Breakthroughs on tailoring pervaporation membranes for water desalination: A review

Ultrafiltration membrane based on chitosan/adipic acid: Synthesis, characterization and performance on separation of methylene blue and reactive yellow-145 from aqueous phase

Here, we report for the first time using of the nontoxic chitosan/adipic acid cross-linked membrane CS/AA in the separation of methylene blue and reactive yellow-145 from aqueous phase. The reason we chose adipic acid as a cross-linking agent is because it gives the cross-linked membrane moderate flexibility due to the presence of four methylene groups in its structure. The structure of the cross-linked membrane CS/AA and their properties were confirmed through, FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and BET analysis. The thermal properties of membrane indicated an improvement in its flexibility and hydrophobicity, but this improvement was accompanied by a decrease in its thermal stability. pHpzc value and porosity of the CS/AA were 7.88, and 73.95 % respectively. The average pore radius distribution ranged from 2 to 27 nm. The prepared cross-linked membrane provides spontaneous and continuous purification of water with a high efficiency. This is due to the membrane CS/AA ability to separate methylene blue and reactive yellow-145 from the aqueous phase almost completely. The results revealed that the removal efficiency and permeation flux for MB were 100 % and 1 L/m2.h respectively at initial dye concentration of (4,8) mg/L, at 1 bar, and the removal efficiency and permeation flux for RY-145 were (94,96) % and (1.06, 2.09) L/m2.h respectively at 100 mg/L and at (1,1.5) bar. Such cross-linked nanopore polymer membranes provide a new approach for emerging novel purification systems, principally in the field of environmental field.

Composite 2D Material-Based Pervaporation Membranes for Liquid Separation: A Review

Today, chemistry and nanotechnology cover molecular separations in liquid and gas states by aiding in the design of new nano-sized materials. In this regard, the synthesis and application of two-dimensional (2D) nanomaterials are current fields of research in which structurally defined 2D materials are being used in membrane separation either in self-standing membranes or composites with polymer phases. For instance, pervaporation (PV), as a highly selective technology for liquid separation, benefits from using 2D materials to selectively transport water or other solvent molecules. Therefore, this review paper offers an interesting update in revising the ongoing progress of PV membranes using 2D materials in several applications, including solvent purification (the removal of water from organic systems), organics removal (the removal of organic molecules diluted in water systems), and desalination (selective water transport from seawater). In general, recent reports from the past 3 years have been discussed and analyzed. Attention has been devoted to the proposed strategies and fabrication of membranes for the inclusion of 2D materials into polymer phases. Finally, the future trends and current research gaps are declared for the scientists in the field.

Recent advances in membrane technologies applied in oil-water separation

Effective treatment of oily wastewater, which is toxic and harmful and causes serious environmental pollution and health risks, has become an important research field. Membrane separation technology has emerged as a key area of investigation in oil-water separation research due to its high separation efficiency, low costs, and user-friendly operation. This review aims to report on the advances in the research of various types of separation membranes around emulsion permeance, separation efficiency, antifouling efficiency, and stimulus responsiveness. Meanwhile, the challenges encountered in oil-water separation membranes are examined, and potential research avenues are identified.

Separation techniques for manufacturing fruit spirits: From traditional distillation to advanced pervaporation process

Separation process is one of the key processes in the production of fruit spirits, including the traditional distillation method and the new pervaporation membrane method. The separation process significantly determines the constituents and proportions of compounds in the fruit spirit, which has a significant impact on the spirit quality and consumer acceptance. Therefore, it is important and complex to reveal the changing rules of chemical substances and the principles behind them during the separation process of fruit spirits. This review summarized the traditional separation methods commonly used in fruit spirits, covering the types, principles, and corresponding equipment of distillation methods, focused on the enrichment or removal of aroma compounds and harmful factors in fruit spirits by distillation methods, and tried to explain the mechanism behind it. It also proposed a new separation technology for the production of fruit spirits, pervaporation membrane technology, summarized its working principle, operation, working parameters, and application in the production of fruit spirits, and outlined the impact of the separation method on the production of fruit spirits based on existing research, focusing on the separation of flavor compounds, sensory qualities, and hazard factors in fruit spirits, along with a preliminary comparison with distillation. Finally, according to the current researches of the separation methods and the development requirement of the separation process of fruit spirits, the prospect of corresponding research is put forward, in order to propose new ideas and development directions for the research in this field.

Macroscopic assembly of 2D materials for energy storage and seawater desalination

Since the discovery of graphene in 2004, two-dimensional (2D) materials have attracted widespread attention due to their excellent physical and chemical properties in the fields of energy, environment, catalysis, and optoelectronics. However, there are still many key problems in the process of practical application. To further promote the potential of 2D materials for practical applications, macroscopic assembly of 2D materials is crucial for the continued development of 2D materials, especially in the fields of energy storage and seawater desalination. Therefore, this review focuses on the latest progress and current status related to the macroscopic assembly of 2D materials, including 1D fibers, 2D films, and 3D architectures. In addition, the application of macroscopic bodies assembled based on 2D materials in the fields of energy storage and seawater desalination is also introduced. Finally, future directions for the macroscopic assembly of 2D materials and their applications are prospected.

Ti2NTx quasi-MXene modified polyamide thin film composite reverse osmosis membrane with effective desalination and antifouling performance

In this study, considering the serious problem of lack of fresh water worldwide and the effectiveness of reverse osmosis (RO) membranes in water purification, we prepared improved RO membranes with two-dimensional quasi-MXene nanosheets. In this study, the MAX phase with the chemical formula of Ti2AlN was prepared through the reactive sintering route. Prosperous preparation of the MAX phase with the hexagonal crystalline structure was approved by an X-ray diffraction pattern. Compacted sheets morphology was recognized for the prepared MAX phase from transmittance electron microscopy and scanning electron microscopy micrographs. Then, Ti2NTx quasi-MXene nanosheets were prepared by selective ultrasonic-assisted exfoliation of the MAX phase. Polyamide (PA) thin-layer composite RO membranes with different weight percentages of Ti2NTx quasi-MXene were fabricated by the interfacial polymerization (IP) method. The addition of ultrasonic-assisted prepared quasi-MXene creates numerous and coherent nanochannels on the surface of the membrane. The optimum membrane with 0.01 wt% of quasi-MXene showed the highest pure water flux of 31.9 L m-2. h-1 with an improved salt rejection of 98.2%. Therefore, these nanosheets showed that they can partially solve the trade-off between water permeability and salt rejection, which is a serious challenge in RO membranes. Also, the membranes containing quasi-MXene showed good resistance against fouling by humic acid. This research can be a scalable development in making high-performance membranes.

A Comparative Analysis of Pervaporation and Membrane Distillation Techniques for Desalination Utilising the Sweeping Air Methodology with Novel and Economical Pervaporation Membranes

This study used the sweeping air approach to conduct a comparative analysis of pervaporation (PV) and membrane distillation (MD) in the context of desalinating saline/hypersaline water. An experimental setup of the sweeping air arrangement was designed and built at a laboratory size to conduct the research. The desalination process using PV used innovatively designed cellulose acetate (CA) membranes specifically adapted for this purpose. Conversely, in the studies involving MD, hydrophobic polytetrafluoroethylene (PTFE) membranes were utilised. CA membranes were fabricated in our laboratory using the phase inversion approach. The physicochemical characteristics of the membranes were assessed using many methodologies, including FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle measurement, and water uptake analysis. This facilitated a more comprehensive comprehension of the impact of the alkaline treatment on these features. The variables that were examined included the kind of membrane, the pore size of the PTFE membrane, the composition of the casting solution of CA, the concentration of the feed solution, the temperature of the feed, and the temperature of the condenser cooling water. The morphologies of the membranes were examined using SEM. The study's findings indicated that the use of MD resulted in a greater flow and a remarkable percentage of salt rejection (% SR). Furthermore, it was observed that the flux was positively correlated with the feed temperature, while it exhibited an inverse relationship with the cooling water temperature. Moreover, it was observed that the impact of the pore size of the PTFE membrane on the desalination process was found to be minimal. The most optimal outcomes obtained were 13.35 kg/m2 h with a percentage salt rejection (% SR) of 99.86, and 17.96 kg/m2 h with a % SR of 99.83 at a temperature of 70 °C, while using MD and PV technologies, respectively. Furthermore, both methods demonstrated the capability to desalinate very salty solutions with a salinity level of up to 160 g/L, thereby yielding potable water in a single step.

Ongoing Progress on Pervaporation Membranes for Ethanol Separation

Ethanol, a versatile chemical extensively employed in several fields, including fuel production, food and beverage, pharmaceutical and healthcare industries, and chemical manufacturing, continues to witness expanding applications. Consequently, there is an ongoing need for cost-effective and environmentally friendly purification technologies for this organic compound in both diluted (ethanol-water-) and concentrated solutions (water-ethanol-). Pervaporation (PV), as a membrane technology, has emerged as a promising solution offering significant reductions in energy and resource consumption during the production of high-purity components. This review aims to provide a panorama of the recent advancements in materials adapted into PV membranes, encompassing polymeric membranes (and possible blending), inorganic membranes, mixed-matrix membranes, and emerging two-dimensional-material membranes. Among these membrane materials, we discuss the ones providing the most relevant performance in separating ethanol from the liquid systems of water-ethanol and ethanol-water, among others. Furthermore, this review identifies the challenges and future opportunities in material design and fabrication techniques, and the establishment of structure-performance relationships. These endeavors aim to propel the development of next-generation pervaporation membranes with an enhanced separation efficiency.

Electrochemical-based processes for produced water and oily wastewater treatment: A review

The greatest volume of by-products produced in oil and gas recovery operations is referred to as produced water and increasing environmental concerns and strict legislations on discharging it into the environment cause to more attention for focusing on degradation methods for treatment of produced water especially electrochemical technologies. This article provides an overview of electrochemical technologies for treating oily wastewater and produced water, including: electro-coagulation, electro-Fenton, electrochemical oxidation and electrochemical membrane reactor as a single stage and combination of these technologies as multi-stage treatment process. Many researchers have carried out experiments to examine the impact of various factors such as material (i.e, electrode material) and operational conditions (i.e., potential, current density, pH, electrode distance, and other factors) for organic elimination to obtain the high efficiency. Results of each method are reviewed and discussed according to these studies, comprehensively. Furthermore, several challenges need to be overcome and perspectives for future study are proposed for each method.

Incorporating charged Ag@MOFs to boost the antibacterial and filtration properties of porous electrospinning polylactide films

Faced with the pollution caused by particulate matter (PM) in the air, the prevalence of infectious diseases, and the environmental burden by use of nondegradable polymers, the existing filter materials such as meltblown cloth of polypropylene cannot satisfactorily meet people's requirements. In this study, Ag nanoparticles were loaded onto ZIF-8 particles by impregnation reduction to prepare the positively charged Ag@ZIF-8. The porous fibrous membranes of Ag@ZIF-8 with polylactide (PLA) were manufactured by electrostatic spinning technology. Due to the inherently charged feature of Ag@ZIF-8 particles and the presence of pores on fibers, the prepared membranes showed a stable good filtration efficiency of over 97 % at different humidity (30-90%RH, relative humidity). Meanwhile, the presence of charge on Ag@ZIF-8 and the synergistic effects of Ag and ZIF-8 particles made the membranes exhibit good antibacterial effects. The width of the inhibition zone of 3 wt%Ag@ZIF-8/PLA membrane reached 1.33 mm for E. coli and 1.35 mm for S. aureus, respectively.

Robust ceramic-based graphene membrane for challenging water treatment with enhanced fouling and scaling resistance

Membrane fouling and scaling are two challenges for efficient treatment of hypersaline wastewater, greatly hindering separation performance and operation stability of desalination membranes. In this work, we report a smooth ceramic-based graphene desalination membrane, exhibiting enhanced anti-fouling and anti-scaling ability and operational performance for efficient treatment of both synthetic and real industrial wastewaters, outperforming polypropylene (PP) membrane. For treatment of hypersaline waters containing organic or inorganic substance, we demonstrate that the graphene membrane exhibits more stable water flux and almost complete salt rejection (>99.9%) during constant operation. Enhanced anti-fouling and desalination performance of graphene membrane could be attributed to the lower attractive interaction force with foulant (-4.65 mJ m-2), lower surface roughness (Ra = 2.2 ± 0.1 nm) and higher affinity with water than PP membrane. Furthermore, an anti-scaling mechanism enabled by graphene membrane is evidenced, with a highlight on the roles of smooth graphene surface with lower roughness, less nucleation sites and lower binding force with scaling crystals. Importantly, even for industrial petrochemical wastewater, such a graphene membrane also exhibits relatively more stable water flux and promising oil and ions rejection during long-term operation, outperforming PP membrane. This study further confirms a promising practical application potential of robust ceramic-based graphene membrane for efficient treatment of more challenging hypersaline wastewater with complicated compositions, which is not feasible by conventional desalination membranes.

Design and Preparation a New Composite Hydrophilic/Hydrophobic Membrane for Desalination by Pervaporation

Herein, experimental and theoretical approaches were used to design a new composite membrane for desalination by pervaporation. The theoretical approaches demonstrate the possibility to reach high mass transfer coefficients quite close to those obtained with conventional porous membranes if two conditions are verified: (i) a dense layer with a low thickness and (ii) a support with a high-water permeability. For this purpose, several membranes with a cellulose triacetate (CTA) polymer were prepared and compared with a hydrophobic membrane prepared in a previous study. The composite membranes were tested for several feed conditions, i.e., pure water, brine and saline water containing a surfactant. The results show that, whatever the tested feed, no wetting occurred during several hours of desalination tests. In addition, a steady flux was obtained together with a very high salt rejection (close to 100%) for the CTA membranes. Lastly, the CTA composite membrane was tested with real seawater without any pretreatment. It was shown that the salt rejection was still very high (close to 99.5%) and that no wetting could be detected for several hours. This investigation opens a new direction to prepare specific and sustainable membranes for desalination by pervaporation.

Electrochemical Interfacial Polymerization toward Ultrathin COF Membranes for Brine Desalination

Ultrathin covalent organic framework (COF) membranes are urgently demanded in molecular/ionic separations. Herein, we reported an electrochemical interfacial polymerization strategy to fabricate ultrathin COF membranes with thickness of 85 nm, by actively manipulate self-healing effect and self-inhibiting effect. The resulting COF membrane exhibited superior performance in brine desalination with the permeation flux of 92 kg m^-2  h^-1 and the rejection of 99.96 %. Our electrochemical interfacial polymerization strategy enriches the fabrication approach of COF membranes and facilitates the rational design of ultrathin membranes.

Emerging Trends in Porogens toward Material Fabrication: Recent Progresses and Challenges

Fabrication of tailor-made materials requires meticulous planning, use of technical equipments, major components and suitable additives that influence the end application. Most of the processes of separation/transport/adsorption have environmental applications that demands a material to be with measurable porous nature, stability (mechanical, thermal) and morphology. Researchers say that a vital role is played by porogens in this regard. Porogens (i.e., synthetic, natural, mixed) and their qualitative and quantitative influence on the substrate material (polymers (bio, synthetic), ceramic, metals, etc.) and their fabrication processes are summarized. In most cases, porogens critically influence the morphology, performance, surface and cross-section, which are directly linked to material efficiency, stability, reusability potential and its applications. However, currently there are no review articles exclusively focused on the porogen pores' role in material fabrication in general. Accordingly, this article comprises a review of the literature on various types of porogens, their efficiency in different host materials (organic, inorganic, etc.), pore size distribution (macro, micro and nano), their advantages and limitations, to a certain extent, and their critical applications. These include separation, transport of pollutants, stability improvement and much more. The progress made and the remaining challenges in porogens' role in the material fabrication process need to be summarized for researcher's attention.

Electric field modulated water permeation through laminar Ti3C2Tx MXene membrane

Controlling water transport is central to a wide range of water-related energy and environment issues. In particular, enhancing the water permeation is highly demanded for practical membrane applications such as water treatment. In this work, we demonstrate that the water permeation through the laminar and electrically conductive MXene membrane can be facilely modulated with electric field. By applying a negative voltage of a few volts on the membrane, the water permeation rate was enhanced by 70 times. Density functional theory calculations and experimental characterizations suggest that the enhancement arises from the enhanced water/MXene interaction under electric field, which manifests itself as enhanced hydrophilicity of the MXene nanosheets. Along with the facilitated water permeation, the rejection rate to dyes of the membrane was kept at a relatively high level, which was 93.1% to Congo red and 94.8% to aniline blue under an applied voltage of -3 V, showing the potential for dye separation and water purification. Considering that there has been increasing interest in utilizing MXene for separations and water treatment, this work should inspire a range of future works in the related area to improve the membrane performance with external stimuli.

Polyphenol modified natural collagen fibrous network towards sustainable and antibacterial microfiltration membrane for efficient water disinfection

Because of their low-cost and high bacterial interception efficiency, large-scale membrane separation technologies like microfiltration (MF) have been widely implemented for water disinfection. However, lack of antibacterial ability and low sustainability are two major drawbacks of most petroleum-based MF membranes, which are normally associated with hazardous issues including biofouling and nonbiodegradable waste. In this work, abundant animal hides, which are by-products of the meat processing industry, were proposed as raw materials to fabricate a sustainable MF membrane due to their natural, hierarchical, and renewable collagen fibrous network (CFN) with inherent biodegradability. After the removal of non-collagen compositions from animal hides, such as hair and fat, through a facile pretreating process base on green chemistry principles, a thin CFN based membrane (CFN-M) with a similar micropore size to that of commercial MF membranes could be produced. Furthermore, inspired by conventional leather tanning technology, tannic acids (TA) were selected as plant polyphenol tanning agent to modify collagen fibers based on tanning chemistry to improve the thermal stability of CFN-M. Moreover, the TA cross-linked CFN-M (TA@CFN-M) exhibited excellent antibacterial properties due to the production of reactive oxygen species (ROS) by the catechol functional group. The resulting TA@CFN-M achieved >99.9% water disinfection efficiency with a flux of ∼150 L m^-2 h^-1 via gravity-driven operation, while simultaneously showing admirable anti-biofouling ability. Different from the commercial MF membrane, based on the green chemistry principle, this work may shed light on designing new sustainable and antibacterial membranes for anti-biofouling water disinfection.

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.

Technology status and trends of industrial wastewater treatment: A patent analysis

Globally, 80% of wastewater, among which 28% came from industry, returned to the ecosystem without treatment or reuse. The discharge of industrial wastewater poses public health and environmental concerns. The necessity and urgency of industrial wastewater treatment (IWT) will bring great challenges to most countries. This paper conducted the patent analysis combined with text mining to quantitatively analyze 11,840 patents related to IWT in the Derwent Innovations Index database. The results showed that: From 1973 to 2020, the number of patents related to IWT annually was increasing consistently. China ranked first in the number of patent publications. In contrast, the United States and some patent organizations, such as World Intellectual Property Organization, produced fewer patents, while they played more important roles in knowledge transfer. The core technology analysis suggested that method, device, material and related industry were hot topics. From activated sludge treatment technology, industrial wastewater treatment technology had gone through a development process from single technology treatment to combined technologies treatment. In the foreseeable future, research on devices for physical treatment, advanced oxidation processes, automated and energy-saving treatment systems were the promising directions.

Robust ultrathin nanoporous MOF membrane with intra-crystalline defects for fast water transport

Rational design of high-performance stable metal–organic framework (MOF) membranes is challenging, especially for the sustainable treatment of hypersaline waters to address critical global environmental issues. Herein, a molecular-level intra-crystalline defect strategy combined with a selective layer thinning protocol is proposed to fabricate robust ultrathin missing-linker UiO-66 (ML-UiO-66) membrane to enable fast water permeation. Besides almost complete salt rejection, high and stable water flux is achieved even under long-term pervaporation operation in hash environments, which effectively addresses challenging stability issues. Then, detailed structural characterizations are employed to identify the type, chemical functionality, and density of intra-crystalline missing-linker defects. Moreover, molecular dynamics simulations shed light on the positive atomistic role of these defects, which are responsible for substantially enhancing structural hydrophilicity and enlarging pore window, consequently allowing ultra-fast water transport via a lower-energy-barrier pathway across three-dimensional sub-nanochannels during pervaporation. Unlike common unfavorable defect effects, the present positive intra-crystalline defect engineering concept at the molecular level is expected to pave a promising way toward not only rational design of next-generation MOF membranes with enhanced permeation performance, but additional water treatment applications.

The development of highly water-permeable membranes is key for the treatment of high salinity waters. Here the authors enhance the water permeability of a metal-organic framework nanoporous membrane via an intra-crystalline defect engineering strategy.

Chitin and derivative chitosan-based structures - Preparation strategies aided by deep eutectic solvents: A review

The high molecular weight of chitin, as a biopolymer, challenges its extraction due to its insolubility in the solvents. Also, chitosan, as the N-deacetylated form of chitin, can be employed as a primary material for different industries. The low mechanical stability and poor plasticity of chitosan films, as a result of incompatible interaction between chitosan and the used solvent, have limited its industrialization. Deep eutectic solvents (DESs), as novel solvents, can solve the extraction difficulties of chitin, and the low mechanical stability and weak plasticity of chitosan films. Also, DESs can be considered for the different chitosan and chitin productions, including chitin nanocrystal and nanofiber, N,N,N-trimethyl-chitosan, chitosan-based imprinted structures, and DES-chitosan-based beads and monoliths. This review aims to focus on the preparation and characterization (chemistry and morphology) of DES-chitin-based and DES-chitosan-based structures to understand the influence of the incorporation of DESs into the chitin and chitosan structure.

Biobased composites from agro-industrial wastes and by-products

The greater awareness of non-renewable natural resources preservation needs has led to the development of more ecological high-performance polymeric materials with new functionalities. In this regard, biobased composites are considered interesting options, especially those obtained from agro-industrial wastes and by-products. These are low-cost raw materials derived from renewable sources, which are mostly biodegradable and would otherwise typically be discarded. In this review, recent and innovative academic studies on composites obtained from biopolymers, natural fillers and active agents, as well as green-synthesized nanoparticles are presented. An in-depth discussion of biobased composites structures, properties, manufacture, and life-cycle assessment (LCA) is provided along with a wide up-to-date overview of the most recent works in the field with appropriate references. Potential uses of biobased composites from agri-food residues such as active and intelligent food packaging, agricultural inputs, tissue engineering, among others are described, considering that the specific characteristics of these materials should match the proposed application.

Advances in biopolymer composites and biomaterials for the removal of emerging contaminants

Domestic, agriculture, and industrial activities contaminate the waterbodies by releasing toxic substances and pathogens. Removal of pollutants from wastewater is critical to ensuring the quality of accessible water resources. Several wastewater treatments are often used. Researchers are increasingly focusing on adsorption, ion exchange, electrostatic interactions, biodegradation, flocculation, and membrane filtration for the efficient reduction of pollutants. Biopolymers are a combination of two or more products produced by the living organisms used to give the desired finished product with a unique attribute. Biomaterials are also similar to traditional polymers by having higher flexibility, biodegradability, low toxicity, and nontoxic secondary byproducts producing ability. Grafting, functionalization, and crosslinking will be used to enhance the characteristics of biopolymers. The present chapter will illustrate some of the important biopolymers and its compos that will impact wastewater treatment in the future. Most commonly used biopolymers including chitosan (CS), activated carbon (AC), carbon-nanotubes (CNTs), and graphene oxide (GO) are discussed. Finally, the opportunities and difficulties for applying adsorbents to water pollution treatment are discussed.

Stable Zr-Based Metal-Organic Framework Nanoporous Membrane for Efficient Desalination of Hypersaline Water

Treatment of hypersaline waters is a critical environmental challenge. Pervaporation (PV) desalination is a promising technique to address this challenge, but current PV membranes still suffer from challenging issues such as low flux and insufficient stability. Herein, we propose in situ nanoseeding followed by a secondary growth strategy to fabricate a high-quality stable metal-organic framework (MOF) thin membrane (UiO-66) for high-performance pervaporation desalination of hypersaline waters. To address the issue of membrane quality, a TiO₂ nano-interlayer was introduced on coarse mullite substrates to favor the growth of a UiO-66 nanoseed layer, on which a well-intergrown UiO-66 selective membrane layer with thickness as low as 1 μm was finally produced via subsequent secondary growth. The PV separation performance for hypersaline waters was systematically investigated at different salt concentrations, feed temperatures, and long-term operation in different extreme chemical environments. Besides having nearly complete rejection (99.9%), the UiO-66 membrane exhibited high flux (37.4 L·m^-2·h^-1) for hypersaline waters, outperforming current existing zeolite and MOF membranes. The membrane also demonstrated superior long-term operational stability under various harsh environments (hypersaline, hot, and acidic/alkaline feed water) and mild fouling behavior. The rational design proposed in this study is not only applicable for the development of a high-quality UiO-66 membrane enabling harsh hypersaline water treatment but can also be potentially extended to other next-generation nanoporous MOF membranes for more environmental applications.

Current evidence in high throughput ultrafiltration toward the purification of monoclonal antibodies (mAbs) and biotechnological protein-type molecules

Pressure-driven membrane-based technologies, such as microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF), have been successfully implemented in recovering different types of biomolecules and high-value-added compounds from various streams. Especially, UF membranes meet the requirements for separating specific bioproducts in downstream processes, e.g. monoclonal antibodies (mAbs), which are recognized as proteins produced mainly by plasma cells. According to the importance and functionality of the mAbs, their recovery is a current challenge with these bioseparations. Nevertheless, mAbs recovery using UF-assisted processes has been smartly performed over the last decade. To the best of our knowledge, there are no reviews of the reported developments using UF technology toward mAbs separation. Therefore, the goal of this paper is to collect and elucidate ongoing research studies implemented for the featured separation of mAbs and other biotechnological protein-type molecules (e.g. adenovirus serotype, extracellular vesicles, red fluorescent protein, cyanovirin-N, among others) via ultrafiltration-aided systems. The literature evidence (e.g. research papers, patents, etc.) has been analyzed and discussed according to the purpose of the study. Importantly, the relevant findings and novel approaches are discussed in detail. To finalize this document, the advantages, drawbacks, and guidelines in applying membrane-based techniques for such a recovery are presented.

Thin-Film Composite Membrane Prepared by Interfacial Polymerization on the Integrated ZIF-L Nanosheets Interface for Pervaporation Dehydration

Thin-film composite (TFC) membranes are attracting wide attention because their ultrathin selective layer usually corresponds to the higher membrane flux for pervaporation. However, the direct preparation of the TFC membranes on ceramic substrates confronted with the great difficulties because the larger pores on ceramic substrate surfaces are detrimental to the formation of an intact polyamide (PA) selective layer produced by interfacial polymerization (IP) reaction. Here, the integrated ZIF-L nanosheets were proposed to be used as an assistance interlayer for the first time to eliminate the existence of the pores of the ceramic support, and provides a better basis for the formation of an intact PA selective layer by IP reaction between TMC and ethylenediamine (EDA). The experimental data obtained in pervaporation (PV) show that the increased flux from 1.1 to 2.9 kg/m²h corresponds to the decreased separation factor from 396 to 110 when the feed concentration of ethanol decreases from 95 wt % to 80 wt % at 50 °C. In addition, the membrane flux increases from 0.8 to 2.5 kg/m²h with a change of the separation factor from 683 to 111 when the operational temperature varies from 30 to 60 °C. These results demonstrate the great potential of the fabricated TFC membranes in practical application for PV dehydration of organic solutions.

Emerging graphitic carbon nitride-based membranes for water purification

Membrane separation is a promising technology that can effectively remove various existing contaminants from water with low energy consumption and small carbon footprint. The critical issue of membrane technology development is to obtain a low-cost, stable, tunable and multifunctional material for membrane fabrication. Graphitic carbon nitride (g-C₃N₄) has emerged as a promising membrane material, owing to the unique structure characteristics and outstanding catalytic activity. This review paper outlined the advanced material strategies used to regulate the molecule structure of g-C₃N₄ for membrane separation. The presentative progresses on the applications of g-C₃N₄-based membranes for water purification have been elaborated. Essentially, we highlighted the innovation integration of physical separation, catalysis and energy conversion during water purification, which was of great importance for the sustainability of water treatment techniques. Finally, the continuing challenges of g-C₃N₄-based membranes and the possible breakthrough directions in the future research was prospected.

Comprehensive review of water management and wastewater treatment in food processing industries in the framework of water-food-environment nexus

Food processing is among the greatest water-consuming industries with a significant role in the implementation of sustainable development goals. Water-consuming industries such as food processing have become a threat to limited freshwater resources, and numerous attempts are being carried out in order to develop and apply novel approaches for water management in these industries. Studies have shown the positive impact of the new methods of process integration (e.g., water pinch, mathematical optimization, etc.) in maximizing water reuse and recycle. Applying these methods in food processing industries not only significantly supported water consumption minimization but also contributed to environmental protection by reducing wastewater generation. The methods can also increase the productivity of these industries and direct them to sustainable production. This interconnection led to a new subcategory in nexus studies known as water-food-environment nexus. The nexus assures sustainable food production with minimum freshwater consumption and minimizes the environmental destructions caused by untreated wastewater discharge. The aim of this study was to provide a thorough review of water-food-environment nexus application in food processing industries and explore the nexus from different aspects. The current study explored the process of food industries in different sectors regarding water consumption and wastewater generation, both qualitatively and quantitatively. The most recent wastewater treatment methods carried out in different food processing sectors were also reviewed. This review provided a comprehensive literature for choosing the optimum scenario of water and wastewater management in food processing industries.

Ongoing progress on novel nanocomposite membranes for the separation of heavy metals from contaminated water

Membranes, as the primary separation element of membrane-based processes, have greatly attracted the attention of researchers in several water treatment applications, including wastewater treatment, water purification, water disinfection, toxic and non-toxic chemical molecules, heavy metals, among others. Today, the removal of heavy metals from water has become challenging, in which chemical engineers are approaching new materials in membrane technologies. Therefore, the current review elucidates the progress of using different concepts of membranes and potential novel materials for such separations, identifying that polymeric membranes can exhibit a removal efficiency from 77 up to 99%; while novel nanocomposite membranes are able to offer complete removal of heavy metals (up to 100%), together with unprecedented permeation rates (from 80 up to 1, 300 L m^-2 h^-1). Thereby, the review also addresses the highlighted literature survey of using polymeric and nanocomposite membranes for heavy metal removal, highlighting the relevant insights and denoted metal uptake mechanisms. Moreover, it gives up-to-date information related to those novel nanocomposite materials and their contribution to heavy metals separation. Finally, the concluding remarks, future perspectives, and strategies for new researchers in the field are given according to the recent findings of this comprehensive review.

Characterization of PVDF/Graphene Nanocomposite Membranes for Water Desalination with Enhanced Antifungal Activity

Seawater desalination is a worldwide concern for the sustainable production of drinking water. In this regard, membrane distillation (MD) has shown the potential for effective brine treatment. However, the lack of appropriate MD membranes limits its industrial expansion since they experience fouling and wetting issues. Therefore, hydrophobic membranes are promising candidates to successfully deal with such phenomena that are typical for commercially available membranes. Here, several graphene/polyvinylidene (PVDF_G) membranes with different graphene loading (0–10 wt%) were prepared through a phase inversion method. After full characterization of the resulting membranes, the surface revealed that the well-dispersed graphene in the polymer matrix (0.33 and 0.5 wt% graphene loading) led to excellent water repellence together with a rough structure, and a large effective surface area. Importantly, antifungal activity tests of films indicated an increase in the inhibition percentage for PVDF_G membranes against the Curvularia sp. fungal strain. However, the antifungal surface properties were found to be the synergistic result of graphene toxicity and surface topography.

Pervaporation Zeolite-Based Composite Membranes for Solvent Separations

Thanks to their well-defined molecular sieving and stability, zeolites have been proposed in selective membrane separations, such as gas separation and pervaporation. For instance, the incorporation of zeolites into polymer phases to generate composite (or mixed matrix) membranes revealed important advances in pervaporation. Therefore, the goal of this review is to compile and elucidate the latest advances (over the last 2-3 years) of zeolite applications in pervaporation membranes either combining zeolites or polymers. Here, particular emphasis has been focused on relevant insights and findings in using zeolites in pervaporative azeotropic separations and specific aided applications, together with novel concepts of membranes. A brief background of the pervaporation process is also given. According to the findings of this review, we provide future perspectives and recommendations for new researchers in the field.

Fabrication and characterization of polyamide thin-film composite membrane via interfacial polycondensation for pervaporation separation of salt and arsenic from water

Pervaporation, mainly utilized to separate azeotropic mixtures, has been paid much attention for desalination in recent years due to its numerous advantages. The membranes based on thin-film composite structure have gained great interest in pervaporation due to their thin thickness, controllable hydrophilicity, and crosslinking density which affects the permeation flux and selectivity of the membranes. In this study, a polyamide thin-film composite (PA-TFC) membrane was fabricated through interfacial polymerization between amine monomers and trimesoyl chloride (TMC) on a polysulfone porous substrate (PSf). Four different diamine monomers, including ethylenediamine (EDA), triethylenetetramine (TETA), m-phenylenediamine (MPD), and piperazine (PIP) were used to investigate the effect of the monomers on the pervaporation performance of the resulting membrane for separation of sodium chloride (NaCl) and arsenate (As(v)) aqueous solution. The physicochemical properties of the membrane were characterized using attenuated total reflection Fourier transform infrared (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and pure water contact angle measurement. Furthermore, the performance of the fabricated membranes was studied by pervaporation separation of 0.15 mg L⁻¹ As(v) and 5 g L⁻¹ NaCl aqueous solution at 40 °C, respectively. The results show that the rejections of the membrane are insignificantly affected by the chemical structures of the amines, and both the As(v) rejection and NaCl rejection are higher than 99.9%. However, the permeation flux decreases in the order of PIP-TMC membrane > TETA-TMC membrane ∼ EDA-TMC membrane > MPD-TMC membrane. Furthermore, the operating conditions are found to affect the separation performance of the PIP-TMC membrane significantly. In particular, the elevating operation temperature profoundly increases the permeation flux, while the increase in high salt concentration leads to a slight decrease in rejection but a significant decline in permeation flux. The derived membrane shows a reasonable permeation flux of 16.1 kg m⁻² h⁻¹ and ca. 99.9% rejection for 1.5 mg L⁻¹ As(v) removal, as well as 13 kg m⁻² h⁻¹ and 99.3% rejection for 30 g L⁻¹ NaCl separation at 60 °C. The sufficient permeation flux and good rejection of As(v) and NaCl of the membrane suggested the promising application of PA-TFC membrane for pervaporation removal of toxic arsenic from water and desalination of seawater.

Pervaporation, mainly utilized to separate azeotropic mixtures, has been paid much attention for desalination in recent years due to its numerous advantages.