• Applied Chemistry for Engineering
• /
• v.23 no.6
• /
• pp.561-566
• /
• 2012

PtRuW/C catalysts were prepared with the different molar ratios of Pt : Ru : W and their compositions were analyzed by energy dispersive X-ray (EDX). The uniform distribution of particles was observed using transmission electron microscopy (TEM). An average crystalline size of 3.5~5.5 nm was calculated based on x-ray diffraction (XRD) data. The electrochemical properties such as electrochemically active surface areas, current densities, specific activities and poisoning rates, were analyzed via CO stripping, linear sweep voltammetry and chronoamperometry. From the analysis, we observed that ternary alloy catalysts, except $PtRu_2W_2/C$, have higher current densities, specific activities and stabilities than those of commercial binary catalysts. Among all in-house catalysts, Pt5Ru4W/C showed the highest specific activity of $121.05mA{\cdot}m^{-2}$ and the lowest poisoning rate of $0.01%{\cdot}s^{-1}$.

• Resources Recycling
• /
• v.22 no.4
• /
• pp.3-11
• /
• 2013

The recovery of molybdenum and vanadium from acid leaching solutions of spent catalysts using solvent extraction has been investigated. Among various acid leaching solutions, sulfuric acid solution is found to be adequate for the recovery of these two metals. The extraction and stripping behavior of the two metals in the absence and presence of other impurity metals by various types of extractants such as cationic, solvating, amine and a mixture of cationic and solvating extractants was discussed. Each type of extractants has advantage and disadvantage in terms of the possibility of separation and of forming a third phase. Among the various types of extractants, a mixture of cationic and solvating extractants seems to be the most promising extractant system for the separation of Mo and V from the acid leaching solutions of spent catalysts.

• Resources Recycling
• /
• v.28 no.5
• /
• pp.68-73
• /
• 2019

Ilmenite is one of the principal ores for the production of titanium dioxide. To produce titanium dioxide with purity higher than 99.9% from ilmenite, Ti(IV) should be separated from the dissolved impurities such as Fe(III), Si(IV), and Mn(II) present in ilmenite. In this work, a hydrometallurgical process was investigated to recover pure titanium dioxide from ilmenite by HCl leaching followed by separation and hydrolysis of Ti(IV). An optimum leaching condition was obtained by investigating the effect of HCl concentration, pulp density, and leaching time on the leaching percentage of Ti(IV), Fe(III), Si(IV), and Mn(II). Ammonium hydroxide and sodium hydroxide solutions were employed as neutralizing agents to hydrolyze Ti(IV) from the stripping solution of Ti(IV). Titanium dioxide of the anatase phase was obtained by calcination of the hydrolyzed precipitates with $NH_4OH$ solution. A hydrometallurgical process can be developed to produce pure $TiO_2$ powders from ilmenite.

• Environmental Engineering Research
• /
• v.24 no.1
• /
• pp.38-44
• /
• 2019

The Biochemical Methane Potential (BMP) of fresh leachate and domestic wastewaters codigestion was determined by laboratory Bach Tests at $35^{\circ}C$ over a period of 90 d using a wide range of leachates volumetric ratios from 0% to 100%. To simulate wastewaters plant treatment step, all the ratios were first air stripped for 48 h before anaerobic incubation. The kinetic of biogas production was assessed using modified Gompertz model and exponential equation. The results obtained showed that cumulative biogas production was insignificant in the case of wastewaters monodigestion while the codigestion significantly improves the BMP. Air stripping pretreatment had positive effect on both ammonium concentration and volatiles fatty acids with reduction up to 75% and 42%, respectively. According to the Modified Gompertz model, the optimal anaerobic co-digestion conditions both in terms of maximal biogas potential, start-up period and maximum daily biogas production rate, could be achieved within large leachate volumetric ratios from 25% to 75% with a maximum BMP value of 438.42 mL/g volatile solid at 50% leachate ratio. The positive effect of codigestion was attributed to a dilution effect of chemical oxygen demand and volatile fatty acid concentrations to optimal range that was between 11.7 to $32.3gO_2/L$ and 2.1 to 7.4 g/L, respectively. These results suggested that the treatment of fresh leachate by their dilution and co digestion at wastewaters treatment plants could be a promising alternative for both energetic and treatment purposes.

• Journal of the Semiconductor & Display Technology
• /
• v.17 no.3
• /
• pp.41-45
• /
• 2018

Two-dimensional (2D) materials have been studied extensively due to their excellent physical, chemical, and electrical properties. Among them, we report the material and device characteristics of tin disulfide ($SnS_2$). To apply $SnS_2$ as a channel layer in a transistor, $SnS_2$ channels were formed by a stripping method and a transfer method. The limitation of this method is that it is difficult to produce uniform device characteristics over a large area. Therefore, we directly deposited $SnS_2$ by atomic layer deposition (ALD) and then performed lithography. This method was able to produce devices with repeatable characteristics over a large area. However, the $SnS_2$ film was damaged by the acetone used as a photoresist (PR) developer during the lithography process, with the electrical properties of mobility of $2.6{\times}10^{-4}cm^2/Vs$, S.S. of 58.1 V/decade, and on/off current ratio of $1.8{\times}10^2$. These results are not suitable for advanced electronic devices. In this study, we analyzed the effect of acetone on $SnS_2$ and studied the device process to prevent such damage. Using polyvinyl alcohol (PVA) as a passivation layer during the lithography process, the electrical characteristics of the $SnS_2$ transistor had $2.11{\times}10^{-3}cm^2/Vs$ of mobility, 11.3 V/decade of S.S, and $2.5{\times}10^3$ of the on/off current ratio, which were 10x improvements to the $SnS_2$ transistor fabricated by the conventional method.

• Resources Recycling
• /
• v.31 no.1
• /
• pp.12-20
• /
• 2022

The smelting reduction of spent lithium-ion batteries results in metallic alloys containing Co, Cu, Fe, Mn, Ni, and Si. A process to separate metal ions from the sulfuric acid leaching solution of these metallic alloys has been reported. In this process, ionic liquids are employed to separate Fe(III) and Cu(II). In this study, D2EHPA and Cyanex 301 were employed to replace these ionic liquids. Fe(III) and Cu(II) from the sulfate solution were sequentially extracted using 0.5 M D2EHPA with three stages of cross-current and 0.3 M Cyanex 301. The stripping of Fe(III) and Cu(II) from the loaded phases was performed using 50% (v/v) and 60% (v/v) aqua regia solutions, respectively. The mass balance results from this process indicated that the recovery and purity percentages of the metals were greater than 99%.

• Proceedings of the Korean Society of Developmental Biology Conference
• /
• 2003.10a
• /
• pp.73-73
• /
• 2003

The present study examined the possibility of long term storage, by cryopreservation in liquid nitrogen, of the sperm of Filefish (Thamnaconus septentrionalis), and the changes in motility, survival rate and ultrastructure of the sperm after freezing and thawing. The sperm was collected by stripping and stored on ice until experiments. For selection of the immobilizing solution, diluted artificial seawater (ASW) of 20, 30 and 40% were tested. The sperm motility was significantly inhibited in 30% ASW, and restored entirely after 100% ASW was added again. Two cryoprotectants, dimethyl sulfoxide ($Me_2$SO) and glycerol, were added to 30% ASW to formulate the extenders at the concentrations between 5 to 20% by volume for freezing. The sperm was diluted at the ratio of 1 :6 with the extenders, inserted into 0.5ml plastic straws and frozen at a freezing rate of $50^{\circ}C$/min to $-100^{\circ}C$ after equilibration for 10 min at room temperature, followed by plunging into liquid nitrogen. The straws were thawed in a $30^{\circ}C$ water bath for 15 sec. The highest post-thawed sperm motility and survival rate were obtained with 5% glycerol Afterward, the effect of different freezing rates was examined using 5% glycerol as a cryoprotectant, and the rate of $20^{circ}C/min to $-80^{\circ}C$ showed the best result Some ultrastructural changes of sperm, such as the detachment of plasmatic and nuclear membranes, destruction of mitochondria, were observed after cryopreservation. Morphological normality of the sperm in 5% glycerol frozen at the ratio of 1$0^{\circ}C$/min to $-80^{\circ}C$ was better than that of others.

• The Bulletin of The Korean Astronomical Society
• /
• v.45 no.1
• /
• pp.64.2-64.2
• /
• 2020

We present the properties of galaxies in filaments around the Virgo cluster with respect to their vertical distance from the filament spine. Using the NASA-Sloan Atlas and group catalogs, we select galaxies that do not belong to groups in filaments. The filament member galaxies are then defined as those located within 3.5 scale length from the filament spine. The filaments are mainly (~86%) composed of low-mass dwarf galaxies of logh2M∗/M⊙ < 9 dominantly located on the blue cloud in color-magnitude diagrams. We observe that the g - r color and stellar mass of galaxies correlate with their vertical distance from the filament spine in which the color becomes red and stellar mass decreases with increasing vertical filament distance. The galaxies were divided into two subsamples in different stellar mass ranges, with lower-mass (logh2M∗/M⊙ ≤ 8) galaxies showing a clear negative g-r color gradient, whereas higher-mass (logh2M∗/M⊙ > 8) galaxies have a flat distribution against the vertical filament distance. We observe a negative EW(Hα) gradient for higher-mass galaxies, whereas lower-mass galaxies show no distinct variation in EW(Hα) against the vertical filament distance. In contrast, the NUV - r color distribution of higher-mass galaxies shows no strong dependence on the vertical filament distance, whereas the lower-mass galaxies show a distinct negative NUV - r color gradient. We do not witness clear gradients of HI fraction in either the higher- or lower-mass subsamples. We propose that the negative color and stellar mass gradients of galaxies can be explained by mass assembly from past galaxy mergers at different vertical filament distances. In addition, galaxy interactions might be responsible for the contrasting features of EW(Hα) and NUV - r color distributions between the higher- and lower-mass subsamples. The HI fraction distributions of the two subsamples suggest that ram-pressure stripping and gas accretion could be ignorable processes in the Virgo filaments.

• Analytical Science and Technology
• /
• v.21 no.2
• /
• pp.129-134
• /
• 2008

Cyclic voltammetry (CV) and square wave stripping voltammetry (SW) analysis of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) using the double-stranded ds calf thymus (DNA) mixed in carbon nanotube paste electrode (PE) were provided. The optimum analytical conditions were determined and the peak potential was 0.2 V vs. Ag/AgCl. The linear working ranges of CV (50-75 ug/L) and SW (5-80 ng/L) were obtained. The precisions of RSD in the 10 ug/L was 0.086% (n=15) and the detection limit was 0.65 ng/L ($2.92{\times}10^{-12}M$) (S/N=3) with 300 s adsorption time at the optimum condition. The method was used to determine the presence of explosive chemicals in contaminated soil samples.

• Analytical Science and Technology
• /
• v.20 no.4
• /
• pp.289-295
• /
• 2007

A simple electric circuit of an infrared photodiode electrode (IPDE) was utilized to monitor iron using square-wave (SW) anodic stripping voltammetry (SV) and cyclic voltammetry (CV). The optimum analytical conditions were determined and were compared with those of common working electrodes. The comparison showed that CV is more sensitive and convenient to use than the common voltammetry methods. At the optimized conditions, the working ranges of 0.1- to 0.8- and 0.85- to 6.0 mg/L iron was obtained. Relative standard deviation of 15 measurements of iron (0.4 mg/L) was 0.09%. The analytical detection limit was found to be $80{\pm}0.6ug/L$, which was applied to iron in waste water.