• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Resources Recycling
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• v.25 no.5
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• pp.57-63
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• 2016

This study were carried out sulfation roasting and selective leaching test for the effective recovery of copper component in concentrate obtained by froth floatation of Autrallian low grade copper ore. The optimum conditions of sulfation roasting were temp. $450^{\circ}C$, $Na_2SO_4$ 2 mole ratio and time 1.5 h, and then selective leaching were room temperature and $H_2O$ or 1M $H_2SO_4$ solutions. Leaching efficiency of optimum sulfation product were 90 wt.% of copper, 20 wt.% of iron and 15wt.% of nickel elements. In this results, it was possible to selective decomposition leaching of the copper component under optimum conditions in this research.

• KSBB Journal
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• v.16 no.1
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• pp.54-60
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• 2001

The activity of microorganisms is an important factor that determines the efficiency of the bacterial recovery of precious metals from low-grade ore. Metal-leaching microorganisms must have a tolerance, within the concentration levels encountered to leached metals. In this study, the tolerance levels of Thiobacillus ferroxidans to the single and mixed metal ions systems, composed of $Zn^{2+}$, $Cu^{2+}$, $Ni^{2+}$, and $Cd^{2+}$ were investigated. When single metal ions of $Zn^{2+}$ (10~60 g/L), $Cu^{2+}$ (1~6 g/L), $Ni^{2+}$ (1~6 g/L), or $Cd^{2+}$ (1~6 g/L) were added to the growth medium of T. ferrooxidans, the iron oxidation rate of this bacterium was not significantly inhibited. The maximum inhibition percentage observed on the iron oxidation rate of T. ferrooxidans was approximately 50% in the medium supplemented with two or three mixed metal ions of $Cu^{2+}$, $Ni^{2+}$, and $Cd^{2+}$. However, when $Zn^{2+}$ was also added to the medium with the other metal ions, the inhibitory effect on the iron oxidation activity of T. ferroxidans was remarkably increased.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.71-81
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• 2007

The marble-type dolomite from the Jasung Mine, which was farmed by duplicated affects of contact metamorphism and subsequent hydrothermal alteration, corresponds to a high-purity dolomite ranging up to above 98wt.% in dolomite contents. The dolomite contain minor impurities such as quartz, muscovite, and pyrite. It is characteristic that the dolomite is fairy Fe-rich corresponding to 0.4 wt.% due to the presence of pyrite of possible hydrothermal origin. The dolomite is nearly white-colored and constituting with subhedral crystals ranging $0.35{\sim}0.46mm$M in size, forming equigranular texture. Compared to the typical high-Ca limestone from the Pungchon Formation, the powder characteristics of dolomite is rather superior in milling efficiency, yields of fine particles, and size distribution. In addition, except for iron contents, the dolomite powder is no less superior than the limestone in quality and characteristics as fillers with respects to not only whiteness, oil absorption, and specific surface area but also shape characters such as elongation ratio, aspect ratio, and sphericity. This good characteristics of dolomite powder seem to be originated basically from comparatively higher grade and crystallinity of dolomite. Higher iron contents and the presence of sulfides prevents the dolomite from application for uses by thermal treatment, except for metallic manufacture. However, if proper ore separation procedure is available, the dolomite can be sufficiently utilized as substitutes for high-Ca limestone in most fields of filler industries.

• Resources Recycling
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• v.30 no.4
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• pp.27-34
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• 2021

In this study, the leaching behavior of vanadium (V) was investigated through CaO roasting and sulfuric acid leaching from domestic V-bearing titanomagnetite (VTM). Changes in the phase according to the amount of CaO added and roasting temperature were analyzed. Regardless of the roasting conditions, perovskite (CaTiO₃) was preferred to form. When the CaO content was increased, the calcium ferrite (CaFeO_x) phase was formed; otherwise, ferrite (Fe₂O₃) was preferred. After CaO was roasted, leaching was performed for 6 h with 1M sulfuric acid at 50℃ and a 10% solid-liquid ratio. Results of leaching revealed that when the roasted product was sintered, V was not sufficiently oxidized, and the leaching efficiency decreased. In addition, when the roasting temperature was low, the leaching efficiency of V decreased due to the influence of unreacted excess CaO. To lower the leaching efficiency of iron and titanium in VTM concentrates, suppressing the formation of CaTiO₃ and CaFeO_x was necessary by minimizing the amount of CaO added. Consequently, a leaching efficiency of 86% V, 4.3% Fe, and 6.5% Ti was obtained when the roasted product of 1150℃ and 10 wt% CaO was leached.

• Journal of the Korean Society for Railway
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• v.8 no.6 s.31
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• pp.520-524
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• 2005

It is consequential to reduce the environmental impact of a product for sustainable development in 21st Century. In the field of transportation, especially, the technological market concerned about reduction and assessment of greenhouse gas emission is expected to be extended. The LCA gas been esteemed and utilized as a realistic alternative greenhouse gas emission is expected to be extended. The LCA has been esteemed and utilized as a realistic alternative to improve the environment by the assessment of environmental impacts. In this study, simplified life cycle assessment(S-LCA), was performed to analyze the environmental impacts quantitatively, which were produced through the life cycle of a electric motor unit(EMU). The object of the present work is rth investigate main parameters of environmental impacts and to establish the plans to improve the environment impact of EMU. As a result of quantitative assessment for environmental impact and manufacturing, the EMU carbody made of SUS showed acidification(AD) and marine water aquatic ecotoxicity(MAET) the most, while that made of Mild showed high impact of global warning(GW) and abiotic resources depletion(ARD). For the SUS EMU, the high AD and MAET impact is occurred by the discharged pollutants during acid-washing process. Also, high value of GW and ARD for Mild EMU is resulted from the consumption of iron ore, coal and crude oil during manufacturing. Therefore, the environment impact of carbody would be decreased by enhancing of energy efficiency and the lightening the weight of it.

• Journal of the Korean Institute of Navigation
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• v.10 no.2
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• pp.31-55
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• 1986

Generally, the development of shipping is characterized by the amount of traffic flow (traffic volume) and seaborne cargo in the sea. Movement of ships is an essential element of constructing the traffic flow which is represented the dynamic movement of ships in the sea, but on the other band the numbers of arriving and departing the port is the basic factor consisting of the static movement of ships. The amount of cargoes by coastal vessels and ocean trade vessels have increased tremendously with the great growth of the Korean economy these days. This increase of the seaborne cargoes has made the Korean coastal traffic flow so congested that this can be a cause of large pollution as well as great marine casualities such as a loss of human lives and properties . And also the future coastal traffic is expected to increase considerably according to our economic development and high dependence upon foreign trade. Under the circumstance, to devise the safety of coastal traffic flow and to take a proper step of a efficient navigation, there is a necessity for analyzing and surveying the coastal traffic trend and the characteristics of cargo movement. In order to grasp the dynamic movement of ships in the Korean coast, O/D analysis is executed. This paper aims to secure the basic data necessary for a comprehensive plan and estimation of vessel traffic management system for the enhancement of safety, order and efficiency of vessel traffic in the Korean coast. The analyzed results of the traffic flow and seaborne cargoes of the Korean coast are summarized as follows : 1) The congestion by the vessels occurred around the ports such as-in proportion of ship's number (proportion of tonnage) -Incheon 18.5%(14.8%), Pohang 5.9% (9.9%), Samil 5.2%(8.3%), Mokpo 8.6%(0.8%), Pusan 13.5%(36.4%), Ulsan 9.1%(16.2%). 2) It is found that the area adjacent to Incheon, Pusan, Ulsan, Channel of Hanryu and South-western area are heavily congested. 3) It is confirmed thatthe area adjacent to Incheon, Pusan, Ulsan, Channel of Hanryu and South-western area are heavily congested. 3) It is confirmed that the coastal vessels are main elements constituting the coastal traffic and that there are much traffic flow among five ports as following through the precise O/D analysis of ship's coastal movement. Incheon-Samil, Ulsan, Pusan, Jeju Pusan -Samil, Ulsan, Incheon, Jeju Pohang -Samil, Inchoen, Jeju Pohang -Samil, Incheon, Jeju Ulsan -Samil, Incheon, Jeju Samil -Ulsan, Pusan, Incheon 4) The amount of cargoes to abroad are in proportion about 81% of total and the amount of coastal cargoes are about 19%. Of those, cargoes in and out to Japan are about 26% and to South-east Asia are about 27%. 5) The chief items of foreign cargoes are oil(38.33%), iron ore(13.98%), bituminoous coal(12.74%), grain(8.02%), lumber(6.45%) in the import cargoes and steel material(21.96%), cement(17.16%), oil(6.81%), fertilizer(3.80%) in the export cargoes. 6) The 80.5% of total export cargoes and 92.4% of total import cargoes are flowed in five main ports. 7) The chief items of coastal cargoes are oil (42.45%), cement(16.86%), steel material (6.49%), anthracite(6.31%), mineral product(4.3%), grain, and fertilizer. Almost 92.24% of total import and export oil cargoes in Korea is loaded and unloaded at the port of Samil & Ulsan.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2085-2095
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• 2000

Red mud is generated as a by-product during the production of aluminum hydroxide from bauxite ore. In this study inorganic coagulants were prepared by leaching aluminum and iron from red mud with acids under various operating conditions. The optimum leaching efficiency of Al and Fe was obtained by contacting red mud with acids of 5M $H_2SO_4$ and 9M HCI with the ratio of 1/10(g/mL) at $85^{\circ}C$ and $25^{\circ}C$, respectively. In addition. the removal experiments of heavy metal ions($Pb^{2+}$, $Cd^{2+}$, $Cu^{2+}$, $Zn^{2+}$, $Cr^{3+}$), turbidity and phosphate phosphorus($PO_4{^{3-}}-P$) in aqueous solutions were also studied in various experimental conditions. As a result, the developed coagulants are found to show a good removal performance of heavy metal ions. turbidity and phosphate phosphorus in aqueous solutions.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.130-140
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• 2014

Rotary kiln burner has been developed continuously to improve process efficiency and exhaust emission. In this study, the characteristics of the flame and exhaust emission were numerically analyzed according to the diameter of primary air nozzle, equivalent ratio of burner, and equivalent ratio at center and side nozzle for development of multi-nozzle burner in the COG(Coke Oven Gas) rotary kiln for sintering iron ore. The results indicated that the flame length and $NO_x$ emission increase, as the diameter of primary air nozzle and equivalent ratio of burner increase. And according to the change of equivalent ratio at the center and the side of the nozzle, the flame length and average temperature in the kiln show very little change but the $NO_x$ emission shows obvious difference. In conclusion, the best design conditions which have satisfying flame length, average temperature and $NO_x$ emission are as follows: $D_2/D_1$ is 1.33, equivalent ratio of burner is 1.25 and center nozzle conditions are Rich.