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The effect of ultrafiltration transmembrane permeation on the flow field in a surrogate system of an artificial kidney
Get PDFRenal Replacement Therapies generally associated to the Artificial Kidney (AK) are membrane-based
treatments that assure the separation functions of the failing kidney in extracorporeal blood circulation.
Their progress from conventional hemodialysis towards high-flux hemodialysis (HFHD) through the
introduction of ultrafiltration membranes characterized by high convective permeation fluxes intensified
the need of elucidating the effect of the membrane fluid removal rates on the increase of the potentially
blood-traumatizing shear stresses developed adjacently to the membrane. The AK surrogate consisting of
two-compartments separated by an ultrafiltration membrane is set to have water circulation in the upper
chamber mimicking the blood flow rates and the membrane fluid removal rates typical of HFHD. Pressure
drop mirrors the shear stresses quantification and the modification of the velocities profiles. The increase on
pressure drop when comparing flows in slits with a permeable membrane and an impermeable wall is ca.
512% and 576% for CA22=5%SiO2 and CA30=5%SiO2 membranes, respectively
Recovery of phenolic compounds from red grape pomace extract through nanofiltration membranes
Get PDFThe winemaking process generates a large amount of residues such as vine shots, stalks, grape pomace, and wine lees, which were only recently considered for exploitation of their valuable compounds. The purpose of this work was to investigate the performance of nanofiltration for the recovery of phenolic compounds, with bioactive capacity like antioxidant, from red grape pomace extract. Four membranes were compared in this study—three cellulose acetate (CA series: lab-prepared by phase inversion) and one commercial (NF90). All membranes were characterized for their hydraulic permeability and rejection coefficients to reference solutes like saccharose, glucose, raffinose, polyethylene glycol, sodium chloride, and sodium sulfate. Permeation flowrates and rejection coefficients towards total phenolics content, antioxidant activity, proanthocyanidins, glucose and fructose were measured in the nanofiltration of grape pomace extract using selected operating conditions. Among the investigated membranes, the CA400-22 exhibited the highest permeate flux (50.58 L/m2 h at 20 bar and 25 °C), low fouling index (of about 23%), the lowest rejection coefficients towards the reference solutes and the best performance in terms of separation between sugars and phenolic compounds. Indeed, the observed rejections for glucose and fructose were 19% and 12%, respectively. On the other hand, total phenolics content and proanthocyanidins were rejected for 73% and 92%, respectively
Recuperação de polifenóis e polissacarídeos de efluentes vinícolas através de processos de separação por membranas
Get PDFOs efluentes vinícolas, especialmente as borras geradas nas trasfegas, possuem um grande potencial poluidor. Por outro lado, estes efluentes são ricos em compostos orgânicos, especificamente polifenóis e polissacarídeos. Consequentemente, estes efluentes podem ser considerados matéria-prima para a recuperação destes compostos. Portanto, o presente trabalho tem por objetivo o desenvolvimento de um processo, baseado em filtração por membranas, para a recuperação de polifenóis e polissacarídeos presentes nos efluentes gerados na segunda trasfega da produção de vinhos tintos. Para tal, foram avaliados e otimizados pré-tratamentos como a sedimentação, variando o pH, e a filtração a vácuo associada a diluições. Posteriormente, foram investigados processos de separação por membranas, nomeadamente microfiltração, ultrafiltração e nanofiltração variando os principais parâmetros de operação, tais como: pressão transmembrana, vazão de recirculação da alimentação e fator de concentração volumétrico. A otimização destes parâmetros foi fundamental para se atingir uma maior produtividade, tanto em termos de fluxos de permeação quanto em termos da recuperação dos compostos de interesse. O processo resultante desta pesquisa consiste na diluição dos efluentes da segunda trasfega e posterior microfiltração, para remoção de turbidez e sólidos em suspensão, resultando na recuperação dos polifenóis e polissacarídeos no permeado da microfiltração, 21% e 5,4% respectivamente. Posteriormente, foi possível separar os polifenóis dos polissacarídeos através de ultrafiltração, de modo que os polissacarídeos majoritariamente ficam na corrente do retido enquanto os polifenóis preferencialmente permeiam as membranas. Na sequência, os polifenóis que permearam a membrana de ultrafiltração podem ser concentrados com nanofiltração, face à membrana NF270 apresentar rejeição a polifenóis superior a 92%. Assim, a integração de diferentes processos de separação por membranas surge como uma alternativa para a recuperação de polifenóis e polissacarídeos bem como para o fracionamento dessas macromoléculas.Winery effluents, especially the wine lees generated in the rackings, have a high pollution potential. However, they are rich in organic compounds, in particular polyphenols and polysaccharides. Consequently, these effluents can be considered as raw material for the recovery of these compounds. Therefore, the present study aims to develop a process based on membrane filtration for the recovery of polyphenols and polysaccharides present in the effluents generated in the second racking from red wines production. For this reason, pre-treatments were evaluated and optimized such as the sedimentation, varying the pH, and the vacuum filtration associated with dilutions. Subsequently, membrane separation processes have been investigated, namely microfiltration, ultrafiltration and nanofiltration, changing the main operating parameters, such as transmembrane pressure, feed recirculation flow rate and volumetric concentration factor. The optimization of these parameters was essential for achieving higher productivity both in terms of permeation flux as in terms of the recovery of the compounds of interest. The process resulting from this research consists of diluting the effluent from the second racking with a subsequent microfiltration for removal of turbidity and suspended solids, thus resulting in the recovery of polyphenols and polysaccharides in the microfiltration permeate, 21% and 5.4% respectively. Later, it was possible to separate the polysaccharides of the polyphenols by ultrafiltration, so that the polysaccharides mainly stayed in the retentate stream, while polyphenols preferentially permeated the membranes. Sequentially, the polyphenols that permeated the ultrafiltration membrane may be concentrated by nanofiltration, considering that the NF270 membrane presented polyphenols rejection higher than 92%. Thus, the integration of different membrane separation processes is an alternative for the recovery of polyphenols and polysaccharides, as well as for the fractionation of these macromolecules
Tratamento e recirculação de água por osmose inversa em processos de fabricação de lentes oftálmicas. Beneficios ambientais e financeiros
No full textMestrado em Engenharia do Ambiente - Instituto Superior de AgronomiaDue to increased environmental awareness and water costs, industries have increase the need to
optimize the use of water by selecting production processes more efficient, with lower water
consumption or through a treatment and recirculation of water.
This study comes from the Essilor Portugal need to reduce the environmental impact and costs of a
water consumption of the main processes for producing ophthalmic lenses, but also the need to
improve the quality of the water process due the quality requirements.
One of the processes of water treating with an increased use in industrial sector, particularly in
processes that require water with very stringent quality characteristics, is reverse osmosis. This
process, thanks to its numerous advantages, including the high capacity and effectiveness of
treatment, occupying small areas, unnecessary regeneration and energy efficiency has proven to be
an economically viable technology.
The objectives of this study are based on the evaluation of the environmental and financial benefits
due the implementation of water treatment and recirculation by reverse osmosis, in processes of
manufacturing of ophthalmic lenses, and also the analysis and optimization of operating conditions.
With this system, of water treatment and recirculation, there was a significant improvement in the
quality of the water for cleaning of ophthalmic lenses in the coating process (the most demanding in
terms of water quality) which serves to protect the surfaces of the lenses from knocks and scratches,
giving them hardness and abrasion resistance.
The water needs, to clean lenses in the coating process is crucial, to ensure the pre-cleaning of the
lens surface before application of the coating and quality of the product, and after the treatment
system implementation there were some improvements of the coating process quality service, in terms
of non quality costs and process yield.
From the analysis of the environmental benefits of the project, we can verifier that there is a reduction
of consumption of resources and materials, which translate into a significant positive impact, combined
with reduced consumption of water and energy.
The present study showed that reverse osmosis is an technology treatment, economically and
environmentally feasible for the specific conditions of the project in question, allowing rapid coverage
of the initial investment, managing to generate a rate return much higher than the capital cost
Fraccionamento de lactossoro de ovelha por tecnologias de membranas e estudo das possiveis utilizações dos concentrados obtidos
No full textDoutoramento em Engenharia Agro-Industrial - Instituto Superior de AgronomiaIn this thesis we studied the efficiency of fractionation of ovine whey by ultrafiltration followed by nanofiltration, in terms of permeation fluxes and apparent rejections. The application possibilities of the concentrates produced were also investigated. Ultrafiltration tests were performed in total recirculation mode under different operating conditions of transmembrane pressure and feed recirculation velocity with membranes ETNA10PP, GR81PP and GR61PP. The membranes ETNA10PP turned out to be the most appropriate for the separation of the whey protein fraction because they allowed higher permeate flux (higher productivity) with apparent rejections coefficients of the protein above 90% and low apparent rejections of lactose, providing a better separation between the two fractions (protein and fraction rich in lactose). So, the membranes ETNA10PP were used in the trials of ultrafiltration, in concentration mode, till a volume concentration factor (VCF) of 4.0. Samples of concentrates were taken for the VCF´s of 1.8, 2.0, 3.0 and 4.0, which were used to manufacture cheese whey, following the traditional process of production. Compared to traditional whey cheese, the curd made from protein concentrates have dried residues, ash and fat contents significantly lower than those determined in traditional whey cheese, whereas concentrations of protein and lactose and the hardness are significantly higher. The nanofiltration of ultrafiltration permeates, performed with membranes NFT50, allowed almost total recovery of lactose and organic matter, measured by chemical oxygen demand. The diafiltration of the lactose concentrates can be used for purposes of purification, according to the intended end application
Tratamento e recirculação de água por osmose inversa em processos de fabricação de lentes oftálmicas. Beneficios ambientais e financeiros
No full textMestrado em Engenharia do Ambiente - Instituto Superior de AgronomiaDue to increased environmental awareness and water costs, industries have increase the need to
optimize the use of water by selecting production processes more efficient, with lower water
consumption or through a treatment and recirculation of water.
This study comes from the Essilor Portugal need to reduce the environmental impact and costs of a
water consumption of the main processes for producing ophthalmic lenses, but also the need to
improve the quality of the water process due the quality requirements.
One of the processes of water treating with an increased use in industrial sector, particularly in
processes that require water with very stringent quality characteristics, is reverse osmosis. This
process, thanks to its numerous advantages, including the high capacity and effectiveness of
treatment, occupying small areas, unnecessary regeneration and energy efficiency has proven to be
an economically viable technology.
The objectives of this study are based on the evaluation of the environmental and financial benefits
due the implementation of water treatment and recirculation by reverse osmosis, in processes of
manufacturing of ophthalmic lenses, and also the analysis and optimization of operating conditions.
With this system, of water treatment and recirculation, there was a significant improvement in the
quality of the water for cleaning of ophthalmic lenses in the coating process (the most demanding in
terms of water quality) which serves to protect the surfaces of the lenses from knocks and scratches,
giving them hardness and abrasion resistance.
The water needs, to clean lenses in the coating process is crucial, to ensure the pre-cleaning of the
lens surface before application of the coating and quality of the product, and after the treatment
system implementation there were some improvements of the coating process quality service, in terms
of non quality costs and process yield.
From the analysis of the environmental benefits of the project, we can verifier that there is a reduction
of consumption of resources and materials, which translate into a significant positive impact, combined
with reduced consumption of water and energy.
The present study showed that reverse osmosis is an technology treatment, economically and
environmentally feasible for the specific conditions of the project in question, allowing rapid coverage
of the initial investment, managing to generate a rate return much higher than the capital cost
Tratamento e recirculação de água por osmose inversa em processos de fabricação de lentes oftálmicas. Beneficios ambientais e financeiros
No full textMestrado em Engenharia do Ambiente - Instituto Superior de AgronomiaDue to increased environmental awareness and water costs, industries have increase the need to
optimize the use of water by selecting production processes more efficient, with lower water
consumption or through a treatment and recirculation of water.
This study comes from the Essilor Portugal need to reduce the environmental impact and costs of a
water consumption of the main processes for producing ophthalmic lenses, but also the need to
improve the quality of the water process due the quality requirements.
One of the processes of water treating with an increased use in industrial sector, particularly in
processes that require water with very stringent quality characteristics, is reverse osmosis. This
process, thanks to its numerous advantages, including the high capacity and effectiveness of
treatment, occupying small areas, unnecessary regeneration and energy efficiency has proven to be
an economically viable technology.
The objectives of this study are based on the evaluation of the environmental and financial benefits
due the implementation of water treatment and recirculation by reverse osmosis, in processes of
manufacturing of ophthalmic lenses, and also the analysis and optimization of operating conditions.
With this system, of water treatment and recirculation, there was a significant improvement in the
quality of the water for cleaning of ophthalmic lenses in the coating process (the most demanding in
terms of water quality) which serves to protect the surfaces of the lenses from knocks and scratches,
giving them hardness and abrasion resistance.
The water needs, to clean lenses in the coating process is crucial, to ensure the pre-cleaning of the
lens surface before application of the coating and quality of the product, and after the treatment
system implementation there were some improvements of the coating process quality service, in terms
of non quality costs and process yield.
From the analysis of the environmental benefits of the project, we can verifier that there is a reduction
of consumption of resources and materials, which translate into a significant positive impact, combined
with reduced consumption of water and energy.
The present study showed that reverse osmosis is an technology treatment, economically and
environmentally feasible for the specific conditions of the project in question, allowing rapid coverage
of the initial investment, managing to generate a rate return much higher than the capital cost
Fraccionamento de lactossoro de ovelha por tecnologias de membranas e estudo das possiveis utilizações dos concentrados obtidos
No full textDoutoramento em Engenharia Agro-Industrial - Instituto Superior de AgronomiaIn this thesis we studied the efficiency of fractionation of ovine whey by ultrafiltration followed by nanofiltration, in terms of permeation fluxes and apparent rejections. The application possibilities of the concentrates produced were also investigated. Ultrafiltration tests were performed in total recirculation mode under different operating conditions of transmembrane pressure and feed recirculation velocity with membranes ETNA10PP, GR81PP and GR61PP. The membranes ETNA10PP turned out to be the most appropriate for the separation of the whey protein fraction because they allowed higher permeate flux (higher productivity) with apparent rejections coefficients of the protein above 90% and low apparent rejections of lactose, providing a better separation between the two fractions (protein and fraction rich in lactose). So, the membranes ETNA10PP were used in the trials of ultrafiltration, in concentration mode, till a volume concentration factor (VCF) of 4.0. Samples of concentrates were taken for the VCF´s of 1.8, 2.0, 3.0 and 4.0, which were used to manufacture cheese whey, following the traditional process of production. Compared to traditional whey cheese, the curd made from protein concentrates have dried residues, ash and fat contents significantly lower than those determined in traditional whey cheese, whereas concentrations of protein and lactose and the hardness are significantly higher. The nanofiltration of ultrafiltration permeates, performed with membranes NFT50, allowed almost total recovery of lactose and organic matter, measured by chemical oxygen demand. The diafiltration of the lactose concentrates can be used for purposes of purification, according to the intended end application
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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