Polypropylene Membrane Research Articles

Water and salts recovery from desalination brines: An exergy evaluation

Exergy analyses are becoming important tools in identifying the less efficient components of plants through the evaluation of the energy lost in entropy production. In this work, this type of analysis was considered for desalination plants based on membrane operations, with specific emphasis on membrane distillation and membrane crystallization for the improvement of the water recovery factor and the recovery of valuable salts from produced brines. The state of the art in the field was firstly presented and discussed. In all literature works, the thermal supply was the highest contributor to exergy losses. However, the use of waste heat or renewable energies can significantly improve the exergy efficiency of the process, as the feed is heated by the available source and enters the process already at the desired temperature. Furthermore, it resulted that the gain for the sale of salts produced by membrane crystallization was able to cover the desalination costs, even without waste heat availability.Then, the exergy analysis of membrane distillation (MD) and membrane crystallization (MCr) working on four different feeds was experimentally carried out. Commercial modules equipped with capillary polypropylene membranes (0.2 µm pore size) were used at fixed feed temperature and flow rate. A high exergy efficiency (72%) was obtained with the Synthetic RO feed (79.9 g/L), together with a high water recovery factor (79%) and brine concentration (around 476 g/L).

Application of Capillary Polypropylene Membranes for Microfiltration of Oily Wastewaters: Experiments and Modeling

Oily wastewaters are considered as one of the most dangerous types of environmental pollution. In the present study, the microfiltration (MF) process of model emulsions and real oily wastewaters was investigated. For this purpose, capillary polypropylene (PP) membranes were used. The experiments were conducted under transmembrane pressure (TMP) and feed flow rate (VF) equal to 0.05 MPa and 0.5 m/s, respectively. It was found that the used membranes ensured a high-quality permeate with turbidity equal to about 0.4 NTU and oil concentration of 7–15 mg/L. As expected, a significant decrease in the MF process performance was noted. However, it is shown that the initial decline of permeate flux could be slightly increased by increasing the feed temperature from 25 °C to 50 °C. Furthermore, Hermia’s models were used to interpret the fouling phenomenon occurring in studied experiments. It was determined that cake formation was the dominant fouling mechanism during filtration of both synthetic and real feeds. Through detailed studies, we present different efficient methods of membrane cleaning. Results, so far, are very encouraging and may have an important impact on increasing the use of polypropylene MF membranes in oily wastewater treatments.

A Functional PEO/LiTFSI-Coated Coated Separator for Electrochemical Lithium-Sulfur Battery

There is a strong interest in exploring next-generation rechargeable batteries that can deliver a high energy density for a long cycle life and a long shelf time at an affordable cost. The commercial lithium-ion battery systems have exhibited the advantages in satisfying all the above-mentioned requirements so that the lithium-ion technology has dominated the battery business for over 30 years. To obtain further upgrades in battery technologies, the current lithium-ion systems based on various lithium-insertion oxide cathodes are mature techniques and have faced the theoretical values in terms of their capacity and energy density values. Moreover, the increasing demands of commercial lithium-ion batteries have encountered the increasing prices and limited availability of the raw materials. To address these issues, the conversion-reaction cathodes featuring an enhanced energy density at an affordable cost garner significant attention.Sulfur cathodes have become appealing as they offer an order of magnitude higher capacity and are abundant. The electrochemical conversion reactions of sulfur with lithium ions provide lithium sulfide, involving two electrons per sulfur and providing a high charge-storage capacity of 1,672 mA∙h g-1. The high-capacity sulfur cathodes enable the packaged lithium-sulfur cells to attain 2-3 times higher energy density than that offered by the current lithium-ion batteries. However, several challenges prevent the practical application of lithium-sulfur batteries. The high resistivity of solid-state sulfur and its end-discharged lithium sulfides as well as the dissolution and diffusion of intermediate liquid-state lithium polysulfides cause the poor electrochemical utilization of sulfur, fast capacity fade, and low Coulombic efficiency of the cell in a short cycle life.Significant improvements have been made in the modification of the material and the structure of the sulfur cathodes and the separators in recent years. This presentation will focus on lithium-sulfur battery separator with a coating layer of mixtures containing poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) on a polypropylene membrane, forming a functional gel polymer electrolyte (GPE) / separator composite. The PEO/LiTFSI-coated polypropylene membrane is configurated to face the sulfur cathode and functions as the restrict film to cease the fast diffusion of liquid-state polysulfides and to stabilize the liquid-state active materials within the cathode region of the cell as the catholyte for enhancing the electrochemical reaction kinetics and stability. As a result, our findings show that the lithium-sulfur cells with the PEO/LiTFSI-coated polypropylene membrane show a high discharge capacity of 1,200 mA∙h g-1, a long cycle life of 200 cycles, and high Coulombic efficiency of above 99%. As a comparison, the same cell with a PEO-coated polypropylene membrane reveals a poor electrochemical utilization and efficiency due to the lack of LiTFSI as the ion-diffusion matrix, resulting in low discharge capacity of 662 mA∙h g-1and poor capacity retention. On the other hand, the same cell with a regular unmodified separator membrane suffers the fast loss of the liquid-state active material, showing a short cycle life of less than 100 cycles. According to the material analysis and electrochemical comparison, the PEO/LiTFSI-coated polypropylene membrane proves its capability in blocking the uncontrolled migration of polysulfides, while allowing the smooth diffusion of lithium ions. In conclusion, our experimental and analytical results prove the PEO/LiTFSI-coated polypropylene membrane as an advanced and a facile separator design in the development of high-loading/content sulfur cathodes in lithium-sulfur batteries for realizing a high energy density.

Comparison of Circular and Parallel-Plated Membrane Lungs for Extracorporeal Carbon Dioxide Elimination.

Extracorporeal carbon dioxide removal (ECCO2R) is an important technique to treat critical lung diseases such as exacerbated chronic obstructive pulmonary disease (COPD) and mild or moderate acute respiratory distress syndrome (ARDS). This study applies our previously presented ECCO2R mock circuit to compare the CO2 removal capacity of circular versus parallel-plated membrane lungs at different sweep gas flow rates (0.5, 2, 4, 6 L/min) and blood flow rates (0.3 L/min, 0.9 L/min). For both designs, two low-flow polypropylene membrane lungs (Medos Hilte 1000, Quadrox-i Neonatal) and two mid-flow polymethylpentene membrane lungs (Novalung Minilung, Quadrox-iD Pediatric) were compared. While the parallel-plated Quadrox-iD Pediatric achieved the overall highest CO2 removal rates under medium and high sweep gas flow rates, the two circular membrane lungs performed relatively better at the lowest gas flow rate of 0.5 L/min. The low-flow Hilite 1000, although overall better than the Quadrox i-Neonatal, had the most significant advantage at a gas flow of 0.5 L/min. Moreover, the circular Minilung, despite being significantly less efficient than the Quadrox-iD Pediatric at medium and high sweep gas flow rates, did not show a significantly worse CO2 removal rate at a gas flow of 0.5 L/min but rather a slight advantage. We suggest that circular membrane lungs have an advantage at low sweep gas flow rates due to reduced shunting as a result of their fiber orientation. Efficiency for such low gas flow scenarios might be relevant for possible future portable ECCO2R devices.

Pharmaceutical wastewater treatment using polypropylene membranes incorporated with carboxylated and PEG‐grafted nanodiamond in membrane bioreactor (MBR)

AbstractThe aim of this work is to prepare polypropylene (PP) membrane by embedding carboxylated(‐COOH) and also polyethylene glycol(‐PEG) functionalized nanodiamond to improve membrane hydrophilicity and decline membrane fouling in pharmaceutical wastewater treatment. Porosity, contact angle, mechanical strength, field emission scanning electron microscopy (FESEM) and membrane pure water permeation analysis were performed for the characterization of the membranes. The membranes with 0.75 wt.% of nanoparticles introduced the highest water flux, porosity and mechanical strength. The performance of PP, PP/ND‐COOH (0.75 wt.%) and PP/ND‐PEG (0.75 wt.%) membranes was studied in a lab‐scale membrane bioreactor (MBR). COD removal was more than 91% in all cases. It was found that antifouling characteristics, membrane resistance (Rm) and specific cake layer resistance (α) of nanocomposite membranes were better than of neat PP membrane. PP/ND‐PEG (0.75 wt.%) membrane exposed highest hydrophilicity and maximum critical flux and anti‐fouling characteristics. The results indicated that embedding nanodiamond in PP membrane can reduce membrane fouling in MBR.

Desalination by direct contact membrane distillation using a superhydrophobic nanofibrous poly (methyl methacrylate) membrane

A practical, high-productive and superhydrophobic nanofibrous membrane was firstly introduced for membrane distillation (MD) process using poly (methyl methacrylate) (PMMA) and the electroblowing process. Wrinkled PMMA nanofibers demonstrated nano/micro-structure improving hydrophobicity greatly. Direct contact membrane distillation (DCMD) performance of the cold-pressed nanofibrous PMMA membrane was assessed using 35 and 150 g/L saline feed waters for 24 h and the results were compared with commercial polytetrafluoroethylene (PTFE) and polypropylene (PP) membranes. The PMMA membrane exhibited highest permeate flux (41.04 and 35.94 kg/m2 h for 35 and 150 g/L feeds, respectively) with stable electrical conductivity (EC) (˂ 5 μS/cm) resulting from superhydrophobicity (164.2°) and high liquid entry pressure (LEP) of 227.3 kPa. Although the commercial membranes presented good DCMD performance for 35 g/L feed, partial pore wetting with final EC of 11.93 and 17.62 μS/cm was measured for the PTFE and PP membranes using 150 g/L feed, respectively. The nanofibrous PMMA membrane is a promising applicant for conducting promising desalination using the DCMD process considering high production rate, simplicity of fabrication process and cost-effectiveness.

Ultrahigh Flux and Strong Affinity Poly(N-vinylformamide)-Grafted Polypropylene Membranes for Continuous Removal of Organic Micropollutants from Water.

The rapid and effective removal of organic micropollutants (OMPs) from water remains a huge challenge for traditional water treatment techniques. Compared with powder adsorbents such as polymers and nanomaterials, the free-standing adsorptive membrane is possible for large-scale applications and shows promise in removing OMPs. Herein, inspired by aquatic plants, a novel free-standing adsorptive membrane (NPPM) with high water flux, strong adsorption affinity, and excellent reproducibility was prepared by one-step UV surface grafting. N-Vinylformamide (NVF) was employed to introduce multiple hydrophilic and hydrogen bonding sites on the surface of commercial polypropylene fiber membranes (PPM). The NPPM exhibits excellent water permeability and ultrahigh water flux (up to 40 000 L/(m2 h)) and could continuously remove a broad spectrum of OMPs from water. Its adsorption performance is 5-100 times higher than that of PPM and commercial membranes. Even in natural water sources such as tap water and river water, the NPPM shows unchanged adsorption performance and high OMPs removal efficiency (>95%). Notably, the NPPM has excellent regeneration performance and can be regenerated by hot water elution, which provides an environmentally friendly regeneration method without involving any organic solvent. Moreover, the synergy between hydrogen bonding and hydrophobic interaction is revealed, and the hydrophobic interaction provided by the hydrophobic substrate is proved to play a fundamental role in OMPs adsorption. The strong hydrogen bonds between the grafts and the OMPs are demonstrated by variable-temperature FTIR spectroscopy (vt-FTIR), 13C nuclear magnetic resonance spectroscopy (13C NMR), and simulation calculations. The strong hydrogen bonds could increase the enthalpy change and enhance the adsorption affinity, so the NPPM has a strong adsorption affinity, which is 100 times that of similar adsorption membranes. This study not only presents an adsorptive membrane with great commercial potential in the rapid remediation of a water source but also opens a pathway to develop an adsorptive membrane with high water flux and strong adsorption affinity.

Microporous formation and evolution mechanism of PTFE fibers/isotactic polypropylene membranes by interface separation

Studying microporous formation and evolution mechanism plays a crucial role in fabricating high-performance microporous membranes. A formation mechanism of PP microporous membranes, different from those reported previously, was proposed based on the interface separation of PTFE fibers and PP matrix during sequential biaxial stretching. The experimental results indicated that the initial microcracks, which were filled by microfibrillated PP, were originated from PTFE fibers-PP matrix interfaces perpendicular to the longitudinal stretching direction. As the strain increased, microfibrillated PP was further elongated, ultimately forming microfibrillated PP membranes at a relatively low strain (200%). The subsequent transverse stretching caused the separation of fibrillated PP to form an excellent microporous structure. As a result, PTFE/PP membranes after biaxial stretching exhibited the narrower pore size distribution, higher porosity, higher N2 flux and pure water flux than β-PP membranes.

Clinical efficacy of simvastatin gel combined with polypropylene membrane on the healing of extraction sockets: A triple-blind, randomized clinical trial.

This study aimed to evaluate dimensional changes, level of soft tissue healing, and pain/discomfort perception in post-extraction sockets filling with 1.2% simvastatin (SIM) gel covered with polypropylene membranes (PPPM). Twenty-six post-extraction sockets of posterior teeth were randomly allocated in two groups: (a) socket filling with 1.2% SIM gel and covered with PPPM (n=13) and (b) socket filling with placebo gel and covered with PPPM (n=13). Cone-beam computed tomography (CBCT) images before and 90days after the extraction enabled alveolar bone dimensional changes calculation using horizontal and vertical measurements. The measurements occurred at three different levels for thickness located 1, 3, and 5mm from the top of the bone crest. The vertical (depth) measure was assessed from the most apical portion of the socket to the bone crest's most coronal portion. Seven days after the extractions, the level of soft tissue healing and pain perception were also analyzed. After 90days of extractions, the dimensional changes in thickness in the test group were significantly smaller in sections A (p=.044), B (p=.036) and C (p=.048) when compared to the control group. The test group showed a significantly lower height-dimensional change than the control group (p<.0001). Soft tissue healing index (p=.63), perception of pain (p=.23), and number of analgesics consumed (p=.25) were similar between groups. Simvastatin at 1.2% compared with placebo effectively reduced the dimensional changes in post-extraction sockets covered with PPPM. There was no significant difference in the level of soft tissue healing and postoperative pain between the test and control groups.

Natural halloysite nanotubes-coated polypropylene membrane as dual-function separator for highly safe Li-ion batteries with improved cycling and thermal stability

Developing low-cost functional separator is urgently needed by high safety and high energy lithium-ion batteries (LIBs), especially for the electric vehicles application. In this work, we present a new type of dual-function separator (HNTs@PP) by coating natural halloysite nanotubes (HNTs) on both sides of a polypropylene (PP) separator to improve battery safety and electrochemical performance. HNTs@PP separators exhibited better electrolyte uptake, wettability, and high ionic conductivity. Compared with traditional ceramic coating, the low-cost and natural abundant halloysite with unique nano hollow tube structure can improve the thermal stability of separators and significantly enhance the cycle and rate performance. Furthermore, the HNTs@PP shows higher lithium anode stability. The three-dimensional network structure of HNTs on membrane surfaces and their ability to react with electrolytes to obtain the additive, LiPO2F2, improve the cycle stability of LIBs greatly. At 1 C and after 300 cycles, the capacity retention rate of the assembled LiCoO2/Li half-cell using HNTs@PP composite separators was 44.42% higher in comparison with LIBs with bare PP separators. Moreover, at the rates of 0.5, 1, 2, and 3 C, the discharge specific capacities when using HNTs@PP separators were 1.77%, 2.63%, 5.80%, and 9.71%, respectively, higher than when using bare PP separators. As a result, the as-prepared HNTs@PP separator is a promising candidate as low-cost functional separator for highly safe and high-energy LIBs.

TiO2 Coated Polypropylene Membrane by Atomic Layer Deposition for Oil–Water Mixture Separation

Polypropylene (PP) membrane has been widely used in water purification and other fields owing to special pore structure, excellent mechanical properties and resistance to acids, alkalis and organic solvents. However, it is difficult for PP to introduce the hydrophilic chemical compositions for oil–water separation. Herein, superhydrophilic and underwater superoleophobic PP membranes were prepared by ALD for efficient gravity-driven oil–water separation. Owing to synergistic effect, oil contact angle of TiO2 coated PP membrane under water can reach above 150°. Hence, TiO2 coated PP membrane has great oil-repelling performance. Because of the superwetting property, TiO2 coated PP membrane can easily separate oil–water mixture and have high separation efficiency (more than 95%). The outstanding recyclability and mechanical stability of TiO2 coated PP membrane suggest the promising potential application in practical oil–water separation.

Performance evaluation of boron removal from wastewater containing high boron content according to operating parameters by air gap membrane distillation

The removal performance of boron from real wastewater was conducted to determine the effect of different parameters on permeate water flux and boron removal efficiency by air gap membrane distillation (AGMD) system in this study. These parameters include boron concentration, membrane pore size, and membrane material. Before real wastewater tests, the experiments were conducted with saline water (%1 (w/v) NaCl) to stabilize the air gap membrane distillation system. Then, experiments were carried out in an air gap membrane distillation system using real wastewater. In the experiments, two different membrane materials (polytetrafluoroethylene (PTFE) and polypropylene (PP)) were used to examine the effect of membrane material. Also, experiments were conducted with membranes that have mean pore size of 0.20 and 0. 45 μ m to examine the effect of membrane pore size on the permeate flux. To evaluate the effect of boron concentration, wastewaters at three different boron concentrations (2598, 2795 and 6242 mg/L B) were treated in the AGMD system. The results illustrate that removal of boron in all conditions was obtained above 99%. In conclusion, increasing boron concentration at feed wastewater, permeate water flux was decreased. When the mean pore size was increased from 0.20 to 0. 45 μ m , permeate flux was enhanced. Furthermore, PP membranes had the maximum permeate flux in AGMD tests. • The increase of boron concentration in feed wastewater had effect on permeate water flux. • The permeate water fluxes were highest for the PP 0.45 membrane for almost all wastewater. • Boron removal efficiency for all wastewater and all membranes was over 99%.

Surface modification of polypropylene membrane by helium plasma treatment for membrane distillation

Helium plasma was used to modify the surface of commercial polypropylene capillary membranes applied for membrane distillation. The membranes were manufactured for microfiltration and had a thin skin layer with low porosity. The plasma reactions such as etching and re-deposition resulted in a substantial modification of the skin layer. The surface porosity and pore diameters increased due to plasma treatment and resulted in 25% enhancement of the permeate flux during membrane distillation (MD). Although the plasma treatment caused hydrophilization of the membrane surface, the resistance of membranes to wetting did not deteriorate and the permeate conductivity at a level of 5 μS/cm was retained for 200 h of the MD process with NaCl solution. The model calculations confirmed that wetting only of the surface pores did not cause a significant decrease in MD efficiency, while the calculated efficiency decreased by 30% when the wetted layer reached half the thickness of the membrane wall. The modified membranes demonstrated good stability and the permeate purity was similar during the 300 h desalination of Baltic Sea Water after three years of their storage. The separation of water contaminated by oil (50 ppm) revealed that hydrophilic compounds on the membrane surface formed in helium plasma treatment significantly reduced oil fouling.

Preparation of Polypropylene/PVDF Composite Membrane by Dip-Coating Method

In this research, a composite membrane was prepared by dipping a hollow fiber polypropylene (PP) membrane in a polyvinylidene fluoride (PVDF) solution. A small concentration of volatile solvent (acetone and tetrahydrofuran/THF) was added to the PVDF solution to form a tight structure in the membrane surface. The influence of PVDF concentration, type of volatile solvents (acetone and THF), and the dip-coating cycle on membrane characteristics, including porosity, swelling degree, and contact angle, were investigated. The flux and rejection of the membranes were also investigated during the filtration of hexane/oil solution. The experimental results showed that low membrane porosity (3%), low swelling degree (0.1%), and high water contact angle (140°) were obtained when 8%wt PVDF was blended with 10%wt acetone and then coated on PP hollow fiber membrane surface with 3 (three) dip-coating cycles. The oil rejection was 68% after 45 minutes of filtration time with a permeate flux of 20 L.m−2.h−1. Higher membrane porosity and permeate flux can be obtained by reducing the dip-coating cycle; however, a lower oil rejection was achieved.

Plasma treatment of polypropylene membranes coated with zeolite/organic binder layers: Assessment of separator performance in lithium-ion batteries

This work aims at improving the state-of-the art of lithium-ion battery (LIB) scientific know-how by presenting a new fabrication protocol for the separator element. A polypropylene (PP) separator is coated on both sides with 4A zeolite using PVDF as binder, and then plasma treated from both sides. The novel separator possesses a substantial higher LiPF6 electrolyte wettability, uptake and ionic conductivity compared to the sole plasma treated PP, PP coated with zeolite 4A on both sides and the PP itself. This behavior is ascribed to the partial disintegration of PVDF polymer upon plasma treatment and the creation of oxygenated groups on its particles and on the internal surface of the PP separator, together with substantial porosity increase of the latter. Using a Li(Ni0.8Co0.1Mn0.1)O2/separator/Li metal coin-cell assembly, it is shown that the cell performance in terms of rate capability is increased more than 30% at C rates of 0.1, 0.2, 0.5 and 1.0 with respect to the LIB constructed using the pristine PP separator.

City membrane training platforms. Health-promoting Spatial Instalations for Children and Teenagers

This article is inspired by the research on membrane training platforms, which has been conducted by the author for over two years. Currently, they are at the stage of building an experimental prototype in a real scale. These studies are the result of cooperation between the Wrocław University of Technology and the Center "Lunares Space - simulated space base" in Piła and the cooperation with the Academy of Physical Education in Wrocław regarding training devices. The membrane training platform is a spatial membrane, mesh, rope or belt installation, stretched elastically on a light and economical, spatial rod structure. A membrane is understood as a bi-curved surface, which is an unstable substrate, generating significant deformations under a load from a human walking on it - simulating walking "in deep snow" or in conditions of reduced gravity. The author's experience, gained in the course of this scientific work, gave him the idea of applying a similar idea to health-promoting urban installations intended for children and adolescents. The author presents this concept against the background of currently known devices with a similar function and character. At the same time, he shows arguments in favor of the implementation of this unconventional proposal, justifying in detail the need to develop this type of activity for children and adolescents, and even for the elderly. The presented proposals for new functional and spatial forms, intended for location in open space, are based on the use of low-cost, single-layer, octagonal and hexagonal bar systems, designed in such a way as to form closed systems, well absorbing forces from polypropylene nets, tapes or membranes stretched inside. According to the author, apart from their functional tasks, these objects could create intriguing, attractive architectural forms, enriching the city space.

Efficient naked eye sensing of tartrate/malate based on a Zn-Xylenol orange complex in water and membrane-based test strips

A new strategy for the real-time and naked-eye quantitative determination of tartrate and malate in aqueous solutions at physiological pH and with practical polypropylene membrane-based tests strips was developed by straightforward assembly Zn2+ ions and xylenol orange (3,3-bis [N,N-bis(carboxymethyl) aminomethyl]-o-cresolsulfonephthalein tetrasodium sodium salt, XO). The chromogenic dinuclear complex [Zn2 (XO) (H2O)x], 1 was studied in-deep as visual chemosensor for aliphatic dicarboxylates, oxyanions and nucleoside triphosphates. Complex 1 was highly sensitive and selective for visual detection of α-hydroxydicarboxylates such as tartrate and malate over non-hydroxylated dicarboxylates (oxalate, malonate, maleate, fumarate and succinate), citrate, oxyanions and nucleoside triphosphates in micromolar concentration range. Addition of tartrate and malate at pH = 7.4, gave rise to rapid color change from purple to golden with detection limit of 11 μmolL−1 for tartrate. On the basis of spectroscopic tools (UV–Vis, 1H NMR) and DFT calculations the efficient colorimetric change upon addition tartrate is attributed to a complexation process, through simultaneous coordination of the carboxylate and hydroxyl groups, to the Zn atoms with high affinity (log K = 5.08) and binding energy calculated in 8.7 kcal mol−1. The complex 1 is an order the magnitude more selective for tartrate than malate.Finally, the combination of complex 1 with polypropylene membranes negatively charged with carboxylate groups on surface generates flexible and cheap tests strips allows for the selective visual detection of tartrate in micromolar concentration range with good selectivity over other common dicarboxylates and oxyanions.

Simultaneous enhancement of nitrate removal flux and methane utilization efficiency in MBfR for aerobic methane oxidation coupled to denitrification by using an innovative scalable double-layer membrane

Endevours on the enhancement of nitrate removal efficiency during methane oxidation coupled with denitrification (AME-D) has always overlooked the role of membrane employed. It would be highly beneficial to enrich the biomass content and to manage biofilm on the membrane, in the utilization of methane and denitrification. In this study, an innovative and scalable double-layer membrane (DLM) was designed and prepared for a membrane biofilm reactor (MBfR), to simultaneously enhance nitrate removal flux and methane utilization efficiency during aerobic methane oxidation coupled with the denitrification (AME-D) process. The DLM allowed quick bacterial attachment and biomass accumulation for biofilm growth, which would be then self-regulated for well distribution of functional microbes on/within the DLM. Upon a high biofilm density of over 70 g-VSS m−2 achieved on the DLM, the methane utilization efficiency of the MBfR was enhanced significantly to over 1.3 times than the control MBfR with conventional polypropylene membrane. The MBfR employed DLM also demonstrated the maximum nitrate removal flux of 740 mg-NO3−-N m−2 d−1 that was approximately 1.64 times of that in control MBfR at continuous-mode operation. This DLM indeed favored the enrichment of Type II aerobic methanotrophs of Methylocystaceae, and methanol-utilization denitrifiers of Rhodocyclaceae that preferentially utilize methanol as the cross-feeding intermediates to promote the methane utilization efficiency, and thus to enhance the nitrate removal flux. These results raised from new designed DLM confirmed the importance of membrane surface properties on the effectiveness of MBfR, and offered great potential to address challenging problems of MBfRs during engineering application.

Electrospun Poly[poly(2,5-benzophenone)]bibenzopyrrolone/polyimide nanofiber membrane for high-temperature and strong-alkali supercapacitor

The separator is an important component for energy storage devices. At present, the membranes for supercapacitors are rare, especially the ones that work with an alkaline electrolyte. Herein, a type of flexible and highly porous polymer hybrid nanofiber membrane was prepared via a facile electrospinning process and served as a separator for supercapacitor’s work with strong alkaline electrolyte. As obtained, poly[poly(2,5-benzophenone)]bibenzopyrrolone/polyimide (PBPY/PI) membrane showed good thermal stability, high mechanical strength, large electrolyte uptake (452%), and fast ion conductivity (0.68 mS/cm). Moreover, PBPY/PI membrane exhibited excellent alkali resistance. The supercapacitor assembled with PBPY/PI membrane showed much better performance than those assembled with a commercial polypropylene membrane and electrospun polyimide nanofiber membrane and was found without capacitance loss after charge/discharge at 30 A/g for 10,000 cycles at 80 °C. The PBPY/PI membrane is a good candidate with temperature resistance and alkali resistance for high-performance supercapacitors.

A Poly(ethylene oxide)/Lithium bis(trifluoromethanesulfonyl)imide-Coated Polypropylene Membrane for a High-Loading Lithium-Sulfur Battery.

In lithium–sulfur cells, the dissolution and relocation of the liquid-state active material (polysulfides) lead to fast capacity fading and low Coulombic efficiency, resulting in poor long-term electrochemical stability. To solve this problem, we synthesize a composite using a gel polymer electrolyte and a separator as a functional membrane, coated with a layer of poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The PEO/LiTFSI-coated polypropylene membrane slows the diffusion of polysulfides and stabilizes the liquid-state active material within the cathode region of the cell, while allowing smooth lithium-ion transfer. The lithium-sulfur cells with the developed membrane demonstrate a high charge-storage capacity of 1212 mA∙h g−1, 981 mA∙h g−1, and 637 mA∙h g−1 at high sulfur loadings of 2 mg cm−2, 4 mg cm−2, and 6 mg cm−2, respectively, and maintains a high reversible capacity of 534 mA∙h g−1 after 200 cycles, proving its ability to block the irreversible diffusion of polysulfides and to maintain the stabilized polysulfides as the catholyte for improved electrochemical utilization and stability. As a comparison, reference and control cells fabricated using a PEO-coated polypropylene membrane and a regular separator, respectively, show a poor capacity of 662 mA∙h g−1 and a short cycle life of 50 cycles.