• Journal of Korean Society of Water and Wastewater
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• v.26 no.6
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• pp.747-756
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• 2012

The purpose of this study was to investigate adsorption characteristics of organo-clays for removal of p-xylene. As part of efforts to examine the adsorption capacities of some organo-clays for p-xylene, batch isotherm tests were carried out. Organo-clay minerals were synthesized under hydrothermal conditions using Na-montmorillonite as host clay and dimethyldioctadecylammonium (DMDA) bromide and benzyldimethyldodecylammonium (BDDA) chloride as organic surfactants, respectively. All synthetic organo-clay minerals were characterized by powder x-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive x-ray spectroscopy (EDX). The modification using dimethyldioctadecylammonium (DMDA) bromide showed the higher adsorption ability for p-xylene than benzyldimethyldodecylammonium (BDDA) chloride. On the other hand, the maximum adsorption capacity, $Q_{max}$ of DMDA modified montmorillonite estimated by Langmuir model was 27.0 mg/g, which was the higher value than other organo-clays.

• Economic and Environmental Geology
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• v.28 no.2
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• pp.139-145
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• 1995

Tungsten skarn mineralization of the Sangdong mine is localized in the interbedded limestone layers of the Myobong Slate Formation and in the limestone of the Pungchon Limestone Formation of Cambrian age. Fluid inclusion, gas composition and Nd-Sr isotope for granites and skarns have been investigated. Gas compositions show $CO_2$ rich in the Sangdong granite and CH, rich in the Nonggeori and Eopyeong granites. The initial $^{87}Sr/^{86}Sr$ and $^{143}Nd/^{144}Nd$ ratios of the Sangdong granites have 0.714~0.716(${\varepsilon}_{Sr}$=138~162) and 0.51173~0.51178(${\varepsilon}_{Nd}$=-14.4~15.5), respectively. And their two stage model ages range from 1687 to 1764 Ma. The granite characterized by high strontium initial ratios and negative eNd value could have originated from the old continental crust source. Low homogenization temperature of the Sangdong granite having $203{\sim}296^{\circ}C$ with 1.9~9.2 NaCl equiv. wt% indicates the post-magmatic hydrothermal alteration temperature. Skarn ore fluid responsible for tungsten mineralization has been evolved from CH, rich fluid of early pyroxene garnet skarn to $CO_2$ rich later quartz-mica skarn.

• Advances in environmental research
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• v.7 no.1
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• pp.53-71
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• 2018

Waste glass disposal causes environmental problems in the cities. To find a suitable green environmental solution for this problem low cost adsorbent in this study was prepared from waste glass. An effective new green adsorbent was synthesized by hydrothermal treatment of waste glass (WG), followed by acidic activation of its surface by HCl (WGP). The prepared adsorbent was characterized by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), and BET surface measurement. The developed adsorbent was used for the removal of heavy metals (Cd, Cu, Fe, Pb and Zn) from well water. Batch experiments were conducted to test the ability of the prepared adsorbent for the removal of Cd, Cu, Fe, Pb and Zn from well water. The experiments of the heavy metals adsorption by adsorbent (WGP) were performed at different metal ion concentrations, solution pH, adsorbent dosage and contact time. The Langmuir and Freundlich adsorption isotherms and kinetic models were used to verify the adsorption performance. The results indicated high removal efficiencies (99-100%) for all the studied heavy metals at pH 7 at constant contact time of 2 h. The data obtained from adsorption isotherms of metal ions at different time fitted well to linear form of the Langmuir sorption equation, and pseudo-second-order kinetic model. Application of the resulted conditions on well water demonstrated that the modified waste glass adsorbent successfully adsorbed heavy metals (Cd, Cu, Fe, Pb and Zn) from well water.

• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3244-3248
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• 2014

Two ethylenediamine cobalt(II) oxalate complexes Co(ox)(en), 1 and $Co(ox)(en){\cdot}2H_2O$, 2 have been hydrothermally synthesized and characterized by single crystal X-ray diffraction, IR spectrum, TG analysis, and magnetic measurements. In 1, Co atoms are coordinated by two bis-bidentate oxalate ions in transconfiguration to form Co(ox) chains, which are further bridged by ethylenediamine molecules to produce 2D grid layers, Co(ox)(en). In 2, Co atoms are coordinated by bridging oxalate ions in cis-configuration to form Co(ox) chains, and the additional chelation of ethylenediamine to Co atoms completes 1D zigzag chain, Co(en)(ox). Two lattice water molecules stabilize the chains through hydrogen bonding. Magnetic susceptibility measurements indicate that both complexes exhibit weak antiferromagnetic coupling between cobalt(II) ions with the susceptibility maxima at 23 K for 1 and 20 K for 2, respectively. In 1 and 2, the oxalate ligands afford a much shorter and more effective pathway for the magnetic interaction between cobalt ions compared to the ethylenediamine ligands, so the magnetic behaviors of both complexes could be well described with 1D infinite magnetic chain model.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2217-2221
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• 2011

We investigated the selective deoxyribonucleic acid (DNA) adsorption on layered double hydroxide (LDH) nanoparticles via studying the interaction between positively charged LDH nanoparticle as adsorbent and negatively charged adsorbates such as methyl orange (MO), fluorescein (FL), and DNA strands. The size controlled LDH $(Mg_{0.78}Al_{0.22}(OH)_2(CO_3)_{0.11}{\cdot}mH_2O)$ was prepared by conventional coprecipitation method, followed by the hydrothermal treatment. According to the adsorption isotherms, the adsorbed amounts of MO and FL were similar, however, that of DNA were much larger. The adsorption behaviors were well fitted to Freundlich adsorption model. The concentration dependent adsorption behavior on LDH surface was described in order to verify the selective DNA separation ability. The result showed that the LDH has advantages in selective adsorption of DNA competing with single molecular anions.

• Journal of Environmental Science International
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• v.27 no.11
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• pp.975-982
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• 2018

In this study, zeolite (Z-C1) was synthesized using a fusion/hydrothermal method from coal fly ash. The morphological structures of Z-C1 were confirmed to be highly crystalline with a cubic crystal structure. Exchange capacities of $Ca^{2+}$ and $Mg^{2+}$ ions in a single and a mixed solution reached equilibrium within 120 min. The exchange kinetics of these ions were well predicted by the pseudo-second-order rate equation. The exchange isotherms of the $Ca^{2+}$ and $Mg^{2+}$ ions matched the Langmuir isotherm better than the Freundlich isotherm. The maximum cation exchange capacities ($q_m$) obtained by the Langmuir isotherm model were 2.11 mmol/g (84.52 mg/L) and 1.13 mmol/g (27.39 mg/L) for the $Ca^{2+}$ and $Mg^{2+}$ ions, respectively.

• Steel and Composite Structures
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• v.47 no.5
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• pp.633-644
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• 2023

Taking a look at the previously published papers, it is revealed that there is a porosity index limitation (around 0.35) for the mechanical behavior analysis of the functionally graded porous (FGP) structures. Over mentioned magnitude of the porosity index, the elastic modulus falls below zero for some parts of the structure thickness. Therefore, the current paper is presented to analyze the vibrational behavior of the FGP Timoshenko beams (FGPTBs) using a novel refined formulation regardless of the porosity index magnitude. The silica aerogel foundation and various hydrothermal loadings are assumed as the source of external forces. To obtain the FGPTB's properties, the power law is hired, and employing Hamilton's principle in conjunction with Navier's solution method, the governing equations are extracted and solved. In the end, the impact of the various variables as different beam materials, elastic foundation parameters, and porosity index is captured and displayed. It is revealed that changing hygrothermal loading from non-linear toward uniform configuration results in non-dimensional frequency and stiffness pushing up. Also, Al - Al2O3 as the material composition of the beam and the porosity presence with the O pattern, provide more rigidity in comparison with using other materials and other types of porosity dispersion. The presented computational model in this paper hopes to help add more accuracy to the structures' analysis in high-tech industries.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.3 no.2
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• pp.39-51
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• 2007

Unconsolidated and permeable alluvial deposit composed of sand and gravel is distributed along the fluvial plain at the Iryong study area. Previous studies on the area show that a single alluvial well can produce at least 1,650m3d-1 of bank infilterated shallow groundwater(BIGW) from the deposit. This study is aimed to evaluate and simulate the influence that seasonal variation of water levels and temperatures of the river have an effect on those of BIGW under the pumping condition and also to compare seasonal variation of COPs when indirectly pumped BIGW or directly pumped surface water are used for a water to water heat pump system as an heat source and sink using 3 D flow and heat transport model of Feflow. The result shows that the magnitude influenced to water level of BIGW by fluctuation of river water level in summer and winter is about 48% and 75% of Nakdong river water level separately. Seasonal change of river water temperature is about $23.7^{\circ}C$, on other hand that of BIGW is only $3.8^{\circ}C$. The seasonal temperatures of BIGW are ranged from minimum $14.5^{\circ}C$ in cold winter(January) and maximum $18.3^{\circ}C$ in hot summer(July). It stands for that BIGW is a good source of heat energy for heating and cooling system owing to maintaining quite similar temperature($16^{\circ}C$) of background shallow groundwater. Average COPh in winter time and COPc in summer time of BIGW and surface water are estimated about 3.95, 3.5, and about 6.16 and 4.81 respectively. It clearly indicates that coefficient of performance of heat pump system using BIGW are higher than 12.9% in winter time and 28.1% in summer time in comparision with those of surface water.

• Economic and Environmental Geology
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• v.25 no.2
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• pp.115-131
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• 1992

Late Cretaceous (90.5 Ma), epithermal gold-silver vein mineralization of the Weolseong and Samchang mines in the Sulcheon area, 60 km southeast of Taejeon, can be separated into two distinct stages (I and II) during which fault-related fissures in Precambrian gneiss and Cretaceous (102 Ma) porphyritic granite were filled. Fluid inclusion and mineralogical data suggest that quartz-sulfide-electrum-argentite-forming stage I evolved from initial high temperatures $({\approx}340^{\circ}C})$ to later lower temperatures $({\approx}140^{\circ}C})$ at shallow depths of about 400 to 700 m. Ore fluid salinities were in the range between 0.2 and 6.6 wt. % eq. NaCl. A simple statistic model for fluid-fluid mixing indicates that the mixing ratio (the volumetric ratio between deep hydrothermal fluids and meteoric water) systematically decreased with time. Gold-silver deposition occurred at temperatures of $230{\pm}40^{\circ}C$ mainly as a result of progressive cooling of ore-forming fluids through mixing with less-evolved meteoric waters. Measured and calculated hydrogen and oxygen isotope values of hydrothermal fluids indicate meteoric water dominance, approaching unexchanged meteoric water values. The geologic, mineralogic, and geochemical data from the Weolseong and Samchang mines are similar to those from other Korean epithermal gold-silver vein deposits.

• Economic and Environmental Geology
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• v.53 no.6
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• pp.781-792
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• 2020

Mine tailings, which are inevitably formed by the development of manganese nodules, manganese crusts, and hydrothermal seafloor deposits, have attracted attention because of their quantity and potential toxicity. However, there is a lack of data on the quantity of mine tailings being generated, their physicochemical properties, and their effects as environmental hazards and on marine ecosystems in general. The importance of treating mine tailings in an environmentally friendly manner has been recognized recently and related reduction/treatment methods are being considered. In the case of deep-sea mineral resource development, if mine tailings cannot be treated aboard a ship, the issue becomes one of the cost of transporting them to land and solving the problem of environmental pollution there. Therefore, the Korea Institute of Ocean Science and Technology conducted research on the harmfulness of mine tailings, their effect on marine ecosystem, the diffusion model of contaminated particles, and candidate purification treatment technologies based on five representative controlling factors: 1) effects of pollution /on the environment, 2) effects of environmental/ biological hazards, 3) diffusion of particles, 4) mineral dressings, and 5) reducing/processing mine tailings. The results of this study can provide a basis for minimizing environmental problems by providing scientific evidences of the environmental effects of mine tailings. In addition, it is also expected that these results could be applied to the treatment of pollutants of different origins and at land-based mining waste sites.