• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.6000-6007
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• 2013

Cr(VI)-heterocyclic complex[Cr(VI)-isoquinoline] was synthesized by the reaction between of heterocyclic compound(isoquinoline) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using Cr(VI)-isoquinoline in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order : cyclohexene$CH_3$, m-Br, m-$NO_2$). Electron- donating substituents accelerated the reaction, whereas electron acceptor groups retarded the reaction. The Hammett reaction constant(${\rho}$) was -0.69(308K). The observed experimental data have been ratiolized. The hydride ion transfer causes the prior formation of a chromate ester in the rate-determining step.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.450-455
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• 2012

The paper includes the utlization of an activated carbon as a potential adsorbent to remove a hazardous fluorescein dye from an aqueous solution. Batch adsorption experiments were carried out for the removal of fluorescein dyes using a granular activated carbon as an adsorbent. The effects of various parameters such as pH, amount of adsorbent, contact time, initial concentration and temperature of the adsoprtion system were investigated. The experimental results revealed that activated carbon exhibit high efficiencies to remove fluorescein dyes from the aqueous solution. The equilibrium process can be well described by Freundlich isotherm in the temperature range from 298 K to 318 K. From adsorption kinetic experiments, the adsorption process followed a pseudo second order kinetic model, and the adsorption rate constant ($k_2$) decreased with increasing the initial concentration of fluorescein. The free energy of adsorption ${\Delta}G^0$), enthalpy ${\Delta}H^0$), and entropy (${\Delta}S^0$) change were calculated to predict the nature adsorption. The estimated values for ${\Delta}G^0$ were -17.11~-20.50 kJ/mol over an activated carbon at 250 mg/L, indicated toward a spontaneous process. The positve value for ${\Delta}H^0$, 33.2 kJ/mol, indicates that the adsorption of fluorescein dyes on an activated carbon is an endothermic process.

• Clean Technology
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• v.17 no.4
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• pp.346-352
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• 2011

The adsorption characteristics of propineb pesticide onto activated carbon has been investigated for the adsorption in aqueous solution with respect to initial concentration, contact time and temperature in batch experiment. The Langmuir and Freundlich adsorption models were applied to described the equilibrium isotherms and isotherm constants were also determined. The Freundlich model agrees with experimental data well. slope of isotherm line indicate that activated carbon could be employed as effective treatment for removal of propineb. The pseudo first order, pseudo second order kinetic models were use to describe the kinetic data and rate constants were evaluated. The adsorption process followed a pseudo second order model, and the adsorption rate constant($k_2$) decreased with increasing initial concentration of propineb. The activation energy, change of free energy, enthalpy, and entropy were also calculated to predict the nature adsorption. The estimated values for change of free energy were -7.28, -8.27 and -11.66 kJ/mol over activated carbon at 298, 308 and 318 K, respectively. The results indicated toward a spontaneous process. The positive value for change of enthalpy, 54.46 kJ/mol, found that the adsorption of propineb on activated carbon is an endothermic process.

• Journal of the Korean Chemical Society
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• v.17 no.2
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• pp.73-79
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• 1973

The ultrasonic absorption of Dodecyl pyridinium bromide (D.P.B.) in aqueous solution has been measured at $20^{\circ}C$ over a range of frequencies between 0.1 mc and 90 mc and a range of concentrations from 5 to 100 mM. The excess absorption was observed only in the solutions the concentration of which was higher than the critical micellar concentration (c.m.c.) both in the presence and absence of salt. The excess absorption of sound and the relaxation frequencies obtained from the absorption curves show a discontinuity with the variation of the concentration of D.P.B. in the neighborhood of 60 mM. Other properties such as viscosity, conductivity and velocity of sound also exhibit such a change near the same concentration. It is concluded that a change in the properties of the micelles of D.P.B. occurs in the neighborhood of this concentration. The mechanism of the observed ultrasonic excess absorption in attributed to the reaction $M_2{\rightleftarrow}M_1+2Br^-$where$M_2$ and$M_1$are two types of micelles. The rate constants of forward and backward reactions are found to be $6.9 {\times} 10^5 sec^{-1)$and $6.7{\times}10^{10}sec^{-1}mole{-2}$ respectively. Some kinetic characteristics including free energy, enthalpy, entropy and activation energy were calculated.

• Journal of the Korean Chemical Society
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• v.25 no.6
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• pp.376-382
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• 1981

The rates and the activation parameters for the reaction of phenacyl bromide with substituted anilines in methanol and dimethylformamide were measured. The effects of substituted anilines were discussed. The rate of the reaction was increased with the electron donating power of substituent and showed larger value in DMF than in MeOH. The isokinetic relationship was shown between ${\delta}H^{\neq}$ and ${\delta}S^{\neq}$, isokinetic temperature was 539 and $400^{\circ}C$ in MeOH and DMF respectively, but p-nitro aniline was deviated from linearity in both solvents caused by solvent effects. The excellent linear relationship between log k and p$K_a$ of substituted anilines was observed by following equation. log k = 0.57p$K_a$-1.28 (r = 0.996) in MeOH at $45^{\circ}C$, log k = 0.65p$K_a$-0.88 (r = 0.970) in DMF at $45^{\circ}C$. From the Hammett plot, this reaction was a nucleophilic displacement of aniline to phenacyl bromide and the following equation was obtained at $45^{\circ}C$. log k/$k_0$ = -2.00${\sigma}$ + 0.06 (r = 0.985) in MeOH; log k/$k_0$ = -2.22${\sigma}$ + 0.08 (r = 0.995) in DMF. Large deviation of p-nitro aniline in DMF is resulted from solvent effects too. From above results, the substituent effect of this reaction can be described as $S_N2$ mechanism and bond formation more proceeds in DMF relative to MeOH.

• Journal of the Korean Chemical Society
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• v.35 no.4
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• pp.343-349
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• 1991

Formation of charge transfer complex between iodine and substituted aniline [aniline, N,N-dimethylaniline(N,N-DMA), 2,6-dimethylaniline(2,6-DMA), 2,4,6-trimethylaniline(2,4,6-TMA)] in CHCl$_3$, CH$_2$Cl$_2$ : CHCl$_3$ (1 : 1), and CH$_2$Cl$_2$ have been studied kinetically by using conductivity method. In the transformation of initially formed outer charge transfer complex to inner complex, the effects of substituted aniline as electron donor and polar medium on the reaction were investigated. The rate of transformation depend on the dielectric contribution of medium and pK$_a$ value of substituted aniline. The order of rate increasing is 2,4,6-TMA, 2,6-DMA, aniline, and N,N-DMA. The activation enthalpy ${\Delta}H^{\neq}$ for 2.5 M-substituted aniline in CHCl$_3$ at 25$^{\circ}C$ is respectively N,N-DMA, 3.47 kcal/mol; aniline, 4.25 kcal/mol; 2,6-DMA, 7.79 kcal/mol and 2,4,6-TMA, 7.96 kcal/mol; and activation entropy ${\Delta}S^{\neq}$ is large and negative value of -41 ~ -55 cal/mol${\cdot}$K.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.358-364
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• 2012

The kinetics of the Fischer-Tropsch synthesis and water gas shift reactions over a precipitated iron catalyst were studied in a 5 channel fixed-bed reactor. Experimental conditions were changed as follows: synthesis gas $H_2$/CO feed ratios of 0.5~2, reactants flow rate of 60~80 ml/min, and reaction temperature of $255{\sim}275^{\circ}C$ at a constant pressure of 1.5 MPa. The reaction rate of Fischer-Tropsch synthesis was calculated from Eley-Rideal mechanism in which the rate-determining step was the formation of the monomer species (methylene) by hydrogenation of associatively adsorbed CO. Whereas water gas shift reaction rate was determined by the formation of a formate intermediate species as the rate-determining step. As a result, the reaction rates of Fischer-Tropsch synthesis for the hydrocarbon formation and water gas shift for the $CO_2$ production were in good agreement with the experimental values, respectively. Therefore, the reaction rates ($r_{FT}$, $r_{WGS}$, $-r_{CO}$) derived from the reaction mechanisms showed good agreement both with experimental values and with some kinetic models from literature.

• Elastomers and Composites
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• v.34 no.2
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• pp.135-146
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• 1999

The thermal degradation kinetics of SBR and tire were studied using a conventional thermogravimetric analysis in the stream nitrogen at a heating rate of 5, 10, 15, $20^{\circ}C/min$, respectively. Thermogravimetric curves and their derivatives were analyzed using various analytical methods to determine the kinetic parameters. The degradation of the SBR and tire was found to be a complex process which has multi-stages. The Friedman method gave average activation energies for the SBR and tire of 247.53kJ/mol and 230.00kJ/mol, respectively. Mean-while, the Ozawa method Eave 254.80kJ/mol and 215.76kJ/mol. It would appear that either. Friedman's differential method or Ozawa's integral method provided satisfactory mathematical approaches to determine the kinetic parameters for the degradation of the SBR and tire. Approximately 86% and 55% of oil products were obtained at a final temperature of $700^{\circ}C$ and a heating rate of $20^{\circ}C/min$ for the SBR and tire respectively.

• Clean Technology
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• v.22 no.4
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• pp.258-268
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• 2016

In this work, carboxymethylcellulose-based composite superabsorbent hydrogels were prepared by electron beam radiation. The composition of carboxymethylcellulose (CMC) varied from 4 wt%, 5 wt%, and 6 wt% to 7 wt% based on the amount of distilled water in the syntheses of hydrogels. Graphite oxide, reduced graphene oxide, activated carbon, and bentonite were used as additives for the synthesis of composite superabsorbent. The effect of CMC composition and the type of additives on the gel properties of the prepared hydrogels was investigated. In order to verify the functional groups in the prepared materials, Fourier transform infrared spectroscopy was used. In addition, mechanical strength, gel fraction, swelling kinetics, and equilibrium swelling ratios were measured for the prepared hydrogels. Swelling experiments were carried out in distilled water, urea solution, and physiological saline water. Prepared hydrogels were reused for 5 times, and gel fraction and swelling ratio were measured at every 24 hours. Among the prepared hydrogels, $C_{5%}GO$ and $C_{5%}rGO$ exhibited excellent mechanical property and relatively high swelling ratios for urea solution and physiological saline water with promising applicability as slow-release fertilizers.

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.342-350
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• 1988

An experimental investigation is made to determine the mechanism of the aquation of $[Co(en)_2Cl_2]^+$ in $Hg^{2+}$ aqueous solution. The progress of reaction is followed UV/vis-spectrophotometrically by a measurment of the absorbance at a specific wavelength of Co(III) complex as a function of time. The aquation of cis-$[Co(en)_2Cl_2]^+$ and trans-$[Co(en)_2Cl_2]^+$ has been found to be first order and second order with respect to the concentration of $Hg^{2+}$ catalyst, respectively. It has been found that the reaction rate for aquation of the trans-form is faster than that of cis-form, and that the product of either cis-form or trans-form is always in the mixture ratio of 97 % to 3 %. Plausible reaction mechanism is proposed for the reaction system on the basis of kinetic data and activation parameters. Theoretical rate equation derived from the proposed mechanism is consistent with the observed one.