• Journal of Korean Society for Atmospheric Environment
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• v.34 no.4
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• pp.554-566
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• 2018

The rice husk contains nutrients which can be easily utilized by microorganisms, and also has a water retaining ability, which played a crucial part in enabling it to become a biofilter media. In this study, we evaluated the applicability of rice husk pellet bio-scrubber as a microbiological carrier. The pelletization experiment of rice husk as a biological media was performed using PVA and EVA binder. Also, the feasibility tests of rice husk as a biological media for odor removal were carried out in order to know whether rice-husk contains useful components as a media for microbiological growth or not. Lastly, a combined test for odor gas absorption and biological oxidation was conducted using a lab scale bio-filter set-up packed with rice-husk pellets as wet-scrubber. The major components of the rice husk were carbon, hydrogen, nitrogen, and oxygen, while carbon acted as the main ingredient which comprised up to 23.00%. The C : N : P ratio was calculated as 45 : 1 : 2. Oxygen uptake rate, yield and decay rate of the rice husk eluent was calculated to be $0.0049mgO_2/L/sec$, 0.24 mgSS/mgCOD and 0.004 respectively. The most stable form of rice husk pellets was produced when the weight of the rice husk, EVAc, PVAc, and distilled water was 10 : 2 : 0.2 : 10. The prepared rice husk pellets had an apparent density of 368 g/L and a porosity of 59.00% upon filling. Dry rice husks showed high adsorption capacity for ammonia gas but low adsorption capacity for hydrogen sulfide. The bio-filter odor removal column filled with rice husk pellets showed more than 99.50% removal efficiency for NH3 and H2S gas. Through the analysis of circulation water, the prime removal mechanism is assumed to be the dissolution by water, microbial nitrification, and sulfation. Finally, it was confirmed that the microorganisms could survive well on the rice husk pellets, which provided them a stable supply of nutrients for their activity in this long-term experiment. This adequate supply of nutrients from the rice husk enabled high removal efficiency by the microorganisms.

• The Journal of Engineering Research
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• v.5 no.1
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• pp.73-87
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• 2004

The synthesis and crystallization of amorphous calcium carbonate($CaCO_3$.$nH_2 O$) obtained from gas-liquid reaction between aqueous solution of calcium hydroxide and carbon dioxide at 15~$50^{\circ}C$ are investigated by electrical conductometry, XRD and TEM. The results are as follows: The initial reaction products prior to the formation of precipitated calcium carbonate is amorphous calcium carbonate. The electrical conductivity values in the slurry are decreased during the formation of amorphous calcium carbonate which covers particle surface of calcium hydroxide and retard the dissolution of calcium hydroxide into the solution. that amorphous calcium carbonate is unstable in the aqueous solution and crystallizes finally to calcite by the through-solution reaction. While amorphous calcium carbonate crystallizes into chain-like calcite, the conductivity values are recovered rapidly and the apparent viscosity of slurry containing higher concentration of calcium hydroxide increase. At below pH 9.5, chain-like calcite separates into individual particles to form precipitated calcium carbonate. The formation and synthetic temperature range of amorphous calcium carbonate is most suitable a primary decreasing step(a-step) at $15^{\circ}C$ in the electrical conductometry.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.743-748
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• 2019

This study focuses on the simulation of wet flue gas desulfurization process for improving the production of gypsum by the utilization of low-grade limestone. At present, high-grade limestone with a $CaCO_3$ content of 94% is used for producing merchantable gypsum. In modeling process, a lot of reactions are considered to develop model. First, the limestone dissolution is simulated by RSTOIC model. Second, SOx absorption and crystallization is used by RCSTR model. Finally the gypsum is separated by using SEPERATORS model. Modeling steps make it easy to reflect further side reactions and physical disturbances. In optimization condition, constraints are set to 93% purity of gypsum, 94% desulfurization efficiency, and total use of limestone at 3710 kg/hr. Under these constraints, the mass flow of low-grade limestone was maximized. As a result, the maximum blending quantity of low-grade limestone for 2,100 kg of high-grade limestone that satisfies constraints is about 1,610 kg.

• Resources Recycling
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• v.23 no.1
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• pp.33-39
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• 2014

In this study, the solubility of Cu, which is a main metal component of wasted PCB, in $CaO-SiO_2-Al_2O_3-MgO$ slag system was investigated. Each 20 grams of Cu chips and the quaternary slag manufactured was placed in an carbon crucible and melted for 10 hours in the temperature between 1673 K and 1825 K to confirm the equilibrium state. The oxygen partial pressure was controlled by the ratio of CO and Ar gas in the range of $10^{-17.23}$ to $10^{-15.83}$ atm. The concentration of Cu in the slag increased with increasing oxygen partial pressure, slag basicity, and MgO content in the slag. The concentration of Cu in the slag decreased with increasing temperature. The Cu dissolution reaction in the slag is an exothermic reaction.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.11
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• pp.1625-1633
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• 2003

This study was conducted to observe effects of dietary acidogenicity value (AV) on rumen fermentation characteristics and nutrients digestibility. The AV of feedstuffs was based on the dissolution of Ca from $CaCO_3$ powder added at the end of a 24 h in vitro fermentation. Three diets were formulated to be iso-energetic and iso-nitrogenous with different AV. Two experiments were involved in this study. In experiment 1, it appears that pH, $NH_3-N$ concentration and A:P ratio tended to decrease, but gas production, VFA production and DM disappearance tended to increase with increasing dietary AV. In experiment 2, the rumen pH tended to decrease in order of high AV>medium AV>low AV treatment, respectively. There were no significant effects of dietary AV on $NH_3-N$ concentration, enzyme activity and nutrient digestibility. In addition, total VFA and individual VFA concentrations tended to increase with increasing dietary AV without significance. In fact, we hypothesized that different dietary AV would affect rumen fermentation and nutrients digestibility because dietary AV was adjusted with fermentable carbohydrate sources. The present results indicate that differences in dietary AV between treatments were too small to affect rumen fermentation and its effects were minimal.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.1
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• pp.157-168
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• 2006

Recently, interest in using Al alloys in ship construction instead of fiber-reinforced plastic (FRP) has increased because of the advantages of A) alloy ships over FRP ships, including high speed, increased load capacity. and ease of recycling. This paper investigated the mechanical and electrochemical properties of Al alloys in a slow strain rate test under various potential conditions. These results will provide reference data for ship design by determining the optimum protection potential regarding hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys do not corrode on formation of a film that has resistance to corrosion in neutral solutions. In seawater, however, $Cl^-$ ions lead to the formation and destruction of a Passive film. In a potentiostatic experiment. the current density after 1200 sec in the Potential range of $-0.68\~-1.5\;V$ was low. This low current density indicates the protection potential range. Elongation at an applied potential of 0 V was high in this SSRT. However, corrosion protection under these conditions is impossible because the mechanical properties are worse owing to decreased strength resulting from the active dissolution reaction in parallel parts of the specimen. A film composed of $CaCO_3\;and\;Mg(OH)_2$ confers corrosion resistance. However, at potentials below -1.6 V forms non-uniform electrodeposition coating, since there is too little time to form a coating. Therefore, we concluded that the mechanical properties are poor because the effect of hydrogen gas generation exceeds that of electrodeposition. Comparison of the maximum tensile strength, elongation, and time to fracture indicated that the optimum protection potential range was from -1.45 to -0.9 V (SSCE).

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.40-46
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• 2007

A laboratory scale experiment on phenol conversion properties by pulsed corona discharge process was carried out. Effects of operating parameters such as applied voltage, input oxygen, and electrode geometry on phenol conversion and solution properties were investigated. Electrical discharges generated in liquid phase increased the liquid temperature by heat transfer from current flow, decreased the pH value by producing various organic acids from phenol degradation, and increased conductivity by generating charge carriers and organic acids. The oxygen supply enhanced the phenol conversion through the ozone generation dissolution and the production of OH radicals. Series type electrode configuration induced more ozone production than reference type configuration because it produced gas phase discharges as well as liquid phase discharges. Therefore, the higher phenol conversion and TOC(total organic carbon) removal efficiency were obtained in series type configuration.

• Journal of environmental and Sanitary engineering
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• v.21 no.3 s.61
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• pp.15-26
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• 2006

As traffic in city-centre around the world continues to increase, so levels of atmospheric pollutants continue to rise. High concentrations of NOx can have negative effects on human health, and we must find new ways to reduce their levels in the air we breathe. Nitrogen oxide gas (NOx), consisting of nitrogen monoxide (NO) and nitrogen dioxide $(NO_2)$ produced using $O_3$ oxidation, at a low concentration corresponding to that on roads as a result of exhaust from automobiles, was carried out to evaluate the removal characteristics of NOx through a laboratory-scale biofilter packed with soil as a packing material. A mixture media (yellow soil (30%): soil (40%): compost (10%): a used briquet (20%)) was applied. After about 1day of operation, the removal efficiency for $NO_2$ in all experiments with a constant condition ($25^{\circ}C$ and water humidity (60%)) was over 98%. The retention times of the section between phase I and phase II for formation and reduction of $NO_3$ NO and $NO_2$ on the initial $NO_3$ concentration was 50min $(O_3:195\;ppb),\;55min\;(O_3:925\;ppb),\;65min\;(O_3:1743\;ppb),\;70min\;(O_3:2616\;ppb),\;75min\;(O_3:3500\;ppb)$, respectively The soil biofilter system is a unique technology that purifies urban air by utilizing the natural processes that take place in the soil. Although some of the processes are quite complex, they can broadly be summarized as adsorption onto soil particles, dissolution into soil pore water, and biochemical.

• Resources Recycling
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• v.27 no.3
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• pp.93-99
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• 2018

Effective extraction of platinum group elements by dissolving waste platinum scrap from the display industry and solvent extraction, was studied. The extracted platinum solution was prepared as a precursor solution for diesel automotive exhaust gas purification catalyst and its catalytic activity was tested. The behavior of aqueous species of platinum was investigated through solution chemistry and based on the existence and behavior of these chemical species, the possibility of extraction and separation was established. By dissolving waste scrap by electrochemical method, the dissolution time of scrap was shortened and the extraction efficiency was increased. Through separation and removal of rhodium component, solvent extraction by TBP, and stripping by hydrochloric acid, Pt-Chloride-$H_2O$ solution was prepared. And then, an platinum amine complex solution through amination reaction with this solution as a raw material was prepared. The possibility of producing high-value platinum compounds from platinum group waste scrap was investigated by preparing platinum amine complex solution and then examining the catalytic activity with this amine precursor on the combustion reaction of carbon black.

• Corrosion Science and Technology
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• v.11 no.3
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• pp.77-81
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• 2012

Cathodic protection(CP) is widely used as a means of protecting corrosion for not only marine structures like ship hulls and offshore drilling facilities, but also underground structures like buried pipelines and oil storage tanks. The principle of CP is that the anodic dissolution of metal can be protected by supplying electrons to the cathode metal. When unprotected structures are nearby to CP systems, interference problems between unprotected and protected structures may be happened. The stray current interference can accelerate the corrosion of nearby structures. So far many efforts have been made to reduce the interference in the electric railway systems adjacent to the underground metal structures like buried pipelines and gas/oil tanks. During recent few decades the protection technologies against stray current induced corrosion have been significantly improved and a number of techniques have been developed. However, there is very limited information an marine environments. Some complex harbor structures are protected by two cathodic protection systems, i.e. sacrificial anode cathodic protection(SACP) and impressed current cathodic protection(ICCP). In this case, when the protection current from sacrificial anodes returns to the cathode through electrolyte, it passes through nearby other low resistance metal structures. In many cases the stray current of ICCP systems influences the function of SACP. In this study, the risk of stray current from the SACP system to adjacent reinforced concrete structures has been verified through laboratory experiments. Concrete and steel pile structures modeled a part of bridge have been investigated in terms of CP potential and current between the two. The variation of stray current according to the magnitude of ICCP/SACP has been studied to mitigate it and to suggest the proper protection criteria.