• Journal of the Korean Electrochemical Society
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• v.3 no.2
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• pp.109-114
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• 2000

The relation between the phase-shift profile fur the intermediate frequencies and the Langmuir adsorption isotherm at the poly-Ir/0.1 M $H_2SO_4$ aqueous electrolyte interface has been studied using ac impedance measurements, i.e., the phase-shift methods. The simplified interfacial equivalent circuit consists of the serial connection of the electrolyte resistance $(R_s)$, the faradaic resistance $(R_F)$, and the equivalent circuit element $(C_P)$ of the adsorption pseudoca-pacitance $(C_\phi)$. The comparison of the change rates of the $\Delta(-\phi)/{\Delta}E\;and\;\Delta{\theta}/{\Delta}E$ are represented. The delayed phase shift $(\phi)$ depends on both the cathode potential (E) and frequency (f), and is given by $\phi=tan^{-1}[1/2{\pi}f(R_s+R_F)C_P]$. The phase-shift profile $(-\phi\;vs.\;E)$ for the intermediate frequency (ca. 1 Hz) can be used as an experimental method to determine the Langmuir adsorption isotherm $(\theta\;vs.\;E)$. The equilibrium constant (K) for H adsorption and the standard free energy $({\Delta}G_{ads})$ of H adsorption at the poly-Ir/0.1 M $H_2SO_4$ electrolyte interface are $2.0\times10^{-4}$ and 21.1kJ/mol, respectively. The H adsorption is attributed to the over-potentially deposited hydrogen (OPD H).

• Korean Journal of Environmental Agriculture
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• v.34 no.3
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• pp.155-160
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• 2015

BACKGROUND: Objective of this study was to investigate adsorption characteristics of $NH_4-N$ to biochar produced from rice hull in respective to mitigation of greenhouse gases. METHODS AND RESULTS: $NH_4-N$ concentration was analyzed by UV spectrophotometer. For adsorption experiment of $NH_4-N$ to biochar, input amount of biochar was varied from 0.4 to 10 g/L with 30 mg/L $NH_4-N$ solution. Its adsorption characteristic was investigated with application of Langmuir isotherm. Adsorption amount and removal rates of $NH_4-N$ were decreased at 53.9% and increased at 20.2% with 10 g/L compared to 0.4 g/L, respectively. The sorption of $NH_4-N$ to biochar produced from rice hull was fitted well by a Langmuir model. The largest adsorption amount of $NH_4-N$ ($q_m$) and binding strength constant (b) were calculated as 0.4980 mg/g, and 0.0249 L/mg, respectively. It was observed that dimensionless constant ($R_L$) was 0.58. CONCLUSION: It was indicated that biochar produced from rice hull is favorably absorbed $NH_4-N$, because this value lie within 0< $R_L$ <1.

• KSBB Journal
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• v.14 no.2
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• pp.141-145
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• 1999

The study was conducted for the efficient utilization of biomaterials such as Chestnut shell which was wasted tremendously as an agricultural by-products. This biomaterials were examined for their removal rate of heavy metal ions as adsorbents in wastewater by batch adsorption experiments. In this experiment, the heavy metal ions used were $\Cd^{2+},\;Fe^{2+},\;Cr^{6+},\;Mn^{2+},\;Cu^{2+}$ and $Pb^{2+}$. The range of time for the removal rates of heavy metal ions were observed about 10 min. The range of high pH for the removal rates of $\Cd^{2+},\;Fe^{2+},\;Mn^{2+},\;Cu^{2+}$ and $Pb^{2+}$ ere observed 7.0-9.0. The range of high pH for the removal rate of $Cr_{6+}$ was observed 2. In the case of raw chestnut shell, the removal rates of $\Fe^{2+},\;Mn^{2+},\;Cu^{2+}$ and $Pb^{2+}$ were above 70 percent. The removal rates of heavy metals in formaline pretreated chestnut shells except $Cd_{2+}$ were above 50 percent and in phosphorylating chestnut shells except $Cr_{6+}$ were above 60 percent. Chestnut shells pretreated by formaline and phosphorylating were not so good enough for improvement of removal rates with pH change in mixed heavy metal solution.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.411-414
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• 2008

본 논문에서는 $CO_2$ 분리용 활성탄의 표면분석 및 흡착속도를 비교하였다. TGA 방법에 의한 흡착속도 데이터를 획득함으로써 분리장치 설계를 위한 기초자료를 획득하였고, 흡착온도에 따른 결과는 흡착온도가 낮을수록, 흡착량이 증가하고 흡착속도 또한 더 빠름을 알 수 있었다.

• Journal of Environmental Science International
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• v.12 no.12
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• pp.1269-1276
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• 2003

In order to know the effect of atuoclaving on the heavy metal removal using chitosan, lead removal capacities and removal rates by various chitosans in aqueous solution were compared according to the various autoclaving time. The lead removal efficiencies and removal rates by the autoclaved chitosan were found to be on the order of 15 min(98％) ＞ 10 min(95％) ＞ 30 min(83％) ＞ 5 min(53％) ＞ 60 min(47％) ＞ 0 min(22％) chitosan. The molecular weight of chitosan was decreased by the increase of autoclaving time. Therefore, the heavy metal removal capacity was not well correlated to the molecular weight. Langmuir isotherm was well fitted to experimental results of equilibrium adsorption on chitosan. In order to examine the process of lead removal by the autoclaved chitosan, TEMs, SEMs and FT-IR analyses were used. The surface of autoclaved chitosan was much more porous and the lead removal was mainly occurred on the surface of chitosan. The structure of autoclaved chitosan was same as that of controlled chitosan.

• The Korean Journal of Nuclear Medicine
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• v.7 no.1
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• pp.51-54
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• 1973

The use of ion-exchange resins for the treatment of radioactive wastes has many advantages, but thes eare rather expensive as compared with the Korean vermiculite. The Korean vermiculite has slightly different chemical constituents from the ones produced in other countries, and its physical properties might be applicable to the management of radioactive waste, in a small nuclear installation. The decontaminating effect of Korean vermiculite for the low-level radioactive liquid was investigated. $^{106}Ru,\;^{90}Sr,\;and\;^{137}Cs$ were utilized for the experiments. The removal rates by Korean vermiculite were calculated for $^{106}Ru,\;^{90}Sr\;and\;^{137}Cs$ and the removal rates increased as the weight of vermiculite in the exchange column increased. The decontaminating constants, $K_d$ of the Korean vermiculite for $^{106}Ru,\;^{90}Sr\;and\;^{137}Cs$ were 2.7, 69.3 and 263ml/g respectively. Through the results of experiments, the application of Korean vermiculite column to the treatment of low-level radioactive waste is quite feasible.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.91-96
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• 2005

This study was performed for the research on the method for reducing non-point pollutant with the gabion which was made of gravel-packed plastic frame, and for the characterization of gabion adsorbing pollutant. The result showed that the concentrations of suspended solid in turbid water were reduced to $77.7{\sim}84.7%$ when the water was flowing through the gabion. The uniformity coefficients on the grain size accumulation curves of the adsorbed pollutant were larger on the large grain size gabion than those on the small grain size gabion, and the coefficients of curvature were smaller on the large grain size gabion than those of the small grain size gabion. The adsorption rates were dependent on the grain size of packed gravel. The rates were smaller on inlet and outlet than those on middle place on the series of gabion.

• Corrosion Science and Technology
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• v.15 no.2
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• pp.43-53
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• 2016

In this study, electrochemical impedance spectroscopy (EIS) was used to examine the changes in the electrochemical properties of biodegradable pure magnesium implanted into Sprague-Dawley rats for three days. The in vivo test results were compared with those of the in vitro tests carried out in Hank's, dilute saline and simulated body fluid (SBF) solutions. The in vitro corrosion rates were 20~1700 fold higher, as compared to the in vivo corrosion rates. This discrepancy is caused by biomolecule adsorption on the surface, which prevents the transport of water into the magnesium surface on in vivo testing. Among the in vitro experimental conditions, the corrosion rate in SBF solution had the least difference from the in vivo implanted specimen.

• International Journal of Advanced Culture Technology
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• v.8 no.2
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• pp.283-288
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• 2020

This study investigated the purification process of groundwater contaminated with zinc and arsenic using a permeable reactive barrier with a zero-valent iron/pumice mixture. We determined the removal rates of the contaminants for 30 days. In this study, column reactor filled with the zero-valent iron/pumice reactive mixture was used. Experimental results showed that the mixture exhibited an almost complete removal of the zinc and arsenic ions. Arsenic was removed via co-precipitation and adsorption processes while zinc ions were asorbed in active sites.The purification process of water from the metal ionscontinued for 30 days with constant hydraulic conductivity because of the enhanced porosity of the pumice and interparticle distance between the zero-valent iron and pumice. Contaminants removal rates and the remediation mechanism for each reactive system are described in this paper.

• Journal of the Korean Applied Science and Technology
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• v.19 no.2
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• pp.108-116
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• 2002

Experimental Study was carried out for benzene desorption by purge gas or evacuation in an activated carbon bed. As purge gas flow rate increased, desorption rate increased due to the higher interstitial linear gas velocity. For various purge gas flow rates, desoption curves almost got together if they were plotted against dimensionless time. At a higher flow rate, mass transfer zone became narrower. Temperature drop in the bed was more fast and severe at higher flow rates and higher outer temperature. It was found out that desorption was almost completed when the temperature in the drop of the bed returned to the initial temperature before temperature drop. Desorption by vacuum purge was completed in shorter time than desorption by purge gas. Countercurrent purge was more effective than cocurrent purge.