A review on advanced nanofiber technology for membrane distillation

Abstract

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.

Keywords

Electrospinning nanofiber membrane distillation desalination

Introduction

The engineered materials have been gained huge interest during the last decades due to improvement in technology and increase in demands. Many of the applications commonly require mechanically strong, corrosion resistance, lightweight, long-lasting, recyclable, easy to process, easy to handle, reproductive, and low price materials. Polymeric materials can fulfill the general demands for upper qualified applications. Currently, polymers are used everywhere in our daily life. Beside inorganic materials, polymers are actively used in nanotechnology. Nanotechnology means the science and technology takes place in nanometer dimensions. The biggest importance of the nanotechnology is their aspect ratio which is related with the large surface area to volume ratios and their quantum effects. It is not simple to import polymer science into nanotechnology.

One of the promising areas of nanofiber is that mainly polymeric materials are used. During the process, the polymeric solution/melt is extruded, drawn or split into very fine fibers using external chemical or physical methods such as an electrical field, drawing force, splitting into smaller pieces. There have been reported various methods in the literature for the preparation of nanofibers. Some of these methods are drawing,¹ electrospinning,^2–5 meltblowing,⁶ template synthesis,^7,8 self-assembly,^9,10 phase separation,¹¹ island in the sea,¹² force spinning,^13,14 and bubble electrospinning.¹⁵ Among all, electrospinning is the most commonly and mostly used method for production of nano-fibers. Electrospinning is so far the most used method for industrial production. More than half of the research arti-cles which related to nanofiber are produced by electro-spinning methods.¹⁴

Electrospinning

Electrospinning basically requires a polymeric solution/ melt and an electrical field. In most of the electrospinning setup designs, there is a feeding unit which transports the polymeric solution/melt into the electrical field. There is a high-voltage supplier connected to the feed solution. On the opposite side of the feed solution, there is a metallic collector which can be oppositely charged or grounded. The electrical field is generated between the feed solution and the opposite side collector. If the generated electrical field overcomes the surface tension of the polymeric solution, Taylor’s cone¹⁶ is observed; then, the solution starts to move toward to collector and under the force and instability initiates, the whipping or splitting of the polymeric solution will be observed. Dur-ing the whipping, the drawing continues until the polymeric solution contacts to the collector. Whipping instability causes bending and stretching of the jet.¹⁷ On the other hand, if there is splitting, the polymeric solution splits into multiple filaments. The solvent starts to evaporate during whipping or splitting. The mechanism of the bending instability was explained by Yarin et al.¹⁸ They calculate the shape of the envelope cone which surrounds the bending loops of the jet during the whipping of polymeric solution. The image of whipping and splitting is shown in Figure 1.

Figure 1.

The whipping and splitting behavior of polymeric jet under the electrostatic field.

Electrospinning methods can be grouped into two as needle and needleless electrospinning. In general, single nozzle or needle system is used in electrospinning system for research goal. In single needle electrospinning system, the polymeric solution is stored inside a needle which is connected to a high-voltage supplier. A syringe pump is used for the feeding of the solution to needle tip as shown in Figure 2. There are various parameters in needle system which has an effective role in the morphology and productivity of nanofibers. These parameters can be categorized into two groups as system and process parameters. The system parameters include the properties of a polymeric solution such as concentration, viscosity, conductivity, surface tension, permittivity, and the molecular weight of the polymer. On the other hand, process parameters are related to devices setup and environment such as applied voltage, the distance between electrodes (tip to collector), the fed rate of solution, the diameter of the needle tip, and ambient conditions. Each parameter affects the surface morphology of the nanofibers. Deitzel et al.¹⁹ showed that defect-free polyethylene oxide (PEO)/water nanofibers were produced at 5.5 kV. When the voltage increased to 9 kV, bead structures took place. The result showed that the applied voltage had a significant effect on the shape of the droplet and beads-free structure. They also found that the PEO solution concentration has a significant effect on the final size and distribution of particles. PEO at a molecular weight 400,000 g/mol, concentrations in the range of 4–10 wt% produced fibers. When the concentration decreased, the fibers have an irregular shape; droplets with fibers were observed during electrospinning. For solutions with a concentration of 15 wt% or more, the viscosity of the PEO solutions became difficult to spin due to force through the syringe needle of the apparatus, and the droplet at the end of the capillary stretched into a thick diameter around 0.5mm. Resultant fibers have a regular, cylindrical morphology and on average have a larger and more uniform diameter. In most cases, an increase in the concentration and the applied voltage results in an increased fiber diameter. Similar results were found in another works.^20–22 Matabola and Moutloali²³ used sodium chloride (NaCl) salt as an additive to polyvinylidene fluoride (PVDF)/dimethyl acetamide solution to improve surface morphology of the nanofibers. Increase in NaCl content yields to increase in fiber diameter. In the previous work, the lithium chloride (LiCl) and tetraethylene ammonium bromide (TEAB) salts were into PEO/water solution in various ratios.^24,25 Adding salt increases the conductivity while decreasing the spinnability and productivity of the nanofibers. It was explained that adding salt to PEO increases the conductivity of the solution which shows a behavior as a conductor. As a result, the solution loses the characteristic of a leaky model which leads to the loss of ability to create Taylor cones.^26,27 The same behavior was observed with adding a various concentration of sodium hydroxide (NaOH) salt into polyvinyl alcohol (PVA)/water solution.²⁸ On the contrary, it was found that adding TEAB and LiCl salts into polyurethane (PUR)/dimethylformamide increased the number of jets which results in higher productivity.^25,29–31 Casper et al.³² prepared polystyrene (PS)/tetrahydrofuran nanofibers in different molecular weight of PS (31,600, 171,000, 190,000, and 560,000 g/mol) at various humidity. The resultant fibers showed that both humidity and the molecular weight affect the surface of electrospun PS. Larger fiber diameter and less uniform pore-shaped nanofibers were produced by increas-ing the molecular weight. Moreover, increasing humidity causes an increase in the diameter, shape, and distribution of the pores. Smooth nanofibers were produced at humidity less than 25%, while pore structures were observed at 30% relative humidity. In another work, various molecular weight polyamide 66 nanofibers were electrospun. Resultant fibers showed that increasing the molecular weight causes an increase in fiber diameter. It was suggested that a critical low molecular weight was necessary for electrospinning.³³ The molecular weight does not only have an effect on fiber diameter but also on the mechanical strength of the fiber. An increase in molecular weight increases the tensile strength and modulus of the nanofiber mat.³⁴

Figure 2.

Diagram of needle electrospinning system.

Using a needle and needle-free electrospinning system, various polymeric solutions were used to produce nanofibers in various applications. Some examples of them are shown in Tables 1 and 2.

Table 1.

Electrospun nanofibers and their application using needle electrospinning system.

Nanofiber	Application
SF, collagen/HA, PANI-chitosan, and PVA/gelatin	Tissue engineering scaffolds or wound dressings^35–38; bone regeneration^39–41
Poly(D,L-lactide-co-glycolide), starch/PCL, PLA	Tissue engineering scaffolds^42–44
PLA, HA, FHA bioceramics, poly(vinylidene fluoride–trifluoroethylene), poly(hydroxybutyrate-co-hydroxyvalerate), PA6/lecithin, and PCL	Biomedical application^45–51
PVA-Ag, vitamin E-loaded SF, and PVA-Au	Cosmetics^52–54
PANI/CPI and PVA/PAA	High-performance energy storage devices⁵⁵
MnO and hexagonal boron nitride/PAN	Lithium-ion batteries^56,57
Graphite	X-ray radiography⁵⁸
PSU amide/PUR	High-performance apparels⁵⁹
Polyimide	Self-cleaning materials⁶⁰
Fluorescent polymers PAA-poly(pyrene methanol)	Optical chemical sensors^61,62
PVDF, Ag/TiO₂ nanofiber, PAN, PSU, and chitosan/PEO	Water purification^63–66
PUR, chitosan/PEO, PVA, PA6, and PA66	Air filtration^66–70
PVA/indium acetate	CO gas sensor⁷¹
PVA/nafilon	Fuel cell⁷²

SF: silk fibroin; HA: hydroxyapatite; PANI: polyaniline; PVA: polyvinyl alcohol; PCL: polycaprolactone; PLA: poly(lactic acid); FHA: fluorhydroxyapatite; PA6: polyamide 6; CPI: carbonized polyimide; PAA: poly(- acrylic acid); PVDF: polyvinylidene fluoride; PAN: polyacrylonitrile; PSU: polysulfone; PEO: polyethylene oxide; PUR: polyurethane; PA66: polyamide 66; MnO: manganese monoxide; Ag: silver; Au: gold; TiO2: titanium dioxide; CO: carbon monoxide.

Table 2.

Electrospun nanofibers and application using needle-free electrospinning system.

Nanofiber	Application
CS, PVA, cellulose acetate, and PUR/copper oxide	Air filtration^73–76
CS/PCL, collagen, gelatin, PCL, and poly(L-lactide-co-glycolide)	Tissue engineering^77,78
Cellulose, PA6, PVDF, PAN, PVDF/	Membrane for water
PAN, PVDF, PUR, and polypropylene	purification^79–84
Gelatin, silk, PCL, CS-PEO, PA6, and dextran	Biomedical applications^{37,83,85–88}
PVA and PA6	Acoustics^89,90
PVA, polyvinyl butyral, PUR, and PAN	High-performanc apparels^91–94e
PVDF	Piezo applications⁹⁵

CS: chitosan; PEO: polyethylene oxide; PVA: polyvinyl alcohol; PUR: poly-urethane; PCL: polycaprolactone; PA6: polyamide 6; PVDF: polyvinylidene fluoride; PAN: polyacrylonitrile.

Single needle electrospinning system is not enough to fulfill the productivity. Various electrospinning systems have already been designed to improve the productivity of the nanofibers. These methods include bubble electrospinning,^96,97 two-layer fluid electrospinning,⁹⁸ multi-jet electrospinning,⁹⁹ conical wire coil electrospinning,¹⁰⁰ edge plate electrospinning,¹⁰¹ rotating roller electrospin-ning,^102,103 wire electrospinning,^104,105 and so on. Compared to needle electrospinning system, needle-free electrospinning system has advantages. For instance, the clogging of needles is a problem and there has to be a proper distance between needles. Otherwise, the electrical fields around needle affect each other and stop the spinning. Both roller and wire electrospinning system are currently used in industrial scale under the trade name Nanospider with a different generation. The first generation of Nanospider is a rotating roller electrospinning patented by Jirsak et al.¹⁰² as shown in Figure 3.

Figure 3.

Diagram of roller electrospinning system.

In the principle of roller electrospinning system, there is rotating roller immersed in a polymer solution tank which is connected to a high-voltage supplier. The polymer solution is fed to the surface of the roller via rotation. Spinning starts on the surface of the roller. The spinning is done in a closed chamber to maintain ambient conditions and keep it stabilized during the process. Both the system and the process parameters play a big role in the final product. The process parameters of the roller electrospinning system are quite different compared to needle electrospinning due to a different setup. In literature by Yalcinkaya et al.,^106–108 the parameters of needle-free electrospinning system are classified as “dependent and independent parameters” as shown in Table 3. On the other hand, the parameters for the wire electrospinning system are still not investigated.

Table 3.

Dependent and independent parameters of needleless electrospinning system.^106–108.

Independent parameters	Dependent parameters
Polymer solution properties (concentration, viscosity, composition, surface tension, conductivity, and molecular weight)	Number of cones and the density of jets
	Lifetime of jets
	Spinning performance and spinning performance/per jet
Applied voltage
Distance between electrodes	Total average Current and current/jet
The velocity of rotating roller	The thickness of polymer solution layer on the surface of the roller
	Force acting on a jet
The velocity of take-up fabric	Spinning area
Geometry of electrode	The distance between neighboring jets
Geometry of collector	Jet length in the stable zone
Ambient conditions (temperature and relative humidity)	Fiber diameter and distribution
	Nonfibrous area
	Launching time of jets

The working principle of the wire electrospinning is different than roller electrospinning. The polymeric solution is placed into a closed tank which is the feeding unit. In the middle of the solution tank, there is a wire passing along to spinning area. The wire is connected to high-voltage supplier. The solution tank is moving back and forth and the solution is feeding on the wire. The second wire electrode is placed on the upward that generally has the opposite charge to the downward wire electrode or is grounded. A conveyor supporting material is placed in front of the upward electrode to collect the nanofibers.¹⁰⁴ Figure 4 shows the schematic diagram of wire electrospinning system.

Figure 4.

Schematic diagram of wire electrospinning system.

The advantages of the wire system compared to the roller are that solution is in a closed tank and the surface of the wire electrode is narrower which increases the electrical field intensity around the wire. Various polymeric solutions are possible to electrospun in industrial scale. The main advantages of nanofibers are their specific surface area, high aspect ratio, extreme porous structure, and small pore size. Nanofibers have shown unique characteristics and enormous application potential. One of the successful application areas of nanofiber is water purification. Nanofiber membranes in the membrane distillation (MD) application are discussed in the next section.

Nanofibers in water purification

Membrane distillation

MD is a water separation process which is one of the emerging desalination technologies for the production of fresh water. Compared to other membrane systems, MD has several advantages, such as higher salt rejection, lower operating temperature than conventional distillation processes, low energy consumption (when the alternative energy source is used), hence there are lower operating pressure requirement less requirements of membrane mechanical properties.¹⁰⁹

The principle is that vapor transport across the hydro-phobic microporous membrane driven by the vapor pressure gradient across the membrane due to a temperature gradient. The volatile solvent evaporates through the membrane via diffusion and/or convection. The vapor is transported to the compartment with low vapor pressure where they are condensed in the cold liquid/vapor phase (Figure 5).

Figure 5.

Illustration of membrane distillation process.

MD technology is applicable for many application areas such as wastewater remediation, sea water distillation, and separation of volatile liquids. Even though the rejection of MD membranes is 100%, this technology has not found a place in the industrial stage. The reason is due to low flux and permeability of the membranes, possible pores wetting and water loss, energy consumption, and machinery cost. Besides disadvantages, there are several advantages of MD, such as full rejection, lower pressure-driven separation process as a result of low requirement for mechanical properties and low operating temperature. There are several configurations of MD unit reported in the literature by Khayet and Matsuura¹¹⁰ and Wang and Chung,¹¹¹ such as direct contact membrane distillation (DCMD), air gap membrane distillation, sweeping gas membrane distillation (SGMD), and vacuum membranedistillation (VMD). The membrane is the most important part of the MD process (Figure 6).

Figure 6.

Some of MD process configurations. (a) DCMD, (b) AGMD, (c) SGMD, and (d) VMD (originate from¹¹⁰). MD: membrane distillation; DCMD: direct contact membrane distillation. AGMD: air gap membrane distillation; SGMD: sweeping gas membrane distillation; VMD: vacuum membrane distillation.

In DCMD, a membrane is placed between permeate and a hotter feed solution. It has to have a temperature gradient between feed and permeate. The membrane is in contact both feed and permeates side. A magnetic stirrer or circulating pumps are used to circulate feed and permeate solu-tion to the membrane surfaces. As a result of heat difference on both sides of the membrane, vapor pressure is generated. The vapor of feed solution is passing through the membrane pores via diffusion or convection.

In air gap membrane distillation (AGMD), there is a gap between permeate and membrane. The membrane is in direct contact with feed solution. The vapor of feed solution is passing through the membranes to air gap and condense on the condensing plate. The filtrated liquid is collected between feed and permeate solution.

In SGMD, instead of a cold feed solution, a cold inert gas sweep in the permeate side of the membrane. The volatile liquid molecules are passing through to membrane pores toward to cold gas side and condensation takes place out of MD module.

In VMD, there is no cooling system. Using a vacuum pump, a lower vacuum pressure is applied to permeate side. The feed side has higher saturation pressure which results in separation of the volatile molecules from the feed solution. As in the SGMD, the condensation takes place out of MD module.

Nanofibers in MD

Several types of membranes and filtration systems are employed in water treatment processes based on their pore sizes and particle filtration as shown in Figure 7. Polymeric materials are mainly used as commercial membranes. Nanofiber material is a relatively new approach to prepare nanofiber-based membranes for micro-filtration and ultrafiltration systems. In MD process, the polymeric membranes should demonstrate high permeability and hydrophobicity without wetting, narrow pores; as well as pore size distribution, thermal stability over a wide range of temperatures and a chemical stability, and possess strong mechanical strength.^109,112 Membranes have to be configured into membrane modules which can be in the type of hollow fiber, spiral wound, and plate modules for practical applications. For an efficient membrane module, the key factors are a membrane with high packing density, good control of concentration polarization and membrane fouling, low operating and maintenance costs, and also cost-efficient production.¹¹³ Considering the properties of efficient membranes, nanofibers seem a good candidate for MD process. Generally, PVDF is preferred due to its solubility and spinnability.^114–116

Figure 7.

Particle size removal range by filtration.

PVDF electrospun nanofiber web in different thickness ranging from 144.4 mm to 1529.3 mm have been prepared and used for desalination of salty water by direct contact MD method. By increasing the electrospinning time, the thickness of nanofiber layer increased so did the liquid entry pressure of water (LEPw). On the other hand, the mean pore size of interfiber space decreased, whereas no significant changes were observed for the diameter of the electrospun fibers (1.0–1.3 mm), the void volume fraction (0.85–0.93), and the water contact angle (WCA; 137.4 – 141.1°). It was observed that permeate flux did not decline linearly with the thickness of the electrospun web. Moreover, the permeate flux reached a value of 15.2×10–³ kg/ m² s (at water feed temperature of 80°C and a permeate temperature of 20°C), and the salt rejection factor was higher than 99.39%. During the 25 h DCMD operating time, no wetting was observed.¹¹⁶

Ebrahimi et al.¹¹⁷ prepared a novel triple-layer configuration with diameter gradient for PVDF nanofiber membranes for the DCMD application. Beads-free PVDF nanofiber layer with thinner diameter was used as an outer layer while thicker PVDF nanofiber layer was used in the middle layer. Results showed that single layer membranes showed a permeate flux 15.4 kg/m²h while triple layers have permeated flux in between 27.8 and 31.5 kg/m²h when salt rejection factors greater than 99.9% were achieved. Results indicate that different membrane configuration has a big role in the evaporation and permeate flux efficiency.

In another work, the surface of the nanofiborus PVDF membranes was modified with titanium dioxide (TiO₂) and 1H, 1H, 2H, 2H-perfluorododecyl trichlorosilane (FTCS) doe desalination by DCMD.¹¹⁸ The TiO₂-FTCS modified PVDF nanofiber membranes possessed high roughness and hydrophobicity (157.1°) with a wetting resistance of 158 kPa and 57% surface porosity. During the short-term DCMD process, the permeate flux was achieved as 73.4 LMH (L/m²h) permeate flux with 99.99% salt rejection while 40.5 LMH permeate flux with 99.98% salt rejection was achieved for the long-term DCMD process using 3.5 wt% NaCl solution. Compared to commercial PVDF membrane (0.45 mm, HVHP4700, Millipore (Burlington, Massachusetts, United States), 46.2 LMH permeate flux), a significant improvement in efficiency was obtained.

In another approach, nanoparticle (NP; aluminum oxide (Al₂O₃)) enhancement PVDF nanofibrous membranes were fabricated using electrospinning system and AGMD was used to remove heavy metals (lead).¹¹⁹ Results showed that commercial PVDF membrane (HVHP29325, 0.22 mm diameter, Millipore) exhibited the lowest flux of around 15 LMH while high fluxes between 16.5 LMH and 20 LMH have been shown by the neat and the composite PVDF membranes with Al₂O₃ NPs.

Polyacrylonitrile (PAN) electrospun membranes with nonwoven structure and quasi-parallel fibrous structure were used for lab-scale AGMD system.¹²⁰ The surface of PAN nanofibers was hydrophobized with surface fluorination treatment. It was found that in the surface fluorinated webs, the fiber orientation combing with the flow direction increased the mass transfer coefficient through the mem-brane and the MD performance in terms of permeate flux.

PVDF electrospun nanofibrous membranes doped with tris(phenanthroline)ruthenium(II) chloride (Ru(phen)₃) were prepared and used for DCMD system.¹²¹ The temperature sensitive Ru(phen)₃ was used as a probe which allowed it to optically monitoring the membrane surface temperature during DCMD experiments. The doping with Ru(phen)₃ confers to the PVDF membrane photochemical activity and its emission intensity linearly decreases by increasing the temperature. The molecular probes and infrared camera used as a tool for monitoring temperature on membrane surfaces online and in real time. During the process, the flux increased from 9 to 15.7 kg/m²h making the temperature of the feed stream rise from 40°C to 60°C, respectively; while the PVDF Durapore commercial membranes (Millipore) presented a flux of 10.67 kg/m²h at a feed temperature of 60°C.

Su et al.¹²² prepared superhydrophobic nanofibrous membranes from silica NPs doped on PVDF fiber. Different dosages of silica NPs were added into PVDF solution for the electrospinning process. The hydrophobicity of the membranes altered by the dosage of silica NPs, and the WCA of the membranes optimized to be 157 + 1°. The characterization tests showed that the incorporation of silica NPs has altered the membrane surface morphology and endowed the composite membrane with the hierarchical structure on the surface and bulk layers as well as increasing the mechanical strength, salt rejection, and water permeation flux of the membranes. The nanofibrous membrane which contains 7.47 wt% silica NPs has a WCA of 152 + 1 and shows high DCMD performance with a water flux of 25.73 kg/m²h, salt rejection rate above 99.99%, and a permeate conductivity below 5.0 mS/cm during a 100 h test period.

TiO₂ nanofiber that consists of ceramic membranes is designed and fabricated by vacuum filtration and fluorination modification.¹²³ The superhydrophobic titania nanofi-brous ceramic membrane is modified by fluorinated holds show an excellent desalination performance with the flux of 12 LMH with a salt rejection of 99.92% at 80 C and a good stability for long-term MD operation in pure and saline water which is compared to those of ceramic membranes with particle aggregation structure.^124–127

Terpolymer (THV) membranes, which consist of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, are fabricated by the electrospinning method for MD application.¹²⁸ The advantage of using THV is their excellent hydrophobicity, mechanical properties, and chemical resistance. After optimization process, it was observed that membrane exhibited a good structure, wetting resistance, and surface hydrophobicity. The optimized membrane had a contact angle of 130.7°C with a mean pore size 0.79 mm, LEPw value of 118 kPa, tensile strength was 5.41 MPa, and the elongation at break was 247.9%, which were 2.47 and 5.61 times higher than those of the prepared PVDF film membrane, respectively. The permeate flux was measured as 4.42 kg/m²h with a salt rejection rate higher than 99.8%. The PVDF film membrane showed 1.93 times less flux than that of the THV membranes.

Jiřıček et al.¹²⁹ used PUR nanofiber layer with varying thickness produced by needle-free industrial electrospinning system for the DCMD process. Different concentra-tion of feed solution was prepared. Prepared nanofiber layer was laminated on a bicomponent polyolefin nonwoven surface to improve the mechanical property of the membrane. Results indicate that, even at the highest NaCl concentration in feed (100 g/kg), the best flux (around 6 kg/ m²h) and energy efficiency was achieved with thicker membranes (25 and 40 g/m² basis weight of membrane).

In their other work,⁸² PVDF nanofiber membranes were tested using the DCMD method. Results showed that PVDF nanofiber membranes had comparable permeate flux with commercially available polytetrafluoroethylene and polysulfone membranes. As a summary, the results indicate that nanofiber webs produced by industrial electrospinning device have a possible application in MD process.

Conclusion

In this review, the properties, the spinning parameters, and the application area of the electrospun nanofibers were discussed. Electrospinning method is a fascinating method to prepare membranes in micro or nanopore size. One can prepare porous structure using various polymeric electrospun nanofiber layers. Electrospun nanofiber layers have higher porosity with uniform pore size distribution compared to conventional membranes. The highly porous structure yields to increase the permeability of the membranes while high surface area allows membranes to be functionalized with ease. It was found that remarkable progress has been made in the fabrications of electrospun membranes for water treatment. MD is one of the most promising application fields for the electrospun nanofiber membranes. The porous structure, hydrophobicity, and the performance of the membrane are crucial for further developments in MD. This review reveals that possible application of nanofiber layers in MD.

Footnotes

Acknowledgements

The author would like to thank Mr. Frederick Fung for his help in language proof-reading.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic and the European Union—European Structural and Investment Funds in the frames of Operational Programme Research, Development and Education—project Hybrid Materials for Hierarchical Structures (HyHi, Reg. No. CZ.02.1.01/0.0/0.0/16_019/0000843).

References

Ondarçuhu

Joachim

Drawing a single nanofibre over hundreds of microns. Europhys Lett 1998; 42(2): 215–220.

Norton

Method of and apparatus for producing fibrous or filamentary material, https://www.google.com/patents/US2048651 (1933, accessed 3 January 2018).

Formhals

Process and apparatus for preparing artificial threads, https://www.google.com/patents/US1975504 (1930, accessed 6 September 2017).

Formhals

. Method and apparatus for spinning, http://www.google.com/patents/US2349950 (1938, accessed 3 January 2018).

Dalton

Grafahrend

Klinkhammer

et al . Electrospinning of polymer melts: phenomenological observations. Polymer (Guildf) 2007; 48: 6823–6833.

Hassan

Yeom

Wilkie

et al . Fabrication of nanofiber meltblown membranes and their filtration properties. J Memb Sci 2013; 427: 336–344.

Wang

Zheng

et al . Template synthesis of carbon nanofibers containing linear mesocage arrays. Nanoscale Res Lett 2010; 5(6): 913–916.

Zelenski

Dorhout

. Template synthesis of near-monodisperse¹ microscale nanofibers and nanotubules of MoS₂. J Am Chem Soc 1998; 120(4): 734–742.

Rolandi

Self-assembled chitin nanofibers and applications. Adv Colloid Interface Sci 2014; 207: 216–222.

10.

Liao

Lin

Liu

et al . Self-assembly mechanisms of nanofibers from peptide amphiphiles in solution and on substrate surfaces. Nanoscale 2016; 8(31): 14814–14820.

11.

Katsogiannis

KAG

Vladisavljević

Georgiadou

Porous electrospun polycaprolactone (PCL) fibres by phase separation. Eur Polym J 2015; 69: 284–295.

12.

Zhang

Peijs

et al . Fabrication and properties of poly(tetrafluoroethylene) nanofibres via sea-island spinning. Polymer (Guildf) 2017; 109: 321–331.

13.

Hammami

Krifa

Harzallah

Centrifugal force spinning of PA6 nanofibers—processability and morphology of solution-spun fibers. J Text Inst 2014; 105(6): 637–647.

14.

Sarkar

Gomez

Zambrano

et al . Electrospinning to forcespinning^™. Mater Today 2010; 13(11): 12–14.

15.

Shao

et al . High throughput preparation of aligned nanofibers using an improved bubble-electrospinning. Polymers (Basel) 2017; 9(12): 658.

16.

Taylor

. Disintegration of water drops in an electric field. Proc R Soc A Math Phys Eng Sci 1964; 280: 383–397.

17.

Shin

Hohman

Brenner

et al . Electrospinning: a whipping fluid jet generates submicron polymer fibers. Appl Phys Lett 2001; 78: 1149–1151.

18.

Yarin

Koombhongse

Reneker

DH.

Bending instability in electrospinning of nanofibers. J Appl Phys 2001; 89(5): 3018–3026.

19.

Deitzel

Kleinmeyer

Harris

et al . The effect of processing variables on the morphology of electrospun nanofibers and textiles. Polymer (Guildf) 2001; 42(1): 261–272.

20.

Zong

Kim

Fang

et al . Structure and process rela-tionship of electrospun bioabsorbable nanofiber membranes. Polymer (Guildf) 2002; 43: 4403–4412.

21.

Meechaisue

Dubin

Supaphol

et al . Electrospun mat of tyrosine-derived polycarbonate fibers for potential use as tissue scaffolding material. J Biomater Sci Polym Ed 2006; 17(9): 1039–1056.

22.

Beachley

Wen

Effect of electrospinning parameters on the nanofiber diameter and length. Mater Sci Eng C Mater Biol Appl 2009; 29(3): 663–668.

23.

Matabola

Moutloali

RM.

The influence of electrospinning parameters on the morphology and diameter of poly(vinyledene fluoride) nanofibers—effect of sodium chloride. J Mater Sci 2013; 48(16): 5475–5482.

24.

Yalcinkaya

Jirsak

Experimental investigation of salt effect on electrospinning parameters and nanofiber morphology. In: Nanocon 2014, 6th international conference, Brno, Czech Republic, EU, 5th–7th November 2014, pp. 785–790. TANGER LTD.

25.

Yalcinkaya

Jirsak

. Influence of salts on electrospinning of aqueous and nonaqueous polymer solutions. J Nanomater. Epub ahead of print 2015. DOI: 10.1155/2015/134251.

26.

Bhattacharjee

Rutledge

. Electrospinning and polymer nanofibers: process fundamentals. In: Ducheyne

(ed) Comprehensive biomaterials. Philadelphia, USA: Elsevier, pp. 497–512.

27.

Yener

Jirsak

. Effect of additive on needle electrospinning system. In: 18th International Conference on Structure and Structural Mechanics of Textile Fabrics (STRUTEX), Liberec, Czech Republic, December 2011, pp. 339–343. Technical University of Liberec.

28.

Yalçınkaya

Yener

Jirsak

et al . Influence of NaCl concentration on the Taylor cone number and spinning performance. In: 18th international conference on structure and structural mechanics of textile fabrics (STRUTEX), TU Liberec, Czech Republic, December 2011, pp. 349–352. Technical University Liberec.

29.

Yalcinkaya

Yener

Cengiz-Çallıoğlu

et al . Effect of concentration and salt additive on Taylor cone structure. In: 4th International conference on NANOCON, Brno, Czech Republic, EU, 23–25 October 2012, pp. 200–203. TANGER LTD.

30.

Cengiz

Jirsak

The effect of salt on the roller electrospinning of polyurethane nanofibers. Fibers Polym 2009; 10(2): 177–184.

31.

Yalcinkaya

Cengiz Callioglu

Yener

et al . Measurement and analysis of jet current and jet life in roller electrospinning of polyurethane. Text Res J 2014; 84(16): 1720–1728.

32.

Casper

Stephens

Tassi

et al . Controlling surface morphology of electrospun polystyrene fibers: effect of humidity and molecular weight in the electrospinning pro-cess. Macromol 2004; 37(2): 573–578.

33.

Guerrini

Branciforti

Canova

et al . Electrospinning and characterization of polyamide 66 nanofibers with different molecular weights. Mater Res 2009; 12(2): 181–190.

34.

Ngadiman

NHA

Noordin

Idris

et al . Influence of polyvinyl alcohol molecular weight on the electrospun nanofiber mechanical properties. Procedia Manuf 2015; 2: 568–572.

35.

Kim

Nam

Lee

et al . Silk fibroin nanofiber, electrospinning, properties, and structure. Polym J 2003; 35: 185–190.

36.

Min

Jeong

Lee

et al . Regenerated silk fibroin nanofibers: water vapor-induced structural changes and their effects on the behavior of normal human cells. Macromol Biosci 2006; 6(4): 285–292.

37.

Sasithorn

Martinová

Fabrication of silk nanofibres with needle and roller electrospinning methods. J Nanomater 2014; 2014: 1–9.

38.

Moutsatsou

Coopman

Georgiadou

Conductive electrospun PANI/Chitosan nanofibers for wound healing applications. Polymers (Basel) 2017; 9: 1–20.

39.

Kim

Jeong

Park

et al . Biological efficacy of silk fibroin nanofiber membranes for guided bone regeneration. J Biotechnol 2005; 120(3): 327–339.

40.

Zhou

Yao

Wang

et al . Greener synthesis of electrospun collagen/hydroxyapatite composite fibers with an excellent microstructure for bone tissue engineering. Int J Nanomedicine 2015; 10(1): 3203–3215.

41.

Linh

Min

Song

et al . Fabrication of polyvinyl alcohol/gelatin nanofiber composites and evaluation of their material properties. J Biomed Mater Res B Appl Biomater 2010; 95(1): 184–191.

42.

Laurencin

Caterson

et al . Electrospun nanofibrous structure: a novel scaffold for tissue engineering. J Biomed Mater Res 2002; 60(4): 613–621.

43.

Komur

Bayrak

Ekren

et al . Starch/PCL composite nanofibers by coaxial electrospinning technique for biomedical applications. Biomed Eng Online 2017; 16: 40. DOI: 10.1186/s12938-017-0334-y.

44.

Alippilakkotte

Sreejith

Benign route for the modification and characterization of poly(lactic acid) (PLA) scaffolds for med-icinal application. J Appl Polym Sci 2018; 135(13): 46056.

45.

Kim

Zong

et al . Control of degradation rate and hydrophilicity in electrospun non-woven poly(D, L-lactide) nanofiber scaffolds for biomedical applications. Biomaterials 2003; 24(27): 4977–4985.

46.

Kim

HE.

Nanofiber generation of hydroxyapatite and fluor-hydroxyapatite bioceramics. J Biomed Mater Res B Appl Biomater 2006; 77B(2): 323–328.

47.

Sencadas

Ribeiro

Nunes-Pereira

et al . Fiber average size and distribution dependence on the electrospinning parameters of poly(vinylidene fluoride-trifluoroethylene) membranes for biomedical applications. Appl Phys A Mater Sci Proc 2012; 109(3): 685–691.

48.

Tong

Wang

An investigation into the influence of electrospinning parameters on the diameter and alignment of poly(hydroxybutyrate-co-hydroxyvalerate) fibers. J Appl Polym Sci 2011; 120(3): 1694–1706.

49.

Nirmala

Park

Navamathavan

et al . Lecithin blended polyamide-6 high aspect ratio nanofiber scaffolds via electrospinning for human osteoblast cell culture. Mater Sci Eng C 2011; 31(2): 486–493.

50.

Enis

Sezgin

Sadikoglu

TG.

Full factorial experimental design for mechanical properties of electro-spun vascular grafts. J Ind Text 2017; 47(6): 1378–1391.

51.

Yalcin Enis

Gok Sadikoglu

. Design parameters for electrospun biodegradable vascular grafts. J Ind Text 2016; 47: 2205–2227.

52.

Nguyen

Kim

Song

et al . Nano Ag loaded PVA nanofibrous mats for skin applications. J Biomed Mater Res B Appl Biomater 2011; 96B(2): 225–233.

53.

Sheng

Fan

et al . Vitamin E-loaded silk fibroin nanofibrous mats fabricated by green process for skin care application. Int J Biol Macromol 2013; 56: 49–56.

54.

Fathi-Azarbayjani

Qun

Chan

et al . Novel vitamin and gold-loaded nanofiber facial mask for topical delivery. AAPS PharmSciTech 2010; 11(3): 1164–1170.

55.

Miao

Yan

Huang

et al . Electrospun polymer nanofiber membrane electrodes and an electrolyte for highly flexible and foldable all-solid-state supercapacitors. RSC Adv 2015; 5: 26189–26196.

56.

Wang

Zhong

et al . A flexible core-shell carbon layer MnO nanofiber thin film via host-guest interaction: construction, characterization, and electrochemical perfor-mances. Carbon NY 2018; 128: 277–286.

57.

Aydın

Çelik

Bozkurt

Electrolyte loaded hexagonal boron nitride/polyacrylonitrile nanofibers for lithium ion battery application. Solid State Ionics 2017; 309: 71–76.

58.

Matsumoto

Mimura

Point X-ray source using graphite nanofibers and its application to X-ray radiography. Appl Phys Lett 2003; 82: 1637–1639.

59.

Tong

Bin-Jie

Preparation and characterization of coaxial electrospun polysulfone amide/polyurethane. J Ind Text 2017; 46(8): 1581–1597.

60.

Liu

Huang

Wujcik

et al . Hydrophobic electrospun polyimide nanofibers for self-cleaning materials. Macromol Mater Eng 2015; 300(3): 358–368.

61.

Lee

Wang

et al . Design, synthesis and electrospinning of a novel fluorescent polymer for optical sensor applications. In: Materials research society symposium—proceedings, Boston, MA, 25–30 November 2001, pp. 403–408. Cambridge: Cambridge University Press.

62.

Wang

Drew

Lee

et al . Electrospun nanofibrous membranes for highly sensitive optical sensors. Nano Lett 2002; 2(11): 1273–1275.

63.

Kaur

Sundarrajan

Gopal

et al . Formation and characterization of polyamide composite electrospun nanofibrous membranes for salt separation. J Appl Polym Sci 2012; 124(S1): E205–E215.

64.

Liu

Bai

et al . Concurrent filtration and solar photocatalytic disinfection/degradation using high-performance Ag/TiO₂ nanofiber membrane. Water Res 2012; 46(4): 1101–1112.

65.

Huang

Arena

Manickam

et al . Improved mechanical properties and hydrophilicity of electrospun nanofiber membranes for filtration applications by dopamine modifica-tion. J Memb Sci 2014; 460: 241–249.

66.

Desai

Kit

et al . Nanofibrous chitosan non-wovens for filtration applications. Polymer (Guildf) 2009; 50: 3661–3669.

67.

Zuo

Zhang

Liu

et al . Free-standing polyurethane nanofiber/nets air filters for effective PM capture. Small 2017; 13(46): 1702139.

68.

Qin

Wang

SY.

Electrospun nanofibers from cross-linked poly(vinyl alcohol) and its filtration efficiency. J Appl Polym Sci 2008; 109(2): 951–956.

69.

Matulevicius

Kliucininkas

Martuzevicius

et al . Design and characterization of electrospun polyamide nanofiber media for air filtration applications. J Nanomater 2014; 2014: 1–13.

70.

Shahrabi

Gharehaghaji

Latifi

Fabrication of electrospun polyamide-66 nanofiber layer for high-performance nanofiltration in clean room applications. J Ind Text 2016; 45(5): 1100–1114.

71.

Lim

Hwang

Chang

et al . Preparation of mesoporous In₂O₃ nanofibers by electrospinning and their application as a CO gas sensor. Sens Actuators B Chem 2010; 149(1): 28–33.

72.

Mollá

Compañ

Polyvinyl alcohol nanofiber reinforced Nafion membranes for fuel cell applications. J Memb Sci 2011; 372(1): 191–200.

73.

Wang

Zhang

Gao

et al . Needleless electrospinning for scaled-up production of ultrafine chitosan hybrid nanofibers used for air filtration. RSC Adv 2016; 6: 105988–105995.

74.

Gao

Liu

et al . Needleless electrospun nanofibers used for filtration of small particles. Express Polym Lett 2013; 7(8): 683–689.

75.

Chattopadhyay

Hatton

Rutledge

GC.

Aerosol filtration using electrospun cellulose acetate fibers. J Mater Sci 2015; 51(1): 204–217.

76.

Ungur

Hrůza

Modified polyurethane nanofibers as antibacterial filters for air and water purification. RSC Adv 2017; 7(78): 49177–49187.

77.

Erickson

Edmondson

Chang

et al . High-throughput and high-yield fabrication of uniaxially-aligned chitosan-based nanofibers by centrifugal electrospinning. Carbohydr Polym 2015; 134: 467–474.

78.

Alamein

Stephens

Liu

et al . Mass production of nanofibrous extracellular matrix with controlled 3D morphology for large-scale soft tissue regeneration. Tissue Eng C Methods 2013; 19(6): 458–472.

79.

Yalcinkaya

Chaloupek

Thin film nanofibrous composite membrane for dead-end seawater desalination. J Nanomater 2016; 2016: 1–12.

80.

Esmaeilzadeh

Mottaghitalab

Tousifar

et al . A feasibility study on semi industrial nozzleless electrospinning of cellulose nanofiber. Int J Ind Chem 2015; 6(3): 193–211.

81.

Fatma

Siekierka

Bryjak

et al . Preparation of various nanofibrous composite membranes using wire electrospinning for oil-water separation. IOP Conf Ser Mater Sci Eng 2017; 254: 10 2011.

82.

Jiřıček

Komárek

Chaloupek

et al . Flux enhancement in membrane distillation using nanofiber membranes. J Nanomater 2016; 2016: 1–7.

83.

Jiřıček

Komárek

Chaloupek

et al . Maximising flux in direct contact membrane distillation using nanofibre membranes. Desalin Water Treat 2017; 73: 249–255.

84.

Zhang

et al . Effect of oriented fiber membrane fabricated via needleless melt electrospinning on water filtration efficiency. Desalination 2014; 344: 266–273.

85.

et al . Gelatin nanofibers prepared by spiral-electrospinning and cross-linked by vapor and liquid-phase glutaraldehyde. Mater Lett 2015; 140: 1–4.

86.

Mašek

Lubasová

Lukáč

et al . Multi-layered nanofibrous mucoadhesive films for buccal and sublingual administration of drug-delivery and vaccination nanoparticles— important step towards effective mucosal vaccines. J Con-trol Release 2017; 249: 183–195.

87.

Maryšková

Ardao

Garcıá-González

et al . Poly-amide 6/chitosan nanofibers as support for the immobilization of Trametes versicolor laccase for the elimination of endocrine disrupting chemicals. Enzyme Microb Technol 2016; 89: 31–38.

88.

Cengiz-Callioglu

Dextran nanofiber production by needle-less electrospinning process. E-Polymers 2014; 14(1): 5–13.

89.

Ozturk

Kalinova

Nergis

et al . Comparison of resonance frequency of a nanofibrous membrane and a homogeneous membrane structure. Text Res J 2013; 83(20): 2204–2210.

90.

Ulrich

Kalinova

Helmholtz resonators systems treated with the nanofibrous membrane. In: Gibbs

(ed) Proceedings of ICSV24, London, 23–27 July 2017, p. 278. IIAV.

91.

Chen

et al . A facile approach to superhydrophobic and superoleophilic graphene/polymer aerogels. J Mater Chem A 2014; 2: 3057.

92.

Yalcinkaya

Komarek

Lubasova

et al . Preparation of antibacterial nanofibre/nanoparticle covered composite yarns. J Nanomater 2016; 2016: 1–7.

93.

Yalcinkaya

Komarek

Lubasova

et al . Producing antibacterial textile material by weaving PVB/CuO nanocomposite fiber covered yarn. In: Nanocon 2014, 6th Int Conf. http://gateway.webofknowledge.com/gateway/Gateway.cgi?%20GWVersion¼2&SrcAuth¼ORCID&SrcApp¼OrcidOrg&DestLinkType¼FullRecord&DestApp¼WOS_CPL&KeyUT¼WOS:000350636300072&KeyUID¼WOS:000350636300072 (2015).

94.

Niu

Gao

Lin

et al . Composite yarns fabricated from continuous needleless electrospun nanofibers. Polym Eng Sci 2014; 54(7): 1495–1502.

95.

Chansaengsri

Onlaor

Tunhoo

et al . Production of polyvinylidene fluoride nanofibers by free surface electro-spinning from wire electrode. Mater Today Proc 2017; 4: 6085–6090.

96.

Liu

JY.

Bubble-electrospinning: a novel method for making nanofibers. J Phys Conf Ser 2008; 96: 12001.

97.

Liu

JH.

Bubble electrospinning for mass production of nanofibers. Int J Nonlinear Sci Numer Simul 2007; 8: 393–396.

98.

Yarin

Zussman

Upward needleless electrospinning of multiple nanofibers. Polymer (Guildf) 2004; 45(9): 2977–2980.

99.

Varesano

Carletto

Mazzuchetti

Experimental investigations on the multi-jet electrospinning process. J Mater Process Technol 2009; 209: 5178–5185.

100.

Wang

Niu

Lin

et al . Needleless electrospinning of nanofibers with a conical wire coil. Polym Eng Sci 2009; 49(8): 1582–1586.

101.

Thoppey

Bochinski

Clarke

et al . Edge electro-spinning for high throughput production of quality nanofibers. Nanotechnology 2011; 22(34): 346301. Epub ahead of print 2011. DOI: 10.1088/0957-4484/22/34/345301.

102.

Jirsak

Sanetrnik

Lukas

et al . A method of nanofibers production from a polymer solution using electrostatic spinning and a device for carrying out the method. WO/ 2005/024101. https://patentscope.wipo.int/search/en/detail.jsf?%20docId¼WO2005024101 (2005, accessed 6 September 2017).

103.

Yener

Jirsak

Comparison between the needle and roller electrospinning of polyvinylbutyral. J Nanomater 2012; 2012: 1–6.

104.

Yalcinkaya

Preparation of various nanofiber layers using wire electrospinning system. Arab J Chem 2016; 8(11): 7030–7036. Epub ahead of print December 2016. DOI: 10.1016/j.arabjc.2016.12.012.

105.

Green

King

Fine fiber electrospinning equipment, filter media systems and methods. US8366986 B2. https://www.google.com/patents/US8366986 (2011, accessed 4 January 2018).

106.

Yalcinkaya

Jirsak

Analysis of the effects of rotating roller speed on a roller electrospinning system. Text Res J 2017; 87(8): 913–928.

107.

Yalcinkaya

Jirsak

. Chapter 4: depen-dent and independent parameters of needleless electrospinning. In: Haider

(ed) Electrospinning—material, techniques, and biomedical applications, 2016, London, UK: InTechOpen, pp. 67–94.

108.

Yalcinkaya

Jirsak

. Dependent and independent parameters of needleless electrospinning. In: Vlakna a textil. London, UK: InTech, pp. 75–79.

109.

Tijing

Woo

Choi

et al . Fouling and its control in membrane distillation—a review. J Memb Sci 2015; 475: 215–244.

110.

Khayet

Matsuura

. Membrane distillation: principles and applications. Elsevier. https://books.google.cz/books/about/Membrane_Distillation.html?id¼5yzHdm8vOqMC&redir_esc¼y (2011, accessed 12 January 2018).

111.

Wang

Chung

TS.

Recent advances in membrane distillation processes: membrane development, configuration design and application exploring. J Memb Sci 2015; 474: 39–56.

112.

Lee

Guo

et al . Enhanced vapor transport in membrane distillation via functionalized carbon nanotubes anchored into electrospun nanofibres. Sci Rep 2017; 7: 41562.

113.

Wang

LK.

Membrane and Desalination Technologies. New York, NY: Humana Press. Epub ahead of print 2011. DOI: 10.1007/978-1-59745-278-6.

114.

Liao

Wang

Tian

et al . Fabrication of polyvinyli-dene fluoride (PVDF) nanofiber membranes by electrospinning for direct contact membrane distillation. J Memb Sci 2013; 425–426: 30–39.

115.

Liao

Wang

Fane

AG.

Engineering superhydrophobic surface on poly(vinylidene fluoride) nanofiber membranes for direct contact membrane distillation. J Memb Sci 2013; 440: 77–87.

116.

Essalhi

Khayet

Self-sustained webs of polyvinylidene fluoride electrospun nanofibers at different electrospinning times: 1. Desalination by direct contact membrane distillation. J Memb Sci 2013; 433: 167–179.

117.

Ebrahimi

Karimi

Ashtiani

FZ.

Characterization of triple electrospun layers of PVDF for direct contact membrane distillation process. J Polym Res 2018; 25: 50.

118.

Ren

Xia

Chen

et al . TiO₂-FTCS modified super-hydrophobic PVDF electrospun nanofibrous membrane for desalination by direct contact membrane distillation. Desa-lination 2017; 423: 1–11.

119.

Attia

Alexander

Wright

et al . Superhydrophobic electrospun membrane for heavy metals removal by air gap membrane distillation (AGMD). Desalination 2017; 420: 318–329.

120.

Cai

Liu

Zhao

et al . Membrane desalination using surface fluorination treated electrospun polyacrylonitrile membranes with nonwoven structure and quasi-parallel fibrous structure. Desalination 2018; 429: 70–75.

121.

Santoro

Vidorreta

Sebastian

et al . A non-invasive optical method for mapping temperature polarization in direct contact membrane distillation. J Memb Sci 2017; 536: 156–166.

122.

Chang

Tang

et al . Novel three-dimensional superhydrophobic and strength-enhanced electrospun membranes for long-term membrane distillation. Sep Purif Tech-nol 2017; 178: 279–287.

123.

Fan

Chen

Zhao

et al . Distillation membrane constructed by TiO₂ nanofiber followed by fluorination for excellent water desalination performance. Desalination 2017; 405: 51–58.

124.

Krajewski

Kujawski

Bukowska

et al . Application of fluoroalkylsilanes (FAS) grafted ceramic membranes in membrane distillation process of NaCl solutions. J Memb Sci 2006; 281(1–2): 253–259.

125.

Cerneaux

Struzyńska

Kujawski

et al . Comparison of various membrane distillation methods for desalination using hydrophobic ceramic membranes. J Memb Sci 2009; 337: 55–60.

126.

Larbot

Gazagnes

Krajewski

et al . Water desalination using ceramic membrane distillation. Desalination 2004; 168: 367–372.

127.

Zhang

Fang

Wang

et al . Preparation and characterization of silicon nitride hollow fiber membranes for seawater desalination. J Memb Sci 2014; 450: 197–206.

128.

Zhang

Yang

et al . Electrospun porous poly(te-trafluoroethylene-co-hexafluoropropylene-co-vinylidene fluoride) membranes for membrane distillation. RSC Adv 2017; 7: 56183–56193.

129.

Jiřıček

Komárek

Lederer

Polyurethane nanofiber membranes for waste water treatment by membrane distillation. J Nanotechnol 2017; 2017: 1–7.