Application Of Ultrafiltration Research Articles

Boosting permeation and separation characteristics of polyethersulfone ultrafiltration membranes by structure modification via dual-PVP pore formers

Asymmetric polyethersulfone (PES) membranes were fabricated from the PES/γ-butyrolactone (GBL)/polyvinylpyrrolidone (PVP) system using non-solvent induced phase separation (NIPS) process. Two types of PVP with different molecular weights (PVP–K30 and PVP-K15) were added as dual pore-forming agents in the dope solution to modify the morphological, physical, permeation, and separation properties of the membranes. Our results demonstrate that high concentration of PVP-K30 in the dope favors the formation of a top skin layer and macrovoids, whereas the PVP-K15 can open the pores on the top surface, shrink the macrovoids, and transform the bi-continuous porous structure toward cellular pores. In the optimal composition of PVP additives (i.e. 8 wt% PVP-K30 and 5 wt% PVP-K15 in this work), the resulted PES membrane exhibits a water flux of 563 L m−2h−1 and a remarkable rejection coefficient over 99% for blue dextran solution, showing a promising potential in ultrafiltration applications.

Modification strategies of polyacrylonitrile ultrafiltration membrane using TiO2 for enhanced antifouling performance in water treatment

The active application of ultrafiltration in various industries requires the development of novel membranes with tailored properties and good fouling resistance. This work is devoted to the improvement of ultrafiltration properties of polyacrylonitrile (PAN) membranes by various TiO2 modification approaches: (1) ex situ method - the introduction of pre-formed micro- or nanoparticles; (2) in situ method - the formation of TiO2 particles in the casting solution; and (3) surface modification method - dynamic deposition of TiO2 on the membrane surface. The effect of the various TiO2 immobilization techniques on the structure of PAN membranes was studied by scanning electron and atomic force microscopies, and the contact angle measurements. The introduction of TiO2 particles improved membrane performance and antifouling stability under UV irradiation in ultrafiltration of industrially important feeds - bovine serum albumin solution (BSA) and coolant lubricant emulsion. The affinity to water of TiO2-modified PAN membrane was confirmed by atomistic molecular dynamics simulations, swelling experiments, and calorimetric study of wetting. PAN membrane with 0.5 wt% TiO2 nanoparticles had the optimal transport characteristics and improved surface self-cleaning ability after UV irradiation: pure water, coolant lubricant, and BSA fluxes (849, 38, and 68 L/(m2h), respectively), and flux recovery ratio after UV-illumination (95%).

Separation of single and mixed anionic dyes in saline solutions using uncharged polyacrylonitrile-tris(hydroxymethyl)aminomethane (PAN-Tris) ultrafiltration membrane: Performance and mechanism

Separation of single or mixed dyes in saline solutions can recover valuable chemicals from dye-containing wastewater. Application of ultrafiltration (UF) in this area is limited by the performance of traditional UF membranes and remains a challenge to achieve high efficacy. Herein, three uncharged polyacrylonitrile-tris(hydroxymethyl)aminomethane (PAN-Tris) UF membranes were adopted for anionic dye separation in saline solutions. These membranes were prepared via in situ modification and characterized by XPS, 1H NMR spectroscopy, contact angle, permeation, mechanical properties, etc. Congo red (CR), methyl blue (MB), and methyl orange (MO) were chosen as model dyes with different sizes and valences. The as-prepared PAN-Tris membranes possessed mean pore sizes ranging from 8.14 to 10.98 nm, but with strong negative zeta potential ranging from −12 to −43 mV at pH 7. Thus, they rejected above 98% CR (with large molecular size) and MB (with high valence), and fractionated the mixtures of CR or MB with MO (with monovalence) in water solutions. The maximum flux of a dye solution reached about 85 L⋅m−2⋅h−1 at 1 bar. Subsequently, the influences of operating pressure, dye concentration, pH value, salt type (NaCl, Na2SO4, MgCl2, or MgSO4) and salt concentration (1000, 5000, or 10000 ppm) on the dye separation property of the membranes were investigated. The results showed that dye rejection behavior depends on the molecular size and valence of dye, as well as membrane property. Thereafter, the electric double layer (EDL) model and the static permeation analysis were combined to investigate the separation mechanism through the changes of the electrostatic effects and effective pore sizes of the membranes in saline solutions. Guided by the revealed mechanism, the MB/CR mixture was successfully separated by using a NaCl solution (≥5000 ppm) for the first time. Overall, this study not only demonstrates that novel UF membranes hold promise for highly effective treatments of dye-containing wastewater, and but also provides an insightful understanding of the dye rejection mechanism that can guide the rational design of UF membranes.

Electrochemistry of new generation conformal polyaniline/carbon scaffolds with monodispersed nanopores and high capacitance

A fully conformal polyaniline film was electrodeposited within a nanoporous carbon scaffold (NCS), maintaining its 3D interconnected pores while increasing its capacitance, ideally suited for capacitive deionization and ultrafiltration applications.

Methods for stability assessment of electrically conductive membranes

The surface properties of electrically conductive membranes (ECMs) govern their advanced abilities. During operation, these properties may differ considerably from their initially measured properties. Depending on their operating conditions, ECMs may undergo various degrees of passivation. ECM passivation can detrimentally impact their real time performance, causing large deviations from expected behaviour based on their initially measured properties. Quantifying these changes will enable consistent performance comparisons across the active and electrically conductive membrane research field. As such, consistent methods must be established to quantify ECM membrane properties. In this work, we proposed three standardized methods to assess the electrochemical, chemical, and physical stability of such membrane coatings: 1) electrochemical oxidation, 2) surface scratch testing, and 3) pressurized leaching. ECMs were synthesized by the most common approach – coating support ultrafiltration (UF) and/or microfiltration (MF) polyethersulfone (PES) membranes with carbon nanotubes (CNT) cross-linked with polyvinyl alcohol (PVA) and two types of cross-linkers (either succinic acid (SA) or glutaraldehyde (GA)). We then evaluated these ECMs based on the three standardized methods: 1) We evaluated electrochemical stability as a function of electro-oxidation induced by applying anodic potentials. 2) We measured the scratch resistance to quantify the surface mechanical stability. 3) We measured physical stability by quantifying the leaching of PVA during separation of a model foulant (polyethylene oxide (PEO)). Our methods can be extended to all types of electrically conductive membranes including MF, UF, nanofiltration (NF), and reverse osmosis (RO) ECMs. We propose that these fundamental measurements are critical to assessing the viability of ECMs for industrial MF, UF, NF, and RO applications.•Anodic-oxidation was used to check the electrochemical stability of ECMs•Depth of penetration resulted from scratch test is an indicator of the electrically conductive membrane coating's mechanical stability•The leaching of the main components forming the nanolayer was quantified to assess the membranes’ physical stability

A Novel Polysulfate Hollow Fiber Membrane with Antifouling Property for Ultrafiltration Application

A Novel Polysulfate Hollow Fiber Membrane with Antifouling Property for Ultrafiltration Application

Asymmetric and bi-continuously structured polyethersulfone (PES) membranes with superior water flux for ultrafiltration application

Asymmetric and bi-continuously structured polyethersulfone (PES) membranes with superior water flux for ultrafiltration application

Synthesis and Characterization of Blended Cellulose Acetate Membranes.

The casting and preparation of ultrafiltration ZnO modified cellulose acetate membrane (CA/ZnO) were investigated in this work. CA membranes were fabricated by phase inversion using dimethylformamide (DMF) as a solvent and ZnO as nanostructures materials. Ultrafiltration (UF) performance, mechanical stability, morphology, contact angle, and porosity were evaluated on both CA- and ZnO-modified CA samples. Scanning electron microscopy (SEM) was used to determine the morphology of the membranes, showing different pore sizes either on rough surfaces and cross-sections of the samples, an asymmetric structure and ultra-scale pores with an average pore radius 0.0261 to 0.045 µm. Contact angle measurements showed the highest hydrophobicity values for the samples with no ZnO addition, ranging between 48° and 82.7° on their airside. The permeability values decreased with the increasing CA concentration in the casting solution, as expected; however, ZnO-modified membranes produced lower flux than the pure CA ones. Nevertheless, ZnO modified CA membranes have higher surface pore size, pore density and porosity, and improved surface hydrophilicity compared with pure CA membranes. The results indicated that the incorporated nano-ZnO tends to limit the packing of the polymer chains onto the membrane structure while showing antifouling properties leading to better hydrophilicity and permeation with consistent UF applications.

Applications of Ultrafiltration, Reverse Osmosis, Nanofiltration, and Microfiltration in Dairy and Food Industry

Food industry is the place to convert raw edible materials to processed foods. Processing foods involves standardization, removal of unnecessary components, addition of essential components, thermal treatments etc. Membrane processes help enhancing the food primely in terms of keeping quality, nutritional value, component recovery and by-products utilization. Feed is given to the membrane system while retentate and permeate are obtained. Components of food can be separated according to size, charge and other characteristics using various membrane processes. The major ones are Ultrafiltration, Reverse Osmosis, Nanofiltration and Microfiltration which are done either single or in combination of more than one process and also in addition with processes such as electrodialysis and vacuum membrane distillation. These processes act as step(s) in the operating procedure of a food or as an alternative method to process the same food with better quality.

Advancements in Sustainable PVDF Copolymer Membrane Preparation Using Rhodiasolv® PolarClean As an Alternative Eco-Friendly Solvent

In this work, Rhodiasolv® PolarClean was employed as a more sustainable solvent for the preparation of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) flat sheet membranes via phase inversion technique by coupling vapour induced phase separation (VIPS) and non-solvent induced phase separation (NIPS) processes. Preliminary calculations based on Hansen solubility parameters well predicted the solubilization of the polymer in the selected solvent. The effect of exposure time on humidity and the influence of polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP) and sulfonated polyether sulfone (S-PES) on membrane properties and performance, were evaluated. Three different coagulation bath compositions were also explored. The obtained membranes, prepared using a more sustainable approach, were compared with those produced with the traditional toxic solvent N-methyl-2-pyrrolidone (NMP) and characterised in terms of morphology, porosity, wettability, pore size, surface roughness and mechanical resistance. The potential influence of the new solvent on the crystallinity of PVDF-HFP-based membranes was also evaluated by infrared spectroscopy. The adjustment of the parameters investigated allowed tuning of the membrane pore size in the microfiltration (MF) and ultrafiltration (UF) range resulting in membranes with various morphologies. From the water permeability and rejection tests, performed with methylene blue dye, the prepared membranes showed their potentiality to be used in MF and UF applications.

Novel High Flux Poly(m-phenylene isophtalamide)/TiO2 Membranes for Ultrafiltration with Enhanced Antifouling Performance

Wide application of ultrafiltration in different industrial fields requires the development of new membranes with tailored properties and good antifouling stability. This study is devoted to the improvement of ultrafiltration properties of poly(m-phenylene isophtalamide) (PA) membranes by modification with titanium oxide (TiO2) particles. The introduction of TiO2 particles improved membrane separation performance and increased antifouling stability and cleaning ability under UV irradiation. The developed membranes were characterized by scanning electron and atomic force microscopy methods, the measurements of water contact angle, and total porosimetry. The transport properties of the PA and PA/TiO2 membranes were tested in ultrafiltration of industrially important feeds: coolant lubricant (cutting fluid) emulsion (5 wt.% in water) and bovine serum albumin (BSA) solution (0.5 wt.%). The PA/TiO2 (0.3 wt.%) membrane was found to possess optimal transport characteristics in ultrafiltration of coolant lubricant emulsion due to the highest pure water and coolant lubricant fluxes (1146 and 32 L/(m2 h), respectively), rejection coefficient (100%), and flux recovery ratio (84%). Furthermore, this membrane featured improved ability of surface contamination degradation after UV irradiation in prolonged ultrafiltration of BSA, demonstrating a high flux recovery ratio (89–94%).

Fabrication and characterization of hydroxyapatite based cow bone polysulfone mixed matrix membrane

In this work, polysulfone (PSf)/hydroxyapatite (HAp) mixed matrix membrane were prepared were prepared by using phase inversion technique for ultrafiltration application. The prepared PSf/HAp mixed matrix membrane were characterized in term of morphological and physicochemical properties by using SEM, contact angle measurement, membrane tensile measurement and membrane porosity. Meanwhile the performance of PSf/HAp mixed matrix membrane was conducted in term of pure water flux (PWF) by using permeability machine. The surface morphology of the MMMs showed the increasing pore number and size as the concentration of HAp increase. The increment weight ratio of the HAp in PSf membrane enhanced the membrane water flux from 113.44 L/m2.h.bar to 228.13 L/m2.h.bar due to increased porosity of the membrane. Meanwhile, the strength of the membrane was increased from 3.82 MPa to 5.2 MPa as HAp increases from 0 to 1.0 wt.% and decreased to 2.49 MPa at 1.5 wt.% HAp. This study suggested that HAp is a promising candidate as additive that can improve PSf membrane performance.

Mitigation mechanism of ozonation in the casein fouling of ultrafiltration membranes: Possible application in dairy wastewater treatment

Membrane fouling control is one topic of concern during the application of ultrafiltration in dairy wastewater treatment. Casein is abundant in dairy wastewater; thus, in this work, preozonation for the casein solutions were carried out, and the membrane fouling behavior was investigated before and after preozonation. To reveal the effect mechanism of preozonation in casein fouling of ultrafiltration membranes, we explored the changes in casein's interfacial forces at the membrane surface, fouling layer structures, and its properties after pre-ozonation. Results showed that the casein molecules without ozonation could hold together tightly to form larger micelles, which were retained on the membrane surface to form a gel scale with poor fluidity and permeability, and also caused the most serious membrane fouling. By contrast, once preozonation occurred, the hydrophobic forces and the hydrogen bonds between membrane and casein, and between casein molecules were disrupted, which not only mitigated the adsorption/deposition of ozone-treated casein onto the membrane surface, but also destroyed the micellar structures of stable casein and resulted in a more open-and-loose fouling layer. Eventually, the membrane showed less fouling. Therefore, preozonation could effectively mitigate casein fouling of ultrafiltration membranes.

Robust ceramic nanofibrous membranes with ultra-high water flux and nanoparticle rejection for self-standing ultrafiltration

Ceramic electrospun nanofibrous membranes (ENMs) are ideal candidates for ultrafiltration applications in harsh environments. However, it has been a great challenge to fabricate ceramic ENMs with sufficient strengths to withstand the water pressure duo to their intrinsic brittleness. In this study, we report an ultra-strong Y3Al5O12-Al2O3 ENM employing graphene oxide (GO) as a sacrificing additive for the first time. The optimized membrane exhibits tensile strengths of 5.63 ± 0.31 MPa after sintering at 900 °C and 3.48 ± 0.44 MPa at 1000 °C. The high strength of the membrane ensures it to be used independently under a pressure up to 160 K Pa. An excellent nano-particle filtration performance is achieved with a high permeation flux of 5718–8494 L m−2 h−1 bar−1 and high rejection efficiencies above 99.75 % in both neutral and acidic water conditions. The work demonstrates a facile route for effective strengthening of ceramic ENMs with their great potential in harsh-environment self-standing ultrafiltration applications.

Sodium Alginate Modified Hydroxyapatite Nanotubes as a Novel Ecofriendly Additive for Preparation of Polyethersulfone Hybrid Ultrafiltration Membranes

Background:: Hydrophilic nanomaterials have been extensively exploited their applications in the field of hybrid water treatment membranes. However, some of the modification process to nanomaterials may be complicated, and the nonselective pores caused by the poor compatibility between nanoparticles and the polymer matrix impair the rejection efficiency for ultrafiltration application. Thus, it is highly desirable to develop a kind of effective nano dopant with favorable compatibility by a facile way for the preparation of ultrafiltration membranes. Objective:: The aim of this study was to fabricate a novel environmentally friendly and low-cost nano additive with good compatibility for the preparation of ultrafiltration membranes. Methods:: Hydroxyapatite nanotubes were prepared via a biomimetic process, and then SA was coated on the surface of hydroxyapatite nanotubes. Subsequently, a series of hybrid ultrafiltration membranes were fabricated with different amounts of modified HANTs and polyethersulfone (PES). Results:: Exhaustive characterizations were conducted for the membranes, including hydrophilicity, porosity, mean pore size, morphologies and UF performance test. The highest water flux of the hybrid membranes displayed 1.9 times that of the original PES membrane. Meanwhile, the hybrid membrane with 0.2% hydroxyapatite nanotubes obtained elevated antifouling ability, achieving a flux recovery ratio of 85.6%. Conclusion:: The facile coating of SA endowed the nanotubes improved hydrophilicity and meanwhile enhanced the compatibility between PES and HANTs. This work provides a facile way in the construction of green nanofillers and promising results in the preparation of hybrid UF membranes.

Algae-laden water treatment with ultrafiltration: effects of moderate oxidation by Fe(ii)/permanganate on hydraulically irreversible fouling and deposition of iron and manganese oxides

Application of ultrafiltration (UF) in algae-laden water treatment is hindered by severe fouling and low retention of soluble organics.

Toughened chitosan-based composite membranes with antibiofouling and antibacterial properties via incorporation of benzalkonium chloride.

Biofouling due to biofilm formation is a major problem in ultrafiltration membrane applications. In this work, a potential approach to solve this issue has been developed by functionalization of chitosan-based membranes with benzalkonium chloride (BKC). The chitosan composite membranes consisting of poly(ethylene glycol) (PEG), multiwalled carbon nanotubes (MWCNT), and BKC were synthesized by mixing the membrane precursors and the antibacterial solution, and casting via an inversed phase technique. The effects of the BKC content on the morphology and performance of the membranes are investigated by varying the BKC feed compositions. The composite membranes demonstrate better antibacterial efficacy against Staphylococcus aureus than Escherichia coli. The permeability and selectivity performances of the composites as filter membranes are examined by employing a dead-end filtration system. Interestingly, enhanced toughness of the membranes is observed as a function of the BKC content. Mechanisms of the structural formation are investigated. The results from SEM, XRD, and FTIR spectroscopy revealed that MWCNT/BKC are located as nanoclusters with π–π stacking interactions, and are covered by PEG chains. The shape of the dispersed domains is spherical at low BKC contents, but becomes elongated at high BKC contents. These act as soft domains with an anisotropic shape with toughening of the brittle chitosan matrix, leading to enhanced durability of the membranes, especially in ultrafiltration applications. The composite membranes also demonstrate improved rejection in dead-end ultrafiltration systems due to high porosity, high hydrophilicity, and the positive charges of the membrane surface.

Synthesis and characterization of crosslinked membranes based on sodium alginate/polyvinyl alcohol/graphene oxide for ultrafiltration applications

Synthesis and characterization of crosslinked membranes based on sodium alginate/polyvinyl alcohol/graphene oxide for ultrafiltration applications

Investigation of Anti-fouling and UV-Cleaning Properties of PVDF/TiO2 Mixed-Matrix Membrane for Humic Acid Removal.

Natural organic matters (NOMs) have been found to be the major foulant in the application of ultrafiltration (UF) for treating surface water. Against this background, although hydrophilicity has been demonstrated to aid fouling mitigation, other parameters such as membrane surface morphology may contribute equally to improved fouling resistance. In this work, with humic acid solution as the model substance, the effects of titanium dioxides (TiO2) types (PC-20, P25, and X500) on membrane anti-fouling and defouling properties were comparatively analysed. The aims are (1) to determine the correlation between membrane surface morphology and membrane fouling and (2) to investigate the anti-fouling and UV-cleaning abilities of PVDF/TiO2 mixed-matrix membranes with different membrane topographies and surface energy conditions. The mixed-matrix membrane with P25 TiO2 exhibited the most significant UV-defouling ability, with a high irreversible flux recovery ratio (IFRR(UV)) of 16.56 after 6 h of UV irradiation, whereas that with X500 TiO2 exhibited both superior anti-fouling and defouling properties due to its smoother surface and its highly reactive surface layer.

STUDY ON ADVANCED TREATMENT OF WASTEWATER BY ULTRA FILTRATION FOR REUSING PURPOSE – ON-SITE PILOTS

Reclaimed water has been greatly applied worldwide recently to augment water supply for non-potable domestic purpose. The present study put an effect on assessing the application of ultra-filtration (UF) on advanced treatment following conventional domestic wastewater treatment and coal mining wastewater for reusing purpose. On-site advanced treatment pilots using UF membrane with the capacity of 1 – 1.5 m3/h were built to treat decentralized domestic wastewater which has a low concentration of organic matters and coal mining wastewater which is abated by chemical-physical process and advanced treatment train. Dissolved oxygen (DO), pH, Chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), volatile suspended solids (VSS), Total Nitrogen (TN) and ammonium-nitrogen (NH4-N) in domestic wastewater and TSS, iron (Fe), manganese (Mn), and hardness of coal mining wastewater were analyzed. The pollutants in domestic wastewater were reduced significantly as of 82% TSS, 86% BOD5, 82% COD, and 96% NH4-N. The removal efficiency in coal mining wastewater reached 93.5% TSS, 67% iron, 68% manganese, and 52% hardness. The analyzed parameters in permeate of both pilots met legislation thresholds of Vietnam technical regulation on domestic water quality, proving that reclaimed water treated by UF can be used for non-potable domestic purposes.