to fabricate nanoscale anionic-cationic multilayers on a substrate through sequential depositions of oppositely charged polyelectrolyte solutions or nanoparticle suspensions (Decher, 1997, Tzeng et al., 2015). The LbL membranes have a significant affinity to water molecules, and the deposited nanolayers result in preferential water transport through the membrane (Zhao et al., 2011, Bolto et al., 2011). The main driving force for the layer-by-layer buildup is Coulombic (electrostatic) interactions between oppositely charged ions, though hydrogen bonding is also an important factor for the assembly (Semenova et al., 1997). This bottom-up approach was first introduced by Iler (1966), and it received great attention for nanoassembly after the work of Decher, 1997, Decher and Hong, 1991. In 1998, Tieke et al. prepared LbL membranes for pervaporative separation of EtOH/water (Krasemann and Tieke, 1998). Since then, a variety of LbL membranes have been prepared for various separations, including gas separation (Krasemann and Tieke, 1998, van Ackern et al., 1998), pervaporation (Krasemann and Tieke, 1998, van Ackern et al., 1998), reverse osmosis (RO) (Choi et al., 2013), forward osmosis (Hu and Mi, 2014), and nanofiltration (NF) (Wang et al., 2012, Wang et al., 2016).
However, the LbL membranes are prone to swelling when exposed to alcohol/water mixtures due to their hydrophilic nature. Both water and alcohols are polar molecules and can swell the polyelectrolyte layers. Therefore, the nanolayers formed by cation-anion interactions are not stable when excessive swelling and interchain stretching occur, resulting in a low selectivity (Semenova et al., 1997, Zhang et al., 2013). Kim et al. (2005) reported that polyelectrolyte multilayers performed differently for different organic/water mixtures, where the polymer coils can be softened or contracted in different organic solvents. Zhang et al. (2013) confirmed that EtOH and IPA can wash away some polyelectrolyte macromolecules deposited onto polyamide membranes, and Poptoshev et al. (2004) showed that polyelectrolyte multilayers may even disassemble in certain organic solvents, resulting in collapse of the membrane structure. In such cases, chemical crosslinking may be used to alleviate membrane swelling and to augment membrane stability and performance (Zhang et al., 2013, Mangindaan et al., 2014, Zhao et al., 2018). Membrane crosslinking restricts the polymer chain mobility and leads to stiff and compact membrane structures. Crosslinked membranes usually have a lower permeation flux and higher separation factor because of increased diffusion resistance and reduced sorption uptake after crosslinking (Bolto et al., 2011, Huang et al., 1999, Hyder et al., 2009). Aldehydes are often used as crosslinking agents as they are reactive with many functional groups in polymers commonly used for pervaporation membranes (Zhang et al., 2013, Huang et al., 1999, Qiu et al., 2011, Qi et al., 2012, Chen et al., 2015, Hua et al., 2017, Liu et al., 2011).
To prepare membranes via the LbL assembly, selecting appropriate substrates and polyelectrolytes are of primary importance. In this study, a thin film composite (TFC) polyamide membrane was chosen as a substrate because of its negative surface charge, which favors the deposition of polycations. Moreover, the number of polyelectrolyte depositions required to prepare a defect free permselective membrane was reduced due to its considerably dense skin layer (Choi et al., 2013, Zhang et al., 2013). Graphene oxide (GO) and polyethyleneimine (PEI) were used as the anionic and cationic depositing components, respectively. GO nanosheets have a unique carbon nanostructure with abundant hydrophilic functional groups, allowing fast passage of water. In addition, GO nanosheets function as polyanions when dispersed in water due to ionization of the hydroxyl and carboxyl groups. Consequently, GO nanosheets can interconnect with polycations (e.g., PEI) through electrostatic attraction and hydrogen bonding (Tzeng et al., 2015, Hu and Mi, 2014, Hu and Mi, 2013, Li et al., 2008, Huang et al., 2017, Wu et al., 2019, Ang et al., 2019, Liu et al., 2015). Therefore, GO may be used as an appropriate anionic nanomaterial to offer a “brick-and-mortar” LbL structure. On the other hand, PEI is a cationic amine polymer, and its hydrophilic nature makes it a popular choice for constructing water-permeating membranes. To improve the performance of the prepared LbL membranes, glutaraldehyde (GA) was used as a crosslinking agent. GA can react with the amine groups in PEI and hydroxy groups in GO, as illustrated in Fig. 1 (Zhang et al., 2013, Hua et al., 2017, Xia et al., 2011).
To our knowledge, there are no reports yet in the literature on the preparation of PEI/GO LbL membranes self-assembled on a TFC polyamide substrate and chemically crosslinked with GA for alcohol dehydration via pervaporation. The objective of this research was to fabricate PEI/GO LbL membranes for dehydration of EtOH and IPA. The effects of crosslinking conditions (e.g., temperature, time, and crosslinker concentration) on the membrane performance were investigated, and the effects of the interactions of these factors were evaluated through a two-level factorial design. The results were used to determine the largely optimal crosslinking conditions by considering the trade-off between permeation flux and separation factor. The effects of the number of bilayers on the membrane performance were also investigated to correlate the layer-by-layer growth and mass transfer resistance quantitatively. Water sorption uptake was also measured to look into the degree of swelling of the bilayers, and the surface hydrophilicity of the membrane was determined using contact angle measurements. The morphology of the membrane was examined using atomic force and electron microscopies. The long-term stability of the crosslinked membrane was also investigated.
Section snippets
Materials
A commercial thin film composite polyamide membrane (supplied by GE Water & Process Technologies, now Suez Water Technologies & Solutions) produced by interfacial polymerization was used as a substrate. Graphite flakes, obtained from Alfa Aesar, were oxidized into GO using potassium permanganate (KMnO4, >99%, Merck), phosphoric acid (H3PO4, 85% solution in water, Acros), hydrogen peroxide 30% (H2O2, 30%, Sigma-Aldrich) and sulfuric acid (H2SO4, 95–98%, Sigma-Aldrich) (Marcano et al., 2010). The
Chemical analysis and microstructure of GO and LbL membranes
Fig. 3 shows the FTIR spectra of the XL(PEI/GO)7, (PEI/GO)7 and chlorine-treated TFC polyamide membranes. For comparison, the FTIR spectrum of GO nanosheets was added (inset) in the figure. The characteristic peaks of GO were observed at 3253 (OH stretching in hydroxyl groups), 1738 (CO stretching vibration in carboxyl groups), 1620 (unoxidized aromatic CC bonds), 1418 (the bending vibration of COH), and 1220 and 1085 (the stretching vibration of CO in epoxy and
Conclusions
This study dealt with preparation of LbL self-assembled membranes using PEI and GO, followed by crosslinking with glutaraldehyde (GA). The membranes were tested for the dehydration of ethanol (EtOH) and isopropanol (IPA) via pervaporation. The following conclusions can be drawn:
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An MLR analysis showed that, of the three main effects, the GA concentration and crosslinking time had a greater influence on membrane performance than crosslinking temperature. However, the impact of the interaction
CRediT authorship contribution statement
Elnaz Halakoo: Conceptualization, Methodology, Data curation, Writing - original draft. Xianshe Feng: Conceptualization, Methodology, Supervision, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
Research support from the Natural Sciences and Engineering Research Council (NSERC) of Canada is gratefully acknowledged.
References (65)
- et al.
Graphene oxide functionalized with zwitterionic copolymers as selective layers in hybrid membranes with high pervaporation performance
J. Membr. Sci.
(2019) - et al.
A review of membrane selection for the dehydration of aqueous ethanol by pervaporation
Chem. Eng. Process. Process Intensif.
(2011) - et al.
Membranes for the dehydration of solvents by pervaporation
J. Membr. Sci.
(2008) - et al.
High-flux composite hollow fiber nanofiltration membranes fabricated through layer-by-layer deposition of oppositely charged crosslinked polyelectrolytes for dye removal
J. Membr. Sci.
(2015) - et al.
Preparation and performance of asymmetric polyetherimide membranes for isopropanol dehydration by pervaporation
J. Membr. Sci.
(1996) - et al.
Layer-by-layer assembly of polyethyleneimine/graphene oxide membranes for desalination of high-salinity water via pervaporation
Sep. Purif. Technol.
(2020) - et al.
Layer-by-layer assembly of graphene oxide membranes via electrostatic interaction
J. Membr. Sci.
(2014) - et al.
Aldehyde functionalized graphene oxide frameworks as robust membrane materials for pervaporative alcohol dehydration
Chem. Eng. Sci.
(2017) - et al.
Vapor transport in graphene oxide laminates and their application in pervaporation
Curr. Opin. Chem. Eng.
(2017) - et al.
Crosslinked chitosan composite membrane for the pervaporation dehydration of alcohol mixtures and enhancement of structural stability of chitosan/polysulfone composite membranes
J. Membr. Sci.
(1999)
Pervaporation separation of aqueous mixtures using crosslinked polyvinyl alcohol membranes. III. Permeation of acetic acid-water mixtures
J. Membr. Sci.
Composite poly(vinyl alcohol)–poly(sulfone) membranes crosslinked by trimesoyl chloride: Characterization and dehydration of ethylene glycol–water mixtures
J. Membr. Sci.
Multilayers of colloidal particles
J. Colloid Interface Sci.
Ultrathin self-assembled polyelectrolyte membranes for pervaporation
J. Membr. Sci.
Self-assembled polyelectrolyte multilayer membranes with highly improved pervaporation separation of ethanol/water mixtures
J. Membr. Sci.
Development of polyion complex membranes based on cellulose acetate modified by oxygen plasma treatment for pervaporation
J. Membr. Sci.
Graphene oxide incorporated thin film nanocomposite nanofiltration membrane for enhanced salt removal performance
Desalination
The chemical crosslinking of polyelectrolyte complex colloidal particles and the pervaporation performance of their membranes
J. Membr. Sci.
Pervaporation dehydration of acetone using P84 co-polyimide flat sheet membranes modified by vapor phase crosslinking
J. Membr. Sci.
Pervaporation separation of water/alcohol mixtures using composite membranes based on polyelectrolyte multilayer assemblies
J. Membr. Sci.
Recent membrane development for pervaporation processes
Prog. Polym. Sci.
The use of factorial design for modeling membrane distillation
J. Membr. Sci.
Double-skinned forward osmosis membranes based on layer-by-layer assembly—FO performance and fouling behavior
J. Membr. Sci.
Dehydration of isopropanol and its comparison with dehydration of butanol isomers from thermodynamic and molecular aspects
J. Membr. Sci.
Synthesis of high flux forward osmosis membranes by chemically crosslinked layer-by-layer polyelectrolytes
J. Membr. Sci.
Hydrophilic membranes for pervaporation: an analytical review
Desalination
Polymeric membrane pervaporation
J. Membr. Sci.
Studies of oxidative degradation in polyamide RO membrane barrier layers using pendant drop mechanical analysis
J. Membr. Sci.
Ultrathin membranes for gas separation and pervaporation prepared upon electrostatic self-assembly of polyelectrolytes
Thin Solid Films
Analysis of the membrane thickness effect on the pervaporation separation of methanol/methyl tertiary butyl ether mixtures
Sep. Purif. Technol.
Performance analysis of solar ethanol distillation
Renew. Energy.
Self-assembly of graphene oxide and polyelectrolyte complex nanohybrid membranes for nanofiltration and pervaporation
Chem. Eng. J.
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