Synthesis of mesoporous materials SBA-15 and CMK-3 from fly ash and their application for CO2 adsorption

A supernatant solution of silicate species extracted from coal fly ash in a power plant by alkali fusion was used in acidic condition to prepare a mesoporous silica SBA-15. The SBA-15 was used as a template for the synthesis of a mesoporous carbon CMK-3 using sucrose as a carbon source. Characterization of the produced mesoporous materials by XRD, N₂ adsorption-desorption, SEM, and TEM confirmed the formation of well-ordered hexagonal mesostructures. Textural properties were found close to those prepared by pure chemicals. SBA-15 after polyethyleneimine impregnation and CMK-3 were tested for carbon dioxide adsorption, successfully demonstrating the possibility of recycling the industrial waste product in a power plant into a useful adsorbent.     

Preparation of platinum-doped hollow spheres and their electrocatalytic activity in water electrolysis

Pure TiO₂ hollow spheres were prepared by using poly(styrene-methacrylic acid) latex particles as template; thereafter, titania hollow spheres were coated by platinum with an appropriate amount of choloroplatinic acid solution to obtain Pt/TiO₂ catalysts. The morphology and structure of nonstructural Pt/TiO₂ hollow spheres were characterized by BET, XRD, TGA, SEM and TEM analysis. In the samples, a remarkably uniform layer of Pt consisting of particles from 5 to 70 nm in size was formed over TiO₂ hollow spheres. We found the electrocatalytic nature of the samples by cyclic voltammetric experiment in acidic solution. The anodic peak current density of 20 wt% Pt-loaded TiO₂ hollow particles was observed 2.5 times higher than that of 5 wt% Pt/TiO₂ in the same experimental condition. Also, the anodic current density of 20 wt% Pt/TiO₂ hollow spheres calcined at various temperatures followed the order: 400 °C≈500 °C>600 °C. The electrocatalytic activity of the Pt-loaded TiO₂ hollow spheres depends on the amount of atomic platinum present in the sample; a higher concentration of platinum results in a larger current density value in anodic sweep, resulting in more oxygen production during electrolysis. Pt/TiO₂ hollow sphere catalysts have also shown long term electrocatalytic stability in acidic media.     

Effects of substituents of imidazolium cations on the performance of dye-sensitized TiO2 solar cells

Imidazolium iodides (Im⁺I⁻s) were synthesized with different substituents of the cation and used as electrolytes in dye-sensitized solar cells (DSSCs), and the effects of such substituents were investigated in terms of the photovoltaic performance of the cells. Synthesized iodides were verified by ¹H-NMR. Among the iodides, 1,3-diethylimidazolium iodide enabled a solar energy conversion efficiency of 4.8% for its DSSC, while 1-(4-acetophenyl)-3-ethylimidazolium iodide rendered an efficiency of 3.1% for its cell. In all cases the short-circuit photocurrent (J _sc) was found to increase with decrease in size of the substituent, which was also verified to be valid in the case of a quasi-solid state DSSC. Results are explained by the electrostatic interactions between solvated Im⁺ and negatively charged species based on the correlation between diffusion coefficients of I⁻ and I₃⁻ and J _sc values. These explanations are supported by steady-state voltammetry and electrochemical impedance spectroscopy (EIS).     

Catalysts characteristics of Ni/YSZ core-shell according to plating conditions using electroless plating

This study aims to develop an anode catalyst for a solid oxide fuel cell (SOFC) using electroless nickel plating. We have proposed a new method for electroless plating of Ni metal on yttria-stabilized zirconia (YSZ) particles. We examine the uniformity of the Ni layer on the plated core-shell powder, in addition to the content of Ni and the reproducibility of the plating. We have also evaluated the carbon deposition rate and characteristics of the SOFC anode catalyst. To synthesize Ni-plated YSZ particles, the plated powder is heat-treated at 1200 °C. The resultant particles, which have an average size of 50 μm, were subsequently used in the experiment. The size of the Ni particles and the Ni content both increase with increasing plating temperature and plating time. The X-ray diffraction pattern reveals the growth of Ni particles. After heat-treatment, Ni is oxidized to NiO, leading to the co-existence of Ni and NiO; Ni₃P is also observed due to the presence of phosphorous in the plating solution. Following heat treatment for 1 h at 1200 °C, Ni is mostly oxidized to NiO. The carbon deposition rate of the reference YSZ powder is ~135%, while that of the Ni-plated YSZ is 1%-6%.     

Physical modification of polypropylene: preparation of fibres dyeable with disperse dyes

Published literature from the past 30 years concerning the removal of dyes from textile effluent has been reviewed. The relationship between the bioelimination by activated sewage sludge and the molecular structure of anionic, water-soluble dyes has been examined. Bioelimination of many commercially available dyes as a mechanism for decolorising textile waste waters has been shown to be an inefficient process. However, the information collated will be used as the basis for development of novel reactive dyes for potential commercial application.     

Grain Boundary Conformed Volumetric Mesh Generation from a Three-Dimensional Voxellated Polycrystalline Microstructure

We present a new comprehensive scheme for generating grain boundary conformed, volumetric mesh elements from a three-dimensional voxellated polycrystalline microstructure. From the voxellated image of a polycrystalline microstructure obtained from the Monte Carlo Potts model in the context of isotropic normal grain growth simulation, its grain boundary network is approximated as a curvature-maintained conformal triangular surface mesh using a set of in-house codes. In order to improve the surface mesh quality and to adjust mesh resolution, various re-meshing techniques in a commercial software are applied to the approximated grain boundary mesh. It is found that the aspect ratio, the minimum angle and the Jacobian value of the re-meshed surface triangular mesh are successfully improved. Using such an enhanced surface mesh, conformal volumetric tetrahedral elements of the polycrystalline microstructure are created using a commercial software, again. The resultant mesh seamlessly retains the short- and long-range curvature of grain boundaries and junctions as well as the realistic morphology of the grains inside the polycrystal. It is noted that the proposed scheme is the first to successfully generate three-dimensional mesh elements for polycrystals with high enough quality to be used for the microstructure-based finite element analysis, while the realistic characteristics of grain boundaries and grains are maintained from the corresponding voxellated microstructure image.     

Decomposition of excess sludge in a membrane bioreactor using a turbulent jet flow ozone contactor

We have investigated the decomposition of excess sludge generated in a membrane bioreactor using a turbulent jet flow ozone contactor (TJC), which induced both hydrodynamic cavitation and ozonation reactions. We monitored the effects of various TJC operating parameters on the properties of the sludge, including the particle sizes, the particle size distribution, and the levels of soluble COD, total COD, and mixed liquor suspended solids. The TJC enhanced the degree of sludge reduction while consuming less energy, relative to conventional ozonation treatment systems, because of the synergic effects of hydrodynamic cavitation and ozonation. The hydrodynamic cavitation generated in the TJC increased the ozone mass transfer efficiency, which in turn promoted the rate of disintegration and solubilization of the sludge particles.     

Multiple effects of operating variables on heat transfer in three-phase slurry bubble columns

Characteristics of heat transfer were investigated in pressurized slurry bubble column reactors whose diameter was either 0.051, 0.076, 0.102 or 0.152 m (ID) and 1.5 m in height, respectively. Effects of gas velocity (U _G ), solid contents (S _C ), pressure (P), liquid viscosity (μ _L ) and column diameter (D) on the heat transfer coefficient (h) between the immersed vertical heater and the column were determined. Multiple effects such as UG and D, P and D, μ _L and D, and S _C and D on the value of heat transfer coefficient were discussed. Temperature fluctuations were also measured and analyzed by adapting chaos theory, which was used to explain the effects of operating variables on the heat transfer in the column. The heat transfer coefficient increased with increasing gas velocity, pressure or solid content in the slurry phase, but decreased with increasing liquid viscosity or column diameter. The decrease trend of h with increasing column diameter was somewhat sensitive when the gas velocity was relatively high (U _G ⩾12 cm/s). The effects of column diameter on the h value became almost linear when the operating pressure (P=4−10 kg _f /cm²), liquid viscosity (μ _L =20−38 mPa·s) or solid content in the slurry phase (S _C =10−20 wt%) was relatively high and gas velocity was relatively low, within these experimental conditions. The heat transfer coefficient was well correlated in terms of dimensionless groups as well as operating variables.     

A Synthetic Approach to Oligomeric Phenylethynylsilylenes

Oligomers consisting of alternating phenylethynyl and monosilyl or disilanyl moieties were synthesized in 15–64% precipitated yields by the reactions of dilithiated ethynylbenzene with dichlorodimethylsilane, dichlorodiphenylsilane, and 1,2-dichloro-1,1,2,2-tetramethyldisilane. Degrees of polymerization were fairly low due to chain termination reactions involving the deprotonation of ethynyl groups by aryllithium species. The presence of butyl chain ends was confirmed by ¹H and ²⁹Si NMR spectroscopy. ²⁹Si NMR spectroscopy was utilized to illustrate the random pattern of connectivity along the oligomer backbones. The oligomers exhibit fluorescent behavior in solution.     

Attenuating Effects of Dieckol on Hypertensive Nephropathy in Spontaneously Hypertensive Rats

Hypertension induces renal fibrosis or tubular interstitial fibrosis, which eventually results in end-stage renal disease. Epithelial-to-mesenchymal transition (EMT) is one of the underlying mechanisms of renal fibrosis. Though previous studies showed that Ecklonia cava extracts (ECE) and dieckol (DK) had inhibitory action on angiotensin (Ang) I-converting enzyme, which converts Ang I to Ang II. It is known that Ang II is involved in renal fibrosis; however, it was not evaluated whether ECE or DK attenuated hypertensive nephropathy by decreasing EMT. In this study, the effect of ECE and DK on decreasing Ang II and its down signal pathway of angiotensin type 1 receptor (AT1R)/TGFβ/SMAD, which is related with the EMT and restoring renal function in spontaneously hypertensive rats (SHRs), was investigated. Either ECE or DK significantly decreased the serum level of Ang II in the SHRs. Moreover, the renal expression of AT1R/TGFβ/SMAD was decreased by the administration of either ECE or DK. The mesenchymal cell markers in the kidney of SHRs was significantly decreased by ECE or DK. The fibrotic tissue of the kidney of SHRs was also significantly decreased by ECE or DK. The ratio of urine albumin/creatinine of SHRs was significantly decreased by ECE or DK. Overall, the results of this study indicate that ECE and DK decreased the serum levels of Ang II and expression of AT1R/TGFβ/SMAD, and then decreased the EMT and renal fibrosis in SHRs. Furthermore, the decrease in EMT and renal fibrosis could lead to the restoration of renal function. It seems that ECE or DK could be beneficial for decreasing hypertensive nephropathy by decreasing EMT and renal fibrosis.