WATER DYANMICS: 3rd International Workshop on Water Dynamics
Hydrothermal Experiments for Understanding Chemical Reaction Diversity of Water / Rock Interaction under Sub‐ and Supercritical States833(2006); http://dx.doi.org/10.1063/1.2207061View Description Hide Description
Chemical reaction diversity was examined by hydrothermal experiments using batch and flow through type autoclaves. Dissolution experiments of granite and quartz with pure water up to 600°C and 60 MPa were carried out in order to evaluate chemical reaction under sub‐and supercritical conditions. The supercritical region up to critical point for water has been inferred to be a homogeneous state, which conforms to a true liquid phase, nor true vapor phase. In terms of dissolution of granite and quartz, the supercritical state, being artificially defined as higher pressures and temperatures of the critical point, can be subdivided into two apparent phases, comprising a ‘liquid‐like’ region and a ‘vapor‐like’ region. The critical point of various kinds of geofluid, which was composed from solution in H2O‐CO2‐X (NaCl) system was experimentally determined by visible type autoclave, attached with transparent sapphire windows. Chemical reaction diversity, depending on location of the critical point for a given solution and apparent phase boundary with respect to chemical reaction within the supercritical state, was recognized by hydrothermal experiments.
Effective Use of Low Temperature Heat Sources by Using Confined State of Water in Various Microporous Absorbents833(2006); http://dx.doi.org/10.1063/1.2207062View Description Hide Description
Energy saving is the most serious issue to sustain our life on the earth. Despite the limiting energy resources, we have been wasting enormous amount of heat from various places, such as factories, transportation systems and even houses, private or public. The exposed heat is difficult to use due to the nature of low temperature and low energy density, although the total amount is very large. We therefore lose much electric energy only to fell room temperatures by few degrees in summer, although electricity should be used for any other higher‐grade objects. Zeolite heat pump was proposed initially for effective use of low grade‐energy for cooling, such as air‐conditioning and refrigeration, but few practical application have been developed so far. Here, I emphasize that we have no other way except for using absorbing states of vapor in micro‐porous materials for effective energy‐conversion from the low grade‐energy. The zeolite‐water combination may be one of the most prospective pair for the object, because the energy state of water molecules in zeolites is so low even at the room temperatures as to be comparable to that of ice at 0K. Zeolite heat pump system should be recognized as a mechanism to extract energy from the low entropy state of zeolitic water.
833(2006); http://dx.doi.org/10.1063/1.2207063View Description Hide Description
ZnS shows high photocatalytic activity, nevertheless the operating wavelength is limited to less than 330 nm. On the other hand, CdS can be used at wavelength up to 512 nm. However, CdS requires Pt as supporting catalyst. We have synthesized Pt‐free Zn xCd1−xS particles with x varying between 0 and 1 by co‐precipitation method and evaluated their photocatalytic activities. The highest photocatalytic activity was recorded for Zn 0.67Cd0.33S particles. Then, Zn xCd1−xS solid solution films were prepared using the above particles by dip‐coating method and their photocatalytic activities were evaluated.
833(2006); http://dx.doi.org/10.1063/1.2207064View Description Hide Description
Global warming becomes more serious problem today. We have to develop new technology for new energy or fixation of carbon dioxide. Biomass is considered to be one of new energies. Methane fermentation is a method to make methane from biomass, such as garbage and fecal of farm animals, by methane fermentation bacteria. It has a problem, however, that bacteria are deactivated due to ammonia, which is made by itself. And much methane fermentation residue is incinerated. Therefore recycling methane fermentation residue is important for effective use of biomass. We research hydrothermal process. Dry steam means unsaturated vapor, we call. It demands a temperature less than 400 °C. And it is expected to accelerate dehydration effect, decompose and extract the organic matter, and make porous material. Thus, we try to apply the dry steam to recycling of organic waste sludge aiming for absorbent. Experiments were conducted at 250–350 °C in nitrogen atmosphere. The carbon products are analyzed by CHNS elemental analysis, and Thermogravimetry. The extractives are analyzed by gas chromatograph.
833(2006); http://dx.doi.org/10.1063/1.2207065View Description Hide Description
Cadmium Sulfide semiconductor has comparatively small band gap and act as photocatalyst under irradiation of visible light. For practical use, it is convenient to fix the photocatalyst on a substrate as a thin film. In this study, we prepared CdS thin film on Ti substrate by Chemical Bath Deposition (CBD). To improve photocatalytic activity, CdS film was annealed and optimum thickness was investigated.
Phase Formation from CaO‐Al2O3‐SiO2 Gels by Soft Hydrothermal Treatment and Their Ammonium and Phosphate Ions Uptake Properties833(2006); http://dx.doi.org/10.1063/1.2207066View Description Hide Description
Several gels in the system CaO‐Al2O3‐SiO2 were investigated under soft hydrothermal conditions. The gels were synthesized by co‐precipitation of Ca(NO3)2⋅4H2O, Al(NO3)3⋅9H2O and Si(OC2H5)4 and were reacted under the following hydrothermal conditions: sample/solution = 0.03, NaOH concentration = 4M, temperature = 110°C and duration = 24–192 hrs depending upon the phase formed. The phases formed by hydrothermal treatment varied according to the starting compositions, being (1) hydroxysodalite in SiO2‐rich compositions, (2) hydroxycancrinite in SiO2 and Al2O3‐rich compositions, (3) katoite in CaO and Al2O3‐rich compositions and (4) calcium silicate hydrate (C‐S‐H) in CaO and SiO2‐rich compositions. The C‐S‐H phase, which is more amorphous in nature, showed the greatest uptake of and .
Superparamagnetic Particle Size Limit of Mn‐Zn Ferrite Nanoparticles Synthesised Through Aqueous Method833(2006); http://dx.doi.org/10.1063/1.2207067View Description Hide Description
Mn0.67 Zn 0.33Fe2O4 nanoparticles with size ranging from 20 to 80 nm have been synthesized using the modified oxidation method. The Curie temperatures for all the samples are found to be within 630 ± 5 K suggesting that there is no size‐dependent cation distribution. Mössbauer studies on the synthesized nanoparticles suggest that the critical particle size limit for superparamagnetism to be about 25 nm at 293 K.
833(2006); http://dx.doi.org/10.1063/1.2207068View Description Hide Description
The concept of a georeactor in geothermal environment has been proposed for direct utilization of geothermal energy in the ground. Chemical processes in the georeactor must accommodate a range of operating conditions, because the georeactor utilizes natural resources that are sometimes difficult to control. Combination of hydrogen generation by solar energy from hydrogen sulfide, and reduction of waste sulfur and its compounds using geothermal energy is environmental energy supply system. The self‐oxidation and reduction of sulfur is the considered to be suitable for the thermal condition around 200 oC. In previous studies, the self‐oxidation and reduction of sulfur proceeded in neutral or alkaline solution. The amount of formed hydrogen sulfide in strong alkaline solution was larger than neutral solution. But it was difficult to use the strong alkaline solution for self‐oxidation and reduction of sulfur to georeactor. Therefore we applied the seawater for sulfur reduction because the seawater is alkalescent solution and it can be available at a low cost. In order to study a self‐oxidation and reduction of sulfur in seawater, we conducted the reaction between sulfur and seawater in hydrothermal conditions using a batch‐type autoclave. The maximum conversion rate of elemental sulfur to hydrogen sulfide with the reactions in seawater is almost 50 % and the highest concentration of formed hydrogen sulfide is 0.026 mol/l in the experiments.
833(2006); http://dx.doi.org/10.1063/1.2207069View Description Hide Description
Calcium hydroxyapatite, Ca10(PO4)6(OH)2:HA, is the inorganic principle component of natural bones and teeth. It has been already suggested that the amount of OH ion in the crystal structure of HA is closely related to the biocompatibility. The amount of OH ion in current HA, however, has not been controlled. In order to prepare more functional HA ceramics, the amount of OH ion must be controlled. In this study, HA ceramics with different OH amount were prepared from fine HA crystals by spark plasma sintering (SPS). In order to reveal the ideal sintering conditions for preparation of transparent ceramics, densification process on SPS was investigated. The samples were pressed uniaxialy under 60 MPa, and then they were heated by SPS at 800 °C, 900 °C and 1000 °C for 10 min with the heating rate of 25 °C⋅min−1. The quantity of OH ion in HA ceramics sintered by SPS was decreased with increasing temperature of sintering. Transparent HA ceramics were prepared by SPS at 900 °C and 1000 °C. In analysis of the densification behavior during sintering of HA by SPS, dominant sintering mechanism was plastic flow of densification. Transparent ceramics should be the most suitable materials to investigate the interface between human cells and ceramics.
833(2006); http://dx.doi.org/10.1063/1.2207070View Description Hide Description
As one of main biomass wastes in Japan, Sugi (Japanese cedar) leaves were chipped and treated for preparation of charcoal at mild temperature (250 – 450 °C) using superheated steam with controllable pressure. After the treatment, the solid residual charcoal was examined by FT‐IR and CHN elemental analysis. The results suggest that degree of carbonization was significantly affected by treating temperature, time and partial pressure of steam. A temperature above 400 °C and a partial pressure of steam above 4 MPa are necessary for accelerating and completing the carbonization within 2 hours. Adsorption experimental results of charcoal show that the residual charcoal has an excellent absorbability for ammonia gas and heavy metal ion Pb 2+. Therefore it is expectable to develop mild superheated steam as reaction medium for preparing valuable charcoal products from biomass wastes with lower energy cost.
833(2006); http://dx.doi.org/10.1063/1.2207071View Description Hide Description
Since bamboo is inclination material with pores of various sizes, there is possibility of the alternative adsorbents of substances. So, absorbents from bamboo are also expected as a material for cleaning water. However, activated carbon is expensive. Then, in order to reduce cost, it is necessary to develop a new carbonization process.
Here, we proposed the original process of carbonization by dry steam which set two generation processes to one. Its stage is simple and it is a reaction at low temperature (300 °C) compared with the generation method.
In this experiment, we developed non‐equilibrium reaction equipment and conducted by changing reaction conditions. Products were analyzed by the observation of their surface and weight change, and investigated the relation characteristic between reaction and water. Then, adsorption of chloroform onto the products was investigated.
As temperature became high, the weight loss became more remarkable with the dry steam. Therefore, it is supposed that dry steam is promoting the carbonization reaction. And the adsorption onto the product (at 300 °C) is higher than the activated carbon. It can be very significant, since it is a reaction in low temperature compared with the generation method.
833(2006); http://dx.doi.org/10.1063/1.2207072View Description Hide Description
Microstructure designed porous hydroxyapatite (Ca10(PO4)6(OH)2) composites with magnetite (Fe3O4) particles or anatase (TiO2) dispersion were prepared by hydrothermal treatment. These composites had micro‐pores of about 0.1–0.5 μm in size. Magnetite / Hydroxyapatite composites should be suitable for medical treatment of cancer, especially in bones, because HA can bond to bones directly and magnetite can generate heat. They must be used for hyperthermia therapies of cancer in bones. Meanwhile, anatase / Hydroxyapatite composite should be suitable for environmental purification, because HA rod‐shape particles expose the specific crystal face, which adsorbs organic contaminants and so on.
833(2006); http://dx.doi.org/10.1063/1.2207073View Description Hide Description
In this study, dense bulks of Y‐zeolite and mesoporous silica with significantly high specific surface areas were successfully synthesized by a hydrothermal hot pressing method to apply as a membrane filter media for the separation of CO2 or H2. Obtained Y‐zeolite bulks possessed the highly dense microstructure without pinhole, pores, and amorphous layer between zeolite grains. Mesoporous silica bulks had also dense microstructure and extremely high specific surface area over 1000 m2/g. The synthesis parameters for densification of Y‐zeolite and mesoporous silica by hydrothermal hot pressing treatments were examined. Their some properties and microstructures were evaluated.
833(2006); http://dx.doi.org/10.1063/1.2207074View Description Hide Description
The reductions of CO2 under hydrothermal conditions were investigated by using the micro autoclave (45cm3) lined with Hastelloy‐C alloy. Sodium hydrogen carbonate (NaHCO3) was used as a starting material. H2 gas was used as reducing agents. NaHCO3 powder, H2 gas and water put into the autoclave simultaneously. The autoclave was heated upto 300°C by induction heater. In this study, effects of pH value of the NaOH solution in the autoclave are investigated. Reaction products were analyzed with gas chromatographs (GC), liquid chromatographs (LC), X‐ray diffractometor (XRD) and Scanning electron microscopy (SEM). The following things were showed in this research: CO2 was reducted to HCOO− and CH4 at high conversion ratio under hydrothermal conditions. HCOO− was formed at high selectivity using Hastelloy‐C reactor in the alkaline solution with Raney Ni catalyst. Raney Ni was exellent methanation catalyst, and CH4 formation progressed via , not via CO. It is cleared that the NaOH solution in the autoclave should be kept pH value 11.0 for the highest conversion ratio from CO2 to useful carbonic compounds (CH4, HCOO−).
833(2006); http://dx.doi.org/10.1063/1.2207075View Description Hide Description
The synthesis of Cu doped ZnS particles by ion‐exchange method and the influence on workable wavelength of light is reported. The workable wavelength of Cu doped ZnS was extended from the same of ZnS (310 nm). The photocatalytic activity of Cu doped ZnS was measured by hydrogen generation experiment using solar simulator and the highest apparent quantum yield was about 11% given from 1% Cu doped ZnS.
833(2006); http://dx.doi.org/10.1063/1.2207076View Description Hide Description
Ceramics is rigid and brittle originally. If the weakness could be overcome, the application will be widely expanded. Itacolumite known as high flexibility rock is the group of sand stone which consist of quartz and slight amount of muscovite. The microstructure of itacolumite has a lot of narrow gaps between the grains, the gap was thought to be formed by the dissolution of minerals in between quartz grains into the groundwater. This narrow space enables a little displacement of the particles, and the rock can bend with stress like plastic deformation. These characters of itacolumite showed the new ceramic functions such as stress relaxation properties and high damping capacity (internal friction Q−1=0.03). The authors tried to develop high damping ceramics by the mimic of itacolumite, and found the Al2O3‐TiO2‐MgO ceramics. The ceramics had stress relaxation properties and high damping capacity (Q−1=0.01) since microcracks were formed during sintering by the discontinuous grain growth and the anisotropic thermal expansion in the cooling process.
833(2006); http://dx.doi.org/10.1063/1.2207077View Description Hide Description
A novel metal nanoparticle synthesis method has been developed, in which metallic Ni nanoparticles with an amorphous‐like structure were selectively deposited on TiO2 fine particles through the reduction from the liquid phase. The addition of Zn proved to decrease the nanoparticles size, leading to the increase in the total area of catalytically active Ni surface. In addition, nanoparticles were highly stabilized by the deposition on TiO2, so that the catalytic activity of Zn‐added TiO2‐supported Ni nanoparticles (Ni‐Zn/TiO2) in the 1‐octene hydrogenation was ca. 10 times higher than that of unsupported Ni nanoparticles.
833(2006); http://dx.doi.org/10.1063/1.2207078View Description Hide Description
Hydrothermal treatment of sludge from a sewage treatment plant was conducted to obtain useful ingredients for culture of specific microbes which can reduce polysulfide ion into sulfide ion and/or hydrogen sulfide. Several additives such as acid, base, and oxidizer were added to the hydrothermal reaction of excess sludge to promote the production of useful materials. After hydrothermal treatment, reaction solution and precipitation were qualitatively and quantitatively analyzed and estimated the availability as nutrition in cultural medium. From the results of product analysis, most of organic solid in sewage was basically decomposed by hydrothermal hydrolysis and transformed into oily or water‐soluble compounds. Bacterial culture of sulfate‐reducing bacteria (SRB) showed the good results in multiplication with medium which was obtained from hydrothermal treatment of sewage sludge with magnesium or calcium hydroxide and hydrogen peroxide.
833(2006); http://dx.doi.org/10.1063/1.2207079View Description Hide Description
To gain a new carbon resource and to decrease the CO2 emission are important task for sustainable development. As a mean for those, we had proposed a process for the reduction of CO2 by hydrothermal method. In this process, CO2, aqueous solution, and reductant are to react under hydrothermal condition, to generate organic compounds. This report is focused on the application of this process to continuous‐type process. In experiments, newly developed continuous‐type equipment has been used. In experiments, carbon steel cutting chaff as a reductant and Ni powder catalyst are settled in the reactor. CO2 gas and solvent were injected continuously into the heated and pressurized reactor. Initial materials are to react under hydrothermal conditions at 200 °C and 2.0 MPa. During the experimental period, reaction gas and liquid are collected successively. The samples are analyzed with GC and TOC. In treatment without Ni powder, organic compound was detected in neither reaction gas nor solution, while the occurrence of CO was confirmed. On the other hand, in the experiment with Ni powder additionally, formic acid was generated. It has been confirmed that the reaction process proceeds even in the continuous‐type treatment including the catalytic effect of Ni.