Pervaporation Process Research Articles

Ionic liquid modified graphene oxide-PEBA mixed matrix membrane for pervaporation of butanol aqueous solutions

This work explored a novel way to modify graphene oxide (GO) with ionic liquid (IL) and incorporate the modified GO into polyether block amide (PEBA) membrane for pervaporation of butanol aqueous solutions. The adsorption properties of GO and ionic liquid N-octylpyridiniunm bis (trifluoromethyl) sulfonyl imide [OPY][Tf2N] modified graphene oxide (IL-GO) for butanol and water were investigated via molecular simulation. Because ionic liquid [OPY][Tf2N] has good butanol affinity and hydrophobicity, the adsorption selectivity of butanol over water by the IL-modified GO increased by about 4 times compared with the pristine GO. Then IL-GO was incorporated into PEBA to fabricate mixed matrix membrane. The membrane was characterized, and the pervaporation performance of the membrane was evaluated. Pervaporation experiments showed that the incorporation of IL-GO is in favour of enhancing the membrane performance. Compared with pristine PEBA membrane, at 35 °C, for 2.5 wt% butanol aqueous solutions, the separation factor and permeation flux of the mixed matrix membrane with 1 wt% content of IL-GO were increased by 31.5% and 18.2%, respectively. Meanwhile, connecting ionic liquid to GO can effectively improve the membrane stability by preventing the loss of ionic liquid in the pervaporation process.

Prospects of Membrane Science Development

Membranes are widely used in modern technology. The demand for different types of membranes and membrane processes is increasing every year. This review summarizes the current state of the art and prospects of membrane science developments including membrane materials for gas separation, pervaporation, and pressure-driven membrane processes; ion-exchange, hybrid, and track-etched membranes; membranes for electrochemical sensors; and mathematical modeling of membrane separation processes and ion and water transport in membrane systems. Studies aimed at improving the selectivity and performance of membranes and their stability are surveyed. New approaches to the synthesis and modification of membranes as well as their advanced applications are discussed.

Titanate nanotubes–incorporated poly(vinyl alcohol) mixed matrix membranes for pervaporation separation of water-isopropanol mixtures

Mixed matrix membranes (MMMs) base on poly(vinyl alcohol) (PVA) incorporated with titanate nanotubes (TNTs), cross-linked with glutaraldehyde, were prepared. The hydrothermally synthesized TNTs and the membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), Thermogravimetric analysis (TGA), Field emission scanning electron microscope (FESEM), and tensile strength analyses. The prepared nanocomposite membranes were used for dehydration of isopropanol by pervaporation process. The effects of the weight fraction of TNTs, feed temperature, and concentration on the performance of the membranes were investigated. The results indicated that incorporation of hydrophilic TNTs could effectively improve the separation performance of PVA membranes in terms of both permeability and separation factor. Based on the results, the separation factor of all nanocomposite membranes was increased. Moreover, the membrane containing 4 wt% of TNTs exhibited the highest separation factor value of 5520, while the maximum value of flux was about 0.126 kg/m2h for the membrane containing 10 wt% TNTs. So, there was about 794% and 741% enhancement in separation factor and flux respectively, compared to the pristine PVA membranes. Consequently, the results confirm incorporating TNTs in the PVA matrix could improve the separation of water from isopropanol aqueous solutions effectively due to the intrinsic hydrophilicity and special structure of TNTs.

Enhanced desalination performance of poly (vinyl alcohol)/carbon nanotube composite pervaporation membranes via interfacial engineering

The dispersion and interfacial interactions between nanofillers and the polymer are two crucial factors affecting the performance of mixed matrix membranes (MMMs). In this study, poly (vinyl alcohol) (PVA) based mixed matrix membranes containing multiwalled carbon nanotubes (MWCNTs) or carboxylic multiwalled carbon nanotubes (C-MWCNTs) were produced via interfacial adhesion, hydrogen bonding or covalent bonding. The desalination performances of the synthesized membranes were compared by the pervaporation (PV) process. A PVA membrane crosslinked with maleic acid (MA) was also prepared for comparison. FESEM and TEM images indicated that the C-MWCNTs were disentangled and dispersed uniformly in the PVA matrix whereas MWCNTs without functional groups readily aggregated. The incorporation of CNTs endowed the PVA/CNT membranes with improved thermal stability, which was confirmed using TGA and DSC measurements. In particular, the altered properties of the PVA/CNT composites enhanced the separation performance compared with the PVA membrane without CNTs. The performance tests showed that the PVA/CNT composite membranes featured remarkably larger water fluxes than control PVA/MA membrane (38.8%–154.1% increase) while maintaining high salt rejection. Thereinto, the overall best performance of 99.91% of salt rejection and 6.96 kg/m2 h of water flux at room temperature (22 °C) was obtained by the PVA/C-MWCNT/MA membrane (19 ± 1 μm thickness) when the feed was synthetic NaCl solution of 35,000 ppm. Kinetic desorption method was applied to compare salt transport properties of the resultant PVA/CNT composite membranes. The salt transport through the PVA/C-MWCNT and PVA/C-MWCNT/MA membranes was significantly restricted with CNT mass fraction. High retention of water flux and salt rejection rates were also obtained by the PVA/C-MWCNT/MA membrane over a 30-h durability test that processed seawater collected from Brighton Beach (Melbourne, VIC, Australia), while the salt rejection for the PVA/C-MWCNT membrane declined with extended operating time indicating that cross-linking of the PVA was necessary for stable MMM performance.

Production and Isolation of n‐Butyl Acrylate Using Pervaporation‐Aided Esterification Reaction: Kinetics and Optimization

AbstractSynthesis of n‐butyl acrylate by esterification of acrylic acid with n‐butyl alcohol was carried out in a batch membrane reactor. Optimization and design of the experiment was accomplished by response surface methodology with Box‐Behnken experimental design. The effects of different parameters like reaction temperature, catalyst concentration, molar ratio of alcohol to acid, and ratio of membrane surface to initial volume on water flux and conversion of acrylic acid were evaluated. A kinetic model for the esterification‐coupled pervaporation process was developed. Kinetic parameters were estimated by a nonlinear optimization technique in the MATLAB optimization toolbox. The experimental and simulation results were applied for developing a concept to effectively conduct a pilot‐scale esterification‐pervaporation experiment.

Stability and pervaporation characteristics of PVA and its blend with PVAm membranes in a ternary feed mixture containing highly reactive epichlorohydrin.

In order to find an alternative for classical distillation in the recovery of ECH/IPA from azeotropic ECH/IPA/water (50/30/20 w/w, %) mixtures, a pervaporation process has been applied. Membranes from the crosslinking of poly(vinyl alcohol)/poly(vinyl amine) (PVA/PVAm) were prepared, and then the membrane stability and pervaporation efficiency of the crosslinked PVA/PVAm membranes were studied for highly reactive ECH systems containing a ternary feed mixture. From the Fourier-transform infrared (FT-IR) spectroscopy analysis, it was observed that all of the membranes were chemically stable for 15 days of immersion in a 50 : 30 : 20 ECH/IPA/water (w/w, %) feed mixture at 60 °C. The degree of membrane swelling increased with increasing PVAm content in the membrane composition, water content in the feed composition, and feed temperature, which was attributed to the increase in the number of hydrophilic sites in the membrane. The field-emission scanning electron microscopy (FE-SEM) study revealed that higher PVAm content membranes (PVAm1.0 and PVAm1.5) show polymer phase extraction in ECH/IPA/water (50 : 30 : 20) (w/w, %) at 60 °C in long-term stability tests. The pervaporation dehydration characteristics for all of the membranes with the feed comprising an ECH/IPA/water (50 : 30 : 20 by weight) azeotropic mixture at 30 °C were examined and excellent pervaporation dehydration efficiency was found. Quantitatively, the flux increased from 0.025 to 0.32 kg (m2 h)−1 and the separation factor decreased from 1908 to 60 with increasing PVAm content in the blended membrane.

Bioethanol Production from Saccharomyces cerevisiae through Conventional and Membrane Batch Fermentation: Experimental and Modeling Studies

Kinetics for bioethanol production from glucose using Saccharomyces cerevisiae (PTCC 24860) was experimentally studied in a batch membrane bioreactor and a conventional bioreactor using a pervaporation process. For pervaporation, a dense hydrophobic polydimethylsiloxane membrane was used. The batch membrane bioreactor resulted in increase of cell density, improved productivity and yield. A generic model was developed which can give a unique description for production of bioethanol within both batch membrane bioreactor and conventional bioreactor. Coupled describing equations of the model were solved by means of genetic algorithm approach. The logistic model considered for expression of growth kinetics and kinetic parameters calculated through the genetic algorithm. The results demonstrated that this generic model is capable to describe reasonably the behavior of both the conventional bioreactor and the batch membrane bioreactor with the highest correlation coefficient (0.979 and 0.987, respectively).

PH-Triggered Membrane in Pervaporation Process.

Dehydration of binary methyl acetate–water mixtures under neutral, acidic, and basic conditions was carried out by using PERVAP composite membranes based on polyvinyl alcohol and poly(1-vinylpyrrolidone-co-2-(dimethylamino)ethyl methacrylate) P(VP-co-DMAEMA). The effects of an acid (HCl) and a base (NaOH) on the separation performance of the membrane during the pervaporation process were investigated. The pH-responsive nature of membranes has been confirmed by swelling tests and analysis of the chemical structure of polymeric membranes. In addition, a mechanism of ring-opening of VP units is proposed and correlated to the changes of membrane separation performance.

Three-component mixed matrix membrane containing [Hmim][PF6] ionic liquid and ZSM-5 nanoparticles based on poly (ether-block-amide) for the pervaporation process

Three-component mixed matrix membranes based on poly (ether-block-amide) (PEBA) were prepared by incorporation of ZSM-5 zeolite nanoparticles and [Hmim][PF6] ionic liquid for the separation of ethyl acetate (EAc) from EAc/water mixtures using the pervaporation process. At first, the dual-layer PEBA/polyethersulfone (PES) membranes containing [Hmim][PF6] in the active layer were prepared and employed in the pervaporation process. It was found that the ionic liquid leached out from the membrane during the pervaporation experiments and decreased the membrane selectivity. In order to avoid leaching out of the ionic liquid, triple-layer membranes consisting of a ZSM-5/PEBA as the top layer on a [Hmim][PF6]/PEBA as the intermediate layer and PES as the support layer were developed. The effect of ionic liquid concentration in the intermediate layer on the membrane separation performance was investigated and the results indicated that the membrane containing 2.5%wt. [Hmim][PF6] had the best separation performance in terms of the pervaporation separation index (PSI). Moreover, the ZSM-5 nanoparticles were added to the intermediate layer of the triple-layer membranes to improve the performance of the membranes. It was found that simultaneous loading of the ZSM-5 and [Hmim][PF6] in the PEBA matrix significantly improved the separation performance of the membrane as the PSI of the prepared three-component mixed matrix membrane was 1.5 times the PSI of the neat PEBA membrane.

Enhanced pervaporation performance of polyamide membrane with synergistic effect of porous nanofibrous support and trace graphene oxide lamellae

Electrospun nanofibrous membrane as a supporting layer has attracted great interests in fabricating high performance composite membranes due to its interconnected porous structure. However, it’s still a challenge to prepare an ultrathin and integrated skin layer on porous and undulating nanofibrous support, thereby restricting its application in pervaporation. Here, graphene oxide (GO) was introduced into amine aqueous phase to form an integrated and compact polyamide (PA) layer on nanofibrous substrate via interfacial polymerization (IP). Under the synergistic effect of high permeability of the nanofibrous scaffold and flexibility of GO lamellae, tiled GO lamellae acting as a skeleton got involved in the initial reaction for the construction of selective PA layer. By loading trace amount of GO in aqueous phase during IP, the selectivity of PA layer was enhanced significantly compared with that of pristine PA layer on nanofibrous scaffold. High permeate flux of 6593 g/m2h with a desirable separation factor of 1491 was achieved using the hybrid membrane with just 0.001 wt% of GO loading for pervaporation dehydrating 90 wt% isopropanol aqueous solution at 70 °C. These results indicated the feasibility of constructing a single homogeneous selective layer on nanofibrous support for high-performance pervaporation process.

Review: membrane materials for the removal of water from industrial solvents by pervaporation and vapor permeation

Organic solvents are widely used in a variety of industrial sectors. Reclaiming and reusing the solvents may be the most economically and environmentally beneficial option for managing spent solvents. Purifying the solvents to meet reuse specifications can be challenging. For hydrophilic solvents, water must be removed prior to reuse, yet many hydrophilic solvents form hard-to-separate azeotropic mixtures with water. Such mixtures make separation processes energy intensive and cause economic challenges. The membrane processes pervaporation (PV) and vapor permeation (VP) can be less energy intensive than distillation-based processes and have proven to be very effective in removing water from azeotropic mixtures. In PV/VP, separation is based on the solution-diffusion interaction between the dense permselective layer of the membrane and the solvent/water mixture. This review provides a state-of-the-science analysis of materials used as the selective layer(s) of PV/VP membranes in removing water from organic solvents. A variety of membrane materials, such as polymeric, inorganic, mixed matrix, and hybrid, have been reported in the literature. A small subset of these are commercially available and highlighted here: poly(vinyl alcohol), polyimides, amorphous perfluoro polymers, NaA zeolites, chabazite zeolites, T-type zeolites, and hybrid silicas. The typical performance characteristics and operating limits of these membranes are discussed. Solvents targeted by the U.S. Environmental Protection Agency for reclamation are emphasized and ten common solvents are chosen for analysis: acetonitrile, 1-butanol, N,N-dimethyl formamide, ethanol, methanol, methyl isobutyl ketone, methyl tert-butyl ether, tetrahydrofuran, acetone, and 2-propanol.

Enhanced Ethanol Separation by Corona-Modified Surface MWCNT Composite PDMS/PES.PVP Membrane

Ethanol separation factor and total flux for a fabricated composite polydimethylsiloxane/polyethersulfone polyvinylpyrrolidone (PDMS/PES.PVP) membrane in the pervaporation process were obtained at 6.25 and 440 g/m2 h, respectively. In order to improve the separation of ethanol as a renewable resource from water, the composite PDMS surface was modified by corona treatment, and the treated surface was coated by multi-walled carbon nanotubes (MWCNTs). Implementation of corona treatment for surface modification leads to enhancement in the ethanol separation factor using a MWCNT surface-coated membrane. Based on the obtained data, for a corona time of 6 min and corona input power of 360 W, the ethanol separation factor was improved from 6.25 to 9.3 and also a total flux of 280 g/m2 h was obtained. Therefore, application of the novel fabricated PDMS/PES.PVP composite membrane with surface modification by corona treatment and MWCNT coating in the pervaporation process at the desired condition has significantly improved the ethanol separation factor (48.8%).

Sorption and pervaporation study of methanol/dimethyl carbonate mixture with poly(etheretherketone) (PEEK-WC) membrane

A dense membrane prepared by using a modified poly ether ether ketone (PEEK-WC) polymer was studied for the pervaporation separation of a binary mixture dimethyl carbonate (DMC) and methanol. Contact angle and mechanical measurements were carried out to study the properties of the membrane as well as SEM analysis to evaluate the surface morphology. The swelling degree of the membrane was studied at different concentrations of methanol. When tested in a pervaporation process by varying methanol concentration and feed temperature, the transmembrane flux was found to be temperature dependent with a value of 0.14 kg/m2⋅h at low concentration of methanol (10 mol%) with its highest separation factor being 13.4 at 30 °C. The flux increased with the increase of the temperature, but the separation factor decreased. Using high concentration of methanol resulted in a high permeance of DMC due to a dragging effect. Selectivity results showed that the composition of the mixture had a strong influence on the membrane performance.

On-Line NIR to Regulate Pervaporation Process: Application for Dehydration.

The regeneration of volatile organic solvents via dehydration tests, from 90 wt %, was evaluated by pervaporation using an on-line near-infrared (NIR) spectrometer. Experiments were performed using a bis(triethoxysilyl)methane (BTESM)-based ceramic HybSi® membrane at temperatures of 20, 30 and 40 °C. The presence of an on-line NIR allows continuous monitoring of the process without sampling, and quickly estimates mass fractions of species in the retentate. Dehydration tests were performed at 30 °C in order to confirm the on-line NIR reproducibility, and closely matched results obtained with an off-line densimeter. These results validated the usefulness of the on-line NIR and provided the same precision whatever the mass fraction in the retentate. A good on-line reproducibility was found, with an agreement between the on-line NIR and off-line densimeter, obtaining an average deviation of ±0.058 wt %, ±0.17 wt % and ±0.049 wt %, respectively, at 20, 30 and 40 °C.

Study on CO2 Desorption Behavior of a PDMS-SiO2 Hybrid Membrane Applied in a Novel CO2 Capture Process.

In this present work, a novel approach has been proposed by which a solvent absorption and membrane desorption methods can significantly reduce the carbon dioxide (CO2) emission and energy consumption. In this method, the CO2 capture processing is based on the combination of membrane and physical solvent. Here, dimethyl carbonate and polydimethylsiloxane (PDMS)-SiO2 nanocomposite were used as the physical solvent and desorption membrane, respectively. However, the main focus of this research was on the CO2 desorption behavior of PDMS-SiO2 hybrid membrane. To do so, the influence of the operating conditions and membrane properties on the pervaporation process to capture CO2 have been investigated. The PDMS-SiO2 hybrid membrane containing 10 wt % SiO2 was the most effective membrane. Results revealed that increase in CO2 concentration from 1.5 to 3 wt % led to decrease in the selectivity from 94 to 47 and increase in flux from 1.7 to 5.38 (kg/m2·h). In addition, an increase in temperature increased the flux and reached the highest level (8.17 kg/m2·h) at 40 °C. However, the selectivity decreased to 36.13. It was found that the addition of SiO2 nanoparticles to the PDMS membrane not only enhanced the membrane performance but also decreased the energy consumption about 75% compared with gas stripping method and mass transfer about 49% compared with pure PDMS membrane. Finally, these results illustrated that such a novel technique used for pervaporation separation process is a green and promising alternative to separate CO2 from the physical solvent.

Separation of benzo[a]pyrene and n-tetradecane mixtures using pervaporation technique and optimization

Benzo[a]pyrene is a carcinogen often present in diesel. For pervaporative removal of benzo[a]pyrene from n-tetradecane, representing a model diesel composition, both conventional as well as statistically designed experimental methods have been carried out. The effect of membrane composition, thickness, the effect of membrane pretreatment time and operating temperature on pervaporative separation have been investigated by response surface methodology, RSM for efficient permeation of target compound. The suitable membrane has been further used to study the effect of different physico-chemical parameters on permeation conventionally. RSM has also been applied to optimize the operational conditions of pervaporation process to maximize the response, i.e., the pervaporation separation index. With the design of experiments, the quadratic response surface models have been developed to link the response with input variables via mathematical relationships. The maximum value of Pervaporation Separation Index obtained is 1.9654 kg m−2 h−1. The optimized process condition’s run time is 10.79 h, the feed PAH concentration is 166.34 ppm with a permeate side pressure of 0.73 mmHg and an operating temperature of 451.25 K.

Influence of feed flow rate, temperature and feed concentration on concentration polarization effects during separation of water-methyl acetate solutions with high permeable hydrophobic pervaporation PDMS membrane

A novel and efficient method is proposed to evaluate the concentration polarization (CP) effect in pervaporation process. The novelty of the method results from the approach towards the CP phenomenon, that proposes the calculation algorithm on the basis of permeate fluxes and feed/permeate compositions as a function of the feed flow velocity only. The main advantage of the method over the approaches available in the literature is that the intrinsic enrichment factor is calculated directly from the experimental data instead of being found as one of the regression parameters. To prove this approach, pervaporation experiments were carried out using commercial hydrophobic composite PDMS based membrane Pervatech for the recovery of methyl acetate (MeAc) from diluted aqueous solutions (0–1.5 wt% MeAc in feed mixture). Pervaporation performance of PDMS membrane was investigated at various feed flow rates in the range 4.8–70 dm3 h−1 and at three different temperatures of feed mixture (i.e. 30 °C, 40 °C, and 50 °C). It was shown that the intrinsic enrichment factor changes noticeably when the process parameters are altered and this change is one of the key factors affecting the concentration polarization modulus value during pervaporative removal of organic compounds from diluted aqueous solutions. With increasing temperature and feed flow rate, the concentration polarization modulus increases, reaching the value close to 1 at temperature of 50 °C and at the average feed flow rate equal to 1.34 cm s−1. Moreover, under these conditions, the thickness of the boundary layer tends to zero.

Silica P123 Membranes for Desalination of Wetland Saline Water in South Kalimantan

Salt water intrusion into the river around wetland areas is affected by the increasing of sea water level. This work aims to fabricate silica P123 membranes applied for desalination of wetland saline water. This type of membranes is produced by combining silica material (TEOS) with P123 as organic polymer. The calcination method was varied from 350°C and 600°C for an hour using RTP method. The desalination via pervaporation process was applied in order to investigate water flux and salt rejection. The results show that membranes calcined at low temperatures obtain good performance compare to high temperature (4.105 and 3.904 kg.m-2.h-1 for water flux and 96.22 and 65.67% for salt rejection obtained from membranes calcined at 350 and 600°C, respectively).

Treatment of Pharmaceutical Process Wastewater with Hybrid Separation Method: Distillation and Hydrophilic Pervaporation

Abstract The work is motivated by an industrial problem, which is alcohol removal from pharmaceutical process wastewater. The aim of the study was to develop a complete hybrid operation is investigated. Ethanol dehydration, in combination with distillation and hydrophilic pervaporation, is used to investigate about the extent of separation of the ethanol-water mixture. The aim of this research is to rigorously model and optimize this hybrid operation in professional flowsheet simulator environment. The number of minimal theoretical plates of distillation column and minimal effective membrane transfer area are determined. Cost estimation is also examined according to Douglas methodology. Considering our results it can be concluded that, the distillation and hydrophilic pervaporation processes are suitable for separation ethanol and water in 99.5 weight percent purity

Desalination Process via Pervaporation of Wetland Saline Water

Water is a very important resource for life on earth. Nowadays, water scarcity is a big issue around the world. Especially people who live in wetland areas, river is an important water source for their daily life. Unfortunately, the water becomes salty due to seawater intrusion into the river. The objective of this work is to apply desalination via pervaporation process of wetland saline water using pure silica membranes employ TEOS (tetraethyl orthosilicate) as a precursor. A two-step acid-base catalysed method has been applied to produce silica sols. The pure silica membranes were calcined under RTP (Rapid Thermal Process) method at 600°C for 1 hour. The various temperatures (20, 40 & 60 °C have been set in pervaporation set up in order to investigate the performance of silica membranes. It was found that at high temperature, silica membranes start to densify and give the lowest rejection compare to lower temperatures (84.9 %). In contrary, there was 100% of water flux increases when the feed temperature increases (from 0.61 to 1.19 kg m-2 h-1)