Surface Morphology Of Membranes Research Articles

Surface-templating of rough interface to efficiently recover aquaculture wastewater using membrane distillation

Aquaculture wastewater contains organics, inorganics, and microalgae, which need to be removed before being discharged into the environment or recycled. These aquaculture pollutants, especially microalgae, will reduce the membrane performance in membrane distillation (MD) process. In this work, nylon taffeta, non-woven and polyester substrates are used for microtextured surface-templating to produce superhydrophobic membranes with exciting water-repellent properties. Micro-scaled structures of different sizes are homogenously and repetitively printed on the membrane surfaces, as illustrated from FESEM and confocal micrographs. Water contact angle for all textured membranes has exceeded 150°, reflecting non-wetted and superhydrophobicity characteristics. Among them, nylon taffeta templated membrane indicates the highest advancing (155°) and receding (146°) contact angles with the lowest hysteresis of 9°. All membranes have undergone MD separation of aquaculture wastewater. Membrane printed using nylon taffeta templated demonstrated the highest flux of 30 kg/m2·h with the least deposited surface foulants. After MD separation, the organics (ammonia) and inorganics (phosphorus, calcium, sodium, magnesium, etc.) also achieved a rejection rate of at least 92%. Nylon taffeta templated membrane has shown a stable flux over 30 h DCMD separation. These findings have qualitatively explained the dynamic behavior of a membrane surface morphology on aquaculture wastewater treatment.

Fenton pre-activated grafted modified PVDF membrane and its application in DCMD desalination

As an efficient membrane separation technology, membrane distillation (MD) technology has broad application prospects in desalination of marine and high-salt wastewater. However, membrane fouling/wetting is still the main factor limiting the industrialization of MD technology. In this paper, a polyvinylidene fluoride (PVDF) micro/nano superhydrophobic membrane was prepared using Fenton pretreatment combined with a surface grafting method. Membrane surface hydrophobicity, chemistry and morphology were characterized using measurements of water contact angle (WCA) and liquid entry pressure (LEP), along with observations using attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The grafted fluorinated SiO2 nanoparticles reduced the surface energy of the PVDF base membrane while at the same time increasing the surface roughness. After modification, the WCA of the PVDF base membrane surface increased from 99° to 155° and the LEP was enhanced from 204 kPa to 235 kPa. Furthermore, the composite membrane revealed stable performance due to the pre-activation by the Fenton solution. The proposed superhydrophobic composite membrane has a great potential to solve the problems of complex membrane pretreatment and prevent damage to the base membrane. The simple method demonstrated here also reduces costs which opens up multiple opportunities for applications in industry.

SUZ-4 zeolite membrane fabricated by dynamic hydrothermal crystallization for pervaporation separation of MeOH/MMA mixture

The SUZ-4 zeolite membrane was prepared on the hollow fiber ceramic membrane via the secondary growth method modified by the dynamic hydrothermal process. The surface morphology and pervaporation (PV) performance of zeolite membranes fabricated by dynamic and static hydrothermal processes were studied. The surface of the zeolite membrane prepared by the dynamic hydrothermal process was covered with rod-shaped crystals, while the static one was full of crystal clusters fabricated by small-sized crystals. Besides, the separation factor of the SUZ-4 zeolite membrane made via dynamic hydrothermal method for separating 10 wt% methanol (MeOH)/methyl methacrylate (MMA) mixture at 50 °C exceed 10000 with a flux of 3.83 kg·m−2·h−1, which was better than the static one and showed excellent long-term stability. This work provided the important assistance for the preparation of SUZ-4 zeolite membranes in the separation of MeOH/MMA and MeOH/dimethyl carbonate (DMC) organic mixtures and demonstrated the great potential of dynamic process in promoting the membrane properties.

Development of poly(ethylene glycol) diacrylate membrane for facilitated CO2/N2 separation

Carbon dioxide (CO2) is responsible for approximately 80% of greenhouse gases emission that is the main source to global climate change causing notable environmental impacts. Poly (ethylene glycol) diacrylate (PEGDA) have polar PEG repeating units, which provide a strong affinity towards carbon dioxide (CO2) molecules has been blended with 3-aminopropyltrimethoxysilane (APTMS) to synthesize membrane for CO2/nitrogen (N2) separation. The new synthesized membrane is studied for potential applications in gas separation and to be implemented in control CO2 emission. APTMS is also used to delay the diffusion between polymer and solvent. In this study, concentration of polymer of PEGDA and casting solvent of APTMS in terms of mol ratio from a range of 0.9:1.1 to 1.3:0.7 is discussed. Based on the results, PEGDA membrane shows best gas separation performance at mol ratio of PEGDA to APTMS of 1:1 where the permeance for both CO2/N2, and CO2/N2 selectivity are 75.21±0.15 GPU, 22.95±0.05 GPU and 3.28±0.12, respectively. An optimal aminosilane/polymer reaction ratio benefits the gas separation performance of the membrane due to the affinity of the membrane towards CO2 and formation of different membrane surface morphology.

Ionic liquid regulated interfacial polymerization process to improve acid-resistant nanofiltration membrane permeance

In order to enhance the permeance of the acid resistance membrane, an ionic liquid (IL) regulating strategy was proposed to rearrange the interfacial polymerization process. Herein, we revisited polyethylenimine (PEI) and cyanuric chloride (CC) as the pristine acid-resistant membrane. 1-aminopropyl-3-methylimidazolium chloride ([AEMIm][Cl]) and 1-aminopropyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide ([AEMIm][Tf2N]) ILs were used to regulate the interfacial polymerization process. Molecular dynamic (MD) simulation was used to reveal IL and PEI diffusion behavior in aqueous solution, membrane pore size distribution, and porosity. The effects of ILs on membrane surface morphology, surface zeta potential, chemical composition, and separation property were analyzed. The IL regulating strategy endow the membrane with uniform smaller pore and higher porosity, thus improved membrane permeance and selectivity simultaneously. For the [AEMIm][Cl] IL, the corresponding AEMIC-PEI-CC membrane showed high permeance of 79.1 L m−2h−1bar−1, which is 1.36 times the pristine PEI-CC membrane, combined with high Y3+ rejection of 97.5%, low H+ rejection of 1.35%. In addition, this membrane showed good acid stability in 30 days long-term test.

Preparation and Characterization of MWCNTs/PVDF Conductive Membrane with Cross-Linked Polymer PVA and Study on Its Anti-Fouling Performance.

Based on carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), a MWCNTs/PVDF conductive membrane was prepared by a vacuum filtration cross-linking method. The surface compositions and morphology of conductive membranes were studied by X-ray photoelectron spectroscopy and high-resolution field emission scanning electron microscopy, respectively. The effects of cross-linked polymeric polyvinyl alcohol (PVA) on the conductive membrane properties such as the porosity, pore size distribution, pure water flux, conductivity, hydrophilicity, stability and antifouling properties were investigated. Results showed that the addition of PVA to the MWCNTs/PVDF conductive membrane decreased the pure water flux, porosity and the conductivity. However, the hydrophilicity of the modified MWCNTs/PVDF conductive membrane was greatly improved, and the contact angle of pure water was reduced from 70.18° to 25.48° with the addition of PVA contents from 0 wt% to 0.05 wt%. Meanwhile, the conductive membranes with higher content had a relatively higher stability. It was found that the conductive functional layer of the conductive membrane had an average mass loss rate of 1.22% in the 30 min ultrasonic oscillation experiment. The tensile intensity and break elongation ratio of the conductive membrane are improved by the addition of PVA, and the durability of the conductive membrane with PVA was superior to that without PVA added. The electric assisted anti-fouling experiments of modified conductive membrane indicated that compared with the condition without electric field, the average flux attenuation of the conductive membrane was reduced by 11.2%, and the membrane flux recovery rate reached 97.05%. Moreover, the addition of PVA could accelerate the clean of the conductive membranes.

Modification of the Surface Morphology and Properties of Graphene Oxide and Multi-Walled Carbon Nanotube-Based Polyvinylidene Fluoride Membranes According to Changes in Non-Solvent Temperature.

The effect of changes in non-solvent coagulation bath temperature on surface properties such as morphology and hydrophilicity were investigated in multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO)-based polyvinylidene fluoride (PVDF) membranes. The properties of pores (size, shape, and number) as well as membrane hydrophilicity were investigated using field emission scanning electron microscopy, Raman spectroscopy, optical microscopy, water contact angle, and water flux. Results showed that the pore size increased with an increase in coagulation temperature. The hydrophilic functional groups of the added carbon materials increased the solvent and non-solvent diffusion rate, which significantly increased the number of pores by 700% as compared to pure PVDF. Additionally, these functional groups changed the hydrophobic properties of pure PVDF into hydrophilic properties.

The role of PAC adsorption-catalytic oxidation in the ultrafiltration performance for treating natural water: Efficiency improvement, fouling mitigation and mechanisms

Powdered activated carbon (PAC) has turned out to be an efficient adsorbent in drinking water treatment, whereas its application integrated with membrane filtration is still controversial because of the combined fouling effect between organic pollutants and PAC. To this end, an integrated process of combining PAC adsorption-catalytic oxidation and membrane filtration was proposed for natural surface water treatment. The synergistic effect of PAC and peroxymonosulfate (PMS) was confirmed through the generation of reactive oxidation species, and both radical oxidative pathways (•OH, SO4•− and O2•−) and nonradical (1O2 and PMS) pathways involved in the process. The removal efficiency of DOC and UV254 was significantly strengthened by PAC/PMS, with removal rates of 56.1% and 64.9%, respectively. The integration of PAC and PMS could significantly enhance the reduction of fluorescent organics, and pollutants with varying molecular weights. The fouling condition of membrane was dramatically alleviated, with the flux increased by 38.9%, and the reversible and irreversible resistances declined by 79.7% and 48.3%, respectively. The major fouling mechanism was significantly changed, and complete pore blocking always played a dominant role, rather than cake filtration. The effectiveness of PAC/PMS was further verified by the characterization of membrane surface morphologies and functional groups. Moreover, the attractive interactions between foulants and membrane were converted to repulsive interactions with the pretreatment of PAC/PMS. The proposed synergistic process was efficient and convenient, which could significantly improve the purification efficiency of conventional PAC-UF system in drinking water treatment.

Membrane Surface Morphology before and after the Reversible Hydrogen Doping of Diffusion Filters

Atomic force microscopy (АFМ) and high-precision scanning electron microscopy methods were used to study the surface of diffusion filter-membranes of alloy Pd93Y7. The formation of alterations in structure in one of membranes was established as a result from the homogenizing annealing at 900°C for 1 hours. It was found that the reversible doping of the membrane alloy with hydrogen caused the dispersion of the diffusion filter-membranes’ surface structure. Differences in changes by the surface structure are determined during the hydrogenation in directional and non-directional flow of hydrogen.

Fabrication and Characterization of GO-Fe3O4/PSF Membrane with Phase Inversion Method

Polysulfones are hydrophobic which can reduce membrane permeability. Permeability can be increased through the application of hydrophilic materials such as GO-Fe3O4 to the polysulfone membrane so that the membrane is hydrophilic. The riset purpose to determine the effect of the percentage weight of different material compositions on the hydrophilicity properties of the polysulfone membrane. Membrane fabrication is carried out using the phase inversion method where the polymer solution is molded in a place and immersed in a coagulation bath containing non-solvent. This solvent exchange causes the polymer to form a solid matrix and become a membrane. The results showed that GO particles were successfully doped with Fe3O4 material shown by XRD analysis at a peak of 35.61˚ with a magnetite phase, while FTIR analysis showed that there was an absorption band characteristic of Fe-O streching vibrations. The results of the contact angle test on the GO-Fe3O4/PSF membrane 0.75 wt per cent were around 73.17˚ which showed the smallest hydrophobic value and the membrane surface morphology had an average pore size of 333.61 nm so that the addition of GO-Fe3O4 composites could increase membrane hydrophilicity.

Nanoporous polyethersulfone membranes prepared by mixed solvent phase separation method for protein separation

Nanoporous polyethersulfone (PES) membranes with high surface porosity and uniform pore size distribution were prepared by combining the phase separation in NMP/nonane mixed solvent system with the traditional nonsolvent induced phase inversion process. The effects of PES concentration, nonane concentration, evaporation time, casting solution temperature, and varied mixed solvent systems on the porous PES membrane surface morphology were thoroughly investigated and optimized. The optimized nanoporous PES membrane showed a high surface porosity with a uniform pore size of 20 nm, rendering an exceptional molecular weight cut-off of as low as 100 k Dalton. In addition, the membrane exhibited a significant molecular size exclusion with water permeance of 121 LMH bar−1, bovine serum albumin (BSA) protein rejection of 60.1%, and γ-globulin protein rejection of 99.5% at 0.5 bar, respectively, demonstrating the potential of the as-prepared nanoporous PES membrane for application in protein separation.

PVDF-TiO2 Hollow Fibre Membrane For Water Desalination

The clean water crisis is increasing along with the increasing human population. Sea water is one of the largest water sources that can be utilized on the earth. However, the high salt concentration dissolved in seawater must be treated before it can use. Desalination is the directly technology for treating seawater with PVDF-TiO2 hollow fibre membrane via pervaporation process. The aim of this research was to determine the performance of PVDF-TiO2 hollow fibre membrane against variations in feed temperature in the artificial seawater pervaporation process. Method for fabrication membrane is using dry-wet spinning method. The result showed that the highest flux permeat occurred at feed temperature of 60ºC, namely 8.96 kg.m-2.h-1 with salt rejection > 92.86%. The result via SEM showed that of the membrane surface morphology, there is a white spot on the membrane surface is TiO2 because the dope solution is too thick. The PVDF-TiO2 hollow fiber membrane in this research is can be applied for seawater pervaporation.

Minocycline hydrochloride loaded mPEG-PCLA membranes: Preparation and in vitro evaluation for periodontitis therapy

This study was aimed at alleviating shortcomings in the treatment of periodontitis by preparation of a biopolymer membrane loaded with minocycline hydrochloride (MH) inserted into periodontal pockets to treat infections. Monomethoxy-poly (ethylene glycol)-poly (ε-caprolactone-co-L-lactide) (mPEG-PCLA) is a biocompatible and biodegradable amphiphilic block copolymer. It, therefore, has attracted considerable attention in drug delivery systems and periodontal treatment. We chose it as a membrane material for MH-drug loading. The MH-loaded membranes were prepared by the solvent casting technique with the content of 5, 8 and 10 wt.%, respectively. Fourier transform infrared spectra (FTIR) revealed no interaction between MH and polymer. The drug-loaded membrane surface morphology was investigated by scanning electron microscopy (SEM). In vitro release studies showed that the initial drug release exceeded 40% within 24 h, followed by a sustained release for up to 2 weeks, which would enable the therapeutic level to maintain over a longer time. The antibacterial activity studies in vitro demonstrated a positive effect on the periodontal pathogen. MH drug-loaded membranes have no adverse effect on the growth of periodontal ligament fibroblasts in the MTT test. The study suggests that mPEG-PCLA membranes containing MH are a potential antibacterial drug delivery system for local treatment of periodontitis.

Enhanced antibacterial activity of chitosan, guar gum and polyvinyl alcohol blend matrix loaded with amoxicillin and doxycycline hyclate drugs

This study focusses on the synthesis of a series of semisynthetic polymeric blended membranes based on chitosan, guar gum and polyvinyl alcohol for the sustained delivery of antibacterial drugs" with "A series of semisynthetic polymeric blended membranes based on GG (guar gum), CS (chitosan) and PVA (polyvinyl alcohol) was fabricated for the sustained delivery of antibacterial drugs. The drug employed in this study includes amoxicillin and doxycycline hyclate. Different ratios of chitosan CS and GG were blended with constant ratio of PVA to synthesize membranes using solution casting method. Fourier transforms infrared (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) study showed the blend formation, surface morphology and crystalline nature of polymeric membranes respectively. Successful bonding among the ingredients was confirmed by crystalline peak of CS cellulose at 22.6˚. Swelling test was used to analyze the water absorbing capacity of the membranes, indicating the hydrophilic nature, making these membranes more liable for drug release application. Results revealed that 25 mg was the ideal amount of drug loaded on blended membrane. Antimicrobial activity was promising against selected bacterial strains and cytotoxicity assay showed that the polymeric membranes have great potential for biomedical field. The membrane (B-2) was considered best amongst all based on the composition and ratio 3:1 of CS to GG, demonstrated good binding between constituents. These membranes can be employed for sustainable drug delivery process due to good swelling, antimicrobial and absorption characteristics.

Influences of sulfonation level on the nanofiltration performance of sulfonated graphene oxide polyamide nanocomposite membranes

In this study, thin-film nanocomposite (TFN) membranes containing sulfonated graphene oxide (SGO) were prepared and used for water desalination. SGO sulfonation level influences on the physicochemical and separation performance of the prepared TFNs were studied. The TFN membranes were synthesized by interfacial polymerization of 1,3-Phenylene diamine (MPD),1,3,5-benzenetricarbonyl trichloride, and sodium dodecyl sulfate as an additive on polyethersulfone support, while GO and SGOs were dispersed in an aqueous solution of MPD. The physicochemical characterization of GO and SGO samples revealed that the sulfonation level of GO greatly influences the interlayer d-spacing, ion exchange capacity, and zeta potential of GO. Morphology analysis confirmed that GO and SGO were incorporated into the polyimide layer and that the SGO sulfonation level greatly influences the surface morphologies of TFN membranes. Generally, SGO incorporated TFN membranes provided higher hydrophilicity, water uptake, and more desirable surface morphologies for the desalination processes. Increasing the sulfonation level from 25 to 50% wt of sulfanilic acid to GO led to a notable improvement in the salt rejection of SGO-incorporated TFNs, and it reached to about 97% for Na2SO4. This was also accompanied by a considerable increase in these membranes' pure water flux, compared to the GO-containing TFN membranes (~ 42%) and the TFC membranes (~ 4 times). Furthermore, the flux recovery ratio of this membrane was about 24% higher compared to the unmodified membranes, indicating the promising influences of the sulfonated groups on the compatibility, recovery and the reuse of TFN membranes.

MOF-Mediated Interfacial Polymerization to Fabricate Polyamide Membranes with a Homogeneous Nanoscale Striped Turing Structure for CO2/CH4 Separation.

Control of the surface morphology of polyamide membranes fabricated by interfacial polymerization is of great importance in dictating the separation performance. Herein, polyamide membranes with a specific nanoscale striped Turing structure are generated through facile addition of Zr-based metal-organic framework UiO-66-NH2 in the aqueous triethylenetetramine phase. Interestingly, accompanied by the degradation of UiO-66-NH2 in aqueous solution, an intermediate complex is in situ formed through the strong interaction between the Zr metal center and the amine group from triethylenetetramine, which can lower amine diffusion and induce a local interfacial reaction, contributing to the generation of a homogeneous nanoscale striped Turing structure. The resulting membranes are used for CO2/CH4 gas separation. Compared with the parent polyamide membrane displaying a CO2/CH4 selectivity of 43.1 and a CO2 permeance of 31.5 GPU, the membrane with 0.02 wt % of UiO-66-NH2 introduced into the aqueous phase shows a higher CO2/CH4 selectivity of 58.3, along with a CO2 permeance of 27.1 GPU. Additionally, when 0.1 wt % of UiO-66-NH2 is incorporated into the aqueous phase, the membrane exhibits a combination of a higher CO2/CH4 selectivity and an enhanced CO2 permeance in contrast with the parent polyamide membrane.

Fractal Dimension Analysis of Ternary Blends Structure: Polypropylene/Chitosan/Sisal Fiber Membranes

Generally, the microstructures of thin and dense skin membranes have a disorderly nature. Due to their extremely complex nature, it is necessary to study the relationship between surface morphology and fractal dimension of microfiltration membrane. The fractal dimension analysis of the polymer composite was study to provide information about the primary pore size and their associations with flux in porous media. The fractal dimensions of membranes were obtained by the box-counting method. The membranes with increased amount of sisal fiber have inter-twined fibrous network with larger pores. The fractal dimension values of the membranes were also high with increasing amount of sisal fiber, with 86%PP/10% SF/4% C having the highest value of 1.9951.

Carbon Nanotubes Doped Poly (arylene) Ether Copolymerised Multiblock Based Proton Exchange Composite Membranes for Fuel Cell Application

The article reports the synthesis of nanophase-separated multiblock poly(arylene ether ketone sulfone) copolymers. A series of hydrophobic oligomers end-capped with decafluorobiphenyl (DFBP) group was reacted with disulphonated poly(arylene ether ketone) copolymer containing 4, 4′-bis (4-hydroxyphenyl) valeric acid moieties to synthesize multiblock copolymer. The copolymers were characterized using 1H-NMR, 13C-NMR, 19F-NMR spectroscopy and Gel Permeation Chromatography. The membranes with high dimensional and thermal stability were obtained through solution casting method. The multiblock copolymers were crosslinked with 6F-bisphenol-A (6F-BPA) based novolac epoxy resin. The functionalized multi-walled carbon nanotubes (f-MWCNTs), in 0.5, 0.7, and 0.9 wt.%, were also incorporated into the polymer matrix in order to prepare nanocomposite membranes. Polymer nanocomposite membranes showed high oxidative stability, and proton conductivity. The surface morphology and composition of polymer nanocomposite membranes were studied using field emission-scanning electron microscopic (FE-SEM), and high-resolution transmission electron microscopic (HR-TEM) techniques. The fuel cell related parameters such as water uptake, proton conductivity, ion exchange capacity, oxidative stability, and methanol permeability were also evaluated. The thermal performance and mechanical behavior of the synthesized polymer nanocomposite membranes were also studied. The nanocomposite membranes showed better fuel cell performance as compared to the pristine membranes.

Preparation and Characterization of Bentonite - Based Ceramic Hollow Fiber Membrane

The use of low-cost clay materials for the fabrication of ceramic membrane has attracted much interest from researchers, and the outcome would be beneficial to the industries. In this study, low-cost bentonite was used for the preparation of hollow fiber ceramic (HFC) membrane. Bentonite powder was initially characterized by field emission scanning electron microscope (FESEM) for powder surface morphology. The bentonite membrane was fabricated through dope suspension mixing, using phase inversion-based extrusion method and sintering processes. The dope suspension was prepared by mixing quantified bentonite powder, dispersant, polymer binder, and organic solvent on a planetary ball mill. This was followed by the extrusion of the dope suspension at a bore fluid rate of 10 mL/min and air gap of 5 cm and finally subjected to the sintering temperatures of 950° C, 1000° C, 1050° C, and 1100° C. FESEM images revealed that bentonite powder has a compacted interlayer order of heterogeneous surface morphology. The resulting bentonite HFC membrane surface morphologies were examined by scanning electron microscopy (SEM), and the structures exhibit asymmetric structure, which was composed of sponge-like and finger-like structures. Due to, its superhydrophilic property and pore size; the membrane contact angle and water flux performance were obtained at 1.90° and ~326 L/m2 .h, respectively. Overall, the results suggest that bentonite can be used in the fabrication of ceramic-based hollow fiber membrane and in addition, can as well be utilized in microfiltration for wastewater treatment.

Modification of CO2-selective mixed matrix membranes by a binary composition of poly(ethylene glycol)/NaY zeolite

Mixed matrix membranes (MMMs) were prepared by Pebax polymers incorporating with two dopants of poly(ethylene glycol) (PEG) and NaY zeolite. The surface morphology, chemical groups, microstructure, thermal properties and gas separation performance of as-obtained membranes were characterized by Scanning Electron Microscope, Infrared Spectroscopy, X-ray Diffraction, Thermogravimetry and Differential Scanning Calorimetry, and gas permeation technology, respectively. The effects of NaY amount, PEG function, permeation temperature and permeation pressure on the microstructure and properties of MMMs were investigated. The results showed that the addition of PEG as secondary composition obviously improved the compatibility of NaY and membrane matrix, and significantly elevated the CO2 permeability and CO2/N2 selectivity. The MMMs prepared by incorporating 20 wt% PEG and 30 wt% NaY zeolite in starting materials exhibited the maximum CO2/N2 selectivity of 107.9 together with the CO2 permeability of 172.6 Barrer. For CO2/N2 mixed gas, the designed membrane could directly enrich the concentration of CO2 from 15% to 96.7% by one step.