• Bulletin of the Korean Chemical Society
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• v.23 no.12
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• pp.1811-1815
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• 2002

We have calculated energies and structures for the hydrogen bonded clusters between trimethyl phosphate and nitric acids. The hydrogen bond lengths between phosphoryl oxygen and the proton of nitric acid are short compared to normal hydrogen bonds, and the H-bond strengths are fairly strong. The hydrogen bond length becomes longer, and the strength becomes weaker, as more nitric acids are bound to the TMP. The average H-bond strengths for the $TMP-(HNO_3)_n$ complexes with n = 1, 2, and 3, are 9.6, 7.9 and 6.4kcal/mol at 300K respectively. Weak hydrogen bonds between nitrate oxygen and methyl proton might contribute to the stability of the clusters. Not only the BSSE but also the fragment relaxation energies should be considered to calculate hydrogen bond strengths for the complexes accurately.

• Journal of Soil and Groundwater Environment
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• v.24 no.6
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• pp.1-8
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• 2019

This study evaluated the relative extraction ratio (RER) of As and heavy metals (Cd, Cu and Pb) in paddy soils using the two types extractant, 0.05 M EDTA and 0.43 M HNO₃. The RER was calculated by dividing the concentrations of metals obtained by 0.05 M EDTA or 0.43 M HNO₃ extraction by those obtained by aqua regia extraction. The RER of 0.43 M HNO₃ was larger than that of 0.05 M EDTA. Correlation analysis indicated there was statistically significant correlation (p<0.001) between the concentration in aqua regia and 0.05 M EDTA or 0.43 M HNO₃. Especially, Cd showed the higher correlation than other metals. Stepwise multiple linear regression analyses indicated soil pH, CEC, organic matter content, and soil texture all influenced the metal extraction rates and bioavailability of the metals.

• Journal of the Korean Chemical Society
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• v.59 no.3
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• pp.238-245
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• 2015

The crystallization and morphology change of amorphous titanias by hydrothermal treatment have been investigated. The amorphous titanias were prepared by pure water hydrolysis of two different precursors, titanium tetraisopropoxide (TTIP) and TTIP modified with acetic acid (HOAc) and characterized prior to hydrothermal treatment. In order to avoid complicate situation, the hydrothermal treatment was performed in a single solvent water with and without strong acids at various temperatures. The effects of strong acid, temperature and time were systematically investigated on the transformation of amorphous titania to crystalline TiO₂ under simple hydrothermal condition. Without strong acid the titanias were transformed into only anatase phase nanoparticle regardless of precursor type, temperature and time herein used (up to 250 ℃ and 48 hours). The treatment temperature and time effected only on the crystalline size, not on the crystal phase et al. However, it was clearly revealed that the strong acids such as HNO₃ and HCl catalyzed the formation of rutile phase depending on temperature. HCl was slightly better than HNO₃ in this catalytic activity. The morphology of rutile TiO₂ formed was also a little affected by the type of acid. The precursor modifier, HOAc slightly reduced the catalytic activity of the strong acids in rutile phase formation.

• Korean Journal of Materials Research
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• v.30 no.8
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• pp.393-398
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• 2020

We propose a novel stripping solution containing acids (HCl and HNO₃), an oxidant [(NH₄)₂S₂O₈], and complexing agents (NaCl and citric acid) to remove surface passivation layers from 14K gold alloys fabricated using an investment casting process. The optimized solution employing only HCl acid is determined by varying molar fractions of HCl and HNO₃ on 14K yellow gold samples. Stripping properties are also identified for red and white gold alloy samples under the optimized stripping conditions. The removal of passivation layers, weight loss, and microstructure evolution are characterized using Raman spectroscopy, a precision scale, and optical microscopy. The proposed stripping solution effectively removes passivation layers more rapidly than conventional cyanide stripping. Weight loss increases linearly for up to 5 min for all 14K gold alloys. Red gold exhibits the greatest weight loss, followed by yellow gold and white gold. The results of microstructural analysis reveal that the conformal stripping occurs according to time. These results imply that the proposed oxidative chloride stripping might replace conventional cyanide stripping.

• Journal of Industrial Technology
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• v.19
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• pp.331-341
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• 1999

We analyzed theoretically the removal efficiency and the particle growth inside the pulse corona discharge reactor to remove $NO_x$ and investigated the effects of process variables such as the NO and $NH_3$ input concentrations. Most of NO is converted into $NO_2$ and $HNO_3$ and the $HNO_3$ reacts with $NH_3$ to form the $NH_4NO_3$ particles. About 6.4% of NO is converted into $HNO_2$ which form the $NH_4NO_2$ particles by reaction with $NH_3$. Some of $NO_2$ follows the reaction pathway to form $NO_3$ and $N_2O_5$. The amount of particles formed inside the reactor is basically determined by the input $NH_3$ concentration. The ratio of NO to $NH_3$ affects the reactor length for particle formation significantly. The higher the input concentrations of NO and $NH_3$ are, the faster the particles grow.

• Carbon letters
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• v.8 no.2
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• pp.108-114
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• 2007

In this work, activated carbon (AC) after $HNO_3$ modification was used as the support during the production of supported $TiO_2$ to increase the high deposition efficiency and the photocatalytic activity. The results of $N_2$ adsorption showed that the BET surface area of samples decreased with an increasing of the concentration of $HNO_3$ due to the penetration of $TiO_2$. From XRD data, a single crystal structure of anatase peak was observed in diffraction patterns for the AC coated with titanium complexes. From the SEM results, almost all particles were aggregated with each other at the carbon surface and AC was covered with $TiO_2$ particles in all of the samples. The EDX spectra show the presence of C, O, Ti and other elements. It was also observed a decreasing of amount of C content with increasing Ti and O content from the EDX. The results of FT-IR revealed that the modified AC contained more surface oxygen bearing groups than that of the original AC. The effect of surface acidity and basity calculated from Boehm titration method was also evaluated from correlations as a function of NaOH, $NaHCO_3$, and $Na_2CO_3$ uptake. The surface modification of AC by $HNO_3$ leads to an increase in the catalytic efficiency of AC/$TiO_2$ catalysts, and the catalytic efficiency increases with increasing of $HNO_3$ concentration.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.4
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• pp.297-303
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• 2002

Fine particles (d$_{p}$ < 2.5 $\mu$m) were measured using an annular denuder system (ADS) in Chongju. The data set was collected on fifty-eight different days with a 24-hr sampling period from October 27, 1995 through August 25, 1996. Particulate nitrate in the ADS was also measured on teflon and nylon filters in series behind denuders to collect HNO$_3$, HNO$_2$, SO$_2$and NH$_3$. From this study. the mean concentration of particulate nitrate of PM$_{2.5}$ in the ADS were seen with the following order: winter (5.05) ＞fall (4.36) ＞spring (3.92) > summer (1.10 $\mu\textrm{g}$/㎥). Nitrate losses, which calculated from the ratio of nylon filter nitrate to the sum of teflon and nylon filter nitrates, varied in the following manner summer (72.2%) > spring (42.6%) > fall (23.5%)> winter (0.4%). Especially, gaseous nitric acid was dominant at temperature higher than 8$^{\circ}C$ while particulate nitrate was major species in total nitrate below that temperature. This indicates the particulate nitrate loss is strongly correlated rather with ambient temperature.e.e.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2819-2822
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• 2009

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.683-689
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• 2003

The cylindrical ${\gamma}$-alumina pellets were prepared using amorphous alumina and pore generating agent. Its were immersed in aqueous solution of the mixture of Fe(NO$_3$)$_3$.9$H_2O$ and $CH_3$COOH, Fe(NO$_3$)$_3$.9$H_2O$ and $CH_3$COOH and HNO$_3$, and Fe(NO$_3$)$_3$.9$H_2O$ and HNO$_3$. The pellets thus were hydrothermally treated at 20$0^{\circ}C$ for 3 h in autoclave, and were investigated morphologies and changes of crystal pore characteristics, $N_2$ adsorption and desorption isotherms, active sites and mechanical strength etc. According to the preparation method, acicular platelet pseudo-boehmite crystals of 0.1~0.3 ${\mu}{\textrm}{m}$ size were transformed into acicular pseudo-boehmite cristals of 0.5~2 ${\mu}{\textrm}{m}$ size having the same crystal structure. When ${\gamma}$-alumina pellets were immersed in aqueous solution of the mixture of Fe(NO$_3$)$_3$.9$H_2O$ and $CH_3$COOH and then were hydrothermally treated, pore volume between 100 $\AA$ and 1000 $\AA$ was increased from 0.34 ㏄/g to 0.86 ㏄/g, and the gap of $N_2$ adsorption and desorption hysteresis loop was decreased due to increasement of pore size. New active site that could adsorb the C-H functional group was created on the catalist. Also, mechanical strength of catalyst was increased from 1.06 ㎫ to 1.36 ㎫.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2677-2682
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• 2011

Direct nitrolysis of 3,7-dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane (DPT) is a feasible way to synthesize HMX, and it has multiple practical applications. In this paper, a new nitrolysis process involving the use of an $N_2O_5-HNO_3$ system catalyzed by acidic ionic liquids (AILs) was developed. The results show that [$Et_3NH$]TsO was the best catalyst among the 28 AILs used and that HMX was formed at a higher yield of 61%, compared to 45% without any AIL. Moreover, with the addition of $N_2O_5$, the yield was further increased to a maximum value of 69%. The AILs were also efficiently recovered by simple extractions without any apparent loss of catalytic activity, even after five runs.