• Journal of the Korean Chemical Society
• /
• v.54 no.6
• /
• pp.671-679
• /
• 2010

The geometrical parameters and binding energies of the benzene ion-water complex [$C_6H_6^+-(H_2O)_n$(n=1-5)] have been investigated using ab initio (MP2) and density functional theory (DFT) with large basis sets. The harmonic vibrational frequencies and IR intensities are also determined to confirm that all the optimized geometries are true minima. Also zero-point vibrational energies have been considered to predict the binding energies. The predicted binding energy of 8.6 kcal/mol for $C_6H_6^+-(H_2O)$ at the MP2/aug-cc-pVTZ level of theory is in excellent agreement with recent experimental result of $8.5{\pm}1$ kcal/mol.

• Journal of the Korean Magnetic Resonance Society
• /
• v.26 no.1
• /
• pp.10-16
• /
• 2022

The phase transition temperatures of CsCoCl₃·2H₂O crystals are investigated via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Three endothermic peaks at temperatures of 370 K (=T_C1), 390 K (=T_C2), and 416 K (=T_C3) were observed for phase transitions from CsCoCl₃·2H₂O to CsCoCl₃·1.5H₂O, to CsCoCl₃·H₂O, and then to CsCoCl₃·0.5H₂O, respectively. In addition, the spin-lattice relaxation time T_1ρ in the rotating frame and T₁ in the laboratory frame as well as changes in chemical shifts for ¹H and ¹³³Cs near T_C1 were found to be temperature dependent. Our analyses results indicated that the changes of chemical shifts, T_1ρ, and T₁ are associated with structural phase transitions near temperature T_C1. The changes of chemical shifts, T_1ρ, and T₁ near T_C1 were associated with structural phase transitions, owing to the changes in the symmetry of the structure formed of H₂O and Cs⁺ ions. Consequently, the structural symmetry in CsCoCl₃·2H₂O crystals based on temperature is discussed by the environments of their H and Cs nuclei.

• Journal of the Korean Chemical Society
• /
• v.9 no.2
• /
• pp.71-74
• /
• 1965

Reduction of Ti(Ⅳ)-oxalate complex on dropping mercury electrode has been studied as a function of oxalate concentration and of pH varied with HCl. Assuming there are equilibrium $TiO(C_2O_4)_2= \;+\;2H^+\;=\;Ti^{+4}\;+\;2C_2O_4\;=\;+\;H_2O,\;K_4$ in addition to $TiO(C_2O_4)_2\;^=\;=\;TiO^{++}\;+\;2C_2O_4=\;K_2\;Ti(C_2O_4)_2\;^-\;=\;Ti^{+3}\;+\;2C_2O_4=\;K_3$ in the system cathodic wave has been well explained for that pH is higher than 0.5. The equilibrium constants $K_2,\;K_3$ and $K_4$ have been to be $2{\times}10^{-12},\;5{\times}10^{-13}$ and $10^{-11}$, respectively. The reduction of Ti(Ⅳ)-oxalate system is $Ti^{+4}\;+\;e\;{\to}\;Ti^{+3}$ in the concentration of hydrochloric acid, higher than 3M.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.5
• /
• pp.457-460
• /
• 1996

The principal elements of the 31P NMR chemical shielding tensors have been determined for three binuclear platinum diphosphite complexes, K4[Pt2(P2O5H2)4·2H2O ("Pt2"), K4[Pt2(P2O5H2)4Cl2]·2H2O ("Pt2Cl2"), and K4[Pt2(P2O5H2)4Br2]·2H2O ("Pt2Br2"), by using a Herzfeld-Berger graphical method for interpreting the 31P MAS spectrum. The orientations of 31P chemical shielding tensor relative to the molecular axis system are partially assigned with combination of the longitudinal relaxation study of HPO32- and the reference to known tensor orientations of related sites; the most chemical shielding component, δ33, is directed along the P-Pt bond axis. A discussion is given in which the experimental principal elements of the 31P chemical shielding tensor are related with the Pt-Pt bond distances in binuclear platinum diphosphite complexes.

• Journal of the Korean GEO-environmental Society
• /
• v.7 no.3
• /
• pp.21-29
• /
• 2006

The treatment performance of ozonation and three types of advanced oxidation processes (AOPs) such as $O_3/H_2O_2$, $O_3/UV$, $O_3/H_2O_2/UV$ was experimentally investigated for the treatment of refractory synthetic dye wastewater. The removal efficiency of $COD_{cr}$, color and biodegradability ($BOD_5/COD_{cr}$) were relatively evaluated in each treatment unit with simulated dye wastewater. Optimal operational conditions of pH, temperature, dosage and circulation flow rate were also investigated. All suggested processes revealed an effectiveness for the removal of color within a short operational time, moreover, $O_3/H_2O_2/UV$ process showed the highest $COD_{cr}$ removal and biodegradability enhancement among proposed oxidation process.

• Journal of the Korean Society of Combustion
• /
• v.20 no.1
• /
• pp.6-14
• /
• 2015

Numerical study was conducted to clarify effects of added $H_2O$ for the downstream interaction between $H_2$-air and CO-air premixed flames in counterflow configuration. The reaction mechanism adopted was Davis model which had been known to be well in agreement with reliable experimental data. The results showed that both lean and rich flammable limits were reduced in increase of strain rate. The most discernible difference between the two with and without having $H_2O$ and/or $H_2$ addition into $H_2$-air and CO-air premixtures was two flammable islands for the former and one island for the latter at high strain flame conditions. Even a small amount of $H_2$, in which $H_2$-air premixed flame cannot be sustained by itself, participates in CO oxidation, thereby altering the CO-oxidation reaction path from the main reaction route $CO+O_2{\rightarrow}CO_2+O$ with a very long chemical time in CO-air flame to the OH-related reaction routes including $CO+OH{\rightarrow}CO_2+H$ with very short chemical times. This intrinsic nature alters flame stability maps appreciably. The results also showed that chemical effects of added $H_2O$ help lean flames at relatively low strain rate be sustained, and suppress the flame stabilization at high strain rates.

• Journal of the Korean Chemical Society
• /
• v.38 no.5
• /
• pp.391-396
• /
• 1994

The hydrolysis of $\alpha-benzoxystyrene(1)$ in strong acidic solution has been investigated kinetically. In perchloric acid concentration lower than 5.5 M($H_o$ < -3.0), hydration paramer $\omega$ = + 7.6, and $\Phi$ = + 0.54 were obtained. The solvent isotope effect $k_{H_2O}/K_{D_2O}$ is 0.72. The substituent effect was found to conform to the Hammett $\sigma^+$ constant with $\rho$ = -0.60. On the basis of these results and other evidence, the hydrolysis of the enol ester proceeds by $A_{AL}$2 type mechanism. In concentration greater than 5.5 M($H_o$ > -3.0), isotope effect, $k_{H_2O}/_{D_2O}$ is 3.32, substituent effect, $\rho$ is -1.60 and the rate is linear with the acidity function, $H_o$. Thus, the mechanism changes one involving initial, and rate-determining olefin protonation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.11a
• /
• pp.369-372
• /
• 1996

We prepared LiMn$_2$O$_4$ by reacting stoichiometric mixture of LiOH.$H_2O$ and MnO$_2$ (mole ratio 1 : 1) and heating at 80$0^{\circ}C$ for 24h, 36h, 48h, 60h and 70h. We obtained through X-ray diffraction that lattice parameter varied as function of heat treatment time. heated cathode active materials at 80$0^{\circ}C$ for 36h, (111)/(311) peak ratio was 0.37. It expected good charge/discharge characteristics. When (111)/(311) peak ratio was 0.37, it will be that crystal structure is farmed very well. In the result of charge/discharge test When heated at 80$0^{\circ}C$ for 36h, charge/discharge characteristic of LiMn$_2$O$_4$is the most property. It agree with our expectation.

• Journal of Environmental Science International
• /
• v.22 no.12
• /
• pp.1561-1569
• /
• 2013

This study carried out a laboratory scale plasma reactor about the characteristics of chemically oxidative species (${\cdot}OH$, $H_2O_2$ and $O_3$) produced in dielectric barrier discharge plasma. It was studied the influence of various parameters such as gas type, $1^{st}$ voltage, oxygen flow rate, electric conductivity and pH of solution for the generation of the oxidant. $H_2O_2$ and $O_3$.) $H_2O_2$ and $O_3$ was measured by direct assay using absorption spectrophotometry. OH radical was measured indirectly by measuring the degradation of the RNO (N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical). The experimental results showed that the effect of influent gases on RNO degradation was ranked in the following order: oxygen > air >> argon. The optimum $1^{st}$ voltage for RNO degradation were 90 V. As the increased of $1^{st}$ voltage, generated $H_2O_2$ and $O_3$ concentration were increased. The intensity of the UV light emitted from oxygen-plasma discharge was lower than that of the sun light. The generated hydrogen peroxide concentration and ozone concentration was not high. Therefore it is suggested that the main mechanism of oxidation of the oxygen-plasma process is OH radical. The conductivity of the solution did not affected the generation of oxidative species. The higher pH, the lower $H_2O_2$ and $O_3$ generation were observed. However, RNO degradation was not varied with the change of the solution pH.

• Environmental Engineering Research
• /
• v.11 no.2
• /
• pp.84-90
• /
• 2006

UV-catalytic oxidation technique was applied for the treatment of bio-refractory character of the leachate, which is generally present in the form of adsorbable organic halogens (AOX). Destruction of AOX was likely to be governed by pH adjustment, quantitative measurement of oxidants, and the selection of oxidation model type. Peroxide induced degradation ($UV/H_2O_2$) facilitated the chemical oxidation of organic halides in acidic medium, however, the system showed least AOX removal efficiency than the other two systems. Increased dosage of hydrogen peroxide (from 0.5 time to 1.0 time concentration) even did not contribute to a significant increase in the removal rate of AOX. In ozone induced degradation system ($UV/O_3$), alkaline medium (pH 10) favored the removal of AOX and the removal rate was found 11% higher than the rate at pH 3. Since efficiency of the $UV/O_3$ increases with the increase of pH, therefore, more OH-radicals were available for the destruction of organic halides. UV-light with the combination of both ozone and hydrogen peroxide ($UV/H_2O_2$ 0.5 time/$O_3$ 25 mg/min) showed the highest removal rate of AOX and the removal efficiency was found 26% higher than the removal efficiency of $UV/O_3$. The system $UV/H2O_2/O_3$ got the economic preference over the other two systems since lower dose of hydrogen peroxide and relatively shorter reaction time were found enough to get the highest AOX removal rate.