Disposal of organic wastes is a social problem of high importance. We previously reported on a decomposition system of organic wastes by the use of thermally excited holes in TiO2 at high temperatures. An appealing feature of our system is that it makes use of a great number of holes formed at, for example, 350°C. In the present investigation, characterization has been carried out on various TiO2 powders that have nearly the same composition but differ in specific surface and particle size in an attempt to screen and select the most powerful powder. The decomposition ability of TiO2 has been evaluated using previously investigated polycarbonate (PC)-coated TiO2 as the model system, with special attention to the interaction between the adsorbate (PC) and the adsorbent (TiO2). As a result, the specific surface was found to play the most important role, and is closely linked to the adsorption amount of PC on TiO2, released energy, spin concentration, deep coloration, as well as to the Raman peak-shift. In addition, the crystallinity is also found to be effective in connection with the lifetime of holes.
Previously involved in complete decomposition (H2O + CO2) of organic wastes (mainly thermoplastic and thermosetting polymers), as well as exhaust of diesel engines by the use of thermally generated holes in TiO2 at about 350–500°C under sufficient O2. Then, we struck on an idea that H2 can be produced in place of H2O under O2-deficient conditions. Because of this, an attempt has been made in the present investigation to produce hydrogen from methanol or methane. Hydrogen is found to be successfully produced from methanol at 350–400°C under 5–20% O2, or from methane at 450–500°C under 50% O2. The conversion efficiency amounts to about 70–85% for methanol while about 40% for methane.
The effects of the synthesis conditions on the size and morphology of silicon dioxide particles prepared in a plasma field were investigated systematically. In this study, silicon dioxide particles were synthesized by a plasma reaction of a mixture of tetraethylorthosilicate and oxygen in a coaxial-type nonequilibrium plasma reactor. Since particles suspended in a nonequilibrium plasma field are known to be charged unipolarly (negatively), the generation of agglomerated particles is expected to be suppressed. An increase in the rf power not only accelerated the plasma reaction, but also enhanced the formation of agglomerated particles. This is considered to be caused by the generation of smaller primary particles with increasing rf power, which led to insufficient particle charging in the plasma. The diameter of the synthesized particles decreased with decreasing residence time. In this case, nonagglomerated particles with a size of less than 10 nm could be produced, in contrast to those in the case of increased rf power. The effects of the precursor concentration on the particle characteristics were also examined. An increase in the precursor concentration resulted in smaller primary particles. In this case, the coagulation between small, and thus insufficiently charged, primary particles were considered to be predominant. Under selected operating conditions, nonagglomerated particles with a diameter of up to 50 nm could be prepared.
Adsorption experiments with chromate ions were carried out employing iron oxyhydroxides (α-, β-, and γ-FeOOHs) in the presence of a weathered granite soil (Masatsuchi) and a clay. The Cr(VI) uptakes on FeOOHs increased with a decrease in pH and attained a plateau value under acidic conditions (pH = 3–5). The Cr(VI) uptakes by α- and γ-FeOOH increased in the presence of the clay, but not significantly in the presence of the Masatsuchi. The Cr(VI) ions were reduced to Cr(III) ions on reaction with organic materials leached from the soil materials to form Cr(III) hydroxides and to precipitate with the FeOOHs. On the other hand, the Cr(VI) uptake by β-FeOOH decreased in the presence of the soil materials; this is presumably due to the competitive interaction with the PO43– ion leached from soil materials. Oxyanions such as SO42– and PO43– and reducing reagents such as SO32– and Fe2+ result in the reduction of the Cr(VI) anions to afford Cr(III) cations, thus interfering with the Cr(VI) uptake by FeOOHs.
The heat transfer performance of a microtube was experimentally investigated to verify its suitability as a temperature control device for supercritical water (SCW) reactions under high-pressure and high-temperature conditions (pressure: 23–45 MPa, temperature: 673–773 K, flow rate: 0.6–4.6 kg/h). The microtube was made of Ni-base alloy 625 and had a microchannel with an internal diameter (ID) of 0.258 mm. Ohmic heating was employed for elevating the temperature of the microtube. Using purified water as the operating fluid for thermal performance evaluation, rapid and effective fluid heating from room temperature to 673 K within 0.05 s was achieved inside the heater and heat exchanger, respectively. The electrical power input was converted to fluid enthalpy by the microtube heater with a thermal efficiency of 75–95%, heating rate of 104–105 K/s, and an overall heat transfer coefficient of 4950–35400 W/(m2 K). Experimental results indicate that the microtube is useful as a temperature control device, and the rapid and effective turbulent heat and mass transfer in the microchannel is suitable for the high-speed temperature control required for SCW reactions.
The kinetics of anodic oxidation of sodium gluconate was studied. The reciprocal of apparent current shows the reciprocal dependence on the concentration of sodium gluconate. The kinetic model correlated well with the experimental results. The rate determining step was found to be the anodic oxidation of gluconate anion to form gluconate free radical. The current of the anodic oxidation of sodium gluconate can be expressed as
i = 0.89[NaC6H11O7]/(0.7357 + [NaC6H11O7])*exp(0.37Fη2/RT)
where F is Faraday’s constant and η2 is the overpotantial of forming gluconate free radical from gluconate anion.
An anodic alumina supported nickel catalyst (Ni/Al2O3/Alloy) was synthesized using a double impregnation method with a high temperature calcination in between, to investigate reactivity performance thereof during steam reforming of methane (SRM) reactions in continuous and daily start-up and shut-down (DSS)-like operations. The catalyst was structurally characterized using X-ray diffraction (XRD), BET and temperature programmed reduction (TPR) technologies. The TPR results showed that almost all nickel content from the first impregnation was transformed into nickel aluminate, whereas nickel from the second impregnation predominantly existed in the more reducible forms of NiO and xNiO·Al2O3 (x < 1). The existence of these NiO and NiAl2O4 phases was identified by XRD. The catalyst provided high and stable SRM reactivity near the equilibrium value, while no deactivation was observed in continuous durability testing for 200 h at 800°C and 130 h at 700°C, and in DSS-like mode operation at 700°C. The investigation of the influence of methane and/or steam treatments on the reactivity of Ni/Al2O3/Alloy showed the catalyst is not disturbed by the methane treatment, whereas it is remarkably deactivated by the steam treatment. In addition, no differences in the reduction effect were found when using hydrogen or methane to regenerate a steamed catalyst.
The growth of the basidiomycete Coriolus hirsutus on soil has been studied in a series of experiments. When the soil was polluted with bisphenol A, elimination of the chemical from the soil was completed for 99% by the 30th day by using an aqueous solution of MYG medium for water content control and setting a well mixed condition of soil. For achieving higher growth rate and larger colony of the fungus on soil, it was found to be necessary that the water content control liquid includes a sufficient amount of nutrients. Microscopic observation on hyphae growth on agar showed that glucose concentration positively influenced on the rate of hyphal tip extension and the colony diameter. Evidence was presented that the removal of bisphenol A from contaminated soil was elevated by increasing the growth of C. hirsutus on soil.
Numerical analyses were conducted for competitive-consecutive reactions in laminar flow to clarify the mechanism responsible for improvements to product yield with microreactors. The conservation equations of species were non-dimensionalized to derive the dimensionless numbers that governed the flow and reaction in microchannels. Three dimensionless numbers were derived: Peclet number Pe, i.e., the ratio of the diffusion time to the convection time, mixing-reaction number φ, i.e., the ratio of the diffusion time to the reaction time, and K, i.e., the ratio of the secondary reaction rate constant to the primary reaction rate constant. As a result of the numerical analyses of the competitive-consecutive reactions for multilayer laminar flow in microchannels, under conditions where convection was more dominant than diffusion Pe > 10, the product yield of the primary reaction depended on φ and K. A diagram to evaluate product yield was prepared using φ and K. The product yield increased with decreasing φ and K.
The effect of device-downsizing upon the continuous extraction of bovine serum albumin (BSA) in an aqueous two-phase system was studied. BSA molecules in the aqueous solution of polyethylene glycol (PEG) were partitioned into that of dextran (Dex) through μm- or mm-sized two-phase flow systems in circular capillary tubes. Mathematical model of BSA extraction kinetics was formulated with dimensionless forms. Four effects of device-downsizing were observed. First, downsizing enlarged the specific interfacial area between a PEG-rich solution and a Dex-rich solution, and in turn, elevated overall volumetric mass transfer rates of BSA in the PEG-rich phase and in the Dex-rich phase. Second, downsizing enlarged the proportion of the cross section of the PEG-rich solution, and in turn, elevated the space-time of the PEG-rich phase flow. Third, downsizing reduced the delay space-time of mass transfer of BSA into the Dex-rich solution. Finally, downsizing enlarged the range of overall volumetric mass transfer rates of BSA extraction. The diminution in size of two-phase flow separator towards micron-size was found to be effective to increase the level of overall volumetric mass transfer rates of BSA extraction.
Dynamic interfacial tension (DIFT) is investigated experimentally for crude oil and several of different aqueous solutions such as alkaline, brine, polymer, and different types of surfactant solutions. A spinning drop tensiometer with high resolution color video camera was employed to measure DIFT. The aqueous solution of NaOH provides a strong effect for interfacial tension (IFT) over the concentration range of 0.1–5 wt%. It was found that 0.5–1.0 wt% NaOH is the optimum concentration range to provide the lowest IFT value of 0.09 and 0.05 mN/m, respectively. The presence of NaCl shows a strong effect on interfacial tension depending upon the NaCl concentration with an optimum concentration of 104 ppm which provides low interfacial tension of 5.78 mN/m after 5 min. The presence of Alcoflood polymer reduces IFT over a short period due to its physico-chemical effect. This study shows the importance of the alkaline presence within the aqueous phase of Alcoflood polymer to make sure that the IFT is sufficiently low. Different types of surfactant materials including non-ionic surfactant of Triton X-100, anionic surfactant of Aerosol OT, cationic surfactant of Hyamine 1622, and demulsifier of Alkan DE-316 were tested. Non-ionic surfactant of Triton X-100 provided the lowest IFT values among the tested surface active materials over the concentration range of 0.1–0.5 wt%.
A micro-flow system comprised of a fused-silica capillary and chemiluminescence detection was developed, in which a wide-bore hydrodynamic chromatography mode was first introduced into the system. The micro-flow system was run with a gravity method or pump flow method for feeding a carrier solution into the capillary. Oxalate–hydrogen peroxide chemiluminescence reaction was adopted as a detection technique. Fluorescent compound (fluorescein isothiocyanate; FITC) and FluoSphere fluorescent polymer particles with particle diameters of 0.02 μm and 1.0 μm were used as model samples in the present system. FITC and FluoSpheres (0.02 μm) with diffusion indexes greater than ca. 1 were delivered into the capillary with average linear velocities under laminar flow conditions, which led to a Gaussian peak on the chemiluminescence profile. On the other hand, FluoSpheres (1.0 μm) with a diffusion index of ca. 0.1 were delivered with the approximately maximum linear velocity and formed a non-Gaussian peak. The mixtures, FITC and FluoSpheres (1.0 μm) as well as FluoSpheres (0.02 μm) and FluoSpheres (1.0 μm), reflected the individual diffusion indexes, indicating two main peaks on the chemiluminescence profiles. An unexpected small Gaussian peak observed with the FluoSpheres (1.0 μm) sample was also observed.