The Experts below are selected from a list of 25908 Experts worldwide ranked by ideXlab platform
Gisela Guthausen - One of the best experts on this subject based on the ideXlab platform.
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in situ mri of alginate fouling and flow in ceramic hollow fiber membranes
Journal of Membrane Science, 2017Co-Authors: F Arndt, S Schutz, Gisela Guthausen, S Schuhmann, Hermann NirschlAbstract:Abstract Magnetic resonance imaging was used to study the impact of Ca 2+ on the fouling behavior of alginate in Dead-End and cross-flow Filtrations. In situ experiments were performed to measure alginate layer formation and flow behavior during Filtration. It was found that magnetic resonance imaging allows for distinguishing different structures of the formed alginate layers. The structure of the alginate layer without the addition of Ca 2+ is a fluid and unordered concentration polarization layer, whereas a dense and stable gel layer is formed on the membrane's surface in case of the Filtration of alginate with Ca 2+ . This was in good agreement with data of Filtration experiments. To overcome the lack of contrast between alginate and surrounding water, the addition of specific contrast agents was necessary in the case of Dead-End Filtration. Using tagging methods, the flow profiles during Dead-End Filtrations were investigated, and it was shown that the addition of Ca 2+ not only influences the fouling layer structure, but also the flow behavior. Furthermore, cross-flow experiments were performed. Here, the outflow effect was successfully used as contrast mechanism.
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new insights into sodium alginate fouling of ceramic hollow fiber membranes by nmr imaging
Aiche Journal, 2016Co-Authors: F Arndt, U Roth, Hermann Nirschl, S Schutz, Gisela GuthausenAbstract:Ceramic hollow fiber membranes are investigated with respect to the fouling behavior. Constant pressure Dead-End Filtration experiments have been performed using alginate as model substance for extracellular polymeric substances. In addition to the evaluation of the Filtration data using conventional cake Filtration model, nuclear magnetic resonance imaging (MRI) was used to elucidate the influence of Ca2+ on the fouling layer structure for alginate Filtration within ceramic hollow fiber membranes. To visualize the alginate layers inside the opaque ceramic hollow fiber membranes by means of MRI, specific contrast agents were applied. Supplementary to multi slice multi echo imaging, flow velocity measurements were performed to gain more insight into the hydrodynamics in the fouled membranes. MRI reveals the structure of the alginate layers with the finding that the addition of Ca2+ to the alginate feed solution promotes the formation of a dense alginate gel layer on the membrane's surface. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2459–2467, 2016
F Arndt - One of the best experts on this subject based on the ideXlab platform.
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in situ mri of alginate fouling and flow in ceramic hollow fiber membranes
Journal of Membrane Science, 2017Co-Authors: F Arndt, S Schutz, Gisela Guthausen, S Schuhmann, Hermann NirschlAbstract:Abstract Magnetic resonance imaging was used to study the impact of Ca 2+ on the fouling behavior of alginate in Dead-End and cross-flow Filtrations. In situ experiments were performed to measure alginate layer formation and flow behavior during Filtration. It was found that magnetic resonance imaging allows for distinguishing different structures of the formed alginate layers. The structure of the alginate layer without the addition of Ca 2+ is a fluid and unordered concentration polarization layer, whereas a dense and stable gel layer is formed on the membrane's surface in case of the Filtration of alginate with Ca 2+ . This was in good agreement with data of Filtration experiments. To overcome the lack of contrast between alginate and surrounding water, the addition of specific contrast agents was necessary in the case of Dead-End Filtration. Using tagging methods, the flow profiles during Dead-End Filtrations were investigated, and it was shown that the addition of Ca 2+ not only influences the fouling layer structure, but also the flow behavior. Furthermore, cross-flow experiments were performed. Here, the outflow effect was successfully used as contrast mechanism.
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new insights into sodium alginate fouling of ceramic hollow fiber membranes by nmr imaging
Aiche Journal, 2016Co-Authors: F Arndt, U Roth, Hermann Nirschl, S Schutz, Gisela GuthausenAbstract:Ceramic hollow fiber membranes are investigated with respect to the fouling behavior. Constant pressure Dead-End Filtration experiments have been performed using alginate as model substance for extracellular polymeric substances. In addition to the evaluation of the Filtration data using conventional cake Filtration model, nuclear magnetic resonance imaging (MRI) was used to elucidate the influence of Ca2+ on the fouling layer structure for alginate Filtration within ceramic hollow fiber membranes. To visualize the alginate layers inside the opaque ceramic hollow fiber membranes by means of MRI, specific contrast agents were applied. Supplementary to multi slice multi echo imaging, flow velocity measurements were performed to gain more insight into the hydrodynamics in the fouled membranes. MRI reveals the structure of the alginate layers with the finding that the addition of Ca2+ to the alginate feed solution promotes the formation of a dense alginate gel layer on the membrane's surface. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2459–2467, 2016
Hermann Nirschl - One of the best experts on this subject based on the ideXlab platform.
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in situ mri of alginate fouling and flow in ceramic hollow fiber membranes
Journal of Membrane Science, 2017Co-Authors: F Arndt, S Schutz, Gisela Guthausen, S Schuhmann, Hermann NirschlAbstract:Abstract Magnetic resonance imaging was used to study the impact of Ca 2+ on the fouling behavior of alginate in Dead-End and cross-flow Filtrations. In situ experiments were performed to measure alginate layer formation and flow behavior during Filtration. It was found that magnetic resonance imaging allows for distinguishing different structures of the formed alginate layers. The structure of the alginate layer without the addition of Ca 2+ is a fluid and unordered concentration polarization layer, whereas a dense and stable gel layer is formed on the membrane's surface in case of the Filtration of alginate with Ca 2+ . This was in good agreement with data of Filtration experiments. To overcome the lack of contrast between alginate and surrounding water, the addition of specific contrast agents was necessary in the case of Dead-End Filtration. Using tagging methods, the flow profiles during Dead-End Filtrations were investigated, and it was shown that the addition of Ca 2+ not only influences the fouling layer structure, but also the flow behavior. Furthermore, cross-flow experiments were performed. Here, the outflow effect was successfully used as contrast mechanism.
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new insights into sodium alginate fouling of ceramic hollow fiber membranes by nmr imaging
Aiche Journal, 2016Co-Authors: F Arndt, U Roth, Hermann Nirschl, S Schutz, Gisela GuthausenAbstract:Ceramic hollow fiber membranes are investigated with respect to the fouling behavior. Constant pressure Dead-End Filtration experiments have been performed using alginate as model substance for extracellular polymeric substances. In addition to the evaluation of the Filtration data using conventional cake Filtration model, nuclear magnetic resonance imaging (MRI) was used to elucidate the influence of Ca2+ on the fouling layer structure for alginate Filtration within ceramic hollow fiber membranes. To visualize the alginate layers inside the opaque ceramic hollow fiber membranes by means of MRI, specific contrast agents were applied. Supplementary to multi slice multi echo imaging, flow velocity measurements were performed to gain more insight into the hydrodynamics in the fouled membranes. MRI reveals the structure of the alginate layers with the finding that the addition of Ca2+ to the alginate feed solution promotes the formation of a dense alginate gel layer on the membrane's surface. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2459–2467, 2016
Clemens Posten - One of the best experts on this subject based on the ideXlab platform.
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electroFiltration improves dead end Filtration of hyaluronic acid and presents an alternative downstream processing step that overcomes technological challenges of conventional methods
Engineering in Life Sciences, 2017Co-Authors: Gozde Gozke, Carolin Prechtl, Frank Kirschhofer, Gerald Brennerweiss, Ursula Obst, Nikolay Krumov, Clemens PostenAbstract:Hyaluronic acid (HA) dispersion obtained from the bacteria Streptococcus equi was concentrated by electroFiltration. In the conventional downstream processing of HA, extraction and precipitation lead to increase in environmental issues, structural changes, and time and energy related costs. Using electroFiltration as an alternative technology delivers solutions to these limitations. Experiments were conducted in order to test the applicability of electroFiltration to downstream processing of the negatively charged HA. The structural changes and molecular weight distributions, often a consequence of the employed separation method, were tested by analysis of the initial dispersions and final products. In comparison to the conventional Filtration, concentration factors were increased up to almost four times without any detectable structural change in the final product.
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improvement of dead end Filtration of biopolymers with pressure electroFiltration
Chemical Engineering Science, 2003Co-Authors: Ralph Hofmann, Clemens PostenAbstract:Abstract Solid/liquid separation of biopolymers such as polysaccharides and proteins is still a problem not solved sufficiently on a technical scale. The main objective of the presented work was to set up a process strategy in order to improve the recovery of biopolymers by Dead-End Filtration. One aspect was the investigation of the influence of the pH value, ionic strength and pressure on the Filtration kinetics of the Dead-End Filtration of the polysaccharide xanthan. pH value and ionic strength have an impact on the hydrodynamic radius and the zeta potential of biopolymers, and thus they have an impact on the filter cake structure and the Filtration kinetics. The main focus was set on the enhancement of the filtrate flux by an electric field. This process, called pressure electroFiltration, leads to a drastic improvement of the Filtration kinetics. The Filtration time was thereby reduced from the range of hours down to minutes. Additionally another strategy was followed up, which aimed at an improvement of the specific filter cake resistance by changing process parameters like the pH and the ionic strength. These parameters influence the polymer–polymer and the polymer–water interactions and thus have an influence on the filter cake properties. Due to the great acceleration of the Filtration kinetics the pressure electroFiltration serves as an interesting alternative to the cross-flow Filtration and the precipitation with alcohol for the separation of biopolymers.
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Biopolymer recovery with the pressure electroFiltration and determination of the biopolymer quality by MAS-NMR and FT-IR techniques
Engineering in Life Sciences, 2002Co-Authors: Ralph Hofmann, Clemens PostenAbstract:The classical Dead-End Filtration of a biopolymer containing suspension is a very inefficient process, since biopolymers, like the polysaccharide xanthan, form an almost impermeable filter cake. The results of this effect are a high specific filter cake resistance and long Filtration durations. For this reason, precipitation combined with centrifugation is often used to separate biopolymers from a fermentation broth. A new Dead-End Filtration process has been developed to overcome this problem. This process is the pressure electroFiltration, with which the Filtration kinetics can be improved drastically. In the experiments performed 99 % of the polysaccharides were recovered from the solution by the pressure electroFiltration. Furthermore, the chemical structure of xanthan was examined with FT-IR and MAS-NMR spectra, before and after the pressure electroFiltration. This was carried out in order to demonstrate a possible chemical or electrochemical reaction of the biopolymer during the electroFiltration.
Xia Huang - One of the best experts on this subject based on the ideXlab platform.
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an analytical model for membrane fouling evolution associated with gel layer growth during constant pressure stirred dead end Filtration
Journal of Membrane Science, 2013Co-Authors: Kang Xiao, Yuexiao Shen, Xia HuangAbstract:Abstract Stirred Dead-End Filtration (SDEF) has been widely used for fundamental studies on membrane fouling caused by soluble and colloidal matter during microFiltration and ultraFiltration. Quantitative description of the SDEF fouling process which usually involves gel layer formation, however, has rarely been reported. In this study, an analytical model was derived based on theories of cake Filtration and concentration polarization, to quantify the gel-associated fouling evolution process during constant pressure SDEF. The model formulates the relationship between Filtration resistance ( R ) and specific permeate volume ( V ) as: V = C 1 + C 2 R + C 3 exp(− C 4 / R )+ V 0 ( C 2 dR / dV −1), where C 1 – C 4 and V 0 are constants. The model enables rigorous definition of characteristic points on the R vs. V curve to divide the fouling evolution process into the initial fouling stage, the gel layer growth stage and the gel layer mature stage. The model also gives a simplified piecewise expression: V = C 1 + C 2 R for the gel layer growth stage and V = C 1 + C 2 R + C 3 exp(− C 4 / R )− V 0 for the mature stage. A two-step fitting approach was proposed for the simplified expression to evaluate the C 1 – C 4 parameters. These parameters were found useful in determining the characteristic points of fouling evolution and further, in quantifying foulant and fouling layer properties including: hydrodynamic diameter and diffusion coefficient of foulant, mass transfer coefficient and boundary layer thickness of concentration polarization, and specific resistance and gel point concentration of gel layer. This model in combination with constant pressure SDEF experiments can serve as a tool for quantitative characterization of fouling propensity and foulant properties, and may thus assist in detailed analysis of fouling mechanisms.
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fouling characteristics in a membrane bioreactor coupled with anaerobic anoxic oxic process for coke wastewater treatment
Bioresource Technology, 2010Co-Authors: Wentao Zhao, Kang Xiao, Yuexiao Shen, Xia HuangAbstract:Abstract Experiments were conducted to investigate the fouling characteristics of a membrane bioreactor combined with anaerobic–anoxic–oxic process for coke wastewater treatment. Supernatant from the oxic tank was characterized as different hydrophilic/hydrophobic fractions by DAX-8 resin, with joint size partition also undertaken. Polysaccharides and proteins, mainly the fraction with molecular weight above 100 kDa, were liable to accumulate in the supernatant. Hydrophilic fraction, mainly contributing to the subclass of molecular weight above 100 kDa, was found most likely responsible for the flux deterioration by means of Dead-End Filtration tests. Analyses of particle and membrane pore size distribution revealed that major foulants had size comparable to the pore diameter. It can be inferred that steric factor (i.e. size exclusion) behaved primarily in the initial stage of fouling, while the role of hydrophobic interaction was of less significance.
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a systematic insight into fouling propensity of soluble microbial products in membrane bioreactors based on hydrophobic interaction and size exclusion
Journal of Membrane Science, 2010Co-Authors: Yuexiao Shen, Kang Xiao, Wentao Zhao, Xia HuangAbstract:Abstract Soluble microbial products (SMPs) contained in membrane bioreactor (MBR) supernatant have been proved to be main foulants. To obtain a comprehensive understanding of the fouling potential of SMPs on the basis of both hydrophilic/hydrophobic properties and molecular size, MBR supernatant of a pilot-scaled system treating municipal wastewater was partitioned into different hydrophilic/hydrophobic fractions by DAX-8 resins, with joint size partition of hydrophilic fraction also undertaken. A series of stirred Dead-End Filtration tests were conducted to investigate the flux decline. Hydrophilic fraction was found the dominant foulant responsible for flux deterioration, which was mainly attributed to the subclass of molecular weight above 100 kDa. The molecular weight distribution and atomic force microscopy images indicated that large molecules in hydrophilic fraction plugged the membrane pores. The backwash tests showed the flux decline caused by hydrophilic fraction was much less recoverable by hydraulic cleaning. It can be inferred that steric factor, i.e. size exclusion was the primary cause in the initial stage of fouling, while the role of hydrophobic interaction was of less significance. Additional modeling work indicates that the main fouling mechanism was complete blocking, further confirming the predominance of size exclusion contributing to membrane fouling by SMPs in MBR supernatant.