Assessment and optimization of electrospun nanofiber-membranes in a membrane bioreactor (MBR) (original) (raw)
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Keywords Highlights A Review of Electrospun Nanofiber Membranes Article info
Electrospun nanofiber membranes Water treatment Adsorptive membranes Membrane distillation Desalination • A new generation of membranes offering higher flux at lower applied pressure • Highly porous with interconnected pores • High specific surface area, suitable for adsorption applications • Have found applications in water treatment, air cleaning, membrane distillation, among many other uses Electrospun nanofiber membranes (ENMs) are new generation of membranes with many favorable properties such as high flux and low pressure drop. Although electrospinning has been known for more than a century, its applications in filtration and separation processes are relatively new. Electrospinning has provided the means to produce ultrathin fibers -as thin as a few nanometers -that can be used in preparing membranes with small and defined pore sizes. In addition, due to the small fiber diameter ENMs exhibit high surface area to volume ratio, making them suitable adsorption media with enhanced capacity compared with conventional adsorbents. This paper familiarizes the reader with the history and laboratory-scale preparation of ENMs, discusses parameters that influence properties of the fibers and the final membranes, and introduces a number of applications in which, ENMs have exhibited superior performances compared to competing conventional processes.
A Review of Electrospun Nanofiber Membranes
2017
Electrospun nanofiber membranes Water treatment Adsorptive membranes Membrane distillation Desalination • A new generation of membranes offering higher flux at lower applied pressure • Highly porous with interconnected pores • High specific surface area, suitable for adsorption applications • Have found applications in water treatment, air cleaning, membrane distillation, among many other uses
Journal of Environmental Science and Health, Part A, 2020
In this study, a novel osmotic membrane was developed by polyamide (PA) coating on the tubular electrospun nanofiber (TuEN) support membrane. Water and reverse salt flux properties of the obtained membrane were investigated by applying pressure in addition to the osmotic forces. Surface characterization of the membrane was carried out by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) analyses and flux performance tests were performed in both cross flow and submerged membrane setups. Applying pressure from the feed to the concentrate side had significant effects on the water and salt fluxes. Higher pressure differences between the feed and concentrate sides resulted in unexpected high water fluxes up to 500 Lm À2 h À1 (LMH). Besides, the pressure helps to transfer the salt content of feed water into the concentrate side, differently from the osmotic process preventing the salinity build-up at the feed side. PA coated TuEN membrane operated under pressure will exhibit a favorable solution in water/wastewater treatment applications, especially for membrane bioreactors (MBR) in terms of preventing salt accumulation in the bioreactor, decreasing the membrane fouling, increasing the volume of product water, and enabling the concentrate management.
A review on advanced nanofiber technology for membrane distillation
The importance of the nanofiber webs increases rapidly due to their highly porous structure, narrow pore size, and distribution; specific surface area and compatibility with inorganics. Electrospinning has been introduced as one of the most efficient technique for the fabrication of polymeric nanofibers due to its ability to fabricate nanostructures with unique properties such as a high surface area and porosity. The process and the operating parameters affect the nanofiber fabrication and the application of nanofibers in various fields, such as sensors, tissue engineering, wound dressing, protective clothes, filtration, desalination, and distillation. In this review, a comprehensive study is presented on the parameters of electrospinning system including applications. More emphasis is given to the application of nanofibers in membrane distillation (MD). The research developments and the current situation of the nanofiber webs in MD are also discussed.
Electrospun Nanofibrous Membranes for Water Treatment
Advances in Membrane Technologies
Nanofibrous structures offer a lot of fascinating features due to large specific surface area. This makes them promising for a wide range of applications, most specifically water treatment. This new generation of highly porous membranes exhibits great prospect to be used in various separation applications due to their distinguished features such as remarkably high porosity (≥90%) and interconnected 3D pore structure. As compared with the conventional techniques, Electrospinning has been highlighted for developing unique porous membranes. Electrospun nanofibrous membranes have been more and more investigated to a lot of advanced water treatment purposes. This chapter reviews the updates on electrospun nanofibrous membranes with a particular prominence in recent accomplishments, bottlenecks, and future perspectives in water treatment. To start, the basic principles of electrospinning are discussed. Next, past and recent efforts for fabricating electrospun MF membranes for various applications are reviewed. The application of electrospun nanofibers as the scaffold for TFC (thin-film composite) membranes in the pressure-and osmotic-membrane processes is then introduced. The new application of electrospun nanofibrous membranes for the thermally-driven MD (membrane distillation) process for water treatment as well as strategies for performance enhancement is discussed. To finish, conclusions and perspectives are stated according to recent developments.
Structure and process relationship of electrospun bioabsorbable nanofiber membranes
Polymer, 2002
An electrospinning method was used to fabricate bioabsorbable amorphous poly(D,L-lactic acid) (PDLA) and semi-crystalline poly(L-lactic acid) (PLLA) nanofiber non-woven membranes for biomedical applications. The structure and morphology of electrospun membranes were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and synchrotron wide-angle X-ray diffraction/small angle X-ray scattering. SEM images showed that the fiber diameter and the nanostructured morphology depended on processing parameters such as solution viscosity (e.g. concentration and polymer molecular weight), applied electric field strength, solution feeding rate and ionic salt addition. The combination of different materials and processing parameters could be used to fabricate bead-free nanofiber non-woven membranes. Concentration and salt addition were found to have relatively larger effects on the fiber diameter than the other parameters. DSC and X-ray results indicated that the electrospun PLLA nanofibers were completely non-crystalline but had highly oriented chains and a lower glass transition temperature than the cast film.
Water Purification and Biomineralization using Nanofibres-Based Membrane Technology
2021
Population of world and industrialization are increasing rapidly due to which the amount of fresh water is decreasing. There is a need to promote a novel costeffective technique to purify the contaminated water. Nanotechnology provides extraordinary nanomaterials with unique properties which can be used to purify the water. In this article the use of polymeric hybrid membranes is discussed. A novel high flux filtration hybrid membrane system, consisting of a three-layer composite with hierarchical structures, i.e. highly porous hydrophilic material coated top layer, an electrospun nanofibrous barrier layer in the middle; for support the bottom layer is made of nonwoven fibrous web to provide high tensile strength up to 40 MPa, more durability and high retention ratio.
Dual-layered electrospun nanofibrous membranes for membrane distillation
Desalination, 2018
Dual-layered electrospun nanofibrous membranes (DL-ENMs) were prepared using the hydrophobic polymer polyvinylidene fluoride (PVDF) and the hydrophilic one polysulfone (PSF). The thickness of each layer was varied by changing the electrospinning time of each polymer solution maintaining the total electrospinning time at 3 h. The characteristics of the DL-ENMs and those of each layer were studied by means of different techniques and the results were compared to the single layer PVDF and PSF ENMs (i.e. SL-ENMs). The prepared DL-ENMs were tested in desalination by direct contact membrane distillation (DCMD) using different sodium chloride feed aqueous solutions. The DCMD permeate flux of the DL-ENMs was found to be higher than that of the PVDF SL-ENM and it increased with the decrease of the PVDF layer due not only to the reduction of the total thickness and to the increase of both the inter-fiber space and the void volume fraction, but also to the reduction of the path between the liquid/vapour interfaces formed at both side of the DL-ENMs. Compared to the proposed SL-ENMs in DCMD, it is better to use DL-ENMs adequately designed with hydrophobic and hydrophilic polymers than SL-ENM with only a hydrophobic polymer.
Fabrication of electrospun nanofibrous membranes for membrane distillation application
2012
Nanofibrous membranes of matrimide were successfully fabricated using electrospinning technique under optimized conditions. Nanofibrous membranes were found to be highly hydrophobic with high water contact angle of 130°. FESEM and pore size distribution analysis revealed the big pore size structure of electrospun membranes even greater than 2µm and the pore size distribution is found to be narrow. Flat sheet matrimide membranes were fabricated via casting followed by phase separation.The morphology, Pore size distribution and water contact angle were compared with the electrospun membranes. Both membranes fabricated by electrospinning and phase separation techniques were subjected to membrane distillation (MD). Electrospun membranes showed high water vapour flux of 56 kg/m 2-h and it is very high compared to the casted membrane as well as most of the fabricated and commercially available highly hydrophobic membranes.
Separation and Purification Technology, 2019
The structure and morphology of self-sustained electrospun nanofibrous membranes (ENMs) are key factors determining membrane performance for filtration applications. In this study, heat post-treatment (HPT) method was applied to modify the structural and morphological properties of polysulfone (PSU) ENMs, to improve their filtration performance and to obtain membranes suitable for wastewater treatment. The influence of the HPT temperature and time on the morphological structure of the PSU ENMs as well as on fouling and filtration performance was investigated. Microfiltration (MF) tests were conducted using humic acid model solutions with a concentration of 15 mg/L at pH 11. Increasing the HPT temperature or time, led to an increase of the mean nanofiber diameter along with a decrease of the mean size of the inter-fiber space, the void volume fraction and the water contact angle of the membranes. ENMs treated with a higher HPT temperature and a longer time exhibited higher nanofibers interconnectivity and a more compact structure with a smaller size of inter-fiber spaces. Under the same MF operating conditions, a commercial polyethersulfone (PES) MF membrane (HPWP, Millipore) had lower filtration performance (i.e. lower performance index, PI, 82 kg/m 2 h) than the treatedoptimized PSU ENMs (i.e. 147 and 133 kg/m 2 h for ENMs 9 and 10, respectively). The obtained results confirm the good performance of the developed PSU ENMs for MF applications.