This review describes the knowledge required for the development of new extractants for the platinum group metals (PGMs), along with the properties of the conventional and new PGM extractants. Understanding the extraction mechanism of the PGMs is absolutely essential for accelerating the development of new extractants. The structural information of the PGM complexes both in an aqueous chloride solution and organic solvent is useful to clarify the extraction mechanism, where recognizing the difference between the inner and outer coordination spheres of the PGM ion is needed. During the PGM extraction from acidic chloride media, the extraction reaction can be divided into two broad categories: coordinative and ion-pair. The coordinative and ion-pair extractions mainly occur in the inner and outer coordination spheres, respectively. Moreover, there are various important factors governing the extraction behavior: the HSAB rule, chelate or size recognition effect, synergistic effect, interfacial activity, hydrophobicity of the extractants, etc. As for the conventional extractants, the extraction properties of palladium, platinum and rhodium with commercially available extractants are described. Among the recent studies of the PGM extraction, the size recognition effect in the outer coordination sphere is featured. Our recent work regarding the new extractants for palladium and rhodium is outlined. The thiodiglycolamide compounds can selectively extract Pd(II) much faster and have a higher oxidation resistance than the conventional extractant, di-n-hexyl sulfide; the tertiary amine compounds containing N,N-disubstituted amide groups can extract about 80% of rhodium at 1 to 2 mol/L hydrochloric acid. This value is the highest ever obtained in rhodium extraction from relatively highly concentrated hydrochloric acid.
Recently, Water and gas pipes are developed frequently because of the increased urban population. When the underground piping is constructed, drawings and signs are needed to drill the ground. However, underground pipings and other buried objects are often buried in different locationscompared with drawings. Underground pipings, the rock and the gravel interfere with construction. It is necessary to avoid this situation. To determine the construction of underground pipes, the non-destructive imaging method previously detects the pipe inside the ground. This paper describes a system of ultrashallow underground imaging method using seismic reflection and seismic giant magnetostrictive transducer. We apply a surface wave analysis using a giant magnetostrictive transducer. We improve the accuracy of P wave velocity. For the high-efficiency setup and the underground imaging succeed. This system combines ultrashallow seismic reflection and the ultra-magnetostrictive transducer. It provides the practical system.
Laboratory experiments were conducted to investigate the behavior of CO2 microbubbles (MBs) and the process of CO2 dissolution under atmospheric pressure by injecting CO2 MBs into deionized water and groundwater. The number of CO2 MBs increased dramatically after starting the CO2 MB generator, thereby increasing the concentration of dissolved CO2. The concentration of dissolved CO2 induced by CO2 MB injection increased approximately four times more rapidly than when CO2 was bubbled. The concentration quickly reached a maximum value which coincides with the theoretical saturation concentration of CO2(aq) solution. Larger CO2 bubbles were injected after the CO2(aq) solution became saturated. The increase in the concentration of dissolved CO2 was accompanied by reductions in both the pH and the density of (CO3)2—. In addition, the high concentration of the CO2(aq) solution was maintained for a relatively long time. These experimental results will assist in developing a practical system for CO2 MB injection, which is a method developed in Japan for geologically storing CO2.
CO2 capture and storage (CCS) is one of the most effective countermeasures against the global warming. Although CO2 aquifer storage is considered a main stream as CCS technology, there is a possibility that the capacity of the aquifer storage is limited and may not sufficient to meet the target reduction of CO2 emission. Therefore, it is good to have other CCS options. In this study, we focus on CO2 storage in the form of gas hydrate. In this method, CO2 is injected into the sub-seabed sand sediments at the condition of low temperature and high pressure, under which CO2 hydrate can stably form. A large amount of CO2 is sequestered as hydrate in the sediments by the reaction with pore water. However, hydrate formation has a great risk to reduce permeability and this may lead to the blockage of gas flow. In order to ensure large sequestration space, it is important that gas front expands over a wide area with avoiding such large permeability reduction. In this study, at first, we conducted experiments, in which CO2 was injected into sand sediment and CO2 hydrate formed in the sediment, to understand the blockage phenomena. Next, based on the experiments, we modelled the gas-water two-phase flow with hydrate formation in the sand sediment and developed a one-dimensional numerical simulator. Finally, we simulated the two-phase flow under the experimental conditions and revealed the blockage mechanism due to hydrate formation.
The adsorption equilibrium tests on fluorine and boron were carried out using several soils (Kuroboku, Yellow brown forest, Kanuma and Peat). Then various analysis and considerations were done on the basis of the experimental results. Adsorbed amount of fluorine per unit mass of soil was ranged as Kuroboku ≒ Yellow brown forest > Kanuma > Peat. Adsorbed amount of boron per unit mass of soil was ranged as Yellow brown forest > Kuroboku ≒ Kanuma > Peat. It was clear that there was less correlation between the BET specific surface area of the soils and the adsorbed amount of fluorine or boron. The clear correlation between the content of individual element (such as Ca, Mg, Al, Fe and Si) in soils and the absorbed amount fluorine or boron could not be recognized. The quantitative correlation between total carbon content in the soils and the absorbed amount of fluorine or boron could not be also recognized. The applications of an ion exchange model and a surface complexation model to data obtained in this work were unsuccessful because of lack of measurement item. However, the application of Langmuir's adsorption equation to our data except some data was successful basically and the application of Frendlich's adsorption equation was successful significantly. It was clarified the adsorption isotherms of fluorine and boron on the soils are represented using Freundlich's adsorption equation and are unaffected by the mass ratio of soil to liquid. The adsorption coefficients and indexes of fluorine and boron were obtained by using Freundlich's adsorption equation. The utilization of the adsorption parameters makes it possible to estimate the adsorbed amounts of fluorine and boron on the soils or the dissolved concentrations of them into liquid phase.
XRD/XAFS analysis were conducted to investigate the As(V) co-precipitation mechanism with ferrihydrite (γ-FeOOH). In As(V) co-precipitation with ferrihydrite, XRD results showed that As(V) complexation to the surface of ferrihydrite was dominant when the initial molar ratio of As/Fe was less than 0.25, whereas surface precipitation of amorphous ferric arsenate was formed when the initial molar ratio of As/Fe was more than 0.5. Both of XANES and EXAFS analysis on K-edge of As showed As(V) co-precipitates with ferrihydrite was the mixture of As(V) adsorbed ferrihydrite and amorphous ferric arsenate. Molar ratio of amorphous ferric arsenate in As(V) co-precipitates was estimated to be more than 0.5 when the initial molar ratio of As/Fe was more than 0.5. These results are in good agreement with the XRD results. EXAFS analysis assuming one surface complex for As-Fe bond showed the coordination number of As to Fe in As(V) co-precipitates increased with increasing the initial molar ratio of As/Fe. Moreover, EXAFS analysis assuming three kinds of surface complexes for As-Fe bond showed the coordination number for 2.85 Å of the atomic distance of As-Fe increased and it for 3.24 Å of the atomic distance of As-Fe decreased with increasing the initial As/Fe molar ratio. All experimental data obtained in this study showed As(V) co-precipitation mechanism shifted gradually from As(V) complexation to the surface of ferrihydrite toward amorphous ferric arsenate with increase in the initial molar ratio of As/Fe.
At two different locations in Kitami City, Hokkaido, cracks have been found in bricks, seemingly due to frost damage. In this research, the mechanism of the occurrence of the cracks in the bricks has been looked into through field investigations and exposure experiment. The field investigations have revealed that some bricks located in sun-exposed areas have a higher frequency to crack and cracks occur in the protruded part of bricks. From the exposure experiment, cracks in the bricks have been found to occur in late winter from the end of February to the end of March. It has also been confirmed that the following unique temperature distribution exists when cracks occur in bricks; in late winter, bricks melt due to the daytime heat. If bricks do not melt completely during the daytime leaving some frozen parts and these remain overnight, the melted areas created during the daytime then refreeze surrounded by the frozen parts due to the low night temperatures. In this research, this frost damage caused by such temperature distribution has been defined as closed-type freeze-thaw phenomenon. From the above results, this article describes the mechanism of frost damage to bricks in Kitami City. The research results are considered useful when brick structures are built in cold regions like Hokkaido, ensuring the appropriate use of bricks.