• 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.

• Resources Recycling
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• v.24 no.1
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• pp.3-11
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• 2015

Soluble silica generated from acid leaching process is very difficult to filter and deceases the purity of products, and thus becomes one of hot issues in hydrometallurgy. This paper reviewed the dissolution and reactivities of silicates in acid solution, and the methods for treatment of soluble silica. Removal of silica with alkaline pre-treatment, crystallization to $SiO_2$ and precipitation behaviour of silica with coagulation under acid conditions were briefly described.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.346-349
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• 2004

국내에 자연 방치된 폐광산에 대한 문제가 대두되면서 폐광산 주변지역에 대한 산성광산폐수와 중금속 광산폐기물의 오염실태조사가 활발히 진행되고 있다. 본 연구는 폐광산의 유출수와 광산폐기물에 주변 오염지하수 내의 중금속 As, Cd, Pb, Fe, Mn, Zn, Cu에 대하여 무기 응집제의 첨가와 pH의 조절에 의한 제거효율을 .실내 배치실험을 통하여 규명하였다. 본 실험을 통하여 황산알루미늄(Al$_2$(SO$_4$)$_3$ㆍ13～14$H_2O$), 염화 제2철(FeCl$_3$ㆍ6$H_2O$), 황산 제2철(Fe$_2$(SO$_4$)$_3$ㆍ n$H_2O$)을 이용하여 오염수내 중금속을 90%이상 제거할 수 있었으며, 폐광산 침출수나 오염 지하수의 중금속 제거에 0.1 wt%의 응집제 첨가만으로 응집제를 이용한 화학적 처리 방법이 효과적으로 사용될 수 있을 것으로 판단되었다.

• Resources Recycling
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• v.24 no.3
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• pp.44-50
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• 2015

Recycling technologies would be required in consideration of increasing demand in lithium ion batteries (LIBs). In this study, the leaching behavior of Ni, Co and Mn is investigated with ammoniacal medium for spent cathode active materials, which are separated from a commercial LIB pack in hybrid electric vehicles. The leaching behavior of each metal is analyzed in the presence of reducing agent and pH buffering agent. The existence of reducing agent is necessary to increase the leaching efficiency of Ni and Co. The leaching of Mn is insignificant even with the existence of reducing agent in contrast to Ni and Co. The most conspicuous difference between acid and ammoniacal leaching would be the selective leaching behavior between Ni/Co and Mn. The ammoniacal leaching can reduce the cost of basic reagent that makes the pH of leachate higher for the precipitation of leached metals in the acid leaching.

• Resources Recycling
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• v.22 no.3
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• pp.43-49
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• 2013

A study on the recovery of lithium and leaching behavior of NCM powder by hydrogen reduction for NCM system Li-ion battery scraps was investigated. The reductive rate was about 93% at $800^{\circ}C$ by hydrogen treatment. The lithium carbonate with 99% purity was manufactured by using $CO_2$ gas and washing method with water for NCM powder after hydrogen reduction. As a result of comparing the powders before and after the hydrogen reduction treatment for acid leaching behavior we obtained 32% enhanced leaching rate of cobalt, 45% enhanced leaching rate of nickel and the 90% leaching effect for manganese by hydrogen reduction at 2M $H_2SO_4$ concentration condition.

• Resources Recycling
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• v.22 no.2
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• pp.44-52
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• 2013

Bioleaching behavior of metal ions for recovery of cobalt and copper from cobalt concentrate was investigated by employing three Aspergillus niger strains. Various factors, such as organic acid generation with fungi type, pH of the culture and pulp density were studied. The results showed that the best fungi for organic acid(citric acid and oxalic acid) generation was A. niger KCTC 6144 using Malt Extract Broth culture at initial pH 3.5. But A. niger KCTC 6985 was more effective for the leaching of cobalt and copper from cobalt concentrate. Our results showed that 82% cobalt and 98% copper was dissolved by A. niger KCTC 6985 at 10g/L pulp density, at pH 3.5 and $24^{\circ}C$ after 15 days incubation.

• Journal of Korea Soil Environment Society
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• v.2 no.2
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• pp.73-79
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• 1997

Removal of the Arsenic components from the closed mine tailings has been attempted by the alkali-leaching method. Two tailings collected from the Daduck and Yuchon mine which were already closed many years ago were leached with caustic soda solutions. The Arsenic components in the leach liquor resulted from the alkali treatment of tailings could be removed fairly well in the form of insoluble calcium-Arsenic compound by the precipitation with calcium chloride. As a result, the extraction of about 60~90% Arsenic from the tailings could be obtained depending on the leaching conditions and the influence of temperature and the slurry density on the extraction of Arsenic was also found to be very small at the NaOH concentration more than 0.5N. In addition, it seemed that a caustic soda solution over 0.5N NaOH could be used repeatedly for the leaching of tailings since the consumption of NaOH was not so great in a leaching of them. As far as the precipitation of Arsenic components was concerned, more than 99% of Arsenic could be precipitated within 10 minutes by the addition of 2wt% CaC12 in to the leach liquor.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.198.1-198.1
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• 2010

고분자전해질 연료전지(PEMFC)의 핵심부품인 스택의 MEA는 전극과 멤브레인 전해질, GDL(Gas Diffusion Layer)로 구성되며, 전극은 Anoth극과 Cathod극으로 나뉘어 각각의 전극 특성에 적합한 전극촉매를 적용하게 된다. Anoth극과 Cathod극은 탄소 지지체 위에 원하는 사양의 희유금속이 도포되어 존재하는데 이들 희유금속은 그 희귀성으로 인해 사용 후 반드시 재사용되어야 한다. 사용된 전극에서의 희유금속 회수는 산침출, 불순물제거, 추출, 탈거 공정으로 이루어지며, 산침출 시 산화제로 사용된 NaOCl로 인한 침출용액 내의 Na+ 이온의 증가는 불순물제거 공정에 의해 반드시 제거되어야 한다. 따라서 본 연구에서는 CCG 방식으로 전극촉매를 GDL에 코팅한 MEA로부터 백금족 희유금속을 회수 시 MEA에 포함되어 있는 소량의 불순물을 제거하고자 한다.

• Resources Recycling
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• v.26 no.1
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• pp.37-42
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• 2017

It has been reported that aqueous indirect carbonation process of calcium silicate mineral could be one of the most promising methods for $CO_2$ sequestration. The process consists of two main steps, extraction of Ca from calcium silicate and carbonation of the extracted solution by $CO_2$. Many types of acids such as HCl and $HNO_3$ can be used in the extraction step of the process. In the case of using aqueous acetic acid solution as the extraction solvent, acetic acid can be reproduced at the carbonation step of the extracted solution by $CO_2$ and recycled to extraction step for reuse it. Industrial by-products such as iron and steel slags are potential raw materials of the indirect carbonation process due to their high contents of calcium silicate. In this study, in order to examine the extraction efficiency of domestic electric arc furnace steel slag by aqueous acetic acid solution, extraction experiments of the slag were performed by using the aqueous acetic acid solutions of varying extraction conditions ; acetic acid concentrations, extraction temperatures and times.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 1999.10a
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• pp.103-106
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• 1999

본 연구에서는 펜톤산화반응에서 과산화수소의 분해촉매로 일반적으로 쓰이는 Fe(II) 형태의 철염대신 Fe$^{\circ}$형태의 분말 철을 이용한 펜톤유사반응(Fenton-like oxidation)에 의한 매립지 침출수(sCODcr 1,100 mg/L, pH 8)의 CODcr 제거특성에 관한 회분식 처리실험을 수행하였다. 실험조건으로는 상온, 상압조건에서 Jar tester를 사용하여 분말 철의 주입 량과 산 세척도, 초기 반응 pH, 과산화수소의 주입 량을 변화시켜가며 침출수의 CODcr 제거효율 의 변화를 관찰하였으며, 이때 과산화수소의 분해 특성과 반응 중 pH의 변화도 함께 분석하였다. 반응은 모든 조건에서 대부분 약 30분 이내에 종료되었으며 그 이후의 반응변화는 미미하였다. 산 세척에 의한 분말 철 표면의 개질로 반응성의 향상을 관찰할 수 있었으며, 분말 철 주입 량을 증가함에 따라 반응속도가 일정하게 증가함을 알 수 있었다. 본 연구에 서 CODcr의 제거 효율에 가장 큰 영향을 보여준 실험변수는 pH 였으며, 원수의 pH(8)를 2-4까지 조절하여 반응을 시켰을 때 최대 75%의 CODcr 제거효율을 얻을 수 있었다. 반응중 pH는 모든 조건에서 시간에 따라 증가하여 약 pH 9에서 더 이상 변화하지 않았다. 용액내 과산화수소의 잔류농도의 곡선은 반응 중 CODcr의 곡선과 유사한 변화를 나타내었다.