• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.302-307
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• 2012

Advanced oxidation processes (AOP) such as O3/activated carbon process and O3/catalysts process were used to compare the decomposition of phenol. Catalysts such as Pd/activated carbon (Pd/AC), Mn/activated carbon (Mn/AC), Co/activated carbon (Co/AC) and Fe/activated carbon (Fe/AC) were prepared by impregnation of Pd, Mn, Co and Fe into the activated carbon of pellet form, respectively. Based on an hour of reactions, the following descending order for the decomposition ratios of dissolved O3 to the 1.48 mg/L of saturated dissolved O3 was observed: Mn/AC (45%) > Pd/AC (42%) > Co/AC (33%) > AC (31%) > Fe/AC (27%). The removal efficiencies of phenol were also arranged in the descending order of AOP as follows: Mn/AC (89%) > Pd/AC (85%) > Co/AC (77%) > AC (76%) > Fe/AC (71%). The remaining ratios (C/Co) of TOC (total organic carbon) after an hour of experiments were arranged in the ascending order of AOP as follows : Pd/AC (0.29) < Mn/AC (0.36) < AC (0.40) < Co/AC (0.49) < Fe/AC (0.51). However, the catalytic effects in the Co/AC and the Fe/AC processes were little in comparison with O3/AC process. The maximum concentrations of intermediates such as hydroquinone and catechol formed from the decomposition of phenol were arranged in the ascending order of AOP as follows: Pd/AC < Fe/AC < Co/AC < AC < Mn/AC. In the case of Pd/AC process, these intermediates were almost disappeared after an one hour of reaction.

• Economic and Environmental Geology
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• v.47 no.1
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• pp.61-69
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• 2014

As we are trying to in-situ treat (purify or immobilize) heavy metals or radionuclides in groundwater, one of the geochemical factors to be necessarily considered is the value of oxidation/reduction potential (ORP) of the groundwater. A biogeochemical impact on the characteristic ORP change of groundwater taken from the KAERI underground was observed as a function of time by adding electron-donor (lactate), electron-acceptor (sulfate), and indigenous bacteria in a laboratory condition. There was a slight increase of Eh (slow oxidation) of the pure groundwater with time under a $N_2$-filled glove-box. However, most of groundwaters that contained lactate, sulfate or bacteria showed Eh decrease (reduction) characteristics. In particular, when 'Baculatum', a local indigenous sulfate-reducing bacterium, was injected into the KAERI groundwater, it turned to become a highly-reduced one having a decreased Eh to around -500 mV. Although the sulfate-reducing bacterium thus has much greater ability to reduce groundwater than other metal-reducing bacteria, it surely necessitated some dissolved ferrous-sulfate and finally generated sulfide minerals (e.g., mackinawite), which made a prediction for subsequent reactions difficult. As a result, the ORP of groundwater was largely affected even by a slight injection of nutrient without bacteria, indicating that oxidation state, solubility and sorption characteristics of dissolved contaminants, which are affected by the ORP, could be changed and controlled through in-situ biostimulation method.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.475-479
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• 2011

Chitosan is a natural polymer that has many physicochemical(polycationic, reactive OH and $NH_2$ groups) and biological(bioactive, biocompatible, and biodegradable) properties. In this study, chitosan nanoparticles were prepared using poly-${\gamma}$-glutamic acid(${\gamma}$-PGA) as gelling agent. Nanoparticles were formed by ionic interaction between carboxylic groups in ${\gamma}$-PGA and amino groups in chitosan. Chitosan(0.1~1 g) was dissolved in 100 ml of acetic acid (1% v/v) at room temperature and stirred overnight to ensure a complete solubility. An amount of 0.1 g of ${\gamma}$-PGA was dissolved in 90 ml of distilled water at room temperature. Chitosan solution was dropped through needle into beaker containing ${\gamma}$-PGA solution under gentle stirring at room temperature. The average particle sizes were in the range of 80~300 nm. The prepared chitosan/${\gamma}$-PGA nanoparticles were used to examine their removal of several heavy metal ions($Cd^{2+}$, $Pb^{2+}$, $Zn^{2+}$, $Cu^{2+}$, and $Ni^{2+}$) as adsorbents in aqueous solution. The heavy metal removal capacity of the nanoparticles was in the order of $Cu^{2+}$ > $Pb^{2+}$ > $Cd^{2+}$ > $Ni^{2+}$ > $Zn^{2+}$.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.445-455
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• 2009

Microbiological sulfate reduction is the transformation of sulfate to sulfide catalyzed by the activity of sulfate-reducing bacteria using sulfate as an electron acceptor. Low solubility of metal sulfides leads to precipitation of the sulfides in solution. The effects of microbiological sulfate reduction on in-situ precipitation of arsenic and copper were investigated for the heavy metal-contaminated soil around the Songcheon Au-Ag mine site. Total concentrations of As, Cu, and Pb were 1,311 mg/kg, 146 mg/kg, and 294 mg/kg, respectively, after aqua regia digestion. In batch-type experiments, indigenous sulfate-reducing bacteria rapidly decreased sulfate concentration and redox potential and led to substantial removal of dissolved As and Cu from solution. Optimal concentrations of carbon source and sulfate for effective microbial sulfate reduction were 0.2~0.5% (w/v) and 100~200 mg/L, respectively. More than 98% of injected As and Cu were removed in the effluents from both microbial and chemical columns designed for metal sulfides to be precipitated. However, after the injection of oxygen-rich solution, the microbial column showed the enhanced long-term stability of in-situ precipitated metals when compared with the chemical column which showed immediate increase in dissolved As and Cu due to oxidative dissolution of the sulfides. Black precipitates formed in the microbial column during the experiments and were identified as iron sulfide and copper sulfide. Arsenic was observed to be adsorbed on surface of iron sulfide precipitate.

• Journal of Korea Soil Environment Society
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• v.3 no.1
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• pp.55-63
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• 1998

This study investigates the contamination mechanism of soil by drainages including acid rains around mining waste sites, and suggests the quantitative methods of prevention against soil contaminations and its alternatives. For these purposes, the dissolution of arsenic in soils, which is one of toxic heavy metals, has been examined experimentally using the artificial acidic solution. Also, in order to prevent dissolution of arsenic by acid rain, the effects of limestone for the neutrality method on the soil were investigated. The arsenic in soil specimen was dissolved by strong acidic solution below pH1.0. The maximum amount of dissolved arsenic increased with decreasing pH value. Furthermore, it was found very effective to use limestones for the neutrality method. The neutralization of limestones in acidic solution was found to follow the equation of chemical reaction-controlling formulation in unreacted-core models.

• Korean Journal of Heritage: History & Science
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• v.52 no.3
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• pp.160-171
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• 2019

The sword with a ring pommel, which was excavated from the first stone chamber of the ancient tombs of Jeongchon Village in Naju, is a sword with a pentagon undecorated ring pommel consisting of a mother sword and two child swords. The sword with an undecorated ring pommel of Jeongchon comprises a ring pommel, a hilt, a knife, and a knife end decoration. This sword was coated with lacquer. The ring pommel is an iron frame covered with silver plate; however the silver tarnished into a light purple due to silver chloride corrosion, and iron corrosion originated from the inside is visible on the surface. Silver chloride corrosion is produced when silver objects are exposed to water, dissolved salts, and dissolved chloride ions when in a buried state. It changes objects into powder, making it difficult to preserve original shapes. The other silver artifacts found in the Jeongchon ancient tombs show similar signs of corrosion. The results of X-ray irradiation and a CT analysis showed that the sword had a ring at the end of the handle, a T-shaped hilt, and was probably connected to the handle end of a knife. If the shape of the mother sword can be inferred from the child swords, the mother sword had a ring pommel, decorations of the handle, covered with silver plate, and a gold ring and a silver line wound around the handle. It is assumed that the ring pommel was connected to the knife by welding because no holes were observed. The end decoration of the knife was made by using an iron plate formed into a shape, half covered by silk, and the other half decorated with silver plate and a gold ring. The sword with an undecorated ring pommel excavated from the ancient tombs of Jeongchon Village comprises the metals of gold, silver, and iron, and includes features of Baekje, Silla, and Gaya, which highlights the influence of surrounding historic sites and various cultures.

• Korean Journal of Environmental Agriculture
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• v.18 no.2
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• pp.109-115
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• 1999

Lead and cadmium were analyzed with different pretreatemnt methods. Paddy soil and wastewater sludge samples were used and the result was compared each other. Pretreatment method affected the concentration obtained from samples significantly. Large difference was illustrated between the results. The concentration by 0.1N HCl extraction method, an official analytical method for soil and solid wastes, was far lower than those by the EPA3050B and mixed-acid digestion methods. The reason might be that metals associated with organics and silicates are not easily extracted by 0.1N HCl, while digestion methods using strong acids and high temperature dissolved all the elements in the samples. It implies that pretreatment method should be specified in addition to concentration on the report of metal analysis for environmental samples. Acid digestion methods are not necessarily good because the concentration obtained does not represent the natural condition which is our concern in many cases. The 0.1N HCl extraction method does not fully represent the natural condition either. The metals associated with organics will be extracted eventually as organics decompose with time. Therefore, proper pretreatment and analytical methods should be developed for specific purpose, and their standardization is recommended.

• Journal of Soil and Groundwater Environment
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• v.11 no.1
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• pp.23-36
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• 2006

Experimental leaching of tailings was performed as a function of times (1, 2, 4, 7, 14, 21 and 30 days) in the laboratory using reaction solutions equilibrated to three different pH set-points (pHs 1,3 and 5). The initial pHs of 5 and 3 stabilized at either 4.6-6.1 or 2.8-3.5 in 2 days and decrease gradually with time afterwards. The results of the leaching tests indicate that the significant increase in the sulfate concentrations and in acidity after 7 days of leaching results from the oxidation of sulfide minerals. There were no significant variations in the extractable Pb found in the leach solutions of pH 5 and 3 within the reaction time (1-30 days), while Zn, Cd and Cu concentrations tend to significantly increase with time. In tailings leaching at an initial pH=1, two trends were observed: i) The 'Zn-type' (Zn, Cd and Cu), with increasing concentrations between days 1 and 30, corresponding to the expected trend when continuous dissolution is the dominant process, ii) the 'Pb-type' (Pb), with decreasing concentrations over time, suggesting rapid dissolution of a Pb source followed by the precipitation of 'anglesite' in relation to the large increase in dissolved sulfates. The high sulfate concentrations were coupled with high concentrations of released Fe, Zn and Cd. Release of Zn and Cd and acidity from these leaching experiments can potentially pose adverse impact to surface and groundwater qualities in the surrounding environment. The kinetic problems could be the important factor which leads to increasing concentrations of trace metals in the runoff water.

• Journal of the Korean GEO-environmental Society
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• v.11 no.8
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• pp.33-40
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• 2010

In this study, evaluation of basic unit of non-point pollutant, which is fundamental evaluation of non-point loading, was conducted using both road point and angle of intersection point in Maesong area, West coast highway by utilizing Event Mean Concentrations(EMC). Concentration of pollutants except heavy metals at these two points rapidly decreased in 30 minutes after start of runoff. According to the results of EMC, for both sampling points, it was determined that the concentrations of TSS(Total Suspended Solid), $BOD_5$(Biological Oxygen Demand), and DOC(Dissolved Organic Carbon) were higher than those of wastewater effluent standard in Korea, however, the concentrations of T-N(Total Nitrogen) and T-P(Total Phosphorus) were lower than those of the standard. In terms of heavy metals, Fe, Pb, and Zn showed higher concentrations than others. When compared with the units established by the Ministry of Environment in Korea, the basic units of $BOD_5$ and T-N in this study were lower. On the other hand, when compared with foreign units, Cu, Pb, and Zn showed approximately 10 times higher concentrations. It was estimated that a long term monitoring should be conducted for obtaining additional data and more reliable basic units for the non-point pollutnats based on the results from this study.

• Journal of the Korean Society for Marine Environment & Energy
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• v.10 no.1
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• pp.21-28
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• 2007

The bioaccumulation of Pb and Cd dissolved in seawater was assessed measuring the concentrations recorded within blue mussel (Mytilus edulis) and oliver flounder (Paralichthys olivaceus) after two weeks exposure period. The Pb and Cd concentration within the whole body of two testing organisms increased according to the exposure concentrations, and the such tendency was clear specially from the mussel. Maximum metal concentration reached $5,260({\pm}70)\;{\mu}g/g$ for Pb reared under 5.0 mg/L Pb, $1,040({\pm}40)\;{\mu}g/g$ for Cd reared under 1.0 mg/L Cd in the mussel, and indicated that the bioaccumulation of Pb and Cd was directly related to the rearing medium concentrations. Bioconcentration factors (BCF) reached very high values for Pb (maximum value: $12,100{\pm}1,400$) in the mussel reared under lowest Pb concentration (0.01 mg/L). The BCF value for Cd in the mussel were also far higher at exposure to low Cd concentration than high Cd concentration. At higher external concentrations, the BCF for Cd and Pb declined. This demonstrated the ability of two testing organisms to rapidly uptake heavy metals particularly when exposed to low external concentration. The mean Pb concentration was slightly higher in the gill of mussel than in the digestive gland, while Cd showed a higher level in the digestive gland than in the gill.