Surface properties of membrane materials and their role in cell adhesion and biofilm formation of microalgae.

In this study, the effects of surface properties of membrane materials on microalgae cell adhesion and biofilm formation were investigated using Chlorella vulgaris and five different types of membrane materials under hydrodynamic conditions. The results suggest that the contact angle (hydrophobicity), surface free energy, and free energy of cohesion of membrane materials alone could not sufficiently elucidate the selectivity of microalgae cell adhesion and biofilm formation on membrane materials surfaces, and membrane surface roughness played a dominant role in controlling biofilm formation rate, under tested hydrodynamic conditions. A lower level of biofilm EPS production was generally associated with a larger amount of biofilm formation. The zeta potential of membrane materials could enhance initial microalgae cell adhesion and biofilm formation through salt bridging or charge neutralization mechanisms.

Fabrication of solid-state nanopores.

Nanopores are valuable single-molecule sensing tools that have been widely applied to the detection of DNA, RNA, proteins, viruses, glycans, etc. The prominent sensing platform is helping to improve our health-related quality of life and accelerate the rapid realization of precision medicine. Solid-state nanopores have made rapid progress in the past decades due to their flexible size, structure and compatibility with semiconductor fabrication processes. With the development of semiconductor fabrication techniques, materials science and surface chemistry, nanopore preparation and modification technologies have made great breakthroughs. To date, various solid-state nanopore materials, processing technologies, and modification methods are available to us. In the review, we outline the recent advances in nanopores fabrication and analyze the virtues and limitations of various membrane materials and nanopores drilling techniques.

Preparation of a Chitosan/Coal Gasification Slag Composite Membrane and Its Adsorption and Removal of Cr (VI) and RhB in Water.

At present, there are many kinds of pollutants, including dyes and heavy metal ions, in wastewater. It is very important to develop adsorbents that can simultaneously remove heavy metal ions and dyes. In this study, a renewable composite membrane material was synthesized using chitosan and treated coal gasification slag. The Cr (VI) maximum adsorption capacity of the composite membrane was 50.0 mg/L, which was 4.3~8.8% higher than that of the chitosan membrane. For the adsorption of RhB, the removal rate of the chitosan membrane was only approximately 5.0%, but this value could be improved to 95.3% by introducing coal gasification slag. The specific surface area of the chitosan membrane could also be increased 16.2 times by the introduction of coal gasification slag. This is because coal gasification slag could open the nanopores of the chitosan membrane (from 80 µm to 110 µm). Based on the adsorption kinetics and adsorption mechanism analysis, it was found that the adsorption of Cr (VI) occurred mainly through the formation of coordination bonds with the amino groups on the molecular chains of chitosan. Meanwhile, RhB adsorption occurred through the formation of hydrogen bonds with the surface of coal gasification slag. Additionally, coal gasification slag can improve the mechanical properties of the chitosan membrane by 2.2 times, which may facilitate the practical application of the composite membrane. This study provides new insight into the adsorbent design and the resource utilization of coal gasification slag.

[Preliminary study on RC membrane permeability and mechanism of seven traditional Chinese medicine alkaloids such as berberine].

In order to analyze the law of membrane permeation of different alkaloids, seven traditional Chinese medicine alkaloids with different parent nucleus and substituent structures, including berberine, palmatine, sinomenine, matrine, oxymatrine, sophoridine, and tetrandrine, were prepared into the simulated solution with same molar concentration, and the membrane penetrating experiments with membrane RC1K and membrane RC5K were carried out. The dynamic transmittance, the total transmittance and the total adsorption rate of each substance were measured, and the scanning electron microscopy (SEM) images of the membrane surface before and after the membrane experiment were considered to predict and analyze the reason of differences in dynamic transmittance of different alkaloids. The results showed that there were significant differences in the dynamic transmittance of the chemical constituents of different alkaloids during penetrating the two membranes. The contamination degree on the surface of the membrane material was also different. The transmittance of the same compound through the RC5K membrane was larger than that through RC1K membrane. Within a certain range, the smaller the pore size of the membrane, the better the selective screening effect on the chemical constituents of traditional Chinese medicine. All the membrane surfaces were less polluted. The difference in transmittance between different substances on the same membrane showed a positive correlation with the difference in structural complexity, providing an experimental basis for the surface modification design in contamination control of membrane materials. In the design of membrane modified material, the surface properties of the membrane can be improved by grafting different polar groups, thereby changing the adsorption characteristics of the membrane surface. The pore size was designed accordingly to achieve the high transmittance and low pollution of the corresponding compounds.

Experimental Investigation into the Failure Mechanisms of Fabric Membrane Materials with Defective Flat Round Cracks.

The emphasis of this study is placed on the investigation into the failure mechanisms of the fabric membranes when exposed to such defective cracks. This experimental study investigates the initial crack of a flat circle and conducts a uniaxial shear test on the membrane materials. The deformation of the membrane materials is obtained through an optical non-contact scanner. Our study has been conducted to assess the crack propagation of fabric membrane materials at different angles. The relationships between crack width and stress together with stress and strain are also obtained. Based on the results, a mechanic of failure on the membrane was proposed. Moreover, new findings into the ductility and energy absorption of the fabric membrane materials have been established to inform the failure mechanisms.

Ionic Polyimine-Based Composite Membrane with Inductive and Complexation Synergistic Effects for Sensitive and On-Site Fluorescent Detection of Volatile Iodine.

Along with the development of nuclear power, concerns about radioactive emissions and the potential for nuclear leakage have been widely raised, particularly of harmful iodine isotopes. However, as a significant component of nuclear air waste, the enrichment and detection of air-dispersed gaseous iodine remain a challenge. In this work, it is focused on developing an attraction-immobilization-detection strategy-based fluorescence method for the on-site detection of volatile iodine, by employing a photoluminescent ionic polyimine network-polyvinylpyrrolidone (IPIN-PVP) composite membrane. This strategy synergizes ion-induced dipole interactions from IPIN and complexation effects from PVP, allowing effective iodine enrichment and immobilization. As a result, the optimized IPIN-PVP membrane exhibits rapid response times of 5 s and a low detection limit of 4.087 × 10-8 m for gaseous iodine. It also introduces a portable handheld detection device that utilizes the composite membrane, offering a practical solution for real-time on-site detection of volatile iodine. This innovation enhances nuclear safety measures and disaster management by providing rapid and reliable iodine detection capabilities.

Ion-Ion Selectivity of Synthetic Membranes with Confined Nanostructures.

Synthetic membranes featuring confined nanostructures have emerged as a prominent category of leading materials that can selectively separate target ions from complex water matrices. Further advancements in these membranes will pressingly rely on the ability to elucidate the inherent connection between transmembrane ion permeation behaviors and the ion-selective nanostructures. In this review, we first abstract state-of-the-art nanostructures with a diversity of spatial confinements in current synthetic membranes. Next, the underlying mechanisms that govern ion permeation under the spatial nanoconfinement are analyzed. We then proceed to assess ion-selective membrane materials with a focus on their structural merits that allow ultrahigh selectivity for a wide range of monovalent and divalent ions. We also highlight recent advancements in experimental methodologies for measuring ionic permeability, hydration numbers, and energy barriers to transport. We conclude by putting forth the future research prospects and challenges in the realm of high-performance ion-selective membranes.

Microalgae cell adhesions on hydrophobic membrane substrates using quartz crystal microbalance with dissipation.

Microalgal cell adhesion and biofilm formation are affected by interactions between microalgae strains and membrane materials. Variations of surface properties of microalgae and membrane materials are expected to affect cell-membranes and cell-cell interactions and thus initial microalgal cell adhesion and biofilm formation rates. Hence, it should be possible to identify the dominant mechanisms controlling microalgal cell adhesion and biofilm formation. The effects of surface properties of three different microalgal strains and three different types of membrane materials on microalgal cell adhesion and biofilm formation were systematically investigated in real time by monitoring changes in the oscillation frequency and dissipation of the quartz crystal resonator (QCM-D). The results revealed that in general a higher surface free energy, more negative zeta potential, and higher surface roughness of membrane materials positively correlated with a larger quantity of microalgae cell deposition, while a more hydrophilic microalgae with a larger negative zeta potential preferred to attach to a more hydrophobic membrane material. The adhered microalgal layers exhibited viscoelastic properties. The relative importance of these mechanisms in controlling microalgae cell attachment and biofilm formation might vary, depending on the properties of specific microalgae species and hydrophobic membrane materials used.

Purifying water with silver nanoparticles (AgNPs)-incorporated membranes: Recent advancements and critical challenges.

In the face of the growing global water crisis, membrane technology is a promising means of purifying water and wastewater. Silver nanoparticles (AgNPs) have been widely used to improve membrane performance, for antibiofouling, and to aid in photocatalytic degradation, thermal response, and electro-conductivity. However, several critical issues such as short antimicrobial periods, trade-off effects and silver inactivation seriously restrict the engineering application of AgNPs-incorporated membranes. In addition, there is controversy around the use of AgNPs given the toxic preparation process and environmental/biological risks. Hence, it is of great significance to summarize and analyze the recent developments and critical challenges in the use of AgNPs-incorporated membranes in water and wastewater treatment, and to propose potential solutions. We reviewed the different properties and functions of AgNPs and their corresponding applications in AgNPs-incorporated membranes. Recently, multifunctional, novel AgNP-incorporated membranes combined with other functional materials have been developed with high-performance. We further clarified the synergistic mechanisms between AgNPs and these novel nanomaterials and/or polymers, and elucidated their functions and roles in membrane separation. Finally, the critical challenges of AgNPs-incorporated membranes and the proposed solutions were outlined: i) Prolonging the antimicrobial cycle through long-term and controlled AgNPs release; ii) Overcoming the trade-off effect and organic fouling of the AgNPs-incorporated membranes; iii) Preparation of sustainable AgNPs-incorporated membranes; iv) Addressing biotoxicity induced by AgNPs; and v) Deactivation of AgNPs-incorporated membrane. Overall, this review provides a comprehensive discussion of the advancements and challenges of AgNPs-incorporated membranes and guides the development of more robust, multi-functional and sustainable AgNPs-incorporated membranes.

A Comprehensive Review on Forward Osmosis Water Treatment: Recent Advances and Prospects of Membranes and Draw Solutes.

Forward osmosis (FO) is an evolving membrane separation technology for water treatment and reclamation. However, FO water treatment technology is limited by factors such as concentration polarization, membrane fouling, and reverse solute flux. Therefore, it is of a great importance to prepare an efficient high-density porous membrane and to select an appropriate draw solute to reduce concentration polarization, membrane fouling, and reverse solute flux. This review aims to present a thorough evaluation of the advancement of different draw solutes and membranes with their effects on FO performance. NaCl is still widely used in a large number of studies, and several general draw solutes, such as organic-based and inorganic-based, are selected based on their osmotic pressure and water solubility. The selection criteria for reusable solutes, such as heat-recovered gaseous draw, magnetic field-recovered MNPs, and electrically or thermally-responsive hydrogel are primarily based on their industrial efficiency and energy requirements. CA membranes are resistant to chlorine degradation and are hydrophilic, while TFC/TFN exhibit a high inhibition of bio-adhesion and hydrolysis. AQPs are emerging membranes, due to proteins with complete retention capacity. Moreover, the development of the hybrid system combining FO with other energy or water treatment technologies is crucial to the sustainability of FO.

Physicochemical Properties of Water-Based Copolymer and Zeolite Composite Sustained-Release Membrane Materials.

A nitrogen fertilizer slow-release membrane was proposed using polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), epoxy resin, and zeolite as raw materials. The effects of the water-based copolymer (PVA:PVP) solution ratio A (A1−A4) and zeolite amount B (B1−B4) on the water absorption rate (XS), water permeability (TS), fertilizer permeability (TF), tensile strength (KL), elongation at break (DSL), and viscosity (ND) of the membrane were explored using the swelling method, a self-made device, and a universal testing machine. The optimal combination of the water-based copolymer and zeolite amount was determined by the coefficient-of-variation method. The results show that the effects of the decrease in A on KL and the increase in B on KL and DSL are promoted first and then inhibited. DSL and ND showed a negative response to the A decrease, whereas XS, TS, and TF showed a positive response. The effect of increasing B on ND, TS, and TF showed a zigzag fluctuation. In the condition of A1−A3, XS showed a negative response to the B increase, whereas in the condition of A4, XS was promoted first and then inhibited. Adding PVP and zeolite caused the hydroxyl stretching vibration peak of PVA at 3300 cm−1 to widen; the former caused the vibration peak to move to low frequencies, and the latter caused it to move to high frequencies. The XRD pattern shows that the highest peak of zeolite is located at 2θ = 7.18° and the crystallization peak of the composite membrane increases with the rise in the proportion of zeolite. Adding PVP made the surface of the membrane smooth and flat, and adding a small amount of zeolite improved the mechanical properties of the membrane and exhibited good compatibility with water-based copolymers. In the evaluation model of the physicochemical properties of sustained-release membrane materials, the weight of all indicators was in the following order: TF > ND > TS > KL > XL > DSL. The optimal membrane material for comprehensive performance was determined to be A2B3.

Essential Design Strength and Unified Strength Condition of ETFE Membrane Material.

This study proposes essential design strength and unified strength condition for ETFE membrane materials based on the structural state-of-stress theory and formula of strength. Firstly, the tested strain data of the uniaxial rectangle-shaped specimen are modeled to obtain its state-of-stress characteristic parameter. Then, the characteristic points in the evolution curve of the characteristic parameter are detected by the cluster analysis (CA) criterion. The characteristic points are the embodiment of the natural law from quantitative change to qualitative change of a system, which define the essential strength and the essential design strength of ETFE membrane materials. Further, the essential principal stresses are derived at the characteristic points in the evolution curves of the characteristic parameters obtained by the state-of-stress analysis of the strain data from the tests of air bubbling models and cruciform specimens. Both essential principal stresses and essential strength lead to the unified formula of strength for ETFE membrane materials. Additionally, the unified strength condition is derived for the design of ETFE membrane material structures. Finally, the essential strength, essential design strength, and the unified strength conditions are compared with the existing conditions, providing a rationality to update the existing analysis and design methods for determining the strength of ETFE membrane materials.

Hybrid Erythrocyte Liposomes: Functionalized Red Blood Cell Membranes for Molecule Encapsulation.

The modification of erythrocyte membrane properties provides a new tool towards improved drug delivery and biomedical applications. The fabrication of hybrid erythrocyte liposomes is presented by doping red blood cell membranes with synthetic lipid molecules of different classes (PC, PS, PG) and different degrees of saturation (14:0, 16:0-18:1). The respective solubility limits are determined, and material properties of the hybrid liposomes are studied by a combination of X-ray diffraction, epi-fluorescent microscopy, dynamic light scattering (DLS), Zeta potential, UV-vis spectroscopy, and Molecular Dynamics (MD) simulations. Membrane thickness and lipid orientation can be tuned through the addition of phosphatidylcholine lipids. The hybrid membranes can be fluorescently labelled by incorporating Texas-red DHPE, and their charge modified by incorporating phosphatidylserine and phosphatidylglycerol. By using fluorescein labeled dextran as an example, it is demonstrated that small molecules can be encapsulated into these hybrid liposomes.

Effects of structural vulnerability of flat-sheet membranes on fouling development in continuous submerged membrane bioreactors.

The relationship between fouling development in a continuous laboratory-scale membrane reactor (MBR/Lab) and the membrane material was investigated using flat-sheet membranes prepared from four materials (polyvinylidene difluoride (PVDF), polyethersulfone, chlorinated polyvinyl chloride, and polytetrafluoroethylene). Further, the characteristics of the suspension liquid in MBR/Lab were compared with those of samples from actual wastewater treatment plants. It was found that, in addition to the membrane material's own characteristics, the structural vulnerability of the membranes had a determining effect on fouling development. The PVDF membrane showed the highest transmembrane pressure during MBR operation and its surface experienced significant damage because of the shearing stress caused by aeration, resulting in the penetration of the membrane by the fouling compounds. The characteristics of suspension liquid in MBR/Lab were almost similar to those in the MBR at a night-soil treatment plant and the aeration tank of a sewage treatment plant.

A review on functional polymer-clay based nanocomposite membranes for treatment of water.

Water is essential for every living being. Increasing population, mismanagement of water sources, urbanization, industrialization, globalization, and global warming have all contributed to the scarcity of fresh water sources and the growing demand of such resources. Securing and allocating sufficient water resources has thus become one of the current major global challenges. Membrane technology has dominated the field of water purification due to its ease of usage and fabrication with high efficiency. The development of novel membrane materials can hence play a central role in advancing the field of membrane technology. It is noted that polymer-clay nanocomposites have been used widely for treatment of waste water. Nonetheless, not much efforts have been put to functionalize their membranes to be selective for specific targets. This review was organized to offer better insights into various types of functional polymer and clays composite membranes developed for efficient treatment and purification of water/wastewater. Our discussion was extended further to evaluate the efficacy of membrane techniques employed in the water industry against major chemical (e.g., heavy metal, dye, and phenol) and biological contaminants (e.g., biofouling).

Comparison study on the performance of two different gas-permeable membranes used in a membrane-aerated biofilm reactor.

This study compared the performance of two different gas-permeable membranes, PVDF and PP membrane, in a membrane-aerated biofilm reactor (MABR). The surface characteristics and membrane pore blocking of these two membrane materials were studied utilizing AFM, SEM and CLSM. The PVDF membrane surface was more rough and hydrophilic, and possessed a better microbial affinity compared to PP. Furthermore, the MABR equipped with a PVDF membrane removed more COD (97.06 ±â€¯0.97%) and TN (85.66 ±â€¯0.87%) compared to the MABR with PP membrane (87.13 ±â€¯0.87% and 71.13 ±â€¯0.71%, respectively). As well, the PP membrane exhibited severe membrane pore blocking and had a lower oxygen transfer rate than the PVDF membrane. It is concluded that the PVDF membrane has potential as an aeration membrane material for MABRs.

Application of Membrane Crystallization for Minerals' Recovery from Produced Water.

Produced water represents the largest wastewater stream from oil and gas production. Generally, its high salinity level restricts the treatment options. Membrane crystallization (MCr) is an emerging membrane process with the capability to extract simultaneously fresh water and valuable components from various streams. In the current study, the potential of MCr for produced water treatment and salt recovery was demonstrated. The experiments were carried out in lab scale and semi-pilot scale. The effect of thermal and hydrodynamic conditions on process performance and crystal characteristics were explored. Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses confirmed that the recovered crystals are sodium chloride with very high purity (>99.9%), also indicated by the cubic structure observed by microscopy and SEM (scanning electron microscopy) analysis. It was demonstrated experimentally that at recovery factor of 37%, 16.4 kg NaCl per cubic meter of produced water can be recovered. Anti-scaling surface morphological features of membranes were also identified. In general, the study provides a new perspective of isolation of valuable constituents from produced water that, otherwise, is considered as a nuisance.