Mixed Cellulose Ester Membrane Research Articles

Diffusion studies of Diclofenac sodium topical gel using Different Synthetic Membranes

Diffusion of the drug from a formulation and across membranes simulating biological cell membranes is the major concern to be taken under consideration while formulating any dosage form. This brings on a major role in those which are to be applied along the skin, since drug needs to first release from the polymer matrix then enter systemic circulation via the skin. The purpose of the study was to compare the dispersion rate of diclofenac sodium from the gel formulation across five different synthetic membranes. In this work, we worked to measure the drug release profile using and using various kinetic models, found out the mechanism of diffusion through membranes on the drug release profile. The evaluation was done by an in vitro drug release system in the laboratory using Franz diffusion cell. Diclofenac sodium topical gel was formulated using carbopol 934 as the gel-forming agent(1). Diffusion studies showed that the highest release was given by mixed cellulose ester membrane (83.16%) in 71.5 hrs. Followed by cellulose acetate membrane (78.1%), cellulose acetate nitrate membrane (75.6), polyether sulphone membrane (70.8%) and sigma cellulose membrane (56.39%). Drug release followed first-order kinetics and Higuchi's model of diffusion from all the membranes with case II and super case II transport mechanisms

Preparation and Characterization of Sulfated Cellulose Nanocrystalline and its Composite Membrane for Removal of Tetracycline Hydrochloride in Water

The removal of antibiotic pollutants remaining in the environmental media has been a big challenge nowadays. Herein, we report a facile and green approach to fabricate an eco‐friendly composite membrane without addition of any toxic polymers or chemical cross‐linking agents to effectively remove the tetracycline hydrochloride in Water. Firstly, the sulfated cellulose nanocrystalline (CNC) was obtained via hydrolysis of sulfuric acid by using microcrystalline cellulose (MCC) as raw material under ultrasonic condition. The as‐prepared CNC has a nanowhisker dimension with 200.2 ± 110.2 nm in length, 15.7 ± 9.3 nm in width, and 7.2 ± 3.1 nm in height. The obtained CNC is cellulose type I as determined by X‐ray diffraction (XRD), while its crystallinity index (CrI) can reach 82.3%. Then, the composite membrane derived from the obtained CNC and commercial mixed cellulose ester (MCE) membrane was facilely prepared through vacuum dewatering process, which is applied to remove tetracycline hydrochloride (Th) in solution. The results showed that the removal efficiency of Th through the neat MCE was only 28 ± 4%, while it could be improved to 58 ± 5% and 89 ± 1%, respectively, by filtering through composite membranes with different contents of CNC deposition. Such effect is derived from the combine factors based on both steric hindrance (sieving) and electrostatic interaction (Donnan) effect of the composite membranes. The development of related CNC materials and composite fabrication processes is in favor of cost‐effective and “green” polymer composites for the remediation of increasing antibiotic pollution and the purification of contaminated water nowadays.

Inactivation of bacterial and fungal spores by UV irradiation and gaseous iodine treatment applied to air handling filters

Exposure to viable bacterial and fungal spores re-aerosolized from air handling filters may create a major health risk. Assessing and controlling this exposure have been of interest to the bio-defense and indoor air quality communities. Methods are being developed for inactivating stress-resistant viable microorganisms collected on ventilation filters. Here we investigated the inactivation of spores of Bacillus thuringiensis var. kurstaki (Btk), a recognized simulant for B. antracis, and Aspergillus fumigatus, a common opportunistic pathogen used as an indicator for indoor air quality. The viability change was measured on filters treated with ultraviolet (UV) irradiation and gaseous iodine. The spores were collected on high-efficiency particulate air (HEPA) and non-HEPA filters, both flattened for testing purposes to represent “surface” filters. A mixed cellulose ester (MCE) membrane filter was also tested as a reference. Additionally, a commercial HEPA unit with a deep-bed (non-flattened) filter was tested. Combined treatments of Btk spores with UV and iodine on MCE filter produced a synergistic inactivation effect. No similar synergy was observed for A. fumigatus. For spores collected on an MCE filter, the inactivation effect was about an order of magnitude greater for Btk compared to A. fumigatus. The filter type was found to be an important factor affecting the inactivation of Btk spores while it was not as influential for A. fumigatus. Overall, the combined effect of UV irradiation and gaseous iodine on viable bacterial and fungal spores collected on flat filters was found to be potent. The benefit of either simultaneous or sequential treatment was much lower for Btk spores embedded inside the deep-bed (non-flattened) HEPA filter, but for A. fumigatus the inactivation on flattened and non-flattened HEPA filters was comparable. For both species, applying UV first and gaseous iodine second produced significantly higher inactivation than when applying them simultaneously or in an opposite sequence.

Functionalized carbon materials for efficient solar steam and electricity generation

Abstract A low-cost, reusable, efficient evaporation system, composed of functionalized carbon black (FCB), has been developed for solar steam and electricity generation. The high evaporation efficiency of 85% under one sun illumination results from the specially designed structures, including FCB as a broadband light absorbing material, a porous hydrophilic mixed cellulose esters (MCE) membrane as a substrate, an airlaid paper as a water path, and a polystyrene foam (PSF) as a thermal insulation. The FCB/MCE film is used as an efficient sunlight absorber (>96%), which is connected by polyethylenimine (PEI). Cycling tests demonstrate that the evaporation system still maintains a stable performance over 14 cycles under the same illumination conditions. The evaporation system can be used not only for preparing clean and pure water but also for solar desalination. More importantly, the evaporation system from carbon materials can reliably generate a sustained voltage of 5 mV at a light density of 1 kWm−2, and it enhances with the increase of the light density.

Synchronous steam generation and photodegradation for clean water generation based on localized solar energy harvesting

Solving the problems of water shortage and water pollution is a vital challenge for sustainable development. Different strategies, such as photodegradation, solar distillation, and filtration, have been proposed to purify contaminated water and generate clean water. Energy-efficient clean water generation technologies play a critical role in augmenting freshwater resources. Solar energy has the potential to increase sustainable clean water production, which is a key facet of the water-energy nexus. In this study, a novel strategy to generate clean water was realized via a synchronous solar distillation and photodegradation technology based on localized solar energy harvesting using a trifunctional solar energy absorbing membrane. The membrane is composited of mixed cellulose ester (MCE) membrane, hedgehog-like hierarchical ZnO particles (HP) and gold nanoparticles (Au NPs). By floating the MCE/HP/Au membrane on rhodamine B contaminated water, the steam generation rate could reach up to ∼8.70 kg/(m2·h) and the concentration of organic pollutant in the residual water could be reduced to ∼30% within two hours’ solar light irradiation. It was found that the coupling between the hierarchical HPs and plasmonic Au NPs could enhance the solar light absorption and energy conversion for photodegradation and thermal generation. This work provides a new strategy for the high efficient utilization of solar energy for the clean water generation.

Sampling, Sorting, and Characterizing Microplastics in Aquatic Environments with High Suspended Sediment Loads and Large Floating Debris

The ubiquitous presence of plastic debris in the ocean is widely recognized by the public, scientific communities, and government agencies. However, only recently have microplastics in freshwater systems, such as rivers and lakes, been quantified. Microplastic sampling at the surface usually consists of deploying drift nets behind either a stationary or moving boat, which limits the sampling to environments with low levels of suspended sediments and floating or submerged debris. Previous studies that employed drift nets to collect microplastic debris typically used nets with ≥300 µm mesh size, allowing plastic debris (particles and fibers) below this size to pass through the net and elude quantification. The protocol detailed here enables: 1) sample collection in environments with high suspended loads and floating or submerged debris and 2) the capture and quantification of microplastic particles and fibers <300 µm. Water samples were collected using a peristaltic pump in low-density polyethylene (PE) containers to be stored before filtering and analysis in the lab. Filtration was done with a custom-made microplastic filtration device containing detachable union joints that housed nylon mesh sieves and mixed cellulose ester membrane filters. Mesh sieves and membrane filters were examined with a stereomicroscope to quantify and separate microplastic particulates and fibers. These materials were then examined using a micro-attenuated total reflectance Fourier transform infrared spectrometer (micro ATR-FTIR) to determine microplastic polymer type. Recovery was measured by spiking samples using blue PE particulates and green nylon fibers; percent recovery was determined to be 100% for particulates and 92% for fibers. This protocol will guide similar studies on microplastics in high velocity rivers with high concentrations of sediment. With simple modifications to the peristaltic pump and filtration device, users can collect and analyze various sample volumes and particulate sizes.

A mussel inspired highly stable graphene oxide membrane for efficient oil-in-water emulsions separation

In this work, a simple coating method was employed to prepare a highly stable graphene oxide (GO) membrane for oil-in-water emulsions separation. By using mussel inspired polydopamine (PDA) as covalent linker, mixed cellulose ester membrane (MCEM) was successfully modified with PDA layer by self-polymerize, then GO nanosheets were attracted onto PDA/MCEM by simple vacuum filtration method, lead to the formation of GO/PDA/MCEM. The as-prepared membranes were characterized by FT-IR, TEM, AFM and contact angle, respectively. The results indicated that GO layer was uniformly coated on the support, and GO/PDA/MCEM had a rough surface and good hydrophilic property. Attributing to both the high adhesive ability of PDA and possible covalent interaction between GO and PDA, GO/PDA/MCEM was highly stable by being immersed in water environment for 12 h. GO/PDA/MCEM was employed to separate Tween-80 stabilized oil-in-water emulsions. The results showed that the prepared GO/PDA/MCEM had effective separation performance and reusability in the oil-in-water emulsions filtration for four cycles. This study provided a feasible, simple and economical way to prepare a highly stable GO-based membrane for oil-in-water emulsions filtration.

Super-hydrophilic copper sulfide films as light absorbers for efficient solar steam generation under one sun illumination

Solar steam technology is one of the simplest, most direct and effective ways to harness solar energy through water evaporation. Here, we report the development using super-hydrophilic copper sulfide (CuS) films with double-layer structures as light absorbers for solar steam generation. In the double-layer structure system, a porous mixed cellulose ester (MCE) membrane is used as a supporting layer, which enables water to get into the CuS light absorbers through a capillary action to provide continuous water during solar steam generation. The super-hydrophilic property of the double-layer system (CuS/MCE) leads to a thinner water film close to the air-water interface where the surface temperature is sufficiently high, leading to more efficient evaporation (∼80 ± 2.5%) under one sun illumination. Furthermore, the evaporation efficiencies still keep a steady value after 15 cycles of testing. The super-hydrophilic CuS film is promising for practical application in water purification and evaporation as a light absorption material.

Fabrication of highly flexible transparent conductive film with a sandwich-structure consisted of graphene/silver nanowire/graphene

Highly flexible transparent conductive films with a sandwich structure consisted of graphene/silver nanowires (AgNWs)/graphene (GAG) were fabricated by a facile method of combining vacuum filtration with acetone vapor treatment. This approach involves two processes: the vacuum filtration of the dispersion solution of the graphene, the AgNWs, and the graphene in turn through a porous mixed cellulose esters membrane (MCEM); the treatment of MCEM using acetone vapor to form a transparent GAG film. The GAG film has sheet resistances of as low as ∼4.6 Ω/□ at the transmittance of ∼81% at 550 nm, and exhibited impressive mechanical robustness against bending, scratching and adhering. This excellent performance can be attributed to the superior properties of the high-quality graphene and its roles of not only connecting the discrete AgNWs but also binding them tightly by its restacking characteristic in a sandwich-structured form. The results suggest that the GAG film has potential applications in flexible electronic and optoelectronic devices.

On-site Determination of Trace Arsenic by Reflection-Absorption Colorimetry of Molybdenum Blue Collected on a Membrane Filter.

An on-site determination method for trace arsenic has been developed by collecting it as molybdenum blue (MB) in the presence of tetradecyldimethylbenzylammonium chloride on a mixed cellulose ester membrane filter and by measuring reflection absorbance (RA) of MB on the filter using a laboratory-made palm-top size reflection-absorbance colorimeter with a red light-emitting diode. The value of RA was proportional to the amount of arsenic up to 0.5 μg with a detection limit of 0.01 μg. The proposed method was successfully applied to soil extract and hot-spring water samples.

Sulfhydryl-functionalised magnetic nanoparticles as sorbent in dispersive solid-phase extraction for the rapid enrichment of mercury species from natural water samples

ABSTRACTThe sulfhydryl-functionalised core-shell Fe3O4@SiO2 magnetic nanoparticles (Fe3O4@SiO2–RSH MNPs)-based dispersive solid-phase extraction method was developed. The goal of this method is the extraction of mercury species from natural water samples. An interesting aspect of the method is that, thanks to the spontaneously aggregate, the MNPs with a sub-30-nm-size range could be fast and efficiently extracted by 0.45 μm pore size mixed cellulose esters membrane filter. Thus, the elution step can be conducted by passing small amounts eluent through the MNPs on the membrane. It is also found that addition of Ag+ to water sample could improve the elution efficiency, and furthermore, minimises the matrix effects during the extraction of mercury species from natural water samples. The feasibility of the method was studied, and extraction efficiency was evaluated. The results showed that, calculated at 5 ng/L spiked concentration levels, absolute recoveries were 89.4%, 91.9% and 64.2%, and enrichment factors (EFs) were 596, 613 and 428, for inorganic mercury, methylmercury and ethylmercury, respectively. The high EFs were achieved in 5 min of overall extraction time. The method was applied to groundwater and river water samples. The results showed that its suitability for use in fast extracting trace levels of mercury species from natural water samples.

Effect of membrane morphology on rising properties of filtration resistance in microfiltration of dilute colloids

The effect of membrane morphology on the flux decline behaviors in dead‐end unstirred microfiltration of very dilute colloids of polystyrene latex was examined using mixed cellulose ester and cellulose acetate membranes with interconnected tortuous pores and track‐etched polycarbonate membranes with uniform straight cylindrical pores. The plots of reciprocal filtration rate against the filtrate volume per unit membrane area for the former two membranes exhibit concave downward curves in the initial period when the membrane pore blocking is significant, whereas the plot for the latter shows a concave upward curve in that period. The former results were described by a serial resistance model consisting of the initial membrane pore blocking followed by filter cake growth, and the latter was represented by a parallel resistance model in which the pore blocking and cake growth develop simultaneously from the beginning of filtration. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3511–3522, 2017

Novel resolution-contrast method employed for investigating electron transfer mechanism of the mixed bacteria microbial fuel cell

Due to the synergy existing in mixed bacteria, electricity-generation performances of the mixed bacteria microbial fuel cell (m-MFC) are better than that of the pure bacteria microbial fuel cell (p-MFC). It is necessary to explore the electron transfer mechanisms of the m-MFC to further improve electricity generation. In this study, a facile “resolution-contrast” method was employed in the two-chamber m-MFC to investigate the electron transfer mechanism using mixed bacteria as the anodic inoculums. The anode was wrapped with a mixed cellulose esters membrane to eliminate the effects of direct extracellular electron transport, while the mediator electron transport was investigated by electrochemical methods. The results showed that both transfer methods existed simultaneously in the m-MFC. The main exoelectrogens were Escherichia coli, Pseudomonas aeruginosa, and Brevundimonas diminuta, and the main redox mediators included 1-hydroxyanthracene-9,10-dione, phenazine-1-carboxylic acid and 2,4-diacetyl phloroglucinol.

Trace Metals Derived from Electronic Cigarette (ECIG) Generated Aerosol: Potential Problem of ECIG Devices That Contain Nickel.

Introduction: ECIGs are currently under scrutiny concerning their safety, particularly in reference to the impact ECIG liquids (E-liquids) have on human health. One concern is that aerosolized E-liquids contain trace metals that could become trapped in respiratory tissues and induce pathology.Methods: To mimic this trapping, peristaltic pumps were used to generate and transport aerosol onto mixed cellulose ester (MCE) membranes where aluminum (Al), arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) were subsequently captured and quantified. The presence of trace metals on unexposed MCE membranes and on MCE membranes exposed to mainstream smoke served as control and comparison, respectively. The presence of these metals was also determined from the E-liquid before aerosolization and untouched by the ECIG device. All metals were quantified using ICP-MS. The ECIG core assembly was analyzed using scanning electron microscopy with elemental analysis capability.Results: The contents (μg) of Al, As, Cd, Cu, Fe, Mn, Ni, Pb, and Zn on control MCE membranes were 1.2 ± 0.2, 0.050 ± 0.002, 0.047 ± 0.003, 0.05 ± 0.01, 0.001 ± 0.001, 0.16 ± 0.04, 0.005 ± 0.003, 0.014 ± 0.006, and 0.09 ± 0.02, respectively. The contents of all trace metals on MCE membranes exposed to aerosol were similar to controls, except Ni which was significantly (p < 0.01) higher (0.024 ± 0.004 μg). In contrast, contents of Al, As, Fe, Mn, and Zn on MCE membranes exposed to smoke were significantly higher (p < 0.05) than controls. The contents of Al, As, Cu, Fe, and Mn on smoke-exposed MCE membranes were also significantly higher (p < 0.05) than their content on aerosol-exposed membranes. The contents per cigarette equivalent of metals in E-liquid before aerosolization were negligible compared to amounts of aerosolized E-liquid, except for Fe (0.002 μg before and 0.001 μg after). Elemental analysis of the core assembly reveals the presence of several of these trace metals, especially Al, Fe, Ni, and Zn.Conclusions: In general, from the single ECIG-device/E-liquid combination used, the amount of trace metals from ECIG-generated aerosol are lower than in traditional mainstream smoke, Only Ni in the ECIG-generated aerosol was higher than control. The most probable source of Ni in this aerosol is the core assembly.

INVESTIGATION OF PRONIOSOMES GEL AS A PROMISING CARRIER FOR TRANSDERMAL DELIVERY OF GLIMEPIRIDE

Objectives: The aim of the study was to develop a proniosomal carrier system that is capable of efficiently delivering entrapped glimepiride over an extended period of time for the treatment of type 2 diabetes. Methods: Proniosomal gels were developed based on span 60 with and without cholesterol. The entrapment efficiency of drug inside niosomes developed from hydration of the proniosomes gel was also characterized. The in vitro release and skin permeation of glimepiride from various proniosomes gel formulations were investigated. The stability studies were performed at 4°C and at room temperature. Results: The maximum entrapment efficiency was obtained when the cholesterol concentration was 10% of total lipid (90.02%). In vitro release through mixed cellulose ester membrane showed sustained release of drug from proniosomes gels. In vitro drug permeation across rabbit skin revealed improved drug permeation and higher transdermal flux with proniosomes gels compared to hydro-alcoholic gel of drug. Also, good physical stability was also achieved with proniosomes gels. Kinetics of in vitro skin permeation showed diffusion model of drug release from formulations. Conclusion: The study proved that the concentration of cholesterol had great influence on the properties of proniosomes gels. Hence, proniosomes preparation containing 10% cholesterol can significantly increase trans-epidermal flux and prolong the release of glimepiride. Peer Review History: Article received on- 1 November 2016, Revised on- 3 December Accepted on- 29 December, Available online 15 January 2017 Academic Editor: Dr. Asia Selman Abdullah, Al-Razi university, Department of Pharmacy, Yemen, asia_abdullah65@yahoo.com Received file: Reviewer's Comments: Average Peer review marks at initial stage: 5.5/10 Average Peer review marks at publication stage: 7.5/10 Reviewer(s) detail: Dr. Heba M. Abd El-Azim, Damanhour University, Egypt, h_m_abdelazim@hotmail.com Dr. Mohamed Derbali, Faculty of Pharmacy, Monastir, Tunisia, mohamed.edderbali@gmail.com Similar Articles: PREPARATION AND CHARACTERIZATION OF TOLTERODINE TARTRATE PRONIOSOMES

Reusable reduced graphene oxide based double-layer system modified by polyethylenimine for solar steam generation

Surface plasmon resonance effects of nanoparticles, generating local hot spots in a water-air interface under sunlight irradiation to drive water into steam, can realize the highly efficient conversion of solar energy. Here, we develop a novel solar steam generation system with double-layer structures, of which the top reduced graphene oxide (rGO) sheets as a light-to-heat conversion layer and the bottom mixed cellulose esters (MCE) membrane as a porous supporting layer. The double-layer system (rGO/MCE) connected by polyethylenimine can convert the absorbed solar energy to heat energy at a water-air interface to enable efficient evaporation (∼60%) under only 1 kW/m2 irradiation. Contrast experiments under a light density of 4 kW/m2 showed that the rGO/MCE membrane achieved the highest evaporation efficiency of 71.8 ± 3%, and its evaporation rate is 4.3 times higher than that of pure water. Cycling tests confirmed that the system still maintained a stable performance over 15 cycles under same illumination conditions. Excellent mechanical stability, low cost, simple preparation and reusability of the rGO/MCE membrane are suitable for a wide range of practical applications in large-scale solar steam generation, sterilization of waste, seawater desalination.

Collagen-graft mixed cellulose esters membrane maintains undifferentiated morphology and markers of potential pluripotency in feeder-free culture of induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) are unique and unlimited clinical sources of stem cell therapy for the regenerative medicine. Feeder layer preparation is an important step for iPSCs production, which is expensive, time-consuming and requires conversance. In the present study, we investigated the maintenance of pluripotency, and stemness of the iPSCs through feeder-free culture on a collagen-grafted Mixed Cellulose Esters membrane (MCE-COL) after three passages during twelve days. Results have demonstrated that the iPSCs cultured on MCE-COL membrane had a fine, typical undifferentiated morphology, increased proliferation rate and significant multi-lineage differentiation potential. Alkaline phosphatase (ALP) staining and pluripotency associated gene markers expression further confirmed that iPSCs cultured on the surface of MCE-COL had more ALP positive colonies and enhanced expression of Oct-4, Nanog, Sox-2 and ALP in comparison with MCE and control groups. Since MCE-COL membrane has three dimensional structure and bioactivity, it has the potential for usage in the feeder-free culture of iPSCs, and could be a suitable candidate to use as a feeder layer in stem cells preparation.

PVC 여과지를 이용한 금속 분석방법에 대한 정확도와 정밀도 평가

Objectives: This study was conducted to evaluate the accuracy and precision of airborne metal analysis using polyvinyl chloride(PVC) membrane filter by pretreatment methods. Methods: A total of 75 spiked PVC samples for Cr, Fe and Mn ranged from 6 ug/sample to 40 ug/sample were used to evaluate recovery rates for three pretreatment methods: acid extraction, hot plate ashing and microwave digestion. For Mn, an additional 75 spiked mixed cellulose ester(MCE) membrane filters were analysed to compare the recovery rates of PVC samples. All samples were analysed with an inductively coupled plasma optical emission spectrometer(ICP-OES) and manganese samples were additionally analyzed by atomic absorption spectrometer(AAS). Results: The overall mean recovery rates of PVC samples for Cr, Fe and Mn were 90% or higher regardless of pretreatment methods, but there were statistically significant differences in recovery rates for Cr(p<0.05) and Mn(p<0.01) samples by pretreatment methods. The biases and the coefficient variations of PVC samples for three metals pretreated with three kinds of pretreatment methods ranged from 1.7% to 4.7% and from 1.6% to 6.5%, respectively. The manganese PVC samples pretreated by microwave digestion and analyzed with ICP-OES had the lowest bias at 1.9% and also showed lower bias than the bias for MCE samples, 2.7%. Conclusions: In order to accurately analyze the metals sampled with PVC membrane filters, microwave digestion and ICP-OES can be recommended.

Measurement of airborne asbestos levels in high traffic areas of Shiraz, Iran, in winter 2014

Aims: Levels of asbestos fibers in ambient air of dense areas of Shiraz, Iran, were monitored in winter 2014. Materials and Methods: Sampling was carried out by directing air flow to a mixed cellulose ester membrane filter mounted on an open-faced filter holder using a low flow sampling pump. Fiber counting on the filters was conducted using both phase contrast microscopy (PCM) method to determine total fibers and scanning electron microscopy (SEM) method to identify nonasbestos from asbestos fibers. Results: The average concentration of asbestos fibers in the ambient air of the study in different areas of Shiraz were 1.18 ± 0.28 PCM f/L and 13.64 ± 2.87 SEM f/L, in which a maximum level was measured in Valiasr square (1.89 ± 0.54 PCM f/L [20.37 ± 5.55 SEM f/L]), and that of in Moallem square was in minimum (1.05 ± 0.47 PCM f/L [12.24 ± 3.04 SEM f/L]). Conclusions: The averages of asbestos fibers in all sampling points were higher than the WHO suggested standards for ambient air (0.05 PCM f/L, 2.2 SEM f/L). This may be attributed to the frequent occurrence of heavy traffic, the existence of relevant industries in and around the city, and the topographic characteristics of the city. Therefore, immediate courses of action such as product substitution, traffic smoothing, and industrial sites relocating should be taken to eliminate asbestos fibers emission.

Demonstration of a gas separator composed of Knudsen pumps

A model gas separator composed of two Knudsen pumps is fabricated. The only energy source of the gas separator is the temperature difference up to 100 K. The temperature difference induces the thermal transpiration flow of the rarefied gas in the micro-pores of the mixed cellulose ester (MCE) membrane in the Knudsen pump. The gas flow and the resultant pressure variation are used to separate the feed mixture of helium and neon gases into two gases having different gas compositions. The fabricated model gas separator, which has 27 cm2 total membrane area, induces 5–6% difference of mole percentage between two product gases under the flow rate 5 sccm of the feed gas. The operation of the gas separator is continuous since the present device as well as the Knudsen pump requires no moving parts.