• Resources Recycling
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• v.16 no.3 s.77
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• pp.44-49
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• 2007

In the present work, the high temperature oxygen pressure leaching behavior of chalcopyrite was studied in sulfuric acid solution. The influence of leaching time, temperature and oxygen partial pressure on leaching process were examined. Leaching rate of copper increased significantly with increasing leaching temperature. Copper recovery reached 87.1% within 2 hours at $200^{\circ}C$ and 10 atm oxygen pressure, while most of the solubilized iron readily re-precipitates as hematite($Fe_2O_3$). It was confirmed that e main leach reaction of chalcopyrite occurred through oxidation with oxygen under oxygen pressure and high temperature(above $150^{\circ}C$). Because sulfur was oxidized entirely to sulfate, passivating elemental sulfur layer was not formed.

• 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.18 no.5
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• pp.44-51
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• 2009

Fundamental study has been made on the recovery of copper from the electronic scrap by hydrometallurgical process. Nitric acid was used as a leaching agent to dissolve the metals such as Cu, Sn, Pb, Fe etc. from the crushed electronic scraps. TBP was employed to extract nitric acid from the strong nitric acid leaching solutions and to reclaim nitric acid. From the experimental results, Cu was effectively leached by 3.0-4.0 M nitric acid. And 95% of nitric acid in the leaching solution was extracted by 60% TBP, and 98% of nitric acid was stripped from the loaded organic phase by distilled water and it was possible to reuse as a leaching agent.

• Resources Recycling
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• v.17 no.5
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• pp.44-51
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• 2008

The removal of minor elements such as Na, Ca and Fe has been performed from domestic aluminum hydroxide of 99.7% purity with organic acids. Oxalic and citric acid were used as the leaching agent, respectively and aluminum hydroxides of different particle size were also employed for the purification with organic acid leaching. Fine grinding of aluminum hydroxide has been tested using ball mills and leaching characteristics of each element have also been examined in terms of leaching parameters such as temperature, acid concentration, and solid density. As a result, it was found that oxalic acid showed higher leaching efficiency than citric acid in the concentration range of 0.1 to 1.0 mole/l and leaching amount of each element was also increased with the acid concentration and reaction temperature. It was observed that about 45% of Na was leached out during ball milling process which implied that the majority of Na contained in aluminum hydroxide was water soluble compound.

• Resources Recycling
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• v.30 no.2
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• pp.53-60
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• 2021

Leaching experiments from single metal and metallic mixtures were conducted to develop a process for the recovery of cobalt, copper, and nickel in spent lithium ion batteries. Inorganic and organic acid solutions without oxidizing agents were employed. No copper was dissolved in the absence of an oxidizing agent in the leaching solutions. The leaching condition to completely dissolve single metal of cobalt and nickel was determined based on acid concentration, reaction temperature and time, and pulp density. The leaching condition to dissolve all of cobalt and nickel from the metallic mixtures was also obtained. Leaching of the metallic mixture with methanesulfonic acid led to selective dissolution of cobalt at low temperatures.

• Journal of Korea Soil Environment Society
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• v.3 no.3
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• pp.21-31
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• 1998

A study on the acid leaching and precipitation has been conducted to remove arsenic from the closed-mine tailings. HCI and H$_2$SO$_4$were used as the leach liquor of arsenic and the tailing obtained from the Da-Duck Mine, which was already closed several decades ago, was also used as the source of arsenic. The effect of the concentration of acid, leaching time and the slurry density on the leaching efficiency of arsenic has been examined. In addition, pH controls and the addition of sodium sulfide were also attempted to remove the arsenic compound as the precipitation from the leachate. After 1 hr leaching by HCI, 40 to 86% of arsenic was leached out depending on the concentration of acid or the slurry density while 47 to 77% of it was leached out by $H_2$$SO_4$. The leaching of arsenic by both acids was almost accomplished within 10 min. and after that only a slight increase in leaching efficiency was observed with leaching time. When the leach liquor was used repeatedly for the leaching of arsenic, the concentration of arsenic in the leach liquor was found to increase continuously although the leaching efficiency was diminished. As far as the precipitation of arsenic in the leachate was concerned, more than 99% of arsenic could be precipitated through the addition of sodium sulfide as the precipitator while the pH controls resulted in the precipitation of up to 84%.

• Resources Recycling
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• v.29 no.6
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• pp.3-14
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• 2020

This study aims to introduce and review on the recovery technologies of rare earth elements(REEs) from coal ash. Many researchers have been carried out by various beneficiation processes, such as particle size separation, magnetic separation, specific gravity, and flotation to recover rare earth elements from coal ash generated from Pulverized Coal(PC) boiler. Through the beneficiation process, it was confirmed that concentration of rare earth elements was much lower than the 4,700 ppm, and that additional enrichment treatment through wet process was needed for the products recovered after the beneficiation process. It was confirmed that the rare earth elements contained in coal ash were applied to the leaching process after pretreatment such as alkali-fusion to improve leaching efficiency. Although beneficiation and leaching methods have been studied, its optimum recovery technologies for rare earth elements not been confirmed up to now, research on the recovery of rare earth contained in coal ash is reported to continue. In case of Korea, the technology for the recovery of rare earth elements from coal ash and coal by-product could not been confirmed up to present. In these reasons, it is urgent to develop technologies such as beneficiation and leaching process continuously.

• Journal of the Mineralogical Society of Korea
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• v.26 no.1
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• pp.9-18
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• 2013

In order to optimize the gold leaching process from refractory sulfide concentrate, a chlorine-hypochlorite solution with varying concentrations and temperatures were applied to salt-roasted concentrate. The concentrate consisted of pyrite, chalcopyrite, and galena, which were turned into hematite through air-roasting at $750^{\circ}C$. Also these concentrates were changed into hematite and nantokite (CuCl)) through salt (NaCl)-roasting at $750^{\circ}C$. The results of the gold leaching experiments showed that the best gold leaching parameters were obtained when the hydrochloric acid-sodium hypochlorite mix was at a ratio of 1 : 2, the added concentration was 1.0 M concentration, the pulp density was 1.0%, and the leaching was done at a $60^{\circ}C$ leaching temperature. The leaching rate for gold was much greater in the roasted concentrate than in the raw concentrate. The leaching rate was greater in the salt-roasted concentrate than in the plain roasted concentrate too. From XRD analysis, quartz was found in the salt-roasted concentrate and in the solid residue from the chlorine-hypochlorite leaching solution at $60^{\circ}C$.

• 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.

• Resources Recycling
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• v.2 no.4
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• pp.23-26
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• 1993

This work is carried out to develop the recovery process of vanadium as vanadium pentoxide and nickel as nickel sulphate from the leaching solution of heavy oil fly ash. First, sodium chlorate solution was added to the leaching solution to oxidize vanadium ions. With adjusting pH of the solution and heating, vanadium ions(V) is hydrated and precipitated as red cake of $V_2O_5$ from the solution. After recovering vanadium, nickel is recovered as ammonium nickel sulfate with crystallization process. From this nickel salt, nickel sulfate which meets the specifications for the electroplating industry can be produced economically. More than 85% of vana-dium and nickel in the fly ash are recovered in this process.