Engineering Nanocomposite Membranes; Fabrication, Modification and Application

The engineering of novel membranes through fabrication and modification using engineered nanoscale materials (ENMs) presents tremendous opportunity within desalination and water treatment. This work presents an endeavour dedicated to investigate the design and fabrication of polymeric membranes and nanoscale materials. Also, to probe the role of nanoscale materials integration on the function of separating membranes aiming to diminish the propensity of the surface to foul.In the first part of the work, an attempt was made to research and compare the potential of versatile UF membranes structures in terms of morphology, surface characteristics and performance. The potential performance of the hand-made fabricated (UF) membranes was systematically evaluated against three organic model foulants with dissimilar origins; humic acid (HA), sodium alginate (NaAlg), and bovine serum albumin (BSA), under different initial feed concentration and pH chemistry. A diverse range of surface characteristics and morphologies have been produced as a result of varying the dope casting solution concentration, which corresponds to the wide range of commercially available UF membranes (6, 10, 35 and 100kDa). Also, a disparate fouling behaviour was observed depending on the membrane characteristics and the organic model foulant used. A one or more pore blocking mechanism were distinctly observed depending on the UF membrane cut-off used.Subsequently, the research presented the development of a novel nanocomposite membrane incorporating antimicrobial nanoparticles which have the potential to lower membrane biofouling. Antibacterial hybrid nanostructures (HNS) comprising of Ag decorated MWCNTs were successfully synthesised with the assistance of microwave irradiation. The HNS were then employed to fabricated antibacterial nanocomposite membranes via the classical phase inversion technique in order to assess their antimicrobial properties against two bacterial species; E. coli and S. aureus. The nanocomposite membranes remarkably displayed antibacterial activity (4.24 and 2.9 log kill) against the two species respectively. A higher stability under crossflow conditions was also demonstrated.Finally, for desalination applications, novel HNS comprising of a mussel-inspired PDA coated M/MO–MWCNTs, were successfully synthesised and used to fabricate TFN membranes. For comparison, four different M/MO (Al2O3, Fe2O3, TiO2 and Ag) nanoparticles (NPs) were in situ synthesised/loaded on the surface of CNTs, and the resultant HNS were further coated with a thin polymeric film of PDA. An intermediate layer of the HNS was then deposited on a PES substrate membrane, and an interfacial polymerisation (IP) process was carried out to render a polyamide (PA) thin layer above the intermediate layer. Both HNS and TFN were characterised using different characterisation tools, and the performance of nanofiltration (NF) membranes was evaluated against monovalent, divalent salts and heavy metal solutions. The fabricated TFN-NF membranes had higher performance in terms of their permeation characteristics compared to the thin film composite TFC membrane (⁓9.6-11.6 LMH), while maintaining their selectivity (≥91%) against both monovalent and divalent salts solutions, and (> 92%) against the multi-component heavy metal solution. The experimental results disclosed a high retention capability for TFC and TFN membranes along with greater potential stability/compatibility within the polymeric PA matrix. This implies that the NF membranes fabricated in this work can be employed for water reclamation purposes

Fabrication of antibacterial mixed matrix nanocomposite membranes using hybrid nanostructure of silver coated multi-walled carbon nanotubes

The function of separation membranes can be significantly improved by the integration of nanoparticles that can improve not only the mechanical properties of the membrane but also reduce the propensity of the surface to foul. The research of the paper presents the development of a novel nanocomposite membrane incorporating antimicrobial nanoparticles which have the potential to lower membrane biofouling; a major problem in many industries that exploit membrane technology. Antibacterial hybrid nanostructures (HNS) comprising of multi-walled carbon nanotubes (MWCNTs) coated with silver nanoparticles (AgNPs) were successfully synthesized via a facile and rapid method using a microwave treatment. The HNS were incorporated into polyethersulfone (PES) ultrafiltration (UF) membranes via the classical phase inversion technique in order to assess their antimicrobial properties against two bacterial species; E.coli and S.aureus. Different techniques were used to characterize HNS powders and a number of loading weights of the HNS were blended with PES flakes to assess the resultant nanocomposite membranes. The nanocomposite membranes displayed an increase in their antibacterial activity against the two species with increasing the loading weight of HNS

Functional materials in desalination: A review

This paper reviews various functional materials used in desalination. Desalination of the abundant seawater resource has emerged as a promising technology to meet the current fresh water demands. For improved performance, often functional materials such as photocatalysts, electrocatalysts, photothermal materials, sorbents, antibacterial materials and magnetic materials are utilized in thermal, membrane-based and other desalination technologies. With an aim to provide an insight on the existing research on functional materials and the purpose behind using such in desalination, this review collates different research studies of various functional properties and the subsequent materials utilized for those properties. New generation materials such as carbon nanotubes (CNTs) and graphene form a major part, where they exhibit multiple functionalities with improved water transport properties, and thus have been deemed as very attractive enhancers to the desalination technology. Nevertheless, most of the functional materials, such as nano-TiO2, nano-zeolites, graphene, CNTs and magnetic nanoparticles suffer from several limitations such as specialized synthesis techniques, agglomeration, leaching and environmental and health concerns. This review focuses on such challenges and suggests improvements for enhanced incorporation of these in the desalination technology. Lastly, emerging new technologies, advanced fabrication methods and novel functional hybrid materials are reviewed to equip the readers with the latest research trends. Thus, a comprehensive review is essential which will provide current and future researchers an insight on the importance and significance of utilizing functional materials in various desalination technologies

Recent progress in nanocomposites based on conducting polymer: application as electrochemical sensors

Abstract Over the years, intensive research works have been devoted to conducting polymers due to their potential application in many fields such as fuel cell, sensors, and capacitors. To improve the properties of these compounds, several new approaches have been developed which consist in combining conducting polymers and nanoparticles. Then, this review intends to give a clear overview on nanocomposites based on conducting polymers, synthesis, characterization, and their application as electrochemical sensors. For this, the paper is divided into two parts: the first part will highlight the nanocomposites synthesized by combination of carbon nanomaterials (CNMs) and conducting polymers. The preparation of polymer/CNMs such as graphene and carbon nanotube modified electrode is presented coupled with relevant applications. The second part consists of a review of nanocomposites synthesized by combination of metal nanoparticles and conducting polymers

Engineering nanocomposite membranes: Addressing current challenges and future opportunities

The engineering of novel membranes through fabrication and modification using engineered nanoscale materials (ENMs) presents tremendous opportunity within desalination and water treatment. In this paper, we present an overview of the applications of ENMs to organic polymeric membranes and desalination. The review will examine the motivation for introducing ENMs into polymeric membranes identifying how the characteristics of the ENMs, such as high surface area to volume ratio and mechanical strength, can be used to optimise and tailor membranes for particular applications. The overview will include ENM's classification, incorporation strategies and how their properties impact on the surface characteristics, robustness, functionality, morphologies and antifouling properties of polymeric membranes. The review will also feature discussion on the current issues facing the development and commercialization of nanocomposite membrane that harness the benefits of ENMs

Thin Film Nanocomposite (TFN) membranes modified with polydopamine coated metals/carbon-nanostructures for desalination applications

Novel hybrid nanostructures (HNS) comprising of a mussel-inspired polymer coated metal/metal oxide (M/MO)–carbon nanotubes (CNTs), were successfully synthesized and used to fabricate Thin Film Nanocomposite (TFN) membranes for desalination applications. For comparison, four different M/MO (Aluminium oxide-Al2O3, Iron oxide-Fe2O3, Titanium dioxide-TiO2 and Silver-Ag) nanoparticles (NPs) were in situ synthesized/loaded on the surface of CNTs, and the resultant HNS were further coated with a thin polymeric film of polydopamine (PDA). An intermediate layer of HNS was then deposited on a PES substrate membrane and an interfacial polymerization (IP) process was carried out to render a polyamide (PA) thin layer above the intermediate layer. Both HNS and TFN were characterized using different characterization tools, including fourier transforms infrared spectroscopy (FTIR), zeta potential (ZP), X-ray diffraction (XRD), raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), surface hydrophilicity/hydrophobicity, and the performance of nanofiltration (NF) membranes were evaluated against monovalent and divalent salts solutions. The fabricated TFN-NF membranes had higher performance in terms of their permeation characteristics compared to the thin film composite TFC membrane, while maintaining their selectivity against both monovalent and divalent salts solutions with only minor variation depending on the incorporated HNS used to prepare the TFN

Fabrication of Carbon and Related Materials/Metal Hybrids and Composites

This Special Issue on “Fabrication of Carbon and related materials/ Metal Hybrids and Composites” presents the importance of the development of new composite and hybrid materials in different fields. It consists of 17 articles contributed by authors from different countries all over the world. The articles can be categorized into four classes. The first class of includes articles focusing on the synthesis of carbon fibers, carbon nanotubes, and graphene hybrid and composite materials. The results include the developments of the methodology and know-how of the synthesis and functionalization of the graphene surface of fibers and nanotubes and their effects on binding with the metal matrix. The second class focuses on the synthesis of new polymeric materials based on pitch/polyethylene composites and their electrical and mechanical properties, including the correlations with its microstructures. Additionally, the second class presents the results of articles, including the synthesis of new biocompatible and eco-friendly metal oxide/polymer materials with antibacterial and antimicrobial activities. The third class includes articles focused on the applications of ceramic metal oxides, such as silica and clays in the development of solar cells and in the fabrications of membranes of water treatments and desalinations. The last part of this Special Issue presents results of the articles focused on high-entropy alloys and metal matrix composites and their weldability

Fabrication of gum arabic-graphene (GGA) modified polyphenylsulfone (PPSU) mixed matrix membranes: A systematic evaluation study for ultrafiltration (UF) applications

In the current work, a Gum, Arabic-modified Graphene (GGA), has been synthesized via a facile green method and employed for the first time as an additive for enhancement of the PPSU ultrafiltration membrane properties. A series of PPSU membranes containing very low (0–0.25) wt.% GGA were prepared, and their chemical structure and morphology were comprehensively investigated through atomic force microscopy (AFM), Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Besides, thermogravimetric analysis (TGA) was harnessed to measure thermal characteristics, while surface hydrophilicity was determined by the contact angle. The PPSU-GGA membrane performance was assessed through volumetric flux, solute flux, and retention of sodium alginate solution as an organic polysaccharide model. Results demonstrated that GGA structure had been successfully synthesized as confirmed XRD patterns. Besides, all membranes prepared using low GGA content could impart enhanced hydrophilic nature and permeation characteristics compared to pristine PPSU membranes. Moreover, greater thermal stability, surface roughness, and a noticeable decline in the mean pore size of the membrane were obtained

Polymeric materials with antibacterial activity: A review

Infections caused by bacteria are one of the main causes of mortality in hospitals all over the world. Bacteria can grow on many different surfaces and when this occurs, and bacteria colonize a surface, biofilms are formed. In this context, one of the main concerns is biofilm formation on medical devices such as urinary catheters, cardiac valves, pacemakers or prothesis. The development of bacteria also occurs on materials used for food packaging, wearable electronics or the textile industry. In all these applications polymeric materials are usually present. Research and development of polymer-based antibacterial materials is crucial to avoid the proliferation of bacteria. In this paper, we present a review about polymeric materials with antibacterial materials. The main strategies to produce materials with antibacterial properties are presented, for instance, the incorporation of inorganic particles, micro or nanostructuration of the surfaces and antifouling strategies are considered. The antibacterial mechanism exerted in each case is discussed. Methods of materials preparation are examined, presenting the main advantages or disadvantages of each one based on their potential uses. Finally, a review of the main characterization techniques and methods used to study polymer based antibacterial materials is carried out, including the use of single force cell spectroscopy, contact angle measurements and surface roughness to evaluate the role of the physicochemical properties and the micro or nanostructure in antibacterial behavior of the materials