Pervaporation Process Research Articles

Understanding the transport enhancement of poly (vinyl alcohol) based hybrid membranes with dispersed nanochannels for pervaporation application

Hybrid membranes, featuring combinations of inorganic and organic materials at the nanometre or molecular level, have been widely reported as providing superior separation performance compared with the traditional polymeric membranes. However, for rational design of membranes, there remains a major doubt as to how each constituent functions in the separation process. Herein, carbon nanotube (CNT) incorporated poly (vinyl alcohol) (PVA) membranes were analysed using pervaporation (PV) process for aqueous mixture separation. The impacts of CNT on the functional properties, morphologies and microscale structures of the PVA/CNT hybrid membranes was investigated by ATR-FTIR, AFM, SEM and positron annihilation lifetime spectroscopy (PALS). Further, a comparison of the interactions between the membrane and solvents (water and ethanol) were identified by swelling test and XRD. The resultant PVA/CNT hybrid membranes were then subject to both desalination and dehydration of ethanol. The results showed that PVA exhibited preferential adsorption of water over ethanol. The addition of CNT enlarged the fractional free volume (FFV) and enhanced water diffusivity (up to 185%), which indicated a diffusion-dominated type of the PVA/CNT hybrid membranes with a synergistic effect of CNT on water transport. The transport of Na+ ions through the membrane was examined to be with larger activation energy than that of ethanol during the separation process. This work investigated the state of polymer as well as the effect of nanofillers in the separation of water vs. non-volatile or volatile component for the first time, which can provide in-depth understanding of the polymer-based hybrid membranes for practical applications.

Mechanism Analysis, Economic Optimization, and Environmental Assessment of Hybrid Extractive Distillation–Pervaporation Processes for Dehydration of n-Propanol

n-Propanol, as an important chemical raw material, is used as a solvent and intermediate in chemical industrial production and drug synthesis. In chemical production, alcohol and water easily form ...

Fabrication and characterization of superhydrophobic PDMS composite membranes for efficient ethanol recovery via pervaporation

Bio-ethanol, clean and renewable, has proved to be a promising alternative energy resource to replace conventional fossil fuels. In its continuous production via the fermentation–pervaporation process, hydrophobic polymer membranes such as polydimethylsiloxane (PDMS) have been developed to enrich ethanol from dilute fermentation broth. However, the efficiency of current ethanol recovery via pervaporation is not high enough for large-scale bioethanol production. To address this issue, we separately fabricated two types of lotus-inspired PDMS composite membranes to combine the beneficial properties (low surface energy and super-hydrophobicity) of superhydrophobic lotus leaves with the pervaporation process and optimized the separation performance. First, we prepared lotus leaf powder/PDMS mixed matrix membranes (MMMs) to exploit the intrinsic properties of lotus leaf’s material. In addition, polydivinylbenzene (PDVB)-coated PDMS composite membranes were fabricated to mimic and make use of the properties coming from the lotus leaf’s hierarchical structure. The morphology, surface chemistry, and pervaporation performance were systematically investigated for all the membranes. And results showed that MMMs at 1.5 wt% lotus powder loading displayed the ideal dispersion condition and increased the total flux of pervaporation process by 22% (750 g∙m−2∙h−1, 6 wt%, 37 °C). For the PDVB-coated PDMS membrane, the hierarchical roughness was successfully established on the PDMS surface, which resulted in a super-hydrophobic surface with water contact angle higher than 150°. As PDVB also has preferential adsorption for ethanol, the PDVB-coated PDMS membrane showed a higher ethanol recovery performance with the separation factor and total flux increased by 13% and 30%, respectively. Therefore, it was demonstrated that PDVB coating is an effective method to fabricate superhydrophobic membranes and both the two lotus-inspired strategies are feasible in optimizing pervaporation performance for ethanol recovery.

Preparation of PVA-PFSA-Si pervaporative hybrid membrane and its dehydration performance

In order to ameliorate the trade-off effect in pervaporation process and to reduce the micro-phase separation of hybrid membrane, polyvinyl alcohol (PVA)-perfluorosulfonic acid (PFSA) blending materials were modified by two inorganic components to prepare PVA-PFSA-Si hybrid membrane. PVA-PFSA-Si membrane was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), contact angle measurements, scanning electron microscopy (SEM), positron annihilation lifetime spectrometer (PALS) and swelling measurements. As a second inorganic modifier, the effect of γ-glycidyloxypropyl trimethoxysilane (GPTMS) on the morphology of hybrid membrane was better than that of γ-aminopropyl triethoxysilane (APTEOS). PVA-PFSA-Si/polyacrylonitrile (PAN) composite membrane was used to pervaporatively dehydrate ethyl acetate (EAc)/H2O binary, EAc/ethanol (EtOH)/H2O ternary EAc/acetic acid (HAc)/EtOH/H2O quaternary solutions. At feed temperature of 40 °C, M8 membrane had the permeation fluxes (J) of 262.7, 215.2 and 182.6 g m−2 h−1 and the separation factors (α) of 6673, 3453 and 5374 for pervaporative dehydration of EAc/H2O (98/2, wt%) binary, EAc/EtOH/H2O (96/2/2, wt%) ternary and EAc/HAc/EtOH/H2O (96/1/1/2, wt%) quaternary solutions, respectively. The pervaporative results showed that PVA-PFSA-Si membrane had the excellent dehydration performances for EAc binary or multicomponent aqueous solutions.

The Effect of Polyethylene Glycol (PEG) on the Performance of Natural Zeolite-PVA Hybrid Ceramic Membrane for Desalination

The seawater desalination process currently uses membrane technology because of relatively lower investment and energy requirements. The process of seawater desalination using membrane process technology can be done in 3 methods, namely reverse osmosis (RO), distillation membrane (membrane distillation / MD) and pervaporation process (PV). This study will examine the performance of a hybrid membrane developed from natural zeolite-TiO2 with polyvinyl alcohol (PVA) in addition to polyethylene glycol (PEG) for desalination of seawater. The addition of PEG to the PVA polymer solution (dope) will increase the membrane resistance (Rm) and seawater rejection. The higher rejection is achieved of 93.77% at the addition of 6% PEG. Fouling resistance (Rf) isn’t affected by PEG concentration. The fouling resistance has good linearity and stability at the addition of 6% PEG.

Life-Cycle Assessment (LCA) of Different Pretreatment and Product Separation Technologies for Butanol Bioprocessing from Oil Palm Frond

Environmental impact assessment is a crucial aspect of biofuels production to ensure that the process generates emissions within the designated limits. In typical cellulosic biofuel production process, the pretreatment and downstream processing stages were reported to require a high amount of chemicals and energy, thus generating high emissions. Cellulosic butanol production while using low moisture anhydrous ammonia (LMAA) pretreatment was expected to have a low chemical, water, and energy footprint, especially when the process was combined with more efficient downstream processing technologies. In this study, the quantification of environmental impact potentials from cellulosic butanol production plants was conducted with modeled different pretreatment and product separation approaches. The results have shown that LMAA pretreatment possessed a potential for commercialization by having low energy requirements when compared to the other modeled pretreatments. With high safety measures that reduce the possibility of anhydrous ammonia leaking to the air, LMAA pretreatment resulted in GWP of 5.72 kg CO2 eq./L butanol, ecotoxicity potential of 2.84 × 10−6 CTU eco/L butanol, and eutrophication potential of 0.011 kg N eq./L butanol. The lowest energy requirement in biobutanol production (19.43 MJ/L), as well as better life-cycle energy metrics performances (NEV of 24.69 MJ/L and NER of 2.27) and environmental impacts potentials (GWP of 3.92 kg N eq./L butanol and ecotoxicity potential of 2.14 × 10−4 CTU eco/L butanol), were recorded when the LMAA pretreatment was combined with the membrane pervaporation process in the product separation stage.

Recovery of cutting oil from wastewater by pervaporation process using natural clay modified PVA membrane.

In this study, the pervaporative dehydration of the cutting oil 'diethylene glycol' (DEG) through a hydrophilic PVA membrane was investigated at various operation temperatures in the range of 333-363 K with a feed mixture containing 0.5-2.0 wt% water. The pervaporation (PV) performance of poly(vinyl alcohol) (PVA) is enhanced by the addition of natural clay kaolin into the pristine membrane. The thermal stability of the membranes was analyzed by thermal gravimetric analysis (TGA). The morphological analysis of the membranes was performed by scanning electron microscope (SEM). Separation success was determined by calculation of flux, selectivity, and PSI. These values were investigated as functions of the clay amount, feed concentration and feed temperature. The obtained results show that PV is an effective method for recycling waste cutting oil from wastewater.

Salt transport in polymeric pervaporation membrane

Abstract The salt transport in a PEBA membrane used in pervaporative desalination was studied. The concentration profile of salt in the membrane during pervaporation was investigated experimentally using a multilayer membrane. The salt was found to be sorbed in the membrane but was not removed during the pervaporative desalination process, and the salt concentration in the membrane varied linearly with position. High purity water was obtained as the permeate as long as the permeate side was kept dry under vacuum. The accumulated salt uptake in the membrane follows the order of MgCl2 > NaCl > Na2SO4. The solubility of salt in the membrane follows the order of MgCl2 > NaCl > Na2SO4. Both the permeability and diffusivity of salt in the membrane follow the order of NaCl > MgCl2 > Na2SO4. The permeability of salt in the membrane is not influenced by the feed salt concentration. It is mainly determined by the diffusion coefficients.

Interlayer-free silica–pectin membrane for sea-water desalination

Water scarcity has become a serious problem worldwide. Research is now looking at the fabrication and use of interlayer-free silica–pectin membranes for sea-water desalination as one potential solution to this problem. This research work investigates the performance of interlayer-free silica–pectin membranes for artificial sea-water desalination. A dual acid–base catalyst process is applied during the sol–gel process used to prepare the membrane's thin layer structure. Membranes were prepared using tetraethyl orthosilicate as the silica precursor and various concentrations of pectin (0 wt%, 0.1 wt%, 0.5 wt% and 2.5 wt%) were used as the “templating” agent. The performance of membranes was evaluated using pervaporation (PV) processes at room temperature (~25°C). The results show that water flux for 0.1 wt% pectin was the highest (4.50 kg m−2 h−1 and 5.73 kg m−2 h−1, at calcination temperatures of 300°C and 400°C, respectively). The fluxes at 0.5 wt% and 2.5 wt% pectin concentration were much lower, compared with 0.1 wt% (3.12–0.51 kg m−2 h−1 for both, at calcination temperatures of 300°C and 400°C). In addition, the salt rejection for all membranes remained excellent, at ~99.9%. This clearly demonstrates that carbon chains in silica matrices may produce smaller and stronger pores.

Review of Pervaporation and Vapor Permeation Process Factors Affecting the Removal of Water from Industrial Solvents.

A recent review article (J Chem Technol Biotechnol 94: 343-365 (2019)) identified several commercially-available permselective materials for drying organic solvents with pervaporation (PV) and vapor permeation (V·P) separation processes. The membrane materials included polymeric and inorganic substances exhibiting a range in the performance characteristics: water permeance, water/solvent selectivity, and maximum use temperature. This paper provides an overview of the factors affecting the design of PV/V·P processes utilizing these membranes to remove water from common organic solvents. Properties of the specific membrane and of the solvent substantially affect the PV/V·P separation. Equally important is the impact of operating parameters on the overall separation. To study these impacts, simplified process performance equations and detailed spreadsheet calculations were developed for single-pass and recirculating batch PV systems and for single-pass V·P systems. Estimates of membrane area, permeate concentration, solvent recovery, permeate condenser temperatures, and heating requirements were calculated. Process variables included: solvent type, water permeance, water/solvent selectivity, initial and final water concentrations, operating temperature (PV) or feed pressure (V·P), temperature drop due to evaporation (PV) or feed-side pressure drop (V·P), and permeate pressure. The target solvents considered were: acetonitrile, 1-butanol, N,N-dimethyl formamide, ethanol, methanol, methyl isobutyl ketone, methyl tert-butyl ether, tetrahydrofuran, acetone, and 2-propanol.

New molecular understanding of hydrated ion trapping mechanism during thermally-driven desalination by pervaporation using GO membrane

The graphene oxide (GO)-based membranes have shown effective salt separation from the brine solution. Although several experimental works have been done to study the salt rejection in the thermal-driven desalination system, the behavior of ions inside the GO nanochannels during the pervaporation process remains mostly unelucidated. Moreover, the previous theoretical studies on the driving force for ion transport within the GO membrane only focused on pressure, voltage, or concentration gradient. Here, we investigated the transport of water molecules and hydrated cations through the GO membrane in a temperature-assisted system by using dispersion-corrected density functional theory (DFT) calculations at PBE/Grimme with the ions under extreme confinement, reactive molecular dynamics (MD) simulations as well as validated by experimental methods. The water permeation increases with temperature, while the transport of cations remains minimal, which was not observed in other non-thermal desalination approaches. We have shown that high temperature eases the binding between the hydrated divalent cations and the oxygen functional groups on the GO nanosheets by reducing the hydration shell. Furthermore, the cross-linked cations inside the GO nanochannel create an accessible corridor for water molecules and block other cations such as Na+. Our simulation results provide a new mechanism of ion transport in the GO membranes by the thermal-driven process, which can be tailored by using other cations with higher charge density and high temperature to speed up the process.

Recovery of 1-ethyl-2-methylbenzene from wastewater by polymeric membranes via pervaporation process

In the present study for the first time, recovery of 1-ethyl-2-methylbenzene from aqueous solution was investigated by pervaporation process with polymeric membranes containing ethylene propylene diene monomer (EPDM), poly dimethylsiloxane (PDMS), poly vinylidenefluoride (PVDF) and poly ether-block-amide (PEBA). After preparation of membranes by solution casting method, the membranes were applied in pervaporation experiments at ambient temperature to determine several parameters such as flux, separation factor and pervaporation separation index (PSI). Scanning electron microscopy (SEM), contact angle, mechanical resistance and degree of swelling analyses were performed to characterize the prepared membranes. SEM images showed a dense and symmetrical morphology in regard to the prepared membranes. Results of contact angle analysis indicated that PDMS and EPDM membranes were completely hydrophobic in comparison with the other prepared membranes. Percent of swelling for all membranes was rather low and all of them swelled lower than 3.5%; however, swelling value for PVDF membrane was approximately negligible (0.3%). EPDM membrane with PSI value of of 653 kg/m2.h and separation factor of 3558, showed a superior performance in pervaporation process compared to the other prepared membranes; however, this membrane presented lower mechanical strength than the other membranes. PVDF membrane showed better results in terms of mechanical strength compared to the other membranes. Considering pervaporation separation index of 248 kg/m2.h and separation factor of 480, which were better than that of PDMS and PEBA membranes, PVDF showed poor performance in PV process compared with EPDM membrane. According to the higher mechanical strength and slight willingness of PVDF membrane to swelling in contact with aqueous feed, performance enhancement of this membrane in the pervaporation process can greatly surpass its position in removing 1-ethyl-2-methylbenzene from contaminated water.

Beer aroma recovery and dealcoholisation by a two-step pervaporation process

Beer aroma recovery and dealcoholisation by a two-step pervaporation process

Optimization and heat integration of hybrid R-HIDiC and pervaporation by combining GA and PSO algorithm in TAME synthesis

The TAME production process involves two main steps. The first step pertains to the reactions that lead to the synthesis of TAME, and the second step to the separation of TAME and recovery of methanol. Part of the TAME reaction and separation is carried out in a reactive distillation (RD) column. The product at the top of the RD column is a methanol- and C5-containing azeotropic mixture which can be isolated through pressure swing distillation (PSD) and extractive distillation (ED) methods. In this paper, the mixture was isolated through the pervaporation (PV) process, and all parameters related to RD and PV were considered as optimization variables, in particular the PV-related parameters such as the permeate stream pressure, the number of modules, and the temperature of inflow to each module. All variables were optimized simultaneously. The GA and PSO algorithms were combined to optimize the process and, additionally, total annual cost (TAC) was used as the objective function. The internally heat integrated distillation column (HIDiC) method was used to reduce the RD column energy costs, and the number of heat exchangers between the two rectifying and stripping sections was obtained using the optimization algorithm. The results showed that the hybrid PV/R-HIDiC process with heat integration was the best arrangement, resulting in a TAC reduction of 30% and 40% compared to the hybrid PV/RD process and the hybrid PSD/RD process, respectively. In this case, the number of trays in rectifying and stripping sections is respectively 22 and 6. The number of heat exchangers obtained by R-HIDiC method is 5, the number of PV modules is 11 and permeate pressure equals 18 as the most important parameters obtained from the optimization algorithm.

Polyacrylonitrile-supported self-aggregation crosslinked poly (vinyl alcohol) pervaporation membranes for ethanol dehydration

Highly water-selective poly(vinyl alcohol) (PVA)/polyacrylonitrile (PAN) pervaporation membranes were prepared by combining self-aggregation crosslinking reactions for PVA through ammonium persulfate (APS) initiations and interface physicochemical structure regulations for PAN supports. The membrane physicochemical properties were tested and the pervaporation performances were investigated by separation of 95 wt% ethanol aqueous. The results showed that the swelling degree and crystalline region of PVA membranes decreased with the increasing of APS content. On the contrary, the gel fraction of PVA membranes increased. Interestingly, the interface physicochemical structure between the PAN support and PVA separation layer played an important role in pervaporation processes. When the PAN supports were treated by sodium hydroxide (NaOH) and tannic acid (Ta), the water fraction in permeation always kept over 99.99 wt%, especially after Ta treatment. After optimization, the membrane based on PVA content of 8 g, 1.25 g self-crosslinking agent of APS and spin-coated onto H2-PAN (PAN modified by NaOH and Ta respectively), showed good permeability-selectivity and long-term performance stabilities. The total flux and water content ratio in permeation were 117.6 g/(m2h) and 99.99 wt% respectively by using the PVA8-1.25/H2-PAN membrane. After running for 120 h, the membranes still displayed a good stability for the ethanol dehydration in the pervaporation process. Importantly, the ethanol solution could be concentrated to over 99.99% using this polyacrylonitrile-based self-aggregation crosslinked poly (vinyl alcohol) pervaporation dehydration membrane.

The in-situ synthesis of a high-flux ZIF-8/polydimethylsiloxane mixed matrix membrane for n-butanol pervaporation

In pervaporation processes, membranes with high flux can relief the cost issue of industry scaling-up due to the required smaller membrane area. Herein, a novel in-situ synthesis (ISS) method was adopted to fabricate ZIF-8/polydimethylsiloxane (PDMS) mixed matrix membranes (MMMs) with outstanding permeability. ZIF-8 with high hydrophobicity, benefiting from its flexible pore structure, can provid a suitable pore structure for selectively recovering organic compounds. In the membrane preparation process, the solution C (PDMS/tetraethyl orthosilicate/Zn2+) and solution D (PDMS/dibutyltin dilaurate/2-methylimidazole) were co-processed other at the C-D interface via spin-coating. ZIF-8 crystallization occurred coupled with PDMS polymerization. An effective active layer was formed including (i) continuous and defect-free PDMS layer and (ii) a ZIF-8/PDMS layer that can add passable diffusion channels, which lifted the barrier of physical incorporation of porous materials. Defect-free MMMs based on ISS method possess unprecedented total flux of 2046.3 g/m2 h (1.6 times higher than pure PDMS membrane) and without any decline in separation factor under 20 wt% ZIF-8 loading for n-butanol pervaporation recovery. The ZIF-8/PDMS MMM prepared by ISS method showed promising in n-butanol separation.

Atomistic simulation study of GO/HKUST-1 MOF membranes for seawater desalination via pervaporation

HKUST-1 is one of the most widely used metal-organic frameworks (MOFs) in gas separation. However, its application in liquid separation is limited due to its relatively low stability in water caused by the interaction of coordinatively unsaturated Cu sites with the water molecules. In this study, molecular dynamics simulations of the pervaporation process are conducted to investigate the desalination performance of composite membranes composed of an HKUST-1 sheet and graphene oxide (GO) layers introduced to enhance its stability in water. The membrane configurations of single or double-layered GO on both sides of the HKUST-1 thin sheet are considered. It is revealed that the composite membranes demonstrate excellent water flux higher than that of ZIF-8 and GO membranes reported earlier. All the considered membranes show complete salt rejection. The water affinity of Cu atoms decreases with the addition of GO layers that improve the stability of HKUST-1 in water. However, this increase diminishes the permeate flux due to the presence of additional barriers in the molecular paths. The simulation results suggest that the HKUST-1 sheet with single-layered GO is a suitable material for pervaporation membrane fabrication.

Progress and Perspectives on Ceramic Membranes for Solvent Recovery.

With the increase in demand for commodities in the world, it is advisable to conserve resources. In the case of liquid wastes generated from pharmaceutical and petroleum industries, an unconventional solution is provided for the regeneration of solvents. However, this solvent recovery can be carried out using various efficient methods. Recently, Mixed Matrix Membranes (MMM) obtained by the addition of nanoparticles into a polymer matrix as reinforcements, or using a material with a well-defined inorganic network as a membrane like zeolite, silica based, Zeolite imidazolate frameworks (ZIFs) and Metal organic frameworks (MOFs), were explored for a solvent recovery process. These membranes possess characteristics such as high selectivity, flux and stability at various environmental conditions for the solvent recovery process. In this review, we have covered the polymer, nanocomposites, and ceramic membranes for solvent recovery through the pervaporation and organic solvent nanofiltration processes. The key challenges faced by the materials such as MOFs, zeolite, silica, zeolite and ZIFs when they are fabricated (through in situ synthesis or secondary growth process) as membranes and separation of solvents to explore for the solvent recovery process are reviewed.

Application of PVA-b-NaY zeolite mixture membranes in pervaporation method

Abstract Pervaporation, an economical, energy-saving and eco-friendly membrane process for separating liquid mixtures, has been considered as a promising candidate for the separation of azeotropic mixtures that are difficult to separate using classical processes. In this study, isopropyl alcohol/water azeotropic mixtures were separated by the pervaporation method using poly(vinyl alcohol)-blended-NaY zeolite (PVA-b-NaY) membranes. For this purpose, different yields of PVA/NaY mixtures were prepared and characterized by using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), water contact angle and atomic force microscopy (AFM). The effect of different parameters, such as PVA/NaY yield, membrane thickness, feed solution concentration and temperature, on the pervaporation performance was examined, and the optimum conditions were determined. The best separation factor was determined to be 2690.4 at a flux of 0.00512 kg/m2.h and an IPA concentration of 87.7%. Based on the research findings, it can be said that PVA-b-NaY membranes are very effective in separating IPA and water using the pervaporation method.

Zeolitic imidazolate framework membranes for gas and water purification

Zeolitic imidazolate frameworks (ZIF) have a flexible structure, controllable pore size, and thus adjustable properties, which make them effective materials for membrane separation. They have been used as a pure membrane in about 55% of cases, and as a structure modifier of mixed matrix membranes in other cases. ZIF-based membranes have been applied in pervaporation, nanofiltration, reverse osmosis and gas separation processes. This manuscript reviews the role of ZIF in promoting the membrane performance. A new performance parameter is defined based on permeability and selectivity, in order to compare the results of published reports. Findings show that the presence of ZIF in mixed matrix membranes improves the performances of pervaporation by 70%, nanofiltration by 211%, and reverse osmosis by 30%. ZIF also improved 11 times the membrane performance in gas separation, compared to the raw membrane.