Clara Casado-Coterillo

Synthesis and characterisation of MOF/ionic liquid/chitosan mixed matrix membranes for CO2/N2 separation

Mixed matrix membranes (MMMs) have been prepared by combining a small amount of highly absorbing non-toxic ionic liquid, [emim][Ac] (IL) (5 wt%), a biopolymer from renewable abundant natural resources, chitosan (CS), and nanometre-sized metal–organic framework (MOF) ZIF-8 or HKUST-1 particles to improve the selectivity of the IL–CS hybrid continuous polymer matrix. The TGA revealed that the thermal stability has been enhanced by the influence of both IL and ZIF-8 or HKUST-1 fillers, while keeping a water content of around 20 wt%, which suggests the potential of such materials for developing high temperature water resistant membranes for CO2 separation. The CO2 and N2 single gas permeation performance was tested at temperatures in the range of 25–50 °C, to compare with the previously reported IL–CS hybrid membranes. The best CO2 permeability and CO2/N2 selectivity performance is obtained for 10 wt% ZIF-8 and 5 wt% HKUST-1/IL–CS membranes, as high as 5413 ± 191 Barrer and 11.5, and 4754 ± 1388 Barrer and 19.3, respectively. This is attributed to a better adhesion and smaller particle size of ZIF-8 than HKUST-1 nanoparticles with respect to the IL–CS continuous matrix, as interpreted by Hansen solubility parameters and Maxwell-based models, modified to account for rigidification, pore blockage and crystallinity of the CS matrix, with very accurate predictions.

Synthesis and Characterisation of ETS-10/Acetate-based Ionic Liquid/Chitosan Mixed Matrix Membranes for CO2/N2 Permeation.

Mixed matrix membranes (MMMs) were prepared by incorporating organic surfactant-free hydrothermally synthesised ETS-10 and 1-ethyl-3-methylimidazolium acetate ionic liquid (IL) to chitosan (CS) polymer matrix. The membrane material characteristics and permselectivity performance of the two-component membranes were compared with the three-component membrane and the pure CS membrane. The addition of IL increased CO2 solubility of the polymer, and, thus, the CO2 affinity was maintained for the MMMs, which can be correlated with the crystallinity, measured by FT-IR, and void fraction calculations from differences between theoretical and experimental densities. The mechanical resistance was enhanced by the ETS-10 nanoparticles, and flexibility decreased in the two-component ETS-10/CS MMMs, but the flexibility imparted by the IL remained in three-component ETS-10/IL/CS MMMs. The results of this work provide insight into another way of facing the adhesion challenge in MMMs and obtain CO2 selective MMMs from renewable or green chemistry materials.

Synthesis and Characterization of ETS-10/Chitosan Nanocomposite Membranes for Pervaporation

Chitosan (CS) and microporous titanosilicate ETS-10/CS mixed matrix membranes (MMMs) were prepared. The pervaporation performance was tested on the water-ethanol mixtures in the range 85–96 wt.% ethanol. The permeate flux increased from 0.45 to 0.55 kg m−2 h−1 at 50°C for the ETS-10/CS MMM with respect to the pure CS membranes. Characterization by SEM and TEM, XRD, DSC, and TGA allowed inferring an intimate contact between the dispersed ETS-10 and the continuous chitosan phase. The 5 wt.% loading of titanosilicate scarcely decreased the hydrophilic character of the mixed matrix membrane but increased the molecular sieving effect on the transport and separation properties, thus affecting the membrane behavior on pervaporation.

Hybrid Ionic Liquid-Chitosan Membranes for CO2 Separation: Mechanical and Thermal Behavior

Abstract Pure chitosan (CS) and hybrid ionic liquid-chitosan membranes loaded with 5 wt% 1-ethyl-3-methylimidazolium acetate ([emim][Ac]) ionic liquid were prepared in order to improve the thermal behavior of supported ionic liquid membranes (SILMs) for CO2 separation. Gas permeability, solubility and diffusivity were evaluated in the temperature range 298–323 K. The temperature influence was well described in terms of the Arrhenius–van’t Hoff exponential relationships. Activation energies were calculated and compared with those obtained for SILMs with the same ionic liquid. The introduction of this ionic liquid in the hybrid solid membrane decreases the permeability activation energy, leading to a lower influence of the temperature in the permeability and diffusivity. Moreover, the thermal behavior is similar to pure chitosan membranes, and the mechanical strength and flexibility were improved due to the introduction of the ionic liquid in the polymer matrix.

Mixed Matrix Membranes for O2/N2 Separation: The Influence of Temperature

In this work, mixed matrix membranes (MMMs) composed of small-pore zeolites with various topologies (CHA (Si/Al = 5), LTA (Si/Al = 1 and 5), and Rho (Si/Al = 5)) as dispersed phase, and the hugely permeable poly(1-trimethylsilyl-1-propyne) (PTMSP) as continuous phase, have been synthesized via solution casting, in order to obtain membranes that could be attractive for oxygen-enriched air production. The O2/N2 gas separation performance of the MMMs has been analyzed in terms of permeability, diffusivity, and solubility in the temperature range of 298–333 K. The higher the temperature of the oxygen-enriched stream, the lower the energy required for the combustion process. The effect of temperature on the gas permeability, diffusivity, and solubility of these MMMs is described in terms of the Arrhenius and Van’t Hoff relationships with acceptable accuracy. Moreover, the O2/N2 permselectivity of the MMMs increases with temperature, the O2/N2 selectivities being considerably higher than those of the pure PTMSP. In consequence, most of the MMMs prepared in this work exceeded the Robeson’s upper bound for the O2/N2 gas pair in the temperature range under study, with not much decrease in the O2 permeabilities, reaching O2/N2 selectivities of up to 8.43 and O2 permeabilities up to 4,800 Barrer at 333 K.

Chitosan feasibility to retain retinal stem cell phenotype and slow proliferation for retinal transplantation

Retinal stem cells (RSCs) are promising in cell replacement strategies for retinal diseases. RSCs can migrate, differentiate, and integrate into retina. However, RSCs transplantation needs an adequate support; chitosan membrane (ChM) could be one, which can carry RSCs with high feasibility to support their integration into retina. RSCs were isolated, evaluated for phenotype, and subsequently grown on sterilized ChM and polystyrene surface for 8 hours, 1, 4, and 11 days for analysing cell adhesion, proliferation, viability, and phenotype. Isolated RSCs expressed GFAP, PKC, isolectin, recoverin, RPE65, PAX-6, cytokeratin 8/18, and nestin proteins. They adhered (28 ± 16%, 8 hours) and proliferated (40 ± 20 cells/field, day 1 and 244 ± 100 cells/field, day 4) significantly low (P < 0.05) on ChM. However, they maintained similar viability (>95%) and phenotype (cytokeratin 8/18, PAX6, and nestin proteins expression, day 11) on both surfaces (ChM and polystyrene). RSCs did not express alpha-SMA protein on both surfaces. RSCs express proteins belonging to epithelial, glial, and neural cells, confirming that they need further stimulus to reach a final destination of differentiation that could be provided in in vivo condition. ChM does not alternate RSCs behaviour and therefore can be used as a cell carrier so that slow proliferating RSCs can migrate and integrate into retina.

Effect of relative humidity on the gas transport properties of zeolite A/PTMSP mixed matrix membranes

Increasing the knowledge of the influence of water vapor in new mixed matrix membranes (MMMs) could favor the integration of novel membrane materials in the recovery of CO2 from wet industrial streams. In this work, the water vapor effect on the N2, CH4 and CO2 permeability through MMMs comprised of 20 wt% hydrophilic zeolite 4A in hydrophobic PTMSP polymer were investigated in the relative humidity range 0–75%. While in the pure PTMSP membranes, the permeability of all gases decreases with water vapor activity, with almost unchanged CO2/N2 and CO2/CH4 selectivities, in zeolite A/PTMSP MMMs, the CO2 permeability increases with increasing water content in the system up to 50% R.H., resulting in an increase in CO2/N2 and CO2/CH4 selectivities with respect to pure PTMSP. Gas sorption was studied so that the effect the residual humidity in the zeolite 4A has on the sorption of the different gases helped explaining the permeability observations. The sorption and humid permeation behavior were evaluated by a simple model equation based on the NELF theory, taking into account the multicomponent gas sorption and diffusion in the presence of humidity, as well as the counteracting effects of the hydrophobic PTMSP and hydrophilic zeolite A in a very accurate way.

Preparation and Identification of Optimal Synthesis Conditions for a Novel Alkaline Anion-Exchange Membrane

The physicochemical and mechanical properties of new alkaline anion-exchange membranes (AAEMs) based on chitosan (CS) and poly(vinyl alcohol) (PVA) polymers doped with unsupported copper nanoparticles (NPs) and copper exchanged over different porous materials were investigated regarding ion-exchange capacity (IEC), OH− conductivity, water uptake (WU), water vapor permeability (WVP), and thermal and mechanical resistance. The influence of the type of filler included in different morphologies and filler loading has been explored using copper exchanged materials such as the layered porous titanosilicate AM-4, layered stannosilicate UZAR-S3, and zeolites Y, MOR, and BEA. Compared to commercially available anion-exchange membranes, the best performing membranes in terms of WU, IEC, OH− conductivity and WVP in this study were those containing 10 wt % of Cu-AM-4 and Cu-UZAR-S3, although 10 wt % Cu-MOR provided better mechanical strength at close values of WVP and anion conductivity. It was also observed that when Cu was exchanged in a porous silicate matrix, its oxidation state was lower than when embedded as unsupported metal NPs. In addition, the statistical analysis of variance determined that the electrochemical properties of the membranes were noticeably affected by both the type and filler loading, and influenced also by the copper oxidation state and content in the membrane, but their hydrophilic properties were more affected by the polymers. The largest significant effects were noticed on the water sorption and transport properties, which gives scope for the design of AAEMs for electrochemical and water treatment applications.

Estimating CO2/N2 Permselectivity through Si/Al = 5 Small-Pore Zeolites/PTMSP Mixed Matrix Membranes: Influence of Temperature and Topology

In the present work, the effect of zeolite type and topology on CO2 and N2 permeability using zeolites of different topology (CHA, RHO, and LTA) in the same Si/Al = 5, embedded in poly(trimethylsilyl-1-propyne) (PTMSP) is evaluated with temperature. Several models are compared on the prediction of CO2/N2 separation performance and then the modified Maxwell models are selected. The CO2 and N2 permeabilities through these membranes are predicted with an average absolute relative error (AARE) lower than 0.6% taking into account the temperature and zeolite loading and topology on non-idealities such as membrane rigidification, zeolite–polymer compatibility and sieve pore blockage. The evolution of this structure–performance relationship with temperature has also been predicted.

Improving gas barrier properties using mixed matrix membranes based on ion exchange capacities of the polymers

Membranes are alternative solution for industrial and domestic separation processes, from water treatment, gas separation, and electrochemical devices. The urgency to limit landfill and petroleum dependency leads the development of new environmentally friendly and economic barrier materials as protective packaging applications (Piringer & Baner, 2000).Chitosan (CS) is a polysaccharide prepared by the deacetylation of chitin. Due to the inherent characteristics, CS has been highly studied as a promising material for membrane separation and active packaging. Poly vinyl alcohol (PVA) can be blended with CS to improve its mechanical properties without reducing hydrophilicity and ion exchange properties (Garcia-Cruz et al. 2015). AM-4 is a layered titanosilicate built of TiO6 octahedra and SiO4 tetrahedra. UZAR-S3 is a layered stannosilicate prepared from isomorphously substitution of Ti by Sn of layered titanosilicate. Both offer a high ion exchange capacity because of the Na+ exchangeable cations between the layers and this contributes to the compatibility with the CS-PVA matrix and the final membrane properties. This work studies the preparation of AM-4- and UZAR-S3/CS-PVA mixed matrix membranes by the direct dispersion and exfoliation of small amounts of AM-4 and UZAR-S3 in the polymer solution. The membranes are characterized regarding their thermal, ion exchange, water uptake, chemical structure and gas barrier properties. The barrier properties were characterized by single gas permeation of N2, O2 and CO2 at 20oC and 2 bar. The best ion exchange capacity and lowest mechanical swelling were those of the UZAR-S3/CS-PVA membrane, which had also lower gas permeability than the pristine CS-PVA membrane. The mechanical swelling of the membranes decreases in the order CS-PVA > AM-4/CS-PVA > UZAR-S3/CS-PVA, probably due to the lower alkylation of ?O-H from free water in the latter membrane than in the others. This also agrees with the lowest permeability of UZAR-S3 compared to AM-4/CS-PVA.