Selection Of Membrane Material Research Articles

Microwave synthesis of NaA zeolite membranes on coarse macroporous α-Al2O3 tubes for desalination

Abstract Membrane-based desalination technology is progressing continuously to meet world fresh water supply. However, selection of suitable membrane materials for this technology is still a challenge. Zeolite membranes are one of the promising candidates for molecular separations, but due to low water flux their applications in desalination technology are very limited. In this work, NaA zeolite membranes on coarse macroporous α-Al2O3 tubes synthesized by microwave-assisted heating method were explored for desalination by pervaporation aiming at improving the water flux. Under the optimized synthesis conditions, the fabricated membrane showed the highest water flux of 9.58 kg/(m2·h) with ion rejection (>99.9%) for the separation of 3.5 wt % (0.6 mol/L) NaCl aqueous solution at 348 K. The effect of operating temperature, feed concentration, and different saline solutions on the desalination performance of the membranes were also investigated in detail. The synthesized NaA zeolite membrane delivered excellent separation performance with stable water flux of 8.24 kg/(m2·h), and total ion rejection (>99.9%) within the investigated period of 72 h for simulated seawater desalination, demonstrating the NaA zeolite membranes would be potential candidates for desalination.

Temperature distribution on dielectric membrane structures for sensitive elements of semiconductor gas sensors

The aim of this article is to show a simulation of temperature distribution on dielectric membrane structures with membranes of different dielectric materials in the measuring mode of a semiconductor gas sensor. The simulation results were obtained using the software package Synopsys TCAD. In various moments of the measuring cycle were obtained two-dimensional temperature distributions on membrane structures. Dependencies of temperature versus time for the variety of the coordinates on membranes, temperature versus coordinates at the sensitive layer area’s highest heat value and temperature versus time in the center of the membranes are presented. Recommendations are given for the selection of membrane material for the heat-insulating membrane structure of sensitive elements for semiconductor gas sensors.

Ultrasonic assisted ultrafiltration process for emulsification of oil field produced water treatment

Ultrafiltration has been proven to be very effective in the treatment of oil-in-water emulsions, since no chemical additives are required. However, ultrafiltration has its limitations, the main limits are concentration polarization resulting to permeate flux decline with time. Adsorption, accumulation of oil and particles on the membrane surface which causes fouling of the membrane. Studies have shown that the ultrasonic is effective in cleaning of fouled membrane and enhancing membrane filtration performance. But the effectiveness also, depends on the selection of appropriate membrane material, membrane geometry, ultrasonic module design, operational and processing condition. In this study, a hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were used and their performance evaluated with oil-in-water emulsion. The steady-state permeate flux and the rejection of oil in percentage (%) at two different modes were determined. A dry/wet spinning technique was used to fabricate the flat-sheet and hollow fibre membrane (HFMs) using Polyethersulfone (PES) polymer base, Polyvinylpyrrolidone (PVP) additive and N, N-Dimethylacetamide (DMAc) solvent. Ultrasonic assisted cross-flow ultrafiltration module was built to avoid loss of ultrasonic to the surrounding. The polyurethane (PU) was synthesized by polymerization and sulphonation to have an anionic group (–OH; –COOH; and –SO3H) on the membrane surface. Changes in morphological properties of the membrane had a significant effect on the permeate flow rate and oil removal. Generation of cavitation and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration by cracking the cake layers and reducing concentration polarization at the membrane surface. The percentage of oil after ultrafiltration process with ultrasonic is about 90% compared to 49% without ultrasonic. Ultrasonic is effective in enhancing the membrane permeate flux and controlling membrane fouling.

No more bonding, no more clamping, magnetically assisted membrane integration in microfluidic devices

The integration of porous membranes with microfluidic devices allows a simple but high-throughput mass transport control for numerous microfluidic applications, such as single-cell separation, sample analysis, and purification. In this study, we demonstrate a novel integration process of porous membranes into microfluidic devices by applying a magnetic field and hydrodynamically stabilizing them. This new approach simplifies the integration process by removing physicochemical bonding between membranes and microfluidic devices, but overcomes many practical issues observed in current methods, such as device leakage, membrane replacement, and membrane material selection. More importantly, our approach allows us to install membranes with diverse physicochemical features and spatial configurations into a single microfluidic device. This additional ability can significantly improve its performance and capability in applications. Finally, we successfully demonstrate the utilization of our membrane device for simple particle separation.

Comparative study of continuous and intermittent ultrasonic ultrafiltration membrane for treatment of synthetic produced water containing emulsion

Studies have shown that the ultrasonic is effective in cleaning of fouled membrane and enhancing membrane filtration performance. But the effectiveness also, depends on the selection of appropriate membrane material, membrane geometry, ultrasonic module design, operational and processing condition. In this study, a hollow and flat-sheet polyurethane (PU) membranes synthesized with different additives and solvent were used and their performance evaluated with synthetic oil-in-water emulsion. The steady-state permeate flux and the rejection of oil in percentage (%) at three different modes were determined. A dry/wet spinning technique was used to fabricate the flat-sheet and hollow fibre membrane (HFMs) using Polyethersulfone (PES) polymer base, Polyvinylpyrrolidone (PVP) additive and N, N-Dimethylacetamide (DMAc) solvent. Ultrasonic assisted cross-flow ultrafiltration module was built to avoid loss of ultrasonic to the surrounding. The generation of cavitation, microjets and Brownian motion by the ultrasonic were the dominant mechanisms responsible for ultrafiltration. The mean size of emulsion oil drop become smaller at higher ultrasonic power and the rejection ratio decreases as the size of oil drop decreases. The experimental results suggest that a more economic use of ultrasonic in O/W emulsion ultrafiltration could be achieved using ultrasonic energy intermittently rather than continuously.

Treatment of thermophilic hydrolysis reactor effluent with ceramic microfiltration membranes.

For an undisturbed operation of two-stage high-pressure fermentation up to 100bar, a particle-free hydrolysate appears to be necessary. This is even more important if the second stage, i.e., the methane reactor, is designed as fixed bed. Here, we present the potential of microfiltration membranes as separation unit after the first stage, which is the hydrolysis. The study included the selection of membrane material, membrane performance investigations, and long-term-behavior during the filtration period. In a series of experiments, the optimum type of membrane material and the mode of operation [either crossflow (CF) or submerged (S)] were determined. Ceramic membranes proved to be the better option to treat the process stream due to their chemical and temperature resistance. The crossflow filtration achieved a sustainable flux of up to 33L/(m2h), while long-term experiments with the submerged membranes confirmed a critical flux of 7L/(m2h). Comparative analyses of hydrolysate and permeate showed that the rejected chemical oxygen demand (COD) as well as total organic carbon (TOC) fraction and thereby the loss of organic carbon in the permeate does not reduce the methane yield.

Electrochemical characterizations and reverse electrodialysis performance of hybrid anion exchange membranes for salinity gradient energy

Reverse electrodialysis (RED) is a technique that utilizes the salinity gradient through ion exchange membranes to generate electrical power. In order to make this technology feasible, innovation is required to improve a critical subcomponent, the ion exchange membrane, especially in the selection of appropriate membrane materials and the design of proper RED membranes. This study presents a novel and cost-competitive method for the design of anion exchange membranes (AEMs) by organic-organic hybridization. The low-cost and charge-possessing polymer, poly (diallyldimethylammonium chloride) and poly (vinyl alcohol) (abbreviated as PDDA and PVA, respectively) are blended in different mass ratios to form an AEM. The effect of various PDDA loadings on the electrochemical characterizations of the membranes was investigated. The key properties such as electrical resistance, permselectivity and ion exchange capacity were found to be improved with increasing the mass blend ratio of PDDA. Specifically, the increase of PDDA mass ratio significantly decreased the level of membrane resistance, which majorly contributed to the performance of RED power generation: reached the maximum power density of 0.58 W/m2. Such fabrication method of AEMs may provide the feasible design strategy of potential ion exchange membranes for a viable RED energy conversion.

Membrane contactor for subsea natural gas dehydration: Model development and sensitivity study

A mathematical model of a membrane contactor using triethylene glycol (TEG) for dehydration of natural gas at subsea operation conditions has been developed. The goal for the membrane contactor is to dehydrate the natural gas to transport pipeline specifications, which are −19 °C at 69 barg. The membrane contactor model is based on a hollow fiber configuration with the gas in the shell side and the liquid absorbent inside the fiber. The shell side gas is modelled as one-dimensional on the assumption of turbulent flow, while the fiber/lumen side is modelled as two-dimensional flow due to the laminar flow. Orthogonal collocation is applied to solve the two-point boundary value problem. The developed model is validated against proprietary high pressure experimental data for dehydration of natural gas with TEG in a membrane contactor. The H2O molar flow removed from the gas phase is predicted by the model with a mean absolute error range of 3–7% compared to the experimental results, based on two methods of calculation due to uncertainty in experimental basis. A sensitivity study was performed to evaluate the effect of membrane properties and operation conditions on the dehydration performance. The main findings are that preferred membrane properties from a separation performance point of view are thin membrane, small fiber diameter, long membrane module, high porosity and high permeability. But, the production of the membrane, stability and long term operation also need to be considered in the selection of membrane material and module parameters. For high pressure subsea operation it is found that the use of a dense layer on the top of the porous support could be favourable to prevent wetting of the membrane. It is found that a wetting of 1% already provides a significant drop in separation performance. For the operation conditions the main findings are that high pressure and low temperature are favourable for the separation. Increasing the gas and liquid flow gives increased flux over the membrane, but also results in increased pressure drop in the module. However, as the membrane contactor will be placed in a system with regeneration of the solvent, the operation conditions should be optimized considering the whole system.

Mass transfer performance of water recovery from flue gas of lignite boiler by composite membrane

Membrane technology is a potential way for water recovery from the flue gas of the lignite boiler. Consider the influences of the micro-scale configuration of the membrane and the operating parameters, the physical process was modeled based on the Stefan Maxwell theory, as well as the composite membrane resistance model for numerical simulation. The mass transfer process of flue gas in coating, transition layer and support layer of the composite membrane was analyzed respectively. The theoretical results were both verified by experiments and numerical simulations. The influences of different materials, pressure difference, porosity and transition layer thickness on the water vapor permeation flux were revealed. The results show that the high Henry coefficient and the high selectivity of water vapor have great advantages in the application, and the increase of pressure, porosity and thickness of the transition layer are all beneficial to increase the water vapor flux. Based on the theoretical model, the multi attribute decision making method was employed to provide suggestions for membrane material selection of gas water recycling in the experimental researches as well as in the engineering applications.

A Novel Hybrid Poly (vinyl alcohol) (PVA)/Poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) Membranes for Reverse Electrodialysis Power System

The ion exchange membrane (IEM) is a primary component in the reverse electrodialysis (RED) system for salinity gradient power generation. A great challenge exists in the selection of appropriate membrane materials and the design of proper RED membranes to optimize such an energy-producing process. This work presents a novel and cost-effective method for preparing hybrid cation exchange membranes by incorporating two organic polymers with fine film-forming ability. The functionalized poly (2,6-dimethyl-1,4-phenylene oxide) (sPPO) polymer with sulfated polyvinyl alcohol (sPVA) is proved to have great potential as a candidate for applications in RED. The prepared membranes showed that an optimal range of sPVA (2–10wt%) improved the permselectivity (up to 87%) and an area resistance (down to 1.31Ω cm2), which is comparable to those obtained with commercially available FKS (Fumasep®, Germany) membranes. The hybrid membrane containing 5wt% of sPVA achieved the highest gross power density at 0.46W/m2. This study shows the potential of using organic-organic hybrid membranes for the RED power generation system.

Polymeric membrane materials selection for high-pressure CO2 removal from natural gas

A quick qualitative comparison of membrane materials is often necessary in the early phases of membrane separation process design. This comparison and final material selection can be complex when a large number of materials and performance properties are involved. In such cases, a model-based material selection method is a very important tool that is needed by the engineers who are responsible for designing membrane separation systems. Therefore, a new performance criterion was proposed in terms of productivity loss. This criterion was used along with other membrane properties such as plasticization pressure, CO2 permeability, and CO2/CH4 selectivity to carry out a multi-objective optimization of membrane material selection for high-pressure membrane gas separation. Results from the analysis revealed that the productivity loss is very essential in evaluating the property of plasticization-resistant membrane materials. It was also shown that membrane material selection can be efficiently optimized using the multi-objective optimization approach.

Interfacial interactions between Skeletonema costatum extracellular organic matter and metal oxides: Implications for ceramic membrane filtration

In the current study, the interfacial interactions between the high molecular weight (HMW) compounds of Skeletonema costatum (SKC) extracellular organic matter (EOM) and ZrO2 or Al2O3, were investigated by atomic force microscopy (AFM). HMW SKC-EOM was rigorously characterized and described as a hydrophilic organic compound mainly comprised of polysaccharide-like structures. Lipids and proteins were also observed, although in lower abundance. HMW SKC-EOM displayed attractive forces during approaching (i.e., leading to jump-to-contact events) and adhesion forces during retracting regime to both metal oxides at all solution conditions tested, where electrostatics and hydrogen bonding were suggested as dominant interacting mechanisms. However, the magnitude of these forces was significantly higher on ZrO2 surfaces, irrespective of cation type (Na+ or Ca2+) or concentration. Interestingly, while HMW SKC-EOM interacting forces to Al2O3 were practically insensitive to solution chemistry, the interactions between ZrO2 and HMW SKC-EOM increased with increasing cation concentration in solution. The structure, and lower charge, hydrophilicity, and density of hydroxyl groups on ZrO2 surface would play a key role on favoring zirconia associations with HMW SKC-EOM. The current results contribute to advance our fundamental understanding of Algogenic Organic Matter (AOM) interfacial interactions with metal oxides (i.e., AOM membrane fouling), and would highly assist in the proper selection of membrane material during episodic algal blooms.

Aromatic polyimide and crosslinked thermally rearranged poly(benzoxazole-co-imide) membranes for isopropanol dehydration via pervaporation

Novel crosslinked thermally rearranged polybenzoxazole (C-TR-PBO) membranes, which show impressive results for isopropanol dehydration, have been obtained via in-situ thermal conversion of hydroxyl-containing polyimide precursors. The polyimide precursors are synthesized by the polycondensation of three monomers; namely, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3′-dihydroxybenzidine diamine (HAB) and 3,5-diaminobenzoic acid (DABA). Due to the incorporation of the carboxylic-group containing diamine DABA into an ortho-hydroxypolyimide precursor, the thermally induced crosslinking reaction can be achieved together with the thermal rearrangement process. Consequently, a synergistic effect of high permeability and high selectivity can be realized in one step. The resultant C-TR-PBO membrane exhibits an unambiguous enhancement in permeation flux compared to its polyimide precursor. Moreover, the newly developed C-TR-PBO membrane displays stable isopropanol dehydration performance at 60°C throughout the continuous 200h. The promising preliminary results achieved in this study may offer useful insights for the selection of membrane materials for pervaporation and new methods to molecularly design next-generation pervaporation membranes.

Measurement of solubility thermodynamic and diffusion kinetic characteristic of solvents in PDMS by inverse gas chromatography

Inverse gas chromatography is a versatile and effective method for the characterization of the solubility thermodynamics and diffusion kinetic of solvent–polymer system with the advantages of fast, low dosage of samples and large range of temperature. Polydimethylsiloxane (PDMS) is well known as an excellent polymer membrane material for its high permeability to gases and liquids and widely used in the separation and purification of bio-fermentation broth which was mainly consisted by acetone, butanol, ethanol and water. In this paper, the inverse gas chromatography method was applied to measure solubility thermodynamics parameters like the infinite dilution activity coefficient and Flory–Huggins interaction parameter between those small molecules and PDMS. The infinite dilution diffusion coefficients were calculated by Van Deemter model over a temperature range of 373.2–413.2K. The diffusion coefficient was fitted with the temperature according to the Arrhenius correlation. The data could help the selection of membrane material in pervaporation or gas separation and the analysis of mass transfer process.

Catalysts used environmental and energy applications set to grow at 5.6%

The rapid development of membrane technology in various applications requires new membrane materials to achieve good separation performance. Materials in great demand are low in cost, easy to prepare, sustainable, and have good separation performance. In addition, consideration of environmental aspects is also crucial in the selection of membrane materials. On the other hand, plastic bottle waste, which increases every year (381.73 million tons), has the property of forming films or thin layers. Therefore, plastic bottle waste as a low-cost, sustainable, and “green” membrane material has great potential. The membrane from PET plastic bottle waste (PET-B membrane) was prepared using the immersion-precipitation phase inversion technique. Modification of the membrane is done by adding LiCl as an additive. Furthermore, the fabricated membranes were tested for their performance in water purification. The results showed that the PET-B membrane had a porosity of 74.8%. The addition of LiCl can increase the porosity of the PET-B membrane to 81.4%. The addition of LiCl caused an increase in flux to 3 times (65.30 Lm-2h-1bar−1 to 171.1 Lm-2h-1bar−1) and an increase in rejection from 64.46% to 99.45%.

Systematic evaluation of dissolved lead sorption losses to particulate syringe filter materials.

Distinguishing between soluble and particulate lead in drinking water is useful in understanding the mechanism of lead release and identifying remedial action. Typically, particulate lead is defined as the amount of lead removed by a 0.45-μm filter. Unfortunately, there is little guidance regarding selection of filter membrane material and little consideration to the possibility of the sorption of dissolved lead to the filter. The objective of this work was to examine the tendency of 0.45-μm syringe filter materials to adsorb lead. Tests were performed with water containing 40 and 24 μg/L soluble lead at pH 7 buffered with 50 mg C/L dissolved inorganic concentration (DIC). The amounts of lead sorbed greatly varied by filter, and only two filter types, polypropylene and mixed cellulose esters, performed well and are recommended. Great care must be taken in choosing a filter when filtering soluble lead and interpreting filter results.

Огляд мембранніх технологій очистки води у водопостачанні та водопідготовці

Traditional technologies of water purification (based on coagulation, settling, oxidation and ion exchange) are ineffective in the modern anthropogenic demand for the quality of drinking and process water. The application of membrane technologies has wide prospects for the creation of new energy saving, eco-safe technological systems. Pervaporation allows effective separation of different water-organic mixtures (sewage treatment and drying of organic solvents) and a mixture of organic substances. The availability of pervaporation is connected with the urgency of problems and high efficiency of the process compared with other separation processes, with the ability to separate azeotropic mixtures, low power consumption, reagentless characteristics and equipment compactness. Restraining objectives of industrial application are: - search and selection of membrane materials that meet specific requirements for a solution of the separation problem; -identification of the main factors that affect the efficiency of separation. The difficulties of membranes choice to solve specific separation problems are connected with the choice of material necessary for optimal separation of the original mixture. Pervaporation is a multifactor process with conjugate heat and mass transfer and phase transitions. Thus, in applied and fundamental aspects it is necessary to study the impact of various factors on the efficiency of the impurities separation from the original mixture. Therefore, the problem of design of membrane apparatus for pervaporisation sewage treatment and study of the influence of technological parameters on the course of this process are important

Disposable Polymeric Electromagnetic Actuated Micropump

A polymer based disposable micropump was designed and evaluated for drug release and control mechanism. The micropump is constructed via hot embossing replication technique with poly(methylmethacrylate) as body structure material and poly(dimethylsiloxane) as membrane. To optimize the membrane material selection in term of deflection and stress distribution, finite element method (FEM) structural analysis was carried out. Under same condition, the behavior of the PDMS polymer is investigated on the thickness and radius variation. The fabricated polymer type micropump ensures 0.0025 liters/min of flow rate with 15 mm H 2O back pressure at 29 Hz.

Research on Polyvinylidene Fluoride Hollow Fiber Hemodialyzers

Hemodialysis is the main treatment of acute and chronic renal failure, and the selection of hemodialysis membrane materials is the key factor that determines the curative possibilities. By changing the membrane forming conditions, we have spun polyvinylidene fluoride (PVDF) hollow fiber membranes with the same inner diameters but different wall thicknesses. Via centrifugal moulding, we have also made membranes into dialyzers to study the mechanical performance of the membranes and the dialysis performance of the dialyzers. The results show that the mechanical performance meets the demand of dialysis. For the dialyzers with 30μm fiber walls, the clearance rates of urea and lysozyme are 90% and 75% respectively, and the rejection rate of bovine serum albumin (BSA) comes to 90% plus. The increase of the mass content of the dope solution polyethylene glycol (PEG) from 19% to 22% decreases the rejection rate of BSA.

Removal of Pesticides by Polymer Membranes

Nanofiltration membranes attract attention to take a role of the high performance purification of water. The purification processes with a little energy consumption are enabled by the selection of membrane materials and driving conditions.