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In this work, a green route for the preparation of S-2-amino-1-butanol in the post-treatment for direct enantioseparation for the antituberculosis drug ethambutol hydrochloride has been explored. T...

Environmental stimuli-responsive membranes have many latent applications in numerous fields, for example, chemical/biological separations, water treatment, drug delivery, self-cleaning material and chemical sensor. In this study, a pH-responsive membrane with in-situ assembled stimuli-responsive microgels on membrane surface and internal channels wall was fabricated by the coagulation step of the phase-inversion process. Interestingly, it was found that poly(4-vinyl pyridine) (P4VP) microgel can be mobilized onto the membrane surface by using an acidic coagulation bath. Meanwhile, the membrane-based materials with different hydrophobic properties showed a great effect on the migration of microgel onto the channel surface. The inner pores of these responsive membranes can self-adjust its size with the changes of outside pH stimulus. Moreover, the gate-controlled water permeability of pH-responsive membranes was explored at the pH interval from pH 2 to pH 6. Investigations revealed that the P4VP microgel-assembled membrane had excellent pH-responsive performance. In addition, these pH-responsive membranes with embedded microgels on surface and inner pores wall also exhibited excellent reversible behaviors and self-cleaning properties.

Exploring a desirable cross-linker applied in cation exchange membranes (CEMs) to improve dimensional stability as well as electrochemical performance has a great signifcance for the current membrane science and technology. In this investigation, a sequence of crosslinked sulphonated polysulfone (SPSF) CEMs has been prepared to explore the influence of the crosslinking functionality on the dimensional stability and electrodialysis (ED) performance of modified membranes. Different cross-linker structures were obtained according to the cross-linker agent content added during the synthesis route. As expected, the membrane surface became smoother with increasing cross-linker content, presumably as result of the denser structure established. The dimension stability increases according to the crosslinking degree applied, whereas the permselectivity of membranes depends on the conjunction of many important and interlinked factors, including the formation of narrow ion transport channels and the variations in the exchanges sites concentration. It was observed that the optimized CEM (60SPSF-C2#) showed the highest NaCl removal ratio (91.7%) during the desalination experiments and exhibited the higher current efficiency (95.7%) and lowest energy consumption (6.55 kWh kg−1). These results suggest the formation of the optimum three-dimensional network configuration for the membrane structure determined by the functionality of cross-liker selected in this investigation.

The present work reports the preparation of a series of novel highly durable imidazolium-decorated anion exchange membranes (AEMs), with 3D network structure, via ultraviolet crosslinking reaction between 1-vinylimidazole and 1,6-hexanedithiol. AEM modified with trimethylamine (TMA) groups (no crosslinking, 45.7%) showed a significantly reduced water uptake within a range of 14.4–23.6% at 80 °C. Due to relatively good alkali-resistant of imidazolium groups and the compact structure stemmed from crosslinking network, the optimum cross-linked AEM (BPPO-Im 0.3) can retard the degradation and exhibits superior alkaline stability in 1.0 M NaOH at 60 °C for over 15 days, compared with TMA modified AEM. In ED application, BPPO-Im 0.3 AEM has a higher NaCl removal ratio of 77.82% than that of commercial AEM-Type II (74.13%) within 3 h experimental time. Accordingly, it shows higher current efficiency (67.43%) and lower energy consumption (1.94 kWh kg−1 NaCl), compared to commercial one (62.83%; 2.05 kWh kg−1). The facile fabrication process and the better-performance are suggestive of that BPPO-Im 0.3 is potentially applicable in ED.

The preparation of quaternary ammonium polysulfone anion exchange membranes (AEMs) with good dimensional stability and alkaline stability is an urgent problem to solve. In response, a series of cross-linked based on polysulfone and 4, 4′-trimethylenedipiperidine (TMDP) as crosslinkers with different degrees AEMs were developed in this work through a simple process. Among the fabricated AEMs, CAPSF-5 exhibits superb alkaline stability in a 1 M KOH aqueous solution at 60 °C for 15 days, whereas the non-crosslinked APSF membrane became tremendously brittle within 24 h and could not be further studied under the same conditions. In addition, even at 60 °C, CAPSF-5 demonstrates a superior dimensional stability compared to the non-crosslinked APSF membrane due to the formation of a dense internal network structure. These observations demonstrate that crosslinked CAPSF membranes can be a viable strategy to improve the deficiency of the polysulfone backbone, especially in terms of alkaline stability.

Anion exchange membrane (AEMs) fouling is a serious problem influencing membrane performance during electrodialysis process(ED), which would increase power consumption and reduce water recovery. In this paper, an aliphatic anion-exchange membrane was prepared from quaternized polyvinyl alcohol (QPVA) via dual cross-linking through annealing treatment and condensation reaction to restrain the membrane water swelling. The Wu% of QPVA membrane could be reduced to 22.87 ± 0.81%. Due to the hydrophilia (59.86 ± 0.21°), negative ζ-potential surface and aliphatic matrix of QPVA, no transition time appeared under our experiment condition, indicating the QPVA membrane was scarcely fouled by SDBS. And the existence of SDBS in dilute solution generated slightly effect on the QPVA membrane resistance and only 7.47 ± 0.21% reduction of the desalination rate in ED process. Furthermore, only distilled water was used as solution or reaction media, without any harmful organic solvents, presenting an environmentally friendly route for the preparation of water-based anion-exchange membrane. So, the excellent anti-fouling performance along with green preparation of QPVA showed its remarkable prospect for desalination purpose in ED process.

Novel anion exchange membranes with enhanced ion exchange capacity, dimensional stability and alkali stability were prepared by a facile synthesis method. Internal crosslinking networks in the resulting membranes were achieved by reacting chloromethylated polysulfone with 4,4′-trimethylene bis(1-methylpiperidine) (BMP), where BMP was used as both a quaternization reagent and crosslinker without requirement of post-functionalization. In order to evaluate the alkali resistance and dimension stability performance of the resulting membranes, the molar ratio of BMP in the resulting membranes was fixed at four different contents: 40%, 60%, 80% and 100%. The obtained membranes were accordingly denoted as CAPSF-N, in which N = 40, 60, 80 and 100, respectively. Due to the dense internal network structure and spatial conformation of the six-membered rings, the resulting CAPSF-N AEMs showed enhanced dimensional structures (at 60 °C, the water uptakes and swelling ratios of CAPSF-N were 8.42% to 14.84% and 2.32% to 5.93%, respectively, whereas those for the commercial AEM Neosepta AMX were 44.23% and 4.22%, respectively). In addition, after soaking in 1 M KOH solution at 60 °C for 15 days, the modified membranes exhibited excellent alkaline stability. The CAPSF-100 membrane showed the highest alkali stability (retained 85% of its original ion exchange capacity and 84% of its original OH− conduction after the alkaline stability test), whereas the non-crosslinked APSF broke into pieces. Additionally, compared to the commercial Neosepta AMX membrane under the same test conditions, the desalination efficiency of CAPSF-100 was enhanced, and the energy consumption was lower.

Developing a durable and antifouling monovalent selective anion exchange membrane is critical in practical electrodialysis (ED) process. Herein, a commercial anion exchange membrane was modified by sulfonated reduced graphene oxide (S-rGO) and polydopamine (PDA). Inspired by biological adhesion from mussels, the PDA coating on the surface of S-rGO-PDA membrane enhanced the stability of S-rGO nanosheets due to strong adhesion. The monovalent anion selectivity was evaluated by means of the Cl - / SO 4 2 - permeselectivity, and stability property was measured by the ion concentration changes of Cl - and SO 4 2 - for a long time application of ED. Moreover, antifouling property was measured by recording the time course of the potential difference in the presence of sodium dodecyl benzene sulfonate (SDBS). The results show that permselectivity of S-rGO-PDA membrane is 2.50, which is higher than pristine membrane (1.08). In addition, S-rGO-PDA membrane is stable, the permselectivity did not change significantly during 70 h ED process. Besides antifouling property of S-rGO-PDA membranes is improved compared with S-rGO membranes.

In this work, we have investigated a series of anion exchange membranes (AEMs) based on brominated poly(2,6-dimethyl-1,6-phenylene oxide) (BPPO) tethered with three saturated heterocyclic quaternary ammonium groups (QAs) of 1-methylpyrrolidine (MPY), N-methylpiperidine (MPRD), and 4-methylmorpholine (MMPH) for electrodialysis (ED) applications, respectively, along with BPPO with trimethylamine (TMA) and Neosepta AMX made for comparison. Our investigations demonstrate that the optimized BPPO-MPRD, having an ion exchange capacity of 1.67 mmol g−1, is highly stable in aqueous KOH (1 mol L−1) with ion exchange capacity retention ratio of 85.1% and hydroxide conductivity retention ratio of 80.3% at 60 °C for over 15 days, relative to other heterocyclic amine decorated AEMs. In ED application process, BPPO-MPRD shows the NaCl removel ratio of 98.8% and energy consumption of 12.58 kWh kg−1, outperforming the Neosepta AMX (97.4% & 15.76 kWh kg−1). The results demonstrate that the as-prepared BPPO-MPRD AEM can be applied in ED.

Inspired by stomata, a series of single or dual thermo-/pH-responsive smart gating membranes (SGMs) were prepared with in situ assembled stimuli-responsive microgels as gates. Highly cross-linked poly(N-isopropylacrylamide-co-methylacrylic acid) P(NIPAM-co-MAA) microgels underwent in situ surface segregation during the acetic acid-assisted phase inversion process, and they were uniformly decorated on the surface of the membranes and the channels. The hydraulic permeability performance of SGMs was studied within the temperature range of 25–70 °C and a wide pH range (spanning pH 3–11). Investigations revealed that microgels based on different NIPAM/MAA ratios provided different thermo/pH-responsive properties to SGMs. Higher NIPAM/MAA ratios determined the thermo-responsive performance, and higher MAA/NIPAM ratios determined the pH-responsive performance. Moreover, the SGMs with in situ assembled microgels on the surface and channel surface have enhanced gating coefficients, stimuli-reversible behaviours and self-cleaning performance.

Layer-by-layer deposition of polycations and polyanions multilayers on the surface of anion exchange membranes (AEMs) is a simple and versatile method to obtain monovalent anion selectivity. However, the stability of the polyelectrolyte multilayers (PEMs) can be compromised by the weak interactions formed between the deposited barrier and the pristine membrane surface. In this sense, cross-linking appears as an efficient method to improve the chemical stability of PEMs by covalent bonding. In this investigation, polyelectrolyte multilayers was coated on commercial AEMs by alternating electro-deposition with polystyrene sulfonate (PSS) and 2-hydro-xypropyltrimethyl ammonium chloride chitosan (HACC). Subsequently, photosensitive molecules (4,4-diazostilbene-2,2-disulfonic acid disodium salt (DAS)) were mixed into the loose multilayers by soaking in the DAS solution and chemical bonds were formed in the membrane by UV irradiation. The chemical composition and structure of the membrane were confirmed and observed by infrared spectroscopy, atomic force microscopy and scanning electron microscopy. The monovalent selectivity and durability were evaluated by electrodialysis (ED) in a Cl - /SO 4 2- system. The optimized membrane was found to have a stable selectivity during the entire duration of testing (76 h), and while a conventional multilayer modified AEMs completely loses its selectivity after 30 h. Furthermore, the modification process improved the monovalent anion selectivity from 0.39 to 4.36. The experimental results demonstrate the effectivity and feasibility of the modified strategy.

Anion exchange membranes (AEMs) with a high ion exchange capacity, striking water uptake and excellent dimensional stability were prepared via an internal crosslinking networks strategy. Internal crosslinking networks were formed by reacting 4,4′-bipyridine with brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). 4,4′-bipyridine not only provides a functional group but also comprises a cross-linking agent without requirements of post-functionalization. The variation of the 4,4′-bipyridine amount into the casting polymer solution was explored to regulate the performance of the anion exchange membranes, and the membrane properties were evaluated by AFM, ion exchange capacity (IEC), water uptake, the linear expansion ratio, tensile strength, thermal stability, membrane area resistance and electrodialysis experiments, etc. The results showed that the cross-linked membrane with the IEC of 1.98 mmol/g has much more outstanding dimensional stability (water uptake: 11.68%; swelling ratio: 3.8%) than non-cross-linked BPPO-Tri membrane (water uptake: 53.26%; swelling ratio: 7.71%) and commercial Neosepta AMX membrane (water uptake: 60.29%; swelling ratio: 5.08%), at the high temperature (50 °C). When being applied in ED application, the cross-linked BPPO-20 membrane (NaCl remove: 59.7%; energy consumption: 5.97 kWh/kg NaCl) exhibits slightly higher desalination efficiency and lower energy consumption than commercial Neosepta AMX membrane (NaCl remove: 58.3%; energy consumption: 6.51 kWh/kg NaCl), suggesting its promising application in ED.

A novel anion exchange membrane (AEM) is developed through poly (sodium 4-styrene sulfonate) (PSS) and hydroxypropyltrimethyl ammonium chloride chitosan (HACC) alternate electro-deposition to enhance the monovalent selectivity. Compared to the commercial original AEM, coating of the (PSS/HACC)N alternate electro-deposition multilayer on the membrane surface dramatically enhance the selectivity of anions. In addition, the permselectivity for monovalent anions of the membranes was investigated by electrodialysis experiments. For comparison, the corresponding Cl−/SO42− were chosen and the average values of permselectivity and separation efficiency of commercial AEM are 0.66 and −0.19 respectively. As result of alternate electro-deposition of PSS/HACC layers, the permselectivity raised up to 2.90 and the separation efficiency also increased up to 0.28 for nine PSS/HACC bilayers needed. Under the optimal fabricating conditions, the area resistance of membrane arrived at 4.52 Ω cm2 with nine PSS/HACC bilayers. Meanwhile, the polarization current-voltage curves and ζ-potential of membranes were also tested to characterize the electrochemical behavior of the modified membrane. The high selectivities of these membranes may enable electrodialysis applications in separation of monovalent and divalent anions.

New polyethersulfone (PES) ultrafiltration hybrid membranes were prepared by doping with different amine-functionalized mesostructured silica (SBA-15) particles added at low weight concentration (0.6% in the synthesis medium). 3-(aminopropyl) trimethoxysilane, N -(3-trimethoxysilylpropyl)ethylenediamine, and N -(3-trimethoxysilylpropyl)diethylenetriamine were used as amine precursors of the fillers obtained by co-condensation and denoted as SBA-15/Monoamine, SBA-15/Diamine, and SBA-15/Triamine, respectively. SBA-15 material functionalized with polyethylenimine was synthetized by hyperbranching polymerization with aziridine. Physicochemical characterization of fillers was achieved by nitrogen sorption, X-ray diffraction, TEM, dynamic light scattering, and elemental analysis. Membrane morphology was assessed in terms of overall porosity by water uptake and surface pore size distribution from FEG-SEM. Hydrophilicity of the membranes was determined by measuring water contact angle. Significant increase of porosity and hydrophilicity was found in all doped membranes, which exhibited substantial improve in water flux in comparison with neat PES membrane. Filtration experiments conducted with BSA protein aqueous solutions (1 g L −1 ) revealed that antifouling ability of doped membranes was gradually enhanced with amine functionalization, especially against reversible fouling. PES/SBA-15/Triamine appeared as the best specimen in both water flux and antifouling behavior with excellent long time permeation performance in repeated cleaning/filtration cycles.

The development of a facile approach to fabricate anion exchange membranes (AEMs) with efficient ionic transport and desirable stabilities (mechanical and dimensional) for various applications is meaningful. In this work, a two-step strategy for the preparation of AEMs with 3D network structure, via cross-linking reaction between 2-chloroacetamide (CAA) modified poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and N,N,N′,N′-tetramethyl-1,4-diaminobutane (TMDAB) has been reported. The as-prepared AEMs with ion-exchange capacity (IEC) in the range of 1.38–1.84 mmol g−1, exhibit the much lower water uptake (13.14–22.45%, 80 °C) relative to the un-crosslinked AEM (35.89%, 80 °C). In addition, due to the presence of fluorine-based 3D network structure, the as-prepared AEMs show much enhanced mechanical and thermal stability in comparison with the un-crosslinked AEM. In the electrodialysis (ED) application, the optimized AEM shows the higher current efficiency (78.6%) and lower energy consumption (2.01 kWh kg−1 NaCl) than those of commercial AEM AEM-Type II (76.4%; 2.26 kWh kg−1), respectively, within 150 min of operation interval. The proposed facile fabrication protocol and the better-performance of optimized PVDF-HFP -based AEM demonstrate the potential ED application.

：Organic solvent nanofiltration (OSN) membranes have gained increasing attention for their wide applications in organic phase system. However, the fabrication method rather than the swelling behavior receives more attention during the OSN testing. In this work, a thin-film composite membrane with an internal cross-linking network by reacting 4,4-bipyridine with brominated poly (2,6-dimethyl-1, 4-phenylene oxide) (BPPO) has been prepared for organic solvent nanofiltration (OSN). The bipyridine groups substituted on the polyphenylene oxide polymer backbone act as cross-linkers and cationic channels for remarkable chemical stability and high solvent permeability. The permeability of the cross-linked BPPO (CBPPO) thin-film membranes exhibited high related to the viscosity and solubility parameter of solvents. The stability of CBPPO membrane was studied via various organic solvent immersing experiments. The result demonstrated that the composite membrane swelling changed to an extent of no more than 2.01%. It can be attributed to the low conformational flexibility of polymer chains with a high crosslinking degree. The ethanol permeation and dye rejection were compared before and after soaking. The calculation of the MWCO and membrane potential of modified CBPPO membranes showed that the swelling behavior of the CBPPO composite membranes is mainly affected by the membrane charge densities rather than the pore size.

This study reports the fabrication of mixed matrix membranes (MMMs) using immersion precipitation phase inversion for promising application in desalination of dye solutions. Aromatic poly(m-phenylene isophthalamide) is used as the polymer material, and the metal–organic framework MIL-53(Al) is added to develop integrally skinned asymmetric membranes. Successful dispersion of MIL-53(Al) particles into the membrane-separating layer is confirmed by scanning electron microscopy. The optimum performance of the membranes is obtained at 0.5 wt % MIL-53(Al) concentration. In particular, the M-0.5 membrane is planned for use in separating dye/salt aqueous mixtures. It is observed that the M-0.5 membrane has a rejection for NaCl and Na2SO4 below 11% and 37%, respectively, in mixed salt/dye solutions. Additionally, the M-0.5 membrane is found to have a rejection rate of 83.9%, 98.3%, and 99.8% for nitroso-R salt, xylenol orange, and ponceau S, respectively, in mixed Na2SO4/dye solutions. The rejection rate for Na2SO...

Nanofiltration (NF) membranes have been used previously for the recovery of dyes, salts, and water from textile wastewaters with high salinity. However, commercially available NF membranes have a high rejection for divalent salts (i.e., Na2SO4), substantially reducing the salt recovery and membrane flux when treating textile wastewater containing Na2SO4. In this study, a tight ultrafiltration membrane (UH004, Microdyn-Nadir) was proposed to fractionate the dye and Na2SO4 in the textile wastewater. The UH004 membrane with a molecular weight cutoff of 4700 Da provided complete passage of monovalent salts, with little rejection of Na2SO4. This significantly increases the filtrate flux that can be achieved with high-salinity wastewater since osmotic pressure and concentration polarization effects are minimized. Furthermore, the retention behavior of four different dyes was evaluated to determine the efficiency of this membrane process. This tight ultrafiltration membrane offered the high retention for direct dyes (i.e., direct red 80, direct red 23, and Congo red) and reactive blue 2. For instance, the UH004 membrane yielded >98.9% rejection for all of the dyes at a pressure of 4 bar even in the presence of 60 g L−1 Na2SO4. Subsequently, an ultrafiltration-diafiltration process was designed to separate a dye/Na2SO4 aqueous mixture with 98% desalination efficiency and greater than 97% dye recovery after 5 diavolumes. These results clearly demonstrate that tight ultrafiltration membranes can be a stand-alone alternative to NF membranes for the effective fractionation of dye and Na2SO4 in the direct treatment of high-salinity textile wastewater.

A series of semi-interpenetrating polymer network (sIPN) composite anion exchange membranes were fabricated depending on immobilized linear PVDF and cross-linked polyepichlorohydrin (PECH), 1,4-diazabicyclo[2.2.2]octane, (DABCO) network through in situ synthetic pathway. A cyclic diamine (DABCO) was used as cross-linking agent and simultaneously improved the ion-exchange capacity by amination. Scanning electron microscopy (SEM) indicated that the composite membranes exhibited a dense and homogeneous structure. Successful formation of PECH-DABCO copolymer within the sIPN membranes was also confirmed by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The PVDF percentage and inherent properties of membranes such as ion exchange capacity (IEC), water uptake (WR), thermal stability, mechanical property, and area resistance were investigated to evaluate their applicability in electrodialysis (ED). The experimental results showed that the composite membrane maintained a good perspec...

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.

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.

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 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

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.

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.

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.

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.

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.

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.

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