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

Natural and recycled materials for sustainable membrane modification: Recent trends and prospects

Despite water being critical for human survival, its uneven distribution, and exposure to countless sources of pollution make water shortages increasingly urgent. Membrane technology offers an efficient solution for alleviating the water shortage impact. The selectivity and permeability of membranes can be improved by incorporating additives of different nature and size scales. However, with the vast debate about the environmental and economic feasibility of the common nanoscale materials in water treatment applications, we can infer that there is a long way before the first industrial nanocomposite membrane is commercialized. This stumbling block has motivated the scientific community to search for alternative modification routes and/or materials with sustainable features. Herein, we present a pragmatic review merging the concept of sustainability, nanotechnology, and membrane technology through the application of natural additives (e.g., Clays, Arabic Gum, zeolite, lignin, Aquaporin), recycled additives (e.g., Biochar, fly ash), and recycled waste (e.g., Polyethylene Terephthalate, recycled polystyrene) for polymeric membrane synthesis and modification. Imparted features on polymeric membranes, induced by the presence of sustainable natural and waste-based materials, are scrutinized. In addition, the strategies harnessed to eliminate the hurdles associated with the application of these nano and micro size additives for composite membranes modification are elaborated. The expanding research efforts devoted recently to membrane sustainability and the prospects for these materials are discussed. The findings of the investigations reported in this work indicate that the application of natural and waste-based additives for composite membrane fabrication/modification is a nascent research area that deserves the attention of both research and industry

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

Laser Doppler Electrophoresis and electro-osmotic flow mapping: A novel methodology for the determination of membrane surface zeta potential

A novel technique employing an Uzigirs dip cell arrangement is used in conjunction with Laser Doppler Electrophoresis for the determination of the surface zeta potential for a UF, NF, and RO membrane. To the authors best knowledge this is the first study employing Laser Doppler Electrophoresis and Electro-osmotic Flow Mapping for membrane surface charge determination. High correlation of the regression fit (R2>0.95) for a carboxylated polystyrene latex particle electrophoretic mobility was achieved at low electrolyte concentrations (1mM and 10mM NaCl), but the reliability and accuracy of the extrapolated zeta potential values were problematic at higher concentration due to high measurement uncertainty (>10% in some cases). Changes in the applied electric field increased the phase resolution of 50mM NaCl electrolyte solutions between 0.5-2.0V. However, the effects of Joule heating at higher voltages compromised 50mM NaCl sample integrity. When compared with the established Tangential Streaming Potential method, Laser Doppler Electrophoresis measurements provided similar zeta potential values and trends indicating that this new methodology can indeed be employed for membrane characterization purposes; however, further research needs to be conducted in order to optimize this new technique and set appropriate operating limits

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

Membrane Technologies for Nitrogen Recovery from Waste Streams: Scientometrics and Technical Analysis

The concerns regarding the reactive nitrogen levels exceeding the planetary limits are well documented in the literature. A large portion of anthropogenic nitrogen ends in wastewater. Nitrogen removal in typical wastewater treatment processes consumes a considerable amount of energy. Nitrogen recovery can help in saving energy and meeting the regulatory discharge limits. This has motivated researchers and industry professionals alike to devise effective nitrogen recovery systems. Membrane technologies form a fundamental part of these systems. This work presents a thorough overview of the subject using scientometric analysis and presents an evaluation of membrane technologies guided by literature findings. The focus of nitrogen recovery research has shifted over time from nutrient concentration to the production of marketable products using improved membrane materials and designs. A practical approach for selecting hybrid systems based on the recovery goals has been proposed. A comparison between membrane technologies in terms of energy requirements, recovery efficiency, and process scale showed that gas permeable membrane (GPM) and its combination with other technologies are the most promising recovery techniques and they merit further industry attention and investment. Recommendations for potential future search trends based on industry and end users’ needs have also been proposed

Natural and recycled materials for sustainable membrane modification : Recent trends and prospects

Funding Information: Nidal Hilal would like to thank Tamkeen for funding the NYUAD Water Research Center under the NYUAD Research Institute Award (project CG007 ). Publisher Copyright: © 2022 The AuthorsDespite water being critical for human survival, its uneven distribution, and exposure to countless sources of pollution make water shortages increasingly urgent. Membrane technology offers an efficient solution for alleviating the water shortage impact. The selectivity and permeability of membranes can be improved by incorporating additives of different nature and size scales. However, with the vast debate about the environmental and economic feasibility of the common nanoscale materials in water treatment applications, we can infer that there is a long way before the first industrial nanocomposite membrane is commercialized. This stumbling block has motivated the scientific community to search for alternative modification routes and/or materials with sustainable features. Herein, we present a pragmatic review merging the concept of sustainability, nanotechnology, and membrane technology through the application of natural additives (e.g., Clays, Arabic Gum, zeolite, lignin, Aquaporin), recycled additives (e.g., Biochar, fly ash), and recycled waste (e.g., Polyethylene Terephthalate, recycled polystyrene) for polymeric membrane synthesis and modification. Imparted features on polymeric membranes, induced by the presence of sustainable natural and waste-based materials, are scrutinized. In addition, the strategies harnessed to eliminate the hurdles associated with the application of these nano and micro size additives for composite membranes modification are elaborated. The expanding research efforts devoted recently to membrane sustainability and the prospects for these materials are discussed. The findings of the investigations reported in this work indicate that the application of natural and waste-based additives for composite membrane fabrication/modification is a nascent research area that deserves the attention of both research and industry.Peer reviewe

Laser Doppler electrophoresis and electro-osmotic flow mapping for the zeta potential measurement of positively charged membrane surfaces

Successful characterization of membranes is of paramount importance for the development and improvement of novel membranes and membrane processes. The characterisation of membrane charge is key to understanding charge interactions between the process stream and the membrane and is typically represented by the surface zeta potential. In a previous paper (Thomas et al., 2017), a novel technique employing an Uzigirs dip cell arrangement used in conjunction with Laser Doppler Electrophoresis was used to characterize the surface of several negatively charged membranes. In this paper, positively charged modified PTFE membranes are fabricated and the novel zeta potential measurement technique is utilised to quantify the resultant membrane charge by use of a positively charged amidine tracer particle. The amidine particles were characterised and shown to have a positive zeta potential of 12.4 mV for the experimental conditions used. A comparative analysis was made between the novel laser Doppler electrophoresis measurements and tangential streaming potential measurements for the positive membrane and the agreement was good. The phase plot and mobility-displacement were of good quality for the data set, with the surface equivalent mobility being 0.632 μmcm/Vs with R2 = 0.977. In addition, a series of experiments were conducted to explore the operating envelope and highlight the pitfalls of the technique, i.e. oppositely charged particles to the surface should not be used. Overall, this work expands the application of the novel zeta potential measurement technique to span all membrane charge types. Thus providing a real benefit to the practicing scientist or engineer by having a reliable, fast and simple zeta potential technique that uses only a very small membrane sample