• Advances in environmental research
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• 제2권1호
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• pp.35-49
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• 2013

Research work on removal of fluoride from water, referred to as water defluoridation, has resulted into the development of a number of technologies over the years but they suffer from either cost or efficiency drawbacks. In this work, enhancement effects of phosphate and silicate on defluoridation of water by low-cost Plaster of Paris (calcined gypsum) were studied. To our knowledge, the influence of silicate on defluoridation was not reported. It was claimed, that the presence of some ions in the treated water samples, was decreasing the fluoride removal since these ions compete the fluoride ions on occupying the available adsorption sites, however, phosphate and silicate ions, from its sodium slats, have enhanced the fluoride % removal, hence, precipitation of calcium-fluoro compounds of these ions can be suggested. Percentage removal of $F^-$ by neat Plaster is 48%, the electrical conductance (EC) curve shows the typical curve of Plaster setting which begins at 20 min and finished at 30 min. The addition of phosphate and silicate ions enhances the removal of fluoride to high extent > 90%. Thermodynamics parameters showed spontaneous fluoride removal by neat Plaster and Plaster-silicate system. The percentage removal with time showed second-order reaction kinetics.

• 센서학회지
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• 제8권6호
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• pp.448-453
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• 1999

Pd-SiC 쇼트키 다이오드를 이용한 수소 가스 센서를 개발하였다. Pd-SiC 쇼트키 다이오드의 수소 가스 감지특성을 I-V 및 ${\Delta}I$-t 분석을 통하여 수소 농도와 온도 함수로서 분석하였다. 또한, 수소 흡착에 의한 Pd-SiC 쇼트키 다이오드의 장벽 높이의 변화를 조사하였다. 수소 원자의 흡착이 다이오드의 장벽 높이의 변화와 관계되는 것을 I-V 분석을 이용하여 정상 상태에서의 가스 반응 속도론에 의하여 확인하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권7호
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• pp.388-393
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• 2000

Hydrogen-sensing behaviors of Pd- and Pt-SiC Schottky diodes, fabricated on the same SiC substrate, have been systematically compared and analyzed as a function of hydrogen concentration and temperature by I-V and$\DeltaI-t$ methods under steady-state and transient conditions. The effects of hydrogen adsorption on the device parameters such as the barrier height are investigated. The significant differences in their hydrogen sensing characteristics have been examined in terms of sensitivity limit, linearity of response, response rate, and response time. For the investigated temperature range, Pd-SiC Schottky diode shows better performance for H2 detection than Pt-SiC Schottky diode under the same testing conditions. The physical and chemical mechanisms responsible for hydrogen detection are discussed. Analysis of the steady-state reaction kinetics using I-V method confirmed that the atomistic hydrogen process is responsible for the barrier height change in the diodes.

• Environmental Engineering Research
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• 제18권4호
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• pp.247-252
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• 2013

In this work, removal of phenol from aqueous solutions by activated red mud was investigated. Scanning electron microscopy and energy dispersive X-ray spectroscopy was used to observe the morphology and surface components of activated red mud, respectively. The effects of various parameters on the removal efficiency were studied, such as contact time, pH, initial phenol concentration, and adsorbent dosage. The removal percentage of phenol was initially increased, as the solution pH increased from 3 to 7, and then decreased above neutral pH. The removal percentage of phenol was decreased by increasing the initial phenol concentrations. Adsorption results show that equilibrium data follow the Freundlich isotherm, and kinetic data was well described by a pseudo-second-order kinetic model. Experimental results show that the activated red mud can be used to treat aqueous solutions containing phenol, as a low cost adsorbent with high efficiency.

• 대한화학회지
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• 제14권3호
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• pp.213-219
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• 1970

In the presence of hydrogen peroxide, the effects of temperature and pH to the catalytic reaction velocity of cupric -thiocyanate and the quantities of reduction products adsorbed on the D.M.E. have been studied by polarographic method. According to these experiments, the following empirical equation has been derived for the relation among temperature $T_i$, concentration of hydrogen ion $pH_i$ and adsorbed cuprous-thiocyanate in moles/$cm^2Z_{ij}$, and rate constant log$K_{ij}$ $$log\;K_{ij}=\frac{1}{T_i}\{A(pH_j)+B\}+C(pH_j)+D$$ $$Z_{ij}=\frac{1}{T_i}\{{\alpha}(pH_j)^{\frac{1}{2}}+{\beta}\}+{\gamma}(pH_j)^{\frac{1}{2}}+{\delta}$$ where, A,B,C,D and {$\alpha},{\beta},{\gamma},{\delta}$ are constants. The Calculated values by both equations are well agreed with empirical values within 8% in the error.

• 환경생물
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• 제39권3호
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• pp.298-310
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• 2021

Prediction of the behavior of heavy metals over time is important to evaluate the heavy metal toxicity in algae species. Various modeling studies have been well established, but there is a need for an improved model for predicting the chronic effects of metals on algae species to combine the metal kinetics and biological response of algal cells. In this study, a kinetic dynamics model was developed to predict the copper behavior(5 ㎍ L^-1, 10 ㎍ L^-1, and 15 ㎍ L^-1) for two freshwater algae (Pseudokirchneriella subcapitata and Chlorella vulgaris) in the chronic exposure experiments (8 d and 21 d). In the experimental observations, the rapid change in copper mass between the solutions, extracellular and intracellular sites occurred within initial exposure periods, and then it was slower although the algal density changed with time. Our model showed a good agreement with the measured copper mass in each part for all tested conditions with an elapsed time (R² for P. subcapitata: 0.928, R² for C. vulgaris: 0.943). This study provides a novel kinetic dynamics model that is compromised between practical simplicity and realistic complexity, and it can be used to investigate the chronic effects of heavy metals on the algal population.

• Membrane and Water Treatment
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• 제13권6호
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• pp.321-335
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• 2022

Copper-based Metal-organic framework (MOF) namely ([Cu (INA)₂]-MOF) is synthesized by ball milling and characterized using scanning electron microscopy (SEM) for the topography, microstructure, and elemental evidence determination, powdered X-ray diffraction (XRD) for the crystallinity measurement, thermogravimetric (TG) analysis was performed to determine the thermal stability of the material, and Fourier transformed infrared (FTIR) spectroscopy for functional groups identification. The use of [Cu (INA)₂]-MOF as hazardous removal material of β-agonists as persistent hazardous micro-pollutants in our environmental water is first reported in this study. The removal efficiency of the Cu-MOF is successfully determined to be 97.7% within 40 minutes, and the MOF has established an exceptional removal capacity of 835 mg L^-1 with 95 % percent removal on Clenbuterol (CLB) even after the 5th consecutive cycle. The Langmuir model of the adsorption isotherms was shown to be more favourable, while the pseudo-second-order model was found to be favoured in the kinetics. The reaction was exothermic and spontaneous from a thermodynamic standpoint, and the higher temperatures were unfavourable for the adsorption study of the CLB. As a result, the studied MOF have shown promising properties as possible adsorbents for the removal of CLB in wastewater.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.354-361
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• 2022

In a direct methanol fuel cell system (DMFC), one of the drawbacks is methanol crossover. Methanol from the anode passes through the membrane and enters the cathode, causing mixed potential in the cell. Only Pt-based catalysts are capable of operating as cathode for oxygen reduction reaction (ORR) in a harsh acidic condition of DMFC. However, it causes mixed potential due to high activity toward methanol oxidation reaction of Pt. To overcome this situation, developing Pt-based catalyst that has methanol tolerance is significant, by controlling reactant adsorption or reaction kinetics. Pt/C decorated with phosphate ion was prepared by modified polyol method as cathode catalyst in DMFC. Phosphate ions, bonded to the carbon of Pt/C, surround free Pt surface and block only methanol adsorption on Pt, not oxygen. It leads to the suppression of methanol oxidation in an oxygen atmosphere, resulting in high DMFC performance compared to pristine Pt/C.

• 공업화학
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• 제24권4호
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• pp.375-381
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• 2013

상업용 니켈 촉매를 사용하여 메탄과 천연가스의 수증기 개질 반응을 각각 수행하였다. 수증기 개질 반응의 변수는 반응 온도와 반응물의 분압이었다. Kinetic data로부터 Power law rate model과 Langmuir-Hinshelwood model의 매개변수를 구하였다. 순수한 메탄을 수증기 개질 반응 실험의 원료로 사용한 경우에는 Langmuir-Hinshelwood model 식은 물론이고 Power law rate model을 사용하여 반응 속도를 적절하게 표현할 수 있었다. 그러나 천연가스 중의 메탄의 수증기개질 반응 속도를 표현하는데 있어서는 Power law rate model보다 Langmuir-Hinshelwood model이 훨씬 더 적합한 것을 확인하였다. 이러한 거동은 천연가스 중에 포함되어있는 메탄, 에탄, 프로판 및 부탄이 동일한 촉매 활성점에 경쟁적으로 흡착하기 때문으로 해석할 수 있었다.

• 자원리싸이클링
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• 제25권4호
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• pp.60-67
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• 2016

본 연구에서는 P507을 포함하고 있는 추출수지를 사용하여 중희토류 원소인 Gd, Tb, Dy의 흡 탈착 반응 메커니즘을 고찰하고 분리를 위한 최적 크로마토그래피법의 반응조건을 도출하였다. 흡 탈착 반응 메커니즘은 흡착등온식인 Langmuir, Freundlich 흡착등온식과, 흡착속도모델인 유사 1차, 2차 반응속도식을 적용하여 고찰하였다. 중희토류 원소의 흡착반응은 단분자층으로 일어난다고 가정하여 흡착등온식을 적용하였고, 잘 일치하여 흡착반응이 단분자층으로 이루어짐을 추측할 수 있었다. 시간별 실험을 진행하여 유사 1차, 2차 반응속도식에 적용한 결과 유사 2차 반응속도식이 추출수지의 중희토류 흡착 메커니즘을 더 잘 표현하였고, 평형흡착량의 실험값은 이론값에 부합하였다. 크로마토그래피법을 이용하여 용리액 HCl 0.25 M 농도조건에서 ${\alpha}^{Tb}_{Gd}=1.24$, ${\alpha}^{Dy}_{Tb}=1.03$으로 분리계수 1이상의 높은 분리조건을 확인하였다. HCl 용리액을 사용하였을 때, 용리액의 농도가 높을수록 분리도는 감소하고 용출구간은 줄어드는 경향을 확인하였다.