Poly (ether) sulfone electrospun nanofibrous membranes embedded with graphene oxide quantum dots with antimicrobial activity

Highly Reliable Performance of Flexible Synaptic Devices Based on PVP-GO QD Nanocomposites Due to the Formation of Directional Filaments

The metallic conductive filament (CF) model, which serves as an important conduction mechanism for realizing synaptic functions in electronic devices, has gained recognition and is the subject of extensive research. However, the formation of CFs within the active layer is plagued by issues such as uncontrolled and random growth, which severely impacts the stability of the devices. Therefore, controlling the growth of CFs and improving the performance of the devices have become the focus of that research. Herein, a synaptic device based on polyvinylpyrrolidone (PVP)/graphene oxide quantum dot (GO QD) nanocomposites is proposed. Doping GO QDs in the PVP provides a large number of active centers for the reduction of silver ions, which allows, to a certain extent, the growth of CFs to be controlled. Because of this, the proposed device can simulate a variety of synaptic functions, including the transition from long-term potentiation to long-term depression, paired-pulse facilitation, post-tetanic potentiation, transition from short-term memory to long-term memory, and the behavior of the "learning experience". Furthermore, after being bent repeatedly, the devices were still able to simulate multiple synaptic functions accurately. Finally, the devices achieved a high recognition accuracy rate of 89.39% in the learning and inference tests, producing clear digit classification results.

CFD-Assisted Process Optimization of an Integrated Photocatalytic Membrane System for Water Treatment

An integrated photocatalytic membrane system (IPMS) was developed for potential use in the remediation of naproxen using real water samples from a drinking water treatment plant. Key parameters such as time, pH, water matrix, mixing speeds, flow rate, and light intensity undeniably affected photocatalytic and membrane separation processes. The system optimization was based on improving irradiation to generate a more reactive species and mass transfer to increase the reaction rate. Upon optimization, IPMS achieved 99% naproxen removal efficiency. Computational fluid dynamics (CFD) simulated the flow patterns and radiation distribution inside the photocatalytic membrane reactor to improve irradiation and mass transfer during operation. The simulated flow field revealed the presence of dead zones with different velocities in the photocatalytic membrane reactor; this limited the mass transfer of reactive species in the reactor, resulting in uneven distribution of reactive radicals. The dead zones were mitigated by increasing the mixing speed, and as a result, convective mass flow improved process performance. The governing parameters (flow patterns and radiation distribution) of the simulated and experimental data were in agreement. The absorption of irradiation by the active site of the membranes improved with light intensity; at higher light intensities, the light irradiated deeper into the membrane. As such, the CoFe2O4 nanoparticles incorporated inside the membrane pores became highly activated, thus enhancing degradation. The obtained space-time yield (STY) (1.23 × 1011 mol/cm2.s) and photocatalytic space-time yield (PSTY) (4.39 × 1011 mol/W.s) showed that the developed IPMS was efficient regarding energy intensiveness and throughput for treatment of pollutants in water.

Recent progress on electrospun nanofibrous polymer membranes for water and air purification: A review

Developing new polymer membranes with excellent thermal, mechanical, and chemical stability has shown great potential for various environmental remediation applications such as wastewater treatment and air filtration. Polymer membranes have been widely investigated over the past years and utilized to overcome severe ecological issues. Membrane-based technologies play a critical role in water purification and air filtration with the ability to act efficiently and sustainably. Electrospun nanofiber membranes have displayed excellent performance in removing various contaminants from water, such as bacteria, dyes, heavy metals, and oil. These nanofibrous membranes have shown good potential to filter the air from tiny particles, volatile organic compounds, and toxic gases. The performance of polymer membranes can be enhanced by fine-tuning polymer structure, varying surface properties, and strengthening overall membrane porosity. In this review, we discuss the involvement of electrospun nanofibrous membranes in different environmental remediation applications. It further reviews the recent progress of polymer membrane development by utilizing nanoparticles and naturally occurring polymers.

Graphene Quantum Dot-Added Thin-Film Composite Membrane with Advanced Nanofibrous Support for Forward Osmosis

Forward osmosis (FO) technology for desalination has been extensively studied due to its immense benefits over conventionally used reverse osmosis. However, there are some challenges in this process such as a high reverse solute flux (RSF), low water flux, and poor chlorine resistance that must be properly addressed. These challenges in the FO process can be resolved through proper membrane design. This study describes the fabrication of thin-film composite (TFC) membranes with polyethersulfone solution blown-spun (SBS) nanofiber support and an incorporated selective layer of graphene quantum dots (GQDs). This is the first study to sustainably develop GQDs from banyan tree leaves for water treatment and to examine the chlorine resistance of a TFC FO membrane with SBS nanofiber support. Successful GQD formation was confirmed with different characterizations. The performance of the GQD-TFC-FO membrane was studied in terms of flux, long-term stability, and chlorine resistance. It was observed that the membrane with 0.05 wt.% of B-GQDs exhibited increased surface smoothness, hydrophilicity, water flux, salt rejection, and chlorine resistance, along with a low RSF and reduced solute flux compared with that of neat TFC membranes. The improvement can be attributed to the presence of GQDs in the polyamide layer and the utilization of SBS nanofibrous support in the TFC membrane. A simulation study was also carried out to validate the experimental data. The developed membrane has great potential in desalination and water treatment applications.

Improved Forward Osmosis Performance of Thin Film Composite Membranes with Graphene Quantum Dots Derived from Eucalyptus Tree Leaves

The major challenges in forward osmosis (FO) are low water flux, high specific reverse solute flux (SRSF), and membrane fouling. The present work addresses these problems by the incorporation of graphene quantum dots (GQDs) in the polyamide (PA) layer of thin-film composite (TFC) membranes, as well as by using an innovative polyethersulfone nanofiber support for the TFC membrane. The GQDs were prepared from eucalyptus leaves using a facile hydrothermal method that requires only deionized water, without the need for any organic solvents or reducing agents. The nanofiber support of the TFC membranes was prepared using solution blow spinning (SBS). The polyamide layer with GQDs was deposited on top of the nanofiber support through interfacial polymerization. This is the first study that reports the fouling resistance of the SBS-nanofiber-supported TFC membranes. The effect of various GQD loadings on the TFC FO membrane performance, its long-term FO testing, cleaning efficiency, and organic fouling resistance were analyzed. It was noted that the FO separation performance of the TFC membranes was improved with the incorporation of 0.05 wt.% GQDs. This study confirmed that the newly developed thin-film nanocomposite membranes demonstrated increased water flux and salt rejection, reduced SRSF, and good antifouling performance in the FO process.

Magnetic Beads of Zero Valent Iron Doped Polyethersolfun Developed for Removal of Arsenic from Apatite-Soil Treated Water

The drop immerses calcium chloride aqueous solution was utilized to prepare the zero valent iron-doped polyethersulfone beads (PES/ZVI) for the efficient removal of arsenic from apatite-soil treated waters. The proposed beads can assist in promoting uptake efficiency by hindering ZVI agglomeration due to a high porosity and different active sites. The PES/ZVI beads were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetism (VSM). The main objective of this study was to investigate the function of new PES/ZVI beads with an increased removal efficiency for the remediation of arsenic ions from the apatite-soil treated waters. A maximum adsorption removal of 82.39% was achieved when the experiment was performed with 80 mg of adsorbent for a contact time of 180 min. Based on the results, a removal efficiency >90% was obtained after 300 min of shaking time with an arsenic concentration of 20 mg·L^-1. The experimental process was fitted with the Langmuir model due to the high R² (0.99) value compared to the Freundlich model (0.91) with an adsorption capacity of 41.32 mg·g^-1. The adsorption process speed was limited by pseudo-second-order (R² = 0.999) and the adsorption mechanism nature was endothermic and physical.

Interdependence of Kinetics and Fluid Dynamics in the Design of Photocatalytic Membrane Reactors

Photocatalytic membrane reactors (PMRs) are a promising technology for wastewater reclamation. The principles of PMRs are based on photocatalytic degradation and membrane rejection, the different processes occurring simultaneously. Coupled photocatalysis and membrane filtration has made PMRs suitable for application in the removal of emerging contaminants (ECs), such as diclofenac, carbamazepine, ibuprofen, lincomycin, diphenhydramine, rhodamine, and tamoxifen, from wastewater, while reducing the likelihood of byproducts being present in the permeate stream. The viability of PMRs depends on the hypotheses used during design and the kinetic properties of the systems. The choice of design models and the assumptions made in their application can have an impact on reactor design outcomes. A design’s resilience is due to the development of a mathematical model that links material and mass balances to various sub-models, including the fluid dynamic model, the radiation emission model, the radiation absorption model, and the kinetic model. Hence, this review addresses the discrepancies with traditional kinetic models, fluid flow dynamics, and radiation emission and absorption, all of which have an impact on upscaling and reactor design. Computational and analytical descriptions of how to develop a PMR system with high throughput, performance, and energy efficiency are provided. The potential solutions are classified according to the catalyst, fluid dynamics, thickness, geometry, and light source used. Two main PMR types are comprehensively described, and a discussion of various influential factors relating to PMRs was used as a premise for developing an ideal reactor. The aim of this work was to resolve potential divergences that occur during PMRs design as most real reactors do not conform to the idealized fluid dynamics. Lastly, the application of PMRs is evaluated, not only in relation to the removal of endocrine-disrupting compounds (EDCs) from wastewater, but also in dye, oil, heavy metals, and pesticide removal.

A comprehensive review on preparation, functionalization and recent applications of nanofiber membranes in wastewater treatment

The direct discharge of significant amounts of polluted water into water bodies causes adverse ecological and human health effects. This severe deterioration in water quality creates significant challenges to meet the growing demand for clean water. Therefore, the world urgently needs environmentally friendly advanced technology to overcome this global crisis. In this regard, nanofiber-based membrane filtration is a promising technique in wastewater remediation because of their huge surface area, extremely porous structure, amenable pore size/pore size distribution, variety of material choices, and flexibility to modification with other functional materials. However, despite their unique properties, fouling, poor mechanical properties, shrinkage, and deformation are major drawbacks of nanofiber membranes for treating wastewater. This review presents a comprehensive overview of nanofiber membranes' fabrication and function in water purification applications as well as providing novel approaches to overcoming/alleviating the mentioned disadvantages. The review first presents nanofiber membrane preparation methods, focusing on electrospinning as a versatile and viable technique alongside discussing the parameters controlling nanofiber morphology. Afterward, the functionalization of nanofiber membranes by combining them with other nanomaterials, such as metal and metal-oxide nanoparticles, carbon nanotubes, metal-organic frameworks, and biomolecules, were demonstrated and discussed. In addition, nanofiber membranes functionalized with microorganisms were highlighted. Finally, we introduced and discussed in detail the most relevant and recent advances in nanofiber applications in wastewater treatment in the context of removing different pollutants (e.g., heavy metals, nutrients, radioactive elements, pharmaceuticals, and personal care products, dyes, and pesticides). Moreover, the promising antimicrobial ability of nanofiber membranes in removing microorganisms from wastewater has been fully underscored. We believe this comprehensive review could provide researchers with preliminary data and guide both researchers and producers engaged in the nanofiber membrane industry, letting them focus on the research gaps in wastewater treatment.

Modification of polyvinylidene fluoride membrane by silver nanoparticles-graphene oxide hybrid nanosheet for effective membrane biofouling mitigation

Membrane biofouling poses severe impacts on the membrane lifespan and performance. In this study, a silver nanoparticles-graphene oxide hybrid nanosheet (AgNPs-GO) was synthesized as a bactericidal agent for effective membrane biofouling mitigation. The surface polymerization between polyvinyl alcohol (PVA) and AgNPs-GO nanosheet improved the stability of inorganic biocidal materials on the membrane surface and had a significant effect on the permeability and rejection performance of membranes. The PVA/AgNPs-GO modified hydrophilic polyvinylidene fluoride (H-PVDF) membrane exhibited an excellent anti-microbial activity in both static contact and filtration modes; nearly 100% inactivation of Pseudomonas aeruginosa in solution and 91% reduction in the membrane surface adhesion were found. The composite membrane with good stability and anti-microbial ability may offer an alternative to alleviate membrane biofouling problem.