• Resources Recycling
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• v.25 no.1
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• pp.3-9
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• 2016

The leaching behavior of gold from waste CPU chip using Iodide/Iodine solution was studied. The direct leaching of gold with Iodide/Iodine solution for CPU chip under the size of 150 mesh showed leaching ratio of 20%. It was assumed that the copper film was produced on the gold particle during grinding process and the copper film prevents lodine/Iodide solution from contacting with leachable gold. Meanwhile, the extraction of gold was improved to 90% by pretreatment process with $HNO_3$ solution. In order to explain the result, EDS and ICP analysis for the leaching residue were conducted. It was found that the copper coated on the surface of the gold particle was removed about 80% by $HNO_3$, resulting in the increment of gold leaching rate.

• Journal of the Korean GEO-environmental Society
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• v.16 no.12
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• pp.37-43
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• 2015

Ground characteristics is important in tunnel structure utilizing the strength of underground. In the case of the fault fracture zone such as weak soil conditions exists in the tunnel section and groundwater leaching occurs at the same time, it happens to occur to excessive displacement or collapse of tunnel frequently. Fault fracture zone is an important factor that determines the direction of displacement and the collapse of the tunnel under construction. Behavior of fault fracture zone is determined depending on the size and orientation of the surface portion of the tunnel. If the groundwater occurs in the face of tunnel, groundwater causes displacement and collapse. And the collapse characteristics of tunnel is a major factor in determining that the time-dependent behavior. It is difficult to accurately predict groundwater leaching from the fault fracture zone in the numerical analysis method and analyze the interaction behavior of groundwater and fault fracture zone. Therefore numerical analysis method has limitations the analysis of ground water in the ground which the fault fracture zone and groundwater occurs at the same time. It is required to comprehensively predict the behavior of tunnel and case studies of tunnel construction. Thus, the location of fault fracture zone is an important factor that determines the direction of displacement and the collapse of the tunnel. In this study, behavior characteristics of the tunnel according to the location of the fault fracture was analyzed.

• Resources Recycling
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• v.23 no.1
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• pp.64-69
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• 2014

For the recovery of Co and Cu, bioleaching behavior of Co, Cu, Fe, Mg, Al by Aspergillus niger culture from the molasses growth medium was investigated. Series of leaching tests have been conducted by varying Aspergillus niger's type, molasses concentration in the growth medium, pulp density and reaction time. The results showed that increase of the molasses concentration in the growth medium from 1% to 4% increased the leaching percentage of Co and Cu and the optimal molesses concentration was found to be 4% in the growth medium. Maxinum 90% of Co and 70% of Cu were dissolved from the leaching test at the 10 g/L pulp density, 4 % of molasses concentration in the growth medium after 21 days by Aspergillus niger KCTC 6985. But in case of using Aspergillus niger KCTC 6144, the maxium leaching percentage of Co and Cu was reached 90% respectively at a pulp density 5 g/L and 4% of molasses concentration.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.414-417
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• 2014

LED scraps consisting of highly crystalline GaN and their leaching behavior are comprehensively investigated for hydro-metallurgical recovery of rare metals. Highly stable GaN renders the leaching of the LED scraps extremely difficult in ordinary acidic and basic media. More favorable state can be obtained by way of high temperature solid-gas reaction of GaN-$Na_2CO_3$ powder mixture, ball-milled thoroughly at room temperature and subsequently oxidized under ambient air environment at $1000-1200^{\circ}C$ in a horizontal tube furnace, where GaN was effectively oxidized into gallium oxides. Stoichiometry analysis reveals that GaN is completely transformed into gallium oxides with Ga contents of ~73 wt%. Accordingly, the oxidized powder can be suitably leached to ~96% efficiency in a boiling 4 M HCl solution, experimentally confirming the feasibility of Ga recycling system development.

• Resources Recycling
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• v.22 no.4
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• pp.62-69
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• 2013

A study on the recovery of lithium and leaching behavior of NCM powder by carbon reduction for NCM-system Li-ion battery scraps was conducted. First of all, the oxide powders of NCM-system with layer structure were decomposed by carbon, lithium was converted to lithium carbonate by carbon reaction at above $600^{\circ}C$. The lithium carbonate powders with 99% purity were manufactured by washing method with water and concentration process for NCM powder after carbon reduction. The reaction yield was approximately 88% at $800^{\circ}C$ by carbon reduction. At this time, leaching efficiency at 2M sulfuric acid concentration was over 99% for cobalt, nickel and manganese.

• Resources Recycling
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• v.10 no.6
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• pp.3-8
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• 2001

This study was examed about leaching behavior in order to separate plasticizer selectively before dechlorination from flexible PVC material in alkali solutions at $80~120^{\circ}C$. The dechlorination of that was not almost occurred below $100^{\circ}C$. But the yield of elution of plasticizer was 100% above 5M NaOH. Therefore, by controlling alkali concentration and reaction temperature, it is possible to extract the plasticizer selectively without taking dechlorination.

• Journal of Korea Soil Environment Society
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• v.3 no.2
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• pp.53-60
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• 1998

The influence of venting on the leaching characteristics of pure gasoline and gasoline contaminated soil was studied. The change of leaching characteristics by venting of contaminated soil column could be characterized by two distinct trends : 1) the leaching concentration in TPH-GRO rapidly decreased with evaporation until the evaporation loss became 75% of the original volume. Afterwards, it gradually decreased. 2) the leaching concentrations of individual components showed initial increase followed by gradual decrease. In general, the relative increase of leaching concentration and the venting time to reach the maximum increased with the molecular weight of the components. It should be noted that the decrease of gasoline concentration in the vented air occurs faster than that in the leaching solution. This indicates that, after removing most of the gasoline by evaporation, the focus of the risk assessment for the residual contaminants should be on the groundwater contamination rather than air pollution.

• Resources Recycling
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• v.10 no.6
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• pp.22-28
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• 2001

A study on the recovery of yttrium was conducted using the phosphor sludges generated in the recycling process of obsolete CRTs. Yttrium was leached by HCl and $HNO _3$. The leaching efficiency of yttrium was extensively investigated in terms of acid concentration, leaching temperature and time, and pulp density. Yttrium and lead was recovered from leaching solutions also by precipitation method. The leaching behavior of yttrium was similar in both acids. The leaching efficiency of yttrium for both acids increased with time at the conditions of 3.0M, $90^{\circ}C$, and 280 g/L of pulp density. After 40 minutes, it was saturated to 93% and 90% for HCl and HNO$_3$respectively. Yttrium was recovered from leaching acid solution by the addition of $H_2$$C_2$$O_4$while lead was removed as $PbSO_4$by $Na_2$ $SO_4$.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.02a
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• pp.73-82
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• 2004

This paper studies the leaching behaviors of pyrochlore-rich synroc incorporated 46.8wt% simulated actinides waste under the five simulated geological disposal media, which included the bentonite, granite, granite ＋ ferroferric oxide, granite ＋ cement, bentonite ＋ ferroferric oxide, respectively. The mass loss rates reached to equilibrium after 182 day and was 10-7 g/$\textrm{mm}^2{\cdot}d$. That suggests the mass loss rate of pyrochlore-rich synroc, loaded 46.8wt% actinides waste, was very low. The surfaces of the leached specimens were analyzed by XRD, SEM/EDS. The experimental results show that the pyrochlore-rich synroc samples in the systems, which contained bentonite and cement, have two new phases formed on the leached specimens surface at $90^{\circ}C$ for 728d; The bentonite and cement can retard the elements leaching; $Fe_3O_4$ can speed the elements leaching; Expect for Ti ion depleted on the sample surface, other ion, such as U, Zr, AI, Ca, were in equable states and Ba ion was enriched during test time, which indicated the simulated disposal media have good ability to retard the leaching behavior of the pyrochlore-rich synroc.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.21-31
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• 2003

IAEA, FT-04-020, and ANS 16.1, standard leaching test methods, were evaluated comparatively with their test results. Leaching index of Co-60 and Cs-137 for all waste forms were above 6.0. Their leaching behavior were contrary according to the type of matrix and leachant. Leachability of Co in cement waste form was higher in simulated seawater than demi. water, and higher in demi. water in paraffin waste form. Leachability of Cs was contrary to Cs. Cumulative fraction leached of Co was higher such as IAEA＞ANS＞FT in cement waste form.