• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1996.12a
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• pp.41-54
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• 1996

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.171-171
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• 2005

• Resources Recycling
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• v.20 no.6
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• pp.63-70
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• 2011

Enviromental friendly leaching process for the recovery of cobalt and copper from the cobalt concentrate was investigated by organic acids as a leaching reagent. The experimental parameters, such as organic acid type, concentrations of leachant, time and temperature of the reaction as well as the solid to liquid ratio were tested to obtain the optinum conditions for the leaching of cobalt and copper. The results showed that citric acid was the most effective leaching reagent among the organic acids used in this experiment. About 99% of cobalt, 95% of copper and 70% of nickel was dissolved by 2.0 M of citric acid. Addition of 3.0 vol.% of hydrogen perioxide was effective to enhance the leaching efficiency and the optinum temperature was found to be about $70^{\circ}C$.

• Resources Recycling
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• v.19 no.6
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• pp.70-76
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• 2010

It was to investigate the optimum leaching conditions for the NaOH hot digestion and hydrochloric acid leaching of Monazite. The optimum condition for NaOH hot digestion was that the concentration of NaOH/TREO mole ratio was 15, the temperature of decomposition $140^{\circ}C$, and reaction time 2 hrs. And the optimum condition for the hydrochloric acid leaching of NaOH hot digestion product was that the concentration of hydrochloric acid was 6N, leaching time 2 hrs and pulp density about 15%. The yield of rare earth oxide was above 90% on the above experimental condition.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.427-434
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• 2013

The leachate from landfill (Andong city) contaminated by foot-and-mouth disease (FMD) contains 44%-50% hydrophilic organic matter, compared with 22%-27% in natural water bodies such as ground water, lake water, and river water. In such natural water, the organic matter content is reduced by the metabolism of microbes in the water. However, in the case of leachate-1 and -2, the concentrations of RTOC (refractory total organic carbon) and RDOC (refractory dissolved organic carbon) were higher than the initial TOC and DOC after burial. According to time elapsed after burial, the concentrations of RTOC and RDOC were decreased below the initial TOC and DOC. In the case of leachate-6 (386 days after burial), RDOC made up 91% of RTOC. This result shows that organic matter in the leachate was composed dominantly of RDOM, most of which was not removed by the metabolism of microbes. Hence, the presence and characteristics of RDOM provide a valuable indication of the effect of leachate on the quality of surface water and ground water. Such information is useful in understanding leachate environments.

• Resources Recycling
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• v.17 no.3
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• pp.48-55
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• 2008

Leaching of copper and silver from mobile phone PCBs(printed circuit boards) with nitric acid was performed to investigate the effects of nitric acid concentrations, leaching temperatures, agitation speeds, and pulp densities on the leaching behaviors of Cu and Ag. The leaching rate considerably increased with increasing acid concentration and temperature. The leaching ratios of Cu and Ag were found to be 96.4% and 96.5%, respectively, under the optimum condition; at $80^{\circ}C$ with 2mol/L $HNO_3$ and 120g/L in pulp density within 39minutes. The kinetic parameters were determined based on the shrinking core model with reaction control corresponding to small particles. The activation energies for the leaching of copper and silver were found to be 45.5kJ/mol and 60.5kJ/mol at $35{\sim}80^{\circ}C$ with 2mol/L $HNO_3$, respectively.

• Resources Recycling
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• v.26 no.6
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• pp.58-64
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• 2017

Leaching of black dross with HCl solution was conducted to find a suitable process to recover valauble materials. In this work, the leaching behavior of the components was compared between black dross and the residues after water treatment. All the components except $TiO_2$ in the black dross were dissolved by HCl solution in the experimental ranges. Treatment of the black dross with water to recover the salts has negative effect on the leaching of $Al_2O_3$, MgO and $SiO_2$. The reactions occuring during the leaching were discussed. At an optimum leaching condition of 3 M HCl and $90^{\circ}C$, the leaching percentage of $Al_2O_3$, MgO and $SiO_2$ was 85, 100 and 40%, respectively.

• Resources Recycling
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• v.25 no.5
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• pp.36-43
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• 2016

The leaching behaviors of copper from chalcopyrite were investigated by sulfuric acid. The leaching of copper was examined according to concentration of sulfuric acid, leaching temperature and addition of hydrogen peroxide and ethylene glycol. The concentrations sulfuric acid and hydrogen peroxide in the leaching solution were increased, the leaching efficiencies of Cu were increased. At $30 -60^{\circ}C$, the leaching efficiency of Cu was increased but it was decreased at $70 - 80^{\circ}C$. The results were due to the increasing of hydrogen peroxide decomposition in the solution above $70^{\circ}C$. In the case of ethylene glycol added at $80^{\circ}C$, the decomposition of hydrogen peroxide was decreased and the leaching efficiency was increased. As a result of SEM analysis of leaching residue after leaching, the residue was found to porous form in the case of the ethylene glycol added and then the leaching efficiency of Cu was increased by the increase of surface area under $60^{\circ}C$ with ethylene glycol.

• 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.18 no.5
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• pp.37-43
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• 2009

The demand for rhenium has considerably increased recently owing to the large-scale consumption in industries and the price of rhenium has increased owing to the lack of supply and its availability. The dust from the roasting of molybdenite was employed to investigate the leaching behavior of rhenium and molybdenum. Leaching experiments were done by varying optimum parameters, such as reaction time, NaOH concentration and leaching temperature. The optimum leaching condition was found to be $4\;mol{\cdot}L^{-1}$ NaOH, 2 hours leaching time, $100\;g{\cdot}L^{-1}$ solid/liquid ratio, $80^{\circ}C$ temperature, and 250 rpm. At this condition, leaching percentage of rhenium and molybdenum was 86.1% and 88.6%, respectively.