Yungoo Song

Phase studies of SrOAl2O3 by emission signatures of Eu2+ and Eu3+

Phase transformation sequences of SrOAl2O3 have been investigated at 1000 and 1250 °C through XRD technique along with emission signatures of Eu2+ and Eu3+. Two phases, i.e., [Sr3Al2O6] and [SrAl2O4], have been observed at 1000 °C as stable phases. These phases were found to be transformed into [SrAl2O4] at 1250 °C.

Effect of mining and geology on the chemistry of stream water and sediment in a small watershed

Chemical characteristics of the stream water and sediment in the small watershed with two distinctive mineralization zones (Cu and Pb−Zn), 7 abandoned mines and an active quarry were investigated to examine the effects of mining activity and regional geology on the chemistry. The stream water affected by the abandoned mines had Ca−SO4 type but the other had Ca−HCO3 type. The mine affected stream water and sediment showed relatively high concentrations of metals (Cu, Pb, Zn, Cd, Co, Ni, Mn, Al and Fe). The concentrations of Al, Mn, Fe and Cu of the stream water collected near an abandoned mine (Guryong) exceeded the EPA surface water quality standards (Al: 5.52 mg L−1, Mn: 1.58 mg L−1, Fe: 1.49 mg L−1, Cu: 0.63 mg L−1). The effect of mining activity on the stream water chemistry was attenuated in a relatively short distance from the source (<200 m) along the watercourse but the signature in the sediment showed a longer lasting effect (about 2 km) than that in the stream water: The residual and reducible forms were the dominant fractions of the heavy metals in the stream sediment. The particulate trnnsportation was the major cause of the dispersion of heavy metals in the watershed. There was a contrasting spatial distribution of background metal concentration in the stream sediment: a relatively higher concentration of Cu in the Cu mineralization zone and a relatively higher concentration of Pb, Zn and Mn in the Pb−Zn mineralization zone.

Supergene vermiculitization of phlogopite and biotite in ultramafic and mafic rocks, central Korea

An X-ray diffraction study of vermiculitized micas in ultramafic and mafic intrusive rocks from Cheongyang, Korea, shows the following weathering sequence: mica → ordered mica/vermiculite interstratification → vermiculite. Electron microprobe analyses show the general trends of K leaching and Ca enrichment with increased weathering. The vermiculitization of phlogopite from ultramafic rocks proceeds by means of a continuous decrease in Al-for-Si tetrahedral substitutions and a progressive increase in Al-for-(Fe2+ + Mg) octahedral substitutions in the early stage of weathering. These substitutions occur to compensate for the excess of negative charge in the mica-like layer, in agreement with currently accepted vermiculitization mechanisms. They change to a slight increase of Al-for-Si tetrahedral substitutions in the late stage of the vermiculitization of phlogopite, owing to the oxidation of Fe despite its low content. However, the behavior of Fe in the late stage of the transformation of biotite into vermiculite is significantly different; that is, Fe increases substantially. The reason for this Fe increase in the late stage remains unresolved. Recalculations of the structural formulas on the basis of several assumptions indicate that the oxidation of Fe is necessary for the vermiculite derived from biotite to form the reasonable structural formulas.

Highly ordered Ge-incorporated akaganeite (β-FeOOH): a tunnel-type nanorod

A highly ordered Ge-incorporated akaganeite with the atomic ratio of Ge/Fe = 0.14 and Cl/Fe = 0.11 was firstly synthesized through hydrolysis and acidification of a mixed solution of FeCl3·6H2O and TEOGe (Ge(OC2H5)4) under the α-Fe2O3 synthesis conditions. The newly synthesized Ge-akaganeite shows a monodisperse nanorod with 15–17 nm in width and ∼200 nm in length, the distinctly enhanced structural ordering and stability, and substantial differences in crystallographic and magnetic features. Here we propose a hypothetical akaganeite model with Ge occupying the tunnel sites as Ge(OH)40 based on crystallographic and chemical analyses.

New occurrence and characterization of Ni-serpentines in the Kwangcheon area, Korea

Abstract Pecoraite and nepouite, Ni-serpentines, occur in the serpentinized ultramafic rocks in the Kwangcheon area, Korea, where the parent rock is classified as harzburgite and/or lherzolite. Pecoraite was precipitated twice from the solution; the early-formed pecoraite coexists with magnetite, millerite, and polydymite both in the Buk- and Nam-sites, while the late-formed pecoraite appears as well-grown colloform and opaque-free phase only in the Buk-site. The typical colloform texture of the late-formed pecoraite strongly indicates that it was precipitated from the solution in supergene conditions. Pecoraite is characterized by its extremely high Ni content and the difference in Fe content between the early- and late-formed pecoraite. Nepouite is distinguished from pecoraite by its prismatic morphology and the large degree of isomorphous substitution between Ni and Mg. The phase relations among coexisting magnetite-millerite-polydymite assemblage with the earlyformed pecoraite suggest that the pecoraite might have precipitated in the extremely limited ƒo2 and ƒs2 environment from the highly Ni-concentrated solutions and is stable at 25°C and 1 bar.

Optimization of Illite Polytype Quantification Method

We proposed the revised full-pattern-fitting method of illite polytype quantification with background correction and scale factor correction of WILDFIREC simulated pattern, and R% value ((Σ|simulated-measured|/simulated)/ n×100) calculation, and then verified the reliability of this method by applying for the test sample (2M1:1M 1:1), and by comparing the result with Grathoff and Moore method (1996). We confirmed that the proposed method showed the error range of less than 3.6%, which is much lower than the previous full-pattern-fitting methods, in spite of the impurities of the test sample. In the comparison with Grathoff and Moore method for 2 tested samples, we obtained the relatively higher 2M1 contents using Grathoff and Moore method, whereas we obtained the reliable results with less than 10% of R% values.

Effective utilization of incinerated municipal solid waste incineration ash: zeolitic material synthesis and silica extraction.

In this study the effective utilization of two types of municipal solid waste incinerator (MSWI) ashes, namely air-cooled ash (ACS) and water-cooled ash (WCS) samples obtained from a municipal solid waste incineration plant, was examined by applying zeolitic material synthesis and silica extraction. The influence of the experimental conditions including the ratio of sample : NaOH solution, the reaction temperature and time, and the concentration of NaOH solution were investigated. The results for the 25 experimental trials can be summarized as: (1) the formation of tobermorite and/or pectolite-1A as a major component in most conditions; (2) the synthesis of hydroxycancrinite as a major phase at 200 °C; (3) a dramatic increase in the extracted SiO2 yield at 1 : 30 value of sample : NaOH ratio and 200 °C, even at short reaction times; and (4) relatively high SiO2 yields for WCS ashes rather than ACS ashes. An increase in the reaction time improved the quantity of synthesized zeolitic materials. The reaction temperature determined the type of zeolite. An increase in the NaOH concentration can be an essential factor to improve zeolitic material synthesis, but it significantly reduced the yield of SiO2 extraction. In conclusion, suitable conditions for obtaining both SiO2 extraction and synthesized zeolites from the ashes of the incinerated solid waste materials should be: 200 °C reaction temperature; a 1 : 30 (g : mL) value for the sample : NaOH ratio; 2 mol L—1 NaOH concentration; and a reaction time of more than 24 h.In this study the effective utilization of two types of municipal solid waste incinerator (MSWI) ashes, namely air-cooled ash (ACS) and water-cooled ash (WCS) samples obtained from a municipal solid waste incineration plant, was examined by applying zeolitic material synthesis and silica extraction. The influence of the experimental conditions including the ratio of sample : NaOH solution, the reaction temperature and time, and the concentration of NaOH solution were investigated. The results for the 25 experimental trials can be summarized as: (1) the formation of tobermorite and/or pectolite-1A as a major component in most conditions; (2) the synthesis of hydroxycancrinite as a major phase at 200 degrees C; (3) a dramatic increase in the extracted SiO(2) yield at 1 : 30 value of sample : NaOH ratio and 200 degrees C, even at short reaction times; and (4) relatively high SiO(2) yields for WCS ashes rather than ACS ashes. An increase in the reaction time improved the quantity of synthesized zeolitic materials. The reaction temperature determined the type of zeolite. An increase in the NaOH concentration can be an essential factor to improve zeolitic material synthesis, but it significantly reduced the yield of SiO(2) extraction. In conclusion, suitable conditions for obtaining both SiO(2) extraction and synthesized zeolites from the ashes of the incinerated solid waste materials should be: 200 degrees C reaction temperature; a 1 : 30 (g : mL) value for the sample : NaOH ratio; 2 mol L(-1) NaOH concentration; and a reaction time of more than 24 h.

Ge-incorporation into 6-line ferrihydrite nanocrystals

A Ge-incorporated ‘6-line’ ferrihydrite with 20% of total Fe3+ sites occupied by Ge4+ was synthesized for the first time through hydrolysis and acidification of the mixed solution of Fe(NO3)3·9H2O and TEOGe (Ge(OC2H5)4). The newly synthesized Ge-ferrihydrite shows a monodisperse nanocrystalline structure with diameters of ∼10 and ∼40 nm with distinctly enhanced crystallinity and stability.

Additional data on reevesite and its Co-analogue, as a new member of the hydrotalcite group

Abstract Reevesite, the Ni-Fe member of the hydrotalcite group, occurs as a secondary mineral in the serpentinized ultramafic rocks of the Kwangcheon area in Korea, replacing the pecoraite-magnetite-millerite-polydymite assemblages in small veins lining cracks and fracture zones. Chemical analyses for the reevesites indicate the presence of the Co-analogue of reevesite and the complete solid-solution between Fe3+ and Co3+. The Co-analogue of the reevesite shows the approximate ratio of 3:1 of divalent to trivalent cations, which is in distinct contrast to the comblainite with the ratio of 2:1 reported by Piret & Deliens (1980). The presence of the complete solid-solution phase between Fe3+ and Co3+ is confirmed by synthesis at room temperature. On the basis of the results, the Co-analogue of the reevesite should be named as a new member of the hydrotalcite group, and thereby be distinguished from the comblainite. The partial substitutions of SO2-4 for CO2-3 in the interlayer region might affect the slight increase of the basal spacing in the reevesite. The synthesis performed suggests that the reevesite could be precipitated under either an alkaline or a neutral environment, if carbonate activity is high enough.

Laboratory Investigation of the Geochemical Behavior of Metals in Paddy Soils Contaminated with Mine Tailings

The geochemical behavior of metals, including Fe, Mn, Pb and Zn, in contaminated paddy soils was investigated during the cultivation of rice crops through laboratory microcosm experiments. From the two paddy fields contaminated by mine tailings, Siheung and Deokeum in Korea, paddy soils were collected and analyzed for their geochemical characteristics. The Siheung paddy soil showed higher levels of heavy metals, whereas the higher potential for the release of metals was anticipated due to the extremely acidic conditions at Deokeum. In microcosm experiments of flooded paddy soils over 18 weeks, Fe and Mn were released in subsurface pore waters by reductive dissolution, and Pb and Zn were dissolved in high amounts at the surface by oxidation of sulfides. Although amorphous Fe oxide-rich layers were formed at the surface of both paddy soils, the release of Pb and Zn were controlled at the surface by these layers only under slightly alkaline conditions at Siheung. Lead and Zn were associated with the reducible and carbonate fractions at the surface paddy soil of Siheung from the sequential extraction on core samples collected during the flooded period. In the acidic conditions at Deokeum, Pb and Zn were continuously released until the late stage of flooding. A great increase in the exchangeable fraction of metals was observed after the soils had drained. The bioavailability of metals for rice crops would be high under acidic conditions at Deokeum, despite the lower levels of heavy metal contamination.