• Proceedings of the IEEK Conference
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.240-244
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• 2001

Recycling process involving mechanical, thermal, hydrometallurgical, and sol-gel step has been applied to recover cobalt and lithium from spent lithium ion batteries and to synthesize LiCoO$_2$from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt could be concentrated with 2-step thermal and mechanical treatment. Leaching behaviors of the lithium and cobalt in nitric acid media was investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO$_3$solution turned out to be an effective reducing agent by enhancing the leaching efficiency. O f many possible processes to produce LiCoO$_2$, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO$_2$with nitric acid, the molar ratio of Li/Co in the leach liquor was adjusted at 1.1 by adding a fresh LiNO$_3$solution. Then, 1 M citric acid solution at a 100% stoichiometry was also added to prepare a gelatinous precursor. When the precursor was calcined at 95$0^{\circ}C$ for 24 hr, purely crystalline LiCoO$_2$was successfully obtained. The particle size and specific surface area of the resulting crystalline powders were 20 пm and 30 $\textrm{cm}^2$/g, respectively The LiCoO$_2$powder was proved to have good characteristics as cathode active materials in charge/discharge capacity and cyclic performance.

• Resources Recycling
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• 제28권5호
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• pp.68-73
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• 2019

Ilmenite is one of the principal ores for the production of titanium dioxide. To produce titanium dioxide with purity higher than 99.9% from ilmenite, Ti(IV) should be separated from the dissolved impurities such as Fe(III), Si(IV), and Mn(II) present in ilmenite. In this work, a hydrometallurgical process was investigated to recover pure titanium dioxide from ilmenite by HCl leaching followed by separation and hydrolysis of Ti(IV). An optimum leaching condition was obtained by investigating the effect of HCl concentration, pulp density, and leaching time on the leaching percentage of Ti(IV), Fe(III), Si(IV), and Mn(II). Ammonium hydroxide and sodium hydroxide solutions were employed as neutralizing agents to hydrolyze Ti(IV) from the stripping solution of Ti(IV). Titanium dioxide of the anatase phase was obtained by calcination of the hydrolyzed precipitates with $NH_4OH$ solution. A hydrometallurgical process can be developed to produce pure $TiO_2$ powders from ilmenite.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제3권1호
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• pp.75-84
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• 1993

Copper coating on graphite powders was carried out by cementation process from copper sulfate solution. Effects of operation variables such as copper ion concentration, stirring speed, reaction time and temperature were investigated to obtain optimum conditions for continuous and uniform copper coating on graphite powders. The activation energy of the copper coating process was found to be 3. 59kcal/mole.

• Resources Recycling
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• 제6권3호
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• pp.36-40
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• 1997

A series of processes has been developed to recover the gold from electronic scrap containing about 200~600 ppm Au. First, mechanical beneficiation including shredding, crushing and screening was employed. Results showed that 99 percent of gold component leaves in the fraction of under 1mm of crushed scrap and its concentration was enriched to about 800 ppm without incineration. The crushed scrap was leached in 50% aqua regia solution and gold was completely dissolved at $60^{\circ}C$ withing 2 hours. Other valuable metals such as silver, copper, nickel and iron were also dissolved. The resulting solution was boiled to remove nitrous compounds in the leachate. Finally, a newly designed electrolyzer was tested to recover the gold metal. More than 99% of gold and silver were recovered within an hour by electrowinning process.

• Resources Recycling
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• 제32권1호
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• pp.33-41
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• 2023

Herein, we selectively recovered Zn and produced ZnSO₄ from electric arc furnace dust using a hydrometallurgical process. The analysis of the properties of the electric arc furnace dust revealed that the Fe content (9.9%) was relatively low while the Mn content (19%) was high as compared to the composition of general dust. Therefore, an appropriate hydrometallurgical process was designed based on the properties of the raw materials. In the leaching process involving the use of 1.6 M sulfuric acid and 20% solid-liquid ratio at 60℃ for 1 h, 85% of the Zn and Mn got dissolved while the Fe was not leached. To selectively recover Zn, a solvent extraction process using D2EHPA as the extractant was chosen, and 99% of the Zn was extracted using 0.8 M D2EHPA with 32% saponification and an O/A ratio of 2 using counter-current 3-stage extraction. Mn was entirely scrubbed with an aqueous sulfuric acid solution of pH 1.5. Finally, Zn was concentrated and stripped using 1.5 M sulfuric acid at an O/A ratio of 4 using counter-current 4-stage stripping. The stripping solution contained 40 g/L of Zn, and 99.9% of ZnSO₄∙H₂O was obtained by vacuum distillation.

• Resources Recycling
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• 제14권6호
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• pp.28-36
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• 2005

A hydrometallurgical process to leach cobalt from the waste cathodic active material, $LiCoO_{2}$, and subsequently to separate it by solvent extraction was developed. The optimum leaching conditions for high recovery of colbalt and lithium were obtained: 2.0 M sulfuric acid, 5 $vol.\%$ hydrogen peroxide, $75^{\circ}C$ leaching temperature, 30 minutes leaching time and an initial pulp density of 100 g/L. The respective leaching efficiencies for Co and Li were $93\%$ and $94.5\%$. About $85\%$ Co was extracted from the sulfuric acid leach liquor containing 44.72 g/L Co and 5.43 g/L Li, using 1.5 M Cyanex272 as an extractant at the initial pH 5.0 and in organic to aqueous phase ratio of 1.6:1 under the single stage extraction conditions. The Co in the raraffinate was completely extracted by 0.5 M Na-Cyanex272 at the inital pH 5.0, and an organic to aqueous phase ratio of 1;1. The cobalt sulfate solution of higher than $99.99\%$ purity could be recovered from waste $LiCoO_{2}$, using a series of hydrometallurgical processes: sulfuric acid leaching of waste $LiCoO_{2}$- solvent extraction of Co by Na-Cyanex 271 - scrubbing of Li by sodium carbonate solution - stripping of Co by sulfuric acid solution.

• Resources Recycling
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• 제29권2호
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• pp.62-68
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• 2020

In new millennium, wide-reaching demands for selective catalytic reduction (SCR) catalyst have been increased gradually in new millennium. SCR catalyst can prevent the NO_x emission to protect the environment. In SCR catalyst the main composition of the catalyst is typically TiO₂ (70~80%), WO₃ (7~10%), V₂O₅ (~1%) and others. When the SCR catalysts are used up and disposed to landfills, it is problematic that those should exist in the landfill site permanently due to their extremely low degradability. A new advanced technology needs to be developed primarily to protect environment and then recover the valuable metals. Hydrometallurgical techniques such as leaching and liquid-liquid extraction was designed and developed for the spent SCR catalyst processing. In a first stage, V and W selectively leached from spent SCR catalyst, then both the metals were processed by liquid-liquid extraction process. Various commercial extractants such as D2EHPA, PC 88A, TBP, Cyanex 272, Aliquat 336 were tested for selective extraction of title metals. Scrubbing and stripping studies were tested and optimized for vanadium and tungsten extraction and possible separation. 3^rd phase studies were optimized by using iso-decanol reagent.

• Resources Recycling
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• 제28권5호
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• pp.3-18
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• 2019

Due to the increasing demand for clean energy, the consumption of lithium ion batteries (LIBs) is expected to grow steadily. Therefore, stable supply of lithium is becoming an important issue globally. Commercially, most of lithium is produced from the brine and minerals viz., spodumene, although various processes/technologies have been developed to recover lithium from other resources such as low grade ores, clays, seawaters and waste lithium ion batteries. In particular, commercialization of such recycling technologies for end-of-life LIBs being generated from various sources including mobile phones and electric vehicles(EVs), has a great potential. This review presents the commercial processes and also the emerging technologies for exploiting minerals and brines, besides that of newly developed lithium-recovery-processes for the waste LIBs. In addition, the future lithium-supply is discussed from the technical point of view. Amongst the emerging processes being developed for lithium recovery from low-grade ores, focus is mostly on the pyro-cum-hydrometallurgical based approaches, though only a few of such approaches have matured. Because of low recycling rate (<1%) of lithium globally compared to the consumption of lithium ion batteries (56% of lithium produced currently), processing of secondary resources could be foresighted as the grand opportunity. Considering the carbon economy, environment, and energy concerns, the hydrometallurgical process may potentially resolve the issue.

• Resources Recycling
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• 제22권2호
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• pp.3-10
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• 2013

Indium is one of the rare metals, and it has been used mainly for preparation of indium tin oxide (ITO). This review investigated the process parameters and the merits and demerits of several methods to recover indium from the leaching solution of secondary resources, such as solvent extraction, ion exchange, and precipitation. D2EHPA has been used mostly as a cationic extractant for indium extraction in moderate acid solutions, while amine extractants are used in strong hydrochloric acid solution. Since the loading capacity of resins for indium is generally small, ion exchange has some advantage over solvent extraction only when the concentration of indium is low.

• Journal of the Korean Ceramic Society
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• 제47권6호
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• pp.618-622
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• 2010

Cost-effective purification methods of silicon were carried out in order to replace the conventional Siemens method for solar grade silicon. Firstly, acid leaching which is a hydrometallurgical process was preceded with grinded silicon powders of metallurgical grade (~99% purity) to remove metallic impurities. Then, plasma treatments were performed with the leached silicon powders of 99.94% purity by argon plasma at 30 kW power under atmospheric pressure. Plasma treatment was specifically efficient for removing Zr, Y, and P but not for Al and B. Another purification step by EB treatment was also studied for the 99.92% silicon lump which resulted in the fast removal of boron and aluminum. That means the two methods are effective alternative tools for removing the doping elements like boron and phosphor.