• 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.365-369
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• 2001

EAF's dust has been treated mainly by pyrometallurgical reduction process in rotary kiln furnace to recover valuable metal elements such as Zn and to avoid the disposal of hazardous materials to waste. Recently, hydrometallurgical eletrowinning of zinc from a zinc-amino chloride solution obtained by the leaching of EAF's dust was developed to recover high grade zinc metal from EAF’s dust. But there are some disadvantages in each process such as difficulty of operation condition control and sticking problem in kiln process and low extractability and recovery of zinc owing to insoluble zinc-ferrite in electrowinning process. We propose a new combined process of pyrometallurgical one and hydrometallurgical one to treat EAF's dust efficiently and economically. In this study, ammonium chloride solution leaching of crude zinc oxide recovered from reduction of EAF's dust was carried out to find out the efficiency of zinc extraction from it and the possibility for performance of eletrowinning in the proposed process. Effects of various leaching variables ruck as leaching temperature, concentration of leaching solution and leaching time were investigated. And the leaching results of the crude zinc oxide were compared with those of EAF's dust. The extraction percents of zinc in ammonium chloride solution leaching of the crude zinc oxide recovered from reduction of EAF's dust were above 80% after 60 minutes of leaching under the leaching condition of 4M NH$_4$CI concentration and above leaching temperature of 7$0^{\circ}C$. And the concentrations of zinc in the leached solution were obtained above 50g/$\ell$. The activation energy calculated for zinc extraction in NH$_4$CI leaching was 58.1 KJ/㏖ for EAF's dust and 15.8 KJ/㏖ for the crude zinc oxide recovered from reduction of EAF's dust.

• Journal of the Korean Wood Science and Technology
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• 제35권5호
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• pp.46-57
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• 2007

The leachability of boron in zinc borate (ZB)-modified oriented strandboard (OSB) from southern wood species was investigated in this study. The leaching experiments were conducted by exposing edge-sealed OSB samples under running water at $31^{\circ}C$ for 8, 24, 72, and 216 h. The results from leached samples were compared with those from the unleached controls. Boron leaching of the modified OSB occurred upon the initial water exposure, and the leaching rate decreased as the leaching time increased. Initial boric acid equivalent (BAE) level, wood species, and sample thickness swelling significantly influenced the leachability. There was no consistent effect of polyethylene glycol (PEG) on zinc borate leaching. The glue-line washing within OSB due to thickness swelling of the test samples under water and decomposition of the borate to form water-soluble boric acid were thought to be two possible causes for the observed leaching. The relationship between assayed BAE and leaching time followed a decaying exponential function for zinc borate treated OSB. From the boron/zinc ratio after each leaching period, boron element in ZB was more or less leachable. The material constant of the regression models allowed comparing the leachability of the modified OSB for various wood species. An unified leaching method for treated wood composite materials is needed.

• Journal of the Korean Chemical Society
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• 제11권1호
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• pp.33-37
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• 1967

The influence of impurities contained in Marmatite ores on leaching of zinc was investigated. The zinc sulfide having the same crystal structure of natural Sphalerite was prepared by heating the zinc sulfide chemically precipitated, at $650^{\circ}C$ in nitrogen atmosphere. The activation energy of the sample was 25.8 kcal per mole in the leach test when oxygen partial pressure was 5 atm. and the value was exceedingly high compared to that obtained in Marmatite ores. Synthetic zinc sulfides added with small amount of each impurities were treated in same procedure. As a result, it was found that the leaching velocity was accelerated sharply when about 1 percent of $Cu^{++}$ was blended to the sample. Larger amount of iron has also same effect but the effect was minor compared to the copper. The other impurities indicated no appreciable catalytic action.

• Journal of Environmental Science International
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• 제7권3호
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• pp.401-408
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• 1998

An experimental research was preformed for the development of an effective process for zinc oxide waste(zinc ash) reuse. Zinc was selectively leached from zinc ash by 30 vol.% D2EHPA In kerosine solution, and the leaching velocity was quite fast. Zinc leached was stripped by sulfuric acid solutions, and the amount of zinc stripped was linearly Increased with the amount of sulfuric acid used. Zinc oxide fine particles were obtained by dropwise adding of sodium hydroxide solution to the resultant aqueous zinc solution at 85$^{\circ}C$.

• Journal of the Korean Chemical Society
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• 제11권1호
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• pp.38-43
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• 1967

In order to explain the positive catalytic action of copper compound for the rate of leaching of zinc sulfide minerals, the electrode and redox potentials of both synthetic and natural sulfides were measured at various conditions of temperatures and pressures. The potentials of Chalcopyrite and copper sulfide were considerably higher than that of zinc sulfide, whereas lead sulfide and Galena had slightly lower potentials than that of zinc sulfide. At elevated temperatures and pressures, the same tendency was obtained. By means of comparing the calculated and measured values of potentials for sulfides, it was suggested that the electrode potentials in acid solution were generated by oxidation of sulfur ion. As a result, it was concluded that the catalytic action of copper compound in the leaching of synthetic zinc sulfide should be arised from the galvanic action between sulfides keeping intimate contact one another in which copper sulfide worked as cathodic and zinc sulfide as anodic part analogous to the metal corrosion under galvanic action.

• Resources Recycling
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• 제9권3호
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• pp.22-28
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• 2000

A study on the recovery of gallium from zinc residues is carried out by alkali leaching using NaOH. The results show that in case of alkali leaching of zinc residues, Zn, K and Si are mainly leached out and Fe and other base metals are scarcely leached out, which results in that gallium is easily recovered by solvent extraction. The leaching efficiency of gallium increases with increasing alkali concentration and solid density. Especially, alkali consumption is considerably reduced by washing the zinc residues with water before leaching in order to eleminate the soluble zinc compounds. The gallium from zinc residues is found to be leached out with a recovery of 80% or higher for 2hrs leaching with 1~1.25 M/L NaOH solution and solid density 333 g/L at $25^{\circ}C$.

• Resources Recycling
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• 제11권4호
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• pp.44-50
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• 2002

Characteristics on the sulfuric acid leaching of zinc and manganese from the spent zinc-carbon battery powders obtained by cushing and magnetic separation, were investigated with the variation of sulfuric acid concentration, reaction temperature, stir-ring speed and solid/liquid ratio. The sample powders were composed of Zn metal, ZnO, $MnO_2$ and $Mn_2$$O_3$. and it was found that the selective leaching of zinc was difficult in this system. At the condition of S/L ratio 1:10, IM H$_2$$SO_4$, $60^{\circ}C$ and 200 rpm, leaching rate of Zn and Mn are 92% and 35% respectively. The concentration of Zn and Mn in the leaching solution are 19.5 g/l, 7.8 g/l and pH of that solution is 0.75. It was confirmed at reducing agent should be added to increase e leaching rate of manganese with sulfuric acid.

• Resources Recycling
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• 제13권1호
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• pp.22-27
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• 2004

Purification on the leaching solution of the crude zinc oxide obtained by the reduction of EAF dust has been carried out. Pb and Cd ions in the leaching solution were precipitated and removed from the solution by the addition of zinc metal powder. The purification condition for electrowinning to obtain the high purity zinc metal was investigated by analyzing the effects of Pb and Cd ion concentrations on the contents of impurities in the recovered zinc metal. The 3 N purity zinc metal was obtained at the electrolysis condition of the concentrations of Pb less than 2 ppm and Cd less than 0.1 ppm in the purified solution. For this purification, the amounts of zinc metal powder more than 8.5 g/l should be added in the crude zinc oxide leached solution.

• Journal of the Korean Chemical Society
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• 제11권1호
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• pp.28-32
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• 1967

The direct acid leaching of domestic Marmatite concentrate at elevated temperatures and pressures was investigated. Almost 100 percent of zinc was extracted from the concentrate liberating free sulfur in 4 hours at $100^{\circ}C$ when the oxygen partial pressure was 5 atm. in sulfuric acid solution. By applying the Arrhenius equation to leach reaction in the range of $60^{circ}$ to $100^{\circ}C$ at the same oxygen partial pressure, 15.7 kcal per mole of activation energy was calculated. At the initial stage of leaching, the rate of reaction increased linearly by increasing temperature and pressure. The concentration of sulfuric acid gave minor effect to leaching velocity in the range of 5 to 20 percent. The particle size should be under 270 mesh for 100 percent extraction of zinc.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.491-492
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• 2006

The horizontal high energy rotor ball mill ($Simoloyer^{(R)}$) is used to break and activate dry solids. It is used for dry-milling and in the vertical mount for wet-milling in leaching processes. Technical electric arc furnace (EAF) dust with high contents of zinc oxide, zinc ferrite and magnetite is efficiently separated by ambient temperature leaching. The process shows promise for industrial application