• Journal of the Korean Chemical Society
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• v.36 no.4
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• pp.517-522
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• 1992

The reaction of ${\beta}$-picoline with substituted benzoyl chlorides has been studied by means of conductometry under various pressures in acetonitrile. From the values of pseudo-first order and second order rate constants, the activation parameters (${\Delta}V{\neq}$, ${\Delta}{\beta}{\neq}$, ${\Delta}H{\neq}$, ${\Delta}S{\neq}$ and ${\Delta}G{\neq}$) and the pressure dependence of Hammett ${\rho}$ value were studied. The activation volume, the activation compressibility coefficient and the activation entropy were all negative. By increasing pressure the rate constant and Hammett ${\rho}$ value were increased, and the reaction mechanism was proceed in bond formation favored.

• Journal of Environmental Science International
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• v.28 no.1
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• pp.55-64
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• 2019

The adsorption properties of $Cs^+$ and $Cu^{2+}$ ions were evaluated by using a polysulfone scoria zeolite (PSf-SZ) composite with synthetic zeolite synthesized from Jeju volcanic rocks (scoria). In order to investigate the adsorption properties, various parameters, such as pH, contact time, reaction rate, concentration, and temperature in aqueous solutions, were evaluated by tests carried out in batch experiments. The adsorption capacities of $Cs^+$ and $Cu^{2+}$ ions increased between pH 2 but achieved equilibrium at pH 4 and above. The adsorption rate increased rapidly up to the initial 24 h, after which it plateaued ; the adsorption rate then sustained at equilibrium from 48 h. The adsorption kinetics of $Cs^+$ and $Cu^{2+}$ ions were described better by the pseudo-second-order kinetic model than the pseudo-first-order kinetic model. The Langmuir model fitted the adsorption isotherm data better than the Freundlich model. The maximum adsorption capacities of $Cs^+$ and $Cu^{2+}$ ions obtained from the Langmuir model were 53.8 mg/g and 84.7 mg/g, respectively. The calculated thermodynamic parameters showed that the adsorption of $Cs^+$ and $Cu^{2+}$ ions on PSf-SZ was feasible, spontaneous and endothermic reaction.

• Journal of Korean Society on Water Environment
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• v.25 no.3
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• pp.459-463
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• 2009

The adsorption features of malachite green onto activated carbon have been investigated for its treatment from aqueous solution. The influential factors were examined the initial concentration of malachite green, reaction temperature, and pH. Under experimental conditions, adsorption equilibrium of malachite green was attained within 2 hr after the adsorption started. The adsorption reaction of malachite green followed the pseudo-second order rate model, and the adsorption rate constants(k2) decreased with increasing initial concentrations of malachite green. Adsorption behavior of malachite green on activated carbon was found to follow the Freundlich model well in the initial adsorbate concentration range. With increase in temperature, the adsorbed amount of malachite green at equilibrium increased, which indicate that the adsorption reaction was endothermic reaction. Thermodynamic parameters for malachite green adsorption reaction were estimated at varying temperatures, and in the pH range of 2-10, adsorption of malachite green increased.

• BMB Reports
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• v.32 no.4
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• pp.326-330
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• 1999

An aspartase purified from Hafnia alvei was inactivated by diethylpyrocarbonate (DEP) in a pseudo-first-order inactivation. The first-order plot was biphasic. The inactivation process was not saturable and the second order rate constant was $1.3\;M^{-1}s^{-1}$. The inactivated aspartase was reactivated with NH₂OH. The difference absorption spectrum of DEP-inactivated vs native enzyme preparations revealed a marked peak around 242 nm. The pH dependence of the inactivation rate suggests that an amino acid residue having a pK value of 7.2 was involved in the inactivation. L-aspartate, fumarate (substrates), and chloride ion (inhibitor) protected the enzyme against inactivation, indicating that histidine residues for the enzyme activity are located at the active site of this aspartase. Inspection of the presence and absence of $Cl^-$ ion demonstrated that the number of essential histidine residues is less than two. Thus, one or two histidines are in or near the aspartate binding site and participate in an essential step of the catalytic reaction.

• Journal of the Korean Chemical Society
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• v.36 no.2
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• pp.174-179
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• 1992

Reaction of aniline and iodine in$CHCl_3,\;CH_2Cl_2 : CHCl_3$(1 : 1), and $CH_2Cl_2$ has been studied kinetically by using conductivity method, Pseudo first-order rate constants ($k_{obs}$) and second-order rate constants ($k_{obs}$/[aniline]) are dependent on the aniline concentration. Second-order rate constants obtained were increased with increasing aniline concentration. We analysed these results on the basis of formation of charge transfer complex as reaction intermediate. From the construction of react ion scheme and derivation of rate equation, we calculated equilibrium constants and activation parameters for the formation and transformation of charge transfer complex. The equilibrium constants were decreased by an increase in the dielectric constant of the solvent and the value is 1.7-3.7$M^{-1}$. The rate of transformation are markedly affected by the solvent polarity. ${\Delta}H^{\neq}$ is about 14.2kJ/mol, and ${\Delta}S^{\neq}$ is large negative value of -243J/mol K.

• Environmental Engineering Research
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• v.23 no.3
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• pp.301-308
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• 2018

We investigated simultaneous removal of heavy metals such as Cr, Ni, and Zn by adsorption onto powdered activated carbon (PAC) and PAC modified with sodium diethyldithiocarbamate (PAC-SDDC). Modification of PAC was confirmed by Fourier transform infrared spectroscopy and Scanning electron microscopy and energy dispersive X-ray spectroscopy. Both PAC and PAC-SDDC reached adsorption equilibrium within 48 h, and the adsorption kinetics followed a pseudo-second order reaction kinetics. The removal of metals was enhanced with increasing both adsorbent dosage and followed the descending order of Cr > Ni > Zn for PAC and Cr > Zn > Ni for PAC-SDDC, respectively. Adsorption kinetics followed pseudo-second order kinetics. Adsorption kinetic results were well fitted by the Freundlich isotherm except for Cr adsorption onto PAC. The optimum pH for heavy metal adsorption onto PAC was 5, whereas that for PAC-SDDC ranged from 7 to 9, indicating that modification of PAC with SDDC significantly enhanced heavy metal adsorption, especially under neutral and alkaline pH conditions. Our results imply that SDDC modified PAC can be applied to effectively remove heavy metals especially Cr in plating wastewaters without adjusting pH from alkaline to neutral.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.10
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• pp.1114-1122
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• 2005

This research investigates the effects of sonication mode, reaction temperature and volume on sonolysis of 1,4-dioxane in order to increase the degradation efficiency and kinetics. The degradation efficiency in case with pulse mode was about 10 % higher than that in case with continuous mode. The degradation profiles in both cases, which were performed without the control of reaction temperature and in 1000 mL, were composed of three steps. However, 1,4-D was mainly degraded in the initiation step as the first portion and the acceleration step as the second portion. The initial step agreed with zero-order expression well, while the acceleration step could be fitted with pseudo 1st-order expression. The kinetic model in case with $5^{\circ}C$ and 300 mL conformed to pseudo 1st-order, while that in cases with $10^{\circ}C$ to $40^{\circ}C$ agreed with zero-order expression. The degradation efficiency and profile of 1,4-D in the experiment with $20^{\circ}C$ and 300 mL was higher and simpler than that in case with $20^{\circ}C$ and 1000 mL. The reaction temperature and volume influence bubble intensity, which was produced in sonication. The increase of bubble intensity induced to augment the production of OH radical in sonication.

• Journal of Environmental Science International
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• v.10 no.4
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• pp.269-273
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• 2001

Biosorption of Pb was evaluated for plants, Persicaria chinensis, Oenanthe javanica and Salvinia natnas. The adsorption equilibrium was reached in about 1hr for Pb and the highest adsorption capacity was 150mg Pb/g biomass at S.natans. Pb adsorption process showed a pseudo second order irreversible reaction. The highest initial adsorption rate was 2000mg pb/g biomass/hr at O.javanica. In spite of pH variation, Pb adsorption capacity by was selection, Pb was selectively adsorved. The selectivity of mixture solution showed the adsorption order of Pb>Cu>Cr>Cd. The Pb adsorption capacity of P. chinensis pretreated with NaOH was increased by 30% in comparison with that of no treatment.

• Environmental Engineering Research
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• v.13 no.2
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• pp.79-84
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• 2008

Adsorption of heavy metals by sawdust was investigated to evaluate the effectiveness of using sawdust to remove heavy metals from aqueous solutions. Kinetic and isotherm studies were carried out by considering the effects of initial concentration and pH. The adsorption isotherms of heavy metals fitted the Langmuir or Freundlich model reasonably well. The adsorption capacity of metal was in the order $Pb^{2+}$ > $Cu^{2+}$ > $Zn^{2+}$. A high concentration of co-existing ions such as $Ca^{2+}$ and $Mg^{2+}$ depressed the adsorption of heavy metal. Adsorption data showed that metal adsorption on sawdust follows a pseudo-second-order reaction. Kinetic studies also indicated that both surface adsorption and intraparticle diffusion were involved in metal adsorption on sawdust. Column studies prove that sawdust could be effective biosorbent for the removal of heavy metals from aqueous phase.

• Environmental Engineering Research
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• v.11 no.6
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• pp.318-324
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• 2006

The higher valence state of iron i.e., Fe(VI) was employed for the oxidation of one of an important toxic ion, cyanide in the aqueous medium. Cyanide was oxidized into cyanate, which is 1,000 times less toxic to cyanide and often accepted for its ultimate disposal. It was to be noted that Fe(VI) is a very powerful oxidizing agent and can oxidize most of the cyanide within few minutes i.e., ca 5 mins of contact. The data was obtained by the UV-Visible measurements for the Fe(VI) decomposition. The UV-Visible data was used to evaluate the overall rate constant for second order redox reaction between ferrate(VI) and cyanide. Also the pseudo first order rate constant was calculated as keeping the cyanide concentration in excess.