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

Comparative Retention Analysis of Intercalated Cations Inside the Interlayer Gallery of Lamellar and Nonlamellar Graphene Oxide Membranes in Reverse Osmosis Process: A Molecular Dynamics Study

Over the past decade, multilayered graphene oxide (GO) membranes have emerged as promising candidates for desalination applications. Despite their potential, a comprehensive understanding of separation mechanisms remains elusive due to the intricate morphology and structural arrangement of interlayer galleries. Moreover, a critical concern of multilayered GO membranes is their susceptibility to swelling within aqueous environments, which hinders their practical implementation. Therefore, this study introduces cation intercalation within GO laminates to elucidate the underlying factors governing swelling behavior and subsequently mitigate it. Moreover, this study performed nonequilibrium molecular dynamics simulations on the cation (Mg2+ or K+)-intercalated lamellar and nonlamellar GO membranes to understand the effect of the arrangement of GO sheets on the retention time of intercalated cations within GO layers, water permeance, and salt rejection mechanism in the reverse osmosis process using cation-intercalated GO membranes. Our results highlight that lamellar GO membranes exhibit higher water permeance, attributed to their well-defined interlayer gallery structure. On the other hand, nonlamellar GO membranes display superior salt rejection due to their complex interlayer gallery structure that impedes salt permeation. Moreover, the structural complexity of nonlamellar GO membranes contributes to greater stability by retention of the more intercalated cations for a longer time within the layers. Furthermore, it is observed that a higher percentage of Mg2+ cations remained inside the GO laminates as compared to K+ cations, hence resulting in the greater stability of the Mg2+-intercalated GO membrane in the aqueous environment.

Electrochemical Opening of Impermeable Nanochannels in Laminar Graphene Membranes for Ultrafast Nanofiltration

Reduced graphene oxide (rGO) could be theoretically used to construct highly permeable laminar membranes with nearly frictionless nanochannels for water treatment. However, their pristine (sp² C-C) regions usually restack into impermeable channels as a result of van der Waals interactions, resulting in a much low permeance. In this study, we demonstrate that the restacked regions could be electrochemically expanded to form ultrafast water transport nanochannels by providing a low positive potential (e.g., +1.00 V vs SCE) to the rGO membrane. Experimental investigations indicate that the structural expansion is attributed to the intercalation of water molecules into the restacked regions, driven by hydrogen bond interactions between water molecules and hydroxyl groups that are electrochemically produced on edges of rGO nanosheets. The structural expansion could be promoted by weakening the graphene-OH^- interactions through intermittent application of the potential. As a result of more ultrafast water transport nanochannels available, the electrochemically treated rGO membranes could have a permeance 2 orders of magnitude higher than that of the pristine one and ∼3 times higher than that of graphene oxide membranes. Because of their smaller average pore size, the rGO membranes also have a higher ionic/molecular rejection performance than graphene oxide membranes.

Review of functionalized nano porous membranes for desalination and water purification: MD simulations perspective

Today, it is known that most of the water sources in the world are either drying out or contaminated. With the increasing population, the water demand is increasing drastically almost in every sector each year, which makes processes like water treatment and desalination one of the most critical environmental subjects of the future. Therefore, developing energy-efficient and faster methods are a must for the industry. Using functional groups on the membranes is known to be an effective way to develop shorter routes for water treatment. Accordingly, a review of nano-porous structures having functional groups used or designed for desalination and water treatment is presented in this study. A systematic scan has been conducted in the literature for the studies performed by molecular dynamics simulations. The selected studies have been classified according to membrane geometry, actuation mechanism, functionalized groups, and contaminant materials. Permeability, rejection rate, pressure, and temperature ranges are compiled for all of the studies examined. It has been observed that the pore size of a well-designed membrane should be small enough to reject contaminant molecules, atoms, or ions but wide enough to allow high water permeation. Adding functional groups to membranes is observed to affect the permeability and the rejection rate. In general, hydrophilic functional groups around the pores increase membrane permeability. In contrast, hydrophobic ones decrease the permeability. Besides affecting water permeation, the usage of charged functional groups mainly affects the rejection rate of ions and charged molecules.

Biotechnological advancements towards water, food and medical healthcare: A review

The global health status is highly affected by the growing pace of urbanization, new lifestyles, climate changes, and resource exploitation. Modern technologies pave a promising way to deal with severe concerns toward sustainable development. Herein, we provided a comprehensive review of some popular biotechnological advancements regarding the progress achieved in water, food, and medicine, as the most substantial fields related to public health. The emergence of novel organic/inorganic materials has brought about significant improvement in conventional water treatment techniques, anti-fouling approaches, anti-microbial agents, food processing, biosensors, drug delivery systems, and implants. Particularly, a growing interest has been devoted to nanomaterials and their application for developing novel structures or improving the characteristics of standard components. Also, bioinspired materials have been widely used to improve the performance, efficiency, accuracy, stability, safety, and cost-effectiveness of traditional systems. On the other side, the fabrication of innovative devices for precisely monitoring and managing various ecosystem and human health issues is of great importance. Above all, exceptional advancements in designing ion-selective electrodes (ISEs), microelectromechanical systems (MEMs), and implantable medical devices have altered the future landscape of environmental and biomedical research. This review paper aimed to shed light on the wide-ranging materials and devices that have been developed for health applications and mainly focused on the impact of nanotechnology in this field.

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.

Rejection Mechanism of Ionic Solute Removal by Nanofiltration Membranes: An Overview

The toxicity of heavy metals can cause water pollution and has harmful effects on human health and the environment. Various methods are used to overcome this pressing issue and each method has its own advantages and disadvantages. Membrane filtration technology such as nanofiltration (NF) produces high quality water and has a very small footprint, which results in lower energy usage. Nanofiltration is a membrane-based separation technique based on the reverse osmosis separation process developed in the 1980s. NF membranes have a pore size of 1 nm and molecular weight cut off (MWCO) of 300 to 500 Da. The properties of NF membranes are unique since the surface charge of the membranes is dependent on the functional groups of the membrane. The rejection mechanism of NF membrane is unique as it is a combination of various rejection mechanisms such as steric hindrance, electric exclusion, dielectric effect, and hydration mechanism. However, these mechanisms have not been studied in-depth due to their complexity. There are also many factors contributing to the rejection of NF membrane. Many junior researchers would face difficulty in studying NF membrane. Therefore, this paper is designed for researchers new to the field, and will briefly review the rejection mechanisms of NF membrane by both sieving and non-sieving separation processes. This mini-review aims to provide new researchers with a general understanding of the concept of the separation process of charged membranes.

Genotypic diversity of 17 cacti species and application to biosynthesis of gold nanoparticles

The genotypic diversity of 17 cacti species were examined and grouped in four clusters using seven inter simple sequence repeat (ISSR) markers. Group representatives (five species) were chosen for AuNPs synthesis in the cacti syrups. To synthesize the Gold nanoparticles (AuNPs), reducing and capping potential of five species of cacti rich in the polyphenolics were explored. Based on the synthesized AuNPs traits (concentration, pH, temperature, and synthesis time), Opuntia pycnacantha with the highest absorption peak at 540 nm was chosen for further characterizations. Varieties of diffraction peaks confirmed the successful synthesis of AuNPs. AuNPs functionalization with the phenolic compounds was confirmed by Fourier transform infrared (FTIR) spectroscopy. At the optimum conditions (pH = 5.0 and T = 60 °C), both dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed more than 87% of AuNPs to be 2.5 nm in size with Zeta potential to be equal to -19.9 mV.

Developing a simple box-behnken experimental design on the removal of doxorubicin anticancer drug using Fe3O4/graphene nanoribbons adsorbent

This paper aims to develop a Box-Behnken experimental design system to optimize the removal process of doxorubicin anticancer drugs. For this goal, Fe₃O₄/graphene nanoribbons was selected as adsorbent and removal of doxorubicin anticancer drug optimized using Box-Behnken experimental design with a selection of four effective factors. A three-level, four-factor Box-Behnken experimental design was used to assess the relationship between removal percentage as a dependent variable with adsorption weight (0.0015-0.01 mg), pH (3-9), temperature (15-45 °C) and time (1-15 min) as independent variables. Optimized condition by Behnken experimental design (pH = 7.36; time = 15 min; adsorbent weight = 0.01 mg and temperature = 29.26 °C) improved removal of doxorubicin anticancer drug about 99.2% in aqueous solution. The dynamic behavior, adsorption properties and mechanism of doxorubicin molecule on Fe₃O₄/graphene nanoribbon were investigated based on ab initio molecular dynamics (AIMD) simulations and density functional theory calculations with dispersion corrections. A closer inspection of the adsorption configurations and binding energies revealed that π-π interactions were the driving force when the doxorubicin molecule adsorbed on Fe₃O₄/graphene nanoribbon. The observed negative adsorption energy signifies a favourable and exothermic adsorption process of the various adsorbate-substrate systems. Besides, AIMD and phonon dispersion calculations confirm the dynamic stability of Fe₃O₄/graphene nanoribbon.

Doxorubicin Anticancer Drug Monitoring by ds-DNA-Based Electrochemical Biosensor in Clinical Samples

In this research, glassy carbon electrode (GCE) amplified with single-wall carbon nanotubes (SWCNTs) and ds-DNA was fabricated and utilized for voltammetric sensing of doxorubicin with a low detection limit. In this technique, the reduction in guanine signal of ds-DNA in the presence of doxorubicin (DOX) was chosen as an analytical factor. The molecular docking study revealed that the doxorubicin drug interacted with DNA through intercalation mode, which was in agreement with obtained experimental results. The DOX detection performance of ds-DNA/SWCNTs/GCE was assessed at a concentration range of 1.0 nM-20.0 µM. The detection limit was found to be 0.6 nM that was comparable and even better (in many cases) than that of previous electrochemical reported sensors. In the final step, the ds-DNA/SWCNTs/GCE showed powerful ability for determination of the DOX in injection samples with acceptable recovery data.

Graphene Oxide as a Pb(II) Separation Medium: Has Part of the Story Been Overlooked?

A key problem associated with the design of graphene oxide (GO) materials and their tuning for nanoscale separations is how specific functional groups influence the competitive adsorption of solvated ions and water at liquid/graphene interfaces. Computation accompanied by experiment shows that OH and COOH exert an influence on water adsorption properties stronger than that of O and H functional groups. The COO- anions, following COOH deprotonation, stabilize Pb(II) through strong electrostatic interactions. This suggests that, among the functional groups under study, COOH offers the best Pb(II) adsorption capacity and the ability to regenerate the sorbent through a pH swing. In line with computation, striking experimental observations revealed that a substantial increase in Pb(II) adsorption occurs with increasing pH. Our findings provide a systematic framework for controlled design and implementation of regenerable C-based sorbents used in separations and desalination.

Size-Dependent Ion Adsorption in Graphene Oxide Membranes

Graphene oxide (GO)-based materials have demonstrated promising potential for adsorption and purification applications. Due to its amphiphilic nature, GO offers the possibility of removing various kinds of contaminants, including heavy metal ions and organic pollutants from aqueous environments. Here, we present size-selective ion adsorption in GO-based laminates by directly measuring the weight uptake of slats. Adsorption studies were conducted in graphene oxide purchased from Nisina Materials Japan prepared using a controlled method. We tuned the interlayer spacing of GO membranes via cationic control solutions using intercalation of very small salts ions (i.e., K⁺, Na⁺, Cl⁻) very precisely to facilitate the adsorption of larger ions such as [Fe(CN)₆]⁴⁻ and [Fe(CN)₆]³⁻. This study demonstrates that if the opening of nanocapillaries within the laminates is bigger than the hydrated diameter of ions, the adsorption occurs within the membranes while for smaller opening, with no ion entrance the sorption occurs on the surface of the membranes.

Mechanical hydrolysis imparts self-destruction of water molecules under steric confinement

Decoding behavioral aspects associated with the water molecules in confined spaces such as an interlayer space of two-dimensional nanosheets is key for the fundamental understanding of water-matter interactions and identifying unexpected phenomena of water molecules in chemistry and physics. Although numerous studies have been conducted on the behavior of water molecules in confined spaces, their reach stops at the properties of the planar ice-like formation, where van der Waals interactions are the predominant interactions and many questions on the confined space such as the possibility of electron exchange and excitation state remain unsettled. We used density functional theory and reactive molecular dynamics to reveal orbital overlap and induction bonding between water molecules and graphene sheets under much less pressure than graphene fractures. Our study demonstrates high amounts of charge being transferred between water and the graphene sheets, as the interlayer space becomes smaller. As a result, the inner face of the graphene nanosheets is functionalized with hydroxyl and epoxy functional groups while released hydrogen in the form of protons either stays still or traverses a short distance inside the confined space via the Grotthuss mechanism. We found signatures of a new hydrolysis mechanism in the water molecules, i.e. mechanical hydrolysis, presumably responsible for relieving water from extremely confined conditions. This phenomenon where water reacts under extreme confinement by disintegration rather than forming ice-like structures is observed for the first time, illustrating the prospect of treating ultrafine porous nanostructures as a driver for water splitting and material functionalization, potentially impacting the modern design of nanofilters, nanochannels, nano-capacitators, sensors, and so on.

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.

Produced Water Desalination via Pervaporative Distillation

Herein, we report on the performance of a hybrid organic-ceramic hydrophilic pervaporation membrane applied in a vacuum membrane distillation operating mode to desalinate laboratory prepared saline waters and a hypersaline water modeled after a real oil and gas produced water. The rational for performing “pervaporative distillation” is that highly contaminated waters like produced water, reverse osmosis concentrates and industrial have high potential to foul and scale membranes, and for traditional porous membrane distillation membranes they can suffer pore-wetting and complete salt passage. In most of these processes, the hard to treat feed water is commonly softened and filtered prior to a desalination process. This study evaluates pervaporative distillation performance treating: (1) NaCl solutions from 10 to 240 g/L at crossflow Reynolds numbers from 300 to 4800 and feed-temperatures from 60 to 85 °C and (2) a real produced water composition chemically softened to reduce its high-scale forming mineral content. The pervaporative distillation process proved highly-effective at desalting all feed streams, consistently delivering <10 mg/L of dissolved solids in product water under all operating condition tested with reasonably high permeate fluxes (up to 23 LMH) at optimized operating conditions.

Breakthroughs on tailoring pervaporation membranes for water desalination: A review

Due to the increase in worldwide population and urbanization, water scarcity is today one of the tough challenges of society. To date, several ongoing initiatives and strategies are aiming to find feasible alternatives to produce drinking water. Seawater desalination is addressed as a latent alternative to solve such an issue. When dealing with desalination, membrane-based technologies (such as reverse osmosis, membrane distillation, pervaporation, among others) have been successfully proposed. Pervaporation (PV) is likely the membrane operation with the less permeation rate but providing high rejection of salts. Thereby, "membranologists" are extensively working in developing new suitable membranes for pervaporation desalination. Therefore, the goal of this review paper is to elucidate and provide a comprehensive outlook of the most recent works (over the last 5-years) at developing new concepts of membranes (e.g. ultra-thin, mixed matrix/composite and inorganic) for desalination, as well as the relevant strategies in fabricating enhanced PV membranes. At this point, an important emphasis has been paid to the relevant insights in the field. This paper also addresses some principles of PV and the main drawbacks of the technique and its membranes. Through reviewing the literature, the future trends, needs, and recommendations for the new researchers are given.

NiO/SWCNTs coupled with an ionic liquid composite for amplified carbon paste electrode; A feasible approach for improving sensing ability of adrenalone and folic acid in dosage form

Electrochemical sensors have shown great appeal for the simultaneous analysis of pharmaceutical compounds. In this way, the presence study described first electroanalytical sensor for simultaneous determination of adrenalone and folic acid. The two-amplified voltammetric sensor was developed by modifying carbon paste electrode (CPE) with NiO/SWCNTs composite and 1-butyl-3-methylimidazolium methanesulfonate (1B3MIMS) and used for simultaneous determination of adrenalone and folic acid. The NiO/SWCNTs was synthesised by a fast and low-cost precipitation strategy and then characterised by EDS, FESEM and XRD methods. The results confirmed a particle size range of ⁓ 26.93-33.87 nm for NiO nanoparticle decorated at SWCNTs. The cyclic voltammetric investigation showed that oxidation potentials of adrenalone and folic acid depend on changing the pH value. The maximum oxidation current for the simultaneous analysis of two compounds occurred at pH = 7.0. In this condition, the sensor showed linear dynamic range 0.01-400 μM and 0.3-350 μM for determination of adrenalone and folic acid, respectively. The NiO/SWCNTs/1B3MIMS/CPE was then used as an ultrasensitive electroanalytical sensor for determination of adrenalone and folic acid in injection samples with recovery ratio between 98.2-103.66 %.

Orbital Overlapping through Induction Bonding Overcomes the Intrinsic Delamination of 3D-Printed Cementitious Binders

3D printing of cementitious materials holds a great promise for construction due to its rapid, consistent, modular, and geometry-controlled ability. However, its major drawback is low cohesion in the interlayer region. Herein, we report a combined experimental and computational approach to understand and control fabrication of 3D-printed cementitious materials with significantly enhanced interlayer strength using multimaterial 3D printing, in which the composition, function, and structure of the materials are programmed. Our results show that the intrinsic low interlayer cohesion is caused by excess moisture and time lag that block the majority of valuable interactions in the interlayer zone between the adjacent cement matrices. As a remedy, a thin epoxy layer is introduced as an intermediator between the adjacent extruded layers, both to improve the interlayer cohesion and to extend the possible time delay between printed adjacent layers. Our ab initio calculations demonstrate that an orbital overlap between the calcium ions, as the main electrophilic part of the cement structure, and the hydroxyl groups, as the nucleophilic part of the epoxy, create strong interfacial absorption sites. These electronic absorptions lead to several iono-covalent bonds between the cement matrix and epoxy, leading to significant improvements in tensile, shear, and compressive strengths as well as ductility of the 3D-printed composites. This is verified by our experimental data, which showed an average of 84% improvement in interlayer bonding. The upward augmentation of interlayer bonding helps 3D printing cementitious material to overcome their intrinsic limitation of weak interlayer cohesion, thereby mitigating/eliminating the key bottleneck of additive manufacturing in constructing materials.

A highly hydrophilic benzenesulfonic-grafted graphene oxide-based hybrid membrane for ethanol dehydration

A new type of hybrid membrane was prepared by blending sodium alginate (SA) with benzenesulfonic-grafted graphene oxide (BS@GO), which showed higher hydrophilicity and more defects or edges than GO to create channels for the transfer of water molecules. BS@GO was synthesized by reacting aryl diazonium salts with graphene oxide (GO). The BS@GO sheets were aligned parallelly to the membrane surface and affected the interactions between the SA chains. BS@GO could improve the hydrophilicity and pervaporation properties of SA-based hybrid membranes. Also, compared to GO fillers, BS@GO fillers could supply higher water permeance to improve the pervaporation flux and separation factor. For the pervaporation of 90 wt% aqueous ethanol at 343 K, the optimum hybrid membrane with 1.5 wt% BS@GO in the SA matrix showed the maximum permeate flux of 703 ± 89 g m^-2 h^-1 (1.4 times higher than that of an SA membrane), and the highest separation factor was 5480 ± 94 (5.6 times higher than that of the SA membrane). Moreover, the hybrid membrane exhibited good stability and separation ability during long-term testing.