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Human actions over the years have aroused concerns due to their potential pollution, causing an increase in the emission of greenhouse gases into the atmosphere. Polymeric membranes have been used to separate these gases and this technology has proved itself very promising since it presents a lower energy consumption when compared to other separation processes. In this study, the effect of calcium carbonate additives and of oyster powder was evaluated on polymeric polyurethane (PU) membranes. The membranes were obtained by the phase inversion technique using two different techniques: immersion precipitation and solvent evaporation. The obtained membranes were tested in the separation of CH4 and CO2 from greenhouse gases, which are the main contributors to the increase of the greenhouse effects. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), permeability and selectivity tests were performed to characterize the synthesized composite membranes. The SEM results showed a dense membrane morphology with an increase in free volume when the additives were incorporated to the PU structure. According to the FTIR results, the membranes obtained did not change the structure of the PU. As for the application tests, all composite membranes showed greater permeability for CH4 gas, due to a greater affinity of the gas with the polymeric matrix. The addition of both CaCO3 and oyster powder to the composition of the polymeric membrane contributed to increase the permeability of the gases tested, due to the increase in free volume.

The high protein content of Arthrospira platensis makes this cyanobacterium a great component of food. Thus, the protein obtained should guarantee the nutrient characteristic, in this case, as bioactivity and techno-functional properties. Membrane separation processes (MSPs) have been highlighted by their capacity to separate proteins and keep their properties. Therefore, MSP was used to concentrate and separate the proteins from A. platensis, which were characterized by their physicochemical and techno-functional properties. Different ultrafiltration (UF) membranes and operational conditions (10- and 50-kDa pore size, conventional and tangential flow, hollow fiber type and pressures of 1.0, 1.5, and 2.0 bar) were tested and associated with diafiltration (DF). The maximized condition of UF/DF (hollow fiber, 50 kDa, tangential flow at 1.5 bar, associated with one DF) was up scaled (pilot scale) and allowed concentrate and permeate fractions with 81.75% and 61.20% of protein, respectively, to be obtained. A protein concentrate with 142 mg L−1 of phycocyanin, 90% of antioxidant activity, with proteins more soluble at high pH (50% soluble protein at pH 7.0) and molecular weight among 5–15 and 100 kDa, was obtained. Protein thermal and emulsifying properties were maintained by the MSP, and the concentrate fraction presented results similar as A. platensis biomass, which confirms the advantage of this method in guaranteeing the protein quality.

Techniques using membranes for the treatment of wastewaters usually promote higher quality of treated water when compared to other processes. Among them, pervaporation has advantages in terms of selectivity in addition to low working pressure, which can prevent clogging problems. Polysulfone and polyurethane have complementary characteristics and are interesting in the context of membranes for industrial applications. In this sense, the aim of this work was to prepare and characterize polysulfone/polyurethane-based membranes and tested them with a simulated wastewater containing the reactive black dye and sodium chloride by pervaporation. In their manufacture, thermal treatment (at 60°C) and photo-radiation treatment (using ultraviolet light) were also applied. The characterizations were performed using different analytical tools. In general, it was possible to verify that all membranes have a dense layer. The thermal analysis allowed to define that the indicated working temperature is below 50°C. With respect to the simulated wastewater treatment, all membranes reached 100% selectivity. Concerning the saline solution, the mean selectivity was around 98.5%. Moreover, the permeate flow values were within the range presented by commercial membranes ranging from 1.6 to 2.4 kg m

Membranas de compósitos Pd/α-Al2O3 com uma e duas camadas de Pd foram preparadas pelo processo electroless plating sobre tubos cerâmicos porosos. A análise de espectroscopia por dispersão de energia confirmou a composição química do suporte cerâmico (Al e O) e da membrana com Pd (Al, O e Pd), bem como a espessura da camada de Pd de 0,8 μm (uma camada) e 1,3 μm (duas camadas). As imagens de microscopia eletrônica de varredura mostraram que a superfície da membrana foi mais uniforme com uma camada do que duas camadas de Pd. O difratograma de raios X registrou picos referentes à fase α-alumina. A porosimetria por intrusão de mercúrio apresentou diâmetro de poro em torno de 5 nm e volume máximo de Hg intrudado de 0,0081 cm3.g-1. Os testes de permeabilidade aos gases mostraram que as membranas possuem seletividade α de 3,79 para o par H2/CO2 com um camada de Pd e de α=3,43 para o par H2/CH4 com duas camadas de Pd. Composite membranes Pd/α-Al2O3 with one and two Pd layers were prepared by electroless plating process on porous ceramic tubes. The analysis by energy dispersive spectroscopy confirmed the chemical composition of the ceramic support (Al and O) and of the membrane with Pd (Al, O and Pd), as well the thickness of Pd layer of 0.8 μm (one layer) and 1.3 μm (two layers). Scanning electron microscopy images showed that the surface membrane was more uniform with one layer than two Pd layers. The X-ray diffraction pattern recorded peaks assigned to α-alumina phase. Mercury intrusion porosimetry showed a pore diameter around 5 nm and maximum intruded Hg volume of 0.0081 cm³.g-1. Gas permeability tests showed that the membranes had selectivity α of 3.79 for H2/CO2 pair with one Pd layer and α=3.43 for H2/CH4 pair with two Pd layers.

The pollution of hydric sources by pharmaceuticals is an issue in many countries, particularly in Brazil. The presence of these substances causes deleterious effects on the environment and human health. One of the main sources of this contamination is domestic sewage, due to the expressive amount of medicines released in their unaltered form. Unfortunately, traditional wastewater treatment is not effective for the removal of pharmaceuticals and, for this reason, membrane technology is an attractive alternative to overcome this issue. In this regard, hydrophilic polymers, such as poly(vinyl alcohol) (PVA), are the most suitable. However, their high affinity with water causes intense swelling, leading to severe modifications in the membrane properties. In view of all these facts, the present work evaluated the swelling of PVA-based membranes, with the aim of finding the membrane preparation method that has the lowest swelling, thereby providing the most suitable characteristics for pharmaceutical removal from wastewater. The membranes were prepared by the casting of a polymeric solution, with PVA as a basis polymer, citric acid as a crosslink agent and glycerol and silver nanoparticles as performance additives. The process optimization was performed using a design of experiments with posterior analysis by the response surface methodology (RSM). The RSM assessed the effect on the membrane swelling of the factors, including citric acid concentration and the time and temperature of crosslinking. The membrane characterization was performed by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy coupled with a field emission gun (SEM-FEG) and water contact angle (WCA) measurements. Overall, the condition that showed the lowest swelling was obtained with 10% of citric acid and crosslinking for 4 h at 130 °C. Under these conditions, the membrane had a mass swelling of 42% and a dimensional swelling of 24%. Additionally, our statistical analysis revealed that the factors with the dominant effects were the citric acid concentration and the temperature of crosslinking. The FT-IR analysis suggested that the crosslinking occurred by an esterification reaction, as showed by the stretching frequencies of C=O at 1710 cm-1 and ester C-O at 1230 cm-1. Moreover, the SEM-FEG images revealed a smooth and flat surface and a dense cross section with a thickness of ~113 μm. Concerning the WCA, the angle was at ~80°, which is characteristic of hydrophilic materials. Finally, the data suggested that it is possible to optimize the membrane preparation process with adequate properties so that it can be subsequently applied to the removal of pharmaceuticals from hospital wastewater. A contaminação dos corpos hídricos por fármacos está sendo observada em diversos países, especialmente no Brasil. A presença dessas substâncias provoca efeitos nocivos, tanto ao meio ambiente quanto à saúde dos seres humanos. O esgoto doméstico é a principal fonte dessa contaminação, uma vez que uma grande quantidade de fármacos ingeridos pelo homem é excretada na sua forma inalterada. Infelizmente, o tratamento convencional de efluentes é pouco eficiente na remoção dessas substâncias e, nesse sentido, uma alternativa é processo de separação por membranas (PSM). Para essa aplicação, os polímeros hidrofílicos, como o poli(vinil álcool) (PVA), são os materiais mais apropriados. Entretanto, essa característica faz com que as membranas de PVA sofram um inchamento intenso quando em contato com a água, o que altera propriedades importantes para os PSM. Nesse contexto, o presente trabalho teve por objetivo avaliar o inchamento de membranas de PVA, a fim de determinar o método de preparação que proporciona o menor inchamento, fornecendo as características mais adequadas para a remoção de fármacos de efluentes. As membranas foram preparadas pelo espalhamento de uma solução polimérica contendo PVA como polímero base, ácido cítrico como agente reticulante, e glicerol e nanopartículas de prata como aditivos de performance. A otimização do processo foi realizada por meio de um planejamento experimental com posterior análise de superfícies de resposta, avaliando-se a influência da concentração de agente reticulante, além do tempo e da temperatura de reticulação no inchamento da membrana. As membranas foram ainda caracterizadas por meio das técnicas de espectroscopia de infravermelho com transformada de Fourier (FT-IR), microscopia eletrônica de varredura com emissão de campo (MEV-FEG) e ângulo de contato com água (WCA). A condição de melhor desempenho foi obtida utilizando-se 10% de ácido cítrico e reticulação por 4 h a 130 °C. Nessas condições, a membrana teve um inchamento mássico de 42% e dimensional de 24%. Também se verificou que a concentração do ácido cítrico e a temperatura de reticulação foram os fatores de maior influência, de acordo com a análise estatística. De modo geral, a análise de FT-IR indicou a reticulação da membrana por meio de uma reação de esterificação, evidenciada pelos estiramentos das ligações C=O em 1710 cm-1 e de C-O de ésteres em 1230 cm-1. As imagens de MEV-FEG, por sua vez, revelaram uma superfície lisa e plana, além de uma secção transversal densa com aproximadamente 113 μm de espessura. O ângulo de contato foi de aproximadamente 80°, típico de materiais de caráter hidrofílico. Finalmente, o conjunto de dados evidenciou que foi possível aperfeiçoar a preparação de uma membrana com características adequadas para a subsequente aplicação na remoção de fármacos de efluentes hospitalares.

An asymmetric membrane of polysulfone (PSf) was synthesized by phase inversion method. Permeation experiments were carried out between 2 to 5 bar pressure, and at temperatures 20 to 45°C. The dense-selective layer of PSf membrane presents regular thickness (about 5 µm), and was not possible to observe the formation of macrovoids in porous layer. The CO2 permeability through membrane was 18.8 Barrer at 35°C and 2 bar pressure, and this relationship between the pressure and the CO2 permeability was described adequately by Dual-mode model. The absence of CH4 permeability at 2 and 3 bar pressure, qualifies the PSf membrane for gases separation with high selectivity in this range.

The membranes properties prepared from water/formic acid (FA)/ polyamide 66 (PA66) and water/hydrochloric acid (HCl)/polyamide 66 (PA 66) systems has been studied. The different solvents interact distinctly with the polymer, affecting the membrane morphology. The asymmetric structure of the membranes showed a dense top layer and a porous sublayer. The membranes M-HCl prepared from HCl/PA 66 system showed a larger dense layer (around 23 μm) in compared to those prepared from FA/PA 66 system (M-FA) (around 10 μm). The membrane morphology was a determinant factor in results of water absorption, porosity and pure water flux. The lower thickness of dense layer in M-FA membranes resulted in a higher water absorption and, consequently, porosity, approximately 50%, compared with M-HCl membranes, approximately 15%. The same trend was observed to permeate flux, the lower thickness of dense layer higher pure water flux.

The membranes prepared from synthetic polymer are used worldwide in separation processes. Polymeric membranes from polyamide 66 (PA 66) in hydrochloric acid (HCl) at the concentrations of 10 and 15 wt.% were prepared by phase inversion method. Poly(vinyl pyrrolidone) (PVP) was used as the polymeric additive in the casting solution to improve the morphology and properties of the PA 66 membranes prepared. The membranes analyzed by Fourier transform infrared (FTIR), maintaining the same chemical structure of pure PA 66 membranes, indicating that the PVP was eliminated in nonsolvent bath. The determination of cloud point showed that PVP addition promotes a thermodynamic instability in the casting solution, reducing the time precipitation and influencing in the dense layer formation of the membrane. The scanning electron microscopy (SEM) showed that the PVP addition promoted a decrease in the thickness of dense layer and an increase in the percentage of the porous sublayer, greater uniformity of pores membrane...

The dissolution of polymers in solvents is an interest area of polymers science and technology due to their applications in films and membranes. The starting point for the preparation of polymer membranes by phase inversion is having a thermodynamically stable solution. In this work, the thermodynamic behaviour of polyamide 66 (PA66) solutions in formic acid (FA) and in hydrochloric acid (HC), was studied to evaluate its physical/chemistry classification. The polymer systems may be divided into five classes (types), which incorporate polymer-low molecular liquid systems, ranging from true solutions to dispersions of polymers in liquids. The polyamide 66/formic acid (PA66/FA) binary system is considered a true solution. Several experiments were performed to verify if the polyamide 66/ hydrochloric acid (PA66/HC ) binary system has all characteristics of true solution. The analysis showed that the PA66/HC binary system presents all characteristics of true solution, including the final morphology of the membranes that are similar obtained membranes by PA66/FA binary system.

Cellulose Acetate (CA) produced from sugarcane bagasse cellulose was used to produce membranes, using poly(ethylene glycol) (PEG 600) as additive. Results showed that PEG 600 was washed out the membranes during the preparation step. Thermal Analysis showed that the temperature of degradation of the membranes increased in 10 °C when PEG 600 was added to the composition, but did not change as more PEG 600 was added in the composition. On the other hand, the crystalline content (%C) of the membranes increased as PEG 600 was added. The addition of PEG 600 also increased the resistance of the membranes to pressure and the pure water flux rate, but membranes produced with PEG 600 content lower than 5% did not present water flux. PEG 600 also increased the coefficient of ion diffusion of the membranes.

In this study, polymer/ceramic composite membranes were prepared and characterized. The polymer used was polyamide 66 (PA66) deposited by dip coating on the inner surface of α-alumina-based (Al2O3) microporous tube. A coating on the ceramic support surface and the formation of the selective layer was analyzed by scanning electron microscopy (SEM) in membranes with one (PA-1) and two layers (PA-2). The results of mercury porosimetry showed that the deposition of the polyamide layers decreases the average pore size. The PA-1 presented an average pore size of 0.35 μm, while the PA-2 presented two peaks of 0.18 and 0.56 μm. Both showed a superior performance than the ceramic support (pore diameter of 0.65 μm). Although, the permeate flux was higher with an impregnation membrane, the number of layers (one or two) just introduced a slight difference in pore statistical analysis. The order of rejection coefficient values for protein molecules is BSA > egg albumin > trypsin. The permeation tests showed that the composite membrane can be applied in ultrafiltration processes with MWCO of 69 kDa.

Cellulose acetates (CA) with different degrees of acetylation were synthesized from cellulose extracted from corn stover. Membranes were prepared for the ultrafiltration process with pure polymers and blend form of CA utilizing a dioxane/acetone system. The membranes were characterized according to their transport properties. The blend form materials presented the best results for application in ultrafiltration experiments. M-TAC/DAC (corn stover triacetate and diacetate) and M-TAC/DAC-Rho (corn stover triacetate and Rhodia diacetate) presented rejection to egg albumin protein of 87.39% and 80.50%, respectively. Thus, MWCO of 45 kDa was determined for these materials.

The aim of this paper was to prepare a poly (vinylidene fluoride) (PVDF) membrane using different non-solvents in the coagulation bath for the phase inversion method. In order to increase the mechanical strength of membranes, facing the pressure of work, was used a macro-porous polyester support. The morphology and structure of the resulting membranes were evaluated by scanning electron microscopy, porosity measurements, water and 1-octanol uptake, contact angle, pure water flux, hydraulic permeability and hydraulic resistance. The morphology and pure water flux changed significantly using ethanol (symmetric membrane) and/or water (asymmetric membrane) as the non-solvent. The symmetric membrane presented a high hydrophobic surface (water contact angle ~136º) and a higher pure water flux and porosity than the asymmetric membrane, which presented a lower hydrophobicity surface (water contact angle ~90º). The morphologies obtained suggest different applications.

Membranas de poliamidas alifáticas são muito utilizadas como barreiras seletivas em processos de microfiltração e ultrafiltração. Neste trabalho membranas de poliamida 66 (PA 66) foram preparadas pelo método de inversão de fases e caracterizadas para aplicação em processos de ultrafiltração. As membranas de PA 66 foram preparadas utilizando dois solventes diferentes, ácido fórmico (AF) e ácido clorídrico (HCl) e água como não-solvente. A análise por Espectroscopia de Infravermelho com Transformada de Fourier (FT-IR) mostrou que a estrutura química da PA 66 não foi alterada com o uso dos solventes na preparação das membranas. O ensaio de compactação com água pura realizado a 1500 kPa de pressão revelou que as membranas preparadas em AF sofreram maior compactação na sua estrutura apresentando fluxo de permeado em torno de 17 L.m-2.h-1 enquanto a membrana preparada em HCl apresentou fluxo de 22,2 L.m-2.h-1. Nos ensaios de ultrafiltração (UF), ambas as membranas apresentaram valores de retenção próximos a 70% para albumina de ovo (45 kDa) e 80% para albumina sérica bovina (69 kDa). Com esse resultado, pode-se concluir que ambas as membranas apresentaram ponto de corte nominal para aplicações em processos de UF. In the present study, polyamide 66 (PA 66) membranes were prepared by phase inversion method and characterized in order to verify their potential application in ultrafiltration processes. PA 66 membranes were prepared using two different solvents, formic acid (FA) and hydrochloric acid (HCl), and water as a non-solvent. Fourier-transform infrared spectroscopy (FT-IR) showed that the chemical structure of PA 66 was not altered by the use of solvents in the preparation of membranes. The compaction experiment with pure water performed at a pressure of 1500 kPa revealed that membranes prepared with FA undergo greater compaction of its structure and had a permeate flux value of approximately 17 L.m-2.h-1 whereas the membrane prepared with HCl had a permeate flux of 22.2 L.m-2.h-1. In the ultrafiltration experiment, both membranes had retention values around 70% for egg albumin and 80% for bovine serum albumin. Based on this result, one concludes that both membranes had nominal cut off values for application in ultrafiltration processes.

Membranas de polisulfona/poliuretano foram preparadas pelo método de inversão de fases. As membranas preparadas com a adição de fotoiniciador foram irradiadas com lâmpada ultravioleta para aumentar a interação entre os polímeros e o suporte de poliéster utilizado. As membranas com e sem adição de fotoiniciador foram caracterizadas através dos testes de resistência química, capacidade de adsorção de água, determinação de densidade, porosidade, morfologia e fluxo permeado de água. A membrana fotoiniciada apresentou poros com paredes bem definidas e maior estabilidade nos testes de resistência química e fluxo permeado. Ambas as membranas apresentaram valores aproximados na adsorção de água e porosidade. Polysulfone/polyurethane membranes were prepared by the phase inversion method and irradiated with an ultraviolet light bulb to increase the interaction between polymers and the polyester support. The membranes with and without addition of fotoinitiator were characterized using tests of chemical resistance, water adsorption capacity, density and porosity determination, water permeate flux and membrane morphology. The membrane treated with the fotoinitiator exhibited well defined pores and greater stability in the tests of chemical resistance and water permeate flux. Both membranes had similar values for the water adsorption and porosity.