A 120-nm silica suspension was permeated through a porous polyethylene (PE) hollow-fiber membrane, as was a solution of deformable elastic particles of poly(N-isopropylacrylamide) (PNIPAM) gel and dextran. The amount adsorbed and flux of permeation were analyzed with ordinary differential equations to obtain adsorption coefficients, maximum amounts adsorbed, and pore-narrowing factors. The thickness of the “silica-deposited layer” on the membrane was 1 μm. In a batch adsorption mode, 5.0 mg of PNIPAM gel and 30 mg of dextran were adsorbed on the PE membrane, with no adsorption on the silica. The PE membrane pores were narrowed by a secondary layer of adsorbed PNIPAM gel. When filtered through the silica-deposited layer, PNIPAM gel occupies gaps, resulting in a reduced permeation flux. Dextran passed through the silica-deposited layer and was partially adsorbed on the PE membrane. The modified membrane can control adsorption, filtration, and flux permeation, which leads to dynamic membrane separations.
Phycobiliprotein (PB) produced by cyanobacteria exhibits an anti-inflammatory effect and anticancer effect, and is expected to be applied as pharmaceuticals. In this study, a PB-containing solution from Nostoc commune was concentrated and separated by an ultrafiltration (UF) membrane module (nominal molecular weight limit (NMWL) 150 kDa, 30 kDa and 10 kDa). When the PB-containing solution was permeated through an UF membrane module of NMWL 10 kDa at 0.07 MPa, the total protein content was concentrated up to 10 times in 30 minutes. To simulate the change in the concentration for the concentrate in the scaled-up treatment, the parameters of the formed cake layer were determined by a mathematical model. The concentration performance of the UF membrane modules was evaluated using the obtained parameters, indicating that the 150 kDa NMWL UF membrane modules were able to concentrate 100 liters of PB-containing solution by 10 times in 15 hours. The 30 kDa and 10 kDa NMWL UF membrane modules showed the possibility of PB separation, as well as protein concentration. The productivity of PB calculated by flux and selectivity was highest for the 30 kDa NMWL UF membrane module.
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