Polypropylene Membrane Research Articles

Rethinking gold mining wastewater treatment with an integrated process of membrane distillation and membrane contactors for minimal waste discard and resource recovery

The generation of wastewater in the mining industry is followed by concerns about the environmental impacts derived from its incorrect disposal. This study intended to simultaneously treat and recover water for reuse, sulfuric acid, and copper from gold mining wastewater, from an innovative integrated system of membrane distillation (MD) and non-dispersive solvent extraction (NDSX). The performance of this system was compared when different polymeric membranes (namely polypropylene (PP), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE)) were tested. The PP membrane yielded better results in terms of distillate flux (0.67 ± 0.32 L/m2h), owing to its reduced thickness compared with the other membranes. However, the PTFE membrane demonstrated superior outcomes in terms of rejection efficiency, achieving values >99.2 %. The occurrence of fouling due to the organic phase was observed, requiring periodical cleaning protocols and the development of oleophobic membranes to reduce the fouling rate in MD. In the extraction and re-extraction processes the PTFE membrane outperformed in terms of extraction efficiency (recovery of 94.0 % for acid and 97.3 % for copper). The results were explained by its greater porosity and lower roughness, variables that directly impacted the mass transfer of sulfuric acid and copper across the membrane. The study, therefore, demonstrates potentiality in the recovery of high-quality water, sulfuric acid, and copper, clearing the path of technologies with the potential to lower the wastewater discarded from industrial facilities.

High-performance electrospun polystyrene-based nanofiber membrane for efficient SO2 capture

It is essential to design a stable membrane material to solve the pollution produced by SO2 emissions. This study aims to fabricate polystyrene (PS) nanofiber membranes, which are applied for flue gas desulfurization. PS nanofiber membranes are fabricated via electrospinning with porous polypropylene (PP) membrane as the support and high hydrophobic PS as the main membrane material. The modified membranes are characterized by scanning electron microscopy, true color confocal microscopy and other analyticalmethods, and the effects of mixed solvent ratio and polymer concentration on the desulfurization performance and on the stability of PS nanofiber membranes are investigated. The results suggest that an optimum hydrophobicity of PS nanofiber membrane is obtained with a water contact angle of 145°, when the polymer concentration is 5 %. The average pore size of PS nanofiber membrane is 1.56 μm, and the liquid entry pressure of water (LEPw) is 0.26 bar and the roughness of membrane is 5.674 μm. The desulfurization performance of the PS nanofiber membrane is better than that of the PP membrane. The SO2 absorption flux of the modified membranes keeps at 7.2 × 10−4 to 7.6 × 10−4 mol·m−2·s−1 during 5 h operating, and SO2 removal efficiency is up to 50 %, which potentially makes contributions to air pollution reduction.

A Magnesium Carbonate Hydroxide Nanofiber/Poly(Vinylidene Fluoride) Composite Membrane for High-Rate and High-Safety Lithium-Ion Batteries.

Simultaneously high-rate and high-safety lithium-ion batteries (LIBs) have long been the research focus in both academia and industry. In this study, a multifunctional composite membrane fabricated by incorporating poly(vinylidene fluoride) (PVDF) with magnesium carbonate hydroxide (MCH) nanofibers was reported for the first time. Compared to commercial polypropylene (PP) membranes and neat PVDF membranes, the composite membrane exhibits various excellent properties, including higher porosity (85.9%) and electrolyte wettability (539.8%), better ionic conductivity (1.4 mS·cm-1), and lower interfacial resistance (93.3 Ω). It can remain dimensionally stable up to 180 °C, preventing LIBs from fast internal short-circuiting at the beginning of a thermal runaway situation. When a coin cell assembled with this composite membrane was tested at a high temperature (100 °C), it showed superior charge-discharge performance across 100 cycles. Furthermore, this composite membrane demonstrated greatly improved flame retardancy compared with PP and PVDF membranes. We anticipate that this multifunctional membrane will be a promising separator candidate for next-generation LIBs and other energy storage devices, in order to meet rate and safety requirements.

Extraction performance of electromembrane extraction and liquid-phase microextraction in prototype equipment

In this comparative study, the performance of liquid-phase microextraction and electromembrane extraction in prototype equipment was evaluated for extraction of ninety basic substances from plasma. Using a commercial EME device based on conductive vials enabled a standardized and comprehensive comparison between the two methods. Extractions were performed from a pH-adjusted donor solution, across an organic liquid membrane immobilized in a porous polypropylene membrane, and into an acidic acceptor solution. In LPME, dodecyl acetate was used as the extraction solvent, while 2-nitrophenyl octyl ether was used for EME with an electric field applied across the system. To assess the extraction performance, extraction recovery plots and extraction time curves were constructed and analyzed. These plots provided insights into the efficiency and effectiveness of LPME and EME, allowing users to make better decisions about the most suitable method for a specific bioanalytical application. Both LPME and EME were effective for substances with 2.0 < log P < 4.0, with EME showing faster extraction kinetics. Small (200 µL) and large vials (600 µL) were compared, showing that smaller vials improved kinetics markedly in both techniques. Carrier-mediated extraction showed improved performance for analytes with log P < 2 in EME, however, with some limitations due to system instability. This is, to our knowledge, the first time LPME was performed in the commercial vial-based equipment. An evaluation of vial-based LPME investigating linearity, precision, accuracy, and matrix effects showed promising results. These findings contribute to a general understanding of the performance differences in vial-based LPME and EME.

Electrosynthesis of Metal-Organic Framework Films with Well-Defined Facets.

The deposition of metal-organic framework (MOF) films with defined exposed facets is important to enhance the performance of these films for, for example, catalysis or separations. In this work, MOF films with specific exposed facets are electrodeposited anodically on various substrates (e. g. on copper-sputtered Si wafers, copper meshes, copper foams, and polypropylene membranes). The influence of the deposition parameters, including the pH of the solution, current density, concentration of linker, and solvent, on the exposed facets of the deposited MOFs was investigated. The results suggest that precise control over the supersaturation during anodic deposition is a possible strategy for synthesizing MOF crystals with well-defined exposed facets. This approach provides a powerful toolbox for various applications requiring crystal facet control of MOF films.

Exodontia with Polypropylene Membrane Followed by Future Implant Installation: Case Report with 10-Years Follow-up

Exodontia with Polypropylene Membrane Followed by Future Implant Installation: Case Report with 10-Years Follow-up

Robust ceramic-based graphene membrane for challenging water treatment with enhanced fouling and scaling resistance.

Membrane fouling and scaling are two challenges for efficient treatment of hypersaline wastewater, greatly hindering separation performance and operation stability of desalination membranes. In this work, we report a smooth ceramic-based graphene desalination membrane, exhibiting enhanced anti-fouling and anti-scaling ability and operational performance for efficient treatment of both synthetic and real industrial wastewaters, outperforming polypropylene (PP) membrane. For treatment of hypersaline waters containing organic or inorganic substance, we demonstrate that the graphene membrane exhibits more stable water flux and almost complete salt rejection (>99.9%) during constant operation. Enhanced anti-fouling and desalination performance of graphene membrane could be attributed to the lower attractive interaction force with foulant (-4.65 mJ m-2), lower surface roughness (Ra=2.2±0.1nm) and higher affinity with water than PP membrane. Furthermore, an anti-scaling mechanism enabled by graphene membrane is evidenced, with a highlight on the roles of smooth graphene surface with lower roughness, less nucleation sites and lower binding force with scaling crystals. Importantly, even for industrial petrochemical wastewater, such a graphene membrane also exhibits relatively more stable water flux and promising oil and ions rejection during long-term operation, outperforming PP membrane. This study further confirms a promising practical application potential of robust ceramic-based graphene membrane for efficient treatment of more challenging hypersaline wastewater with complicated compositions, which is not feasible by conventional desalination membranes.

Surface modification of polypropylene hollow fiber membranes using fluorosilane for CO2 absorption in a gas-liquid membrane contactor

Conventional methods for improving the hydrophobicity of polypropylene (PP) membranes to prevent wetting phenomena require complex pretreatment procedures in order to activate the surface for enabling the reaction with fluorosilane (FS)-based materials. This study successfully prepared PP membrane contactors with enhanced hydrophobicity through a simple single-step dip-coating method using perfluoroether-grafted silanes for CO2 capture. The FS coating layer on the PP membrane surface was confirmed through ATR-FTIR spectroscopy, XPS, FE-SEM, and EDS. Furthermore, the evaluation of the CO2 absorption performance and long-term stability of the FS-coated PP membrane according to the variation of the gas flow rate (50, 100, 200, 400, and 800 mL/min) confirmed the superior chemical stability and durability of our membranes to those of previously reported hydrophobic membranes. The as-prepared FS-coated PP membrane expands the application scope of gas-liquid membrane contactors for CO2 capture from the flue gas of coal-fired power plants.

Plasma-grafting surface modifications to enhance membrane hydrophobicity for brine membrane distillation

In this study, a novel approach is presented to significantly enhance hydrophobicity and performance in direct contact membrane distillation (DCMD) against concentrated reverse osmosis (RO) brines by modifying commercially available polypropylene (PP), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE) membranes using RF-plasma/absorption-grafting treatments with controlled fluorination. Grafting with 1H,1H,2H,2H-perfluorodecyl-triethoxysilane (PDTS) in an anhydrous medium was employed. Morphological, chemical, and electrokinetic surface analyses revealed increased hydrophobic properties, with fluoropolymers achieving the limit of superhydrophilicity and maintaining the original morphology. Modified membranes demonstrated stable percent salt rejection and moderately higher permeate flux yields than commercial counterparts, with improvements of 14 % for PP, 25 % for PVDF, and 9 % for PTFE. The two-step RF-Plasma-O2 treatment and silane absorption-grafting technique effectively enhance surface hydrophobicity and anti-wetting effect of these different inert polymeric membranes, improving their performance for membrane distillation (MD) in all cases. The findings of this study have significant implications for the development and optimization of membrane distillation and related technologies, especially in areas with limited access to high-quality energy and in industries that deal with highly concentrated feeds such as RO brines.

Guided Bone Regeneration with BoneHealTM Membrane after Explantation of Fractured Implant: Case Report

Implantoprosthetic rehabilitation has become the main method to reestablish totally or partially edentulous patients, with a high success rate. However, some complications can cause implant loss. The main one is periimplantitis, with bone loss around the osseointegrated implant. However, implant fractures or incorrect implant position may compromise implant rehabilitation and require implant removal. Several techniques can be used for implant explantation, and the dental surgeon should opt for the easiest and most conservative technique, ensuring the greatest preservation of remaining bone tissue and aiming at the future reinstallation of another osseointegrated implant. Sometimes, associated Guided Bone Regeneration techniques may be necessary in conjunction with future implant installation, using various procedures or biomaterials. The purpose of this article is to present the case of a patient who underwent explantation of a fractured implant. A polypropylene membrane (BoneHealTM) was used and an implant was reinstalled 8 months after explantation.

Advanced super-wetting biaxial polypropylene membrane with hierarchical rough surface for multipollutant removal from oily wastewater

The hazardous toxicity of oily wastewater creates a negative impact on the environment and ecosystem that has made water separation an open challenge on a global scale. A promising and workable tactic to prevent contaminations and effective water separation from oily wastewater has been proved using cutting-edge advanced polymeric membrane-based separation technology. Excessive hydrophobicity, contamination vulnerability, and membrane fouling are recurring and crippling problems for the treatment of oily wastewater. To overcome these difficulties, we design a facile, scalable, and highly efficient layer-by-layer modification technique using polyethylene imine and levo-3,4 dihydroxyphenylalanine cross-linked multi-layer assembled rough biaxial polypropylene membrane surface. The synergistic development of the rough surfaces causes the embeddedness of wetting properties of the modified membrane with excellent superhydrophilicity (0º) and underwater superoleophobicity (∼164.3º). Such great underwater superoleophobicity shows a superior oil-repulsive property that helps to achieve high separation efficiency (99.9 %) and permeate flux (2325.3 L m−2 h−1). Additionally, our modified membrane holds excellent anti-bacterial properties against S. aureus and E. coli bacteria with 92.8 % and 88.6 % viability, respectively. Notably, this highly efficient modified membrane is capable of removing multi pollutants (oil particles and bacteria) from oily wastewater in a more energy-efficient way.

Surface Modification of PP and PBT Nonwoven Membranes for Enhanced Efficiency in Photocatalytic MB Dye Removal and Antibacterial Activity.

In this study, we developed highly efficient nonwoven membranes by modifying the surface of polypropylene (PP) and poly(butylene terephthalate) (PBT) through photo-grafting polymerization. The nonwoven membrane surfaces of PP and PBT were grafted with poly(ethylene glycol) diacrylate (PEGDA) in the presence of benzophenone (BP) and metal salt. We immobilized tertiary amine groups as BP synergists on commercial nonwoven membranes to improve PP and PBT surfaces. In situ Ag, Au, and Au/Ag nanoparticle formation enhances the nonwoven membrane surface. SEM, FTIR, and EDX were used to analyze the surface. We evaluated modified nonwoven membranes for photocatalytic activity by degrading methylene blue (MB) under LED and sunlight. Additionally, we also tested modified membranes for antibacterial activity against E. coli. The results indicated that the modified membranes exhibited superior efficiency in removing MB from water. The PBT showed the highest efficiency in dye removal, and bimetallic nanoparticles were more effective than monometallic. Modified membranes exposed to sunlight had higher efficiency than those exposed to LED light, with the PBT/Au/Ag membrane showing the highest dye removal at 97% within 90 min. The modified membranes showed reuse potential, with dye removal efficiency decreasing from 97% in the first cycle to 85% in the fifth cycle.

Formation of solid RbCl from aqueous solutions through membrane crystallization

Rubidium (Rb) is a very precious alkali metal with a high economic value. Of the rubidium compounds, RbCl is probably the most widely used. In the present work, RbCl crystals were obtained by vacuum membrane crystallization (V-MCr). Two different membranes were utilized: (i) one in polypropylene (PP) and (ii) one in poly(vinylidene fluoride)(PVDF). The membranes differ in material but have equal pore and porosity, and the experiments with the two membranes were conducted at the same temperature, vacuum pressure and flow rate values. While RbCl crystals were not obtained with the PVDF membrane due to wetting, good crystals were achieved from experiments with the PP membrane, with dispersion of crystal size distribution around of the average size of just 33.6 %. Another important result is that, in addition to the operating conditions, the membrane material is decisive for the success or failure of the membrane crystallization operation.

Preservation of Peri-Implant Mucosa by the Use of Polypropylene Membrane After Dental Extraction: A Case Report

After dental extraction, bone resorption of the alveolar walls and invagination of the gingival tissue are expected. Bone resorption is usually greater in thickness than in height. In addition, the loss of gingival tissue can favour peri-implant mucosal defects, causing a risk to the integrity of this natural mechanical barrier, which is the peri-implant gingival tissue. Guided Tissue Regeneration and Guided Bone Regeneration techniques and procedures can be applied, although the success rate is variable and sometimes difficult to achieve. The use of polypropylene membrane has been widely used after dental extraction to maintain blood clot. This in turn is a natural endogenous precursor, consisting of pluripotent cells necessary for bone neoformation. The purpose of this article is to present the case of maintaining the peri implant keratinised gingiva strip - as a mechanical barrier to protect the implant neck - after tooth extraction and osseointegrated implant installation.

Ultrasound assisted membrane-assisted solvent extraction for the simultaneous assessment of some drugs involved in drug-facilitated sexual assaults by liquid chromatography-tandem mass spectrometry

A simple and highly efficient ultrasound assisted membrane-assisted solvent extraction (MASE) pre-treatment method for urine has been developed and validated for the simultaneous determination of twenty-two drugs involved in drug-facilitated sexual assaults (DFSAs) by liquid chromatography-tandem mass spectrometry. MASE was performed with 4.0 mL of urine (pH adjusted at 12), 400 μL of hexane as an organic solvent inside the polypropylene membrane, and ultrasonication (45 kHz, 120 W) for 10 min. A pre-concentration factor of 40 was achieved after evaporation (N2 stream) and re-dissolution in 100 µL of methanol. Analytes were separated using a Zorbax Eclipse Plus C18 column under gradient elution with aqueous 10 mM NH4HCO3 (pH 8.0) and methanol as mobile phases. Matrix-matched calibrations allowed the assessment of DFSA drugs of quite different octanol–water partition coefficients (Ko/w), from 1.32 101 for pregabalin to 2.45 105 for clomipramine (Log P values from 1.12 (pregabalin) to 5.39 (clomipramine)). The limit of detection (LOD) was between 0.0075 to 0.37 µg L−1, with analytical recoveries ranging from 73 to 103%, and relative standard deviations (RSDs) within the 2–20% range. The applicability of the method was demonstrated after analysing urine samples under forensic investigation.

Synergistic effect of underwater superoleophobicity and photo-Fenton oxidation on improving anti-fouling performances of filtration membranes for oily wastewater separation

Underwater superoleophobic membranes can inhibit the adhesion of oil droplets and efficiently reduce oil-fouling. However, under the action of transmembrane pressure, the oil inevitably adheres to the membranes, which is difficult to be removed by facile washing. Here, an excellent coupling of underwater superoleophobicity and photo-Fenton oxidation is reported for desired anti-fouling performances. Briefly, composite polypropylene (PP) membranes with stable underwater superoleophobicity and excellent photo-Fenton oxidation efficiency were constructed by depositing hydrophilic α-FeOOH nanorods and mussel-inspired coating in turn. Various stable water-in-oil emulsions can be effectively separated with the obtained membranes. Most importantly, in the presence of H2O2 and visible light, α-FeOOH nanorods can photo-Fenton oxidize oil and dye that break through the underwater superoleophobic defense layer. Therefore, the reversible fouling ratio (Rr-L) and the flux recovery ratio (FRR-L) improve to 76.8 ± 3.2% and 87.2 ± 2.4% respectively, while the irreversible fouling ratio (Rir-L) decreases to 9.9 ± 0.2% for separation pump oil-in-water emulsion containing methylene blue. This work has great potential and strategic value in the treatment of oily wastewater and the preparation of advanced filtration and anti-fouling membranes.

In vivo evaluation of bone regeneration using ZIF8-modified polypropylene membrane in rat calvarium defects.

The profound potential of zeolitic imidazolate framework 8 (ZIF8) thin film for inducing osteogenesis has been previously established under in vitro conditions. As the next step towards the clinical application of ZIF8-modified substrates in periodontology, this in vivo study aimed to evaluate the ability of the ZIF8 crystalline layer to induce bone regeneration in an animal model defect. Following the mechanical characterization of the membranes and analysing the in vitro degradation of the ZIF8 layer, in vivo bone regeneration was evaluated in a critical-sized (5-mm) rat calvarial bone defect model. For each animal, one defect was randomly covered with either a polypropylene (PP) or a ZIF8-modified membrane (n = 7 per group), while the other defect was left untreated as a control. Eight weeks post surgery, bone formation was assessed by microcomputed tomography scanning, haematoxylin and eosin staining and immunohistochemical analysis. The ZIF8-modified membrane outperformed the PP membrane in terms of mechanical properties and revealed a trace Zn+2 release. Results of in vivo evaluation verified the superior barrier function of the ZIF8-coated membrane compared with pristine PP membrane. Compared with the limited marginal bone formation in the control and PP groups, the defect area was almost filled with mature bone in the ZIF8-coated membrane group. Our results support the effectiveness of the ZIF8-coated membrane as a promising material for improving clinical outcomes of guided bone regeneration procedures, without using biological components.

Solar energy-based electromembrane extraction using agarose gel for the determination of nonsteroidal anti-inflammatory drugs from biological samples: An environmentally friendly strategy

This paper presents the application of solar energy as a renewable resource in gel electromembrane extraction (G-EME). The extraction driving force (electrical field) generated from solar energy is stored through photovoltaic panels and significantly contributes to reducing the emission of greenhouse gasses. Moreover, the replacement of the polypropylene membrane and organic extracting solvents with biodegradable agarose membrane and the aqueous extracting solutions makes the presented approach compatible with the principles of green chemistry. Naproxen (NAP) and ibuprofen (IBF) were extracted from urine samples to the aqueous acceptor phase containing an anode electrode situated on the other side of the agarose gel membrane. Acceptable linearity was obtained in the concentration ranges of 6–100 and 9–100 μg. L − 1 with detection limits of 2 and 3 μg. L − 1 for NAP and IBF, respectively.

Evaluation of Malassezia furfur Biofilm Formation on Polypropylene Membrane

The Malassezia yeast species colonize on the skin immediately after birth and could be found on the healthy skin flora for life. Although they are more frequently involved in the etiology of common skin infections in the community, particularly Malassezia furfur could cause life-threatening infections such as fungemia. Detection of biofilm during the colonization of these yeasts on the skin is an important criterion for its virulence. Since they are lipophilic yeasts, commonly used biofilm detection methods are not applicable to the Malassezia strains. The aim of the study was to describe the growth and measurement of M.furfur isolates on a polypropylene membrane to demonstrate their biofilm-forming capacities. Twenty-seven M.furfur strains colonized in the newborns were included in the study. Basically, sterile polypropylene membranes were placed on different polysorbates (tween 20, 40, and 80) which were spread on Sabouraud dextrose agar. Ten µl saline suspension of M.furfur was dropped on the polypropylene membrane and incubated in standard growth conditions for three days. Later, the visible colony was removed gently by washing with running water and the biofilm structure formed on the membrane was stained with safranin. The stained biofilm was photographed. Performing image analysis, the values obtained against background activity were digitized according to the specified protocol. Moreover, XTT reduction test was performed and the measured metabolic activity results were compared with the safranin-stained biofilm data. The safranin hydrolysis of the strains was measured spectrometrically. Twenty-five (92.6%) of the strains included in the study were stained with safranin, which indicated the presence of biofilm on the polypropylene membrane. The strains grown with tween 20 and tween 80 formed a higher biofilm layer density than those supplied with tween 40. Isolates with low and high biofilm-forming capacity were clearly separated by tween 20 (p< 0.05). XTT activity was detected in 26 (96.3%) isolates. No correlation was found between biofilm density obtained by the described method and XTT reduction. It was observed that hydrolysis of safranin did not affect the biofilm evaluation method. In this study, it was shown that as a result of sufficient diffusion through hydrophobic membranes, polysorbate-based growth factors could maintain measurement of the biofilm layer formed by lipophilic M.furfur strains. The best grouping properties for M.furfur were obtained with tween 20 which could determine low and high level of biofilm formation. Image analysis was used with high performance for this method. As conclusion, the utilization of different hydrophobic membranes and dyes would lead to the development of new techniques for the application in other lipophilic yeasts.

Preparation of highly efficient antibacterial non-woven by facile plasma-induced graft polymerizing of DADMAC

The development of surface modification technology for temperature sensitive fibers has been a huge challenge. In this work, a novel technique based on cold plasma treatment was developed for the preparation of anti-bacterial polypropylene (PP) fibers. The results showed that plasma treatment introduced a rough surface and polar groups, which acted as the anchor point and initiators for diallyldimethyl ammonium chloride (DADMAC) graft-polymerization. The fabricated PP membranes presented a high bacterial sterilization rate, as well as excellent adhesion force and washing durability. After ultrasonic treatment for 30 min, the physical coating sample had lost anti-bacterial effect, while the plasma grafted sample still showed a sterilization rate of 91.67%. This work provided a clean and novel DADMAC grafting method and it is also applicable for anti-bacterial material fabrication.