Thin film composite membranes comprising of polyamide and polydopamine for dehydration of ethylene glycol by pervaporation

Synthesis, characterization and application of chitosan functionalized and functional graphene oxide membranes for desalination of water by pervaporation

The use of graphene sheets in water treatment is increasing due to its adsorption capacity, reactivity, catalytic action and surface area. The challenges linked to wastewater treatment are vast due to the constant influx of various pollutants. Can the challenges of water desalination and purification be encountered by graphene-based composites and membranes?.The current work describes the synthesis of graphene oxide (GO) using modified Hummers' method. GO was functionalized with chitosan and used as adsorbents. On the other hand, it was reported that the surface of thin-film-composite (TFC) polyamide membranes was modified in order to desalinate highly saline water using pervaporation. The findings showed that GO synthesized by modified Hummers' method has a greater capacity for the adsorption of sodium ion and have better regeneration performance. Functionalization with chitosan increased adsorption capacity from 680.2 to 740.5 mg/g at the initial concentration of 45,000 mg/l of Na+ ions. On the other hand, modification in membrane comprises the chlorine treatment of surface of polyamide membrane. Layer-by-layer (LbL) deposition of positively charged polyethyleneimine (PEI) and negatively charged graphene oxide (GO) was followed. The PEI/GO LbL membrane's pure water flux was twice as high as compare to the original membrane. The synthesized membrane was tested against the aqueous solutions containing Na2SO4, MgSO4, NaCl and MgCl2 salts for their desalination. At different concentrations, a water flux of 8.9 kg/m2h with a huge salt rejection (>99.9%) was attained for every tested salt. It was observed that CS functionalized GO and GO membrane showed higher adsorption capacity and improved regeneration performance can be measured as an operational and active adsorbent for sea water desalination.

Development and Investigation of Hierarchically Structured Thin-Film Nanocomposite Membranes from Polyamide/Chitosan Succinate Embedded with a Metal-Organic Framework (Fe-BTC) for Pervaporation

Thin-film composite membranes (TFC) obtained by the formation of a selective layer on a porous membrane-substrate via interfacial polymerization (IP) are indispensable for separation procedures in reverse osmosis, nanofiltration, pervaporation, and gas separation. Achieving high selectivity and permeability for TFC membranes is still one of the main challenges in membrane science and technology. This study focuses on the development of thin film nanocomposite (TFN) membranes with a hierarchically structured polyamide (PA)/chitosan succinate (ChS) selective layer embedded with a metal-organic framework of iron 1,3,5-benzenetricarboxylate (Fe-BTC) for the enhanced pervaporation dehydration of isopropanol. The aim of this work was to study the effect of Fe-BTC incorporation into the ChS interlayer and PA selective layer, obtained via IP, on the structure, properties, and performance of pervaporation TFN membranes. The structure and hydrophilicity of the developed TFN membranes were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM), along with water contact angle measurements. The developed TFN membranes were studied in the pervaporation dehydration of isopropanol (12-30 wt % water). It was found that incorporation of Fe-BTC into the ChS interlayer yielded the formation of a smoother, more uniform, and defect-free PA ultrathin selective layer via IP, due to the amorpho-crystalline structure of particles serving as the amine storage reservoir and led to an increase in membrane selectivity toward water, and a slight decrease in permeation flux compared to the ChS interlayered TFC membranes. The best pervaporation performance was demonstrated by the TFN membrane with a ChS-Fe-BTC interlayer and the addition of 0.03 wt % Fe-BTC in the PA layer, yielding a permeation flux of 197-826 g·m^-2·h^-1 and 98.50-99.99 wt % water in the permeate, in the pervaporation separation of isopropanol/water mixtures (12-30 wt % water).

Pervaporation as a Successful Tool in the Treatment of Industrial Liquid Mixtures

Pervaporation is one of the most active topics in membrane research, and it has time and again proven to be an essential component for chemical separation. It has been employed in the removal of impurities from raw materials, separation of products and by-products after reaction, and separation of pollutants from water. Given the global problem of water pollution, this approach is efficient in removing hazardous substances from water bodies. Conventional processes are based on thermodynamic equilibria involving a phase transition such as distillation and liquid-liquid extraction. These techniques have a relatively low efficacy and nowadays they are not recommended because it is not sustainable in terms of energy consumption and/or waste generation. Pervaporation emerged in the 1980s and is now becoming a popular membrane separation technology because of its intrinsic features such as low energy requirements, cheap separation costs, and good quality product output. The focus of this review is on current developments in pervaporation, mass transport in membranes, material selection, fabrication and characterization techniques, and applications of various membranes in the separation of chemicals from water.

A Review of Recent Developments of Pervaporation Membranes for Ethylene Glycol Purification

Ethylene glycol (EG) is an essential reagent in the chemical industry including polyester and antifreeze manufacture. In view of the constantly expanding field of EG applications, the search for and implementation of novel economical and environmentally friendly technologies for the separation of organic and aqueous–organic solutions remain an issue. Pervaporation is currently known to significantly reduce the energy and resource consumption of a manufacturer when obtaining high-purity components using automatic, easily scalable, and compact equipment. This review provides an overview of the current research and advances in the pervaporation of EG-containing mixtures (water/EG and methanol/EG), as well as a detailed analysis of the relationship of pervaporation performance with the membrane structure and properties of membrane materials. It is discussed that a controlled change in the structure and transport properties of a membrane is possible using modification methods such as treatment with organic solvents, introduction of nonvolatile additives, polymer blending, crosslinking, and heat treatment. The use of various modifiers is also described, and a particularly positive effect of membrane modification on the separation selectivity is highlighted. Among various polymers, hydrophilic PVA-based membranes stand out for optimal transport properties that they offer for EG dehydrating. Fabricating of TFC membranes with a microporous support layer appears to be a viable approach to the development of productivity without selectivity loss. Special attention is given to the recovery of methanol from EG, including extensive studies of the separation performance of polymer membranes. Membranes based on a CS/PVP blend with inorganic modifiers are specifically promising for methanol removal. With regard to polymer wettability properties, it is worth mentioning that membranes based on hydrophobic polymers (e.g., SPEEK, PBI/PEI, PEC, PPO) are capable of exhibiting much higher selectivity due to diffusion limitations.

Hetero-lattice intergrown and robust MOF membranes for polyol upgrading

Metal-organic framework membranes are frequently used in gas separations, but rare in pervaporation for liquid chemical upgrading, especially for separating water from polyols, due to lack of highly compact and robust micro-architecture. Here, we report hetero-lattice intergrown membranes in which amino-MIL-101 (Cr) particles embedded into the micro-gaps of MIL-53 (Al) rod arrays after secondary growth. By means of high-resolution TEM and two-dimensional topologic simulation, the connection between these two distinct MOF lattices at molecular-level and their crystallographic geometry harmony is identified, which leads to a close-knit structure at crystal boundaries of membranes. Typically, the membrane shows a separation factor as high as 13,000 for 90/10 ethanediol/water solution in pervaporation, yields polymer-grade ethanediol, and saves ca. 32% of energy consumption vs. vacuum distillation. It has a highly robust micro-architecture, with great tolerance to high pressure, durability against ultrasonic therapy and long-term separation stability over 600 h.

Thin-film nanocomposite NF membrane with GO on macroporous hollow fiber ceramic substrate for efficient heavy metals removal

The ceramic membrane has been widely used in the wastewater treatment based on the chemical resistance and superior separation performance. A robust and defect-free thin-film nanocomposite (TFN) nanofiltration (NF) membrane on the macroporous hollow fiber ceramic (HFC) substrate was novelly developed for heavy metals removal. Before interfacial polymerization (IP), the aqueous solution of graphene oxide (GO) grafted with ethylenediamine (EDA) was deposited on the HFC substrate by vacuum filtration. Then, a thin polyamide (PA) film was fabricated by EDA and 1,3,5-trimesoyl chloride (TMC), followed by heat treatment. The effects of GO content and EDA concentration on the performance of the NF membrane have been systematically investigated. The results showed that when the GO content was 0.015 mg·mL^-1 and the EDA concentration was 0.75 wt.%, the as-prepared eGO₃/PA-HFC membrane had a rejection rate of 94.12% for MgCl₂ and a pure water flux of 18.03 L·m^-2·h^-1. Additionally, the removal ability of eGO₃/PA-HFC membranes for heavy metal ions was satisfactory (93.33%, 92.73%, 90.45% and 88.35% for Zn²⁺, Cu²⁺, Ni²⁺ and Pb²⁺, respectively). The study explored further that it was efficient and stable for heavy metal ions removal during 30 h in the simulated tap water and mining wastewater, which indicated that the eGO/PA-HFC membrane has great application potential in wastewater treatment.

Fabrication, Properties, Performances, and Separation Application of Polymeric Pervaporation Membranes: A Review

Membrane separation technologies have attracted great attentions in chemical engineering, food science, analytical science, and environmental science. Compared to traditional membrane separation techniques like reverse osmosis (RO), ultrafiltration (UF), electrodialysis (ED) and others, pervaporation (PV)-based membrane separation shows not only mutual advantages such as small floor area, simplicity, and flexibility, but also unique characteristics including low cost as well as high energy and separation efficiency. Recently, different polymer, ceramic and composite membranes have shown promising separation applications through the PV-based techniques. To show the importance of PV for membrane separation applications, we present recent advances in the fabrication, properties and performances of polymeric membranes for PV separation of various chemicals in petrochemical, desalination, medicine, food, environmental protection, and other industrial fields. To promote the easy understanding of readers, the preparation methods and the PV separation mechanisms of various polymer membranes are introduced and discussed in detail. This work will be helpful for developing novel functional polymer-based membranes and facile techniques to promote the applications of PV techniques in different fields.

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.

Toward enhanced conductivity of high-temperature proton exchange membranes: development of novel PIM-1 reinforced PBI alloy membranes

Polymers of intrinsic microporosity are for the first time incorporated into PBIs to form some novel alloys for HT-PEMFC applications.

Microporous Organic Materials for Membrane-Based Gas Separation

Membrane materials with excellent selectivity and high permeability are crucial to efficient membrane gas separation. Microporous organic materials have evolved as an alternative candidate for fabricating membranes due to their inherent attributes, such as permanent porosity, high surface area, and good processability. Herein, a unique pore-chemistry concept for the designed synthesis of microporous organic membranes, with an emphasis on the relationship between pore structures and membrane performances, is introduced. The latest advances in microporous organic materials for potential membrane application in gas separation of H₂ , CO₂ , O₂ , and other industrially relevant gases are summarized. Representative examples of the recent progress in highly selective and permeable membranes are highlighted with some fundamental analyses from pore characteristics, followed by a brief perspective on future research directions.

Nanoparticles Embedded in Amphiphilic Membranes for Carbon Dioxide Separation and Dehumidification

Polymers containing ethylene oxide (EO) groups have gained significant interest as the EO groups have favorable interactions with polar molecules such as H₂ O, quadrupolar molecules such as CO₂ , and metal ions. However, the main challenges of poly(ethylene oxide) (PEO) membranes are their weak mechanical properties and high crystallinity nature. The amphiphilic copolymer made from PEO terephthalate and poly(butylene terephthalate) (PEOT/PBT) comprises both hydrophilic and hydrophobic segments. The hydrophilic PEOT segment is thermosensitive, which facilities gas transports whereas the hydrophobic PBT segment is rigid, which provides mechanical robustness. This work demonstrates a new strategy to design amphiphilic mixed matrix membranes (MMMs) by incorporating zeolitic imidazolate framework, ZIF-71, into the PEOT/PBT copolymer. The resultant membrane shows an enhanced CO₂ permeability with an ideal CO₂ /N₂ selectivity surpassing the original PEOT/PBT and Robeson's Upper bound line. The nanoparticles-embedded amphiphilic membranes exhibit characteristics of high transparency and mechanical robustness. Mechanically strong composite hollow fiber membranes consisting of PEOT/PBT/ZIF-71 as the selective layer were also prepared. The resultant hollow fibers possess an excellent CO₂ permeance of 131 GPU (gas permeation units), CO₂ /N₂ selectivity of 52.6, H₂ O permeance of 9300 GPU and H₂ O/N₂ selectivity of 3700, showing great potential for industrial CO₂ capture and dehumidification.

Surface modification of chitosan film via polydopamine coating to promote biomineralization in bone tissue engineering

Chitosan-based material has been widely used as bone substitute due to its good biocompatibility and biodegradability. However, the hydrophobic surface of chitosan film constrains the osteogenesis mineralization in the process of bone regeneration. For this reason, we develop a novel polydopamine-modified chitosan film suitable for bone tissue engineering applications by a simple and feasible route in this study. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the process of surface modification. For comparison, surface wettability, the capacity of mineralization in vitro, and biocompatibility of the chitosan film and the polydopamine-modified chitosan film were assessed. Research results indicate that the polydopamine-modified chitosan film has good hydrophilicity. It is very evident that the polydopamine treatment significantly influences the biomineralization capacity of the chitosan-based substrates, which enhance the growth rate of apatite on the modified chitosan film. Besides, MC3T3-E1 osteoblast experiments demonstrate that the cells can adhere and grow well on the polydopamine-modified chitosan film. It is anticipated that this polydopamine-modified chitosan film, which can be prepared in large quantities simply, should have potential applications in bone tissue engineering.

Bio-inspired Ni2+-polyphenol hydrophilic network to achieve unconventional high-flux nanofiltration membranes for environmental remediation

A Ni²⁺-polyphenol network was synthesized as a hydrophilic coating to achieve highly efficient nanofiltration membranes with an unconventional high flux for dye wastewater remediation.

High-Performance Polymers for Membrane CO2 /N2 Separation

This Concept examines strategies to design advanced polymers with high CO₂ permeability and high CO₂ /N₂ selectivity, which are the key to the success of membrane technology for CO₂ capture from fossil fuel-fired power plants. Specifically, polymers with enhanced CO₂ solubility and thus CO₂ /N₂ selectivity are designed by incorporating CO₂ -philic groups in polymers such as poly(ethylene oxide)-containing polymers and poly(ionic liquids); polymers with enhanced CO₂ diffusivity and thus CO₂ permeability are designed with contorted rigid polymer chains to obtain high free volume, such as polymers with intrinsic microporosity and thermally rearranged polymers. The underlying rationales for materials design are discussed and polymers with promising CO₂ /N₂ separation properties for CO₂ capture from flue gas are highlighted.

Comb-shaped phenolphthalein-based poly(ether sulfone)s as anion exchange membranes for alkaline fuel cells

A series of novel comb-shaped phenolphthalein-based poly(ether sulfone)s was synthesized for preparing anion exchange membranes (AEMs).

Enhanced CO2 separation performance of P(PEGMA-co-DEAEMA-co-MMA) copolymer membrane through the synergistic effect of EO groups and amino groups

PEDM copolymer membrane showed excellent gas separation performance through synergistic effect of EO and amino.

Highly selective thin film composite hollow fiber membranes for mixed vapor/gas separation

In the present study, thin film composite membranes have been prepared using an interfacial polymerization method.