https://uvadoc.uva.es/handle/10324/48904 Wed, 08 Apr 2026 05:15:56 GMT 2026-04-08T05:15:56Z https://uvadoc.uva.es/handle/10324/61580 Copoly(o-hydroxyamide)s (HPA) and copoly(o-hydroxyamide-amide)s (PAA) have been synthesized to be used as continuous phases in mixed matrix membranes (MMMs). These polymeric matrices were blended with different loads (15 and 30 wt.%) of a relatively highly microporous porous polymer network (PPN). SEM images of the manufactured MMMs exhibited good compatibility between the two phases for all the membranes studied, and their mechanical properties have been shown to be good enough even after thermal treatment. The WAX results show that the addition of PPN as a filler up to 30% does not substantially change the intersegmental distance and the polymer packing. It seems that, for all the membranes studied, the free volume that determines gas transport is in the high end of the possible range. This means that gas flow occurs mainly between the microvoids in the polymer matrix around the filler. In general, both HPA- and PAA-based MMMs exhibited a notable improvement in gas permeability, due to the presence of PPN, for all gases tested, with an almost constant selectivity. In summary, although the thermal stability of the PAA is limited by the thermal stability of the polyamide side chain, their mechanical properties were better. The permeability was higher for the PAA membranes before their thermal rearrangement, and these values increased after the addition of moderate amounts of PPN. Sat, 01 Jan 2022 00:00:00 GMT https://uvadoc.uva.es/handle/10324/61580 2022-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/59961 In this work, CO2 adsorption at 273.15 K and N2 adsorption at 77 K of mixed matrix membranes has been studied, as a method to directly determine their fractional free volume (FFV). These membranes consist of a continuous phase of copoly(o-hydroxyamide)s (HPA) or copoly(o-hydroxyamide-amide)s (PAA) and a relatively highly porous polymer network filler (PPN1). Both the pure copolymers and the mixed matrix membranes (MMMs) have been analyzed before and after a thermal rearrangement (TR) process. The CO2 adsorption results have allowed characterizing the pore size distribution of the studied membranes in the 3–15 Å range, by using the Non-Local Density Functional Theory (NLDFT). Whereas the N2 adsorption has allowed determining the pore size distributions in the range between 20 and 250 Å. The experimental determination of the pore volume and the density allows the direct calculation of the membranes’ free volume fractions, which were in good agreement with the most usual FFV evaluation methods. In addition, part of the pore volume detected by N2 adsorption was associated with defects and poor integration of the membrane components. This correction has allowed us to make a new evaluation of the density of these materials. Sun, 01 Jan 2023 00:00:00 GMT https://uvadoc.uva.es/handle/10324/59961 2023-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/48939 Nanofiltration flux and selectivity depend on the mass transfer through the nanometric pores. Among other factors, including charges and dielectric constant for the charged species, viscosity is of crucial relevance. Here we study how viscosity changes in confined media in the nanometric range. The models found in the literature, that assume that the ratio of the viscosity of water on the pore walls over that in bulk water is a constant, are totally unsatisfactory to predict the dependence of the Darcy constant on temperature. Pure water flux is studied as a function of temperature for three commercial ceramic membranes. For these membranes, we fit flow versus temperature with a quite good fitting assuming that the first layer of water on the cylindrical pore walls move with a viscosity . If the flow is assumed to follow a Carman-Kozeny equation, according to its more realistic granular nature, the resulting porosity and mean grain size are in accordance with the data known and measured by atomic force microscopy (AFM). Wed, 01 Jan 2020 00:00:00 GMT https://uvadoc.uva.es/handle/10324/48939 2020-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/48934 Mixed matrix membranes, MMMs, consisting of variable loads of a porous polymer network, PPN, within an o-hydroxipolyamide, HPA (6FCl-APAF, made from the reaction between 2,2-bis[4-chlorocarbonylphenyl)hexafluoropropane, 6FCl, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, APAF), have been thermally treated to induce the rearrangement of HPA to a polybenzoxazole (β-TR-PBO). HPA is 6FCl-APAF was loaded with a PPN synthetized, by us, by combining triptycene (TRP) and trifluoroacetophenone (TFAP). Mechanical, thermal and morphological properties of the membranes have been determined. CO2/CH4 selectivity of MMMs decreased slightly both when the PPN load was augmented and when thermal rearrangement took place. The changes in selectivity can be attributed mostly to solubility effects for β-TR-MMMs and to diffusive effects for the MMM from neat HPA. CO2 and CH4 permeabilities increased to the 2008 Robesońs upper bond for an optimal 30% PPN load both before and after thermal rearrangement. These relatively good permselectivities are explained in terms of compaction, rigidity, fractional free volumes and filling-matrix interactions. Wed, 01 Jan 2020 00:00:00 GMT https://uvadoc.uva.es/handle/10324/48934 2020-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/48933 Forward osmosis (FO) plays an increasingly important role in membrane processes because of its advantages compared to traditional pressure-driven membrane processes. There are different types of water-selective FO membranes. In this study, a biomimetic hollow fiber module comprising an active layer of polyamide thin film composite (TFC) with integrated aquaporin proteins and an effective area of 0.6 m2 is used to study the rejection of 24 Contaminants of Emerging Concern (CECs). The rejections obtained for all the contaminants studied were higher than 93 % and for 19 of them rejections of up to 99 % were reached. It was observed that although all the tested compounds showed rejections very close to 100 %, they were not completely recovered in the feed solution which makes the retention within the membrane an important factor to be considered. Hence, two membrane rinses were necessary after each membrane operation to completely recover each contaminant. The results were analyzed considering the physicochemical properties (molecular weight, charge and hydrophobicity) of the contaminants. Fri, 01 Jan 2021 00:00:00 GMT https://uvadoc.uva.es/handle/10324/48933 2021-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/48931 Three AFC membranes from PCI, of the thin film composite (TFC) nanofiltration type, have been characterized by using XPS, AFM, Contact angles, Zeta potential and permeation experiments. This plethora of complimentary methods portrays a deep and exhaustive description of these membranes that could be used to tune fabrication and modification of nanofiltration membranes to get better properties. Morphological properties, including porosity, water permeability, fractal dimension, Wenzel parameter and roughness, correlate well with pore sizes. While functional characteristics as, for example wettability correlate well with the O/N ratio. Increasing O/N ratios should be interpreted as caused by increasing PVA coverages. The charge on the membrane’s surface is ordered in a different way for different pH but are quite similar anyway. The effect of charges on retention of 1:1, 1:2 and 2:1 salts (as tested with NaCl, Na2SO4 and CaCl2) increases with increasing O/N and wettability. Consequently, the trend of salt retentions can be explained in terms of the PVA coverage and the details of the amphoteric behavior of the three AFC membranes studied. Wed, 01 Jan 2020 00:00:00 GMT https://uvadoc.uva.es/handle/10324/48931 2020-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/48930 Membrane technology is of significant importance in water treatment applications, and also gaining momentum in other separations due to advantages such as environmentally friendly operation, less complex and lower-cost operating conditions compared to alternative options. To provide for sustainable and efficient membrane-based applications, the selection of appropriate membranes is crucial. Such a selection is based on membrane characterization, which offers critical information on parameters such as porosity, average pore size and pore size distribution (PSD). The two main classes of characterization methods are direct and indirect, with the latter having a theoretical basis, being more affordable, and also generally being able to characterize larger membrane areas compared to the direct techniques. This study reviews the indirect membrane characterization methods, the key theoretical backgrounds of which are the Young-Laplace equation, Kelvin equation, Gibbs-Thomson equation, and spectroscopy-based equations. The mathematical details are first presented, followed by the measurement details and experimental requirements, and finally the studies on membrane characterization via indirect methods. The advantages and limitations of each method are also discussed. For a complete understanding of the membrane, indirect methods may need to be complemented with direct ones and also with appropriate retention experiments of the feeds of interest. Fri, 01 Jan 2021 00:00:00 GMT https://uvadoc.uva.es/handle/10324/48930 2021-01-01T00:00:00Z https://uvadoc.uva.es/handle/10324/48908 A hydroxypolyamide (HPA) manufactured from 2,2-bis(3-amino-4-hydroxy phenyl)-hexafluoropropane (APAF) diamine and 5′-terbutyl-m-terphenyl-4,4′′-dicarboxylic acid chloride (tBTpCl), and a copolyimide produced by stochiometric copolymerization of APAF and 4,4′-(hexafluoroisopropylidene) diamine (6FpDA), using the same diacid chloride, were obtained and used as polymeric matrixes in mixed matrix membranes (MMMs) loaded with 20% (w/w) of two porous polymer networks (triptycene-isatin, PPN-1, and triptycene-trifluoroacetophenone, PPN-2). These MMMs, and also the thermally rearranged membranes (TR-MMMs) that underwent a thermal treatment process to convert the o-hydroxypolyamide moieties to polybenzoxazole ones, were characterized, and their gas separation properties evaluated for H2, N2, O2, CH4, and CO2. Both TR process and the addition of PPN increased permeability with minor decreases in selectivity for all gases tested. Excellent results were obtained, in terms of the permeability versus selectivity compromise, for H2/CH4 and H2/N2 separations with membranes approaching the 2008 Robeson’s trade-off line. The best gas separation properties were obtained when PPN-2 was used. Finally, gas permeation was characterized in terms of chain intersegmental distance and fraction of free volume of the membrane along with the kinetic diameters of the permeated gases. The intersegmental distance increased after TR and/or the addition of PPN-2. Permeability followed an exponential dependence with free volume and a quadratic function of the kinetic diameter of the gas. Fri, 01 Jan 2021 00:00:00 GMT https://uvadoc.uva.es/handle/10324/48908 2021-01-01T00:00:00Z