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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>
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>
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.
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>
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.