Simulation of polymerization-induced phase separation of a polymer gel from a multifunctional monomer was carried out using the phase field method. The mobility was assumed to depend negatively and sigmoidally on the volume fraction of the polymer, considering the steric rigidity of the polymeric species of the multifunctional monomer. The results showed that the volume ratio of the polymer phase and solvent phase was well responsive to the volume fraction of the polymer. The whole of the system was composed of the polymer phase, and no solvent phase was formed even when the volume fraction of the polymer was less than 0.6. It was also revealed that the solvent phase formed a bimodal morphology, in which the smaller solvent phases were dispersed in the polymer phases, while the larger solvent phases had a continuous or dispersed morphology. Inversion of the gradient of chemical potential near the interface between the larger solvent phase and the polymer phase was proposed as a mechanism for the formation of the bimodal morphology. The feature of the phase structure of the macroporous silica prepared via polymerization-induced phase separation qualitatively agreed with the simulation results.
Recently, molten salt has attracted attention as an attractive liquid phase for gas-liquid processes at high temperature. Then a method of estimating the gas–liquid interfacial area in molten salt is required. However, the experimental and theoretical methods to estimate the gas bubble size in molten salt systems have not yet established. Especially, there is a lack of experimental techniques to directly observe the bubble formation in a high temperature system. The experimental observation of growth, stretch and detachment of bubbles is also necessary for modeling and numerical simulation. Thus, at first, this study tried to construct a reliable experimental method for observing the bubble formation in a high-temperature liquid. Clear images of the progress of bubble formation could be recorded by the experimental setups proposed in this study. The bubble formed in sodium nitrate was clear, spherically shaped and the shape was maintained longer than in aqueous system. Secondly, using this images, the bubble size generated in molten sodium nitrate was measured. The measured value was compared with the estimated values of the empirical formula established in the aqueous system. At dynamic conditions, where the difference of the physical properties has no effect on the bubble size, the same equation was applicable to those two quite different solutions. However, at static conditions, the measured bubble size was larger than the estimated value. It suggested that the empirical formula established for the aqueous system could not sufficiently estimate the effect of the surface tension in a molten salt solution.
Cyanide has been traditionally employed in gold industries such as leaching of gold ores and gold-containing wastes as well as gold plating. For the purpose of recovering the trace concentrations of gold from effluents from such industries, fundamental studies including adsorption isotherm studies for evaluating thermodynamic parameters of this system and incineration behavior of the adsorbent were conducted using a novel adsorbent prepared by the reaction of commercial cellulose with concentrated sulphuric acid. The uptake of Au(I) was drastically improved after the addition of NaClO under acidic condition. Complete recovery of Au(I) was successfully achieved using this adsorbent from model solutions, indicating its potential in the application of trace concentration of Au(I) from actual waste cyanide solutions.
LIX84-I was successfully immobilized and encapsulated in polymeric particle. Characterization of Cu(II) extracted into the polymeric particles impregnated with LIX84-I was also performed. Cu(II) ions were successfully extracted from an acidic solution and a constant value at a higher initial concentration of Cu(II) in the aqueous phase was achieved. Complex formation between Cu(II) and LIX84-I was identified via visual identification of a green cloudy powder. The extraction behavior of Cu(II) with the polymeric particles conformed well to Langmuir-type adsorption. However, when considering the purity of LIX84-I, it was suggested that two LIX84-I molecules reacted with one Cu(II) ion in the polymeric particles. Furthermore, the Fourier transform infrared spectrum showed an interaction between the polymeric particle wall and extractant. In addition, the electron paramagnetic resonance spectrum indicated that the structure of the LIX84-I-Cu(II) complex in the polymeric particles is a distorted octahedral structure composed of two LIX84-I, which consist of two nitrogen and two oxygen atoms, and two water molecules in axial positions of complex molecules, and its geometrical structure is similar to that in the solvent extraction system.
Using computational thermofluid dynamics, we calculated the fluid temperature from the enthalpy and mole fractions of chemical species and the inner wall temperature from thermal equilibrium with radiative heat transfer. The fluid and wall temperatures were approximately found using a temporary solution in the iterative part of the polynomial equations. We carried out combustion simulations using Newton’s method and the approximate method introduced in this study, and calculated the fluid and wall temperatures. The computed temperatures from both methods agree completely; furthermore, over 20% reduction in computational time compared to current methods was achieved. Therefore, the approximate method is useful for computations concerning steady–state thermofluids, such as those in combustion simulation.
In this study, the hyperbola kinetic model of simultaneous catalytic hydrolysis CS2 and COS was investigated. Through the experimental results, it can be found that catalytic hydrolysis of CS2 and COS is the controlling step for the whole reaction. Meanwhile, the theoretical calculation results showed that COS is easier to adsorb on the surface of catalyst than CS2. The XPS results showed that H2S was oxidized to elemental sulfur and sulfate was the main reason for the deactivation of the catalyst.
Catalytic activities of calcium hydroxyapatite (HAp) and β-type tricalcium phosphate (β-TCP) were examined for use in the oxidative dehydrogenation (ODH) of isobutane. β-TCP was catalytically inactive for the ODH of isobutane, but stoichiometric HAp afforded a high isobutene yield (5.6%). The isobutane conversion and isobutene selectivity of HAp depended on the atomic ratio of Ca/P. HAp with Ca/P=1.67 showed the highest isobutene selectivity and isobutene yield among the HAp catalysts with different Ca/P ratios. The characterization of the acidic-basic properties showed that these properties affect the catalytic performance of HAp, and that its basicity is necessary for high catalytic activity. To improve the catalytic activities of calcium phosphates, they were impregnated with Cr. Despite a much lower surface area for β-TCP, Cr-impregnated β-TCP showed a higher isobutene yield (up to 8.4%) than that of Cr-impregnated HAp. The results of the XPS measurement showed that the Cr3+ species on calcium phosphates, owing to basicity, worked as active sites in the ODH of isobutane.
A macroporous TiO2 photocatalyst loaded with fine magnetite particles was prepared by the PMMA-templating method for the degradation of methylene blue. The photocatalyst particles synthesized in this study were porous and had uniform macropores. The size of macropores on the photocatalyst was easily controlled by selecting a proper size of PMMA microspheres used as a template. The size of PMMA spheres commercially available were 0.15–1.5 µm, finally leading to porous products with the pore size of 0.14–1.0 µm, which gave rise to high BET surface areas of 14–58 m2/g. In the photocatalytic degradation of methylene blue, the highest activity was exhibited with the porous TiO2 possessing the smallest pores and highest surface area among the various-sized photocatalysts. The high surface area attributing to the controlled porous structure effectively contributed to an improvement of the degradation performance.
Simulated moving-bed chromatography (SMBC) separation of a solution containing three different saccharides was investigated by real-time, inline monitoring of the concentration of each saccharide with Fourier transform near-infrared spectroscopy (FT-NIRS). We built partial least squares (PLS) regression models to estimate the saccharide concentrations based on preprocessed spectral data in the wavenumber range 6,100–5,440 cm−1 that excludes the water absorption band. To verify the calibration model, we performed separation of the raw material solution of the test set using SMBC, and confirmed that the predicted concentration of each saccharide from the calibration model corresponds well with the actual measured concentration of each saccharide obtained by HPLC. The collection range can be adjusted online using the monitoring values in order to maximize the purity and yield of the target saccharides.
Chitosan has been widely utilized as a porous scaffold material for cartilage regeneration. During the preparation process of chitosan scaffolds, toxic chemical cross-linkers, such as glutaraldehyde, have been used for cross-linking of chitosan molecules. We previously developed chemical cross-linker-free chitosan sponges formed only by freeze-thawing an aqueous solution of chitosan-gluconic acid conjugate (CG). In the present study, we applied the CG cryosponges as scaffolds for cartilage tissue engineering. CG cryosponges with low gluconic acid content showed a defined porous structure and high stability in cell culture medium supplemented with fetal bovine serum that originally contained a low level of lysozyme, a hydrolysis enzyme for chitosan. A favorable mean pore size of the cryosponges for cartilage regeneration (100–300 µm) was accomplished by freezing the CG solution at −30°C. Proliferation and glycosaminoglycan production of bovine chondrocytes were facilitated in plain CG cryosponges compared with those cross-linked with glutaraldehyde. These results demonstrated that the CG cryosponges were promising scaffolds for cartilage tissue engineering.
CaCO3–Al(OH)3 mixtures with different Ca/(Ca+Al) molar ratios (0.33–0.91) were calcined at different temperatures (623–1473 K). The calcination product was mixed with fly ash, it contaminated by oxioanions, sand (α-quartz) and fumed silica (amorphous) to solidify before measuring the compressive strength of the solids. The crystalline compounds that contribute to the solid strength were identified by XRD to investigate the effect of calcination conditions and the influence of oxoanions on fly ash solidifying reaction. The calcination product at 1273 K with Ca/(Ca+Al)=0.83 that contained both CaO and Ca9Al6O18 provided the highest compressive strength of solidified fly ash, forming Ca2SiO4 and subsequently Ca3Al2SiO4(OH)8. The strength of solidified fly ash was lowered by oxoanion coexistence because the oxoanions consumed CaO in the calcination product, while the oxoanion leaching from fly ash was suppressed.
The Na2S solution was adopted to extract mercury, especially the mobile Hg from heavy mercury contaminated soil. The mercury species in soil were determined by using US EPA3200 sequential extraction procedure. The Hg extraction ratio, which depended on process parameters, such as liquid [mL]/solid [g] ratio of the solution and soil (5 : 1–20 : 1), the Na2S solution concentration (0.1–0.7 mol/L), leaching time (2–24 h) and heating temperature (25–80°C) were systematically investigated. It was shown that the total content of Hg in the soil was about 168 mg/kg, including mobile Hg 104 mg/kg, semi-mobile Hg 17 mg/kg and non-mobile Hg 47 mg/kg. Mobile Hg exhibited high toxicity and bioactivity accounted for 62% of total Hg. According to the extraction experiments, it was indicated that Na2S solution could effectively extract Hg from heavy mercury contaminated soil. Under the optimal conditions, namely, liquid [mL]/solid [g] ratio of 10 : 1, the Na2S solution concentration of 0.7 mol/L, the leaching time of 4 h and the heating temperature of 25°C, the Hg extraction ratio of total Hg reached 72%. The mobile Hg, in particular, was removed as high as 86%.