Novel polyelectrolyte membranes were prepared from pure solutions of alginate (Alg), carrageenan (Car) and their mixtures. The films were crosslinked and sulfonated and then, characterized by several ...techniques: ionic exchange capacity (IEC), water uptake, mechanical thermal properties, and also functional properties such as methanol permeability and proton conductivity. The results show that Alg/Car membranes have a ductile behavior. Low carrageenan concentrations have a weak thermoprotective effect, which slightly delays both Tg and Tm of prepared membranes. The methanol permeability of Alg/Car membranes increase with the carrageenan content varying from 0.55 × 10−6 cm2 s−1 for Alg/Car 100/00 to 4.89 × 10−6 cm2 s−1 for Alg/Car 80/20. The Proton conductivities of the membranes increase with the carrageenan content from 9.79 × 10−3 S cm−1 for Alg/Car 100/00 until 3.16 × 10−2 S cm−1 for Alg/Car 80/20 at 90 °C. Finally the proton transfer mechanism is discussed in terms of the conductivity activation energy and the dependence of the proton diffusion coefficient with the temperature has been studied.
•Membranes of alginate with κ-carrageenan have been studied for DMFC application.•Proton conductivity and methanol permeability increase with the carrageenan content.•Carrageenan diminishes the stability of the membranes above a 20 wt% content.•Large increase of the static permittivity at 20 wt% Car is explained by percolation.
•The significance of treatment with NaOH on chitosan film structure was studied.•Three effects were identified deprotonation, phosphate extraction and deacetylation.•Hydrated and anhydrous polymorphs ...were present in the CH–NaOH films.•Films with a more compact and disordered structure were obtained.
In this paper, we examine the significance of treatment with NaOH on chitosan (CH) film structure to obtain biodegradable materials for several applications. In order to determine the structure of the films, an analysis based on SEM, FTIR spectroscopy and X-ray diffraction data was performed. In addition, the consequences of this treatment were evaluated by swelling index measurements and mechanical testing. As result of FTIR and X-ray analysis, three effects were identified: the deprotonation and phosphate extraction, which allowed new hydrogen bonds to form, and a higher CH deacetylation. These studies also revealed that two hydrated and anhydrous polymorphs were present in the CH–NaOH films. Moreover, the new hydrogen bond and the reduction of N-acetyl groups produced films with a more compact and disordered structure, reducing their swelling characteristics and increasing their brittleness. The introduction of a mild NaOH treatment is a versatile tool to obtain chitosan films with interesting and tunable properties.
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Water reclamation and reuse are economically and environmentally important issues for industries. Costly and ineffective treatments such as coagulation, flocculation, and/or ...biological treatment are the most widely used technologies for these processes. The aim of this paper is to study membrane separation to treat biodiesel wastewater as an alternative. To achieve this goal, two commercial nanofiltration membranes were used to treat medium-high strength wastewater. An Inopor Nano tubular ceramic membrane was used in a cross-flow module and a NF99HF Alfa Laval polymeric flat sheet membrane was used in a dead-end filtration cell. Wastewaters were prepared and treated with these membranes achieving maximum fluxes of permeate of 53.1 L h-1 m-2 for the ceramic membrane and 12.2 L h-1 m-2 for the polymeric membrane at 20 bar and 30 °C. The results shows a chemical oxygen demand retention between 80–85 % were obtained for both membranes, while the retention of ionic species due to changes in electrical conductivity was 76–89 %. Transmembrane pressure, organic load, hydraulic permeability, cross-flow velocity, wastewater characterization and fouling resistance-in-series analysis were also made and analyzed in detail in order to explore the actual use of nanofiltration.
Membranes with different degrees of hydrophilicity were prepared from PVDF and PMMA. The hydrophilicity was determined by using the contact angle technique. The distribution of pore radius was ...obtained from polydispersed solute permeation, scanning electron microscope (SEM) and hydraulic permeability. A higher hydrophilic character with the increase of PMMA in the casting solution and the appearance of larger macrovoids in the porous substructure were found without a substantial modification of the selective surface structure. However, a significant effect of compaction was evidenced due to the transmembrane pressure on membranes with high content of PMMA. An effluent from an engine factory was used to study the ultrafiltration performance of the prepared membranes. These assays show that membranes with a higher content of PMMA lead to a lower fouling.
•The effect of weight ratio of Chitosan (CH) to Pectin (PEC) is studied.•The methanol permeability of CH/PEC membranes decreases with the amount of Pectin.•Proton conductivities of CH/PEC membranes ...decrease until a ratio composition of 1:1.•DSC studies reveal excision of ionic pairs between carboxylic and ammonium groups.•Proton diffusion coefficients decrease one order of magnitude in CH/PEC membranes.
Novel blend membranes have been prepared from Chitosan (CH), Pectin (PEC) and their mixtures. The obtained samples were cross-linked and sulfonated before characterization. The results show that CH/PEC membranes display structural changes on the chemical and physical properties as a function of composition. DSC analysis reveals an endothermic peak due to the scission of the ionic pairs between carboxylic groups and ammonium groups, which produces a strong change on physical properties such as methanol permeability and proton conductivity. The methanol permeability decreases with the amount of Pectin from (4.24±0.04)×10−6cm2/s for pure Chitosan membrane to (1.51±0.03)×10−6cm2/s for blend CH/PEC membranes when the amount of Pectin is 50% (v/v). The proton conductivities of the blend membranes follow a similar behavior. For a pure CH membrane the conductivity is 2.44×10−3S/cm, decreasing with pectin content until the composition 50/50 (v/v), in which the conductivity drops almost one order of magnitude.
This work concerns to the development and characterisation of support, active layer and tubular composite membranes (CM) from natural aluminosilicates as principal components (clay, bentonite, ...feldspar, quartz, alumina). The selection of these raw materials was primarily based on their low cost and they are locally produced. In the substrates preparation, the effect of materials compositions, additives, particle sizes, paste rheological properties, and drying-sintering temperatures was investigated. The consolidated ceramic substrates were characterised by SEM, DTA–TG, X-Ray diffraction, Hg intrusion, mechanical resistance, and water flux measurements. Extrusion has been used as the forming process of tubular support. The CM was fabricated depositing a thin active layer by slip-casting method on the support. The CM sintered at 1200°C showed the best structural characteristics, porosities of 50%, active layer pore size between 0.08 and 0.55μm. The CM hydraulic permeabilities (10–274L/hm2kPa) were comparable and greater than several inorganic commercial membranes and CM obtained from other researches. The CM microfiltration effectiveness was tested with different substances from food industry, i.e. slaughterhouse wastewater treatment and goat milk pasteurisation. The obtained results, insoluble residue rejections (100%) and high bacterial removal (87–99%), make the ceramic CM suitable for microfiltration processes.
This research focuses on the description of the spatial and temporal distributions of mobulid ray species (
Mobula birostris
,
Mobula mobular
,
Mobula thurstoni
,
Mobula tarapacana
and
Mobula ...munkiana
) using data from the observer program (1993–2014) of the Inter-American Tropical Tuna Commission (IATTC). The tuna purse seine operations in the region extend from 70 to 150°W to 20°S-30°N. Significant differences on the captures per sets between fishing modes and species were found. Results showed that the most common species taken are
M. thurstoni
,
M. mobular
and
M. birostris
in School sets (sets on unassociated tuna schools). The temporal distributions showed high variability of the catches by species and years. The spatial distribution showed several areas of importance depending of the type of fishing, such as the coast of Peru, Galagapos or the Costa Rica Dome, and possible relationships with some oceanographic processes of the eastern Pacific Ocean (i.e. coastal and seasonal upwelling systems). The frequency of the captures per set showed that, although the greatest numbers caught in a set were very low (around 53.7% of sets with one capture), in some areas and periods there were captures of aggregates of hundreds of individuals of some of these species, such as Galapagos Islands during December, Costa Rica Dome during August, or Baja California during June. These events are of biological interest, and may offer good opportunities for conservation. This project has been developed with the aim of identifying the most important areas for these bycatch species and thus, improving the knowledge on them to reduce their mortality.
► PVDF membranes can be modified with glycidyl methacrylate (GMA) by gamma-rays induce graft polymerization method. ► The grafted membrane can be sulfonated by an epoxy opening reaction. ► Modified ...membranes have a higher number of pores and with smaller size than the unmodified one. ► Grafted membranes do not show irreversible fouling. ► Grafted membrane permeates can be directly discharged into the rivers due to the low values of COD measured.
This work describes the synthesis of charged poly(vinylidene fluoride) (PVDF) membranes. Cationic membranes were prepared by graft modification using radiation-induced polymerization. Glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EDMA) were used as monomers and after graft polymerization the former was sulfonized with sodium sulfite. Membrane characterizations were carried out by FTIR-ATR, SEM-EDS, ionic exchange capacity, hydraulic permeability and liquid–liquid displacement. FTIR-ATR and SEM-EDS analysis revealed that increasing grafting degree increased the amount of the sulfonic group in the membranes. Sulfonated membranes showed smaller pore sizes and higher pore density than the original PVDF membrane. Oil/water ultrafiltration tests with the charged PVDF membranes showed interesting permselectivity performance; high oil retention values (
R
>
98%), low chemical oxygen demand in the permeate solution (COD
<
59
mg
L
−1). In addition, low fouling (<16.6%) and negligible irreversible fouling of the charged membranes was observed during the ultrafiltration tests.
One of the most used methods for studying the rigidification of polymer matrices in composite membranes is differential scanning calorimetry. Glass-transition temperatures give information about ...filler-polymer interaction and the rigidity of the polymer matrix. In this study, optical microscopy, mechanical property testing, and X-ray diffraction, instead of differential scanning calorimetry, were used to study both poly(ether imide) (PEI) matrix rigidification and activated carbon-PEI interfacial adhesion. Then, the permselective properties of the mixed matrix membranes were interpreted. The change in rigidity in these composite membranes was in agreement with the decrease in the flexibility of the composite materials as the filler content increased. This fact was confirmed by the tension and elongation data and X-ray diffraction (DRX) measurements. However, the Young's modulus value decreased as the carbon content increased. There was an increase in all of the gas permeability coefficients measured in the composites compared with that of PEI. As the particle size grew, a low particle surface area and a poor interfacial adhesion were observed. The carbon agglomerates acted as sites of stress concentration within the polymeric matrix. This decreased the intercatenary distances and limited the movement of polymer chains, which resulted in a more rigid matrix. The higher selectivity of the H₂/CH₄, H₂/CO₂ and O₂/N₂ systems observed in the composite membranes revealed that there were both a preferential sorption of certain gases in the carbon surface or carbon-polymer interface and a molecular size exclusion, which were responsible for that increment, despite the poor interfacial adhesion.
As in the brain reserve concept, a larger cervical canal area may also protect against disability. In this context, a semiautomated pipeline has been developed to obtain quantitative estimations of ...the cervical canal area. The aim of the study was to validate the pipeline, to evaluate the consistency of the cervical canal area measurements during a 1-year period, and to compare cervical canal area estimations obtained from brain and cervical MRI acquisitions.
Eight healthy controls and 18 patients with MS underwent baseline and follow-up 3T brain and cervical spine sagittal 3D MPRAGE. The cervical canal area was measured in all acquisitions, and estimations obtained with the proposed pipeline were compared with manual segmentations performed by 1 evaluator using the Dice similarity coefficient. The cervical canal area estimations obtained on baseline and follow-up T1WI were compared; brain and cervical cord acquisitions were also compared using the individual and average intraclass correlation coefficients.
The agreement between the manual cervical canal area masks and the masks provided by the proposed pipeline was excellent, with a mean Dice similarity coefficient mean of 0.90 (range, 0.73-0.97). The cervical canal area estimations obtained from baseline and follow-up scans showed a good level of concordance (intraclass correlation coefficient = 0.76; 95% CI, 0.44-0.88); estimations obtained from brain and cervical MRIs also had good agreement (intraclass correlation coefficient = 0.77; 95% CI, 0.45-0.90).
The proposed pipeline is a reliable tool to estimate the cervical canal area. The cervical canal area is a stable measure across time; moreover, when cervical sequences are not available, the cervical canal area could be estimated using brain T1WI.
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