• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.798-802
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• 1996

The photochemical decomposition of aqueous ammonia in the absence (saturated with argon) and the presence of O2 (saturated with air or oxygen) has been investigated using 184.9 nm UV light. The decomposition of ammonia depended on the concentration of oxygen in the solution. With increasing the concentration of oxygen, the decomposition of ammonia diminishes. Hydrazine is found the major product from the irradiation. In the presence of oxygen, hydrogenperoxide was also produced. The product yields depended also on the concentration of oxygen in the solution. The initial quantum yield of the products and of the ammonia decomposed were determined. Probable reaction mechanisms for the reaction were presented from the products analysis.

• Bulletin of the Korean Chemical Society
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• v.29 no.3
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• pp.555-561
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• 2008

In air stripping of ammonia from the aqueous solution, a new removal model was presented considering the equilibrium principles for the ammonia in aqueous solution and between the aqueous and air phase. The effects of pH, temperature and airflow rate on the ammonia removal were evaluated with the model. In addition, the saturation degree of ammonia in air was defined and used to evaluate the effect of each experimental factor on the removal rate. As pH (8.9 to 11.9) or temperature (20 to 50 oC) was increased, the overall removal rate constants in all cases were appeared to be increased. Our presented model shows that the degrees of saturation were about the same (0.45) in all cases when the airflow condition remains the same. This result indicates that the effect of pH and temperature were directly taken into consideration in the model equation. As the airflow increases, the overall removal rate constants were increased in all cases as expected. However, the saturation degree was exponentially decreased with increasing the airflow rate in the air phase (or above-surface) aeration. In the subsurface aeration the saturation degree remains a constant value of 0.65 even though the airflow rate was increased. These results indicate that the degree of saturation is affected mainly by the turbulence of the aqueous solution and remains the same above a certain airflow rate.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.179.1-179.1
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• 2011

Pretreatment of cellulosic biomass is necessary before enzymatic saccharification and fermentation. The objective of this study was to evaluate the effect of combined aqueous ammonia-dilute sulfuric acid treatment on cellulosic biomass. Miscanthus was pretreated using aqueous ammonia and dilute sulfuric acid solution under high temperature and pressure conditions to be converted into bioethanol. Aqueous ammonia treatment was performed with 15 %(w/w) ammonia solution at $150^{\circ}C$ of reaction temperature and 20 minutes of reaction time. And then, dilute sulfuric acid treatment was performed with 1.0 %(w/w) sulfuric acid solution at $150^{\circ}C$ of reaction temperature and 10 minutes of reaction time. The compositional variations of this combined aqueous ammonia-dilute sulfuric acid treatment resulted in 68.0 % of cellulose recovery and 95.7 % of hemicellulose, 81.3 % of lignin, 89.1 % of ash removal respectively. The enzymatic digestibility of 90.5 % was recorded in the combined pretreated Miscanthus sample and it was 14.7 times higher than the untreated sample. The ethanol yield in the Simultaneous Saccharification and Fermentation was 90.4 % of maximum theoretical yield based on cellulose content of the combined pretreated sample and it was about 98 % compared to the ${\alpha}$-cellulose ethanol yield.

• Journal of Photoscience
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• v.6 no.4
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• pp.177-181
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• 1999

The photochemical transformation of carbon monoxide in aqueous ammonia solution has been investigated at 25${\pm}$0.1$^{\circ}C$ using 184.9 nm UV light. Amination and carbonylation processes were carried out by irradiating the aqueous ammonia solution saturated with carbon monoxide, and the formation of formamide, urea, hexamethylenetetramine, formaldehyde, glyoxal and hydrazine was observed. The formation of hydrazine was affected by the presence of ammonia, and the formation of carbonyl compounds such as formaldehyde and glyoxal was influenced by the presence of carbon monoxide. The formation of formamide, urea and hexamethylenetetramine was affected by both ammonia and carbon monoxide. The initial quantum yields of the products were determined and probable mechanisms for the photochemical reaction were presented on the basis of product analysis.

• Korean Chemical Engineering Research
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• v.53 no.4
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• pp.417-424
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• 2015

In this study, the pretreatment of Helianthus tuberosus residue had been performed. The two-stage pretreatment on flow-through process were applied in the interests of increase of sugar production yield on enzymatic saccharification. The delignification by aqueous ammonia and the fractionation of hemicellulose by sulfuric acid solution as pretreatment solution were confirmed for effects of enzymatic saccharification. Two-stage pretreatment process was performed using aqueous ammonia and sulfuric acid. The first step was performed with aqueous ammonia for 40 min at $163.2^{\circ}C$ and the second step was performed with sulfuric acid solution for 20 min at $169.7^{\circ}C$. And then, the first step was performed with sulfuric acid solution and the second step was pretreated with aqueous ammonia. At this time, the glucose production was 30.7 g and the glucose yield was 72.4% in the first step process with aqueous ammonia. And, the glucose production was 20.9 g and the glucose yield was 49.3% in the first step process with sulfuric acid solution.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.5
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• pp.451-457
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• 2000

Experimental investigations on the effect of two kinds of additives ; aqueous NaOH solution and ammonia(NH$_3$) for removal of NOx and SO$_2$ simultaneously by corona discharge were carried out. The simulated combustion flue gas was[NO(0.02[%])-SO$_2$(0.08[%])-$CO_2$-Air-$N_2$] Volume percentage of aqueous NaOH solution used was 20[%] and $N_2$flow rate was 2.5[$\ell$/min] for bubbling aqueous NaOH solution Ammonia gas(14.81[%]) balanced by argon was diluted by air. NH$_3$ molecular ratios(MR) based on [NH$_3$] and [NO+SO$_2$] were 1, 1.5 and 2.5 The vapour of aqueous NaOH solution and NH$_3$was introduced to the main simulated combustion flue gas duct through injection systems which were located at downstream of corona discharge reactor. NOx(NO+NO$_2$) removal rate by injecting the vapour of aqueous NaOH solution was much better than that by injecting NH$_3$however SO$_2$removal rate by injecting NH$_3$was much better than that by injecting the vapour of aqueous NaOH SO$_2$removal rate slightly increased with increasing applied voltage. When the vapour of aqueous NaOH solution and NH$_3$were simultaneously injection NOx and SO$_2$ removal rate were significantly increased.

• New & Renewable Energy
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• v.6 no.4
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• pp.6-14
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• 2010

Pretreatment of cellulosic biomass is necessary before enzymatic saccharification and fermentation. Extrusion is a well established process in food industries and it can be used as a physicochemical treatment method for cellulosic biomass. Aqueous ammonia soaking treatment at mild temperatures ranging from 60 to $80^{\circ}C$ for longer reaction times has been used to preserve most of the cellulose and hemicellulose in the biomass. The objective of this study was to evaluate the effect of extrusion treatment on aqueous ammonia soaking method. Extrusion was performed with miscanthus sample conditioned to 2mm of particle size and 20% of moisture content at $200^{\circ}C$ of barrel temperature and 175rpm of screw speed. And then aqueous ammonia soaking was performed with 15%(w/w) ammonia solution at $60^{\circ}C$ for 1, 2, 4, 8, 12 hours on the extruded and raw miscanthus samples respectively. In the combined extrusion-soaking treatment, most compositions removal occurred within 1~2 hours and on a basis of 1 hour soaking treatment values, cellulose was recovered about 85% and other compositions, including hemicellulose, are removed about 50% from extruded miscanthus sample. The combined extrusion-soaking treated and soaking only treated samples were subjected to enzymatic hydrolysis using cellulase and ${\beta}$-glucosidase. The enzymatic digestibility value of combined extrusion-2 hours soaking treated sample was comparable to 12 hours soaking only treated sample. It means that extrusion treatment can shorten the conventional long reaction time of aqueous ammonia soaking. The findings suggest that the combination of extrusion and soaking is a promising pretreatment method to solve both problems for no lignin removal of extrusion and long reaction time of aqueous ammonia soaking.

• Korean Journal of Materials Research
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• v.10 no.6
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• pp.445-449
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• 2000

Nickel ferrite $(Ni_{0.75}Fe_{2.25}O_4$ was synthesized by co-precipitation method in order to investigate its behavior under conditions of the reactor coolant system in pressurized light water nuclear power plants. Ammonia or potassium carbonate was used as a solution pH control agent, and aqueous ammonia or potassium carbonate solution or secondary distilled water was used as a co-precipitate washing agent. The effects of the pH control agent and the co-precipitate washing agent on the production yield on the basis of the Ni/Fe molar ratio and the particle characteristics of final products were investigated by XRD, SEM, EDX and XPS. The production yield was almost congruent with that of the initial aqueous mixture in case of using potassium carbonate as a pH control agent, while in case of using ammonia, it was quite changed. The difference seemed to be due to the effects of $Ni^{2+}{\leftarrow}NH_3$complexation in the aqueous solution and of the pH of co-precipitate washing agent.

• Bulletin of the Korean Chemical Society
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• v.6 no.6
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• pp.329-333
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• 1985

A procedure for the preparation of peptizable pseudoboehmite has been described in detail based upon a process of neutralization of an aqueous aluminum sulfate or chloride solution with aqueous ammonia. In order to obtain peptizable pseudoboehmite products, carefully controlled conditions were required in the whole processes of neutralization, aging, washing, and drying. The optimum conditions experimentally found are the following. The aluminum salt solution is neutralized with aqueous ammonia until the final pH of the solution reaches 10.0 to 10.8 or 9.0 to 9.3 for the sulfate of chloride, respectively. The alumina gel formed is subjected to aging at $80^{\circ}C for about 3 hours and washed with water more than 5 times to reduce the residual sulfate or chloride ion in the final products to less than 4%. The pseudoboehmite gel thus obtained should be dried oven at 80 to $100^{\circ}C for a few to several hours depending on the selected temperatures.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.10
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• pp.817-824
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• 2002

A diffusion absorption refrigerator is a heat-generated refrigeration system. It uses a three-component working fluid consisting of the refrigerant (ammonia), the absorbent (water) and the auxiliary gas (typically hydrogen). This system has no moving parts and the associated noise and vibration. In this study, the operating characteristics of diffusion absorption refrigerator are investigated through cycle modeling and simulation. System parameters considered in this study are the charged concentration of ammonia aqueous solution, the concentration difference between absorber inlet and outlet and the system pressure determined by the amount of auxiliary gas charged. It was found that there exists a critical value of concentration difference that maximizes the refrigerating capacity. And the lower the system pressure, the higher the refrigerating capacity.