• 한국분말재료학회지
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• 제25권5호
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• pp.390-394
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• 2018

Metallic tantalum powder is manufactured by reducing tantalum oxide ($Ta_2O_5$) with magnesium gas at 1,073-1,223 K in a reactor under argon gas. The high thermodynamic stability of magnesium oxide makes the reduction reaction from tantalum oxide into tantalum powder possible. The microstructure after the reduction reaction has the form of a mixture of tantalum and magnesium oxide, and the latter could be entirely eliminated by dissolving in weak hydrochloric acid. The powder size in SEM microstructure for the tantalum powder increases after acid leaching in the range of 50-300 nm, and its internal crystallite sizes are observed to be 11.5 to 24.7 nm with increasing reduction temperatures. Moreover, the optimized reduction temperature is found to be 1,173 K as the minimum oxygen concentration is approximately 1.3 wt.%.

• 한국환경보건학회지
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• 제35권5호
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• pp.376-385
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• 2009

The characteristics of Lake Cheonhoji water and sediment were investigated in oder to utilize these as fundamental materials for the management of lake water quality. The hydrographic properties of Lake Cheonhoji which are relatively low chance of nutrients loading from the watershed and a long retention time of lake water, lead to the probability of high lake productivity. It was also observed that lake water showed stratification during summer and complete mixing during fall, even though water depth was relatively shallow. The trophic state was eutrophic to hypertrophic from summer to late fall. The overall properties of the sediment were oligohumic, high ignition loss and high composition of NAIP and Resid.-P, which might serve as potential pollution sources of lake water quality. In laboratory scale experiments, it was observed that leaching potential of nutrients in the sediment was greatly dependant upon water temperature and dissolved oxygen. Finally, water pollution in Lake Cheonhoji was considered to be largely due to the adverse cycle of uncontrollable eutrophication, which resulted in the subsequent occurrence of dead algae and animal plankton, organic sedimentation, reduction of dissolved oxygen and nutrients leaching, which again reinforced the cycle of eutrophication in the lake.

• 한국분말재료학회지
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• 제19권6호
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• pp.405-411
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• 2012

Recovery of copper powder from copper chloride solution used in $MoO_3$ leaching process was carried out using a cementation method. Cementation is a simple and economical process, necessitating less energy compared with other recovery methods. Cementation utilizes significant difference in standard reduction potential between copper and iron under standard condition. In the present research, Cementation process variables of temperature, time, and added amount of iron scraps were optimized by using design of experiment method and individual effects on yield and efficiency of copper powder recovery were investigated using bench-scale cementation reaction system. Copper powders thus obtained from cementation process were further characterized using various analytical tools such as XRF, SEM-EDS and laser diffraction and scattering methods. Cementation process necessitated further purification of recovered copper powders and centrifugal separation method was employed, which successfully yielded copper powders of more than 99.65% purity and average $1{\mu}m$ in size.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제10권S_2호
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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.

• 한국분말재료학회지
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• 제24권4호
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• pp.315-320
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• 2017

There has been much interest in recycling electronic wastes in order to mitigate environmental problems and to recover the large amount of constituent metals. Silver recovery from electronic waste is extensively studied because of environmental and economic benefits and the use of silver in fabricating nanodevices. Hydrometallurgical processing is often used for silver recovery because it has the advantages of low cost and ease of control. Research on synthesis recovered silver into nanoparticles is needed for application to transistors and solar cells. In this study, silver is selectively recovered from the by-product of electrodes. Silver precursors are prepared using the dissolution characteristics of the leaching solution. In the liquid reduction process, silver nanoparticles are synthesized under various surfactant conditions and then analyzed. The purity of the recovered silver is 99.24%, and the average particle size of the silver nanoparticles is 68 nm.

• 한국토양비료학회지
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• 제16권4호
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• pp.311-317
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• 1983

논토양성분(土壤成分)의 용탈(溶脫)에 미치는 볏짚의 영향(影響)을 구명(究明)하기 위하여 논토양(土壤)에 볏짚을 시용(施用)하고 투수조건하(透水條件下)에서 수도(水稻)를 재배(栽培)하면서 침투수중(浸透水中) 용탈성분(溶脫成分)을 분석(分析) 검토(檢討)한 결과(結果)는 다음과 같다. 석회(石灰)와 고토(苦土)의 용탈(溶脫)은 초기(初期)에는 볏짚시용(施用)의 영향(影響)을 받았고 후기(後期)에는 수도근(水稻根)의 영향(影響)을 받았으며 철(鐵)과 망간의 초기용탈(初期溶脫)은 볏짚시용(施用)에 의(依)한 토양환원(土壤還元) 발달(發達)의 영향(影響)을 받았으나 후기(後期)에는 수도근(水稻根)의 영향(影響)을 크게 받아 증대(增大)되었다. 칼리, $NH_4-N$, 염소(鹽素) 등(等)의 용탈(溶脫)은 볏짚시용(施用)의 영향(影響)이 크지 않았으며 $CO_2$의 용탈(溶脫)은 볏짚의 영향(影響)을 받아 증대(增大)되고 동시(同時)에 수도근(水稻根)의 영향(影響)이 컸다. 침투수중(浸透水中) 용탈(溶脫)되는 양(陽)이온과 음(陰)이온의 양(量)은 대체로 같은 당량비(當量比)였으며 양(陽)이온은 석회(石灰)와 고토(苦土), 철(鐵), 음(陰)이온은 $HCO_3{^-}$과 $SO_4{^{-2}}$이 중요(重要)한 용탈성분(溶脫成分)이었다.

• 자원리싸이클링
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• 제24권4호
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• pp.32-37
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• 2015

이차전지 재료 등으로 사용되는 코발트는 콩고 민주공화국 등 일부 국가에 편중되어 있다. 국내 코발트의 안정적인 공급을 위한 해외 코발트광과 코발트 제련 기술의 확보는 필수적이다. 이에 본 실험에서는 콩고산 코발트 정광(Co ~ 8 wt%, Cu ~ 19 wt%, Fe ~ 3 wt%)을 용융환원시켜 얻어지는 합금상에 매트 내 황의 비율을 달리해 만든 2가지 조성의 매트를 제조했으며, 주된 원소는 19 ~ 21wt% Co, 39 ~ 41wt% Cu, 7 ~ 9wt% Fe이다. 매트 분쇄산물을 autoclave를 이용한 고온고압침출법으로 3가지의 영향(산화제 유무, 침출제인 황산 농도, 매트 제조 시 투입되는 황 함량)을 고려해 실험을 진행했다. 먼저 산화제(산소)의 존재는 Co 침출률 향상을 위해 필수적이며 낮은 농도의 황산을 사용하더라도 Co를 전량 침출시킬 수 있다. 둘째 산소 분위기에서 높은 황산농도는 Cu와 Fe의 침출률을 증가시켜 선택적인 Co 침출을 방해한다. 마지막으로 매트 내 황 함량은 Co의 침출률에는 영향이 크지 않음을 알 수 있었다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.386-390
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• 2003

To evaluate the potential capacity of mine wastes in the production of heavy metal containing acid water, samples from depths of 0, 30 and 60cm were collected and analyzed. The waste from surface showed the lowest pH which indicates the oxidation of wastes and the capacity of contamination of the area around the waste file. And the lower pH values of leachate of the wastes through the leaching tests with pH controlled water(3, 4, 5) may indicate that minerals producing the acidity still exist. Reduction of sulfur contents in wastes after the leaching test well fit to the increased contents of iron oxide.

• 한국물환경학회지
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• 제27권6호
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• pp.862-867
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• 2011

Pozzolanic-based stabilization/solidification (S/S) is an effective and economic remediation technology to immobilize heavy metals in contaminated soils. In this study, quick lime (CaO) was used to immobilize cadmium and zinc present in waste mine contaminated clayey sand soils. Addition of 5% quicklime to the contaminated soils effectively reduced heavy metal leachability after 2 bed volume operation below the drinking water regulatory limits. Lime addition was revealed to increase the immobilization for all heavy metals in tested pH ranges, so it could be an optimal choice for short-term remediation of heavy metal contaminated soil. The mass balances for these column tests show metal reduction of 92% for Cd and 87% for Zn of total resolved mass in case of 5% lime application.

• 자원리싸이클링
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• 제10권6호
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• pp.9-14
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• 2001

폐리튬이온전지의 재활용 일환으로 양극활물질인 $LiCoO_2$로부터 Co와 Li을 회수하기 위하여 황산침출거동을 조사하였다. 황산 2M용액, $75^{\circ}C$ 조건에서 환원제를 첨가하지 않은 경우, $LiCoO_2$로부터 Li가 거의 100% 침출되는 반면에 Co는 같은 조건에서 40% 이하의 침출율을 보였다. Co의 침출율을 향상시키기 위하여 과산화수소를 환원제로 2~20 vol%범위에서 사용하였다 10 vol% 이상의 과산화수소를 첨가하였을 때, Co와 L거 침출율은 모두 95% 이상 이었다. 이는 환원제로서 과산화수소가 Co(III)를 Co(II)로 환원시켜 침출이 용이해졌기 때문으로 생각된다. 황산농도, 온도, 과산화수소 첨가량이 증가함에 따라 Co와 L리 침출율은 증가한 반면에 초기 광액농도가 증가할수록 Co와 L긴 침출율은 감소하였다. 이상의 조업변수 실험을 통하여 코발트계 리튬이온전지의 양극활물질인 $LiCoO_2$의 황산침출에서 황산농도 2 M, 침출온도 $75^{\circ}C$,초기광액농도 100 g/L, 과산화수소 첨가량 20 vol%에서 30분의반응시간이 침출 최적조건으로 생각된다.