• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.355-365
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• 2022

Precipitation and phase transition of iron minerals in mine drainage greatly affect the behavior of trace elements. However, the precipitation of ferrihydrite, one of the major iron minerals precipitated in drainage, and the related behavior of trace elements have hardly been studied. In this study, the effects of pH change and time on mineral precipitation characteristics in mine drainage from the Munkyeong coal mine were investigated, and the behavioral changes of trace elements related to the precipitation of these minerals were studied. In the case of precipitated mineral phases, goethite was observed at pH 4, and 2-line ferrihydrite mixed with small amount of 6-line ferrihydrite was mainly identified at pH 6 or higher. In addition, it was observed that the precipitation of calcite additionally increased as the pH increased in the samples at pH 6 or higher. The occurrence of goethite was probably due to the phase change of initially precipitated ferrihydrite within a short time under the influence of low pH. Our results showed that the concentration of trace elements was strongly influenced by pH and time. With increasing time, Fe concentration in the drainage showed a abrupt decrease due to the precipitation of iron minerals, and the concentration of As existing as oxyanions in the drainage, also decreased rapidly like Fe regardless of the pH values. This decrease in As concentration was mainly due to co-precipitation with ferrihydrite, and also partly to surface adsorption on goethite at low pH in drainage. Contrary to this observation, the concentration of other trace elements, such as Cd, Co, Zn, and Ni was greatly affected by the pH regardless of the mineral species. The lower the pH value, the higher the concentration of these trace elements were observed in the drainage, and vice versa at higher pH. These results indicate that the behavior of trace elements present as cations is more greatly affected by the mineral surface charge influenced by the pH values than the type of the precipitated mineral.

• Economic and Environmental Geology
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• v.55 no.5
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• pp.531-540
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• 2022

Various iron minerals that precipitate in acid mine drainage have a great influence on the concentration change and mobility of trace elements in the drainage during phase transition to other minerals as well as the precipitation process. This study investigated the change of mineral properties and the behaviors of trace elements influenced by pH and time for the precipitates collected from the acid mine drainage treatment system of the Dalsung mine, where schwertmannite is mainly precipitated. However, the main mineral precipitated in the drainage was goethite, suggesting schwetmannite has already undergone a phase transition to goethite to some extent, and it was observed that at higher pH, the peak width at half maximum of XRD peak was narrower. This can be interpreted as the transformation of small amount of amorphous schwetmannite to goethite or an increase in the crystallinity of goethite, and it showed that the higher the pH, the greater this change was. The concentration of Fe was also greatly affected by the pH values, and as the pH increased, the concentration of Fe in the drainage decreased. With increasing time, the Fe concentration increased and then decreased, which can be interpreted to indicate the dissolution of schwertmannite and precipitation of goethite. This mineral change probably resulted in the rapid increase of the concentration of S at initial stage, but its concentration was stabilized later. The concentration of S is also related to the stability of schwetmannite, showing a high concentration at a low pH at which schwertmannite is stable and a low concentration at a high pH at which goethite is stable. The trace elements present as cations in the drainage also showed a close relationship with the pH, generally the lower the pH, the higher the concentration, due to the solubility changes by the pH, and the precipitation and the changes in mineral surface charge at high pH. On the other hand, in the case of As, existing as an anion, although it showed a high concentration at low pH, its concentration increased with time at all pH values, which is probably related to the concentration of Fe which can be coprecipitated in the drainage, and the increase of As concentration with time is also considered to be related to the decrease in schwertmannite rather than the mineral surface charge.

• Journal of Wetlands Research
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• v.25 no.4
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• pp.274-283
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• 2023

Buffer zones, an example of nature-based solutions, offer wide range of environmental, social and economic benefits due to their multifunctionality when applied to watershed areas promoting blue-green connectivity. This study evaluated the effects of buffer zone application to the water quality of Yongdam reservoir tributaries. Particularly, the challenges and improvement of the buffer zone design were identified and suggested, respectively. Water and soil samples were collected from a total of six sites in Yongdam reservoir from September 2021 to April 2022. Water quality analyses revealed that among the sites monitored, downstream of Sangjeonmyeon Galhyeonri (SG_W_D2) was found to have the highest concentration for water quality parameters turbidity, total suspended solids (TSS), chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN). This finding was attributed to the algal bloom observed during the sampling conducted in September and October 2021. It was found through the soil analyses that high TN and TP concentrations were also observed in all the agricultural land uses implying that nutrient accumulation in agricultural areas are high. Highest TN concentration was found in the agricultural area of Jeongcheonmyeon Wolpyeongri (JW_S_A) followed by Jucheonmyeon Sinyangri (JS_S_A) while the lowest TN concentration was found in the original soil of Sangjeonmyeon Galhyeonri (SG_S_O). Among the types of buffer zones identified in this study, Type II-A, Type II-B and Type III were found to have blue-green connectivity. However, initially, blue-green connectivity in these buffer zone types were not considered leading to poor design and poor performance. As such, improvement in the design considering blue-green network and renovation must be considered to optimize the performance of these buffer zones. The findings in this study is useful for designing buffer zones in the future.

• Korean Journal of Soil Science and Fertilizer
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• v.12 no.2
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• pp.99-107
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• 1979

The properties, land use and genesis of the Jang-weon series, Planosol-like soils, distributed in Cheong-do area were investigated. Planosol-like soils in Korea have been believed unsuitable for perennial crops but 34.6% (594ha) of the Jang-weon soils in Cheongdo-gun are used for perennial crops such as apples, persimmons, peaches, mulberry etc. With productivity more or less equal to alluvial soils. The reason for high productivity and a working hypothesis for the genesis of the fragipan is suggested with discussion.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.18-23
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• 2010

This work investigated the catalytic reaction characteristics of $H_2$ SCR applied at low temperature ($80{\sim}150^{\circ}C$) using Pt catalyst supported on $TiO_2$. The experiments were performed in terms of $H_2O$, $O_2$ in reaction gas, calcination temperature of the Pt catalyst, $H_2$/NOx mole ratio, space velocity. $H_2O$ was an inhibitor of reaction on $H_2$ SCR using Pt catalyst, catalytic performance increased as $O_2$ concentration decreased. Nevertheless, $NH_3$ slip generated by the reaction between NOx and $H_2$ in the absence of $O_2$. While it was effective to calcine less than $600^{\circ}C$ by phase transition and the catalytic performance increased as $H_2$/NOx mole ratio increased. However, $H_2$ slip was not observed at that increase mole ratio by $H_2$ oxidation to $H_2O$.

• 보존과학연구
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• s.35
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• pp.57-71
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• 2014

As results of this study about the restoration and production techniques of the ridge-end roof tiles excavated from middle gate site in Bunhwangsa Temple, the ridge-end tile was considered that can be combined with four distinguished parts such as a body with upper and lower portions, a back, a belly, and a wing. And also some patterns can be verified. The body and the wing were piled up the coil clay and the back-side was bonded. The pileup process was assumed that three types of wood tools were applied to bond the facing surfaces. After the completion of the pileup process, the entire exterior was retouched by hand. For touching the inside, bare hands or some tools like a wooden branches were used to scratch and to re-face a clay plasterwork. And also, the stamped patterns which produced by framework were bonded to the body. The results from the XRD and the TG-DTA, Tridymite which shows the phase transition in more than $867^{\circ}C$ could not be identified, and also the endothermic reaction peak at $1063^{\circ}C$ showed the result that the alkali feldspar such as the albite was changed into a different mineral at $1050^{\circ}C$. Therefore, the ridge-end tiles can be considered that the firing temperature was below $867^{\circ}C$.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.660-667
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• 2010

In this research polyimide, Matrimid 5218, hollow fiber membrane was used to recover sulfur hexafluoride($SF_6$) which is one of the six greenhouse gases from $N_2/SF_6$ mixture gas. Fibers were spun from using dry-wet phase inversion method. The module was manufactured by fabricating fibers after surface coating with silicone elastomer. The scanning electron microscopy(SEM) studies showed that the produced fibers typically had an asymmetric structure; a dense top layer supported by a sponge-like substructure. The developed module had a permeance of 0.78-1.36 GPU for $N_2$ with $N_2/SF_6$ selectivity of 2.44-5.08 at various pressure and temperature. For recovery of $SF_6$, a membrane module and 10 vol.% $SF_6$ from $N_2/SF_6$ mixture gas was used. The effects of various operating condition such as pressure, temperature, and retentate side flow rate were tested. When pressure and temperature were increased and retentate flow rate was decreased, the $SF_6$ purity in recovered gas was increased up to 37.5 vol.% with decreasing recovery ratio. When retentate flow rate was increased pressure and temperature was decreased, the $SF_6$ recovery ratio in retentate side was increased up to 89% with decreasing the $SF_6$ purity in retentate side.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.795-801
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• 2012

Nanoparticles have received significant attention because of their unusual characteristics including high surface area to volume ratios. Thiol ligand have been used as stabilizers of metal nanoparticles since Brust et al. They reported the preparation method of ligand capped metal nanoparticles by protecting the nanoparticles with a self-assembled monolayer of dodecanethiolate. In this method, volatile organic compounds (VOCs) were used as sovents. This study was carried out to replace these VOCs with room temperature ionic liquids (RTILs). We used two type of ILs to prepare metal nanoparticles. One is a hydrophobic IL, [BMIM][[$PF_6$] (1-Butyl-3-methylimidazolium hexafluorophosphate) purchased from IL maker, C-Tri from Korea and the other one is a hydrophilic one, [BMIM][Cl] (1-Buthy-3-methylimdazolium chloride) sinthesized by us. In the case of preparing Ag and Au nanoparticles using [BMIM][Cl], we didn't use phase transition reagents and ethanol because it has hydrophilic property and preparing Au, Ag nanoparticles using [BMIM][[$PF_6$] the method is as same as Brust et al.'s except using [BMIM][[$PF_6$] instead of organic solvent because it has hydrophobic property. FT-IR and UV-vis, TEM, TGA analysis have been used in an attempt to determine the particle size and verify functional groups. The particle size obtained from TEM was very similar to those obtained by Brust et al. This is a clear example of ligand capped metal nanoparticles prepared using ionic liquids. And the experimental result demonstrated ionic liquids can act as a highly effective medium for the preparation and stabilization of gold and silver metal nanoparticles.

• Korean journal of applied entomology
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• v.16 no.1 s.30
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• pp.21-31
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• 1977

The study has been carried out to compare the pathogenicity, physiological characteristics and genetic reliability between rough colony type strain and smooth colony type strains of Pseudomonas mori (Boyer et Lambert) Stevens which were isolated from diseased plant parts in 5 different areas throughout country. The results are summarized as follow. 1. The rough colony type strain showed more agressive reactions to tested host plant varieties than smooth colony type strains though there was no differences in the appearence of lesion types caused by both strains. 2. Both colony types were differentiated morphologically in that the rough colony type strain was having more than 200r long filamentous body without flagella where as the smooth colony type strains have short rods with one or several polar flagella. 3. The colony of smooth type strains was circular, entire, smooth and opaque, while the rough type strain shelved endulated, irregular margin, rough and wrinkled colony on nutrient agar media. 4. There were no differences between both colony types in the physiological and serological test. 5. Both of smooth and rough colony type strains showed genetic reliability through more than 100 succeeding cultures on the media, and were stable to various chemicals such as 1 to 3 percent of NaCl, 5 kinds of organic acid and 4 kinds of antibiotics.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.644-651
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• 1999

In this experiment the Iron phthalocyanine (FePc) films on Si-wafer and alumina pallet were prepared using vacuum sublimation with conditions of changing reaction time, temperature, and deposition rate. Then, some samples were annealed following annealing. Techniques such as XRD, SEM, and resistance measurement method, were dedicated to characterize the changes of surface structure, phase transformation and electric resistance sensitivity in accordance with change of film thickness. In proportion to the decrease of deposition temperature from $370^{\circ}C$ to $350^{\circ}C$, intensities of (200), (011), (211) and (114) planes of $\alpha$-phase were decreased and (100) plane of $\beta$-phase were appeared. The film thickness were controlled by regulating the volume of precursor material during rapid deposition. As a result, it was observed that crystalline particle size had been increased according to the increase of film thickness and $\alpha$-phase transformed to $\beta$-phase. In consequence of measuring the crystallinity of films annealed between $150^{\circ}C$ and $350^{\circ}C$, $\alpha$- to $\beta$-phase transformation was appeared to begin at $150^{\circ}C$ and completely transformed to $\beta$-phase at $350^{\circ}C$. Electric resistance sensitivity of FePc film to $NO_x$ gas along temperature change of FePc films was observed to be more stable with the decrease of the film thickness.