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The incumbent water stress scenario imposes wastewater valorisation to freshwater, promoting technology for its effective treatment. Wastewater from fertiliser factories is quite problematic because of its relevant acidity and solute content. Its treatment through vacuum membrane distillation (VMD) was evaluated through laboratory scale tests at 40 °C and 25 mbar vacuum pressure with polytetrafluoroethylene and polypropylene flat-sheet porous membranes. The wastewater from a partially disused Italian industrial site was considered. VMD distillate fluxes between 22 and 57.4 L m−2 h−1 (LMH), depending on the pore size of the membranes, along with very high retention (R &gt, 99%) for anions (Cl−, NO3−, SO42−, PO43−), NH4+, and chemical oxygen demand (COD) were observed. Laboratory scale reverse osmosis (RO) tests at 25 °C and increasing of the operating pressure (from 20 bar to 40 bar) were carried out with a seawater desalination membrane for comparison purposes. Permeability values around 1.1 LMH/bar almost independently of the operating pressure were observed. Lower retentions than those measured from VMD tests were found. Finally, for any given RO operating pressure, the flux recovery ratio (FRR) calculated from permeate fluxes measured with pure water before and after wastewater treatment was always much lower that evaluated for VMD membranes.

The disposal of wastewater resulting from olive oil production (olive mill wastewater, OMW) is a major issue for olive oil producers. This wastewater is among the most polluting due to the very high concentration of organic substances and the presence of hardly degradable phenolic compounds. The systems proposed for OMW treatment are essentially based either on conventional chemical-physical, biological and thermal processes, or on membrane processes. With respect to conventional methods, membrane processes allow to separate different species without the use of chemicals or heat. This work deals with the use of the integrated pressure-driven membrane processes for the treatment of OMW. They consist of a first stage (microfiltration, MF) in which a porous multichannel ceramic membrane retains suspended materials and produces a clarified permeate for a second stage (reverse osmosis, RO), in order to separate (and concentrate) dissolved substances from water. Laboratory scale experiments with different small flat sheet RO membranes were first carried out in order to select the most appropriate one for the successive bench scale tests with a spiral wound module having a large membrane surface. The aim of this test was to concentrate the dissolved substances and to produce water with low salinity, chemical oxygen demand (COD), and reduced phytotoxicity due to a low content of phenolic compounds. The trend of the permeate flux and membrane retention as a function of the volume concentration ratio was investigated. The influence of OMW origin and its aging on the membrane performance was also studied.

Membrane distillation is a promising thermally driven separation process that can be used for water desalination. The primary requirement of this technique is the hydrophobicity of the membrane, so polymeric membranes are mainly used as the ceramic ones are intrinsically hydrophilic. In this work, in order to modify the water wettability, Al2O3 commercial tubular membranes with different pore sizes were functionalized using methyltrichlorosilane. The main aim of the work was to verify in depth the effects and the success of this hydrophobizing treatment. The effect of silanization on pore size and geometry was evaluated using scanning electron microscopy as well as gas permeation in order to highlight possible morphological changes in the membrane structure. No evident modification was detected. The hydrophobicity was assessed by measuring water contact angles which increased from about zero for the pristine supports up to 145° for the modified membranes. After treatment, the water entry pressures ranged between 0.7 and 2.1 bar. Further analyses were carried out in order to elucidate the amount of silicon grafted to the Al2O3 particles and its distribution. Finally, the modified membranes were tested in a vacuum membrane distillation plant at different temperatures (50, 70 and 90 °C) using as feed both deionized water and a highly concentrated NaCl solution (90 g/L). Very satisfactory performances were obtained. The permeate fluxes were comparable – or even higher – to those registered for a polypropylene membrane used as a reference. The separation properties were evaluated during the NaCl solution tests and were close to the full rejection of salt in any operating condition.

Polyvinylidene fluoride (PVDF) was used for membrane preparation using the nonsolvent induced phase separation (NIPS). In this paper, the effect of the polymer concentration in the dope solution and the nonsolvent bath composition is widely investigated. In particular, the effect of increasing concentrations of ethanol in the coagulation bath on the morphology and characteristics of the membranes, as well as on their performance in membrane distillation of pure water and a brine was evaluated. FESEM analysis, coupled with contact angle determination highlighted different coagulation paths that allowed to obtain superhydrophobic membranes at higher ethanol concentrations. Moreover, the polymer concentration had major effects on the overall porosity and pore size of the membrane. By tuning the membrane preparation conditions, it was possible to obtain membranes that showed great distillate flux as well as a complete salt rejection during the vacuum membrane distillation tests.

Experimental trials are usually needed to integrate information reported on data sheets in order to properly drive membrane choice. It results in data-sets where each membrane is characterised by several performance descriptors. Multivariate data-mining (i.e. chemometrics) effectiveness in analysing such data-sets has been demonstrated through the comparison of seven commercial membranes. Each membrane was represented as an object described by 15 features got from trials with different single-component test solutions. Tree cluster analysis based on Ward amalgamation method was employed for multivariate data mining. The algorithm progressively grouped the membranes in clusters, adopting the Euclidean distance in the 15-dimensional feature space as a measure of similarity. Thus, a graphical output consisting into a similarity tree representing the membrane taxonomy was obtained. A restricted number of membranes, selected as representatives of each identified cluster, underwent to further experiments...

This paper is dedicated to the development of a proper membrane for a membrane contactor-based air conditioning system. Based on mass transfer analysis and knowledge of membrane formation, guidelines for the most appropriate membrane were made.

Electrodialysis (ED) is applied in different fields of industry (Strathmann 2010). It has found wide application in water and wastewater treatment, stabilization of wine, whey demineralization and also for recovery of valuable components associated with the depuration of wastewater. New treatment processes can be designed by integration with other membrane processes as well as nanofiltration an reverse osmosis. Aim of the work is the study of electrodialysis process with some model salt solutions and the attempt to apply it to some industrial wastewater. Electrodialysis tests were mainly performed using model solutions containing nitrates, ammonia or metals. Few tests have been carried out on some real effluents as coke oven wastewater or olive mill wastewater, which were treated in the electrodialysis plant after reverse osmosis concentration. In the present paper some results about the ED treatment of solution containing high copper concentration will be shown.

Thermal comfort control in electrical vehicles calls for air conditioning systems with a low energetic demand. The paper describes a pilot system developed in the frame of the “Xeric” EU project in order to study the effect of different operating variables (e.g. desiccant temperature, air velocity) on the performance of hydrophobic membrane based on desiccant air humidification/dehumidification. The overall vapour mass transfer coefficient was estimated in different conditions. By evaluating the membrane mass transfer resistance of the membrane through a modified desiccant inverted cup method, the experimental estimation of the mass transfer resistances in the fluid phases was done. The data obtained through the pilot system are of great interest for the development of air condition systems based on membrane contactors to be used in vehicles cabins.

This paper deals with the preparation of novel polytetrafluoroethylene (PTFE) membranes from an aqueous dispersion of fluorinated polymer and a pore forming agent (PFA) sintered onto the outer surface of a porous tubular support. Different membranes were obtained by varying the ratio between PTFE and PFA in the starting dispersion as well as the number of dispersion layers sintered on the support. Membranes were characterized through scanning electron microscopy and gas–liquid displacement porosimetry. Distillation tests of the membrane were carried out on a laboratory scale unit fed with a NaCl solution. The characteristics and performance of the membranes were compared with those of commercial porous PTFE tubulets.

The synthesis of thin, defect-free and long lifetime Pd-based membranes for H2 separation is still a challenging task. A porous support is necessary in order to give mechanical stability to very thin layers. Sintered porous metal supports are very promising candidates having numerous advantages over the widely studied ceramic supports. The deposition of a non-metallic barrier between the stainless steel support and the Pd dense layer can prevent the intermetallic diffusion of elements from the support to the Pd-based layer and improve the characteristics (e.g. pore size, topography) of the support surface which actually limits the minimum Pd thickness required in order to obtain high selectivity membranes. In the present paper, the deposition of intermetallic barrier layers made of alumina obtained via sol gel technique was investigated using commercial porous stainless steel supports, both with their original roughness and after a mechanical smoothing treatment. The quality of the deposited alumina layer was related to the surface characteristics of the supports, sol composition (aluminium and additive content) and viscosity. Pd dense layers were grown via electroless plating technique on the alumina barrier by activation with an additional Pd doped thin alumina layer.

Starting from a registered patent, the aim of the present study was to improve the osmotic dehydration (OD) process of Protected Designation of Origin Genovese basil leaves by composite experimental design. The contemporary optimization of both process variables and mixture composition allowed enhancing the quality of the dried product. A tentative substitution in the OD brine of the polyalcohol sorbitol with the novel food trehalose was also performed. Sensorial techniques and headspace analysis were applied to monitor changes in appearance, texture, flavor and color. The best appearance and aroma of dried leaves were obtained at 67.5C with a dipping time of 55 s in a brine containing 65% water, 20% sorbitol and 15% NaCl. Using trehalose did not lead to a significant improvement of the quality of the final product. This experimental approach could be successfully used, also on industrial scale, for the optimization of similar OD processes. PRACTICAL APPLICATION The paper shows the optimization of an osmotic dehydration (OD) process by composite design in order to simultaneously optimize both the process variables and the brine composition. This experimental approach can be successfully used, also on industrial scale, for the optimization of similar OD processes, with the aim to enhance the quality of the dried food and to limit their changes in appearance, texture, flavor and color.

Modern membrane technologies are useful for enhancing the concentration of phenolic antioxidants in olive mill waste water (OMWW) to produce concentrates with valuable applications in functional foods. Three types of OMWW concentrates, each with different levels of solute concentration and purity, were obtained from a single OMWW batch and dissolved in two extra virgin olive oils to achieve saturated solutions. Three addition levels were considered. Accelerated aging testing of the oils was performed at 60 °C and the samples were analyzed after two, four, and 6 weeks of aging. D-optimal design was used to select the 26 experiments that allowed the evaluation of the influence of the different variables on oil stability. The addition of OMWW concentrates resulted in a significant increase in the Radical Scavenging Activity (RSA) of the olive oils. Under these mild experimental conditions, the moderate formation of fatty acid hydroperoxides was probably masked by interfering compounds.

Liquid–liquid displacement porometry (LLDP), is proposed to estimate the molecular weight cut-off value of Ultrafiltration (UF) membranes. Several commercial UF membranes are analysed by using LLDP and their pore size distributions have been used to estimate the molecular weight cut-off as should be obtained by dextran retention. Results compared reasonably with nominal cut-off values given by manufacturers. The method offers a fast and accurate way to assign cut-off values for UF membranes, without having to perform expensive and time consuming solute retention tests, which bring results very often difficult to compare due to the difficulties in the standardization of such methods.

Reverse osmosis (RO) and nanofiltration (NF) processes gain more and more interest in the desalination market. Recently, seawater reverse osmosis (SWRO) has become more widespread, using relatively large plants, whilst NF is being applied before thermal desalination, as an advanced treatment for increased efficiency of thermal processes. A proper and reliable seawater treatment before RO and NF, capable to retain suspended solids that cause fast fouling and plugging of sensitive spiral wound membrane modules, is a key to success of desalination processes. Reliability, high and constant quality of permeate, regardless of changes in seawater characteristics, are major advantages of microfiltration/ultrafiltration (MF/UF) over conventional pre-treatment, allowing a stable and high performance of RO and NF processes. This experimental work evaluates performance of two different UF, hollowfibre membrane modules, when fed directly with raw seawater taken from the industrial harbour of Genoa. The study reports the performance of nanofiltration process fed with UF permeate versus the performance of NF fed with raw seawater.

Several UF membranes with fairly different structure have been characterized by using a liquid–liquid displacement porometer, which has been developed under a close collaboration of our laboratories. Three polysulfone membranes from Millipore and three polycarbonate membranes from Nuclepore–Whatman were studied. The results of pore size distributions showed nice reproducibility and accuracy. The technique is also able to accurately evaluate membrane porosity for membranes with simple cylindrical pore-like structure. In addition the possibility to estimate MWCO, by LLDP results, makes the technique very useful for process selection. Finally SEM pictures of the Millipore membranes show that usual porosimetric liquids do not alter membrane structure.

The effect of preparative parameters on the characteristic of PVDF-based microporous layers (MPL) for proton exchange membrane (PEM) fuel cell was investigated. Physical properties of MPL involving electrical resistance, gas permeability and microstructure were examined. The results show that the characteristics of MPL were affected by preparative parameters, such as PVDF concentration, type of electrically conductive filler and its loading, PVDF/electrically conductive filler ratio, as well as type of PVDF solvent. The PEM fuel cell performance test demonstrates that the obtained MPL has a great potential and interest for further study and development.

Commercial ceramic tubular membranes made by Tami ® have been characterized by several techniques. Their pore size distributions (PSD) have been obtained by liquid–liquid displacement porosimetry (LLDP). Computerized image analysis (CIA) of SEM pictures has been used to get information on the width of the active layer of the studied membranes. These values of thickness have helped to evaluate the porosity of the membranes and to get representative radii from measurements of the permeability to several gases and liquids. A fully automated porosimeter designed by us has been used in the determination of pore size distributions. Results show a good accuracy and reproducibility of LLDP measurements. Binary and ternary liquid mixtures have been used to wet and penetrate into the membrane pores when performing LLDP leading to quite similar results when an effective surface tension is assigned for the ternary mixture. This procedure can be used to calibrate the technique to be extended to thick ultrafiltration and even to nanofiltration membranes.

Gas–liquid membrane contactors were applied to remove carbon dioxide from a gas stream by using an aqueous monoethanolamine (MEA) solution as absorbent. Various modules composed by different numbers of commercial polypropylene capillary membranes were constructed and tested in a laboratory-scale plant fed with a N2–CO2 gas mixture. Attention was especially focused on the CO2 removal efficiency of the different membrane modules when gas flow rate was increased from 5 up to 360 L/h. A mathematical model was developed to simulate the absorption process in order to predict gas removal efficiency from the knowledge of the system physical parameters. The overall membrane mass transfer coefficient kM was determined and used to compare experimental and predicted removal efficiencies. A good agreement between the developed model and experimental results was found.

Membrane bioreactors have been extensively studied for the treatment of domestic wastewater. In this paper we describe the application of membrane bioreactors for the depuration of non-civil wastewater coming from the washing of mineral oil storage tanks. Microfiltration hollow-fibre membranes were submerged in the bioreactor where the biomass used the hydrocarbon as a substrate. The performance of the submerged membrane bioreactor was analysed in terms of COD and hydrocarbon removal during different experiments that showed the high efficiency of the system. Particular care was taken in carrying out the operations in the sub-critical flux region. The reactor performance was very high, with removal efficiencies ranging between 93% and 97%, also when the concentration of hydrocarbon was very high. Moreover, the hydraulic retention times used in this work were lower compared to those used in an activated sludge process. Some kinetic parameters for the COD and the hydrocarbon removal were assessed.

iofouling is the undesirable accumulation of microorganisms on the membrane surface and it is one of themajor problems affecting the performance and the economy of many membrane installations for the treatment ofseawater and wastewater. Unlike inorganic fouling, biological fouling due to microorganisms can be dependent ontheir growth rate. The paper examines from a theoretical point of view the influence of the membrane recoveryratio on the concentration of biomass in the membrane module. An attempt of validation of the model has been triedusing a submerged microfiltration hollow-fibre membrane set-up.

In this study, electrically conductive microporous layers (MPLs) were prepared through the phase inversion technique by coagulation in a water bath of a mixture of either poly(vinylidene fluoride) or sulfonated poly(vinylidene fluoride) and graphite and carbon black as electrically-conductive fillers (ECFs). The novel gas diffusion layers (GDL) were obtained by casting the MPLs on a wet proof carbon cloth. Poly(vinylidene fluoride) (PVDF), due to its excellent chemical stability, thermal resistance and hydrophobic character was proposed in place of the more expensive and less processable PTFE. Moreover, sulfonated poly(vinylidene fluoride) (PVDFS, 1.9% sulfonation degree) it was investigated as binding agent in order to obtain MPLs with improved characteristics especially in view of the possibility of preparation of gas diffusion electrodes (GDEs) by the deposition of electro-active catalysts. MPLs morphology, water contact angle, electrical resistance, and through-plane air permeability were carefully examined. The PVDF and PVDFS MPLs were assembled with a catalysts coated Nafion membrane and the performance of the resulting membrane electrode assemblies were compared in a fuel cell fed with air and hydrogen. While electrical resistance of MPLs was slightly influenced by the different preparation conditions, the air permeability considerably increased by switching the solvent from N-methyl-2-pyrrolidone (NMP) to dimethyl sulfoxide (DMSO) and by increasing the air exposure time of the composite film after casting as confirmed by the morphological analysis through scanning electron microscopy. As an indication of the MPLs performance, at the operating current density of 0.60 A cm−2, the single cell voltage of the proton exchange membrane fuel cell (PEMFC) was enhanced from about 0.43 to 0.5 V for PVDF based MPLs to about 0.60 V of PVDFS based MPL. The use of the phase inversion technique open several possibilities to tailor the MPL structure to specific fuel cell applications and moreover offers a more straightforward and scalable preparation method.

Both consumers and the food industry are increasingly interested in aromatic herbs, not only as flavoring agents, but also for their content in biologically active compounds. Sweet basil (Ocimum basilicum L.) is a very important culinary herb and a functional ingredient marketed fresh, dried, or frozen. At present, drying is by far the most widely used basil preservation method, thus ensuring microbiological safety and extending basil shelf-life. Nevertheless, during drying, a series of physical and chemical changes that may have an adverse effect on basil quality may take place. Such alterations include changes in its flavor and appearance, mainly caused by the loss of volatile components and the formation of new compounds. Both these aspects are important quality factors with a deep impact on the consumers’ acceptance of the product. In this chapter the most commonly used drying methods are described and their impact on the sensorial and nutritional properties of this raw material are analyzed.

A polypropylene hollow fiber membrane contactor was utilized to absorb CO2 from a gas stream into an aqueous solution. Three reagents were studied: monoethanolamine, piperazine, and potassium carbonate. Attention was focused on the possible intrusion of absorbent in the membrane pores, which reduces the solute mass-transfer rate. Membrane/liquid interface was thoroughly characterized. The removal efficiency of the reagents contacted with a CO2/N2 stream was assessed. It is shown that potassium carbonate and piperazine could be considered interesting candidates for applications in membrane contactors, as they appear more successful than monoethanolamine in ensuring proper and stable conditions at the membrane/liquid/gas interface.

Porous membranes were prepared by immersion in pure water or in water–NaOH baths of poly(vinylidene fluoride) solutions in different types of solvent ( N , N -dimethylformamide or 1-methyl-2-pyrrolidone or triethylphosphate). Membranes were characterized through ultrafiltration tests, scanning electron microscope observations and vibrational spectroscopy (FT-Raman and FT-IR) measurements. The presence of NaOH in the immersion bath caused not only chemical dehydrofluorination of the polymer but also affected the membrane formation thus leading to membranes with different structures, permeability and retention properties. Membrane prepared by coagulation in NaOH rich bath were treated with NaOCl and H 2 O 2 to attack the double bonds and to obtain membrane with improved hydrophilicity.

Porous membranes and dense films were prepared from polysulfone solutions in N-methyl-2-pyrrolidone (NMP) containing different types and amounts of clay. Commercial clays supplied by Southern Clay, either unmodified (Cloisite Na) or organically modified (Cloisite 30B and Cloisite 93A), were used. The clay behavior in the organic solvent was dependent on the presence and type of the organic compatibilizer: Cloisite containing Na ions did not swell in NMP, whereas those with the organic compatibilizer swelled, though to a different degree. Electron microscopy observations were made to examine the clay dispersion in the membrane structure. At variance with Cloisite Na and Cloisite 93A formed microaggregates, Cloisite 30B yielded nanostructures composed of both single sheets and well-ordered multilayer silicate clusters, which were characterized by an interlayer distance higher than that of the neat clay. The increase in the distance between the layers of Cloisite 30B was related to the formation of intercalated nanocomposites, whereas the presence of single sheets well distributed in the polymer matrix supported the occurrence of delaminated nanocomposites. The intercalation of the polymer into clay layers was confirmed with wide-angle X-ray diffractometry. The addition of Cloisite 30B to the casting solution influenced the phase-separation process in the coagulation bath. Therefore, by the variation of the layered-silicate concentration in the casting solution, membranes with different morphological structures and ultrafiltration properties were obtained. Cloisite 30B was also found to improve the wettability and mechanical properties of dense films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3637–3644, 2007

Polyvinylidene fluoride (PVDF) membranes were prepared by water immersion of a binary PVDF-solvent solution cast on the outer surface of a porous tubular support. During immersion the free shrinkage of the cast solution was hindered by the support and consequently the nascent membrane was subjected to a stretching action that caused pore formation. A laboratory scale device was realized for casting operation and some preparative parameters were studied to control the deposition of the PVDF solution on the porous support. Membranes were characterized through scanning electron microscope observations, air permeability measurements, ultrafiltration tests and membrane distillation experiments. These latter were carried out with a laboratory unit fed with 3 w/v% aqueous NaCl solution at 69°C. The membranes were housed in a tubular cell with the feed flowing on the shell side and the sweeping air in the membrane lumen. The effect of feed and gas velocity on the membrane performance was investigated and the obtained results were compared with those of commercial tubular membranes tested on the same unit. The influence of casting parameters on the morphology and permeation properties of the membranes was also studied.

Laboratory membrane reactors have been studied with the main aim of using such types of devices in kinetic studies of gas−liquid and gas−liquid−solid reactions. As a matter of fact, these reactors allow a better control of the gas−liquid mass transfer phenomena thanks to the absence of emulsions and foams, the interfacial area being constant and stable with different flow rates, and the modular design and ease of scale-up.Four different reactors have been tested to determine what impacts gas absorption from the internal part of the membrane-tube toward the liquid, both in the absence and in the presence of a chemical reaction. In particular, two different agitated reactors have been used: one well-stirred without membranes and the other moderately stirred and containing a coiled bundle of membranes. These two reactors had exactly the same size and stirrer, with the presence of the membrane being the unique difference. The performances of these reactors have been compared for both the physical absorption ...

The catalytic membrane reactor and the inert packed bed membrane reactor were studied in the vapour phase selective oxidation of toluene. Different feeding policies for the membrane were explored and their influence on the selectivity to the desired products (benzaldehyde and benzoic acid) was investigated. The active phase was prepared by depositing vanadium on a Al2O3–TiO2 support prepared through the sol–gel technique. Higher selectivity to benzaldehyde was obtained using the catalytic membrane reactor. Differences were seen in the catalytic membrane reactor performance only when the active phase was heavily charged along the membrane cross-section. # 2004 Elsevier B.V. All rights reserved.

Layered membranes were prepared by sequential grafting—by means of redox initiators—of water-soluble monomers, with oppositely charged ionic groups, onto ultrafiltration (UF) polyacrylonitrile (PAN) membranes at room temperature. Grafting of a single layer of 2-hydroxyethylmethacrylate (HEMA) onto a PAN membrane gave a highly grafted membrane with a relatively high water flux. Bilayered membranes with various properties containing poly-2-(dimethylamino)ethyl methacrylate (p-2DMAEMA) as the bottom layer and polymethacrylic acid or polystyrenesulfonic acid (p-SSA) as the upper layer were prepared and compared—by means of infrared spectroscopy and electron microscopy—with single-layered membranes of grafted polyhydroxyethylmethacrylate. Layered membranes exhibited a significant decline in water flux in comparison with the initial UF membranes. The flux could, however, be manipulated by controlling the concentration of monomers, the time of grafting, and the number of layers. When four layers of p-2DMAEMA and p-SSA were sequentially grafted onto a PAN membrane, pure water fluxes were stable over a wide range of pH values and did not change over long storage times. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 509–520, 2005

Liquid–liquid displacement porosimetry (LLDP) has been used to analyse very regular track-etched polymeric membranes in the ultrafiltration (UF) range, with a nominal pore diameter of 50 nm. A fully automated porosimeter has been used in the evaluation of pore size distributions and results have been compared with image analysis performed on scanning electron micrographs (SEM–CIA) of the membranes. Comparison gives a nice agreement between both results (mean pore radius of 23.6 nm for LLDP results and 24.0 nm for SEM–CIA performed on the same samples used for LLDP). A not so satisfactory agreement is obtained for other indirectly evaluated parameters as porosity (means of 1.4 and 2.1%) or the mean total number of pores (19.6×10 12 pores/m 2 , from LLDP and 11.1×10 12 pores/m 2 for SEM–CIA). These results show that LLDP measurements have good accuracy and reproducibility and that the analysing fluid mixtures used do not significantly modify neither the chemical nature nor the structure of the membrane material used. Of course, ulterior research should be made in order to elucidate the influence of solvents and other parameters of the LLDP analysis. Membranes so regular as track-etched UF ones could be used as appropriate standards to refine the technical parameters for LLDP.

The gas phase oxidation of toluene was studied as an alternative way to obtain benzaldehyde and benzoic acid. A traditional support (TiO2) and a new mixed Al2O3–TiO2 support for the active catalyst element, vanadium, was used. The oxidation process was investigated by either using a packed bed reactor or inorganic membrane reactors. Vanadium was deposited on the supports (powder or inorganic membranes) through either ion exchange or impregnation from a solution of ammonium metavanadate. The catalysts were characterized in terms of vanadium content and distribution, morphology, specific surface area and porosity. The reaction runs quantified catalytic activity of the catalysts prepared. The effect of the temperature and of the hydrocarbon=oxygen ratio was investigated. Selectivity to intermediate oxygenated products was higher for vanadium supported by Al2O3–TiO2 and when the hydrocarbon to oxygen ratio was higher, the formation of carbon oxides was lowered. Finally inorganic membrane reactors were explored using different reactor configurations (i.e. both the reactants, toluene and oxygen, were flowed inside a inorganic membrane tube with catalytic walls, or were forced through the membrane from the internal side to the outer side).

In order to investigate the effectiveness of vibrational spectroscopy in the characterization of polymeric membranes, several poly(vinylidene fluoride) (PVDF) membranes with different porous structures were prepared by the phase inversion process using different casting solvents. An accurate analysis of the Fourier transform Raman (FT-Raman) and the Fourier transform infrared (FTIR) spectra was performed for each sample and the scanning electron microscopy (SEM) results were noted. To highlight the specific problems related to porosity and surface roughness in the acquisition of spectra by different sampling techniques, the attenuated total reflection (ATR) and photoacoustic spectroscopy (PAS) spectra were compared with corresponding spectra obtained from dense films. A detailed analysis of these spectra highlighted their ability in determining the differences in the polymer structure between the two membrane sides. This indicates that (considering the results given by all the different techniques) thorough qualitative membrane characterization can generally be achieved. Moreover, the good quality spectra of the PVDF membrane provide information on a portion of material which depends on its structure, highlighting the usefulness of FTIR-PAS in studying porous materials which, as a rule, give low quality infrared spectra when other sampling techniques are used. However, the complex and inhomogeneous structure of these materials can make quantitative analysis more, or less, difficult.

The results of preliminary experiments for the production of new tomato juices based on the introduction of a microfiltration (MF) stage before the reverse osmosis (RO) stage are reported. Ceramic multichannel membranes with an average pore size in the micrometer tenths were used in the MF stage to obtain a clarified serum to be concentrated by RO and a concentrated pulp to be used for remixing with the RO concentrate, in order to formulate new tomato juices. High temperature and pressure resistant spiral-wound RO membranes were used to concentrate the clarified serum up to 14–15 Brix with permeate fluxes around 20 L/m2h..

Poly(vinylidene) fluoride (PVDF)-ZrO2 composite membranes were prepared by casting and immersion into a water bath of ternary suspensions obtained by adding additional amounts of ZrO2 particles to PVDF solutions. Methods to obtain an intimate dispersion of the inorganic particles in the PVDF solutions were developed. A large variety of supported and unsupported membranes were prepared by varying some of the preparative parameters such as: the PVDF solvent (N-methyl-2-pyrrolidone or triethylphosphate), the total concentration and the PVDF/ ZrO2 ratio in the ternary dispersion. Membranes were also cast from a binary solution of PVDF and solvent for comparison purposes. All the obtained membranes were characterized by scanning electron microscope observations and ultrafiltration tests. The effect of the above-mentioned preparative parameters on the structure, flux and dextran retention properties of the membranes is discussed.

Producción Científica, Structural and surface properties of two commercial polysulfone ultrafiltration membranes have been evaluated by different techniques. Pore size distributions have been determined by Liquid–Liquid Displacement Porosimetry (LLDP) as well as by image analysis performed onto Field Emission Scanning Electron Microscopy (FESEM) images of the membrane surfaces. Fourier TransformInfrared Spectroscopy (FTIR) has been used to investigate membrane composition, and in particular, to obtain proper information on the presence of an additive within the membrane structure. Porosimetric results obtained by the two independent techniques compared reasonably well and the Molecular Weight Cut Off (MWCO) of the two membranes estimated from LLDP pore size distribution was found to be in good agreement with the nominal values given by manufacturers., Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA302U13)

Poly(vinylidene fluoride) (PVDF) was modified by chemical treatments in order to obtain a functionalized polymer suitable for the preparation of ultrafiltration membranes with improved hydrophilicity and fouling resistance. Membranes obtained from the modified polymer as well as from the unmodified one were characterized through pure water permeability measurements and ultrafiltration tests with a dilute solution of skim milk. The fouling tendency of the membranes was measured from the relative reduction in water permeability before and after ultrafiltration. Dense films were also prepared and characterized through contact angle measurement in order to obtain a preliminary evaluation of the hydrophobicity. Vibrational spectroscopy (FT-IR and FT-Raman) techniques were effectively used to investigate the functionalities introduced by the chemical treatments.

The flux of ultrafiltration membranes may be severely reduced when treating low-molecular-weight hydrophobic solutes even though the cut-off of the membrane is orders of magnitudes greater than the size of the solute molecules. In this investigation, the flux reduction was correlated to the membrane pore size using octanoic acid as a model substance. As a comparison, the pore size was also determined by measuring the retention of a dextran solution and by using the liquid-liquid displacement porometry method (LLDP). The membranes used were four asymmetric polysulphone and polyethersulphone membranes with nominal molecular weight cut-off (NMWCO) between 6 and 50 kDa. It is shown that the use of a low-molecular-weight hydrophobic solute may provide a rapid and simple method of characterising hydrophobic ultrafiltration membranes, both regarding their sensitivity to flux reduction due to adsorption, and their pore-size distribution (C) 1998 Published by Elsevier Science B.V. All rights reserved. (Less)

The present chapter deals with multi-phase catalytic membrane reactors where the reactants distributed in different fluid phases meet on catalytic sites located in the structure of a catalytic membrane. The aim of the chapter is to summarize the features of catalytic membrane reactors applied to gas - liquid and liquid – liquid systems in order to show the capabilities, advantages and limitations of this class of emerging multi-phase reactors. In multi-phase systems, the catalytic membrane is usually used as an interface between two fluid phases and allows strict control of the reactant mass transfer with enhancement of the overall heterogeneous kinetics. Moreover, the particular features of the catalyst structured as a membrane can improve the intrinsic kinetics and the catalyst’s effectiveness. This chapter, by discussing some relevant points of catalytic membranes applied to multi-phase systems, aims at being a simple starting point for researchers who would like to begin their investigation in this fascinating field. After an introduction devoted to a first general description of multi-phase reactor systems, the chapter illustrates several contact modalities between reactants distributed in two different phases and the catalytic membrane. The role of mass transfer phenomena and reaction kinetics in multi-phase catalytic membrane reactors is discussed on the basis of simple well-known chemical engineering principles and modelling examples. Typical materials for multi-phase membrane reactors are briefly listed. Finally, some typical applications (e.g., hydrogenation and oxidation reactions) are reported.

Membranas de poliamidas alifáticas são muito utilizadas como barreiras seletivas em processos de microfiltração e ultrafiltração. Neste trabalho membranas de poliamida 66 (PA 66) foram preparadas pelo método de inversão de fases e caracterizadas para aplicação em processos de ultrafiltração. As membranas de PA 66 foram preparadas utilizando dois solventes diferentes, ácido fórmico (AF) e ácido clorídrico (HCl) e água como não-solvente. A análise por Espectroscopia de Infravermelho com Transformada de Fourier (FT-IR) mostrou que a estrutura química da PA 66 não foi alterada com o uso dos solventes na preparação das membranas. O ensaio de compactação com água pura realizado a 1500 kPa de pressão revelou que as membranas preparadas em AF sofreram maior compactação na sua estrutura apresentando fluxo de permeado em torno de 17 L.m-2.h-1 enquanto a membrana preparada em HCl apresentou fluxo de 22,2 L.m-2.h-1. Nos ensaios de ultrafiltração (UF), ambas as membranas apresentaram valores de retenção próximos a 70% para albumina de ovo (45 kDa) e 80% para albumina sérica bovina (69 kDa). Com esse resultado, pode-se concluir que ambas as membranas apresentaram ponto de corte nominal para aplicações em processos de UF. In the present study, polyamide 66 (PA 66) membranes were prepared by phase inversion method and characterized in order to verify their potential application in ultrafiltration processes. PA 66 membranes were prepared using two different solvents, formic acid (FA) and hydrochloric acid (HCl), and water as a non-solvent. Fourier-transform infrared spectroscopy (FT-IR) showed that the chemical structure of PA 66 was not altered by the use of solvents in the preparation of membranes. The compaction experiment with pure water performed at a pressure of 1500 kPa revealed that membranes prepared with FA undergo greater compaction of its structure and had a permeate flux value of approximately 17 L.m-2.h-1 whereas the membrane prepared with HCl had a permeate flux of 22.2 L.m-2.h-1. In the ultrafiltration experiment, both membranes had retention values around 70% for egg albumin and 80% for bovine serum albumin. Based on this result, one concludes that both membranes had nominal cut off values for application in ultrafiltration processes.

A new easy method for the preparation of polymeric nanocomposites supporting metal nanoparticles is presented. The method concerns the use of a layered inorganic ion exchanger converted in the proper metallic form and exfoliated to act as filler of organic polymers with twofold aim of obtaining a composite (or nanocomposite) and to have metal ions that can be suitably reduced with a proper reducing agent to form metal nanoparticles. This strategy has been applied to the system polyvinylidene fluoride (PVDF) filled with layered a-zirconium phosphate in copper form. Several physical techniques (X-ray powder diffraction, atomic force microscopy, high resolution transmission electron microscopy) have been used to characterize the Cu-nanoparticles, whose dimensions range from 5 to 200 nm for those placed inside or on the surface of the polymeric matrix respectively, depending on the dispersion degree of the inorganic filler. The method is simple and can be used for different polymeric matrices and/or metal ions in order to produce metal/polymer systems with promising technological application.

Atomic force microscopy (AFM) has been used to investigate the surface of ultrafiltration and microfiltration ceramic membranes. The AFM has been shown to resolve the feature of the γ-Al 2 O 3 selective skin layer of ultrafiltration membranes providing information on both the size and shape of the γ-Al 2 O 3 particles as well as the surface roughness of the skin. When applied to study α-Al 2 O 3 microfiltration membranes the AFM has been shown to yield results very similar to those obtained by conventional scanning electron microscopy.

The opportunity of using mesitylene solvated Pt atoms for the deposition of Pt catalyst on inorganic membranes is shown. The catalytic activity of the membrane reactor has been tested using the hydrogenation of benzene as model reaction. The performance of the membrane reactor has been compared with that of a conventional packed bed using γ-Al2O3 powder impregnated with Pt. The effect of the feeding configuration has been investigated, and the results show a membrane effect due to the different degrees of accessibility of pores of different size. For alumina powder we have obtained an activation energy of 12.9 kcal/mol, which well agrees with the data reported in literature. The membrane reactor, instead, exhibited an activation energy ca. 60% lower. The preliminary porometry results have shown a slight effect of the platinum deposition process on membrane permeability.

Four different microfiltration (MF) membranes were analysed with respect to porosity and protein adsorption. Liquid displacement porosity (LDP) and adsorption of 14 C-labelled β-lactoglobulin were used as characterization methods. LDP showed a clear pore size distribution for all membranes analysed, with maximally 10% of the pores having at least 90% of the permeability. The protein adsorption came to equilibrium within 30 minutes, giving decreased permeabilities for all membranes. The permeability loss could not be modelled as a simple membrane pore restriction, but the protein load corresponded to a monolayer of protein adsorbed on and in the membranes.