A computational fluid dynamics（CFD）method coupled with a ternary phase diagram is developed to simulate anti-solvent crystallization. As a model case, KCl–ethanol anti-solvent crystallization in a Y-shaped mixer was adopted for this study. Flow and mass concentration in the Y-shaped mixer are simulated using CFD. Local supersaturation is calculated based on the effects of anti-solvent concentration on physical properties such as solubility and the diffusion coefficient. Crystal nucleation and growth are calculated using a population balance model. Effects of anti-solvent concentration on the nucleation and growth rate are also considered. To couple CFD with crystallization process calculation, notation of the concentration and time step size are specifically investigated. The mixing state and crystallization process in the KCl–ethanol system, which are difficult to measure, were simulated successfully. Results demonstrate that this calculation method is an effective means to quantify the effects of local distribution of anti-solvent concentration on the crystallization process.
In the present study, reaction tests were undertaken with the goal of removing the calcium ions that cause scaling in the mother solution used for salt making. First, caustic soda and carbon dioxide gas were added to seawater-based brine that had been concentrated by electro-dialysis with an ion-exchange membrane. This technique allows calcium ions to be selectively removed from the brine. The calcium ion concentration decreased to 0.002 mol/L. Then, the amount of sodium hydroxide required is 0.2 mol per 1 L of brine. The amount of carbon dioxide that can be captured is 0.10 g per 1 g of salt produced. Then the ratio of aragonite in the sludge increased with a decrease of the sodium hydroxide addition rate and an increase of the carbon dioxide addition rate. So it is thought that the ratio of aragonite accelerates by a low in local super-saturation. Next, the brine from which the calcium ions had been removed was evaporated. No calcium scale precipitate was observed as a result of the evaporation process. The effect on sodium yield of the salt-making evaporator was minimal.
The conversion of light energy, especially solar energy, into other forms is an essential technology in modern science. This report describes our studies on the applications of light energy to mass transfer, water vaporization and seawater desalination. The photo isomerization of azobenzene compound is a powerful approach for transforming light energy. When UV and visible light that induce the molecular motion of azobenzene group by repetitive photo isomerization are irradiated to porous material with modified azobenzene compound, the release of molecules and the flow of solvents are accelerated. Irradiation of UV and visible light to water on azobenzene modified anodized alumina membrane produces the permeation of the water through the membrane. As this membrane permeation of water is caused from the evaporation of the water by repetitive isomerization of azobenzene, the purification and desalination of water are achieved by a distillation effect. Seawater desalination is also achieved using dye modified hydrophobic PTFE membranes under the irradiation of simulated sunlight. This process provides a freshwater production method from seawater only using solar energy without the consumption of fossil fuels, contributing to a sustainable solution for global water shortage.
The phosphorous removal ability of hydrotalcite reconstructed in seawater（CHT-SW）was examined in comparison with that of lime and the hydrotalcite reconstructed in NaCl solution（CHT-NaCl）. Phosphorous removal of CHT-SW is higher than that of CHT-NaCl in the solution with a wide pH range, and pH of the solution after treatment is buffered to 8.5 due to the buffering ability of hydrotalcite, while that is strong alkaline using lime. These results suggested that it is possible to produce hydrotalcite with novel properties using seawater.
This study aims to collect fundamental data for recovery of Mg resources from RPB. In the experiment, calcium hydroxide（CH）was added to RPB provided by a salt producing company to precipitate magnesium hydroxide（MH）, and the crystals were evaluated. The CH was added to the solution as powder or supersaturated aqueous solution（milk of lime）.
It was confirmed that the peak intensity of MH increases as the concentration of RPB from XRD patterns decreases when milk of lime is added. When CH was added as a powder, MH was precipitated independently of the concentration of RPB, and the peak intensity of MH was constant.
The shape of the products was observed by SEM. It was confirmed that when added as powder, the particle size becomes relatively larger than when added as milk of lime. The morphology was indicated to be spherical when added as milk of lime, and an irregular shape when added as powder.
On the other hand, it was found that decreasing the concentration of RPB to perform the reaction increased the pH after the reaction and increased the yield. Therefore, this study is considered to be useful as fundamental data to develop a recovery process of MH from RPB.
Intergranular stress corrosion cracking（SCC）in sensitized 304 stainless steel was monitored using acoustic emission（AE）, corrosion potential, and visualization for Fe2＋ dissolution. The visualization revealed the location and timing of the SCC initiation and growth. Blast-type AE signals were detected in both the initial and growth stages of SCC, which were identified from the corrosion potential. In the initial stage, the AE and corrosion potential fluctuation was detected at relatively the same time, and pitting corrosion was observed. The AE sources in the initial stage were the evolution, movement, and departure of gas due to local cathodic reaction. In the growth stage, the AE was stronger than that in the initial stage, but its generation rate was relatively low and not related to the SCC growth rate. The AE source was the segregation of undissolved grain boundaries by tensile loading at the SCC tip.
Ozone/oxygen mixed gas with different bubble diameters is supplied to ion-exchanged water or fulvic acid aqueous solution, and the effects of bubble diameter on initial ozone dissolution and reaction rates are quantified. As a result, it was clarified that both rates of the initial dissolution and reaction of ozone represent －0.5 order relative to the bubble diameter.
A flotation test was conducted for a culture fluid of marine diatoms, Chaetoceros gracilis, using a Venturi tube. Triacylglycerol in the foam increased as a result of flotation of cells using microbubbles without any coagulant and pH adjustment. It was found that an increase in air flow rate promoted the flotation of cells.
The objective of this study was to investigate the influence of calcium ions（Ca2＋）on the fouling propensity of a thin-film composite reverse osmosis（RO）membrane by alginate. Under the experimental conditions investigated in this study, an increase in Ca2＋ of up to 0.2 mmol/L accelerated the fouling of the RO membrane. However, the fouling propensity was not influenced by concentrations of Ca2＋ above 0.2 mmol/L. This result could be explained by the content of Ca2＋ in the fouling layer, which increased when the concentration of Ca2＋ in the feed water was 0.25 mmol/L or less and reached a plateau above 0.25 mmol/L.