Dehydration of water/t-butanol mixtures by pervaporation: comparative study of commercially available polymeric, microporous silica and zeolite membranes

Conceptual study on extraction of formic acid from the electrolyte after electroreduction of CO2: Desalination and dehydration using a high-silica chabazite zeolite membrane

Here, we propose a two-step pervaporation system with a high-silica CHA (chabazite) membrane, which has sufficient resistance to water and acid, to demonstrate the extraction and condensation of the formic acid formed by electroreduction of CO2. The kinetic diameters of water and formic acid are similar and smaller than the pore size of CHA, while the hydrated electrolyte ions (e.g., K+ and Cl-) are larger than the pore size of CHA. Consequently, the electrolyte ions are separated from the mixture of water and formic acid in the first desalination process, and then water molecules are easily removed from the mixture in the second dehydration process. From 300 ml of an approximately 3 wt% formic acid aqueous solution containing 0.5 M KCl, 10 ml of 18.2 wt% formic acid was obtained.

Recent Advances of Pervaporation Separation in DMF/H2O Solutions: A Review

N,N-dimethylformamide (DMF) is a commonly-used solvent in industry and pharmaceutics for extracting acetylene and fabricating polyacrylonitrile fibers. It is also a starting material for a variety of intermediates such as esters, pyrimidines or chlordimeforms. However, after being used, DMF can be form 5–25% spent liquors (mass fraction) that are difficult to recycle with distillation. From the point of view of energy-efficiency and environment-friendliness, an emergent separation technology, pervaporation, is broadly applied in separation of azeotropic mixtures and organic–organic mixtures, dehydration of aqueous–organic mixtures and removal of trace volatile organic compounds from aqueous solutions. Since the advances in membrane technologies to separate N,N-dimethylformamide solutions have been rarely reviewed before, hence this review mainly discusses the research progress about various membranes in separating N,N-dimethylformamide aqueous solutions. The current state of available membranes in industry and academia, and their potential advantages, limitations and applications are also reviewed.

A Review on Mixed Matrix Membranes for Solvent Dehydration and Recovery Process

Solvent separation and dehydration are important operations for industries and laboratories. Processes such as distillation and extraction are not always effective and are energy-consuming. An alternate approach is offered by pervaporation, based on the solution-diffusion transport mechanism. Polymer-based membranes such as those made of Polydimethylsiloxane (PDMS) have offered good pervaporation performance. Attempts have been made to improve their performance by incorporating inorganic fillers into the PDMS matrix, in which metal-organic frameworks (MOFs) have proven to be the most efficient. Among the MOFs, Zeolitic imidazolate framework (ZIF) based membranes have shown an excellent performance, with high values for flux and separation factors. Various studies have been conducted, employing ZIF-PDMS membranes for pervaporation separation of mixtures such as aqueous-alcoholic solutions. This paper presents an extensive review of the pervaporation performance of ZIF-based mixed matrix membranes (MMMs), novel synthesis methods, filler modifications, factors affecting membrane performance as well as studies based on polymers other than PDMS for the membrane matrix. Some suggestions for future studies have also been provided, such as the use of biopolymers and self-healing membranes.

Scalable crystalline porous membranes: current state and perspectives

Crystalline porous materials (CPMs) with uniform and regular pore systems show great potential for separation applications using membrane technology. Along with the research on the synthesis of precisely engineered porous structures, significant attention has been paid to the practical application of these materials for preparation of crystalline porous membranes (CPMBs). In this review, the progress made in the preparation of thin, large area and defect-free CPMBs using classical and novel porous materials and processing is presented. The current state-of-the-art of scalable CPMBs with different nodes (inorganic, organic and hybrid) and various linking bonds (covalent, coordination, and hydrogen bonds) is revealed. The advances made in the scalable production of high-performance crystalline porous membranes are categorized according to the strategies adapted from polymer membranes (interfacial assembly, solution-casting, melt extrusion and polymerization of CPMs) and tailored based on CPM properties (seeding-secondary growth, conversion of precursors, electrodeposition and chemical vapor deposition). The strategies are compared and ranked based on their scalability and cost. The potential applications of CPMBs have been concisely summarized. Finally, the performance and challenges in the preparation of scalable CPMBs with emphasis on their sustainability are presented.

Progress on Silica Pervaporation Membranes in Solvent Dehydration and Solvent Recovery Processes

Separation processes aimed at recovering the solvent from effluent streams offer a means for establishing a circular economy. Conventional technologies such as distillation are energy-intensive, inefficient and suffer from high operating and maintenance costs. Pervaporation based membrane separation overcomes these challenges and in conjunction with the utilization of inorganic membranes derived from non-toxic, sufficiently abundant and hence expendable, silica, allows for high operating temperatures and enhanced chemical and structural integrity. Membrane-based separation is predicted to dominate the industry in the coming decades, as the process is being understood at a deeper level, leading to the fabrication of tailored membranes for niche applications. The current review aims to compile and present the extensive and often dispersive scientific investigations to the reader and highlight the current scenario as well as the limitations suffered by this mature field. In addition, viable alternative to the conventional methodologies, as well as other rival materials in existence to achieve membrane-based pervaporation are highlighted.

Effects of different plasticizers on highly crosslinked NaAlg/PSSAMA membranes for pervaporative dehydration of tert-butanol

Polystyrene sulfonic acid-co-maleic acid (PSSAMA) crosslinked sodium alginate (NaAlg) membranes were developed by incorporating diethyl phthalate (DEP), dibutyl phthalate (DBP) and dioctyl phthalate (DOP).

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.

Inorganic Membranes: Preparation and Application for Water Treatment and Desalination

Inorganic membrane science and technology is an attractive field of membrane separation technology, which has been dominated by polymer membranes. Recently, the inorganic membrane has been undergoing rapid development and innovation. Inorganic membranes have the advantage of resisting harsh chemical cleaning, high temperature and wear resistance, high chemical stability, long lifetime, and autoclavable. All of these outstanding properties made inorganic membranes good candidates to be used for water treatment and desalination applications. This paper is a state of the art review on the synthesis, development, and application of different inorganic membranes for water and wastewater treatment. The inorganic membranes reviewed in this paper include liquid membranes, dynamic membranes, various ceramic membranes, carbon based membranes, silica membranes, and zeolite membranes. A brief description of the different synthesis routes for the development of inorganic membranes for application in water industry is given and each synthesis rout is critically reviewed and compared. Thereafter, the recent studies on different application of inorganic membrane and their properties for water treatment and desalination in literature are critically summarized. It was reported that inorganic membranes despite their high synthesis cost, showed very promising results with high flux, full salt rejection, and very low or no fouling.

Polymeric Nanocomposite Membranes for Next Generation Pervaporation Process: Strategies, Challenges and Future Prospects

Pervaporation (PV) has been considered as one of the most active and promising areas in membrane technologies in separating close boiling or azeotropic liquid mixtures, heat sensitive biomaterials, water or organics from its mixtures that are indispensable constituents for various important chemical and bio-separations. In the PV process, the membrane plays the most pivotal role and is of paramount importance in governing the overall efficiency. This article evaluates and collaborates the current research towards the development of next generation nanomaterials (NMs) and embedded polymeric membranes with regard to its synthesis, fabrication and application strategies, challenges and future prospects.

Materials for next-generation molecularly selective synthetic membranes

Materials research is key to enable synthetic membranes for large-scale, energy-efficient molecular separations. Materials with rigid, engineered pore structures add an additional degree of freedom to create advanced membranes by providing entropically moderated selectivities. Scalability - the capability to efficiently and economically pack membranes into practical modules - is a critical yet often neglected factor to take into account for membrane materials screening. In this Progress Article, we highlight continuing developments and identify future opportunities in scalable membrane materials based on these rigid features, for both gas and liquid phase applications. These advanced materials open the door to a new generation of membrane processes beyond existing materials and approaches.

Zeolite membranes – a review and comparison with MOFs

The latest developments in zeolite and MOF membranes are reviewed, with an emphasis on synthesis techniques. Industrial applications, hydrothermal stability, polymer-supported and mixed matrix membranes are some of the aspects discussed.

Pervaporation study for the dehydration of tetrahydrofuran-water mixtures by polymeric and ceramic membranes

Pervaporation technology can effectively separate a tetrahydrofuran (THF) solvent-water waste stream at an azeotropic concentration. The performance of a Sulzer 2210 polyvinyl alcohol (PVA) membrane and a Pervatech BV silica membrane were studied, as the operating variables feed temperature and permeate pressure, were varied. The silica membrane was found to exhibit a flux of almost double that of the PVA membrane, but both membranes had comparable separation ability in purifying the solvent-water mixture. At benchmark feed conditions of 96 wt% THF and 4 wt% water, 50 degrees C and 10 torr permeate pressure, the silica membrane flux was 0.276 kg/m(2)hr and selectivity was 365. For both membranes, flux was found to increase at an exponential rate as the feed temperature increased from 20 to 60 degrees C. The flux through the silica membrane increases at a 6% faster rate than the PVA membrane. Flux decreased as permeate pressure was increased from 5 to 25 torr for both membranes. The amount of water in the permeate decreased exponentially as the permeate pressure was increased, but increased linearly with increasing temperature. Optimum conditions for flux and selectivity are at low permeate pressure and high feed temperature. When a small amount of salt is added to the feed solution, an increase in flux is observed. Overall models for flux and permeate concentration were created from the experimental data. The models were used to predict scale-up performance in separating an azeotropic feed waste to produce dehydrated THF solvent for reuse and a permeate stream with a dilute THF concentration.