Ceramic Nanofiltration Research Articles

Nanofiltration membrane bioreactor for removing pharmaceutical compounds

The application of a nanofiltration membrane bioreactor (NF-MBR) has been investigated for the treatment of two pharmaceutical compounds (cyclophosphamide and ciprofloxacine). A new type of ceramic nanofiltration (NF) membrane has been employed for the filtration of acclimated activated sludge artificially doped by these antibiotics. The performance of the NF-MBR was monitored during approximately 4 months, in order to evaluate the long term operational stability of the system and the potential effect of the high sludge retention time on antibiotics degradation. The hypothesis of this study lies in the development of NF membrane and its cut-off support in order to (i) retain micropollutants and (ii) increase micropollutant concentration in the bioreactor. The two antibiotics are weakly degraded even with acclimated sludge, and only a small fraction of these compounds was retained when the fouling of the membrane increased. COD, total suspended solids (TSS) and colour were effectively removed. No unclogging operation was necessary (4 months of operation without chemical cleaning). The biodegradability, retention and adsorption mechanisms have been also studied.

Seawater desalination in Mexican Pacific coast by a new technology: use and perspectives

abstract Mexico is a country with problems of water supply in its northern and central territories, as they are semiarid and due to the increase of nonsustainable water use pattern. The major population and productivity activities are located in these areas of the country. Membrane technologies to achieve the elimination of the dissolved ions from seawater or brackish water are some of the most suitable processes to diversify water supply options because of the long coastline that Mexico has: 9,330 km (7,338 km in the Pacific Ocean). Even reverse osmosis using polymeric membranes is the most used technology; ceramic membranes have some advantages as they are chemically and mechanically more resistant and they have a longer life time and less environmental impact once they are discarded; but as their pore size is larger, they are in the range of nanofiltration (NF). The main objective of this research was to evaluate the performance of a new desalination technology using modified ceramic NF membranes with seawater from Mexican Pacific coast. The study was done for one year and the results demonstrated that these modified NF ceramic membranes have a potential scope to be used as a partial desalination of seawater or as the main process to reduce specific ions.

An improved phenomenological model for prediction of solvent permeation through ceramic NF and UF membranes

Permeation of water and organic solvents through ceramic nano-filtration and ultra-filtration membranes is investigated and a predictive model is proposed. The development of the model started from the Hagen–Poiseuille equation, which assumes the viscosity as the main influencing parameter for the permeation, and introduces several correction factors to account for the surface phenomena that arise in a nanotube due to solvent–membrane surface interactions: capillarity, polarity and steric hindrance. The correction terms are functions of the pore size, so that the model can be applied indistinctly to both UF and NF membranes. The model shows good predictive capability for pure solvent permeation in both ranges. The model is extended to both aqueous and organic solvent mixtures. Only the physical parameters of the single solvents are needed to have good predictions, with the exception of the mixture viscosity. Only the mixture acetonitrile/water shows an anomalous behavior. This is explained with the formation of complexes, which are increasing the effective radius of the mixture.

REMOVED: Unraveling the Solvent Flux Behavior of Ceramic Nanofiltration Membranes

This article has been removed: please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy ). This article has been removed at the request of the Executive Publisher. This article has been removed because it was published without the permission of the author(s).

Reduction of chlorination byproducts in surface water using ceramic nanofiltration membranes

In this study, two ceramic nanofiltration membranes with a molecular weight cutoff of 450 Da (NF450) and 1000 Da (NF1000) were used to reduce the concentration of organic matter (OM) in natural water, and the effect on the formation of disinfection by-products (DBPs) was evaluated. The effects of pressure, conductivity and pH were studied. The formation of trihalomethanes, haloacetic acids, haloacetonitriles and haloketones was evaluated. The results of the study indicated that the permeation flow rate of NF1000 was greater than that of NF450. An increase in the operating pressure improved the efficiency of OM removal and reduced the formation of DPBs. Over 75% of the formation potential of trihalomethanes was eliminated using NF450 membrane. The NF1000 membrane produces smaller decreases in trihalomethanes. As the conductivity increased from 900 μS/cm to 4000 μS/cm, the reduction of trihalomethanes decreased from 51% to 22% and from 80% to 39% for NF1000 and NF450 respectively. The flow through NF450 and NF1000 decreased when the pH of the solution decreased from pH 8.3 to pH 4.5. The values of trihalomethanes rejections at pH 8.3 were 79% and 58% for NF450 and NF1000 respectively, and these values decreased to 65% and 40% at pH 4.5.

Development and characterization of chemically stabilized ionic liquid membranes-Part I: Nanoporous ceramic supports

Stabilization of a room temperature methylimidazolium cation based ionic liquid (IL) into the pores of ceramic nanofiltration (NF) membranes was achieved by means of a novel in situ, pressure assisted imbibition/reaction method. The complete coverage of the nanopores void space by the synthesized IL phase, introduced an additional parameter that was pursued in parallel to the challenge of stabilization. The purpose was to develop hybrid membranes that will exhibit solely the gas solvation/diffusion properties of the IL. A silane functionalized ionic liquid phase of 1-methyl-3-(1-trialkoxysilylalkyl) imidazolium as cation and hexafluorophosphate as anion, was first synthesized and subsequently grafted onto the pore surface. The CO 2/CO separation performance of the modified membranes was quite significant. The maximum CO 2/CO separation factors achieved were 11 at 30 °C, 25 at 50 °C, 12 at 100 °C and 5 at 230 °C. The respective CO 2 permeability values were 226, 520, 715 and 2000 Barrer. The stability of the developed membranes has been verified, in 3 sequential cycles of heating/cooling, in the temperature range between 25 and 250 °C and under a differential pressure up to 0.5 MPa.

Solvent flux behavior and rejection characteristics of hydrophilic and hydrophobic mesoporous and microporous TiO 2 and ZrO 2 membranes

This paper describes solvent flux and rejection behavior of different hydrophilic TiO 2 membranes and a hydrophobic ZrO 2 membrane. Solvents and solutes used range from polar to non-polar. Additionally, the temperature effect on permeability and rejection of solutes through these membranes was examined. It was found that the solvent permeabilities through microporous hydrophilic membranes with MWCO 275 and 1400 Da do not obey the viscous flow transport mechanism, in contrast to the permeability through mesoporous TiO 2 membrane with MWCO 7000 Da. Decrease of the pore size increased deviation from the viscous flow mechanism. Obtained aqueous and polar solvent fluxes were high. This raises opportunities for industrial applications. Moreover, permeabilities of the non-polar solvents can be increased to acceptable levels by working at elevated temperatures through the mechanism of activated permeability. The hydrophobic membrane showed very high non-polar solvent fluxes and remarkably low water permeabilities. Here, no surface interactions can be considered, due to the lack of hydroxyl groups on a membrane surface. Thus, transport through this membrane is related with viscosity decrease at higher temperature and is closer to viscous behavior than for the hydrophilic membranes with similar pore sizes. Rejections of the solutes did not change with temperature and were high when the hydrophilic membranes were used. The non-polar solute bromothymol blue in toluene showed high rejections, unlike some other literature data. The hydrophobic membrane showed much higher fluxes, but rejections were lower than expected. The results of this study are representative for the ceramic nanofiltration membranes currently available on the market.

Coupled series–parallel resistance model for transport of solvent through inorganic nanofiltration membranes

In this work, permeation of a number of different classes of solvents through commercial TiO 2 and ZrO 2 ceramic nanofiltration membranes was measured. A wide variety in permeate flux levels were observed. Solvent permeation was found to be a function of solvent characteristics (viscosity, surface tension, effective molecular diameter and dielectric constant) along with membrane characteristics (surface tension, average pore size diameter and dielectric constant). This paper also presents a new mathematical model based on parallel convection–diffusion theory which relates permeation of solvent molecules to three different resistances in the surface and the main body of the membrane. Transport resistances are defined by easily measurable solvent and membrane properties as indicated above. The model was tested on a series of permeability experiments of water, acetonitrile, methanol, methyl ethyl ketone, ethylacetate, ethanol, tetrahydrofuran, 1-propanol, 1-butanol, toluene, cyclohexane and n-hexane, carried out with HITK275 and HITK2750 membranes (Inoceramic, Germany). Compared to the existing models, which are able to make predictions only for a given class of solvents (polar or apolar), the new model can surprisingly fit the results of the permeation study for all solvent classes, and even for water. The maximum deviation from experimental results was calculated as 4.8%.

Ionic liquid imbibition of ceramic nanofiltration membranes

Imbibition kinetics of (ionic) liquids in asymmetrically structured ceramic nanofiltration membranes are investigated experimentally and theoretically. Results of this are employed as a means for a novel preparation method of immobilized liquid membranes (ILM) for gas separations. ILM are composed of liquid domains situated within micro-structured porous supports such as nanofiltration membranes. Experimental investigation of imbibition kinetics is performed by a freezing method: a dyed liquid intrudes into a nanofiltration membrane (support) which afterwards is frozen in liquid nitrogen. The frozen liquid layer thickness in the support is analyzed by light microscopy. Four different support types and two liquids, i.e. the ionic liquid [BMIM][Tf2N] and a silicone oil are employed. The experimental findings are successfully modelled by an adapted Washburn Equation (WE) whose applicability and premises are discussed. Different proposed modelling approaches for representation of the highly asymmetric structure of the employed ceramic nanofiltration membranes are evaluated. A monolayer model, which assumes a uniform pore diameter throughout the whole support is best suited to describe the experimental findings and constitutes a means for the investigated in situ membrane preparation. This semi-empirical Washburn approach is well suited to describe imbibition of both liquids into porous networks where non-continuum physics prevail.

‘Click’ Dendritic Phosphines: Design, Synthesis, Application in Suzuki Coupling, and Recycling by Nanofiltration

Abstractmagnified imageA new synthetic route towards stable molecular‐weight enlarged monodentate phosphine ligands via ‘click’ chemistry was developed. These ligands were applied in the Pd‐catalyzed Suzuki–Miyaura coupling of aryl halides and phenyl boronic acid. The supported systems show very similar activities compared to the unsupported analogues. Moreover, recycling experiments by means of nanofiltration using ceramic nanofiltration membranes demonstrate that these systems can be recovered and reused efficiently.

Comparison Studies of Applied Pressure and Concentration Gradient Driving Forces in Ceramic Nano-Filtration Membrane for the Production of Intravenous Salt Solution

In this study, the boundary-resistance layer model and solution-diffusion model were used to investigate the applied driving pressure force technique and the concentration driving force technique, respectively, for the production of intravenous drip solution. A 5 kD monolithic membrane coated with Al2O3 and TiO and NaCl aqueous solution as the feed solution was used. The results show that the boundary-resistance layer model diffusivity coefficient, D = 1.8A—10-9 m2 sec-1 and the mass transfer coefficient, k = 1. 19- 10-4 m sec-1 which were both slightly higher than the solution-diffusion model. Applying Fick's law for the solution diffusion model, the calculated operating pressure inside the lumen was 15 kPa. Clearly, the findings suggested that the boundary-resistance layer model should be chosen for the production of pure and sterile intravenous salt solution as it provided higher diffusivity and mass transfer coefficient than the solution-diffusion model. © 2007 Asian Network for Scientific Information.

Pervaporation properties of fluoroalkylsilane (FAS) grafted ceramic membranes

Changing the hydrophilic character of ceramic membranes into hydrophobic ones is nowadays of particular interest. The originally hydrophilic character of ceramic membranes can be changed by grafting hydrophobic molecules on the surface. Fluoroalkylsilanes (FAS) are a group of compounds which can be efficiently used to create the hydrophobic character of different surfaces. The grafting process can be performed by a reaction between -OH surface groups of the ceramics and ethoxy groups (-O-Et) presented in organosilane compounds. The aim of this work was to prepare FAS-modified pervaporation ceramic membranes by grafting alumina and/or titania ceramic nanofiltration membranes with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (C8) molecules and to determine the properties of such modified hydrophobic ceramic membranes in the pervaporation process used for the desalination of different salt solutions and for the removal of organic solvents of different hydrophobicity [i.e., ethanol (EtOH) and methyl t-butyl ether (MTBE)] from water. It was found that transport and selective properties of grafted membranes depended on the type of ceramics and the grafting conditions. In general, FAS grafted titania membranes were more permeable and more selective than alumina ones. In the case of desalination it was found that salt rejection was practically 100%; there was no salt found in the permeate. Pervaporation flux in contact with an aqueous salt solution was dependent on the kind of salt, its concentration and feed temperature. FAS grafted membranes prepared from titania showed much higher permeation fluxes compared with alumina ones. Both membranes showed high selectivity towards the organic component of water–organic mixtures. The selectivity factor of FAS-TiO 2 (grafted in 0.1 M C8), FAS-TiO 2 (grafted in 0.01 M C8) and FAS-Al 2O 3 (grafted in 0.01 M C8) membranes in contact with water–MTBE (2 wt.% MTBE) solution was 95, 45 and 23, respectively. The C8 molecules grafted on the titania ceramics underwent conformation change from a tangled form into the straightened one when the C8 environment changed from pure water to a water–organic or water–electrolyte solution. The concentration range in which this conformation change occurred was dependent on the hydrophobicity of organic solvent molecules presented in the solution. In the case of more hydrophobic MTBE molecules the tangled–straightened form change of FAS molecules occurred in a concentration range 0–0.1 mol. % MTBE.

Stability and selectivity of a multiphase membrane, consisting of dimethylpolysiloxane on an ionic liquid, used in the separation of solutes from aqueous mixtures by pervaporation

A novel ionic liquid ([(C3H7)4N][B(CN)4]) was immobilized and coated by silicon in a ceramic nanofiltration module; this multiphase membrane shows a high selectivity (separation factor up to 177) and stability (over nine months) during separation of 1,3-propanediol from aqueous mixtures by vacuum pervaporation.

Innovative methods for the characterization of ceramic nanofiltration membranes modified by TEOS/O3 chemical vapor deposition

Innovative methods for the characterization of ceramic nanofiltration membranes modified by TEOS/O3 chemical vapor deposition

Electrochemical and Electrokinetic Aspects of Ceramic Nanofiltration Membranes

Membrane separation in the nanofiltration range does not only result from a pure sieving effect of the pore structure, but is also strongly influenced by the surface charge properties of the membrane surface and the surface of the pore waits. In the case of liquid saturated oxide ceramic membranes, a surface charge results from dissociated surface groups and adsorbed ions. The aim of the present research therefore is the electrochemical and electrokinetic determination of the charges of ceramic nano-filtration membranes under varying electrochemical conditions and the influences of these effects on the filtration properties. Oxide ceramic nanofiltration membranes of TiO2 were characterized. Direct methods for determining the membrane charges use electrokinetic effects like streaming potential (tangential and perpendicular method). Indirect methods use measurements of the etectromotive force and the salt rejection during permeation measurements. The investigations show the possibility for adjusting the separation characteristic up to a nearly complete salt rejection by choosing the appropriate pH-value, concentration and the kind of the salt solution. Using magnitude and sign of the streaming potential the separation properties with salt solutions can be predicted. This could be checked by cross-flow filtration experiments.

Characteristics and application of new ceramic nanofiltration membranes

In this study, the characteristic and filtration behaviour of a newly developed ceramic nanofiltration membrane was studied and compared to other commercial ceramic nanofiltration membranes currently available. It could be shown that it was possible to produce a ceramic membrane with separation properties in the nanofiltration range and with permeability rates clearly superior to that of polymer nanofiltration membranes. The ceramic membrane was used in tests involving the treatment of textile wastewater, alkaline solutions from bottle washing machines and pickling bath solutions.

Characteristics and application of ceramic nanofiltration membranes.

In this paper we report on the characteristic and filtration behavior of a newly developed ceramic nanofiltration membrane and compare it with other commercial ceramic nanofiltration membranes currently available. It is shown that it is possible to produce a ceramic membrane with separation properties in the nanofiltration range and with permeability rates that are clearly superior to those of polymer nanofiltration membranes. The ceramic membrane was used in tests involving the treatment of textile wastewater, alkaline solutions from bottle washing machines, and pickling bath solutions.

Separation of Isomeric Xylenes Using Cyclodextrin-Modified Ceramic Membranes

Cyclodextrin (CD)-modified ceramic membranes for the separation of xylene mixtures were investigated. CDs were directly immobilized to the surface of TiO2/Al2O3 ceramic nanofiltration membranes, and a cross-linking agent was used to obtain further stabilization of the CD layer. Pervaporation tests showed that the order of permeation from ternary xylene mixtures was m-xylene > o-xylene > p-xylene. In p-xylene/m-xylene binary mixtures, the separation was a strong function of the feed concentration ratio. The selectivity of p-xylene over m-xylene changed from 1.53 at 4 vol % to 0.72 at 32 vol % of p-xylene in the feed. To describe these observations, a mathematical model was derived based on Stefan−Maxwell theory assuming a surface-diffusion mechanism. Model parameters including sorption isotherms were obtained from experiments. The Stefan−Maxwell diffusion coefficients are obtained from molecular dynamics simulations. Finally, this model predicted the experimental observations well and revealed that the sel...

Direct Synthesis of Ceramic Membranes by Sol-Gel Process

Ceramic ultrafiltration and nanofiltration membranes (TiO2) are prepared by sol-gel route using a special arrangement which allows the reaction of the reactants directly in the pores of a tubular Al2O3 support or on its surface, respectively. By this direct synthesis the number of technological steps can be reduced which is the main advantage of the method. The produced layers are well joined with the Al2O3 support and the reaction can be adjusted by various technological parameters. The dried and sintered coatings are characterized by X-Ray diffraction, FESEM and AFM. In addition, pore size distribution and filtration properties are investigated and discussed.

Development and characterization of ceramic nanofiltration membranes

Ceramic ZrO2 and TiO2 nanofiltration membranes were produced by using a polymeric sol gel route. The influence of different parameters like additives and solvents onto the hydrolysis and polycondensation properties of the sols was studied by IR- and NMR-spectroscopy and viscosity measurements. The prepared ceramic membranes were characterized by different methods. Structure and phases were investigated by X-ray diffraction, thickness and quality by the aid of SEM and FESEM. The membranes exhibit an average pore size in the range of 1–2 nm as determined from N2-adsorption–desorption measurements. The filtration properties of the membranes were examined by filtration tests with two colouring agents. A cut-off value of less than 1000 Da was determined.