• Bulletin of the Korean Chemical Society
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• v.33 no.4
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• pp.1279-1284
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• 2012

Silica supported $Cs_{2.5}H_{0.5}PMo_{12}O_{40}$ catalyst was prepared through sol-gel method with ethyl silicate-40 as silicon resource and characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, nitrogen adsorption-desorption and potentiometric titration methods. The $Cs_{2.5}H_{0.5}PMo_{12}O_{40}$ particles with Keggin-type structure well dispersed on the surface of silica, and the catalyst exhibited high surface area and acidity. The catalytic performance of the catalysts for benzene liquid-phase nitration was examined with 65% nitric acid as nitrating agent, and the effects of various parameters were tested, which including temperature, time and amount of catalyst, reactants ratio, especially the recycle of catalyst was emphasized. Benzene was effectively nitrated to mononitro-benzene with high conversion (95%) in optimized conditions. Most importantly, the supported catalyst was proved has excellent stability in the nitration progress, and there were no any other organic solvent and sulfuric acid were used in the reaction system, so the liquid-phase nitration of benzene that we developed was an eco-friendly and attractive alternative for the commercial technology.

• Journal of Soil and Groundwater Environment
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• v.20 no.6
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• pp.55-61
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• 2015

Based on the literature study for the determination of perchlorate in soil we chose the ion chromatography as a measurement method and decided to use 70 mM KOH as an eluent to avoid the interference derived from the co-elution of pyrophosphate (P₂O₇⁴⁻), tripolyphosphate (P₃O₁₀⁵⁻). Also we proposed to use air dried soil through 0.15 mm sieve and distilled water as an extractant. Under the these basic concepts, we carried out the experiments to set up the detail procedure like solid to liquid ratio (S/L ratio), extraction time, device for extraction and indicating factors for quality control (e.g. precision, accuracy, MDL, LOQ). In case of time and device for extraction, 5 hours of mechanical shaking or 1 hour of centrifugation showed better precision and accuracy than that of sonication for 1 hour According to these results, we proposed the extraction method combining 5 hours of mechanical shaking with 1 hour of centrifugation. From the aspect of S/L ratio, the ratio of 1/2 or 1/3 showed resonable precision and accuracy. In case of the ratio of 1/2, there would be some problems in the separation process when the proportion of fine particle is high. Therefore, we proposed the extraction ratio of solid to liquid as 1/3 instead of 1/2. With the consideration of cost effectiveness and soil salinity, we proposed the use of cartridge for removing the interfering anions like chloride, sulfate and carbonate in specific sample such as saline soil.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.70-74
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• 2016

In this study, the effects of citrate buffer pretreatment conditions (solid-to-liquid ratio, reaction temperature, pH and concentration of buffer) on enzymatic hydrolysis of E. intestinalis for total reducing sugar (TRS) production were investigated. As a results of the citrate buffer pretreatment, a 5.40% hydrolysis yield was obtained under conditions including 1:10 solid-to-liquid ratio, 0.25 M citrate buffer (pH 3.5) at $140^{\circ}C$ for 60 min. The maximum hydrolysis yield of 18.68% was obtained to enzymatic hydrolysis after pretreatment. This result is 1.81 times higher than that of control.

• Journal of the Mineralogical Society of Korea
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• v.32 no.1
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• pp.1-14
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• 2019

This study used microwave-nitric acid leaching with the aim of removing penalty elements such as As and Bi. Moreover, enhanced gold content from the gold concentrate sample. The leaching conditions were changed: leaching time, nitric acid concentrations and solid-liquid ratio; In order to improve the removal of penalty elements. As a result of the experiment; sample weight loss rate, As and Bi removal rate and gold content in the solid-residues have been increased when the nitric acid concentration and leaching time were increased while the solid-liquid ratio was decreased. The leaching conditions for the maximum As and Bi removal and gold content were: leaching with a 6.0 M nitric acid solution doing 5 min. At these, the solid-residue sample weight loss was 87 %. As removal rate was 98.23 % and Bi was completely removed (100 %). Furthermore, gold content increased from 81.36 g/t to 487.32 g/t. The XRD of the solid residue showed that pyrite disappeared as the nitric acid concentration was increased, whereas sulfur peaks was increased, too.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1644-1650
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• 2023

In spent fuel reprocessing, UO₂(DBP)₂ (U-DBP) can be deposited in stainless steel equipment. U-DBP must be removed by dissolution and the process must not cause corrosion to stainless steel. This study was conducted to find the best scheme for dissolution. U-DBP was manufactured by the titrimetric sedimentation method. The effects of different factors on the dissolution of U-DBP were investigated. For example, solid-liquid ratio, hydrazine carbonate solutions with different mass components, mixed solutions containing different concentrations of H₂O₂, and different carbonates. The results indicated that U-DBP does not have a regular crystal morphology. With the increase of the solid-liquid ratio and the mass fraction of hydrazine carbonate, the concentration of U(VI) at the dissolution equilibrium increases gradually. The addition of H₂O₂ has a great promotion effect on the dissolution. However, when the concentration of H₂O₂ is greater than 0.5 M, the dissolution solution may have an erosive effect on the stainless steel. (NH₄)₂CO₃ can increase the dissolution capacity of dissolved U-DBP, but it may also accelerate the corrosion of stainless steel.

• Korean Journal of Materials Research
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• v.12 no.10
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• pp.825-830
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• 2002

The growth rate of solid grains in TiC-XC-2vol% and TiC-XC-30vo1% Ni cermets, where X=Zr, W or Mo, was fitted to an equation of the form $d^3$-$do^3$=Kt. The grain growth behavior during liquid phase sintering at 1673K decreased markedly with addition of $Mo_2$C or WC and increased with addition of ZrC. The contiguity ratio was greater in the alloys with smaller growth rate constant and decreased with increasing Ni content in the $TiC-Mo_2$C-Ni cermet. The grain growth mechanism could be explained by the effect of contiguous grain boundaries in restricting the overall grain growth.

• Journal of the Korean Ceramic Society
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• v.17 no.3
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• pp.158-162
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• 1980

The experiments of suspension hydration were performed in the mixtures of slag and water or NaOH solutions which were made up with a liquid/solid ratio of 10. The liquid phase of the suspension was chemically analysed and discussed. When slag was in contact with water, CaO component was released from slag grains into the solution. The amounts of $SiO_2$ and $Al_2O_3$ liberated in the solution were very low as compared with CaO, for the impermeable coating of $SiO_2$, $Al_2O_3$-rich gel was formed on the surface of slag grains. The hydration was considered to be inhibited by this impermeable coating. The weak hydraulic property of slag was based on slowly released CaO and dissolved Na, K components which increased pH in the solution.

• Food Science and Biotechnology
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• v.18 no.4
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• pp.996-1000
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• 2009

Sapium japonicum was extracted by a pressurized liquid. Operating parameters such as the type and the ratio of solvent to water, temperature, pressure, and number of extractions were investigated as the main variables that influence the extraction efficiencies of total phenolics (TP). MeOH extracted the highest level of TP as 50.4 mg GAE/g compared to 48.8 and 27.2 mg GAE/g with $H_2O$ and EtOH, respectively. $EtOH:H_2O$ (40:60, v/v) was found to be the best solvent for TP extraction as 90.3 mg GAE/g compared to 85.0 and 84.3 mg GAE/g in 40:60 and 60:40 of $MeOH:H_2O$, respectively. TP were increased with the increase of the number of extraction steps. TP content was increased by 11% as the extraction temperature was increased from 40 (97.4) to $50{\circ}C$ (108.3 mg GAE/g). The optimum extraction conditions of TP were; extraction solvent, $EtOH:H_2O$ (40:60, v/v); temperature, $50{\circ}C$; pressure, 10.2 MPa; 2 extraction steps.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.21-24
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• 2014

In the entrained-flow coal gasifier, coal ash turns into a molten slag most of which deposits onto the wall to form liquid and solid layers. Critical viscosity refers to the viscosity at the interface of the two layers. The slag layers play an important role in protecting the wall from physical/chemical attack from the hot syngas and in continuously discharging the ash to the slag tap at the bottom of the gasifier. For coal with high ash melting point and slag viscosity, CaO-based flux is added to coal to lower the viscosity. This study evaulates the effect of critical viscosity temperature and ash/flux ratio on the slag behavior using numerical modelling in a commercial gasifier. The changes in the slag layer thickness, heat transfer rate, surface temperature and velocity profiles were analyzed to understand the underlying mechanism of slag flow and heat transfer.

• Food Science and Preservation
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• v.30 no.5
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• pp.785-796
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• 2023

The aim of this study was to elucidate chemical structures and rheological properties of arabinogalactans (AGs) isolated from three legumes including black gram (BG), great northern bean (GNB), and California small white bean (CSWB). The ratio of galactose to arabinose (G/A) in three legumes increased in the order of BG > GNB > CSWB. The rheological measurements of 1-5% (w/v) AG solutions revealed Newtonian and non-Newtonian flow behaviors. BG exhibited yield stress, indicating plastic behavior. Small-amplitude oscillatory tests indicated viscoelastic properties of BG, GNB, and CSWB ranging from solid-like, paste-like, and liquid-like behaviors, respectively. Small-strain oscillatory tests were conducted to assess the structure recovery of the AGs after pre-shearing. G" values of BG and GNB increased, but those of CSWB remained constant after shearing. These results suggest that the chemical structures of the AGs, particularly their G/A ratios, influence their rheological properties.