Protein fouling of modified microporous PET track-etched membranes

Low energy-consumption oriented membrane fouling control strategy in anaerobic fluidized membrane bioreactor

Anaerobic fluidized membrane bioreactors (AFMBR) has attracted growing interest as an emerging wastewater treatment technology towards energy recovery from wastewater. AFMBR combines the advantages of anaerobic digestion and membrane bioreactors and shows great potential in overcoming limiting factors such as membrane fouling and low efficiency in treating low-strength wastewater such as domestic sewage. In AFMBR, the fluidized media performs significant role in reducing the membrane fouling, as well as improving the anaerobic microbial activity of AFMBRs. Despite extensive research aimed at mitigating membrane fouling in AFMBR, there has yet to emerge a comprehensive review focusing on strategies for controlling membrane fouling with an emphasis on low energy consumption. Thus, this work overviews the recent progress of AFMBR by summarizing the factors of membrane fouling and energy consumption in AFMBR, and provides targeted in-depth analysis of energy consumption related to membrane fouling control. Additionally, future development directions for AFMBR are also outlooked, and further promotion of AFMBR engineering application is expected. By shedding light on the relationship between energy consumption and membrane fouling control, this review offers a useful information for developing new AFMBR processes with an improved efficiency, low membrane fouling and low energy consumption, and encourages more research efforts and technological advancements in the domain of AFMBR.

Surface Modification of Polyethylene Terephthalate Track-Etched Membranes by 2,2,3,3,4,4,5,5,6,6,7,7-Dodecafluoroheptyl Acrylate for Application in Water Desalination by Direct Contact Membrane Distillation

In this work, the surfaces of poly (ethylene terephthalate) track-etched membranes (PET TeMs) with pore sizes of 670-1310 nm were hydrophobized with 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate (DFHA) by photoinitiated graft polymerization. Attenuated total reflection FTIR spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDX), and contact angle measurements were used to identify and characterize the TeMs. The optimal parameters for graft polymerization were determined as follows: polymerization time of 60 min, monomer concentration of 30%, and distance from the UV source of 7 cm. The water contact angle of the modified membranes reached 97°, which is 51° for pristine membranes. The modified membranes were tested for water desalination using direct contact membrane distillation (DCMD) method. The effects of membrane pore size, the degree of grafting, and salt concentration on the performance of membrane distillation process were investigated. According to the results obtained, it has been concluded that large pore size hydrophobic TeMs modified by using DFHA could be used for desalinating water.

Developing tardigrade-inspired material: Track membranes functionalized with Dsup protein for cell-free DNA isolation

When developing functionalized biomaterials, the proteins from extremophilic organisms, in particular unique tardigrade disordered proteins, are of great value. The damage suppressor protein (Dsup), initially discovered in the tardigrade Ramazzottius varieornatus and found to be an efficient DNA protector under oxidative and irradiation stress, has been hypothesized to possess a good potential for the development of the material, which can isolate cell-free DNA. With this in mind, DNA-nonadsorbing polyethylene terephthalate track membranes have been functionalized using the Dsup protein via covalent bonding with glutaraldehyde. The filtration experiments have verified the ability of track membranes with the immobilized Dsup protein to adsorb cell-free DNA, with an accumulation capacity of 70 ± 19 mg m-2. The resulting track membrane-based biomaterial might be used in various devices for filtration and separation of cell-free DNA molecules from biological solutions and environmental samples, and also for their accumulation, storage, and further manipulation.

Environmentally friendly loading of palladium nanoparticles on nanoporous PET track-etched membranes grafted by poly(1-vinyl-2-pyrrolidone) via RAFT polymerization for the photocatalytic degradation of metronidazole

Nanoporous track-etched membranes (TeMs) are highly versatile materials that have shown promise in various applications such as filtration, separation, adsorption, and catalysis due to their mechanical integrity and high surface area. The performance of TeMs as catalysts for removing toxic pollutants is greatly influenced by the pore diameter, density, and functionalization of the nanochannels. In this study, the synthesis of functionalized poly(ethylene terephthalate) (PET) TeMs with Pd nanoparticles (NPs) as catalysts for the photodegradation of the antibiotic metronidazole (MTZ) was methodically investigated and their catalytic activity under UV irradiation was compared. Before loading of the Pd NPs, the surface and nanopore walls of the PET TeMs were grafted by poly(1-vinyl-2-pyrrolidone) (PVP) via UV-initiated reversible addition fragmentation chain transfer (RAFT)-mediated graft copolymerization. The use of RAFT polymerization allowed for precise control over the degree of grafting and graft lengths within the nanochannels of PVP grafted PET TeMs (PVP-g-PET). Pd NPs were then loaded onto PVP-g-PET using several environmentally friendly reducing agents such as ascorbic acid, sodium borohydride and a plant extract. In addition, a conventional thermal reduction technique was also applied for the reduction of the Pd NPs. The grafting process created a surface with high-sorption capacity for MTZ and also high stabilizing effect for Pd NPs due to the functional PVP chains on the PET substrate. The structure and composition of the composite membranes were elucidated by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, thermogravimetry, contact angle measurements and energy dispersive X-ray (EDX), X-ray photoelectron (XPS) and Fourier transform infra-red (FTIR) spectroscopies. The effects of different types of reducing agents, pH, the amount of loaded catalyst and MTZ concentration on the MTZ catalytic degradation efficiency of the obtained composites were investigated. The efficiency of the catalyst prepared in the presence of ascorbic acid was superior to the others (89.86% removal at 30 mg L^-1 of MTZ). Maximum removal of MTZ was observed at the natural pH (6.5) of the MTZ solution at a concentration of 30 mg per L MTZ. The removal efficiency was decreased by increasing the catalyst dosage and the initial MTZ concentration. The reaction rate constant was reduced from 0.0144 to 0.0096 min^-1 by increasing the MTZ concentration from 20 to 50 mg L^-1. The photocatalyst revealed remarkable photocatalytic activity even after 10 consecutive cycles.

Nanoparticle-Embedded Polymers and Their Applications: A Review

There has been increasing interest in the study and development of nanoparticle-embedded polymeric materials and their applications to special membranes. Nanoparticle-embedded polymeric materials have been observed to have a desirable compatibility with commonly used membrane matrices, a wide range of functionalities, and tunable physicochemical properties. The development of nanoparticle-embedded polymeric materials has shown great potential to overcome the longstanding challenges faced by the membrane separation industry. One major challenge that has been a bottleneck to the progress and use of membranes is the balance between the selectivity and the permeability of the membranes. Recent developments in the fabrication of nanoparticle-embedded polymeric materials have focused on how to further tune the properties of the nanoparticles and membranes to improve the performance of the membranes even further. Techniques for improving the performance of nanoparticle-embedded membranes by exploiting their surface characteristics and internal pore and channel structures to a significant degree have been incorporated into the fabrication processes. Several fabrication techniques are discussed in this paper and used to produce both mixed-matrix membranes and homogenous nanoparticle-embedded polymeric materials. The discussed fabrication techniques include interfacial polymerization, self-assembly, surface coating, and phase inversion. With the current interest shown in the field of nanoparticle-embedded polymeric materials, it is expected that better-performing membranes will be developed soon.

Hydrogen Isotope Separation Using Graphene-Based Membranes in Liquid Water

Hydrogen isotope separation has been effectively achieved electrochemically by passage of gaseous H₂/D₂ through graphene/Nafion composite membranes. Nevertheless, deuteron nearly does not exist in the form of gaseous D₂ in nature but as liquid water. Thus, it is a more feasible way to separate and enrich deuterium from water. Herein, we have successfully transferred monolayer graphene to a rigid and porous polymer substrate, PITEM (polyimide track-etched membrane), which could avoid the swelling problem of the Nafion substrate as well as keep the integrity of graphene. Meanwhile, defects in the large area of CVD graphene could be successfully repaired by interfacial polymerization resulting in a high separation factor. Moreover, a new model was proposed for the proton transport mechanism through monolayer graphene based on the kinetic isotope effect (KIE). In this model, graphene plays a significant role in the H/D separation process by completely breaking the O-H/O-D bond, which can maximize the KIE, leading to increased H/D separation performance. This work suggests a promising application for using monolayer graphene in the industry and proposes a pronounced understanding of proton transport in graphene.

Recent Developments and Perspectives of Recycled Poly(ethylene terephthalate)-Based Membranes: A Review

Post-consumer poly(ethylene terephthalate) (PET) waste disposal is an important task of modern industry, and the development of new PET-based value added products and methods for their production is one of the ways to solve it. Membranes for various purposes, in this regard are such products. The aim of the review, on the one hand, is to systematize the known methods of processing PET and copolyesters, highlighting their advantages and disadvantages and, on the other hand, to show what valuable membrane products could be obtained, and in what areas of the economy they can be used. Among the various approaches to the processing of PET waste, we single out chemical methods as having the greatest promise. They are divided into two large categories: (1) aimed at obtaining polyethylene terephthalate, similar in properties to the primary one, and (2) aimed at obtaining copolyesters. It is shown that among the former, glycolysis has the greatest potential, and among the latter, destruction followed by copolycondensation and interchain exchange with other polyesters, have the greatest prospects. Next, the key technologies for obtaining membranes, based on polyethylene terephthalate and copolyesters are considered: (1) ion track technology, (2) electrospinning, and (3) non-solvent induced phase separation. The methods for the additional modification of membranes to impart hydrophobicity, hydrophilicity, selective transmission of various substances, and other properties are also given. In each case, examples of the use are considered, including gas purification, water filtration, medical and food industry use, analytical and others. Promising directions for further research are highlighted, both in obtaining recycled PET-based materials, and in post-processing and modification methods.

Graft Polymerization of Stearyl Methacrylate on PET Track-Etched Membranes for Oil-Water Separation

In this article, results of PET track-etched membranes (PET TeMs) hydrophobized by photo-induced graft polymerization of stearyl methacrylate (SM) inside the pores were presented. The effects of monomer concentration, time of irradiation and the nature of the solvent on the degree of grafting and membrane morphology were investigated. The PET TeMs with pore diameters ranging from 350 nm (pore density of 1 × 108 pore/cm2) to 3.05 µm (pore density of 1 × 106 pore/cm2) were hydrophobized and tested for oil-water separation by using hexadecane-water and chloroform-water emulsions. Studies have shown high separation performance for membranes (up to 1100 mL/m2·s) with large pore diameters while achieving a high degree of purification.

Radioactive waste treatment technology: a review

Radioactive waste is generated from activities that utilize nuclear materials such as nuclear medicine or power plants. Depending on their half-life, they emit radiation continuously, ranging from seconds to millions of years. Exposure to ionizing radiation can cause serious harm to humans and the environment. Therefore, special attention is paid to the management of radioactive waste in order to deal with its large quantity and dangerous levels. Current treatment technologies are still being developed to improve efficiency in reducing the hazard level and waste volume, to minimize the impact on living organisms. Thus, the aim of this study was to provide an overview of the global radioactive waste treatment technologies that have been released in 2019–2021.

Porous polymeric membranes: fabrication techniques and biomedical applications

Porous polymeric membranes have shown great potential in biological and biomedical applications such as tissue engineering, bioseparation, and biosensing, due to their structural flexibility, versatile surface chemistry, and biocompatibility. This review outlines the advantages and limitations of the fabrication techniques commonly used to produce porous polymeric membranes, with especial focus on those featuring nano/submicron scale pores, which include track etching, nanoimprinting, block-copolymer self-assembly, and electrospinning. Recent advances in membrane technology have been key to facilitate precise control of pore size, shape, density and surface properties. The review provides a critical overview of the main biological and biomedical applications of these porous polymeric membranes, especially focusing on drug delivery, tissue engineering, biosensing, and bioseparation. The effect of the membrane material and pore morphology on the role of the membranes for each specific application as well as the specific fabrication challenges, and future prospects of these membranes are thoroughly discussed.

Kinetic and Isotherm Study of As(III) Removal from Aqueous Solution by PET Track-Etched Membranes Loaded with Copper Microtubes

This paper reports on the synthesis and structure elucidation of track-etched membranes (TeMs) with electrolessly deposited copper microtubes (prepared in etched-only and oxidized polyethylene terephthalate (PET) TeMs), as well as on the comparative testing of arsenic (III) ion removal capacities through bath adsorption experiments. The structure and composition of composites were investigated by X-ray diffraction technique and scanning electron and atomic force microscopies. It was determined that adsorption followed pseudo-second-order kinetics, and the adsorption rate constants were calculated. A comparative study of the applicability of the adsorption models of Langmuir, Freundlich, and Dubinin-Radushkevich was carried out in order to describe the experimental isotherms of the prepared composite TeMs. The constants and parameters of all of the above equations were determined. By comparing the regression coefficients R2, it was shown that the Freundlich model describes the experimental data on the adsorption of arsenic through the studied samples better than others. Free energy of As(III) adsorption on the samples was determined using the Dubinin-Radushkevich isotherm model and was found to be 17.2 and 31.6 kJ/mol for Cu/PET and Cu/Ox_PET samples, respectively. The high EDr value observed for the Cu/Ox_PET composite indicates that the interaction between the adsorbate and the composite is based on chemisorption.

Functionalization of PET Track-Etched Membranes by UV-Induced Graft (co)Polymerization for Detection of Heavy Metal Ions in Water

Nowadays, water quality monitoring is an essential task since environmental contamination and human exposure to heavy metals increased. Sensors that are able to detect ever lower concentrations of heavy metal ions with greater accuracy and speed are needed to effectively monitor water quality and prevent poisoning. This article shows studies of the modification of flexible track-etched membranes as the basis for the sensor with various polymers and their influence on the accuracy of detection of copper, cadmium, and lead ions in water. We report the UV-induced graft (co)polymerization of acrylic acid (AA) and 4-vinylpyridine (4-VPy) on poly(ethylene terephthalate) track-etched membrane (PET TeMs) and use them after platinum layer sputtering in square wave anodic stripping voltammetry (SW-ASV) for detection of Cu²⁺, Cd²⁺, and Pb²⁺. Optimal conditions leading to functionalization of the surface and retention of the pore structure were found. Modified membranes were characterized by SEM, FTIR, X-ray photoelectron spectroscopy (XPS) and colorimetric analysis. The dependence of the modification method on the sensitivity of the sensor was shown. Membrane modified with polyacrylic acid (PET TeMs-g-PAA), poly(4-vinylpyridine) (PET TeMs-g-P4VPy), and their copolymer (PET TeMs-g-P4VPy/PAA) with average grafting yield of 3% have been found to be sensitive to µg/L concentration of copper, lead, and cadmium ions. Limits of detection (LOD) for sensors based on PET TeMs-g-PAA are 2.22, 1.05, and 2.53 µg/L for Cu²⁺, Pb²⁺, and Cd²⁺, respectively. LODs for sensors based on PET TeMs-g-P4VPy are 5.23 µg/L (Cu²⁺), 1.78 µg/L (Pb²⁺), and 3.64 µg/L (Cd²⁺) µg/L. PET TeMs-g-P4VPy/PAA electrodes are found to be sensitive with LODs of 0.74 µg/L(Cu²⁺), 1.13 µg/L (Pb²⁺), and 2.07 µg/L(Cd²⁺). Thus, it was shown that the modification of membranes by copolymers with carboxylic and amino groups leads to more accurate detection of heavy metal ions, associated with the formation of more stable complexes.