• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.87-92
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• 2006

The steam reforming of methane over Ru-promoted $Ni/Al_2O_3$ was carried out. Compared with $Ni/Al_2O_3$, which needs pre-reduction by $H_2$, $Ru/Ni/Al_2O_3$ catalysts exhibited relatively higher activity than conventional $Ni/Al_2O_3$. According to $H_2-TPR$ of reduced or used catalysts and $CH_4-TPR$, it was revealed that the reduction of $RuO_x$ by $CH_4$ decomposition begins at a lower temperature ($220^{\circ}C$) and the reduced Ru facilitates the reduction of NiO, and leads to self-activation. To improve metal dispersion, the catalyst was soaked in 7 M aqueous $NH_4OH$ for 2 h at $45^{\circ}C$ while stirring. As a result, $Ru/Ni/Al_2O_3$ catalysts with aqueous $NH_4OH$ treatment have higher activity, larger metal surface area (by $H_2$-chemisorption), and small particle size (by XRD and XPS). It is noted that the amount of noble metal could be reduced by aqueous $NH_4OH$ treatment.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.22-27
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• 2006

Thermal treatment and ozone oxidation methods were examined to reuse waste activated sludge (WAS) produced from a livestock wastewater treatment plant. Analysis of WAS property was made to study usefulness of the recycled waste as fertilizer. From the results of quantitative analysis, WAS particles were found to be composed of 44.25 wt% carbon, 8.43 wt% nitrogen, and 1.35 wt% phosphorus. It was confirmed that the inactivation of pathogenic microorganism was required from the quantitative analysis of microbes. From the results of TSS, COD, SCOD, and pathogenic microorganism measurement, the optimal operating conditions of thermal treatment and ozone oxidation were determined to be 70, 10 min and $0.6L\;O_3/L\;solution{\cdot}min$, 60 min, respectively. The optimized thermal treatment and ozone oxidation represented the efficient pathogen inactivation and particle dissolution, respectively. However, the two methods examined were not themselves sufficient but they need to combine with another treatment for the effective reuse of wastes.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1164-1173
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• 1996

Treating methods and characteristics of waste from a nuclear fuel powder conversion plant were studied. To recovery or treat a trace uranium in liquid waste, the ammonium uranyl carbonate(AUC) filtrate must be heated for $CO_2$ expelling, essentially. Uranium content of final treated waste solution from fuel powder processes for a heavy water reactor(HWR) could be lowered to 1 ppm by the lime treatment after the ammonium di-uranate(ADU) precipitation by simple heating. Otherwise, in case of the waste from fuel powder processes for a pressurized light water reactor(PWR), it is result in 0.8 ppm as a form of uranium peroxide such as $UO_4{\cdot}2NH_4F$ compounds. Optimum condition was found at $101^{\circ}C$ by the simple heating method in case of HWR powder process waste. And in case of PWR powder process waste, optimum condition could be obtained by precipitating with adding hydrogen peroxide and adjusting at pH 9.5 with ammonia gas at $60^{\circ}C$ after heating the waste In order to expelling $CO_2$. As the characteristics of recovered uranium compounds, median particle size of ADU was increased with pH increasing in case of HWP waste. Also, in case of uranium proxide compound recovered from PWR waste, the property of $U_3O_8$ power obtained after thermal treatment in air atmosphere was similar to that of the powder prepared from AUC conversion plant.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.588-596
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• 1994

A decomposition reaction of bauxite ore with $(NH_4)_2SO_4$ was investigated to prepare Al component pregnant solution for the direct product of high purity $Al_2O_3$ from low grade bauxite ore. Al component in the bauxite was sulfatized to $NH_4Al(SO_4)_2$ or $Al_2(SO_4)_3$ in this decomposition. The optimum conditions of the decomposition for bauxite ore were reaction temperature of $425^{\circ}C$, reaction time of 40min, $(NH_4)_2SO_4$ weight ratio to bauxite of 7.0 and particle size of bauxite ore of -200mesh. The optimum leaching conditions of sulfated bauxite ore were leaching temperature of $100^{\circ}C$, leaching time of 1hr and pulp density of 200ml $H_2O$ to sulfated ore of 1.0g bauxite. Under the above mentioned decomposition and leaching conditions, 94% of Al component in the bauxite ore was extracted.

• Korean Journal of Environmental Agriculture
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• v.24 no.3
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• pp.203-209
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• 2005

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.

• Journal of Bio-Environment Control
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• v.12 no.3
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• pp.166-172
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• 2003

Rockwool slabs used for hydroponic cultures are expected to have potential to be reused after breakdown as a growing medium component for hydroponic culture of vegetables and cut flowers, pot plants, or plug plants. This study was conducted to test the feasibility of using particles of used rockwool slabs (PURS) mixed with woodchips for growing plug seedlings of ‘Nokkufang’ pepper. In the first experiment growth of pepper seedlings was tested in media of steam sterilized PURS mixed with chestnut woodchips (CW), which was weatherized for six months and screened through 2.8 mm or 5.6 mm sieves, at 100:0, 75:25, 50:50, 28:75 or 0:100 (%, v/v). In the second experiment growth of pepper seedlings was tested in 20 different media containing steam sterilized PURS mixed with 4 mm chestnut woodchips (CW), 4 mm pinc woodchips (PW), coir, peatmoss, or perlite. In the first experiment, there were no significant growth differences as affectcd by particle size of CW, while the overall best growth was achieved il1 the control and l00% PURS. In the second experiment, seedling growth was enhanced as compared to the control in 100% PURS or PURS mixed with peatmoss, coir, or perlite. In contrast, growth was suppressed as the proportion of peatmoss or coir mixed with PURS decreased and the proportion of CW increased. Growth was better in the PURS + peatmoss than in the 100% PURS or PURS + coir, and when woodchips were mixed with coir than peatmoss.

• Journal of Bio-Environment Control
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• v.10 no.2
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• pp.88-94
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• 2001

Physical and chemical properties, the salt accumulation and leaching of salt by water of coal fly ash ball (ash ball) were evaluated in comparison with perlite and granule rockwool (rockwool). Bulk density, particle density, solid phase, and porosity of ash ball were 0.93 g.cm$^{-3}$ , 2.29 g.cm$^{-3}$ , 40.6%, 59.4%, respectively. The bulk density of ash ball was greater, while porosity was smaller, than that of perlite and rockwool. Saturation moisture capacity was 52% in ash ball, 71% in perlite, and 90% in rockwool. Water contents after drainage for 1 hr of ash ball, perlite, and rockwool were 21%, 27%, and 80%, respectively. Water content of small granules (3-5 mm) of ash ball was 5% greater than that of large (7-15 mm) grannules. The ash ball was a weak alkali substrate with pH 7.6, but not electric conductivity (EC), of the nutrient solution supplied to ash ball slightly increased. When the absorption of mineral ions to substrates were analyzed, ash ball and RW absorbed mainly PO￣$_4$. On tomato culture, salt accumulation in ash ball substrate was similar to that in perlite. Most of the salts in the ash balls were removed by submerging the substrate eight times in distilled water. It is concluded that water holding capacity of ash ball substrate was lo as compared to other substrates, but air permeability, and water diffusion was excellent, making control of medium water content easy.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.656-662
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• 2013

The iron oxide ($Fe_3O_4$) particles in the coolant of the secondary system of a nuclear power plant reduce the heat transfer performance or induce corrosion on the surface of the heat transfer tube. To prevent these problems, we conducted a study to improve the dispersion stability of iron oxide using polymeric dispersant injection in simulated secondary system water. The three kinds of anionic polymers containing carboxyl groups were selected. The dispersion characteristics of the iron oxide particles with the polymeric dispersants were evaluated by performing a settling test and measuring the transmission, the zeta potential, and the hydrodynamic particle size of the colloid solutions. Polymeric dispersants had a significant impact on the iron oxide dispersion stability in an aqueous solution. While the dispersant injection tended to improve the dispersion stability, the dispersion stability of iron oxide did not increase linearly with an increase in the dispersant concentration. This non-linearity is due to the agglomerations between the iron oxide particles above a critical dispersant concentration. The effect of the dispersant on the dispersion stability improvement was significant when the dispersant concentration ratio (ppm, dispersant/magnetite) was in the range of 0.1 to 0.01. This suggests that the optimization of dispersant concentration is required to maximize the iron oxide removal effect with the dispersant injection considering the applied environments, the iron oxide concentration and the concentration ratio of dispersant to iron oxide.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.178-184
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• 2017

This study was aimed to investigate the tensile behaviors of PE(Polyethylene) fiber-reinforced highly ductile cementitious composites with different combinations of micro silica sand and normal sand(river sand) with maximum particle size of 4.75 mm. Flow test result indicated the increase of flowability with higher replacement ratio of river sand. There was no noticeable difference in the mean compressive strength with different replacement ratio of river sand, but the variation in the compressive strength increased as higher amount of river sand was adopted for the replacement. The difference in the uniaxial tensile strength was negligible, but the tensile strain capacity was significantly influenced by the replacement ratio of river sand. It is thought that increased density of multiple cracks induced improved tensile strain capacity when higher percentage of river sand was adopted for fine aggregate. The deviation in the strain capacity increased as the replacement ratio of river sand was higher, as in the compressive strength. This study presented the feasibility of using normal sand instead of micro silica sand for highly ductile cementitious composites with equivalent or better uniaxial tensile performance, even though it might increase the deviation in the performance.

• Food Science of Animal Resources
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• v.37 no.1
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• pp.123-133
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• 2017

The development of a new manufacturing process, a two-step temperature treatment, to modulate the physicochemical properties of nanoparticles including the size is critical. This is because its physicochemical properties can be key factors affecting the cellular uptake and the bioavailability of bioactive compounds encapsulated in nanoparticles. The aims of this study were to produce (beta-lactoglobulin) ${\beta}-lg$ nanoparticles and to understand how two-step temperature treatment could affect the formation and physicochemical properties of ${\beta}-lg$ nanoparticles. The morphological and physicochemical properties of ${\beta}-lg$ nanoparticles were determined using atomic force microscopy and a particle size analyzer, respectively. Circular dichroism spectroscopy was used to investigate the secondary structure of ${\beta}-lg$. The surface hydrophobicity and free thiol groups of ${\beta}-lg$ were increased with a decrease in sub-ambient temperature and an increase in mild heat temperature. As sub-ambient temperature was decreased, a decrease in ${\alpha}-helical$ content and an increase in ${\beta}-sheet$ content were observed. The two-step temperature treatment firstly involved a sub-ambient temperature treatment from 5 to $20^{\circ}C$ for 30 min, followed secondly by a mild heat temperature treatment from 55 to $75^{\circ}C$ for 10 min. This resulted in the production of spherically-shaped particles with a size ranging from 61 to 214 nm. Two-way ANOVA exhibited the finding that both sub-ambient and mild heat temperature significantly (p<0.0001) affected the size of nanoparticles. Zeta-potential values of ${\beta}-lg$ nanoparticles were reduced with increasing mild heat temperature. In conclusion, two-step temperature treatment was shown to play an important role in the manufacturing process - both due to its inducement of the conformational changes of ${\beta}-lg$ during nanoparticle formation, and due to its modulation of the physicochemical properties of ${\beta}-lg$ nanoparticles.