We propose an original system to measure two transport properties of aqueous solutions, diffusion coefficient and Soret coefficient, in the same optical system by using laser holography real-time interferometry. First, the validity and reliability of this measurement method were examined. Diffusion coefficients were calculated for NaCl and KCl solutions by using the time variation of the thickness of the interference fringes, since the analytical solution of the diffusion equation follows a normal distribution, and the results were in good agreement with the literature value. The Soret coefficients were calculated for NaCl solutions from the position of the interference fringes at a certain time, the analytical solution of the diffusion equation including the thermal diffusion term, and the diffusion coefficient calculated above, and were in good agreement with the measured values in previous studies. After confirming the validity of the results, both transport properties were measured in a Na₂CO₃ solution of 10 wt%, for which there are few literature values. In addition, the error factors for this measurement were clarified, and the uncertainty ranges of the measurement value were estimated. The present method utilizes the relationship between the refractive index of the solution, temperature, and concentration to analyze the interference fringes that coincide with the isorefractive index line, which simplifies the calculation of the diffusion coefficient and Soret coefficient compared to existing methods.

Approximately 13,000,000 m³ of cesium-contaminated soil has been generated since the Fukushima nuclear power plant accident, and the volume of this waste needs to be reduced. To remediate the contaminated soil so it is suitable for recycling, approximately 70% of the Cs must be removed. Solid–liquid extraction is one method used for separation of Cs from soil, but it creates Cs-contaminated wastewater that requires further treatment. In solid–liquid extraction, the Cs is mainly adsorbed by a layered mineral, such as vermiculite (VRM), and then desorbed using a salt solution. The percentage of Cs desorbed does not reach 70%; therefore, improved methods are required for treatment of Cs-contaminated soil. In this study, we propose a method for remediation combining classification, magnetic separation, and liquid–liquid extraction in addition to solid–liquid extraction with a salt solution. The objective of this study was to evaluate the Cs removal performance of this method using simulated soil. In extraction experiments with various salt solutions, the optimum extractant was an aqueous solution containing K⁺ ions. The change in Cs desorption with time for each mineral was measured using a KCl solution and fitted with a three-site desorption model. The desorption rates were lower for minerals containing frayed edge sites (FES). Approximately 70% of the Cs was removed from the simulated soil with the combined unit operations. Magnetic separation combined with solid–liquid extraction was effective for remediation of contaminated soil. Because Cs moves to FES and porous structures in the soil with increases in the adsorption time, the Cs desorption rate for minerals with FES decreased with increasing adsorption time. The Cs removal performance of this remediation method may be lower in contaminated soils with low levels of Cs adsorption. In this case, the desorption rate could potentially be improved by altering the solid–liquid extraction conditions; however, this needs to be explored further.

Perfluorosulfonic acid membranes are widely used in membrane dehumidifiers because of their high water vapor permeance, but the permeance is strongly dependent on operating temperature and relative humidity. In this study, based on the water vapor permeance of a perfluorosulfonic acid membrane measured in a quasi-equilibrium state using a single capillary membrane over a wide range of temperature and relative humidity (10–40°C, 0–90% RH), the water vapor permeance was formulated, and the simulation was applied to the dehumidification performance of commercial perfluorosulfonic acid membrane dehumidifiers. The simulation target was not limited to a single capillary module operating over a wide range of operating temperature and humidity conditions; for use in practical applications, external and self-sweep simulations were performed in a multi-capillary module. Good agreement between experimental and calculated values was obtained in the comparative verification of the relative humidity at each outlet.

The influences of the weighing tool shape and vessel shape in the buoyancy weighing-bar method for size distribution measurement of floating particles were experimentally investigated. Hollow glass beads were used as floating particles. The floating particle size distributions were measured using different combinations of weighing tools (rod, square rod, or sheet) and vessels (square vessel or graduate cylinder). When the graduated cylinder was used as the vessel, the floating particle size distribution could be measured using the square rod or sheet as the weighing tool. When the rod was used as the weighing tool, the floating particle size distribution could be measured using the square vessel. The location of the weighing tool did not influence the particle size distribution.

We investigated the dry reforming of methane using a spouted bed DBD plasma reactor filled with 212–500 µm alumina and zeolite as catalysts. The effects of plasma conditions such as frequency, applied voltage, electrode position, presence of catalyst, and flow state of catalyst particles on the conversion ratio of reaction gas and selectivity of produced gas were evaluated experimentally. Dry reformation of methane was possible by using DBD plasma, and the conversion ratio varied greatly depending on the plasma conditions. By increasing the applied voltage from 7 to 13 kV, the CO₂ conversion ratio was increased by a factor of 8.6. The conversion ratio was increased by increasing the frequency and could also be improved by adjusting the electrode position. It was found that the gas flow rate had the greatest effect on the conversion ratio, and that the conversion rate decreased semi-proportionally as the gas flow rate increased. The conversion ratio also differed greatly depending on the flow state of the catalyst, and the highest conversion ratio was obtained under the fixed bed condition. However, in the fixed bed, the electrode temperature increased rapidly with the rapid increase in power consumption, and stable modification was difficult. On the other hand, a decrease in conversion ratio due to plasma deactivation under the spouted bed condition was confirmed. However, it was found that the conversion ratio can be improved and stable operation is possible if the gas flow rate allows good contact between the plasma and the catalyst particles.

Disodium hydrogen phosphate dodecahydrate is a latent heat storage material that is expected to be applied to indoor air conditioning and floor heating, but the heptahydrate is stable at above the melting point of the dodecahydrate and can therefore crystallize and accumulate in the melt of the dodecahydrate during a long-term thermal cycle of heat storage and heat release, thereby reducing the latent heat of storage material. To avoid such phase segregation, an excess amount of water is generally added relative to the liquidus line of the heptahydrate on the phase diagram, but this has the drawback of reducing the latent heat. In addition, it is extremely difficult to predict the transient behavior of phase transition of the heptahydrate during heat storage and heat release by means of the phase diagram in the equilibrium system. In this study, to make clear the correspondence between the phase transition behavior of the material and the phase diagram, thermal cycle tests in the temperature range of 243–353 K were performed on aqueous solutions of 24.7–52.9 wt% disodium hydrogen phosphate, and phase change behaviors were observed from the obtained cooling and heating curves. Three crystal phases were identified, namely, a eutectic mixture of dodecahydrate and water, dodecahydrate, and heptahydrate, and their melting points were in agreement with the phase diagram. However, the positions of the liquidus lines of dodecahydrate and heptahydrate were different from the phase diagram, indicating that they were on the higher concentration side.