• Economic and Environmental Geology
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• v.51 no.5
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• pp.401-407
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• 2018

For the treatment of heavy metals in the mine drainage from the closed mine area, various methods such as passive, active and semi-active treatments are considered. Among contaminated elements in the mine drainage, Mn is one of the difficult elements for the treatment because it needs high pH over 9.0 for its concentration to be reduced. In this study, the efficiency of various slag complex reactors (slag (S), slag+limestone (SL) and slag+Mn coated gravel (SG)) on Mn removal in the presence of Fe, which is a competitive element with Mn, was evaluated to investigate effective methods for the treatment of Mn in mine drainage. As a result of experiments on Mn removal without Fe during 358 days, using influent with $30{\sim}50Mn{\cdot}mg/L$ and pH 6.7 on the average, S reactor showed continuously high Mn removal efficiency with the average of 99.9% with pH 8.9~11.4. Using the same reactors, Mn removal experiments with Fe during 237 days were conducted with the influent with $40{\sim}60Mn{\cdot}mg/L$. The pH range of effluent reached to 6.1~10.0, which is slightly lower than that of effluent without Fe. S reactor showed the highest range of pH with 7.1~9.9, followed by S+L and S+G reactor. However, the efficiency of Mn removal showed S+L>S>S+G with the range of 94~100%, 68~100% and 68~100%, respectively in spite of relatively low pH range. S+L reactor showed the most resistance on Fe input, which means other mechanisms such as $MnCO_3$ formation by the carbonate prouced from the limestone or autocatalysis reaction of Mn contributed to Mn removal rather than pH related mechanisms. The evidence of reactions between carbonates and Mn, rhodochrosite ($MnCO_3$), was found from the X-ray diffraction analysis of precipitates sample from S+L reactor. From this study, the most effective reactors on Mn removal in the presence of Fe was S+L reactor. The results are expected to be applied for the Mn containing mine water treatment in the presence of Fe within the relatively low range of pH.

• The Korean Journal of Pesticide Science
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• v.2 no.1
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• pp.46-52
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• 1998

The hydrolysis rate of insecticidal buprofezin(IUPAC : tert-butylimino-3-isopropyl-5-phenylperhydro-1,3,5-thiadiazin-4-one) in the range of pH 2.0 and 12.0 have been examined in 15%(v/v) aqueous dioxane at $45^{\circ}C$. The hydrolysis mechanism of buprofezin is proposed from the pH-effect, solvent effect(${\ell}{\gg}m$), thermodynamic parameter(${\Delta}H^{\neq}$=11.12 $Kcal{\cdot}mol^{-1}$ &, ${\Delta}S^{\neq}=5.0e.u.$), rate equation and hydrolysis product, l-isopropyl-3-phenyl urea. General acid catalyzed hydrolysis and specific acid catalyzed($k_{H3O+}$) hydrolysis through $A-S_{E}2$ and A-2(or $A_{AC}2$) reaction mechanism with orbital-control reaction proceed below pH 8.0 and above pH 9.0, the nucleophilic addition-elimination, $Ad_{N}-E$ mechanism via tetrahedral($sp^{3}$) intermediate is initiation by general base catalyzed($k_{H2O}$) reaction. Buprofezin was more stable in alkaline ($k=10^{-8}sec.^{-1}$) than acid solutions from the sigmoid pH-rate profile. And the half-life($t=\frac{1}{2}$) of hydrolysis reaction in neutral aqueous solution(pH 7.0) at $45^{\circ}C$ was about 3 months.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.746-751
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• 2002

Fluidized bed combustion is a coal combustion technology that can reduce both SOx and NOx emission; SOx is removed by limestone that is fed into the combustion chamber and the NOx is reduced by low temperature combustion in a fluidized bed combustor and air stepping, but $N_2O$ generation is quite high. $N_2O$ is not only a greenhouse gas but also an agent of ozone destruction in the stratosphere. The calcium oxide(CaO) is known to be a catalyst of $N_2O$ decomposition. This study of $N_2O$ decomposition reaction in fixed bed reactor packed over CaO bed has been conducted. Effects of parameters such as concentration of inlet $N_2O$ gas, reaction temperature, CaO bed height and effect of $CO_2$, NO, $O_2$ gas on the decomposition reaction have been investigated. As a result of the experiment, it has been shown that $N_2O$ decomposition reaction increased with the increasing fixed bed temperature. While conversion of the reaction was decreased with increasing $CO_2$ concentration. Also, under the present of NO, the conversion of $N_2O$ decomposition is decreased. From the result of kinetic study gained the heterogeneous reaction rate on $N_2O$ decomposition. In the case of $N_2O$ decomposition over CaO, heterogeneous reaction rate is. $\frac{d[N_2O]}{dt}=\frac{3.86{\times}10^9{\exp}(-15841/R)K_{N_2O}[N_2O]}{(1+K_{N_2O}[N_2O]+K_{CO_2}[CO_2])}$. In this study, it is found that the calcium oxide is a good catalyst of $N_2O$ decomposition.

• Current Research on Agriculture and Life Sciences
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• v.26
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• pp.23-30
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• 2008

In this paper, when the silk fabric was modified by ethylene cyanohydrine, the reaction mechanism between both was studied at various treatment conditions such as curing temperatures and times, ethylene cyanohydrin concentrations and $ZnCl_2$ concentrations. Through the FT-IR and DSC analyses of the treated silk fabrics, we found the results as follows : It was observed in FT-IR analysis of the treated silk fabrics that the -OH characteristic peak($3,450cm^{-1}$)position and shape were all changed when drying and curing treatment conditions were at $80^{\circ}C$ for 3 minute and $110^{\circ}C$ for 2.5 minute, and the concentration of the $ZnCl_2$ was 0.1%. It indicated that the -OH group of the silk participated in the reaction between the silk fabric and ethylene cyanohydrin. From the DSC analysis, it was found that the pyrolysis temperatures of the treated silk fabrics by ethylene cyanohydrin which was processed in the same condition, were all increased from $311^{\circ}C$ to ab. $320^{\circ}C$. From the FT-IR analyses of the silk fabrics treated by ethylene cyanohydrin at the various concentrations of $ZnCl_2$, it was found that the -OH characteristic peaks($3,450cm^{-1}$) were similar to the nontreated one except that of the fabric treated at the $ZnCl_2$ conconcentration of 0.8% when drying and curing treatment conditions were at $80^{\circ}C$ for 3minute and $110^{\circ}C$ for 2.5 minute, and the concentration of the ethylene cyanohydrin was 5%. In the case of the $ZnCl_2$ concentration of 0.8% solution, a lot of change were observed in peak. From the DSC analysis of the treated silk fabrics which was processed in the same condition, it was showed that the pyrolysis temperatures of treated silk fabric were all increased from $311^{\circ}C$ to ab. $320^{\circ}C$, which was no relation with the concentration of $ZnCl_2$.

• Clean Technology
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• v.26 no.4
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• pp.329-335
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• 2020

Methanol synthesized from renewable hydrogen and captured CO2 has recently attracted great interest as a sustainable energy carrier for large-scale renewable energy storage. In this study, molten carbonate fuel cell's performance was investigated with the direct conversion of methanol into syngas inside the anode chamber of the cell. The internal reforming of methanol may significantly improve system efficiency since the heat generated from the electrochemical reaction can be used directly for the endothermic reforming reaction. The porous Ni-10 wt%Cr anode was sufficient for the methanol steam reforming reaction under the fuel cell operating condition. The direct supply of methanol into the anode chamber resulted in somewhat lower cell performance, especially at high current density. Recycling of the product gas into the anode gas inlet significantly improved the cell performance. The analysis based on material balance revealed that, with increasing current density and gas recycling ratio, the methanol steam reforming reaction rate likewise increased. A methanol conversion more significant than 90% was achieved with gas recycling. The results showed the feasibility of electricity and syngas co-production using the molten carbonate fuel cell. Further research is needed to optimize the fuel cell operating conditions for simultaneous production of electricity and syngas, considering both material and energy balances in the fuel cell.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.36-43
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• 2024

Fishing net waste (FNW) constitutes over half of all marine plastic waste and is a major contributor to the degradation of marine ecosystems. While current treatment options for FNW include incineration, landfilling, and mechanical recycling, these methods often result in low-value products and pollutant emissions. Importantly, FNWs, comprised of plastic polymers, can be converted into valuable resources like syngas and pyrolysis oil through pyrolysis. Thus, this study presents a process for generating high-purity hydrogen (H₂) by catalytically pyrolyzing FNW in a CO₂ environment. The proposed process comprises of three stages: First, the pretreated FNW undergoes Ni/SiO₂ catalytic pyrolysis under CO₂ conditions to produce syngas and pyrolysis oil. Second, the produced pyrolysis oil is incinerated and repurposed as an energy source for the pyrolysis reaction. Lastly, the syngas is transformed into high-purity H₂ via the Water-Gas-Shift (WGS) reaction and Pressure Swing Adsorption (PSA). This study compares the results of the proposed process with those of traditional pyrolysis conducted under N₂ conditions. Simulation results show that pyrolyzing 500 kg/h of FNW produced 2.933 kmol/h of high-purity H₂ under N₂ conditions and 3.605 kmol/h of high-purity H₂ under CO₂ conditions. Furthermore, pyrolysis under CO₂ conditions improved CO production, increasing H₂ output. Additionally, the CO₂ emissions were reduced by 89.8% compared to N₂ conditions due to the capture and utilization of CO₂ released during the process. Therefore, the proposed process under CO₂ conditions can efficiently recycle FNW and generate eco-friendly hydrogen product.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.174-177
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• 2010

In this study, non-catalytic transesterification from rapeseed oil using supercritical methanol was carried out by varying the operation parameters such as temperature ($320{\sim}365{^{\circ}C}$), time (0~20 min), pressure (10~35 MPa), molar ratio of oil to methanol (1 : 15~60) and agitation speed (0~500 rpm). In order to evaluate the effects of reaction parameters on the content of fatty acid methyl esters (FAMEs), we carried out the study using a batch reactor. The content of FAMEs increased when the temperature increased. However, the content of FAMEs decreased with temperature above $335^{\circ}C$ and time above 5 min. The content of FAMEs increased with increasing the molar ratio of methanol to oil but the content of FAMEs was slightly affected by molar ratio of oil to methanol above 1 : 45 and pressure above 20 MPa. It was found that the agitation speed above 100 rpm slightly affected the content of FAMEs. The highest content of FAMEs in biodiesel (95%) was obtained under the reaction conditions: temperature of 335 ${^{\circ}C}$, time of 10 min, pressure of 20 MPa, molar ratio of 1 : 45 (oil to methanol) and agitation speed of 250 rpm.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.651-654
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• 2009

In this study, non-catalytic transesterification using supercritical methanol was performed for preparation of biodiesel from palm oil. In order to investigate the effects of reaction parameters such as molar ratio of methanol to oil(30:1~60:1), pressure(8~25 MPa), temperature($320{\sim}350^{\circ}C$), agitation speed(0~1,000 rpm) and time(0~20 min) on the content of fatty acid methyl esters(FAMEs), we carried out the study using a batch reactor. With increasing molar ratio of methanol to oil, the content of FAMEs increased. However, the content of FAMEs was little affected by molar ratio above 45 and pressure above 20 MPa. The content of FAMEs increased when the temperature increased. However, the content of FAMEs decreased with temperature above at $350^{\circ}C$ and with time above 5 min. It was found that the agitation speed above 500 rpm scarcely affected the content of FAMEs. The highest content of FAMEs in biodiesel(95%) was obtained under the reaction conditions: temperature of $335^{\circ}C$, pressure of 20 MPa, molar ratio of 45:1(methanol to palm oil), agitation speed of 500 rpm and time of 10 min.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.678-683
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• 2012

Ceria is one of the most important catalytic materials which can be used in three-way catalysts, waste water treatment, petroleum refining, etc. So far, many methods have been studied to produce ceria nanoparticles. In this study, ceria nanoparticles were prepared via solvothermal synthesis using supercritical methanol in short reaction time using a batch reactor. The size of synthesized ceria nanoparticles in supercritical methanol is 6 nm without capping agent, which is smaller than that made in supercritical water at the same conditions of $400^{\circ}C$ and 30 MPa. Size difference results from density and critical point difference between water and methanol and slow reaction rate at the surface of ceria particles in supercritical methanol which reduces crystal growth rate. Several organic compounds were added to modify the surface of ceria nanoparticles, and in-situ surface modification was confirmed by FT-IR and TGA analysis. Surface modified ceria nanoparticles have excellent dispersibility in organic solvent. Size and shape of surface modified ceria particles can be controlled by adjusting molar ratio of modifier to precursor and selection of modifier.

• Korean Chemical Engineering Research
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• v.54 no.1
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• pp.11-15
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• 2016

Proton Exchange Membrane Fuel Cells (PEMFC) instead of batteries is appropriate for long time flight of unmanned aero vehicles (UAV). In this work, $NaBH_4$ hydrolysis system supplying hydrogen to PEMFC was studied. In order to decrease weight of $NaBH_4$ hydrolysis system, enhancement of hydrogen yield, recovery of condensing water and maintenance of stable hydrogen yield were studied. The hydrogen yield of 3.4% was increased by controlling of hydrogen pressure in hydrolysis reactor. Condensing water formed during air cooling of hydrogen was recovered into storage tank of $NaBH_4$ solution. In this process the condensing water dissolved $NaBH_4$ powder and then addition of $NaBH_4$ solution decreased system weight of 14%. $NaBH_4$ hydrolysis system was stably operated with hydrogen yield of 96% by 2.0g Co-P-B catalyst for 10 hours at 2.0L/min hydrogen evolution rate.