Nanofiltration

Gold (Au) nanosols stabilized with poly(vinylalcohol) can be used as homogeneous oxidation catalysts, both in water and in a variety of alcoholic solvents. Under 0.5 MPa O2 pressure, 1,2-diols with varying chain length, such as 1,2-propanediol or 1,2-octanediol, are oxidized to the corresponding α-hydroxy-carboxylates with total chemoselectivity. The activity of the sol is of the same order as previously reported for stabilized nanoparticles deposited on carbon supports. The stabilized sols retain their activity over extended periods. The Au metal colloids can efficiently be recycled by means of a nanofiltration, either from an aqueous reaction medium, or from an organic solvent. The most suitable membranes for the Au sol recuperation are cellulose acetate membranes for the aqueous filtration, and poly(dimethyl)siloxane membranes for the solvent resistant filtration. Recycling tests after nanofiltration show that catalytic activity is largely preserved in consecutive runs.

This study investigated the removal efficiency and mechanisms of water contaminants (mainly N-nitrosamines) during municipal wastewater reclamation by a membrane bioreactor (MBR) and nanofiltration (NF) hybrid system. The removal of bulk water contaminants was governed by the microbial activities in the MBR and molecular weight cut-off (MWCO) of the NF membranes. The removal of N-nitrosamines by the MBR was primarily attributed to biodegradation by aerobic bacteria, which can be determined by the reactivity of the amine functional groups with the catabolic enzymes (removal efficiency=45-84%). Adsorption and formation of membrane fouling can enhance the removal of N-nitrosamines by the NF membranes. However, size-exclusion is found to play a major role in the removal of N-nitrosamines by the NF membranes since the removal efficiencies of N-nitrosamines varied significantly depending on molecular weight of the N-nitrosamines and MWCO of the NF membranes (removal efficiency: NE90>NE...

Hollow fiber membranes using Polyethersulfone (PES) were fabricated inhouse using phase inversion technique by modification with synthesized chargedsurface modifying macromolecules (cSMM). The cSMM comprise with end-group component of Hydroxybenzene sulfonate or Hydroxybenzene carboxylate. The electrical properties of the membranes were modeled by utilizing the combination of irreversible thermodynamic model, Steric-Hindrance Pore (SHP) model and Teorell-Meyer-Sievers (TMS) model. The negatively-charged of the modified hollow fiber membranes was calculated based on sodium chloride rejection performance. The analysis of the modeling results revealed that sulfonate induce negative 1.61 electrical properties compared to carboxylate that is negative 1.49 for the modified PES membranes.

The extraction of essential oil from vegetable matrices with supercritical fluids is a promising technology which is still searching for an economical method to recycle the dense carbon dioxide (CO 2 ). The use of the reverse osmosis membrane separation process can be an alternative to avoid the intense depressurization step which is necessary for the recovering of the extracts. The membranes exhibit satisfactory permeability for supercritical CO 2 filtration, with very good resistance under the severe experimental operating conditions. In this work, four commercial reverse osmosis and nanofiltration membranes were applied to perform the separation of limonene and supercritical carbon dioxide. The tests were conducted under a pressure of 12 MPa, a transmembrane pressure of 0.5 MPa and a temperature of 40 • C. Pure CO 2 flux, limonene + CO 2 flux and the limonene retention factor were measured. The highest limonene retention factor was above 0.94.

This paper is designed to provide an overview of the main membrane-assisted processes that can be used for the removal of toxic inorganic anions from drinking water supplies. The emphasis has been placed on integrated process solutions, including the emerging issue of membrane bioreactors. An attempt is made to compare critically recently reported results, reveal the best existing membrane technologies and identify the most promising integrated membrane bio/processes currently being under investigation. Selected examples are discussed in each case with respect to their advantages and limitations compared to conventional methods for removal of anionic pollutants. The use of membranes is particularly attractive for separating ions between two liquid phases (purified and concentrated water streams) because many of the difficulties associated with precipitation, coagulation or adsorption and phase separation can be avoided. Therefore, membrane technologies are already successfully used on large-scale for removal of inorganic anions such as nitrate, fluoride, arsenic species, etc. The concentrated brine discharge and/or treatment, however, can be problematic in many cases. Membrane bioreactors allow for complete depollution but water quality, insufficiently stable process operation, and economical reasons still limit their wider application in drinking water treatment. The development of more efficient membranes, the design of cost-effective operating conditions, especially long-term operations without or with minimal membrane inorganic and/or biological fouling, and reduction of the specific energy consumption requirements are the major challenges.

Contact angle measurements (captive bubble technique) were used to determine the surface energy of three experimental thin-film composite nanofiltration membranes and a commercial nanofiltration membrane (Hydranautics NTR 7450). The two experimental membranes of practical interest were thin film composites (diblock copolymer on a polysulfone support layer). The two blocks were poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(1,1-dihydroperfluorooctyl methacrylate) (PFOMA). The concept was to devise a membrane material that takes advantage of the low adhesion of PFOMA to prevent fouling and the hydrophilic nature of PDMAEMA to produce high water permeation rates. Hydranautics NTR 7450 is a sulfonated polysulfone membrane that purportedly lessens fouling because the surface is more hydrophilic. The change in surface energy upon wetting, permeation of water containing natural organic matter (NOM) and chemical cleaning was of interest. Wetting caused reorganization of the experimental block copolymer surface to move more of PDMAEMA block to the membrane-water interface. After permeation of ultrapure water, however, the surface became more hydrophilic. After permeation of NOM containing water, the surface of both experimental and commercial membranes reached about the same surface energy, indicative of adsorption of NOM. The contact angle measurements were used to calculate a negative change in surface free energy for all but the PFOMA membrane; hence, with this exception, the deposition of NOM into a layer adjacent to the membrane surface was spontaneous. Scanning electron micrographs and atomic force micrographs showed that rigorous chemical cleaning failed to remove the NOM. Although the new polymeric materials were not more resistant to NOM fouling than commercial membranes, the surface energy calculations may help in the search for more successful polymers. Systematic study of charge, molecular size and specific functional groups of NOM on membrane fouling warrants further research to understand why similar fouling occurred on very different polymeric materials.

Coagulation MIEX Ò Nanofiltration DBPs a b s t r a c t Potentially the most effective means of controlling disinfection by-products (DBPs) is to remove precursors before disinfection. To understand relationships between physical properties, treatability and DBP formation, nine natural organic matter (NOM) surrogates were studied. Their DBP formation and removal by coagulation, MIEX Ò anion exchange resin and two nanofiltration membranes was measured. Whereas treatability of NOM surrogates was explained in terms of their physicochemical properties, the same was not true of DBP formation. Hence it was not possible to selectively remove compounds which generate high amounts of DBPs. Instead, precursor removal strategies based upon empirical DBP formation potential testing are more apt. Under conditions simulating full-scale performance, MIEX Ò did not offer improved performance over coagulation. A hydrophobic nanofiltration membrane proved successful for removing neutral, hydrophilic surrogates, and hence is also suitable for DBP precursors of this character.

In this study the selectivity of two nanofiltration (NF) membranes was tested with the aim of increasing the sugar content of grape must used for wine production. The composition of grape must, concentrate, permeate and the rejection values for selected physicochemical parameters is presented. In particular, the NF membranes provided a high rejection for sugars (range 77–97%), whereas the malic acid was retained to a low extent (range 2–14%). A two-stage NF process of grape must remove a permeate volume of 14%, thus allowed concentration of the sugars, i.e. the potential alcohol, to ca. 16%. The wine obtained from a grape must treated by NF membrane was high in total plyphenols and DO (optical density) at 420 nm.

The importance of wastewater treatment in the food industry is growing nowadays, because of the rising cost of water and because of environmental pollution. The aim of this study was to decrease the chemical oxygen demand (COD) of two different wastewaters originated from the food industry. If the treated water is drained into natural water, the COD has to be below 125 mgO 2 /L, if it is released into sewer the limit is 800 mgO 2 /L. Reverse osmosis and nanofiltration membranes were investigated for wastewater treatement. Experiments were carried out at constant temperature and recycle flow rate, the permeate flux, salt rejection and COD were measured continously. During concentration experiments the fouling of the membranes was observed.

There is a need for a low cost, sensitive, on-line sensor to assess the integrity of membrane modules used in the water industry for water treatment, membrane bioreactors and for pre-treatment prior to using nanofiltration or reverse osmosis. A sensor addressing this need is described whose operating principle is based on measuring the differential pressure across a membrane that intercepts a portion of the permeate from the pre-treatment module(s) relative to the differential pressure across a valve. The latter can be adjusted to maximize the sensitivity of the instrument. A dimensionless metric based on the differential pressures is defined and corroborated with the Silt Density Index. The sensitivity of this Integrity Sensor is demonstrated by its response to cutting one fiber in a UF pre-treatment module that contains 1500 hollow fibers.

In this study, we report the effects of shear rates and polymer concentrations in the formation of asymmetric nanofiltration membrane using a simple dry/wet phase inversion technique. Employing the combination of irreversible thermodynamic model, solution-diffusion model (Spiegler-Kedem equation), steric-hindrance pore (SHP) model and Teorell-Meyers (TMS) model, the transport mechanisms and membrane structural properties were determined and have been characterized for different cases of those formation parameters. The experimental and modeling showed very promising results in terms of membrane performance with interesting structural details. The optimum shear rate (critical shear rate) was found to be at about 203.20 s −1 and the best polymer concentration toward the formation of high performance nanofiltration membrane is in the range of 19.60-23.10%. The modeling results suggested that the pore radius of the membranes produced lies within the range of pore radius of 29 commercial available membranes. This study also proposed that the electrolytes transport through nanofiltration membrane was dominated by a convection factor which accounted approximately 30% more than a diffusion factor. This study also indicated that shear rate and polymer concentration were found to affect the membrane performance and structural properties by providing, to a certain extent, an oriented membrane skin layer which in turn exhibiting an improvement in membrane separation ability.

Adequate rejection of a variety of inorganic and organic compounds is necessary if reverse osmosis (RO) and nanofiltration (NF) membranes are to be used for space mission wastewater reuse. Three ersatz space mission wastewaters defined by NASA having different pH (2.6-8.9), conductivities (3980-12,640 mS/cm), and amounts of organic compounds (50-2400 mg/L as carbon) were tested to determine the membrane flux and the solute rejection for five RO and two NF membranes that are commercially available. The results show that the rejection of ions depends upon the solution pH which influences electrostatic repulsion. However, the rejection of dissolved organic carbon (DOC) depends upon the composition of the wastewater. The DOC rejection (80-95%) was the highest for the wastewater containing dextran (molecular weight 15-20 k) compared with the other ersatz wastewaters having detergent and urea as the major carbon sources (31-83%). The wastewater having the greatest conductivity (12,640 mS/cm) and DOC (2400 mg/L) showed a greater flux decline (71-96%) than the other ersatz wastewaters (37-82%) having lower conductivities (3980-6980 mS/cm) and DOC (50-660 mg/L) for the RO and NF membranes. The ratio of solute radius (r i,s ) to effective membrane pore radius (r p ) was employed to compare ion rejection. For ionic compounds, the rejection is higher than 70% when the r i;s =r p ratio is greater than 0.5 for both the RO and NF membranes with all wastewaters. r

A pilot study was conducted to determine whether membrane treatment on a side stream of recirculating cooling-tower water could reduce overall water usage and discharge. The treated permeate was returned to the cooling tower while the concentrate was discharged to the sanitary sewer. Flow rates, pressures and water chemistry were monitored. The pilot demonstrated potential substantial water savings. Maximum make-up water and discharge reduction were 16% and 49%, respectively. As high as possible permeate recovery is needed to maximize water conservation. Silica scaling on the membranes limited water savings in this pilot. Development of membranes with a solute-rejection capacity less than the 92% average of the membranes used in the pilot would assist in optimizing water savings. Decreased water outlays compensated for the additional energy used by membrane treatment. Scaling control is critical for economic operation.

Due to their excellent resistance to a range of solvents, integrally skinned polyimide membranes have been used to achieve selective separations in a range of solvent-based industrial and lab-scale chemical operations. These include: homogeneous catalyst recycle, petrochemical dewaxing, solvent exchange and chiral resolutions. However, despite the widening scope of use of these membranes, there is still little understanding of how the microstructure defines their separation performance. As a first step towards determining this, integrally skinned nanofiltration membranes were fabricated by phase inversion using Lenzing P84 polyimide. The microstructures of these membranes, dry and wetted in solvent, were investigated by SEM, TEM and ESEM (where appropriate).SEM and TEM imaging of dry membranes revealed that this type of polyimide membrane has three microstructurally distinct polyimide layers, not the two indicated in prior literature. Furthermore, TEM images reveal nano-sized pore-like features in the polyimide structure, which indicate that the transport mechanism is probably neither only solution-diffusion nor only pore flow. ESEM imaging showed that when saturated in ethanol at the working pressure of the ESEM (5.50 Torr), the microstructure of the membranes changes; it is wispy and thus quite different to the more solid polymer nodules and interconnected polymer network observed in the dry membranes. Thus, transport and separation mechanisms based on the structure of the dry membranes may not be accurate. Overall, these results indicate that the current theory used to describe polyimide membrane mass transfer and separation performance (where it is based on dry membrane microstructures), most likely needs to be rethought.

This study aims to evaluate the performances of the membrane processes during the treatment of blue whiting peptide hydrolysates. Ultrafiltration with high molecular weight cut-off (MWCO) can be used for the separation between peptides and non-hydrolyzed proteins. A membrane of MWCO 20 kDa was tested on hydrolysates containing 11.4 g of peptides per liter of solution. Steady fluxes were satisfactory (100 l/h/m 2 at 12 bars and 15°C) but the nitrogenized matter retention is approximately 30%, which leads to a considerable peptide loss in the permeate.

The role of chemical and physical interactions in natural organic matter (NOM) fouling of nanofiltration membranes is systematically investigated. Results of fouling experiments with three humic acids demonstrate that membrane fouling increases with increasing electrolyte (NaC1) concentration, decreasing solution pH, and addition of divalent cations (Ca2+). At fixed solution ionic strength, the presence of calcium ions, at concentrations typical of those found in natural waters, has a marked effect on membrane fouling. Divalent cations interact specifically with humic carboxyl functional groups and, thus, substantially reduce humic charge and the electrostatic repulsion between humic macromolecules. Reduced NOM interchain repulsion results in increased NOM deposition on the membrane surface and formation of a densely packed fouling layer. In addition to the aforementioned chemical effects, results show that NOM fouling rate increases substantially with increasing initial permeation rate. It is demonstrated that the rate of fouling is controlled by an interplay between permeation drag and electrostatic double layer repulsion; that is, NOM fouling of NF membranes involves interrelationship (coupling) between physical and chemical interactions. The addition of a strong chelating agent (EDTA) to feed water reduces NOM fouling significantly by removing free and NOM-complexed calcium ions. EDTA treatment of NOM-fouled membranes also improves the cleaning efficiency dramatically by disrupting the fouling layer structure through a ligand exchange reaction between EDTA and NOM-calcium complexes.

In the present work energy savings in clarified thin sugar juice pre-heating and concentration are presented by integrating a new pressure-driven multistage membrane process with multiple-effect evaporator (MEE). The thin sugar juice is concentrated from 15 w% to 50 w% with membrane and from 50 w% to 70 w% in MEE. The new process will not only reduce the energy consumption of thin juice concentration process significantly but will also reduce the requirements of energy and heat transfer area of heat exchangers for pre-heating the thin juice before evaporation by 70%. The existing sugar factories may increase the capacity of their evaporation station through the integration of the new membrane process while new factories to be built will have a smaller sized evaporation station with more energy efficiency and environmentally friendly process performance and with a significantly smaller carbon footprint.

The potential of incorporating polymeric solvent resistant nanofiltration (SRNF) membranes for biodiesel separation processes was investigated. Eight types of commercial polymeric nanofiltration membranes (Solsep 030705, Solsep 030306F, Starmem 240, Starmem 120, Desal-DL, Desal-DK MPF-34 and MPF-44) were chosen and screened for their abilities to separate the methyl esters-rich effluent (biodiesel) from the mixture of the homogeneous catalyst, free glycerin and excess methanol after the transesterification process at various separation pressures and constant temperature. Scanning Electron Microscope (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were used to examine any changes to all the membranes studied. In order to enhance the SRNF membrane performance, the transesterification product properties was modified by reducing the alkalinity value. Results showed that for 3 membranes (Solsep 030705, Solsep 030306F, Starmem 240), the permeability of transesterification product after the alkalinity modification increased linearly to the operation pressures. The other 5 membranes namely Starmem 120, Desal-DL, Desal-DK, MPF-44, MPF-34 membranes gave dismal results. Out of the eight tested membranes, it was found that Solsep 030705 membrane gave the most promising result. Analysis of the used membranes showed minor differences on functional groups after the application.

In this work, solvent recovery from soybean oil/hexane miscellas (1:3, w/w) was studied. Flat sheet polymeric membranes, polysulfone and polysulfone/polyamide based, used in reverse osmosis, nanofiltration and ultrafiltration, were tested. The effects of pressure (13-27 bar) and temperature (21-49 • C) on permeate flux, oil retention and separation of free fatty acids (FFA) were evaluated by a 2 2 complete factorial design, with three central points and four axial points. Increased pressure resulted in a higher permeate flux though the retention of oil and free fatty acids by the membranes has decreased. However, higher temperatures showed positive effects on the permeate flux, retention of oil and free fatty acids permeation. The highest oil retention (67.12%) was observed for low pressure (15 bar) and high temperature (45 • C).

The objective of this study was to investigate the physico-chemical parameters that determine the retention of phenolic compounds in aqueous solution by nanofiltration membranes. To this purpose, fundamental properties of two membranes (NF90 and NF270) were determined from their observed performance. Molecular weight cut-offs (MWCO) were determined using crossflow filtration of different molecular weights of polyethylene glycol (PEG). Their mean pore size was also estimated by the steric hindrance pore (SHP) model using neutral organic solutes (saccharides). The salt retention sequence of membranes was determined using single aqueous solutions of Na 2 SO 4 , NaCl and CaCl 2 . Retention of phenolic compounds by NF270 was lower than that of NF90, because of its larger pore size. The influence of the solute adsorption upon the NF90 membrane retention was described by the molecular hydrophobicity of organic compounds. Finally, the effect of solution chemistry upon the membrane retention of phenol and resorcinol was investigated at different pH values. Near the isolelectric point of the membranes, minimum organic retention and maximum flux were observed due to membrane electroneutrality.

An investigation on the recovery of chromium from the effluent of a chrome-tanning bath has been performed using nanofiltration (NF) followed by reverse osmosis (RO). The experiments are conducted using a rectangular cross flow cell under laminar and turbulent regimes. Significant flux enhancement is achieved using thin wires as turbulent promoters. The performance criteria are evaluated in terms of the concentration of chromium, COD, BOD, TDS, TS, pH, and conductivity of the permeate. The effects of different operating parameters on permeate flux and observed retention of chromium are evaluated experimentally. The retention of chromium is found to be 91-98% for NF and 98.8-99.7% for RO for the experimental conditions of this study. Concentrations of chromium and COD of the final permeate are well within the permissible limits.

The retention of single (NaCl) and mixed (Na 2 SO 4 + NaCl) salt solutions by nanofiltration membranes was analysed using principal component analysis (PCA). Seven variables-five different membranes (Desal-5DK, NF 270, NF Filmtec, NF 20 and ESNA-1-LF), flux and salt concentration-were taken into account in the analysis. The dependences of NaCl retention on these variables for single and mixed solutions were evaluated by PCA.

In this paper, vertical scanning interferometry (VSI) and atomic force microscopy (AFM) were used to characterize the topography of several nanofiltration and reverse osmosis membrane surfaces. Comparing roughness results from the two different characterization techniques revealed unique results for the various membrane surfaces. Roughness values tended to be higher from the interferometry measurements compared to those from AFM measurements for the same membranes. This was attributed to the inability of the AFM to capture dramatic changes in surface height of several microns or more. Based on interferometric measurements surface roughness was also found to increase with increasing scan-size up to a scan-size of 250,000 m 2 after which it remained relatively constant. Because such large scan-sizes are too large to be captured through AFM measurements interferometry appears to provide a more comprehensive characterization of membrane surface roughness.

The article deals with the possibilities of treating highly fluorinated brackish drinking waters using a polyamide nanofiltration (NF) membrane. Our approach is based on the phenomenological model of Spiegler, Kedem and Katchalsky under a dilute solution condition but neglecting the charges carried by the membrane used (denoted NF45 from Dow, USA). We have calculated the phenomenological parameters, F (the membrane reflection coefficient) and P s (the solute permeability), and observed that F can be linked to the hydration energy of halide ions. Furthermore, P s appeared to be linked to a kind of electrolyte. Then F values are highly dependent on the nature of the anion present in the salty solutions. If NF is generally dedicated to the elimination of divalent ions, the present work studied the potentialities of selectively separating the following single halide salts: NaF, NaCl, NaI, LiF and LiCl. For the first time we have checked that selective defluorination can be attained using a NF membrane showing a predominantly solutiondiffusion mass transfer.

This paper investigates the influence of molecular size and hydrophobicity of dissolved organic compounds in aqueous solution on retention. In a first part, the influence of hydrophobicity was investigated for organic molecules with a similar molecular weight below the molecular weight cut-off (MWCO) of the membrane and a different hydrophobicity, expressed by the logarithm of the octanol-water partition coefficient (log P). A good correlation was found between the hydrophobicity and the retention: molecules with a high log P (hydrophobic) generally had a low retention, while molecules with a negative log P (hydrophilic) showed a high retention. This could be explained by hydration of the molecules. In a second part, the correlation between the retention of molecules with a molecular weight above the MWCO of the membrane and their hydrophobicity was studied. It was found that a high hydrophobicity lowers the retention, but the influence of hydrophobicity decreases if the molecular size (compared to the MWCO of the membrane) increases. Finally, the influence of adsorption on retention was investigated. An increase in permeate concentration and thus a decrease of the corresponding retention, as a function of time, was observed for hydrophobic compounds, until saturation of the membrane was reached (steady-state retention).

Driving force membrane processes seem to be most useful for water treatment. Reverse osmosis, nanofiltration and ultrafiltration have been applied to phthalate removal from water. In the experiment three membranes RO-DS3SE were tested for reverse osmosis, membrane NF-DS5DK for nanofiltration and UF-DSGM for ultrafiltration, all of them from Osmonics, Inc. (USA). All membranes were tested under specified conditions (for RO, NF -2.0 MPa, UF -0.3 MPa) and they showed a high degree of phthalate removal from water -from 97.6% to almost 99.9%. Microextraction (solid phase extraction, SPME with CV/DVB-carbowax/divinylobenzene phase) was used for phthalate extraction from the aquatic matrix, while gas chromatography (GC) with FID detector was used for their quantitative-qualitative monitoring.

At "Debiensko" Desalination Plant salt crystallizer is supplied with untreated brine concentrated by RCC evaporation method that results in high energy consumption and huge amount of post-crystallization lye. Nanofiltration pre-treatment of coalmine brine was then considered to improve plant outcome. Desal-5L (Osmonics) nanofiltration membrane was found to be suitable for the above purpose. The rejection coefficients were found as follows (%): Ca 2+ − 68.8, Mg 2+ − 71.6, SO 4 2− − 98.0, Cl − − 11.9, that lets us to estimate the composition of NF permeate at 85% recovery to be as follows (g/L): Ca 2+ − 0.242, Mg 2+ − 0.188, SO 4 2− − 0.064, Cl − − 32.2. The performance of crystallization step was then estimated based on chemical composition of NF permeate and compared with operational data from "Debiensko" Desalination Plant. The energetic efficiency of the presently operated coal mine brine treatment system was compared with the one involving NF softening as the pretreatment for low energy VC thermal desalination in place of seeded VC (RCC presently applied). This comparison shows that unit energy consumption decreases from ca 970 kWh per 1 t of evaporated salt for untreated brine concentrated by RCC method to ca 450 kWh/t when low energy VC evaporation is applied. At the same time the amount of salt in post-crystallization lye decreases from approx. 110 kg per 1 t of evaporated salt produced to ca 50 kg.

Wastewater effluent organic matter (EfOM) was isolated into different fractions including colloids, and hydrophobic (HPO) and transphilic (TPI) fractions. The EfOM isolates were characterized by different techniques, for example, size exclusion chromatography (SEC) with on-line UVA and DOC detectors, Fourier transform infrared (FTIR), specific UVA (SUVA), and total sugars analysis. The colloidal fraction is primarily composed of polysaccharides, proteins, and/or aminosugars, providing a hydrophilic character. The HP0 and TPI fractions possessed characteristics of humic substances, i.e. high aromaticity and carboxylic functional groups. A superimposition of the EfOM isolates reflects characteristics of bulk wastewater effluents, consisting of refractory natural organic matter (NOM) conveyed from the drinking water source and soluble microbial products (SMP) derived during biological processes of wastewater treatment. Each EfOM isolate exhibited different characteristics in fouling of NF and UF membranes due to their distinct characters. The colloidal fraction showed high flux decline and fouling on NF and UF membranes primarily due to the effects of pore blockage. The HP0 and TPI fractions exhibited less fouling and flux decline than the colloids due to their molecular size as well as electrostatic repulsion between organic acids and the membrane surface. However, hydrophobic interactions play a significant role with hydrophobic membranes, causing a reduction of permeate flux. Membrane autopsies using FTIR identified functional groups of organic foulants, supporting the evidence of flux decline by each EfOM isolate. Polysaccharides and/or aminosugars from the colloids in wastewater effluent were found to play an important role in fouling of NF and UF membranes.

A rapid, reliable and cheap method of characterizing the molecular weight cut-off (MWCO) of commercial and in-house fabricated membranes used in aqueous applications has been developed. MWCO can be determined by performing a single run of pressure filtrations with a mixture of polyethylene glycols (PEGs) in aqueous solution using one of two PEG oligomer mixtures: PEG 200 to PEG 1000 for nanofiltration membranes or PEG 1000 to PEG 6000 for low MWCO ultrafiltration membranes. Analysis is via a repeatable and accurate reverse phase high performance liquid chromatography (HPLC) method through a cheap chemical-bonded silica-based C8 column which finely resolves each of the PEG oligomers. Detection is via a low temperature evaporative light scanning detection (ELSD) method that resolves peaks to a molecular weight difference of just 44 g mol−1 (corresponding to the CH2–O–CH2 structural unit difference between the oligomers), allowing the most precise ever one-filtration determination of MWCO. MWCO testing of commercially available membranes (from Koch, Filmtec™ and Hydranautics) confirmed the method gives MWCO in the expected range. Consequently, this new and refined method can effectively replace the previously required time consuming and costly multiple filtrations of individual PEG oligomers and other compounds for the determination of membrane MWCO for aqueous applications.► One-filtration PEG based MWCO quantification for aqueous applications developed. ► Based on a high resolution reverse phase HPLC-ELSD analysis for PEG mixtures. ► Resolves MWCO within 44 g mol−1 giving the most precise ever one-filtration method. ► Produced accurate MWCO compared to manufacturers values for five commercial NF membranes.

The objectives of this research were to investigate the rejection efficiency of salt and hydrophobic fraction of natural organic matter, to study the flux decline behavior with a spiral wound nanofiltration membrane, and also to survey the influence of water chemistry on membrane performance. Experiments were conducted using a cross flow pilot-scale membrane unit with a full circulation mode. Humic acid was used as hydrophobic organic matter and NaCl as background electrolyte. Results showed that flux reduction increased with increasing ionic strength and humic acid concentration, and with lower pH. The rejection efficiency of organic and salt decreased with the decrease in pH and increase in ionic strength, because of osmotic pressure increase, leading to permeate flux decline and decrease in salt rejection. In addition, the improved salt rejection was likely due to Donnan exclusion by humic material close to membrane surfaces. The average rejection efficiency of humic acid and salt ranged between 91.2%-95.25% and 63.6%-80%, respectively. Dissolved organic carbon concentration was less than 0.57mg/L in permeate for all experiments. With increasing organic concentration, the charge of the membrane surface has become more negative due to the adsorption of organic foulants on the membrane surface, and thus increased the electrostatic repulsion. However, the increasing surface charge had the potential to result in a larger molecular weight cut-off of a fouled membrane due to membrane swelling which can lead to lower rejection solutes. Therefore, results of this study indicated that membrane fouling may significantly affect the rejection of organic and ion solute.

In this study, product recovery and process water recycling in a model Cleaning-in-Place (CIP) wastewater containing anionic and nonionic surfactants, dye, and salt generated from the production of a liquid dishwasher detergent was investigated using a two-step nanofiltration (NF) process. In the first step, a loose NF membrane was used for product recovery, especially surfactants and dye. Effects of pH (3, 5, 7, and 10), temperature (25 and 40 • C), and transmembrane pressure (8, 12, 16, and 20 bar) on the membrane performance were evaluated. The best results were obtained at pH 5, 25 • C, and 20 bar which provided the highest levels of both recovery and rejection of surfactants, dye, and salt. In the second step, the quality of permeate obtained from the loose NF membrane under the conditions providing the best performance was improved using a tight NF membrane. Even better rejections were achieved from the experiments with this NF membrane. Experimental results showed that recovery of surfactants and dye was achieved for re-using in the production of liquid dishwasher detergent, and the permeate was obtained in much the same quality of the water used in the first step of the CIP system using the loose membrane and tight membrane, respectively. In addition, the flux decline caused by the concentration polarization and fouling was evaluated for both membranes. Fouling on the surface of membranes was characterized with atomic force microscopy (AFM) and contact angle measurements.

Viruses are nanometer size organisms (range from 18 to 250 nm) that can potentially contaminate the feedstocks from animal or human origins used to manufacture biopharmaceutical products. Various measures are taken to ensure the optimal viral safety of this class of products. Selection and screening of starting materials play an important role in safeguarding from the introduction of viruses into the downstream processing but they have limits in specificity and sensitivity. Purification methods of protein biopharmaceutical products may also contribute to viral reduction, but since viruses exhibit a wide range of biochemical characteristics and resistance to physico-chemical treatments, complete elimination of infectious agents is not guaranteed. Therefore, the viral safety of animal derived biopharmaceutical products is well recognized to rely largely upon the use of deliberately introduced and validated viral inactivation and/or removal steps. A major progress in viral safety has been made recently by the development and availability of biocompatible viral filtration (also known as nanofiltration) systems using membranes of a pore size as small as 15 nm; these systems are specifically designed to allow, depending upon membrane used, typically over 4 to 6 logs of virus removal under conditions ensuring good protein permeability and recovery. Validation studies and production experience throughout the world have demonstrated that viral nanofiltration is a robust and reliable viral reduction technique that can be applied to essentially all biological products. This review analyzes the virus risks of biopharmaceutical products (human plasma derivatives, horse and sheep plasma-derived products, recombinant proteins and monoclonal antibodies), the various viral inactivation methods used at present, and the increasing role that viral nanofiltration is playing in assuring the safety of biopharmaceutical products.

The water characterisation is generally challenging regarding the pre-treatment operation up-stream reverse osmosis. The classical parameters are not applicable due to analytical limitations, and/or the sensibility of those parameters is too low compared to the water fluctuation behaviour measured on full-scale water treatment plants. The evaluation of the water fouling potential could be a more sensible parameter, supplementing the analytical tools actually used for design purpose.

In this work, lactic acid recovery from clarified fermentation broths by nanofiltration was studied. The effect of feed concentration, flow rate, transmembrane pressure and pH on flux and rejection were analysed. The separation efficiency of nanofiltration membranes in the treatment of ionic solutions may be explained by the combination of size and charge effects. In the case of lactic acid solutions, the ratio of lactate ions to non-ionized lactic acid affects the rate at which both pass through nanofiltration membranes. At pH values around 5.0, which are typical values in industrial fermentations, lactic acid is mainly found in the dissociated form. Two polyamide nanofiltration membranes were used: DK2540C ® (Filtration Engineering) and AFC80 ® (PCI Membrane Systems). A strong influence of pH on lactic acid transport through these membranes was observed. The pH value affected both rejection and permeate flux. Rejection increased with pH while flux decreased with this variable. However, at high feed concentrations, solute retention was much lower as the Donnan exclusion effect was attenuated. At the acidic pH required to convert lactate into undissociated lactic acid (pH 3.0), the recovery of lactic acid must be improved in order to reduce lactic acid losses and increase purity.

Lactose retention was predicted by means of the Donnan Steric Partioning model (DSPM) and the Kedem–Spiegler model (KSM). Retention and permeate flux were measured using single lactose solutions and ultrafiltered whey (UF-whey) as feed solutions. The experiments were performed at constant pH with NF200 and desal 5 DL nanofiltration membranes supplied by Dow-Chemical (USA) and GE-Osmonics (USA), respectively. The two models were able to predict reasonably well the pattern and tendencies of lactose retention as a function of permeate flux when either a lactose solution or UF-whey was used as feed. The best predictions were obtained with the KSM. This model was observed to be able to predict lactose retention in the presence or absence of ions without providing any information about the membrane structure. However, the DSPM provides information about the charge, the thickness–porosity ratio and the pore size of the membranes. This contributes to a better understanding of the transport mechanism in nanofiltration processes. The presence of salts increased the values of the fitted mean pore radius and the fitted thickness/porosity ratio of the membranes. For the two membranes tested lactose retentions were lower in the case of UF-whey. This was explained taking into account the effect of salts on membrane performance.

This paper presents experimental data and modelling for three commercial nanofiltration membranes (NF90, NF270, N30F) used to treat highly concentrated different salts solutions (KCl, Na 2 SO 4 , and MgSO 4 ) in a crossflow filtration set-up at a salinity level similar to that of seawater. The main parameters that have been studied in this work are feed pressure and salt concentration. The experimental data were correlated and analysed using artificial neural network (ANN) and Spiegler-Kedem model. Through the latter model, the reflection coefficient of all studied membranes and the solute permeability have been determined for all membranes at different salinity levels. The ANN's prediction of rejection vs. pressure and rejection vs. permeate flux for all investigated salt solutions is discussed. The results showed that both NF90 and NF270 produced a high rejection in the range of 95-99% at a pressure greater than 5 bar for Na 2 SO 4 , and MgSO 4 salts, while for KCl the rejection was in the range of 30-89%. N30F gave relatively medium rejection and flux for Na 2 SO 4 and MgSO 4 salts and very low rejection and flux for KCl. A good agreement has been obtained using the ANN predictions and the experimental data with a deviation not more than 5% for most of the cases considered. The ANN interpolative performance for the medium concentration H. Al-Zoubi et al. / Desalination 206 (2007) 42-60 43 levels (which were not represented in the training phase) is shown to be of lesser quality. A comparison between ANN model and Spiegler-Kedem model is also discussed.

Ultrafiltration is one of the most fascinating technologies, which has been introduced for application in the dairy industry. Ultrafiltration makes it possible to improve the quality of traditional dairy products, to create new food staffs, to utilize dairy by-products (such as whey) to a much greater extent for human nutrition and to prepare milk ingredients to be used in the entire food industry.

A nanofiltration-based method is presented for selectively separating soluble Mg(II) species from seawater, with the aim of using the Mg-loaded brine for either enriching desalinated water with magnesium ions or for enhancing precipitation of struvite from wastewater steams. Two 2.4 commercial NF membranes were tested under varying operational conditions. The membrane that was chosen for further investigation (DS-5 DL, Osmonics) showed lower Cl:Mg and Na:Mg concentration ratios in the brine, and improved performance (with respect to the investigated process) at high recovery values. Since the addition of antiscalants was perceived detrimental to the downstream uses of the brine, the aquatic chemistry program PHREEQC was used to simulate the critical (highest) recovery values at which no CaSO 4 would precipitate, assuming two concentration polarization factors. To prevent CaCO 3 precipitation at the critical recovery values a theoretical calculation was performed (PHREEQC) to determine the required strong acid dosages to the raw seawater. Using the DS-5 DL membrane at 64% recovery, the attained Mg(II) concentration in the brine was 3500 mg/l. Therefore, for attaining 12.15 mg Mg/l of desalinated water the brine should be dosed to the water at a 1:288 ratio, resulting in additional concentrations of 32.5 mg SO 4 −2 /l, 89.3 mg Cl − /l, 39.4 mg Na + /l, 3.3 mg Ca +2 /l, and 0.01 mg B/l. The overall cost of the proposed process was estimated at 0.00098 $/m 3 product water, i.e. approximately five times lower than two assessed alternative processes and more than one order of magnitude cheaper than implementing direct dissolution of chemicals, using either MgCl 2 or MgSO 4 .

The incomplete rejection of certain pesticides, disinfection by-products, endocrine disrupting compounds, and pharmaceutically active compounds has been reported during full-and pilot-scale high-pressure membrane applications. Since the removal of these compounds in water and wastewater treatment applications is of great importance where a high product water quality is desired, an understanding of the factors affecting the permeation of solutes in high-pressure membrane systems is needed. In this paper, findings of a comprehensive literature review are reported, targeting membrane rejection mechanisms and factors affecting rejection. The following key solute parameters were identified to primarily affect solute rejection: molecular weight (MW), molecular size (length and width), acid disassociation constant (pK a ), hydrophobicity/hydrophilicity (log K ow ), and diffusion coefficient (D p ). Key membrane properties affecting rejection that were identified include molecular weight cut-off, pore size, surface charge (measured as zeta potential), hydrophobicity/hydrophilicity (measured as contact angle), and surface morphology (measured as roughness). In addition, feed water composition, such as pH, ionic strength, hardness, and the presence of organic matter, was also identified as having an influence on solute rejection. From the knowledge gained during the literature review, a rejection diagram was proposed, which qualitatively allows prediction of solute rejection if certain solute and membrane properties are known. r

Les techniques séparatives à membranes se développent considérablement depuis quelques années. Grâces à la mise en oeuvre de nouveaux matériaux, les membranes sont de plus en plus performantes et remplacent progressivement les domaines réservés de la distillation, de l'échange d'ions ou des traitements chimiques. Contrairement aux procédés concurrents, les techniques à membrane permettent un fonctionnement continu, sans passage par une phase intermédiaire. La technique la plus récente, la moins coûteuse et la plus facile à mettre en oeuvre reste la nanofiltration (NF). Cette dernière offre des possibilités beaucoup plus vaste au niveau de la séparation entre les différents solutés dans la mesure où elle fait appel à deux mécanismes de transfert, dont les sélectivités sont très différentes : (i) l'un convectif comme en ultrafiltration (UF) et (ii) l'autre diffusif comme en osmose inverse (OI). En jouant sur les conditions opératoires (pression, taux de conversion, vitesse de circulation, etc.), il est alors possible de moduler entre ces deux mécanismes et atteindre la sélectivité désirée vis-à-vis des ions cibles, sans ajout d'aucun produit chimique, par exemple : l'excès d'ions fluorures à éliminer dans les eaux saumâtres à potabiliser ou encore les ions biologiquement actifs comme K + , Mg ++ , Cu ++ , Zn ++ présents dans l'eau de mer et susceptibles d'être extrait par NF pour la préparation d'eaux isotoniques bioactives.