• Resources Recycling
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• v.32 no.2
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• pp.3-11
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• 2023

The aim of this study was to develop a physical treatment method for obtaining iron concentrate with a grade higher than 60% from slag generated in the Waelz Kiln (WK) process. The size of the WK slag used in this work was several millimeters, with T-Fe and ZnO contents of 40.24% and 1.03%, respectively. The slag samples were pulverized in a laboratory rod mill for various grinding times, followed by a magnetic separation test under a low magnetic intensity of 0.05 T initially. The results showed that the highest iron grade was obtained from samples with a grinding time of 10 min. Additionally, for a grinding time of 20 min, the highest grade and recovery ratios were achieved at a magnetic intensity of 0.8 T. Based on these findings, the optimal physical treatment process proposed in this study resulted in iron concentrates with a grade of 61.34% and an enrichment ratio of 1.52.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03a
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• pp.268-288
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• 2004

최근 도로, 철도, 고속철도, 지하철과 같은 사회간접시설의 확충과 더불어 암반을 대상으로 하는 프로젝트가 급격하게 증가하고 있으며, 유류, 가스, 폐기물, 농축산물에 대한 지하암반저장에 대한 사회적 요구가 증가하고 있어 암석 및 암반을 대상으로 하는 암석역학(Rock Mechanics)과 암반공학 (Rock Engineering)에 대한 최근의 연구동향 및 현황의 관심이 증가되고 있다. 따라서 암석역학 및 암반공학 분야에 대한지금까지의 연구개발활동에 대한 정리뿐만 아니라 최근 연구동향을 고찰함으로서 앞으로의 암반공학분야에 대한 새로운 방향을 고민하고 연구할 시점이라 생각된다.(중략)

• THE HEALTH and ORGANIC FARMING
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• no.221
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• pp.1-12
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• 2005

제27회 한국유기농업대회 성황리 개최/농림부장관 격려사/우리의 산야초/겨울철 토양의 영양관리는 이동성이 어려운 칼슘과 고토 그리고 붕소를/제27회 한국유기농업대회 이모저모/'자원순환형농업 활성화 방안'/"우수 농축산물 합리적 생산이력 관리 방안"세미나/"농업,환경 문제와 연계 필요"/"충북,근교농업 준비 갖춰야"/전남,친환경농업기금 500억조성/농어업특위,'도시민을 농어촌으로'/태안군,웰빙 6쪽마늘 생산단지 조성/우리조상들이 연구한 물이야기/착각하고 있는 잘못된 웰빙/토양다발성 병해 예방/바이러스병 어떻게 전파되며, 어떻게 막아낼것인가?/시설채소의 병해방제/협회저농약9호/"금수강산"가격인상 안내/우수농산물코너/본 협회 인증위원회 개최/12월중 협회 일정 안내/배추 무사마귀병은 무와 윤작으로/미.영,급식등 '어린이영양'법제화/11월중 새식구 명단/협회소식/약이되는 웃음,약이 되는 웃음 운동/다층식 지렁이 사육시스템 개발/친환경 먹거리 대체의학센터 충주에 건립/미국?, 화학원료 넣어도 유기농산물?/멕시코도 유기농 제품 바람/과일껍질 이용한 아이디어 살림법/서식환경의 파괴

• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Korean Journal of Microbiology
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• v.51 no.4
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• pp.448-452
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• 2015

The bacterial strain that was isolated from chinese cabbage rhizosphere, showed inhibition of yeast growth. This strain was identified as Pseudomonas fluorescens BB2 by API 20NE test and 16S rRNA gene sequence analysis. P. fluorescens BB2 strain produced antibiotics against yeast as a secondary metabolite effectively when the culture was carried out in YM medium with 3% glucose at $20^{\circ}C$. The protein antibiotic of BB2 strain which was concentrated by ammonium sulfate precipitation and n-butanol extraction inhibited the growth of yeast with the minimal inhibitory concentration of $10{\mu}g/ml$ against Candida albicans KCTC 7965, and the growth of yeast was completely inhibited at $80{\mu}g/ml$. The hydrophilic fraction of n-butanol extraction inhibited the growth of Bacillus cereus ATCC 21366, showed orange halo on chrome azurol S plate, which means the fraction contained iron chelating siderophore. The results of crystal violet uptake through the cell membrane showed that membrane permeability was increased about 9% than control, when the concentration of hydrophobic antibiotic against yeast C. albicans was $60{\mu}g/ml$. As a result, the antibiotic produced by P. fluorescens BB2 against yeast Candida is considered antimicrobial peptide, and this is the first report in the genus Pseudomonas.

• Resources Recycling
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• v.32 no.1
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• pp.50-59
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• 2023

The amount of dust generated during the dissolution of scrap in an electric arc furnace is approximately 1.5% of the scrap metal input, and it is primarily collected in a bag filter. Electric arc furnace dust primarily consists of zinc and ion. The processing of zinc starts with its conversion into pellet form by the addition of a carbon-based reducing agent(coke, anthracite) and limestone (C/S control). These pellets then undergo reduction, volatilization, and re-oxidation in rotary kiln or RHF reactor to recover crude zinc oxide (60%w/w). Next, iron is discharged from the electric arc furnace dust as a solid called Fe clinker (secondary by-product of the Fe-base). Several methods are then used to treat the Fe clinker, which vary depending on the country, including landfilling and recycling (e.g., subbase course material, aggregate for concrete, Fe-source for cement manufacturing). However, landfilling has several drawbacks, including environmental pollution due to leaching, high landfill costs, and wastage of iron resources. To improve Fe recovery in the clinker, we pulverized it into optimal -sized particles and employed specific gravity and magnetic force selection methods to isolate this metal. A carbon-based reducing agent and a binding material were added to the separated coarse powder (>10㎛) to prepare briquette clinker. A small amount (1-3%w/w) of the briquette clinker was charged with the scrap in an electric arc furnace to evaluate its feasibility as an additives (carbonaceous material, heat-generating material, and Fe source).