콩고산 코발트 정광으로부터 제조한 매트의 고온고압침출

김건하,강가희,김수경,손정수,권경중,Kim, Gunha,Kang, Ga-hee,Kim, Sookyung,Sohn, Jeongsoo,Kwon, Kyungjung 한국자원리싸이클링학회 2015 資源 리싸이클링 Vol.24 No.4

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. Cobalt is abundant only in some countries including Democratic Republic of the Congo. It would be necessary to secure overseas Co ores and Co extraction technology. Two kinds of matte varying the sulfur content were manufactured by smelting reduction of Co concentrate containing ~8 wt% Co, ~19 wt% Cu, and ~3 wt% Fe. The amount of Co, Cu and Fe was concentrated to 19~21 wt%, 39~41 wt%, and 7~9 wt% respectively in the resulting matte. High-pressure leaching of matte was performed in an autoclave with considering the effect of oxidizing agent, $H_2SO_4$ concentration as a lixiviant, and the amount of sulfur added to the matte. An oxidizing agent (oxygen) is necessary to improve Co leaching efficiency enabling usage of a dilute $H_2SO_4$ leaching agent. An increase in $H_2SO_4$ concentration prevents selective leaching of Co, and the sulfur content in matte has a minor influence on the Co leaching efficiency.

강우시 영양염류의 토사결합 유출

김건하,김영철,이동률 대한환경공학회 2003 대한환경공학회 학술발표논문집 Vol.2003 No.12

Effects of Non-Point Source Pollution on the Concentration of Pathogen Indicator Organisms in the Geum River Basin, Republic of Korea

김건하,Joong Hyun Yur 대한토목학회 2004 KSCE JOURNAL OF CIVIL ENGINEERING Vol.8 No.2

The pathogen indicator organism means pathogen associated non-pathogenic microorganisms for easier identification of the contamination. The pathogen indicator organisms can be used for estimating the impacts of non-point source pollution as their concentration is flow rate dependent. This study aims to determine the concentration of the pathogen indicator organisms in the Geum River basin and to understand the impacts of the non point source pollution on the water quality. In this study, total coliform, fecal coliform, and Escherichia coli concentrations were monitored at eight sites in the Geum River Basin. Total coliform concentration showed a high correlation with the flow rate, and a tendency of higher concentration for more agricultural land use in a monitored area. From the analysis of the relationship between flow rates and contaminant loads or concentration, two curves explained the relationships for the low flow and high flow conditions, respectively. Load duration curves were developed to estimate the impact of non-point source pollution on the water quality. From the load duration curve analysis, it can be understood that the water qualities of the Geum River are affected by non-point pollution significantly compare to the magnitude of point source pollution.

Sustainability of the In Situ Bio-barriers for Contaminant Containment in Residual Soils

김건하,Jong Heun Kim 대한토목학회 2004 KSCE JOURNAL OF CIVIL ENGINEERING Vol.8 No.2

An iterative dynamic condensation method for the model reduction is presented in this paper. Dynamic condensation method has been widely applied to large finite element models for faster computation of the natural frequencies and mode shapes. It has also been used in correlation of test-analysis models, vibration control, and structural dynamic optimization. Based on the subspace iteration method, an iterative dynamic condensation technique is employed. The proposed method has three advantages compared with other iterative schemes proposed in the past: (1) The convergence is much faster than all these methods, especially when the eigenpairs of the reduced model are close to those of the full model. (2) Since the dynamic condensation matrix is independent of the eigenpairs of the reduced model, it is unnecessary to calculate the stiffness and mass matrices in every iteration. (3) The convergence of the iterative scheme can be proved simply. Two iteration schemes, which are based on the convergence of the eigenvalues of the reduced model, are introduced. Numerical examples are presented to verify the effectiveness of this technique.

IWA DipCon 2003 학술대회 참가기

김건하 대한토목학회 2003 대한토목학회지 Vol.51 No.9

금강에서의 병원균 부하 추정

김건하,여중현,이동률 대한환경공학회 2003 대한환경공학회 학술발표논문집 Vol.2003 No.12

토양의 산/염기 완충능의 모델링

김건하 한국지하수토양환경학회 1998 지하수토양환경 Vol.3 No.3

토양의 산/염기 완충능은 토양-오염물질-공극수로 이루어진 시스템의 pH에 직접적인 영향을 미치므로 오염물질의 토양내 거동예측시에 많은 영향을 미치는 매우 중요한 토양의 성질이다. 본 연구는 이중확산층이론과 two layer electrostatic 흡착모델을 응용하여 토양의 산/염기 완충능의 이론모델을 유도하고 이 모델의 적용절차를 제시하였다. 산-염기 적정실험을 통하여 두 종류의 카올리나이트의 완충능을 실측하고 이를 본 연구에서 개발된 모델의 예측치와 비교하였다. Acid/Base buffer capacity of soil is very important in prediction of contaminant transport for its direct impact on pH change of the system composed of soil-contaminant-water, In this research, diffuse double layer theory as well as two layer electrostatic adsorption model are applied to develop a theoretical model of buffer capacity of soil. Model application procedures are presented as well. Buffer capacity of Georgia kaolinite and Milwhite kaolinite was measured by acid-base titration. Model prediction and experimental results are compared.

Effect of Individual and District-level Socioeconomic Disparities on Cognitive Decline in Community-dwelling Elderly in Seoul

김건하,이혜아,박혜숙,이동영,조인호,최성혜,최경규,정지향 대한의학회 2017 Journal of Korean medical science Vol.32 No.9

This study was to investigate the effects of individual and district-level socioeconomic status (SES) on the development of cognitive impairment among the elderly. A 3-year retrospective observational analysis (2010–2013) was conducted which included 136,217 community-dwelling healthy elderly who participated in the Seoul Dementia Management Project. Cognitive impairment was defined as 1.5 standard deviations below the norms on the Mini-mental status examination. In the individual lower SES group, the cumulative incidence rate (CIR) of cognitive impairment was 8.7% (95% confidence interval [CI], 8.64–8.70), whereas the CIR in the individual higher SES group was 4.1% (95% CI, 4.08–4.10). The CIR for lower district-level SES was 4.7% (95% CI, 4.52–4.86), while that in the higher district-level SES was 4.3% (95% CI, 4.06–4.44). There were no additive or synergistic effects between individual and district-level SES. From this study, the individual SES contributed 1.9 times greater to the development of cognitive impairment than the district-level SES, which suggests that individual SES disparities could be considered as one of the important factors in public health related to cognitive impairment in the elderly.

가축매몰지 환경 관리

김건하 대한환경공학회 2017 대한환경공학회 학술발표논문집 Vol.2017 No.11

Neuroprotective Effect of Lacosamide on Hypoxic-Ischemic Brain Injury in Neonatal Rats

김건하,변정혜,은백린 대한신경과학회 2017 Journal of Clinical Neurology Vol.13 No.2

Background and Purpose Lacosamide (LCM) is an antiepileptic drug that enhances the slow inactivation of sodium channels and modulates collapsin response mediator protein-2. LCM was recently demonstrated to exert a neuroprotective effect in a murine model of trau¬matic brain injury and status epilepticus. Assuming the same underlying excitotoxicity-related brain injury mechanism, we hypothesized that LCM would have a neuroprotective effect in hypoxic-ischemic brain injury. Methods We divided rats into three groups at each testing session: pre- or postfed with LCM, fed with normal saline, and sham. A hypoxic-ischemic brain injury was induced by subjecting 7-day-old rats to right carotid artery coagulation followed by 2.5 h of exposure to 8% oxygen. The animals were killed on postnatal day 12 to evaluate the severity of brain damage. Open field testing was also performed between week 2 and week 6, and the Morris water maze test was performed in week 7 after hypoxia-ischemia. Results The incidence of liquefactive cerebral infarction was lower in rats prefed with LCM at 100 mg/kg/dose, with the mortality rate being higher at higher doses (200 and 300 mg/kg/dose). The infarct areas were smaller in LCM-prefed rats in several brain regions including the hemisphere, hippocampus, cortex, and striatum. Spatial learning and memory function were better in LCM-prefed rats (p<0.05). No effect was observed in postfed rats. Conclusions This study suggests that LCM pretreatment exerts a neuroprotective effect on hypoxia-ischemia in neonatal rats. The obtained results suggest that LCM pretreatment could be used as an effective neuroprotective method for neonates under hypoxic-ischemic condi¬tions including heart surgery.