Poly(ether-b-amide) (Pebax® grade 1074) is a waterproof breathable block copolymer containing soft poly(ethylene oxide) and rigid polyamide 12 segments. Its intrinsic gas permeabilities to nitrogen, oxygen, methane, helium, hydrogen, and carbon dioxide were tested under different feed pressures (0.3 – 2.5 MPa) and temperatures (20 – 80 °C). This helps to obtain a comprehensive understanding of the polymer, because prior work reported in the literature addressed only a few gases and used inconsistent membrane preparation and test methods. Relatively high polar (or quadrupolar)/nonpolar gas selectivity were observed. CO2/N2 selectivity was demonstrated to be as high as 105±0.4 in Pebax®1074, with CO2 permeability coefficient of approximately 180±1 Barrer at room temperature. Additionally, the effects of solvent used in membrane preparation, heat treatment, membrane thickness, and polymer solution concentration on the membrane permeability were evaluated. Pebax® is a highly breathable material, thus its application as breathable chemically-resistant protective clothing was studied. Dimethyl methylphosphonate (DMMP) – a sarin simulant – was selected as the challenge agent. The liquid pervaporation of pure water (simulating perspiration) and pure DMMP were measured for Pebax®1074, Pebax®2533, nitrile, latex, poly(vinyl chloride), low density polyethylene, silicone, and silicone-polycarbonate copolymer under pervaporation mode. Pebax®1074 was not only the most water permeable material but also the most selective of all the tested materials for water/DMMP – making it a very promising material for this application.

Orientador: Maria Regina Wolf Maciel / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-08T23:42:41Z (GMT). No. of bitstreams: 1 Perioto_FabianoRomero_D.pdf: 1193759 bytes, checksum: 59c15d9b760f3098c6e92c822d878e78 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho de tese, foram realizadas a modelagem e a simulação dos processos de separação pervaporação e osmose inversa aplicados a sistemas binários. A premissa empregada foi o desenvolvimento de metodologias de predição das variáveis de processo da pervaporação e osmose inversa independentes de dados experimentais destes processos; os dados necessários para a predição destas variáveis foram propriedades fundamentais dos componentes puros da alimentação. A partir de uma revisão bibliográfica dos modelos existentes para o processo de pervaporação, foi definida uma metodologia de predição das variáveis de processo baseado no modelo solução-difusão. A etapa inicial da metodologia foi o desenvolvimento de um programa de cálculo das composições de sorção na membrana, baseado no modelo UNIQUAC e no método de contribuição de grupos UNIFAC, adaptados ao uso de polímeros. O programa foi validado pela aplicação a sistemas ideais e não-ideais sob o ponto de vista termodinâmico. Os resultados empregando o modelo UNIQUAC apresentaram boaconcordância com os dados experimentais; no caso dos resultados obtidos via UNIFAC para solventes orgânicos obteve-se um bom ajuste dos dados experimentais, mas, no caso da água, os resultados obtidos pelo modelo não foram adequados. Na segunda etapa da metodologia, foram realizados o estudo da predição do coeficiente de difusão na membrana, a partir do modelo do volume livre, seguindo a abordagem de Fick e Maxwell-Stefan; a determinação dos parâmetros necessários ao respectivo modelo; a aplicação a casos estudos e uma análise paramétrica. Os resultados obtidos concordaram bem com os dados experimentais. Com isto, a partir dos valores de sorção e coeficientes de difusão, foi elaborado um programa para a predição do processo de pervaporação; o programa foi aplicado a casos estudos citados na literatura. Foi também estudada a aplicação da pervaporação ao sistema fenol-água, considerando uma membrana de poli (dimetil siloxano) como agente de separação. Os resultados concordaram bem com os dados experimentais disponíveis e mostraram que uma melhor seletividade e performance de separação foram obtidos em concentrações de fenol na alimentação inferiores a 0,2 % molar. A etapa final do trabalho foi a elaboração de um programa para simulação do processo de osmose inversa tendo como base um modelo derivado da mecânica-estatística. A partir dos parâmetros do modelo, foram preditos a rejeição e fluxo do permeado da mistura etanol-água em uma membrana de poliamida. O coeficiente de difusão de Maxwell-Stefan em alta pressão foi predito e empregado na simulação da osmose inversa / Abstract: In this work, the modelling and simulation of pervaporation and reverse osmosis processes for binary mixtures were carried out. The development of prediction methodologies for process variables of pervaporation and reverse osmosis without the necessity of experimental data was the general guideline followed; the experimental data used in these methodologies were the fundamental properties of pure components of feed. Based on the literature review for available models for pervaporation process, a prediction methodology according to the solution-difusion model was choosen and developed. The inicial step for the methodology elaboration was the development of a software for sorption composition determination in the membrane, based on the UNIQUAC model and UNIFAC group contribution method, both suitable for polymer applications. The software was validated applying it forideal and non-ideal systems on thermodynamic viewpoint. The results obtained according to the UNIQUAC model agreed well with experimental data; in the case of the results obtained by the UNIFAC method when applied for organic solvents, it was obtained a good agreement with experimental data, but, on the other hand, for the water, the results showed that the model must be improved. In the second step of methodology development, the study of the prediction of the diffusion coefficient in the membrane according Fick and Maxwell-Stefan approaches, the determination of models parameters, the validation of the prediction method with experimental data and a parametric sensitivity analysis were carried out. The results agreed well with experimental data. So, using the sorption compositions and diffusion coeficients calculated, it was developed a software for pervaporation prediction; the software was applied for some cases of literature. It was also studied the application of pervaporation to phenol-water system using poly(dimethylsiloxane) as selective barrier. The results agreed well with available experimental data and showed that a best selectivity and separation performance were achieved for phenol concentration lesser than 0.2% molar in the feed side. The final step of this work was the development of a software for simulation of reverse osmosis process based on a mecanical-statistical model. By using the model parameters, the rejection and permeate flux of ethanol-water mixture were predicted in a poliamide membrane. The diffusion coefficient of Maxwell-Stefan in high pressure was predicted and used in the reverse osmosis simulation / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

Abstract Limited oil resources, environmental concerns and legislation promoting renewable energy and restricting carbon dioxide emissions have increased biofuel production in recent years. Other alternatives besides bioethanol and biodiesel are also needed to fulfil the continuously increasing transportation fuel demand. Production processes should be material, energy and resource efficient and sustainable, i.e. causing as low negative economic, environmental and social impacts as possible. There are still some limitations and development areas to be solved before feasible industrial biofuels and biochemicals production processes are obtained. The production of biobutanol and bioethanol was studied in this work. Production processes, challenges and improvement requirements were considered especially in the case of the Acetone-Butanol-Ethanol (ABE) fermentation process. In addition, the sustainability assessment of biofuels production was discussed and an indicator-based approach to sustainability evaluation for different raw materials was used. Pervaporation as a product removal and purification method was experimentally studied. Two different applications were tested: a hydrophobic composite membrane with polydimethyl siloxane and polyacrylonitrile layers was used for the separation of acetone, n-butanol and ethanol from dilute aqueous solutions on a laboratory scale, and a hydrophilic polyvinyl alcohol membrane was applied for the dehydration of bioethanol at a pilot-scale. Results indicated that pervaporation can be used as a separation technique in biofuels production processes. New knowledge obtained during the research also promotes the efficient and sustainable production of biofuels and biochemicals and the development of industrial-scale applications. / Tiivistelmä Rajalliset öljyvarannot, huoli ympäristöstä sekä uusiutuvaa energiaa tukeva ja hiilidioksidipäästöjä rajoittava lainsäädäntö ovat lisänneet biomassapohjaisten polttoaineiden ja kemikaalien valmistusta ja käyttöä viime vuosina. Jatkuvasti kasvavan polttoainetarpeen täyttämiseksi tarvitaan myös muita vaihtoehtoja nykyisin käytössä olevien bioetanolin ja -dieselin lisäksi. Tuotantoprosessien tulisi olla materiaali-, energia- ja kustannustehokkaita sekä kestäviä aiheuttaen mahdollisimman vähän haitallisia taloudellisia, sosiaalisia ja ympäristöllisiä vaikutuksia. Biokemiallisissa, käymisen avulla tapahtuvissa polttoaineiden valmistusprosesseissa on kuitenkin vielä rajoitteita ja kehitystarpeita, jotka tulee ratkaista kannattavan teollisen mittakaavan tuotannon mahdollistamiseksi. Tässä työssä tutkittiin biopolttoaineiden, erityisesti biobutanolin ja -etanolin, valmistusta. Tuotantoprosesseja on esitelty työssä haasteiden ja kehitystarpeiden näkökulmasta. Lisäksi on käsitelty biopolttoaineiden tuotannon kestävyyden arviointia ja osoitettiin tapa verrata eri raaka-aineiden kestävyyttä valittujen indikaattoreiden avulla. Työn kokeellisessa osuudessa tutkittiin pervaporaatiota tuotteiden (asetoni, n-butanoli, etanoli) erotuksessa ja puhdistuksessa. Kahta eri sovellusta testattiin: hybrofobista polydimetyylisiloksaani- ja polyakrylonitriili-kerroksista koostuvaa komposiittikalvoa käytettiin asetonin, n-butanolin ja etanolin erottamiseen erilaisista vesiliuoksista laboratoriomittakaavan laitteistolla sekä hydrofiilistä, polyvinyylialkoholi-kalvoa bioetanolin vedenpoistoon pilot-mittakaavassa. Lisäksi testattiin aktiivihiilisuodatuksen käyttöä bioetanolin esipuhdistuksessa haitallisten komponenttien osalta ennen pervaporaatiota. Koetulokset osoittavat, että pervaporaatiota voidaan käyttää biopolttoaine-sovellusten erotusmenetelmänä. Tutkimuksen aikana saatu uusi tieto edistää biomassapohjaisten polttoaineiden ja kemikaalien tehokasta ja kestävää tuotantoa ja kehitystä kohti teollisen mittakaavan sovelluksia.

Worldwide demand for energy is increasing rapidly, partly driven by dramatic economic growth in developing countries. This growth has sparked concerns over the finite availability of fossil fuels and the impact of their combustion on climate change. Consequently, many recent research efforts have been devoted to the development of renewable fuels and sustainable energy systems. Interest in liquid biofuels, such as ethanol, has been particularly high because these fuels fit into the conventional infrastructure for the transportation sector. Ethanol is a renewable fuel produced through the anaerobic fermentation of sugars obtained from biomass. However, the relatively high energy demand of its production process is a major factor limiting the usefulness of ethanol as a fuel. Due to the dilute nature of the fermentation product stream and the presence of the ethanol-water azeotrope, the separation processes currently used to recover anhydrous ethanol are particularly inefficient. In fact, the ethanol separation processes account for a large fraction of the total process energy demand. In the conventional ethanol separation process, ethanol is recovered using several distillation steps combined with a dehydration process. In this dissertation, a new hybrid pervaporation-distillation system, named Membrane Dephlegmation, was proposed and investigated for use in ethanol recovery. In this process, countercurrent vapour-liquid contacting is carried out on the surface of a pervaporation membrane, leading to a combination of distillation and pervaporation effects. It was intended that this new process would lead to improved economics and energy efficiency for the entire ethanol production process. The Membrane Dephlegmation process was investigated using both numerical and experimental techniques. Multiphase Computational Fluid Dynamics (CFD) was used to study vapour-liquid contacting behaviour in narrow channels and to estimate heat and mass transfer rates. Results from the CFD studies were incorporated into a simplified design model and the Membrane Dephlegmation process was studied numerically. The results indicated that the Membrane Dephlegmation process was more efficient than simple distillation and that the ethanol-water azeotrope could be broken. Subsequently, a pilot-scale experimental system was constructed using commercially available, hydrophilic NaA zeolite membranes. Results obtained from the experimental system confirmed the accuracy of the simulations.

Membrane-based acid gas (e.g., CO2) separation, gas dehydration and humidification, as well as solvent dehydration are important to the energy and process industries. Fixed carrier facilitated transport membranes can enhance the permeation without compromising the selectivity. The development of suitable fixed carrier membranes for CO2 and water permeation, and understanding of the transport mechanism were the main objectives of this thesis. Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) composite membranes were developed using microporous polysulfone (PSF) or polyacrylonitrile (PAN) substrates. The PDMAEMA layer was crosslinked with p-xylylene dichloride via quaternization reaction. Fourier transform infrared, scanning electron microscopy, adsorption tests, and contact angle measurements were conducted to analyze the chemical and morphological structure of the membrane. It was shown that the polymer could be formed into thin dense layer on the substrates, while the quaternary and tertiary amino groups in the side chains of PDMAEMA offered a high polarity and hydrophilicity. The solid-liquid interfacial crosslinking of PDMAEMA led to an asymmetric crosslinked network structure, which helped minimize the resistance of the membrane to the mass transport. The interfacially formed membranes were applied to CO2/N2 separation, dehydration of CH4, gas humidification and ethylene glycol dehydration. The membranes showed good permselectivity to CO2 and water. For example, a CO2 permeance of 85 GPU and a CO2/N2 ideal separation factor of 50 were obtained with a PDMAEMA/PSF membrane at 23oC and 0.41 MPa of CO2 feed pressure. At 25oC, the permeance of water vapor through a PDMAEMA/PAN membrane was 5350 GPU and the water vapor/methane selectivity was 4735 when methane was completely saturated with water vapor. On the other hand, the relative humidity of outlet gas was up to 100 % when the membrane was used as a hydrator at 45oC and at a carrier gas flow rate of 1000 sccm. For used for dehydration of ethylene glycol at 30oC, the PDMAEMA/PSF membrane showed a permeation flux of ~1 mol/(m2.h) and a permeate concentration of 99.7 mol% water at 1 mol% water in feed. This work shows that the quaternary and tertiary amino groups can be used as carriers for CO2 transport through the membrane based on the weak acid-base interaction. In the presence of water, water molecules in the membrane tend to form a water "path" or water "bridge" which also help contribute to the mass transport though the membrane. In addition, CO2 molecules can be hydrated to HCO3-, which reaction can be catalyzed by the amino groups, the hydrated CO2 molecules can transport through the water path as well as the amino groups in the membrane. On the other hand, for processes involving water (either vapor or liquid) permeation, the amino groups in the membrane are also helpful because of the hydrogen bonding effects.

Pervaporation (PV), a non-porous membrane separation process, is gaining considerable attention for solvent separation in a variety of industries ranging from chemical to food and pharmaceutical to petrochemicals. The most successful application has been the dehydration of organic liquids, for which hydrophilic membranes are used. However, during pervaporation, excessive affinity of water towards hydrophilic membranes leads to undesirable swelling (water absorption) of the membrane matrix. To control swelling, often hydrophilic membranes are crosslinked to modify physicochemical (surface and bulk) properties. Since the transport of species in pervaporation is governed by sorption (affected by surface and bulk properties) and diffusion (affected by bulk properties), it is essential to study the effect of crosslinking on the surface and bulk physicochemical properties and their effects on separation performance. This thesis focuses on the effect of crosslinking on the physicochemical properties (e.g., crystallinity, hydrophilicity, surface roughness) of hydrophilic polymeric membranes and their dehydration performance alcohol-water mixtures. Poly(vinyl alcohol), PVA was used as the base polymer to prepare membranes with various morphologies such as homogeneous, blended (with Chitosan, CS) and composite (with poly(sulfone), PSf) structures. Before applying the crosslinked membranes for the PV dehydration of alcohols, the physicochemical characterization were carried out using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), tensile testing, contact angle and swelling experiments. The crosslinked membranes showed an increase in surface hydrophobicity from the contact angle measurements as compared to the uncrosslinked membranes. AFM surface topography showed that the membrane surfaces have nodular structures and are rough at the nanometer scale and affected by the crosslinking conditions such as concentration and reaction time. Surface hydrophobicity and roughness was found to increase with increasing degree of crosslinking. DSC measurements showed an increase in melting temperature of the polymer membranes after crosslinking. For the PV dehydration of ethanol, a decrease in flux and an increase in selectivity were observed with increase in the degree of crosslinking. Effects of membrane thickness (of PVA layer) for crosslinked PVA-PSf composite membranes were studied on PV dehydration of ethanol. Total flux and selectivity were statistically analyzed as a function of the membrane thickness. In general, the outcome agrees with the solution-diffusion (S-D) theory: the total flux was found to be significantly affected by the PVA layer thickness, while the selectivity remains nearly unaffected. Using the S-D theory, the mass transfer resistance of the selective layers was calculated and found to increase with thickness. The relatively small change observed for selectivity has been related to the crosslinking of the PVA layer that increases the surface hydrophobicity of the membrane. Chitosan-Poly(vinyl alcohol), or CS-PVA, blended membranes were prepared by varying the blending ratio to control membrane crystallinity and its effect on the PV dehydration of ethylene glycol. The blended membranes were crosslinked interfacially with trimesoyl chloride (TMC)/hexane. The crystallinity of the membrane was found to decrease with increasing CS wt% in the blend. Although the crosslinked CS-PVA blend membranes showed improved mechanical strength, they became less flexible as detected in tensile testing. The resulting crosslinked CS-PVA blended membranes showed high flux and selectivity simultaneously, for 70-80wt% CS in the blend. The effect of feed flow-rate was studied to find the presence of concentration polarization for 90wt% EG in feed mixture as well. The crosslinked blend membrane with 75wt% CS showed a highest total flux of 0.46 kg/m2/h and highest selectivity of 663 when operating at 70oC with 90wt% EG in the feed mixture. Effects of crosslinking concentration and reaction time of trimesoyl chloride (TMC) were studied on poly(vinyl alcohol)-poly(sulfone) or PVA-PSf composite membranes. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophilicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with PV dehydration of ethylene glycol-water mixtures at a range of concentrations (30 to 90wt% EG). The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. A central composite rotatable design (CCRD) of response surface methodology was used to analyze PV dehydration performance of crosslinked poly(vinyl alcohol) (PVA) membranes. Regression models were developed for the flux and selectivity as a function of operating conditions such as, temperature, feed alcohol concentration, and flow-rate. Dehydration experiments were performed on two different alcohol-water systems: isopropanol-water (IPA-water) and ethanol-water (Et-water) mixtures around the azeotrope concentrations. Judged by the lack-of-fit criterion, the analysis of variance (ANOVA) showed the regression model to be adequate. The predicted flux and selectivity from the regression models were presented in 3-D surface plots over the whole ranges of operating variables. For both alcohol-water systems, quadratic effect of temperature and feed alcohol concentration showed significant (p < 0.0001) influence on the flux and selectivity. A strong interaction effect of temperature and concentration was observed on the selectivity for the Et-water system. For the dehydration of azeotropic IPA-water mixture (87.5wt% IPA), the optimized dehydration variables were found to be 50.5oC and 93.7 L/hr for temperature and flow-rate, respectively. On the other hand for azeotropic Et-water mixture (95.5wt% Et), the optimized temperature and flow-rate were found to be 57oC and 89.2 L/hr, respectively. Compared with experiments performed at optimized temperature and feed flow-rate, the predicted flux and selectivity of the azeotropic mixtures showed errors to be within 3-6 %.

Membrane-based acid gas (e.g., CO2) separation, gas dehydration and humidification, as well as solvent dehydration are important to the energy and process industries. Fixed carrier facilitated transport membranes can enhance the permeation without compromising the selectivity. The development of suitable fixed carrier membranes for CO2 and water permeation, and understanding of the transport mechanism were the main objectives of this thesis. Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) composite membranes were developed using microporous polysulfone (PSF) or polyacrylonitrile (PAN) substrates. The PDMAEMA layer was crosslinked with p-xylylene dichloride via quaternization reaction. Fourier transform infrared, scanning electron microscopy, adsorption tests, and contact angle measurements were conducted to analyze the chemical and morphological structure of the membrane. It was shown that the polymer could be formed into thin dense layer on the substrates, while the quaternary and tertiary amino groups in the side chains of PDMAEMA offered a high polarity and hydrophilicity. The solid-liquid interfacial crosslinking of PDMAEMA led to an asymmetric crosslinked network structure, which helped minimize the resistance of the membrane to the mass transport. The interfacially formed membranes were applied to CO2/N2 separation, dehydration of CH4, gas humidification and ethylene glycol dehydration. The membranes showed good permselectivity to CO2 and water. For example, a CO2 permeance of 85 GPU and a CO2/N2 ideal separation factor of 50 were obtained with a PDMAEMA/PSF membrane at 23oC and 0.41 MPa of CO2 feed pressure. At 25oC, the permeance of water vapor through a PDMAEMA/PAN membrane was 5350 GPU and the water vapor/methane selectivity was 4735 when methane was completely saturated with water vapor. On the other hand, the relative humidity of outlet gas was up to 100 % when the membrane was used as a hydrator at 45oC and at a carrier gas flow rate of 1000 sccm. For used for dehydration of ethylene glycol at 30oC, the PDMAEMA/PSF membrane showed a permeation flux of ~1 mol/(m2.h) and a permeate concentration of 99.7 mol% water at 1 mol% water in feed. This work shows that the quaternary and tertiary amino groups can be used as carriers for CO2 transport through the membrane based on the weak acid-base interaction. In the presence of water, water molecules in the membrane tend to form a water "path" or water "bridge" which also help contribute to the mass transport though the membrane. In addition, CO2 molecules can be hydrated to HCO3-, which reaction can be catalyzed by the amino groups, the hydrated CO2 molecules can transport through the water path as well as the amino groups in the membrane. On the other hand, for processes involving water (either vapor or liquid) permeation, the amino groups in the membrane are also helpful because of the hydrogen bonding effects.

Pervaporation (PV), a non-porous membrane separation process, is gaining considerable attention for solvent separation in a variety of industries ranging from chemical to food and pharmaceutical to petrochemicals. The most successful application has been the dehydration of organic liquids, for which hydrophilic membranes are used. However, during pervaporation, excessive affinity of water towards hydrophilic membranes leads to undesirable swelling (water absorption) of the membrane matrix. To control swelling, often hydrophilic membranes are crosslinked to modify physicochemical (surface and bulk) properties. Since the transport of species in pervaporation is governed by sorption (affected by surface and bulk properties) and diffusion (affected by bulk properties), it is essential to study the effect of crosslinking on the surface and bulk physicochemical properties and their effects on separation performance. This thesis focuses on the effect of crosslinking on the physicochemical properties (e.g., crystallinity, hydrophilicity, surface roughness) of hydrophilic polymeric membranes and their dehydration performance alcohol-water mixtures. Poly(vinyl alcohol), PVA was used as the base polymer to prepare membranes with various morphologies such as homogeneous, blended (with Chitosan, CS) and composite (with poly(sulfone), PSf) structures. Before applying the crosslinked membranes for the PV dehydration of alcohols, the physicochemical characterization were carried out using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), tensile testing, contact angle and swelling experiments. The crosslinked membranes showed an increase in surface hydrophobicity from the contact angle measurements as compared to the uncrosslinked membranes. AFM surface topography showed that the membrane surfaces have nodular structures and are rough at the nanometer scale and affected by the crosslinking conditions such as concentration and reaction time. Surface hydrophobicity and roughness was found to increase with increasing degree of crosslinking. DSC measurements showed an increase in melting temperature of the polymer membranes after crosslinking. For the PV dehydration of ethanol, a decrease in flux and an increase in selectivity were observed with increase in the degree of crosslinking. Effects of membrane thickness (of PVA layer) for crosslinked PVA-PSf composite membranes were studied on PV dehydration of ethanol. Total flux and selectivity were statistically analyzed as a function of the membrane thickness. In general, the outcome agrees with the solution-diffusion (S-D) theory: the total flux was found to be significantly affected by the PVA layer thickness, while the selectivity remains nearly unaffected. Using the S-D theory, the mass transfer resistance of the selective layers was calculated and found to increase with thickness. The relatively small change observed for selectivity has been related to the crosslinking of the PVA layer that increases the surface hydrophobicity of the membrane. Chitosan-Poly(vinyl alcohol), or CS-PVA, blended membranes were prepared by varying the blending ratio to control membrane crystallinity and its effect on the PV dehydration of ethylene glycol. The blended membranes were crosslinked interfacially with trimesoyl chloride (TMC)/hexane. The crystallinity of the membrane was found to decrease with increasing CS wt% in the blend. Although the crosslinked CS-PVA blend membranes showed improved mechanical strength, they became less flexible as detected in tensile testing. The resulting crosslinked CS-PVA blended membranes showed high flux and selectivity simultaneously, for 70-80wt% CS in the blend. The effect of feed flow-rate was studied to find the presence of concentration polarization for 90wt% EG in feed mixture as well. The crosslinked blend membrane with 75wt% CS showed a highest total flux of 0.46 kg/m2/h and highest selectivity of 663 when operating at 70oC with 90wt% EG in the feed mixture. Effects of crosslinking concentration and reaction time of trimesoyl chloride (TMC) were studied on poly(vinyl alcohol)-poly(sulfone) or PVA-PSf composite membranes. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophilicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with PV dehydration of ethylene glycol-water mixtures at a range of concentrations (30 to 90wt% EG). The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. A central composite rotatable design (CCRD) of response surface methodology was used to analyze PV dehydration performance of crosslinked poly(vinyl alcohol) (PVA) membranes. Regression models were developed for the flux and selectivity as a function of operating conditions such as, temperature, feed alcohol concentration, and flow-rate. Dehydration experiments were performed on two different alcohol-water systems: isopropanol-water (IPA-water) and ethanol-water (Et-water) mixtures around the azeotrope concentrations. Judged by the lack-of-fit criterion, the analysis of variance (ANOVA) showed the regression model to be adequate. The predicted flux and selectivity from the regression models were presented in 3-D surface plots over the whole ranges of operating variables. For both alcohol-water systems, quadratic effect of temperature and feed alcohol concentration showed significant (p < 0.0001) influence on the flux and selectivity. A strong interaction effect of temperature and concentration was observed on the selectivity for the Et-water system. For the dehydration of azeotropic IPA-water mixture (87.5wt% IPA), the optimized dehydration variables were found to be 50.5oC and 93.7 L/hr for temperature and flow-rate, respectively. On the other hand for azeotropic Et-water mixture (95.5wt% Et), the optimized temperature and flow-rate were found to be 57oC and 89.2 L/hr, respectively. Compared with experiments performed at optimized temperature and feed flow-rate, the predicted flux and selectivity of the azeotropic mixtures showed errors to be within 3-6 %.

Orientadores: Maria Regina Wolf Maciel, Mario Eusebio Torres Alvarez / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-11T16:17:30Z (GMT). No. of bitstreams: 1 Araujo_WilsonAndaleciode_D.pdf: 2993508 bytes, checksum: 29abb03a65a80f6c9835367e0cb49d50 (MD5) Previous issue date: 2008 / Resumo: Os processos de separação com membranas (PSM) têm sido considerados como alternativa a processos clássicos de separação. Esta é uma área de estudo que apresenta uma forte interdisciplinaridade. Há um crescente interesse nestes processos para diversas aplicações como, por exemplo, tratamento de efluentes industriais, desalinização de águas, purificação e concentração de correntes da indústria alimentícia. A separação, em geral, não envolve mudança de fase, o que significa economia no consumo de energia e operações a temperaturas moderadas. Na tecnologia de separação com membranas, os componentes das misturas líquidas ou gasosas são separados ao permearem de forma seletiva através de uma membrana. As membranas podem ser poliméricas ou cerâmicas. A corrente de alimentação é dividida em duas correntes de saída: a que permeou através da membrana (permeado) e a corrente concentrada retida (¿retentate¿). Estes processos têm sido aplicados no processamento de bebidas, sucos, e aromas. Neste trabalho, dois PSM foram estudados, a Osmose Inversa (OI) e a Pervaporação (PV). Experimentos em escala piloto foram realizados empregando-se o processo de OI (membrana de poliamida) para a concentração de suco de laranja a 20°Brix. Avaliou-se a retenção de compostos de voláteis (acetaldeído, metanol e etanol) monitorando-se as correntes de alimentação e permeado. Os resultados de retenção de aromas obtidos não foram satisfatórios. A membrana apresentou baixas retenções para os voláteis monitorados na temperatura usada para realização dos experimentos. Na segunda etapa do trabalho, o processo de PV foi avaliado para recuperação de um importante éster do suco de laranja, o etil butirato. O software PERVAP, um simulador Fortran essencialmente preditivo, foi empregado no estudo de desempenho do processo para duas membranas, polidimetilsiloxano (PDMS) e polioctilmetilsiloxano (POMS). Realizou-se a predição de propriedades de membranas poliméricas para incremento da capacidade preditiva do simulador. Foram empregados métodos de contribuição de grupos para predição das propriedades dos polímeros. Os dados de viscosidade preditos para o POMS viabilizaram a realização de cálculos para obtenção de parâmetros requeridos para operação do simulador. A abordagem proposta proporcionou maior versatilidade ao simulador / Abstract: The membrane separation processes (MSP) have been considered as alternative for conventional separation processes. In this research area a strong interdisciplinarity is observed. There is an increasing of interest for these processes considering many aplications (e.g., industrial wastewater treatment, water desalination, purification and concentration of food industry streams). The separation usually does not requires phase change, which means energy savings and moderate temperatures. A membrane separation system separates an inlet stream into two effluent streams known as the permeate and the retentate. The permeate is the portion of the fluid that has passed through the membrane. Whereas the retentate stream contains the constituents that have been rejected by the membrane. The membrane can be polymeric or ceramic. These processes have been applied for processing beverages, juices and aromas. In this work, two of these processes were studied, Reverse Osmosis (RO) and Pervaporation (PV). Pilot scale experiments were accomplished using RO (poliamide membrane) for concentrating single strength orange juice at 20ºBrix. The retention of volatile compounds (acetaldehyde, methanol and ethanol) was evaluated by monitoring feed and permeate streams. The retention results obtained were unsatisfactory. The membrane presented low retention for monitored volatiles under studied temperature conditions. In the second stage of this work, the PV process was evaluated for recovering an important ester of orange juice, the ethyl butyrate. The PERVAP software, an essentially predictive Fortran simulator, was used for evaluating process performance considering two membranes, polydimethylsiloxane (PDMS) and polyoctylmethylsiloxane (POMS). It was accomplished the prediction of properties for polymeric membranes targeting the software predictivity improvement. Viscosity data predicted for POMS was crucial for calculating parameters required by simulator. The predictive approach proposed improved the software versatility / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

Abstract Volatile Organic Compounds (VOCs) in wastewaters from the chemical industry are of major concern because of their environmental and health impacts. The reclamation of VOCs from wastewaters would not only reduce the hazard to the environment but also contribute to an efficient use of resources. The thesis explores the reclamation of n-butanol and dichloromethane from sodium chloride containing mixtures by pervaporation. Another aim was to gain understanding of mass transport phenomena during the pervaporation of multicomponent systems, and the effect of sodium chloride on the pervaporation performance. In this work, the reclamation of n-butanol and dichloromethane was conducted as a sequence of pervaporation stages which utilised first hydrophobic and then hydrophilic membranes. The objective was to segregate the mixture of n-butanol/dichloromethane/sodium chloride/water into three different streams: a re-use quality concentrate of VOCs, brine, and discharge quality purified water. The effect of the experimental variables, VOCs feed concentration, feed temperature and sodium chloride content on the performance of the pervaporation stages was studied. A statistical design, response surface methodology, was used to further resource efficiency. The results indicate the potential of pervaporation for the reclamation of n-butanol and dichloromethane from aqueous mixtures. A single step of pervaporation of n-butanol/dichloromethane/sodium chloride/water systems using the CMX-GF-010-D (Celfa) and PERTHESE® 500-1 (P 500-1) membranes does not sufficiently concentrate the VOCs for direct re-use. It is also demonstrated that the electrolyte does not permeate through the membranes and does not affect their separation effectiveness significantly. The pervaporation of the water/dichloromethane/n-butanol system using the hydrophilic poly(vinyl alcohol)-titanium dioxide/polyacrylonitrile/polyphenylene sulfide (PVA-TiO2/PAN/PPS) membrane is effective for dewatering purposes. The membrane shows impermeable features towards dichloromethane in the studied conditions. The analysis of the mass transport phenomena demonstrates that, under the experimental conditions studied, the resistance towards the mass transport of the compounds through the membrane is mainly exhibited by the membrane itself. This study also shows the advantage of analysing the effect of temperature on membrane permeation by the permeation activation energy instead of by the apparent activation energy.