• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.421-426
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• 2001

The pneumatic classification and acidic leaching behaviors of phosphor sludge have been examined to establish the recycling system of rare earth components contained in waste fluorescent lamp. At first, separation characteristic of rare earth components and calcium phosphate in phosphor sludge was investigated by pneumatic classification. After pneumatic classification of phosphor sludge, rare earth components were leached in various acidic solutions and sodium hydroxide solution. For recovery of soluble component in leaching solution, rare earth components were separated as hydroxide and oxalate precipitations. The experimental results obtained are summarized as follows: (1) In classification process, rare earth components in phosphor sludge were concentrated to 29.3% from 13.3%, and its yield was 32.9%. (2) In leaching process, sulfuric acid solution was more effective one as a leaching solvent of rare earth component than other solutions. Y and Eu components in phosphor sludge were dissolved in sulfuric acid solution of 1.5 k㏖/㎥, and other rare earth components were rarely dissolved in leaching solution. Leaching degrees of Y and Eu were respectively 92% and 98% in the following optimum leaching conditions; sulfuric acid concentration is 1.5 k㏖/㎥ , leaching temperature 343 K, leaching time 3.6 ks and pulp concentration 30 kg/㎥. (3) Y and Eu components of phosphor sludge contained in waste fluorescent lamp were, effectively recovered by three processes of pneumatic classification, sulfuric acid leaching and oxalate precipitation methods. Their recovery was finally about 65 %, and its purity was 98.2%.

• 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.

• Resources Recycling
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• v.32 no.3
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• pp.38-44
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• 2023

Leaching tests were conducted using sulfuric acid and sodium hydroxide solutions to remove impurities from domestic graphite concentrate. As a result of the leaching experiment using sulfuric acid solution and sodium hydroxide solution, respectively, the difference of removal efficiency was insignificant when the concentration of sodium hydroxide or sulfuric acid was 2 mol/L or more. The fixed carbon content increased with increasing the temperature in the sulfuric acid solution leaching, while it remains constant above 150℃ in sodium hydroxide solution. For the repeated sequential leaching tests, the leaching conditions were 2 mol/L NaOH, 200℃, 1 hour in the sodium hydroxide solution leaching and 2 mol/L H₂SO₄, 100℃, 1 hour in the sulfuric acid solution leaching, respectively. When sulfuric acid leaching followed by sodium hydroxide solution leaching was repeated 5 times, the fixed carbon increased to 99.95% and ash content decreased to 0.048%, while the fixed carbon increased to 99.98% and ash content was reduced to 0.018 when sodium hydroxide solution leaching followed by sulfuric acid solution leaching was repeated 5 times.

• Clean Technology
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• v.28 no.2
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• pp.103-109
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• 2022

Nd-Fe-B waste permanent magnet contains about 20~30% rare earth elements and about 60~70% iron elements, and the rare earth and iron components were recovered through sulfuric acid leaching and fractional crystallization. Oxidation roasting was not performed for separation and recover of the rare earth and iron elements. The leaching characteristics were confirmed by using as variables the sulfuric acid concentration and the mineral solution concentration ratio. Sulfuric acid leaching was carried out for 3 hours for each sulfuric acid concentration. The leached solid phase was characterized for its crystalline phase, composition, and quantitative components by XRD and XRF analysis, and the filtrate was analyzed for components by ICP analysis. With sulfuric acid leaching at 3M sulfuric acid concentration, neodymium compounds were formed, the iron content was the least, and the recovery rate was high. After the filtrate remaining after sulfuric acid leaching was subjected to fractional crystallization through evaporation and concentration, the neodymium component was found to be concentrated 7.0 times and the iron component 2.8 times. In this study, the recovery rate of waste permanent magnets through sulfuric acid leaching and a fractional crystallization method without an oxidation and roasting process was confirmed to be about 99.4%.

• KSBB Journal
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• v.13 no.3
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• pp.312-319
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• 1998

The dilute-acid pretreatment/hydrolysis of hemicellulose in oak wood using a percolation reactor was investigated. The experimental conditions ranged 160∼180$^{\circ}C$ and 0.05∼0.2 wt.% sulfuric acid. XMG(xylan+mannan+galactan) recovery was higher when sulfuric acid was used as leaching solvent than water. Also it was important for high XMG recovery to keep leaching temperature higher after reaction. XMG recovery was decreased as the size of wood chips was increased. At an optimum condition (reaction condition= 170$^{\circ}C$, 0.1% sulfuric acid, 1ml/min, 10min, leaching condition=0.1% sulfuric acid, 2mL/min, 20 min), the product yield and the sugar concentration were about 92% and 2.7%, respectively.

• Journal of the Korean Chemical Society
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• v.11 no.1
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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.

• Resources Recycling
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• v.11 no.4
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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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• v.10 no.2
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• pp.20-26
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• 2001

Sulfuric acid leaching of Mn, Co and Fe from spent petrochemical catalyst was performed using hydrogen peroxide as a reducing agent. Low extraction of Mn, Co and Fe was obtained by only sulfuric acid. When hydrogen peroxide were added as a reducing agent, the high extraction of these metals could be obtained. Different from ordinary leaching, the extraction per-centages of metal components decreased with elevating leaching temperature in this process. Under the optimum condition, the extraction percentages of Mn, Co and Fe were 93.0% , 87.0% and 100% respectively.

• Resources Recycling
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• v.30 no.3
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• pp.41-46
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• 2021

Methanesulfonic acid (MSA) can be considered effective in the leaching of metals because of its advantageous physical and chemical properties. The chemical reactivities of MSA and sulfuric acid were compared based on their structures and the dissolution data of Co and Ni metal. The inductive and resonance effects play a vital role in the chemical reactivities of these two acids. The dissolution percentages of Co and Ni in the sulfuric acid solution were higher than those in the MSA solution under the same experimental conditions. Considering the strong acidity of MSA and the high solubility of its metal salts, MSA can be employed as a leaching agent for the recovery of metals.

• Resources Recycling
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• v.24 no.6
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• pp.24-30
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• 2015

The sulfuric acid leaching of ferromanganese dust was studied. The effect of acid concentration, reaction temperature, stirring rate, particle size and solid to liquid ratio on Mn and Fe extraction in the solution were investigated. It was found that the leaching rate of Mn and Fe increased with increasing reaction temperature and sulfuric acid concentration. Examination of data by shrinking core model suggested that the leaching rate is controlled by chemical reaction at the surface of particle. The activation energy for the leaching reaction of Mn and Fe were calculated to be 79.55 kJ/mol and 77.48 kJ/mol, respectively.