• Korean Chemical Engineering Research
• /
• v.43 no.1
• /
• pp.9-15
• /
• 2005

In order to know the electrochemical decomposition characteristics of ammonia to nitrogen, this work has studied several experimental variables on the electrolytic ammonia decomposition. The effects of pH and chloride ion at $IrO_2$, $RuO_2$, and Pt anodes on the electrolytic decomposition of ammonia were compared, and the existence of membrane equipped in the cell and the changes of the current density, the initial ammonia concentration and so on were investigated on the decomposition. The performances of the electrode were totally in order of $RuO_2{\approx}IrO_2>Pt$ in the both of acid and alkali conditions, and the ammonia decomposition was the highest at a current density of $80mA/cm^2$, over which it decreased, because the adsorption of ammonia on the electrode surface was hindered due to the evolution of oxygen. The ammonia decomposition increased with the concentration of chloride ion in the solution. However, the increase became much dull over 10 g/l of chloride ion. The $RuO_2$ electrode among the tested electrodes generated the most OH radicals which could oxidized the ammonium ion at pH 7.

• Journal of Korean Society for Atmospheric Environment
• /
• v.22 no.4
• /
• pp.431-439
• /
• 2006

Catalytic oxidation of benzene, toluene and xylene (BTX) using regenerated metal oxide catalysts (ZnO-CuO, NiO, $Fe_2O_3$, ZnO, CrO) were investigated in a fixed bed flow reactor to evaluate their feasibility for the purpose of removing volatile organic compounds (VOCs). Four kinds of pre-treatment methods such as gas (air and hydrogen), acid aqueous solution, alkali aqueous solution and cleaning agent were used to find out the optimal regeneration conditions. The physico-chemical properties of the used and regenerated catalysts were characterized by BET and TPR (Temperature Programmed Reduction). The used catalysts showed high conversion ratio and the catalytic ability of toluene oxidation was in the order of ZnO-CuO>$Fe_2O_3$>NiO>ZnO>CrO. We found that the acid aqueous pre-treatment (0.1 N HNO$_3$) was the best way to enhance the catalytic activity of $Fe_2O_3$. In addition, air and hydrogen gas treatment were optimal for NiO and ZnO-CuO catalysts, respectively. Furthermore, the decomposition of BTX depends on the type of a catalyst and a gas molecule.

• Journal of the Korean Chemical Society
• /
• v.13 no.2
• /
• pp.137-140
• /
• 1969

This investigation was made to evaluate the corrosion inhibiting effects of urotropine for mild steel in HCl. 1) Formaldehyde produced by the decomposition of urotropine also showed positive inhibiting effects. 2) In the presence of the ions, such as $Cu^+$, $Cu^{++}$, $Fe^{+++}$, $SO_3^=$, $SO_4^=$, $NO_2^-$, $NO_3^-$, $Cr_2O_7^=$, the inhibiting capacity of the urotropine was decreased. Alkali and alkaline-earth metal ions had no effects but the halogen ions improved it. 3) From measurements of polarization curves, it was assumed that the anode reaction was more retarded by the urotropine and the halogen.

• Journal of the Korean Institute of Gas
• /
• v.15 no.3
• /
• pp.74-78
• /
• 2011

$BF_3$ gas has been used for semiconductor manufacturing process and applied in plasma etching, chemical vapor deposition, chamber cleaning processes etc,. $BF_3$ provides Boron and acts as a p-type doping in electrode in semiconductor. In this study, we investigate thermaldecomposition of alkali-boron complexes and suggest a simple way to produce $BF_3$ from $NaBF_4$ and $KBF_4$.

• Journal of the Korean Chemical Society
• /
• v.5 no.1
• /
• pp.56-59
• /
• 1961

Ion exchange procedure was studied for the separation of thorium from the acidic solution obtained by means of decomposition of monazite with alkali solution. Present cation exchange method consists of adsorption of cations from the sample solution (ca. 0.6N HCl acidic) onto Amberlite IR-120 resin, elution of all of the rare earth cations with 700 ml. of 2N Hydrochloric acid, and recovery of the thorium by elution with 200ml. of 6N sulfaric acid. Thorium recovery by the ion-exchange method mentioned above, was quantitative, and it is concluded that this ion-exchange method may be used not only for industrial separation of thorium from rare earths but also for quantitative determination of thorium with relative error, ${\pm}1.0.$.

• Proceedings of the Membrane Society of Korea Conference
• /
• 2004.05a
• /
• pp.39-42
• /
• 2004

Ceramic membranes have attracted a great attention because they have excellent resistance to most organic solvents and can be used over a wide temperature range. Especially, titania (titanium oxide, TiO$_2$) shows excellent chemical resistance and can be used both acidic and alkali solutions, and therefore, titania is one of the most promising materials for the preparation of porous membranes; titania membranes having pore sizes in the range of nanofiltration (NF) to ultrafiltration (UF) membrane have been prepared by the sol-gel process (Tsuru 2001).(omitted)

• Textile Coloration and Finishing
• /
• v.8 no.3
• /
• pp.16-23
• /
• 1996

In order to know the change of weight loss, crystallinity, crystallite size(010) plane, and thermal properties of PET films which had before drawn and annealed at various temperature. It were treated in sodium triethylene glycolate-triethylene glycol(STEG-TEG) were prepared. The following results were abtain. The weight loss of PET films were increasing with increaing treated time in STEG-TEG solution and It showed a linear rlationship to the treated time. The crystallinity and crystallite size(010) plane of PET films decreased with increasing decomposition ratio when PET films were treated with before annealed under 16$0^{\circ}C$. The crystalline region on the surface of samples were decompose to thermal unstable crystalline structure

• Journal of the Korean Wood Science and Technology
• /
• v.37 no.3
• /
• pp.255-264
• /
• 2009

To evaluate the effects of chemical pretreatments of lignocellulosic biomass on enzymatic hydrolysis process, Populus euramericana was pretreated for 1 hr with 1% sulfuric acid ($H_2SO_4$) at $150^{\circ}C$ and 1% sodium hydroxide (NaOH) at $160^{\circ}C$, respectively. Before the enzymatic hydrolysis, each pretreated sample was subjected to drying process and thus finally divided into four subgroups; dried or non-dried acid pretreated samples and dried or non-dried alkali pretreated samples and chemical and physical properties of them were analyzed. Biomass degradation by acid pretreatment was determined to 6% higher compared to alkali pretreatment. By the action of acid ca. 24.5% of biomass was dissolved into solution, while alkali degraded ca. 18.6% of biomass. However, reverse results were observed in delignification rates, in which alkali pretreatment released 2% more lignin fragment from biomass to the solution than acid pretreatment. Unexpectedly, samples after both pretreatments were determined to somewhat higher crystallinity than untreated samples. This result may be explained by selective disrupture of amorphous region in cellulose during pretreatments, thus the cellulose crystallinity seems to be accumulated in the pretreated samples. SEM images revealed that pretreated samples showed relative rough and partly cracked surfaces due to the decomposition of components, but the image of acid pretreated samples which were dried was similar to that of the control. In pore size distribution, dried acid pretreated samples were similar to the control, while that in alkali pretreated samples was gradually increased as pore diameter increased. The pore volume which increased by acid pretreatment rapidly decreased by drying process. Alkali pretreatment was much more effective on enzymatic digestibility than acid pretreatment. The sample after alkali pretreatment was enzymatically hydrolyzed up to 45.8%, while only 26.9% of acid pretreated sample was digested at the same condition. The high digestibility of the sample was also influenced to the yields of monomeric sugars during enzymatic hydrolysis. In addition, drying process of pretreated samples affected detrimentally not only to digestibility but also to the yields of monomeric sugars.

• Journal of Korean Society on Water Environment
• /
• v.25 no.6
• /
• pp.979-983
• /
• 2009

The mean pH of wastewater discharged from the plating process is 2, so a less amount of alkali is required to raise pH 2 to 5. In addition, if sodium sulfite is used to raise pH 5 to 9 in the secondary treatment, caustic soda or slaked lime is not necessary or only a small amount is necessary because sodium sulfite is alkali. Thus, it is considered desirable to use only $FeSO_4{\cdot}7H_2O$ in the primary treatment. At that time, the free cyanide removal rate was highest as around 99.3%, and among heavy metals, Ni showed the highest removal rate as around 92%, but zinc and chrome showed a low removal rate. In addition, the optimal amount of $FeSO_4{\cdot}7H_2O$ was 0.3g/L, at which the cyanide removal rate was highest. Besides, the free cyanide removal rate was highest when pH value was 5. Of cyanide removed in the primary treatment, the largest part was removed through the precipitation of ferric ferrocyanide: $[Fe_4(Fe(CN)_6]_3$, and the rest was precipitated and removed through the production of $Cu_2[Fe(CN)_6]$, $Ni_2[Fe(CN)_6]$, CuCN, etc. Furthermore, it appeared more effective in removing residual cyanide in wastewater to mix $Na_2SO_3$ and $Na_2S_2O_5$ at an optimal ratio and put the mixture than to put them separately, and the optimal weight ratio of $Na_2SO_3$ to $Na_2S_2O_5$ was 1:2, at which the oxidative decomposition of residual cyanide was the most active. However, further research is required on the simultaneous removal of heavy metals such as chrome and zinc.

• Nuclear Engineering and Technology
• /
• v.53 no.4
• /
• pp.1210-1217
• /
• 2021

The analysis of ⁴¹Ca in concrete generated from the nuclear facilities decommissioning is critical for ensuring the safe management of radioactive waste. An analytical method for the determination of ⁴¹Ca in concrete is described. ⁴¹Ca is a neutron-activated long radionuclide, and hence, for accurate analysis, it is necessary to completely extract Ca from the concrete sample where it exists as the predominant element. The decomposition methods employed were the acid leaching, microwave digestion, and alkali fusion. A comparison of the results indicated that the alkali fusion is the most suitable way for the separation of Ca from the concrete sample. Several processes of hydroxide and carbonate precipitation were employed to separate ⁴¹Ca from interferences. The method relies on the differences in the solubility of the generated products. The behavior of Ca and the interfering elements such as Fe, Ni, Co, Eu, Ba, and Sr is examined at each separation step. The purified ⁴¹Ca was measured by a liquid scintillation counter, and the quench curve and counting efficiency were determined by using a certified reference material of known ⁴¹Ca activity. The recoveries in this study ranged from 56 to 68%, and the minimum detectable activity was 50 mBq g^-1 with 0.5 g of concrete sample.