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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Development of instrumentation for the investigation of surface regeneration for candle filters

Gregory, Sean, January 2001 (has links)
Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 102 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 80-81).
22

Macromolecular fouling during membrane filtration of complex fluids

Ye, Yun, School of Chemical Engineering & Industrial Chemistry, UNSW January 2005 (has links)
Macromolecular components, including protein and polysaccharides, are viewed as one type of major foulants in the complex feed membrane filtration systems such as membrane bioreactor (MBR). In this thesis, the mechanisms of macromolecular fouling including protein and polysaccharide in the complex feed solution are explored by using Bovine serum albumin (BSA) and alginate as model solution. During the filtration of BSA and washed yeast with 0.22 ????m PVDF membrane, it was found that the critical flux of mixture solution was controlled by washed yeast concentration while the existence of BSA significantly changed the cake reversibility of much larger particles. The fouling mechanisms of alginate, as a model polysaccharide solution, were investigated both in dead end and crossflow membrane filtration. In the dead end experiments, it was found that the cake model appears to fit the entire range of the ultrafiltration data while the consecutive standard pore blocking model and cake model are more applicable to microfiltration membranes. The alginate was featured with high specific cake resistance and low compressibility despite some variations between different membranes. The specific cake resistance ( c ) is similar to c of BSA and actual extracellular polymer substance (EPS) in MBR systems reported in the literature, and higher than that of many colloidal particles. In a system contained alginate-particles mixture, it was found that the existence of alginate dramatically increased the cake specific resistance and decreased the cake compressibility. The fouling mechanism of alginate was also studied using long term cross flow filtration under subcritical flux. A two-stage TMP profile similar to that typically observed in MBR was obtained, confirming the important role of EPS during membrane fouling in MBR. In addition to adsorption, trace deposition of alginate also contributed to the initial slow TMP increase during the subcritical filtration. TMP increase during the long-term filtration was found not only due to the increase of the amount of deposition, but also the increase of specific cake resistance. A combined standard pore blocking and cake filtration model, using a critical pore size for the transition time determination, was developed and fit the experimental results well.
23

Macromolecular fouling during membrane filtration of complex fluids /

Ye, Yun. January 2005 (has links)
Thesis (Ph. D.)--University of New South Wales, 2005. / Also available online.
24

Ultrasonic measurement of membrane fouling during microfiltration of natural brown water

Mbanjwa, Mesuli Bonani January 2007 (has links)
Thesis (MTech (Engineering))--Cape Peninsula University of Technology, 2007 / The removal of the colour-eausing natural organic matter (NOM) from natural brown water (NSW) to be used for drinking purposes is of paramount importance. One of the methods available to remove NOM from NSW is the use of pressure-driven membrane separation systems. One of the limitations in efficiently applying membrane filtration in the treatment of NOM-eontaining water is membrane fouling that is caused by foulants, such as NOM, that accumulate on the membrane surface and in the membrane pores. Microfiltration (MF), as a membrane separation system, is susceptible to severe membrane fouling during membrane filtration of NSW. Fouling is characterized by a rapid decline in permeate flux and loss of productivity. Progress in developing more effective control and prevention of fouling is impeded by the absence of suitable fouling measurement and characterization techniques. An in situ method for measuring membrane fouling is necessary for detection of membrane fouling during MF of NSW at the eartiest stages so that the corrective actions can be taken before fouling is permanently adsorbed onto the membrane surface. In this study, an ultrasonic-based method was effectively used to detect and measure the growth of membrane fouling dUring MF of NSW, in situ. Fouling exp~riments results showed the formation of a new peak on the ultrasonic response echo signal due to the presence of a fouling layer on the surface of the membrane. The ultrasonic signals acquired during the in-situ detection of membrane fouling were analysed using wavelet transforms (WTs). Wavelet analysis was applied to differential signals to obtain additional information about fouling. Differential signals were calculated by subtracting the baseline measurement signals from the test signals. The presence of the fouling layer on membranes was verified by atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses of the fouled membranes.
25

Removal of organic foulants from capillary ultrafiltration membranes by use of ultrasound.

Nel, A. M. 03 1900 (has links)
Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2006 / Fouling is a serious problem in membrane filtration, caused by pore plugging and adsorption of rejected macromolecules or other solutes in the membrane system. This requires periodic cleaning of membranes, which can add considerably to the overall cost of plant operation owing to lost productivity related to down-time, the cost of the chemicals used in cleaning, higher pressures and associated pumping costs to maintain membrane productivity, as well as reduced lifetime of the membranes. Ultrasound has recently been suggested as a promising approach to combating fouling in membranes. In principle it can be used on-line and may even eliminate the use of chemical cleaning or alternative measures completely, which could lead to major advances in the development and implementation of membrane technology. The objective of this investigation was therefore to assess the feasibility of using ultrasound to mitigate fouling in capillary ultrafiltration systems applied to water containing natural organic matter. Experimental work was conducted with a small laboratory-scale capillary membrane module. Ultrasound was introduced into the system by means of an ultrasonic probe operating at a fixed frequency of approximately 30 kHz, generating a maximum acoustic power density of 130 W/cm2 with a nominal power output of 50 W (IKA Labortechnik Staufen, United Kingdom, U50). Five systems were investigated, viz. aqueous solution of Congo Red dye, ultrapure water, coloured ground water from the George region, water from the Steenbras dam, as well as an aqueous solution of dextran. In most cases, ultrasonication resulted in an increase in the permeate flux. This increase could partly be attributed to an increase in the temperature and thus a decrease in the viscosity of the fluid and partly to enhanced mass and energy transfer due to sonication. Based on experiments done with the Congo Red dye and ultrapure water, no damage as a result of ultrasonication could be discerned in the membrane filter, except when there was direct contact between the ultrasonic probe and the membrane materials. Permeate quality analyses confirmed that sonication does not damage the membrane material – no degradation of permeate quality was found specifically during sonication intervals. In conclusion, ultrasound indeed appeared to be an effective approach to remove foulants associated with natural organic matter from membranes. However, an issue not addressed by this study, but apparent from the literature, is that the effect of ultrasound is strictly local and this has major implications for the scaleup of such ultrasound systems.
26

Cleaning of micro- and ultrafiltration membranes with infrasonic backpulsing.

Shugman, Emad Musbah 12 1900 (has links)
Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Membrane fouling is universally considered to be one of the most critical problems in the wider application of membranes in filtration separation. Fouling is caused by the deposition of particles not only on the surface of the membrane, but also inside the membrane pores, which reduces permeate flux and leads to a reduction of the efficiency and the longevity of the membrane. The backpulsing cleaning method can be used to remove deposited foulants from the surface of the membrane, without having to shut down the plant. Ultrasonic time-domain reflectometry (UTDR) is a nondestructive technique, used to detect and measure the growth of fouling layer on the membrane surface during microfiltration and ultrafiltration processes. In this study flat-sheet microfiltration (MF) and ultrafiltration (UF) membranes were fouled during a cross-flow filtration processes using dextrin, yeast or alumina (feed pressure 100 kPa and feed flow rate 0.45 liter/minute), in a flat cell. Infrasound frequency backpulsing, in the permeate space, was used to clean the membranes. Backpulsing was carried out using the permeate water or soap solutions. The peak pressure amplitude of the pulses used to clean the membranes was 140 kPa, the pulsing was applied at a frequency of 6.7 Hz. The main objectives of this research were: (1) to obtain a fundamental understandimg of how foulants deposit on membrane surfaces and how the foulant deposits can be removed using the backpulsing cleaning technique during MF and UF, (2) to use the ultrasonic measurement technique for monitoring the growth and removal of the fouling layer on the membrane surface and (3) Use scanning electron microscopy (SEM) as a direct measurement technique to analyze the structure the foulant deposits on membrane surfaces before and after cleaning. Results showed that a flux value of between 55% and 98% of the clean water flux value can be achieved by backpulsing cleaning. UTDR was successfully applied to monitor membrane cleaning and provide information about the growth and removal of fouling layers on the membrane surface. / AFRIKAANSE OPSOMMING: Membraanaanvuiling is wêreldwyd bekend as een van die mees kritieke probleme wat die wyer aanwending van membrane vir skeidingsprosesse benadeel. Aanvuiling word veroorsaak deur die deponering van partikels, nie net op die oppervlak van die membraan nie, maar ook binne-in die membraanporieë, wat die volgende tot gevolg het: 'n afname in vloed deur die membraan, 'n afname in die effektiwiteit van die membraan, en 'n korter membraanleeftyd. Die teenpulsskoonmaakmetode kan gebruik word om die aanvuilingslaag vanaf die membranoppervlakte te verwyder sonder dat dit nodig is om die membraantoetsapparaat af te skakel. Ultrasoniese-tydsgebied-weerkaatsing (UTW) is 'n nie-vernietigende tegniek wat gebruik kan word om die groei van 'n aanvuilingslaag op 'n membraanoppervlakte tydens mikrofiltrasie (MF) of ultrafiltrasie (UF) te identifiseer en te meet. In hierdie studie is plat-vel MF en UF membrane bevuil gedurende 'n kruisvloeifiltrasieproses deur gebruik to maak van dekstraan, gis of alumina, in 'n plat sel. Infraklank-frekwensieteenpols, in die permeaatgebied, is gebruik om die membrane skoon te maak. Hiervoor is die proseswater of 'n seepoplossing gebruik. Die maksimum drukamplitude van die pulse wat gebruik is was 140 kPa, en die puls was aangewend teen 'n frekwensie van 6.7 Hz. Die hoofdoelwite van hierdie studie was die volgende: (1) om inligting in te win oor hoe aanvuilingsmateriale op membraanoppervlaktes gedeponeer word tydens MF en UF en hoe hulle verwyder kan word deur gebruik te maak van die teenpulsskoonmaaktegniek; (2) om van die teenpulsskoonmaaktegniek gebruik te maak om die groei van die bevuilingslaag asook die verwydering daarvan op die membraanoppervlakte te monitor; en (3) om van skandeerelektronmikroskopie (SEM) as 'n direkte analitiesetegniekgebruik te maak om die struktuur van die aanvuilingsmateriaal voor en na die die skoonmaakproses te analiseer. Deur gebruik te maak van teenpulsskoonmaak kon die membraanvloed tot tussen 55–98% van die oorspronklike suiwerwatervloed verbeter word. Sodoende is ultrasoniese-tydsgebiedweerkaatsing suksesvol gebruik om die skoonmaak van membrane te monitor asook om inligting in te win i.v.m. die groei en verwydering van die aanvuilingslae op die membraanoppervlaktes.
27

System hydrodynamics to reduce fouling of air-sparged immersed flat-sheet microfiltration membranes

Hamann, Martin Louis 12 1900 (has links)
Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Immersed membrane systems hold many operational and environmental advantages in biological treatment of wastewater. However, immersed membrane filtration have only found application in niche markets to date because of higher capital and operating costs associated with membrane fouling. But with capital costs on the decline as membranes become less expensive, immersed membrane systems are increasingly considered as an attractive alternative to conventional treatment processes. Operating costs remain high however, since energy intensive techniques such as air-sparging are required to limit membrane fouling. Improving the air-scouring efficiency of air-sparged immersed membranes can significantly reduce operating costs and unlock the immersed membrane system technology to wider application. The aim of this study was to identify factors that will improve air-scouring efficiency in order to produce guidelines that will help in the development of an immersed microfiltration membrane system with a resulting lower operating cost. Although, the research was done on a flat-sheet microfiltration membrane, the guidelines obtained can be used for the development of any immersed microfiltration membrane arrangement. An airlift reactor set-up was chosen for this study. Six system hydrodynamic factors were evaluated in a factorial design to determine their effects on the cross-flow velocity profile. They were the downcomer area to riser area ratio, top clearance distance, bottom clearance distance, aeration intensity, water depth and air sparger location. It was found that the air-scouring efficiency was increased by generating a cross-flow velocity profile with increased magnitude and uniformity, but absolute uniformity of the cross-flow velocity profile was found to be a prerequisite for optimisation of air-scouring efficiency. Downcomer area to riser area ratio was found to be 99.9% significant in determining the magnitude of the cross-flow velocity profile. Two models were developed to respectively predict the relative magnitude and uniformity of the cross-flow velocity profile. By using these two models, a methodology was developed to design an airlift reactor set-up that would produce system hydrodynamics with an improved air-scouring efficiency. / AFRIKAANSE OPSOMMING: Gesonke membraanstelsels beskik oor talle bedryfs- en omgewingsvoordele in biologiese behandeling van afvalwater. Maar weens die hoër kapitaal- en bedryfskostes wat gepaardgaan met membraanbevuiling, kon gesonke membraanstelsels tot op hede nog net toepassing in nismarkte vind. Maar soos kapitaalkoste daal met al hoe goedkoper membrane beskikbaar, word gesonke membraanstelsels al hoe aanlokliker as ‘n alternatief vir konvensionele behandelingsprosesse. Bedryfskostes bly egter hoog aangesien energie-intensiewe tegnieke soos lugborreling benodig word om membraanbevuiling te vertraag. Deur die effektiwiteit van die skropaksie wat lugborreling aan gesonke membrane bied te verbeter, kan ‘n beduidende besparing in bedryfskostes teweeggebring word om sodoende die uitgebreide toepassing van gesonke membraanstelsel tegnologie moontlik te maak. Hierdie studie het ten doel gehad die identifisering van faktore wat lugskropaksie effektiwiteit kan verbeter en om riglyne op te stel vir die ontwikkeling van ‘n gesonke mikrofiltrasie membraanstelsel met gevolglik laer bedryfskostes. Alhoewel hierdie navorsing ‘n plat-blad mikrofiltrasie membraan gebruik het, kan die riglyne steeds vir enige gesonke mikrofiltrasie membraanuitleg gebruik word. Daar is besluit op ‘n lugligter-reaktor opstelling vir hierdie studie. Ses stelselhidrodinamika faktore is geëvalueer in ‘n faktoriale ontwerp om hul effekte op die kruisvloei snelheidsprofiel te bepaal. Hulle was die afvloei-area tot opvloei-area verhouding, topruimte-afstand, bodemruimte-afstand, belugtingsintensiteit, waterdiepte en belugterligging. Daar is bevind dat die lugskropaksie effektiwiteit verhoog word wanneer ‘n kruisvloei snelheidsprofiel geskep word met ‘n verhoogde grootte en gelykvormigheid, maar die absolute gelykvormigheid van die kruisvloei snelheidsprofiel is gevind om ‘n voorvereiste te wees vir optimale effektiwiteit. Afvloei-area tot opvloei-area verhouding is gevind om 99.9% beduidend te wees in die bepaling van die snelheidsprofiel se grootte. Twee modelle is ontwikkel om afsonderlik die relatiewe grootte en gelykvormigheid van die kruisvloei snelheidsprofiel te voorspel. Die modelle is in ‘n metodologie vervat vir die ontwerp van ‘n lugligter opstelling met stelselhidrodinamika wat verbeterde lugskropaksie effektiwiteit sal skep.
28

Simultaneous minimisation of water and energy within a water and membrane network superstructure

Buabeng-Baidoo, Esther January 2016 (has links)
A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2015 / The scarcity of water and strict environmental regulations have made sustainable engineering a prime concern in the process and manufacturing industries. Water minimisation involves the reduction of freshwater use and effluent discharge in chemical plants. This is achieved through water reuse, water recycle and water regeneration. Optimisation of the water network (WN) superstructure considers all possible interconnections between water sources, water sinks and regenerator units (membrane systems). In most published works, membrane systems have been represented using the “black-box” approach, which uses a simplified linear model to represent the membrane systems. This approach does not give an accurate representation of the energy consumption and associated costs of the membrane systems. The work presented in this dissertation therefore looks at the incorporation of a detailed reverse osmosis network (RON) superstructure within a water network superstructure in order to simultaneously minimise water, energy, operating and capital costs. The WN consists of water sources, water sinks and reverse osmosis (RO) units for the partial treatment of the contaminated water. An overall mixed-integer nonlinear programming (MINLP) framework is developed, that simultaneously evaluates both water recycle/reuse and regeneration reuse/recycle opportunities. The solution obtained from optimisation provides the optimal connections between various units in the network arrangement, size and number of RO units, booster pumps as well as energy recovery turbines. The work looks at four cases in order to highlight the importance of including a detailed regeneration network within the water network instead of the traditional “black-box’’ model. The importance of using a variable removal ratio in the model is also highlighted by applying the work to a literature case study, which leads to a 28% reduction in freshwater consumption and 80% reduction in wastewater generation. / GR2016
29

Utilização dos componentes lignocelulósicos do bagaço de cana-de-açúcar para produção de membranas / Utilization of lignocellulosic components of sugarcane bagasse for production of membranes

Simone Coelho Nakanishi 16 December 2010 (has links)
Pensando em um melhor aproveitamento para o excedente do bagaço de cana, esse trabalho tem como objetivo a obtenção de membranas de acetato de celulose composta com ligninas oxidadas, ambos isolados do bagaço da cana. Para tal, os componentes macromoleculares do bagaço foram separados, aplicando-se um pré-tratamento de explosão a vapor para retirada da parte hemicelulósica e um tratamento com hidróxido de sódio para a separação da lignina e obtenção da polpa bruta de celulose. Essa polpa foi branqueada e acetilada e, posteriormente, foram sintetizadas membranas deste acetato de celulose, incorporando-se lignina oxidada a estas membranas com o objetivo de aumentar a capacidade de retenção de metais destas membranas. Assim, pretende-se obter um produto com maior valor comercial, que tem aplicações em tratamento de água e efluentes, podendo contribuir ainda mais para a manutenção do ambiente. As membranas foram sintetizadas por inversão de fase, utilizando dois métodos distintos: I. por evaporaçãoprecipitação e, II. por imersão em banho de coagulação. O material acetilado foi analisado por IR, confirmando-se a acetilação pelo aparecimento de bandas características do acetato e analisadas quanto ao grau de substituição, caracterizando um diacetato. As membranas sintetizadas pelo método I foram analisadas por MEV, constatando-se membranas de estrutura densa para todas as composições, e mais rígidas que uma membrana preparada a partir de um triacetato comercial, de acordo com os dados da análise dinâmico-mecânica. Foram realizados ainda, testes de permeabilidade e retenção de cobre. Apesar de rígidas, resistiram a pressões de até 20 bar. A membrana aditivada com lignina oxidada por lacase foi a que apresentou melhor desempenho nesse teste, atingindo maior fluxo necessitando menor pressão. No teste de retenção de cobre, apresentaram uma capacidade média de 15%, correspondendo a 50,5 mg Cu2+/g lignina. As membranas sintetizadas pelo método II foram analisadas por MEV, constatando-se diferenças na morfologia quando a lignina é adicionada dissolvida em NaOH. As análises térmicas mostraram a Tg do material perto de 80°C, além de evidenciar uma maior estabilidade térmica do material aditivado com lignina oxidada, comparado ao material sem lignina e com lignina original. No teste de permeabilidade, realizado aqui à pressão constante de 10 bar, a membrana sintetizada apenas com o acetato de celulose de bagaço de cana não apresentou fluxo. As membranas aditivadas com lignina original e lignina oxidada apresentaram fluxo, de 3,5 e 6,1 L/h.m2 respectivamente. O fato foi atribuído à morfologia das membranas, dado que as duas últimas, que apresentaram fluxo, possuem estrutura porosa, enquanto a outra possui estrutura densa. No teste de retenção de cobre, foi possível visualizar o efeito da adição da lignina na membrana, que aumenta 3,5 vezes a capacidade de retenção de cobre e, ainda, o efeito da oxidação da lignina, que aumenta em mais 50 % essa capacidade de retenção em comparação à adição apenas da lignina original. Contudo, os resultados indicam que as membranas sintetizadas, principalmente as membranas aditivadas com lignina oxidada, são promissoras para o objetivo proposto. / Thinking of a better use for the surplus of sugarcane bagasse, this study aims to obtain membranes of cellulose acetate composite with oxidized lignins, both isolated from sugarcane bagasse. To this purpose, the macromolecular components of bagasse were separated by applying a steam explosion pre-treatment for removal of hemicellulose and a treatment with sodium hydroxide to separate the lignin and obtaining of crude cellulose pulp. This pulp was bleached and acetylated, and subsequently cellulose acetate membranes were synthesized incorporating oxidized lignin in these membranes in order to increase the metal retention capacity of them. Thus, we intend to obtain a product with higher commercial value, which has applications in water and effluent treatment, which can further contribute to the maintenance of the environment. The membranes were synthesized by phase inversion, using two different methods: I. evaporation-precipitation and II. immersion in coagulation bath. The acetylated material was analyzed by FTIR, confirming the acetylation by the appearance of bands characteristic of acetate and analyzed for degree of substitution, featuring a diacetate. The membranes synthesized by method I were analyzed by SEM, verifying dense structure for the membranes in all compositions, and more rigid than a membrane prepared from a commercial triacetate, according to the data of dynamic mechanical analysis. Tests about permeability and copper retention also were done. Although rigid, they resisted to pressures up to 20 bar. The membrane added with lignin oxidized by laccase showed the best performance in this test, reaching higher flow requiring less pressure. In the test of copper retention, they showed an average retention capacity of 15%, corresponding to 50.5 mg Cu2+/ g lignin. The membranes synthesized by method II were analyzed by SEM, noting differences in morphology when the lignin is added dissolved in NaOH. Thermal analysis showed the Tg of the material near 80 °C, besides showing a higher thermal stability of the material added with oxidized lignin compared to material without lignin and with original lignin. In the permeability test, held at constant pressure of 10 bar, the membrane synthesized with only cellulose acetate cane bagasse showed no flow. The membranes added with original lignin and oxidized lignin showed flow of 3.5 and 6.1 L/h.m2, respectively. The fact was attributed to the morphology of the membranes, since the two latter, which showed flow, have porous structure, while the other has a dense structure. In the test of copper retention, it was possible to visualize the effect of the addition of lignin in the membrane, which increases 3.5 times the cupper retention capacity and, the effect of lignin oxidation, with increases in more 50% this retention capacity in comparison to the addition of the lignin in the original form. However, the results indicate that the synthesized membranes, mainly membranes added with oxidized lignin, are promising for the proposed objective.
30

Utilização dos componentes lignocelulósicos do bagaço de cana-de-açúcar para produção de membranas / Utilization of lignocellulosic components of sugarcane bagasse for production of membranes

Nakanishi, Simone Coelho 16 December 2010 (has links)
Pensando em um melhor aproveitamento para o excedente do bagaço de cana, esse trabalho tem como objetivo a obtenção de membranas de acetato de celulose composta com ligninas oxidadas, ambos isolados do bagaço da cana. Para tal, os componentes macromoleculares do bagaço foram separados, aplicando-se um pré-tratamento de explosão a vapor para retirada da parte hemicelulósica e um tratamento com hidróxido de sódio para a separação da lignina e obtenção da polpa bruta de celulose. Essa polpa foi branqueada e acetilada e, posteriormente, foram sintetizadas membranas deste acetato de celulose, incorporando-se lignina oxidada a estas membranas com o objetivo de aumentar a capacidade de retenção de metais destas membranas. Assim, pretende-se obter um produto com maior valor comercial, que tem aplicações em tratamento de água e efluentes, podendo contribuir ainda mais para a manutenção do ambiente. As membranas foram sintetizadas por inversão de fase, utilizando dois métodos distintos: I. por evaporaçãoprecipitação e, II. por imersão em banho de coagulação. O material acetilado foi analisado por IR, confirmando-se a acetilação pelo aparecimento de bandas características do acetato e analisadas quanto ao grau de substituição, caracterizando um diacetato. As membranas sintetizadas pelo método I foram analisadas por MEV, constatando-se membranas de estrutura densa para todas as composições, e mais rígidas que uma membrana preparada a partir de um triacetato comercial, de acordo com os dados da análise dinâmico-mecânica. Foram realizados ainda, testes de permeabilidade e retenção de cobre. Apesar de rígidas, resistiram a pressões de até 20 bar. A membrana aditivada com lignina oxidada por lacase foi a que apresentou melhor desempenho nesse teste, atingindo maior fluxo necessitando menor pressão. No teste de retenção de cobre, apresentaram uma capacidade média de 15%, correspondendo a 50,5 mg Cu2+/g lignina. As membranas sintetizadas pelo método II foram analisadas por MEV, constatando-se diferenças na morfologia quando a lignina é adicionada dissolvida em NaOH. As análises térmicas mostraram a Tg do material perto de 80°C, além de evidenciar uma maior estabilidade térmica do material aditivado com lignina oxidada, comparado ao material sem lignina e com lignina original. No teste de permeabilidade, realizado aqui à pressão constante de 10 bar, a membrana sintetizada apenas com o acetato de celulose de bagaço de cana não apresentou fluxo. As membranas aditivadas com lignina original e lignina oxidada apresentaram fluxo, de 3,5 e 6,1 L/h.m2 respectivamente. O fato foi atribuído à morfologia das membranas, dado que as duas últimas, que apresentaram fluxo, possuem estrutura porosa, enquanto a outra possui estrutura densa. No teste de retenção de cobre, foi possível visualizar o efeito da adição da lignina na membrana, que aumenta 3,5 vezes a capacidade de retenção de cobre e, ainda, o efeito da oxidação da lignina, que aumenta em mais 50 % essa capacidade de retenção em comparação à adição apenas da lignina original. Contudo, os resultados indicam que as membranas sintetizadas, principalmente as membranas aditivadas com lignina oxidada, são promissoras para o objetivo proposto. / Thinking of a better use for the surplus of sugarcane bagasse, this study aims to obtain membranes of cellulose acetate composite with oxidized lignins, both isolated from sugarcane bagasse. To this purpose, the macromolecular components of bagasse were separated by applying a steam explosion pre-treatment for removal of hemicellulose and a treatment with sodium hydroxide to separate the lignin and obtaining of crude cellulose pulp. This pulp was bleached and acetylated, and subsequently cellulose acetate membranes were synthesized incorporating oxidized lignin in these membranes in order to increase the metal retention capacity of them. Thus, we intend to obtain a product with higher commercial value, which has applications in water and effluent treatment, which can further contribute to the maintenance of the environment. The membranes were synthesized by phase inversion, using two different methods: I. evaporation-precipitation and II. immersion in coagulation bath. The acetylated material was analyzed by FTIR, confirming the acetylation by the appearance of bands characteristic of acetate and analyzed for degree of substitution, featuring a diacetate. The membranes synthesized by method I were analyzed by SEM, verifying dense structure for the membranes in all compositions, and more rigid than a membrane prepared from a commercial triacetate, according to the data of dynamic mechanical analysis. Tests about permeability and copper retention also were done. Although rigid, they resisted to pressures up to 20 bar. The membrane added with lignin oxidized by laccase showed the best performance in this test, reaching higher flow requiring less pressure. In the test of copper retention, they showed an average retention capacity of 15%, corresponding to 50.5 mg Cu2+/ g lignin. The membranes synthesized by method II were analyzed by SEM, noting differences in morphology when the lignin is added dissolved in NaOH. Thermal analysis showed the Tg of the material near 80 °C, besides showing a higher thermal stability of the material added with oxidized lignin compared to material without lignin and with original lignin. In the permeability test, held at constant pressure of 10 bar, the membrane synthesized with only cellulose acetate cane bagasse showed no flow. The membranes added with original lignin and oxidized lignin showed flow of 3.5 and 6.1 L/h.m2, respectively. The fact was attributed to the morphology of the membranes, since the two latter, which showed flow, have porous structure, while the other has a dense structure. In the test of copper retention, it was possible to visualize the effect of the addition of lignin in the membrane, which increases 3.5 times the cupper retention capacity and, the effect of lignin oxidation, with increases in more 50% this retention capacity in comparison to the addition of the lignin in the original form. However, the results indicate that the synthesized membranes, mainly membranes added with oxidized lignin, are promising for the proposed objective.

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