• Title/Summary/Keyword: oxidative leaching

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Dissolution of Pb from the Complex Sulphide Concentrates Containing Galena and Arsenopyrite by Alkaline Oxidative Leaching (황비철광(黃砒鐵鑛)과 방연광(方鉛鑛)의 혼합황화광(混合黃化鑛)의 알카리산화(酸化)에 의한 Pb침출(浸出))

  • Youn, Ki-Byoung
    • Resources Recycling
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    • v.17 no.3
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    • pp.42-47
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    • 2008
  • In this work, the dissolution behavior of Pb from the complex sulphide concentrates containing Galena and Arsenopyrite by alkaline oxidative leaching was studied. The influences of leaching temperature, oxygen partial pressure, leaching time and NaOH concentration of leaching solution were examined at the leaching conditions in the range of $100^{\circ}C{\sim}140^{\circ}C$ temperature, $40psi{\sim}100psi\;PO_2$ and $0.5M{\sim}2M$ NaOH concentration. The optimum result was obtained at the leaching condition of leaching temperature $120^{\circ}C$, 100psi $PO_2$, leaching time 30min. and 2M NaOH concentration of leaching solution.

Removal and Separation of Metallic Constituents from the By-product Recovered from Gold Mine Tailings (금(金) 광산(鑛山) 폐광미(廢鑛尾)로부터 회수(回收)된 금속광물(金屬鑛物) 부산물(副産物) 중의 금속성분(金屬成分) 분리(分離), 제거연구(除去硏究))

  • Youn, Ki-Byoung
    • Resources Recycling
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    • v.19 no.3
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    • pp.9-15
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    • 2010
  • Domestic gold mine tailings, generally, contain a lot of non-metallic silica and clay minerals. These minerals can be separated from the tailings by various physical separation methods and used as raw materials for cements and ceramic products. In these physical separation procedures, metallic complex sulfides, in which Au and metallic constituents such as Pb, As and Fe were concentrated, were obtained as a by-product. These metallic constituents should be removed or separated from the by-product to extract Au efficiently. In this work, removal and separation processes of Pb, As, and Fe from the by-product were investigated. Pb was removed to under 3% by using alkaline oxidative leaching at the leaching condition of $120^{\circ}C$, 2M NaOH, 100psi $Po_2$, 250r.p.m., 4 wt.% solid and 30 min. leaching time. The leached residue was roasted and separated magnetically to obtain a non-magnetic product contained <0.2% As, <3% Fe and high concentrated Au more than 8,000 ppm.

Reprocessing of fluorination ash surrogate in the CARBOFLUOREX process

  • Boyarintsev, Alexander V.;Stepanov, Sergei I.;Chekmarev, Alexander M.;Tsivadze, Aslan Yu.
    • Nuclear Engineering and Technology
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    • v.52 no.1
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    • pp.109-114
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    • 2020
  • This work presents the results of laboratory scale tests of the CARBOFLUOREX (CARBOnate FLUORide EXtraction) process - a novel technology for the recovery of U and Pu from the solid fluorides residue (fluorination ash) of Fluoride Volatility Method (FVM) reprocessing of spent nuclear fuel (SNF). To study the oxidative leaching of U from the fluorination ash (FA) by Na2CO3 or Na2CO3-H2O2 solutions followed by solvent extraction by methyltrioctylammonium carbonate in toluene and purification of U from the fission products (FPs) impurities we used a surrogate of FA consisting of UF4 or UO2F2, and FPs fluorides with stable isotopes of Ce, Zr, Sr, Ba, Cs, Fe, Cr, Ni, La, Nd, Pr, Sm. Purification factors of U from impurities at the solvent extraction refining stage reached the values of 104-105, and up to 106 upon the completion of the processing cycle. Obtained results showed a high efficiency of the CARBOFLUOREX process for recovery and separating of U from FPs contained in FA, which allows completing of the FVM cycle with recovery of U and Pu from hardly processed FA.

Extraction of Caffeine from Spent Coffee Grounds and Oxidative Degradation of Caffeine (커피 찌꺼기의 카페인 용출 및 산화분해 특성)

  • Shin, MinJeong;Kim, Young-Hun
    • Journal of Environmental Science International
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    • v.27 no.12
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    • pp.1205-1214
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    • 2018
  • During the past few decades, significant increase in the consumption of coffee has led to rapid increase in the production of coffee waste in South Korea. Spent coffee waste is often treated as a general waste and is directly disposed without the necessary treatment. Spent Coffee Grounds (SCGs) can release several organic contaminants, including caffeine. In this study, leaching tests were conducted for SCGs and oxidative degradation of caffeine were also conducted. The tested SCGs contained approximately 4.4 mg caffeine per gram of coffee waste. Results from the leaching tests show that approximately 90% of the caffeine can be extracted at each step during sequential extraction. Advanced oxidation methods for the degradation of caffeine, such as $UV/H_2O_2$, photo-Fenton reaction, and $UV/O_3$, were tested. UV radiation has a limited effect on the degradation of caffeine. In particular, UV-A and UV-B radiations present in sunlight cause marginal degradation, thereby indicating that natural degradation of caffeine is minimal. However, $O_3$ can cause rapid degradation of caffeine, and the values of pseudo-first order rate constants were found to be ranging from $0.817min^{-1}$ to $1.506min^{-1}$ when the ozone generation rate was $37.1g/m^3$. Additionally, the degradation rate of caffeine is dependent on the wavelength of irradiation.

The Leaching of Gold-silver from Refractory Gold Concentrate by Chlorine-hypochlorite Solution (염소-차아염소산 용액에 의한 저항성 금 정광으로부터 Gold-silver 용출)

  • Cho, Kang-Hee;Kim, Bong-Ju;Oh, Su-Ji;Choi, Seoung-Hwan;Choi, Nag-Choul;Park, Cheon-Young
    • Journal of the Mineralogical Society of Korea
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    • v.25 no.3
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    • pp.123-130
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    • 2012
  • Leaching experiments of gold and silver from roasted concentrate were carried out using a chlorine-hypochlorite solution. The leaching rate of gold was 75% at 1.5:1 ratio of chlorine and hypochlorite and increased to 81% with adding 1 M NaCl. However, at 1% pulp density and at $65^{\circ}C$, the leaching rates of Au were close to 100%. XRD analysis identified quartz in the solid residues after digestion of roasted concentrate with aqua regia or chlorine-hypochloride leaching solution. This suggests that the gold may not be leached out of the quartz in aqua regia or chlorine-hypochlorite solution. In order to leach the gold from the quartz, the concentrate will have to be pre-treated through ultra-fine grinding or treated with stronger oxidative agents.

Leaching of Molybdenite by Hydrochloric Acid Solution Containing Sodium Chlorate (NaClO3를 함유한 염산용액으로 몰리브데나이트광의 침출)

  • Nguyen, Thi Nhan Hau;Nguyen, Thi Thu Huong;Lee, Man Seung
    • Resources Recycling
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    • v.31 no.5
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    • pp.26-33
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    • 2022
  • Molybdenum is widely used in many materials; thus, its recovery from ores and secondary resources has attracted considerable attention. In this study, the leaching of molybdenite ore using hydrochloric acid containing sodium chlorate as an oxidizing agent was studied. The effects of several variables, such as the concentrations of HCl and NaClO3, reaction temperature and time, and pulp density, on the leaching of the ore were investigated. Under strong acidic and oxidizing conditions, the sulfide in the ore was dissolved as a sulfate ion, which formed gypsum with Ca(II), leading to a decrease in the leaching percentage of Mo(VI) from the ore. The leaching percentage of molybdenum was greater than 90%, while those of iron, calcium, and silicon were 38, 29, and 67%, respectively, under the optimum conditions: 2.0 M HCl, 0.5 M NaClO3, pulp density of 5 g/L, temperature of 90 ℃, and treatment time of 60 min.

Behavior of Oxidative Precipitation of High-Arsenic (III) Solution Utilizing Activated Carbon with Air Injection (공기와 활성탄 병용에 의한 용액 중 고농도 3가 비소의 산화-침전 거동 연구)

  • Kim, Rina;Kim, Gahee;Kim, Kwanho;You, Kwang-suk
    • Resources Recycling
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    • v.30 no.4
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    • pp.11-19
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    • 2021
  • Arsenic (As) oxidation followed by precipitation from a high-As(III)-containing leaching solution derived from a sulfidic ore was investigated in this study to remove aqueous As from the solution using activated carbon (AC) with air injection as an oxidant. To obtain the initial leaching solution, a domestic sulfidic ore was leached in a sulfuric acid solution at pH 1 and 50℃ for 95 h, and approximately 7 g/L of Fe and 3 g/L of As were leached out. To determine the effect of the oxidative reaction utilizing AC with air injection, the leaching solution was tested under the following five oxidative conditions at an initial pH of 1 and 90℃ for 72 h: air-only injection; air injection with 1, 5, and 10 w/v% of AC addition; and H2O2 addition. The tests in the presence of both air and AC revealed that the oxidation kinetics and As removal were improved by the reaction between the metallic species and the surface group formed on the AC surface. In addition, the greater the amount of AC added, the better was the reaction efficiency, removing 93-94% of As with more than 5 w/v% of AC addition. Finally, X-ray diffraction analysis confirmed that the precipitate formed from the oxidative reaction was scorodite (FeAsO4·2H2O).

Recovery of Gallium and Indium from Zinc Residues by Acid Leaching (산침출에 의한 아연제련잔사로부터 갈륨 및 인디움의 회수)

  • 이화영;김성규;오종기
    • Resources Recycling
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    • v.2 no.2
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    • pp.22-26
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    • 1993
  • The flowsheet for the recovery of gallium and indium from zinc residues has been established based on the sulfuric acid treatment. In comparison with the alkali treatment, the method proposed in this work allowed the recovery of indium together with gallium. The majority of iron contained in leach liquor could be removed through the two-stage neutrallization under oxidative or reductive atmosphere. Crude gallium and indium could be obtained through the alkali and/or acid leaching of the products generated from the above treatment. In addition, cementation of indium with zinc powders could also be used for the concentration of it from weak acid solutions.

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The Leaching Behavior of Unirradiated $UO_2$ Pellets in Wet Storage and Disposal Conditions

  • Park, Geun-Il;Lee, Hoo-Kun
    • Nuclear Engineering and Technology
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    • v.28 no.4
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    • pp.349-358
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    • 1996
  • The leaching behavior of uranium from unirradiated CANDU UO$_2$ fuel pellet in the spent fuel wet storage and disposal conditions has been investigated. A modified IAEA leach test method was used, and then the extent of leaching was monitored by analysis for uranium in the leachant. The leach test has been performed in various leachants(demineralized water and boric acid solution at pH=6, synthetic granite groundwater) for a long-term period of 5.4 years, and the effect of temperature on the leach rate of uranium has been analyzed. The leach rates of uranium at $25^{\circ}C$ were dependent on the leachants. Over initial 100 days of leach periods, the leach rate in groundwater was the highest in three leachants and no significant differences of leach rates ore observed in the demineralized oater and boric acid solution. But these leach rates in three leachants around 2,000 days at $25^{\circ}C$ appeared to be reached the steady rates in the range of 1~5$\times$10$^{-8}$ g/$\textrm{cm}^2$ day. The leach rate of uranium in groundwater shooed to be independent of the temperature, but those in both demineralized water and boric acid solution increased with temperature. These results show that the leaching behavior of uranium from UO$_2$ fuel in both the demineralized water ann boric acid may be controlled tv the surface oxidative.dissolution reaction of UO$_2$ and the leach rate of uranium in groundwater at room temperature could mainly be controlled by the complex reaction of dissolved uranyl ions with carbonate ions and no variation of leach rate of UO$_2$ in groundwater with temperature may be due to the local deposition of passivating uranyl phases on the surface.

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Leaching Behavior of Vanadium and Possibility of Recovery of Valuable Metals from VTM Concentrate by Sulfuric Acid Leaching (바나듐함유 티탄철석 정광으로부터 황산 침출법에 의한 바나듐의 침출거동 및 유가금속의 회수가능성)

  • Joo, Sung-Ho;Shin, Dong Ju;Lee, Dongseok;Park, Jin-Tae;Jeon, Hoseok;Shin, Shun Myung
    • Resources Recycling
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    • v.31 no.1
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    • pp.65-77
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    • 2022
  • A study was conducted in Korea on the leaching behavior and possibility of recovery of vanadium and other valuable metals from domestic vanadium titanomagnetite (VTM) by direct acid leaching. In this study, a VTM concentrate containing 0.8% V2O5 was used, and the ratio of magnetite to ilmenite was calculated as 1.9:1 by using the HSC program. The leaching behavior of vanadium from the VTM was similar to that of iron, and it was affected by the concentration of sulfuric acid and temperature. Further, titanium could be leached in the form of TiOSO4 at a temperature higher than 75℃. To improve the leaching efficiency of V, Fe, and Ti in VTM, reductive sulfuric acid and oxidative sulfuric acid leaching were performed. When Na2SO3 was used as a reducing agent, the leaching rate of vanadium was 80% of that in that case of leaching by sulfuric acid. Similarly, the leaching rate of titanium increased from 20% to 50%. When Na2S2O8 was used as an oxidation agent, most of the vanadium was leached, and the main residue found by XRD analysis was ilmenite. In studies on the possibility of recovering valuable metals, the selective extraction of metals is hardly achieved by solvent extraction from oxidation leaching solutions; however, in this study, Cyanex 923, a solvation extractant from reductive leaching solutions, could selectively extract Ti.