Publications by Chaoyang Feng
Desalination, 2002
Hollow-fiber membranes were prepared by the dry/wet spinning technique from polyvinylidene fluori... more Hollow-fiber membranes were prepared by the dry/wet spinning technique from polyvinylidene fluoride (PVDF) dope solutions containing the solvent N, N-dimethylacetamide and the non-solvent additive 1,2-ethanediol. Ethanol aqueous solution, 50% by volume, was used as internal and external coagulants. The effect of the non-solvent additive concentration on the morphological properties of the hollow fibers was studied in terms of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The pore size, the nodule size and the roughness parameters at the inner and outer surfaces of the hollow fibers were studied by AFM. The liquid entry pressure of water (LEPw) and the porosity of the hollow fibers were evaluated. The pore size was also determined by the gas permeation test and by the solute transport using ultrafiltration of polyethylene glycol (PEG) and polyethylene oxides (PEO). A comparative study was made between the membrane characteristics parameters obtained from the different characterization techniques.
Two approaches for preparing thin-film membranes from immiscible co-continuous polymer blends are... more Two approaches for preparing thin-film membranes from immiscible co-continuous polymer blends are presented. Approach 1 involves the melt blending of co-continuous polymer blends followed by the selective extraction of one of the phases and results in a microporous membrane material of high void volume. In that case, the pore size is defined by the phase size of one of the phases in the blend and hence composition, interfacial tension, viscosity ratio and other parameters influencing phase morphology can be used to control porosity. For that first approach, the blend system studied is high density polyethylene/polystyrene, compatibilized with SEBS (styrene-ethylene-buthylenestyrene) triblock copolymer. Both symmetric and asymmetric type membranes can be obtained. The symmetric membrane demonstrates porosity ranging from 80 to 230 nm. It is shown that extraction time can be used to develop asymmetry in the membrane and the effects of extraction time on the morphology, pore size distribution and performance are presented. High flux values and high apparent rejection factors estimated from permeability testing indicate that these materials could have potential in a variety of membrane applications.
Papers by Chaoyang Feng
BMC Ecology, 2016
Cadmium (Cd) is one of the most toxic heavy metals and has recently become a global concern. The ... more Cadmium (Cd) is one of the most toxic heavy metals and has recently become a global concern. The eco-toxicological effects of Cd in soilplant system are attracting more and more attention. Now many studies are mainly related to the effects of Cd on herbs and crops, and less information is on ornamental plants. Therefore in the present study, the eco-toxicological responses of five ornamental plants (Lonicera japonica Thunb., Weigela florida cv. Red Prince, Ginkgo biloba L., Parthenocissus quinquefolia and Parthenocissus semicordata) to Cd were investigated. Five Cd treatment concentrations (0, 5, 10, 25 and 50 mg L −1) were set. The results showed that the difference of physiological and biochemical characteristics in the plants under different Cd concentrations, such as antioxidant enzyme activity, chlorophyll contents and cell membrance permeability. The maintenance of high superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) activities in L. japonica was observed along with the increased Cd concentration, suggesting that the plant had better tolerance than another four plants, and had strong internal detoxification mechanisms to Cd stress. The results will provide an important scientific reference for remediation and management of Cd-contaminated soil.
The author has granted a nonexclusive license allowing Library and Archives Canada to reproduce, ... more The author has granted a nonexclusive license allowing Library and Archives Canada to reproduce, publish, archive, preserve, conserve, communicate to the public by telecommunication or on the Internet, loan, distribute and sell theses worldwide, for commercial or noncommercial purposes, in microform, paper, electronic and/or any other formats. L'auteur a accorde une licence non exclusive permettant a la Bibliotheque et Archives Canada de reproduire, publier, archiver, sauvegarder, conserver, transmettre au public par telecommunication ou par I'lnternet, preter, distribuer et vendre des theses partout dans le monde, a des fins commerciales ou autres, sur support microforme, papier, electronique et/ou autres formats.
Journal of Applied Polymer Science, 2006
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Journal of Membrane Science, 2001
The morphology of the inner and the outer surfaces of polyetherimide (PEI) hollow fibers were stu... more The morphology of the inner and the outer surfaces of polyetherimide (PEI) hollow fibers were studied by atomic force microscopy (AFM). The effect of the spinning conditions, namely, the bore liquid flow rate on the surface characteristics was investigated. Bore liquid flow rate was varied between 0.1 and 0.4 ml/min. The pore sizes at the outer and inner surfaces of the hollow fibers were affected by the bore liquid flow rates. Bore liquid flow rates also influenced the ultrafiltration performances of the hollow fiber membranes. The alignment of nodule aggregates to the direction of bore liquid flow was observed.
Journal of Membrane Science, 2001
All-inorganic membranes that are composed entirely of sepiolite, a naturally occurring Mg-silicat... more All-inorganic membranes that are composed entirely of sepiolite, a naturally occurring Mg-silicate clay mineral, have been fabricated. Pinhole-free, self-bonded membranes with transecting pores in the large mesopore to macropore size range were obtained. Characterization of the thermally treated membranes by PXRD has revealed that the sepiolite is transformed into ‘sepiolite anhydride’ by heating in air at elevated temperatures. SEM studies have subsequently shown that the air dried membranes do not develop cracks or other similar flaws even after being subjected to temperatures as high as 750°C for several hours. Calcined sepiolite membranes were tested for the ultrafiltration of high molecular weight poly(ethylene glycol) and poly(ethylene oxide) molecules in aqueous solution. The MWCO was determined to be close to 300 000 for all of the membranes that were studied in the preliminary tests. Significant membrane fouling was observed, which dramatically reduced the permeation flux r...
Journal of Membrane Science, 2007
This paper explores the viability of developing high surface area pre-filters through electrospin... more This paper explores the viability of developing high surface area pre-filters through electrospinning. Pre-filters are regularly used in removing particulate contaminants that can have a deleterious effect on downstream membrane elements such as ultrafiltration and nanofiltration. They should possess high internal surface area and thus sub-micron size fibers are ideal. In this study, polysulfone nanofibers were electrospun into membranes and their ability to remove micro-particles from solution was investigated. The nanofibrous membranes possess high porosity together with high surface area to produce high flux pre-filters with high loading capacity. The membrane had a bubble-point of 4.6 μm and was able to remove above 99% of 10, 8 and 7 μm particles without any permanent fouling. However, the membrane was observed to foul irreversibly by 2 and 1 μm particles with a ‘cake-layer’ forming on the membrane surface. Below 1 μm, the membrane behaved as a depth filter with 0.5 and 0.1 μm ...
Desalination, 2003
Polyethersulfone (PES) hollow-fiber membranes were prepared by the dry-wet spinning method and th... more Polyethersulfone (PES) hollow-fiber membranes were prepared by the dry-wet spinning method and then heated in an oven at different temperatures to investigate the effect of heat-treatment on their ultrafiltration performance. It was found that the hollow-fiber membranes shrank by heat treatment, as evidenced by a decrease in flux and an increase in solute separation, although there was no visible change in the hollow-fiber dimension. The best results were obtained when the hollow fibers were heated at 150°C. A further investigation was made on the effect of the heating period, while the temperature was fixed to 150°C. It was found that the best combination of the temperature and the heating period was 150°C and 5 min.
Journal of membrane science, 1994
Separation and …, 2004
Dense (homogeneous) membranes were prepared from poly (2, 6-dimethyl-1, 4-phenylene oxide)(PPO) b... more Dense (homogeneous) membranes were prepared from poly (2, 6-dimethyl-1, 4-phenylene oxide)(PPO) by using 1, 1, 2-trichloroethylene as a solvent at 25, 35, 45, 55 and 65° C evaporation temperature. The effect of temperature used for evaporation of solvent on the ...
Journal of Membrane Science, 2004
Hollow fiber membranes for hemodialysis were prepared from polyethersulfone (PES) and poly(vinyl ... more Hollow fiber membranes for hemodialysis were prepared from polyethersulfone (PES) and poly(vinyl pyrrolidone) (PVP) (PES/PVP=18/3 and 18/6 by weight) solution in N,N-dimethylacetamide by the dry wet spinning method. Hollow fibers were then heated either in hot water (95 °C for 30 min) or in air (150 °C for 5 min). These membranes were characterized by ultrafiltering dextrans of different molecular weights (200 ppm in water) at room temperature and an operating pressure of 5 psig. It was observed that the water flux of the hollow fiber increased significantly when heat-treated in water, while decreased when heat-treated in air. On the other hand, molecular weight cut-off (MWCO) of the hollow fiber increased slightly when heat-treated in water, while decreased drastically when heat-treated in air. The morphology of the surfaces of the hollow fibers was studied by atomic force microscope (AFM) in terms of surface roughness. The roughness of both inner and outer surface decreased upon h...
Horticulture Research, 2021
Sugars, especially glucose and fructose, contribute to the taste and quality of tomato fruits. Th... more Sugars, especially glucose and fructose, contribute to the taste and quality of tomato fruits. These compounds are translocated from the leaves to the fruits and then unloaded into the fruits by various sugar transporters at the plasma membrane. SWEETs, are sugar transporters that regulate sugar efflux independently of energy or pH. To date, the role of SWEETs in tomato has received very little attention. In this study, we performed functional analysis of SlSWEET7a and SlSWEET14 to gain insight into the regulation of sugar transport and storage in tomato fruits. SlSWEET7a and SlSWEET14 were mainly expressed in peduncles, vascular bundles, and seeds. Both SlSWEET7a and SlSWEET14 are plasma membrane-localized proteins that transport fructose, glucose, and sucrose. Apart from the resulting increase in mature fruit sugar content, silencing SlSWEET7a or SlSWEET14 resulted in taller plants and larger fruits (in SlSWEET7a -silenced lines). We also found that invertase activity and gene exp...
Journal of Membrane Science, 2001
Novel inorganic membranes were prepared from clay (sepiolite) suspensions, which were formed by d... more Novel inorganic membranes were prepared from clay (sepiolite) suspensions, which were formed by dispersing clay particles in water either by applying ultrasonic wave or by magnetic stirring. Films can be formed easily from such suspensions due to fibrous nature of sepiolite. Thus, this offers a method much simpler than the conventional sol–gel method. The membranes were further tested for ultrafiltration of polyethylene glycol and polyethylene oxide solutes of different molecular weights. It was found that the correlation between the separation and the Einstein–Stokes radius of solute fits the log-normal distribution very well. The mean pore size of 23–26 nm and the standard deviation of 1.91–2.04 were obtained from the above correlation. It was also found that the mean pore size and the pore size distribution did not depend very much on the membrane preparation method.
Transportation Research Part D: Transport and Environment
Polymer, 2002
Polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared using the solvent spinning me... more Polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared using the solvent spinning method. N,N-dimethylacetamide was the solvent and ethylene glycol was employed as non-solvent additive. The effect of the concentration of ethylene glycol in the PVDF spinning solution as well as the effect of ethanol either in the internal or the external coagulant on the morphology of the hollow fibers was investigated. The prepared membranes were characterized in terms of the liquid entry pressure of water measurements, the gas permeation tests, the scanning electron microscopy, the atomic force microscopy, and the solute transport experiments. Ultrafiltration experiments were conducted using polyethylene glycol and polyethylene oxides of different molecular weights cut-off as solutes. A comparative analysis was made between the membrane characteristic parameters obtained from the different characterization techniques.
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Publications by Chaoyang Feng
Papers by Chaoyang Feng