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권성현(Sung-Hyun Kwon),조대철(Daechul Cho) 한국청정기술학회 2013 청정기술 Vol.19 No.2
굴 패각분말을 함유한 석고시험체를 통하여 1차원 열전달 특성을 조사하였다. 굴패각 성분의 함유량이 늘어날수록 기공을 포함한 시험체의 구조적 변형에 근거하여 흡착과 같은 물리화학적 특성이 증가함에 따라 시험체 전체의 열전달 특성도 달라질 것으로 예측되었다. 푸리에(Fourier) 열전도 방정식을 기초로 하여 1차원 슬랩의 열전도 현상을 수치모사한 결과 패각 분말의 배합도 및 각 성분재료의 열전달관련 물리적 계수에 따라 상당한 열전도 분포의 변화를 관측할 수 있었으며 이는 모형실험 결과와도 잘 부합하였다. We investigated one-dimensional thermal conduction for gypsum objects incorporating oyster shell powder. We presumed that according to the portion of oyster shell in the hybrid structure conductive characteristics of that would also change as some physicochemical properties such as volatile organic compound (VOC) adsorption were found to be changed considerably. Based on Fourier"s 2nd law of heat conduction an analytical analysis in a flat slab (one axis perpendicular to an infinite plane) was performed. We found that composition of oyster shell and conduction-related coefficients and parameters could greatly influence on the thermal profile of that conduction, and some model experiments also served for it in the affirmative.
해양 퇴적물의 혐기적 용출특성과 이에 미치는 산소발생제 CaO<SUB>2</SUB>의 영향에 대한 연구
권성현(Kwon, Sung-Hyun),조대철(Cho, Dae-Chul) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.10
실험실 규모의 모사 실험을 통하여 해양 부영양화를 촉진하는 퇴적물의 용출 특성을 연구하였다. 즉 pH, ORP, 질소성분, 인성분 등 주요 환경인자를 분석하고 그에 따른 용출율을 계산하였다. 또한 산소발생제인 과산화칼 슘을 이용하여 자연적 용출의 제어효과를 분석하였다. 산소발생제 처리에 따라 호기적 조건으로의 퇴적토 환경변화 가 일어났으며 COD, NH3-N의 용출율이 감소하고 질산화 촉진으로 NOx 성분은 증가하였다. 총인과 인산염인도 Ca 이온의 불용화 기작에 의거 감소하였다. 이에 따라 퇴적토의 용출로 인한 해양 부영양화 억제 방법론을 정립하고자 한다. We studied the release characteristics of the marine sediment which could facilitate sea eutrophication through some lab-scale simulation experiments. Environmental indicators such as pH, ORP(oxidation reduction potential), nitrogens, and phosphates were measured in order to calculate the corresponding release rates. CaO2, an oxygen releasing compound was used to determine how it would effect on the natural process of sedimental release. COD, ammonia nitrogen, phosphorous compounds were less released under the oxic environment caused by CaO2. This basic data will help developing methodology for reducing marine eutrophication which may be initiated by the sedimental release.
굴패각 모르타르에의 휘발성 유기화합물 흡착에 대한 연구
권성현(Sung-Hyun Kwon),조대철(Daechul Cho) 한국청정기술학회 2013 청정기술 Vol.19 No.2
굴패각과 석고를 대상으로 고형화시킨 후 포름알데히드 및 벤젠으로 대표되는 휘발성 유기화합물(volatile organic compounds, VOCs)를 흡착챔버 내에서 노출시켜 흡착특성을 관찰하였다. VOC를 챔버에 노출 후 굴패각과 같은 친환경재료를 혼입한 모르타르를 각각 개별적으로 주입한 후 180분간 흡착특성을 고찰하였다. 굴 패각분말을 0, 10, 30, 50%로 혼입한 시험체를 대상으로 포름알데히드와 VOC(벤젠, 톨루엔, 자일렌)를 27.7~28.5 mg/㎥의 고농도 조건과 175~150 μg/㎥의 저농도 조건에서 각각 노출시켜 흡착성 실험을 수행한 결과, 전반적으로 노출된 조건과 무관하게 굴패각의 혼입 함량이 많을수록 흡착성이 증가함을 관찰할 수 있었다. 또한 대류-확산-흡착이 고려된 모델을 사용하여 실험과 비교하였다. 확산계수 및 확산 길이(diffusion length)로 대변되는 흡착재의 친화력(affinity)을 고려한 모델을 시험한 결과, 피흡착제의 종류와 흡착재의 친화성에 따른 차이를 잘 표현하였으며 전반적으로 실험데이터와 일치하는 경향을 보였다. VOCs such as formaldehyde and benzene in a control chamber were adsorbed onto gypsum incorporating oyster shell powder, which was solidified and dried. VOC was first exposed in air and then gypsum mortar was placed in the chamber for 180 min for adsorption. The mortar was prepared with 0, 10, 30, and 50% of oyster shell powder. Two initial concentrations of VOCs including formaldehyde were 27.7~28.5 mg/㎥ or 175~150 μg/㎥. We found out that the initial concentrations did not seem to make any difference in adsorption performance but higher oyster content strongly led to higher adsorption. We used a convectiondiffusion-adsorption model to compare the experiment. The model which considers diffusion coefficients of adsorbates and affinity of the adsorbents well represented the experimental data with a fair agreement.
재활용 패각의 산-염기치환 반응을 통한 과산화칼슘의 제조와 산소발생 특성
권성현 ( Sung Hyun Kwon ),유길선 ( Gilsun Yoo ),조대철 ( Daechul Cho ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회지 Vol.36 No.2
The Korean coastal sediment area is apt to be contaminated by prevailing aquafarming and inland eutrophic sources. Furthermore, oyster shells are being overproduced every year with little recycling. Oxygen-releasing compounds (ORCs) are paramount in bioremediation or bioaugmentation. Calcium peroxide, one of the primary ORCs, was prepared using recyclable oyster shells via acid?base reactions based on double replacement, and this was followed by oxidation with hydrogen peroxide. Hydrogen peroxide, which is known to be effective as oxidizing agent, required an optimum dose for higher content of oxygen in the final product, because the literature shows that the oxidative reaction is reversible. A variety of concentrations of HCl and NaOH were examined in stoichiometry for the breakdown of calcium carbonates (or CO<sub>2</sub> production) and formation of calcium hydroxide in the initiation reaction. Acid and base overdoses helped the oxygenation reaction to be extended further, thus leading to calcium peroxide with the highest content of oxygen at a combination of 6 N-12 N acid-base treatment. With an elevated temperature, more oxygenated calcium peroxide was likely to be formed. Carbon dioxide and free oxygen during the experiments were determined with DO probing and gas capture in a water bath.
미세조류 Botryococcus braunii의 배양조건 최적화 및 지질축적 향상
권성현 ( Sung Hyun Kwon ),이은미 ( Eun Mi Lee ),조대철 ( Dae Chul Cho ) 한국환경과학회 2012 한국환경과학회지 Vol.21 No.7
Several tests and experimental work have been done for identifying the best growth conditions and accumulated amount of lipid moiety in B. braunii, a microalga(UTEX 572) in terms of media composition. The specific growth rate was found to be the highest at 0.15 g/L-day when the phosphorus concentration was doubled with the other ingredients at the normal level. Experiments for varied media compositions revealed that the accumulation of lipid was the highest at 48% (dry cell weight based) in the nitrogen deficient medium and its corresponding specific growth rate was comparative to that in the normal BG 11 medium. In the bubble column experiments, carbon dioxide containing air produced four times more cell mass than air only. Light and glucose addition also enhanced cell mass with maximum, 1.8 g/L and accordingly 42% of lipid composition, which turned out to be a better strategy for higher lipid-producing microalgal culture.
해양생물 Botryococcus braunii에서 유래한 바이오연료의 고급생산기술: 전처리 용매추출법
권성현 ( Sung-hyun Kwon ),조대철 ( Daechul Cho ) 한국환경과학회 2019 한국환경과학회지 Vol.28 No.11
A lipid-enriched strain of Botryococcus braunii (UTEX 572) was cultivated in a semi-batch aeration tank to enhance biomass as well as to develop intracellular lipids and fatty acids. A 30 day period of incubation produced 1.39 g/L of biomass and 0.31 g/L of total lipids in the biomass. The grown biomass was pre-treated using several methods to extract the total lipid content efficiently: ultrasonication was found to yield the highest percentage of lipids-namely 19.8% per biomass. Direct heating of biomass in an autoclave also showed better performance than when using only conventional solvent extraction. To enhance the biomass harvest and lipid extraction efficiency, coagulation and flocculation steps were added to the extraction process. It is noteworthy that not only the solvent type but also the solvent/biomass ratio greatly affected efficiency. In addition, the moisture content of the harvested(wet) biomass affected the efficiency significantly. This study elucidated the need for future research on optimizing this extraction process.