Thin Porous Layer Research Articles

An All Hydrophilic Fluid Diode for Unidirectional Flow in Porous Systems

AbstractA fluid diode that allows fluid flow in one direction but blocks fluid flow in the opposite direction has wide applications including oil recovery, drug delivery, and lab‐on‐a‐chip microfluidics. Many studies are conducted to facilitate directional liquid motion on the solid surface or across thin porous layers. However, the self‐driven one‐way flow inside porous systems still remains a significant challenge. Here, a novel all‐hydrophilic fluid diode (AHFD) made of porous materials with asymmetric pores is reported, which allows capillary flow in a chosen direction. The direction‐dependent flow process and the breakthrough pressure are experimentally and theoretically examined. The proposed AHFD can have many potential applications such as functional protective clothing, microfluidic valve, and oil–water separator, and the idea can be extended to develop other all lyophilic fluid diodes such as oleophilic diode.

Flows of Dehaven Fluid in Symmetrically Curved Capillary Fissures and Tubes

In this paper, an analytical method for deriving the relationships between the pressure drop and the volumetric flow rate in laminar flow regimes of DeHaven type fluids through symmetrically corrugated capillary fissures and tubes is presented. This method, which is general with regard to fluid and capillary shape, can also be used as a foundation for different fluids, fissures and tubes. It can also be a good base for numerical integration when analytical expressions are hard to obtain due to mathematical complexities. Five converging-diverging or diverging-converging geometrics, viz. variable cross-section, parabolic, hyperbolic, hyperbolic cosine and cosine curve, are used as examples to illustrate the application of this method. Each example is concluded with a presentation of the formulae for the velocity flow on the outer surface of a thin porous layer. Upon introduction of hindrance factors, these formulae may be presented in the most general forms.

Experimental Study of Nucleate Pool Boiling of R-134a and R-410a on a Porous Surface

ABSTRACTBoiling heat transfer enhancement is influenced by the surface distinctiveness of the boiling region. Porous surface is being widely used to enhance boiling heat transfer in the industry. An experimental study is carried out to investigate the characteristics of the pool boiling heat transfer for different fluid, namely, pure refrigerant (R-134a) and quasi-azeotropic mixture (R-410A). The test is performed on a thin porous layer over a copper tube placed horizontal at saturation temperature of 7°C and also to determine its potential application to flooded refrigerant evaporators. The diameter of the coated tube was 25.4 mm, a length of 116 mm. A coated tube had a porous layer thickness of 42.2 µm. In the experimental range (5 to 50 kWm−2) the boiling heat transfer coefficients are 1.25 to 2 times higher than those of the uncoated surface. For boiling within the porous surface, simplified predicted equations of various investigators are analyzed.

Porous polymer coatings on metal microneedles for enhanced drug delivery.

We present a simple method to coat microneedles (MNs) uniformly with a porous polymer (PLGA) that can deliver drugs at high rates. Stainless steel (SS) MNs of high mechanical strength were coated with a thin porous polymer layer to enhance their delivery rates. Additionally, to improve the interfacial adhesion between the polymer and MNs, the MN surface was modified by plasma treatment followed by dip coating with polyethyleneimine, a polymer with repeating amine units. The average failure load (the minimum force sufficient for detaching the polymer layer from the surface of SS) recorded for the modified surface coating was 25 N, whereas it was 2.2 N for the non-modified surface. Calcein dye was successfully delivered into porcine skin to a depth of 750 µm by the porous polymer-coated MNs, demonstrating that the developed MNs can pierce skin easily without deformation of MNs; additional skin penetration tests confirmed this finding. For visual comparison, rhodamine B dye was delivered using porous-coated and non-coated MNs in gelatin gel which showed that delivery with porous-coated MNs penetrate deeper when compared with non-coated MNs. Finally, lidocaine and rhodamine B dye were delivered in phosphate-buffered saline (PBS) medium by porous polymer-coated and non-coated MNs. For rhodamine B, drug delivery with the porous-coated MNs was five times higher than that with the non-coated MNs, whereas 25 times more lidocaine was delivered by the porous-coated MNs compared with the non-coated MNs.

Porous germanium formed by low energy high dose Ag+-ion implantation

A technical approach is proposed for the synthesis of thin porous PGe layers with Ag nanoparticles based on low-energy high-dose implantation of single-crystal c-Ge metal ions. To demonstrate a successes of this technique, we performed an Ag+-ion implantation of a polished c-Ge substrates with an energy of 30 keV at a dose of 1.5⋅1017 ion/cm2 and a current density of 5 μA/cm2. Methods of scanning electron and atomic force microscopy, as well as EDX analysis and electron backscattered diffraction was shown that as a result of the implantation on the c-Ge surface a porous amorphous PGe layer is formed of a spongy structure consisting of a network of intersecting Ge nanowires with an average diameter of ∼10–20 nm. At the ends of the nanowires, the synthesis of Ag nanoparticles is observed. It was found that the formation of pores during Ag+-ion implantation is accompanied by efficient spattering of the Ge surface.

Continuum-Scale Modeling of Liquid Redistribution in a Stack of Thin Hydrophilic Fibrous Layers

Macroscale three-dimensional modeling of fluid flow in a thin porous layer under unsaturated conditions is a challenging task. One major issue is that such layers do not satisfy the representative elementary volume length-scale requirement. Recently, a new approach, called reduced continua model (RCM), has been developed to describe multiphase fluid flow in a stack of thin porous layers. In that approach, flow equations are formulated in terms of thickness-averaged variables and properties. In this work, we have performed a set of experiments, where a wet 260hbox {-}upmu hbox {m}-thin porous layer was placed on top of a dry layer of the same material. We measured the change of average saturation with time using a single-sided low-field nuclear magnetic resonance device known as NMR-MOUSE. We have employed both RCM and the traditional Richards equation-based models to simulate our experimental results. We found that the traditional unsaturated flow model cannot simulate experimental results satisfactorily. Very close agreement was obtained by including the dynamic capillary term as postulated by Hassanizadeh and Gray in the traditional equations. The reduced continua model was found to be in good agreement with the experimental result without adding dynamic capillarity term. Moreover, the computational effort needed for RCM simulations was one order of magnitude less than that of traditional models.

Features of photoluminescence and transmission spectra of thin film porous silicon layers on insulator substrates

In the paper thin film porous silicon layers on insulator substrates were investigated. Silicon thin film (200-300 nm) was formed by ion-beam and sputter deposition on sapphire and polycorrundum. Than porous silicon was formed by chemical etching in mixture of hydrofluoric acid and sodium nitride. Some of samples were annealed in nitrogen atmosphere at 850 C before porous silicon formation.According to AFM investigation surfaces of porous silicon on polycorrundum and sapphire demonstrate different crystallographic orientation. On polycorrundum typical for (111) orientation triangles can be seen but on sapphire there are no marked crystallographic figures. So it can be assumed that initial silicon layers were approximately crystalline and replicate substrate orientation. In the other hand silicon crystalline orientation significantly affect porous silicon layer properties including optical properties.Transmission spectra of thin porous layers is shifted to shortwave region in comparison with initial silicon film spectra. In some spectra non-typical increase of transmission in UV and IR region is observed possibly due to photoluminescence.High temperature annealing prior to porous silicon formation drastically changes transmission spectra of resulting porous silicon layer despite silicon film transmission spectra did not change significantly. This can be explained by influence of initial crystal structure on velocity and direction of porous silicon formation. By this way it is possible to control optical properties of porous layers. Special interest should be taken to effect of transmission spectra inversion for samples obtained by ion-beam deposition.Photoluminescence of porous silicon thin layer was exited by ultra-violet light (285 nm) and signally differs from photoluminescence of porous silicon on bulk silicon. Beside typical for bulk porous silicon peaks at 600-700 nm also few peaks in green and blue region are observed. In the same time main peak is shifted to shortwave region (500 nm) compared to 600-700 nm.Photoluminescence spectra of porous silicon on insulator confirm most popular theories of porous silicon photoluminescence mechanism in particular correlation of photoluminescence with size of nanocrystallites. Also theory of superposition of few photoluminescence bands is proven because for stand alone porous layers these bands are separated.Ref. 13, fig. 8.

Heat and mass transfer for liquid film condensation along a vertical channel covered with a thin porous layer

The problem of heat and mass transfer enhancement of liquid film condensation by covering a porous layer on one of channel vertical plates has been numerically investigated. The liquid film falls down on one plate of a vertical channel under mixed convection. The wetted plate is covered with a thin porous layer and externally subjected to a uniform cooling heat flux while the second plate is dry and isothermal. The effects of porosity, porous layer thickness and the ambient conditions on the heat and mass transfer performance and on the liquid film condensation have been examined in detail. The numerical results show that the heat and mass transfer performance at the liquid-gas interface during the liquid film condensation is enhanced by the presence of the porous layer.

Novel approach for III-N on Si (111) templates fabrication by low-temperature PA MBE using porous Si layer

We report on successful growth of GaN nanorods by low-temperature plasma-assisted molecular beam epitaxy on a Si(111) substrate with and without preformed thin porous Si layer (por-Si). The deposited GaN initially forms islands which act as a seed for the wires. Porous structure of the por-Si layer helps to control nucleation islands sizes and achieve homogeneous distribution of the nanorods diameters. In addition 850 nm-thick crack-free GaN layer was formed on Si(111) substrate with preformed por-Si layer.

Hydrophobic and porous cellulose nanofibrous screen for efficient particulate matter (PM2.5) blocking

Particulate matter (PM2.5) pollution in air seriously affects public health. However, both bulk thickness and the accumulation of PM particles typically lead to a quick decline in the air permeability and large pressure drops of the conventional air clean membranes. In this work, we choose cellulose nanofibers (CNFs, a low cost, biodegradable and sustainable material) to form a hydrophobic and porous CNF thin layer on a stainless steel screen (300 mesh with pore size of 48 µm) through a simple filtration-assisted gelation process and subsequent polydimethylsiloxane modification. The prepared hydrophobic CNFs/stainless steel screen demonstrates highly efficient PM2.5 blocking based on size-sieving effect, fast air permeability and long-term durability under natural ventilation conditions in the relative humidity range from 45% to 93%. This technique holds great potential for indoor PM2.5 blocking under natural ventilation conditions.

A Wettability Metric for Characterization of Capillary Flow on Textured Superhydrophilic Surfaces.

Surface wettability is typically characterized by measuring the static contact angle of a sessile droplet placed on the surface. For extremely wetting surfaces on which liquid spontaneously spreads into a thin liquid film, the near-zero static contact angle is not amenable to measurement and does not fully describe the wetting behavior. There are unmet needs in microfluidics, boiling heat transfer enhancement, and antifogging applications for a metric to characterize highly wetting (i.e., superhydrophilic) textured surfaces based on their capillary-driven liquid pumping performance, as a supplement to the contact angle for this highly wetting regime. To describe the wetting behavior, the textured surface can be approximated as a thin porous layer through which the liquid spreads. An analytical model is developed for the volumetric flow in this layer, which reveals a single superhydrophilicity metric that captures the wetting behavior for a given liquid. A simple experimental approach is proposed to characterize this metric by measuring the volumetric liquid intake into the surface from a filled capillary tube. This approach is validated by characterizing micropillared superhydrophilic surfaces of known geometry; the predicted and measured wetting behaviors show good agreement. The metric proposed in this study offers a simple approach for accurately characterizing and differentiating highly wetting surfaces based on their liquid pumping ability.

Modeling and analysis of short-period transient response of a single, planar, anode supported, solid oxide fuel cell during load variations

The main motivation for this study was to analyze transient responses of a solid oxide fuel cell (SOFC) during load variations, which can possibly cause fuel starvation within porous anode active layer and, consequently, accelerate the degradation rate of the SOFC. Simulation approach was taken into consideration. For this purpose, three-dimensional (3-D) dynamic model of a single, planar, anode supported SOFC was built. The model is also briefly presented in this paper. The paper focuses on detailed transient analysis of current density (J), power density (P), fuel utilization (FU) and electrical conversion efficiency (η) after a step change of voltage (load). The simulation results also give us valuable data about local mass fractions of fuel species that cannot be measured in realistic devices. It is shown that fuel starvation occurs when the J (load) is increased by approximately 100% and FU is above 0.85 at final value of J (when steady state is assumed). Moreover, the time-dependent profile of FU give us guideline for setting appropriate inlet flow rate of fuel to prevent fuel starvation. The results show that a SOFC with very thin (ds = 0.1 mm) porous anode support layer is prone to fuel starvation during large load variation. Using a thicker porous anode support layer (ds = 0.5 mm) is proposed to avoid fuel starvation and, consequently, mitigate the degradation of a realistic SOFC. The P and η of modeled SOFC are also analyzed during large load variations. The η increases with increasing the ds from 0.1 mm to 1.0 mm. The results indicate the improvement of η by appropriate design and control of a realistic SOFC.

La2-XPrxNiO4+δ-Based Efficient SOFC Cathodes: Effect of Microstructure, Composition and Architecture

Solid oxide fuel cells (SOFCs) operating at intermediate temperature (500 – 700 °C) have attracted much attention due to high energy conversion efficiency, fuel adaptability and low emissions [1]. Both composition and microstructural /architectural design of the cathode film play an important role in obtaining the optimal electrochemical performances in this temperature range [2-9]. Recently, Ln2NiO4+δ (Ln = La, Pr, Nd) rare-earth nickelates have displayed promising oxygen electrode performance because of their interesting structure, transport and catalytic performance. Among nickelates, Pr2NiO4+δ presents excellent electrochemical properties at intermediate temperatures while it is characterized by a rather poor chemical stability in comparison to La2NiO4+δ. The preparation of efficient oxygen electrode materials which present very low degradation rates is still a challenge. The present study is focused on designing Pr doped lanthanum nickelates, La2-xPrxNiO4+δ with 0 ≤ x ≤ 2 with the aim of finding the best compromise between chemical stability and optimized electrochemical performance. First, single and double layered La2NiO4+δ electrodes with controlled microstructure were deposited on Ce0.9Gd0.1O2-δ (CGO) electrolyte using electrostatic spray deposition (ESD) or/and screen-printing (SP). The microstructure of La2NiO4+δ films has been optimized by varying some key process parameters. A coral-like microstructure of La2NiO4+δ films was successfully obtained resulting from nozzle to substrate distance, flow rate, substrate temperature deposition time equal to 50 mm, 1.5 mL/h, 350 °C and 3 h, respectively [6]. Electrochemical properties of La2NiO4+δ deposited symmetrically on CGO were measured by impedance spectroscopy. They are found to be strongly dependent on the cathode microstructure and architecture. For example, a double layer La2NiO4+δ cathode, consisted of 3-D coral nanocrystalline film (average particle size ~ 150 nm) with a continuous nanometric dense sub-layer (100 nm) at the electrode/electrolyte interface, prepared by ESD and topped by a La2NiO4+δ current collector prepared by SP, shows the best performance leading to the polarization resistance (Rpol) down to 0.42 Ω cm² at 600 °C (Fig 1) [6]. In a second part, this double layer design was extended toLa2-xPrxNiO4+δ (with x = 0, 0.5, 1 and 2) cathodes with a view to taking advantage of the complimentary properties of the two extreme compositions Pr2NiO4+δ and La2NiO4+δ, i.e. higher electronic conductivity of Pr2NiO4+δ superior stability of La2NiO4+δ. The chemical stability and polarization resistance (Rpol) were found to decrease when the Pr content was increased. Polarization resistance (Rpol) equal to 0.42, 0.12 and 0.08 Ω cm2 at 600 °C has been obtained for La2NiO4+δ, LaPrNiO4+δ and Pr2NiO4+δ, respectively. Among the complete La2-xPrxNiO4+δ solid solution, LaPrNiO4+δ shows the best compromise between electrochemical properties (the lowest Rpol value available in the literature for this composition, 0.12 W cm2 at 600 °C) and chemical stability in air (up to 30 days at 700 °C) [9]. Finally, the role of the electrode/electrolyte interface has been investigated on the polarization resistance of La2NiO4+δ and Pr2NiO4+δ cathodes. For this purpose, the thin dense nickelate sub-layer was replaced by a thin porous (~3-4 mm) composite layer based on a mixture of CGO (deposited by SP) and La2NiO4+δ or Pr2NiO4+δ (deposited by ESD). As a consequence, further reduction in Rpol down to 0.16 (Fig 1) and 0.04 Ω cm2 was successfully obtained for La2NiO4+δ and Pr2NiO4+δ, respectively [8]. This composite LnNO-CGO sub-layer is playing an important role in enhancing the electrochemical properties of these cathodes leading to the lowest Rpol values available in the literature for these compositions, to the best of our knowledge. This talk will end with our latest results incorporating a LnNO-CGO composite sub-layer to the double layer LaPrNiO4+δ electrode, the most promising composition in terms of electrochemical properties and chemical stability.

Role of surface modification on physicochemical properties of luminescent YPO4:Tb nanorods

Highly crystalline, luminescent YPO4:Tb (core), YPO4:Tb@LaPO4 (core/shell) nanorods (NRs) were prepared by urea based co-precipitation process at low temperature. The synthesis method involves important advantages such as its simplicity, low-cost precursor, eco-friendly, rapidness and high reaction yields. X-ray diffraction, transmission electron microscopy, energy dispersive-x-ray analysis, FTIR, UV/vis, excitation and emission spectral techniques were employed to investigate the crystals structure, crystallinity, morphology, surface chemistry, optical and photoluminescence properties of the as-prepared samples. The silica surface coating was verified from EDX and FTIR spectral studies. TEM micrograph indicates the well crystalline, irregular size rod-shaped nanostructures, which were covered with a porous thin silica layer. The emission spectra were dominated by a 5D4→7F5 transition in all three samples, but the core/shell nanostructured shows strongest emission intensity because of reduction in nonradiative transition rate. Silica-modified core/shell/Si NRs exhibits high solubility with good colloidal stability in respect to core/shell NRs due to the influence of optically active silica. The morphological, nanostructural, high solubility in an aqueous solvent along with strong green photoluminescence makes them a suitable candidate for biomedical applications.

Selective Electrodes for Mixed Reactant Fuel Cells

Objectives We examine the option to operate fuel cells, in particular solid oxide fuel cells (SOFCs), on a mixture of fuel with air and apply the same mixture to both the anode and cathode. This kind of cell is referred to as a mixed-reactant fuel-cell (MR-FC or MR-SOFC). Operating a fuel cell on a uniform mixture of the reactants allows significant changes in the cell design having, potentially, higher power density and higher fuel utilization as well as enabling the use of porous electrolyte thin layers and lowering production costs. To achieve this the symmetry has to be broken by using different materials as catalysts for the anode and cathode. The primary challenge is selectivity, allowing the anode only fuel oxidation by oxygen ions emerging from the solid electrolyte and the cathode only oxygen reduction while all materials in the cell should not catalyze the direct chemical reaction within the mixture. The aim is to discuss potential ways to achieve that selectivity and test it. Selectivity is in particular a challenge in MR- SOFCs as they should operate at elevated temperature where many reactions are active and selectivity is difficult to be achieved. New results Selectivity can be controlled by materials properties, cell design in particular the electrode design and operation conditions.1 The following material properties affect selectivity: the work function, electron energy levels and energy band banding at the surface, point defects, in particular in the surface layer, generation of local electrical fields by surface additives and tendency towards reduction of the oxides in the cell which serve as the electrolyte, electrodes and possibly also as the interconnects and current collectors. Proper electrode design can enhance selectivity taking advantage of the different diffusion coefficients and concentration gradients in the gas components i.e. fuel, oxygen and reaction product. Working conditions that can contribute to selectivity are: temperature, flow rate hence residence time in the hot zone and electrical current drawn from the cell as it affects the concentration gradients in the gas phase at the electrodes. These factors apply to all mixed reactant fuel cells and allow to enhance selectivity in them. They are crucial for the high temperature MR-SOFCs. Test design is discussed suggesting that first each material is tested separately to screen those that enhance the forbidden chemical reaction within the gas mixture. Preliminary experimental results are reported. The procedure suggested to test selectivity and cell performance is discussed. Moderately diluted hydrogen can be used as the fuel in the mixture, as found experimentally contrary to common believe, despite the high temperatures used (600°C) as long as no catalyst is present. It is emphasized that single chamber SOFC reported so far are not true MR-SOFCs as one of the electrode is not selective. Significance Determining the catalytic properties of materials, in the present case those relevant to solid oxide fuel cells, is of general interest and importance. Achieving selectivity will provide the basic necessary condition for the construction of mixed reactant solid oxide fuel cells. Once this is achieved accelerating reaction rates will be the next challenge. Acknowledgement This research was supported by Israel Science Foundation ISF under grant No. 699/11. References I. Riess, Funct. Mater. Lett. 8 1540010 (2015).

Sustained drug release from surface modified UHMWPE for acetabular cup lining in total hip implant

Despite sterilization and aseptic procedure, bacterial infection remains a key challenge in total hip arthroplasties. This fact emphasizes the urgent need for development of new implant systems, which should releases the drug in a controlled manner without sparing its mechanical and tribological properties. In this study, the lining material of the acetabular cup, in total hip implant, has been modified for sustained release of drugs, which should be available throughout the site of implantation to fight the post-operation bacterial infection. A modified solvent based etching and lypolization technique has been used to engineer a thin porous surface layer on ultra-high molecular weight polyethylene (UHMWPE) substrate, which is clinically used as acetabular-cup lining. Gentamicin loaded chitosan solution has been impregnated into modified surface, which suitably gets released over a long period. The main challenge was to keep the mechanical and tribological behavior of this lining material unaffected after the modification. Modified surface offers reduction in friction coefficient and wear rate, by 26% and 19%, respectively, in comparison to UHMWPE, which is encouraging towards the intended application. Hardness and elastic modulus decreases slightly, by 27% and 20%, respectively, possibly due to improper impregnation of chitosan inside porous surface. However, after drug release, the modified surface regains the mechanical and tribological behavior similar to unmodified UHMWPE. Surface modified UHMWPE have shown an impressive release profile for drug up to 26days and released >94.11% of the total drug content. In vitro antibacterial tests have proven that the modified surface of UHMWPE can effectively release the drug and fight against infection. This surface engineered acetabular cup lining is a promising candidate in the area of drug eluting implant, which can bring a significant advancement to the functionality of commercially used orthopedic implants by providing inherent capacity for fighting infections in-vivo.

Non-enzymatic hydrogen peroxide detection at NiO nanoporous thin film- electrodes prepared by physical vapor deposition at oblique angles

In this work we report a non-enzymatic sensor for hydrogen peroxide (H2O2) detection based on nanostructured nickel thin films prepared by physical vapor deposition at oblique angles. Porous thin films deposited on ITO substrates were characterized by X-ray diffraction analysis, scanning electron microcopy (SEMs), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques such as Cyclic Voltammetry (CV) and Constant Potential Amperometry (CPA). The microstructure of the thin films consisted of inclined and separated Ni nanocolumns forming a porous thin layer of about 500nm thickness. Prior to their use, the films surface was electrochemically modified and the chemical state studied by CV and XPS analysis. These techniques also showed that Ni2+/Ni3+ species were involved in the electrochemical oxidation and detection of H2O2 in alkaline medium. Main analytical parameters such as sensitivity (807mAM−1cm−2), limit of detection (3.22μM) and linear range (0.011–2.4mM) were obtained under optimal operation conditions. Sensors depicted an outstanding selectivity and a high stability and they were successfully used to determine H2O2 concentration in commercial antiseptic solutions.

Drag reduction of circular cylinders by porous coating on the leeward side

The present paper describes the effect of drag reduction of circular cylinders due to a porous coating on their leeward sides. To investigate the coating effect, experiments were conducted in a wind tunnel of Goettingen type. Systematic drag measurements were carried out for different cylinder configurations and flow velocities. The drag measurements were complemented by pressure and particle image velocimetry (PIV) flow field measurements around selected cylinders. The Reynolds numbers were varied in the subcritical range of$3\times 10^{4}<Re<1.4\times 10^{5}$. The results show that a thin porous layer on the leeward side, either incorporated in the cylinder shape or applied on the cylinder surface, leads to an increase of base pressure on the leeward side of the cylinder. It causes a reduction of drag and dampens oscillation amplitudes when compared to a cylinder without coating. Results obtained for different configurations with varying key parameters (coating angles, layer thicknesses and pore sizes of the porous material) clearly indicate the drag-reducing and amplitude-damping potential of leeward coating. The amount of drag reduction and amplitude damping depends on the combination of key parameters. It was demonstrated that the lowered drag coefficients$c_{d}$were almost constant in the tested range of Reynolds numbers. A maximum reduction of drag of 13.2 % was measured. In addition, the results revealed a strong reduction of the pressure fluctuations around cylinders with a leeward coating due to the shift of the vortex region further downstream.

Effect of combination dope composition and evaporation time on the separation performance of cellulose acetate membrane for demak brackish water treatment

The coastal areas in Indonesia often have a problem of clean water lack, because the water is classified as brackish water. Therefore, this research investigated the fabrication of CA membranes using phase inversion method for brackish water treatment. Investigation was conducted to study the effect of combination dope composition and evaporation time on separation performance and morphology of the memrbane. Membrane was fabricated by dry-wet phase inversion technique with variation of polymer concentration 17, 18 and 20 wt% in the total solid and evaporation time of 5, 10 and 15 seconds, respectively. The asymmetric membranes were characterized by permeability test through rejection and flux measurements using brackish water as feed. The experimental results from SEM images analysis showed that all the membranes have a thin small porous layer and thicker sub-structure of larger porous layer formed asymmetric membrane. Moreover, the greater polymer concentration is resulting smaller pore size and smaller membrane porosity. The longer evaporation time was also resulted in denser membrane active layer. The best membrane performance was observed at the composition of 20 wt% CA polymer, 1 wt % polyethylene glycol with the solvent evaporation time of 15 seconds.

Preparation of porous diffusion dialysis membranes by functionalization of polysulfone for acid recovery

Asymmetrically porous anion exchange membranes for acid recovery by diffusion dialysis are prepared by one-step functionalization of chloromethylated polysulfone (PSF) ultrafiltration membrane via reaction with N,N,N′,N′-tetramethyl-1,3-propanediamine (TMPDA) to achieve simultaneous crosslinking and quaternization. The performance of the resulting TMPDA modified PSF (TPSF) membranes can be easily tailored by controlling the reaction time in TMPDA solution and thus the charged density and crosslinking degree. The TPSF membranes exhibit excellent diffusion dialysis performance, especially high acid dialysis coefficient, stemming from the porous matrix and thin selective layer (<0.6µm). The optimized TPSF membrane has an acid dialysis coefficient of 0.065mh−1 and a separation factor of 34.0, which are 6.6 and 0.84 times greater than the corresponding values of the commercial DF-120 membranes at the same testing condition using a mixture of HCl and FeCl2 solution as feed solution. The membranes reported in this work are promising for scale-up for industrial acid recovery applications.