Papers by Keyword: Porous Membrane

Abstract: The scarcity of drinking water is currently a critical issue in many parts of the world. Providing clean/urgent longer limited to natural sources. Wastewater treatment has become an urgent necessity in many countries, particularly in the Middle East and North African regions characterized by a desert climate. Hence, the development of effective methods for wastewater treatment is vital to overcome this water shortage. The present study attempts to explore the use of local clay from the United Arab Emirates (UAE) to prepare porous ceramic membranes (flat disk shape) for the purpose of removing toxic heavy metals from contaminated water. Two types of ceramic membranes were prepared by powder metallurgy method; the first type was prepared by uniaxial compression of the clay powder with particle size ≤ 250 μm, followed by sintering. The second type of membrane was composed of an activated carbon/clay powder mixture at different ratios (0.5%, 3% w/w). The activated carbon was used as an agent to form porosity in the plain clay membrane. The activated carbon was found to affect the final characteristics of the flat disk membranes sintered at 1000°C. 3% w/w activated carbon/clay powder was found to induce 19% porosity in the flat disc. The flat disc membranes were also characterized by X-ray diffraction, and scanning electron microscopy, X-ray fluorescence. The plain clay and 3% w/w activated carbon membranes were tested for their efficiency for water permeation. The results proved that the UAE clay could be considered as a promising material for the fabrication of ceramic membranes for prospective use in the removal of water contaminated with heavy metals.

Abstract: The operating efficiency of asymmetric porous and composite membranes with a thin non-porous selective layer was compared in the processes of CO₂ absorption and desorption in gas-liquid membrane contactors using aqueous solutions of monoethanolamine (MEA) with low concentration (<14 %). Composite membranes were prepared by direct deposition of poly (1-trimethylsilyl-1-propyne) (PTMSP) in a hollow fiber membrane module. The effects of gas flow rate and MEA solvent linear velocity on the CO₂ mass transfer were evaluated. Porous membranes were shown to be more effective in the process of CO₂ absorption, because they allow to remove more than 90 % of CO₂ from the gas mixture during one pass of the solvent through the contactor. Composite membranes were more promising for CO₂ desorption, since they provide half as much of the solvent vapor losses with comparable desorbed CO₂ fluxes (0.12-(STP)/(m²·h)). The contributions of membrane and liquid phase to the overall mass transfer resistance during the CO₂ absorption process were estimated. It was demonstrated that deposition of a thin selective layer from a highly permeable PTMSP with a thickness of only 3 μm increases the membrane contribution to the total mass transfer resistance from 10-20 % to 60-80 %.

Abstract: Polymer membranes with fixed pore size or narrow pore size distribution can be used for special separation. However, polymer membranes prepared by conventional method usually have wide pore size distribution and the pore size is hard to control. Here we prepared a porous polymer membrane with uniform pore size via spraying a blend of polystyrene (PS) and polyethylene oxide (PEO) on a filtration paper. Dissolving the water-soluble component (PEO) forms the pore and varying the ratios of PEO in the blend controls the pore size. The pore size and size distribution are also affected by processing parameters, such as the flow rate of solution and carrier gas, and gap length. The morphologies of the membrane are observed using scanning electron microscopy (SEM). The novel polymer membrane with controllable and uniform pore size will be used for the separation of solutes with predictable sizes.

Abstract: A novel method called hot-pressing method of preparing porous membrane was firstly reported in this paper. Compared with other method such as none-solvent induced phase separation method, melt-spinning and cold-stretching method, the hot-pressing method was simple, easy to operate, environment-friendly. First, a silica needle arrays (SNA) template with a hexagonal close-packed structure was prepared by TAFE method. Then the SNA template was used to press into the plastic wrap in order to form the uniform pores. After that, a uniform porous membrane was prepared. The diameter of the porous membrane was affected by the pressure of hot-pressing as well as the hot-pressing temperature.

Abstract: Poly (vinylidene fluoride) (PVDF) hybrid membranes reinforced by hydrophilic nanoSiO₂ particles were fabricated from PVDF/N-dimethylacetamide (DMAc)/γ-butyrolactone (γ-BL) system via thermally induced phase separation (TIPS) process. Surface and cross-sectional morphology of membranes were characterized by scanning electron microscope (SEM). The properties such as permeability, mechanical performances and antifouling property were also determined. The results showed that the pore size of membrane surface became smaller, while cross-sectional morphology was changed from bicontinuous structure to cell structure, the pore size became larger and majorities of closed pores became open with the addition of hydrophilic nanoSiO₂ particles in the system. Compared with pure membrane, pure water flux of hybrid membrane increased by 30.3%, i.e. from 290 to 378 L/(m²·h·0.1MPa), antifouling property increased from 63.1% to 80.2%. Meanwhile, tensile strength and elongation at break increased by 70.6% and124%, respectively.

Abstract: Biomaterial is one of the good candidates for porous membrane preparation according to its environmental friendliness. In this work, the porous membranes of silk fibroin (SF) were prepared by solution casting with the addition of polyethylene glycol (PEG) and glutaraldehyde (GTA) aiming to improve the porosity and oxygen permeability of SF membrane. The conformation of SF was changed from random coil to β sheet form after treatment with MeOH. The interaction existing between SF chains and both PEG and GTA were characterized using Fourier Transform Infrared spectroscopy (FT-IR). The addition of PEG could produce more porosity in the membrane than GTA confirmed by their morphology observed from scanning electron microscopy (SEM). Moreover, the swelling behavior of the SF-PEG and SF-GTA membranes depended on the porous structure of the membrane which directly correlated to their oxygen permeability. The porosity of the SF membranes increased with the increase of PEG and GTA contents up to 40% and 3%w/w, respectively. After that, their porosity decreased as seen through the SEM and water swelling results. In addition, the SF-PEG membrane turned out to have higher degrees of both porosity and oxygen permeability than the SF-GTA membrane which related to its water swelling behavior.

Abstract: The treatment of peripheral nerve injuries is still one of the most challenging tasks in neurosurgery, as functional recovery is rarely satisfactory in these patients. The concept behind the use of biodegradable nerve guides is that no foreign material should be left in place after the device has fulfilled its task, so as to spare a second surgical intervention. In a previous study, flexible and biodegradable chitosan-γ-glycidoxypropyltrimethoxysilane (GPTMS) hybrid membranes exhibited better cytocompatibility in terms of osteoblastic cells than chitosan membrane. Porous chitosan hybrid membranes, derived by freeze-drying the hybrid gels, showed that the cells were attached and proliferated both on the surface and into pores. The aim of the present study was to evaluate the influence of these chitosan hybrid membranes in terms of their inflammatory response and remodeling of connective tissue during wound-healing processes before use as a periphery nerve graft. The porous chitosan hybrid membranes showed good biocompatibility and improved posttraumatic axonal regrowth and functional recovery.

Abstract: Use the keratin liquid which solved from wool with urea and 2-mercaptoethanol to prepare wool keratin porous membrane at different concentration and frozen temperature. Observe the morphological structure of the membrane by SEM and analyze the SEM pictures. The experimental results indicate that the liquid concentration and frozen temperature are inversely proportional to the porous membrane aperture and porosity, but proportional to the porous membrane density.

Abstract: The progress in the use of templating method for the controlled synthesis of nano, meso and macro porous materials opens many new application areas, one of which is the water treatment membrane. This paper presents a critical review on the fabrication of water treatment membrane using the templating method. Three templating methods are investigated including the block copolymer templating method, the polystyrene beads templating method, and the particles templating method. The future research directions are also discussed.

Abstract: The most promising methods for high purity hydrogen production are membranes separation such as polymer, metal, ceramic and composites. It is well known that Pd and Pd-alloys membranes have excellent properties for hydrogen separation. However, it has hydrogen embrittlement and high cost for practical applications. Therefore, most scientists have studied new materials instead of Pd and Pd-alloys. On the other hand, ceramic materials are great in resistance to acids and chemically stable under high operating temperature. Recent research in cermet materials for membrane applications interests to permeability and selectivity of hydrogen. High purity hydrogen can be produced through simple process by membrane. Recently, research in ceramic composites for membrane applications attract to hydrogen separation. Porous ceramic membrane process which has high permeability and hydrogen flux is chemically and thermally stable. Therefore, they are attractive for applications in hydrogen production process. However, porous ceramic membrane had low selectivity, hard to produce high purity hydrogen. Many studies were carried out Pd and Pd alloys coating, they were fabricated dense cermet membrane. In this work, ACZ ceramic membrane was fabricated disk type membrane by cold isostatic press (CIP) and then coated Pd and Pd-alloys.. It was characterized by XRD, SEM, EDX and BET. Also, we estimated the hydrogen permeability by Sievert's type hydrogen permeation membrane equipment.