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Sol-gel modified ceramic membranes for gas separation
advantages relative 1-0 other membrane fabrication processes in terms of the high asymmetry of the membranes, the easy adjustment of pore sizes, and the ability to easily modify pore surfaces during the synthesis of particles. A number of approaches were examined for placement of particles and stabilisation of these latex composite membra.nes (LCMs). Filtration of particles with reactive surface groups t-hat provide covalent linkages at the contact points in the particle array proved most effective in obtaining stable membranes. These membranes had narrow size distributions in both the UF and MF range, and were capable of being cleaned and backflushed. The were membranes characterised in terms of gas permeabilities, pure water electron permeabilities and rejection microscopy. The properties of LCMs were also examined during filtration of monodispersed latex particles and a broadly dispersed dextran mixture. S. Jons, I! Ries, C.J. McDonald: J Membrane Science 155(l) 79--99 (31 March 1999).
Sol-gel modified ceramic membranes for gas separatioln Ceramic membranes based on an alumina with two support successive layers of alumina of decreasing pore size and a sol-gel top layer, were characterised by gas permeability experiments and used for separating binary H, and N, gas mixtures. A mathematical model based on mass balance calculations was developed to predict the composition of the permeated gas as a function of rhe different experimental pai-ameters. No gas diffusion assumption is made, and it allows us, after a previous characterisation of the membrane, to find the optimal conditions for gas separation. A. Conesa, A. FernPndez Roura, J.A. Pitarch, I. Vicente-Mingarto, M.A. Rodriguez: 1. M’embmne Science 155(I) 123-131 (31 March 1999).
Hollow-fibre PEEK microfiltration membranes A procedure for obtaining highperformance, large internal diameter (ID >I mm) hollow-fibre microfiltration membranes from poly(ether ether ketone) (PEEK) is reported. A simple mixture of isomers of diphenylphthalate is a good solvent for employing the thermal-phase inversion process to obtain PEEK membranes. Obtaining large-ID hollow fibres with substantial transmembrane requires melt flux sufficient strength during spinning to prevent excessive drawing of the extruding fibre. The use of a second leachable polymer to the blend satisfies the conditions, and polysulfone is found to provide superior membranes relative to either poly(etherimide) or poly(ether, sulfone) as a second polymer. membranes PEEK obtained using this process have better chemical resistance to a concentrated warm surfactantioil solution M.F. Sonnenschein: .p Applied Polymer Science 72(2) 175-181 (11 April 1799).
Performance of ceramic membranes at high pressure and temperature Microporous silica membrane manufacturing technology has been scaled-up and tubes with several hundred cm2 of membrane surface area have been prepared. Practical problems in applying hightemperature ceramic membrane technology, such as sealing and ceramic metal joining, have been solved successfully at the pilot scale. Experiments show that the membranes developed are capable of selectively separating hydrogen from a gas mixture containing hydrogen at elevated pressures and temperatures. Permselectivity values for H,/CH, separation are as high as 28. The gas separation performance of membranes is influenced by the flow conditions
on both the feed and permeate sides of the membrane. Non-ideal flow conditions can reduce the separation efficiency and strongly influence the performance of ceramic membrane separators. By performing high--temperature, high-p ressure separation experiments and simulation of the non-ideal flow effects around the membrane, the influence of the flow effects has been predicted. of the pilot-scale OP eration membrane separator is simulated by a two-dimensional, one-phase mathematical model which predicts the basic features of the separator from an engineering point-of-view. A comparison b,etween the experimental data and the modelling results concludes that the dispersion model predicts the membrane separator performance much better than the simplified model, which assumes plug flow on both sides of the membrane separator. M.K. Koukou, N. Papayannakos, N.C. Markatos, M. Bracht, H.M. Van Veen, A. Roskam: J Membrane Science 155(2) 241-259 (12 April 1999).
Crossflow membrane filtration of oily waste water The effect of an external electric field on the flux in crossflow membrane filtration of a model oily waste water was studied using a carbon fibrelcarbon composite membrane as a cathode. Limiting fluxes for low flow rate increased significantly under the conditions studied, from 75 l/m*lh without an electric field to more than 350 l/lm2h using an electric field. The experimentally determined increase in the limiting flux showed good agreement with the theoretical value of 430 l/m2h calculated using a simple model. The limiting flux increase was affected by the electrophoretic mobilny of the oil droplets and the applied electric field strength. When there were no cakes without an electric field due to the high flow rate, the flux increase when using an electric field under at the same conditions was minimal. The
critical electric field strength was determined, and experimentally obtained values compared with calculated values. Reducing the crossflow velocity above the critical electric field strength increased the flux, or had no effect, depending on the size of the particles. Permeate quality was also improved to some extent when using the electric field, and a membrane with a large pore size could be used when an electric field was applied. The main disadvantage in using the membrane as a cathode was foaming at the membrane surface, causing less flux enhancement as the conductivity of the feed increased. It was not possible to restore the flux to the original value by applying an electric field after filtration of the oil emulsion without an electric field. An intermittent electric field was thus not efficient enough for keeping the flux at high level. H.M. Huotari, I.H. Huisman, G. Trag%rdh: 1. Membrane Science 156(l) 49-60 (24 April 1399).
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Sol-gel modified ceramic membranes for gas separatioln Ceramic membranes based on an alumina with two support successive layers of alumina of decreasing pore size and a sol-gel top layer, were characterised by gas permeability experiments and used for separating binary H, and N, gas mixtures. A mathematical model based on mass balance calculations was developed to predict the composition of the permeated gas as a function of rhe different experimental pai-ameters. No gas diffusion assumption is made, and it allows us, after a previous characterisation of the membrane, to find the optimal conditions for gas separation. A. Conesa, A. FernPndez Roura, J.A. Pitarch, I. Vicente-Mingarto, M.A. Rodriguez: 1. M’embmne Science 155(I) 123-131 (31 March 1999).
Hollow-fibre PEEK microfiltration membranes A procedure for obtaining highperformance, large internal diameter (ID >I mm) hollow-fibre microfiltration membranes from poly(ether ether ketone) (PEEK) is reported. A simple mixture of isomers of diphenylphthalate is a good solvent for employing the thermal-phase inversion process to obtain PEEK membranes. Obtaining large-ID hollow fibres with substantial transmembrane requires melt flux sufficient strength during spinning to prevent excessive drawing of the extruding fibre. The use of a second leachable polymer to the blend satisfies the conditions, and polysulfone is found to provide superior membranes relative to either poly(etherimide) or poly(ether, sulfone) as a second polymer. membranes PEEK obtained using this process have better chemical resistance to a concentrated warm surfactantioil solution M.F. Sonnenschein: .p Applied Polymer Science 72(2) 175-181 (11 April 1799).
Performance of ceramic membranes at high pressure and temperature Microporous silica membrane manufacturing technology has been scaled-up and tubes with several hundred cm2 of membrane surface area have been prepared. Practical problems in applying hightemperature ceramic membrane technology, such as sealing and ceramic metal joining, have been solved successfully at the pilot scale. Experiments show that the membranes developed are capable of selectively separating hydrogen from a gas mixture containing hydrogen at elevated pressures and temperatures. Permselectivity values for H,/CH, separation are as high as 28. The gas separation performance of membranes is influenced by the flow conditions
on both the feed and permeate sides of the membrane. Non-ideal flow conditions can reduce the separation efficiency and strongly influence the performance of ceramic membrane separators. By performing high--temperature, high-p ressure separation experiments and simulation of the non-ideal flow effects around the membrane, the influence of the flow effects has been predicted. of the pilot-scale OP eration membrane separator is simulated by a two-dimensional, one-phase mathematical model which predicts the basic features of the separator from an engineering point-of-view. A comparison b,etween the experimental data and the modelling results concludes that the dispersion model predicts the membrane separator performance much better than the simplified model, which assumes plug flow on both sides of the membrane separator. M.K. Koukou, N. Papayannakos, N.C. Markatos, M. Bracht, H.M. Van Veen, A. Roskam: J Membrane Science 155(2) 241-259 (12 April 1999).
Crossflow membrane filtration of oily waste water The effect of an external electric field on the flux in crossflow membrane filtration of a model oily waste water was studied using a carbon fibrelcarbon composite membrane as a cathode. Limiting fluxes for low flow rate increased significantly under the conditions studied, from 75 l/m*lh without an electric field to more than 350 l/lm2h using an electric field. The experimentally determined increase in the limiting flux showed good agreement with the theoretical value of 430 l/m2h calculated using a simple model. The limiting flux increase was affected by the electrophoretic mobilny of the oil droplets and the applied electric field strength. When there were no cakes without an electric field due to the high flow rate, the flux increase when using an electric field under at the same conditions was minimal. The
critical electric field strength was determined, and experimentally obtained values compared with calculated values. Reducing the crossflow velocity above the critical electric field strength increased the flux, or had no effect, depending on the size of the particles. Permeate quality was also improved to some extent when using the electric field, and a membrane with a large pore size could be used when an electric field was applied. The main disadvantage in using the membrane as a cathode was foaming at the membrane surface, causing less flux enhancement as the conductivity of the feed increased. It was not possible to restore the flux to the original value by applying an electric field after filtration of the oil emulsion without an electric field. An intermittent electric field was thus not efficient enough for keeping the flux at high level. H.M. Huotari, I.H. Huisman, G. Trag%rdh: 1. Membrane Science 156(l) 49-60 (24 April 1399).
Next
month News Industry trends
Commercial news New product releases Contracts
Features Developments and applications around the world
Research Trends Latest membrane research
Patents World, US and European membrane patents
NetScope The best membrane sites reviewed