Search

Nanofiltration (NF) membranes, especially loose NF membranes, trigger a growing interest for the fractionation of concentrated organic matters/salt mixtures in addition to the production of pure water. This study presents an in-depth characterization of two superhydrophilic loose NF membranes (Sepro NF 6 and 2A, Ultura). The physical characterization included the determination of the molecular weight cut-off (MWCO), pore size distribution, membrane morphology, surface charge, roughness and hydrophilicity. This was combined with a chemical characterization, i.e., by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), to determine the intrinsic membrane properties. The chemical characterization demonstrates that both Sepro NF membranes are poly(piperazineamide) based, showing the modification chemistry for the top layer through XPS measurement. Specifically, Sepro NF 6 and NF 2A membranes were found to have a superhydrophilic surface (contact angle for Sepro NF 6: 14.3±0.9°; that for Sepro NF 2A: 21.7±1.4°) with a low roughness, offering a potential advantage over conventional NF membranes in minimizing membrane fouling. Sepro NF 6 and NF 2A membranes had a mean effective pore size of 0.64±0.03 nm and 0.52±0.01 nm (corresponding to MWCOs of 862±80 Da and 493±53 Da), respectively. In terms of filtration performance, Sepro NF 6 showed a high permeability of 16.7 L m −2 h −1 bar −1 with 88.9% salt transmission for 0.01 mol L −1 NaCl solution, and a slightly lower permeability and salt transmission was obtained for Sepro NF 2A, which is desired for an effective fractionation of target organic matter/salt mixtures.

Selectivity for monovalent cations is an important property of cation exchange membranes (CEMs). The cation exchange membranes of the CSO modified with polyethyleneimine type have a higher selectivity for monovalent cations than the multivalent cations. Unfortunately, the loss of selectivity for these kinds of CSO seems to be unavoidable due to fouling and degradation of polyethyleneimine groups. In this situation, a “re-modification” technique was developed for recovery of fouled CSO, activating the fouled CSO by methanol and a sulfuric acid solution with ultrasonic vibration, followed by a layered surfacial electro-deposition method to prolong the lifetime of cation exchange membranes. A series of electrodialysis experiments for Na+/Ca2+ separation was performed for evaluating and comparing the monovalent cation selectivity of the samples. The restoration of the surface and cross section morphology after “re-modification” was demonstrated by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As a result of the re-modification method the membranes with chemically degraded polyethyleneimine were again made functional. The ion exchange groups of the CSO modified with polyethyleneimine were successfully recovered, giving the membrane a high permselectivity again.

Loose nanofiltration (NF) membranes can be used to treat textile wastewater effectively, providing an attracted avenue for resource recovery (i.e., dye purification and salt reuse) at the premise of the integration of high dye retention and salt permeation. However, the issue of membrane fouling has to be adequately addressed in view of its practical application. In this study, superhydrophilic loose NF membranes (Sepro NF 6 and NF 2A, Ultura) were applied for textile wastewater treatment. Synthetic solutions containing dyes and NaCl were used as the feed stream of a NF unit. It was found that two factors, namely cake-enhanced concentration polarization and the formation of a dye cake layer, dramatically deteriorated the flux of NF membranes with a synergic effect. In viewpoint of realistic application, diafiltration of a binary dye/salt mixture indicates that cake-enhanced concentration polarization plays a dominant role for the low membrane flux. As the diafiltration continued, cake-enhanced concentration polarization was alleviated with a decreasing concentration of salt in the feed. At the subsequent post-concentration procedure, the formation of a dye cake layer slightly compromised the membrane flux, but the negative impact of cake-enhanced concentration polarization was negligible due to the small quantity of salt remained in the feed.

Poly(vinyl chloride) (PVC) ultrafiltration membranes with improved antifouling and antibiofouling properties were prepared by non-solvent induced phase inversion using a hyperbranched polyamidoamine as additive. PVC reacted into the casting solution with the commercial polyamidoamine nanomaterial Helux-3316 by means of a nucleophilic substitution reaction. The composition of neat and functionalized membranes was studied by ATR-FTIR and elemental composition. Amino groups were tracked using the fluorescent dye fluorescamine. Surface ζ-potential and water contact angles were used to measure surface charge and hydrophilicity of tested membranes. The incorporation of amino groups increased membrane hydrophilicity and surface porosity, which resulted in enhanced permeability. Functionalized membranes displayed antifouling behaviour revealed upon filtering BSA solutions and lower irreversible fouling than PVC membranes. The attachment of Helux moieties to PVC yielded membranes with antibiofouling functionality explained by the interaction of positively charged Helux moieties with the negatively charged cell envelopes. Growth reduction for cells attached to the membrane surface during filtration reached up to 1-log for the gram-positive bacterium S. aureus. This investigation revealed that the incorporation of the hyperbranched nanomaterial in concentrations in the order of 1 wt% in the casting solution provides significant benefits to membrane performance, in terms of permeability and antifouling potential.

Smart gating membranes with self-regulating nanopores/nanochannels are highly desirable for water gating and separation of small molecules. Based on the nanochannels in the graphene oxide (GO) membrane, we designed positive thermo- and negative pH-responsive GO/hydrogel composite membranes (GOGMs) through a simple filtration-accumulation of GO sheets and hydrogels. The shape-flabby hydrogels can be perfectly inlaid between two GO sheets by changing their shape, and also act as a bond between GO and substrates. Thermo- and pH-responsive hydrogels embedded between the GO sheets impart adjustable water channels to the GO membrane. The channel tunability of hydrogel-studded GO membrane derives from the size conversion of hydrogel and the constant layer spacing of GO sheets. The hydraulic permeability of GOGMs was explored within the wide pH range of 2–6 and the temperature interval of 20–44 °C. The results revealed that the hydraulic permeability of the GOGMs can be reversibly adjusted with a high thermo- and pH-responsive gating coefficients. The GOGMs with self-regulated channels have various permeability properties for small molecules under different conditions. Moreover, the membrane thickness and the ratio of microgel to GO both have an effect on the water permeation and response performance of the GOGMs. These environmental stimuli-responsive membranes with thermo- and pH-responsive channels has numerous potential for applications in smart gating systems, liquid-based controlled release systems and smart separation systems.

In digital printing, a high salt content in dye solutions is detrimental, which calls for effective strategy for dye/salt fractionation. In this study, a loose nanofiltration (NF) membrane Sepro 2A was employed to desalinate diverse dye species (2 reactive dyes and 4 cationic dyes). This membrane, with a molecular weight cutoff of 490 Da, showed consistently high rejections to all the reactive and cationic dyes (>97.7%). Operational conditions such as dye concentrations and applied pressures have limited effects on the rejection of the membrane. An integrated NF-diafiltration process, involving a pre-concentration and a diafiltration step, was specifically designed for the fractionation of dye/NaCl mixtures. This loose NF membrane showed >99.7% rejection to reactive dyes (reactive blue 2 and reactive orange 16) and ca. 99.3% salt removal with ca. 2.0% dye loss after 5.0 diavolumes. However, the NF membrane experienced a 15.9% loss to methylene blue due to the lower rejection to this model cationic dye (97.2%). The current study provides important insights into dye/salt fractionation by loose NF membranes for digital ink-jet printing. © 2017 Elsevier B.V.

In this work, textile wastewater is explored for resource recovery in a hybrid loose nanofiltration (NF)-bipolar membrane electrodialysis (BMED) process for fractionation of dyes and salt, in view of dye purification and water and salt reuse. A loose nanofiltration membrane, i.e., Sepro NF 6 (Ultura), found to have a low salt rejection (0.27% in 120 g·L–1 NaCl solution) and high rejection for direct dyes and reactive dyes (≥99.93%), was used for fractionation of dye/salt mixtures through diafiltration. In diafiltration, the addition of pure water with a volume factor of 5.0 can effectively remove the NaCl salt by using Sepro NF 6 with an invariable dye concentration, in view of the recovery of high purity dyes. The overall salt rejections in diafiltration for the dye/salt mixtures with 40, 50 and 60 g·L–1 NaCl are 2.2%, 1.8% and 1.1%, respectively, enabling a further treatment by BMED. Subsequently, application of BMED for reuse of salt-containing NF permeate demonstrates that desalinated water with ∼100 ...

In the textile industry, high salinity waste streams are a challenge urging for the recovery and purification of dyes and salts (e.g., NaCl), requiring a treatment going beyond the classical filtration by e.g., reverse osmosis to produce pure water. In this work, two commercial loose nanofiltration (NF) membranes (Sepro NF 6 and NF 2A, Ultura) are proposed to fractionate dye/salt aqueous mixtures. It was observed that both NF membranes have a salt rejection −1 of NaCl at 6 bar. Furthermore, both membranes have >99.6% retention of direct dyes (direct red 80, direct red 23, and congo red), even though 40.0 g L −1 NaCl is present, indicating salt addition has no obvious impact on the dye retention. The combination of a low salt rejection and a high dye rejection indicates the feasibility for the reuse of salt from fractionation in forward osmosis and bipolar membrane electrodialysis. Application of diafiltration for an aqueous mixture containing direct red 80 (1000 ppm) and NaCl (~20 g L −1 ) by both membranes demonstrates that above 95% of NaCl is removed from aqueous mixture, and −1 NaCl remains after the addition of pure water with a volume factor of 4.0 in the feed solution. At the premise of excellent diafiltration performance, concentration as the post-treatment for dye recovery expectedly indicates direct red 80 is concentrated by a factor of 4.0 for both membranes while keeping the salt concentration with a very slight increase. Over 99.9% dye retention in both diafiltration and concentration procedures yields a very high recovery since

The binary TiO 2 –ZrO 2 particles were better alternative to TiO 2 particles as photocatalyst to reduce humic acid fouling in photocatalytic membrane reactor. The structure of the TiO 2 –ZrO 2 particles was strongly dependent upon the content of zirconium as an additive. A composition of 50% TiO 2 with 50% ZrO 2 was optimal in terms of physicochemical properties. The effect of TiO 2 –ZrO 2 particles on the reduction of humic acid fouling was further improved by the presence of divalent cations such as calcium. Nevertheless, the stability of polymeric membranes in longer-term operation using a hybrid photocatalytic membrane reactor for water treatment applications may remain a challenge.

To avoid particle agglomeration and to improve membrane antifouling property, commercial TiO2 particles were modified with polyaniline (PANI) by in situ polymerization. SEM and FTIR analysis confirmed the incorporation of PANI on the surface of the TiO2 particles. The average size of PANI/TiO2 nanoparticles is in the range of 10–67 ± 3 nm. The preparednanoparticles are used as surface and inner nanofiller additives and dispersed into the polysulfone (PSf) to obtain ultrafiltration nanocomposite membranes via phase inversion method. The surface hydrophilicity of nanocomposite membrane increases with increasing nanoparticles (0 to 1.5 wt %) concentrations. The membrane morphology indicates that nanocomposite membranes exhibited larger surface pore size, higher porosity, more finger-like pores, and less macrovoids than the control PSf membrane. The experimental results indicate that the 1.0 wt % of PANI/TiO2 content membrane depicted excellent hydrophilicity, water permeability, and better antifouling property with high rejection. Bovine serum albumin and humicacid were used as model foulants. The protein adsorption study showed that PANI/TiO2 content membranes adsorbed more at the isoelectric point of BSA solution and decreased as the solution pH increases. Higher nanoparticles content (1.5 wt %) membrane outcomes are elucidated and affected and resulted in significant particle agglomeration. Finally, obtained experimental results show that the nanocomposite membranes have higher flux and better antifouling property than the control PSf membrane.

This paper presents a new method to extract knowledge from existing data sets, that is, to extract symbolic rules using the weights of an Artificial Neural Network. The method has been applied to a neural network with special architecture named Enhanced Neural Network (ENN). This architecture improves the results that have been obtained with multilayer perceptron (MLP). The relationship among the knowledge stored in the weights, the performance of the network and the new implemented algorithm to acquire rules from the weights is explained. The method itself gives a model to follow in the knowledge acquisition with ENN.

Metal oxides nanoparticles are of potential interest for pressure-driven membranes in view of flux increase and reduced fouling resistance. In this study, polyethersulfone (PES) flat-sheet membranes were manufactured by the phase inversion method for wastewater treatment application. A PES membrane was modified by dispersing nanoparticles of TiO2, Al2O3 and ZrO2 in a PES solution. Nanoparticles size distribution was characterized by scanning electron microscope (SEM) and dynamic light scattering (DLS) method to explore the effect of nanoparticle aggregation. Furthermore, membranes were characterized by hydrophilicity (contact angle), morphology (SEM), porosity, and thermal analysis (TGA). Membrane fouling was studied with BSA and humic acids as model organic foulants. Entrapped metal oxides changed the membrane morphology to more open and porous structure and the antifouling property and long term flux stability of metal oxide modified membranes were significantly enhanced. Strong correlations were observed between some physico-chemical properties such as, porosity, hydrophilicity and permeability of modified membranes with the spatial particle distribution in the membrane structure. The fouling resistance of modified membranes was significantly reduced, showing that the particle distribution is a key parameter for the membrane fouling reduction. The rejection potential of new membranes was hardly affected.

Two commercial thin film composite polyamide reverse osmosis (BW-30) and nanofiltration (NF-90) membranes were studied for sorption of 2-nitrophenol and 2-chlorophenol. Adsorption kinetics and equilibrium on the surface of both membranes were studied. The rate of adsorption was adequately modeled by a linearized form of the pseudosecond-order kinetics in all cases. Adsorption isotherms obtained from equilibrium experiments were quite similar, except for the 2-nitrophenol/BW-30 system, which showed a higher maximum adsorption capacity. Experimental adsorption isotherms were compared with Freundlich and Langmuir models; the Langmuir model yields the best fit in all cases, suggesting the formation of a fouling monolayer onto the membrane surface. Organic deposition onto the membrane surface systematically increased hydrophobicity and diminished roughness. A strong graphical correlation was found between the relative flux decline and the organic concentration decrease in the feed. As expected, solute rejection was higher for the RO membrane (BW-30) than for the NF membrane (NF-90); the lowest rejection values were found for 2-nitrophenol. This was attributed to the increase of the solute concentration on the membrane surface due to organic sorption, which enhanced the driving force for diffusion through the membrane.

Coniferous trees such as eucalyptus used to be preferred for papermaking because the cellulose fiber in the pulp of these species are longer, therefore making for stronger paper. In this study, the proposed neural network method solves in an efficient way, how to build prediction models in engineering. The system has been applied to predict amount of wood for production of paper, in which the coefficients can explain the variable with more influence over the variable to forecast. Obtaining a good prediction and as simple as possible, i.e. with the least number of forecast variables.

Capability of nanofiltration membranes (NF) to remove pharmaceutical active compounds from wastewater streams was investigated. Sulfamethoxazole, diclofenac sodium, hydrochlorothiazide, 4-acetamidoantipyrine, nicotine and ranitinide hydrochloride were selected as model compounds since they are widely produced as pharmaceutical agents. Two commercially available polyamide nanofiltration membranes (NF-90 and NF-270 from Dow FilmTec) were tested. Solute retention by NF-90 membrane was very high in all cases (over 95%), whereas NF-270 retention systematically appeared lower ranging from 75% (nicotine) to 95% (ranitidine hydrochloride). Temporal evolution of flux decline was also investigated. The influence of physicochemical properties of both membrane and solutes on membrane performance was analyzed to explore the main solute-membrane interactions that determine the solute transfer across the membrane. The influence of operation pressure on NF-90 and NF-270 rejection was also studied.

Received 4 August 2011; accepted 22 November 2011DOI 10.1002/app.36542Published online 24 February 2012 in Wiley Online Library (wileyonlinelibrary.com).ABSTRACT: A systematic investigation of the influenceof the manufacturing conditions on the structure and per-formance of thin-film composite (TFC) membranes is pre-sented for polyamide (PA) supported by poly(ethersulfone) (PES). The TFC membranes were composed of anultrathin PA layer synthesized by interfacial polymeriza-tion on top of a porous PES support layer formed byimmersion precipitation. For the PES support layer, therole of the wetting pretreatment, initial casting film thick-ness, and relative air humidity were studied. Assuming astrong correlation between the thermodynamics and thehydrodynamics of the casting process, we derived newinsights from scanning electron microscopy images andthe experimental data. In view of optimization of the fluxthrough the membranes, a wetting pretreatment should beavoided. Important polymer savings were obtained with-out a loss of performance through a decrease in the cast-ing thickness in combination with the use of a verysmooth support. Last but not least, a high air humidityduring casting was found to inhibit the formation of a dense,defect-freeskinlayer.ForthePA layer, the interfacial poly-merization method, the drying method, and the curing timewere studied. The clamping of the membrane in a framewith one side in contact with the piperazine (PIP) solutionand the other side to the air yielded the highest membraneflux and rejection with the lowest use of PIP and trimesoyl-chloride solution. Because of the absence of a uniform PIPsolution layer for some drying methods, nodular PA struc-tures could be observed in the macrovoids of the underlyingPES layer because of hexane intrusion; this resulted in a dra-matic decrease in the flux. Moreover, the omission of thedrying step did not result in a significant loss of perform-ance and enhanced the ease of operation. Finally, a curingtime of 8 min was found to be optimal.

Although several studies explored the use of nanoparticles as additives in membrane structures, mixed matrix membranes still suffer from difficulties in synthesis and applications. In this paper, a new outlook on enhancement of membranes with nanoparticles is proposed by using ZnO as an alternative to TiO2. Although ZnO has attractive features that potentially could fill the objectives of mixed matrix membranes with lower cost and better performance, challenges in development remain. This paper investigates the synthesis of ZnO enhanced membranes and evaluates the performance of mixed matrix membranes with ZnO nanoparticles. Polyethersulfone (PES) membranes manufactured by diffusion induced phase inversion in N-methyl-pyrrolidone (NMP) using a range of procedures were blended with ZnO nanoparticles in a wide range of concentrations from ultralow to high (0.035–4 wt%). It was shown that the new membrane materials embedded with ZnO nanoparticles have significantly improved membrane features. The influence of the ZnO nanoparticles on the characteristics of PES/ZnO membranes was investigated with microscopic observations, contact angle measurement, filtration experiments, fouling resistance determination and observation of the rejection of selected dyes. The results showed an overall improvement compared to the neat membranes in terms of permeability as well as dye rejection and fouling resistance by adding ZnO nanoparticles even in small and ultralow concentrations.

This study describes the influence of polyethersulfone (PES) sublayers on the performance of polyamide (PA) reverse osmosis membranes. Asymmetric polymeric sublayers were synthesized by using the DIPS technique (Diffusion Induced Phase Separation). Sublayers are optimized mainly with respect to hydrophilicity, permeability and rejection potential by adjusting synthesis procedures. Parameters that were found to have an influence are the type of solvent (DMF and NMP were used), the air humidity, processing time, and concentrations of polymer. By carefully controlling these parameters, it was possible to prepare a range of sublayers with different characteristics, in the ultrafiltration–nanofiltration area. To visualize membrane surface characteristics, both scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were performed. In addition, titanium (TiO2) nanoparticles were assembled with polyethersulfone (PES) membranes at ultralow concentrations of nanoparticles to characterize TiO2/PES composite membranes and evaluate their permeate flux and solute rejection. Subsequently, a polyamide top layer was added by interfacial polymerization using typical reagents both in the aqueous and in the organic phase. The membrane performance was evaluated in terms of flux and salt rejection. Experimental design was performed in order to obtain the importance of some experimental variables during the polymerisation process. It was found that depending on the type of sublayer used in the procedure, a different membrane performance could be obtained.

This paper reports the fabrication and characterization of polyethersulfone-TiO(2) (PES-TiO(2)) nanoparticle composite membranes made from synthesis casting solution consisting of various compositions of polymer solvents (DMF and EtOH) and TiO(2) additive. The results also revealed that the membrane permeation and rejection rates, pore size, and porosity were dependent on the TiO(2) and EtOH concentrations. Nanoparticles were characterized by zeta potential measurements, TEM observations, and measurement of particle size distributions. Zeta potential measurements in aqueous solution demonstrated that the TiO(2) particles size is dominated by electric double layer interactions. Addition of EtOH promotes the increase of the clusters size as consequence of a double effect: reduction of the dielectric constant of solution and the depletion of the suspension field determined by the action of the polymer chains. The observed effects as result of EtOH addition and increase of TiO(2) concentration were similar: both procedures provoked an increase of macrovoid dimensions. The modified membranes by TiO(2) incorporation showed a structural change from a sponge-like to a finger-like structure. Strong correlations were observed between the hydrophilicity and the permeability of manufactured membranes. The formation mechanism of TiO(2)-blended membranes was altered, in a similar way, as result of EtOH at different contents of nanoparticles. Fouling resistance of modified membranes was significantly improved showing that EtOH addition is a suitable procedure for the membrane performance improvement. The rejection potential of membranes is hardly affected by the nanoparticles and EtOH incorporation into the polymeric solution.

TiO2 nanoparticles are of potential interest for nanofiltration membranes in view of flux increase and improved fouling resistance. Conclusions from published studies, however, cannot be translated to other applications because results depend on specific parameters of which the precise effect is still unknown. In this study, PES flat-sheet membranes were manufactured for wastewater treatment application. The effects of TiO2 nanoparticles as additive on the preparation of polyethersulfone (PES) blend nanofiltration membranes were investigated in terms of pure water flux, hydraulic membrane resistance (permeability) and solute rejection performance. A polyethersulfone (PES) membrane was modified by dispersing nanoparticles of titanium oxide (TiO2) in a PES solution. The membranes were prepared with 30 wt.% of polymer PES by phase inversion method. 1-Methyl-2-pyrrolidone and deionized water were employed as solvent and coagulant, respectively. Membrane fouling was explored with humic acids as a model organic...

In this paper the performance of a three stage process with commercial as well as tailor-made polyethersulphone (PES) membranes for the purification of sweeteners from Stevia rebaudiana Bertoni was evaluated. Retentions of the sweeteners for a synthetic mixture and plant extract in combination with flux decline measurements indicated that, in contrast with the laboratory-made membranes, on most commercial membranes a foulant layer was formed that influenced the separation performance negatively. For the plant extract, the best commercial membrane (PW010) had a selectivity and flux similar to the best laboratory-made membrane (27% PES), but the laboratory-made membrane was preferred because it showed a slightly lower retention of the sweeteners, as desired. Starting from an extract purity of 11% with the overall process (microfiltration, ultrafiltration, nanofiltration) a purity of 37% and a yield of 30% could be reached.

The performance of commercial reverse osmosis (TFC-HR, BW-30) and nanofiltration (NF-90) membranes was evaluated for phenol and eleven phenolic derivatives in aqueous solution. The correlation between flux decline and organic retention was investigated. Molecular hydrophobicity, related to organic solute adsorption on the membrane surface, was studied in order to describe membrane and solute interactions. The influence of type and position of the substituted functional groups in the benzene ring was analyzed. A systematic decrease in relative flux was obtained when the additional functional group on the aromatic ring shifted from hydroxyl to chloro and finally to nitro. For the same sequence, consistent diminutions in solute retention were found for all membranes. In addition, the membrane retention usually increased following the sequence para → meta → ortho , a trend especially marked for the NF-90 membrane. For polyhydric phenols, the retention also increases as the sequence: mono → di → tri. In both cases, steric hindrance is recognized as the main factor determining the membrane performance.

The present work aims to study the viability of combining heterogeneous photocatalysis and nanofiltration as an innovative strategy to improve atrazine elimination from aqueous solution by advanced oxidation processes. In order to promote the photocatalytic oxidation of atrazine, the selective separation of the intermediate products was explored by means of membrane filtration. Two nanofiltration membranes (NF-90 and NF-270) were tested to study their performance for aqueous solutions of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), cyanuric acid (2,4,6-trihydroxy-1,3,5-triazine), desethyl-desisopropyl-atrazine (2-chloro-4,6-diamino-1,3,5-triazine) and ammeline (2-hidroxy-4,6-amino-1,3,5-triazine). The influence of membranes and solutes properties on the organic rejection and flux decline was evaluated. Experimental flux declines were systematically small, although the values obtained for NF-90 were slightly larger than those found for NF-270. The highest difference was observed in the cas...

The performance of nanofiltration and reverse osmosis membranes (NF-90 and TFC-HR) to retain the intermediate products of phenol chemical oxidation in aqueous solution was examined. Physical properties of the active layer of both membranes, such as roughness and hydrophobicity, were examined and pure water permeability was determined. Temporal evolution experiments of permeate relative flux and solute rejection were carried out for aqueous phenol, catechol, resorcinol, hydroquinone, malonic acid, oxalic acid, acetic acid, and formic acid. Physicochemical properties of solutes and membranes were used to analyse the filtration performance. NF-90 membrane exhibited lower relative fluxes for every solute than the corresponding to TFC-HR membrane. In addition, differences in flux decline between members of the same type of solute (aromatic and carboxylic) were also more evident for NF-90 membrane. At natural pH, rejection selectivity between phenolic solutes and dicarboxylic acids was higher for NF-90 membrane than for TFC-HR membrane. Except for oxalic acid, the sieving effect seems to be predominant over other mechanisms for the TFC-HR membrane; however, NF-90 rejection performance cannot be solely explained through steric hindrance interaction. In order to compare rejection selectivity between aromatic and carboxylic solutes of similar molecular weight at the same solution pH, performance of NF-90 membrane for dicarboxylic acids was investigated at solution pH higher than natural one. Experiments evidenced that selective separation between phenols and dicarboxylic acids can be achieved at solution pH around 5.

Equilibrium adsorption experiments of phenol, 3-chlorophenol, 4-chlorophenol, and 3-nitrophenol aqueous solutions on NF90 membrane were conducted to obtain the corresponding adsorption isotherms at 25 oC. Single-compound solutions with concentration ranging from 0.1 to 8 mmol L− 1 were used. Freundlich and Langmuir models were compared to the experimental isotherms and their characteristic parameters were obtained from linear fits. In addition, the adsorptive behaviour of twelve aqueous phenolic compounds on the NF90 membrane was studied in order to investigate the relationship between adsorption and retention of selected solutes. An inverse correlation between the adsorbed amount, at the same equilibrium concentration (1 mmol L− 1), and retention was found. The influence of the molecular hydrophobicity and dipole moment of phenolic compounds on membrane adsorption, solute retention and water flux decline was also investigated.

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.

The aim of this work is to study the concentration, temperature and pH dependences on retention for phenol and malonic acid single solutions and their mixtures. Crossflow filtration experiments were performed to measure transport of these organic compounds across a commercially available thin-film composite nanofiltration membrane (NF-90) in the temperature range 20–41°C. The influence of the feed solution pH on the rejection of phenol was verified as well. In addition, the contribution of the membrane-solute interactions on solute retention has been established.

Fouling is one of the main disadvantages of membrane processes. Fouling can be mitigated by incorporating inorganic particles into the membrane. Composite membranes containing the inorganic fillers show higher pore size, porosity, and hydrophilic character than the neat PES membrane, which contributes to a better permeability. In this research, PES ultrafiltration membranes are prepared using both commercial and synthesized metal-organic framework materials (MOF) as well as ZnO particles as fillers. Among the different fillers used, MOF particles produce a better effect on the permeability of the membrane than ZnO particles. The synthesized Zn/Co-MOF-74-type materials have good structural stability in the polymeric matrix and the MOF-PES membrane maintains its performance after a series of cycles of BSA water solution. Tested MOF-PES membrane also shows higher BSA rejections and permeate flux than the neat PES membrane, demonstrating that it is possible to enhance the flux without losing the selectivity of the membrane. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41633.

We report on the pressure dependence of the bandgap bowing in the ZnTe 1 m x Se x alloy, in the whole composition range. The bandgap bowing parameter is shown to increase almost linearly with pressure from 1.23 at ambient pressure to 1.6 at 7 GPa. Saturation effects observed in the pressure dependence for x =0.1 and x =0.2 are shown to be related to the direct-to-indirect crossover. Results are discussed and interpreted in the framework of structural relaxation models for gap bowing. A prediction of these models (the negative bowing of the o 15 m ;X 1 transition) is shown to be compatible with the fact that the direct-to-indirect crossover pressure increases with the Se content.

We report on the optical properties of high pressure semiconducting phases in ZnTe 1 m x Se x . In the Te rich side, the cinnabar phase is observed in the upstroke between typically 9.5 and 12.5 GPa with a pressure interval of existence that decreases with increasing the Se content. In most studied samples, the indirect absorption edge could be determined, with values of the bandgap increasing with the Se content and ranging from 1.2 to 1.7 eV. In the downstroke, the cinnabar phase is observed in the whole composition range but its bandgap can not be unambiguously determined in the Se-rich side, as it coexists with rocksalt or zincblende phases. The indirect semiconducting rocksalt phase is observed in the Se-rich side, with an indirect bandgap of the order of 0.7 eV. Within the experimental errors, the bandgaps of both the cinnabar and NaCl phases are pressure insensitive, in agreement with first-principles pseudopotential band structure calculations, that predict very low pressure coefficients for both ...

A new ultrafiltration membrane was developed by the incorporation of binary metal oxides of the type Ti(x)Zr(1_x)O2 inside polyethersulfone. Physico-chemical characterization of the binary metal oxides demonstrated that the presence of Ti in the TiO2–ZrO2 system results in an increase of the size of the oxides, and also their dispersity. The crystalline phases of the synthesized binary metal oxides were identified as srilankite and zirconium titanium oxide. The effect of the addition of ZrO2 can be expressed in terms of the inhibition of crystal growth of nanocrystalline TiO2 during the synthesis process. For photocatalytic applications the band gap of the synthesized semiconductors was determined, confirming a gradual increase (blue shift) in the band gap as the amount of Zr loading increases. Distinct distributions of binary metal oxides were found along the permeation axis for the synthesized membranes. Particles with Ti are more uniformly dispersed throughout the membrane cross-section. The physico-chemical characterization of membranes showed a strong correlation between some key membrane properties and the spatial particle distribution in the membrane structure. The proximity of metal oxide fillers to the membrane surface determines the hydrophilicity and porosity of modified membranes. Membranes incorporating binary metal oxides were found to be promising candidates for wastewater treatment by ultrafiltration, considering the observed improvement in flux and anti-fouling properties of doped membranes. Multi-run fouling tests of doped membranes confirmed the stability of permeation through membranes embedded with binary TiO2–ZrO2 particles.

Novel hybrid ultrafiltration membranes have been prepared by incorporation of mesostructured functionalized silica particles in polyethersulfone. Physico-chemical characterization of synthesized materials was accomplished to determine the textural and structural properties of particles by nitrogen adsorption-desorption and TEM. A successful functionalization of silica with amine and carboxylic groups was confirmed by means of MAS-NMR. Membrane surface morphology was studied in terms of pore size distribution, porosity and hydrophilicity, suggesting a great influence of mesostructured silica incorporation in polyethersulfone on the polymer matrix configuration. Membrane functions were significantly improved as a result of a considerable increase of water permeation without affecting negatively the membrane selectivity. The antifouling membrane properties were also enhanced, especially against irreversible fouling. Multi-run fouling tests of modified membranes confirmed the stability of permeation through membranes doped with mesostructured functionalized silica particles.

Línea Investigación: Línea 1. Procesos de depuración de aguas residuales The coupling of membrane separation and photocatalytic oxidation has been studied for the removal of pharmaceutical pollutants. The retention properties of two different membranes (nanofiltration and reverse osmosis) were assessed. Comparable selectivity on the separation of pharmaceuticals were observed for both membranes, obtaining a permeate stream with concentrations of each pharmaceutical below 0.5 mg/L and a rejected flux highly concentrated (in the range of 16-25 mg/L and 18-32 mg/L of each pharmaceutical for NF-90 and BW-30 membranes, respectively), when an initial stream of six pharmaceuticals was feeding to the membrane system (10 mg/L of each pharmaceutical). The abatement of concentrated pharmaceuticals of the rejected stream was evaluated by means of heterogeneous photocatalytic oxidation using TiO2 and Fe2O3/SBA-15 in presence of hydrogen peroxide as photo-Fenton system. Both photocatalytic treatments showed remarkable removals of pharmaceutical compounds, achieving values between 80 and 100 %. The nicotine was the most refractory pollutant of all the studied pharmaceuticals. Photo-Fenton treatment seems to be more effective than TiO2 photocatalysis, as high mineralization degree and increased nicotine removal were attested. This work can be considered an interesting approach of coupling membrane separation and heterogeneous photocatalytic technologies for the successful abatement of pharmaceutical compounds in effluents of wastewater treatment plants. Tecnología Química y Ambiental

The application of nanoparticles as additives in membrane synthesis for improving the resistance of membranes against fouling has triggered recent interest in new membrane types. However, most nanoparticle-enhanced membranes suffer from the tradeoff between permeability and selectivity. In this paper, nano-WS2 was explored as the additive in membrane synthesis by non-solvent induced phase separation (NIPS). Blended PES–WS2 flat-sheet membranes with the incorporation of ultra-low concentrations of nanoparticles (from 0.025% to 0.25%, WS2/PES ratio) were manufactured and investigated in terms of permeability, fouling resistance and solute rejection. Remarkably, a significant enhancement in the permeability was observed as a result of the incorporation of ultra-low fractions of nano-WS2 to the membrane structure. The optimum permeability values were obtained for modified membranes with 0.075–0.10% nanoparticle/polymer concentration ratios. In general, fouling resistance and solute rejection were significantly enhanced by the incorporation of nanoparticles into the membrane structure. Specifically, fouling resistance increased by around 50%.

Doping of nanofiltration membranes with TiO2 nanoparticles was studied in the ultralow concentration range, in the absence of photocatalysis. Blended polyethersulfone/TiO2 flat-sheet membranes were manufactured and investigated in terms of pure water flux, permeability, fouling resistance and solute rejection. The membranes were synthesized at four different polymer concentrations by the phase inversion method, using 1-methyl-2-pyrrolidone (NMP) and deionized water as solvent and coagulant, respectively. The influence of TiO2 addition was investigated in an unusually low concentration interval (0.035–0.375 wt%). The membrane morphology was studied by determining particle size distributions of TiO2 to explore the effect of nanoparticle aggregation. Furthermore, membranes were characterized by hydrophilicity (contact angle), morphology (SEM), porosity, mechanical strength (bursting pressure) and thermal analysis (TGA). Membrane fouling was studied with humic acids as model organic foulants. Overall, a remarkable improvement in the permeability was observed with the addition of ultralow amounts of nanoparticles to the polymer. The optimum permeability was found to be as low as 0.085 wt%, using a constant rejection of dyes as the boundary condition. It was shown that rejection of solutes is not negatively influenced by the increase in permeability. In addition, the resistance against membrane fouling was found to be above 12% for the TiO2 blended membranes.