• Resources Recycling
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• v.26 no.5
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• pp.77-84
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• 2017

White and black dross are resulted from the recycling of aluminum. There are no established processes to recover valuable materials from black dross. Hydrometallurgical processes seem to be suitable for the treatment of aluminum dross. The salts in the black dross are recovered by dissolving with water. The residues are treated by either alkaline or acid leaching. Although the leaching rate of alumina by NaOH is lower than that by acid, its intermediates are more suitable to the production of alumina-based materials. The future direction for the treatment and recovery of valuable materials from aluminum dross is discussed.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.478-481
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• 2001

The spent petrochemical catalyst used in the manufacturing process of terephthalic-acid contains valuable metals such as cobalt and manganese. To recover these metals, sulfuric acid leaching was performed with hydrogen peroxide as a reducing agent. Low extractions of Mn, Co and Fe were obtained by sulfuric acid leaching without reducing agent. With adding hydrogen peroxide as a reducing agent, the high extraction of these metals could be obtained. Different from general leaching experiment, the extraction rates of metal components were decreased with increasing reaction temperature in this case. Under the optimum condition, the extraction rates of Mn, Co and Fe were 93.0%, 87.0% and 100% respectively.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.130-133
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• 2002

Solder leaching resistance of the metal electrode is an important factor with regard to adhesion properties of ceramic substrate. In the Low Temperature Co-fired Ceramics (LTCC), Ag-Pd or Ag-Pt pastes are used instead of pure Ag paste to prevent leaching. Solder leaching behavior of the Ag-Pd paste in relation to LTCC raw material powder size was investigated. First fabrication of LTCC green tape with different particle size was done. LTCC substrates with Ag-Pd electrode were prepared using conventional multilayer ceramic process. Dipping test was performed to test solder leaching behavior of the electrode. Ag-Pd electrode on LTCC substrate with smaller particle size achieved higher solder leaching resistance.

• International Journal of Concrete Structures and Materials
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• v.9 no.3
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• pp.283-294
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• 2015

In the present study, a porous concrete with alkali activated slag (AAS) and coal bottom ash was developed and the effect of carbonation on the physical property, microstructural characteristic, and heavy metal leaching behavior of the porous concrete were investigated. Independent variables, such as the type of the alkali activator and binder, the amount of paste, and $CO_2$ concentration, were considered. The experimental test results showed that the measured void ratio and compressive strength of the carbonated porous concrete exceeded minimum level stated in ACI 522 for general porous concrete. A new quantitative TG analysis for evaluating $CO_2$ uptake in AAS was proposed, and the result showed that the $CO_2$ uptake in AAS paste was approximately twice as high as that in OPC paste. The leached concentrations of heavy metals from carbonated porous concrete were below the relevant environmental criteria.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.10 no.S_2
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• pp.89-95
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• 2001

The solidification and leaching characteristics of cyclone ash collected from an industrial incineration plant were investigated. Cement and calcium hydroxide were used as the solidifying materials. The leaching characteristics of the solidified cyclone ash were found to vary depending on both the quantitative and the qualitative aspects of the solidifying materials. Except for copper and lead, all the heavy metal ions in the leachate of the solidified material composed of 10~20 % cement or 10~20 % calcium hydroxide were found to be within their standard limit. Moreover, all the heavy metal ions were also observed to be within satisfactory limits in the leachate obtained from the solidified material composed of 30 % cement or 30 % calcium hydroxide. Therefore, to satisfy the standard compressive intensity and permissible limits of heavy metal ions leached from solidified material, it would appear that a 30 % proportion of either additive in the solidification product can meet the required standard for the leachate. The cost of solidifying cyclone ash per ton for ash-30 % cement and ash-30 % lime was calculated as 26,750 and 26,070 won, respectively. Accordingly, significant reduction in the waste toxicity and mobility as well as an improvement in the engineering properties of the solidified products were successfully achieved.

• Resources Recycling
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• v.26 no.2
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• pp.39-45
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• 2017

In order to exclude the effect of uneven distribution of gold in anode slime, the dissolution of gold and silver from the metal mixture was investigated in different systems, such as the mixture of hydrochloric acid and oxidizing reagents ($H_2O_2$, NaClO and $HNO_3$), thiosulfate and thiourea. In the mixture of HCl and either $HNO_3$ or $H_2O_2$, Au was completely dissolved but the leaching percentage of Ag was around 1%. In both thiosulfate and thiourea solution, gold was not dissolved at all. The presence of ferric ion in acidic thiourea solution showed a favorable effect on the leaching of silver but further study is necessary to elucidate the combined effect of ferric ion and sulfuric acid.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.6
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• pp.217-221
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• 2005

The evaporation amounts of volatile Cd, Pb and Zn were characterized by measuring their total concentrations in the EAF dust-clay bodies with various mixing ratio and heat treatment temperature. TCLP test was conducted for evaluating the chemical stabilities of the heavy metal elements. Evaporation amounts and leaching concentrations of heavy metal components were strongly dependent on the mixing ratio and heat treatment temperature. The evaporation of the heavy metal components in EAF dust was effectively suppressed by increasing the clay content. The leaching concentrations of heavy metal components were decreased with increasing clay content and temperature. 20 wt% EAF dust-80 wt% clay sample shows nearly zero evaporation and leaching concentrations of heavy metal components. XRD analysis showed that peak intensities of major crystalline phases such as franklinite and quartz were decreased with increasing the heat treatment temperature which means that the stabilization mechanism of the heavy metals was related with the vitrification process of the $SiO_2$ in the clay.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.05a
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• pp.23-27
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• 2005

Electrogenerated chlorine leaching of used printed circuit board was Investigated in hydrochloric acid solution. The used printed circuit board contained about 45% of metal component, in which copper was about 84%. The leaching rate was greatly effected by current density and agitation. Utilization of electrogenerated chlorine was enhanced by increasing agitation and lowering current density. Leaching of copper was suppressed, while the minor metal elements, such as aluminum, lead, and tin, dominated the leaching at the initial stage.

• Resources Recycling
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• v.28 no.5
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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 Environmental Impact Assessment
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• v.16 no.1
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• pp.35-43
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• 2007

Vitrified aggregates obtained by using mine tailings were evaluated using various leaching methods to assess their environmental safety. The leaching tests in this study include continuous batch leaching, Dutch availability leaching, pH-stat and tank diffusion test as well as TCLP (Toxicity Characteristic Leaching Procedure), which is commonly adopted. Vitrification technique has successfully been applied treating some solid wastes containing high level of heavy metals, such as EAF (Electric Arc Furnace) dust and mine tailings. The potentially most leachable element among trace metals was As and theoretically about 7% of total concentrations in the aggregate can be released under extreme condition. Zinc was leached about 4% and the other trace metals including Cd, Cr and Pb were hardly released from the vitrified mine tailing aggregate.