Search

The set of various ceramic substrates Al2O3-100nm, TiO2-75nm, ZrO2-3nm, and ZrO2-200nm were used in the hydrophobization process with different silane-based modifiers fluorinated and fluorine-free, possessing different reactive groups (ethoxy, methoxy, and chlorine) and different length of the alkyl-chain (C6 and C16). It was investigated how these variables can influence the features of the material and then transport and separation properties. A comprehensive material study including evaluation of morphological, wetting and structural properties was performed and referred to the membrane performance in membrane distillation. Transport features, particularly various driving forces (range 105–685 mbar) and their impact on the overall membrane performance were studied. The highest grafting effectiveness was observed for superhydrophobic Al2O3-100nm-C16Cl3 (contact angle 154°, hysteresis 10°) possessing critical surface tension of 12.4 mN m−1 and polar part of surface free energy 1.1 mN m−1. Improvement in mechanical properties determined by nanoindentation of all tested ceramics after hydrophobization was observed. Al2O3-100nm-C6OEt3 has the best transport properties. Such results were ensured by an appropriate substrate selection with the highest level of hydroxyl groups ready for modification on pristine material and lower reactivity of ethoxy groups in comparison to chlorine one. All membrane possessed a very high salt rejection coefficient ca.99%.

A novel method of polyethersulfone membrane modification with α-amylase entrapped in polymeric micelles is proposed to improve the antifouling properties of membranes. The immobilization of α-amylase is performed by its incorporation into micelles based on commercial polymeric surfactants (Tetronic®-701 and Tetronic®-90R4) with their subsequent adsorption on the membrane surface. The size of micelles loaded with enzyme depends on the nature of the surfactant and is equal to 400 and 100 nm for Tetronic®-701 and Tetronic®-90R4, respectively. Biocatalytic activity and membrane stability in the process of starch ultrafiltration are discussed in the paper. The optimal pH was found to be 6.5–7.5 for Tetronic®-701 and 6.0–6.5 for Tetronic®-90R4 micelles. The activity of enzyme entrapped in the micelles, adsorbed on the membrane surface, increased 1.5–1.8 times. The starch conversion rate of 80–90% was observed for membranes with immobilized α-amylase. The biocatalytic activity of immobilized enzyme was maintained at a high level during five cycles of regeneration. Moreover, the layer of micelles with incorporated α-amylase on the membrane surface reduced the effect of concentration polarization due to starch hydrolysis. The micelle immobilization caused hydrophilization of the surface and an increase in the number of bound water molecules which prevented the formation of a cake in the boundary layer.

Performances of various hydrophilic and hydrophobic commercial membranes were evaluated in the pervaporative separation of binary organic-organic mixtures. The research was performed for the following binary mixtures: acetone-ethanol, ethanol-butanol, and acetone-butanol using chosen commercial membranes: DuraMem™150 (polyimide), Pervap 1060 (poly(dimethylsiloxane)) and Pervap 2216 (poly(vinyl alcohol)). For the assessment of membrane performance, in organic-organic pervaporation, transport and separation features (pervaporative separation index and separation factor) were taken into account. Regardless the membrane nature, the same component of the separated mixture was preferentially transported across the membrane. The assessment of membrane performance was additionally discussed by using Hansen's Solubility Parameters. The detailed physicochemical analyses focused on contact angle, spreading pressure and surface free energy with their components calculation were performed. The established physicochemical parameters were in a good accordance with the observed changes during pervaporative separation of organic-organic mixtures. Furthermore, an investigation of traces of water presence in feed of organic-organic mixtures on the membrane performance was discussed.

Fluorinated membranes have significant importance in separation due to their inertness, fouling resistance. A novel modification methodology of poly(vinylidene fluoride) (PVDF) membranes was developed employing piranha reagent to activate the fluorinated surface followed by consecutive grafting with 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (FC6). Membranes were implemented in membrane distillation for the removal of hazardous volatile organic compounds (ethyl acetate - EtAc) from water. Octyl group functionalized membranes were also tested for comparison. Membranes were characterized using AFM, ATR-FTIR, SEM, DSC, XRD, goniometric and porometry techniques. Results showed a significant improvement in the membrane performance. Flux of EtAc and PSI changed in the following way between pristine (JEtAc = 1.8 kg h−1 m−2, PSI = 33 kg h−1 m−2) and 1-min activated membrane (JEtAc = 3.0 kg h−1 m−2, PSI = 72 kg h−1 m−2). Furthermore, for functionalized sample with FC6 the performance was following JEtAc = 5.2 kg h−1 m−2 and PSI = 227 kg h−1 m−2. The activation and functionalization influenced significantly material properties. Higher roughness, contact angle and more open structure were noticed after 1-min activation (RMS = 182 nm, CA = 122°, 0.797 µm) in comparison to pristine one (RMS = 142 nm, CA = 116°, 0.551 µm). An improvement of mechanical features was also observed comparing pristine (Fadh = 25.2 nN, H = 0.13 GPa, E = 2.10 GPa) and the membrane functionalized by FC6 (Fadh = 19.3 nN, H = 0.27 GPa, E = 2.38 GPa).

International audience; The new type of efficient pervaporative separation hybrid materials based on cellulose acetate propionate (CAP) and doped with 1-methyl-3-(4-vinylbenzyl)-1H-imidazol-3-ium chloride polymerizable ionic liquid (PIL) monomers (12.3–44.4 wt%) were elaborated for dehydration of propan-2-ol. Broad material and physicochemical characterization of membranes was performed including assessment of physicochemical, equilibrium, transport, and separation properties. Incorporation of PIL results in the plasticization of CAP based membranes. Additionally, with increasing loading of PIL from 12.3 to 44.4 wt% values of thickness-normalized Pervaporation Separation Index (PSIN) increase 1.6–2.4 times comparing to unloaded membrane (pure CAP). The distance parameters calculated on the base of the Hansen's solubility parameters were additionally employed to interpret swelling and pervaporative properties of membranes as well as to discuss interactions between solvents and prepared membranes. Lower value of distance parameter between pristine CAP and ethanol corresponds to the highest molar swelling degree of CAP based membranes. Swelling of CAP-PIL membranes in contact with water, ethanol, and propan-2-ol increased with of the increasing PIL content due to the hydrophilic character of ionic liquid. The gathered data provided insight into the potential applicability of the novel hybrid separation materials for pervaporative separation of liquid-liquid mixtures. © 2017 Elsevier B.V.

Three new reactive ionic liquids (RILs) based on the imidazole derivatives were synthesized and used as carriers in polymer inclusion membranes (PIMs) composed of cellulose triacetate (CTA) as a polymer matrix and o–nitrophenyl octyl ether (NPOE) as a plasticizer. The effect of alkyl chain length (C1, C4, and C8) in the imidazolium cation of RILs on the transport and separation properties was evaluated. From among three synthesized RILs only the RIL with the longest alkyl chain (RILC8_Br) can be successfully applied as the carrier for Cd(II) removal from multicomponent aqueous chloride solution containing also Cu(II), Pb(II), and Zn(II) ions. The effects of the stripping phase composition, HCl concentration in the feed solution, and the carrier content in the membrane on the separation performance and transport effectiveness were studied. The results indicate that the RILC8_Br ionic liquid enables selective transport of Cd(II) ions and their active concentration in the stripping solution with the fluxes reaching a value of 2.7 × 10−10 mol/cm2s. In the investigated feed solution concentration range, the selectivity order was found to be Cd(II) > Zn(II) > Pb(II) ≫ Cu(II) and it was independent of the experimental conditions. For a description of the transport kinetics a model similar to the first-order reversible reaction equations was applied and its applicability was proved.

Polyvinylideneflouride (PVDF) has considerable usage in different disciplines including sensors, piezoelectric materials, biomedical application as well as membranes. In this paper, facile and effective method for the activation of inert PVDF surface and molecular grafting of this material is presented. Mild concentration of piranha reagent used to generate hydroxyl groups on the surface of the polymer through a free radical reaction. Functionalization was investigated as a function of reaction time and concentration. For characterization, various analytical methods and techniques were employed including infrared spectroscopy, scanning electron microscopy, X-ray diffraction, atomic-force microscopy, and contact goniometry. Physicochemical properties including contact angle, surface free energy, surface tension, work of adhesion as well as morphological properties (e.g. pore size distribution and roughness) were evaluated. Subsequently, membranes were tested for desalination, volatile organic compounds removal, and apple juice concentration in various modes of membrane distillation. Significant increase in pore size (53%), surface roughness (43%), and flux (from ca. 8 kg m-2 h-1 to 10.5 kg m-2 h-1) were found. Fouling mitigation was also noticed in comparison to unmodified membranes. Flux decline was equal to 37.5% and 5.1% for unmodified PVDF and PVDF membrane activated for 1 min by 20% Piranha reagent, respectively.

Decay of paintings, i.e. cracking and lifting of the picture layers is caused mainly by harmful influence of light, temperature and fluctuations in humidity. This paper describes the application of various hydrophobic porous membranes in the paintings' humidification which is a very important element of the treatment of paintings of canvas and other historical artefacts. Five hydrophobic porous membranes made of polypropylene (PP), polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), possessing different porosity (60–85%) and average pore size (0.14−0.55 µm) were investigated. Morphology and porosity of membranes were evaluated using SEM and modified bubble point method. Surface properties of membranes were determined by contact angle, surface free energy, and AFM analysis. Subsequently, membranes were assessed in the humidification of the artificially aged paintings. Results showed that all examined hydrophobic porous membranes can be used for the conservation of destroyed paintings. The process was dependent on the time and membrane pore size. It was also found that the membrane thickness has an impact on the efficiency of the humidity gain.

In this work, we introduce a reliable and direct method to activate fluoropolymers via integrating covalent labile ones for further modification. Basic piranha solution was used for the first time to functionalize polymeric surface with hydroxyl moieties. Subsequently, surfaces were modified with a varied molecular grafting. Materials were characterized and tested in several separation processes, including air-gap membrane distillation, osmotic membrane distillation, and microfiltration. This method deciphers surface architecture for various applications not only in membranes but also in variety of fields where functionalized fluoropolymers are employed. The work is also comparing membranes activated with acid and base piranha. The latter produced much more stable and resistant membranes with respect to the acid-treated ones. Systematic and material characterization on the molecular level, with the implementation of various spectroscopic, microscopic, and other techniques, was performed to prove and assess the generated, highly effective separation materials. The presented method opened the gate for fast and easy production of advanced functionalized fluoropolymers.

Two ion-exchange membranes possessing perfluorinated backbone and sulfonic groups (i.e. Nafion ® 120 and IonClad™ R4010) with lithium(I) counter-ions were investigated. The interactions between solvents of different polarity and the ion-exchange membranes with various morphologies were taken into account in order to better understand solvation and dissociation phenomena of the ion-pairs. Pervaporation of polar (i.e. water, methanol)–nonpolar (i.e. methyl acetate, dimethyl carbonate) liquid mixtures was carried out. It was revealed that the increase of the polar component concentration above 2 wt% in the feed mixture leads to dissociation of ion-pairs in Nafion membrane, which is reflected by the rapid increase of the polar component partial flux. In the case of IonClad membrane the dissociation of the ion-pairs during pervaporation was observed only when water was a polar feed component. The dissociation of ion-pairs was also evidenced in infrared study by observing the shift of symmetric stretching vibrations (ν s ) bands of sulfonic groups to the lower wavenumbers, compared to the membrane in the dry state. The symmetric stretching vibrations (ν s ) bands of the dry Nafion membrane and membrane solvated with water and methanol were equal to 1071 cm −1 , 1058 cm −1 , and 1054 cm −1 , respectively. In the case of IonClad membrane the symmetric stretching vibration (ν s ) bands changed in contact with water from 1047 cm −1 (dry membrane) to 1037 cm −1 . The dissociation of the ion-pairs did not occur in IonClad membrane equilibrated with methanol, which is also consistent with the result obtained during pervaporation.

The initially hydrophilic micro- and macroporous ceramic membranes were successfully hydrophobized by grafting with fluoroalkylsilane (FAS) molecules. The influence of diverse parameters (e.g. type of molecule, duration of grafting, concentration of FAS solution, type of solvent) on the resulting hydrophobic surface was investigated. The liquid entry pressure of water (LEPw) was used as a measure of the hydrophobization efficiency. The prepared membranes were subsequently investigated in vacuum membrane distillation (VMD) process using pure water and water–organic solvent solutions as feed mixtures. It was found that permeate flux of pure water is strictly correlated with LEPw value. The selectivity of membranes in contact with water–organic mixtures depends strongly on the pore size of the hydrophobized membrane. Microporous membrane are much less efficient in the separation of organics from water (separation factor of ethyl acetate – EtAc in the range 1.3–30) comparing with macroporous ones (separation factor of EtAc in the range 32–60). The results were also discussed assuming the various mechanism of transports through porous ceramic membranes. These latter results were additionally compared with the results obtained for hydrophobic polymeric membranes (separation factor of EtAc in the range 25–450).

Novel heterogeneous membranes based on poly(ether block amide) and poly(dimethylsiloxane) were prepared and modified by incorporating the grafted alumina oxides into the polymer matrix. Membranes were subsequently used for separation of organic solvent mixtures (ethyl acetate/ethanol and ethyl acetate/isopropanol). There were four types of grafting compounds applied in this research: octyltriethoxysilane (C6), 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FC6), tetradecyltriethoxysilane (C12), 1H,1H,2H,2H-perfluorotetradecyltriethoxysilane (FC12). The influence of incorporation of grafted alumina oxide on physicochemical, equilibrium, transport, and separation properties was investigated. Pervaporation results were assessed using thickness-normalized Pervaporation Separation Index (PSIN) and separation factor (β). Additionally, membrane performance and equilibrium properties were discussed using Hansen's Solubility Parameters. It was found that incorporation of grafted alumina oxide improved membranes performances. The best efficiency during the separation of ethyl acetate/ethanol and ethyl acetate/isopropanol mixtures was found for membranes modified by alumina oxides grafted with octyltriethoxysilane (βEtAc/EtOH = 3.9, βEtAc/IPA = 3.4) and 1H,1H,2H,2H-perfluorotetradecyltriethoxysilane (βEtAc/EtOH = 4.3, βEtAc/IPA = 3.6). Moreover, the presence of water traces (in the range 0.1–0.3 wt%) in feed and permeate was monitored and correlated to the membrane material features. It was found that the presence of water in permeate depends on the character of the membrane and the filler used. The enrichment factor of water for PDMS/(Al2O3+FC12) obtained during separation of EtAc/EtOH and EtAc/IPA was equal to 1.11 and 0.95, respectively.

The objective of this study is related to the modification of polyethersulfone membranes with α-amylase incorporated into chitosan-based polymeric micelles in order to reduce the membrane fouling. Amphiphilic chitosan derivatives have been synthesized through grafting of palmitic (PA) and stearic (SA) acids onto low-molecular weight chitosan. CMC values of palmitoyl and stearoyl derivatives of chitosan are equal to 5.7·10−2 mg/mL and 3.9·10−2 mg/mL, respectively. Whereas, the size of polymeric micelles amounted to 707 ± 64 nm and 609 ± 57 nm for Chit-g-PA and Chit-g-SA, accordingly. The obtained micelles with enzyme have been adsorbed onto the surface of polyethersulfonic membranes. Modified membranes are characterized by high stability of the coating over time, thanks to the surface-active properties of chitosan derivatives and electrostatic interactions. The antifouling biocatalytic properties of modified membranes were studied in the process of starch filtration. The unmodified membrane showed the lowest permeability with an increase in the concentration of starch solutions due to dramatically increased cake formation. The permeability of modified membranes has been improved remarkably compared to the pristine one during starch ultrafiltration. The cake resistance of modified membranes decreases 6-fold, compared to the unmodified PES one. Furthermore, the effect of concentration polarization is attenuated owing to starch hydrolysis by α-amylase incorporated into polymeric micelles. The maximum activity of α-amylase immobilized on PES membrane is observed in the pH range of 6.5–7.5 and the higher resistance of enzyme to acidic media compared to the native one has been shown. High stability and reusability of immobilized α-amylase has been demonstrated. The degree of starch conversion reduces by 35% and 30% after 10 cycles for a membrane modified with Chit-g-PA and Chit-g-SA, respectively.

Hydrophobic alumina and titania micro and mesoporous ceramic membranes were prepared by grafting of C6F13C2H4Si(OEt)3 (C6) molecules and subsequently applied in a pervaporation (PV) process to the removal of hazardous organic solvents (MTBE, EtAc and BuOH) from binary aqueous solutions. The transport and separation properties of investigated membranes were discussed. Additionally it was found that membrane material and grafting time have an important impact of the pervaporative properties. All tested membranes were selective toward organics. Titania membrane was the most efficient and was characterized by the highest value of PSI and the highest value of permeate flux of organic compounds in water–EtAc (JEtAc=1.1 kg h−1 m−2; PSIEtAc=140 kg h−1 m−2) and water–MTBE (JMTBE=1.0 kg h−1 m−2; PSIMTBE=194 kg h−1 m−2) systems. This behavior of titania membrane was also discussed based on the Hansen solubility parameters. In presented work the evaluation of MTBE removal degree with titania modified membrane from water binary mixture in the pervaporation process was discussed.