Nobuyuki Fujii

Ultrasound-enhanced membrane-cleaning processes applied water treatments: influence of sonic frequency on filtration treatments.

Ultrasound (US) cleaning technique was applied to remove fouling of ultrafiltration (UF) and microfiltration (MF) membranes which were used to treat peptone and milk aqueous solutions, respectively. Membrane operations were performed by cross-flow filtration with 60 kPa operating pressure in an US field. The US employed had 28, 45 and 100 kHz frequency with 23 W/cm(2) output power. For each polymeric membrane made of polysulfone UF and cellulose MF, cleaning experiments were carried out with and without US after fouling. The fouled UF and MF membranes showed volume flux decline, but the membrane property was recovered by US irradiation. It was found in 28 kHz frequency that water cleaning was effective for recovery of declined condition due to fouling. Also, US-enhanced permeability of membranes was discussed in both membrane systems. We observed that US decreased the fouling condition in both membrane systems when US was irradiated before fouling. It was found that 28 kHz frequency US could enhance formation of the fouled layer in both filtration systems of peptone and milk solution.

Ultrasound effect on cross-flow filtration of polyacrylonitrile ultrafiltration membranes

Ultrasound effects on permeate flux and rejection of solute were studied by using two types of polyacrylonitrile (PAN) ultrafiltration (UF) membranes reinforced with non-woven cloth. The membrane was set in cross-flow UF cell and the filtration was carried out by permeating 1 wt% dextran solutions under 30 kPa until steady-state flux was obtained. Then, ultrasound with 45 kHz of frequency was irradiated on the UF cell in water. It was found that the ultrasound irradiation significantly increased the permeate flux of different molecular weight (MW) dextran solutions. Evidence was presented that ultrasound irradiation was effective to enhance the membrane permeate flux for dextran solution.

Molecular imprinting of caffeine and its recognition assay by quartz-crystal microbalance

Phase inversion precipitation method was applied to prepare molecularly imprinted polyacrilonitrile (PAN) copolymers. Three types of PAN copolymers with pyridine and styrene moieties were used for caffeine (CAF) imprinting. For encoding shape of the template molecules into the polymer, polymer solution involving the template molecule was coagulated in water non-solvent. After the template extraction from the resultant polymer, binding amounts of CAF and CAF analogous molecules to the CAF-imprinted polymer were evaluated by using 6 MHz quartz-crystal microbalance (QCM). As QCM attached with CAF-imprinted polymer was immersed into CAF solution, the QCM frequency decreased and then saturated at constant value. We demonstrated recognition properties of the CAF-imprinted polymers by observation of the frequency change for various imprinted and unimprinted polymers. It was observed that PAN copolymer having 4-vinylpyridine (4-Py) moieties showed a large difference of the frequency decrease between the imprinted and unimprinted polymers. Evidence was presented that the CAF-imprinted polymer having 4-Py moieties highly recognize CAF molecules. Also, the selectivity of the CAF-imprinted polymers was investigated using CAF analogous molecules.

Heterogeneous photocatalytic synthesis of ammonia from water and nitrogen

Abstract Photocatalytic synthesis of ammonia from water and nitrogen was performed. Binary wafered catalysts prepared with semiconductor powder (TiO2, SrTiO3, CdS or GaP) and platinum black, where the copolymer of ethylene and vinylalcohol was used as a binder, were found to be more effective to yield ammonia than the semiconductor powders alone.

Molecular imprinted Nylon-6 as a recognition material of amino acids

Abstract Nylon-6 was functionalized by phase inversion molecular imprinting technique to introduce l -glutamine recognition property. For imprinting l -glutamine in the polymer, 20 wt.% of Nylon-6-formic acid solution with 8 wt.% of l -glutamine template was used for the phase inversion process in water. The resulted polymer including the template molecule was washed with acetic acid solution to extract the template from the polymer. The substrate binding experiments of the l -glutamine imprinted polymer were examined in aqueous l -glutamine, d -glutamine, l -glutamic acid, and d -glutamic acid solution. The binding of l -glutamine increased with the increase of the amino acid concentration from 5 to 20 μM. The value of equilibrium binding constant for l -glutamine, KE=4.9×105 M−1, was larger than that for d -glutamine, KE=1.5×105 M−1. The recognition experiments were extended to membrane filtration and quartz-crystal microbalance response by using the imprinted Nylon-6. Evidence was also presented by FT-IR analysis that the amide–hydrogen-bonding interaction between the imprinted Nylon-6 and template was originated for the amino acid recognition.

A kinetic study of the thermal decomposition of polyesters by controlled-rate thermogravimetry

A kinetic study of the thermal decomposition of engineering polyesters has been made by means of controlled-rate thermogravimetry (CRTG), a procedure that is a part of controlled-rate thermal analysis (CRTA). Various decomposition rates were used in the constant decomposition rate control (CDRC) experiments, in order to estimate the apparent activation energy without prior knowledge of the actual mechanism. The kinetic equations governing the thermal decomposition of poly(ethylene terphthalate) (PET) and poly(butylene terphthalate) (PBT) were determined. The kinetic parameters of these polyesters were estimated from both, the CDRC curve and evolved-gas components, obtained from the simultaneous TG-MS system, and corresponding to a kinetic-model-supported random scission of the main chain and with L=2. It is concluded that analytic techniques using the thermogravimetric traces obtained from different decomposition rates at CDRC are capable of establishing unique kinetic parameters. CRTG (CRTA) offers significant advantages in this field of study when dealing with thermal decomposition of polymers.

Recognition characteristics of dibenzofuran by molecularly imprinted polymers made of common polymers

Dibenzofuran (DBF) recognition was studied by a molecularly imprinted polymer (MIP) made of commercially available polymers: polyvinyl chloride (PVC), polysulfone, polystyrene, and polyacrylonitrile. Preparation of MIPs was carried out by phase inversion of the polymer. Respective polymer solutions were coagulated with DBF template in water (non-solvent). In addition, reference polymers without the template were prepared in same manner as unimprinted polymers. After the DBF template was extracted from the solidified polymers by washing with methanol (MeOH), recognition experiments of DBF by the imprinted polymers were carried out for DBF in MeOH solutions. Equilibrium constants for DBF were calculated from saturation binding kinetics. Equilibrium experiment results reveal that recognition was effective for DBF binding to the DBF-imprinted polymer, especially for the imprinted PVC.

pH effect on molecular size exclusion of polyacrylonitrile ultrafiltration membranes having carboxylic acid groups

Polyacrylonitrile copolymer membranes with filtration performance controlled by pH were prepared by phase inversion technique. The pH sensitive molecular sieve effect on transport of macromolecular solute was compared in both copolymer membranes having acrylic acid (AA) and methacrylic acid (MA) segments. The water permeation rate through the membranes was remarkably decreased by the surrounding pH change from acid to alkali condition. The molecular weight cut-off data obtained by the dextran permeation at pH 4, 6 and 10 indicated that pore size of the membrane is significantly reduced in the alkali condition. Without and with 0.1 M NaCl in the permeate solution, different molecular sieve effects were observed in the copolymer membrane with the AA segments, whereas the membrane with MA segments made no significant change. Evidence was presented that the carboxylic acid segmental conformation is associated with the pH sensitive molecular sieve effect of the copolymer membranes.

A combined thermogravimetric-gas chromatographic/mass spectrometric analysis (TG-GC/MS) using a high resolution TG technique☆

A new combination system of TG-GC/MS using high resolution TG technique is reported. The present high resolution TG technique is a dynamic rate control (DRC) method that belongs to the controlled rate thermal analysis (CRTA). In this technique, the heating rate of the sample is dynamically and continuously varied in response to changes in the samples decomposition rate. In the present study, the performance and applicability of this system is illustrated by using the thermal decomposition of polyimide/polytetrafluoroethylene/graphite (PI/PTFE/GR) resin. The presented data demonstrate that this novel feature improves resolution and enhances the accuracy of identification and quantification. It is concluded that the present method gives more detailed information than that obtained from the conventional method, even for materials decomposing through consecutive and close-lying reactions.

Shock tube study of the rate coefficient of H + O2 → OH + O

Abstract The H + O 2 → OH + O reaction was reexamined by monitoring OH radical concentrations using cw UV laser absorption spectroscopy in H 2 -O 2 -Ar test gas heated by 1850-3550 K shock waves. The rate coefficient expression (1.0 ± 0.1) × 10 14 × exp(−7690 ± 250 K/T) cm 3 mol −1 s −1 was derived. Fitting the present data together with those of Shin and Michael [J. Chem. Phys. 95 (1991) 262] gave k 4 = (7.6 ± 0.7) × 10 13 exp(−7065 ± 140 K/ T ) cm 3 mol −1 s −1 for the temperature range 1100–3550 K. The reverse reaction rate coefficient was found to be (9.3 ± 0.8) × 10 12 cm 3 mol −1 s −1 independent of temperature from 1850 to 3550 K.