Nitrate Reduction without Ammonium Release using Fe-loaded Zeolite

Lee Seunghak,Lee Kwanghun,Lee Sungsu,Park Junboum Korean Society of Soil and Groundwater Environment 2005 지하수토양환경 Vol.10 No.1

영가 철을 이용한 질산성 질소 환원에 대한 연구는 지금까지 활발히 진행되어 왔지만, 이 반응에서 생성된 암모늄 부산물에 대한 적절한 처리과정은 아직 보고되지 않았다. 하지만, 암모늄은 먹는 물 수질기준에 의해 지하수 오염물로 분류되고 있어 (허용치 0.5 mg-N/L), 질산성 질소로 오염된 지하수 정화에 영가 철을 단독으로 사용하는 것에는 한계가 있다. 따라서, 본 연구의 목적은 질산성 질소를 환원함과 동시에 이 과정에서 발생하는 암모늄을 제거할 수 있는 반응물질을 개발하는데 있다. 본 연구에 사용한 Fe-loaded zeolite는, 제올라이트와 Fe(II) 용액을 교반시켜 제올라이트 구조 안으로 Fe(II)를 흡착유도하고, 이를 sodium borohydride로 환원하는 과정을 통해 제작되었다. Fe-loaded zeolite 제작에 사용된 Fe(II) 용액의 농도를 실험을 통해 산정하고, 이를 통해 Fe-loaded zeolite를 제작한 후, Fe-loaded zeolite의 질산성 질소 제거 성능을 확인하기 위해 두 가지 pH조건에서 회분식 실험을 수행하였다. 80시간의 반응을 통해 Fe-loaded zeolite는 초기 pH가 3.3인 경우 약 $60\%$의 질산성 질소를, pH가 6인 경우는 약 $40\%$의 질산성 질소를 제거하였고, 암모늄 부산물은 전혀 검출되지 않았다. 영가 철의 경우, 각 초기 pH조건에서 Fe-loaded zeolite보다 뛰어난 질산성 질소 제거성능을 보였지만, 반응 후 상당량의 암모늄 부산물을 생성하였다. 질산성 질소와 암모늄을 포함한 질소(-N)제거 효능의 관점에서 Fe-loaded zeolite의 경우 pH 3.3과 6의 경우에서 각각 $60\%$와 $40\%$의 제거효율을 보인 반면, 영가 철의 제거효율은 무시할만한 수준으로 나타났다. Nitrate reduction with zero valent iron $(Fe^0)$ has been extensively studied, but the proper treatment for ammonium byproduct has not been reported yet. In groundwater, however, ammonium is regarded as contaminant species, and particularly, its acceptable level is regulated to 0.5 mg-N/L. for drinking water. This study is focused on developing new material to reduce nitrate and properly remove ammonium by-products. A new material, Fe-loaded zeolite, is derived from zeolite modified by Fe(II) chloride followed by reduction with sodium borohydride. Batch experiments were performed without buffer at two different pH to evaluate the removal efficiency of Fe-loaded zeolite. After 80 hr reaction time, Fe loaded zeolite showed about $60\%$ nitrate removal at initial pH of 3.3 and $40\%$ at pH of 6 with no ammonium release. Although iron filing showed higher removal efficiency than Fe-loaded zeolite at each pH, it released a considerable amount of ammonium stoichiometrically equivalent to that of reduced nitrate. In terms of nitrogen species including $NO_3-N$ and $NH_4^+-N$, Fe-loaded zeolite removed about $60\%\;and\;40\%$ of nitrogen in residual solution at initial pH of 3.3 and 6, respectively, while the removal efficiency of iron filing was negligible.

Phosphorous recovery from sewage sludge using calcium silicate hydrates

Lee, Chang-Gu,Alvarez, Pedro J.J.,Kim, Hee-Gon,Jeong, Seongpil,Lee, Seunghak,Lee, Ki Bong,Lee, Sang-Hyup,Choi, Jae-Woo Elsevier 2018 CHEMOSPHERE - Vol.193 No.-

<P><B>Abstract</B></P> <P>Phosphorous is an essential limiting nutrient for which there is no substitute. Its efficient recovery from sewage treatment plants is important to mitigate both dependence on limited reserves of exploitable phosphate rock and eutrophication of surface waters. Here, we evaluate the use of calcium silicate hydrates (CSH) to recover phosphorous eluted from sewage sludge. Phosphorous elution experiments were conducted with acid and base leaching solutions. The phosphorous recovery efficiency with CSH was compared to that with other calcium compounds, and the final product was analyzed to assess its potential value as fertilizer. Dried sewage sludge from the West Lake Ecological Water Resource Center, South Korea, having 123 g-P kg<SUP>−1</SUP>, was used for these tests. About 55% of the phosphorus in the sludge was released with an elution solution of 0.1 M H<SUB>2</SUB>SO<SUB>4</SUB>. A dose of 15 g L<SUP>−1</SUP> of CSH recovered 89.6% of the eluted phosphorous without the need for additional pre-treatment, and the resulting calcium phosphate product (in brushite form, based on XRD analysis) exhibited superior settleability than that resulting from Ca(OH)<SUB>2</SUB>- and CaCl<SUB>2</SUB>-induced precipitation. XRD peaks of the calcium sulfate hydrate (in gypsum form) and residual CSH were also observed. The final product contained a relatively high content of the total P<SUB>2</SUB>O<SUB>5</SUB> eluted in a 2% citric acid solution (43.1%), which suggests that it might be readily used to fertilize crops.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Phosphorous eluted from sewage sludge can be effectively recovered by CSH. </LI> <LI> 55% of the phosphorus in the sludge (123 g-P/kg) was released into 0.1 M H<SUB>2</SUB>SO<SUB>4</SUB>. </LI> <LI> 15 g/L of CSH recovered 89.6% of the eluted phosphorus without further treatment. </LI> <LI> The resulting calcium phosphate product from CSH exhibited superior settleability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Oxidizing Capacity of Periodate Activated with Iron-Based Bimetallic Nanoparticles

Lee, Hongshin,Yoo, Ha-Young,Choi, Jihyun,Nam, In-Hyun,Lee, Sanghyup,Lee, Seunghak,Kim, Jae-Hong,Lee, Changha,Lee, Jaesang American Chemical Society 2014 Environmental science & technology Vol.48 No.14

<P>Nanosized zerovalent iron (nFe<SUP>0</SUP>) loaded with a secondary metal such as Ni or Cu on its surface was demonstrated to effectively activate periodate (IO<SUB>4</SUB><SUP>–</SUP>) and degrade selected organic compounds at neutral pH. The degradation was accompanied by a stoichiometric conversion of IO<SUB>4</SUB><SUP>–</SUP> to iodate (IO<SUB>3</SUB><SUP>–</SUP>). nFe<SUP>0</SUP> without bimetallic loading led to similar IO<SUB>4</SUB><SUP>–</SUP> reduction but no organic degradation, suggesting the production of reactive iodine intermediate only when IO<SUB>4</SUB><SUP>–</SUP> is activated by bimetallic nFe<SUP>0</SUP> (e.g., nFe<SUP>0</SUP>–Ni and nFe<SUP>0</SUP>–Cu). The organic degradation kinetics in the nFe<SUP>0</SUP>–Ni(or Cu)/IO<SUB>4</SUB><SUP>–</SUP> system was substrate dependent: 4-chlorophenol, phenol, and bisphenol A were effectively degraded, whereas little or no degradation was observed with benzoic acid, carbamazepine, and 2,4,6-trichlorophenol. The substrate specificity, further confirmed by little kinetic inhibition with background organic matter, implies the selective nature of oxidant in the nFe<SUP>0</SUP>–Ni(or Cu)/IO<SUB>4</SUB><SUP>–</SUP> system. The comparison with the photoactivated IO<SUB>4</SUB><SUP>–</SUP> system, in which iodyl radical (IO<SUB>3</SUB><SUP>•</SUP>) is a predominant oxidant in the presence of methanol, suggests IO<SUB>3</SUB><SUP>•</SUP> also as primary oxidant in the nFe<SUP>0</SUP>–Ni(or Cu)/IO<SUB>4</SUB><SUP>–</SUP> system.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2014/esthag.2014.48.issue-14/es5002902/production/images/medium/es-2014-002902_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es5002902'>ACS Electronic Supporting Info</A></P>

Weight and Length of the Prosopocoilus astacoides blanchardi in Indoor Rearing

Kyoung Sik Yang,Jong-Du Lee,Doseung Lee,Jong chul Lee,Yoonji Lee,Seunghak Lee,Weon-Jong Yoon,Yong-Hwan Jung 한국응용곤충학회 2019 한국응용곤충학회 학술대회논문집 Vol.2019 No.10

Sensor Node Localization by Three Mobile Anchors in the Wireless Sensor Networks

LEE, Seunghak,KIM, Namgi,KIM, Heeyoul,LEE, Younho,YOON, Hyunsoo The Institute of Electronics, Information and Comm 2011 IEICE transactions on information and systems Vol.94 No.10

<P>For the deployment of sensor networks, the sensor localization, which finds the position of sensor nodes, is very important. Most previous localization schemes generally use the GPS signal for the sensor localization. However, the GPS signal is unavailable when there is an obstacle between the sensor nodes and satellites. Therefore, in this paper, we propose a new localization scheme which does not use the GPS signal. The proposed scheme localizes the sensors by using three mobile anchors. Because the three mobile anchors collaboratively move by themselves, it is self-localizable and can be adopted even when the sensors are randomly and sparsely deployed in the target field.</P>

Silicone oil-based selective SiOC coating onto hydrophobic rGO-MoS2 composite materials to achieve ultra-stable composite anodes in sodium-ion batteries

Seunghak Lee,Eunjeong Seok,Haeun Kang,Dohyub Park,Minjun Kim,Dayoung Kam,Minsu Choi,Hyung-Seok Kim,Wonchang Choi 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.126 No.-

Molybdenum sulfide (MoS2) has a 2-D open framework structure and provide delocalized sodium ion diffusionand intercalation within the MoS2 structure. The structure exhibits a high theoretical capacity dueto its wide interlayer spacing (6.2 Å). Therefore, MoS2 has recently been used as an anode material insodium-ion batteries (SIBs). However, it exhibits inferior cycle performance and rate characteristicsdue to its low electronic conductivity and volume change during continuous operation, which restrictits use as an anode material in SIBs. Herein, a MoS2 surface modified with hydrophobic reduced grapheneoxide (rGO-MoS2) was dispersed in silicone oil, which is the starting material for silicon oxycarbide(SiOC), and subsequently used to prepare a MoS2 composite with a SiOC coating-layer surface modifiedwith rGO (rGO-MoS2@SiOC) via single pyrolysis reaction. rGO expands the interlayer spacing of MoS2,improving the electronic conductivity, and the SiOC layer capable of accommodating the volume expansionof MoS2 supports the insufficient buffer layer provided by rGO alone to form a conductive pathwaythat suppressed any adverse reactions at the electrode and electrolyte interface. The rGO-MoS2@SiOCcomposite exhibits a high reversible capacity of 532.5 mAh g1, no capacity fading even after 100 cycles,and superior rate characteristics.

Development of SPRi-Protein Chip for Depigmenting Agent Screening

Seunghak BAEK,Man-ki SON,Babitha SUMATHY,Hyang-Bok LEE,Dung Hoang NGUYEN,Yu ri LEE,Eun-Ki KIM 한국생물공학회 2009 한국생물공학회 학술대회 Vol.2009 No.10

Developing a Process Model for Optimizing Linear Process Plans Based on Three Types of Buffers and Brute-Force Algorithm

Lee, Seunghak,Lee, Seunghyun,Son, Jaeho Informa UK (TaylorFrancis) 2016 JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEE Vol.15 No.2

Effect of a ZnO buffer layer on structural and electrical properties of ZnO:Al,P thin films grown by RF magnetron sputtering

Shin, Seunghak,Kim, Changhun,Lee, Jung-A.,Heo, Young-Woo,Lee, Joon-Hyung,Kim, Jeong-Joo Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.14

<P><B>Abstract</B></P> <P>Structural and electrical properties of ZnO:Al<SUB>0.01</SUB>P<SUB>0.04</SUB> thin films were investigated with respect to the growth temperature of the ZnO buffer layers deposited by RF magnetron sputtering. The ZnO buffer layers on <I>c</I>-plane sapphires showed three different types of in-plane orientation relationships between ZnO and Al<SUB>2</SUB>O<SUB>3</SUB> at different growth temperatures: ZnO[10 1 ̅ 0] // Al<SUB>2</SUB>O<SUB>3</SUB>[10 1 ̅ 0] at 200°C, a mixture of ZnO[10 1 ̅ 0] // Al<SUB>2</SUB>O<SUB>3</SUB>[10 1 ̅ 0] and ZnO[10 1 ̅ 0] // Al<SUB>2</SUB>O<SUB>3</SUB>[11 2 ̅ 0] at 300°C, and ZnO[10 1 ̅ 0] // Al<SUB>2</SUB>O<SUB>3</SUB>[11 2 ̅ 0] at 600°C. The in-plane orientation of the ZnO:Al<SUB>0.01</SUB>P<SUB>0.04</SUB> thin film followed the orientation of the ZnO buffer layer regardless of its growth temperature. The ZnO:Al<SUB>0.01</SUB>P<SUB>0.04</SUB> film grown on a ZnO buffer layer deposited at 600°C had a carrier concentration of 1.18 × 10<SUP>16</SUP> cm<SUP>−3</SUP>, mobility of 7.16 × 10°cm<SUP>2</SUP>/(Vs), and resistivity of 7.36 × 10<SUP>1</SUP> Ωcm, indicating <I>p</I>-type characteristics.</P>

벤처캐피탈 유형별 IPO 보증역할: 독립벤처캐피탈과 사내벤처캐피탈 비교

이승학 ( Seunghak Lee ),윤병섭 ( Byungseop Yoon ) 한국중소기업학회 2018 기업가정신과 벤처연구 Vol.21 No.3

본 연구는 2008년 1월 1일부터 2017년 12월 31일까지 10년 연구기간 동안 코스닥시장에 IPO한 기업 중 CVC가 투자한 기업 87개, IVC가 투자한 기업 74개를 표본으로 CVC와 IVC 사이 투자지분율, 공모비율 등의 분석을 통해 보증역할의 차별성을 논의하였다. 첫째, 벤처캐피탈을 IVC와 CVC로 양분하고 양 집단 사이 어느 유형이 저가발행을 완화하는 데 보다 더 공헌을 하는지 분석한 결과 AR(1.1), CAR(1.3), CAR(1.7) 구간에서 CVC가 IVC보다 초과수익률과 누적초과수익률에 체계적으로 유의한 음(-)의 영향을 미치고 있었다. 이는 전략적 목적의 투자를 선호하는 CVC가 재무적 목적의 투자수익률을 추구하는 IVC보다 보증역할을 더 충실히 한다고 판단할 수 있다. 둘째, 벤처기업이 IPO할 때 벤처기업에 투자한 벤처캐피탈의 투자지분율에 따라 초과수익률의 변화를 분석한 결과 CVC 지분율이 높을수록 IVC 지분율이 높을 때 보다 초과수익률이 낮게 나타나 CVC가 IVC보다 보증역할이 더 우월함을 보여주고 있다. 셋째, 벤처기업이 IPO할 때 공모비율에 따라 초과수익률이 어떻게 나타나는지 분석한 결과 CVC 공모비율이 높을수록 ICV 공모비율이 높을 때 보다 초과수익률이 낮게 나타나 CVC가 IVC보다 보증역할이 더 우월함을 보여주고 있으며, AR(1.1), CAR(1.3) 구간에서 나타나는 유의한 음(-)의 영향이 이를 증명하고 있다. 이는 Wang and Wan(2013)의 연구를 지지한다. This study analyzed that which types of groups contribute more to mitigating low-cost issuance after dividing venture capital into IVC and CVC. This study discussed the differentiation of the certification role through analysis of investment share and public offering ratio between CVC and IVC on the sample of 87 companies invested by CVC and 74 companies invested by IVC among the KOSDAQ market during 10-year research period from January 1, 2008 to December 31, 2017. The results are as follows. First, an analysis of which type more contributes to the mitigation of low-cost issuance between the two groups showed that CVC had a systematically significant negative (-) effect on abnormal return and cumulative abnormal return than IVC at section AR (1.1), CAR (1.3), CAR (1.7). This can be judged that CVC, which prefers investment for strategic purposes, is more faithful to its certification role than IVC, which pursues return on investment for financial purposes. Second, the analysis of whether the investment share of venture capital invested in venture business shows low abnormal return when venture business do IPOs. showed a significant difference between each section AR (1.1), CAR (1.3), CAR (1.7), CAR (1.30). The higher the share of venture capital investments invested in venture business in each segment, the more systematically significant negative impact on abnormal return of venture IPOs. The higher the share of the CVC invested in venture business, the more likely it can be accepted as the certification role of CVC to mitigate the low-cost issue of the venture IPO. Third, an analysis of whether the abnormal return is low for venture business’ IPO according to the public offering ratio found that the higher public offering ratio, the more significant negative (-) effect was found in the interval AR (1.1), CAR (1.3). This can be seen as a certification role of venture capital, which distributes risks and increases efficiency of operation, while reducing low-cost issuance of IPO. Therefore, it can be judged that the higher the public offering ratio, the more closely the IPO price is decided to market value, demonstrating the certification role of venture capital that mitigates the low-cost issuance of IPO. However, there is a need to identify the certification role of venture capital by dividing the target companies according to the level of the CVC and IVC investment share and revealing the portion of the investment share that shows a slightly lower abnormal return.