Yasuzo Sakai

Reversible adsorption of calcium ions by imprinted temperature sensitive gels

With the aim of developing polymeric gels sensitive to external stimuli and able to reversibly adsorb and release divalent ions, copolymer gels of N-isopropylacrylamide (NIPA) and methacrylic (MAA) monomers were prepared. We chose calcium as a target divalent ion. Two MAAs form a complex with a calcium ion, and the NIPA component allows the polymers to swell and shrink reversibly in response to temperature. The adsorbing site develops an affinity to target ions when the adsorbing molecules come into proximity, but when they are separated, the affinity diminishes. To enhance the affinity to calcium, an imprinting technique was applied using Ca2+ and Pb2+ ions as templates in methylsulfoxide and dioxane media, respectively. The adsorption capacity of the imprinted gels was compared with that of the nonimprinted gels, and the effects of the templates, the solvents, and the amount of methacrylic monomers used in the synthesis and the medium temperature over the Ca2+ adsorption capacity of the gels from aqueou...

BOD sensor using magnetic activated sludge

Abstract A biochemical oxygen demand (BOD) sensor, consisting of a Pb(−)|NaOH|Pt|O 2 (+) electric cell, was constructed. The sensor is basically one application of a dissolved oxygen electrode. Magnetic sludge was prepared by mixing magnetite powder with acclimated activated sludge. A magnetic cathode, comprised of a Sm-Co magnet plated with platinum, was covered by a Teflon membrane; magnetic sludge was simply layered on the membrane by magnetic attraction. The magnetic sludge decomposed the BOD component with consumption of oxygen. The BOD could therefore be determined by measuring the electric current produced by the BOD sensor. This current was then converted into the concentration change of oxygen transported through the Teflon membrane from the magnetic sludge layer.

Immobilized enzyme reaction controlled by magnetic heating : γ-Fe2O3-loaded thermosensitive polymer gels consisting of N-isopropylacrylamide and acrylamide

Abstract Invertase and γ-Fe 2 O 3 (8–24%) were immobilized in a copolymer gel of N -isopropylacrylamide (NIPA) and acrylamide (AAm) ( NIPA AAm gel). Sucrose hydrolysis was studied using a column packed with NIPA AAm gel immobilized enzyme under exposure to a magnetic field (effective value 830 Oe, maximum value 1,170 Oe, 1.68–2.66 kHz). The column temperature rose from 24–25 to 31–56°C due to the heat generated from magnetic hysteresis loss. When the magnetic field was applied, the overall concentration of reducing sugars in the outlet solution increased initially and then decreased due to thermal shrinkage of the gel support. This result clearly demonstrates the potential utility of the present gel-entrapment system in the magnetic control of immobilized enzyme reactions.

Magnetic forced sedimentation of flocs in activated sludge supplemented with ferromagnetic powder of iron oxide

Aiming to increase the sedimentation rate of flocs prepared by the activated sludge process, the effect of the application of ferromagnetic powder of iron oxide (magnetic powder) and a gradient magnetic field on the sedimentation process was examined. The volumetric loading rate of Polypepton was kept to 200–1,000 mgl−1 d−1 during 7 d in the activated sludge supplemented with 2,000 mg l−1 of magnetic powder. When a gradient magnetic field was applied, the initial zone settling velocity in the case of the Polypepton loading rate of 1,000 mg l−1 d−1 was found to be 36 times faster than that in the case of the control.

Sewage Treatment under Conditions of Balancing Microbial Growth and Cell Decay with a High Concentration of Activated Sludge Supplemented with Ferromagnetic Powder

Abstract In order to decrease excess sludge production, the treatment of synthetic sewage was carried out under conditions of balancing microbial growth and cell decay with a high concentration of activated sludge supplemented with a ferromagnetic powder (magnetic sludge). The leakage of magnetic sludge was prevented by the combined treatment of magnetic separation and gravitational sedimentation. COD Cr , removal and effluent suspended solids concentrations were maintained at 85–94% and 5–24 mg l −1 , respectively, over 30 d. Meanwhile, mixed-liquor volatile suspended solids concentration in the aeration tank remained virtually constant and excess sludge was not produced.

Simultaneous removal of organic and nitrogen compounds in intermittently aerated activated sludge process using magnetic separation

Magnetic separation was introduced to an activated sludge process to improve the solid-liquid separation characteristics of the sludge. The process was operated with the intermittent aeration method and applied for the removal of organic matter and nitrogen in wastewater. The activated sludge supplemented with magnetite (Fe3O4) powder (magnetic sludge) exhibits a ferromagnetic property and deposited on the surface of magnetic disks due to magnetic force. The magnetic separation apparatus (composed of rotary magnetic disks and scrapers) separated treated water from the sludge suspension of 13–22 g VSS l−1 within 5 min. Compared with the sedimentational separation process, the magnetic separation technique showed better performance. Simultaneous removal of about 89% of TKN and about 92% of soluble CODCr in influent was performed under loading rates of 0.92 g CODCr l−1 d−1 and 0.10 g TKN l−1, respectively, with a non-aeration/aeration cycle of 40/20 min.

Enhancement of ethanol formation by immobilized yeast containing iron powder or Ba-ferrite due to eddy current or hysteresis

Abstract Heat generation due to eddy currents and hysteresis induced by alternating magnetic field was utilized for the enhancement of ethanol formation catalyzed by immobilized yeast. A gel containing 2% sodium alginate, 4.2% dry yeast and 15, 30 or 50% iron powder (or Ba-ferrite) was prepared in CaCl 2 solution to immobilize the yeast. The gel was cut into cylindrical pieces of φ 2 mm × 2 mm. The cylindrical pieces of gel were placed inside a column through which culture medium flowed at a constant temperature. The ethanol concentration increased by 12% with immobilized yeast containing 50% iron powder at 5,000 Hz and 200 Oe of alternating magnetic field due to eddy currents. A similar result was obtained (14% increase) using immobilized yeast containing 50% Ba-ferrite at 2,000 Hz and 400 Oe of alternating magnetic field due to hysteresis. These effects corresponded to a 4°C rise in temperature in the gel.

Simultaneous removal of organic matter and nitrogen from milking parlor wastewater by a magnetic activated sludge (MAS) process.

The magnetic activated sludge (MAS) process is a modification of the conventional activated sludge process to improve the solid-liquid separation characteristics. It was developed to reduce the production of excess sludge and the time required for the conventional activated sludge process. In this study, actual milking parlor wastewater was treated with a MAS process and no sludge was removed. The effectiveness of continuous aeration and intermittent aeration in removing organic matter and nitrogen were compared. Both processes were highly efficient at removing chemical oxygen demand (COD) (averaged 91% removal) and ammonium nitrogen (NH(4)-N) (averaged 99% removal). In marked contrast to the continuous aeration process, the 30-min aeration/90-min non-aeration cycle of the intermittent aeration process rapidly reduced the nitrate nitrogen (NO(3)-N) concentration to near-zero. This result indicates that NO(3)-N was almost completely denitrified via nitrite nitrogen (NO(2)-N) to nitrogen gas. Removal of organic material and nitrogen can be considered to have occurred simultaneously in the single tank of the MAS process.

Enhancement of enzyme reaction of magnetically anisotropic polyacrylamide gel rods immobilized with ferromagnetic powder and β-D-galactosidase in an alternating magnetic field

An immobilized polyacrylamide gel containing beta-D-galactosidase and Sr-Ba-ferrite was magnetized in a static magnetic field. The gel rods (10 mm long, O 2 mm) exhibiting magnetic anisotropy could move at lower than 100 Hz but not at higher than 250 Hz in an alternating magnetic field of 200 Oe. In case of immovability of gel rods, the apparent enzymic activity increased 3 times higher under exposure of an alternating magnetic field of 500 Oe (570 Hz). It could be explained that the ferromagnetic powder inside the gel might vibrate under the influence of elasticity of gel in the alternating magnetic field of 100 or 500 Oe and 0.2-12 kHz. This might facilitate faster diffusion of the substance inside the gel and transportation of the substrate and the product through the surface of gel. Consequently, the enzyme reaction was apparently activated.

Citric Acid Fermentation by Magnetic Drum Contactor : Use of Methanol and Ethanol for Higher Production

Use of methanol or ethanol in the magneto-biotechnological technique was found to be enhance citric acid production in a magnetic drum contactor operation with Aspergillus niger AJ 117173. Continuous and repeated-batch fermentations were conducted with the addition of 2% ethanol. Continuous fermentation for 50 d gave a better citric acid yield (85%) and average productivity (3.8 g.l(-1).d(-1)) than repeated-batch fermentation over 60 d (65%, 2.3 g.l(-1).d(-1)).