Kazuho Nakamura

Adsorption behavior of BSA in microfiltration with porous glass membrane

The fouling mechanism during dead-end microfiltration of bovine serum albumin (BSA) with porous glass membrane was investigated from the point of BSA adsorption onto the pore surface of membrane under the condition of pH 5.0 and ionic strength 0.01. The location of BSA retention was confirmed by comparing the filtration performance between dead-end mode and cross-flow mode. During the dead-end microfiltration BSA was retained only by the adsorption on the pore surface. The adsorption was irreversible and of multilayer type, which consists of the adsorption on clean pore surface, i.e. the primary adsorption, and that on preadsorbed pore surface, i.e. the secondary one. The adsorption isotherm was high affinity type. The adsorption rate was proportional to the feed rate of BSA, and the proportional coefficient was dependent on the adsorption process. The flux decline was correlated quantitatively with the amount of adsorbed BSA from the pore radius narrowing model by adsorption.

Comparison of Polytetrafluoroethylene Flat-Sheet Membranes with Different Pore Sizes in Application to Submerged Membrane Bioreactor

This study focused on phase separation of activated sludge mixed liquor by flat-sheet membranes of polytetrafluoroethylene (PTFE). A 20 liter working volume lab-scale MBR incorporating immersed PTFE flat-sheet membrane modules with different pore sizes (0.3, 0.5 and 1.0 μm) was operated for 19 days treating a synthetic wastewater. The experiment was interrupted twice at days 5 and 13 when the modules were removed and cleaned physically and chemically in sequence. The pure water permeate flux of each membrane module was measured before and after each cleaning step to calculate membrane resistances. Results showed that fouling of membrane modules with 0.3 μm pore size was more rapid than other membrane modules with different pore sizes (0.5 and 1.0 μm). On the other hand, it was not clear whether fouling of the 0.5 μm membrane module was more severe than that of the 1.0 μm membrane module. This was partly because of the membrane condition after chemical cleaning, which seemed to determine the fouling of those modules over the next period. When irreversible resistance (Ri) i.e., differences in membrane resistance before use and after chemical cleaning was high, the transmembrane pressure increased quickly during the next period irrespective of membrane pore size.

Separation Properties of Wastewater Containing O/W Emulsion Using Ceramic Microfiltration/Ultrafiltration (MF/UF) Membranes

Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from these systems. Membrane filtration has large potential for the efficient separation of O/W emulsion for reuses of treated water and detergent. The separation properties of O/W emulsions by cross-flow microfiltration and ultrafiltration were studied with ceramic MF and UF membranes. The effects of pore size; applied pressure; cross-flow velocity; and detergent concentration on rejection of O/W emulsion and flux were systematically studied. At the condition achieving complete separation of O/W emulsion the pressure-independent flux was observed and this flux behavior was explained by gel-polarization model. The O/W emulsion tended to permeate through the membrane at the conditions of larger pore size; higher emulsion concentration; and higher pressure. The O/W emulsion could permeate the membrane pore structure by destruction or deformation. These results imply the stability of O/W emulsion in the gel-layer formed on membrane surface play an important role in the separation properties. The O/W emulsion was concentrated by batch cross-flow concentration filtration and the flux decline during the concentration filtration was explained by the gel- polarization model.

Membrane Separation in Bioseparation

Membrane separations are widely used in bioseparation processes. Bioseparation processes consist of the following four processes, that is, cell harvesting/removal of cell debris, concentration, purification and polishing. In these separation processes microfiltration (MF) is used in removal of cells or cell debris, ultrafiltration (UF) in concentration of biomaterials of high molecular weight and biomass, reverse osmosis (RO) including nanofiltration (NF) in concentration of organic acid, amino acid and saccharide, and electrodialysis (ED) in desalting. Besides the conventional applications mentioned above, more sophisticated membranes, membrane modules and equipments are developed and utilized. In this report the following topics are reviewed ; 1) the rotating membranes and their filtration performances in the separation of cells or cell debris, 2) the hybrid membrane separation of cell debris combined with centrifuge, 3) application of adsorptive membranes for affinity separation and membrane chromatography, 4) pervaporation of aroma compounds and 5) membrane extraction.